What you drinking with that chili? ;^) At 05:15 PM 12/22/2008, Bev Christian wrote: >That was supposed to be "to think". Too bad Spell Check doesn't >check that sort of thing. >Bev > >----- Original Message ----- >From: TechNet <[log in to unmask]> >To: [log in to unmask] <[log in to unmask]> >Sent: Mon Dec 22 20:12:30 2008 >Subject: Re: [TN] Underfill, inhibition due to leftover activators >in the flux residue > >Phil, >I have had more time outthink about this now. A good chili on a winter >night helps. :) > >This could be really bad news. I have not heard of this before. The good >news is that the joints most at risk during thermal cycling and drop are the >ones the farthest from the neutral point, which is where (neutral point) you >are finding the phenomenon. Even so, I am concerned. Now I am wondering >how many other combinations are doing this? >Bev >RIM > >-----Original Message----- >From: TechNet [mailto:[log in to unmask]] On Behalf Of Phillip Bavaro >Sent: Monday, December 22, 2008 6:02 PM >To: [log in to unmask] >Subject: [TN] Underfill, inhibition due to leftover activators in the flux >residue > >I have made quite a few test samples and discovered that a certain >underfill material will exhibit inhibited cure when it comes in contact >with solderpaste flux residues at the center of a very dense BGA component. >The rest of the underfill beneath the BGA will harden like normal. >We don't clean nor plan on starting to clean our assemblies. >DVT testing does not show any defects due to underfill adhesion. > > >Background: >We used a four up ABAB panel which goes through SMT twice. >BGAs only passing through the oven once consistently show the problem. >Two passes through the reflow oven (ABAB flip) and the problem goes away. >This means that half of our test samples still have soft material in the >pocket at the center where the power ground pins are located. >We measure peak temperature in this area and have found that raising the >peak temperature helps quite a bit but does not eliminate the inhibition >entirely. >The manufacturers of the paste and the underfill acknowledge the issue but >do not have a solution. > >Has anyone else run into similar compatibility issues with a paste and >underfill? > >In the event that we cannot work out the root cause, and decide to make a >change, I am trying to come up with a list of all the manufacturers of >underfill. > >So far I have found 8 major underfill manufacturers but would appreciate >knowing about more if there are any. > >3M >Ablestik >Epotek >Henkel >Hysol >SP&S >Sunstar >Zymet > >Thanks in advance, > >Phil > >--------------------------------------------------- >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 >----------------------------------------------------- > >--------------------------------------------------------------------- >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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