I agree that the soldermask should be equal to or lower then the pad for the best assembly with the lowest defect level. ______________________________ Reply Separator _________________________________ Subject: PTF - screened EMI shielding Author: [log in to unmask] at corp Date: 12/8/95 12:44 PM \0 TO: I1263600 IBMMAIL ipc internet technical query FROM: DSTEWART EX2 D.Stewart - Product Development Manager. DATE: 8 December 1995 SUBJECT: PTF - screened EMI shielding REFERENCE: assembly I have just read an article from Circuitree on the use of screen printed polymer thick film for EMI shielding. This technology has been known by us for some time, but up to now it has not been asked for. Before I start a project to characterise the process, I would like to know if people are using this process for their EMI shielding on SMD boards. As all the SM gurus and solder paste experts keep telling you assembly people that, ideally soldermask must be below the level of the pad, how do you cope with effectively 3 layers of soldermask and one layer of copper paste, over the top of your tracks (which always seem to end in a pad !!)? Circuit Wise, Photocircuits and AMP+Akzo are all mentioned in this article as using this technology, so let's hear from you, if not your customers, on what effect this has. Dougal Stewart Exacta Circuits Scotland