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If crimping is so unreliable, I have to ask why does basically every vehicle manufacturer use crimps everywhere and particularly on things like engine wiring harnesses?

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why does basically every vehicle manufacturer use crimps everywhere and particularly on things like engine wiring harnesses? Done properly, crimps are better for automotive.

If you look at how those crimps are put together, they're done with a special crimping machine and a special type of connector. The type of connector is usually multiple crimps for a large wiring harness in a single male/female plastic connector with polarization. The wire gauge is correcty matched to the connector type, and the system is carefully quality tested. They crimp millions of those connections in a mass production system and discard the ones that don't pass the quality tests.

The kinds of crimps that I'm complaining about, the ones used for installing aftermarket car stereos, are a totally different type. I'm talking about the ones you buy at Radio shack where you're supposed to stuff two wires of god-knows-what gauge into a smooth metal tube and then hope that it stays put after you squeeze the tube with a pair of pliers. The tube doesn't bite into the wire the way the B-shaped crimps on the vehicle harnesses do. Edit: Look at the molex PDF that g_attrill just linked and you'll see what I mean.

I'm not saying all crimps are bad, I'm saying that when you personally are installing an aftermarket car stereo, and you need two wires of random gauge to stay stuck together, you're better off soldering and shrink-tubing them.

On the other hand, even when you do have a mass-produced wiring harness made with a special crimping machine, you can still run into trouble.

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Electrically, a crimped connection is highly-conductive-wire to highly-conductive-connector.

A solder joint has poorly-conductive (comparitively) tin/led inserted between the two, producing more of an impedance mismatch, and therefore more signal reflection from the joint.

Cheers

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The difference between lead, silver and copper conductivity is very small.

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DC resistance is not "impedance", but the two are quite related.
Cheers

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..Your point that a solder joint won't handle strain is well-taken...

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The information in these pages is provided to give guidance on various techniques not usually identified with a specific standard. These are recommended practices that will result in reliable products. They are not, however, intended to be hard requirements, assumed to be supplemental to existing standards, or judged as the only acceptable method that can be used for the particular topic. For each topic covered herein, there can be several other techniques or procedures not described that can provide equivalent reliability, and their use should not be discouraged because they're not included in these pages.

This information should not be used if it conflicts with any contractual or program-specific requirements. Unless otherwise specified, these pages fall in order of precedence behind the contract, approved drawings, and any standards imposed on the program.

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This debate is informative, answering some questions and raising more. I've probably gotten myself into trouble by choosing solder, but given enough time and information, I can learn the task.

The solder-type RCA connectors I'm using have a flat - solder post. Can I solder wire onto a flat surface? My cheap RadioShack RCAs have holes posts. The "high end" - is just a flat surface and the + is a depression to receive the wire. Tempted to drill a hole in the - receiver to thread the wire.

The RCAs are where strain relief is my biggest concern. I'm considering hot gluing or caulking the wires at the end of the connector to help them.

How do I better join two (or more) wires before soldering them? Should I twist individual strands from both wire, then twist together the whole mass? Seems like risking metal fatigue.

I chose clear thin walled heat shrink tubing, but it seems thin. I probably should have got the thick walled for stronger support... but I think it had a higher shrink temp that I didn't want to mess with.

I chose standard tin/lead solder (two spools: one with and one without flux) over 4% silver solder because I didn't think I could handle the higher melting temp of the silver.

Maybe I'll try testing some soldering and shrinking this weekend. Eventually I'll get it figured out.

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What a -fabulous- disclaimer!

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Can I solder wire onto a flat surface?

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I'm surprised flux is that important. Described as "an agent to clean the metalic contacts" it seems almost pointless. My wires and RCA connectors are fresh out of the box, never used, making me wonder why they need cleaning.

I hope my solder with active rosin flux core will do the trick. Still waiting for my radio to come in (since the first was "lost in the mail") before I can start...

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flux does something chemically that allows the solder to really bond to the surface of the metal in a way that just heat alone won't.

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In reality, the chemistry of flux interactions at oxide surfaces is complicated and involves acid-base, oxidation-reduction, and coordination-type and adsorption-type reactions. Most fluxes react as Bronsted-Lowry acids with metallic oxides to form their respective salts and water, and the salts serve as surfactants that promote solder wetting.

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reducing the surface tension of the liquid solder