[Not yet Brad... I'm still waiting for it to show up...] We use a separate .035 in. diameter surface pad (land with no hole) for test points instead of using vias. No issues or problems with that method and we avoid the extra cost of the via-in-pad method. We will save that solution for really unavoidable footprint issues that must use it. DFT or 'Design for Test' is one of the subjects being discussed by Gary Ferrari on Wednesday March 28th at PCB Design WEST in Santa Clara California... last week of this month. http://www.pcbwest.com/conf/technical.html <http://www.pcbwest.com/conf/technical.html> If they want to learn more about the options and requirements for DFT, I would recommend that they attend his presentation. I wish I could go but we have to much do and they can't live without me for a week... (It's nice to know I'm needed... :-)) Maybe I will get to attend PCB East this Fall. You will have to come back to San Diego some time soon and do another great presentation for our DC members like the one you did at Palomar College in my classroom on Flex Circuits... We really enjoyed that one. All the best, Bill Brooks PCB Design Engineer, C.I.D.+ Tel: (760)597-1500 Fax: (760)597-1510 Datron World Communications, Inc. Vista, California _____ From: Brad Saunders [mailto:[log in to unmask]] Sent: Wednesday, March 14, 2007 8:58 AM To: (Designers Council Forum); Brooks,Bill Subject: Re: [DC] One sided issue Bill, I agree. The volcanic reaction is one form of "popcorning", also I have seen many cases of solderball spewing from broken LPI at the PTH. I am a big fan of the plug then LPI method however where folks must use the via for test (.8 BGA) I love the capped via. That is where only vias are drilled and plated then filled. PTH for component mounting (ie connector) are then drilled and plated; this plating covers the existing vias in a copper cap or also known as Via In Pad: VIP. Thanks for the input, it was a great sanity check. [By the way Bill, did you get the copy of that Flex presentation?] Brad ----- Original Message ----- From: Brooks,Bill <mailto:[log in to unmask]> To: [log in to unmask] <mailto:[log in to unmask]> Sent: Wednesday, March 14, 2007 12:55 PM Subject: Re: [DC] One sided issue Let me see if I understand the implied issue... If they are tenting the vias on one side I would suggest recommending another more reliable option to your customer. We plug the vias with soldermask here rather than 'tent' them for a couple of reasons... one, a single sided or broken tent is a moisture or chemical trap and can compromise or damage the board or assembly during assembly processing or even in storage. Two, from my own experience, we had a batch of tented boards make it into assembly with compromised tents, (ones that did not completely cover the holes on either side) and when we ran the boards through re-flow soldering we observed in inspection a large number of the vias expelling solder balls and contaminants from the holes as the heated gasses and moisture inside them expanded rapidly... (Kind of like little volcanoes)... We avoid the single sided tents for that exact reason... Plugging the holes completely is much more reliable and we have not had any problems since. Does that help at all? Best regards, Bill Brooks PCB Design Engineer, C.I.D.+ Tel: (760)597-1500 Fax: (760)597-1510 Datron World Communications, Inc. Vista, California -----Original Message----- From: Brad Saunders [mailto:[log in to unmask]] Sent: Tuesday, March 13, 2007 2:02 PM To: [log in to unmask] <mailto:[log in to unmask]> Subject: [DC] One sided issue Hello Folks, What are the reliability thoughts on a PCB configuration as follows: 013 PTH via ENIG finish (prior to soldermask) with one side without mask and the other a dryfilm soldermask. The board is approx .080 thick. Thanks, Brad ---------------------------------------------------------------------------- ----- DesignerCouncil Mail List provided as a free service by IPC using LISTSERV 1.8d To unsubscribe, send a message to [log in to unmask] <mailto:[log in to unmask]> with following text in the BODY (NOT the subject field): SIGNOFF DesignerCouncil. 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