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June 2011

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Subject:
From:
Chris Mahanna <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Chris Mahanna <[log in to unmask]>
Date:
Thu, 9 Jun 2011 11:59:58 -0400
Content-Type:
text/plain
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text/plain (207 lines)
The wetting forces away from the knee cause to solder to coalesce over the bad part without dissolution/forming a joint at the bad part.  This will be your first clue in the microsection as it can be seen at maybe 200X.
When the wetting forces decrease (from multiple soldering cycles or T/H preconditioning from 003), the healing decreases.

Chris

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Gary Robinson
Sent: Thursday, June 09, 2011 11:19 AM
To: [log in to unmask]
Subject: Re: [TN] Black Pad?

We run a blank board but it is from a different Lot code and appears to solder fine.
Maybe we try an run one through reflow oven then wave?

To answer some of the other questions -
Both profiles are in spec
Reflow Peak at 244 - TAL - 88sec
overall time is 5 min ramp to peak

Wave -
Ramp to 140 and soak with  .5 Deg/sec increase to 163 for 1.3 min.
Delta is 10 deg C (big Xfrmr)
Contact Time - 2.4 Sec


On Thu, Jun 9, 2011 at 9:58 AM, Tontis, Theodore < [log in to unmask]> wrote:

> Would it be possible to run a bare board through the wave that hasn't 
> been through the reflow process?
>
> Ted T.
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Wenger, George M.
> Sent: Thursday, June 09, 2011 9:38 AM
> To: [log in to unmask]
> Subject: Re: [TN] Black Pad?
>
> Steve,
>
> I agree with your assessment about possible oxidation of Ni 1st pass 
> and dewetting during wave soldering.
>
> Regards,
> George
> George M. Wenger
> Senior Principal Reliability / FMA Engineer Andrew Corporation - 
> Wireless Network Solutions
> 40 Technology Drive, Warren, NJ 07059
> (908) 546-4531 Office (732) 309-8964 Mobile
> E-mail: [log in to unmask]
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Steve Gregory
> Sent: Thursday, June 09, 2011 9:59 AM
> To: [log in to unmask]
> Subject: Re: [TN] Black Pad?
>
> Hi Gary,
>
> I got your pictures this morning, and have them posted now:
>
> http://stevezeva.homestead.com/Joint_1.JPG
>
> http://stevezeva.homestead.com/Joint_2.JPG
>
> http://stevezeva.homestead.com/via.JPG
>
> Although the pictures show some non-wetting happening, it's difficult 
> to see what exactly is going on.
>
> You say that the component side seems fine, it's just when you're 
> trying to wave solder is when you see the problem. Maybe you have thin 
> gold, and when the boards were fresh, the SMT was able to solder fine. 
> But then after the boards went through reflow, the underlying nickel 
> oxidized so badly that solder wasn't able to wet?
>
> Steve
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Gary Robinson
> Sent: Wednesday, June 08, 2011 4:46 PM
> To: [log in to unmask]
> Subject: [TN] Black Pad?
>
> We have noticed a problem only on ENIG boards in our WAVE process that 
> looks similar to Black Pad but do not know how to identify or where to 
> begin to find a resolution to the problem.  We were hoping an expert 
> may have experience in seeing this problem.  Here are some facts - 1.  
> Black residue is on the vias and thts on the solder side. Please see 
> the attached images.
> 2.  Component Side SMT Parts do not exhibit the same problems.
> 3.  Boards are processed PbFree - SAC305, Pacific 2009m No Clean Water 
> Based flux 4.  THTs will not wet after residues appear (for touch up 
> process) 5.  Blowholes appear to accompany the defect but are not 
> always present.
>
> Thanks for your help in advance.
>
>
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