Effect Of Contact Pad’s Roughness And Ni–P Plating Thickness On Leadless Packages’ Shear Strength Variation

• Main Authors: Lau, Kok Tee, Munawar, Rose Farahiyan, Arif@Harip, Afraha Baiti, Ong, C. G.
• Format: Article
• Language: English
• Published: The Korean Institute of Electrical and Electronic Material Engineers 2020
• Online Access: http://eprints.utem.edu.my/id/eprint/24642/2/LAU2020.PDF; http://eprints.utem.edu.my/id/eprint/24642/; https://link.springer.com/article/10.1007/s42341-020-00218-8
• Institution: Universiti Teknikal Malaysia Melaka

Studies on shear strength of thin small leadless packages (TSLP) focused predominantly on solder and refow factors. Contact pad’s surface roughness (Ra) and Ni–P thickness factors, though rather important, have not been reported widely. Thus, the current study investigates the efect of TSLP’s contact pad, in terms of Ra and Ni–P’s thickness, on shear strength variation of the TSLP after being soldered on PCB. The Ra was controlled by using diferent 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 Infneon’s specifcations. 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 Ra exhibited a wide shear strength variation. In addition, thicker Ni–P signifcantly enlarged the shear strength variation of TSLP when the etched surface of the contact pad’s Ra is low. After solder refow, the contact pad’s high Ra 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.