Questions Regarding Underfill Options

Kay Parker is a Technical Support Engineer based at Indium Corporation's headquarters in Clinton, N.Y. In this role she provides guidance and recommendations to customers related to process steps, equipment, techniques, and materials. She is also responsible for servicing the company's existing accounts and retaining new business.

Edithel is a chemical engineer with 20 year experience in manufacturing & process development for electronic contract manufacturers in US as well as some major OEM's. Involved in SMT, Reflow, Wave and other assembly operations entailing conformal coating and robotics.

It's a bit difficult to answer this question without knowing all the applications details.

In a capillary underfill process, the fluid is typically dispensed along one edge of the chip so that the fluid is pulled under the component. Whether you dispense too much or too little depends on the gap underneath the die. You also need to consider how much fluid needs to remain along the edge and what the keep-out zone should be around the die. You should see fluid on the other side of the die. There are a lot of papers that discuss how to calculate the optimal amount of fluid under the chip.

In other underfill processes, high pressure can be used to drive fluid under the die. The fluid type typically used is a molding compound.

If the fluid must be applied through a hole in the shield, there are several techniques that can be used, but depend upon the specific requirements and geometries of the part on hand.

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