Ryan:
Based on my failure to make clear the conditions under which 450°F is a
suitable wave solder temperature, I also would have agreed with Graham.
I've responded to Graham's posting with more details, however. I hope
the expanded thesis will make you a bit more amenable to my position.
I liked Hans contributions because they expand the whole scope of the
dialog. When I first tied into this forum, the focus was very narrow and
overlooked the multitude of process, materials and environmental issues
that rise up once a seemingly simple change in solder composition is
fully examined.
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]
Ryan Grant wrote:
>
> 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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