Hi Inge, Have your *.doc file posted. It's here: http://stevezeva.homestead.com/Steve1.doc Steve -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Inge Sent: Thursday, October 28, 2010 4:21 AM To: [log in to unmask] Subject: [TN] Cracks in BGA solderjoints I have sent some photos to Steve for you. I avoid to put any name on the phenomenon, as that seems to start fruitless debates. Instead I focus on what we found. The balls lifted after tempcycling, as like you lift your fried egg from the pan. When you look at the underside of the egg, there is a smooth and even surface, supposed you got oil or butter in the pan. Likewise, when we looked at the separation faces on these superBGAs, we saw a flat, smooth and even surface, as if the balls had been solidified on a glass plate. Nearly no microjoints at all, except a little arount the perifphery. This smooth surface was nanometer thick (still BGA balls) and behind that, a micrometer thick layer of extremly crystalline Tin-Nickel layer. Experts from Ericsson determined that layer as caused by overheated IMCs. We tried to examine the nanometer smooth layer, which was the very sort of separation interface, but the result was hard to interprete, and there was no further investigation. We cooperated with Xilinx, who made several microscopic surveys, but we never got to know if the failure was related to Xilinx or the boards or to our process, because one day the problem disappeared. We had lost lots of boards an we were of course happy, but myselft, I am still curious and wonder who was the murderer. Inge ----- Original Message ----- From: "Paul Edwards" <[log in to unmask]> To: <[log in to unmask]> Sent: Thursday, October 28, 2010 5:06 AM Subject: Re: [TN] AW: [TN] Cracks in BGA solderjoints - Found word(s) list error in the Text body Gunter, I would also look at the possibility that the PCB had some organic contamination embedded in the Au... This could explain the micro-voids at the Ni-Au interface and just above it... We have found organic contaminates in the Au surface of ENIG PCBs due to the surface roughness of the Au... These subsequently were trapped by the surface tension of the flux and later by the solder's surface tension... The volume of the contaminating material was too small to develop sufficient buoyancy to migrate along or from the surface through the solder... Is this PCA assembled with W/S solder paste with a relatively fast cool-down rate OR is it a thick PCB with a relatively thin BGA soldered to it?? Paul Paul Edwards Surface Art Engineering -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Grossmann, Guenter Sent: Wednesday, October 27, 2010 5:51 AM To: [log in to unmask] Subject: [TN] AW: [TN] Cracks in BGA solderjoints - Found word(s) list error in the Text body Dear Colleagues Thanks a lo for the first answers. - No, the BGAs have not been reworked - Most failures occur in the field, some are found after production - We didn't find any separations after only printing solderpaste and soldering. - It's not only the corner balls, the defects are found statistically in the array Günter >-----Ursprüngliche Nachricht----- >Von: TechNet [mailto:[log in to unmask]] Im Auftrag von Joyce Koo >Gesendet: Mittwoch, 27. Oktober 2010 13:26 >An: [log in to unmask] >Betreff: Re: [TN] Cracks in BGA solderjoints > >Spalling of the IMC? Are those reworked? >-------------------------- >Sent using BlackBerry > > >----- Original Message ----- >From: Inge [mailto:[log in to unmask]] >Sent: Wednesday, October 27, 2010 07:17 AM >To: [log in to unmask] <[log in to unmask]> >Subject: Re: [TN] Cracks in BGA solderjoints > >I think it's not cracks in the BGA, but snacks in the BGA. At least what >I >found once >/Inge > > >----- Original Message ----- >From: "Grossmann, Guenter" <[log in to unmask]> >To: <[log in to unmask]> >Sent: Wednesday, October 27, 2010 9:36 AM >Subject: [TN] Cracks in BGA solderjoints > > >Hi Technetters > >I have an effect in BGA solder joints that I have never seen before. >In microsections and in FIB preparations I see cracks between the IMC >and a >slightly darker region towards the Ni which I assume to be a P enriched >zone >of the Ni. However, the cracks are somewhere in the width of the solder >joint and they are quite short running out to a row of pores that look >somehow like Kirkendall voids. >Is there still a possibility to place one or two pictures? Kim's IPC >site >doesn't work. > >Best regards > >Günter > > > >______________________________________________________________________ >This email has been scanned by the MessageLabs Email Security System. >For more information please contact helpdesk at x2960 or >[log in to unmask] >______________________________________________________________________ > >--------------------------------------------------- >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 email has been scanned by the MessageLabs Email Security System. >For more information please contact helpdesk at x2960 or >[log in to unmask] >______________________________________________________________________ > >--------------------------------------------------- >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 transmission (including any attachments) may contain confidential >information, privileged material (including material protected by the >solicitor-client or other applicable privileges), or constitute non- >public information. 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