The address is a little different.  It has the word "-request" after the 
word TechNet to subscribe.
 ----------
From: Automata
To: dabonz; jasatt; mimall; 'Matthew Leary'
Cc: [log in to unmask]
Subject: RE: vias


Matt, If I understand your question correctly, the answer is quite =
elementary.  Generally, a four layer board has circuitry on the two =
outerlayers and the internal cores are a power plane and a ground plane. =
 To pass a conductor from the top to the bottom, the internal layers =
have a clearance etched in the copper larger than the=20
hole that is going through.  When you laminate the layers together the =
clearance area fills in with epoxy.

At locations where you want a conductor to connect to the ground plane =
(or power plane) there is no clearance on the plane. =20

You can subscribe to the IPC technet by sending mail to the same address =
you sent your question to with the word subscribe in the subject field =
and no text in the body.  I doubt you want an average twenty five or =
thirty messages per day from people who build or use boards listing all =
their travails.


 ----------
From:  Matthew Leary[SMTP:[log in to unmask]]
Sent:  Monday, January 13, 1997 4:51 PM
To:  [log in to unmask]
Subject:  vias

Hi guys,
     I wound up here thanks to Yahoo and I do have aquestion for you,=20
although I do not know if I am in any position to ask you to answer me.  =

If I need to sign up for something, could you fill me in.  Anyway my=20
question is this:=20

 A via passes through a four layer board, is a hole=20
drilled in the ground and the power layers.  What is used to insulate =
the=20
ground and power layers from the solder that eventually will fill this=20
hole?  Is it a form of mask?  I thought mask prevented it from the top =
of=20
a layer (i.e. the top of the board), but not the width if a board is =
cut.=20
 Anyway, please get back to me on this.  Thanks.
                         Matt
                         [log in to unmask]

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