Mike,

If you are planning to use RoHS compliant solder on an assembly that was 
processed through Tin-Lead processes, you could get mixing of the two solder 
types creating non-standard alloys with unpredictable results. There has been 
some discussion of this previously in this forum and you might find useful 
information in the archives.

Blair

On Mon, 6 Dec 2010 16:58:23 -0500, Laroe, Michael 
<[log in to unmask]> wrote:

>Thanks Kevin..
>
>The Solders were chosen after a DOE was done on each comparing them to 
others alike approx 7yrs ago. We also restrict the operators from using 
additional flux so that the remaining material left behind has definitely seen 
temps well above 170oC.. Knowing this I know the flux left behind is definitely 
benign.  However, if additional flux is absolutely needed then there are specific 
cleaning instructions to ensure nothing corrosive, conductive is left behind.  
Also, the Kester Flux core we are using is the 66 which contains 3.2% Flux 
content which allows a much better flow than the standard 2%..
>
>Given this can you see any other reason not to use the Kester for both 
requirements.
>
>Thanks again,
>
>Mike
>
>-----Original Message-----
>From: TechNet [mailto:[log in to unmask]] On Behalf Of Glidden, Kevin
>Sent: Monday, December 06, 2010 4:51 PM
>To: [log in to unmask]
>Subject: Re: [TN] HandSoldering Using NC Solders
>
>Mike,
>That's a big one.  The answer is that you need to choose the best solder(s) 
for your application(s).  It is likely your two solders were selected by two 
different people at two different times.  When choosing materials, talking to 
the manufacturers about the products, getting samples, and comparing them 
head-to-head goes a LONG way.  You must also consider reliability.  The best 
flux formulation is simply not the one that allows you to solder a rusty nail to 
the hull of a ship.  An important factor is how you plan to clean your parts 
after soldering is all done, how well you can ensure you get all the residues 
removed, and the potential impact of any residues remaining on the 
assemblies.  I suggest you start by reading through some tech articles on 
cleaning.  This forum, the industry magazines, Foresite, and ACI are some 
good starting resources.  Bottom line - you don't pick solder materials solely 
on the basis of supplier or cost.
>Good luck.
>
>-----Original Message-----
>From: Mike Laroe [mailto:[log in to unmask]]
>Sent: Monday, December 06, 2010 4:06 PM
>To: [log in to unmask]
>Subject: [TN] HandSoldering Using NC Solders
>
>Currently my company has been using two different Alloys for handsoldering
>both Leaded and RoHs No-Clean Assy's.  For the leaded requirement we are
>using AIM and for Rohs we are using Kester.  We currently stock 4 different
>sizes of each (.015", .020", .025", .031")..  My question and thought is to
>phase out the AIM and strictly only use the Kester for both Leaded and Rohs
>Assy's.  All the Soldering is done with Metcals using the 700 & Pwr Tips.  Are
>there any reasons I shouldn't do this?
>
>Thanks for your help in advance,
>
>Mike Laroe
>Mfg Engineer
>

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