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.
Solder paste holds everything on a circuit board together. If it melts, very bad things will happen: Components can fall off of the board. The lead content of solder paste is one thing that affects the maximum temperatures by which the paste will melt.
Most leaded solder paste will melt at around 160 degrees celsius. If used to assemble a circuit board, the board itself will not be suitable for high temperatures. Getting your solder paste ready for high-temperature PCBs is a quick fix: All you need to do is assemble your circuit boards with unleaded solder paste or at least solder paste that does not contain a lot of lead.
Another thing you can do to modify materials to make them ready for high-temperature environments is to alter the design. To do this, you’ll need to keep a lot more distance between your heat, creating components on your board than usual. It is another quick solution that can use. Aside from making adjustments in design, it is also good to know the details of heat management for any given circuit board.
Why materials are important for high temperature PCB?
The only real difference between PCBs that can handle high temperatures and those that do not is that heat is managed much more in a high-temperature PCB. It is common knowledge that heat causes things to expand. However, many do not know that all of the small parts in a circuit board expand from heat. If these parts expand too much, they will fail.
The problem here is how this heat can be managed to prevent a circuit board’s components from expanding too much or too quickly. Knowing this is useful because if it is possible to manage this kind of heat, it may not be necessary to seek out circuit board materials and components that need to withstand such extreme temperatures in the first place. You might be able to make a few adjustments.
Oxidation is something that can affect PCB temperatures. The majority of PCB assemblers greatly overlook this and if the oxidation can be micromanagement, so is heating. Most PCBs contain dielectric materials that are covered by copper laminate. It prevents oxidation from rising temperatures. If the worn or dielectric material does not cover the copper laminate, the dielectric materials will oxidize much faster from the heating process.
It is one example of practicing good heat management and precautions when assembling a circuit board. Sometimes basic heat management in your design can get PCBs ready for high temperatures. Another form of heat management in PCBs is understanding how to measure heat expansion in PCBs’ materials and components.
How thermal expansion relates to high temperature PCB?
There is no avoiding the thermal expansion that takes place when components and materials in PCBs experience rising temperatures.
However, it is possible to measure thermal expansion. It is carried out using the coefficient of thermal expansion (also known as CTE). The CTE can determine the rate of thermal expansion for PCB materials and components.
The Celsius temperature scale, the coefficient of thermal expansion expressed in parts per million. The physical equations involving the CTE are extremely complex, far too complex to express in one article. However, this video explains the physics behind the CTE: