How Do You Design PCB Assys for High-Reliability Applications?

Design PCB Assys for High-Reliability Applications

When it comes to electronic control systems, no other piece of equipment is as vital as the circuit board. Almost every feature in the modern automobile is controlled by a PCB. This small but mighty component is programmed to perform system essential commands no matter how big or small the vehicle may be. This is just one of many examples of how PCBs are used to help make our lives easier and safer. However, as with any piece of technology, there are issues that could arise from a poorly executed or designed circuit board. The occurrence of these problems is why it is so important to follow design for reliability (DfR) principles when designing your pcb assy.

One of the most significant PCB design issues is EMI susceptibility. Electromagnetic interference can corrupt signals and cause a circuit to malfunction. Using proper signal routing, shielding, and grounding techniques can reduce EMI interference. This includes the use of shielded connectors, grounding all conductive surfaces, and ensuring that traces do not cross or share power and signal lines. Increasing the thickness of your PCB will also improve EMI resistance.

Another key issue is thermal performance. In high-reliability applications, components are often operating near their temperature limits. This is why it is important to select the right material for your PCB. Choosing a material with a higher thermal conductivity will allow your circuit to dissipate heat more efficiently, thus improving performance and reducing the risk of failure.

Other important considerations are dimensional stability and mechanical integrity. As the industry moves towards smaller form factors, maintaining robust mechanical properties is a challenging task. This can be accomplished through the use of advanced materials or innovative structural designs.

How Do You Design PCB Assys for High-Reliability Applications?

In addition to ensuring a stable PCB, it is important to ensure the quality of the components that are used. Using industrial grade components will help ensure that the board can handle the harsh conditions of its intended environment. Additionally, implementing proper soldering and assembly practices will help reduce the likelihood of premature failures due to micro-cracks or fatigue.

Finally, the PCB should be printed with a legend that contains the name of the components and any test points. This information is useful in assembling, testing, and servicing the unit. Originally silkscreen printing was used, hence the alternative name for PCBs known as “silkscreen printed.” Today a more precise method called liquid photo imaging is employed, which produces more accurate legends on a variety of different media.

The area of a PCB that should not be soldered is covered with an imaged mask. This is usually green in color, but other colors are available as well. The photo-sensitive coating on the bare substrate is imaged with a dry film solder mask, exposed to light and developed to remove unexposed areas. This enables the bare laminate to be coated with copper for the final manufacturing process.

This involves inspectors visually examining PCBs for obvious defects such as solder bridges, misaligned components, and missing parts. While simple and low-cost, MVI is limited by human error and is not feasible for high-density boards or high-volume production.