Influence Of High Temperature On Circuit Board
Circuit board is the soul of electronic products, plays a vital role in the operation of electronic products.With the increasing density of PCB integration, the circuit design becomes smaller and lighter, and the heat sources from different sources affect the circuit performance in different ways. The heat may be produced by a component mounted on the circuit board, or by an external heat source from the circuit board. Engineers of high power radar systems are familiar with the enormous heat generated by vacuum tube amplification devices such as klystron and traveling wave tube (TWTs). In recent years, high density amplified semiconductor devices, such as gallium nitride (GaN) transistors installed on the circuit board, can not only improve the power level of RF / microwave signals, but also generate local hot spots. The external heat sources of PCB, such as automotive electronic systems, also increase the temperature of the circuit and bring about reliability problems.
The complicated situation is that the circuit board is a composite material, including dielectric layer and conductive metal layer. They have different expansion rate and different high temperature function. The properties of the PCB can be measured by thermal expansion coefficient (CTE). It describes the amount of expansion of a material. Ideally, if the PCB dielectric layer is laminated to the thermal expansion coefficient and dielectric material of copper or other conductive metal thermal expansion coefficient is close in value, so that the two materials can be synchronized in high temperature, which can avoid the stress in the interface of two different materials. The reliability of circuit designers often concern at high temperature, some circuit functions associated with this, for example, metal multilayer circuit boards of different layers are interconnected via hole between the dielectric and metal conductive material (PTH).
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