This should be explained on the master drawing. Either way is okay per IPC.

In the case of boards with edge connectors, IMHO, one should follow the
JEDEC precedent and spec metal to metal at the finger. In other cases the
dielectric thickness might be most critical, in yet other cases the overall
mask to mask might be critical.

The designer is responsible to understand the implications of variation in
the board stack-up and specify the design requirements on the drawing,
allowing maximum freedom to fabricators.

Guy Ramsey
Senior Lab Technician / Instructor


E-Mail: [log in to unmask] <mailto:[log in to unmask]>
Ph: (610) 362-1200 x107
Fax: (610) 362-1290



-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Ken Patel
Sent: Tuesday, August 21, 2001 6:18 PM
To: [log in to unmask]
Subject: [TN] Fab thickness Measurement


All,
How the fab thickness is being measured per IPC? Is it metal to metal or
solder mask to solder mask? And which is called overall thickness of the
fab?

re,
Ken Patel

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