Moldex3D Blog: How to Consider the Influences of Different Component Contact Angles in Capillary Underfill Simulation

Capillary Underfill (CUF) in IC packaging process involves dispensing epoxy resin on the side of the flip chip and filling the bottom of the flip chip by surface tension. Moldex3D IC Packaging module supports Capillary Underfill simulation. With that, users can simulate capillary flow behaviours.

During the underfilling process, the flow front of epoxy is in contact with many different components, such as PCBs, solder balls, silicon dies, and more. The properties of surface tensions at contact faces vary with different components. In order to shorten the gap between simulation and the reality, Moldex3D takes the surface tension property into account by providing the contact angle parameter setting of epoxy with different components.

Workflow – Specify the contact angle parameters of the epoxy with different insert components

Step 1: First, create an Encapsulation (IC package) analysis project and then import the Capillary Underfill model. There are four types of insert materials which contact the epoxy resin in this case study: solder ball, silicon die, Cu pad, and Through Silicon Via (TSV).

Step 2: Launch the Process Wizard, select Capillary Underfill in the analysis types, switch to the Underfill Setting tab and then click Advanced to set contact angle parameters. In the Surface Tension tab, specify the contact angle parameter at the interface of epoxy with each different component.

Step 3: After other project setting and filling analysis calculation is completed, the influences of different component contact angles in the underfill flow front can be observed. There are three sets of contact angle settings in this case study: A. All of the contact angles are 30 degrees; B. All of the contact angles are 10 degrees; C. All of the contact angles are different values. According to the results, the flow front is significantly affected by different contact angle parameters, and show different filling trends.

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