Molding compounds having a controlled thermal coefficient of expansion, and their uses in packaging electronic devices

摘要

Plastic (or resinous) materials used to package (or support) electronic devices typically have thermal coefficients of expansion exceeding that of the device to be packaged. A "loading" material (agent) having a coefficient of expansion significantly less than the "base" plastic material (molding compound), less than that of the die, and preferably zero or negative over a temperature range of interest, is mixed with the "base" plastic material to produce a plastic molding compound with a lower overall thermal coefficient of expansion. Titanium dioxide, zirconium oxide and silicon are discussed as loading agents. The loading material is mixed into the plastic molding compound in sufficient quantity to ensure that the resulting mixture exhibits an overall thermal coefficient of expansion that is more closely matched to that of the electronic device. Reduction of the absolute thermal coefficient of expansion of the plastic material (independent of any matching criteria) additionally serves to reduce thermal stress cracking of plastic package bodies during rapid thermal cycling, such as occurs during vapor soldering.