Wide area vertical expansion (WAVE/sup TM/) package design for high speed application: reliability and performance

A two metal flex-based WAVE package has been developed to replace four metal rigid based PBGA package. High board-level reliability was the primary motivation for this project and an equivalent electrical performance was a challenging target. All the package dimensions were maintained the same as the reference package to allow direct replacement. As a result of the one-year-long development program, the required reliability and performance goals were met successfully. This paper mainly describes the WAVE package design for reliability and performance. Optimal lead design is the most important step for reliable package development. The WAVE geometry model (WAVEGM) was developed to analyze the lead type, lead orientation, bump height, and injection lift height. The 2-metal flex tape was chosen to replace the original 4-metal rigid substrate due to its thinner dielectric layer, lower dielectric constant and improved trace/space design capability. The electrical performance was verified by both simulation and actual measurements of a test device.