Browse Prior Art Database

Forming Patterns

IP.com Disclosure Number: IPCOM000091745D
Original Publication Date: 1968-May-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 31K

Publishing Venue

IBM

Related People

Sprott, CN: AUTHOR

Abstract

A method, for controlling the formation of patterns as for printed circuit boards, provides sensitive registration for aligning a pattern on a light-sensitive coated board in relation to the perforations or holes. The method minimizes coating runout from the perforations when the coating is developed after the pattern is exposed on it. The method also facilitates removal of the coating from the interior of the perforations.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 78% of the total text.

Page 1 of 2

Forming Patterns

A method, for controlling the formation of patterns as for printed circuit boards, provides sensitive registration for aligning a pattern on a light-sensitive coated board in relation to the perforations or holes. The method minimizes coating runout from the perforations when the coating is developed after the pattern is exposed on it. The method also facilitates removal of the coating from the interior of the perforations.

Coated board 1 is shown at A prior to exposure. A cross-section on the line B-B is shown at B. Board 1 has a tin-lead plated through-hole, annulus, 2 and copper laminations on both sides at 3 and 4. It is covered with a light-sensitive coating 5.

A prior pattern in the form of a photographic negative 6 is shown at C. A pattern 7 according to this method appears at D. The prior pattern has entirely clear circles at the perforation locations. The pattern at D has opaque, black, circles located concentrically inside the clear circular areas to form rings.

In a prior method, the negative 6 at C is placed in intimate contact with board 1, the clear areas on the negative allowing light to expose the coating. The clear circles on negative 6 are slightly smaller than the outside diameter of the related tin-lead annulus. Negative 6 is aligned on board 1 by eliminating the crescent color contrast between the grey tin-lean annulus and the bright copper in the clear circular areas on the negative.

In this method, pattern 7 is also placed...