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Preventing Corrosion of Deleted Printed Circuit Lines

IP.com Disclosure Number: IPCOM000081643D
Original Publication Date: 1974-Jul-01
Included in the Prior Art Database: 2005-Feb-28
Document File: 2 page(s) / 29K

Publishing Venue

IBM

Related People

Miller, LF: AUTHOR

Abstract

The conductive lines on printed circuits or electronic ceramic modules comprise a conductive layer 2 covered with another metal 1 which aids its corrosion resistance. In printed circuits, typically copper is used as the conductor 2, and solder on its surface aids corrosion resistance. In ceramic modules, refractory metals such as molybdenum, tungsten or mixtures of these metals with noble metals are used as the conductors 2 and they are covered with solders, plated copper or nickel, or gold.

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Preventing Corrosion of Deleted Printed Circuit Lines

The conductive lines on printed circuits or electronic ceramic modules comprise a conductive layer 2 covered with another metal 1 which aids its corrosion resistance. In printed circuits, typically copper is used as the conductor 2, and solder on its surface aids corrosion resistance. In ceramic modules, refractory metals such as molybdenum, tungsten or mixtures of these metals with noble metals are used as the conductors 2 and they are covered with solders, plated copper or nickel, or gold.

When it is desired to interrupt a conductive circuit at a particular spot, the conductive line 2 at that spot is opened by cutting with a knife blade, or burnout with a directed laser beam or electron beam, as shown in Fig. 2. However, at the deletion site 3, the underlying relatively corrosive metal 2 is exposed.

The wound can be protected and the underlying metal recovered, by reflowing the coating metal 1 onto the exposed base metal 2, as shown in Fig. 3. In the laser delete operation, the power of the laser is reduced or the beam defocused and redirected over the deleted area 3, to melt the covering metal 1 which proceeds to wet the exposed edges. Thus, the corrosion tendency at the deleted site 3 is reduced.

Alternatively, a localized flame or other source of local heat can be used to refuse the coating metal 1 and wet the underlying base metal 2 with it. Where applicable, a flux can be used to aid the wetting of the...