Thermal performance of flip chip ball grid array packages

As processor speeds have increased, flip chip packages are frequently used because of the improved electrical performance than can be achieved with an array of very short, low inductance bumps used for power and ground. Both ceramic (FC-CBGA) and plastic laminate (FC-PBGA) substrates are commonly used for the packages. Historically, the ceramic substrate FC-CBGA packages offer improved electrical performance because of the ability to design with a large number of layers in the packages and small vias permitting effective power and ground planes. Unfortunately, the ceramic substrate packages are perceived to have limited usefulness in applications where solder joint fatigue is considered to be a limiting factor. The plastic laminate FC-PBGA packages have much better solder joint lifetime, but the question of the difference in thermal performance between the two styles of packages must be addressed. This paper compares the thermal performance of 360 ball 25/spl times/25 mm package. The junction to case thermal resistance with the bare die is identical between the two packages; hence, the thermal performance with a heat sink is very similar.