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Formation of Circuit Layout Including Bulk Metal Electrode

IP.com Disclosure Number: IPCOM000093073D
Original Publication Date: 1967-May-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 49K

Publishing Venue

IBM

Related People

Puttlitz, KJ: AUTHOR [+2]

Abstract

A circuit layout is formed on an insulating substrate that includes a bulk metal electrode bonded to a conductive pattern on the substrate. In A, a paste containing Pt-Au is screened and fired upon a ceramic substrate to form a conductive pattern. In B, a 3 mil thick copper sheet, whose underside is coated with a lead-tin solder and fluxed, is placed over the substrate in contact with the fired pattern.

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Formation of Circuit Layout Including Bulk Metal Electrode

A circuit layout is formed on an insulating substrate that includes a bulk metal electrode bonded to a conductive pattern on the substrate. In A, a paste containing Pt-Au is screened and fired upon a ceramic substrate to form a conductive pattern. In B, a 3 mil thick copper sheet, whose underside is coated with a lead-tin solder and fluxed, is placed over the substrate in contact with the fired pattern.

After a solder reflow cycle during which the copper sheet is bonded to the pattern, a screened etchant resist of the same configuration as the underlying fired pattern is applied to the top surface of the copper sheet. An initial immersion in an etching bath preferentially etches the copper. A second immersion in another etching solution containing fluoroboric acid and H(2)O(2) follows to remove excess solder.

The resulting desired bulk metal including circuit layout is shown in C. The increased thickness derived from a bulk metallic system improves strength, conductivity, flatness, weldability, and heat dissipation. Also, if desired, the bulk electrode can extend beyond the edge of the substrate to be used as a tab, riser wire, etc.

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