I recently attended a presentation by Tom Hausherr where he indicated
that the IPC was leaning towards the use of "rounded rectangle pads" for
surface mount... I think this is what he means by 'radius lands'. This
means they remove the sharp corners of the rectangle lands 'rounding'
them...
Bill Brooks | Datron World Communications, Inc.
PCB Designer/Engineer | Office: 760-602-7004| Fax: 760-597-3777 |
[log in to unmask]
1808 Aston Avenue, Suite 230, Carlsbad, CA 92008 | www.dtwc.com
Performance You Require. Value You ExpectTM
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Brad Saunders
Sent: Monday, July 26, 2010 7:21 PM
To: [log in to unmask]
Subject: Re: [TN] 0201 footprint requirements
We had found that no square pads was a good thing. With radii corners
on all lands we saw much, much less de-wetting, stencils cleaned easier,
less slump, components jockeyed better, but alas there were issues in
database compatibility and repeatability especially between fabricators
and stencil suppliers.
We turned the corner on the radius and stayed square. you dig?
Brad
Sorry for the late response.
----- Original Message -----
From: Werner Engelmaier<mailto:[log in to unmask]>
To: [log in to unmask]<mailto:[log in to unmask]>
Sent: Tuesday, July 13, 2010 4:07 PM
Subject: Re: [TN] 0201 footprint requirements
Hi Brad,
When you say 'radius lands'-what exactly do you mean? Can you share
your experiences?
Werner
-----Original Message-----
From: Brad Saunders <[log in to unmask]<mailto:[log in to unmask]>>
To: [log in to unmask]<mailto:[log in to unmask]>
Sent: Tue, Jul 13, 2010 3:58 pm
Subject: Re: [TN] 0201 footprint requirements
Howdy Bill,
I was delighted to see Werner's answer on this question. I had done
very
exhaustive reliability study on solder joint reliability specifically
related to
footprint design and we concluded exactly what Werner was able to say
so
eloquently. I found later the footprint also was a political platform
and to
satisfy a consensus I constructed a formula that would give a bit of
pad to the
sides and ends. I knew it would not subtract from reliability and -so
long as
it didn't get to big I was OK- it did allow me to round off pad sizes
which is
very nice, also I was able to manipulate center spacing which
additional
benefits.
But don't grow that length under your parts... and don't get me going
on radius
lands verses square.
Boston Brad
----- Original Message -----
From: Brooks, Bill<mailto:[log in to unmask]<mailto:[log in to unmask]>>
To:
[log in to unmask]<mailto:[log in to unmask]<mailto:[log in to unmask]:T
[log in to unmask]>>
Sent: Wednesday, July 07, 2010 2:37 PM
Subject: [TN] 0201 footprint requirements
I am looking for some assistance with the pad geometries for 0201
caps
and resistors...
Is there or is there not an industry consensus on what the optimum
pad
geometry should be for them?
What I am hearing from our assembly houses differs greatly from what
is
published in IPC-7351 and the land pattern tool from PCB Matrix.
Is the max material condition footprint actually a recipe for
tombstoning?
What have you folks seen? What do you recommend?
Bill Brooks | Datron World Communications, Inc.
PCB Designer/Engineer | Office: 760-602-7004| Fax: 760-597-3777 |
[log in to unmask]<mailto:[log in to unmask]<mailto:[log in to unmask]
o:[log in to unmask]>>
1808 Aston Avenue, Suite 230, Carlsbad, CA 92008 |
www.dtwc.com<http://www.dtwc.com/<http://www.dtwc.com%3chttp//www.dtwc.c
om/>>
Performance You Require. Value You ExpectTM
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