We use water-soluble solder flux washed with hot water-softener treated tap water on sensitive analog fiberoptics
receiver circuits. We have never seen any leakage problems (signals as low as 1 x10-9 amps).
What concerns me is any flux residue - concerned that humidity (our fiberoptic products are used outside in climates like
Florida) so leakage from residues could cause problems.
Bob Landman
H&L Instruments, LLC
On Sep 7, 2010, at 8:22 AM, Robert Kondner wrote:
> Doug,
>
>
>
> I did forget to mention to blow the water off the board with an air gun, a
> very important step.
>
>
>
> Tap water limits are about 500mg per L, at least that is my quick check on
> the web. Sounds like a lot compared to what I see here but lets use that
> number.
>
>
>
> Lets assume I have a 1mm drop (1/2 sphere) per square inch of PCB, that is
> about 1/2 mm cubed. (Drops are very small after the air gun.
>
>
>
> 1 L = 10**6 mm cubed.
>
>
>
> So, on my board I can expect .250g/10**6 = .25ug / in squared. Wow, sounds
> low, did I miss a few magnitudes of 10 somewhere?
>
>
>
> So how bad is tap water again?
>
>
>
> I saw some specs allowing 10ug/in**2 so I guess that means I can have 40
> drops of tap water per in **2.
>
>
>
> Thanks
>
> Bob Kondner
>
>
>
>
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Douglas Pauls
> Sent: Tuesday, September 07, 2010 9:14 AM
> To: [log in to unmask]
> Subject: Re: [TN] Hand Soldering
>
>
>
> Ohhhh, I beg to differ. Water soluble fluxes are more active and will
>
> probably do OK for soldering, but they also represent a danger if you do
>
> not totally remove them or if some of it flows into places and does not
>
> get rinsed out. What really makes me nervous about your approach is your
>
> choice of equipment and cleaners. Tap water sucks as a cleaner and hot tap
>
> water only slightly better. You might be able to remove the visible
>
> residues, but will still have invisible residues that will cause problems.
>
> In some cases, you are putting on more contaminants with the tap water
>
> than you are removing.
>
>
>
> We use low residue fluxes here on class three product and have a number of
>
> cases where the the residues are left in place. It is simply a matter of
>
> finding a flux and cleaning combination that works well together, and
>
> limiting the amount of additional flux you add. A skilled operator can do
>
> soldering with no more flux than is in the core of the wire. You may need
>
> a slightly larger core.
>
>
>
> Ken, I would suggest this short list to you. Use either Kester 245 low
>
> residue flux (P3 core) or Alpha Telecore Plus (also P3 core). Both are
>
> standards here and work well for soldering. For topical cleaning
>
> solutions, try Kyzen's Cybersolv 141b or Chemtronics Flux-Off Heavy Duty.
>
> Both these cleaning agents work well with the fluxes I named.
>
>
>
> Doug Pauls
>
> Rockwell Collins
>
>
>
>
>
>
>
> Robert Kondner <[log in to unmask]>
>
> Sent by: TechNet <[log in to unmask]>
>
> 09/06/2010 01:27 PM
>
> Please respond to
>
> [log in to unmask]
>
>
>
>
>
> To
>
> [log in to unmask]
>
> cc
>
>
>
> Subject
>
> Re: [TN] Hand Soldering
>
>
>
>
>
>
>
>
>
>
>
>
>
> Ken,
>
>
>
> In my mind there is absolutely no question, hand assemble using Water
>
> Soluble flux. A good spray under hot water cleans well.
>
>
>
> During final assembly or rework I might use a no clean at spots. The only
>
> problem is the no clean is VERY DIFFICULT to remove so don't try. It
>
> detracts from board appearance.
>
>
>
> It the spot being reworked is a sensitive analog circuit they rework
>
> using
>
> Water Soluble. For anything close to fine pitch SMT you should be applying
>
> liberal quantities of Water Soluble flux, only way to rework.
>
>
>
> You can get a little "Water Pick" real cheap. Load it with hot water and
>
> you can you can really get down into the nooks and crannies.
>
>
>
> Bob Kondner
>
>
>
> -----Original Message-----
>
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Kenneth Wood
>
> Sent: Monday, September 06, 2010 8:30 AM
>
> To: [log in to unmask]
>
> Subject: [TN] Hand Soldering
>
>
>
> Hi all.
>
> What is the best setup for hand soldering as far as solder / cleaner?
>
> Rosin core? Water soluble? No-Clean?
>
> What cleaner too?
>
>
>
> I've been using rosin core with various cleaners but I have a hard time
>
> with
>
> the white residue the cleaners leave.
>
>
>
> Thanks
>
> Ken
>
>
>
>
>
>
>
>
>
>
>
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