Hmmm... in a word, No.

I'm not sure what you are driving at but finished plated thru holes are
dependant upon a lot of variables... location, diameter, relationship to
other holes and the board edge, plating thickness, drill wear, runout in the
gears that drive the positioning of the drill machine chucks, drift of the
drill when stack drilling, there are probably thousands of variables...

Hitting the target is harder than setting the goal.   But the designer is
tasked with setting the expectation and criteria for the hole to be created
so that it can be manufactured and assembled under any circumstance. That is
what I am talking about. The size and tolerance of the acceptable plated
hole diameter to be set such that it takes all of those variables into
account and then specifies it such that when it is delivered within the
tolerances specified, it will work with the fixtures, tooling, insertion or
pick and place machines, etc. and within the parameters that they require to
assemble, test, and manufacture the board successfully.

That is designing. Not pulling a number out of a hat and applying a rule of
thumb tolerance to it and calling it good... leaving the assembler, and
manufacturer to figure out how in the heck they are going to accomplish that
feat...

Best regards,

Bill Brooks - KG6VVP
PCB Design Engineer, C.I.D.+, C.I.I.
Tel: (760)597-1500 Ext 3772 Fax: (760)597-1510
Datron World Communications, Inc.
_______________________________________
San Diego Chapter of the IPC Designers Council
Communications Officer, Web Manager
http://dcchapters.ipc.org/SanDiego/
http://pcbwizards.com

-----Original Message-----
From: EIMCNews [mailto:[log in to unmask]]
Sent: Monday, February 13, 2006 4:49 PM
To: [log in to unmask]; Brooks,Bill
Subject: Re: [TN] Hole size specs

Bill,

Doesn't this assume that each hole diameter is the same?  In reality, given
the variations or differences in plated hole thickness, are they ever the
same?

Regards,

Roger Mouton

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