A study of the thermal characteristics of a conductive adhesive chip attach process

Electrically conductive adhesives (ECAs) have been proposed as an alternative to solder in the surface mount (SMT) and flip chip attach (FCA) applications. This paper describes the development of a transient heat transfer model of a chip bonding process using the ECA bumps. The chip is heated using a top thermode directly contacting the chip and the card is heated from the back side (Z=0) using a heater. A detailed three-dimensional heat transfer model to account for the conduction, heat storage and convection and radiation from the card is developed using the finite volume technique. The spatial and temporal temperature distributions are studied through initial ramp-up, dwell and cool-down processes. It is seen that the bump temperatures are dominated and controlled by the heating process near the chip as opposed to heating the back side of the card. The numerical model is verified via actual measurements and the agreement is within 15 percent.