RELIABILITY IMPACT OF COPPER-DOPED EUTECTIC TIN-LEAD BUMP AND ITS VOIDING UPON FLIP CHIP ASSEMBLIESAuthors: David Ihms and Shing Yeh
Company: Delphi Electronics & Safety
Date Published: 4/8/2008 Conference: SMTA China
A significant incidence of solder voiding was observed in the SnPbCu bumps and its effect upon reliability performance is also documented. X-ray analysis was used to statistically measure the incidence of solder voiding. The impact of solder voiding upon flip chip solder joint reliability has been a controversial topic. There is a concern that large solder bump voids; > 50% of the bump diameter, either created by poor pad wetting or poor bump processing, can lead to current crowding and poor solder bump features susceptible to early solder fatigue. Flip chips were prepared with an increased incidence of solder voiding during the bumping process and their reliability performance was compared to typical voided solder bumps from current production environment. The susceptibility of assembled flip chips to damage during handling was also evaluated by board-bending tests with typical-level and high incidence solder bump voiding. It is shown that the increased solder voiding does not significantly impact the reliability of the solder joints nor make them susceptible to damage from handling. However, the addition of Cu in the Sn-37Pb solder has significantly increased flip chip reliability, particularly against diffusion related failure mechanisms, regardless of the increasing level of bump voiding.
Key words: SnPbCu, flipchip, reliability, solder voiding
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