Patent ID: 7413110

Claim:
A method of reducing stress between substrates of differing materials, comprising the steps of: applying solder on a first substrate; reflowing by melting the solder on the first substrate and allowing the solder and first substrate to cool to form a cladded substrate; applying a medium on a second substrate, wherein the medium has a solidus temperature higher than a solidus temperature of the solder applied to the first substrate; placing the cladded substrate on the second substrate having a substantially different coefficient of thermal expansion than the first substrate; reflowing the cladded substrate and the second substrate to a temperature that melts the solder used on the second substrate; enabling the cladded substrate and the second substrate to cool after reflow such that thermal stress caused by the substantially different coefficient of thermal expansion between the first and second substrates is avoided between the solidus temperature of the solder on the second substrate and the solidus temperature of the solder on the first substrate as the cladded substrate and the second substrate cool down immediately after reflow.