I would not clean tinned stranded wire with alcohol; this will just drive
the flux residue higher up the wire. Do not, do not, do not use an
alkaline material even to clean the flux residue, alkaline solutions will
wick up the wires worse than anything.
Use a heavy rosin or resin based flux with very little activator. and
don't clean it.
Karen Tellefsen - Electrical Testing
Alpha / 109 Corporate Blvd./ S. Plainfield, NJ 07080
[log in to unmask]
908-791-3069
From: "Nutting, Phil" <[log in to unmask]>
To: <[log in to unmask]>,
Date: 06/09/2014 10:26 AM
Subject: Re: [TN] tinning wires - flux entrapment and long term
reliability
Sent by: TechNet <[log in to unmask]>
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]] On Behalf Of Stadem, Richard D.
Sent: Monday, June 09, 2014 9:30 AM
To: [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]] On Behalf Of Carl VanWormer
Sent: Friday, June 06, 2014 8:20 AM
To: [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]>
http://cipherengineering.com<http://cipherengineering.com/>
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