Abstract

The present paper is a study on flip-chip open bump failure mechanism. Initial electrical testing showed open circuit condition. Scanning acoustic microscope (C-SAM) identifies delamination on particular bump(s). Initial cross-sectional images suggested that the separation took place at Al – TiW interface. However, EDS analysis on the separated surface indicated the presence of Al metal at both sides of the separation, which raises a question of why the Al layer is cracked or separated instead of interface de-lamination. Research in literature and investigation at assembly line points an ultrasonic cleaning step in manufacturing process as a contributor to the open bump failure. Examining virgin dice after bump removal observed crack in nitride passivation around the bump neck, indicating high stress level during passivation film deposition and/or bump formation process. Hence it is concluded that ultrasonic cleaning in device assembly aggravates preexisting stress in weak bump(s), resulting in latent failure in field application.

This content is only available as a PDF.
You do not currently have access to this content.