As one type of the most advanced PCB (Printed Circuit Board), IC substrate PCB has exploded in both popularity and applications together with any layer HDI PCB and flex-rigid PCB, now widely applied in telecommunications and electronics updates. IC substrate is a kind of substrate used to package bare IC (integrated circuit) chips, connecting chips and circuit boards. In this passage, follow us and get into IC substrate PCB for more professional knowledge. Please check and read the content we provide for you below.If you want to order PCB product, please check and custom your order online. What is the divination of IC substrate of PCB? IC substrate is a type of base board used to package bare IC (integrate circuit) chip. Connecting chip and circuit board, IC belongs to an intermediate product with the following functions: • it captures semiconductor IC chip;• there’s routing inside to connect chip and PCB;• it can protect, reinforce and support IC chip, providing thermal dissipation tunnel. What are the classifications of IC substrate of PCB? Classified by package types · BGA IC Substrate. This kind of IC Substrate performs well in thermal dissipation and electrical performance and can dramatically increase chip pins. Therefore, it is suitable for IC package with pin count exceeding 300.· CSP IC Substrate. CSP is a type of single chip package with light weight and miniaturized scale, featuring similarly size with IC. CSP IC substrate is mainly used in memory products, telecommunication products and electronic products with a small number of pins.· FC IC Substrate. FC (Flip Chip) is a type of package by flipping chip, featuring low signal interference, low circuit loss, well-performed performance and effective thermal dissipation.· MCM IC Substrate. MCM is an abbreviated form of multi-chip module. This type of IC substrate absorbs chips with different functions into one package. As a result, the product can be an optimal solution due to its attributes including lightness, thinness, shortness and miniaturization. Naturally, since multiple chips are packaged into one package, this type of substrate doesn’t perform so well in signal interference, thermal dissipation, fine routing etc. Classified by material attribute · Rigid IC Substrate. It is primarily made by epoxy resin, BT resin or ABF resin. Its CTE (coefficient of thermal expansion) is approximately 13 to 17ppm/°C.· Flex IC Substrate. It is primarily made by PI or PE resin and features CTE 13 to 27ppm/°C· Ceramic IC Substrate. It is primarily made by ceramic materials such as Aluminium oxide, Aluminum nitride or silicon carbide. It features a relatively low CTE which is approximately 6 to 8ppm/°C Classified by bonding technology • Wire Bonding• TAB (Tape Automated Bonding)• FC Bonding What is the application of IC substrate of PCB? IC substrate PCBs are mainly applied on electronic products with light weight, thinness and advancing functions, such as smart phones, laptop, tablet PC and network in fields of telecommunications, medical care, industrial control, aerospace and military. Rigid PCBs have followed through a series of innovations from multilayer PCB, traditional HDI PCBs, SLP (substrate-like PCB) to IC substrate PCBs. SLP is just a type of rigid PCBs with similar fabrication process approximately semiconductor scale. What are the difficulties of IC substrate manufacturing? Compared with standard PCB, IC substrate has to conquer manufacturing difficulties for its implementations of high performance and advanced functions. IC Substrate ManufacturingIC substrate is thin and easy to be deformed, which is especially protruding when a board is less than 0.2mm thick. To overcome this difficulty, breakthroughs have to be made in terms of board shrinking, lamination parameters and layer positioning system so that substrate warpage and lamination thickness can be effectively controlled. Microvia Manufacturing TechnologyMicrovia technology consists of the following aspects: conformal mask, laser-drilled micro blind via technology and plated copper filling technology. · Conformal Mask aims to logically compensate laser-drilled blind via opening and blind via aperture and positions can be directly defined through copper openings.· Laser-Drilled Microvia fabrication is correlated with the following technological aspects: via shape, aspect ratio, side etching, left gel under via etc.· Blind Via Copper Plating is correlated with the following technological aspects: via filling capability, blind via openness, sinking, copper plating reliability etc. Patterning and Copper Plating TechnologyPatterning and copper plating technology is correlated with the following technological aspects: circuitry compensation technology and control, fine line fabrication technology, copper plating thickness uniformity control. Solder MaskSolder mask manufacturing for IC substrate PCB consists of via filling technology, solder mask printing technology etc. Up to now, IC substrate PCB allows less than 10um for surface height difference and surface height difference between solder mask and pad should not be over 15 um. Surface FinishSurface finish for IC substrate PCB should emphasize thickness uniformity and up to now, surface finish that can be accepted by IC substrate PCB includes ENIG/ENEPIG. Inspection Capability and Product Reliability Test TechnologyIC substrate PCB calls for inspection equipment that is different from that used for traditional PCB. In addition, engineers have to be available that are capable of mastering inspection skills on the special equipment.Wanna know PCB knowledge? Check and read for more.
PCB Glossary ⋅ 07/29/2021 17:37
Backplane in PCB
The term Backplane PCB generally refers to larger format printed circuit boards that are used as backbones for connecting several PCBs together to ultimately form a computer bus. they serve as a connection center between active duty PCBs. Backplane PCBs often incorporate a wide variety of features including blind / buried vias, high-speed / high-signal integrity materials, back drilling, and controlled impedance. In this passage, we will provide all the details information of backplane in PCB. If you are curious about it, please check and read the content to learn professional knowledge.If you want to order PCB product, please check and custom your order online. What is the definition of backplane in PCB？ Backplane PCB, also called motherboard, is a type of baseboard responsible for carrying function boards including daughter boards or line cards. The major task of backplane board is to carry daughter boards and to distribute power to function boards so that electrical connection and signal transmission can be achieved. Therefore, the system function can be acquired through the cooperation between backplane and its daughter boards. As IC (Integrated Circuit) component features increasingly higher integrity and I/O count keeps rising, together with rapid progress that is made in electronic assembly, high frequency of signal transmission and the development of high-speed digitalization, the functions of backplane board gradually cover function board carrying, signal transmission and power distribution. In order to implement those functions, backplane boards have to reach higher requirement in terms of layer count (20 to 60 layers), board thickness (4mm to 12mm), via count (30,000 to 100,000), reliability, frequency and signal transmission quality. Accordingly, to obtain such high requirement in performance, backplane PCB fabrication have to be confronted with rigorous challenge on board thickness, board size, layer count, alignment control, back drilling depth and stub. In other words, all the mentioned aspects are definitely key issues as far as backplane fabrication is concerned. This article aims to display the key difficulties met in backplane PCB fabrication process and discuss some handy tips based on PCBCart’s more than ten years’ manufacturing experience. What are the features and benefits of backplane in PCB？ · Ease of assembly as circuit 1 and 1,000 are built with the same tooling guaranteeing reproducibility· Larger sized backplanes eliminates “jumper” cabling within a chassis improving reliability, lowers assembly cost and creates stronger signal integrity· High performance materials for high speed digital applications· Wide range of material selections to suit the design from power to high-speed (56gb) applications· Copper weight variability to carry high speed signal or power within one design· Precision back-drilling for high-speed signal integrity What are the difficulties of backplane PCB manufacturing? Alignment Control Alignment control is the foremost manufacturing difficulty as far as ultra-multi-layer PCB fabrication is concerned since bad alignment control will possibly lead to shorts. Alignment control is affected by numerous procedures and elements among which layer stack-up most matters. Multi-layer PCBs usually have three types of compositions: mass-lam, pin-lam and thermocouple heating. Tips:· The optimal composition method lies in pin-lam since it won’t arouse shock effect on core board.· When pin-lam can’t be applied due to some limitations, copper-iron rivets plus short dowels will be a good selection.· As pin-lam stack-up is used, which category of pins is used is extremely significant. For example, we find that four pins are used to perform better than eight circular pins, compatible with the requirement on alignment control. Drilling Technology Due to high thickness of backplane board, drilling is possibly too short to reach the board. Too long drilling tool, however, tend to suffer from breaking during drilling process. In addition, too much dust may block the hole and burr may be caused, dramatically reducing backplane PCB performance. Tips:· CCD method should be applied in drilling backplane board and CCD marker depends on the hole drilled through X-ray drilling.· Drilling depth can be accurately determined through the application of depth control in a conductive way. Electroplating Capability Due to high thickness of backplane board, the aspect ratio will be high as well. To make sure sufficient copper at hole, if the electroplating cannot be deep enough, sufficient copper will be inside hole while too much copper will be left at hole mouth, affecting aperture, leading via aperture and copper thickness at hole wall to be incompatible. Tips:· Pulse plating solution should be compared with DC plating solution in terms of plating capability, reliability and solution stability.· New DC plating solution should be used, such as EP. ICD Analysis ICD tends to be occurred during the process of high-frequency material fabrication, causing dramatic quality risk on electrical connection and long-term reliability. The cause for ICD and its solution should be summarized so that such issues can be avoided in the process of backplane PCB manufacturing. The cause for ICD issue lies in the resin gel residue left on inner copper layer and insufficient cleaning is carried out. Tips:· Board material aging extent should be analyzed to stop resin due to insufficient aging being left on inner copper layers.· Drilling parameter control should be optimized to certify that gel residue has been eliminated. Backdrilling Stub As far as high-speed signal transmission is concerned, stub will lead signal to be distorted or even signal transmission failure. Therefore, the negative effect caused by stub on high-speed signal transmission should be clarified. Up to now, it can be summarized that when the length of stub is less than 0.25mm, its effect on signal is quite low and can be ignored. As a result, stub length should be controlled within 0.25mm. Tips:Stub length should be controlled within 0.25mm to minimize its effect on signal transmission quality.Wanna know PCB knowledge? Check and read for more.
PCB Glossary ⋅ 07/29/2021 17:15
Copper clad laminate
Substrates are very important to PCB manufacturing and divided into 2 types: organic substrates and inorganic substrates. Copper Clad Laminate, abbreviated to CCL, is a type of base material of PCBs. With glass fiber or wood pulp paper as reinforcing material, a copper clad board is a type of product through lamination with copper clad on either one side or both sides of reinforcing material after being soaked in resin. In this passage, we will tell you details about copper clad laminate in PCB. Please check and read the content we prepare for more professional knowledge.If you want to order PCB product, please check and custom your order online. What are the classifications of copper clad laminate? According to different classification standards, CCLs can be classified into various categories: • Based on CCL mechanical rigidity, we have rigid CCL (FR-4, CEM-1, etc.) and flex CCL. Rigid PCBs depend on rigid CCLs while flex PCBs are on flex CCLs (flex-rigid PCBs are on both rigid CCLs and flex CCLs).• Based on insulation material and structures, we have organic resin CCL (FR-4, CEM-3, etc.), metal-base CCL, ceramic-base CCL etc.• Based on CCL thickness, we have standard thickness CCL and thin CCL. The former one requires at least 0.5mm thickness while the latter can be thinner than 0.5mm. Copper foil thickness is excluded from CCL thickness.• Based on reinforcing material types, we have glass fiber cloth base CCL (FR-4, FR-5), paper base CCL (XPC), compound CCL (CEM-1, CEM-3).• Based on applied insulation resin, we have epoxy resin CCL (FR-4, CEM-3) and Phenolic CCL (FR-1, XPC). What are the essential factors of copper clad laminate? CCLs only perform well when catering to performance requirements in the following aspects: • Appearance. Issues may be caused on copper foil due to unexpected elements in manufacturing process such as dent, scratch, resin point, wrinkle, pinhole, bubble etc. All those problems will definitely lead to low performance of CCL and then PCB. Therefore, an excellent CCL should be flat and smooth in appearance. • Size. Since CCLs are base material of PCB boards, they have to conform to size requirements corresponding to PCBs. Parameters concerning the size of CCLs include length, width, diagonal deviation and warpage, each of which has to meet specific requirement. • Electric performance. This is an essential mission for a PCB so any aspect affecting its electric performance has to be carefully designed including dielectric constant (Dk), dielectric loss tangent (Df), volume resistance, surface resistance, insulation resistance, arc resistance, dielectric breakdown voltage, electric strength, Comparative Tracking Index (CTI) etc. • Physical performance. Parameters concerning physical performance of a CCL include dimensional stability, peel strength (PS), bending strength, heat resistance (including thermal stress, Td, T260, T288, T300), punching quality etc. • Chemical performance. Chemical performance of a CCL has to meet the requirements of flammability, chemical reagents resistance, Tg, Z-axis coefficient of thermal expansion (Z-CTE), dimensional stability etc. • Environmental performance. It has to cater to the requirements in terms of water absorption etc. CCL quality judgment should be carried out by PCB Fab Houses. Take PCBCart for example, it applies IPC-4101C as a manufacturing standard and uses IPC-TM-650 for CCL testing. Accordingly, such measures lead CCLs to be qualified substrate of PCBs. What are the materials of copper clad laminate? Copper FoilCopper foil is a cathodic electrolytic material deposited on a thin, continuous layer of metal foil on the base of the circuit board. It is easily bonded to an insulating layer, accepting a printed protective layer, and corroded to form a circuit pattern. Prepreg:A prepreg (from pre-impregnated) is fibreglass impregnated with resin. The resin is pre-dried, but not hardened, so that when it is heated, it flows, sticks, and is completely immersed. Prepregs are thus fibreglass strengthened by an adhesive layer (similar to FR4 material). The name of each prepregs derives from the type of fibreglass used. The prepreg types of different suppliers vary in thickness; in addition there are the versions "SR" Standard Resin, "MR" Medium Resin "and" HR "High Resin, depending on the resin content. The best possible material is used depending on the desired final thickness, layer structure or impedance. The mentioned thicknesses are thus to be considered only as examples. What is the trend of copper clad laminate? In order to cater to the regulations of RoHS (Restriction of Hazardous Substances), higher requirements are brought on CCLs in terms of heat resistance and reliability. Modifications are implemented from the following two aspects: • Halogen-free CCL. It refers to CCLs whose content of chlorine (Cl) and bromine (Br) is controlled within 900ppm while their overall content is no more than 1500ppm. Performance comparison between halogen-free CCLs and ordinary FR-4 CCLs is summarized into the following table. • Lead-free CCL. It refers to copper clad PCBs whose surface mounting is carried out without the application of lead-free solder. The main resin of lead-free CCLs is brominated epoxy resin. According to the regulations of RoHS, six substances such as PBB and PBDE are no longer used in CCLs. Compared with DICY curing system (with dicyandiamide as curing agent) applied in ordinary FR-4 CCLs, lead-free CCLs take advantage of PN curing system (with Phenol-formaldehyde resin as curing agent).Wanna know PCB knowledge? Check and read for more.
PCB Glossary ⋅ 07/26/2021 17:16
BGA in PCB
BGA packaging technology began to be applied in the 1990s. Now it is mainly applied to the packaging of high-end devices, with considerable development space. BGA is a kind of encapsulation technology in which many spherical convex points distributed in array form are soldered on the bottom or upper surface of the module. Among all the packaging typed of semiconductor IC. In this passage, we will provide you everything about BGA in PCB, please follow us and read the content we prepare.If you want to order PCB product, please check and custom your order online. What are the classifications of BGA in PCB？ There are many types of BGA packaging, the general shape structure is square or rectangular. According to the arrangement mode of solder ball welding, it can be divided into peripheral type, staggered type and full array type BGA. According to the different substrates, it can be divided into 3 types as following: PBGA (Plastic Ball Grid Array)CBGA (Ceramics Ball Grid Array)TBGA (Tape Ball Grid Array) PBGA Some PBGA are encapsulated as cavity structures, which are divided into 2 types: cavity up and cavity down. This kind of PBGA with cavity is designed to enhance its heat dissipation performance, which is called thermal enhanced BGA, or EBGA, or CBGA (Cavity Plastic Welding Ball Array). The advantages of PBGA packaging are as follows: · Good thermal match with PCB board.· During reflow soldering, the self-aligning of the solder ball, that is, the surface tension of the solder ball, can be used to achieve the alignment requirements between the solder ball and the pad.· Low cost.· Good electrical performance. CBGA CBGA has the longest history in the BGA packaging series. Its base substrate is multilayer ceramics. The metal cover board is welded on the base substrate with sealed solder to protect the chip, lead and pad. The welding ball material between the solder ball and the package body needs to use cryogenic eutectic solder 63Sn37Pb. The advantages of CBGA packaging are as follows: · Good air tightness, high humidity resistance, and high long-term reliability of packaging components.· Better electrical insulation performance than PBGA devices.· Higher packaging density than PBGA devices.· Better heat dissipation than PBGA devices. TBGA TBGA is a cavity structure. There are two ways of interconnection between the chip and substrate encapsulated by TBGA: inverted solder bonding and lead bonding. The chip is connected in the flexible multi-layer wiring belt. The circumferential array solder ball used as circuit I/O end is installed under the flexible carrier belt. Its thick sealing cover board is a radiator (heat sink), and also plays the role of strengthening the encapsulation body, so that the solder ball under the flexible substrate has better coplanability. Chip bonding on the copper heat sink of the core cavity. The bonding leads of the chip bonding pad and the multi-layer flexible wiring ad are used to realize interconnection. The circuit chip, lead, and flexible load pad are encapsulated with a sealant. The advantages of TBGA are as follows: · The flexible loading belt of the packaging body and the thermal matching performance of PCB board are good.· During reflow soldering, the self-aligning of the solder ball and the surface tension of the solder ball can be used to achieve the alignment requirements between the solder ball and the pad.· Is the most economical BGA packaging.· Better heat dissipation performance than PBGA structure. What are the features of BGA? · More I/O. Since BGA encapsulated solder balls are arranged under the encapsulated substrate in the form of array, the number of I/O of the device is greatly increased, the size of the encapsulation body is reduced, and the space od assembly is saved.· High packaging yield reduces cost.· The contact surface between BGA’s array welding ball and substrate is large and short, which is conducive heat dissipation.· The pin of BGA array welding ball is short, which shortens the signal transmission path, reduces the lead inductance, electrical resistance and improves the circuit performance.· Improve the coplanability of I/O terminal and reduce the loss caused by poor coplanability in the assembly process. · BGA is suitable for MCM encapsulation and can achieve high density and high performance of MCM.· The IC of BGA and fpBGA is stronger and more reliable than the foot-shaped package of detail spacing.Wanna know PCB knowledge? Check and read for more.
PCB Glossary ⋅ 07/26/2021 09:17
Stretchable PCB technology
Even though stretchable printed circuit board technology employs usual production and subsequent assembly steps, the laminate is Polyimide or Polyurethane. Polyimide or Polyurethane comes with the advantage of producing stretchable printed circuit boards with significantly low investment costs. To assemble the substrate's components quickly, plenty of manufacturers employ one of the below methods. Manufacturers mainly reinforce the laminate locally by using a special coating or an interposer. However, the ultimate method is to employ a technology known as Stretch-Rigid. As opposed to connecting two rigid boards by a flexible PCB such as in Rigid-Flex construction, Stretch-Rigid works better and efficiently. In this passage, we will focus on the stretchable PCB and the application of it. Please check and read the content we prepare to learn more information.If you want to order PCB product, please check and custom your order online. What are the advantages of stretchable PCB? Stretchable PCBs are explicitly designed to save space while improving flexibility to meet smaller and mounting designs of high density.Additionally, it also helps in reducing the process of assembly while enhancing reliability at the same time. In short, stretchable PCBs are the only solution that ensures miniaturization and the movement of electronic devices. There are several advantages associated with stretchable printed circuit boards worth mentioning. For instance, stretchable PCBs can be twisted, bent, and moved without the risk of damaging the conductor. Additionally, special packaged sizes and several outlines get permitted with stretchable printed circuit boards. That is not all. Stretchable PCBs provide outstanding electrical performance. They come with a low dielectric constant that gives room for the electrical transmission of signal and impressive thermal properties that make cooling very easy. Better yet, stretchable PCBs can operate well under high temperatures, unlike rigid PCBs. Stretchable PCBs provide higher assembly output and reliability due to reduced internal connections hardware. Furthermore, there is little error during assembly since this is a PCBs designed or manufactured for one-way assembly. Stretchable boards can alter their positions with ease while remaining tethered electrically to each other all the time. Briefly speaking, some of the reasons to use stretchable PCBs as opposed to rigid ones include: • Reduced weight and space• They meet changing flexing requirements• Flexing for ease of service and installation• Increase repeatability and reliability• Excellent thermal management• Reduce the costs of assembly• Does away with connectors• They provide uniform electrical characteristics for circuitry that require high speeds What is the working principle of stretchable PCB? While the thermoplastic Polyurethane used by manufacturers as substrate meant for stretchable PCBs can stretch easily, copper traces inhibits it from spreading. The reason for this is because copper is not malleable enough for such purposes. Manufacturers use their confidential lay-up techniques and specialized press for bonding RA copper foil or standard ED on the Polyurethane substrate. Upon completing this step, they then use normal subtractive wet-etching printed circuit board steps to fabricate the stretchable circuits. Since adding several layers of Polyurethane substrate and adhesive minimizes stretchability, most stretchable PCBs are double-sided or four layers at the most. Manufacturers apply polyurethane solder masks to finished PCBs to maintain a uniform elastomer design. The assembly of stretchable PCBs employs the normal off-the-shelf surface mounting components soldered on the copper tracks. Since the parts are rigid, the places where the elements get positioned is impossible to stretch. In short, the concept of stretchable PCBs is some small islands of severe nature that holds few SMD components. These SMD components are interconnected using some conductive paper foil on stretchable substrates. To ensure that traces of copper found on the substrate flex or bend without damage, designers give a horseshoe shape to the copper traces. After that, the horseshoe shapes are placed alternatively at 180° to allow them to meander along a path that would have been taken by straight marks. While other different ways, such as triangular shapes, can stretch, they exhibit high-stress levels and bring about lower reliability. What are the applications of stretchable PCB? Mainly, applications that call for a stretched printed circuit board use are on bent or non-flat surfaces. These come in as some of the significant users of stretchable PCBs. It is evident that such applications are on the increase, and so are stretchable PCBs. A traditional rigid PCB can’t be comfortable placed or used on integrated surfaces such as implanted devices or wearables. Devices and components used in smart textiles, biomedical applications, sports, safety, and leisure are often irregular in shape. With such irregular shapes, a printed circuit board has to follow the form required for efficient integration. While it’s possible to develop a flexible circuit shape like a cylinder or cone, stretchable circuits can easily fit into any surface. Having said, stretchable PCBs find use in plenty of applications from consumer clothing to complex positioning and medical applications, among others. For example, stretchable PCBs can be placed inside a shoe's sole to measure pressure using embedded sensors. They do so by collecting user data based on free movement. Stretchable PCBs are also placed inside bandages as they contain pressure sensors that can efficiently measure the contact pressure. The ability to measure contact pressure is a vital factor in handy, especially when handling open wounds.Wanna know PCB knowledge? Check and read for more.
PCB Glossary ⋅ 07/23/2021 17:17
As a part of the whole machine, a printed circuit board generally cannot constitute an electronic product, and there must be a problem of external connection. Electrical connections are required between circuit boards, circuit boards and off-board components, printed circuit boards and equipment panels. The selection of the best combination of reliability, process and economy is one of the important contents of pcb board design. There are many ways to connect externally, and you have to choose flexibly according to different characteristics. In this passage, we will focus on the PCB interconnect. Please check and read the content we prepare for more professional knowledge.If you want to order PCB product, please check and custom your order online. What are the methods of PCB interconnect？ Soldering The advantages of this interconnection method are simple, low cost, high reliability, and can avoid the faults caused by poor contact. Disadvantages are not easy to change or not very convenient for maintenance. This method is generally applicable to components with fewer external leads. 1. Soldering of PCB Leads: This method does not require any connector clip, as long as soldering directly and firmly the external interconnection points on PCB with the PCB components or other components outside, such as the speaker in the radio, battery box and so on. The points needing attention when soldering interconnections on PCB are as follows: · Soldering pads for leads shall be placed as far as possible on the edge of PCBs and arranged in the same size to facilitate soldering and maintenance. · In order to improve the mechanical strength of the wire connection, it’s necessary to avoid damage to the solder pads or printed leads caused by the leads being pulled. In addition, the holes should be drilled near the solder joints on the PCBs to allow the leads to pass through the holes on the solder side of the PCBs, and then insert the holes of solder pads from the component side for soldering. · Arrange or tie the leads neatly, and fix them with PCB through line-card or other fasteners to prevent the leads from breaking due to movement. 2. Soldering of PCB Flexible Flat Cable: The two PCBs are connected by flexible flat cables, which is reliable and not prone to connection errors, and the relative position between the two PCBs is not limited. Directly soldering between PCBs, are often used to connect the two PCBs at an angle of 90 degrees. After connecting, it becomes an integral PCB part. Connector Clip In more complex instruments and equipment, the interconnection methods of connector clip is often used. This "building block" structure not only ensures the quality of mass production, but also reduces the cost of the system and facilitates debugging and maintenance. When device fails, maintenance personnel don’t need to check the component level. That is, in order to check the cause of the failure, until check to the specific component. This work will take quite a long time.), as long as maintenance personnel judge which PCB is abnormal, they can immediately replace that PCB, which cannot only eliminate faults in the shortest time, but shorten the downtime. Thus, it can improve the utilization rate of the device. In addition, the replaced PCB can be repaired in plenty of time and used as spare parts after repair. 1. PCB Socket Interconnection: This interconnection is often used in more complex instruments and devices. This method makes the printed plug from the PCB edge, and the plug part is designed according to the size of the socket, the interconnection points, the contact distance, the location of the positioning holes and so on, so as to make it match with the special PCB socket. When manufacturing PCB, the plug part needs to be gold-plated to improve wear resistance and reduce contact resistance, which has the simple assembly, great interchangeability, good maintenance performance, and is suitable for standardized mass production. The disadvantage of this method is that the cost of PCB is increased, and the requirements of PCB manufacturing precision and process are higher. In addition, its reliability is poor. For example, it often lead to poor contact because the plug part is oxidized or socket spring aging. In order to improve the reliability of external interconnection, the same outgoing line is often drawn out in parallel through the contacts on the same side or both sides of PCB. 2. Standard Pin Interconnection: This method can be used for PCB external interconnection, especially in small instruments commonly used pin connection. Two PCBs are connected by a standard pin, and they are generally parallel or vertical as it is benefit for the mass production.Wanna know PCB knowledge? Check and read for more.
PCB Glossary ⋅ 07/23/2021 17:05
Stray capacitance in PCB
Capacitance is the property of a set of conductors or an electric conductor measured accurately by the quantity of separated electric charge (Geaghan, 2013). Capacitance is often stored on it per unit change or fluctuation in electrical potential. It is worth mentioning that capacitance also indicates related storage of electrical energy. Stray capacitance is a type of capacitance; unwanted, excess, or preferably unavoidable capacitance induced in a variety of electronic components because of their parallel alignment is typically known as stray capacitance. In this passage, we are going to talk about stray capacitance. Please check and read the content we prepare below.If you want to order PCB product, please check and custom your order online. What are the effects of stray capacitance in PCB? In high voltage and high-frequency systems, conductors do not need another conductor to produce capacitance between them. It is because it is induced merely by interaction with the environment. Note that in Printed Circuit Boards (PCB), this often results in plenty of unwanted or unnecessary capacitance that may impact the performance of a system. Electronic design automation computerized programs that are used in designing most commercial printed circuit boards could calculate the stray capacitance and other parasitic impacts of both circuit board traces and components and tend to include them invaluable simulations of circuit operation. This is known as parasitic extraction (Kao, Lo, Singh, & Basel, 2001). Using the figure below, we can easily calculate the stray capacitance for a conductor in any PCB substrate. Note that this capacitance may theoretically be used in a variety of places that need small discrete capacitors, but it is, in most cases, an inefficient way. It is important to remember that in a majority of higher frequency amplifiers, the stray capacitance may combine easily with some stray inductance, like component leads, to form various resonant circuits, which can also lead to a phenomenon called parasitic oscillations. In almost all inductors, the parasitic capacitance may resonate with the inductance at some high frequency to make an inductor self-resonant; this is known as the self-resonant frequency. Above this specific frequency, the inductor has capacitive reactance. Designers of electric circuits try their best to minimize or eliminate stray capacitances, if possible. They often do this by carefully keeping all of the leads of electronic parts concise and grouping these parts in a way that eliminates capacitive coupling. The stray capacitance of a load circuit attached firmly to the output in op-amps may lower their bandwidth. A majority of high-frequency electric circuits need specialized design techniques like careful separation of components and wires, guard rings, power planes, ground planes, shielding between output and input, termination of strip lines, and lines to minimize the impacts of unwanted capacitance. What are the trends of stray capacitance in PCB? Three main factors in capacitor construction determine the number of stray capacitances created. All these factors affect stray capacitance by impacting the amount of electric field flux that would develop for a specific amount of electric field force (this is the voltage between any two plates) Plate SpacingKeeping all other factors constant, more spacing between plates gives less stray capacitance; on the other hand, closer plate spacing can produce more stray capacitances. Closer plate spacing can result in a higher field force, And for any particular voltage applied to the two plates, this results in a relatively high field flux (charge accumulated on both scales). Plate AreaAll other variables constant; more plate area provides more stray capacitance while less plate area generates less stray capacitance. Dielectric MaterialKeeping all other variables constant, the higher permittivity of a dielectric material produces greater stray capacitance, while less permittivity of a dielectric material produces less stray capacitance. Relative permittivity indicates the permittivity of materials; it is close to a vacuum (pure) (Rubin and Ho, 2018). For instance, glass with a relative permittivity of seven has seven times the standard permittivity of vacuum. It hence will lead to the production of an electric field flux that is seven times stronger compared to that of a pure vacuum, when all other variables are equal. In this chapter, we have discussed the different trends in stray capacitances and the factors that have an impact on stray capacitance. In the next section, we will consider some ways to lower stray capacitance. How to reduce stray capacitance? In many applications, the stray capacitance between multiple signal lines could deplete or impact the whole design. It is worth mentioning that at lower frequencies, the stray capacitance can often be ignored. However, at high frequencies, it could be the main problem in electric circuits. We can control stray capacitances at the layout level. Stray capacitances often arise due to an electrical coupling generated between a signal line and the other signal line or the substrate and a signal line. It is worth mentioning that in many designs, it can become essential to lower stray capacitance of a specific net regarding other signals. These are a few of the most effective methods for decreasing stray capacitance: 1. Increasing the spacing between the various nets from the specific set is crucial (for which stray capacitance is quite important). 2. I am using higher metals for those nets where the stray capacitance is vital. 3. Avoiding excess parallel routing of metals 4. Place another reference signal between various networks that require low stray capacitance (where the stray capacitance is not essential). It is called shielding. This chapter discusses four ways you can reduce stray capacitance. In the next section, we will discuss stray capacitance in transformers.Wanna know PCB knowledge? Check and read for more.
PCB Glossary ⋅ 07/22/2021 16:56
PCB tombstone effect
In the reflow soldering of SMT, the components will desoldering because of warp. This is Manhattan effect. We call it “tombstone”. Manhattan effect usually appears in the reflow soldering process of CHIP components (such as capacitor and resistor). The smaller the component, the more likely it is to occur. And the reason is: When the solder paste on the solder pads at both ends of the component is melted in reflux, the surface tension of the two soldered ends of the component is unbalanced. Before welding, the two ends of the chip Multi-layer Ceramic Capacitors (MLCC) are temporarily positioned with solder paste and board pads. When the welding is successfully completed, they become part of the assembled circuit board. Once the two ends are unevenly wetted when melting tin, the uneven surface tension generated on the two ends will cause one of the ends to slide off the substrate, or the entire MLCC will rise or even stand up. It looks like a tombstone, usually called a tombstone phenomenon, and sometimes called a suspension bridge phenomenon. This phenomenon directly affects the quality and reliability of the printed circuit board and the whole machine. At the same time, it will increase the manufacturer’s repair rate and increase the cost.If you want to order PCB product, please check and custom your order online. What are the causes of tombstone effect? To understand what causes tombstoning, you first have to understand what “wetting” means to describe a process of attaching components to a bare board with solder. Wetting is an ideal situation when the solder is applied to your board has reached an ideal fluid state and can attach properly to a component lead or pad. Take a simple SMD resistor as an example, which has two pads. In an ideal process, the solder will attach itself to both pads and complete its wetting process at the same time on both ends. No tombstoning issues here. But you run into a problem when the wetting process of solder is unbalanced. Like when the solder on one pad completes its wetting process before the other, which results in one side of a component solidifying while the other is still in process, and so begins the game of tug-o-war. Of course, the wet pad ends up winning, pulling up the other pin still in the process of wetting, and the entire component gets tilted on its side, looking like a tombstone. As you can imagine, identifying exactly what caused this uneven wetting can be quite the detective work as there are so many variables in play during a typical wave reflow process. Some of the most common causes of a tombstoning issue on a PCB can include: · The temperature of the reflow oven being uneven, which can cause the solder to begin and finalize its wetting process at different times on your PCB layout.· Solder paste being applied to your board in a non-uniform application across all of your pads which can lead to wetting beginning and ending at different times.· There’s also the varying sizes of pads themselves, with SMT pads having their own set of tolerances that are often ignored but can affect the accuracy of solder applications. How to prevent tombstone effect? One day you might get a call or an email from your manufacturer saying that you have an issue with tombstoning on your PCB. And then you’ll probably sit there with a puzzled look on your face. What the heck is tombstoning you’ll ask, and why are you calling me about it? Tombstoning is just one of many issues that can occur during the soldering process when all of your components get attached to a bare board. And since the beginning of PCB manufacturing, tombstoning has been and continues to be an issue. While a bunch of articles on the web point the fingers of blame at manufacturers for tombstoning issues, the truth is you also have a part to play as well. So let’s dispel once and for all what tombstoning is, and what you as a PCB designer can do to prevent it at design time. What Can I Do About This Problem? So now you understand tombstoning, and what it looks like on your PCB design. But you might be saying to yourself – everything I just read above sounds like an issue with the manufacturer’s process, so isn’t this their problem? Well, Yes and no. While many of the causes of tombstoning are directly related to manufacturing imperfections, there are still some factors that you can influence. Like making a mistake on pad dimensions when creating a part, or using a tombstone loving PCB finish. Here are our top five tips that you can implement in your very own design process to lessen the chance of tombstoning: Double Check Your Component Pad DimensionsWhen you’re drudging through the process of creating your own parts, it can be easy to mess up your pad dimensions without realizing it. This could be a simple mistake like making the pad dimensions too small or too large or making one pad larger than the other. Whichever mistake happens, that extra copper is going to act as a heat sink during your wave soldering process, causing one side of your pad to complete this wetting process earlier than the other. To solve this, always make sure that you make your component footprints according to the exact specifications in your manufacturer’s datasheet. There’s no good reason to make component pads larger than necessary. The next time you make a footprint, try using this IPC-7351B calculator which can help you to precisely calculate land patterns based on exact component dimensions. Consider Using a Different PCB FinishIf you’re working with tiny component sizes, like 0402 or 0201, which are known for tombstoning problems, then consider using an alternative to the traditional Hot Air Solder Leveling (HASL) on your board. While an HASL finish is the industry norm thanks to its low cost and wide availability, it’s also prone to causing uneven surface finishes, which can impact the solder wetting process on your components. There are several other board finishes you can consider using depending on your design constraints, like immersion tin, immersion gold, or OSP. Pay Attention to Your Component Placement and RoutingThe chances are that different trace widths on two sides of a component haven’t been that big of a deal for you to consider, but with the risk of tombstoning on tiny component packages, it is. When working with these smaller components, carefully inspect both your component placement and routing to ensure that all of the traces connecting to your pads are equal in width. It’s also a good practice to connect traces in a similar orientation, either along your x-axis or y-axis. Otherwise, you might get variable heat dissipation with differently angled traces. Inspect the Inner Layers of Your Board for Copper CoverageIt’s not just the top and bottom layers of a board that can cause tombstoning issues. Sometimes the culprit might be hiding out in the inner layers of your board. If an inner layer of your board has a large copper area that covers only one part of a component pad but not the other, then this will most likely cause an uneven heating process during wave soldering. To prevent this, always make sure that the copper on the inner layers of your board covers both sides of a component’s pads.Wanna know PCB knowledge? Check and read for more.
PCB Glossary ⋅ 07/20/2021 17:42
PCB impedance matching
Do you know impedance matching? Impedance matching means that when source is transmitted, the load impedance must be equal to the characteristic impedance of the transmission line. In this passage, we will provide everything about impedance matching. If you are curious about this topic please check and read the content we prepare.If you want to order PCB product, please check and custom your order online. What is the importance of impedance matching in PCB? Here’s a news flash: PCB design has become more complex. Whether in the consumer or industry market, high-speed and high-frequency devices have become the norm. And this is only the beginning. When we work with these ultra-high-frequency designs, we must account for the fundamentals. As an example, impedance matching often became an afterthought for design teams working with lower and medium frequencies. However, impedance matching challenges RF and microwave circuit design because the window for error decreases as frequency increases. High speed digital circuits require very stable controlled impedances because of the impact on bit error rate and the potential for pulse distortion, reflection, and EMI. Proper circuit operation depends on impedance matching—or the ability of the circuit to efficiently transfer signals from the source into the routing and then from the routing to the load. Impedance—if not treated correctly—has a remarkably negative impact on circuit performance. Without the proper impedance matching, reflections can exist along the path from the source to the load. Until attenuation occurs, the signals happily propagate back and forth in the trace and interfere with the transmitted signal. Reflections and standing waves in high frequency lines mix with desired signals—and form a witch’s brew of amplitude and phase distortion. The direct results of this interference include data jitter and a reduction in the signal-to-noise ratio. As the distance from the source to load increases, standing waves cause impedance to ebb and flow. What is the working principle of impedance matching? Good PCB design requires attention to fundamentals. When considering the impact of impedance on a circuit, we need to consider the fundamental relationships between resistance, reactance, and impedance. Everyone knows that a resistance opposes a steady electric current and—as a result—reduces energy. Reactance measures the opposition to current caused by a capacitance or an inductance. While a perfect resistance does not vary with frequency, the impact of changing frequencies on a capacitor or an inductor causes inductive (XL) or capacitive (XC) reactance to change with the frequency of an AC signal. With all those things in mind, let’s make the jump to impedance. We know that impedance is the total opposite of a device or circuit to the flow of an alternating current. In addition, we also know that the impedance of a capacitor has an inversely proportional relationship to capacitance while the impedance of an inductor has a direct relationship with inductance. How to make impedance matching? Well-controlled impedance means that the trace impedance is constant at every point along the path on the PCB. This means that wherever the trace travels, even if it changes layers, the impedance should be the same throughout the part, from the source to the destination. We don’t have much control over the impedance in the driver or in the load but, we can control the impedance on the PCB. So, we want to have matching circuitry on the PCB that matches the impedance of the source and load. Therefore, we can ensure a consistent appearance throughout the entire path. There are a few important design criteria that we need to consider. Keep in mind that many of the problems relating to reflections relating to EMI can be prevented by good PCB design techniques. Another crucial point is the choice of materials. In the past, typically FR4 was specified. But, with high-speed designs, the use of the correct laminate is critical. The use of a material with a lower dielectric constant (Dk) is advisable and preferred. This not only ensures the best signal performance, but it will also minimize any signal distortion or phase jitter of the signal. From the table, you can see that material like Isola FR408 provides a consistent dielectric constant of 3.7. So, it is essential to choose the laminate material carefully. Otherwise, you might see an inconsistency in operation between board batches: one batch of boards might work and the next batch of boards you order might not. Another important criterion is the loss tangent or dissipation factor. This is a measure of the signal loss as the signal propagates down the transmission line on the PCB. For very high-frequency designs you would want to select the lowest loss material. From the table, you can see that the different laminates having varying loss tangents. So, you would need to select the material that is the most suitable for your application and specify this in your manufacturing notes. Ensure that the bare laminate used in the PCB fabrication process complies with IPC4101 grade. It is important to ensure good dielectric spacing between the copper and the laminate that it is bonded to in order to achieve a consistent electrical performance of the trace running across the PCB. An additional point to consider in selecting the laminate material is the fiberglass weave pattern. A typical PCB core and prepreg substrates are constructed from various woven fiberglass fabrics bound together with epoxy resin. The glass and epoxy each have different Er/Dk values, resulting in an inhomogeneous medium for signal propagation. A loose weave pattern produces less uniform dielectric constants in the PCB laminate that can cause trace impedance variation and propagation skews. The higher the frequency, the more evident this problem will be. The tighter the weave pattern, the more uniform the dielectric constant. So, it is better to practice to choose a tighter weave so the signal moves over more glass than anything else. The outcome of this will be a very consistent dielectric constant throughout the PCB.Wanna know PCB knowledge? Check and read for more.
PCB Glossary ⋅ 07/20/2021 17:35
Turnkey PCB assembly
The meaning of “turnkey” projects is any product or service that comes ready for the buyer to operate. In terms of PCB assembly, turnkey assembly is a service where all aspects of the PCB project are handled by your supplier on your behalf. The supplier procures parts and components and assemblies the PCB. Turnkey PCB assembly typically uses cloud-based software and powerful machinery to put together circuit boards more efficiently and at a greater volume than small and medium businesses can handle on their own. Turnkey PCB assembly is an electronic assembly solution offering efficient and cost-effective means of building and testing circuit boards for new products, with the shortest lead times possible. In this guide, we’ll discuss the meaning of turnkey solutions for PCB assembly and the benefits associated with it. In this passage, we will focus on the topic and please come and check the content we prepare for more information.If you want to order PCB product, please check and custom your order online. What are the advantages of turnkey PCB assembly? The most obvious benefit of turnkey PCB assembly is that businesses don’t have to take their focus off critical processes like continual innovation to spend time figuring out the assembly side. There’s no need to expend time and energy finding the best component costs, going through a frustrating process of procurement and then needing an in-house team to assemble them skillfully. The most significant benefits of turnkey assembly include: Cost Reduction With a turnkey contract, there is no extra cost to deliver freight to an assembly workshop, meaning you save a significant amount of money. Turnkey services also have good working relationships with component manufacturers and can almost always get a better price for parts than small or medium businesses. Issue Identification A major time and money-saving advantage of turnkey PCB assembly is the ability to spot potential issues before the circuit boards make it into any products. As part of the process, you submit a netlist file to the assembler. Before assembly begins, the assembler will check to be sure specifications match the application and identify any errors that may be present. Should any errors be found, you have the opportunity to correct the design and avoid being saddled with thousands of unsuitable circuit boards. Streamlined Management Dealing with multiple vendors can be stressful and a time drain, especially on small businesses with fewer human resources to go around. With turnkey manufacturing solutions, you stand a far less chance of experiencing a miscommunication because you’re managing multiple channels of interaction. These potential miscommunications can happen between you and a vendor, or even between vendors, and can lead to derailment of your timeline and wasted money. Your turnkey supplier will likely provide you with a single point of contact through which all business will be conducted, providing you with peace of mind and lightening the burden of management in the assembly of PCBs. What are the differences of Partial Turnkey and Full Turnkey? Turnkey PCB assembly comes in two varieties: partial and full. Partial turnkey services are a form of consignment manufacturing, in which only part of the assembly process is outsourced. In a partial turnkey project, the technology developer retains responsibility for a portion of the supply chain. This can mean involvement in purchasing or assembly. The consignment model sees the tech developer in charge of obtaining, sorting and packaging materials for delivery to the assembler. For businesses that already have a majority of the necessary parts on hand, partial turnkey services can expedite the manufacturing process and save money. However, if you don’t have parts, aren’t sure where to order the right ones or don’t know which components are right for your circuit board design, full turnkey service is the more appropriate option. Full turnkey PCB assembly sees your assembly provider do all the work of putting your circuit boards together. They source the parts and create the circuit order. All you have to do is provide: · A bill of materials· Gerber Files· Product dimensions· Packaging and shipping information Please note, if you do not have the resources listed above please reach out to us and we can help procure everything needed to start the process. A full turnkey service is naturally more of an investment than a partial or consignment service, but it can dramatically improve your experience with acquiring PCBs — especially if you are new to dealing with circuit boards.Wanna know PCB knowledge? Check and read for more.
PCB Glossary ⋅ 07/20/2021 09:23
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