PCB laser drilling process
When using HDI technology for PCB designing, plenty of microvias are included. These microvias that appear to be blind structures are small in size and require precise controlled depth drilling. This precision can only be achieved using lasers. In this passage, we will focus on the PCB laser drilling topic and if you are going to learn more knowledge please check and read the content below.If you want to order PCB product, please check and custom your order online. What are the advantages of PCB laser drilling? The advantages of using lasers are listed below: · Non-contact process: Laser drilling is a non-contact process and hence the damage induced on the material by drilling vibration is eliminated. · Precise control: We can control the beam intensity, heat output, and duration of the laser beam. This helps to create different hole shapes and offers high accuracy. · High aspect ratio: One of the most important parameters of a drilled hole on a circuit board is the aspect ratio. It is the ratio between the drilled depth and the diameter of the hole. Since lasers can create holes with very small diameters, they provide a high aspect ratio. A typical microvia has an aspect ratio of 0.75:1. · Multi-tasking: Laser machines used for drilling can also be used for other manufacturing processes like welding, cutting, etc. Lasers can drill 2.5 to 3-mil vias on a thin flat glass reinforcement. In the case of an unreinforced dielectric (with no glass), it is possible to drill 1-mil vias using lasers. Hence, laser drilling is recommended for drilling microvias. What are the methods of PCB laser drilling? Single-pulse/shot laser drillingAs the name suggests, in single-pulse laser drilling, a single shot of laser beam is fired at the material to create the required hole. In this method, both the source of the laser and the work material is kept static. Percussion laser drillingIn percussion drilling, a series of laser pulses are shot at the work material repeatedly. During this process, there is no relative motion between the laser beam and the workpiece. This form of laser drilling effectively creates deeper and precise holes with smaller diameters as compared to single-shot laser drilling. TrepanningTrepanning is the process in which a laser beam is guided around a predefined locus. This locus is the center of the via to be drilled. It is used in situations where the diameter of the via to be cut is larger than the laser beam diameter. The accuracy of the via is determined by the movement of the beam. Helical laser drillingHelical laser drilling is a method in which the laser beam follows a helical path for movement while rotating about its own axis with respect to the workpiece. A dove prism controls the movement of the laser beam. What are the considerations of PCB laser drilling? During laser drilling, there are a few aspects regarding the circuit board that should be considered. Given below are two of the important ones. Non-homogeneity of the stack-upThe non-homogeneity of the PCB materials used in the stack-up is the main consideration while using lasers. Different materials absorb energy at different rates. For example, FR4 resin absorbs light energy at the same rate as the glass fibers and leaves a clean hole. BT epoxy resin vaporizes at a rate faster than glass and hence leaves glass fibers in the hole. In situations like these, obtaining complete accuracy with lasers becomes difficult. Therefore, it is recommended to keep the homogeneity of the multilayer PCB stack-up as much as possible. If we use materials that have different optical and thermal properties, the way the laser beams react with them will also be different, leading to inaccurate drilling. The thickness of copperThe minimum thickness of the target copper layer should be twice the thickness of the top copper layer to be penetrated. Apart from a few challenges that may arise, we can surely say that lasers are the best choice to create microvias in PCBs. Given the ever-increasing demand for reducing the board size and increasing the wiring density, laser-drilled microvias are crucial in PCB manufacturing. Creating diminished holes with extreme accuracy without affecting the integrity of the board is a difficult task. Laser drilling is the best way to manufacture such compact boards.Wanna know PCB knowledge? Check and read for more.
PCB Knowledge ⋅ 08/16/2021 09:52
PCB Design Basics Tutorial
Since PCB design is a very important process during the PCB manufacturing. It involves setting up the board parameters, determining its outline, routing the components, and generating the production documents. It is necessary to know the basic knowledge of it. Please check and read the content we prepare for you below.If you want to order PCB product, please check and custom your order online. What are the PCB design basics? While designing a new PCB, it is necessary to adhere to design basics. If neglected, it will result in a poor board design that will be very difficult to manufacture. Therefore, it is necessary to pay attention to the following concepts: Choose appropriate components and package sizes As a board designer, you should thoroughly study the BOM and examine the parts that go into the design. When there is sufficient space on the board, you may opt for larger components for resistors and capacitors. It is beneficial to use a 0603 or 0805 size capacitor/resistor instead of a 0402/0201. Select the smaller package version of the component if you have spacing issues. Moreover, choose your appropriate component and package based on the required current, voltage, and frequency. Smaller components are manufactured by various vendors. It allows designers to choose alternate parts without modifying the schematic or layout, providing a timely solution for components that are not in stock. Furthermore, it is crucial to decide the appropriate size of the package during the PCB design phase. It is recommended to choose smaller packages only when necessary; otherwise, choose larger packages. Using too many small component packages can create issues during circuit board assembly, which leads to difficulties during cleaning and reworking. Avoid long lead-time components The unavailability of components can cause considerable delays. So, it is better to check the availability while confirming component spacing. If your component has a long lead-time, order it immediately. It can be beneficial to have alternate components with the same footprint. Assembly vendors can also procure the widely available parts so that every component will be readily available when it is time to assemble the boards. Schematic checks A schematic is a well-structured circuit diagram that represents the electrical connections between various electronic components. Schematic design basics often get ignored. Make sure you verify the following: · Verification of pin numbering and labels in component symbols· A polarity check for all the polarized components· Overlapping labels and Pins· Ensuring the base, collector, and emitter pins according to the schematic symbols, datasheet, and footprint package· Validation of the component value, location, and reference designators· Descriptions of the schematic symbols· Off-page connectors· Checking the inter-sheet reference· Decoupling capacitor check for all ICs, ground pin separation according to the signal type (analog, digital, signal, ground)· Netlist check for design correctness and wrong connections· Add test points to all important signals· Test points are required to check the electrical conductivity of the board. It is necessary to add test points for all important signals to facilitate electrical tests (E-test) and in-circuit tests (ICT). Keep an eye on the following: Board side: If possible, all test points should be located on the same side of the board to facilitate testing.Minimum test point distance: The minimum distance between test points is 0.100 inches. It maximizes test effectiveness.Test point distribution: Distributing test points evenly on a circuit board makes testing easier with multiple probes.Area for taller components: Designating the area for taller components can streamline the testing.Manufacturing tolerances: Make sure to consider manufacturing tolerances while designing a layout to accommodate a space for test points. Make sure your BOM is up to date while designing A BOM is a detailed list of all the components required to produce a product. Keep your BOM up to date while designing, and if you make any changes to your design, ensure you have also implemented those changes in your bill of materials. For example, if you change the part number in the schematic, update the BOM as well. Before you validate your BOM file, ensure that all the active parts are included in it. The parts should be validated with respect to the following fields: · Serial number· Part description· Designators matching the schematic· Quantity of the parts· MPN · VPN · DNI (do not install) components Stack-up preparation in PCB design Stack-up is an important attribute in the basics of multilayer PCB design. It defines the structure of a multilayer circuit board in a sequential manner. Stack-up provides information about the material thickness and copper weights that are vital for circuit board manufacturing. When boards are precisely stacked, electromagnetic emissions and crosstalk are reduced, and the signal integrity is improved. Know your board’s mechanical constraints, which include board thickness and component height. It is important to know the controlled impedance requirements, including the number of differential pairs, as it will impact the number of layers in your board. The routing density of the circuit board will also impact the number of layers. Choose a PCB material based on the fastest rise time. Verify the manufacturability of your stack-up using our free Stack-up Planner. The following parameters are necessary for the planner: · The PCB material (FR4, I-Speed, Rogers, etc.) depends on the frequency requirements and environment.· Layers including signal and power layers.· Impedance requirements such as 50Ω single-ended, 90Ω differential, or 100Ω differential· Copper thickness (½ or 1 or 2 ounces) Carefully inspect your footprint development Schematic, complete BOM, and stack-up are the backbone of your circuit board. It is easier to create footprints for some components when they come in standardized packages. In most cases, the footprints of standard packages are available in the software’s library (Altium Designer, Allegro, etc.). Otherwise, you will have to create it based on the datasheet of the component. Confirm library components match the recommended land pattern provided in the datasheet. After designing your footprint, do a quality check. Mark your component orientation. Footprints must be checked for top and bottom views, pin pitch, and height. Ensuring the accuracy of your footprint as per the land pattern will eliminate issues during assembly. Placement of components Once the mechanics of the board have been finalized, next is placing components. The proper component placement on a PCB leads to better performance and signal quality. It begins with placing the parts which are at the specified locations according to the design requirements. These components usually consist of connectors and their associated parts. Following that, the main components such as the CPU, memory, and analog circuits will be placed in their proper positions. The third step involves placing auxiliary components such as crystals, decoupling capacitors, and series resistors. Wanna know PCB knowledge? Check and read for more.
PCB Knowledge ⋅ 08/12/2021 17:13
Decoupling Capacitor Placement PCB
Do you know what is decoupling capacitor in PCB? In this article, we will provide you everything about decoupling capacitor in PCB, please check 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 decoupling capacitor? In the strictest sense, there isn’t a specific component that’s defined as a decoupling capacitor. Rather, the term decoupling capacitor refers to the function of a capacitor in an electronic circuit. A decoupling capacitor is one that stabilizes the voltage on the power supply plane. In any design that involves semiconductor ICs, you’ll always need decoupling capacitors. That’s because the voltage supplied to the components is far from ideal. Unlike the perfect horizontal line depicted in theory, voltage readings in real-life applications tend to fluctuate even if you’ve got the cleanest power supply. The decoupling function as reservoir and it acts in two ways to stabilize the voltage. When the voltage increases above the rated value, the decoupling capacitor absorbs the excessive charges. Meanwhile, the decoupling capacitor releases the charges when the voltage drops to ensure the supply is stable. Often, you’ll need at least two coupling capacitors of different values to stabilize the voltage supplied to a component’s VDD pin. A capacitor in the range of 10 uF acts as a larger buffer to smoothen low-frequency fluctuations. High-frequency changing in voltage is dealt with a smaller capacitor, typically around 100 nF. Why decoupling capacitor placement in PCB matters? Ever wonder what would happen if you skipped decoupling capacitors in your design? I’ve done that for curiosity and here are a few signs to look out for. An onboard microcontroller will have trouble operating as the voltage fluctuation can send it into brownout mode where it gets reset. Any attempts to get reliable ADC conversion will be futile, as the analog voltage supply is anything but stable. If you’re to send a PCB board that has no decoupling capacitors installed to the field, you’ll have weirder problems due to the greater electrical noises. So, does placing a few decoupling capacitors on the PCB solve the problems? It depends. The placement of decoupling capacitors is crucial to mitigating voltage fluctuations. If you’re not placing the capacitors at the right place, the effect will be minimal at best. In some cases, the wrong placement of decoupling capacitors can be a problem by itself, as it could pick up EMI coupled onto the copper trace. Where to place decoupling capacitor placement in PCB? Unlike finding the best spot for a modern vase, placing decoupling capacitors is easier. The golden rule of decoupling capacitor placement is to minimize the distance between the component’s voltage pin and the capacitor. This means you’ll need to place the decoupling capacitor as close as possible to the IC’s pin. If you’re designing a multilayer PCB, place the capacitor beneath the component’s pad. On a single-layer design, the capacitor is placed near to the pin and routed with a short trace. As mentioned, you’ll need a 10uF and a 100 nF capacitor to stabilize against low and high-frequency fluctuations. The 100 nF capacitor should be placed closest to the voltage pin followed by the 10 uF capacitor. Repeat the process for as many VDD pin on the IC. There are some cases where the lack of space prevents the 1 decoupling capacitor per pin principle. In such instances, you’ll still need a minimum of 1 decoupling capacitor per component. · Place the capacitor near the signal source: Decoupling capacitors should be placed as close as possible to the source for decoupling the signal. This means the caps should be placed on the pin for ICs and near the connector for I/O signals. · Connect capacitor in series for I/O signal traces: To remove low-frequency transients from input and output signals, the capacitor should be connected in series with the trace. High-frequency will pass through the capacitor, but low-frequency and DC will be blocked. Additionally, small caps should be used for high-frequency transients and large caps for low-frequency transients. · Put the capacitor in parallel for power pins and grounds: Decoupling the I/O signal paths and power distribution and grounding is not that important, but the elimination of AC or coupling of DC is critical. Therefore, the capacitor should be connected in parallel with the signal path. · To minimize high-frequency EMI, connect a capacitor in parallel with a resistor: Decoupling capacitors can also be connected in parallel with resistors to filter out unwanted HF while allowing LF and DC to flow through. · Connect the capacitor before the ground plane connection: Connect the capacitor to the component pin before connecting it to the via to reach the power plane. This ensures smooth current flow through the plane. · Place the capacitor on the same layer as the digital and analog ground pours: Decoupling capacitors can also be used to separate analog and digital signals. This is accomplished by connecting a capacitor between AC and digital PCB ground pours.Wanna know PCB knowledge? Check and read for more.
PCB Knowledge ⋅ 08/12/2021 17:03
How to Choose Components for PCB？
During the PCB assembly process, components are very important to affect the performance and quality of the finished boards. How to choose components for PCB? In this article, we will focus on the topic, if you are curious about the methods please check and read the content we provide to learn more knowledge.If you want to order PCB product, please check and custom your order online. What are the main factors before choosing components for PCB？ Performance and Design RequirementsPCB components must be selected keeping in mind the design and performance requirements of the individual circuit. The components play an essential role in enabling the PCB board to perform its intended function. Therefore, the person selecting the components must understand the exact functions of the PCB board that is being designed. Once the engineer understands the intricacies and functionalities of the particular design, they can choose the right PCB components to bring that design into fruition. Technological Innovations and AdvancementsThe latest advancements in web-based technology have made the task of component selection much easier. Smart digital tools for electronic component selection can be used by modern engineers to choose the perfect components for each PCB design. These web-based tools allow engineers to save time and money when selecting the PCB components. They can just check the online inventories of component manufacturers and select the components that they need for a particular design. Market Rates and Value AnalysisAn experienced engineer, who has a thorough understanding of PCB electronics will be able to accurately gauge the effectiveness of a specific PCB component vis-a-vis its market value. The engineer must also compare the price of a component to that of local products that are similar in design, or different versions of the same component. This will allow the engineer to choose the component that provides the best value for money and cost efficiency, allowing the business to gain a competitive edge over other companies operating in the field. Durability and LongevityOne of the most important factors that must be taken into account when selecting PCB components is the quality and longevity of the product. High-quality and durable components are always more beneficial and cost-effective in the long run, even when they are slightly more expensive at the time of purchase. A PCB board made from high-quality components will be more durable and require fewer repairs over the course of its life. For instance, using circuit breakers instead of fuses and software control instead of manual switches can dramatically increase the longevity of a circuit. Furthermore, high-quality and properly sized dissipative devices such as resistors, inductors, and semiconductors ensure that the internal temperature of the circuit board always stays within reasonable limits. Guidelines of choosing components for PCB Think about Component Footprint DecisionsThroughout the schematic drawing phase, consider footprint and landpattern decisions that will need to be made in the layout phase. See the following suggestions for things to consider when making component choices based on part footprints. Remember that footprints include both the electrical pad connections and the mechanical (X, Y and Z) dimensions of the part. This includes the body outline of the part as well as the pins that attach to the PCB. When selecting components, consider any housing or packing restrictions on both top and bottom sides of the final PCB. Some components (such as polarized capacitors) may have height clearance restrictions that need to be considered as part of the component selection process. When initially starting a PCB design, consider drawing a basic board outline shape and placing some of the larger or critically-placed components (such as connectors) that are planned to be used. In this way, a quick virtual rendering of the board (without routing) can be visualized to give a relatively accurate representation of the relative positioning and component heights of the board and components. This will assist in ensuring that the parts will fit inside the packaging (plastic, chassis, mechanical frame, etc…) after the PCB is assembled. Invoke the 3-D Preview mode from the tool menu to review your board. Landpatterns show the exact pads or hole shapes on the PCB to which the part will be soldered. These copper patterns on the PCB may also contain some basic shape information. The landpatterns need to be sized correctly to ensure proper soldering and to ensure proper mechanical and thermal integrity of the connecting parts. When designing the PCB layout consider how the board will be manufactured or if hand soldered, how the pads will be accessed. Reflow soldering (solder paste that is melted in a controlled oven) can handle a wide variety of surface mount devices (SMDs). Wave soldering is typically used to solder the backside of the board to fix through-hole components but can handle some SMD parts placed on the backside. Often with this technique, any bottom side SMDs will have to be orientated in a special direction and may to have pad modifications to be able to be soldered in this way. Component choices can change throughout the design process. Choosing which parts should be Plated Through Hole (PTH) or Surface Mount Technology (SMT) early in the design process can assist the entire planning of the PCB. Consider parts costs, availability, part area density and power dissipation among other things. From a manufacturing perspective SMD components are typically less expensive than through-hole parts and are typically more readily available. For small to medium prototyping projects, larger SMDs or through-hole parts may be preferred to facilitate hand soldering and to facilitate better pad and signal access for troubleshooting and debugging steps. Use Good Grounding PracticesMake sure the design has sufficient bypass capacitors and ground planes. When using ICs, make sure appropriate decoupling capacitors are used near the supply to a ground location (ground plane preferably). Appropriately sized capacitors depend on the application, the capacitor technology and the frequencies involved. When bypass capacitors are placed across the power and ground pins and located close to the appropriate IC pins, a circuit’s electromagnetic compliance and susceptibility performance will be optimized. Assign Virtual Parts FootprintsRun a bill of materials (BOM) to check for virtual parts. Virtual parts do not have footprints associated with them and will not be transferred to layout. Generate a BOM and review all the virtual components on the design. The only entries should be power and ground signals as these are considered virtual parts and are specially handled in the schematic environment and not the layout. Unless used solely for simulation purposes, parts that are shown in the virtual section should be replaced with parts having footprints. Ensure You Have Complete BOM DataCheck for adequate data in the BOM report. After running the BOM report, review it and work on populating any incomplete part, vendor or manufacturer information for all of these parts. Sort Reference DesignatorsTo assist in the sorting and reviewing of the BOM, ensure reference designators are contiguously numbered. Check Spare GatesTypically, all of the spare gates should have the inputs connected to a signal to prevent the inputs from floating. Make sure you review any spare or forgotten gates so that unwired inputs can be adequately connected, if required. In some cases, if the inputs are left to float, the whole system may not function properly. For example, consider a dual opamp used in a design. If only a single opamp is used in a dual-section IC part, it is suggested that either a single-section IC be designed-in or for the unused portions, a ground be placed at the input and an appropriate unity gain (or otherwise) feedback network be placed with the amplifier to ensure the correct functionality of the part.Wanna know PCB knowledge? Check and read for more.
PCB Knowledge ⋅ 08/11/2021 17:08
Solder mask matte VS glossy
As a very essential step of PCB manufacturing process, solder mask. Most fabricators will likely default to a gloss surface finish, the more popular choice of the two. How to choose matte or glossy solder mask for your boards? Please check and read the content we provide to learn more information.If you want to order PCB product, please check and custom your order online. What are the advantages of matte solder mask & glossy solder mask? Matte solder mask Your preferences in PCB appearance will also determine whether you’ll want a matte finish instead of a glossy solder mask. A matte finish may make some aspects of fabrication easier. However, an experienced PCB company will provide quality results regardless of solder mask finish. The potential advantages of a matte finish include: · Visibility during inspection: A matte finish does not have shine under any lighting used during inspection. As a result, you can more easily see the PCB’s details.· Problem detection: Matte finishes make problems more evident than glossy finishes. During inspection, it becomes easier to detect issues on a matte finish due to increased visibility.· Solder ball reduction: Research suggests that matte finishes reduce a PCB’s risk of solder ball formation. Data indicates that a lower gloss level on PCBs results in lower solder ball levels. Glossy solder mask Many of the benefits of a solder mask finish depend on the customer’s aesthetic preferences. You might choose a glossy finish over a matte solder mask due to: · Aesthetic value: Because of glossy finishes’ role as the default choice for solder masks, many customers consider them the classic PCB appearance. Their shine gives them what many perceive as a more modern look.· Appearance of wear: The reflective properties of a glossy finish tend to make signs of wear look less prominent.· Scratch resistance: Because of its harder surface, a glossy finish has higher scratch resistance than a matte finish. Why to choose glossy finish than matte finish? The main difference between a gloss finish and a matte finish is an aesthetic one, and many people feel that a gloss finish simply looks better. Gloss solder masks are shiny. They reflect light and look lighter, while matte finishes are dull and dark. Gloss solder mask has a hard shell finish while a matte finish is softer looking. Matte finishes may also scratch more easily and show residue or surface cosmetics better, although scratches on a gloss finish will show more. If you expect the look of your PCB will have a positive effect on your assemblers or anyone who may end up looking at them, you may want to go with the gloss finish. Just keep in mind that the high light reflectivity can be a nuisance to vision during assembly in some cases. As a PCB customer, you may want to choose a glossy finish over a matte finish when: · Appearance matters for your PCB: In applications where appearance impacts your PCB marketing, a glossy finish can help by increasing aesthetic appeal.· You have no specific preference: If you don’t have a particular finish preference, remember that glossy finishes serve as the industry default for most suppliers. Why to choose matte finish than glossy finish? Although it is no more cost-effective or efficient to choose a matte finish over a glossy one, there is one consideration that may cause some to prefer the matte finish, and it involves solder balls. If you are concerned that solder balls may be a problem for you, you may be inclined to choose a matte finish. This is because, while there are several factors that contribute to solder balls, one is the level of surface roughness. The smoother the surface, the more likely it is that solder will ball up. The theory behind this is that molten solder behaves differently on rough surfaces and smooth surfaces. On rough surfaces, it tends to form a convex shape, reducing the area solder balls can attach to, while on smoother surfaces it tends to take a concave shape. Since matte finishes are softer and more porous, as opposed to the smooth, hard shell of the glossy finish, many experts feel that a matte finish will result in fewer solder balls. With all of this said, glossy finishes are used all the time on PCBs, so you may not find this to be a particular problem. When you’re considering your choice of solder mask finish, you might prefer a matte option in these situations: · You want to streamline production as much as possible: When you consider production accuracy a top priority, a matte finish may give you more peace of mind during fabrication. However, skilled PCB companies should detect errors in either finish type.· Participation in quality assurance matters to you: If you plan to inspect your PCB yourself after production, a matte finish can help with the process. It shows errors more clearly for you to provide accurate feedback to your PCB manufacturer.Wanna know PCB knowledge? Check and read for more.
PCB Knowledge ⋅ 08/10/2021 17:26
PCB edge plating guidelines
Since plating is very common in PCB manufacturing, sometimes PCB manufacturers can extend this technique to edge plating, connecting the top and bottom planes of a PCB by electroplating around its external edges. In this passage, we will focus on PCB edge plating and please check and read the content we provide.If you want to order PCB product, please check and custom your order online. What are the applications of PCB edge plating? Several industries require edge-plated boards, especially in applications that require better support for connections such as for boards that slide into metal casings. Edge plating has other uses as well as it improves the current-carrying capabilities of the board, provides edge connection and protection, and offers the possibility of edge soldering to improve fabrication. Although edge plating on printed circuit boards is a simple addition in most cases, fabricators need specialized equipment and trained personnel for the process. Designers must take care that internal power planes do not come up to the edge, and fabricators must make sure there is a gap before they take up edge plating. Designers must make sure there is a band of copper on both edges of the top and bottom side, as the plating will connect to these copper bands. Now edge plating PCB has been widely used in many industries, particularly in applications that need better support for connections, for example for circuit boards that slide into metal casings. What’s more, edge plating has other benefits as follows: · Improve the current-carrying capabilities of PCB;· Offer edge connection and protection;· Offer the possibility of edge soldering to improve fabrication. In fact, PCB manufacturers need to fabricate the circuit boards with specialized equipment and trained personnel for the process although edge plating on printed circuit boards is a simple addition in many cases. In addition, designers need to make sure that there is a band of copper on both edges of the top and bottom side, because the plating will connect to the copper bands. So we will try our best to do the precise checks so that keep everything safe. For example, the PCB castellation should never lead the internal power planes to the edge of the circuit board, as it can make the edge plating short-circuited. What’s more, we need to make sure that there is a gap before the edge plating process while fabricating the circuit board for edge soldering. What is the process of PCB edge plating? As you know, there are a great deal of challenges for a multilayer PCB manufacturer mainly in how to prepare the plated edges and the life span adhesion of the plated material, what’s more, it needs the precision handling in PCB manufacturing that is used for edge PCB soldering. We can make sure that the PCB edge castellation thoroughly prepares edges surfaces, which applies the plated copper for prompt adhesion and processes the circuit board to make sure the long-term adhesion between each layer. Needless to say, we can control the potential hazard for plated through hole and edge plating with a controlled process during printed circuit board manufacturing for edge soldering. So the most important concern is the creation of burrs, which result in discontinuities in plated through hole walls and limits the life of adhesion of the edge plating. The outer contours, to be metalized, must be milled before through-hole plating process, as the metallization of the edges take place during this fabrication step. After the deposition of copper, the intended surface finish is finally applied to the edges. Fabrication Issues: 1. Copper Peeling -Plating over a large substrate surface can lead to the plated copper peeling due to a lack of adhesion strength. We address this by first roughening the surface through a combination of chemical and other proprietary means. Next, we employ direct metallization, which has a higher copper bond strength, to prepare the surface for plating.2. Burrs -Often edge plating, especially on castellation holes, can result in burrs from the final machining process. We apply a modified, proprietary process flow that results in the burrs being polished down to the edge of the feature. Fab Note: 1. The antenna position of the gold pad is too large, affecting customer soldering or signal transmission.2. The inner edge pad is connected to the wires on the board, resulting in a short circuit.3. The stamp hole is designed at the edging groove and must be handled in the 2nd drilling process.4. Through the process-related manufacture of the individual PCBs as a panel, a continuous metallization of the outer edges is not possible. No metallization can be applied where the small panel bridges are located.5. One request, the slide plating metallization can be covered with solder mask. When purchasing edge plating boards, you must confirm with your PCB supplier the possibility of manufacturing PCBs with plating process, and extent to which the fabricator can edge plate the PCB. Your Gerber files or fab drawing should indicate in a mechanical layer where they need slide plating, and the surface finish they need on it. Most manufacturers prefer a selective ENIG as the only surface finish suitable for round castellation. What is the limitation of PCB edge plating? Because fabricators need to hold the circuit boards within the production panel in PCB prototype, they can’t plate the complete-length edge. Therefore, there are some gaps required to place rout tabs. It needs routing the circuit board profile at the place when fabricating the circuit boards with edge plating, and the edge plating is required before starting the process of through-hole plating, which remove v-cut scoring on a PCB that needs to undergo edge plating.Wanna know PCB knowledge? Check and read for more.
PCB Knowledge ⋅ 08/10/2021 17:18
HDI PCB design guidelines
High density interconnects (HDI) layout refers to a set of techniques used to layout a PCB when traces widths generally drop below 8 mils (0.2 mm). These techniques are designed to ensure you can fit a higher density of components onto a single board, allowing you to keep your board size small while increasing component count. Not all boards need HDI layout techniques for a number of reasons, while some components require HDI techniques for proper routing.If you want to order PCB product, please check and custom your order online. What are the features of HDI PCB design? An HDI board requires smaller vias to make layer transitions, particularly in fine-pitch BGA components and more traces per sq. mm. In order to accommodate fine-pitch components, you'll find the following typical features in an HDI layout: Smaller vias: HDI boards use microvias (mechanically or laser drilled), blind/buried, and staggered vias for layer transitions. These vias have smaller aspect ratios than typical through-hole vias. In order to use these vias with finer pitch components, their diameters are smaller, which then limits their useful depth. Thinner traces: The thinner traces used in HDI boards are required to make connections to vias on each layer, as well as to in-pad vias. The thinner traces also allow higher trace density, thus the term HDI. Higher layer count: We've built non-HDI boards with high layer counts, but HDI board layer counts can easily reach 20 or more layers when working with high pin density components (e.g., FPGAs). Lower signal levels: HDI boards are not used for high voltage or high current. This is because the high field strength between neighboring lines will cause ESD, and high currents will cause excessive temperature rise in conductors. What are the technologies of HDI PCB design? The difficulties of HDI PCB fabrication lie in micro-via fabrication, via metallization and fine lines. 1. Micro-via fabrication Micro-via fabrication has always been the core problem in HDI PCB manufacturing. There are two main drilling methods: 1). As for ordinary via drilling, mechanical drilling is always the best choice for its high efficiency and low cost. With the development of mechanical processing capacity, its application in micro-via has been on the way as well. 2). There are two types of laser drilling: photothermal ablation and photochemistry ablation. The former refers to the process during which the operated material is heated to be melted after absorbing laser with high energy and is evaporated off with via formed. The latter refers to the result caused by high-energy photons in UV zone and with laser length more than 400nm. 2. Via metallization The biggest difficulty for via metallization is it is difficult for plating to reach uniform. As for the deep-hole plating technology for micro-via, besides the usage of plating solution with high dispersing power, via plating solution on plating devices should be upgraded in time that can be accomplished by either strong mechanical stirring or vibration, ultrasonic stirring, horizontal spraying. Also, the humidity of via wall must be increased before plating. 3. Fine lines The implementations of fine lines include traditional image transfer and laser direct imaging. Traditional image transfer has the same process with the ordinary chemical etching to form lines. As for laser direct imaging, photographic film isn't needed while images are formed directly on photosensory membrane through lasers. UV wave light is used to operate so that liquid anti-corrosion solution is capable of meeting demands of high resolution and simple operation. What are the basic HDI PCB design guidelines? When working with fine-pitch BGA, and the traces and vias that connect to it, there are some basic guidelines that apply to any HDI layout. 1. Always check your manufacturer's capabilities. You should generally do this anyways before planning a new design, but nowhere else is this more important than in HDI design. Not all manufacturers have the same capabilities in this area, and it's best to check with your desired manufacturer before you create an HDI layout that can't be fabricated. 2. Keep track of spacing between traces and pads. The same idea applies in 1 mm pitch BGAs, the only point that changes is scaling to microvia sizes. Solder mask clearance values are typically on the same size as your trace width. The solder mask clearance depends on the pad size and your pad pitch. 3. Don't use staggered vias or ELIC if you don't need them. The whole point of HDI routing is to provide as much space as possible for routing on the surface and inner layers. While it might be tempting to stack across the entire span of the substrate, don't take up the extra space unless it's really necessary. 4. Opt for fewer layers. High layer count boards bring more assembly steps and manufacturing costs. If you follow the previous guideline, you can significantly reduce the cost per board. 5. Don't forget about signal integrity when working with HDI boards. Any HDI layout will need to be designed with high speed design guidelines in mind, or high frequency guidelines if you're working with an RF board. The same signal integrity rules that apply in typical PCBs still apply in HDI PCBs, it's just a matter of scaling. In an HDI board that requires impedance controlled routing, you'll need to carefully design your traces and stackup to ensure your impedance is consistent with your signaling standard.Wanna know PCB knowledge? Check and read for more.
PCB Knowledge ⋅ 08/09/2021 17:29
EMI and EMC in PCB design
There are multiple alternative automated EMI/EMC tools during the PCB design process. In this article, we will provide you every detail about EMI and EMC in PCB design. Please check and read the content we prepare below and learn more professional knowledge.If you want to order PCB product, please check and custom your order online. What are PCB design rules for checking tools? PCB design is so complicated that numerous layers and lines are concerned in it. For engineers, it's quite difficult and boring to manually check the routing of each EMI/EMC key network. Automated tools are capable of extracting PCB design from CAD files and reporting positions violating design rules to users. Generally speaking, these software tools can allow users to predetermine design rules as limiting condition and can even create new rules under the condition of available PCB technologies and speed. PCB rule checkers can be repeatedly applied during the period of PCB design in order to ensure the design without violating important EMC rules. If PCB is only examined in the final design step, modification in accordance with rules will possibly take much time and even can't be implemented. The examination of multilayer PCB design during the period of design results in the avoidance of large-scale modification based on EMC rules following. PCB design rule checker runs at a very large speed and examines the design rules of each PCB. Nevertheless, these tools just simply provide some hint for users and fail to provide instructions according to the order of severity concerning rules breaking. Some newly-presented PCB software checking tools are capable of associating phenomena of rules breaking and reflecting the information about data rate of signals and degree of rules breaking, which is beneficial for designers to eliminate specific occurrence of rules breaking. What are simulation tools in PCB design? Simulation tools are applied to accurately analyze a small part of overall system. No matter how great screen captures suppliers provide, present EMI/EMC modeling tools fail to do "all the work" since modeling can't replace software engineers and it is only one of tools used by EMI/EMC engineers. EMI/EMC engineers are required to determine which design part that is in need of forward analysis and modeling. Generally speaking, multi-grade model is required to be established on unresolved issues and the simulation result of the model at the last grade supplies input information to the model at the next grade. This method makes model optimized by separately processing the special issue in each part and integrating the results. Therefore, compared with the modeling for one time that is too "pushy", multi-grade simulation is capable of analyzing issues with larger scale. Besides, EMI/EMC engineers need to better understand the problem and modeling technology so as to find out more multi-grade simulation points of division. a. Quasi-static simulators Quasi-static simulators are applied to extract parameters of inductance, capacitance and resistance of system components such as electrical parameters of connector. However, the dimension of components has to be far smaller than the wavelength of harmonic wave with the largest frequency. This type of tools is capable of quickly calculating the parameters of equivalent circuit and parameters can be applied in circuit simulators such as SPICE. One of conditions in terms of implementation of quasi-static condition lies in the requirement that modeling object has to be with small electric size. This type of simulation consists of electric field and magnetic coupling without transmission delay of waves, which is because that modeling object has such a small electric size that it fails to cause delay to coupling between electric field and magnetic field. If components fail to meet the requirement of small size, full-wave modeling method has to be applied. b. Full-wave simulation tools Different from quasi-static simulators, full-wave simulation tools have no requirement of small electric size to components. Instead, Maxwell's equations are fully solved without simplification and numerous types of styles are available for full-wave electro-magnetic modeling technology. As the best simulation technology, full-wave simulation tools have become the most commonly-used simulation tools of developers and educators while it receives the most argument as well. Lots of full-wave simulation technology is only applied in specific structures and calculation method modification for different problems is so complicated. Some full-wave simulation technology isn't generally applied, requiring deep understanding in terms of electric-magnetic knowledge and modeling technology. Moreover, some are only applied for far field such as the determination of radar section of a military device. Different full-wave simulation technologies feature advantages in different aspects and the best modeling technology is to find the specific simulation requirement that is suitable for a certain problem. The most pervasive EMI/EMC full-wave simulation modeling technologies include method of moment (MoM), finite difference time domain (FDTD) technology, finite element method (FEM), transmission line matrix (TLM) and partial element equivalent circuit (PEEC) technology. These different full-wave simulation technologies are actually different manifestations of Maxwell's equations. For example, MoM applies integral equation of Maxwell's equations. Conductors/metals are required to be cut into units with small electric sizes (The current on each stage of conductor is supposed to be constant). The current and all the currents on other component units can be calculated through source. As soon as the current on all the conductor units is obtained, the overall generated electric field and/or magnetic field can be calculated at last. • FDTD: The differential form in Maxwell's equations is applied in FDTD with the adjacent medium to be air and common modeling takes place with the combination of metal and dielectric. The space compatible with simulation objects is divided into volume elements with small electric size. Each volume element is defined by dielectric constant (ε), magnetic conductivity (μ) and conductivity (δ). As the name indicates, FDTD is mainly applied in time domain so model is capable of receiving wide-band response with pulse as excitation function. After the simulation of FDTD, time domain solution can be transformed into frequency domain solution. • FEM: It is another type of form in Maxwell's equations, whose typical application is frequency solution. Similarly, the air in the model and all the other materials has to be divided into units with small electric sizes. Variational technology is applied by FEM to solve Maxwell's equations. • TLM: As another form in Maxwell's equations, the typical application lies in time domain solution. Basically, the space area of modeling objects is divided into multiple 3D transmission line nodes on each of which transmission/reflection can be inferred by node impedance. Each unit is compatible with one node. • PEEC: This technology is the newest full-wave method in the field of EMI/EMC with integral form in Maxwell's equations in which all relationship between unit fields is replaced by circuit relations. The connections between all units are implemented by local mutual inductance and capacitance. Solvers such as SPICE are applied to simulate overall circuits and solution current and voltage parameters are transformed into fields like MoM. Up to now, simulation tools become so powerful that engineers have to depend on them. However, they fail to replace engineers' basic understanding on electromagnetism and EMI/EMC design. For primary simulation, novice engineers are suggested to take some training and refer to some learning materials to master how to divide overall product/device into multiple simulation modules and explain the simulation result. Finally, they should learn to verify whether the simulation results can correctly reflect modeling objects and ensure compatibility with basic physical theories.Wanna know PCB knowledge? Check and read for more.
PCB Knowledge ⋅ 08/09/2021 17:20
How to check quality of PCB?
During the PCB manufacturing, it’s very important to control the quality of the finished boards. However, how to check quality of PCB products? In this passage, we will focus on the topic, please check and read the content we provide to learn more professional PCB knowledge.If you want to order PCB product, please check and custom your order online. Why to check quality of PCB? Printed Circuit Boards are the most used and basic assembly unit applied by all types of electronic devices. All functions and performance of devices are implemented mainly by PCBs. PCB is the heart of electronic devices and both their quality and reliability is directly correlated with quality and reliability of electronic equipment. Nowadays, intelligence and miniature of electronic devices leads to increasingly smaller size and complicated structures of PCBs. In terms of PCB performance, it can be testified that even if schematic is correctly designed, subsequent assembly and debugging will still be influenced if PCB design and manufacturing receive low-qualified processing while undemanding quality inspection is carried out on PCBs. Therefore, it's especially important to implement quality control in the process from PCB design to PCB manufacturing. The task in quality control of PCBs comes primarily in effective administration, monitoring and measurement on PCB design, circuit board manufacturing and PCB inspection. How to do quality control in PCB design? In order to ensure quality in PCB design, your task should cover the following three aspects. • Validity of PCB design file has to be ensured Project leader should be responsible for checking PCB design file and corresponding approval procedures have to be implemented so that validity of PCB design files has to be ensured. • Manufacturability of PCBs has to be ensured Project leader and technologist should strictly conform to technological requirement in order to ensure manufacturability of PCBs. Technological requirement can be directly listed on design drawings if it is relatively simple. Otherwise, it has to be summarized into a text that is saved in additional file. No matter what is the simplicity of technological requirement, it has to be explained ACCURATELY, CLEARLY and REASONABLY. Technological requirement after checking should not only meet the present production craft level with high cost effectiveness but also leave much convenience to implementation of subsequent assembly, debugging and checking. As a value-added option for our Assembly services, we offers Free DFM Check. If any issues were detected, our engineers would get in touch with you immediately to solve the issue as quickly as possible with you prior to scheduling PCB manufacturing accordingly. • Testability and Normalization has to be ensured Standardiser implements normalization checking in terms of test points, structural style, dimensions, routing, through-hole via and characters so as to ensure testability and manufacturability of PCBs which should conform to requirement of national and industrial standardization. How to do quality control in PCB manufacturing? In order to ensure quality in PCB design, your task should cover the following three aspects. • Capability of manufacturers has to be ensured Quality department, together with sourcing department should investigate and approve aptitudes and manufacturing capability of PCB manufacturers in order to ensure their sufficient manufacturing capability on your design project. PCBBUY features extended custom PCB manufacturing capabilities for a comprehensive range of PCBs including Aluminum PCB, HDI PCB, High-Tg PCB, Halogen-free PCB, Flex PCB, Flex-rigid PCB, etc. and PCB Assembly services. • Checking and confirmation have to be constantly done prior to manufacturing PCB designers have to check and confirm the design drawings that will be applied by manufacturer for many times prior to manufacturing. Since PCB design can't be successful just after one trial and modifications have to be made time and time again, PCB manufacturers will hold multiple versions of design drawings. So it's necessary to carefully check and confirm the final design drawing provided by manufacturer prior to practical manufacturing so that manufactured PCBs conform to requirement of the last version. • Much attention should be paid to the key procedures of PCB manufacturing The quality of key procedures of PCB manufacturing influences a lot on performance and reliability of PCBs and quality control on that has to be strengthened. The key technological procedures formulated by PCB manufacturer have to be monitored and checked including etching, via mentalization etc. so as to ensure absence of burr, gap, bridge defect and void. Furthermore, quality control has to be overtaken on stacking of multi-layer PCBs in order to ensure the thickness, adhesive intensity and positional accuracy. Since gold plating is usually required by high-frequency PCBs and micro-strip boards, specific gold plating operation instructions have to be made in order to ensure the thickness and purity of plating plane. Quality Control in PCB Inspection Quality control in PCB inspection refers to monitoring and measurement of PCBs in strict accordance with inspection through visual inspection or the application of professional equipment. The inspection result has to be stored. If special requirement needs obtaining, specific acceptance rules have to be made additionally. Specific PCB inspection items will be introduced in subsequent articles.Wanna know PCB knowledge? Check and read for more.
PCB Knowledge ⋅ 08/09/2021 17:14
PCB inspection standard
After PCB fabrication, inspection has to be carried out in order to determine whether the quality is compatible with design requirement. It can be put that quality inspection is the important insurance of product quality and smooth implementation of subsequent procedures. In this passage, we are going to tell you the standard of PCB inspection methods.If you want to order PCB product, please check and custom your order online. What is inspection standard? PCB inspection standard comes primarily in the following aspects: a. Standards made by each country;b. Military standard of each country;c. Industrial standard such as SJ/T10309;d. PCB inspection operation instruction enacted by device supplier;e. Technological requirement labeled on PCB design drawings. For PCBs that have been determined as a key board in a device, besides regular inspections, those key characteristics parameters and indexes have to be focused and inspected from head to toe. What are the inspection items? No matter what type of PCBs, they have to go through similar quality inspection methods and items. Based on inspection method, quality inspection items usually include visual inspection, general electrical performance inspection, general technological performance inspection and metalized via inspection. • Visual inspection With the help of ruler, vernier caliper or magnifying glass, visual inspection is simple to be carried out. The inspected content includes: a. Board thickness, surface roughness and warpage.b. Dimensions of appearance and assembly, especially assembly dimensions compatible with electric connectors and lead rail.c. Integrity and clearness of conductive patterns and existence of bridging short circuit, open circuit, burr or voids.d. Surface quality, existence of pit, scratch or pin holes on printing traces or pad.e. Positions of pad vias and other vias. It should be inspected that whether vias are missed or inaccurately punched, whether via diameter is compatible with design requirement or not and whether there are nodules and voids.f. Pad plating quality and extent of firmness, roughness, brightness and void of bulge defect.g. Coating quality. Whether plating flux is even and firm and position correct and whether flux is even and its color meets concerning requirement.h. Character quality such as whether they're firm, clear and clean with no scratch, penetration or disconnection. • General electrical performance inspection There are two kinds of tests under this type of inspection: a. Connecting performance test. During this test, multimeter is generally applied to inspect the connectivity of conductive patterns with focus on metalized via of double-sided PCB and connectivity performance of multi-layer PCB. For this test, PCBCart provides general inspection before each fabricated PCB leaves its warehouse in order to ensure the implementation of its basic functions.b. Insulating performance test. This kind of test aims to inspect insulating resistor on the same plane or between different planes in order to ensure the insulating performance of PCB. • General technological inspection General technological inspection covers solderability and plating adhesion inspection. For the former, wetting performance of solder to conductive patterns is inspected. For the latter, it can be inspected by qualified tips that are first sticked to plating plane to be inspected and then are pulled off quickly after even pressing. Next, plating plane should be observed to ensure whether fall-off takes place or not. Furthermore, some inspections can be selected based on practical situations such as copper foil anti-falling intensity and metalized via anti-pulling intensity. • Metalized via inspection Quality of metalized vias plays a role of extreme significance for double-sided PCBs and multi-layer PCBs. Lots of breakdown happening to electric module or even the whole device lies in quality issues of metalized vias. Therefore, it's quite necessary to pay more attention to the inspection of metalized vias. Metalized via inspection covers the following aspects: a. Metal plane of via wall should be complete, smooth and void of empty holes or nodules.b. Electrical performance inspection should be carried out in accordance with short circuit and open circuit of pad and metalized via plating plane, resistance between via and leads.c. Resistance change rate of vias shouldn't be over 5% to 10% after environmental test.d. Mechanical intensity refers to adhesive intensity between metalized via and pad.e. Metallographic analysis test is responsible for inspection in terms of plating plane quality, thickness and uniformity of plating plane, and adhesive intensity between plating plane and copper foil. Metalized via inspection usually comes in combination of visual inspection and mechanical inspection. Visual inspection is to observe PCB with it placed under the light and complete and smooth via wall is capable of reflecting light evenly. However, via wall containing nodules or voids won't be so bright. For volume manufacturing, inspections should be implemented by on-line inspection equipment such as Flying Probe Tester. Owing to complicated structure of structure of multi-layer PCBs, once problems are observed in the process of subsequent unit module assembly testing, it's difficult to position breakdowns quickly. As a result, inspection of their quality and reliability has to be very strict. Apart from regular inspection items mentioned above, other inspection items include the following parameters concerning resistance of conductor, resistance of metalized vias, short circuit and open circuit of inner layers, insulating resistance between all lines, adhesive intensity of plating plane, adhesion, anti-heat shock, impact resistance to mechanical shock, current intensity etc. Each index has to be obtained through the application of professional equipment and methods.Wanna know PCB knowledge? Check and read for more.
PCB Knowledge ⋅ 08/09/2021 09:32
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