Good thought. The slow cool down associated with larger parts will give what
are effectively shrink holes (like in a solder pot) especially with Sn96.
[On hand soldering parts with poor solderability operators tend to put more
solder on as well which exacerbates the problem.]
The solutions offer themselves, but you could also consider using a SAC
alloy. The different structure of the solder on solidification should help.
If nothing else the "cracks" will be more rounded.
A final thought to double dot and cross the Ts and Is. In the unlikely event
the turrets are brass they should have a NI or Cu barrier plate to prevent
the solder sucking out Zn. This would certainly lead to a cracked appearance
if not cracks.
Regards
Mike Fenner
Indium Corporation of Europe
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 David D. Hillman
Sent: Wednesday, September 15, 2004 11:50 PM
To: [log in to unmask]
Subject: Re: [TN] HMP Solder Joint Cracking
Hi Bryan! One possible root cause to explore is that the "cracks" you have
observed are actually shrinkage voids/cavities that intercept the solder
joint surface. There have been several studies (NIST, NCMS) that have show
that the high tin content solder alloys can form small shrinkage cavities
that terminate at the solder joint surface. These shrinkage cavities could
easily be mistaken for cracks. I recommend you microsection one of the
suspect solder joints to see if you have a crack or a shrinkage cavity.
Good Luck.
Dave Hillman
Rockwell Collins
[log in to unmask]
"Kerr, Bryan"
<bryan.kerr@AMSJV To: [log in to unmask]
.COM> cc:
Sent by: TechNet Subject: Re: [TN] HMP Solder
Joint Cracking
<[log in to unmask]>
09/15/2004 10:27
AM
Please respond to
TechNet E-Mail
Forum; Please
respond to "Kerr,
Bryan"
The cracks occur immediately on alloy solidification - I've watched it
happen under a scope. Can't be sure that some don't occur later but that is
a worrying thought which could affect reliability.
Cheers
Bryan
-----Original Message-----
From: Marsico, James [mailto:[log in to unmask]]
Sent: 15 September 2004 16:21
To: 'Kerr, Bryan'
Subject: RE: [TN] HMP Solder Joint Cracking
When are the cracks occurring? Ate the assemblies thermally stressed after
the terminals are soldered? Do the cracks occur after a wire is soldered
to
the turrets?
Jim Marsico
Senior Engineer
Production Engineering
EDO Electronics Systems Group
[log in to unmask] <mailto:[log in to unmask]>
631-595-5879
-----Original Message-----
From: Kerr, Bryan [SMTP:[log in to unmask]]
Sent: Wednesday, September 15, 2004 11:07 AM
To: 'Marsico, James'; IPC Mailing List (E-mail)
Subject: RE: [TN] HMP Solder Joint Cracking
Thanks Jim
We are seeing some of the edge solderability issues that you
mention
however
there is definite cracking as shown in microsections done by
ourselves.
Another batch of pins has better solderability at the edge however
we still
get cracks occurring.
Cheers
Bryan
-----Original Message-----
From: Marsico, James [mailto:[log in to unmask]]
Sent: 15 September 2004 16:04
To: 'TechNet E-Mail Forum'; 'Kerr, Bryan'
Subject: RE: [TN] HMP Solder Joint Cracking
*** WARNING ***
This mail has originated outside your organization,
either from an external partner or the Global Internet.
Keep this in mind if you answer this message.
We've seen this problem in the past. The main culprit, in our
case,
was the
solderability of the terminal on the corner of the swaged area.
What looks
like a crack may be an unsolderable line around the periphery of
the
swaged
area. Try dipping the swaged end of a terminal into a solder pot
and see if
the corner edge wets.
Jim Marsico
Senior Engineer
Production Engineering
EDO Electronics Systems Group
[log in to unmask] <mailto:[log in to unmask]>
631-595-5879
-----Original Message-----
From: Kerr, Bryan [SMTP:[log in to unmask]]
Sent: Wednesday, September 15, 2004 10:35 AM
To: [log in to unmask]
Subject: [TN] HMP Solder Joint Cracking
Hi
We are fitting a swaged turret terminal and soldering using
96% Tin
4%
Silver alloy and have experienced cracks running around the
edge of
the
swage solder joint - between the pin and the solder.
Re-soldering
gets rid
of it in most but not all cases. I have thought that
perhaps
some
stress
relaxation is occurring in the swage area (brass base
material)
during
soldering resulting in these cracks.
Can anyone shed any light on this problem ?
Cheers
Bryan Kerr
Principal Quality Engineer
Process and Materials Laboratory
AMS Hillend
:::::::::::::::::::::::::::
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Messages sent via this medium may be subject to delays, non-delivery and unauthorized alteration. This email has been prepared using information believed by the author to be reliable and accurate, but Indium Corporation makes no warranty as to accuracy or completeness. In particular, Indium Corporation does not accept responsibility for changes made to this email after it was sent. Any opinions or recommendations expressed herein are solely those of the author. They may be subject to change without notice.
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