JPS61238966A - Wet chemical method for obtaining metal layer - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application: The present invention relates to a method for obtaining a metal layer wet-chemically by depositing the metal layer on a cleaned and as roughened surface of a substrate. .

Prior Art: Various and non-metallic substrate materials have been provided with metallic layers to achieve specific functional or decorative properties. Furthermore, this substrate material must be durable in a wide variety of post-processing or practical applications. In particular, a sufficiently high degree of stable adhesion between the substrate material and the metal layer is a fundamental prerequisite for practical use. This adhesion is
It must also be sufficient in the case of high mechanical loads, which may occur in particular during thermal stress due to high temperatures or during heat exchange.

In general, the adhesion strength of a metal layer to a non-metallic substrate is not high enough to be able to prevent bubble formation of the metal layer during thermal stress, as occurs, for example, in the case of soft solder brazing. .

For this reason, it is currently possible to obtain a metal layer during thermal stresses when plating insulators only by additionally expensive and uneconomical methods, such as, for example, vacuum evaporation techniques, cathode sputtering techniques or CVD techniques. This applies.

Problem to be Solved by the Invention: The problem to be solved by the invention is that, in particular, brazing with soft solder, which is customary in electrical technology, is performed on an electrically insulating substrate by a process.
having the highest possible bond strength and being thermally loadable;
The purpose of the present invention is to describe a method of the L concept to produce wet chemical plating that can be produced economically.

Means for solving the problem The object consists in depositing at least one electrically conductive gas-permeable and vapor-permeable layer as a single metal layer from at least one electrolyte solution containing essentially inorganic components; - solved by exposing this layer to at least one heat treatment in such a way that volatile components of the electrolyte embedded in the layer are removed. Advantageous embodiments and further developments can be discerned from the claims 2 to 17.

The present invention recognizes that the mechanical stress between the substrate and the metal layer is not only due to differences in thermal expansion behavior, but also to changes in the materials themselves and to gaseous precipitation between the materials. Based on. That is, when electroplating metals, more or less large amounts of hydrogen and various, often organic, electrolytes are used.
Additives are co-introduced into the metal layer. Also, electrolyte residues and/or water residues are buried during the deposition, especially on the roughened substrate. All these substances, depending on the temperature used, give rise to high gas pressures by desorption, evaporation and/or decomposition, which allow the gas to diffuse or be carried away without destroying the metal layer. This gas pressure can be reduced by separating the layer from the substrate material over a more or less large area. The better the adhesion strength, the higher the temperature used may be. A temperature as high as possible is important, especially for brazing and welding processes.

The present invention specifically produces a bubble-free wet chemical copper plating on a ceramic substrate, and the adhesion strength of the bubble-free wet chemical copper plating is determined by brazing at about 280° C. for about 20 seconds. For example, it remains retained during the process of brazing with soft solder or during the process of brazing hard solder at 400° C. for about 5 seconds.

Examples: The invention will now be explained in more detail with examples: Example 1 Aluminum oxide (AQ) having a thickness of about 0.6 mm
, O399.5%) is immersed in a sodium hydroxide melt to remove the glassy "burn-on film" by a known method, and then the ceramic substrate is soaked in deionized water using ultrasonic waves. Clean thoroughly. The spores are chemically catalyzed on the currentless metal deposit by known methods by successive treatments in a solution of tin(II) chloride, in water and in a solution of palladium chloride and a final wash in deionized water. A layer is produced on the ceramic surface. A copper-base layer approximately 0.3 microns thick is deposited onto this ceramic surface from a currently commercially available chemical copper bath. Subsequently, this layer is pre-strengthened by electroplating to approximately 2 μ of copper from an electrolyte of the following composition: Copper diphosphate 1 (10 g/f2 potassium diphosphate 280 g/f2 potassium nitrate)
15g/Q concentrated ammonia solution
2 mQ/Q deposition is carried out at a pH number of 8.7, a bath temperature of 60° C. and a current density of 2 A/dm2. This layer was washed in deionized water and then dried at 300 °C under a nitrogen atmosphere.
Heat-treat for 15 minutes. Thereafter, approximately 15μ of water is removed from the bath.
Strengthen to full thickness. This copper layer is heat treated at 400° C. in a nitrogen atmosphere for 10 minutes. This copper layer does not contain air bubbles,
Presents an impeccable appearance. After obtaining the metal strip by photoetching technique, this copper layer is approximately 0.5N/
It can be separated from the ceramic surface with a peeling force of mm.

Example 2: A ceramic substrate made of aluminum oxide is pretreated as in Example 1 and provided with a copper base layer by chemical currentless deposition. Reinforcement by electroplating to a layer thickness of approximately 15μ is carried out from an electrolyte having the following composition: copper fluoroborate 2409/Q fluoroboric acid 209/ρ boric acid
209/σ 1)) T = t,.

Additionally, finely divided aluminum oxide 59/Q, the particle size of which is less than IOμ, in particular in the range from 1μ to 5μ, is suspended in the electrolyte by vigorous stirring. Deposition is carried out at 30 °C and a current density of 5 A/d m2. The copper layer exhibits a uniform silk matte appearance and is 0.6 N/mm after thermal stressing at 4°Oμ for 20 minutes under nitrogen atmosphere.
It has a peeling force of 7 and does not contain air bubbles.

Example 3: A ceramic substrate is prepared as in Example 1 and provided with a copper base layer. Instead of the concentrated ammonia solution, a 1% hydroxide kawaram solution is added dropwise to the copper electrolyte of Example 1 until the pH value is 87. The electrolyte has a milky white color due to colloids from the base copper phosphate. The substrate was placed in this electrolyte for 60 minutes.
1 °C and 2 A, continuously at a current density of /4 m2
Reinforced to a total thickness of 5μ. The copper layer has the appearance of a silk mat, is bubble-free after thermal stressing at 400'C for 20 minutes under nitrogen atmosphere, and exhibits a peel force of 0.5 N/mm2.

Example 4: Aluminum oxide (A
120399, 5%) by immersion in a sodium hydroxide solution to remove the glassy "scorch film" in a known manner, and the ceramic substrate was thoroughly soaked in deionized water using ultrasonic waves. Wash. A spore layer catalytically acted upon in a chemically current-free metal deposition by means of known methods by successive treatments in a solution of tin(II) chloride, in water and in a palladium chloride solution and a final wash in deionized water. is produced on the ceramic surface. A copper-base layer approximately 0.2 microns thick is deposited onto this ceramic surface from a currently commercially available chemical copper bath. This copper-base layer is then coated in a conventional electroplating copper sulfate bath, currently commercially available, in which particles of graphite having a particle size of less than 10 microns and a concentration of about 15 g #2 are suspended. Reinforce to full thickness. The copper layer produced, which has a dark matte appearance, is annealed under a hydrogen atmosphere at a temperature of about 400° C. for about 10 minutes. Subsequent microscopic examination reveals no air bubbles in the copper layer.

Example 5: A ceramic substrate made of aluminum oxide was pretreated as in Example 1 and chemically current-free to a thickness of approximately 0.2μ.
A copper base layer is provided. This copper base layer was subsequently produced with the addition of a dispersion preparation containing polyacrylic esters with a concentration of approximately 10 g/& and currently available under the trade name "Acronal 4 F". from a currently commercially available electroplating copper bath in which the particles are suspended to a layer thickness of about 7 microns. The copper layer has the appearance of a wire mat and is heated at a temperature of about 400°C under a nitrogen atmosphere.
No bubbles are shown after 0 minutes of heat treatment (thermal post-treatment).

The invention is not limited to the examples described;
It can also be used in the same way in meaning. Thus, for example, instead of the A(2203-particles) mentioned above, particles of 5iOz, Si3N4 or SiC can also be embedded in the metal layer.

Claims (1)

[Claims] 1. A method for obtaining a metal layer wet-chemically by depositing the metal layer on a cleaned and as roughened surface of a substrate, in which at least one electrically conductive layer is used as the metal layer. a gas-permeable and vapor-permeable layer is deposited from at least one electrolyte containing essentially inorganic components, and this layer is subjected to at least one heat treatment for volatilization of the electrolyte embedded in the layer. A method for obtaining a metal layer wet-chemically, characterized by exposure in such a way that the sexual components are removed. 2. Depositing the metal layer as a continuous layer consisting of at least two electrically conductive gas-permeable and vapor-permeable layers, such that volatile components embedded in the layer are removed after deposition of each layer. Claim 1, which performs heat treatment
The method described in section. 3. The electrolyte contains fine inorganic particles with a melting point higher than 200K, and these particles are incorporated into the conductive layer so that it becomes gas and vapor permeable upon precipitation from the electrolyte. The method according to claim 1 or 2, embedded in 4. A method according to any one of claims 1 to 3, in which the electrically conductive layer is deposited in a layer thickness that ensures the required gas and vapor permeability. 5. Electrolytes are SO_4, PO_4, P_2O_7, CN
^-, Cl^-, BF_4^- and/or NH_2SO
5. The method according to any one of claims 1 to 4, comprising at least one anion of _3^-. 6. The method according to any one of claims 1 to 5, wherein the electrolyte contains inorganic colloidal particles having a diameter of less than 10 μm. 7. The method according to any one of claims 1 to 6, wherein the electrolyte contains inorganic colloidal particles having a diameter of less than 1 μm. 8. Process according to any one of claims 1 to 7, characterized in that the particles are generated in the electrolyte on the basis of an adjustable concentration ratio and/or on the basis of an adjustable pH value. 9. The method as claimed in claim 1, wherein the particles are deposited in the metal layer, preferably by thermal post-treatment. 10. The substrate consists essentially of a ceramic, and the metal layer deposited on the ceramic contains essentially copper, in which ceramic particles having a diameter of less than 10 μm and a concentration of about 5% are present. A method according to any one of claims 1 to 9, wherein the method is buried. 11. Suspending the particles in an electroplating bath, depositing a metal layer in which the particles are embedded from the electroplating bath, and reducing the volume of the particles embedded in the metal layer by physical-chemical post-treatment. A method according to any one of claims 1 to 10 for reducing. 12. Claims 1 to 1, in which particles having a diameter within the range of 0.1 μ to 20 μ are suspended in the plating bath.
The method described in any one of items up to item 1. 13. Particles having a diameter within the range of 0.1 μm to 20 μm are first applied on the substrate by an adhesive layer or an adhesion mediating layer, and then a plating layer is deposited on the particles by wet chemical method. The method according to any one of the ranges 1 to 12. 14. The method according to any one of claims 1 to 13, wherein the particles contain carbon and/or an inorganic component or an organic component. 15. Any of claims 1 to 14, wherein the volume of the particles is reduced by essentially selected dissolution and/or decomposition and/or sublimation during physical-chemical post-treatment. or the method described in item 1. 16. The physicochemical post-treatment essentially consists of a thermal post-treatment such that the volume of the particles is reduced by decomposition and/or evaporation and/or sublimation. The method described in any one of the preceding paragraphs. 17. A method according to claims 1 to 16, in which a redox reaction is used to reduce the volume of the particles in a physical-chemical post-treatment.