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August 2017

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Subject:
From:
Yuan-chia Joyce Koo <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Yuan-chia Joyce Koo <[log in to unmask]>
Date:
Tue, 29 Aug 2017 16:19:45 -0400
Content-Type:
text/plain
Parts/Attachments:
text/plain (215 lines)
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]
>
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