Hello

Can somebody provide me with a softcopy of the latest draft from JSTD 020 -
Lead free.

Siggi
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Kind regards / Mit freundlichen Grüßen

Dr. Siegmund Zweigart
New Technology Manager

Solectron GmbH
Solectronstrasse 2              Fon. ++49 7032 998 194
D - 71083 Herrenberg         Fax  ++49 7032 998 222

e-mail: [log in to unmask] <mailto:[log in to unmask]> 
internet: www.solectron.com <http://www.solectron.com> 
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        ----------
        From:  Kay Nimmo [SMTP:[log in to unmask]]
        Sent:  Montag, 2. Dezember 2002 17:01
        To:  [log in to unmask]
        Subject:  Re: [LF] Lead-Free Wave Soldering

        Hi Keith
         
        The alloys were of a standard specification - no added P or other
control elements.
         
        Kay

                -----Original Message-----
                From: [log in to unmask] [mailto:[log in to unmask]]
                Sent: 29 November 2002 02:12
                To: [log in to unmask]
                Subject: Re: [LF] Lead-Free Wave Soldering
        	
        	
                Kay,
        	
                In this e-mail I am just responding to your point about
comparative dross rates.
        	
                As you acknowledge, comparative drossing studies of tin-lead
and the various lead-free alloys are difficult to carry out because dross
rates are dependent on many factor, the alloy composition being only one of
them.  Different wave soldering machines have different dross generation
characteristic. And the rate in any particular machine is affected by
process temperature, pump speed and even the depth of solder in the pot.
If the data comes from actual production then the flux being applied to the
boards can have an effect on the weight and character of the dross
collected.   
        	
                However, another important factor is the trace additions
that most solder makers use to try to control drossing.   For example, many
solder makers add phosphorus as a dross reduction agent.  This has been of
limited use in tin-lead solders, often just changing the oxide species
generated, but seems to be even less effective in lead-free solders while
appearing to have some undesirable side effects.   Other methods of
controlling dross rates have been found to be more effective in lead-free
systems and are being used by some solder makers.
        	
                The point is that if dross rates of various lead-free
solders are compared without taking into account the question of what dross
control additive, if any, is incorporated in the solder the results are of
little value.   In quoting the comparative results for SnAg, "Castin" and
SnCu you do not mention whether the SnAg and SnCu alloys were made up only
from the two elements listed or whether they were proprietary alloys that
may incorporate specific dross control technology.
        	
                The following data should be assessed in the light of the
foregoing qualifications. It was obtained from three machines in commercial
production that were converted from tin-lead to lead-free so that machine
characteristics should not be a factor.   And the same flux (high solids
rosin based) was used with both tin-lead and lead-free so that tis not a
factor.   And dedrossing procedures were similar.  
        	
                For a period of one month (22 working days)
        	
                Sn-Pb (63/37)   115 
        	
	
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Search previous postings at: http://listserv.ipc.org/archives
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information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315
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