Wiring or Splice

[Dale M.]

A comment that Ol'fogasaurus made, set a little bell ringing...

I don't know if it has been really covered, but one should NEVER use acid core solder or a acid flux on electrical connections........ Only rosin core solders or rosin based fluxes (non corrosive) should be use on electrical work...

Acids if not properly neutralized will cause corrosion in wire adjoining solder joint thus promoting failure....

Acid core solder and fluxes may be ok on fuel tanks a radiators and plumbing but not electrical applications....

Dale

[raygreenwood]

Solder joints will rarely if ever fail....mechanically. However they do fail electrically at a rate that is vastly higher than a "proper" crimped connector. By this I mean that solder is a very poor choice for resistance sensitive components like fuel injection...

I'm not sure I understand. Most sensitive electronic devices have PCBs stuffed with components that are all soldered. I can see vibration breaking the junction between flexible wire and soldered wire, but I can't see the resistance issue here. Manufacturers always look for a faster way to build stuff. A crimped wire harness is faster to build than a soldered one, especially back in the day when it was all hand made. Also, most battery connections are soldered so it's not a 100% rule.

Actually no. The crimped harness and soldered harness are nearly identical in production time. All soldered harnesses past the mid 50's were all machine soldered. It was NOT a cost issue. In fact....crimped harnesses are MUCH more expensive than soldered ones. Modern connectors alone...cost more than the wire in many cases.
In the old days...40's through 60's.....there was little or no resistance sensitivity and almost no complexity within automotive harnesses. Solder was just fine. The harness cost was almost negligable anyway. I have more wires in my heater system of my 412 than many cars had in the whole car in 1950.

Battery compartments of cheap electronic devices...not for automotive or for aircraft....may be soldered, but most really good devices are crimped. Many OEM car battery connectors are CAST to the end of the cable....not soldered. BIG difference. There is no entrained air or voids and the lead. Many are then staked of peened about teh cable jacket for strain relief. None of them are actually soldered.

Sensitive electronic device wiring looms have no solder joints on external wire connectors whatsoever if they are of any quality at all.
PCB soldering is a different animal. All of the parts on "most" production PCB's for aircraft and automotive are either wave soldered or machine soldered. The key here is that each soldered component is rigidly connected to the PC board and the board itself is suspended and vibration damped with grommets.

The reason ALL OEMS went to crimped connectors started when they went to electroluminescent dash lighting and resistance sensitive engine components. Thats the only reason. Cost had nothing at all to do with it. A harness with 100+ soldered connections can be made in a jig or even by hand....at about half the cost of a crimped harness using costly but precise, copper and phosphor bronze, tin plated connectors and male-female plug assemblies. The modern connectors alone will cost the OEM about $125 for 100 connectors (or more for fuel injection cobnnectors)....add to that about $30-60 for plugs. A 100 wire harness takes about 5 minutes to strip ends and place within a soldering jig where all of teh connector rings or tabs are held in place. Most times....they were then soldered all at one time in about a minute. Even on hand soldered harnesses (which would rarely have more than 50-60 wires)....a skilled operator would spend at best...20-30 minutes soldering. Compare 45 minutes orf labor with the approximate $200 worth of plugs and connectors.

Chrysler had the very first electroluminescent dash isntruments in the late 1960's. They were great....but a miserable failure from the reliabilty standpoint because of the soldered connectors.
The only wires you ever see anymore in modern cars that are actually soldered are point to point wires on on a PCB....and even those are very few and very short and are usually the first failure points if they are not taped down, or potted to keep the wire from vibrating at the solder joint.

The resistance issue comes from voids...which you cannot guarantee are not there and corrosion.

Looking at the mechanical solder joints of a PCB and saying there is solder so solder must be fine for anything electrical or electronic...is not correct.

Also...if you look at very modern PCB's...there are almost no wires whatsoever. There is getting to be even less wave soldering than ever. Most is screen printed and Inkjet printed solder paste dots in a very precise pattern. All "connectable" components are then induction solder in a precise jig or by pick-and-place robotic equipment onto the board. Anything that interconnects is done by printed circuit trace and by plug in bridges. A wire that can vibrate at a solder joint is the weak link on any PCB.
Likewise.....a solderjoint on a flexible cable system is teh weakest link in that system. Wiring is flexible precisely so it can move. A solder joint is a rigid link in a flexible system. That creates long term fatigue...which creates long term fractures you cannot see. Those gather moisture and corrode....that causes resistance rise. Ray