DE19823112A1 - Dielectric substrates for producing electrochemical electrodes - Google Patents

Abstract

Dielectric substrates (1) are sensitized, prior to nucleation and metallization, by printing with a zinc acetate paste (2) and heat treating to form a zinc oxide layer (3). Substrates of glass, quartz, ceramic etc. are sensitized, prior to nucleation (especially with Pd nuclei) and metallization, by printing with a paste of 5-20 g zinc acetate (2) dissolved in a mixture of 1 l 96% acetic acid and 80-150 g cellulose acetate and then heat treating to form a zinc oxide layer (3).

Description

Field of application of the invention

The invention relates to a method for producing a hafifär carrier layer for Palladium seeds on dielectric substrates, especially on glass. Through the application With this method, there is the possibility, in subsequent steps, of metal layer systems, for example for use as electrochemical electrodes.

State of the art

Glass as a carrier of metal layers or metal layer combinations offers the following advantages:

• - High surface quality of the metal layer due to the low roughness of the Substrate surface,
• - transparency of the uncoated substrate areas,
• - better dielectric and insulating properties compared to plastic substrates.

A long-used process for metallizing glass is the manufacture of mirrors by reducing silver salt solutions.

In other previously known methods for pretreating glass substrates [1, 2, 3] for electroless metallization of dielectric substrates, palladium nuclei are generated on the glass surface using various methods, including the following:

• - treatment with a chalk slurry,
• - Cleavage of the oxide network on the glass substrate surface by the action of alkaline solutions and creation of metal-O-Si bonds,
• - neutralization of excess alkalis by exposure to acidic media, for example an aqueous HCl solution,
• - Exposure to tin (II) salt solution and activation of the substrate surface with PdCl ₂ solution.

In [4] the deposition of an electrolessly deposited metal layer on glass or other dielectrics by converting a tin oxide layer into a divalent tin salt described, the divalent tin as a reducing agent for the production of Pd nuclei from Pd ions is used.

In [5] a solution of zinc acetate in ethanol is sprayed onto substrates that are at 400 ° C were heated. This creates a zinc oxide layer that can be used as a germ carrier and is suitable for Adsorption of Pd seeds is used. The Pd ions are in a copper bath without Current flow through the existing reducing agent in situ reduced to palladium.

Another method for the metallization of glass is described in [6]. Between The glass surface and metal layer are those that act as adhesion promoters organic polymer layer. Thus, the metallization is not on the glass, but on the plastic surface.  

Criticism of the state of the art

The Z. B. from the mirror production known methods of electroless deposition of Metal layers from silver salt solutions lead to layer thicknesses of max. 50-100 nm. This Layers contain pinholes and are not adhesive. A transfer of this procedure to the task according to the invention, in which mechanical forces on the metal layer act and where there is constant contact with electrolytic solutions therefore not possible.

Metallization processes based on the known methods for electroless metallization based on glass lead to layers with uneven layer thickness and less Adhesive strength, which favors stresses leading to the formation of cracks in the metal layer become.

Previously known processes using oxidic intermediate layers (SnO ₂ , ZnO) require a high level of technological effort (e.g. SnO _{2 has} to be heated in an additional reaction chamber and treated with chlorine gas) and are therefore cost-intensive.

Processes in which polymeric interlayers are used to increase the adhesive strength (Photoresist) are generated, for. B. due to swelling in electrolytic Solutions unsuitable as supports for metal layers for electrochemical electrodes.

task

The invention has for its object a compared to the previously known Methods improved method for sensitization of dielectric substrates, especially glass, for the electroless deposition of adhesive metal layers.

solution

The problem is solved by a paste of 5 to 20 g of zinc acetate mixed with 1 l Acetic acid and 100 to 150 g of cellulose acetate (substitution rate: 40% acetyl groups) a glass surface is applied and the coated surface is then heated to 400 ° C , whereby a zinc oxide film is formed. This zinc oxide film is made by exposure activated with a palladium chloride solution and can then be metallized without current.

Embodiment

A glass substrate treated in an alkaline hot degreaser at 60 ° C and rinsed with acetone is printed with a 0.4 ... 0.6 mm thick film of a paste of the following composition ( Fig. 1):

• - 1 l 96% acetic acid p.a.
• - 5 to 20 g zinc acetate p.a.
• - 80 ... 150 g cellulose acetate

The prepared glass substrate is placed in a heating oven heated to 400 ° C to form a zinc oxide film ( Fig. 2). It stays there for 30 to 60 minutes without using a protective gas. The cooling takes place slowly in standing air.

The zinc oxide film is activated by immersion in a palladium chloride solution (pH = 2 ... 3) with palladium ions and then rinsed ( Fig. 3). Then it is coated with a nickel-phosphor layer at pH <5 in a nickel bath ( Fig. 4).

A galvanic gold layer is made from a cyanide gold bath on the nickel phosphor Layer deposited.

Presentation of the advantages of the invention

The advantage of the invention is the low outlay in terms of apparatus for generating a Adhesive germ carrier layer for electroless metallization, an even distribution the palladium seeds and using screen printing technology to raise awareness. In process When printing, a germ carrier image is already created, which is a continuous one Additive technology allowed to build up the metal layer system.

literature

[1] Khoperia, TN; et al .: Process for producing a metal coating on products made of non-metallic substances. DD 113569 (1975); DE 24 48 148 (1976)
[2] Wein, S .: Nickel and Cobalt Films. Glass ind. 40 (1959), pp. 476-477, 498, 500-502.
[3] Hofmann, H .; Spindler, J .: Tagungsband 68, Galvanotechnik 1982, publisher: KdT Suhl, pp. 151-160.
[4] Archer, August-Friedrich. Process for the electroless chemical production of a structured metal layer. DE 42 20 621 A1. 1994.
[5] Yoshiki, Aleksandruk, Hashimoto, Fujishima: Electroless Copper Plating Using ZnO Ihm Film Coated on a Glass Substrate, in Journal of the Electrochemical Society, Vol. 141, No. 5 May 1994.
[6] Honma, H .; Koshio, T .; Hotta, S .; Watanabe, H .: "Fabrication of Nickel Film on a Glass Disk By Electroless Nickel Plating". in Plating & Surface Finishing, 1995, p. 60 ff.

Reference list

1

carrier

2nd

Zinc acetate paste

3rd

Zinc oxide layer

4th

Seed layer

5

Metal layer

Illustrations

Fig.

1: Substrate with structured sensitizing paste

Fig.

2: substrate with zinc oxide film

Fig.

3: Substrate with palladium ions diffused into the zinc oxide film

Fig.

4: substrate with nickel-phosphor coating deposited on ZnO film

Claims (4)

1. A method for sensitizing supports made of glass, quartz, ceramics or the like ( 1 ), wherein a seed layer with crystallization nuclei, in particular Pd nuclei, is produced before the metallization, characterized in that a paste of 5 to 20 g of zinc acetate dissolved in a mixture of 1 l of 96% acetic acid and 80 ... 150 g of cellulose acetate ( 2 ) are printed on and converted into a zinc oxide layer ( 3 ) by thermal treatment. 2. The method according to claim 1, characterized in that the thermal treatment at a temperature of 390 to 450 ° C without a drying or preheating process. 3. The method according to the preceding claims, characterized in that to form the seed layer ( 4 ) the activation solution has a pH of 2.5 to 3.5 and the exposure time is 1 to 5 seconds. 4. The method according to claim 1 to 3, characterized in that an electrolessly deposited nickel-phosphor layer ( 5 ) is generated, on which galvanically and / or electrolessly an adapted metal layer system is built (z. B. NiP 1 micron and Au 5th µm).