METHODS FOR GAINING RELIABILITY IN UNDERFILL APPLICATIONS
Voids or air gaps in underfill are a common problem across underfill applications, from the smallest die on flex to the largest BGA. The consequences of having voids in underfilled parts depend on the package design and use model. Voids typically result in a loss of reliability. This article explores strategies for troubleshooting void problems.
Detecting Voids
If you have determined there is a voiding problem, you probably already have a method of detecting the voids; however, different methods can be useful for troubleshooting. Three of the most common methods for detecting voids are the use of a glass die substrate, ultrasonic imaging, and destructive testing of a cross section or breaking the die off the part. Using a glass die or substrate can be helpful. This method provides instant feedback during testing and can be used to help understand flow patterns to optimize underfill speed. Using underfill materials of different colors can also help visualize the flow. The disadvantage of this method is that flow and voiding behavior may be slightly different for glass parts than actual production parts.
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