Peter: > You must have a bad batch of glue or a bad bottle. Normally glue lasts > several days after the bottle is open. You should send a sample of the > glue to the manufacturer to be analyzed. The liquid you see may not be > water, but the solution the glue is in. It may be easier to repeat the > process with known good glue, even if it has to be done manualy. Regards, Ramon > Hi Technet, > > I didn't receive many responses when I asked if anyone has come across > seeing the moisture-within-the-glue defect underneath SMT components. > > In order to remove the mositure off the assembled units, I am > experimenting > with various low temp. baking cycles. I like to ask if anyone have > experience removing moisture that was trapped within the glue underneath > SMT components (0805s)? > > Due to other thermal sensitive T/H components on the boards I am limited > to > 100C baking or less. > > Rgds, > Peter > > > > Date: Thu, 28 Aug 2003 13:29:00 -0400 > Reply-To: [log in to unmask] > Sender: TechNet <[log in to unmask]> > From: joyce <[log in to unmask]> > Organization: EXFO-TO > Subject: Re: Moisture under chip capacitors > X-To: "TechNet E-Mail Forum." <[log in to unmask]>, > "Peter L." <[log in to unmask]> > In-Reply-To: <[log in to unmask]> > Content-Type: text/plain; charset="iso-8859-1" > > It is epoxy based material. If you see voids, it got be there before > curing.... > jk > > >-----Original Message----- > >From: TechNet [mailto:[log in to unmask]] On Behalf Of Peter L. > >Sent: Thursday, August 28, 2003 12:26 PM > >To: [log in to unmask] > >Subject: Re: [TN] Moisture under chip capacitors > > > > > >The adhesive was printed and cured at no more than 2deg/s and > >150degC for 100secs. > > > >The particular adhesive used was Epibond 7275. We suspected > >that it was a material related issue - either the glue was > >mishandled and left too long on the line, or old/ expired > >batch of glue was used. > > > >Any suggestion on method to drive the moisture away under the > >components? Baking conditions? > > > > > >Rgds, > >Peter > > > > > > > > > >>Date: Mon, 25 Aug 2003 07:47:30 -0400 > >>Reply-To: [log in to unmask] > >>Sender: TechNet <[log in to unmask]> > >>From: joyce <[log in to unmask]> > >>Organization: EXFO-TO > >>Subject: Re: Moisture under chip capacitors > >>X-To: "TechNet E-Mail Forum." <[log in to unmask]>, > > Peter Lee <[log in to unmask]> > >>In-Reply-To: <000001c36abe$e03472d0$7e63ad8e@homeg8br34o791> > >>Content-Type: text/plain; charset="iso-8859-1" > > > >>What is the adhesive and how was it cured? > > jk > > > >>-----Original Message----- > >>From: TechNet [mailto:[log in to unmask]] On Behalf Of Peter Lee > >>Sent: Monday, August 25, 2003 12:11 AM > >>To: [log in to unmask] > >>Subject: [TN] Moisture under chip capacitors > >> > >> > >>Technet, > >> > >>I have come across a rash of failed assemblies that have 0805 > >>capacitors and resistors, bottom side glued, wave soldered > >and washed. > >>Trouble shooter reported touching up the solder joints on a few areas > >>and the boards would pass test. > >> > >>I had a look at one board which was reported to have a 0805 56K > >>resistor with "drifting" values. I pulled the component off > >>mechanically in order not to apply any heat and noticed several > >>mini-voids within the adhesive body. I have seen solder bridge within > >>the glue before but this was the first time I saw wet residue within > >>the voids. > >> > >>You can view a sample image from Steve's web site: > >>http://www.stevezeva.homestead.com/files/SMTAdhesive.jpg > >> > >>The > >>image showed the bottom side of the cracked resistor after removal > >>(white), with a portion of solder mask (green) and SMT adhesive (red). > >> > >>I used a 8mil stencil. The thermal profile was verified and conformed > >>to the slope/ curing specs. > >> > >>Has anyone seen this before? Any explanation as to how the void was > >>formed and how moisture got tapped in? Does anyone re-use > >their glue on > >>the line or throw away any left-over to avoid moisture in the glue? > >> > >> > >> > >>Rgds, > > --------------------------------------------------- > Technet Mail List provided as a service by IPC using LISTSERV 1.8e > 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 > 847-509-9700 ext.5315 > ----------------------------------------------------- > --------------------------------------------------- > Technet Mail List provided as a free service by IPC using LISTSERV 1.8e > 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 > 847-509-9700 ext.5315 > ----------------------------------------------------- > > --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 1.8e 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 847-509-9700 ext.5315 -----------------------------------------------------