Characterization of flexural and thermo-mechanical behavior of plastic ball grid package assembly using moiré interferometry

Flexural and thermo-mechanical behavior of a wire-bond plastic ball grid array (WB-PBGA) package assembly is characterized using moiré interferometry. Fringe patterns are recorded and analyzed at several bending loads and temperatures. Detailed global and local deformations of the assembly are investigated. The deformations caused by the thermally induced bending are compared with those caused by the mechanical bending. The results reveal that global bending modes are similar but the deformations at the critical locations are significantly different; the sign (direction) of the shear strain caused by the mechanical bending is the opposite of that caused by the thermal loading. The implication of the opposite bending on board level reliability is discussed.