[PCB_FORUM] Re: Tooling holes

1)      Fabricators do NOT use your PCB tooling holes as their tooling
holes.  Theirs are located on the periphery of the panels where the customer
data is not located.

2)      Dimensions should always be referenced to something tangible such as
a hole (never an imaginary location).  Plated  vs non-plated?  Not an issue.
I recommend that you have a datum located on the finished product so that
you can double-check dimensions.  Locating them off the product on a tooling
rail may be ok at the fabricator but won't validate a finished product.

 

I think you're double-counting your tolerances when you are obsessing over
the NP tolerance vs P tolerance for dimensioning.  You should have an
overriding dimension that needs to be checked if this is going to be an
issue.

 

Sounds like you need to convince your mgmt to send you on a fab road trip.
Most fabricators welcome engineers/designers to view the process and explain
all of this on the tour. J

 

 

From: icu-pcb-forum-bounce@xxxxxxxxxxxxx
[mailto:icu-pcb-forum-bounce@xxxxxxxxxxxxx] On Behalf Of Mark Salberg
Sent: Tuesday, March 24, 2009 9:53 AM
To: Cadence User Group
Subject: [PCB_FORUM] Tooling holes

 

Hello Group,
This is regarding tooling holes.

We are required add 2, 3 or 4 .125 NP "tooling" holes.
NP normally used for tighter hole size tol (+/-.002")
Also tooling hole to tooling hole location tol =+/- .003".
At our internal assembly, these are only used in assembly on an "old"
stencil screener.

Questions:
1. Do fab vendors use these for fab tooling or do they use their own from
the fab panel.
(i.e.) stack-up, registration, test during fab, etc...

2. Is it necessary to have a NP hole as a dimension datum?
We normally do, but if I have a board (ex) all PTH with plated mounting
holes...should I add a NP hole just for a dimension datum? 

I believe that the center of a plated hole is as close in tol location as a
NP hole. but the finished hole size is tighter on a NP hole.

Regards,
Mark

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