A study of compact thermal model topologies in CFD for a flip chip plastic ball grid array package

Abstract

Phone: (5 12) 420-9273Austin, TX Tempe, A 2 ABSTRACT A previously validated detailed model of a 119-pin Flip-Chip Plastic Ball Grid Array (FC-PBGA) package was created and validated against experimental data for natural convection and forced coirvection environments. Next, two compact models were derived, a two-resistor model (created using the JEDECstandard based computational approach), and a multi-resistor model (created using the DELPHI optimization approach that was boundary condition independent within engineering accuracy). The compact models were placed in natural convection and forced convection (velocities of 1 and 2 m/s) environments with and without a heatsink. Based on the agreement obtained between the detailed model and compact model simulations, the accuracy and validity of the two compact models was assessed. Of the two compact thermal models considered, the Delphi multi-resistor model provided the same predictive estimates (within 5 % ) as simulations involving a detailed thermal model of the package in natural and forced convection environments both with and without attached heatsinks. Some thermal modeling issues were addressed with respect to implementation of compact thermal models with attached heatsinks. IN TR 0 D U CTIO NCreating validated thermal models of electronic packages has always been a challenge in the electronics industry. Existing metrics such as junction-to-case thermal resistance and junction-to-am bient thermal resistance are sometimes useful as figures of merit, but have proven to fail spectacularly in many real environments (Dutta [l]). This is because these measures typically are reported for ill-defined boundary conditions, and are also by definition subject to large variations depending on the environment.In order to improve the ability of design engineers to model electronic parts successfully, project DELPHI (Development of Physical models for an Integrated design environment) was launched in 1993 by several European end-users with the specific aim of creating a methodology for the generation of thermal models that would be independent of the environmental boundary conditions (Rosten and Lasance [2]). This project has produced an established methodology for creation of two types of thermal modelsa "detailed" model (representing the package in sufficient geometric detail so as to capture all relevant thermal paths accurately; KEY WORDS: electronic package, component-leve] thermal and a "compact" model (a much reduced model consisting of a thermal resistance network that would still capture the thermal behavior of the parts accurately, and predict die-junction temperatures to a high behavioral model; air cooling; plastic ball grid array; compact model, thermal resistance NOMENCLATURE Therm a1 conductivity, (W/[m KI) k P Power, (W)

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