Test Fixture Contactor
Abstract:RF performance of a test board with a contactor is analyzed using FDTD simulationThe contactor is central to the design of high volume RF test fixtures. It acts as the final link connecting the test system to RF IC and high-speed digital IC packages. With digital clock speeds and RF frequencies increasing, the performance degradation due to the contactors cannot be ignored. This example demonstrates how EMPro helps you to quickly analyze and understand the impact of the contactors to the overall test results.
The design of contactors impacts the product’s cost, its manufacturing time, and eventually product success. Since contactors are designed for a specific test fixture application, it is very important for test engineers to quickly analyze and understand the impact of the contactors to the overall tester performance and accuracy. EM simulations greatly reduce the cycle time of contactor designs. FEM and FDTD field solvers are both suitable. In many cases the FDTD field solver is faster and more memory efficient than FEM technology for contactor geometries.
In this example an ADS layout design of the test board is brought into EMPro, where a 3D model of contactor is added and a full 3D EM simulation using FDTD is run.
Figure 1: ADS layout design of test board
Figure 2: 3D contactor model in EMPro
Figure 3: 3D contactor model combined with test board layout in EMPro
Two simulation approaches were compared. First, separate EM simulations of the board and contactor were completed, the resulting S-parameter files were cascaded in an ADS schematic design, and a linear circuit simulation was run. In the second approach, a single EM simulation of the board + contactor was completed. The second approach includes the effects of coupling and discontinuities between the board and contactor, and these effects can be seen as the difference between the two curves in Figure 4.
Figure 4: Simulation results
There are few possible sources of discontinuity between the board and contactor shown in Figure 5. These discontinuities would not show up when we simulate the board and contactor separately, but are accurately modeled when we do a full 3D simulation of the board and contactor together.
Figure 5: Discontinuities between the board and contactor that are accurately modeled using full 3D EM simulation
Full 3D simulations with FDTD speed the design of test contactors and provide insight on how coupling and discontinuities impact overall tester performance.