Pan Pacific Symposium Conference Proceedings


Author: Horatio Quinones
Company: Asymtek
Date Published: 2/2/1999   Conference: Pan Pacific Symposium

Abstract: The mechanical and environmental properties and ultimate reliability of any encapsulated semiconductor package depend greatly on the liquid encapsulation material (liquid molding compound) used and the process by which it is applied. The body of data extolling the virtues of properly applied encapsulants covers the full range of package configurations, including direct chip attach (DCA), chip-scale-package (CSP), and cavity packages such as the ball grid array (BGA). The proper method of applying or dispensing encapsulants, or in other words the ‘best dispensing practices’, depends on the effects of temperature as one of several important factors.

Although extensive data exists on encapsulant material characterization, including time and temperature dependencies (i.e., viscosity, Tg, CTE, etc.), not as much is known on the subject of the thermal effects on the actual process of dispensing. Using a model of a popular cavity-down ball grid array package design with several different sources of encapsulant heating, this paper will present experimental results on how best to heat the encapsulant and package to enhance flowout and to optimize surface flatness. The principle focus is on investigation of heating the substrate, the needle and the fluid chamber (prior to dispensing).

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