Here is the what Perfag specifies about board thickness (Perfag is a
specification for PCB, commonly used by PCB manufacturers) :

"The thickness tolerance is +-10%.

The thickness should be measured as follows :

a. by the PCB manufacturer :
just after lamination, i.e. including the copper foil of the outer layers

b. by the customer :
if possible over edge connector terminals, otherwise over clean-etched
laminate, adding the nominal thichness of the outer layers' copper foils and
substracting the nominal thickness of any masks.

Design note :
On plug-in boards, the clearance in the guide rails should be ensured with
respect to the total thickness of the board, possibly by withdrawng any
solder masks from the board edges.

In case where finished copper thickness is considered critical, the customer
should consult the PCB manufacturer."


Marie Magnin

FIRSTEC SA
Rue du Grand Pré 70
CH 1211 Genève 2

Tél.   : +41(0)22 918 36 85
Fax   : +41(0)22 918 36 93
mailto:[log in to unmask]
http://www.firstec.ch


> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]]On Behalf Of Franklin D Asbell
> Sent: lundi, 3. mars 2003 15:49
> To: [log in to unmask]
> Subject: [TN] PC Board thickness measurement
>
>
> In what IPC specification is board thickness measurement (location)
> referenced?
>
> I'm looking for where overall thickness is mentioned. I'm receiving
> conflicting information on whether the required board
> thickness is to be
> measured over foil copper (multilayer, after layup), over
> soldermask/glass,
> or over final finish.
>
> And is there information differentiating between OSP or flat
> coatings and
> HASL or reflow if final thickness is measured over...final finish...
>
> Thanks.
>
> Franklin
>
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