Automotive PCB design guidelines
To achieve the smart operational requirements of advanced automotive systems necessitates following specific essential automotive PCB design guidelines. These guidelines can be best understood by first exploring the challenges of designing boards for these vehicles. In this article, we will focus the features of automotive PCB, please check the content we prepare to learn more information about it.If you want to order PCB product, please check and custom your order online. What are the performances attributes of automotive PCB? • Multiple categories of automotive PCBs Automobiles combine machinery and electronic equipment. Modern automobile technology integrates traditional technique and advancing scientific technology, such as manual inner decorating parts and advancing GPS. In modern automobiles, there is electronic equipment with different functions at different positions and different functions derive from different types of PCBs. According to substrate materials, automotive PCBs can be classified into two main categories: inorganic ceramic-based PCB and organic resin-based PCB. Ceramic-based PCB features high temperature resistance and excellent size stability, making it directly applied in motor system with high temperature. However, it features bad ceramic manufacturability and high cost. At present, with the development of resin substrate material in terms of its heat resistance capability, resin-based PCB has been widely applied in automobiles with substrate material with different performances applied in different positions. Generally speaking, Flexible multilayer PCBs and Rigid PCBs are applied in normal gauges indicating vehicle speed and mileage and air conditioner equipment. Double-layer or multi-layer PCBs and Flex PCBs are used in audio and video entertainment equipment inside automobiles. For communication and wireless positioning equipment and security control equipment, multi-layer PCBs, HDI printed circuit boards and Flex PCBs are applied. • Different reliability requirements for PCBs at different positions Concerned with public security, automobiles belong to high-reliability product category, so automotive PCBs have to pass some reliability tests apart from ordinary requirements such as dimension, size, mechanical and electric performance. a. Thermal Cycling Test (TCT) Five grades classified according to different positions of automobiles. b. Thermal shock test Automotive PCBs are more applied in the environment with high temperature, which is especially true for Thick Copper PCBs that have to deal with external heat and self-producing heat. As a result, automotive PCBs have a higher requirement on heat resistance. c. Temperature humidity Bias (THB) test Because automotive PCBs stay in multiple environments, including rainy day or humid environment, it's quite necessary to implement THB test for them. The test condition includes the following elements: temperature (85°C), humidity (85%RH) and bias (DC 24V, 50V, 250V or 500V). THB test has to consider CAF migration of PCBs. CAF usually takes place between adjacent vias, via and line, adjacent lines or adjacent layers, leading to insulation reduction or even short circuit. Corresponding insulation resistance depends on distance between vias, lines and layers. What are the characteristics during automotive PCB design? • High-frequency substrate board Automotive collision-resistance/predictive braking safety system plays a role as a military radar device. Since automotive PCBs are responsible for transmitting microwave high-frequency signals, substrate with low dielectric loss needs to be applied with the ordinary substrate material to be PTFE. Different from FR4 material, PTFE or similar high-frequency substrate materials require special drilling speed and feeding speed during drilling. • Thick copper PCB Automotive electronics brings more heat energy owing to high density and power and hybrid power and electromotives tend to require more advancing electric power transmission system and more electronic functions, which leads to more requirements on heat dissipation and large current. It's relatively easy to fabricate thick copper double-layer PCBs while it's much more difficult to fabricate thick copper multi-layer PCBs. The key point lies in thick copper image etching and thickness vacant filling. Inner routes of thick copper multi-layer PCB are all thick copper and therefore and graphic transfer photo-induced dry film is also relatively thick, requiring extremely tremendous etch resistance. Thick copper graphic etching time will be long and etching equipment and technical condition in the best state so as to ensure complete routings of thick copper. Surface difference is relatively large between inner conductor of thick copper multi-layer PCB and insulating substrate material and ordinary multi-layer board lamination fails to totally fill resin with cavity generated. In order to solve this problem, thin prepreg with a high content of resin should be applied as much as possible. Copper thickness of inner routings on some multi-layer PCBs is ununiform and different prepregs can be applied in areas with a large thick copper difference or a small difference. • Component embedment Component embedded PCBs were massively applied in mobile phones in order to increase assembly density and decrease component size, which is acquired by other electronic equipment as well. Therefore, component embedded PCBs are also applied in automotive electronic equipment. According to different component embedment methods, there are numerous manufacturing methods for component embedded PCBs. Component embedded PCBs for automotive electronics have mainly 4 manufacturing methods • HDI technology One of the key functions for automotive electronics lies in entertainment and communication among which smart phones and tablet PCs require HDI PCBs. Thus, technologies contained in HDI PCBs such as micro via drilling & plating and lamination positioning are applied in automotive PCB manufacturing.Wanna know PCB knowledge? Check and read for more.
PCB Knowledge ⋅ 08/07/2021 17:33
How to do SMT soldering？
In the practical manufacturing, soldering defects usually take place. the soldering issues seen in this stage aren't completely caused by reflow technology because SMT soldering quality is closely correlated with manufacturability of PCB pad. How to do SMT soldering？Check and read the content we prepare below for more knowledge.If you want to order PCB product, please check and custom your order online. What is preparation of BOM? As one of the most important composites in SMT, the quality and performance of BOM is directly correlated the quality of reflow soldering. Specifically, the following aspects have to be taken into consideration: a. Component packaging has to meet the automatic mounting requirement of mounter. b. Component figure has to meet the requirement of automatic SMT in that it has to have standard shape with high dimension accuracy. c. Solderable ends of components and PCB pad soldering quality should meet the requirement of reflow soldering and solderable ends of components and pad are not polluted or oxidized. If solderable ends of components and PCB pad suffer from oxidation, pollution or damp, some soldering defects will possibly take place such as bad wetting, pseudo soldering, solder beads or cavity. This is especially true for humidity sensor and PCB administration. Humidity sensors have to be stored in drying cabinet after vacuum packaging and it's necessary to roast them prior to manufacturing next time. What are the essential factors in SMT soldering? Solder Paste Printing technology primarily aims to solve problems concerning incompatibility of solder paste printing amount (filling amount and transferring amount of solder paste). Based on professional statistics, with PCBs correctly designed, 60% of PCBs for rework are caused as a result of bad solder paste printing. In solder paste printing, three important "S"s must be remembered: solder paste, stencil and scraper. If correct selections are made, excellent printing effect can be obtained. Quality of solder paste As a necessary material for reflow soldering, solder paste is a kind of paste solder evenly mixed by alloy powder and paste flux (rosin, diluents, stabilizer etc.) among which alloy powder is the key element to composition of solder joints. Flux is the critical material to eliminate surface oxidation, increase wettability and ensure quality of solder paste. In terms of quality, generally speaking, 80% to 90% of solder paste belongs to metal alloy while it accounts for 50% in terms of volume. Solder paste quality insurance comes primarily in two aspects: storage and application. Solder paste is usually stored between 0 and 10°C or stored according to requirement of manufacturers. Stencil design The key function of stencil lies in uniform solder paste coating on PCB pad. Stencil is a must-be in printing technology and its quality directly influences quality of solder paste printing. Up to now, there are three methods to manufacture stencils: chemical corrosion, laser cutting and galvanoformung. Stencil design won't be ensured until the following aspects are fully considered and suitably dealt with. Scraper Scrapers, to some extent, make a difference to printing quality based on their different hardness material and shapes. Generally, steel scrapers with nickel plating are used and scrapers with 60° are ordinarily applied. If there are through-hole components, scrapers with 45° are advised so that tin amount on through-hole components can be increased. Printing parameters Printing parameters mainly encompass scraper speed, scraper pressure, stencil down-release speed, stencil cleaning mode and frequency. Restrictive relationship does occurs between angle of scraper and stencil and viscosity of solder paste, so printing quality of solder paste won't be ensured until these parameters are correctly controlled. Generally speaking, a low speed of scraper leads to relatively high printing quality with possibility of vague shape of solder paste. Furthermore, an extremely low speed even decreases manufacturing efficiency. On the contrary, s high speed of scraper will possibly lead to insufficient solder paste filling in net hole. Too much scraper pressure may lead to insufficient tin and increasing abrasion between scraper and stencil while extremely low pressure leads to incomplete solder paste printing. Equipment accuracy During printing products with high density and small space, printing accuracy and repeated printing accuracy will affect stability of solder paste printing. PCB support PCB support is an important adjustment content for solder paste printing. If PCB lacks effective support or features an unsuitable support, high thickness of solder paste or uneven solder paste. PCB support should be arranged flat and uniform in order to guarantee closeness between stencil and PCB.Wanna know PCB knowledge? Check and read for more.
PCB Knowledge ⋅ 08/06/2021 17:25
PCB surface finish types and comparison
Confronted with so many types of surface finish on PCB pad or land, how should we select the best type of surface finish for our PCBs? This article is a comprehensive guideline for you to refer to. In this passage, we are going to compare the differences of the surface finish types of PCB. Check the content for more professional knowledge about it.If you want to order PCB product, please check and custom your order online. What are the attributes of each PCB surface finish? OSP OSP, short for Organic Solderability Preservative, refers to a thin film that is formed at the surface of bare copper in a chemical method. This film features oxidation resistance, thermal shock resistance and anti-wettability, more suitable for developing requirement of SMT in electronic industry. Here are advantages of OSP surface finish: 1). Suitable for PCB with SMT and fine line space;2). Capable of stopping copper surface from oxidation, suffering repeated heat shock and compatible with multiple solder and easy for soldering;3). Beneficial to smoothness of PCB;4). Environment friendly;5). Contributive for low cost; Of course, OSP film is so thin that it's easy to be scratched and engineers have to be very careful since once film is broken, solderability won't be insured. HASL HASL, short for Hot Air Solder Leveling, refers to dipping PCB into melting solder bath and then redundant soldering tin is blown away from PCB surface or metalized via through hot wind so that a smooth, uniform and bright soldering tin coating can be obtained. As users' requirement on PCB with flux coating on bare copper increases, HASL receives fast development. Boards have to meet the following requirement after HASL: 1). All solder coating layers have to be smooth, uniform and bright with no defects such as knot or exposing copper. In addition, soldermask can never suffer from bubbles, falling off or color changing and copper under soldermask should never be oxidized or change color. There shouldn't be foreign matters on the surface of PCB or in via and soldering tin shouldn't be there either.2). Thickness of soldering tin layer should be in the range from 3μm to 8μm with overall covering soldering tin layer and solderability as principles.3). Traditional soldering tin layer containing lead is increasingly be cancelled and lead-free soldering tin with tin as core, coupled with infinitesimal copper or nickel. The key is to maintain solderability. Melting point of lead-free solder tin is higher than that with lead by 30°C so heat resistance of substrate material and reliability of through-hole vias on the board will be challenged. ENIG ENIG, short for Electroless Nickel and Immersion Gold, refers to first deposition of nickel layer and then gold layer on copper surface of PCB through chemical electroplating. Chemical nickel player and gold layer have been massively applied owing to their advantages including good dispersibility, solderability, wiring bond performance, soldering performance and their compatibility with all kinds of flux. Compared with OSP and HASL, ENIG is capable of meeting multiple assembly requirements with functions of solderability, connection, wiring and heat dissipation. Moreover, both board surface and SMD pad are smooth, suitable for fine lines. Immersion gold on nickel surface is actually a replacement reaction. In principle, when nickel surface is totally covered by copper, gold precipitation will stop. However, as a result of too many holes on the surface of gold layer, nickel under gold with multiple holes will still be dissolved and gold will still continue to be precipitated on nickel with an increasingly low speed until it stops. ENIG is simple to operate without need of technical leads. But black pad will possibly take place in the process of soldering, leading to reliability issue. At present, ENIG is still an important type of surface finish and new nickel coating solution has been developed, which is capable of effectively controlling stability of solution and decreasing brittleness of nickel layer for more flexibility. PH value of new type of immersion gold solution tends to be neutral with gold content greatly decreased, leading to obvious reduction of cost and corrosion. What are the new types of PCB surface finish? With PCBs developing towards high density and high performance, some present surface finishes fail to meet all requirements. T In accordance to the problems occurred by ENIG and ENEPIG, here are some solutions. EPIG or EPAG Due to the bad influence of nickel layer on fine circuit and high-frequency signals and nickel's complete inadequacy, thin ENEPIG is applied as a solution to disadvantages of ENIG and ENEPIG. Chemical palladium/gold plating is applied to replace ENIG and ENEPIG. Without the participation of nickel, surface finish becomes so thin that deformation won't be generated to circuit. Moreover, high-speed signal transmission loss is decreased as well. A variation of ENIG is EPIG (Electroless Palladium/Immersion Gold) whose palladium layer is 0.1μm thick and copper layer 0.1μm thick. Through experiment and test, EPIG is concluded to be with good reliability and expansibility. Another variation is EPAG (Electroless Palladium/Autocatalytic Gold) with the thickness of palladium layer 0.15μm and copper 0.1μm, suitable for wiring bonding of gold lines and copper lines. Advantages of EPAG include better high-frequency attribute, suitable for fine space circuit as a result of thin coating, reliable soldering or wiring bonding and reduction in procedure and cost. Electroless nickel ImAg (Ni/Ag) In spite of low cost and excellent solderability of ImAg, it tends to be easily oxidized owing to its bad anti-corrosion capability. As a result, some improvement has been done with Ni/Ag introduced. Nickel features good conductivity and solderability while nickel has anti-corrosion capability. With similar technology with ENIG and ImAg, Ni/Ag is developed from practical perspectives. Ni/Ag features palladium thickness in the range from 2μm to 6μm and that of silver 0.1μm. HASLEN HASLEN is the combination between HASL and electroless nickel. Usually, nickel is difficult for wetting and plating as a result of oxidation when it's exposed to air, so liquid flux is developed based on DES. Compared with HASL, the advantages of HASLEN include: a nearly unlimited life span as a result of higher anti-oxidation reliability; higher reliability owing to its high temperature resistance; avoidance of black pad; low cost. SENIG/OSP Electronic package arouses a lot of requirements on PCB surface finish. Miniature and lead-free trend of electronic assembly put higher requirements on surface finish, which is why SENIG/OSP occurs. This type of technology is complicated in that after the formation of PCB pattern and soldermask pattern, imaging is implemented to protect copper surface for OSP and expose copper surface for ENIG after which photo-induced resistant layer is eliminated to complete OSP. The key point of these technologies lies in corrosion resistance of electroless nickel layer.Wanna know PCB knowledge? Check and read for more.
PCB Knowledge ⋅ 08/06/2021 17:15
Future scope of PCB
As the basis of all electronic devices, PCBs feel intense pressure for development and growth. With consumers pushing for slimmer and faster devices, and with industries seeking improved functionality, the PCB must continue developing into the future.If you want to order PCB product, please check and custom your order online. What is the future of PCB? 1. PCB Board CamerasBoard cameras, alternatively called PCB cameras, are cameras that are mounted directly onto a circuit board. These PCB cameras consist of a lens, aperture and image sensor and are designed to take both digital pictures and videos. Due to their size, board cameras have several applications across a variety of industries. These include: • Consumer Electronics: Board cameras have found a great deal of utility in consumer electronics, particularly in handheld mobile devices. Today, smartphones, tablets, laptops and other small handheld electronics commonly use board cameras. Consumer electronics companies are constantly pushing for smaller and more powerful cameras. • Medical Instruments: In particular, small board cameras have found a niche in the medical industry for non-invasive and minimally invasive procedures. Pill-sized cameras are now in use that can be swallowed by patients so doctors can take comprehensive videos and images from inside the digestive tract without invasive surgery. Also wearable cameras are gaining traction during surgeries as an instructional tool. • Surveillance Technology: Because PCB cameras are so small in size, they are easy to conceal inside objects, making them an excellent choice for surveillance uses. Many consumers, security companies and organizations use these small cameras to monitor their homes and businesses for intruders. As the technology improves, its surveillance applications continue to grow. 2. 3D Printed Electronics3D printing technology is probably one of the most exciting technological innovations in recent years. From 3D-printed organs to firearms and ammo, 3D printing has accomplished some incredible things in a variety of industries. The PCB industry is no different. 3D PE can potentially provide immense technical and manufacturing benefits for both circuit manufacturing companies and their clients — especially when compared to traditional 2D PCBs. These advantages include: • Novel Designs: By allowing circuits to be printed on top of an existing shape, 3D PE manufacturing techniques enable circuits to take new and incredible shapes that were simply not possible with traditional PCB manufacturing. 3D PEs can be shaped to fit any circuit carrier while still combining electronic, optic and mechanical functions. This enables new product features and optimizations. Not only can 3D PEs be shaped, but they can also be scaled to print on components larger than anything possible using 2D PCB manufacturing methods. • Improved Efficiency: Since 3D PE manufacturing is an additive process that uses digital methods, it is much more conservative in its materials usage than 2D PCB manufacturing. The system only applies as much material as is needed and nothing more, meaning materials are used more efficiently. Additionally, the digital aspect of the production process increases overall accuracy by removing sources of human error. While circuits will still sometimes fail using this method, increased automation reduces the likelihood of failure, improving overall efficiency. • Environmentally Friendly: Since there is no actual limitation on the type of substrate material that can be used in 3D PE manufacturing, PCB Houses can select any material they like. This makes environmentally-friendly production much easier as they can choose low-cost, recyclable materials. 3. PCB AutoplacersMost PCBs today include an autorouter in their design. This PCB component routes electronic functions throughout a board to model the characteristics of the PCB layout, therefore making the automation process much easier. As of today, automatic placement tools haven't achieved acceptance in the PCB manufacturing industry at large. The reason lies primarily in the difference between autoplacer and autorouter constraints: • Autorouters: Routing constraints are mainly dictated by the characteristics of the board, which can be easily modeled within the PCB design environment. These properties include the number of layers, the spacing between tracks, connection distances and layer directions. • Autoplacers: The constraints that dictate component placement can be driven by mechanical considerations. These include the shape of the product casing, ergonomic issues like button positioning, heat dissipation and pick-and-place optimization. 4. High-Speed CapabilitiesToday's world is incredibly fast-paced, demanding that people and technology move quickly as well. As the years pass, we expect things to get even faster - that includes electronics. To allow our devices to keep up with this growing demand for speed, PCB technology will need to adapt accordingly. The generally agreed-upon definition of a high-speed PCB is one where the integrity of the signal is affected by the circuit layout. This can mean different things: • Digital Signal: In digital PCB signals, the intelligence is contained in the digital pulses. Therefore, effects on signal integrity can manifest as delayed or canceled digital signals. • Analog Signal: In a high-speed analog circuit, the intelligence is in the shape of the signal. In these cases, signal integrity problems will appear as altered signal shapes. 5. A Focus on Flexible PCBs Several industries are pushing the trend toward flexible PCBs, including: • LED Lighting: LED lighting is wildly popular as a bright yet energy-efficient alternative to traditional incandescent bulbs. For LED strip lighting, flexibility is key along the length of the strip so customers can bend the strip to suit their needs. Flexible PCBs bring about this necessary functionality. • Wearable Technology: Today, wearable electronic devices are becoming ever more popular, with the global market expected to reach $30.6 billion by 2020. These electronics are often embedded into clothing and flexible accessories such as smart socks, belts and wristbands. Even some sports helmets now incorporate sensors, using PCBs, to monitor shock and speed. Flexible PCBs are necessary for these applications, both for the sake of flexibility and for handling shock and vibration. • Flexible Displays: Flexible displays have enjoyed attention for years but are still relatively rare to find and aren't in general use yet due to the high manufacturing costs. However, once those production costs come down, flexible devices are expected to be the next big thing in mobile technology. Able to handle shocks and stresses better than typical rigid designs, flexible displays will be likely to lead to flexible smartphones and tablets. This will probably require everything else in the device to be bendable as well, including PCBs. • Medical Instrumentation: Medical device innovation has so far focused mostly on two technology trends: miniaturization and flexibility. Flexible multilayer PCBs enable medical device designers to accomplish both, by allowing for compact circuitry on a flexible substrate. Flexible PCBs are also favored for their reliability and biocompatibility, as their connections are consistent and their substrates are compatible for contact with human tissues. 6. Biodegradable PCBsElectronic waste, AKA e-waste, is one of the biggest environmental concerns of the modern era. This type of waste includes electronic items like computers, laptops, TVs, smartphones and household appliances, many of which contain parts that are neither biodegradable nor environmentally-friendly. While e-scrapping has become popular in recent years, e-waste continues to be a problem as people try to find ways to get rid of old electronics. PCBs are a large part of this issue. Some PCB materials don't degrade very well and often end up in landfills, polluting the surrounding soil. This issue is compounded by the fact that the chemicals used during PCB manufacturing process are often harmful to the environment if not properly disposed of. Considering how many electronics the average consumer goes through over the course of a decade, along with the industry trend toward short-lived electrical products, this can mean a lot of thrown-out PCBs bringing harm to the environment.Wanna know PCB knowledge? Check and read for more.
PCB Knowledge ⋅ 08/06/2021 17:05
Rigid flex PCB manufacturing process
In this passage, we are going to provide the details of rigid flex PCB manufacturing process. If you are going to learn more professional knowledge, check the content below for more information. The rigid-flex PCB manufacturing process is time consuming and laborious when compared to traditional rigid board fabrication. It involves several steps that must be carried out with extreme accuracy. Mishandling or misplacing any of the flexible components in the board affects the efficiency and durability of the final assembly substantially.If you want to order PCB product, please check and custom your order online. What are the features of rigid flex PCB? Due to development trend of aerospace products including light weight, miniaturization, multifunction and assembly densification, higher requirement has been set up for Printed Circuit Board (PCB) technology and manufacturing process. Flexible PCBs are a type of circuit boards that are made of flexible substrate material and feature more advantages than ordinarily rigid PCBs: • Lower thickness• Lighter weight• Dynamically bendable• Accessible for 3D interconnection assembly• Higher freedom on electronic design and mechanical design• More space saving How to select materials for rigid flex PCB? Manufacturing technologies of flex-rigid PCBs differ from each other in accordance with different types of PCB boards and the essential technology leading to the differences is fine circuit manufacturing technology and microvia manufacturing technology. As electronic products tend to develop towards light weight and miniaturization, multifunction and assembly densification, advanced PCB boards attracting the most attention include HDI flex-rigid PCBs and embedded flex-rigid PCBs. What is the manufacturing process of rigid flex PCB? Rigid-flex circuit board manufacturers assemble the boards by following the steps listed below. 1. Preparing the Base Material – The first step involved in the board fabrication is preparing/cleaning the laminate. The laminate, which contains copper layer – with adhesive or adhesiveless coating – must be cleaned thoroughly before processing with other fabrication processes. This pre-cleaning is important because, copper coils are normally offered by vendors with anti-tarnish features to provide oxidation protection. However, this coating poses a hindrance to rigid-flex PCB manufacturing, hence must be removed. 2. Circuit Pattern Generation – Generating circuit patterns is the next step followed by the laminate preparation. Nowadays, this circuit pattern exposure is done using two main techniques, such as: • Screen Printing – This technique is popular as it can generate the required circuit patterns/deposits directly onto the surface of the laminate. The total thickness is not more than 4–50 microns. • Photo Imaging – Photo imaging is the oldest, but still the most popularly used technique for depicting the circuit traces on the laminate. In this method, a dry photoresist film consisting of the desired circuitry is placed in close contact with the laminate. This assembly is then exposed to UV light, which helps transfer the pattern from the photomask to the laminate. The film is then chemically removed, leaving behind the laminate with the desired circuit pattern. 3. Etch the Circuit Pattern – Following the circuit pattern generation, next is etching the copper laminate containing the circuit pattern. Rigid-flex manufacturers either dip the laminate in an etch bath, or it is sprayed with an etchant solution. Both sides of the lamination are etched simultaneously to achieve the desired results. 4. Drilling Processes – Now, the time is for drilling required number of holes, pads, and vias. High speed drilling tools are used to make precision holes. To create ultra-small holes, rigid-flex circuit boards manufacturers use laser drilling techniques. Usually, Excimer YAG, and CO2 lasers are used to drill small and medium holes in the substrate. 5. Through-hole Plating – This is one of the crucial steps in rigid-flex PCB manufacturing process that must be carried out with extreme precision and care. After holes with required specifications are drilled in, they are deposited with copper, and chemically plated. This is done to form layer to layer electrical interconnection. 6. Apply Cover lay or Covercoat – It is crucial to protect the top and bottom side of the flex circuit by applying a cover lay. This is done to provide comprehensive protection to the circuit from aggressive weather conditions, harsh chemicals, and solvents. In most cases, manufacturers use a polyimide film with adhesive as a cover lay material. Cover lay material is imprinted onto the surface using screen printing, which is then cured with UV exposure. In order to ensure proper adhesion of the cover lay material on to the substrate, cover lays are laminated under specified limits of heat and pressure. Unlike the cover lay material, which is a laminated film, covercoat is a material that is literally applied onto the surface of the substrate. The decision regarding the type of coating must be made after considering the manufacturing methods, materials used, and the application areas. Both cover lay and covercoat augment the electrical integrity of the entire assembly. 7. Cutting out the Flex – Blanking or cutting the individual flex board from the production panel is yet another important step that must be executed with caution. When producing rigid-flex PCBs in high volume, manufacturers usually choose the hydraulic punching method. However, the same is not chosen for prototyping or small production runs due to the high tooling cost involved. When creating prototype rigid-flex PCBs in small production runs, a specialized blanking knife is used. 8. Electrical Testing and Verification – The last and final stage in rigid-flex circuit boards manufacturing is testing and verification. The boards undergo stringent electrical testing for continuity, isolation, circuit performance, and quality against the design specifications. Several kinds of testing methods are used, including grid and flying probe test methods.Wanna know PCB knowledge? Check and read for more.
PCB Knowledge ⋅ 08/05/2021 17:36
PCB visual inspection methods
Electronic components are first stuck to PWBs through the application of SMT and/or AI technology and then a couple of electronic sections are combined together to make final products. Through image amplification, character capturing or image processing, comparison will be made between practical products and input data so that product quality can be guaranteed. In this passage, we will provide all the details of PCB visual inspection methods. Please check and read the content below for more professional knowledge.If you want to order PCB product, please check and custom your order online. Why PCB visual inspection is important? Gradual development of technology leads electronic manufacturing technologies to non-stop improvement. As a result, electronic products tend to become miniaturized with densification being increasingly protruding. Moreover, as components become downsized and PCBs (Printed Circuit Boards) have to accept increasingly higher density interconnections, mounting density has rocketed to a high extent, leading to increasingly higher product quality requirement. Therefore, inspection on product quality during electronic manufacturing process is never insignificant. Apart from potential trend of modern electronics, visual inspection with the help of visual inspection devices demonstrates more merits than traditional naked-eye inspection. • Naked-eye inspection is tiring with low efficiency.• Naked eyes fail to meet the inspection requirement of miniaturized component inspection.• Naked-eye inspection is bad for working staff's eyesight and difficult to capture accurate inspection result. Nevertheless, depending on visual inspection devices, labor intensity will be greatly decreased with inspection efficiency upgrading. Up to now, visual inspection under inspection devices has been widely applied in all phases of electronics manufacturing. What is the application of visual inspection in component quality control? Component manufacturing has long seen much significance of visual inspection because it works for silkscreen, line loop resistance, inductance, polarity and orientation. All the aspects mentioned above are inspected by staff in naked eyes and higher subjectivity tends to be generated and staff are easy to suffer from fatigue. As a result, component quality accuracy and reliability are hard to be captured. By amplifying image through inspection devices prior to inspection, defects will become clearer and staff will be confronted with less fatigue. What is the application of visual inspection in PCB quality control? Even the most simplified version of PCB manufacturing process still contains 10 steps at least. When it comes to PCB quality control inspection, most attention has to be paid to the following inspection items: foreign matter, copper exposion, scratch, insufficient plating, incorrect silkscreen, ineven solder paste and pads, residual copper, and imaging. All those defects are hardly observed through naked eyes. At present, visual inspection methods or devices for PCB quality control include: • AOI equipment for bare PCB inspection. AOI ranges for bare PCB boards cover short circuits, open circuits, residual copper, vacancy etc.• Magnifying glass. Magnifying glass is only capable of inspecting defects that are exposed on the surface of PCB. This method is seldom leveraged in modern electronics manufacturing.• Naked-eye inspection. Naked-eye inspection is an old-school inspection method although it seldom meets constant improvement of quality control and PCB design density. As a result, reliability and stability of naked-eye inspection are hard to be ensured.• Optical video display system combining naked-eye inspection and AOI. This system displays PCB images on monitor through magnifying them to make inspection easier. What is the application of visual inspection in SMT/AI technology? SMT is now the most prevalent assembly technology in electronics manufacturing. Printed Circuit Board assembly process with the application of SMT mainly include: solder paste printing, mounting, reflow solder, cleaning, inspection and rework. All inspection devices applied in all phases of manufacturing include: magnifying glass, microscope, ICT (In-Circuit Test), flying probe test, AOI, AXI and function test among which magnifying glass, microscope, AOI and AXI belong to the range of visual inspection. Visual inspection will cause different inspection results and targets by placing on different stations during SMT assembly process. • After Solder Paste Printing Solder paste printing is the first procedure of SMT assembly and its quality directly determines that of final products. Thus, it's of much necessity to arrange visual inspection after solder paste printing. Up to now, solder paste printing inspection is carried out through the following methods: a. On-line or off-line solder paste inspection, which mainly displays 3D configurations of solder paste that has been printed on pads on the monitor so that defects can be exposed in terms of thickness, volume, displacement, vacancy, excessive or insufficient solder paste.b. Magnifying glass.c. CCD inspector. It displays magnified images on the monitor so that operators will be aware of printing quality. • After Chip Mounting Partially-assembled PCBs go over visual inspection after chip mounting before reflow soldering, leading mounting defects to be exposed at an early time. As a result, volume faulty products can be avoided and maintenance and rework cost will be dramatically reduced as well. This phase depends on the following visual inspection devices: a. AOI prior to reflow oven. This helps defects to be exposed including missing components, displacement, polarity and orientation.b. Magnifying glass.c. CCD inspector. • After Reflow Soldering Inspection after reflow soldering shares equivalent visual inspection devices with those before reflow oven, mostly AOI, magnifying glass and CCD. Apart from the stations mentioned above calling for visual inspection, a lot more stations need visual inspection as well such as maintenance station, barcode inspection, and stations for special components inspection including BGAs, ICs, connectors etc.Wanna know PCB knowledge? Check and read for more.
PCB Knowledge ⋅ 08/04/2021 18:17
How to make double sided PCB？
In this passage, we will provide an easy method to produce a double-side PCB so that electronics majors and engineers can have a better alternative. You could rear the content below for more professional information.If you want to order PCB product, please check and custom your order online. What are the fast manufacturing methods of double sided PCB？ PCB manufacturing primarily comes in two methods: chemical mode and physical mode. Nowadays, the most prevalent PCB fabrication methods high schools take advantage of are thermal transfer printing and physical engraving. The former belongs to chemical domain while the latter to physical domain. • Thermal Transfer Printing To carry out thermal transfer printing, first, an ordinary laser printer is used to print PCB image onto specialized thermal transfer paper. Then, PCB image that has been printed on thermal transfer paper is transferred on Copper Clad Laminate (CCL) through thermal transfer equipment. Finally, a high-precision PCB is produced after later processes including etching and PCB drilling. In high school labs, thermal transfer printing is leveraged to produce high-precision PCBs and can be achieved in one hour. When it comes to double-side PCB fabrication, the protruding issue lies in misalignment that hasn't been successfully solved with current manufacturing method used. As a result, double-side PCBs fabricated in thermal transfer printing method fail to optimally work on electronic products. Thermal transfer printing sticks to the following PCB fabrication process: 1. Bottom PCB image is printed on a piece of thermal transfer paper by an ordinary laser printer. 2. Top PCB image is printed on another piece of thermal transfer paper by an ordinary laser printer. 3. Two pieces of thermal transfer paper are closely stuck to a well-cut double-side CCL. Clear tape can be used to fix the position of paper and plate to avoid misalignment. 4. Thermal transfer printing is carried out by putting CCL with thermal transfer paper stuck into thermal transfer printing equipment. A CCL with PCB image printed on is then obtained after cooling. 5. Etching and PCB drilling are then implemented. Among all the phases of thermal transfer printing for PCB fabrication, application of Step 3 can accurately lead to alignment of two pieces of thermal transfer paper. When it comes to Step 4, however, misalignment tends to be caused in thermal transfer equipment. As a result, a double-side PCBs can be hardly successfully manufactured unless a couple of trials have been made. • Physical Engraving Based on basic principles of physical engraving, physical engraving conforms to milling principle with extra or unnecessary parts of CCL milled off. The applied equipment is actually a type of small CNC drilling and milling machine that is also called circuit board engraving machine. In the process of double-side PCB manufacturing, after one side is finished milling, board should be flipped over for milling on the other side of the board. The flipping process possibly leads to misalignment that should be corrected through software and hardware so that rejection rate of double-side PCBs will be reduced. • Comparison between Thermal Transfer Printing and Physical Engraving According to the comparison between the two methods, thermal transfer printing performs better than physical engraving in terms of the following aspects: 1. CNC drilling and milling machine features relatively high cost and takes up more lab space. Thermal transfer printing machine features low cost and takes up less space than CNC drilling and milling machine. 2. A Double-side PCB can be completed within one hour when thermal transfer printing is used. In spite of possible misalignment calling for multiple times of thermal transfer printing, a double-side PCB can be fabricated within three hours at most. CNC drilling and milling machine, however, takes more time, at least four hours. Furthermore, CNC drilling and milling machine can deal with only one piece of PCB board simultaneously while thermal transfer printing is capable of producing multiple double-side PCBs within the same time period. How to improve the double sided PCB manufacturing methods? In order to solve misalignment issue that is protruding in traditional thermal transfer printing, this article will provide an improved thermal transfer printing method for PCB fabrication with the following steps. 1. Bottom PCB image and mirror top PCB image are printed onto the same thermal transfer paper and through holes of bottom PCB image and top PCB image are linearly symmetrical. 2. Thermal transfer paper is folded along symmetrical line and covered onto well-cut double-side CCL. 3. Double-side CCL with thermal transfer paper covered on is then put into thermal transfer printing equipment for thermal transfer printing. The folding part first enters thermal transfer printing equipment and a CCL with PCB image printed on can be obtained after cooling. 4. Etching and PCB drilling. The above process can effectively defeat misalignment issue that always takes place in traditional thermal transfer printing for PCB fabrication by printing top and bottom PCB images on the same thermal transfer paper. As a result, a reliable double-side PCB can be smoothly fabricated all at once. PCB image printing on the same piece of thermal transfer paper can be completed based on any PCB design software holding different operations. All in all, this improved thermal transfer printing method for PCB fabrication is the most effective one for electronics majors or engineers who can use to produce double-side PCBs in a lab.Wanna know PCB knowledge? Check and read for more.
PCB Knowledge ⋅ 08/04/2021 17:57
How to test solder joints？
When it comes to optimal BGA assembly achievement, BGA solder joints play an essential role in contributing to the final quality of BGA assembly. Therefore, this article will discuss some effective measures for quality control on BGA solder joints. In this passage, we are talking about the measures for controlling the BGA solder joints in PCB manufacturing. Come and check the content below for more professional knowledge.If you want to order PCB product, please check and custom your order online. What are the common issues of BGA solder joints inspection? Up to now, as far as manufacturers involved in electronics assembly concerned with BGA components used at a medium or large scale, soldering defects of BGA components are exposed through the implementation of electrical tests. Other methods to control assembly process quality and identify defects on BGA solder joints include sample test on paste screening, X-ray inspection and electrical test analysis. It's an extremely challenging task to meet assessment requirement for electrical test on BGA components since it's quite difficult to pick up test points under BGA components. Thus, electrical tests can never be relied on BGA defects inspection and assessment, which increases the cost of defect removal and rework to some extent. Electrical tests can only judge whether current is on or off when BGA components get connected. With non-physical solder joint test assisted, it'll be beneficial for assembly process improvement and SPC (Statistical Process Control). BGA SMT assembly is just a fundamentally physical connecting technology. To be able to determine and control the quality of such a type of process, physical elements should be known and inspected affecting its reliability on long-term operation such as solder paste amount, alignment between leads and pad and wettability. What are the defects of BGA solder joints? Open Circuit in Non-collapsible BGA Solder Joints Open circuits at non-collapsible BGA solder joints usually result from pad pollution. Because solder fails to get pad on PCB wetted, it'll climb onto solder balls and then on component surface. As is discussed in previous part, electrical test can determine the existence of open circuits but fails to determine the real cause of defects. With cross-section X-ray inspection technology applied, image slices obtained between pad and component layer can be used to distinguish open circuits occurring as a result of pollution. Open circuits as a result of pollution tend to generate small pad radius and large component radius, distinctions between component radius and pad radius can be used to determine whether open circuits take place as a result of pollution. If open circuits take place due to insufficient solder, difference between component radius and pad radius will be very small and this type of difference can be only indicated by cross-section X-ray inspection devices. Voiding in Collapsible BGA Solder Joints Voiding in collapsible BGA solder joints takes place because flowing steam is stopped at solder connections with low eutectic point, which is a leading defect held by collapsible BGA components. During the process of reflow soldering, since the influence of floatage generated by voiding concentrates at component surface, majority of solder joint failures take place there as well. Voiding can be eliminated through preheating during reflow soldering process and short preheating time adding and relatively low preheating temperature. If voiding goes beyond regulated size, number or density, the reliability of components will be dramatically reduced. Voiding in collapsible BGA components can be clearly indicated by cross-section X-ray image slice. Some voiding can be determined and measured within those images or indirectly indicated by the obvious image at BGA solder joints. How to fix solder joints with BGA inspection? It's of essential significance to test physical features of BGA solder joints and determine the method of reliable connection achievement during assembly process because the feedback provided by the test is associated with adjustment of each process or calls for parameter adjustment of solder joints. Physical tests are capable of demonstrating changes of paste screening and everything concerning BGA solder joints during the whole reflow soldering process. Moreover, they are also capable of indicating all the situations concerning all BGA components mounted on a PCB (printed circuit board) or across different PCBs. For example, during the process of reflow soldering, the change of extreme environment humidity along with cooling time will be quickly reflected through BGA voiding count and size. After BGA components are well manufactured, assembly process still needs numerous tests but with inspection depth reduced. Up to now, X-ray inspection devices applied by lots of manufacturers for electrical test result analysis also holds issues of their incapability to test the reflow soldreability of BGA soldering joints. With an X-ray inspection device applied, the image of solder printed on pad indicates as "shadow" since solder is above solder joint. When it comes to non-collapsible BGA components, shadow also takes place due to front-positioned solder balls. An X-ray inspection device with only cross-section X-ray inspection technology is capable of breaking the limitation mentioned above because cross-section X-ray inspection devices can get hidden defects exposed of solder joints and can demonstrate BGA soldering connections through the focus on solder joints on pad layer. When it comes to solder volume and its distribution at solder joints, cross-section images or horizontal slices are applied for measurement. Together with multiple slice measurement of same-type BGA solder joints, 3D test can be effectively provided.Wanna know PCB knowledge? Check and read for more.
PCB Knowledge ⋅ 08/03/2021 17:22
Flexible PCB assembly process
There are lots of advantages of flexible PCB such as flexible structure, small volume and light weight. Capable of expanding towards 3D space, flexible PCB improves freedom degree of circuit design and mechanical design. In this passage, we will focus on the assembly process of flexible PCB. Please check and read the content we prepare for more information.If you want to order PCB product, please check and custom your order online. What is the structure of flexible PCB? In accordance with structural types, flexible PCBs can be classified into the following categories: · Single-side flexible PCB, which features a simple structure and is easily fabricated.· Double-side flexible PCB, which features a far more complicated structure than single-side flexible PCB, calling for more control difficulties.· Multi-layer flexible PCB, which features a more complicated structure than 2-layer flexible PCB and its fabrication quality is more difficult to control.· Single-side rigid-flex PCB· Double-side rigid-flex PCB· Multi-layer rigid-flex PCB Single-side rigid-flex PCB, double-side rigid-flex PCB and multi-layer rigid-flex PCB are more difficultly fabricated than the first three types of flexible PCBs, featuring far more complex structures. What is the material of flexible PCB? Based on structure of flexible PCB, materials contributing to flexible PCB include insulating substrate material, adhesive, metal conductor layer (copper foil) and cover layer. Primary material for flexible PCB has to be flexible insulating film that plays a role as a carrier with excellent mechanical and electrical performance. Ordinary materials include polyester and polyimide film and the latter is used in majority. Along with research and development of new materials, selective materials become so diversified that other types of substrate materials are available like PEN and thin FR4 apart from the ordinary materials. What are the assembly properties of flexible PCB? From Flexible PCB to Rigid PCB Flexible PCB tends to get deformed due to its light weight and thinness, incapable of being directly assembled on SMT manufacturing line like rigid PCB. Thus, to successfully implement assembly on flexible PCB, it has to be fixed on rigid carrier or tray so that it can be dealt with like rigid PCB. Flatness, accuracy of positioning and consistency of board carrier play a key role in completing product quality, which is where flexible PCB assembly focuses on. Low Density Up to now, because flexible PCB features higher cost than rigid PCB, majority of flexible PCBs are only applied for connections between modules with different functions based on product cost concern. As a result, the number of components ready to be assembled on flexible PCB is relatively low with low assembly density. Generally speaking, the number of components is within 50 and some boards contain only two connectors. Large Number of Panels Flexible PCB is mainly used in miniaturized electronic products such as cell phones and digital cameras so that the area of single board is small. Furthermore, the number of components assembled on single board is quite low, so in order to improve assembly efficiency, panels are usually applied for assembly after which they will be separated through punching. Wide Applications of Auxiliary fixtures during Assembly Process Lots of auxiliary fixtures participate in flexible PCB assembly due to its deformation and damage features, including flexible PCB baking fixture, board carrying tray, electrical test fixtures, function test fixtures and cutting fixtures. High Requirement on Product Quality Since flexible PCB is usually applied in the environment calling for repeating bending and control accuracy, components assembled on flexible PCB have to be able to meet the demands of their application environment. As a result, flexible PCB calls for higher requirement in terms of cleanliness, anti-static precautions and soldering reliability than rigid PCB. In addition, owing to prevalence and acceptance of lead-free manufacturing technologies, flexible PCB assembly has to face up with some technical challenges. High Assembly Cost Compared with rigid PCB assembly, flexible PCB assembly leads to a high overall cost, which is especially true in the starting phase. As a result of wide range of applications of fixtures, long manufacturing period, low rate of equipment utilization, higher demands of accessories and staff and higher requirement on manufacturing environment and product quality. The application range becomes increasingly larger as electronic products develop and flexible PCB assembly technology constantly improves and become optimized with manufacturing and assembly cost gradually decreasing, which will thereafter lead flexible PCB to step further into wider range of applications.Wanna know PCB knowledge? Check and read for more.
PCB Knowledge ⋅ 08/02/2021 09:19
Flexible PCB material
Flexible circuits are members of electronic and interconnection family. They consist of a thin insulating polymer film having conductive circuit patterns affixed thereto and typically supplied with a thin polymer coating to protect the conductor circuits. The technology has been used for interconnecting electronic devices since the 1950s in one form or another. It is now one of the most important interconnection technologies in use for the manufacture of many of today's most advanced electronic products. In this passage, we will tell you everything about basic material flexible PCB. Please check and read the content we prepare below to learn more information.If you want to order PCB product, please check and custom your order online. What is the substrate material improvement? The functions of film substrate material lie in its capability to provide conductor carrier and insulating medium between circuits. Moreover, it has to be able to be bent and curled. Usually-applied substrate material for flexible PCB includes PI (polyimide) film and PET (polyester) film apart from which polymer film is also available like PEN (polyethylene nphthalate), PTFE and Aramid etc. Substrate materials film should be picked up based on their performance and cost. The leading substrate material for flexible copper clad laminate (FCCL) covers PI, a type of thermosetting resin that won't reach a temperature to become softened or be able to flow. However, it can still maintain flexibility and elasticity after thermal polymerization, which is different from majority of thermosetting resin. PI features high thermal resistance and excellent electrical characteristics. However, PI leads to high humidity absorption and bad tear strength, which should be improved. Upgraded PI film features humidity absorption of 0.7% which is much lower than ordinary rate that is 1.6% and features higher dimensional stability, converting from ±0.04% to ±0.02%. Both flexible CCL and rigid CCL call for environmental requirement that is halogen free, which is an inevitable and stringent trend of electronics industry. Based on regulations released by EU (Europe Union) and lots of countries, 6 types of hazardous substances are forbidden to be available in electronic devices since July, 2006 and PCBs including flexible PCBs mustn't contain brominated flame retardant. PET resin features agreeable mechanical and electrical performance and its biggest disadvantage is bad heat resistance, leading it to be incapable of direct soldering and assembly. Performance of PEN is better than that of PET and worse than that of PI so that the applications of PEN keep going up. In the world, categories of applicable plastic film exceed 2000 among which there must be some types suitable for flexible PCB fabrication. Thus, as applications of flexible PCBs become expanded, new flexible PCB substrate material will be applied. Adhesive plays a role in bonding copper foil and substrate material film and its ordinary classifications cover PI resin, PET resin, modified epoxy resin and acrylic resin among which modified epoxy resin and acrylic resin are more used owing to their high adhesive force. What is two-layer PI substrate material? Flexible CCL usually contains three layers: polyimide, adhesive and copper foil. Since adhesive tends to reduce flexible PCB performance, especially electrical performance and dimensional stability, two-layer flexible CCL (2L-FCCL) without adhesive is developed. In addition, because 2L-FCCL doesn't contain adhesive that might contain halogen, it's good for environmental protection and is capable of meeting the demand of lead-free soldering by improving temperature from 220°C to 260°C to 300°C. Performance comparison between 2L-FCCL with no adhesive. Three types of manufacturing methods of 2L-FCCL are available:• Electroplating• Film coating• Lamination By comparing three methods, it can be concluded that deposited electroplating metal layer on polyimide film is easy to be produced in rolling and thinner substrate material and copper foil can be picked up with low cost. Film coating is applicable for mass-volume production with a low cost. Lamination works better on double-side board fabrication. What is LCP substrate material? To essentially modify disadvantage of polyimide substrate material, liquid crystal polymer (LCP) is newly developed. As thermoplastic LCP film is covered with copper foil, which then receives constant hot pressing, single-side or double-side CCL will be obtained. This type of CCL features a water absorption rate that is only 0.04% and dielectric constant that is 2.85 (1GHz), compatible with demands of high-frequency digital circuits. Polymer features a liquid state and it will be melted into hot melting liquid crystal polymer (TLCP). When it comes to merits of TLCP, it can be molded through injection and fabricated by pressing into thin film that will be substrate material for PCB and flexible PCB. Moreover, it is capable of going through secondary processing, recycled and reused. Owing to low humidity absorption, high-frequency suitability and thermal dimensional stability of TLCP, it starts being applied in flexible PCB. What is new copper foil? Leading conducting material of flexible PCB is copper or copper foil and sometimes alloy is also used including aluminum, nickel, gold and silver etc. Apart from conduction, conductor layer should be flexibility resistant. In accordance with different manufacturing methods, copper foil is classified into electro deposit (ED) copper foil and rolled and annealed (RA) copper foil. Difference between the two types of copper foil lies in different crystal shapes: RA copper foil features a column array shape, leading to even and flat structure, accessible to roughening and etching processing. ED copper foil features fish scale, leading to smooth copper foil with good toughness, but inaccessible to roughening or etching processing. As far as dynamically flexible PCB is concerned calling for high flexibility, RA copper foil is usually applied. Currently, high-density flexible PCB mainly depends on ED copper foil. To be able to compatible with requirement of mass-volume production of PCB whose pitch is within the range from 40μm to 50μm, new demands are laid. One is that copper foil surface should receive low roughness and the other is that copper foil should be ultra thin.Wanna know PCB knowledge? Check and read for more.
PCB Knowledge ⋅ 08/02/2021 09:13
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