Title:

Solder Bridging in SOP Package

Author(s):

Flordeliza Trabado, Marites Mandia, Lucila Mella, Eva Marie Ratilla, Intel Philippines Mfg., Inc.

Gist:

Solder bridging, a plating defect which may be fostered by plating technologies shifting to higher speeds and higher current densities, is of important consideration for fine pitch packaging. A peculiar type of solder bridging occurring on the surface of the molding compound in between the leads was investigated in this paper. The aim of this paper is to understand the root cause of this uncommon solder bridging. Surface activation during trimming fostered by misaligned leadframe to mold package creates crevices and rough surfaces which have the propensity to attract the tin lead during plating. The combined effect of the high speed plating process and active plastic surface predisposes the electrodeposition of solder on this area. The strong electrolytic fluxes prevalent in high current density conditions during high speed strip-to-strip solderplate vis-a-vis the almost stationary rack plating further promotes the deposition of tin lead despite the absence of direct contact to conductive lead. To address this solder bridging problem, factors minimizing surface roughness as well as additional bake were done to deactivate the plastic surface. Reformulation of the plating chemistry to increase additive levels, especially those of antioxidant, was also done to retard electrodeposition. These actions eliminated this solder bridging phenomenon.

Published in :

ASEMEP 1996 Proceedings; August, 1996