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:[log in to unmask]>
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:[log in to unmask]<mailto:[log in to unmask]>>
http://cipherengineering.com<http://cipherengineering.com/>
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