AN-0003

Thermal Considerations for PAs AN-0003 Thermal Considerations for Power Amplifiers Overview Proper heatsinking to control junction temperature is an extremely important consideration for use of all power amplifiers. Gallium Arsenide (GaAs) devices can tolerate considerably higher junction temperatures than Silicon (Si), but due to its lower thermal conductivity, it requires more consideration than Si to remove heat. The thermal conductivity of GaAs is only about one third that of Si, and it has a nonlinear relationship with temperature (the conductivity worsens with increasing temperature). Although many factors inside and outside the package influence the junction temperature, the end user of the power amplifier can control the implementation of the connection and layout on the printed circuit board (PCB). The choice of the board material and thickness, the number of thermal vias placed beneath the part and the design of the heatsink are all important factors in properly using the part under difficult thermal requirements. Application Requirements ANADIGICS power amplifiers are typically packaged in LPCC (Leadless Plastic Chip Carrier) packages. These packages offer excellent thermal characteristics due to the thin copper paddle used for mounting the chip. The part itself (bare die) is also very thin and enables very good heat dissipation. A cross section of the package is shown in Figure 1. Gold Wire Mold Compound DIE 0.9mm Lead Solder Plating Copper Lead Frame Die Atta...