Breakdown phenomena in power integrated packages

Tests have been performed on a test pattern designed to study the effects of applying voltage to the inside of the package. The need to apply high voltage to the internal connections of the package, without discharges occurring outside the package, has led to the design of a metal frame having only two leads spaced 16 mm apart. Specimens having three different distances between the bonding pads (60 mu m, 100 mu m, and 160 mu m) have been prepared. Test patterns for the three kinds have been subjected to breakdown tests by applying an increasing 50 Hz voltage. No meaningful breakdown voltage (BDV) difference appeared between the results for each test set, demonstrating that the discharges occur not in the encapsulant, but through the passivation layer. Consequently, new test patterns having a double thickness oxide layer have been manufactured in order to stress the encapsulant with a higher field strength. The discharge test results have shown increased values of BDV, yet no meaningful differences between the BDV of each set have been found, indicating that the discharge path was through the oxide layer even with a double layer. The results support the possibility of implementing power plastic packages which work at higher than usual voltage by modifying the metal frame.<
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