Michael, Dr. Johnson also identified a rotary brush prep process of reworked underfilled BGA/CSP sites that also improved the Mech Shock survivability even more. Probably due to roughing up of the solder mask which improved underfill adhesion. Bruce Misner > ---------- > From: WEEKES, MICHAEL HS-SNS[SMTP:[log in to unmask]] > Reply To: TechNet E-Mail Forum.;WEEKES, MICHAEL HS-SNS > Sent: Wednesday, May 15, 2002 10:35 AM > To: [log in to unmask] > Subject: Re: [TN] BGA's on ruggedized assemblies... > > Is underfill really reworkable - I know rework may be feasible, but let's > be > honest about the detrimental effects of the thermal effect and > contamination > of a site where underfill was applied, cured, heated and > mechanically/chemically removed. I welcome comment - our assemblies are > too > expensive to scrap out. Any personal experience with any loctite or other > "reworkable" undefilled - I rank "reworkable" up there with "washable, but > not soluble". > > -----Original Message----- > From: [log in to unmask] [mailto:[log in to unmask]] > Sent: Tuesday, May 14, 2002 8:01 PM > To: [log in to unmask] > Subject: Re: [TN] BGA's on ruggedized assemblies... > > > Our Rockwell friends, through the fumes of Mountain Dew and Coke, will say > "No" if your attachment processes are good enough. Personally, though, > after some early (low level) vibration failures with some third party > designed and assembled boards, I built some more to my own spec and > introduced underfilling as an insurance policy. I hope to be able to > vibration qual test boards with and without underfilling to see if this > process is really necessary. > > To answer your question, it depends .... on your processes, the operating > conditions and expected life of the product, and maybe even the board and > BGA materials. Underfill manufacturers claim that using underfill can > improve the fatigue life of BGA solder joints by a factor between 3 and 5, > but it is another process and it involves heating boards an extra time (if > you use the capillary action type underfill) to carry out the underfill > process and cure the material. The no-flow type is applied and cured > concurrently with the assembly of the BGA onto the board and doesn't > involve the extra thermal excursion. > > I recommend you try qualifying boards with underfill and without it to see > if you need the extra process. Underfilling is not necessary in all > situations, nor a recommendation, but it won't do any harm either if you > want to use it anyway. > > Peter > > > > [log in to unmask] 15/05/2002 05:08 AM > Sent by: TechNet <[log in to unmask]> > > Please respond to "TechNet E-Mail Forum."; Please respond to SteveZeva > > To: [log in to unmask] > cc: (bcc: DUNCAN Peter/Asst Prin Engr/ST Aero/ST Group) > Subject: [TN] BGA's on ruggedized assemblies... > > > > > > > > > Hi All! > > Gotta question, when BGA's are used on ruggedized assemblies (at least > Level-4, probably Level-5), is underfilling BGA's recommended, or a > necessity? > > Thanks, as always... > > -Steve Gregory- > > > > [This e-mail is confidential and may also be privileged. If you are not > the > intended recipient, please delete it and notify us immediately; you should > not copy or use it for any purpose, nor disclose its contents to any other > person. Thank you.] > > -------------------------------------------------------------------------- > -- > ----- > Technet Mail List provided as a free service by IPC using LISTSERV 1.8d > 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 delivery of Technet send e-mail to [log in to unmask]: > SET > Technet NOMAIL > 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/html/forum.htm for additional > information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 > ext.5315 > -------------------------------------------------------------------------- > -- > ----- > > -------------------------------------------------------------------------- > ------- > Technet Mail List provided as a free service by IPC using LISTSERV 1.8d > 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 delivery of Technet send e-mail to [log in to unmask]: > SET Technet NOMAIL > 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/html/forum.htm for additional > information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 > ext.5315 > -------------------------------------------------------------------------- > ------- > --------------------------------------------------------------------------------- Technet Mail List provided as a free service by IPC using LISTSERV 1.8d 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 delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL 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/html/forum.htm for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 ---------------------------------------------------------------------------------