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.
> _______________________________________
---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 1.8e
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Technet
To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL)
To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest
Search the archives of previous posts at: http://listserv.ipc.org/archives
Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815
-----------------------------------------------------
|
