Thanks Dean! That was great some information
From: DesignerCouncil
[mailto:[log in to unmask]] On Behalf Of Dean Stadem
Sent: Thursday, June 10, 2010 3:16 PM
To: [log in to unmask]
Subject: Re: [DC] Follow up ~ IPC 0201 land-pattern
Round pads sometimes work well because during reflow the surface
tension of the molten solder will pull more uniformly in every direction.
Square pads tend to have the end fillet larger than the side fillets, and
because of this and the fact that the paste on one end or the other may go
liquidus first, it is easier for the surface tension of the molten solder to
lever up the smaller 0402, 0201 and 00105 chips.
Another way to overcome this is to use standard square pads, but
purposely set up the pick and place machine program to place the components at
about a 30 degree angle. This way the molten solder needs to straighten the
part out first before it can lever one end or the other up. By the time it
straightens the part out both pads are in liquidus and the movement ensures
contact with the molten solder on each end of the chip, and prevents the
tombstoning. It may not completely end the issue, but it certainly reduces it.
And horseshoe-shaped paste deposits on square pads have been known
to work very well. I don’t know why. Ask your mother.
R. Dean Stadem
Consulting Engineer
Analog Technologies
Corp./Lumagine, Inc.
11441 Rupp Drive
Burnsville, MN 55431
(952)894-9228
-----Original Message-----
From: DesignerCouncil [mailto:[log in to unmask]] On Behalf Of Heidel,
Jeff
Sent: Wednesday, June 09, 2010 5:26 PM
To: [log in to unmask]
Subject: Re: [DC] Follow up ~ IPC 0201 land-pattern
Is anyone using round pads
for their 0201s? I have seen some artwork recently with round pads and I
was wondering what the advantages or disadvantages would be.
From: DesignerCouncil
[mailto:[log in to unmask]] On Behalf Of Pete Waddell
Sent: Wednesday, June 09, 2010 3:30 PM
To: [log in to unmask]
Subject: Re: [DC] Follow up ~ IPC 0201 land-pattern
Fred, I asked around a bit
this morning, especially I asked Mike Buetow what he hears from CMs. The
verdict I hear is, it depends on the CM. I’m gonna do some more
research and let ya know what I find.
p.
From: DesignerCouncil
[mailto:[log in to unmask]] On Behalf Of Fred Dark
Sent: Wednesday, June 09, 2010 4:21 PM
To: [log in to unmask]
Subject: [DC] Follow up ~ IPC 0201 land-pattern
Hi All - to date what is the recommended land
pattern for an CC0201 to avoid issues at assembly...?
Regard's, Frederick Dark Jr.
Manager Senior PCB Designer
Crestron Electronics, Inc.
22 Link Drive Rockleigh N.J. 07647
P:201.750.7004 ext.11320
F:210.767.5772
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