Jim,
        I must agree with Graham.  I would dare say that MOST companies are
currently wave soldering eutectic tin/lead with their solder pot
temperatures between 480 and 500 degrees Fahrenheit.
        However, that still doesn't help the higher temperatures of surface
mount.  Ironically, many of the consortium's papers have indicated that
problems with lead-free wave solder may push the industry to pure SMT.
However, as Hans pointed out with electrolytic capacitors, this is probably
unlikely since an easy way to overcome the high SMT temperatures is to
revert back to through-hole.  ("I shudder at the thought").

Ryan Grant
Advanced Technology Engineer
MCMS
(208) 898-1145
[log in to unmask]


> -----Original Message-----
> From: Graham Collins [SMTP:[log in to unmask]]
> Sent: Tuesday, December 05, 2000 1:44 PM
> To:   [log in to unmask]
> Subject:      Re: [LF] AW: [LF] Component Durability
>
> Jim
> I was both amused and puzzled by your email (I say this because otherwise
> you might infer I was offended, not an applicable emotion in this case)
>
> How do you read David's email as saying "many companies set their wave
> solder temperatures much higher than necessary (or desirable)"????  I do
> not read his email as saying that, he states that it is possible to solder
> between not 450 - but doesn't offer an opinion that it is desired.  What
> the heck are you basing that on?   Yes, I have heard of companies running
> their wave at 450 or so, but to make the statement that higher than that
> is not necessary - I'm not buying what you are selling.
>
> My wave solder is set at 500F.  Why?  Not based on a "lack of knowledge"
> thanks very much.  Now, I will admit I have only run experiments down to
> 475F and up to 510, but not running experiments at 450 was a no brainer
> for us, not based on some ignorance.  If the results are bad at 480 and
> get worse at 475 it's an odd leap of faith to assume 450 will be better.
> If you think you can run 10 layer 2 oz copper boards at 450 F I really
> want to know what kind of wave solder machine you are using.
>
> If or when we convert to lead free the operating temperatures will be
> based on experiments, not on numbers picked out of the air.  But maybe we
> can get some of your local ballot counters to help with the math  :-)
>
> have a good week.
>
> regards
>
> Graham Collins
> Process Engineer, Litton Systems Canada, Atlantic Facility
> (902) 873-2000 ext 6215
>
> >>> [log in to unmask] 12/05/00 02:52PM >>>
> David:
>
> I'm delighted you've weighed in with your excellent points. We can
> always count on your for scientific approaches to issues too often
> addressed via emotions.
>
> As you've noted, many companies already set their wave solder
> temperatures much higher than necessary (or desirable). They then
> experience problems ranging from distortion of circuit boards to higher
> component failure rates. When the new solders are implemented, it will
> not be possible to reduce temperatures to the 450?F range that makes
> sense with current tin/lead. And I fear that those companies already
> running at excessive temperatures will, in their lack of knowledge, turn
> the heat even higher.
>
> Your other point about the higher tin content dissolving leads, end caps
> and other metal parts is indeed cause for concern and not widely
> recognized.
>
> Summing up, then, it seems to me we end up with a process that is not at
> all friendly to the components (regardless of whether the environment is
> or is not better off). Would you concur? If not, what am I overlooking?
>
> Jim Smith
> Managing Director
> Cambridge Management Sciences, Inc.
> 4285 45th St. S.
> St. Petersburg, FL 33711-4431
> Tel: (727)866-6502 ext. 21
> Fax: (727)867-7890
> eMail: [log in to unmask]
>
>
>
> dsuraski wrote:
> >
> > Actually, there are several companies out there running lead-free alloys
> in
> > wave soldering at a "drop-in" temperature as compared to Sn/Pb.  The
> reasons
> > for this are two-fold: First, many companies run Sn/Pb at a higher
> > temperature than absolutely necessary.  The operating window for Sn/Pb
> in a
> > wave is about 425 to 500F, but most companies are at the very high end
> of
> > this (490-500+F).  In these cases, many lead-free alloys may be used at
> the
> > same temp.  Basically, the temperature range for lead-free alloys begins
> > where the range for Sn/Pb ends, and there normally is crossover (BTW,
> this
> > also is often the case with hand soldering).  Second, one of the reasons
> for
> > exceeding a solder's liquidus in wave soldering is to reduce the
> solder's
> > surface tension sufficiently to promote drainage, etc.  As with SMT, the
> > superheat temperature needed for most lead-free alloys is not as high as
> > with Sn/Pb due to the surface tension characteristics of lead-free
> alloys.
> > Therefore, it usually is possible to get by with a peak temperature only
> > slightly above the liquidus.  As with Sn/Pb, though, a higher peak temp
> can
> > promote better wetting.
> >
> > As far as temperature concerns relating to lead-free alloys, the
> greatest
> > emphasis should be placed on SMT.  My primary concerns for wave
> soldering
> > relate to the high tin content of lead-free alloys, which tend to
> dissolve
> > the standard materials in wave soldering machines now.  Specifying a
> > "lead-free compatible" wave machine can help. Also, some alloys such as
> > Sn/Cu offer poor wetting and sometimes require nitrogen and/or very
> > aggressive flux chemistries to achieve adequate soldering.
> > ----- Original Message -----
> > From: "Jim Smith" <[log in to unmask]>
> > To: <[log in to unmask]>
> > Sent: Tuesday, December 05, 2000 1:16 PM
> > Subject: Re: [LF] AW: [LF] Component Durability
> >
> > Hans:
> >
> > You've confirmed my worst fears. As I point out in my note to Doug Romm
> > here, wave soldering (if it survives the change in alloys) is an even
> > more hostile environment than reflow ovens. How (or can) we handle those
> > conditions?
> >
> > Jim Smith
> > Managing Director
> > Cambridge Management Sciences, Inc.
> > 4285 45th St. S.
> > St. Petersburg, FL 33711-4431
> > Tel: (727)866-6502 ext. 21
> > Fax: (727)867-7890
> > eMail: [log in to unmask]
> >
> > "" wrote:
> > >
> > > ----------
> > > Von: jsmith / unix ([log in to unmask])
> > > An: [log in to unmask]
> > > Betreff: [LF] Component Durability
> > > Datum: Montag, 4. Dezember 2000 22:03
> > >
> > > It is surely not the question, if component makers are able ore unable
> > > to produce robust components (I?m sure they do their best), it?s the
> > > simple physical limit: for all kinds of plastic capacitors the melting
> > > point of the foil is not changeable, so this technology and industry
> > > will be killed by the leadfree enthusiasts. Similar for the
> electrolytic
> > > capacitors, the boiling temperature of the electolyte is not
> manipulable
> > > as one wants. You mentioned the ceramics, it is also wellknown, that
> all
> > > kind of ceramics are thermoshock sensitive, the higher the solder
> tempe-
> > > rature, the higher the shock. Also the mismatch of the different
> expansion
> > > coefficients, while the soldered component cools down on the board
> from
> > > the higher soldering level leads to cracks. One question at the end,
> > > if You buy a new car, do You prefer a "green" antiblocking brakes
> system,
> > > or the "old" one?
> > >
> > > With kind regards,
> > >
> > >         Hans Juergen Bauer
> > >         Industrial Engineering
> > >         Passive Components
> > >         Qualification
> > >
> > >         ALCATEL Stuttgart
> > >
> > > Pondering some recent postings on this forum, I began questioning some
> > > of the assertions that eliminating lead is feasible. Specifically, I
> > > wondered about the current inability (or, at least, lack of rating) of
> > > many parts to survive temperatures in the 260?C range (many larger
> > > ceramic capacitors, for example, are not warranted to survive
> immersion
> > > in solder above approximately 230?C for even a few seconds). If lead
> is
> > > removed from solder, the components will be required to survive at
> 260?C
> > > or higher for quite a large number of seconds.
> > >
> > > If the components can be made to tolerate higher temperatures without
> > > degradation when new solder(s) with higher melting temperature(s) are
> > > introduced, why haven't component manufacturers already made their
> > > devices more robust?
> > >
> > > Jim Smith
> > > Managing Director
> > > Cambridge Management Sciences, Inc.
> > > 4285 45th St. S.
> > > St. Petersburg, FL 33711-4431
> > > Tel: (727)866-6502 ext. 21
> > > Fax: (727)867-7890
> > > eMail: [log in to unmask]
> > >
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