Hi Bob,
It wasn't oxidized copper anyone was worried about, as all component leads
had coatings well before HSD was ever implemented. The real problem was
"what" they were coated with! It varied from nickel, to tin, to solder, to
gold, to silver, to palladium, to just about anything. There were so many
variants in lead and terminal coatings, which would all contaminate solder
pots and reflow tanks in different ways, that the powers that be in the
Department of Defense (Defense Logistics Agency, primarily DESC -- the
Defense Electronics Supply Center) finally put their foot down and went to
HSD as a standard.
Well, that actually didn't last terribly long, because solder in not a
cure-all and caused some of its very own problems. The biggest problem it's
causing now is that it doesn't conform with international requirements for
RoHS that are cutting in next year.
Copper, once exposed to air, is always oxidized -- it's just a matter of how
badly. Mild flux used in solder removes the oxide instantly and very well,
so it really doesn't matter much if you pre-tin conductors before using
them, or just tin them as they're being used. It amounts to the same thing.
That's why I can't see the purpose of pre-tinning copper which will later be
soldered using the same flux and alloy -- it's like doing the same work,
twice.
The "hot solder dip" mandate doesn't exactly go back to the Stone Age...it
goes back to about 1985. And it's no longer a mandate, since we now use so
many surface mount components that *cannot* be hot solder dipped.
73!
WB2WIK/6
-----Original Message-----
From: Bob Henderson [mailto:bob@cytanet.com.cy]
Sent: Monday, January 17, 2005 2:37 PM
To: Steve Katz; 'Paul Playford'; 'W2RU - Bud Hippisley'; 'Tower Talk'
Subject: Re: [BULK] - RE: [TowerTalk] Re: Cutting braid
Fascinating stuff Steve, but my recollections are that oxidised copper is a
bitch to solder. Doesn't that have something to do with the decision to
"hot solder dip" or pre tin component leads back in the stoneage?
Now back to my cave!
Bob, 5B4AGN, P3F
> In the interim, few component manufacturers use tinned
> leads any more, only because this proved to be a
> solution to a problem that didn't really exist.
> (WB2WIK/6)
>
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