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PC Board Debugging & Troubleshoot Guidelines

PC Board Debugging & Troubleshoot Guidelines

Engineers have to test the PCB thoroughly to see if it’s functional and fulfills its purpose of design. But, some manufacturers don’t do it which leads to intermittent issues or PCB failure, and such issues are hard to deal with while debugging. Whereas it becomes a disaster if a PCB fails in the field. You can avoid PCB issues by testing it thoroughly, besides it should be built by a good manufacturer. First, you should know the basic troubleshooting methods, so let’s begin.

Basic PCB Troubleshooting and Debugging

PCB of a printed circuit board has copper traces and insulators to connect heavy components to develop an advanced circuit. It is a great challenge to troubleshoot a circuit board in terms of thickness, size, signals, layers, and the types of different components as they are all very important.
Some circuit boards are simple and don’t need a deep inspection, but there are also complex PCB designs that need special tools for troubleshooting. Generally, the basic test is easy to do through ordinary equipment to assess the currents, traces, and signals on the PC Board.

Choosing the Right Tools

Simple troubleshooting of a Printed Circuit Board involves a few tools, such as a multimeter which is quite common. But, deep troubleshooting of complex boards depends on high-end tools, especially if the problem is big. Like, you will have to use the oscilloscope, an LCR meter, a logic analyzer, and the power supply to assess a circuit board’s response in terms of function.

A Visual Inspection

Initially, you have to test your circuit board visually to see some obvious issues, such as overheating, overlapping of traces, burnt or damaged components, as well as the missing parts of a PCB. You can detect the burnt components through smell as they are not easy to detect otherwise. PCB components often get burnt due to overheating or excessive current. Sometimes the components bulge due to high temperature or heat which helps you identify the damage, like in the case of electrolytic capacitors.

PC Board Debugging & Troubleshoot Guidelines
PC Board Debugging & Troubleshoot Guidelines

Physical Testing

After visual inspection of your PCB comes the physical testing by applying the power to the board. You can easily find hot spots on the circuit board by touching its surface. So, you don’t need a costly thermographic camera to find heated areas. After finding the hot parts, you should cool them with compressed air to see how PCB components function at low temperatures.

How To Troubleshoot Or Debug A PCB Deeply

Experts use four techniques for PCB tests which come up with both pros and cons. Some common methods are ICT, cable scan, flying probe, and a functional test, so let’s study them one by one.

1: The Flying Probe Technique

This method of PCB troubleshooting involves multiple probes that check the PCB by flying around. Like, there are two to six probes in this case. This technique is ideal for large circuit boards, like backplanes. It is also cheaper than the ICT, and it debugs the pcb assembly issues that occur due to poor solder connections. The flying probe also checks components’ presence and their polarities and different values. It is a simple test and can handle the revisions of a PCB.

Cons of The Flying Probe

The flying probe techniques have some flaws in terms of PCB functionality testing, unlike ICT. The flying probe also works slowly compared to ICT because several probes contact the entire PCB testing points. However, it is ideal for low volume PCBs and its total cost is also lower than other techniques.

2: ICT Or In-Circuit For PCB Troubleshoot

The ICT is a PCB testing technique that involves multiple probes which are also called the bed of nails. In this process, the ICT probes connect with the testing points of the entire PCB to check its circuits to see if the assembly is correct or wrong. Like, it tests the bad solder joints or short circuits.

This method can perform even a deeper test by adding other modules or adapters to it. ICT also tests the overall function of PCB and values of the critical components.

Cons Of ICT

Though ICT is a great tool for PCB testing, it has some disadvantages too. Like, it has costly fixtures ranging from $8000, and they go up to $ 15000. Besides, the cost increases with any changes in the technique.

You can have maximum benefits from ICT if the technician knows the testing software and other tools. ICT is the best method for large volume testing.

3: The CableScan

Another troubleshooting technique is the cablescan, which is ideal for PCBs with several connectors having a complicated interface, like the backplanes. The tester attaches the cablescan with the circuit board and it tests all the pins against each other to evaluate the assembly issues, like a solder opening or shorts.

Cablescan also helps check jumpers’ configuration and quality of the diode, besides, it also accesses the capacitance and resistance.

Cons Of Cablescan

There are some flaws with cablescan due to its limits. Like, you have to see the size of the connectors it can test in one go. Moreover, it involves an additional cost to create the hardware interface.

You have to get wetting connectors, but their wiring with the system gets delayed due to the cost or other issues. The cablescan technique and its setup take lots of time, depending on the number of connectors and their complexity.

4: Functional Testing Technique

Another essential thing is to see if a PCB is ready to function or not. The functional test consists of test probes, software, and connected cables, and it determines PCB behavior according to design specifications.

The CM can also create the hardware and software or test fixtures to test the PCB function. This process is ideal for simple and small PCB layout designs. The engineers also develop fixtures for a bench test and make a plan to target the assembly issues involving less time and cost to assess the components. The functional test also helps see if the entire circuitry is working as you want. However, you need detailed debugging to find different faults and remove them.

Role of Engineers and Technicians In PCB Troubleshooting

You need experienced people to troubleshoot a PCB, such as engineers and technicians. Besides, these experts should know how to use the testing tools. Like, in the case of ICT, the engineer should know how to test the semiconductor. He should also know the DFT, end-user applications, as well as ICT optimization. The knowledge of hardware and software development is equally important.

When it comes to the cablescan, the troubleshoot company should have a huge inventory of already built connector interfaces. You can reduce the development cost and time by having all resources in hand.

Likewise, the technicians should debug with a flying probe according to the circuit board. In other words, the testing method should be compatible with the PCB design.

Most engineers use the LabView for a functional test, as it works according to the frequencies, variable supply levels, and several other PCB requirements. Such a deep examination of the PCB involves less amount of hardware, unlike surface-level testing.
Both basic and deep troubleshooting methods help you to find the right PCB issues, leading to an effective product by removing those issues.

Frequently Asked Questions

What Is ICT In PCB Troubleshooting?
ICT is a PCB testing technique that involves multiple probes which are also called the bed of nails. The ICT probes connect with the testing points of the entire PCB to check its circuits to see if the assembly is correct or wrong.
What Is The Flying Probe In PCB Debugging?
This method of PCB troubleshooting involves multiple probes that check the PCB by flying around. There are two to six probes in this case. This technique is ideal for large circuit boards, like backplanes. It debugs the assembly issues that occur due to poor solder connections.

What Is The Role Of A Functional Test In PCB?
The functional test consists of test probes, software, and connected cables, and it determines PCB behavior according to design specifications. The functional test also helps see if the entire circuitry is working as you want.
Is Basic Troubleshooting Enough For Circuit Boards?
No, the basic testing involves only visual and physical tests at basic levels. You need deep testing with specific tools, especially for complicated circuits.

Final Thoughts

PCB of a printed circuit board has copper traces and insulators to connect heavy components to develop an advanced circuit. It is a great challenge to troubleshoot a circuit board in terms of thickness, size, signals, layers, and the types of different components as they are all very important.
Some circuit boards are simple and don’t need a deep inspection, but there are also complex PCB designs that need special tools for troubleshooting. Generally, the basic test is easy to do through ordinary equipment to assess the currents, traces, and signals on the PCB. Whereas deep troubleshooting involves different techniques.
Would like to know more about PCB debugging, troubleshooting printed circuit board assembly? Email us at sales@pnconline.com

PC Board Fabrication, V-Scoring-Purpose and Benefits

PC Board Fabrication, V-Scoring-Purpose and Benefits

PCB or a printed circuit board has different holes, cuts, and elements, and V-scoring is one of them. V-scoring pre separates the PCB and designers also call it V-groove because a groove resembling V is cut on the circuit board’s top and bottom. Generally, the depth of the groove is 1/3 of the board depth and there is a thin layer between two Vs for the board processing.

The boards with V-grooves are either end to end or side by side with adjacent edges. The groove helps break boards with a little force, and you can divide a single panel into several parts with the help of V cuts.

Purpose of V-Scoring

Manufacturers use V-scoring while combining an array’s circuit boards for an effective assembly. It makes the assembly process less hectic, and you can easily set apart the assembled PCBs.

V-scoring helps to reduce pressure during the placement of SMD components on the circuit board by an SMT machine, and while separating the assembled PCBs.

The PCB panel helps manufacturers to insert the components at a high speed, using one panel at a time, rather than one circuit board.

The panel boards are loaded with their parts through an automated machine that performs the pick-and-place function.

These uses motivate PCB engineers, manufacturers, and buyers to use the V-grooves.

Specifying V-Scoring

Engineers specify V-scoring according to the groove depth, or a distance between the two grooves or Vees through a cross-section. The residual material in this case is known as Web. Each measurement has to be equal, including 1/3rd on the top, bottom, as well as a 1/3 web in the center.

The practice of the 90 degrees or the 30 degrees scoring is also there in some cases. However, the 90 degrees scoring is easy to break compared to the 30 degrees scoring.
You can alter these measurements according to your needs, depending on the array size and the ease of separating the boards later on.

You have to use a 30-degree cutter for a score-line cutting with a certain depth. You can calculate the rest of the web based on the material thickness. However, the tolerance of +/- .002″ is essential in this case.

When to Use a Jump Score

Jump score is used in some conditions though it is not that common. In jump score, the score does not go from one end to another, instead, it ends before the circuit boards end. Like, the cutting blade stops before another end comes. The jump scoring provides a firm array while assembly.

Some V-Scoring Terms

There are certain terms to consider while making PCBs with V grooves, and we will discuss them one by one.
• PCB board has some borders or extra material that helps in making a panel, and they are called Rails or Waste Tabs. They enhance a panel’s mechanical strength, allowing an extra material or borders that help to clamp a panel while assembling.
• Another term used in V-scoring is Fiducials which are marks being etched on the borders or a PCB’s inner surface, like on upper and lower layers of copper. Fiducials help the SMT assembly to identify the position of the PCB and SMD components.
• The other important elements are tooling holes located on a PCB’s four corners. The manufacturers use these holes to align a PCB during drilling and routing. Like, the alignment that involves the SMT carriers, solder plate printing, and PCBs’ final assembly.

Process of V-Scoring

It involves two blades being beveled at 30o, or 45o, or 60o, and the blade resembles a wheel with several gears or knives that make V-grooves. Both top and bottom blades rotate while cutting. When the PCB assembly is over, an individual assembly of the board occurs by dividing the sub panels.

Rules To Follow In V-Scoring

Some fabricators think that the perfect size of the board is compatible with an 18”×24” sheet of CCL, but this is not so. Because the fabricator has to use some part of the sheet while processing. Both customer and manufacturer should discuss the kind of a PCB they require, besides, it should be the best.

Some Rules for Exceptional Circumstances

1. There should be zero space between two circuit boards
2. If you opt for V-scoring, your PCB’s size should be at least 75×75 mm, and it can go up to 450 x1250 mm. So, the scoring won’t be successful if the board size is not as per the rule.
3. Make sure the V-scoring path or line is straight, whether it’s continuous like end to end, or discontinuous like jump scoring.
4. For a perfect V-groove, the minimum thickness of the board should be 0.6mm.
5. You can choose the groove angles from 30o, 45o, or 60o.
6. The space between the PCB edges and parts should be a minimum of 6.35 mm
7. The minimum distance between the PC Board Fabrication outline and V-grooves’ line has to be 0.35mm.

Benefits of V-Scoring

• V-scoring helps to use a PCB surface effectively
• It helps reduce the manufacturing cost by fabricating many boards on one PCB.
• It helps to place more than one circuit through one assembly, helping in precise sub-assembly.
• V-scoring tools are cost-effective, portable, and require minimum maintenance.
• It helps save time as it allows you to separate different parts from a final assembly.

Drawbacks of V-Scoring

There are some restrictions of V-scoring like it is not suitable for PCBs with components placed near edges.
V-scoring can affect the PCB structure, reducing its strength due to the mishandling of a solder machine. However, fabricators apply jump scoring to maintain a PCB’s strength. You can read the above section to understand the jump scoring.
In the case of V grooves, you have to allow a 0.05 inches clearance between the grooves and components. The blade should not come between the components, especially for taller parts. Likewise, you should keep enough clearance for components located on the wide connection surface.

Difference Between PCB Scoring and PCB Panels With Tab-Routing

The PCB design determines if you should choose V-scoring or tab-routing. However we have a guideline for better selection, but you have to follow it.
1. The circuit board shape helps to select the right scoring. Like, V-scoring is suitable for rectangular or square PCBs, whereas the tab-routing goes well with an irregular shape.
2. You should choose a tab-routing if the components are hanging on the PCB edges. Besides, the tab-routing does not affect the edge quality. Whereas V-scoring makes edges rough.
3. V-scoring works faster than tab routing, besides, it is cost-effective than tab-routing in terms of labor.
4. At the same time, there is less wastage of material in V-Scoring compared to the tab-routing, which also reduces the total cost.
5. It also depends on the number of boards in an array and the number of PCBs in both directions, including the X and Y planes.

Frequently Asked Questions

What Is The Difference Between The PCB And PCBA?

The process is the same, but it involves two stages. Like, PCB is just a circuit board with components, whereas PCBA is an assembled board with necessary components, and it is ready for application.

What is Jump-Scoring and Its Use?

Jump scoring involves a cut that starts from one end of PCB but it stops before the other end, unlike V-scoring. Jump scoring strengthens a board for multiple processes.

What Is Tab-Routing In PCBs?

Tab routing helps you to process different circuit boards on one panel. It also helps you to isolate boards by breaking the tabs that exist between various boards.

What Is The PCB Penalization?

A process of connected small boards in a single array is called the PCB penalization. It helps fabricators to move the circuit boards while assembly.

What SMT Stands For In PCB?

SMT stands for Surface Mount Technology, and it’s a process of installing the electrical components on the PCB directly. Whereas the component installed through SMT is known as SMD or Surface Mount Device.

Final Thoughts on V-Scoring

PCB fabrication becomes economical by adopting cost-effective processes, including V-scoring. The boards with V-grooves are either end to end or side by side with adjacent edges. The groove helps break boards with a little force, and you can divide a single panel into several parts with the help of V cuts.

It involves less routing space, so you can add several rows in the PCB panel to be fabricated. It eliminates the wastage of the laminate, besides, V-grooves also save money and time by streamlining the PCB processing and manufacturing.

V-scoring helps to reduce pressure during the placement of SMD components on the circuit board by an SMT machine, and while separating the assembled PCBs.

V-scoring tools are cost-effective, portable, and require minimum maintenance. Moreover, it helps save time as it allows you to separate different parts from a final assembly.
But, V-scoring can affect the PCB structure, reducing its strength due to the mishandling of a solder machine.

Interested to know more about V-scoring or PCB assembly services, email us at sales@pnconline.com

PC Board Fabrication for High-Speed Circuits

PC Board Fabrication for High-Speed Circuits in Pcb Assembly

PC Board Fabrication for High-Speed Circuits?
PC Board Fabrication

If you have seen printed circuit boards (well, I am sure you have seen one) then you must wonder how they are made and how they are managing your electrical devices. Nowadays, a multiple-layer printed circuit board is managing the most critical electronic devices. From your laptop to your phone and other devices are relying completely on printed circuit boards. Printed circuit boards may seem uninteresting to you but once you get deep into it, it’s an interesting and worth knowing subject. Let’s imagine, how a printed circuit board is working in the device you are using right now, and it will boost your interest. Now the question may arise about the manufacturing of the circuit board. How is a printed circuit board manufactured and prepared?

There are few rules in the designing and manufacturing of printed circuit boards that need to be followed. The material being used in the circuit board matters a lot. The main purpose of the material is to provide insulation between the conducting layers of the copper foil and pass electricity. Essentially four basic layers need to be followed in manufacturing a printed circuit board. The format of these layers is:
• Silkscreen
• Solder mask
• Copper
• Substrate

Initially, there were only two choices available for the PCB’s. One is a rigid circuit and the oter is a flexible circuit. Now as the electronics industry has been developed the boom in printed circuit boards can also be seen easily. Now we have a choice of different printed circuit boards for different devices. For example, various frequency ranges and antennas.

But the thing that needs attention is that the base material used in the manufacturing process of printed circuit boards is still the same. And the material used as a base for the printed circuit board still falls into the rigid category of the printed circuit boards. Now let’s understand what a substrate is.

What is the substrate?

Let’s imagine a building. What is the base of the building on which it is relying entirely? The ground, right? Similarly for the manufacturing of printed circuit boards, we need to build a base first. And the same as the building should have a reliable and strong ground, the printed circuit board also requires a good and efficient material with a number of characteristics in order to stand out in the world of electronics.

The substrate is the first physical layer of the circuit board on which the traces and components are relying. If you want to manufacture a reliable and high-quality printed circuit board, choosing the right and recommended material for the substrate layer is the first step you should go for. There are a variety of choices available when you get to choose the material of the substrate. But first, let’s understand why it is important to give this much attention to substrates.

Importance of substrate

There should be a solid shape and structure for the PC Board so that the other layers, traces, and components can easily rely on it. A strong canvas and platform are required to better hold all the components. The overall performance of the printed circuit board would be affected by the quality of the substrate. A soft substrate offers more space for designing options. On the other hand, hard and rigid substrates increase the durability of the circuit board. Similarly, if we need multiple designs on the printed circuit board then we may use multiple substrates for each layer. As we need to be concerned about the non-conductive material so the substrate decided should be able to withstand heat and dielectric constant also.

Now let’s have a look at different types of substrate with an explanation so you can understand how substrates are suitable in particular circuit boards. Moreover, the substrate is the reason for the stability of the printed circuit boards. It protects the board from bending by providing it with a hard or flexible surface. For example, the computer motherboard is probably the most common substrate you can see now. The motherboard is a multiple-layer printed circuit board. You can see that other components and traces are connected to the surface in such an efficient and best way.

Rigid Substrate:

As we have discussed before, the rigid substrate is always a good choice when we want a strong and dielectric circuit. Also, the rigid substrate can cross up to 350 degrees, so it is a noteworthy operating temperature. Rigid substrates are preferred when you want a PCB in a way that it can be repaired and maintained easily. It is easy to mark the affected area because of the clear view of the board. Rigid substrates are the best choice for critical situation usage devices for example LEDs used in medical surgeries. Ceramic-based substrates are the most common these days. Common examples are aluminum nitrate and aluminum. Rigid substrates offer high thermal stability and low expansion and are easier for the pcb assembly process.

Soft Substrate:

There are renowned benefits of using soft substrate in a printed circuit board. Soft substrate act as a shield in a hazardous environment. You can make a corrosion-proof, waterproof, and shockproof printed circuit board by using the soft substrate. This advantage is not provided by most rigid substrates. The dielectric material or glass material can be protected by epoxy coating around the filler. The soft substrate also provides resistance against chemicals and radiations. The melting point is high in them. Soft substrates have made the wearable concept possible. It is now possible to enable printed circuitry in tight areas just because of the soft substrate used in it. Although flexible material used in circuit boards is expensive, it provides better functionality by reducing the weight of the overall circuit.

Flex-Rigid substrate:

Sometimes a PCB requires easy fixation. Lightweight can also be a condition to follow. In this case, flex-rigid can accommodate the requirement perfectly. Specific flexible substrates such as R0400 are used in circuit board manufacturing; they are simple to machine and precision built. They are the most lightweight substrate, so it is possible to reduce weight and space up to 50 percent. Because of these features, flexible substrates are the best available choice for most printed circuit boards.

FR-4:

If you want to build a complex and multilayer printed circuit board then FR-4 is the way to go. They are also known as fire retardants, and they offer high resistance against flames because of the bromide present in them. There are several subcategories of FR-4 such as TG and FR-4 Roger. The other advantage of this substrate is that it is cost-friendly. Highly optimal performance of microwave frequency in the printed circuit board can be achieved by using RF-4 because of their strength to weight ratio. This is also a reason for their affordable design.

Now we have analyzed the reasons why we should go for good substrates. Let’s also understand the materials of the substrate. Because the quality of the substrate plays an important role in deciding the efficiency and reliability of the PCB as well as the end product.
Ceramic substrates are usually preferred because of the high magnitude of the thermal conductivity as compared to conventional printed circuit board material.

Commonly used substrate materials are Al2O3, AIN and FRx. alumina is preferred because it offers high resistivity, the best dielectric strength, good thermal and corrosion stability, and the best mechanical power. Its major disadvantage is a delay in propagation signal because of the relatively high rate of dielectric constant. It is also difficult to draw away heat and the reason is low thermal conductivity.

That’s why ceramic materials are under development. The main purpose of these developments is to improve the existing material. Integrated circuits are one of the best examples. As they perform complex functionality, it is important to build a printed circuit board with multiple layers. The low dielectric material is used in these circuits.

Similar polyimide is also used as a substrate in printed circuit boards. It offers wide temperature ranges and better chemical resistance. Its electrical properties are also good. Typically, these PCBs are used in cameras, antennas, entertainment devices, calculators, and instrumental panels. The other material that is recommended in the substrate is PTFE, this offers low dissipation and maximum temperature stability and would require a fixture for the printed circuit board assembly process. These are used in antennas, the aerospace industry, and power amplifiers.

There are many other examples of the best substrate materials that many industries are using for manufacturing better-printed circuit boards. The end goal is to provide stability and reliability under severe conditions. Also, it is preferred to use substrate material that is beneficial for critical industries and helpful in industries such as medical and aerospace.

The entire printed circuit board is relying on the substrate as it provides the basic foundation. The other components such as silkscreen, copper foils, and traces can do good if the basic physical layer is good. That’s the reason you should take some more time in deciding your substrate material and type. This will be a key to your PCB’s better performance.

Are you looking for the best substrate material for your PCB manufacturing and smt assembly? PNCONLINE is your ultimate solution. Just write us at sales@pnconline.com to get customized rates for your PCB manufacturing solutions.

Flexible Printed Circuit Board Overview

Introduction

On a slightly less romantic level, it would not be feasible to have such a standard laptop or mobile phone without flexible print circuit technology, which enables components to be linked electrically, in a dynamic, three-dimensional fashion. Flexible circuit technology has a long history that dates back over 100 years. The early patent activity emphasizes the fact that inventions such as Thomas Edison, Frank Sprague, and others in the early twentieth century experimented on ideas for flexible circuit materials and designs that were only used on a commercial basis in recent decades.

Background

Flexible printed circuits (FPCs) are the heart and soul of flexible films and thin layers of conducting traces. These typically represent the flexible circuit laminate base that can be used to connect electronic equipment – such as the LCD screen or a laptop’s keyboard – as a reliable cable replacement, or electronic components can be directly fitted to it through solder or conductive adhesive to form a completed, flexible printed circuit board.

Flexible printed circuits
Flexible printed circuits

Flexible PCB advantages

Flexible, FPCs may be bent and curved to provide more flexibility of application design and operation. Flexible circuits may also be adapted to tiny or inappropriately shaped areas, which cannot be supported by conventional rigid circuits. There is another benefit of flexible PC Board is that to reduce the weight of the motherboard of the application, they need less space. The effective utilization of existing areas also helps to improve thermal management and reduce the dissipation of heat.

Flexible PCBs may also be more dependable and longer-lasting compared to stiff PCBs, particularly in situations where constant vibration and mechanical stress are experienced. Based on soldered wires and hand-connected connector models, standard connecting methods are replaced by flexible printed circuits, with exceptional weight and thickness, and with strong mechanical resistance.

Think for example of connecting numerous electronic equipment, such as dashboards, display, and man-machine interfaces, in the automobile industry (rotary controls, buttons, etc.). All these gadgets are exposed to constant mechanical strains and vibrations and need a stable connection in all vehicle operating circumstances. Flexible printed circuits ensure zero reliability, durability, and maintenance in the automobile industry.

Flexible PCBs
Flexible PCBs

Flexible printed circuit boards provide a variety of possible advantages including:

  • Flexible PCBs provide cost-effective benefits that include decreased requirements for materials and packaging, reduced component replacement costs, and assembly mistakes that may lead to repair requirements.
  • These advantages make flex PCBs suitable for a broad variety of sectors, including consumer electronics, transport, medical, communications, military, automotive, industrial applications, and aerospace.

Missing Dielectric Material Callouts

Flexible and stiff flexible circuits are made utilizing a variety of material types to satisfy a broad range of physical and electrical costs and performance criteria. Because of this variation, the designer must give comprehensive information on the dielectric materials to be utilized about the potential problems associated with each choice. It is suggested that designers learn about the cost and performance options available. The Internet is filled with information about flexible circuit materials and how they may be utilized. This issue may also be helped by the PCB manufacturer. The fundamental kinds of flex materials are:

  • Adhesive materials without acrylic binding the copper to dielectric polyimide
  • Adhesive materials with acrylic copper bonding with dielectric polyimide
  • Flammable and non-flammable laminates, covers, and bonding flakes.

Incomplete or Insufficient Rigid-Flex Base Material Type Definition

The selected base material determines the rigid-flex circuit’s performance limitations in-process and field operation in many applications. For most solders devoid of plumage, the highest temperature requirements for soldering may be as high as 260°C, which usually requires the use of polyimide laminates. The choice of material and its electrical characteristics may, however, influence other performance problems.

One important issue is to control the characteristic impedance of the system and guarantee signal integrity with increasingly prevalent designs of higher-frequency circuits (these latter subjects will be given more attention later). The requirements for the temperature range of the stiff laminates used in rigid-flex structures must also be taken into account and handled. The stiff material should be capable of high temperatures. Polyimide laminate is a frequent callout, although epoxy resins are often appropriate for better applications.

Copper Type and Thickness Callout

Whilst many metal foils are available for flexible circuits, copper is the most frequently utilized metal for electronic interconnections. It is extremely conductive, mixable (making it flexible and foldable), reasonably easy to manufacture via graving and placing, and relatively cheap. The copper type most often used for flexible circuits is roll and copper (RA copper) with the greatest characteristics for dynamic flex applications.

The choice of type and thickness for the copper design should correspond to the electrical and mechanical requirements for use. Thicker copper is usually utilized for greater energy and thinner copper for circuits requiring repetitive bending (dynamic flexing). The options of thickness are many, but at present, one ounce (17μm or 0.7mils) and one ounce (35μm or 1 mil) are the most utilized for creating flexible circuit laminates. Additional copper may often be placed on the circuit, and this should also be taken into account in the specification. If the designer is unsure, he should seek the assistance of engineers for advice.

Flex Circuits
Flex Circuits

Cover layer or Solder Mask Over Flex Circuits

Covers are polymer materials used for the covering and protection of the copper traces of the flex circuit product. As is indicated, many solutions for the protection of the circuits are accessible and they meet various design criteria in terms of cost, performance, and flexural durability optimization. It is essential to describe the choice not only of the kind of cover material but also of the thickness required. This may be extremely significant for certain building types, especially when a flex circuit experiences dynamic flexing during usage.

As far as costs are concerned, a flexible solder mask is usually the cheapest. Someone or two-layer flexible circuits, which are not subjected to repeated flex cycles or severe radius curves, may be covered with a solder mask epoxy-based to flex without breaking. However, this is not advised if the design needs severe or dynamic flexing.

The second choice is the laminated cover. These materials are usually identical to the flexible core materials and are best suited for flexible dynamic circuit applications. The cover is a polyimide sheet with one side acrylic adhesive. It is usually pre-machined to open the sheet where the final finish is needed.

The cover sheets are typically coated with specific pads in a laminating machine to ensure that the copper characteristics of the flex layer are conformed. For rigid-flex circuits, the overlayer is usually reduced to not exceed 50 miles in the rigid part. The aim is to ensure that all the plated holes in the stiff-flex are empty of any acrylic adhesive, since they may influence the integrity of the hole wall plating.

Flexible Printed Circuit Board disadvantages

Although there are many significant benefits, the FPC technology also has several inconveniences or downsides. First and foremost, FPCs have significant one-time startup costs compared to conventional rigid PCBs. The initial expenses associated with the circuit and prototype design are greater than for rigid PCBs because flexible systems are developed for highly particular purposes. If the cost is a deciding factor in the choice of the kind of PCB, the use of FPC technology is preferable only for not too low manufacturing quantities.

The difficulty of fixing or changing the PCB when it is rebuilt is another drawback. In this situation, in reality, the protection film that covers the circuit must first be removed, the procedure carried out and protection restored. In order to provide their clients with this kind of product, flexible PCBs are quite a new technology and not all manufacturers are prepared. Moreover, considerable care must be exercised during the assembling stage, because the circuit may be easily destroyed by improper handling or by unauthorized people.

Structure

The historical electric connection methods have been revolutionized, typically for connecting various portions of the same circuit or different electronic devices by introducing flexible PCBs. The flexible PCB-based solution enables significant space, weight, and costs to be reduced compared to an equivalent solution using rigid PCBs due to its flexibility and compactness as well as the high density of electrical connections available. Many kinds of cable systems, frequently manual in multiple applications, have been replaced with flexible printed circuits which reduce overall electrical cable costs by up to 70%.

Interested in getting your Flexible PCB design ready at economical rates in USA? Get it done at PCNONLINE.

Final Thoughts

In the last few years, the FPC business has expanded significantly led by the development of wearable and electromedical devices that are increasingly tiny and light. Flexible PCBs may remove connector and cable requirements in many applications, enhance connection reliability and reduce assembly time, assembly cost, and total device sizes. We can state that flexible PCBs have enabled new in conclusion, fascinating applications to be implemented that are not possible with conventional rigid PCBs.

Flexible printed circuits, from cars, VCRs, camcorders, cell phones, and SLR cameras up to the complex military and aviation systems, are present in all areas. There are numerous high-profile uses of flexible circuits. One example is the employment of flexible-circuit technology in the Sojourner, a robot that explored the Mars surface and collected data in the summer of 1997, in the stiff flexible wire harnesses employed.

Do you have any further questions? Feel free to write us at sales@pnconline.com

Smt Assembly Conformal Coating

SMT Assembly Conformal Coating

Definition

Conformal coating is a thin layer of protected polymeric coating applied to printed circuit boards (PCBs) and electronic components. Its goal is to provide environmental and mechanical protection for the components and circuits, allowing them to last longer and be more reliable. It maintains long-term surface insulation resistance values by being electrically insulating, ensuring the assembly’s operational integrity. It also prevents corrosion by acting as a barrier to airborne pollutants from the operational environment, like salt spray.

Conformal coatings are often applied in the 25-250 micron range. Parylene films, on the other hand, are applied significantly thinner and can be fractions of a micron thick. Conformal coatings are a flexible covering that will secure the printed circuit board assembly from the environment it is in by filtering out air pollutants and ensuring long-term interface resistance value while also allowing any moisture trapped in the circuit board to dissipate.

The notion of conformal electronics coating was first conceived and refined through research decades ago to suit the rigorous requirements of the military. HumiSeal was a pioneer and leader in that early research and the company has remained a pioneer and leader for over 60 years as the technology has spread to a variety of industries, including:

  • Industrial Controls
  • Automobiles like Hybrid and Electric Vehicles
  • Aerospace
  • Telecoms
  • Traditional and renewable energy
  • White thing

 Conformal coating types

While there are many other types of coatings, including a few specialist forms, five primary categories are depending on the chemical makeup of the substances.

  1. Urethane Resin (UR):

Single-part or two-part urethane resins are available. It is chemically resistant as well as humidity resistance. On the other side, it is simple to remove and rework with a soldering iron.

  1. Acrylic Resin (AR):

Preformed acrylic polymers that have been dissolved in a solvent are known as acrylic. Typically, they are one-part compounds. It is inexpensive and simple to apply and remove. During the curing method, there is no distortion.

  1. Epoxy Resin (ER):

Epoxy coatings are typically two-part compounds, but a one-part option is also available. It has moistures. It performs admirably in adverse conditions.

  1. Silicone Resin (SR):

Silicone resin coatings are one-component materials that are frequently used on devices that will be exposed to severe temperatures. Even at high temperatures, it performs excellently. It can stick to almost any PCB material.

  1. Parylene (XY)

Chemical vapor deposition is the method used to apply parylene coatings. When heated, parylene turns into a gas. It is then placed in a vacuum chamber to polymerize and form a film after cooling. After that, the film is applied over the circuitry. It is translucent and colorless. It is the ideal solvent for coating and can be done at room temperature.

Uses of conformal coating

When today’s dynamic electronics are faced with significant environments, additional protection is required to ensure proper operation. Moisture, salt sprays, strong chemicals and solvents, vapors, dust, abrasion, and even organic assault have all been proved to be resistant to conformal coatings. Furthermore, it has been demonstrated that the impact of mechanical stress and disturbances on the circuit and its functionality in severe temperature ranges can be reduced by using the right material. Conformal coatings protect the product while also improving its reliability. As a result, the negative impacts of early field failures are reduced, as is the potential cost. We use conformal coating for:

  • It works as a moisture and humidity-resistant barrier, resulting in lower leakage currents, converse, and electrical and chemical transfer throughout the board.
  • The coating has the potential to improve the strength of dielectric conductors.
  • The coating provides a high level of insulation safety, allowing conductor space to be reduced.
  • It prevents the board from chemical and corrosive attacks that can cause corrosion. It also protects against damage caused by hard handling, as well as thermal and mechanical load.
  • The coating prevents particle pollutants from reaching the board’s surface.

 Method of conformal coating

The following are types of common Printed Circuit Board conformal coatings:

  1. Brushing

Brushing a conformal coating is a popular method of application. Although this is a simple procedure, it needs the use of a trained operator to ensure the coating’s quality and finish. A brush, a container for storing the coating, and a specified area for application are all required. The coating material is dipped in the brush and applied to the board.

The type of brush, operator competence, coating viscosity, the environment, and the coating material all affect the brushing method’s quality. It has many benefits, including ease of use, simplicity, and reduced process control needs. This method is ideal for rework and low-volume production. In this process, we use hands and are thicker and less pleasing artistically. This is the ideal option for individuals who don’t have the tools to use other options or who are working on a few boards at once.

  1. Spraying:

This procedure produces a better surface polish and is more cost-effective, but it does not penetrate the board deeply. Spraying, which is also preferable for low-volume production, is time-consuming because all parts that do not require coating must be masked. Spraying with aerosols, batch spraying, and selective spraying are all part of this approach.

A spray gun is included with an aerosol. It’s a coating with a solvent basis. Aerosol spraying in a spray booth is a low-cost option. This procedure is superior to brushing because of the inexpensive setup costs, high process speed, simplicity, and final quality.

Batch spraying utilizes a compressed air spray cannon to provide a high-quality coating finish. For the setup, you’ll need a spray gun, a spray booth, and an air compressor. In this operation, it’s crucial to get the spray gun set up with the right atomization pressure and material supply. It’s also crucial to get the coating’s viscosity just correct. It has features such as inexpensive setup costs and flexibility.

Spraying selectively only coatings selected areas. The coating isn’t applied to regions that need to be masked, like connectors and other components. The coating is done with the use of a customized robot system that uses various spray patterns. Valve selection, board material, and board arrangement are all important considerations. The correct spray valve and coating viscosity must be selected.

All sorts of conformal coatings are supported by the spray approach, and designing for this procedure necessitates a high level of technical knowledge. As a result, spray application requires significant capital expenditure. In addition, the material’s performance over time and changes in the control environment must be monitored.

  1. Dipping:

Dipping is the process of immersing a board in a coating solution and then removing it. This process is ideal for high-volume assembly since it is quick, precise, and penetrates the board, coating the entire assembly. However, to eliminate leakage, masking must be flawless, rendering many boards unsuitable owing to design. This approach can only be used on boards that take coating on both sides.

This is a conventional procedure that involves dipping the pcb assembly into a tank of coating chemicals. The speed of immersion, coating dwell time, and board withdrawal speed are the variables that determine the process. Acrylics and urethanes, which are solvent-based conformal coatings, are recommended for dipping. It’s a high-speed process that can be used in batch or in-line processes.

The conformal coating manufacturing process

In the conformal coating production process, there are eight main steps:

Cleaning:

The cleaning eliminates a variety of residues that result from operator handling, soldering, machine use, and pollution from the environment.

Priming:

Priming is the process of applying a preliminary coating to a board before applying the conformal coating. It improves adherence and produces a binding layer to keep the coating in place. The amount of priming required varies depending on the type of resin.

Masking:

The function of masking is to prevent the conformal coating from being placed on the parts and selected board sections. Because of the insulating nature of the coating, certain regions of the circuit board must remain uncoated. Many materials are used in masking.

Cure and dry:

There is a difference between Cure and dry. That is:

Cure:

This means that the coating achieves the desired qualities (electrical and mechanical) and that the board is protected while in use.

Dry:

This assures that the PCB is laminated and suitable for the users to operate. It could take anywhere from a few minutes to several days.

Checking:

In the procedure, it is the most crucial stage. Manual inspection, UV lamp visibility, and automated optical inspection are all included.

Benefits of conformal coating

When it comes to choosing parylene coating that meets standards, there are several clear advantages and benefits. Because there is no liquid phase in this technique, there will be no pooling of coating in low regions. Furthermore, it will not bridge in substrate features. Furthermore, this sort of coating is extremely pure and is one of the best dielectric qualities available. It’s one of the purest polymer types. It also possesses the best mechanical and gas barriers, allowing it to suit a wide range of coating requirements, even when applied in thin layers.

It protects against impurities such as dust, filth, fungi, moisture, chemicals, thermomechanical stress, mechanical shock, and vibration, as well as environmental, mechanical, electrical, and chemical issues.

Finally, remember the project and the electronics’ user needs in mind when selecting a coating for your printed circuit board or other electronics. It’s necessary to preserve the board, but it’s even more critical to cover it with the right material. When choosing a coating type, keep the environment in mind as well as any rework or repair requirements.

Smt Assembly
Smt Assembly

At PNC, get your conformal coatings done at affordable rates. Contact us at sales@pnconline.com