Abstract: A module (20) can include a first substrate (12) comprised of a first material, at least a second substrate (22) comprised of at least a second material, selectively applied solder (14) of a first composition residing between the first substrate and at least the second substrate, and selectively applied solder (16) of at least a second composition residing between the first substrate and at least the second substrate. Preferably, no crack will exist in the module as a result of a reflow process of the solder due to the CTE mismatch between the first and second substrates. The different selectively applied solder compositions can have different melting points and can be solder balls, solder paste, solder preform or any other known form of solder.

Abstract: A method (80) of reducing stress between substrates of differing materials includes the steps of applying (82) solder (16) on a first substrate (14), reflowing (84) the solder on the first substrate to form a cladded substrate (30), applying (85) a medium such as flux or solder on a second substrate (42) having a substantially different coefficient of thermal expansion than the first substrate, placing (86) the cladded substrate on the second substrate, and reflowing (88) the cladded substrate and the second substrate such that thermal stress caused by the substantially different coefficient of thermal expansion between the first and second substrates is limited to when a temperature approximately reaches below a solidus temperature of the solder on the first substrate.

Abstract: A method (80) of reducing stress between substrates of differing materials includes the steps of applying (82) solder (16) on a first substrate (14), reflowing (84) the solder on the first substrate to form a cladded substrate (30), applying (85) a medium such as flux or solder on a second substrate (42) having a substantially different coefficient of thermal expansion than the first substrate, placing (86) the cladded substrate on the second substrate, and reflowing (88) the cladded substrate and the second substrate such that thermal stress caused by the substantially different coefficient of thermal expansion between the first and second substrates is limited to when a temperature approximately reaches below a solidus temperature of the solder on the first substrate.

Abstract: A module (20) can include a first substrate (12) comprised of a first material, at least a second substrate (22) comprised of at least a second material, selectively applied solder (14) of a first composition residing between the first substrate and at least the second substrate, and selectively applied solder (16) of at least a second composition residing between the first substrate and at least the second substrate. Preferably, no crack will exist in the module as a result of a reflow process of the solder due to the CTE mismatch between the first and second substrates. The different selectively applied solder compositions can have different melting points and can be solder balls, solder paste, solder preform or any other known form of solder.