In a previous article LINQSTAT: Volume Resistivity vs. Volume Conductivity vs. Surface Resistivity where we describe the differences between Volume Resistivity and Surface Resistivity, we also raise the question, “Why does CAPLINQ give “less than” values (ie. <200,000 ohms per square-cm) instead of Typical Values?”
Given the wide specification range of LINQSTAT VCF low-level volume conductive film, some older products could have fallen into the MVCF or Medium-Level volume conductive film range.
So why are “less than” values given for surface resistivity of conductive plastics?
The answer that was previously given refers to the nature of the product itself. LINQSTAT Volume Conductive Film is a carbon-loaded polyethylene. As such, there are necessarily some differences in the conductivity over the entire surface and the data that CAPLINQ provides is meant to be a minimum, repeatable value that can be used in the design of the final product.
However, this is not the full answer, which is what I want to explain in more detail here. Both LINQSTAT VCF-Series products and LINQSTAT MVCF-Series products are carbon-filled conductive plastics that both use the same base plastic and both use conductive filler. The VCF-Series products are typically listed as having an surface resistivity of <200,000 ohms/square. This is due to the process that is used to blow the plastic, that the dispersion of the carbon can be quite wide. In some batches, the conductivity could be as high as 200,000 ohms/square but in others, it could be as low as 35,000 ohms/square. In the case of the 35,000 ohms per square, this product actually falls within specification of the MVCF-Series products. We are now moving away from this process to be able to give more consistent batch-to-batch results.
Can tighter specifications be given for the LINQSTAT conductive plastics?
The answer is yes. The MCVF-Series and XVCF-Series products, use this new process. For these products, another process is used that can drastically improve batch-to batch consistency. Though we do still have stock and continue to manufacture some of the old VCF-Series materials, we are slowly planning to phase out this process in favor of the new one. This process is slightly (about 15%) more expensive, but like you our other customers need to have more consistent lot-to-lot deliveries.
Which series of LINQSTAT conductive plastic films does this affect?
This affects only the VCF-Series products. The MVCF-Series and the XVCF-Series products all use the new process and the existing VCF-Series will gradually change to an LVCF-Series (for low-level conductive films) once the process is introduced for these products too.
How can I be sure what the specification or tolerance of the LINQSTAT material is?
First, you can check the technical datasheet to see what is called out, and then you can ask for the Certificate of Analysis (CoA) of the requested product. For example, here are the specifications for LINQSTAT conductive plastic. As you can see on this certificate, the surface resistivity values are within specification, but do not have the lower-level conductivity we would expect.
Visit caplinq.com to learn more about conductive materials including our broad range of electrically conductive plastics and antistatic tapes and films. If you have any questions, please don’t hesitate to contact us if you have further questions on the specifications of electrically conductive plastic.