Yes, we did. Also had it included in the CH-65B Cleaning Handbook. I have
sent a copy of that section to Steve Gregory to post.
Doug Pauls
Principal Materials and Process Engineer
Rockwell Collins
On Mon, Sep 8, 2014 at 9:09 AM, David Hillman <
[log in to unmask]> wrote:
> 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@rockwellcollins
>> > .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
>> > [log in to unmask]<mailto:[log in to unmask]
>> ><mailto:
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