Content area
Full Text
Keywords
Semiconductors, Encapsulation, Optimization, Electronic packaging
Abstract
Liquid encapsulation techniques have been used extensively in advanced semiconductor packaging, including applications of underfilling, cavity-filling, and glob top encapsulation. Because of the advanced encapsulation materials and the automatic liquid dispensing equipment involved, it is very important to understand the encapsulation material characteristics, equipment characteristics, encapsulation process development techniques in order to achieve the encapsulation quality and reliability. In this paper, the authors will examine the various considerations in liquid encapsulation applications and address the concerns on material characterization, automatic liquid dispensing equipment/process characterization and the encapsulation quality and reliability. The discussions will be helpful for future material and process development of semiconductor packages.
Introduction
The encapsulants are materials used to protect semiconductor devices and interconnects (e.g. wire bonding and solder bumps) from moisture, ozone, ultraviolet radiation and corrosion damages. They also protect the parts from mechanical damages like bending, vibration and fatigue caused by thermal shock and cycling during actual life applications. They also act as a dielectric insulation.
Transfer molding technology has long been used to encapsulate the traditional semiconductor devices in huge volume production. However, due to the market trends for higher density and smaller form factor packages, more compact and flexible encapsulation techniques are required for advanced packaging technologies including ball grid array (BGA) packages, chip scale packages (CSPs), flip chip and direct chip attach (DCA), where a liquid encapsulant is often used to seal the semiconductor devices and interconnects.
The liquid dispensing application can be categorized as dam and filling, underfilling, cavityfilling and glob top encapsulation. The key focuses for the liquid encapsulation application are material wettability and flow characteristics, the material curing characteristics, the material mechanical and thermal properties (e.g. Young's modulus and matched coefficient of thermal expansion (CTE)), and interface adhesion to other materials and the reliability.
In this paper, we will discuss various aspects of the liquid encapsulation application in the semiconductor packaging. That information could be used to achieve quality and reliable encapsulation process and material development.
Description of liquid encapsulation application
Liquid encapsulation application can be categorized as follows.
Underfilling process
Underfilling has been widely used to improve solder joint reliability of area array flip chip die or CSPs attachments both for use in internal...