Dear Werner and all,
As a reader of this forum, I would be very happy to discuss this topic with you. However, I don't have much more informations than you as I am not involved in supraconducting interconnections. I had access to the same reports as you and can only guess what could be the possible causes of the incident.
And, as you may imagine, I am not an official/authorised spoke person from the CERN, so I could never discuss things that are not public and will never talk in the name of the organisation.
Sorry not to have sharper informations
Best regards
sylvain
________________________________
From: [log in to unmask] [mailto:[log in to unmask]]
Sent: vendredi, 19. juin 2009 19:09
To: [log in to unmask]; Sylvain Kaufmann
Subject: Re: [TN] LGA assembly question
Hi Sylvain,
Could you give us the details about the solder joint failure that shut down the accelerator. There are all kinds of rumors floating around and it would be nice to have the facts.
Regards,
Werner Engelmaier
Engelmaier Associates, L.C.
Electronic Packaging, Interconnection and Reliability Consulting
7 Jasmine Run
Ormond Beach, FL 32174 USA
Phone: 386-437-8747, Cell: 386-316-5904
E-mail: [log in to unmask], Website: www.engelmaier.com
-----Original Message-----
From: Sylvain Kaufmann <[log in to unmask]>
To: [log in to unmask]
Sent: Fri, Jun 19, 2009 9:49 am
Subject: [TN] LGA assembly question
Ioan,
Merci pour le retour.
One question more if I may: did you set a different placement force as you would
have used for a BGA for example, or did "regular" setting work well?
Bev, sorry I answered your question personnaly, I sent my reply too quickly. To
sumarize for others, in my mind QFN are packages with a ground/thermal plane in
middle and signals connection in periphery. And LGA is like a BGA but with
square pads and no balls.
I am concerned about shorts because this device is a DC/DC tha
t can drive up to
12 amps and I would not see these assemblies burn because of assembly issues.
Thank you again
Regards
sylvain
-----Original Message-----
From: TechNet [mailto:[log in to unmask] <mailto:[log in to unmask]> ] On Behalf Of Ioan Tempea
Sent: vendredi, 19. juin 2009 15:16
To: [log in to unmask]
Subject: Re: [TN] LGA assembly question
Bonjour Sylvain,
I have recently done several boards with the exacly same components, in almost
the same conditions as yours. I had ENIG/Pick'n'place/lead-free SAC305. The only
difference was I did convection reflow.
They print well, they solder well. I would not dread shorts, this package is
more lenient than QFNs. The only 2 special things I have observed were:
- The thermal demand is higher than for regular BGAs. I had metal top BGAs on
the same board, still the LGAs were 10 deg C colder. In order to bring the LGAs
at 240deg C I had to bump the BGAs up to 250 deg C.
- Hard to control voiding
Since I am not familiar with vapour phase, maybe the above will not be an issue
for you.
Regards,
Ioan Tempea, ing.
t : 450-967-7100 ext : 244
[log in to unmask]
www.digico.cc
P N'imprimer que si nécessaire - Print only if you must -----Message
d'origine----- De : Sylvain Kaufmann [mailto:[log in to unmask] <mailto:Sylvain.Kaufmann@ CERN.CH?> ] Envoyé :
19 juin 2009 09:06 À : [log in to unmask] Objet : [TN] LGA assembly question
Dear Technetters,
Our assembly workshop has to assemble 4 prototype boards where LGA packages with
133 connections are used. I allready worked with BGAs or QFNs but never with LGA
packages and I am concerned about shorts/open that could occur.
Provided that I cannot run tests and conditions are as followed:
- ENIG surface finish boards
- Vapor phase reflow soldering
- Pick and Place machine
- Leadfree or lead containing solder can be used
Would some of you be kind enough to share experiences/advices so that we would
have little chances to successfuly assemble these boards?
Thank you in advance for your help.
S. Kaufmann
************************************************************
Sylvain Kaufmann
CERN / European laboratory for particle physics Site de Meyrin
1211 Geneva 23
Switzerland
Dpt: EN-ICE-DEM (int mail J06600)
Phone: +41 22 767 37 02
Fax: +41 22 766 87 77
E-mail: [log in to unmask]
Web: www.cern.ch
http://cern.ch/dem
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