Hi Nagaraj,

Most likely you were asked the deviation because the line width/spacing were
smaller on those designs. So 3/8 oz base copper is easy to each. The fab
usually still starts with 1/2 oz foil, but goes through microetch process to
get more copper removed. 

Plating time won't change much, if change at all. You need 1 mil in the
holes so that still adds up to 1 oz on surface with 3/8 oz base. And there
will be no cons even if plating time do change a little more.

Best Regards,

Jason Zhao
VP of North America Operations
Sunshine Circuits
3400 Silverstone Drive, Suite 139, Plano, TX 75023
US Cell 510-468-4412, China Cell 131-62722392
www.sunshinepcbgroup.com
-------------
We will be exhibiting at PCB WEST 2013.  Come see us at Booth #111.

September 25th, 2013, Santa Clara Convention Center, San Jose, CA.

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Nagaraj Shanmugam
Sent: Wednesday, August 07, 2013 8:18 AM
To: [log in to unmask]
Subject: [TN] Starting copper foil thickness on External layers

Hi All,

We have pcb fab notes calling as - "starting copper weight can be 0.5oz  as
long as the finish copper weight is 1 oz" (or 2oz on high power designs)
Now, few fabricators started to ask for deviation to use 3/8oz for starting
copper instead 0.5oz and will make finished copper thickness required in
plating.

What are the pros and cons of having smaller copper foil thickness  as
starting copper weight?
I am concerned about the planarity of the surface due to longer plating time
on 3/8oz.

Appreciate any information on this.
Thanks,
Nagaraj.

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