I agree with Dave, but I also want to point out that most component vendor's recommendations for solder volume, pad size or shape (or any other process parameters, for that matter) are just that, recommendations, and merely a good starting point that is proven to work for some applications, but never for all. The information that has been provided on the inverse relationship between stencil thickness or solder volume and the number of Hippity Hop solder joints is very conclusive and should be at least one of the first process adjustments, along with perhaps adding additional tacky flux in very small amounts to the oxidized solder balls first. I like to brush on a very, very thin layer of Alpha WS 619 or WS 820 to the connector side prior to placement into the paste. If that does not work or even makes the issue worse, then go to the thicker stencil to increase the pressure of the molten solder balls onto the molten solder pillows on the pads. The flux brushing does wonders for HOP on BGAs, but be sure to use only a wood-handled toothbrush with hogshair bristle to eliminate any chance of triboelectric ESD charging. This is important even for a mechanical connector, because you do not want to charge up any component with a nylon brush and place it onto ESD-sensitive CCAs.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of David Hillman
Sent: Tuesday, August 29, 2017 8:11 AM
To: [log in to unmask]
Subject: Re: [TN] Dried flux
HI folks - I am in George's camp as I don't see any solderball surface condition in the photos that I would call "odd". The HOP picture shows most of the solder volume went to the connector side rather than the pad. As George suggested, I would look at the process in terms of solder paste deposition and also the reflow profile. You might slow the conveyor speed down slightly so that both the connector and pad are closer in temperature so the solder doesn't favor either for wetting behavior.
Dave
On Mon, Aug 28, 2017 at 6:36 PM, George Wenger <[log in to unmask]>
wrote:
> Steve,
>
>
>
> I looked at the photos Steve (Gregory) posted for you and I agree with
> his comment about not seeing a dull flux residue on the balls. The
> photos certainly show "typical" HIP defects. I'm also curious what
> your stencil thickness is. One thing we found some time ago is that
> the occurrence of HIP defects decreased when with stencil thickness as
> increased and increased when the stencil thickness was decreased. I
> would also suggest that you map the locations of the HIP defects to
> see if they are most often in the same locations. It might also be
> helpful to look at or photograph the stencil print deposits to see if
> the HIP defects occur where the stencil printed deposit is minimum.
>
>
>
> George Wenger
>
>
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Steven Kelly
> Sent: Monday, August 28, 2017 7:21 PM
> To: [log in to unmask]
> Subject: Re: [TN] Dried flux
>
>
>
> Thanks Steve for your help. Somewhere along the line I owe you a good
> Canadian Beer. Steve Kelly
>
>
>
> Sent from my iPhone
>
> Steve Kelly
>
> Phone: (416) 750-8433
>
> Cell: (416) 577-8433
>
>
>
> On Aug 28, 2017, at 6:11 PM, Steve Gregory <
> <mailto:[log in to unmask] 3cmailto:[log in to unmask]>
> [log in to unmask]<mailto:[log in to unmask]>>
> wrote:
>
>
>
> 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/partial_ball_thumb.jpg
>
>
>
> <http://stevezeva.homestead.com/dull_solder.jpg>
> http://stevezeva.homestead.com/dull_solder.jpg
>
>
>
> <http://stevezeva.homestead.com/Head_in_pillow_1.jpg>
> http://stevezeva.homestead.com/Head_in_pillow_1.jpg
>
>
>
> <http://stevezeva.homestead.com/Head_in_pillow_2.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 <
> <mailto:[log in to unmask] %3cmailto:[log in to unmask]>
> [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]
> :[log in to unmask]> mailto:[log in to unmask]<mailto:
> [log in to unmask]>]
>
> Sent: August-25-17 2:26 PM
>
> To: TechNet E-Mail Forum < <mailto:[log in to unmask]
> to:[log in to unmask]> [log in to unmask]<mailto:[log in to unmask]>>; Steven
> Kelly < <mailto:[log in to unmask]:[log in to unmask]>
> [log in to unmask]<mailto:[log in to unmask]>>
>
> Cc: Steve Gregory <
> <mailto:[log in to unmask]:[log in to unmask]>
> [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> tel:
> 360-675-1322>
>
> Fx: 206-624-0695< <tel:206-624-0695> tel:
> 206-624-0695>
>
> Cl: 360-544-2289< <tel: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> https://goo.gl/maps/mMjg43rXeFB2
>
>
>
> -----Original Message-----
>
> From: TechNet [ <mailto:[log in to unmask]:[log in to unmask]>
> mailto:[log in to unmask]<mailto:[log in to unmask]>] On Behalf Of Steven
> Kelly
>
> Sent: Friday, August 25, 2017 11:13 AM
>
> To: <mailto:[log in to unmask]:[log in to unmask]> [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]:
> [log in to unmask]> mailto:[log in to unmask]<mailto:
> [log in to unmask]>]
>
> Sent: August-25-17 11:00 AM
>
> To: 'TechNet E-Mail Forum' < <mailto:[log in to unmask]
> to:[log in to unmask]> [log in to unmask]<mailto:[log in to unmask]>>; Steven
> Kelly < <mailto:[log in to unmask]:[log in to unmask]>
> [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]:[log in to unmask]>
> mailto:[log in to unmask]<mailto:[log in to unmask]>] On Behalf Of Steven
> Kelly
>
> Sent: Friday, August 25, 2017 10:26 AM
>
> To: <mailto:[log in to unmask]:[log in to unmask]> [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]:
> [log in to unmask]> mailto:david.hillman@
> rockwellcollins.com<mailto:[log in to unmask]>]
>
> Sent: August-25-17 10:06 AM
>
> To: TechNet E-Mail Forum < <mailto:[log in to unmask]
> to:[log in to unmask]> [log in to unmask]<mailto:[log in to unmask]>>; Steven
> Kelly < <mailto:[log in to unmask]:[log in to unmask]>
> [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
>
> <mailto:[log in to unmask]:
> [log in to unmask]:david.hillman@
> rockwellcollins.com%3cmailto:[log in to unmask]>
> [log in to unmask]<mailto:david.hillman@rockwellcollins
> .com
> ><mailto:[log in to unmask]<mailto:david.hillman@
> rockwellcollins.com>>
>
>
>
> On Thu, Aug 24, 2017 at 1:11 PM, Steven Kelly <
> <mailto:[log in to unmask] %3cmailto:[log in to unmask]>
> [log in to unmask]<mailto:[log in to unmask]><
> <mailto:[log in to unmask]:[log in to unmask]> mailto:
> [log in to unmask]<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
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