[sdiy] 0.100 pin header reliability.

Chromatest J. Pantsmaker chromatest at azburners.org
Mon Nov 15 21:30:52 CET 2010


Yeah, mobile homes (the kind of pre-built house that gets delivered on
a trailer, but then doesn't really ever move again) always had
aluminum wiring.  It was cheaper and it was lighter.

On Mon, Nov 15, 2010 at 12:18 PM, Graham Atkins
<gatkins at blueyonder.co.uk> wrote:
> 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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