Some recommendations for the thermal design of electronic components due to temperature cycling and thermal shock

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Source: Ruikai Instruments. 1. For devices with high heat dissipation requirements, it is recommended to use substrates with good thermal conductivity. The heat dissipation capacity of the PCB itself affects the efficiency with which heat is dissipated from the device. To improve the PCB’s heat dissipation capabilities, substrates with good thermal conductivity can be used, such as metal-based printed circuits and ceramic-based printed circuits (high-alumina ceramics, alumina ceramics). 2. For surface-mounted components with plastic encapsulation, it is advisable to avoid using lead frames and pin materials with low CTE, such as 42# alloy and KOVAR. Such materials reduce the CTE of components, resulting in a significant mismatch with the higher CTE of FR4 or similar PCB materials; using such pin materials also leads to soldering problems. 3. For components with high power dissipation, special attention should be paid to the effect of the thermal gradient caused by power dissipation. Because in this case, even if the CTE of the component and the substrate match, the effect of power dissipation cycles within the component may be greater than the effect of ambient temperature cycles. 4. Surface-mounted fuses have a poorer heat dissipation performance compared to equivalent through-hole fuses, requiring additional cooling measures. 5. When using power resistors, the heat conduction from the power resistors to the radiator or chassis can be improved by employing mechanical fastening or thermosetting plastics. 6. For power resistors with a power rating greater than 2W, a piece of copper foil needs to be designed at the bottom of the device in order to reduce the risk of burning of the printed circuit board in the event of failure.