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June 2013

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From:
"Nutting, Phil" <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Nutting, Phil
Date:
Thu, 20 Jun 2013 15:05:47 +0000
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Thanks for that Dave!

From: [log in to unmask] [mailto:[log in to unmask]]
Sent: Thursday, June 20, 2013 10:56 AM
To: TechNet E-Mail Forum; Nutting, Phil
Subject: Re: [TN] Mixing solders,

Hi Phil - I agree and as Richard detailed, the big question is whether the cleaning process adequately removes all of the water soluble residues. If that can be demonstrated, then there should be no incompatiblity concerns and things would be good to go. I also take the same approach for mixing solder alloys - need to conduct some testing to make sure that you are not being setup for failure. Since most of the leadfree alloys are very close to each other in terms of composition, the risks are lower but I am pretty conservative and having some test confirmation is always good - it can be used to show your customers that you are doing "due diligence" in making process choices. As a material engineer I love all of the new materials but as a process engineer, the new materials give me headaches.

Dave



From:        "Nutting, Phil" <[log in to unmask]<mailto:[log in to unmask]>>
To:        <[log in to unmask]<mailto:[log in to unmask]>>
Date:        06/20/2013 08:37 AM
Subject:        Re: [TN] Mixing solders,
Sent by:        TechNet <[log in to unmask]<mailto:[log in to unmask]>>
________________________________



Dave and Steve,

I totally agree on mixing flux.  However, on the presumption that the OA flux has been removed by washing before rework it would seem acceptable to then use no-clean core flux.

My bigger question, assuming OA flux was removed before, does it matter which of the RoHS alloys are used in the two processes? Is there an issue with intermixing the SAC305, SN100C, SC995e or other alloys?

These are possible issues we have here with several different CMs, several different manufacturing groups and several different soldering requirements (materials being soldered).

Phil Nutting

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of David D. Hillman
Sent: Thursday, June 20, 2013 9:15 AM
To: [log in to unmask]<mailto:[log in to unmask]>
Subject: Re: [TN] Mixing solders,

Hi Steve - I'll have to pay Doug and use his tag line - "It depends"!
Anytime you mix two different flux systems, especially a water soluble and a low residue (aka no clean), there may be an issue of incompatibility that could result in a really hard lacquer (best case) or a really cool corrosion cell (worst case).  My recommendation would be to advise the customer that the mixing of the two flux systems would not be advised unless some testing can be conducted to ensure no detrimental reactions would occur. A second option would be to check with the flux supplier to see if they have any compatibility data. If the fluxes come from two different suppliers, don't waste your time asking that question as they won't have the answer. Good Luck.

Dave Hillman
Rockwell Collins
[log in to unmask]<mailto:[log in to unmask]>



From:   Steven Kelly <[log in to unmask]<mailto:[log in to unmask]>>
To:     <[log in to unmask]<mailto:[log in to unmask]>>
Date:   06/20/2013 08:02 AM
Subject:        [TN] Mixing solders,
Sent by:        TechNet <[log in to unmask]<mailto:[log in to unmask]>>



Hi All,
I have been looking in the archives but can't seem to find what I want an answer to . I have a customer who wants us to use water soluble RoHS for the SMT process but wants no-clean RoHS for the touch-up. Is this recommended? Regards Steve Kelly


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