The printed circuit boards (PCBs) are compact-sized and contribute to the functioning of electronic devices. Although all printed circuit boards look the same for a layman, they differ in terms of designs, components, and performance for a PCB engineer and electronics services experts. Having said this, it is quite common to ask what differentiates a reliable PCB from an inferior one. This post offers insights into the features of a reliable PCB and steps taken during the printed circuit board assembly or PCB assembly to improve their reliability.

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Tips to Differentiate the Reliable PCBs from Inferior Quality Ones

Conducting a visual inspection is the best way to identify the good quality PCBs from bad ones. The following pointers will be helpful in this context.

  1. Examine If the PCB Is Clean: This is the simplest test to check the reliable PCB on this list. When following good practices of PCB assembly, the manufacturers always take care to remove any dust or dirt from the surface of the PCB. If the PCB is not cleaned properly then it can lead to poor connections and poor solder joints.
  2. Check the PCB with Established Standards and Requirements: The best way to start is by comparing your PCB with the Design Rules Check and the Electrical Rules Check Constraints. You can refer to them to get the trace widths, gap widths, design and manufacturing requirements and so on. After this, you can also check the PCB against the performance requirements such as power consumption of the PCB, its performance, and so on.
  3. Check the Placement of Components on the PCB: The components on a PCB look the same, but on close inspection, you will find that they are placed in a certain way to create an impact. Unknown to you, this placement directly impacts the performance of the printed circuit board. The inductors are placed at a certain distance from each other. This helps avoid the electromagnetic interference that is caused due to coupling if they are placed nearby. Similarly, the inductors must not be placed near the metallic components. If so, the inductor values may be affected due to the magnetic fields produced by metallic components. Similarly, extra care must be taken to place the thermistors and power resistors. Both these are heat-producing components.
  4. Examine the Traces on the PCB: You can check the traces on the PCB. The traces will be covered by a solder mask, which is generally green in color. The solder mask is a polymer layer, which protects the traces from shorts and oxidation. Sometimes, the mask layer may be available in other colors as well. Generally, the layers at the bottom and top of the PCB are visible. However, if you are looking at a multi-layer PCB, these layers may not be visible. However, checking the external layers is still helpful. Be sure to check if the traces appear straight without any sharp bends. These sharp bends can cause performance issues in high frequency and high power traces.
  5. Check the Trace Lengths: The lengths of traces must be matched in the circuits that may require a timed relationship between signals. This becomes more important when routing a clock signal of high speed to multiple chips. The trace lengths ensure all signals reach their destinations with the same delays. For checking this, you need to refer to the schematics to understand which signal lines would require the timing relationships.
  6. Check Grounds: In multiple layer printed circuit boards, at least half of the inner layers would be the ground plane and power supply. The PCB designs featuring digital and analog sections will have split ground planes that are joined at a common point. This is generally done to avoid the current spikes arising from digital sections. If not addressed, these spikes would affect the analog section. If the PCB comprises two layers then ensure the ground return traces for each sub-circuit are kept separate and made to join the power negative terminal in combination. However, if the ground of any sub-circuit joins directly to the power negative terminal then it can lead to more performance issues such as voltage drop across the trace and so on.
  7. Check the Placement of Decoupling Capacitors: Every PCB component must be powered properly to perform. These components are connected to each other on the board through traces and placed at an appropriate distance from the power supply. Decoupling capacitors are also added to the circuit to prevent electromagnetic noise. Generally, they are placed near the power pins of the chips. If the chip comprises several VDD pins then it may require at least one decoupling capacitors. If the decoupling capacitors are placed farther from the pins then their efficiency may decrease. Check if the decoupling capacitors are placed accurately on the circuit board.
  8. Examine the Heat Dissipation of the PCB: The PCBs will have both types of components – high and low heat producing ones. The later ones are very delicate and must be protected carefully. So, heat dissipation considerations must be made on the PCB. For instance, the heat generating components must be kept away from delicate ones and cooling fans or heat sinks must be introduced wherever necessary to keep the temperature under control. Generally thermal reliefs are used by experienced designers to curb heat during the wave soldering process. If not done properly, this may lead to heat transfer to ground planes, which would damage the traces.

The above points discussed are only a few tips that would help you distinguish high-quality PCBs. However, if you aren’t sure of these, you can approach an expert in your organization or an electronic engineer to verify the circuit design and functionality. After all, the printed circuit board drives the performance of an electronic circuit, and a streamlined PCB assembly process culminates into reliable PCB assemblies. If you are an electronics designer looking to partner with trusted and experienced electronic manufacturing services provider, then look no further. Suntronic offers a wide range of electronic manufacturing services, specializing in printed circuit board assembly services among others. The company provides a broad range of PCBA services to its clients in consumer and industrial electronics, military, oil and gas, and networking and communications sectors. You can get in touch with a member of our experienced team to discuss your design and they will help you with the right services and methods.