Crimp only. Must have the correct terminals, wire to suit & crimping tool.
For automotive use, this is definitely the better way to go.
It's possible to get good solder joints in automotive applications (requires a high level of skill, say NASA/Aerospace standards), but there tends to be too much variability in it that reduces reliability.
Even a good solder technician makes a higher number of errors vs. the correct crimp tool for the correct terminals in the hands of a properly trained/skilled operator.
The "trick" to this result, is that the tooling and terminals remove more human error, as well as have some technical advantages (no solder to wick up past the wire's insulation, causing a failure point in a high vibration environment).
Moisture can be an issue as well if the joint isn't sealed in either connection (corrosion). There are products that can allow this to be done properly though, so this issue can be mitigated. Where it's a problem, is if it's skipped or the wrong product/s used for the application.
The type of flux used also matters in regard to corrosion. Organic based fluxes in particular (usually listed as water soluble), will "eat" a joint in the presence of moisture unless you get it all cleaned off first.
Soldering is for circuit boards, not wiring.
Point to point wiring as well in products that aren't subjected to vibration (don't see as much of this anymore though).
Note: you must use the proper tools though.
This and proper training are the key.
Poor tools and/or poor training (i.e. don't know how to orient the terminal correctly, wire strip length is wrong, or the wrong terminal is used per the application) usually tend to be the reasons why so many complain about crimp terminals not being anywhere near as good as solder.
Seems reasonable IMHO that if all someone has seen are bad crimps (and can't recognize good from bad), they'd come to the conclusion that crimp terminals on the whole are total ****. Which I suspect is the reason so many have such an opinion.
Note: In all of the above examples those guys are using really high quality ($$$) crimp tools and connectors.
Yep. Good tools aren't cheap, but not all good ones actually cost that much.
For example, there are some interchangeable die models that come in notably cheaper without sacrificing the quality (vs. $300 - 400 per tool for every terminal used). Pressmaster makes a good one, as does Rennsteig and Knipex.
One thing with these though, as they may not have locators, making operator skill even more important (where/how to locate the terminal correctly in the nest).
High quality crimp >>>> highly skilled solder job >>> crappy crimp > crappy solder job.
For automotive use, I agree.
This would change in other areas though, as there may not be a crimp method available, such as PCB's.
If you are willing to invest the time to learn how to solder properly, and committed to making every connection right, maybe solder is for you.
Keep in mind, a good soldering station (temp controlled) can equal or out-cost a good crimp tool. For example, JBC would run you $400 or more. Weller, Ersa, or OKI (Metcal) aren't far off either. Depending on the wire gauge, Hakko might come closer to parity (i.e. FX-951 if you're not dealing with heavy gauge wire).
I dont see them talking about cars or other machinery there?
Same principles are applicable though (need high reliability and repeatability in a vibration environment that doesn't cost a fortune).
I also can't see how if you crimp, solder, then heat shrink you are doing anything wrong.
When it's crimped, microfractures are formed which actually strengthen the metal. It also creates something called a
cold weld between the terminal and wire used, which is reason this method is used (provides excellent electrical and mechanical properties to the joint, which make it desirable).
Heating it anneals the terminal, which both weakens the metal in the terminal, and it can also fracture/break the cold welds that were created during the crimp. Now you *may* end up with acceptable electrical characteristics if the soldering work is done properly, but the mechanical properties are notably decreased as a result.
It may function long enough you don't see/notice anything (breaks after you sell the vehicle for example).