Customer Brief: Bittware

At BittWare, a leading supplier of hybrid signal processing boards, CFdesign is the tool of choice to find the right balance of power, conductivity, weight, size and ruggedness.

As example, CFdesign  played an integral role in developing BittWare’s ruggedized 3U cPCI processing board, known as the GT3U.

The principal challenge was cooling a 10-watt FPGA chip underneath the mezzanine of the frame, where there was only a small amount of space to provide cooling.  BittWare also had to select the best thermal materials to maximize conductivity for the gap pad positioned between metal and non-metal surfaces.

“I started with a default design that represented the simplest, cheapest solution,” says Andy Buonviri, lead mechanical engineer for the GT3U.

Integration and auto-mesh

Integration between CFdesign and SolidWorks allows Bittware to set up and conduct iterative design studies without any translation, conversion, or data loss.  Volumes, void-filling, boundary conditions and material properties are assigned automatically, and associativity of all geometry is maintained as the part or assembly moves between SolidWorks and CFdesign.

Automatic meshing in CFdesign eliminates the need to fine-tune the mesh to get all the elements correct, a process that in traditional CFD takes too much time. “With auto-mesh, I can open a SolidWorks model with dozens of different component shapes and sizes and have it meshed in about 30 seconds,” says Buonviri.

20 geometry changes, 10 material changes, 1 trip to the thermal chamber

The first look at the GT3U in CFdesign quickly revealed where temperature rises were the worst.  It was then a series of back and forth between SolidWorks and CFdesign to optimize the design.  BittWare did about 20 iterations changing the model and another 10 or so changing material properties, adjusting power dissipation of components, making power supply changes, and working to get the best gap-pad material.

The solution was to have the frame wrap around the edges of the card so it made contact with the chassis cold wall on both the top and bottom surfaces.  Because the biggest rise in temperatures occurred in the gap pad, he selected the best-performing thermal materials for the pad.

“This process gives a lot of confidence in the quality of the final design,” says Buonviri.  “When we do the physical environmental testing in a thermal chamber it’s usually just to verify what we’ve already calculated in CFdesign.  It’s one set of tests, without the need to adjust things as you go, which takes time and money.”