Ohm y gosh, Dewey seems to have had a sense of humor extraction. That is what comes from having to work from ohm with a Ducati sat in the garage crying out "ride me"........8-) John John Burke (408) 515 4992 -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Whittaker, Dewey (EHCOE) Sent: Thursday, July 05, 2007 2:49 PM To: [log in to unmask] Subject: Re: [TN] Soldermask Thickness Masking my inhibitions and my humor not withstanding, I will not lecture on the fallacies of relying on the insulating properties of the Solder Mask to achieve your as designed minimum dielectric spacing requirements. However some of the reasons are as follows: * Per IPC-6012B, solder resist(mask)thickness is not measured unless specified in the procurement documentation * Per IPC-6012B, if thickness measurement is required it shall be of the microsection of parallel conductors on the E coupon * Per IPC-SM-840D, if a specific thickness is required it shall be AABUS * Per IPC-SM-840D, if a specific breakdown voltage is required or allowed it shall be AABUS * Per IPC-SM-840D, the PB Fabricator shall confirm that solder mask material shall meet or exceed the minimum value of 500 VDC per 0.001 in. of thickness when tested in accordance withIPC-TM-650, Method 2.5.6.1. * Per IPC-SM-840D, the PB Fabricator shall confirm that any thickness of solder mask shall meet an absolute minimum breakdown voltage of 500 VDC. * Per your own comments and knowing nothing else, the PB was tested to meet 500 VDC minimum and you tested at 1200 volts. If after your verification that the proper thickness was specified/achieved per bullet two and you had proper design spacing's, you are left with the following: * Improper cure of the solder mask * Improper registration * Loss of adhesion due to contamination or application * Contamination of the substrate prior to application * Reduced SIR values due to improper cleaning/application * Electrical migration paths formed due to improper cleaning/application(especially if failure was after exposure to humidity) I know it's revolting that I've lost my capacitance for humor. It must be that I am working from ohm. Dewey -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Hogg, Blair K. Sent: Thursday, July 05, 2007 8:37 AM To: [log in to unmask] Subject: [TN] Soldermask Thickness We switched PC board suppliers for one of our products a while back and have started having hipot issues with components that are connected to main 110VAC input voltage arcing through the soldermask to tracks underneath at 1200V hipot voltage. I'm pretty sure I'll get a few responses that say that we shouldn't be using the soldermask as an insulator, however, since the change in supplier seems to coincide with the onset of problems, I've been asked to evaluate the soldermask thickness as a potential contributor to the problems. I would some recommendations on how to measure the thickness of the soldermask. Thanks, Blair ******************************************************************* This email and any files transmitted with it are confidential and intended solely for the use of the individual or entity to whom they are addressed. 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