[PCB_FORUM] Re: 0402, 0603 round pads

  • From: "Peter" <peter_pietrangelo@xxxxxxxxxxxxx>
  • To: <icu-pcb-forum@xxxxxxxxxxxxx>
  • Date: Fri, 5 Jan 2007 05:22:27 -0800

I repeat; 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.

 

I add, over 60M units last year from one division shipped this way from one
division. 

 

 

  _____  

From: icu-pcb-forum-bounce@xxxxxxxxxxxxx
[mailto:icu-pcb-forum-bounce@xxxxxxxxxxxxx] On Behalf Of J Wages
Sent: Friday, January 05, 2007 4:36 AM
To: icu-pcb-forum@xxxxxxxxxxxxx
Subject: [Norton AntiSpam] [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

 

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