CSP and Flip Chip Underfill Processes and Tools For Efficient Manufacturing
Review of CSP and Flip Chip Underfill Processes and When To Use the Right Dispensing Tools For Efficient anufacturing
By Steven J. Adamson
Asymtek, A Nordson Company
2762 Loker Ave. West, Carlsbad, CA 92008
tel: 1-760-930-7274
Abstract：
The need to underfill chip scale package (CSP) and Flip Chip devices has been understood for some time, particularly in portable applications. The concept of using liquid glue materials is an operation that manufacturing engineers would like to replace – they are looking to minimize material handling and increase throughput. Many different approaches to underfill have been tried but they usually compromise reliability or result in a less efficient process, when all factors are taken into consideration.
This paper reviews common underfill material choices and the methods of material application. In addition, this paper attempts to show the impact on throughput and board design that the different approaches have on the underfill operation.
Introduction
The question of how to improve the underfill process has seen many potential solutions, such as no-flow materials and corner dots. Numerous papers have been presented on No-Flow underfills but this material has yet to find wide acceptance in industry. Clearly something was not considered in the problem definition stage. At the same time the technology of dispensing conventional capillary underfills keeps improving with long-life fluids and automated dispensing equipment that does not require operator intervention for several days. As a new technology is developed the need to understand the problem fully is tantamount and must be continuously evaluated to avoid having a solution to a problem that no longer exists. However existing suppliers to the market do not stand still and this can also cause the problem definition statement to change. So what is the status of underfill technology?
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