Journal of SMT Article

PoP Rework - A Case Study

Author: Robert Wettermann
Company: BEST Inc.
Date Published: 1/31/2015   Volume: 28-1

Abstract: PoP (package on package) rework presents multiple challenges including but not limited to the correct placement of warped devices, inspection of the multiple layers found in stacked devices, removal of underfilled PoPs and the removal and replacement of RF shields covering the PoP. This discussion is a case study of various techniques that were attempted for a specific PoP rework project and the methods which yielded consistent rework yields. The multiple attempts at different processes and their outcomes will be discussed and the lessons learned will be presented.

After reviewing the challenges involved in reworking PoP devices, the actual rework process will be documented as per the end user requirements. This paper points out both the successful and unsuccessful techniques for the rework application.

After using the more traditional approach of device removal including chemical and heat softening of the underfill material, a high speed mechanical milling process along with vibration dampening tooling allowed the device to be removed without applying heat to the board. This resulted in no component or pad damage.

Keywords: 

Package on package, PoP, PoP rework, X-ray inspection, PoP warpage, RF shield rework, stacked package



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