CCC (Current Carrying Capacity)
PariPoser® material has multiple short columns of nickel particles per contact position. This results in a low resistance and low inductance path for the current compared to most connector geometries.
/CRES (Contact Resistance): Durability over 500K cycles and over Time
A common test of spring durability is to quickly cycle the contact for up to 500K cycles while measuring the CRES. For a test of 1.0mm pitch material, the average CRES remained at 5-10 mΩ for the full range of 500K cycles.
A lot of 1.0mm pitch PariPoser (used in a connector) was measured for CRES every year for 12 years without taking a set and with minimal changes to its CRES. The test was designed to detect a “set” of the material that could be measured in a change of CRES.
Alignment
The contact pads on either side of the PariPoser® material need to be precisely aligned. If they are not aligned, they might make a connection to the wrong pad – as shown below:
Stickiness
Silicone is slightly sticky. It feels like a yellow “post-it” note. This characteristic can be helpful during the handling of PariPoser® material – since it will tend to stay in the place where it is positioned. It can be a nuisance though, because small particles of dust are not easily blow away.
Handling & Cleanliness
All interconnects need to be clean – and PariPoser® material is no exception. Since the material is so thin and stretchy, cleaning contamination off the material has to be done delicately.
When handling the material, special care need to be taken to avoid contamination from Sulphur.
Sulphur reacts with the Silver plating on the particles to form Silver Sulfide – the same thing that is called “tarnish” on silverware. Silver Sulfide has a high resistivity. Sulphur compounds are sometimes found on clean room gloves and in hand lotions.
Since each application is unique, please contact the Paricon sales engineers for advice on handling and cleaning procedures for your project.
Normal Force
The integrity of a contact is often determined by the force exerted on a target by the contact. Spring pins typically have a normal force rating from 15 – 100 grams. Some high-power spring pins have a normal force of up to 200 grams. Cantilever beam contacts used in connectors typically have a normal force of 30 – 100 grams depending on the plating material and the degree of shock and vibration that will be experienced. In most cases, the contact geometry has a reduced-sized touch point that concentrates the force.
The integrity of a PariPoser® contact is determined by the pressure exerted on the target. The required pressure per contact target is 240 psi (171 grams per mm2). Since the size of the pads gets smaller or larger when the pitch changes, the amount of force per contact also needs to change to maintain the proper pressure.
This table will give you an idea of how to determine the force per PCB contact.
Low force might result in higher CRES, and high force might result in crushing the nickel particles.
The Force vs. Compression curve of an elastomer is very different from a traditional spring pin. To get the right force using an elastomer, the compression needs to be carefully calculated and controlled.
RF characteristics and simulations
Because of the potential benefits PariPoser material offers for high-speed interconnects, there have been many test reports done under many circumstances. Many of the test results were favorable at bandwidths of 40Gz – 60Gz. One experiment conducted at the University of Erlangen in Germany, reported favorable attenuation results ( < -1 dB) up to 110 GHz.
There have also been many simulations conducted under many different circumstances. The simulation of only the PariPoser material and the PCB pads starts with this kind of a geometry. The green columns are the nickel particles and the red circles are the PCB/DUT pads. Some of the pads are assigned to be Ground, and some are assigned to be Signal.
Variables that impact the simulated RF results are pitch, material thickness, size of the particles, pad shape/size, the ground/signal patterns, and the traces used to approach the pads. Some typical ANSYS HFSS simulation results done with standard Paricon design standards and a pattern of one signal surrounded by eight grounds are summarized below:
The simulated curves for the 0.4mm pitch material:
Further simulations with different patterns of PariPoser® configurations can be done at specialized signal integrity consulting firms. For a complete simulation study, all the trace geometries to/from the PariPoser® material have to be included.
Comparison of PariPoser® material to other conductive elastomers
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Some conductive elastomers use small diameter, insulated, cut wires.
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Some conductive elastomers are made with conductive plugs that are inserted into a non-conducting carrier. The carrier might be a polyimide sheet or a layer of non-metallic elastomer.
Comparison of PariPoser® material to Spring Pins
PariPoser® contacts are much shorter than spring pins, and have the potential for very high bandwidths.
PariPoser® contacts have a low CRES and limited compression per contact location.