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Subject:
From:
George Wenger <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, George Wenger <[log in to unmask]>
Date:
Mon, 28 Aug 2017 19:36:09 -0400
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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]:[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]:[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]:[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>

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                              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]:[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:[log in to unmask]<mailto:[log in to unmask]>]

Sent: August-25-17 10:06 AM

To: TechNet E-Mail Forum < <mailto:[log in to unmask]:[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]:[log in to unmask]:[log in to unmask]> [log in to unmask]<mailto:[log in to unmask]><mailto:[log in to unmask]<mailto:[log in to unmask]>>

 

On Thu, Aug 24, 2017 at 1:11 PM, Steven Kelly < <mailto:[log in to unmask]:[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]

 

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