Injection moldable Thermoplastic have always been used to save costs and this is due to the very fast process that can generate significant detail in a part. The cost savings get even larger when product designers begin to leverage Thermoplastics in a functional way beyond just a covering or a skin. Functional thermoplastics bring additional properties to the product that uses them and in this discussion. Below we’ll discuss EMI/RFI Shielding in Thermoplastics.
Regulations often require electronic devices to eliminate emissions from their device. The electromagnetic interference (EMI) that comes from electronics needs to be contained inside the device. Normal thermoplastics do not keep the EMI inside the device and older techniques to attenuate the EMI were by plating the inside of the device. The plating is conductive and helps to generate a Faraday cage around the electronics, thus blocking it from going outside the device.
Modern functional thermoplastics can provide EMI/RFI Shielding in the pellet itself, eliminating the need for plating and offering more design flexibility. Material manufacturer’s will add carbon fiber, stainless steel fiber or nickel coated carbon fiber to a thermoplastic matrix to provide EMI/RFI Shielding properties. Above is a picture of pellets of an RTP Company product that offers EMI/RFI Shielding. Longer pellets and the pellet blend show you that this material has a lot of additives or fillers.
Part design, mold design and the injection molding process all need to be tailored for these types of material. The grade that Hi-Tech recently made parts from ran like cement when compared to most thermoplastics. Meaning that it didn’t want to go long flow lengths and required larger runners and sprues. Most thermoplastics when purged melt into a large continuous melt. The photo at the bottom of this article is of the melt of this EMI/RFI Shielding material from RTP. As you can see, the airshot was much stiffer than normal thermoplastics and the amount of filler prevented it from developing into a pool. It is likely that the fillers are also somewhat thermally conductive and cause purge or air shots to cool off quickly.
Below is a link to RTP Company’s webpage on EMI/RFI Shielding materials. Below is also a link to SABIC Innovative Plastic’s webpage on EMI/RFI Shielding materials.
If you need help designing or manufacturing thermoplastic components, please reach out to Hi-Tech using our Contact Us. Thanks.