1. Field of the Invention
The present invention relates to an organopolysiloxane gel composition that yields a cured product via an addition reaction of an organopolysiloxane, and relates particularly to an organopolysiloxane gel composition that yields a cured product that can be used favorably for protecting ICs or hybrid ICs and for encapsulating power modules and the like.
2. Description of the Prior Art
Silicone gels and silicone potting materials are addition reaction-curable organopolysiloxane compositions which comprise an organohydrogenpolysiloxane having hydrogen atoms bonded to silicon atoms (namely, SiH groups), an organopolysiloxane having alkenyl groups such as vinyl groups bonded to silicon atoms, and a platinum-based catalyst, and which yield a cured product via an addition reaction of the SiH groups to the alkenyl groups such as vinyl groups. These silicone gels and silicone potting materials exhibit excellent levels of heat resistance, weather resistance, oil resistance, cold resistance, and electrical insulation, and also exhibit low elastic modulus values and low levels of stress, and as a result, they are widely used in the protection of vehicle-mounted electronic components and household electronic appliance components. In recent years, with the ongoing trend towards smaller and lighter electronic componentry, the density of IC components, and the density of the wiring such as wire bonding used to connect these IC components to substrates have continued to increase. Because conventional silicone gels are of comparatively low viscosity they exhibit favorable flow properties, but the cured compositions lack satisfactory strength and elongation properties, and are weak relative to large positional displacements, with the gel cured products sometimes rupturing. In contrast, it is known that compositions that yield cured products with satisfactory strength relative to displacement suffer from higher viscosity, with a corresponding deterioration in the flow properties during the encapsulation step.
Organohydrogenpolysiloxanes having SiH groups that also include branching points are disclosed in Japanese Patent Publication No. 2,510,577 and Japanese Patent Publication No. 2,849,027. However, the cured products of the gel compositions disclosed in these publications deform readily and are prone to rupture when subjected to a large displacement.