George, What did Lucent do about pressfit connectors while you were there? Bev RIM -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Wenger, George M. Sent: Monday, September 07, 2009 12:09 PM To: [log in to unmask] Subject: Re: [TN] Need clever comments What is the PCB surface finish that shows a Tin whicker Ingemar, What is the PCB surface finish that shows a Tin whicker on inside of the PRH barrel of the non soldered board in Photo #1 that Steve posted? Regards, George George M. Wenger Andrew Solutions Senior Principal FMA / Reliability Engineer 40 Technology Drive, Warren, NJ 07059 (908) 546-4531 [Office] (732) 309-8964 [Cell] [log in to unmask] -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Hernefjord Ingemar Sent: Monday, September 07, 2009 7:22 AM To: [log in to unmask] Subject: [TN] Need clever comments Hi all, need some professional backup regarding MIL quality boards. Objects: FR-4 Class III double-sided multi-layer boards, populated with SOICS, BGAs,and a lot of passive components. Observation 1 : the non soldered board have lots of Tin whiskers on inside of the PTH barrel. My thought is this: if whiskers can grow long before the board is assembled, then ain't it likely that even CAF can be generated? See photo 1. Observation 2: Copper has somehow penetrated the solder mask. This can be found everywhere along the conductor traces. You need a very good light microscope and a SEM to see it. See photo 2. Board data: Copper with 0.8 micrometer Immersion Tin. No nickel barrier. Solder mask thickness not specified. Application: Typical MIL-883 environment Q1: What is your opinion about that thin Tin directly on copper? I dislike the concept. Copper is very mobile at high temperatures, and combined with humidity, there can be leakage currents and corrosion issues. Even if the boards are CCd, there is a risk with copper . Q2: I gave the advice to introduce a nickel barrier, but our customer claimed, that they can't because of pressfit connectors and pressfit test pins on the board. Furthermore, they had heard that one cannot have nickel platings when pressfitting, because the nickel will crack and oxidize and cause electrical disfunction. Is this your opinion too? Are there any relevant testing behind such statements? Thanks in advance Inge --------------------------------------------------- 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 ----------------------------------------------------- ---------------------------------------------------------------------------- -------------------- This message is for the designated recipient only and may contain privileged, proprietary, or otherwise private information. 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