Rework Challenges for Smart Phones and Tablets
This paper reviews the challenges and process steps needed for successful repair of surface mount devices on very densely packaged circuit boards.
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Authored By:
Paul Wood
OK International / Metcal
Garden Grove, CA
Summary
Smart phones are complex, costly devices and therefore need to be reworked correctly the first time.
In order to meet the ever-growing demand for performance, the complexity of mobile devices has increased immensely, with more than a 70% greater number of packages now found inside of them than just a few years ago. For instance, 1080P HD camera and video capabilities are now available on most high end smart phones or tablet computers, making their production more elaborate and expensive.
The printed circuit boards for these devices are no longer considered disposable goods, and their bill of materials start from $150.00, with higher end smart phones going up to $238.00, and tablets well over $300.00.
The implementation of the surface mount devices have become key components for mobile products by offering increased component density and improved performance. For example, the newer style DDR memory integrated components use less power and work at twice the speed of former versions. It is not surprising that most component manufacturers now produce these surface mount devices as small as 1mm square.
Mobile products generally use an epoxy underfill to adhere components to the printed circuit board in order to meet the mechanical strength requirements of a drop test. Reworking glued components is the most difficult application in the electronics industry, and needs to be addressed as a process.
Conclusions
This paper reviews the challenges and processes needed for successful repair of surface mount devices and the associated devices present on a printed circuit board assembly.
A robust and repeatable rework process is essential for high rework yields. Proper preparation and application of solder and flux will add to the robustness and repeatability of the process. Reclamation of expensive components can be worthwhile if safely removed. The paper pays particular attention to the challenges associated with underfill epoxy and the lack of a robust, repeatable process and the need for a better solution for pad cleaning and preparation. Additionally, the industry lacks a reliable approach to removing epoxy from printed circuit boards which needs to be
addressed.
Initially Published in the IPC Proceedings
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