Copper does not corrode in the since that iron does. Copper is a near noble element that behaves more like aluminum; it forms a passivative layer that penetrates only a few microns into the material. Think of aerial copper wire (so called open wire) used by the phone companies for many years. Where I live, the aerial copper wire that was installed in the early 20s is still in place and functions as well as it did 90 years ago. Best regards Lee J. Lee Parker, Ph.D. JLP Consultants LLC 804 779 3389 ----- Original Message ----- From: "Hogg, Blair K." <[log in to unmask]> To: <[log in to unmask]> Sent: Tuesday, March 06, 2007 4:43 PM Subject: Re: [TN] immersion silver and exposed copper in small vias I guess I'll have to replace all that corroded copper pipe in my house with the plastic kind.... -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Steve Gregory Sent: Tuesday, March 06, 2007 4:24 PM To: [log in to unmask] Subject: Re: [TN] immersion silver and exposed copper in small vias Or the Statue of Liberty... -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Ian Hanna Sent: Tuesday, March 06, 2007 3:26 PM To: [log in to unmask] Subject: Re: [TN] immersion silver and exposed copper in small vias That's why they build church roofs out of it I suppose... -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Kevin Glidden Sent: Tuesday, March 06, 2007 4:20 PM To: [log in to unmask] Subject: Re: [TN] immersion silver and exposed copper in small vias Is this really true? I have only been at this around 7 yrs, but everything I was ever taught says exposed Cu is not allowed for risk of corrosion. -----Original Message----- From: Wayne Thayer [mailto:[log in to unmask]] Sent: Tuesday, March 06, 2007 3:52 PM To: [log in to unmask] Subject: Re: [TN] immersion silver and exposed copper in small vias And what's wrong with exposed copper? You certainly aren't going to try and solder down there, are you? Copper does not corrode quickly, and if its going to be in a corrosive environment, you're going to have to conformal coat anyway! The silver is put on boards only to extend the solderability lifetime of the bare copper, not as a protectant to prevent opens due to corrosion. This is not a reliability issue at all. Wayne Thayer >>> [log in to unmask] 3/6/2007 12:10:08 pm >>> Hi Fran The amount of mask intruding into the hole will depend on the application method. Our curtain coat operation can cause the mask (circa 1-2 microns) to penetrate about 1/3rd into the hole from both sides but it has not affected the silver taking on the remaining surface. Is the mask too thick at the hole entrance to prevent the plating solution getting good access? You may also need to confirm by micro section what your customer thinks he is seeing. Is the mask covering all the hole surface? Hope this helps. Regards Alistair Alistair F Murray MICT Technical Manager Artetch Circuits Limited England UK Direct Dial: 01903-712931 www.artetch.co.uk -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Fran Juliot Sent: 06 March 2007 15:58 To: [log in to unmask] Subject: [TN] immersion silver and exposed copper in small vias Our customer is questioning what they feel is exposed copper in 8 mil vias holes on silver boards. We feel there is mask residue in the holes which does not allow silver to take. These are holes that are allowed to be plugged. Has anyone else ran into this issue with thier customers and do you have the same look or are your small vias covered with silver all the way through the via? --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 15.0 To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/archives Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 ----------------------------------------------------- --------------------------------------------------- Technet Mail List 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