X-Ray inspection (at an angle, not top down) is tricky as the joints have no appreciable height. Absolutely no visual inspection is possible (unlike most BGAs, where you can see at least the outermost row). We also observed voiding under the prototype LGAs we assembled. I made sure that the board design was per the manufacturer spec and printed solder 1:1 with the pad and using our standard 2 mil reduction (1 mil on each dimension). Both soldered about the same, no difference in voiding.
Regards,
Amol
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Inge
Sent: Friday, June 19, 2009 9:22 AM
To: [log in to unmask]
Subject: Re: [TN] LGA assembly question
Hi Bev,
LGAs have higher standoff (solder pad contra board pad) and have a little
better signal integrity. If QFNs have any parameters better than LGA, I
don't know.
Normally, we do not make any other difference between them than solder
amount.
/Inge
----- Original Message -----
From: "Bev Christian" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Friday, June 19, 2009 3:08 PM
Subject: Re: [TN] LGA assembly question
Sylvain,
Please enlighten us as to your understanding of the differences between
a QFN and an LGA.
Bev
RIM
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Sylvain Kaufmann
Sent: Friday, June 19, 2009 9:06 AM
To: [log in to unmask]
Subject: [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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