steve, depend upon your layout balance, your PWB can warp even use stencil/profile as per part's vendor recommendation... HOP issue is complicated. If your "connector" adjacent to a large part (heat sucker), you will get un-even reflow of the part, and get more chance for HOP... Best is get rid of flux residue - clean with flux removal (brush well - or send part to cleaner... sock may not do the job... make sure the residue got away - no white stuff left... Or use aggressive flux/paste (water soluable) and clean well of your PWA... one way of the other, it will cost you money... jk On Aug 29, 2017, at 8:38 AM, Steven Kelly wrote: > Hi All, > The connector supplier is the one who told us this was dried flux > residue- the pictures may not be the best but these joints are > duller than the surrounding joints. > The stencil /profile is per the connector manufacturer’s > recommendation. > We have built approx.. 20 parts to date. 14 have no issues . The > other 6 have 1-3 head pads each with head in pillow issues – no > pattern to the failure. We have traced two failures to “dull joints”. > > Regards Steve Kelly > > > From: Steve Gregory [mailto:[log in to unmask]] > Sent: August-28-17 6:12 PM > To: [log in to unmask] > Cc: Ed Popielarski <[log in to unmask]>; Steven Kelly > <[log in to unmask]> > Subject: Re: [TN] Dried flux > > Hi Steve, > Sorry it's taken me so long to get you pictures posted, but I had > to sort out some issues with the software for my web page. Windows > 10 and all it's updates made things a little difficult for a while, > but I've gotten things straightened out now. Here are your photos: > > http://stevezeva.homestead.com/partial_ball_thumb.jpg > > http://stevezeva.homestead.com/dull_solder.jpg > > http://stevezeva.homestead.com/Head_in_pillow_1.jpg > > http://stevezeva.homestead.com/Head_in_pillow_2.jpg > To be honest, I'll have to take your word for it but I couldn't see > any flux residues in your photo. They must be there, I just can't > see them. May I ask how thick the stencil is that you're printing > the paste with? Just curious is all. Also, who makes the connector? > Steve > > > On Mon, Aug 28, 2017 at 7:50 AM, Steven Kelly > <[log in to unmask]<mailto:[log in to unmask]>> wrote: > Thanks Steve for posting these for me. > The first picture called partial ball is a picture of one of the > balls on the connector as received. > Second picture is what the supplier has called dried flux on the > connector as received > Third picture shows what we call head in pillow > Fourth picture - different view of third picture > > Thanks for everyone's help on this . Regards Steve Kelly > > > -----Original Message----- > From: Ed Popielarski > [mailto:[log in to unmask]<mailto:[log in to unmask]>] > Sent: August-25-17 2:26 PM > To: TechNet E-Mail Forum <[log in to unmask]<mailto:[log in to unmask]>>; > Steven Kelly <[log in to unmask]<mailto:[log in to unmask]>> > Cc: Steve Gregory <[log in to unmask]<mailto:[log in to unmask]>> > Subject: RE: [TN] Dried flux > > Steve Gregory (cc'ed herein) has graciously offered his time and > dataspace to post Technet pix on his site. > > Forward your pics to Steve, I'm certain he will oblige! > > Regards, > > Ed Popielarski > Engineering Manager > > > 970 NE 21st Ct. > Oak Harbor, Wa. 98277 > > Ph: 360-675-1322<tel:360-675-1322> > Fx: 206-624-0695<tel:206-624-0695> > Cl: 360-544-2289<tel:360-544-2289> > > > > “It's one kind of victory to slay a beast, move a mountain, > and cross a chasm, but it's another kind altogether to realize that > the beast, the mountain, and the chasm were of your own design.” > https://goo.gl/maps/mMjg43rXeFB2 > > -----Original Message----- > From: TechNet [mailto:[log in to unmask]<mailto:[log in to unmask]>] On > Behalf Of Steven Kelly > Sent: Friday, August 25, 2017 11:13 AM > To: [log in to unmask]<mailto:[log in to unmask]> > Subject: Re: [TN] Dried flux > > Hi all, > Want to post some pictures - can someone please give me direction. > Thanks. Steve Kelly > > -----Original Message----- > From: Bev Christian > [mailto:[log in to unmask]<mailto:[log in to unmask]>] > Sent: August-25-17 11:00 AM > To: 'TechNet E-Mail Forum' > <[log in to unmask]<mailto:[log in to unmask]>>; Steven Kelly > <[log in to unmask]<mailto:[log in to unmask]>> > Subject: RE: [TN] Dried flux > > Steve, > From what people are saying, it is more and more likely that it IS > the flux residue. You say: "On average we are getting 1-3 failures > per 200 joints." That pretty well eliminates gross part warpage. > > Minor point of interest: > With regards to part warpage (or boards), they can test fine for > planarity both before and after reflow. That doesn't mean they > weren't warped DURING reflow. > Bev > > -----Original Message----- > From: TechNet [mailto:[log in to unmask]<mailto:[log in to unmask]>] On > Behalf Of Steven Kelly > Sent: Friday, August 25, 2017 10:26 AM > To: [log in to unmask]<mailto:[log in to unmask]> > Subject: Re: [TN] Dried flux > > Hi Dave, > The parts come vacuum sealed and after opening we have a fairly > short period of time to assemble. Manufacturer also said the “dull > ball” on the connector is common for lead-free solder ( agree) and > is not considered related to the failure. Its’ mainly because tin > constituent appears on the surface. ( I understand that) Then they > say the “residue” which we identified on the ball is considered to > be flux and is not related to the head in pillow. > But only a few of the 200 or so balls exhibit this issue and I am > not saying we do not have other issues but we have traced some of > the head in pillow to a couple of the so-called flux residue > balls . On average we are getting 1-3 failures per 200 joints. > We have measured the flatness of the rigid stiffener – looks OK to > us – co-planarity is .002- .004 after convection reflow. > Reviewing what Bev said yesterday- pasting – we looked at it 3 > times but doing it again. > I also have pictures of what we call an incomplete ball which I > would like to post but I need a refresher course on how to do this. > > Thanks for everyone’s help. > Steve Kelly > > From: David Hillman > [mailto:[log in to unmask]<mailto:david.hillman@rockwel > lcollins.com>] > Sent: August-25-17 10:06 AM > To: TechNet E-Mail Forum <[log in to unmask]<mailto:[log in to unmask]>>; > Steven Kelly <[log in to unmask]<mailto:[log in to unmask]>> > Subject: Re: [TN] Dried flux > > Hi Steve - We use a number of "bga style" connectors where there is > a solder charge/preform on the connector which is designed to > combine with the solder paste deposit creating sufficient solder > volume and good solder joint integrity. I am not familiar with the > having these types of connectors with "dried flux" - flux has a > shelf life so the manufacturer's comment doesn't make much sense. > From a practical point, the flux in the solder paste deposit is > doing the bulk of the oxide scrubbing action so dried flux > contribution is most likely a moot point. But - the fact that the > manufacturer did not acknowledge the possible shelf life issue is > dis-concerning. > > Dave Hillman > Rockwell Collins > [log in to unmask]<mailto:david.hillman@rockwellcollins > .com><mailto:[log in to unmask]<mailto:david.hillman@ro > ckwellcollins.com>> > > On Thu, Aug 24, 2017 at 1:11 PM, Steven Kelly > <[log in to unmask]<mailto:[log in to unmask]><mailto:[log in to unmask] > om<mailto:[log in to unmask]>>> wrote: > Hi All, > I have a new hi-density BGA connector I am trying to assemble. When > the supplier makes the connector they "solder balls onto the > pin" (lead free). We see dried flux on the balls and when we solder > the connector we are getting a few joints with head in pillow. The > connector manufacturer says the dried flux is not an issue - is > this true? Thanks. Steve Kelly > > > > > -- > Steve Gregory > Kimco Design and Manufacturing > Process Engineer > (208) 322-0500 Ext. -3133 > > [http://fileserver1.kimco.net/PublicDocs/KDMsig200.png] > > This email and any attachments are only for use by the intended > recipient(s) and may contain legally privileged, confidential, > proprietary or otherwise private information. Any unauthorized use, > reproduction, dissemination, distribution or other disclosure of > the contents of this e-mail or its attachments is strictly > prohibited. If you have received this email in error, please notify > the sender immediately and delete the original.