This extract is from the University Erlangen-Nuremberg Report – available upon request.
What Results should I expect ?
This example will help you understand what you should expect for a board to board (B2B) connection using PariPoser® elastomer between two PCB’s. The signal integrity results were excellent (see figure 1). The elastomer material had almost no impact to the signal integrity of the existing design. Insertion loss (S21) is -3dB at 40 GHz and Return loss (S11) is -18 dB at 40GHz.
What does the test setup look like ?
The test setup consists of two identical PCBs with microstrips on the top layer. One of them is turned upside down and overlapped with the other, and clamped together. The traces are narrowed in the overlap region to maintain an impedance of 50 Ω (See Fig 2)
How does the Impedance profile look?
The impedance profile of this assembly, obtained by frequency domain reflectometry, is shown in Fig 3.
The impedance of the microstrip line is about 48.5 Ω due to PCB production tolerances. The dashed black line shows the impedance profile of the assembly without polymer inserted. The impedance profile is slightly changed in the contact region by inserting the PariPoser elastomer, leading to a capacitive drop at the 0.23 ns point. This capacitive behavior in the transition region can mainly be attributed to the geometry change due to the additional elastomer thickness of 60 microns.