Ted,

Both stack-ups are correct as long as you can live with either one of them.
For consistency purpose you may want to stick with the original one and
change the overall thickness spec. 

However if I were to build your boards based on your original stack-up, I
would consider overall thickness 0.062"+/- 0.006" a hard requirement but
each individual dielectric thickness for reference only. In other words, I
would consider any call-outs without tolerance for reference only. 

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
High Mix, High Tech, Low-Mid Volume PCB Manufacturer
www.sunshinepcbgroup.com

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Theodore J Tontis
Sent: Friday, November 22, 2013 10:11 AM
To: [log in to unmask]
Subject: [TN] PCB stack up question

I have a 6 layer stack up specified on my gerbers as:

0.0004 mil solder mask
0.0014 mil top layer 1oz copper
0.0086 mil 2 X 2116 prepreg
0.0014 mil inner 1 1oz copper
0.0140 mil core
0.0014 mil inner 2 1oz copper
0.0086 mil 2 X 2116 prepreg
0.0014 mil inner 3 1oz copper
0.0140 mil core
0.0014 mil inner 4 1oz copper
0.0086 mil 2 X 2116 prepreg
0.0014 mil bottom layer 1oz copper
0.0004 mil solder mask

0.0620 mil total stack up +/- 0.006

Our CM's vendor is requesting I change either
A: adjust the 14mil core to 12mil to meet 62±6mil finished thickness.
B: relax the finished thickness to 65±6mil..
C: control the board thickness with 62±6mil exclude the solder mask
thickness.

Their stack up is as follows:

0.0005 mil solder mask
0.0020 mil top layer 1oz copper
0.0091 mil 2 X 2116 prepreg
0.0012 mil inner 1 1oz copper
0.0142 mil core
0.0012 mil inner 2 1oz copper
0.0085 mil 2 X 2116 prepreg
0.0012 mil inner 3 1oz copper
0.0142 mil core
0.0012 mil inner 4 1oz copper
0.0091 mil 2 X 2116 prepreg
0.0020 mil bottom layer 1oz copper
0.0005 mil solder mask

0.0649 mil total stack up +/- 0.006

I got my stack up from a local vendor I've worked with in the past.
Our CM has measured some of their bare boards at 0.070 and 0.071 mil thick.

Which stack up is correct or am I missing something important?


Ted T.


Theodore J. Tontis CID
Senior Manufacturing Engineer
[cid:[log in to unmask]]<http://www.eaton.com/>
11131 Adams Road
Franksville, WI 53126
Office 262-835-1552
Cell 262-510-3145
Fax 262-835-1544


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