The reliability of a semiconductor is determined by the junction temperature, which in turn is dependent on several factors including device layout and mounting, package thermal resistance, PCB layout, heat sink interface, and ambient operating temperature. This application note describes PCB layout guidelines for the best thermal performance and reports on junction temperature measurements of the TRF1123 and the TRF1223. Finally, the failure rate of the TRF1123 and the TRF1223 are calculated using measured junction temperatures and known reliability data for the MESFET process.

The TRF1123 and TRF1223 are GaAs Monolithic Integrated Circuit MMICs packaged in a low-cost, 5 mm x 5 mm, 32-lead leadless plastic chip carrier (LPCC) package. The package has an 8 mil thick copper base (paddle) that extends through the bottom of the package. The package is designed to solder reflow the paddle to a ground pad on the PCB so that a low thermal resistance and excellent RF performance is achieved. The die is attached to the copper paddle using high thermal conductivity silver epoxy: Ablestik Ablebond 84-1 LMIS. The epoxy thickness is kept to a minimum. For the junction temperature test, the die are mounted in packages which have the tops removed so that the surface of the die is visible for infrared temperature measurement.