Steve,
Your pattern is very close to what I use for regular 0402 chip
resistors. If I convert mine to metric I get, 0.51mm x 0.63mm pads on 1.14
centers. Carried the precision one more place just so that you would see the
slight differences.
However I have a second 0402 land pattern for 0402 capacitors or
inductors, typically they are a little thicker part and have more metalization
on the end caps. My 0402C land pattern is 0.51mm x 0.71mm pads on 1.07mm
centers.
From my experience the sizing you are using should not be a problem. If
they were talking about keeping your pads precisely the same size and just
moving them closer together then you may see an issue with solderballs as the
solder is moved more under the non-metalized portion of the body. However, that
is highly dependant on solder paste and other issues. Currently we homeplate
all of our chip components for solderpaste because this has become a
significant problem with our current solderpastes and processing.
Sincerely,
Brad Velander
Senior PCB Designer
Northern Airborne Technology
#14 - 1925 Kirschner Road,
Kelowna, BC, V1Y 4N7.
tel (250) 763-2329 ext. 225
fax (250) 762-3374
-----Original Message-----
From: Steve Allen [mailto:[EMAIL PROTECTED]
Sent: Thursday, January 12, 2006 9:49 AM
To: Protel EDA Discussion List
Subject: [PEDA] 0402 Land Pattern
Hi,
I'd like to hear some recommendations for 0402 land patterns. I've
had good success with
0.6 MM X 0.55MM with 1.1MM centers. Below is a crude drawing:
______ ______
| | | | 0.55MM
|_____ | |_____ |
0.6MM
|------1.1MM ------|
One board assembly shop wants pads closer together to prevent tomb
stoning. Another shop vehemently advises against having pads closer together.
So what should I do? What are your experiences and recommendations?
Thanks,
Steve Allen
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