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January 2011

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Subject:
From:
"Stadem, Richard D." <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Stadem, Richard D.
Date:
Mon, 17 Jan 2011 15:59:47 -0600
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I see a fairly large piece of string or thread and two inspection arrows in the solder in the pictures. It may be time to clean the solder pot thoroughly. Items such as string, labels, etc, will not show up in the pot analysis, as that analysis is typically only for various metal alloys (tin, antimony, indium, bismuth, lead, gold, silver, etc.) However, the analysis should be done first to help determine just what should be done with the solder in the pot. You may need to thoroughly clean out all the dross and flux lining the inside walls of the sump and then just add tin to get it slightly above 63%, or it may be so contaminated with other alloys that you may need to take out all or most of the old solder, clean the sump, and replace with fresh solder.

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Steve Gregory
Sent: Monday, January 17, 2011 2:56 PM
To: [log in to unmask]
Subject: Re: [TN] Board failure due to fibber like fragments of alloy after wave soldering

Hi Cedric,

 

What does your last solder analysis say? You do get your pot analyzed don't
you?

 

Steve

 

 

****

From: TechNet [mailto:[log in to unmask]] On Behalf Of Cedric ORAIN
Sent: Monday, January 17, 2011 2:57 PM
To: [log in to unmask]
Subject: [TN] Board failure due to fibber like fragments of alloy after wave
soldering

 

After wave soldering of boards with both SMD and PTH components, 18% of the

boards failed during ICT.

The failure is due to shorts between SMD pads. 

 

These shorts are caused by "fibber like" fragments entrapped in solder

joints. We are looking for root cause of this level of waste.

 

These fragments are very similar in aspect with dross that we found on the

top of the wave "head" after the pump stop. You can see dross picture in the

pictures posted here:

 

http://ipc-technet.groupsite.com/gallery/17663

 

The alloy is Sn63Pb37 and the flux is an alcohol based no-clean flux.

Soldering under air atmosphere. The design of the board is ok. Dross is

removed daily.

 

Did you ever encountered this kind of issue (I mean with such a rate of

defect)?

I'm wondering if the aspect of the dross shown in the picture is normal or

is it due to a pollution (metallic pollution: high Cu rate?? / organic

pollution : epoxy, fiber glass fragments ...). 

 

Thanks for your in advance for your help and support,

 

Best regards,

 

Cedric ORAIN



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