Design trade-offs and reliability of power circuit substrates with respect to varying geometrical parameters of direct copper bonded Al/sub 2/O/sub 3/ and BeO

High-Temperature High-Power Packaging Techniques for HEV Traction Applications

“…Very thick copper layers lead to fracture of the ceramic substrate and failure after much fewer thermal cycles. This effect can also be observed in published peel strength data for Alumina and Beryillia DBC substrates, where a decrease in peel strength is observed as the copper thickness increases [41]. Similar analysis conducted by one DBC vendor ‡ suggests that similar performance is exhibited by AlN DBC.…”

“…It is also interesting to note that the overall bond strength of the DBC substrate may be impacted by the soldering process used to bond the die to the substrate or the substrate to a base-plate. Published data clearly indicates that fluxless soldering processes which utilize hydrogen to inhibit oxide formation can dramatically reduce the bond strength between the copper and ceramic layers [41]. For example, forming gas which contains 10% hydrogen and 90% nitrogen and is commonly used in this process, attacks the oxide bond and dramatically weakens the substrate.…”