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May 2003

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From:
Mike Fenner <[log in to unmask]>
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Date:
Thu, 29 May 2003 16:05:57 +0100
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As asked I think two areas are jumbled here. Pb-free processing will require
a higher process temp, but this is to accommodate the higher MP of the
Pb-free solder, not the finishes.
By and large lots of finishes on component leads do not contain lead now and
may never have. Calling them quote lead free unquote doesn't change anything
technically.
By the same token a change from a finish which happens to contain lead to
one of these no lead containing finishes is almost certainly not going to
have a huge impact. You could even now be using a dual sourced component,
one with lead and one without, for example, and not making any distinction.
It is true that some alternative finishes may involve a theoretical small
increase in soldering temp or time (see a related thread on this in the last
few weeks), but as you already accommodate  no lead finishes [now known as
lead free] it shouldn't make any practical difference.
You will still need to audit your components of course, not just for the
lead free construction, but for the temp withstand.



Regards

Mike Fenner

Applications Engineer, European Operations
Indium Corporation
T: + 44 1908 580 400
M: + 44 7810 526 317
F: + 44 1908 580 411
E: [log in to unmask]
W: www.indium.com
Pb-free: www.Pb-Free.com



-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Ofer Cohen
Sent: Thursday, May 29, 2003 4:06 PM
To: [log in to unmask]
Subject: [TN] Combination Leadless and SnPb


Hi all,
Lately I receive messages from components manufacturers, stating they are
moving from Tin-Lead finish to lead-less finish (not specified which one -
my regular question that regularly is not being answered). Most of the
components are still with the SnPb finish, the PCBs Tg are 145 deg C, unless
I had a specific need (extra depth, for instance to move to what is
currently called high Tg (and in the future will probably be the standard
boards) and the pastes are, of course, SnPb, hence would not survive the
higher soldering temperature needed to tickle the lead-less finish.

Should I modify the work processes? Should I wait? Are there any
workmanship/ reliability effects to these changes? Helppppppppppp...

Regards
Ofer Cohen
Quality Assurance Manager
Seabridge Ltd.

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