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Printed Circuit Board With Holes Only Plated

IP.com Disclosure Number: IPCOM000085183D
Original Publication Date: 1976-Mar-01
Included in the Prior Art Database: 2005-Mar-02
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Durfee, HF: AUTHOR [+4]

Abstract

By plating only the through-holes of a printed-circuit board, the thickness of external circuits is defined by the thickness of the copper foil laminated to the substrate, since there is no buildup of plated copper on the surface. The steps for producing the printed-circuit board with the holes only plated are as follows: 1. The printed-circuit panel cores are prepared in the usual manner. 2. The cores are laminated together using epoxy glass prepreg with 3/4 ounce copper foil on both external surfaces of the core. 3. The composite board is drilled where the plated through-holes are desired. 4. The through-holes are cleaned and the drilled panel is covered with a thin conductive layer of electroless copper, both on the surface and in the holes. 5.

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Printed Circuit Board With Holes Only Plated

By plating only the through-holes of a printed-circuit board, the thickness of external circuits is defined by the thickness of the copper foil laminated to the substrate, since there is no buildup of plated copper on the surface. The steps for producing the printed-circuit board with the holes only plated are as follows:
1. The printed-circuit panel cores are prepared

in the usual manner.
2. The cores are laminated together using epoxy

glass prepreg with 3/4 ounce copper foil on both

external surfaces of the core.
3. The composite board is drilled where the plated

through-holes are desired.
4. The through-holes are cleaned and the drilled panel

is covered with a thin conductive layer of

electroless copper, both on the

surface and in the holes.
5. A photoresist material is applied to the external

exposing the photoresist under a dot pattern such

that the surface will be covered with a photoresist

except over the holes, and thereafter

developing the photoresist from over the holes.
6. The holes are then plated either with electroless

or electrolytic copper to the desired thickness.
7. The photoresist is stripped away and another coat

of photoresist is applied, exposed to a mask to

define the external circuit pattern,

and developed.
8. The external circuitry is then etched in the 3/4

ounce copper, the holes being protected from the

etchant by the photoresist tents over the holes.
9. The photoresist is stripped and all su...