Anything you want to know about stripping, tinning, crimping, etc, outside of IPC 620 is in NASA-STD-8739.4A – 2016-06-30
Here is an excerpt from page 43 of 101, but also on many other pages. Just search under the word "flux" within the 8739 standard.
a. The portion of stranded wires that will eventually become a part of the finished solder connection shall be coated with tin-lead solder and cleaned prior to attachment. Additional flux may be used.
b. The flux shall be applied so that it does not flow under the insulation except for traces carried by solder wicking.
c. Flux shall be removed with cleaning solvent applied so that its flow under the conductor insulation is minimal.
d. Wire strands shall be discernible after tinning.
e. Solder wicking shall not extend to a portion of the wire which is required to remain flexible.
f. Solder build-up or icicles within the tinned wire area shall not affect subsequent assembly steps.
g. The length of untinned strands measured from the end of the tinned portion to the beginning of the wire insulation shall not be greater than 1 wire diameter.
10.1.3 Insulation Irregularity. Mechanical or thermal stripped insulation irregularity is acceptable if it does not exceed 1/4 of the outside diameter of the wire, including the insulation.
10.1.4 Insulation Clearance. The following requirements apply:
a. Soldered Connections.
(1) The insulation shall not be imbedded in the solder joint.
(2) The contour of the conductor shall not be obscured at the termination end of the insulation.
(3) The insulation clearance shall be less than two wire diameters, including insulation, but in no case shall permit shorting between adjacent non-electrically common conductors.
(4) Insulation clearance shall be referenced from the first point of contact of the conductor to the terminal.
b. Crimped Connections.
(1) The minimum insulation clearance for all crimped connections shall be 0.25mm (0.01in.).
(2) The maximum insulation clearance for conductors 20AWG and smaller shall be 0.75mm (0.03in.).
NASA-STD-8739.4A – 2016-06-30
44 of 101
(3) The maximum insulation clearance for conductors 18AWG and larger shall be 1.25mm (0.05in.).
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Carroll (US), Thomas A
Sent: Tuesday, March 19, 2019 9:54 AM
To: [log in to unmask]
Subject: Re: [TN] Flux Corrosion of Stranded Wire
Dave,
Hopefully you can find the diamond in the rough by reviewing the following. I not 100% sure if what you are looking for is in one of these references but it can be a starting point:
1. J.T. Menke, “Military Electronics—A History and Projection,” Paper 328, Corrosion/ 89 (New Orleans, LA), National Association of Corrosion Engineers, 1989
2. Handbook for Corrosion Prevention and Deterioration Control in Electronic Components and Assemblies, MIL-HDBK-1250A, U.S. Army Missile Command, Redstone Arsenal, AL, June 29, 1992
3. W.J. Willoughby, “Design Guidelines for Prevention and Control of Avionic Corrosion,” Department of the Navy Document NAVMAT P 4855-2, June 1983
4. A.S. Brar and P.B. Narayan, Materials and Processing Failures in the Electronics and Computer Industries: Analysis and Prevention, ASM International, 1993
5. L.W. Ekman, Spacecraft Wire Harness Design Considerations, Interconn. Technol., March 1994, p 26–30
6. C. Harper, Electronic Packaging and Interconnection Handbook, 2nd ed., McGraw-Hill, 1997
7. L.D. Kapner, Alternative Fluxes for Hi-Rel Assemblies, Circuits Assem., Feb 1993, p 66–70
Good Luck,
Regards,
Tom
Thomas A. Carroll, CQA, FAA ODA Unit Member for BDS
Supplier Quality Engineer
Boeing Defense, Space and Security - East Region Supplier Quality
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-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of David Hillman
Sent: Monday, March 18, 2019 5:53 PM
To: [log in to unmask]
Subject: [TN] Flux Corrosion of Stranded Wire
Hi team - hey, looking for some assistance. I am looking for some published references (papers or book sections) on the issue of flux corrosion of stranded wire. Oddly, I don't have anything I can find in my reference library and this is an "old" topic so there are not going to be any modern papers. Its pretty much a industry best practice in terms of what not to do with flux when soldering stranded wire but I can't find what I thought would be a easy task. I did look in Manko and Klein Wassink but nothing there. I did find some good stuff in Barrie Dunn's recent Materials & Processes book. If anyone can point me in a good direction, I owe ya a Diet Coke!
TIA
Dave Hillman
Collins Aerospace
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