Printed-Circuit Board (PCB) layout is critical to both thermal
and RF performance. It is therefore crucial that designers
consider the heat source as well as how the heat will be removed
before the electromechanical design is finished. Texas
Instruments, Inc. (Dallas, TX) offers a white paper on this
subject titled, "Junction Temperature of TRF1123/TRF1223 and
Recommended PCB Layout Guidelines." Specifically, this seven-
page document describes the PCB layout guidelines for optimal
thermal performance while reporting on junction-temperature
measurements for the TRF1123 and TRF1223 monolithic microwave
integrated circuits (MMICs). It concludes by calculating the
failure rate of those MMICs using measured junction temperatures
and known reliability data for the MESFET process. The TRF1123
and TRF1223 are galliumarsenide (GaAs) MMICs packaged in a 5
5-mm, 32-lead, leadless-plastic-chip-carrier (LPCC) package. An
8-mil-thick copper base (paddle) extends through the bottom of
the package. The package is designed to