ABSTRACT
Electronic circuit assemblies often must survive under hostile operating conditions. Such conditions often exist in automotive or military and aerospace applications. Such assemblies often employ surface mount integrated circuit packages, which attach to the printed wiring substrate by soldering their leads. One solution to the problem is use a solder joint lead encapsulant to bond the integrated circuit firmly to the printed wiring board. These encapsulants are typically epoxy compounds, containing a filler to match the coefficient of thermal expansion to that of solder, and formulated to have a glass transition temperature higher than the upper service temperature. The new solder joint lead encapsulant is a reactive hot melt epoxy. Thus, lower processing temperatures can be used than the temperature required for traditional epoxy encapsulants. Processing operations, which take place after placement of the reactive hot melt encapsulant, should suffice to cure the hot melt. However, temperature rises in the application itself will further the state of cure.
