Technology

PariPoser® material is good for high-speed interconnects, because it is so thin. It’s good for power interconnects because it has a high Current Carrying Capacity (CCC). It’s good for high-durability applications because the material does not take a set. And, it’s good in wet environments because it is impervious to liquids.

When the material is relaxed, the silver-plated particles at the end of the columns stick out a bit from the silicone. So, as soon as contact is made, these columns immediately conduct current. As the material is compressed (typically <30% of the thickness), the metal particles push against each other, and the CRES drops down to about 10-20 mΩ.

Silicone has an unusually low Young’s modulus in comparison to its bulk modulus. To facilitate compression at the pad locations, there needs to be some adjacent area into which the silicone can squeeze. Typically, that area is the space between the PCB or DUT pads – as shown in the illustration below. The expansion areas need to be uncluttered (no solder mask, no traces, and no components).

When the pitch of the contacts (and the size of the pads) gets bigger or smaller, there should still be 6-10 columns for each pad, so the spacing of the columns and the size of the particles must be adjusted for each pitch. (Small PCB pads need more closely spaced columns and thus smaller particles.) Each column has 4-5 particles, so when the diameters of the particles change, the overall thickness of the elastomer sheet will also change.

PariPoser® material can be attached to a metal or plastic frame, keeping the material taut and making it easier to handle, with a higher temperature rating (up to 150°C). When not mounted on a stretch frame, the loose material’s temperature rating is 100°C.

When mounted taut on a stretch frame, the silicone is already a bit thinner than normal due to the stretch, and it takes more thermal expansion before the silicone fills in the interstitial spaces.

Thermal cycling within the specified limits of -50°C to +150°C will result in very little variation in CRES. Actual thermal cycle results for 1.0mm pitch material are shown below. The cycles were repeated many times with consistent results.

In addition to the vertical CTE effect, there might also be horizontal expansion and contraction. The CTE differences among the interconnection materials (PariPoser® material, the PCB, and the DUT) might result in horizontal misalignments.