Title:

Low-Stress Leadframe Design for Plastic IC Packages

Author(s):

Navin Bhandarkar, Lim Thiam Beng, Institute of Microelectronics, Singapore

Gist:

This paper presents a leadframe design which reduces thermal deformation and stress on the die, while improving the moldability of plastic IC packages that employ leadframes. The design works works by splitting the die pad into several sections joined together by flexible expansion joints. The splitting of the die pad allows relative motion between the sections of the pad and breaks down into smaller segments the total die pad length that is rigidly attached to the chip. These two factors reduce the magnitude of the mismatch between coefficients of thermal expansion (CTE) and out-of-plane deformations during assembly, diminishing die stress and enhancing moldability. The study showed that this new design achieves as much as 50% reduction in die warpage during processes prior to molding. Voiding and incomplete filling during molding have likewise been eliminated. This improved leadframe also results in superior package performance under moisture sensitivity testing, making it a viable alternative to existing solid-pad leadframe designs.

Published in :

46th Electronic Components and Technology Conference Proceedings, 1996