At 10:45 AM 9/10/2009, Stadem, Richard D. wrote: >Or hanging around the Laundromat with his .44 automatic. .44 automatic? I didn't take Steve for a Desert Eagle sort of guy. >-----Original Message----- >From: TechNet [mailto:[log in to unmask]] On Behalf Of Inge >Sent: Thursday, September 10, 2009 11:25 AM >To: [log in to unmask] >Subject: Re: [TN] Need clever comments > >I will post a handful SEM images to Steve, so you get an idea what it's >all >about. >It may take a while, because he is probably on the market place to buy >curtains and wallpaper >for his new appartment. Or jogging. Or having a drink on the balcony. >/Inge > > >----- Original Message ----- >From: "Inge" <[log in to unmask]> >To: <[log in to unmask]> >Sent: Thursday, September 10, 2009 5:10 PM >Subject: Re: [TN] Need clever comments > > > > Jack &Paul, FYI. > > > > Today I had a close look at the cross sections. What I found was this: > > > > 1. The Tin plating was done AFTER solder mask (Jack was right) > > 2. The solder mask was very uneven, thickness between 5um and 25 um. > > 3. Despite the corrupted surface, the solder mask is homogenous, no > > vertical cracks found. > > 4. The copper that I found earlier on top of the conductor, i.e. on >the > > solder mask, that copper had no connection with the conductor copper. > > Which means that these contaminations had NOT migrated through the >solder > > mask. > > 5. I can still not figure out from where the copper contaminations >come. > > > > So, all that remains is the question about the copper contaminations >tha > > embedded in the very surface of the solder mask. I have to adjust my > > report and resend it to our customer and the board maker. > > > > Thanks to your critisism, I can now redo the analys, starting from a >more > > correct standpoint. > > > > Your are great! > > > > /Inge > > > > > > > > > > ----- Original Message ----- > > From: "Inge" <[log in to unmask]> > > To: <[log in to unmask]> > > Sent: Wednesday, September 09, 2009 8:09 PM > > Subject: Re: [TN] Need clever comments > > > > > >> Jack, > >> > >> SMOBC is the common industrial standard, as you pointed out, however, > > >> there ARE some fabricators that apply the solder mask after >Tin/Lead-ing > >> the copper traces. The later method has an obvioius disadvantage, see > > >> below quoted from an article written by US Environmental Agency: > >> > >> " This method predominates for several reasons. Copper is a surface >that > >> lends itself to rigorous cleaning, which is essential for solder mask > > >> adhesion. Tin-lead under solder mask will liquefy during soldering >and > >> may cause the mask to blister and peel. The hot air solder leveling > >> process generally produces less waste water and introduces less lead >into > >> the waste water stream than tin-lead plating and reflow. Despite >these > >> advantages, well-known disadvantages also exist. The shelf-life of >hot > >> air solder leveled circuits is short and solder thicknesses on pads >and > >> hole barrels is notoriously difficult to control. For these reasons, >a > >> small minority of specifications continue to call for tin-lead plate >and > >> reflow or other alternati air solder leveling, nomenclature >screening, > >> and finally, gold edge plating if necessary. " > >> > >> I think that is what happened to our boards....." cause the mask to > >> blister and peel"... > >> > >> Another paper describes Tin under solder mask this way: > >> > >> " Facility F initially was concerned with the soldermask breakdown >where > >> the Tin leaches underneath the soldermask....etc" > >> > >> Quoted from EPA (United States Environmental Protection Agency. > >> > >> When I started the investigation (had just some hours to spend before > > >> reporting the result!), I was fully convinced that these boards were > >> SMOBC, but our customer said they used tinning before soldermask. I >have > >> asked for a confirmation from the board fabricator, but got no >answer. > >> > >> Thanks for your comment, good critics. > >> > >> Inge > >> > >> > >> ----- Original Message ----- > >> From: "Jack Olson" <[log in to unmask]> > >> To: <[log in to unmask]> > >> Sent: Wednesday, September 09, 2009 4:44 PM > >> Subject: [TN] Need clever comments > >> > >> > >>>I know I'm late to the game, but I can't resist asking this question: > >>> > >>>>From my experience, the tin is applied AFTER soldermask, so > >>> you have mask over bare copper, and tin over exposed copper. > >>> > >>> The tin in PHOTO2.JPG in the exposed area looks beautiful, > >>> so isn't the question (ignoring the whiskers for the moment) > >>> "How can bare copper erupt through the mask?" > >>> > >>> Unless I missed one of your previous posts, it seems to me that > >>> any speculation about copper poking through the tin finish is > >>> irrelevant. I'm only addressing Question 2 below, but you mentioned > >>> introducing a nickel barrier, and that will not be plated under the >mask > >>> either, will it? only on exposed circuitry... > >>> > >>> just wondering, > >>> Jack > >>> > >>> > >>> -=-=-=- > >>> > >>> *Subject:* Need clever comments *From:* Hernefjord Ingemar < > >>> [log in to unmask]> *Reply-To:* TechNet E-Mail Forum < > >>> [log in to unmask]>, Hernefjord Ingemar ><[log in to unmask]> > >>> * > >>> Date:* Mon, 7 Sep 2009 13:21:54 +0200 *Content-Type:* text/plain > >>> > >>> > >>> 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 > >>> ----------------------------------------------------- > >> > >> --------------------------------------------------- > >> 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 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 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 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 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 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