Pan Pacific Symposium Conference Proceedings


ADHESION OF FLIP-CHIP UNDERFILLS TO VARIOUS DIE PASSIVATIONS BEFORE AND AFTER ACCELERATED ENVIREMENTAL EXPOSURE

Authors: Mark Dimke, Ph.D.
Company: Dexter Electronic Materials
Date Published: 2/13/2001   Conference: Pan Pacific Symposium


Abstract: With the ever-increasing reliability requirements and price pressures of electronic packages, it becomes more important than ever to understand the fundamental failure modes in packages. Packaging engineers can then use this information to minimize that failure mode and yield the highest reliability devices with the least time spent in materials qualifications. Given that the delamination of the flip-chip underfill to the die passivation is the most common failure initiation mechanism in flip-chip packages , this study endeavors to elucidate the performance of various flip-chip underfills to the three most common die passivations. (Benzocyclobutene (BCB), Polyimide and Silicon Nitride) It has been shown that measuring adhesion values for underfills to passivations strongly correlates to the overall reliability of flip-chip packages. Given this strong correlation it appears that there would be great value in knowing the adhesion of various flip-chip underfills to the passivations and even more importantly how that adhesion is maintained over the course of a rigorous but typical set of reliability requirements.

This study evaluates adhesion between the flip-chip underfill and the passivation utilizing a die shear methodology. The test vehicle utilized for this study is a 100-mil square peripherally bumped die provided by Flipchip Technologies. The die are identical with the exception of the three passivations being examined. Six different underfills were evaluated for adhesion after the listed environmental exposures; initial, JEDEC 3 utilizing a 260° C reflow, JEDEC 3 plus 24 Hr. Pressure Cooker Testing (PCT), JEDEC 3 plus 96 Hr. PCT, JEDEC 3 plus 168 Hr. PCT and JEDEC 3 plus 1000 cycles condition B.

Results of the study will demonstrate passivation/underfill combinations that have good adhesion through environmental exposure. The use of this data will allow packaging engineers to more judicially choose the materials sets for the flip-chip packages and reduce the number of trials required for qualifications. In addition, this study will chronicle the evolution of adhesion in underfill materials.

Key words: Flip-chip, underfills, passivation



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