Many times the inner-layer pads for component mounting holes can be
smaller;  the reason for having larger pads on the outer layers is to allow
for a proper solder fillet to form around the component lead.

The IPC has guidelines that can be used to determine the minimum diameter
for internal layer pads.  Use the formula and table of IPC-2221, section
9.1 (pages 70-72) to determine the correct size.  Be sure and use the
Minimum Internal Supported Annular Ring dimension for your calculations
(Table 9-2).  Also note that for inner layers, you MUST use the maximum
drill size, not maximum plated hole diameter, for the calculations.

You're welcome.

 Roger M. Stoops,       PCB Designer

 Spectra Precision Inc. Ph:     937.233.8921
 5475 Kellenburger Rd.     937.233.4574 ext
 Dayton, OH 45424-1099  288
 USA                    Fax:    937.233.7511

                        Member IPC
                        Designer's Council,
                        C.I.D.







                    Denis Seguin
                    <dseguin@PARA        To:     [log in to unmask]
                    DOX.CA>              cc:
                    Sent by:             Subject:     [TN] Padstacks info for multi layer
                    TechNet
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                    05/19/00
                    01:27 PM
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                    Denis Seguin





Hi,

Since I`m new at this...

I would require some informations concerning the padstacks on multi-layer
board.
what should be the dimensions of the pads of a through hole component, on
the inner layers compared to the ones on the external layers of the board?
Should they be bigger or smaller (by how much?) or the same size?

I belive smaller but I'm not sure.

Thank You.

Denis Seguin
CAD Department.
P A R A D O X
S E C U R I T Y        S Y S T E M S
Email: [log in to unmask]

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