Re: Lead-free Solder ( continued ... )
- From: "Arfa Daily" <arfa.daily@xxxxxxxxxxxx>
- Date: Fri, 23 Mar 2007 01:02:28 GMT
"Jamie" <jamie_ka1lpa_not_valid_after_ka1lpa_@xxxxxxxxxxx> wrote in message
news:AgFMh.45$nT3.18@xxxxxxxxxxxxxxx
Arfa Daily wrote:
Hi allwell, i do use it and i don't like the finish i get from it how ever,
Friend of mine also in the electronic service business just called me to
tell of a conversation he had in the pub last night with one of his
friends. Turns out this guy is a washing machine service engineer with
his own business of many years. He told my friend that from a business
point of view, he is delighted with lead-free solder, because in the last
year or so it has boosted his profits significantly. This is because of
the number of bad joints that he now sees on items such as solenoids. He
is firmly convinced that the lead-free solder, being a harder material
that doesn't stick well in the first place to items with a large thermal
inertia, cannot take the vibration that a washing machine subjects it to.
This seems altogether reasonable to me.
Just this morning, I have repaired a NAD CD player that would play for
anything between 5 and 45 minutes, before randomly failing. No amount of
physical provocation would bring on the fault, nor correct it when it
occured. It would need to be left off for about a half hour before it
would play again. Just for sport, I tried a laser, but of course, that
wasn't it. I then took the board out, and went over it with a headband
magnifier. I then found two perfect cracked-right-round joints on a
connector. The joints had that traditional lead-free straight-sided
volcano like shape. Once these had been attended to, and the original
laser put back in, everything was fine.
Is it just me, or does anyone else have concerns for the wider
implications of this nonsense technology that has replaced a mature and
reliable technology in the dubious name of that new great ( and some
would say false ... ) god, "Green" ? If washing machines can vibrate
these joints into submission, I sincerely hope that the exemptions that
the avionics and automotive electronics industries currently enjoy, never
get rescinded ...
Arfa
we do like using it on repairing old electronic boards that have high
wattage R's on the board that create cracks when hot. I find in those
cases you can increase the heat on the tip and force it to flow nicely
which gives a good bond on those hot running components.
Trouble with that philosophy, is that the jury is still out on whether you
can reliably mix leaded and non-leaded solder. Some solder manufacturers say
that you can, whilst others say that you can't. A number of independant
metalurgical experts are of the opinion that by mixing the two solders, the
long term integrity of the joint will be compromised. There is actually no
requirement in the legislation to repair equipment that was originally
manufactured with leaded solder, with anything other than leaded solder.
Somewhere around the shop, I have an old reel of leaded high melting point
solder that I used to use for that sort of thing, but haven't in a long
time. It was originally for resoldering those spring-off resistors -
remember them ?
Just as an aside, after this morning's NAD, this afternoon I had a Sony home
cinema - one of the DAV series - I dunno, a 300 or 500 or some such. It had
the usual problem of thinking that it was in headphone mode, but instead of
the common bad connector, this time, it was yet more lead-free bad joints on
the power amp PCB. As well as the ones on the bottom of the connector that
were causing the headphone problem, it also had cracked-around joints on
just about all of the six channels' output filter chokes, a problem which
you've probably all seen more than once on these, and also on the output
relays. Now these are problems that have developed, as the boards are old
enough that if they were original production drys, they would have showed
long ago. I accept that drys also 'develop' with leaded solder on certain
components that suffer high levels of thermal cycling in use, but the amount
of drys on this one board, all on components that are either fairly large,
or subject to mechanical vibration stress ( the relays ) rather than thermal
issues, leads me to believe that there is a different failure mechanism at
work here, possibly related to the lack of ductility of lead-free compared
to leaded solder.
As far as the suggestion of manufacturers having to hand work bunches of
components as the boards roll off the line, I can't imagine any way that
this could be accomplished in a practical or cost-effective way.
Arfa
.
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