Whenever the topic of soldering wires comes up, I drone on about the time the customer unit came back, suffering from uncured flux that had wicked up under the wire insulation.  After several months in the wet-spray environment, the unit failed with an open circuit up inside the insulation.  When I tugged on the wire, the soldered part of the stranded wire stayed on the connector pin and the rest of the wire pulled off, leaving a 5mm length of copper wire strands sticking up from the good solder joint.  

Is there any way to keep flux from wicking up the strands?

Thanks,
Carl



Carl B. Van Wormer, P.E., AE7GD
Senior Hardware Engineer
Cipher Engineering LLC
    21195 NW Evergreen Pkwy Ste 209
    Hillsboro, OR  97124-7167
    503-617-7447x303
    [log in to unmask]     http://cipherengineering.com


-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Theodore J Tontis
Sent: Thursday, November 05, 2015 10:53 AM
To: [log in to unmask]
Subject: Re: [TN] Pierced Terminal

It is not a defect but it is clearly stating something is not right which could lead to a defect. I would say this is a process indicator and push back on the supplier asking why there are discrepancies in the two images. My guess is they do not have a clear or well defined process and one or two assemblers are using a different process. A different process could include the amount of flux used, temp of the soldering iron, tip, type of solder.... Bottom line, show your supplier what you want and ask them to review their process for variation.  

As for coating over NC flux residue, I would do environmental testing to confirm it will not be an issue before I give it a thumps up to use the combination of flux type and coating in production. Once it's out in the field and there are failures the damage is already done. Just my personal opinion. 

Ted T 

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Stadem, Richard D.
Sent: Thursday, November 05, 2015 12:16 PM
To: [log in to unmask]
Subject: Re: [TN] Pierced Terminal

Yes, the coating is applied directly over the NC residue. It CAN lead to issues; you need to do your homework to ensure the coating you are using is compatible with the flux residues. This is usually done by working with the flux vendors, they are quite knowledgeable in this area. 

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Thierolf, Chris @ MPSG - SPD
Sent: Thursday, November 05, 2015 11:59 AM
To: [log in to unmask]
Subject: Re: [TN] Pierced Terminal

So in the case of conformal coat, this is applied over top the residue? Does this lead to latent issues?

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Ed Popielarski
Sent: Thursday, November 05, 2015 12:35 PM
To: [log in to unmask]
Subject: Re: [TN] Pierced Terminal

I agree 100%. "No clean" flux really should be called "Don't clean"! The bad guys (ionics) don't necessarily "go away", they are well encapsulated in the residue. Disturbing the residue is opening Pandora's box.

Ed Popielarski
Engineering Manager


                               970 NE 21st Ct.
                              Oak Harbor, Wa. 98277

                              Ph: 360-675-1322
                              Fx: 206-624-0695
                              Cl: 949-581-6601



-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Steve Gregory
Sent: Monday, November 02, 2015 8:34 AM
To: [log in to unmask]
Subject: Re: [TN] Pierced Terminal

Hi Chris,

Sorry I was out on Friday, so I apologize for the late response. I have your pictures posted, they are here:

http://stevezeva.homestead.com/Chris_Flux_Residue.jpg

As Guy said, I would leave it alone. I agree that an attempt to clean this you would run the risk of wicking things up into the insulation. IMHO, it looks fine to me.

Steve

On Thu, Oct 29, 2015 at 5:43 PM, Thierolf, Chris @ MPSG - SPD < [log in to unmask]> wrote:

> I'm seeking some input to a solder condition that gets scrutinized in 
> many directions. For the soldering of a stranded 10-12awg stranded 
> wire to a pierced resistor terminal, a no clean L0 or L1 (RO/RE) flux 
> is used with
> 63/37 solder. This is a single solder joint on a panel mount resistor, 
> so no PCB involved. Flux residue is observed and assembly rejected by 
> QC but manufacturer claims its no worry, and no clean flux. My 
> observation says it presents no electrical or operational issue, not a 
> violation of J-STD-001, but perhaps a visual issue per IPC-A-610, sec
> 10.6.4 "Flux residue inhibits visual inspection" if floor inspector 
> claims he cannot see the solder joint clearly, which has occurred. We 
> can state "clean the solder joint" (relatively speaking), but what 
> really is clean in this case? Should we be forced to inspect these 
> joints with 4x mag, as some are doing, or generate a simple guideline 
> that allows residue up to a certain level? What is this level?
>
> I have a picture of a failed solder joint if interested, but not sure 
> where to upload.
>
>
> ______________________________________
> [Disc3.png]
> Chris Thierolf
> Principal EE and Project Engineer
> L-3 Electronic Systems Segment
> SPD Electrical Systems
> 13500 Roosevelt Boulevard
> Philadelphia, PA 19116
> Phone: (215) 698-6390    Fax: (215) 677-4736
>
>
> ________________________________
> CONFIDENTIALITY NOTE: This electronic transmission, including all 
>
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