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Landless Plates Through Hole Photoresist Masking Process

IP.com Disclosure Number: IPCOM000078892D
Original Publication Date: 1973-Mar-01
Included in the Prior Art Database: 2005-Feb-26
Document File: 2 page(s) / 67K

Publishing Venue

IBM

Related People

Chumbres, LG: AUTHOR [+2]

Abstract

This is method for producing landless plated-through holes in printed circuit board, using a film-type photoresist process where resist over holes is photographically removed.

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Landless Plates Through Hole Photoresist Masking Process

This is method for producing landless plated-through holes in printed circuit board, using a film-type photoresist process where resist over holes is photographically removed.

Hole 19 is drilled through a copper-clad board 18 at a location where plated- through hole connectors are desired and all exposed surfaces are sensitized and plated. The electroless plating produces a thin-conduc- tive coating 20 on the interior surfaces of hole 19, as well as on the original surface cladding 21 and 34 of board 18. Tenting photoresist material 22, 29 is placed over the surface of drilled board 18 and covered with masks 23, 30. A desired circuit pattern is produced in the tented photoresist by using light, represented by arrows 24, 25 and 31, 32. The circuit pattern includes hole configurations having diameters not greater than drilled hole 19.

In the first species negative or positive photoresist is placed on both sides of board 18 and the holes in photoresist 22, 29 are made smaller than the drilled holes 19, using a separate photomask. In a second species, positive photoresist 22 or 29 is placed on one surface of the board 18 at a time and the holes in the positive photoresist are made precisely equal in size to the drilled holes 19, using the board itself as a photomask.

The exposed photoresist layer 22 is developed to provide circuit pattern apertures 27 and hole configuration aperture 28. An etching resist materi...