Please ignore that last message - sorry, wrong Rick.

----- Original Message ----- 
From: "Rick Smith" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Wednesday, December 06, 2006 10:21 AM
Subject: Re: [LF] JCAA/JGPP Lead-Free Solder Project summary


> Pratap,
>
> I have to stick my big ugly face in this one, having worked on MIL-SPEC LF
> products as early as 1984,  and more recently bringing up LF computer
> products in China for one of the big boys mentioned here, I think there is
> a legitimate concern for reliabilty of consumer & business electronics
> under this poorly thought out LF switch.
>
> I believe LF solder joints are and can be more robust than SnPb in
> engineered applications where the product has been designed for it;
> component packages have sufficient thermal resistance to handle rework in
> most all non BGA applications.
>
> However, having been in numerous factories, I can tell you that FPY on
> soldering many types of LF BGAs has been hit by as much as 20% at some
> EMs, and in most cases the failed BGAs are being reworked with process
> that either significantly exceeds 260 component spec, or  has a dwell time
> above 220 that kills the flux and leaves a crappy unreliable solder
> joints. Many of the companies we work for don't have n2, and few if any
> can afford to use hydrogen to over come the flux issues a long dwell
> induces, and extending the time over the transistion temp of the laminate
> is not acceptable.  I believe today in the early transition to LF, most of
> these reworked commercial products are being shipped to unsuspecting end
> users and it may come back to haunt the industry.
>
> Using SAC 305 spheres in SnPb solder offers about an 8 Deg C break,
> however the rest of the board & components have to be able  to meet solder
> temps for LF, or you have other issues with components such as FETS,
> Electrolytics, and more.
>
> If you have taken a look at package/pad pcb/pad/ sphere/size ratios of
> some of the industries larger BGAs that are being soldered in the computer
> industry right now, and having worked for working for IBM, you should know
> that many of these new package designs have land patterns specified that
> violate the 1:1 (+/-10%) ratio in order to have enough room to route
> circuitry under the BGAs.  Its been well documented in our industry that
> pad ratios outside of the rules are a board-level reliability issue, and
> now we are taking these BGAs thru a process that inherently sees more
> defects which requires rework in process that blows the limits of the
> materials to smitherines...(did I spell that right).
>
> Anyways without rambling more- I agree with much of Werner's analysis.
>
>
>
> Rick Smith
> Product Engineering
> Celestica Aerospace Technologies Corporation
> 4616 West Howard Lane
> Building One Suite 100
> Austin, Texas 78728
> Phone: 512-615-8591
>
>
>
> Pratap Singh <[log in to unmask]>
> Sent by: Leadfree <[log in to unmask]>
> 12/05/2006 09:21 PM
> Please respond to
> "(Leadfree Electronics Assembly Forum)" <[log in to unmask]>; Please respond
> to
> Pratap Singh <[log in to unmask]>
>
>
> To
> [log in to unmask]
> cc
>
> Subject
> Re: [LF] JCAA/JGPP Lead-Free Solder Project summary
>
>
>
>
>
>
> Werner,
>
> I am really disappointed that a person of your experience and background
> is
> on anti-LF band wagon. You are taking a position that does not go with the
> test data and field observations being generated by LF products being
> shipped around the world for the last 5 years.
>
>
>
> Here is some of what people are saying:
>
>
>
> "There are now more than 2000 lines around the world running SN100C some
> since 1999 with more than 500 million boards in service and so far no in
> service reliability issues have come to our attention.
>
> K. Sweatman, Nihon Superior Co. Ltd."
>
>
>
> "There is no doubt that we are still on the learning curve as far as Q&R
> is
> concerned. However, as you know from events where hard data is  being
> sliced
> and diced in the public eye, there is tremendous progress  being done in
> that area.  There has not been massive generalized failures thus far, that
> I
> am aware of. There will definitely be issues in applications where
> workmanship requirements and design-for-reliability principles are
> violated.
> But then again, we have had similar problems with SnPb assemblies for many
> years.  I get a few of those land on my desk on a regular basis, including
> on products used in mild environments. It always boils down to minimal or
> poor joint quality and/or insufficient-to-total lack of
> design-for-reliability." Dr Jean-Paul Clech, email dated 12/5/06 on this
> forum.
>
>
>
> If you do not agree with these statements, it is OK with me, I will not
> say
> that you are wrong but simply that is your opinion. Time will tell what
> happens to LF product in the field over the next 5 year. What data I have
> seen so far and read about it in publications, the Sky is not falling.
>
> As part of a team at IBM, we implemented LF solder on a 22 inch x 24 inch
> 22
> layer PCB with 0.016 drilled PTHs (30,000 count) and used that board in
> main
> frame computers. The field failure rate of solder joint was as a matter
> fact
> lower than previous technology that used SnPb product for 360 series
> system.
>
>
>
> Last year, I had the opportunity to develop a LF soldering process (using
> Indium alloy 182) for a project at University of Texas, Austin. SnPb was
> not
> used because it could not provide enough joint strength for ZrCu bus bars
> that were soldered to a BeCu current distribution disk. The
> electro-mechanical assembly (a propulsion motor) weighed almost 750 lbs
> and
> each bus was passing 1000 amps. This application is an example of very
> high
> rotational stresses and electrical loading. Long live LF.
>
>
>
> Have a good day.
>
>
>
> pratap singh
>
> ____________________________________
>
> Tel/Fax: 512-255-6820; Cell: 512-663-8903
>
> www.rampinc.com ; EMail: [log in to unmask]
>
>
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> -------------------------------------------------------------------------------
> Hi Pratap,
> I cannot help but correct you on a number of misconceptions.
> You state:
>> Several papers on LF reliability and comparison with SnPb joints by
> people
>> like Dr. John-Paul Clech, Dr Craig Hillman, K. Sweatman of Nihon
> Superior
>> and others have stated these observations.
>> 1.  LF is better than SnPb when stresses are low and medium intensity.
> ( A large majority of product applications fall in this category)
> 2.  Under highly stressed conditions like aviation, SnPb joints are
> better LF joints.
> A: I know all of these people and they would never make such a statement
> in
> terms of product reliability, but only in terms of accelerated test
> results—
> this in not the same thing by any stretch of the imagination.
>
>> Dell has shipped > 30 million LF
>> products of various types (notebooks, Desktops, Displays and Printers)
> as
>> mentioned by Dr. Randy Schueller. These products are performing as well
> as
>> SnPb products or better according to him (November 2006 CTEA
> presentation at
>> Austin, Texas).
>> A: Wrong, there are laptop computers failing because of solder joint
> failures.
>>
>> No body is being forced to go LF. It is a simple business decision; if
> one
>> wants to play in global economy then one has to follow what the customer
> (an
>> individual, a company or a country) wants. If US companies think LF is
> not
>> in their interest, they can continue SnPb production and simply sell the
>> product in US market only and not in EU.
>> A: Wrong, of course you are forced to go LF--otherwise you are out of
> business; just look at the SWATCH product that they could not procuse with
> LF.
> ...and have you really thought about what you are saying in the last
> sentence; I
> don't think so!
>
> Werner
>
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> -------------------------------------------------------------------------------
>
>
> 

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