Design for reliability of Hi-density Leadless Array (HLA#x2122;) package

摘要

HLA™ (Hi-density Leadframe Array) is a new leadframe-based technology that breaks the legacy QFN lead finger constraints and offers a solution to high I/O package requirements in the industry. It can replace many types of leadframe and BGA technologies. As a leadframe-based product, it has limitless design flexibility and allows the designer to design the package around the die. I/O counts of HLA can rival some of the fine pitch BGA products. In the past, in order to gain more leads in a leadframe product, the body size must be increased, which results in longer bond wires and the accompanying issues with wire bond, mold sweep, higher inductance, etc. HLA technology allows routing under the die, so growing the package is no longer necessary. Body sizes in certain lead counts and die sizes of QFN or QFP can generally be reduced by several sizes in an HLA. Like other new packages, reliability is also a key question for all customers. HLA can meet MSL level 1. Currently, HLA package of 5x5 mm body size passed drop test according to IPC/JEDEC standards. Passing other board level tests, such as TCOB (temperature cycle on board) in a leadless leadframe technology, like HLA and standard QFN package, has design and process challenges not normally encountered in substrate- based BGA packages. This paper reveals the structure of HLA package. To improve the TCoB life time, a 5x5 mm HLA package was used as test vehicle for TCoB reliability study, some factors including die size, die thickness, leadframe design and mold compound property are studied. Based on these studies, corresponding FEA model was constructed to simulate the TCoB fatigue life. With a certain confidence on the correlation result, some more FEA were studied to improve larger HLA body size such as 8x8 mm. With proper material selection, it is possible to improve the TCoB life of an 8x8 mm HLA to over 1000 cycles.