Hi Brian,

I'll not name names here, but we have an optocoupler in an 8 pin 0.4" wide DIP package that clearly states on the data sheet for the Solder Reflow Temperature Profile and the Recommended Pb-Free IR Profile that "non-halide flux should be used".  There is no mention of wave soldering.  Interestingly enough this note only appears on one vendors data sheet.  The other manufacturers that make the same part say nothing about halides.

This seems a lot of research and change for a minority part.  Kind of like the push for lead-free.

Phil

-----Original Message-----
From: Brian Ellis [mailto:[log in to unmask]] 
Sent: Wednesday, February 29, 2012 2:49 AM
To: TechNet E-Mail Forum; Phil Nutting
Subject: Re: [TN] halides in water soluble fluxes

You have roused my curiosity, Phil. What are the parts that can withstand halide-free WS fluxes but not halide-containing ones, and why? 
I could understand it for some chemical sensors but optical??? Have you discussed this with your parts manufacturer? Does he give a reason for eschewing halides or is it aqueous processes that he does not like? What is his view on halide-containing rosin fluxes?

Please let me warn you that you would need to re-qualify your process because you may find that the halide-free fluxes may be a lot more difficult to clean, especially with a DI-water only wash. You may find that there may be more corrosive residues on the washed boards.

For me, assuming that my thoughts are justified, using your current process with one small modification, perhaps not requiring re-qualification, will fill the bill. That is to have a static bath containing a chelating neutraliser (not a saponifier) between the soldering and cleaning operations. A couple of minutes or so will solubilise any heavy metal halides or organic halides and will "kill" 
the excess acidity of any WS flux. I used to recommend Lonco 2051-B-3 but I think this is no longer available. I think Alpha have one called Rinse-Aid and I suppose Kester, Multicore etc. may have equivalents.

Have you thought that many components are supplied with halides galore? 
Component manufacturers often use halide fluxes for tinning their products, often with little or even no cleaning. Much tinned copper wire uses a zinc chloride/hydrochloric acid flux and the only cleaning is running it through a damp sponge followed by a sponge with a waxy substance!

If your components are really sensitive to halide ions, I would say that ion chromatography will be an essential part of your qualification process, no matter which flux you use.

Finally, have you thought about using your existing process but adding the sensitive components by hand, soldering with an evaporative halide-free no-clean flux, after cleaning? this may a simple cheap way round your problem, especially if the quantities are small.

Brian

PS Inge: Thanks for the plug. The IPC were kind enough to allow me to mention the availability of the book on this forum a few months ago but I don't want to abuse their hospitality, other than to say there is now a download version as well as the hard copy. I'm now the publisher as well as the author!



On 28/02/2012 21:12, Phil Nutting wrote:
> We have some parts that are sensitive to halides in flux, specifically some thru-hole opto devices.  We are currently using a water soluble flux that contains halides.  In doing some very quick research it looks like the WS fluxes have halides and the NC fluxes do not.
>
> Is there a halide free WS flux for lead-free wave soldering (foam application)?
>
> We need the WS fluxes because we currently use a DI water only batch wash system.  Washing the boards is mandatory for our applications.
>
> Thanks in advance,
>
> Phil Nutting
> Design for Manufacturing Engineer
> Kaiser Systems, Inc.
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> >
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