EMI Shielding

1. Theory
2. Test results

Theory

Typical Gold plated EMI shielding is wiped with each opening and closing of enclosure.

Particle Interconnect replaces the need for wiping with lower contact forces.

Examination of particle uniformity

6-12 μ particles coated with Ni and Cu, and pressed onto Cu. SEM at 1090x magnification, 60 degree angle.

Cross-section of Particle Interconnect pad

Demonstrates uniformity & planarity of particle protrusion above photoresist.

• 0.020" diameter x 0.003" tall nickel Particle Interconnect pad on 1 oz copper.
• Using 25 micron particles. Planarity of 1/2 particle diameter.

Picture courtesy of Larry DiFrancesco.

Particle Interconnect via

Connecting two conducting surfaces together.

Particle closeup	Connector closeup

Test results

Lifetest comparison of Particle Interconnect vs. other sockets

Tested to failure.

This graph illustrates the exceptionally long remate life the Particle Interconnect coating provides a contact. Since the non-wiping action of the particles does very little damage to the mating surface, contacts last for 1,000,000 insertions or more. While this number is higher than the most applications require, it does testify to the robustness of connections using Particle Interconnect coatings.

Contact resistance (milli-Ohm) vs. holddown force (gram-force)

Courtesy of Amp

These graphs show how Particle Interconnect coated contacts compare to traditional scrubing contact surfaces as regard to contact force and resistance. They illustrate the exceptionally low contact force of Particle Interconnect, showing this force to be at the test limit of 10 grams.

More importantly, the graphs show how consistently Particle Interconnect coatings perform between remate cycles. While tin and gold plated contacts 40 to 100 gram range initially, this performance was inconsistent and tended to degrade between remates because of oxide growth.

0.25" diameter hemispherical probes vs. 63/37 tin-lead coated surface.

Bright tin probe vs. control (no PI)	Bright tin probe vs. 20-25 μ PI
. 0.010" BeCu, 0.250" Ni, 0.150" SnPb. . 20 to 80,000+ milli-Ohms, 1 to 9 remates. . No scrubbing action.	. 0.010" BeCu, 0.250" Ni + PI, 0.150" SnPb. . 6 to 9 milli-Ohms (one ignored), 1 to 6 remates. . No scrubbing action against PI.

Gold Probe vs. Control (no PI)	Gold probe vs. 20-25 μ PI
. 0.010" BeCu; 0.250" Ni; 0.150" SnPb. . 20 to 80,000+ milli-Ohms, 1 to 9 remates. . No scrubing action.	. 0.010" BeCu; 0.250" Ni + PI; 0.150" SnPb. . 8 to 14 milli-Ohms, 1 to 8 remates. . No scrubbing action against PI.