Montana wrote:I keep seeing this come up on this board, especially concerning SVA work.
Within the professional motorsport industry and the OEM car loom manufacturing, no-one joins wires with solder.
Because it is time consuming, costly, and requires higher level skill than crimping. It also and has health and enviromental 'issues'.
A poor quality pre-insulated crimp (the likes of which come from halfords) is indeed a bad thing, and soldering would be preferable to those.
Winding the bare ends together and wrapping in Cellotape would be preferable!
However, the fact remains, two metals of similar hardness will weld/join if enough force is applied. For example, you can produce an actual friction weld of two metals with a aluminium spade connector and copper wire with a proper crimp tool.
No crimptool will apply enough pressure to fusion weld dissimilar materials. I have never seen an electrical crimptool that has achived a friction/fusion weld.
We weld aluminum to stainless steel for oil well head heat exchangers. It requires a massive explosive force to bond the two. Yes I'm talking a real detonation!
The process was found by accident in the Vietnam war. Fused aluminium and steels at the point of weapon impact on tanks aircraft etc.
Aluminium has an extremely tough oxide layer (which reforms very quickly even after mechanical removal). So much so, it is used as as abrasive, Aluminium oxide grit etc.
When actually welding aluminmum, as in a TIG process. The AC waveform positive half cycles are used to strip the oxide layer off, to allow molecular bonding/welding to take place. and requires a level of energy that is an order of magnitude that it would be impossible to achive with a hand crimptool.
Apart from the fact, I know of no method without using an 'alloy' (in between) to join copper to aluminium.
The commercially available spade/crimp connectors are tinned copper/copper alloy. Not aluminium.
The Americans use aluminium conductors/connectors often with dire results!
Because of this, and the fact it then only produces one stress point is the reason critical joints are done this way
With soldering, you have to strip wire, removing insulation, then join using a third party compound and then re-insulate. Not only this, but solder can oxidise and corrode very easily leading to cracking. Solder is also solid, producing at least two points of stress on any given joint.
A crimp will certainly put the conductor strands under 'pressure'.
Solder will oxidise on its surface. Where it is in contact with the conductor strands it has actually excludes the air/oxygen and PREVENTS corrosion !
Lead is, has been, and still remain an material with an extremely high impermeability, so much so it blocks harmful radition, let alone oxygen/water
Yes modern solders arn't lead, but the synthetic equivlent is almost as good.
Even a soldered lapped joint has a far better positive contact area than a crimp. The major problem with soldered joints failing through flex fatigue, is caused by 'wicking'. The main cause of this, is poor soldering technique. Crimps will equally, if not more so, at the crimp pinch point, if mechanical support is not given to the wire.
As such, given reasonable equipment (decent crimps and tools are expensive) a crimp is ALWAYS better than soldering.
'Horses for courses' A blanket statement, as above, is not true.
Obviously in regard to components, such as relays and diodes, they have to be soldered, but the pressure is taken away as they are generally mounted.
On a PCB ? Or by mounting lugs?
On a PCB, relays are normally only secured by their soldered joints, and the conformal coating may help stick them down (a bit). As for diodes, transistors, large electrolytic capacitors etc are sercured normally by their leads.
Strange when I've seen components 'shocked' from PCB etc it very unlikely at the soldered joint, but at the lead to body connection.
Now obviously you dont have to take my word for it, I may be lying
but recently PPC magazine did an article, so here are the relevant parts:
Bear this in mind for any SVA work.................
I bet those '80% failures' are the result of badly made 'mechanical electrical connections' i.e. terminal blocks, scotchlocks, and crimps!
But NOT Soldered joints!
The chances of either failing in your Mustang, if done reasonably well is highly unlikelyMy knowledge is from 'field' obtained experience, and almost 30 year as a trained engineer.
(Senior QA test, Senior design engineer Marconi (GEC) , then technical Director of a bespoke industrial equipment supplier.)
Here the current project we're involved in:
P.s We normally crimp connections for mechanical placement, then solder to to prevent oxidization and lower connection resistance, then heat shrinkable adhesive lined connector shells.
I 'll dig out some commercially made (not be us) failed crimps and post the pics. This from an environment which isn't all that harsh
