Abstract: A process and combination of materials for underfilling a surface-mount IC device (12), such as a flip chip, for the purpose of increasing the thermal cycle fatigue life of the terminals (14) that attach the device (12) to a thin-laminate organic circuit board (10), such as a printed wiring board (PWB) or printed circuit board (PCB). The process parameters and materials, including the underfill (20), masking (22) and cleaning materials used, exhibit a synergistic effect that increases thermal cycle fatigue resistance to a level at which a flip chip processed in accordance with this invention is capable of reliably withstanding at least 1000 one-hour cycles between -40.degree. C. and 150.degree. C. The materials and the manner in which the device (12) and circuit board (10) are prepared for application of the materials are critical to eliminating tendencies for inconsistent reliability in underfilled SM devices.

Abstract: A method and encapsulation material are provided for processing an electronic circuit assembly having surface mount integrated circuit packages mounted with soldered leads to its substrate, in which encapsulation of the soldered lead joints serves to enhance the fatigue life of the solder joints. The encapsulation material is a reactive hot melt epoxy that is curable at temperatures significantly lower than that required for previous epoxy-based encapsulation materials. As such, processing of the circuit assembly is greatly facilitated, while the benefit of encapsulated solder joints is achieved for the assembly. The encapsulation material further includes a latent curative and a filler material for lower the coefficient of thermal expansion of the encapsulation material.

Abstract: A method and encapsulation material are provided for processing an electronic circuit assembly having surface mount integrated circuit packages mounted with soldered leads to its substrate, in which encapsulation of the soldered lead joints serves to enhance the fatigue life of the solder joints. The encapsulation material is a reactive hot melt epoxy that is curable at temperatures significantly lower than that required for previous epoxy-based encapsulation materials. As such, processing of the circuit assembly is greatly facilitated, while the benefit of encapsulated solder joints is achieved for the assembly. The encapsulation material further includes a latent curative and a filler material for lower the coefficient of thermal expansion of the encapsulation material.

Abstract: Conformal coating materials are provided for forming a protective conformal coating on the surface of an electronic assembly. The conformal coating materials are characterized by being hot melt materials, in that they are each initially a solid or semisolid at approximately room temperature, a liquid at an elevated temperature at which the coating material is applied to the electronic assembly, and solidify upon cooling to a temperature corresponding to a service temperature of the electronic assembly. As such, the coating systems can be rapidly applied through various highly controllable techniques associated with hot melt dispensing equipment. In addition, the coating systems quickly solidify upon cooling to allow handling of the electronic assembly. The conformal coating systems may be nonreactive, indicating that the system can be remelted, or reactive, indicating that a post-application curing process occurs over time at a temperature less than the elevated application temperature.

Abstract: A method is provided for processing an electronic circuit assembly having surface mount integrated circuit packages mounted to its substrate, in which ingress of a conformal coating into a void present between the IC package and the substrate is prevented by a masking composition which forms a barrier around the IC package prior to the conformal coating process. The masking compositions are hot melt materials, in that each is initially a solid at roughly room temperature, melts to become a liquid at an elevated temperature at which the masking composition is applied to the electronic assembly, and forms a solid upon cooling to a temperature corresponding to a service temperature of the electronic assembly. As such, the masking compositions can be rapidly applied through various highly controllable techniques, and will quickly and sufficiently solidify upon cooling to allow handling of the electronic assembly.