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Passivation of Copper Surfaces in Printed Circuit Manufacture

IP.com Disclosure Number: IPCOM000091885D
Original Publication Date: 1968-Jun-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Jones, AS: AUTHOR [+4]

Abstract

A protective film is formed on exposed spots at the bottom of pores in a developed resist image defining a very fine circuit pattern on a copper substrate. Such a film is realized by immersing the substrate in this iodide bath and applying gentle agitation. Potassium Iodide 200 gms. Iodine 60 gms. Water to 1 liter Temperature 75 degrees C.

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Passivation of Copper Surfaces in Printed Circuit Manufacture

A protective film is formed on exposed spots at the bottom of pores in a developed resist image defining a very fine circuit pattern on a copper substrate. Such a film is realized by immersing the substrate in this iodide bath and applying gentle agitation. Potassium Iodide 200 gms.

Iodine 60 gms.

Water to 1 liter

Temperature 75 degrees C.

The protective iodide film formed between branches of the resist image can be quickly removed by immersing the substrate, without agitation, in a solution of 10% w/v sodium thiosulphate. The spots of protective film at the bottom of the pores are not removed because of their small size and the formation of air bubbles. After etching the copper and removing the resist image, the spots of iodide film can be removed with sodium thiosulphate solution.

Also, a copper substrate bearing a dry resist coating can be immersed in the iodide bath before the resist is exposed. Thus, protective spots of iodide are formed on the surface at the bottom of pores in the coating. Iodide spots left on the copper surface after exposure and development of a resist image are undercut and removed when chromic acid or ferric chloride solution is used to etch the copper.

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