Hi Bob - as Richard detailed, you need to get down to the flux supplier
application engineers for that detail of information. And nope, I don't
have a clue on why something so fundamental isn't a standard data point on
the tech data sheet.
Dave
On Mon, Sep 8, 2014 at 9:28 AM, Robert Kondner <[log in to unmask]>
wrote:
> Dave,
>
> I did look into this issue, several times. I still sense a bit of "Hog
> Wash" on this subject. I am trying to separate the hogs here.
>
> Go take a look at the Kester 951 data sheet. No "Deactivation
> Temperature" spec there.
>
> Go take a look at Kester 2331-ZX, now this stuff you need to clean.
> Again no "Deactivation Temperature" specified.
>
> So I suggest you get ahold of some flux supplier application folks and ask
> them for "Minimum Processing Temperature for Flux Deactivation". I don't
> think you will find such a specification.
>
> Thanks,
> Bob K.
>
>
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of David Hillman
> Sent: Monday, September 08, 2014 10:10 AM
> To: [log in to unmask]
> Subject: Re: [TN] tinning wires - flux entrapment and long term reliability
>
> Hi Bob - as Richard detailed, if you get ahold of the flux supplier
> application folks, they have the necessary data for setting up an adequate
> profile and temperature range, application depenedent. The whole "no clean"
> topic drives me batty - the proper term is "low residue" as I don't have
> my flux suppliers dictating when I should or should not clean. A case of
> marketing edging out engineering on the correct use of technical terms.
>
> Hey Doug - didn't you and Bill Kenyon have a nice synopsis on the "no
> clean vs low residue" topic?
>
> Dave
>
> On Mon, Sep 8, 2014 at 8:57 AM, Robert Kondner <[log in to unmask]>
> wrote:
>
> > Dave,
> >
> > Ok, so if a manufacturer says a flux is categorically "No Clean" we
> > should believe it, right? :-)
> >
> > Offhand I never recall seeing a Minimum Temperature specification for
> > the use of any flux. I recall finding usage temperature ranges, and
> > you find info on how long the flux is active, find statements about
> > must be cleaned or no clean, but have you ever seen a flux with a
> > minimum processing window to be qualified as a "No Clean"?
> >
> > From experience I know that heating profiles of PCB assemblies in
> > reflow ovens are selected such that all the flux does not completely
> "Burn Off".
> > In fact profiles where the flux remains active is what helps make nice
> > shiny solder joints, everyone loves those.
> >
> > I have not seen one shred of evidence in flux usage information that
> > suggest leaving flux residue is safe IF it has been heated to some
> > temperature for some specific length of time. All I see are fluxes
> > listed as "Must Clean" or "No Clean".
> >
> > Do you know of any flux called "You Might Need to Clean"?
> >
> > Bob K.
> >
> >
> > -----Original Message-----
> > From: TechNet [mailto:[log in to unmask]] On Behalf Of David Hillman
> > Sent: Monday, September 08, 2014 9:23 AM
> > To: [log in to unmask]
> > Subject: Re: [TN] tinning wires - flux entrapment and long term
> > reliability
> >
> > Hi Bob - all fluxes have a temperature range, or at least a minimum
> > temperature value, that they should be heated to to accomplish two tasks:
> > (1) attack/remove the oxides that inhibit the formation of a good
> > solder wetting; (2) decompose the activators such that they are benign
> > in the flux residue. The flux suppliers know their formulations and
> > can provide temperature recommendations to ensure we can create
> > adequate reflow profiles in our processes.
> >
> > Dave
> >
> > On Mon, Sep 8, 2014 at 7:58 AM, Robert Kondner
> > <[log in to unmask]>
> > wrote:
> >
> > > Richard,
> > >
> > > So, I ask:
> > >
> > > Does a rosin based "No Clean" flux need to be completely heated to
> > > high temperature to "De-Activate" the flux?
> > >
> > > If what Dave say is correct the answer is no. I think?
> > >
> > > Bob K
> > >
> > > -----Original Message-----
> > > From: TechNet [mailto:[log in to unmask]] On Behalf Of Stadem, Richard D.
> > > Sent: Monday, September 08, 2014 8:29 AM
> > > To: [log in to unmask]
> > > Subject: Re: [TN] tinning wires - flux entrapment and long term
> > > reliability
> > >
> > > Dave, I never knew that about RMA fluxes. This is valuable
> > > information, and I thank you for it.
> > > dean
> > >
> > > From: David Hillman [mailto:[log in to unmask]]
> > > Sent: Friday, September 05, 2014 4:03 PM
> > > To: TechNet E-Mail Forum; Stadem, Richard D.
> > > Subject: Re: [TN] tinning wires - flux entrapment and long term
> > > reliability
> > >
> > > Hi Richard - I can provide some additional information. The value of
> > > rosin based fluxes is that when using the proper soldering
> > > temperatures and dwell times, the resulting flux residues are not
> > > mobile, ionic species that can participate in corrosion reactions
> > > (note that there is always an exception to the rule). The rosin
> > > portion of rosin based fluxes can "bind up" any mobile, ionic
> > > species if they are not completely consumed in the soldering
> > > reaction. That is why rosin based fluxes are very robust in
> > > soldering processes. As George and others detailed, "no clean' is a
> > > horrible material descriptor as it is a process categorization
> > > rather than a material categorization. The better term is "low
> > > residue" and as others detailed, not all low residue materials are
> > > created equal. Many low residue fluxes are rosin based materials so
> > > they have applicability for wiring tinning but an engineer has to do
> > > their homework to make sure there is process compatiblilty. And yes,
> > > when folks attempt to use water soluble fluxes in the same manner as
> > > rosin fluxes, bad things happen. The wire tinning process you
> > > learned has its credibility in the rosin chemistry (the IPA
> > > relavence isn't as critical
> > or necessary as Brian can/has detailed) and is supported by the
> > products you detailed.
> > >
> > > I believe Doug and Bill Kenyon put together a "letter" on this topic
> > > and I'll see if Doug can find that for posting thru Steve.
> > >
> > > Dave Hillman
> > > Rockwell Collins
> > > [log in to unmask]<mailto:david.hillman@rockwellcolli
> > > ns
> > > .com
> > > >
> > >
> > > On Fri, Sep 5, 2014 at 3:00 PM, Stadem, Richard D. <
> > > [log in to unmask]<mailto:[log in to unmask]>> wrote:
> > > I started out in life as a small child with a very large pair of
> > > safety glasses and a leather apron, tinning wires in my father's
> > business.
> > > I later re-learned how to do this from two much older engineers, who
> > > had retired from RCA and Honeywell, and they had been using this
> > > method since they were little boys in their father's shop.
> > > I have also taught this method to my three sons, as there still
> > > seems to be no end of wire tinning requirements even today.
> > >
> > > 1. When stripping the wires, leave the tag end of the insulation
> > > hanging on the end of the wire. This helps prevent the strands from
> > > fraying during handling.
> > > 2. When ready, pull off the tag end of the insulation. Dip the
> > > stripped end of the wire first in IPA up to the end of the insulation.
> > > 2. Then dip the wire in the RMA flux up to about halfway to the
> > > insulation. Use only RMA flux whenever tinning wires, never OA or
> > > water soluble flux, and never no-clean flux.
> > > 3. Then dip the fluxed end into the solder right up to within .010"
> > > from the insulation and hold for 1 or 2 seconds. This allows the
> > > solder to wick just under the insulation.
> > > 4. Pull the wire out of the solder and "swirl" in clean IPA, and
> > > then lay the wires down flat on a piece of absorbent paper towel.
> > > 5. If an ultrasonic cleaner can be used, ie, the wires are not
> > > soldered to any CCA or any electronic components, then instead of
> > > laying them on the paper towel, drop them into the US cleaner with a
> > > solution of 90% DI water and 10% IPA. Do not exceed the 10% IPA
> > > percentage or you will have a new company swimming pool, but also
> > > you will be minus a few operators and you will gain many new friends
> > > at OSHA and Davidovich, Davidovich, and Rabinovitch, Atty's at Law.
> > > 6. Once all of the wires have been cleaned for a minimum of 10
> > > minutes in the US bath, take them out and dry them on a clean paper
> towel.
> > >
> > > This is a time-tested method, dating back to the late 1950s.
> > >
> > > My understanding (and it may be flawed) is that RMA is used because
> > > even if small amounts are not dissolved in the IPA, whatever
> > > residues that do remain are relatively harmless, because they are
> > > weakened by the IPA already in the wire strands, and after tinning,
> > > most if not all is removed during the "swirling" in IPA. When the
> > > wires are laid down on the paper towel, the IPA and the flux solids
> > > are drawn out, and any remaining residues left behind are relatively
> harmless.
> > >
> > > I do know that this method of tinning wires was used in the old
> > > Apollo program.
> > > It was also used on the Neartip Mark 5 Torpedo Guidance and Control
> > > systems.
> > > It was also used on the older Mark 2 Torpedoes.
> > > It was also used on the Advanced Lightweight Torpedo.
> > > It was used on the Apache, C5B, Augusta, F-15, F-16, FA-18 avionics
> > > systems, including the flight control computers, the ring laser
> > > gyros, the altimeters, the wind speed indicators, the flapper
> > > controls, the CMRA and HMRA Cruise Missiles, The CH46/CH47 avionics
> > > sets, the Space Shuttle wiring, and about 400-500 commercial jet plane
> wiring sets.
> > >
> > > I have yet to hear of any wires broken off from corrosion under the
> > > insulation.
> > >
> > > I have heard of many wires corroding away because either water
> > > soluble flux or no-clean fluxes were used. Water soluble fluxes do
> > > not wash out or dilute when dipped in alcohol or water (at least not
> > > very well). Ditto with no-clean fluxes.
> > >
> > >
> > > My only concern is that there are RMA fluxes, and there are RMA
> > > fluxes, and some may be more aggressive than others.
> > >
> > >
> > >
> > > -----Original Message-----
> > > From: TechNet [mailto:[log in to unmask]<mailto:[log in to unmask]>] On
> > > Behalf Of Nutting, Phil
> > > Sent: Friday, September 05, 2014 11:56 AM
> > > To: [log in to unmask]<mailto:[log in to unmask]>
> > > Subject: Re: [TN] tinning wires - flux entrapment and long term
> > > reliability
> > >
> > > Dusting off an old thread here (yes Brian, I listened to your
> > > request for not changing threads). I've been thinking about the
> > > "best" method of wire tinning for some time now and this thread
> > > makes me think the we should dump our no-clean cored wire solder in
> > > favor of something that
> > is more innocuous.
> > >
> > > I have an old roll of Kester 63/37 "44" core saved from years ago
> > > before the switch to lead-free. Is this acceptable for long term
> > > soldered wire reliability. If not, what are the recommendations? I
> > > guess knowing RA or RMA along with manufacturer and "model" would be
> > > useful. Hopefully it is available in 63/37 and lead-free alloys.
> > >
> > > Thanks in advance for sharing your knowledge and experience,
> > >
> > > Phil Nutting
> > >
> > > -----Original Message-----
> > > From: TechNet [mailto:[log in to unmask]<mailto:[log in to unmask]>] On
> > > Behalf Of Carl VanWormer
> > > Sent: Tuesday, June 10, 2014 11:55 AM
> > > To: [log in to unmask]<mailto:[log in to unmask]>
> > > Subject: Re: [TN] tinning wires - flux entrapment and long term
> > > reliability
> > >
> > > There sure are a lot of scare stories about flux and reliability.
> > > I'm now wondering if a solution based on crimping some sort of
> > > ferrule or machined pin onto the ends of the wires and then
> > > soldering those metal parts into the PCB holes might be a more
> > > reliable approach. Have any of
> > "you guys"
> > > seen that type of solution to this problem?
> > >
> > > 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<tel:503-617-7447x303>
> > > [log in to unmask]<mailto:[log in to unmask]>
> > > http://cipherengineering.com
> > >
> > >
> > >
> > > -----Original Message-----
> > > From: TechNet [mailto:[log in to unmask]<mailto:[log in to unmask]>] On
> > > Behalf Of Karen Tellefsen
> > > Sent: Tuesday, June 10, 2014 6:00 AM
> > > To: [log in to unmask]<mailto:[log in to unmask]>
> > > Subject: Re: [TN] tinning wires - flux entrapment and long term
> > > reliability
> > >
> > > I would use Kester 186-18 instead for tinning. Alpha 615-15 is
> > > another good choice.
> > >
> > > Karen Tellefsen - Electrical Testing Alpha / 109 Corporate Blvd./ S.
> > > Plainfield, NJ 07080 [log in to unmask]
> > > <mailto:[log in to unmask]> 908-791-3069<tel:908-791-3069>
> > >
> > >
> > >
> > >
> > > From: Steve Gregory <[log in to unmask]<mailto:[log in to unmask]>>
> > > To: <[log in to unmask]<mailto:[log in to unmask]>>,
> > > Date: 06/09/2014 05:43 PM
> > > Subject: Re: [TN] tinning wires - flux entrapment and long term
> > > reliability
> > > Sent by: TechNet <[log in to unmask]<mailto:[log in to unmask]>>
> > >
> > >
> > >
> > > Hi Richard,
> > >
> > > Good information! But can I ask a question about a particular
> > > no-clean flux? It's about Kester 951. In their datasheet they say
> > > that it contains a "corrosion inhibitor" such that no corrosion
> > > products are formed when bare copper surfaces are exposed to humid
> > > environments. Do you have any idea what that might be?
> > >
> > > We use it as a touch-up flux for our no-clean soldering and do use
> > > it to tin wires. I know that some of that flux gets somewhere where
> > > it doesn't get cleaned, and probably didn't get exposed to a lot of
> > > heat when you're doing point-to-point touch-up and soldering with a
> > > single
> > iron.
> > >
> > > We haven't had an issue with this flux, at least any that I know of.
> > > But it doesn't mean that there isn't one. The operators sometimes
> > > complain when they use it because it evaporates so fast though.
> > >
> > > Just curious what the "corrosion inhibiter" might be. The SDS says
> > > the flux contains ethanol (50-65%), isopropanol (20-25%), n-butyl
> > > acetate (5-10%), methanol (2.5-5%), and adipic acid (1-2.5%).
> > > Everything listed is pretty much a solvent except for the adipic acid.
> > >
> > > Steve
> > >
> > >
> > > -----Original Message-----
> > > From: TechNet [mailto:[log in to unmask]<mailto:[log in to unmask]>] On
> > > Behalf Of Stadem, Richard D.
> > > Sent: Monday, June 9, 2014 2:23 PM
> > > To: [log in to unmask]<mailto:[log in to unmask]>
> > > Subject: Re: [TN] tinning wires - flux entrapment and long term
> > > reliability
> > >
> > > I agree with George, and also with many others who feel that
> > > cleaning with IPA is not a very good approach.
> > > I should have mentioned also that through the years that I have seen
> > > wires tinned with RMA flux, then soaked in IPA, then that was
> > > followed by a DI wash.
> > >
> > > The old-time engineers back in the 60s and 70s showed me by using 3
> > > stages of wires cut open to show what the strands looked like under
> > > the insulation. Different oldtimers showed me this trick more than
> > > once, and I have never forgotten it.
> > >
> > > First, the operators were trained to insert the wires into the RMA
> > > flux only halfway up the stripped portion (generally 1/8th inch to 1/4"
> > > striplength).
> > > Next, the operator was trained to insert the wire only up to just
> > > below the end of the insulation. Some of the RMA flux would always
> > > ride up to the insulation, and the solder would actually flow just
> > > under the insulation, seldom more than .050" past the end of the
> > > insulation. In other words, if you stop the stranded wire just short
> > > of the insulation, the solder continues to wick up to a point just
> > > under
> > the end of the insulation.
> > > Then, when the wires were not cleaned with IPA at all, the cutaway
> > > view would always show a small amount of flux just under the end of
> > > the insulation.
> > > When cleaned in the IPA only, but not followed with a water wash,
> > > when you cut the insulation away you "sometimes" saw a very small
> > > amount of
> > flux.
> > > But when you did all three, any flux residue under the insulation
> > > (if
> > > present) could not be seen. It does not mean it wasn't there; it
> > > just was not visible even at 20X.
> > >
> > > And in all cases, the oldtimers were never concerned with RMA flux
> > > residues being left behind under the insulation; they felt it was
> > > not a concern even to leave the RMA flux behind, with no cleaning.
> > >
> > > But NOT water soluble (OA) and NOT no-clean fluxes. The no-clean
> > > activators are sometimes even more aggressive than RMA. That is
> > > still
> > true.
> > > So I stand by the statement that when tinning wires, only RMA flux
> > > should be used, some type of solvent should be used to at least
> > > suspend the RMA solids, and some type of final rinse or wash process
> > > should be used. If all of those are done, I do not think there is
> > > ever a concern for the wires rotting away under the insulation.
> > >
> > > And one more item: If you are just cleaning tinned wires (no
> > > connector bodies, sleeving, circuit boards or components,etc.) I
> > > have found that following the solvent clean with an ultrasonic
> > > cleaning process where the entire wire or wire assembly is immersed
> > > in hot DI water with a 6% saponifier will get all of the flux out
> > > from under the end of the insulation.
> > >
> > > I am talking about the end of the insulation, not 1/2" up the
> > > insulation or anything like that.
> > >
> > >
> > >
> > > -----Original Message-----
> > > From: TechNet [mailto:[log in to unmask]<mailto:[log in to unmask]>] On
> > > Behalf Of Wenger, George M.
> > > [Contractor]
> > > Sent: Monday, June 09, 2014 1:21 PM
> > > To: [log in to unmask]<mailto:[log in to unmask]>
> > > Subject: Re: [TN] tinning wires - flux entrapment and long term
> > > reliability
> > >
> > > As someone who sent 33 years working in the "Bell System" were
> > > solder assembly quality/reliability was the primary concern, I'll
> > > throw my two cents into this discussion. I've never like the name
> "No-Clean".
> > > Any flux used for soldering that doesn't go through a cleaning
> > > process would be a "No-Clean" if the meaning is it wasn't cleaned
> > > off. The old BellCore (now
> > > Telcordia) GR-78 gives criteria for determining if a soldering flux
> > > residue needs to be cleaned off for reliability reasons.
> > > If you make a solder joint with a flux and don't clean it off and it
> > > passes the BellCore reliability testing then we would consider that
> > > flux a reliable "Leave-Behind" flux meaning if the flux residue
> > > wasn't cleaned off there were no reliability risks. In general most
> > > of the old fluxes classified as R & RMA passed the "leave-Behind"
> > > requirement. In fact, our experience was that especially for RMA
> > > fluxes the reliability was much better if you did leave them behind
> > > rather than tried to clean them. If you take an RMA flux and try
> > > cleaning it with alcohol (which isn't a very good solvent) what you
> > > wind up doing is dissolving and removing most of the rosin in the
> > > flux residue, which is what was encapsulating the ionic activators,
> > > which in turn allowed any ionic activators to be mobile and the
> > > first time the humidity increased you had the worse case for
> > > corrosion (moisture,
> > activators, and electrical potential).
> > >
> > > I can see that with a low-solids type "No-Clean" flux that the flux
> > > would wick up the braided wires and yes when a soldering iron was
> > > placed on where you wanted to make the solder joint the flux
> > > activators would be heated and reduce oxides and allow a good solder
> > > joint to form but the flux that wicked up the wires may not have
> > > gotten to a high enough temperature to de-activate the activators
> > > and then the humidity goes up in use you could have a problem. If I
> > > were pre-tinning braided wires I would only us an RMA flux qualified
> > according to BellCore GR-78 to be a "Leave-Behind".
> > >
> > > Regards,
> > > George
> > > George M. Wenger
> > > Failure Signature & Characterization Lab LLC
> > > 609 Cokesbury Road, High Bridge, NJ 08829
> > > (908) 638-8771<tel:%28908%29%20638-8771> Home (732)
> > > 309-8964<tel:%28732%29%20309-8964>
> > > Mobile E-mail [log in to unmask]<mailto:[log in to unmask]>
> > > [log in to unmask]<mailto:[log in to unmask]>
> > >
> > >
> > > -----Original Message-----
> > > From: TechNet [mailto:[log in to unmask]<mailto:[log in to unmask]>] On
> > > Behalf Of Carl VanWormer
> > > Sent: Monday, June 09, 2014 12:59 PM
> > > To: [log in to unmask]<mailto:[log in to unmask]>
> > > Subject: Re: [TN] tinning wires - flux entrapment and long term
> > > reliability
> > >
> > > I've heard stories of no-clean and hand soldering causing problems.
> > > In an IR-reflow oven, all of the no-clean flux achieves the
> > > passivation temperature, becoming inert. With hand soldering, the
> > > flux melts, runs away from the heat source, and penetrates any tiny
> > crevice it can find.
> > > There is an area at the perimeter of the heated area that is hot
> > > enough to cause the flux to flow, but not hot enough to cause it to
> > become active.
> > > If this is true, than this is the problem I'm worried about.
> > > Comments, please?
> > >
> > > 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<tel:503-617-7447x303>
> > > [log in to unmask]<mailto:[log in to unmask]>
> > > http://cipherengineering.com
> > >
> > >
> > > -----Original Message-----
> > > From: TechNet [mailto:[log in to unmask]<mailto:[log in to unmask]>] On
> > > Behalf Of Steve Gregory
> > > Sent: Monday, June 09, 2014 9:49 AM
> > > To: [log in to unmask]<mailto:[log in to unmask]>
> > > Subject: Re: [TN] tinning wires - flux entrapment and long term
> > > reliability
> > >
> > > It's been some years back, but we were building a cabinet along with
> > > all the boards and cables. The cables had silver plated braided
> > > shielding over them and we would have to solder the shield wires to
> > > either a lug or contact. We were using manufacture XXX no-clean flux.
> > > It had been a rainy spring that year, and rained about every other
> > > day for at least a month, so you know the humidity was high.
> > >
> > > One of the supervisors came to me after that month and said; "Steve,
> > > we got a problem, all the cables in the cabinets are turning green..."
> > > so I went and looked at them. Sure enough the shield wires were
> > > turning green, and it was down close to the end sections of the
> > > cables where they had been
> > > soldered:
> > >
> > > http://stevezeva.homestead.com/files/Green_Junk_1.jpg
> > >
> > > http://stevezeva.homestead.com/files/Green_Junk_2.jpg
> > >
> > > http://stevezeva.homestead.com/files/Green_Junk_3.jpg
> > >
> > > http://stevezeva.homestead.com/files/Green_Junk_Close.jpg
> > >
> > > I had a hard time figuring out how this was happening, because right
> > > at the ends where the soldered connection it was fine. The
> > > connections were soldered and cleaned with alcohol. Best I could
> > > figure was that the operators had flux on their fingers when they
> > > handled the cables and got the flux up on the cable where it wasn't
> > > reacted with heat, and wasn't cleaned, and with the high humidity
> > > that we had that month turned the shield wire green.
> > >
> > > We switched the no-clean flux to manufacture XXX and the problem
> > > went
> > away.
> > >
> > > Steve
> > >
> > >
> > > -----Original Message-----
> > > From: TechNet [mailto:[log in to unmask]<mailto:[log in to unmask]>] On
> > > Behalf Of Nutting, Phil
> > > Sent: Monday, June 9, 2014 8:25 AM
> > > To: [log in to unmask]<mailto:[log in to unmask]>
> > > Subject: Re: [TN] tinning wires - flux entrapment and long term
> > > reliability
> > >
> > > So for many years I have followed the discussion about flux cleaning
> > > and alcohol always get mentioned as a great way of dissolving the
> > > flux and depositing it on a much wider area. There has to be a
> > > better way to "clean" the wire entrapped flux if it really must be
> > > cleaned. I agree that OA flux is not a good solution. My current
> > > choice is to use
> > "no-clean"
> > > flux cored solder when tinning wires and then leave it alone.
> > > Soldering the wire into the board can then be done with "no-clean"
> > > or other flux cored solder. Where we do not make anything that is
> > > designed as mission critical this process seems to work for us.
> > >
> > > Phil Nutting
> > >
> > > -----Original Message-----
> > > From: TechNet [mailto:[log in to unmask]<mailto:[log in to unmask]>] On
> > > Behalf Of Stadem, Richard D.
> > > Sent: Monday, June 09, 2014 9:30 AM
> > > To: [log in to unmask]<mailto:[log in to unmask]>
> > > Subject: Re: [TN] tinning wires - flux entrapment and long term
> > > reliability
> > >
> > > You do not tell us what flux you are using.
> > > But as a general rule, one must never tin insulated wires using OA
> flux.
> > > Only RMA or no-clean should be used, and that followed by dipping
> > > the tinned ends in alcohol.
> > >
> > >
> > > -----Original Message-----
> > > From: TechNet [mailto:[log in to unmask]<mailto:[log in to unmask]>] On
> > > Behalf Of Carl VanWormer
> > > Sent: Friday, June 06, 2014 8:20 AM
> > > To: [log in to unmask]<mailto:[log in to unmask]>
> > > Subject: [TN] tinning wires - flux entrapment and long term
> > > reliability
> > >
> > > My understanding:
> > > While tinning wires with conventional soldering methods, the wire is
> > > heated and the flux-cored solder is applied to the wire. As the
> > > flux is melted, it wicks up between the wires and the solder flows
> > > in, wetting the wires. The liquefied flux flows up the wires
> > > farther than the solder, and some of the un-passivated flux is
> > > trapped inside the insulation, around the Copper strands where the
> solder stopped flowing.
> > >
> > > My experience:
> > > One of our control modules had failed in an automotive "road splash"
> > > environment. Our connector terminals had been soldered to the wires
> > > that came out of the "waterproof" strain-relief assembly.
> > > Troubleshooting let me to cable harness with an open circuit between
> > > a wired connector pin and the other end of the wire. The wire and
> > > pin looked good, but a gentle tug on the pin popped the 5mm length
> > > of soldered wire out of the wire's insulation, revealing a
> > > discoloration at the end of the solder-flow where the Copper wire
> > > had been
> > "disappeared".
> > > A few mm inside the wire insulation, there was another discolored
> > > blob at the end of the wire's total length of good Copper wire. Our
> > > conclusions of "not quite waterproof" and "chemistry experiment" led
> > > me to be concerned about the problem.
> > >
> > > Current worry:
> > > We have a product with a "requirement" that some 16-gauge stranded
> > > Copper wires be soldered to our PC board. The plan is to have the
> > > cable assembly arrive with pre-tinned wires, and then the wires will
> > > be soldered to the board with "no-clean" flux. The product is not
> > > expected to be in the water, but may be "near" a wet environment,
> > > maybe mounted in a pouch on some motorcycle gear. I'm worried about
> > > the tinning process forcing un-passivated flux up, inside the
> > insulation, to wait for a "humid"
> > > condition to start another "chemistry experiment."
> > >
> > > Questions:
> > >
> > > 1. Assuming we must solder wires to my PC board, is there any
> > > guidance on how to keep "chemistry experiments" from happening on my
> > > product?
> > >
> > > 2. Are there any other "very small" connection methods for 15 Amp
> > > wires that I should consider that I might be able to fit on my tiny
> > > PC board that would eliminate my worry?
> > >
> > > 3. Am I just being overly paranoid?
> > >
> > > 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
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> > ><mailto:
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> > > http://cipherengineering.com<http://cipherengineering.com/>
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