Anti-static, dissipative, conductive — the words get used interchangeably, and that causes real problems. The specification that matters is resistivity, and it comes in two flavours.
Volume resistivity describes how easily charge moves through the bulk of the material. Surface resistivity describes how it moves across the face. For a fixture that touches a PCB on one face, surface resistivity is the number that governs performance. For a liner in a powder chute, volume resistivity dominates.
Most semiconductor customers specify 10 to the power 6 through 10 to the power 9 ohms for both, which places the material firmly in the dissipative band: slow enough to prevent a spark, fast enough to bleed charge away before it builds. Truly conductive materials below 10 to the power 4 ohms can damage devices by discharging too quickly. Carbon-black loaded grades are the usual route; the trade-off is that they are black, opaque, and slightly weaker in impact than the unfilled polymer.
Need a material recommendation?
Send us the application and we will reply with two or three candidate grades and a price.
1 comment