IWLPC (Wafer-Level Packaging) Conference Proceedings


Author: Flynn Carson & Tae Sung Jeong
Company: STATS ChipPAC Ltd.
Date Published: 11/3/2005   Conference: IWLPC (Wafer-Level Packaging)

Abstract: The drop test performance of Fine-pitch Ball Grid Array (FBGA) semiconductor packages used in handheld consumer applications has emerged as a critical issue as such assemblies have transitioned to lead free. For such handheld consumer products, such as cellular phones, passing the drop shock test is the most important solder joint reliability test requirement to be met if the device is going to survive in the field. Lead free solder balls applied to such FBGA packages have different material properties and form different intermetallic compounds (IMCs) at the interface between solder ball and package or board than the eutectic Sn-Pb balls formerly employed. In general, the use of such lead free alloys has increased the susceptibility of such packages to failure due to drop shock or manufacturing process that introduce similar stress on the solder joint.

In order to better understand and improve the performance of lead free solder with respect to drop test, many factors that influence the drop test performance of lead free FBGA packages were evaluated. One of the most important factors evaluated was different solder ball pad finishes. This study revealed that the solder ball alloy and flux used to apply the ball to the package are significant factors that influence the drop test performance. Such performance is dependent on the pad finish used. Through optimization of lead free solder ball alloy and flux used for each pad finish, robust drop test performance can be demonstrated.

Key words: FBGA, lead free packaging, lead free solder, ball pad finish, flux, drop shock test.

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