Polyimide Restructuring, An Application For Low-K/Ultra-Low-K Die and Lead-Free Bump Integrity ImprovementAuthor: Roden Topacio
Company: AMD, Inc.
Date Published: 5/17/2010 Conference: ICSR (Soldering and Reliability)
Now, while the industry is moving to the use of ultra-low-K dielectric as the die technology is shrinking to 45 nm and below, and while the use of lead-free bump earns more and more attention, the industry is searching for a solution to protect simultaneously the low-K/ultra-low-K die and the lead-free bump. The brittleness and weakness of the IMC layer of a lead-free bump has been one of the biggest concerns in the transition to lead-free bump. Lead-free solder materials are also relatively less ductile than eutectic solder; this increased stiffness can lead to significant stresses that make the brittle intermetallic crack, particularly when operating temperatures are high or there is a significant mismatch between the coefficients of thermal expansion between the die and the substrate.
This paper will discuss how a restructured polyimide layer can offer a stress buffer for both the die and the lead-free bump, including discussions on how the polyimide can be restructured to improve its adhesion to the underfill.
Key words: POU, Lead-free, ultra-low-K, polyimide.
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