Thermal Characterization of Packaged RFIC, Modeled vs. Measured Junction to Ambient Thermal Resistance

Thermal characterization of a semiconductor device is the determination of the maximum junction temperature (Tjmax) of the die circuit during worst case operating conditions, as well as the thermal resistances of the semiconductor package alone, and attached on the second level to a Printed Circuit Board (PCB). The die junction temperature (Tj) is directly related to the life of the product, and is used in reliability calculations to rate the power on hours the product can produce during its life. The higher the circuit junction temperature during operation, the quicker product end of life will be reached. The maximum junction temperature of the die cannot exceed the maximum temperature specified in the technology's design and reliability specifications. In today's wireless market, devices are getting smaller in size and power dissipations are on the rise. This produces higher heat fluxes on the semiconductor die producing higher junction temperatures. The design of both the package that encapsulates the die and the printed circuit board it is attached to become instrumental in removing heat from the die. This is a study characterizing an RFIC silicon germanium (SiGe) die packaged in an exposed paddle QFN 20 lead package that is soldered to an assumed PCB. Thermal modeling done in ANSYS 5.7.0 was correlated to measured results using a JEDEC compliant system for semiconductor packaging thermal measurements. The test system used for this study is a "Phase 10 Thermal Analyzer" from Analysis Tech in Wakefield, MA.

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