A Mechanism for Board Warpage by Thermal Expansion of Surface Mounted Connector

A mechanism of printed circuit (PC) board warpage caused by a thermal mismatch between a surface mounted connector and a PC board is demonstrated. Both the increase and the decrease in temperature enlarge the space between the PC board and the surface mounted (SM) connector. Basically four nondimensional parameters control this mechanism. They are the thermal strain mismatch, the ratio of bending stiffnesses of the PC board and the SM connector, the ratio of elongation stiffnesses, and one geometric parameter. In practical applications, these parameters can be evaluated only when structural details of the electronic package are determined. Though the board warpage by the mechanism discussed herein is small for practical applications, this warpage could induce a sufficient tensile force in soldered joints that could cause damage.