Thermal Cycle Reliability Assessmen of Bowed PCB Assemblies
Authors: Michael Meilunas, Lars Bruno and Bo Eriksson Company: Universal Instruments Corporation, Ericsson AB Date Published: 9/17/2017
Abstract: Circuit board assemblies for various server or telecom infrastructure applications often need to fit into rigid enclosures or racks to provide their intended function. Warpage of such circuit assemblies during the solder reflow process is not uncommon and must be accommodated in final product assembly. Bolting warped boards into server racks and other structures forces them flat and imposes strain on the various solder interconnects on the surface of the board. Reliability testing of surface mount solder joints is most often done with laboratory thermal cycling of unstressed boards. It is anticipated that any additional solder joint preload arising from a mechanically distorted board will negatively affect the measured solder joint reliability. This study evaluates the reliability consequences of board bending by imposing from 0 up to 2% bend from the asreflowed condition concurrent with thermal cycle exposure. Various component types were tested including CBGA 625, 2512 resistors, LGA 133, PBGA 1156 packages.