Hi Scott,
For the same solder joint height, square and even more though rectangular pads give slightly higher cycles-to-failure in ACT.
Werner
-----Original Message-----
From: Post, Scott E <[log in to unmask]>
To: [log in to unmask]
Sent: Fri, Jun 19, 2009 9:57 am
Subject: Re: [TN] LGA assembly question
I'm curious if anyone knows of a supplier of dummy LGAs for process development
and reliability testing, especially daisy chained with representative die. BGAs
without balls are readily available, but I haven't seen any with square pads in
the little bit of looking I've done.
Scott Post
Delphi
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Sylvain Kaufmann
Sent: Friday, June 19, 2009 9:49 AM
To: [log in to unmask]
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 that 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]] 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]] 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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