부산대학교 도서관

Studies on shear strength of thin small leadless packages (TSLP) focused predominantly on solder and refl ow factors. Contact pad’s surface roughness (R a ) and Ni–P thickness factors, though rather important, have not been reported widely. Thus, the current study investigates the effect of TSLP’s contact pad, in terms of R a and Ni–P’s thickness, on shear strength variation of the TSLP after being soldered on PCB. The R a was controlled by using different Cu alloy leadframes, etchant’s pH and etching conveyor speeds. A shear test was conducted on the soldered TSLP using the Dage Series-4000-Bond-Tester as per Infi neon’s specifications. The shear test data was supported by failure mode results in the form of scanning electron microscopy images and energy-dispersive X-ray analysis. The present work revealed that TSLP with high contact pad’s R a exhibited a wide shear strength variation. In addition, thicker Ni–P signifi cantly enlarged the shear strength variation of TSLP when the etched surface of the contact pad’s R a is low. After solder refl ow, the contact pad’s high R a and Ni–P thickness triggered the formation of more heterogeneous pores in the solder region of the solder joint between TSLP and PCB. This resulted in shear failure at the porous solder region and heterogeneous shear strength of the soldered TSLP.