Very interesting discussions.
The thermal solution in the high power packages posts another challenge.
The thermal solution can result in large temperature gradient between the
case (exterior) and the solder of the component. This is especially true for
large component. More heat is then needed to ensure adequate temperature at
the solder. The rest of the board will now experience an even higher
temperature than the case temperature of the component concerned.
I am not too optimisity that a generalised board reflow temperature of ~235C
will be possible.
Best regards
Wong Ee Hua
Member Technical Staff
Institute of Microelectronics
> -----Original Message-----
> From: Romm, Doug [SMTP:[log in to unmask]]
> Sent: Wednesday, August 01, 2001 6:07 AM
> To: [log in to unmask]
> Subject: Re: [LF] Industries With Worker Elevated Blood Lead Levels
>
> Dongkai, very good point. I should have provided more details. The work
> ongoing by various sources has and is attempting to show that the
> temperature distribution across the PWB can be controlled within 10-15C
> across the PWB. I must preface my statements by saying that I am not an
> expert on reflow equipment or reflow profile characterization. I can only
> comment based on what I have read.
>
> I think it is accepted that SnAgCu solder alloy can be reflowed at ~235C,
> the key is being able to limit the worst case peak temperature on the PWB
> or components by controlling the profile setup. I have seen a few reports
> and a number of discussions from various sources on this issue. Some of
> the reports I have seen are indicating positive results, however I do not
> know if these reports are in the public domain yet.
>
> I see 2 major efforts going on to address the high-temperature issue:
>
> 1. Many component suppliers are working to characterize/qualify the latest
> material sets for plastic packages to be able to improve upon moisture
> sensitivity performance of plastic packages at elevated reflow
> temperatures (>235C).
>
> 2. Other individuals and organizations are attempting to show that a peak
> reflow of 260C (worst case) may be too high and it is possible to reflow
> SnAgCu solder at lower peak temperatures by using controlled temperature
> distribution.
>
>
>
> It is my personal belief that if one of these efforts (or a combination of
> the 2) succeeds and the high-temperature hurdle associated with SnAgCu
> solder is eliminated, lead-free transition will occur even more quickly
> than current industry roadmaps show. Just my opinion.
>
> Yours is a very good question. This is the kind of discussion that will
> (possibly) help to resolve lead-free issues.
>
>
>
>
> Best regards,
>
> Doug Romm
> Member Group Technical Staff
> Texas Instruments
> <http://www.ti.com/sc/leadfree>
>
>
>
>
>
> ----Original Message-----
> From: [log in to unmask]
> [mailto:[log in to unmask]]
> Sent: Tuesday, July 31, 2001 4:41 PM
> To: [log in to unmask]; Romm, Doug
> Subject: RE: [LF] Industries With Worker Elevated Blood Lead Levels
>
>
>
> My question is: Even we assume that the statement "SnAgCu solder can
> be adequately reflowed at peak temperatures in the range of 235-245C" is
> true, some of the boards experience temperature delta as high as 25C -
> Wouldn't that still put the temperature for certain locations (and
> components) on the board in the 260C range?
>
>
> Regards,
> Dongkai Shangguan, Ph.D.
> Manager - Advanced Process Technology
> FLEXTRONICS
> 2090 Fortune Drive, San Jose, CA 95131
> Phone: (408) 428 1336 Fax: (408) 576 7988
> E-mail: [log in to unmask]
>
> -----Original Message-----
> From: Romm, Doug [mailto:[log in to unmask]]
> Sent: Tuesday, July 31, 2001 10:11 AM
> To: [log in to unmask]
> Subject: Re: [LF] Industries With Worker Elevated Blood Lead
> Levels
>
>
>
> Chuck,
>
> I don't speak for all component manufacturers, but since you
> specifically mentioned Texas Instruments, I will make a few brief comments
> on our strategy. This is not intended to be a marketing statement but
> rather an educational statement based on TI strategy and my knowledge of
> other IC suppliers' plans.
>
> TI (and much of our competition) is committed to providing
> lead-free solutions for our customers who demand them. Fortunately, TI
> has been supplying a Pb-free component finish (NiPd) for leadframe based
> packages since 1989. The vast majority of our internally built
> leadframe-based packages have been built with a lead-free finish since
> that time. We are now in the process of converting from NiPd to NiPdAu
> finish. For externally built packages (built at assembly subcontractors)
> and those package types (area array) that are not currently built in a
> lead-free finish we are now working to qualify lead-free finishes. We see
> the demand for lead-free components from our major customers and we (as
> are most of our competitors) are responding to that demand.
>
> Of course the major issues are:
>
> - Backward compatibility: Fortunately for TI our lead-free
> finish option for internally-built leadframe packages has proven to be
> solderable with both SnPb (current) as well as SnAgCu solders (primary
> lead-free solder choice). Thus, we are able to supply this lead-free
> package finish for either SnPb or Pb-free processes. As lead-free finish
> options are investigated and qualified 'backwards compatibility' is a key
> issue. I think it's safe to say that the majority of our competitors and
> subcontract assembly houses are investigating Pb-free replacements to be
> used in their post-mold solder plating baths, primarily pure Sn or some
> other Sn-bearing solder. Each component supplier will need to either
> insure backward compatibility of their chosen lead-free finish or clearly
> state compatibility restrictions. It is not cost effective (my opinion,
> someone else may disagree) to run 2 different solders (SnPb and Pb-free)
> in solder plating lines. However, I'm not privy to detailed plans of
> other suppliers, so it may be that some will choose to run 1 SnPb plating
> line and a separate Pb-free plating line. Logistics of tracking component
> finish types is a major issue here.
>
> - High-temperature processing: This is truly a (if not
> 'the') major hurdle to being able to supply Pb-free components that can be
> used in a Pb-free soldering process. The issue is what peak temperature
> end users will use in their reflow ovens. Currently most plastic packages
> are rated for moisture sensitivity with a peak reflow temperature of 235C
> (or lower). When SnAgCu soldering processes use a peak reflow temperature
> above 235C there is a range of impact from 'no impact' to a drop of a few
> levels in moisture sensitivity performance. Several papers have been
> published on this topic. Component suppliers are working to qualify new
> material sets for high-temperature processing. Each supplier will have to
> state their capability to their own customers. Also, industry consortia
> and committees are producing work which indicates SnAgCu solder can be
> adequately reflowed at peak temperatures in the range of 235-245C. There
> are also published papers on this issue. It is possible the the peak
> temperature to be used in reflow processes for SnAgCu solder will not be
> much greater than current peak temperatures.
>
>
> In the big picture, yes, a component supplier could still
> supply SnPb finished-components once a lead-free solution has been
> implemented. But if the majority of customers want lead-free, reliability
> is good with the lead-free solution (equivalent or better than with SnPb
> finish), and the lead-free solution is backward compatible then it makes
> sense to convert to 'total' lead-free.
>
> If you want more details on TI specific plans contact me
> offline (don't copy the world!). Also, I'm sure other component suppliers
> will be glad to supply their plans to you.
>
> Best regards,
>
> Doug Romm
> Member Group Technical Staff
> <http://www.ti.com/sc/leadfree>
>
>
>
>
>
>
> -----Original Message-----
> From: Charles Dolci [ <mailto:[log in to unmask]>]
> Sent: Tuesday, July 31, 2001 11:19 AM
> To: [log in to unmask]
> Subject: Re: [LF] Industries With Worker Elevated Blood Lead
> Levels
>
>
> Harvey:
> Yes, Sun and others did get an exemption (so far, we don't
> know if that
> exemption will survive the final legislative reviews) for
> servers and storage
> arrays.
> The problem with that is that it exempts a "use", not a
> product per se.
> Disk drives that are used in storage arrays are exempt, disk
> drives used in PC's
> are not, even thought the disk drives may be otherwise
> identical.
> Microprocessors in servers are exempt, microprocessors in
> home electronics are
> not, even though they may be otherwise identical (or nearly
> so).
> The problem is that 95% (my GUESS) of electronics are not
> exempt, so who will
> supply the electronic components and parts for the exempted
> products? Can that
> 5% of the market demand a leaded product? Is Texas
> Instruments going to run two
> fab lines, one lead-free for 95% of the world, and one
> leaded for those few
> customers that make servers? Servers and storage arrays
> consume X% of the
> demand for disk drives. Will disk drive makers run two
> assembly lines, one with
> lead, one without?
> As we all know, anything can be done, so it is not
> impossible; but the question
> then becomes "what is the cost of that component that
> contains lead?"
> I just don't see, AS A PRACTICAL MATTER, that the exemption
> does much good.
>
> I hope I am wrong, I was once before.
>
> Chuck Dolci
>
>
> *MIME-Version: 1.0
> *Content-Transfer-Encoding: 7bit
> *From: Harvey Miller <[log in to unmask]>
> *Subject: Re: [LF] Industries With Worker Elevated Blood
> Lead Levels
> *X-To: [log in to unmask]
> *To: [log in to unmask]
> *
> *Chuck
> *You must know that servers were explicitly exempted from
> the lead ban on May
> *15 by the EU Parliament, along with storage systems, etc.
> *
> *Sun Microsystems will not have to go lead-free to sell in
> Europe.
> *
> *But even if that were't the case, are we all supposed to
> give in to the
> *lead-free folly without a fight?
> *
> *One way to fight for Truth is to support the IPC on two
> fronts. Get your
> *company to support the IPC-EIA-EPA life cycle study
> iniatiative.
> *(Call David Bergman or Fern Abrams for information) And
> support the IPC
> *(along with 35 other trade associations) suit against the
> EPA's outrageous
> *100 pound reporting requirement for lead use. It's based
> on the same phoney
> *toxicity arguments that the extreme European fanatics used
> in starting the
> *lead-free solder travesty.
> *
> *And write President Bush. We have to help build some
> backbone in Japan and
> *Europe, by example. There really is a lot of intelligence
> there. They just
> *lack our independant spirit, but I hear things might be
> changing.
> *
> *Fight!
> *
> *Harvey Miller
> *
>
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>
>
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> Please visit IPC web site (
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> information, or contact Keach Sasamori at [log in to unmask] or
> 847-509-9700 ext.5315
>
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>
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To unsubscribe, send a message to [log in to unmask] with following text in
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Search previous postings at: www.ipc.org > On-Line Resources & Databases > E-mail Archives
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