Underfill encapsulant materials

Underfill encapsulant materials have certain properties.

Underfill encapsulant material properties are almost the same as those of encapsulation molding compounds used for standard microchip encapsulation, with two differences:

• For underfill encapsulant rheological data, the Herschel-Bulkley-WLF model includes one additional term, h (thickness), as described in the Herschel-Bulkley-WLF viscosity model.
• Underfill encapsulants include an additional data category, surface tension, as described below.

Surface tension data

In underfill encapsulation, when the encapsulant is dispensed, the driving force is the capillary force at the melt front. In order to analyze this dispensing process, surface tension data is required to analyze the dispensing process. To model surface tension, the dynamic temperature-dependent surface tension model by Han is used, which can be represented as follows.

The surface tension and the equilibrium contact angle can be described by the equations given in the Dynamic surface tension model.