[sdiy] 0.100 pin header reliability.

[Graham Atkins]

Aluminium for wiring ?

Are you sure about that, sounds highly unlikely, never heard of  
aluminium
conductors. Steel, copper alloys, silver, even gold but not aluminium.

Graham

On 15 Nov 2010, at 17:32, cheater cheater wrote:

> Hi Harry,
>
> On Mon, Nov 15, 2010 at 15:31, Harry Bissell  
> <harrybissell at wowway.com> wrote:
>> I have rarely (in fact never) seen aluminum as a metal in connector  
>> pins.
>> Usually they are steel (cheap) or brass, or beryllium copper...
>
> People say the same about aluminum for 220V wiring in houses... well,
> don't go to eastern Europe then :-) Some blocks have had each single
> (brick) wall ripped up, 20-30 years after having been built :) The
> "fake walls" out of wood and plaster are not popular at all these
> parts.. it all goes into the wall between bricks etc.
>
> What I've said applies to steel connectors in the same way, though.
> The expansion coefficient is about 2% higher in steel than in copper,
> so that's not much, but maybe it's enough to break a cold weld when
> the crimped assembly is heated up to soldering temperatures..
>
> Cheers,
> D.
>
> On Mon, Nov 15, 2010 at 15:31, Harry Bissell  
> <harrybissell at wowway.com> wrote:
>> I have rarely (in fact never) seen aluminum as a metal in connector  
>> pins.
>> Usually they are steel (cheap) or brass, or beryllium copper...
>>
>> Aluminum does not solder well at all using any standard electronic
>> solders... (i hear there are fluxes for this, but have never needed  
>> them...)
>>
>> H^) harry
>>
>>
>> ----- Original Message -----
>> From: cheater cheater <cheater00 at gmail.com>
>> To: Dave Kendall <davekendall at ntlworld.com>
>> Cc: synth-diy at dropmix.xs4all.nl
>> Sent: Mon, 15 Nov 2010 04:05:11 -0500 (EST)
>> Subject: Re: [sdiy] 0.100 pin header reliability.
>>
>> Hi Dave,
>> to prevent breaking of soldered cable, have it zip tied to the PCB
>> about 2 cm away from the spot it was soldered to. Zip tie first,
>> solder second, so that the solder solidifies in the right shape.
>>
>> With regards to soldering of crimped connectors: there might be
>> several things at play here, but I'm not good enough with my  
>> chemistry
>> to know if they actually make an impact. Maybe someone can tell me if
>> my intuitions here are right or wrong.
>> 1. three/four metals (aluminum for the connector, copper for the  
>> cable
>> and solder, tin for the solder) make for different electrical
>> properties, oxides migrate differently
>> 2. the solder crystals change shape over time. I understand there's
>> some sort of evolution to solid solder that makes it eject oxides?
>> This could not only separate the cold weld but also make it dirty  
>> with
>> oxides. Maybe someone can confirm this.
>> 3. Is solder perhaps more reluctant to make a cold weld with  
>> aluminum,
>> than bare copper touching bare aluminum? If you solder first and  
>> crimp
>> second, you're crimping against tin. This also has the effect that  
>> the
>> tin soldered to the cable and/or connector might separate off what it
>> was soldered to, making an even worse connection
>> 4. If you crimp first and solder second, the heat is going to expand
>> the aluminum more than it expands the copper wire - aluminum has a
>> higher linear coefficient of thermal expansion - effectively
>> un-crimping the connector. I don't think it's going to re-seat itself
>> nicely back to being crimped afterwards, but I don't know. My guess
>> here is that you actually need a lot of force to create a cold weld,
>> and this force is not going to be supplied by the shrinking connector
>> alone. Besides, there might be solder in that space now, which messes
>> up the connection
>> 5. My intuition is that at least the better connectors have the leafs
>> produced in such a way that the crystalline structure is good for
>> making cold welds. Heating up changes this structure, quite possibly
>> for worse.
>>
>> It would be interesting to know if any of this actually holds up
>> according to theory.
>>
>> Regarding saving time: I read this thread and I think to myself...
>> isn't it much better to just buy ready cables?... They'll be crimped
>> much better than you can do it anyways, they'll be much cheaper in  
>> the
>> end, and they don't cost you time..
>>
>> Cheers,
>> D.
>>
>> On Sat, Nov 13, 2010 at 02:58, Dave Kendall  
>> <davekendall at ntlworld.com> wrote:
>>>
>>> On Nov 13, 2010, at 00:50, Paul Perry wrote:
>>>>
>>>> I think that when soldering decreases reliability it is because
>>>> the solder wicks up the wire away from the joint & stiffens the  
>>>> wire,
>>>> which then tends to flex sharply at the end of the solder & break  
>>>> there.
>>>
>>> That makes sense. But wouldn't that same potential weakness also  
>>> apply to a
>>> wire either directly soldered to the PCB pad, or to a PCB pin?.  
>>> I've had
>>> that happen on some perfboard prototype builds using stranded wire  
>>> that got
>>> some rough handling. (the soldered joints to PCB pins weren't  
>>> reinforced by
>>> heatshrink or hellerman sleeves or anything, so I wasn't too  
>>> surprised...)
>>>
>>> This is an interesting thread, thanks for everyone's input.
>>>
>>> cheers,
>>> Dave
>>>
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>> --
>> Harry Bissell & Nora Abdullah 4eva
>>
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