[PCB_FORUM] Re: 0402, 0603 round pads

From: "Macindoe, Gary" <Gary.Macindoe@xxxxxxx>
To: icu-pcb-forum@xxxxxxxxxxxxx
Date: Fri, 5 Jan 2007 10:32:18 -0600
Thanks Jim, our volume is very low, so I'm not going to worry about it
for now.  I'll continue with the square pads.

Good info, thanks for the reply.

 

Regards,

Gary

 

  

Gary E. MacIndoe

PCB Design Engineer

Longmont, Colorado

 

amd.com

gary.macindoe@xxxxxxx

________________________________

From: icu-pcb-forum-bounce@xxxxxxxxxxxxx
[mailto:icu-pcb-forum-bounce@xxxxxxxxxxxxx] On Behalf Of J Wages
Sent: Friday, January 05, 2007 5:36 AM
To: icu-pcb-forum@xxxxxxxxxxxxx
Subject: [PCB_FORUM] Re: 0402, 0603 round pads

 

Small discrete footprints with rounded or beveled pads  (each outside
corner beveled at 45 degrees for 20% of the pad width) on 0402 & 0603's
benefit in the alignment process in both wave soldering and reflow
assembly methods due to the greatest amount of solder being at the
center of the component axis. I have been strictly contracting layout
for the last 5 years and the assembly vendors that have measured this
approach have found approximately 10 to 15% decrease in component
misalignment issues. This yield ratio is, of course, subject to the
manufacturers expertise and equipment. Unfortunately, many companies are
not willing to adjust their "golden library footprints". Why? ... and
I'm sure you've all heard this before..."Cuz this is the way we always
do it!" 

I have also used the beveled 0402 pads for use in placing decoups within
a 1mm BGA via fan-out grid. This requires some other pad size/geometry
refinements and are not as reliable, but if you need BGA pin decoupling,
as apposed to area decoupling, it's the way to go. Of course many large
companies are banking on yield savings and designing out decoupling
losses, so are very reluctant to use this approach. We used the 0402
with octagon pad geometries for 50 mil & 1mm BGA fan-out decoupling at
Sanmina-SCI with a pretty good success ratio, although I don't remember
what those numbers were. I do remember that it definitely creates a
yield reduction. The same old battle; Yield vs signal integrity. A good
discussion to initiate with your assembly house. 

 

Jim S. Wages / SR. PCB Layout Designer:  

Cary, NC - H: 919-466-1596 Cell: 919-484-2963

 

-----Original Message-----
From: icu-pcb-forum-bounce@xxxxxxxxxxxxx
[mailto:icu-pcb-forum-bounce@xxxxxxxxxxxxx] On Behalf Of Peter
Sent: Thursday, January 04, 2007 11:26 PM
To: icu-pcb-forum@xxxxxxxxxxxxx
Subject: [PCB_FORUM] Re: 0402, 0603 round pads

 

We use square and rectangular for 0201, 0402, 0603 and etc. These are
used on designs running at a million / month volume and all lead free. 

 

I work for Flextronics.

 

________________________________

From: icu-pcb-forum-bounce@xxxxxxxxxxxxx
[mailto:icu-pcb-forum-bounce@xxxxxxxxxxxxx] On Behalf Of Austin Franklin
Sent: Thursday, January 04, 2007 6:53 PM
To: icu-pcb-forum@xxxxxxxxxxxxx
Subject: [Norton AntiSpam] [PCB_FORUM] Re: 0402, 0603 round pads

 

Hi Gary,

 

I use round pads for my 0402s on the opposite side of 1mm BGAs.  That
way I can keep the decoupling caps and termination resistors right
there.  Works fine, haven't had any yield problem.

 

Regards,

 

Austin

        -----Original Message-----
        From: icu-pcb-forum-bounce@xxxxxxxxxxxxx
[mailto:icu-pcb-forum-bounce@xxxxxxxxxxxxx]On Behalf Of Macindoe, Gary
        Sent: Thursday, January 04, 2007 6:05 PM
        To: icu-pcb-forum@xxxxxxxxxxxxx
        Subject: [PCB_FORUM] 0402, 0603 round pads

        Hey guys,

         

        Man has it been quiet (or am I not receiving forum e-mails?).

         

        So, I've been looking at some designs from a couple of other
groups within the company.

        Both of them have their 0402 and 0603 foot prints with round
pads (0402 = rd25).

         

        Is anyone out there also using round pads for 0402s and 0603s,
and why?

         

        They have oval pads for their 0805s and 1206s also.

         

        I still have square or rectangular for all of the above.  Could
it have something to do

        with lead free?

         

        Thanks and Happy New Year!

         

        Gary

         

         

        Gary E. MacIndoe

        PCB Design Engineer

        Longmont, Colorado

         

        amd.com

        gary.macindoe@xxxxxxx
[PCB_FORUM] Re: 0402, 0603 round pads

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