CFD analysis of automatic test equipment

In many cases the goal of CFD modeling is the accurate prediction of chip junction temperatures within large electronic enclosures that contain numerous boards, flow obstructions, and other thermal/fluid modeling challenges. Although, it is often impractical to develop a single, coherent CFD model that accurately predicts system and board level performance, many electronic enclosures demand such an approach. Automatic test equipment (ATE) for testing semiconductors easily fits into this category. Reliable operation of ATE is critically dependent on maintaining a stable thermal environment within the test head. The complex architecture of the test head, containing heavily populated boards arranged in a radial manner, makes it impractical to accurately predict board and system level performance discretely. This paper documents a successful methodology to model complex systems that require simultaneous system and board level thermal/fluid interactions. First, a CAD model was created integrating the board and system level geometry. This CAD model was then used as the basis for the CFD modeling approach. The CFD software package used was CFDesign 5.0, a finite element fluid flow and heat transfer solver. CFDesign´s ability to import geometry using any industry-standard format and quickly prepare it for simulation was the key to creating a CFD model that accurately predicts both system and board level thermal performance concurrently. Employing the above CAD and CFD tools in concert with experimentally validated assumptions, chip junction temperatures were accurately predicted as well as their sensitivities to system level characteristics.