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Small Variations in Thermal Interface Application Found to Drive Long-Term Efficiency Losses in Power Converters
Recent reliability assessments of industrial power converter systems suggest that inconsistencies in the application of thermal interface material (TIM) can result in measurable efficiency loss and long-term thermal degradation. Although heat issues are often attributed to circuit layout or load conditions, engineers are increasingly identifying the root cause within the heat sink assembly itself.
According to field data from multiple manufacturing environments, variations in paste thickness and distribution can introduce thermal resistance differences as small as 0.1 K/W - enough to cause gradual performance drift over time. These deviations may not be evident during initial testing but they can accumulate under continuous thermal cycling.
Common contributing factors include:
- Excess or insufficient thermal paste volume
- Uneven spread across contact surfaces
- Missing or misaligned interface layers
“These are small manufacturing steps, but they have system-level consequences,” said Diotec's engineers involved in the analysis. “A stable thermal path depends not only on component selection, but on the uniformity of the interface between them and heatsink.”
Diotec made an impressive comparison on Power Schottky Diodes, which were subjected to a High Temperature Reverse Bias Test (HTRB). Without thermal paste between parts and heatsink, there were 36/77 failures after 135 h only, with Ir going into thermal runaway. With correctly applied thermal paste, there were 0/77 failures, and Ir reaching stable values over 1000 h.
These findings highlight a broader principle of reliability in power electronics: performance is not solely determined by materials or design, but also by the stability of the interfaces that connect them to the ambient.