I have a very great interest in learning more about the effects of
trying to solder a 99% tin BGA solderball using a 63/37 tin/lead solder
paste, and especially the problems seen in trying to solder an
interposer (pin array) with these different alloys. Any info you can
steer me towards would be extremely helpful, and I would be very
grateful for it.
Thanks,
R. Dean Stadem
[log in to unmask]
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of David D. Hillman
Sent: Tuesday, August 09, 2005 2:41 PM
To: [log in to unmask]
Subject: Re: [TN] [DC] Lead-free design changes and impacts?
Hi Bill! There's nothing rocket science about the paper we published at
the CMAP conference in May at Toronto. The basic principles are that if
you subject a Pbfree solderball (BGA, CSP, FC - area array components)
to a tin/lead reflow soldering process, you have the potential of
getting a very non-uniform solder joint microstructure which can degrade
the solder joint integrity. The degradation is due to the fact that your
are diffusing the tin/lead into the Pbfree solderball instead of melting
the solderball. The severity of the degradation is going to be dependent
on the level of microstructure non-uniformity and your use environment.
Additionally, ENIG finishes appear to be more problematic than immersion
tin or immersion silver pwb surface finishes. Rockwell Collins isn't the
first to document this phenomena - there have been a number of very good
papers on the topic at several of the electronic conferences [our
Rockwell photos just look
better than the photos in the other papers : - ) ]. Most of the
papers document that if you can achieve a uniform solder joint
microstructure then the solder joint integrity isn't compromised. I'll
ask Steve to post the ppt file on his website. I can send the paper out
to those folks who have an interest.
Dave Hillman
Rockwell Collins
[log in to unmask]
"Brooks,Bill"
<[log in to unmask]
>
To
Sent by: TechNet [log in to unmask]
<[log in to unmask]>
cc
Subject
08/09/2005 12:31 Re: [TN] [DC] Lead-free design
PM changes and impacts?
Please respond to
TechNet E-Mail
Forum
<[log in to unmask]>
; Please respond
to
"Brooks,Bill"
<[log in to unmask]
>
Ioan,
I will check with Dave Hillman on Technet and forward your comments to
our Manufacturing Engineers... since we are still planning to be using
eutectic tin/lead solder for some time we need to be conscious of that
issue and make sure to get the BGA packages with tin/lead solder balls
or we run the risks you speak of... Thanks.
I will also notify our purchasing department that they need to watch for
any changes to BGA packages going lead free...
Perhaps Dave will have more data he can post or send to me to help
inform us of the potential for failures on BGA lead free packages when
soldered with Tin/lead solder.
Best regards,
Bill
-----Original Message-----
From: Tempea, Ioan [mailto:[log in to unmask]]
Sent: Tuesday, August 09, 2005 9:46 AM
To: [log in to unmask]
Subject: Re: [DC] Lead-free design changes and impacts?
Yep, big trouble.
Check with Dave Hillman on TN, he very recently wrote a paper showing
what is happening. You have a good intuition, the 2 alloys will not
completely mix giving reliability issues of which the most important is
cracking at the interface with the PCB.
Regards,
Ioan
> -----Original Message-----
> From: DesignerCouncil [SMTP:[log in to unmask]] On Behalf Of
Brooks,Bill
> Sent: Tuesday, August 09, 2005 12:20 PM
> To: [log in to unmask]
> Subject: [DC] Lead-free design changes and impacts?
>
> There is one potential change that I really have not had time to look
into
> yet... maybe someone else has already looked at the BGA packages and
> determined whether or not the 'lead-free' solder balls under the
> packages will be an issue if you're soldering process does not go
lead-free???...
> Those with RoHS exemptions will still be buying lead-free parts
> because
they
> can't get the tin/lead versions anymore, they will be phased out...
> Will they run into soldering problems if the lead-free solder balls
> don't collapse at eutectic solder melting temps?
>
> Best regards,
>
> Bill Brooks - KG6VVP
> PCB Design Engineer, C.I.D.+, C.I.I.
> Tel: (760)597-1500 Ext 3772 Fax: (760)597-1510 Datron World
> Communications, Inc.
> _______________________________________
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