Cause analysis on abnormal failure of copper-substrate pin fin heat sink for new energy vehicle

The new energy vehicles are playing more and more important role in energy conservation and environmental protection. With regard to the new energy vehicles, the power module is a key device which converts the direct current (DC) into the alternating current (AC). Considering a great deal of heat generated by the power module during operating, a kind of pin fin heat sinks with nickel-phosphorus coating is specially designed and manufactured, so as to prevent the power module from thermal damage. In view of this, the reliability of the pin fin heat sinks must be strictly evaluated before putting into use. However, during the corrosion resistance tests, some suspected corrosion defects occurred on the pin fin heat sinks, by which the newly-designed pin fin heat sinks were judged as unqualified. Aimed at this special failure, a series of characterization methods and comprehensive analysis were carefully performed. Through systematic assessment and analysis, the so-called local corrosion was excluded and the explosive release of local hydrogen in nickel-phosphorous coating was determined as the root cause of radial defects. Meanwhile, four kinds of typical manufacturing defects for the pin fin heat sinks were characterized and discussions were also given in detail for the formation causes and affecting factors. Based on the obtained conclusions, the effective countermeasures are put forward for improving plating quality and the achievement of the paper is also helpful for better understanding the operating safety and reliability of new energy vehicles.