Coating processes – With pretreatment of the base – Preapplied reactant or reaction promoter or hardener
Reexamination Certificate
2000-05-30
2002-06-18
Barr, Michael (Department: 1762)
Coating processes
With pretreatment of the base
Preapplied reactant or reaction promoter or hardener
C427S097100, C427S098300, C427S123000, C427S165000, C427S169000, C427S305000, C427S306000, C427S343000, C427S376200, C427S404000, C427S437000, C427S438000, C427S443100
Reexamination Certificate
active
06406750
ABSTRACT:
BACKGROUBND OF THE INVENTION
The present invention relates to a substrate having on its surface catalyst nuclei, a process of forming the catalyst nuclei on the substrate, a process of electroless-plating the substrate, a process of producing a modified zinc oxide film, and a modified zinc oxide film, which are useful for formation of transparent semiconductor electrodes on glass sheets, plastic sheets, or films used for liquid crystal displays, touch-panels, or solar cells, formation of Cu circuits on printed wiring boards, and formation of electronic part circuits such as formation of Cu wiring on Si substrates used for VLSIs.
In recent years, along with a reduction in sizes and an increase in performances of portable telephones, portable terminal instruments, and note-type personal computes, the packaging density of electronic part circuits has become higher, and correspondingly such circuits have been required to be electroless-plated with no defect. To effectively electroless-plate circuits on non-conductive substrates, metal palladium (Pd) particles are made to adsorb on the non-conductive substrates before electroless plating.
The conventional Pd catalysts, however, are disadvantageous in that the particle size is large and the density of the catalysts adsorbing on a substrate is low. An electroless plating film, which is formed by making the above Pd catalysts adsorb on a substrate and electroless-plating the substrate, has a problem that an initial precipitation layer has a low nuclei density and contains a large number of defects. Accordingly, it has been expected to develop an electroless plating film with no defect in the initial deposition layer.
On the other hand, since a zinc oxide film has a general property that the resistivity is increased after the film is left in air, it is difficult to practically utilize the zinc oxide film as a transparent conductive film.
SUMMARY OF THE INVENTION
A first object of the present invention is to provide a substrate having on its surface catalyst nuclei, which allows the formation of an electroless plating film including a dense initial precipitation layer with no defect.
A second object of the present invention is to provide a process of forming catalyst nuclei on a substrate, which is capable of forming catalyst nuclei on a non-conductive portion to be electroless-plated of a substrate.
A third object of the present invention is to provide a process of electroless-plating the non-conductive portion of the substrate on which the catalyst nuclei have been formed.
A fourth further object of the present invention is to provide process of producing a modified zinc oxide film which has good optical and electric characteristics and less variation in resistivity and thereby suitably used as a transparent conductive film.
A fifth object of the present invention is to provide the modified zinc oxide film produced by the above modified zinc oxide film production process.
The present inventors have examined to achieve the above objects, and found that fine catalyst particles adsorb on a non-conductive substrate at a high density by sensitizing the substrate by using a sensitizing solution containing stannous ions (Sn
2+
), activating the substrate by using a first activator containing silver ions and a second activator containing palladium ions, and finally activating the substrate by the second activator containing palladium ions, and that an electroless plating film with no effect in its initial precipitation layer is obtained by electroless-plating the non-conductive portion of the substrate on which the fine catalyst particles have been formed.
The present inventors have also found that the surface of a zinc oxide film, which is formed on a non-conductive portion of a substrate by activating the surface of the substrate in accordance with the above catalyst nuclei formation treatment and electroless-plating the non-conductive portion, can be modified by dipping the film in a modifier composed of a water solution containing at least one trivalent metal cation such as In
3+
, A
1
3+
, Ga
3+
, Tb
3+
, Y
3+
, Eu
3+
, Bi
3+
, Ru
3+
, Ce
3+
, and Fe
3+
, whereby the surface of the film is covered with the above trivalent metal or the oxide thereof by substitution reaction and adsorption reaction of zinc and the metal, and that when the modified film is heated, the variation rate of the resistivity of the modified film after the modified film is left in an atmosphere with a temperature of 60° C. and a humidity of 90% for 5 to 10 days becomes as very small as 120% or less of the initial resistivity, and thereby the modified zinc oxide film is effective to be used as a transparent electrode of a liquid crystal display or a touch-panel, or a transparent semiconductor for a solar cell or the like. On the basis of the above knowledge, the present invention has been accomplished.
To achieve the first object, according to a first aspect of the present invention, there is provided a substrate having a non-conductive portion to be electroless-plated, on the surface of which metal catalyst particles composed of silver nuclei and palladium nuclei each having an average particle size of 1 nm or less adsorb at a nuclei density of 2000 nuclei/&mgr;m
2
or more;
wherein the metal catalyst particles are produced by sensitizing the non-conductive portion by dipping the substrate in a sensitizing solution containing bivalent tin ions, activating the non-conductive portion by dipping the substrate in a first activator containing silver ions, and activating the non-conductive portion by dipping the substrate in a second activator containing palladium ions.
The average surface roughness of the metal catalyst particles may be in a range of 0.5 nm or less.
The ratio in weight of silver particles to palladium particles may be in a range of 1:10 to 10:1.
To achieve the above second object, according to a process of forming catalyst nuclei on a substrate, comprising the steps of:
preparing a substrate having a non-conductive portion to be electroless-plated;
sensitizing the non-conductive portion by dipping the substrate in a sensitizing solution containing bivalent tin ions;
activating the non-conductive portion by dipping the substrate in a first activator containing silver ions; and
activating the non-conductive portion by dipping the substrate in a second activator containing palladium ions;
whereby catalyst particles composed of silver nuclei and palladium nuclei each having an average particle size of 1 nm or less adsorb on the non-conductive portion at a nuclei density of 2000 nuclei/&mgr;m
2
or more.
The sensitizing step and the first activating step using the first activator containing silver ions may be repeated by several times.
To achieve the third object, according to a third aspect of the present invention, there is provided a process of electroless-plating a substrate comprising:
preparing a substrate having a non-conductive portion to be electroless-plated;
sensitizing the non-conductive portion by dipping the substrate in a sensitizing solution containing bivalent tin ions;
activating the non-conductive portion by dipping the substrate in a first activator containing silver ions;
activating the non-conductive portion by dipping the substrate in a second activator containing palladium ions; and
electroless-plating the non-conductive portion thus activated by dipping the substrate in an electroless plating solution;
wherein catalyst particles composed of silver nuclei and palladium nuclei each having an average particle size of 1 nm or less, at both the activating steps, adsorb on the non-conductive portion at a nuclei density of 2000 nuclei/&mgr;m
2
or more.
The electroless plating solution may be selected from the group consisting of an electroless nickel plating solution, an electroless copper plating solution, and an electroless zinc oxide plating solution.
The substrate may be a silicon substrate on the surface of which either of a Ta film, a TaN film and a TiN film is formed, and the e
Hatase Hiroshi
Izaki Masanobu
Saijo Yoshikazu
Barr Michael
Osaka Municipal Government
Sughrue & Mion, PLLC
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