Some other issues regarding safety - if your product is UL Listed or Certified the conductive coating will need to be listed in the UL Plastics Recognized Component Directory as well as the applicator of the conductive coating and the supplier of the raw plastic material. I had the experience of going through this about three years ago on one of our medical devices. If all three are not in the UL directory, UL will want to run the appreciate lab tests and cost goes up on project. Due to our low volumes we decided to change the plastic case over to an aluminum one. The device has UL Certification (UL2601) and also passed the required EMI/RFI tests (EN60601-1-2). Additionally - we experienced problems with the coating adhering to the plastic we used. If we would of done our homework up front and assured that the conductive material and plastic was listed in the UL directory (metallized parts - QMRX2)we would not have experienced this problem as the adhesion testing was already done by the applicator of the material! Hope this provides you with a little more insight & good luck!
-----Original Message----- From: George Tang [mailto:gt...@convergenet.com] Sent: Wednesday, November 03, 1999 8:24 PM To: Westerdahl, Eric Cc: 'EMI-PS Group' Subject: Re: Conductive Coating There are many different types of conductive coatings available. Silver paint is very conductive, less than 5 ohms per square inch. But it is not as scratch resistant as sheet metal surfaces. Electroless copper / nickel plating is very conductive and durable. You can get as low as 1 ohm per square inch. If you don't, your plating is not thick enough. This plating should pass the safety fault current test, as long as the safety ground wire makes "surface area" contact with the plating and not "point" contact. This plating has 60 dB shielding effectiveness for frequencies above 30 MHz, since it is much thicker than the skin depth. You need the thickness for the safety fault current. The best feature of the plating is that it allows you to mold your chassis into one piece of plastic with no extra metal pieces to assemble. It's kinda nice that way. :-) go to www.ccoatings.com or call (972) 851-0460 George Tang "Westerdahl, Eric" wrote: > Our company has decided to use a conductive coating to mitigate some EMI > problems on one of our units. We have not used this method before. I have > a question as to the correct resistivity of the coating. What range should > I be looking at, and does the range change if the frequency of the strong > signal are high or low? > > The equipment is IEC 950 and EMC Directive stuff with many noisy DC motor > and motor controller combinations. Most of the signals we are concerned > about are at the lower end of the CISPR 22 region. 30 to 150 MHz. > > Eric Westerdahl > Regulatory Engineer > Roll Systems, Inc. > eric_westerd...@rollsys.com > > --------- > This message is coming from the emc-pstc discussion list. > To cancel your subscription, send mail to majord...@ieee.org > with the single line: "unsubscribe emc-pstc" (without the > quotes). For help, send mail to ed.pr...@cubic.com, > jim_bac...@monarch.com, ri...@sdd.hp.com, or > roger.volgst...@compaq.com (the list administrators). --------- This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators). --------- This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
