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CAF – Conductive Anodic Filament: an undesirable conducting filament in the substrate of a circuit board

  • Multilayer boards with many layers
  • Industrial electronics
  • Automobile electronics
  • Fineline trace structures
  • High temperature electronics

What are the considerations of High-temperature PCB?

The glass transition temperature of PCB, referred to as “Tg”, indicates the point at which the PCB material will begin to transform. If the operating temperature exceeds the designated Tg value, the board will begin to change from a solid to a liquid state, which is likely to have an adverse effect on its ability to function.

Standard PCBs are manufactured with materials offering a TG value of 140°C, which can withstand an operating temperate of 110°C. While this may not be suitable for extreme-temperature processes, that are commonplace in applications such as automotive, industrial or high-temperature electronics. In these situations, a PCB made from FR-4 material can often provide the best solution.

What is the PCB heat dissipation?

The two primary methods of removing heat from a circuit board are convection and conduction. While radiation plays a critical role in thermodynamics, in the context of high temperature circuit boards this mode of energy emission is the least consequential, yet is still present and may be a consideration in the presence of reflective circuit boards.

In high temperature circuit board construction, heat sinks are essential for redirecting heat and keeping temperatures manageable. PCB heat sinks are large, corrugated structures that contain a large amount of surface area ideal for this purpose. Copper or aluminum backing conduct heat away from the heat-generating surface and transfer them to the heat sink. Convection then allows this heat to be distributed along the ridges of the heat sink, often cooled by aid of a fan.

Keeping these principles in mind, a variety of options can be used to increase efficiency of heat management. Liquid cooling systems, larger heat sinks and conductors, and different materials are all considerations that can be made. However, each of these decisions will also influence the end design, making it potentially more expensive, heavier, or requiring more power to operate.

How to select proper material for High-temperature PCB?

FR-4 and polyimide are the two most common materials that PCBs use to base their other components. When dealing with higher temperatures, PCBs created from these two base materials will not last. They are certainly not optimal for any device that contains more currents that warrant a PCB that can resist higher temperatures.

It raises the question: How can materials like these be upgraded to withstand the amount of heat that high-temperature PCBs can withstand? And a better question is this: How can these materials be acquired without using too many resources?

It is what you should be thinking about when coming up with materials for high-temperature PCBs. Unless you have the kind of budget where you can purchase new materials to create high-temperature PCBs, you’ll want to explore ways to customize your current materials to where they can be compatible with high-temperature PCBs.

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