WO2005087979A2

WO2005087979A2 - A method and a device for deposition of a metal layer on a non-conducting surface of a substrate

Info

Publication number: WO2005087979A2
Application number: PCT/DK2005/000163
Authority: WO
Inventors: Thomas Bill; Lars Erup; Per MØLLER
Original assignee: Frontcoat Technologies Aps; Danmarks Tekniske Universitet
Priority date: 2004-03-11
Filing date: 2005-03-10
Publication date: 2005-09-22
Also published as: WO2005087979A3

Abstract

A method and a device for depositing a metal layer on a non-conducting surface of a substrate. (a) A liquid composition containing metal ions is directed to at least a part of the surface and (b) a reductive agent is directed to at least a part of the surface. The metal ions are reduced in situ into the metallic form in those parts onto which both (a) and (b) have been directed. The reduction reaction and the adherence to the non-conducting surface is supported by treatment with physical energy such as treatment with corona discharge, atmospheric plasma, flame treatment, microwave, infrared light and/or UV light. Selective surface treatment is obtained based on electroless plating whereby the surface is printed on with metal and reducer as ink by conventional printing such as inkjet printing and tampon printing electrodes and conducting surfaces with Cu, Ni, Au and Ag.

Description

A method and a device for deposition of a metal layer on a nonconducting surface of a substrate

Technical field The present invention relates to a method and a device for deposition of a metal layer on a non-conducting surface of a substrate.

Technical background

Electrolytic and electroless plating of electrically conductive surfaces are well known in the art. In case of non-conductive materials electroless plating normally requires a complicated pre-treatment of the surface whereby the surface is activated by a catalytic metal, such as palladium.

US5318803 (Bickford et al.) discloses a method for conditioning a surface of a dielectric substrate material for the electroless plating of a conductive metal thereon. The surface is first contacted with a catalytic metal salt or complex solution and then with a reducing agent to reduce the metal cations to zero-valent metal and with an electroless metal plating bath to deposit the metal in the zero-oxidation state on the surface. Thereafter the surface is contacted with a second catalytic metal salt or complex wherein the metal cation of the second catalytic metal undergoes ion exchange with the metal in the zero-oxidation state. Finally the surface is contacted with a second electroless metal plating bath. By this method the substrate to be metallized has to be immersed into an electroless plating bath. Thus the method cannot be used for substrates which do not withstand electroless plating baths.

JP2002047574 A (Ishikawa Kinzoku Kogyo KK) discloses an electroless plating method whereby a catalyst of mixed nickel and copper hydroxide is provided on the surface of a non-conductive object using a solution of a strong reducer. Then the object is washed in a reduction liquid having the same reducer. After this wash the ob- ject is plated in an electroless plating bath. A plating skin layer is uniformly formed on the surface of the non-conducting object. Also by this method the substrate to be metallized has to be immersed into an electroless plating bath. Thus the method cannot be used for substrates which not withstand electroless plating baths.

WO0035259 (Naundorf et al.) discloses a method for producing fine metallic con- ductor structures on an electrically non-conductive substrate. An electrically non- conductive organic heavy metal complex is applied to the substrate as a film. This film is then selectively subjected to ultraviolet laser radiation whereby heavy metal seeds are released and the area is metallized by chemical reduction. The film of organic heavy metal complexes remains unreacted in the areas which have not been exposed with ultraviolet laser radiation and must be removed before the metallization which necessitates an effective rinsing which can be problematic in case of sensitive substrates. Furthermore use of ultraviolet laser radiation may be hazardous to health.

JP2000129453 A (Inoac Corp KK) discloses metal plating of non- electro- conductive foam by spraying metal salt aqueous solution on a reducer layer where reduced metals are precipitated to form conductive layer followed by electro-plating. A reducer containing mixture of reduction material and binder is formed on a non-electro- conductive foam surface. Metal salt aqueous solution of a reducing metal is sprayed on the reducer layer and a conductive layer is formed by precipitation of reduced metal on the surface. A metal plated layer is formed by electric plating on conductive layer to form non-conducting foam having continuous pores. The process is used for metal plating of non-electro conductive foam having continuous pores. Also by this method the substrate has to be immersed into an electroless plating bath. Thus the method cannot be used for substrates which not withstand electroless plating baths.

WO9854378 (Stremsdoerfer) discloses chemical metallization of non-conducting substrates by splattering oxidising/reducing (Ox/Red) aerosol(s). The method con- sists in splattering in at least two successive splattering phases, alternating with relaxation phases by fixing the duration of the splattering phases between 0.01 and 5 s, and the duration of the relaxation phases between 0.01 and 10 s. The method is applicable to the metallization of plastics, anti-corrosion treatment, treatment for reducing coefficient of friction and electromagnetic armouring. WO9854378 does not teach selective metallization or how to metallize substrates with bad adhesion prop- erties.

WO9721849 (Cardiac) discloses a method for producing a metal coated non- conductive substrate by a) contacting a substrate with a solution of a noble metal compound in such a manner that noble metal ions are adsorbed to the surface of the substrate; b) treating the substrate with a non-contaminating reducing agent so as to reduce the surface-adsorbed noble metal ions to their elemental state; and c) coating the substrate with a metal in an electroless metal-plating bath to form a metal coated substrate. By this method the substrate to be metallized has to be immersed into an electroless plating bath. Thus the method cannot be used for substrates which not withstand electroless plating baths. Furthermore the method is not suitable for direct selective metallization.

US4965094 (Fuchs) discloses a method for forming silver coatings on ceramic filter material. The surface is first sensitized by applying thereto a solution comprising a silver ammonia complex and a solution comprising a reducing agent. This forms a thin silver coating which is then silver plated. The method is especially adapted to silver coatings on ceramic filter material and is not applicable for selective metallization or metallization of substrates with bad adhesion properties.

JP 2001 011643 A discloses a plating method for a non-conducting surface. First a catalyst containing primer coating film is formed by application of the primer material and drying. Then a solution containing silver, copper or nickel ions and a solution of a reducing agent are sprayed from separate spray nozzles forming a metallic layer capable of electroplating. The deposition of the metal layer is not taught to be direct on the non-conducting surface. Thus JP 2001 011643 A teaches first to provide the surface with a catalyst bound by means of a primer containing a polymer binder such as an acrylic, polyurethane or epoxy based binder. This treatment with a primer followed with drying make the method complicated and excludes plating of surfaces being sensitive to solvents or heat.

WO2004/068389 (CIT Ltd.; published 12 August 2004) discloses a method of forming a conductive metal region on an substrate, comprising depositing on the substrate a solution of a metal ion, and depositing on the substrate a solution of a reducing agent, such that the metal ion and reducing agent react together in a reaction solution to form a conductive metal region on the substrate. The metal ion and reduc- ing agent deposit leaves a chemical waste in the form of cations or anions. Furthermore the metal ion and the reducing agent are both used in the form of liquid solutions which each are deposited in a desired pattern for example by inkjet printing. In this way immersion techniques are avoided. To control the reaction on the substrate use is made of a catalytic activator solution, preferably deposited on the substrate followed by evaporation of the solvent before the metal ion and reducing agent are deposited. To ensure good adhesion the activator solution may include a binder for example polyvinylbutyral. Such treatment with activator solution followed by an evaporation step make the method complicated and expensive. The method can only be used on polymeric substrate and only be deposit by inkjet printing, furthermore the reaction between the metal ion and reducing agent leaves a waste on the surface which need to washed away. This method also excludes for depositing alloys and metal-like semiconductors metals like silicon. The use of inkjet printing is only suitable for planar substrate surfaces.

US 2004 01 51 014 Al (Spealαnan august 2004) discloses a method of forming an electrical circuit component using the technique of drop on demand printing to deposit droplets of deposition material, said method comprising depositing a plurality of droplets on a surface to form a patterned electronic device comprising multiple discrete portions. No special features for adhesion enhancement of metal to substrate are disclosed. Furthermore the deposited metals consist of nano-particles and metallic pastes which need to be baked with heat to be conductive. US 4,668,533 (Miller May 1987) discloses an imagewise deposition of ink onto a substrate such as a circuit board, by ink jet technology in a two step process in which the ink is employed either as an activator or as a sensitizer. Special features for enhanced adhesion are not disclosed.

US 6,754,551 (Zohar et al. June 2004) discloses a jet dispensing print system for dispensing a liquid or viscous, jettable substance as a pattern onto the surface of a printed circuit board (PCB) in an industrial manufacturing PCB production line. The patent is silent about adhesion enhancement.

JP 2,232,238 (Shingo et al. 1990) discloses a method to obtain a improvement in adhesion of printing ink or the like by subjecting a sheet of thermoplastic resin or thermoplastic elastomer containing additives to corona discharge or plasma dis- charge treatment in an inert gas atmosphere containing 5.45 vol. % hydrogen gas. Shingo does not mention metallization.

US 5,798,078 and US 6,066,286 (David 1998) discloses methods of sulfonating a polymer, by exposing sulfur dioxide and oxygen to free radical producing energy and contacting the polymer with the product of the preceding step. Desirably, the steps of exposing sulfur dioxide and oxygen to free radical producing energy and contacting the polymer with this product are performed in a reduced pressure environment. Another method of sulfonating a polymer includes contacting the polymer with sulfur dioxide and oxygen and exposing the contacted polymer to free radical producing energy. David does not mention any metallization process.

In general it is difficult to plate non-conducting substrates and often a physical and/or chemical pre-treatment of the surface is necessary. In case of sensitive substrate materials such pre-treatment may cause problems. Furthermore most plating methods require immersion of the substrates in an aggressive plating bath. Especially in case of selective plating it is desirable to avoid any aggressive exposure of those areas which are not to be plated. Furthermore the prior art methods for metallization of non-conductive materials are generally complicated and expensive and often the adhesion to the substrate is unsatisfactory.

Accordingly there is a need for a method for depositing metal on a substrate having a non-conducting surface which is less aggressive against the substrate and is cost- efficient, but still ensures an efficient adhesion between the substrate and the deposited metal.

Brief description of the invention

It has now been possible to deposit a metal layer on a non-conducting material without the necessity of activation by a complicated and/or aggressive pre-treatment of the surface to be coated and still with an excellent adhesion between the metal and a broad range of substrate materials.

Accordingly the present invention relates to a method for depositing a metal layer on a non-conducting surface of a substrate, characterized by directing onto at least a part of the surface a) a metal component which is a liquid composition including an organic or inor- ganic metal compound with the metal at a positive oxidation stage and optionally one or more adjuvants and/or additives stabilizing a metal ion solution and/or controlling the rheological and other properties of the composition, and b) a reducer component including a reductive agent being able to reduce the metal of the metal compound into the metallic form in situ on said part of the sur- face, and optionally one or more adjuvants and/or additives controlling the Theological and other properties, whereby the deposition process is supported by a treatment with physical energy.

This treatment with physical energy supports (initiates and activates) the deposition process. The treatment will additional improve the adhesion between the metal and the surface primarily by formation of chemical bonds. The present invention also provides a device for depositing a metal layer on a surface of a substrate, characterized by a) a means for directing onto at least a part of the surface a metal component which is a liquid composition including an organic or inorganic metal compound with the metal at a positive oxidation stage and optionally one or more additives stabilizing a metal ion solution and/or controlling the rheological and other properties of the composition, b) a means for directing onto at least a part of the surface a reducer component including a reductive agent being able to reduce the metal of the metal compound into the metallic form in situ on said part of the surface, and c) a means for treating the surface with physical energy.

Furthermore the present invention relates to an article having a non-conducting sur- face with a metal layer deposited on the surface obtainable by the inventive method.

The inventive method is based on a direct reduction of positive metal ions in situ whereby the metallic form is generated directly on the surface and in case of selective deposition only on the areas of the surface to be plated. An important feature is that the reduction reaction involved in the deposition as well as the interface bonding between the substrate surface and the metal layer formed is supported by one ore more treatments with physical energy.

Examples of such treatments with physical energy are a treatment with corona dis- charge, atmospheric plasma, flame treatment, microwave, infrared light and/or UN light.

The inventive treatment with physical energy can be carried out as one or more steps. Thus one step may be a pre-treatment of the non-conductive substrate prior to the treatment with the metal component. Such pre-treatment can lead to various chemical bonds between the substrate and the metal ensuring a close contact be- tween the substrate during the following reduction to the metallic form. An alternative or supplementary step of treatment with physical energy can be carried out after both the metal component and the reducer component have been directed to the substrate surface. This step supports the reduction reaction as well as possible reactions with the substrate surface increasing the adherence.

A further possibility is to carry out a treatment with physical energy simultaneously with the freatment with the reducer component according to step b).

The method gives initial fonnation of small metal clusters directly on the surface which generally ensures a good adhesion. This adhesion is further supported by one or more treatments with physical energy which besides supporting the reduction reaction also supports a possible reaction between the metal and the underlying surface material.

The extent of applicability of the invention appears from the following detailed description. It should, however, be understood that the detailed description and the specific examples are merely included to illustrate the preferred embodiments, and that various alterations and modifications within the scope of protection will be ob- vious to persons skilled in the art on the basis of the detailed description.

Detailed description of the invention

By use of the inventive method it is possible to deposit a metal on a non-conducting material without a complicated activation process and with an excellent adhesion to the underlying substrate.

The underlying principle of the inventive method is that metal in the metallic form, i.e. with oxidation stage 0, is formed in situ on the surface to be deposited by a reduction process using a reductive agent which is brought to react on the surface with an organic or inorganic metal compound with the metal at a positive oxidation stage. Thus the metal compound with the metal at a positive oxidation stage and the reduc- tive agent are brought together on the surface by contacting the metal component with the reducer component on the surface.

A further important feature is that the adhesion to the substrate as well as the reduc- tion process are supported by a physical energy supplied to the site of the reacting metal compound on the substrate surface to be plated with the metal.

The metal compound is directed onto at least a part of the surface in the form of a liquid composition if necessary also containing adjuvants and/or additives stabiliz- ing a metal ion solution and/or controlling the rheological and other properties of the composition.

As stated above the metal component is used as a liquid composition including the metal compound. The term liquid composition includes any flowable or fluid com- position. Thus the metal component may either be a dispersion or a solution of the metal compound in a solvent, generally a polar solvent, especially water. When the metal compound is insoluble in the solvent, such as metal hydroxides in water, the metal compound may be present as a sufficiently fine dispersion. In case of soluble metal compounds, such as salts, the metal part will be present as metal ions.

Examples of additives controlling the rheological and other properties of the liquid composition containing the metal compound are any conventional additive known in the art for adjusting the rheological and other properties of liquid compositions provided they do not react in a non desired way with other ingredients of the composi- tions.

A variety of materials, e.g. polymers and thickening agents can be employed in the metal component and/or in the reducer component to provide high or low viscosity solutions with enhanced properties. Examples of additives for a component to be printed on a substrate includes - but are not limited to - gelatin, Arabic gum, hy- droxyethyl starch, cellulose ethers, polyvinyl alcohol, polyvinylpyrrolidone, peptones, polyamides and polyacrylamides.

Further additives having influence on the rheological and other properties are conventional surfactants. Examples of sufactants are

- anionic surfactants such as alkyl sulfates (e.g. lauryl sulfates such as sodium lauryl sulfate), ether sulfates (e.g. ammonium or sodium laureth sulfate) phosphate esters, sulfonates (e.g. alpha olefin sulfonates, dodecyl benzene sulfonate, isopropylamine dodecyl benzene sulfonate, naphthalene sulfonate, sulfo succinates (DOS)), taurates and isethionates;

- amphoteric surfactants such as acetates (e.g. mono- or di-sodium alkylampho- mono- or di-acetates), propionates (e.g. mono- or di-sodium alkylampho-mono- or di-propionate), betaines, and sultaines,

- cationic surfactants such as ether amines and their acetate salts, ethoxylated amines, lactates, amine oxides, cefriumonium chloride, amidoamines, imidazolines, esteramines, acid thickeners, corrosion inhibitors, wax emulsions, quats, aroyl and alkyl ammonium chlorides, and emulsifiers, and

- nonionic surfactants such as ethoxylates and copolymers (e.g. linear and branched alcohol ethoxylates, alkyl phenol ethoxylates, and EO/PO equivalents), alkyl esters, sorbitan esters, alkoxylates, alkoxylate ethers, alkanolamides, lanolin derivatives, fatty acids, fatty alcohols, waxes and proteins (e.g. gelatin and hydrolized collagen).

Examples of further additives controlling the rheological and other properties of the liquid composition are antistatic agents, humectants, sarcosines, carcosinates, su- crose emulsifiers and pentaerythrityl stearates.

In an embodiment the reducer component can be in a liquid form whereby the reductive agent may be directed onto at least a part of the surface as a solid dissolved in a liquid, such as water, or as a liquid per se, and may, if appropriate, be mixed with adjuvants and/or additives controlling the rheological and other properties. Examples of additives controlling the rheological and other properties of the reductive agent in a liquid form or as a liquid composition will be the same as those used in the liquid composition containing the metal compound.

According to a preferred embodiment the reducer component is a reductive flame or gas which may be activated by heat or plasma activation. Such flame or gas is directed on the site of the metal component already deposited on the surface to be plated. An important advantage of this embodiment is that the by products formed by the reduction reaction as well as possible excess of the reducer are removed as gas or vapour leaving no residue on the surface.

The metal ion in the metal component may be in a stabilized form. Such stabilization may be by chelation with a hydroxy acid such as citric acid, malic acid, lactic acid and hydroxyacetic acid. Thus Ni ions can be chelated as the hexaquonickel ion with the hydroxyacetate anion:

[NlfHjOJep ⁺ HOCHaCOO^' + 2HjO

For plating with Au or Ag conventional stabilizers for electroless Au or Ag plating can be used, such as lead nitrate.

The stabilized metal ion can be reduced with a flame or hydrogen gas or plasma activated hydrogen gas as the reducer component. The reduction is supported by the treatment with physical energy, which treatment may include one or more steps prior to, simultaneous with and/or after the direction of the reducer component onto the surface. In one embodiment of the inventive method the substrate is heated with microwaves after the metal compound and the reductive agent have been brought to react in situ on the surface. Such after-treatment with microwaves can support (initiate and/or activate) reduction of positive metal ions into the metallic form. Depending on the na- ture of the substrate material, the heat from the microwaves may further introduce a chemical bonding, a mechanical bonding or a combination of both between the substrate and the reduced metal.

In principle this subsequent treatment (after-treatment) by heating could be carried out by any means for heating. However, in case the substrate material is heat sensitive, the use of microwaves has turned out to be advantageous because the substrate material is only heated in a minor degree and only in the areas adjacent to the reaction medium. To ensure a suitable after-treatment with microwaves, the reaction medium, that is the mixture of the metal and reducer components should include a polar material such as a polar solvent exemplified by water.

Thus by using microwaves the heat energy is transferred selectively to small metal clusters whereby they melt down into the surface or react chemically with the surface. On the other hand areas which are not to be plated will remain without substan- tial increase of temperature in spite of the heating with microwaves.

The frequency range of microwaves may differ from different authors but is generally considered to be the range between infrared light and radio waves. For use by the present invention any wave frequency being able to heat the reaction mixture on the substrate without excessive heating of parts of the subject in some distance from the reaction mixture will in principle be usable. In the present description and claims the term "microwaves" is intended to include all such usable waves. Typically the microwaves have a frequency of 0.1 to 3000 GHz, preferably 0.3 to 300 and more preferred 0.5 to 30 GHz. In a preferred embodiment the inventive method is especially useful for the preparation of a metal deposition in a pre-selected pattern. Thus such patterns, such as electrical conducts on a non-conductive substrate, can be obtained by directing the metal component and/or the reducer component selectively on the non-conducting surface in a pre-selected pattern. Specially preferred for this embodiment is the use of a flame or gas as the reducer component as no residues is left neither on the sites wherein the metal is disposed nor on the sites to be left free of the metal deposit. It is also possible to pre-freat the surface by directing a catalytic activator component selectively in a desired pattern. Such selective direction of the activator component, the metal component and/or the reducer component may be carried out by means of a conventional printing technique or by means of one or more syringes. It is an important advantage that the selective patterns are obtainable without complicated masking.

Accordingly useful means for directing the metal component and/or the reducer component to the surface to be plated can be syringes which are especially useful when the access to the surface is difficult, such as on the inner wall of a channel. In case a larger area is to be plated the directing means can be spray nozzles (spray guns).

A cost-efficient technique for directing the metal component and/or the reducer component to the surface to be plated is based on conventional printing technique. Examples of useful printing techniques are digital printing such as inkjet printing, screen-printing (serigraphic printing), tampon printing, gravure printing (intaglio printing), letterpress printing, relief printing and plain printing.

Use of a conventional printing technique for the inventive method is very advantageous because such printing technique can be carried out in a very cost-efficient way. Thus the printing machine can be arranged at the end of a process line to met- allize the blank materials. For example a polymer blank leaving an injection mould- ing machine may be directed further to a printing machine where it is finished by the inventive plating method.

In a further embodiment of the invention the non-conducting surface of the substrate is activated with a catalytic activator. Thus, before applying the metal component and the reducer component on the raw substrate, a catalyst component can be applied. Also this can be done in a pre-selected pattern by conventional printing techniques. When the printed catalyst area reacts with the metal component and the reducer component, a metal structure grows where the activating seed material has been printed. Typically catalyst components could be Pd, Sn, Ni, Ru, Pt and Rh.

The inventive method can be used by a direct metal plating process where the desired metal layer is formed in situ by the reaction between the metal ions in the metal component and the reductive agent in the reducer component. It is also possi- ble to use the method for direct plating of a minor portion of a metal to form clusters thereof. After such treatment the previously non-conducting surface can be plated with the same or another metal by a conventional electroless or electrolytic plating technique.

Thus in the present specification and claims the term "metal" as used in connection with the metal component includes the main metal to be plated as well as metal being disposed in a minor amount to be used as a seed metal or catalytic activator metal to be used as a pre-treatment before a conventional electroless and/or electrolytic plating process. Furthermore, it is possible to deposit a semiconductor material such as silicon by the inventive method. Accordingly the term "metal" shall also include silicon and similar semiconductors in the present specification and claims.

In the present specification a number of embodiments are disclosed wherein the metal compound is dissolved and the metal part is present as metal ions. For practi- cal reasons the metal group of the metal compound with the metal at a positive oxidation stage will in some cases generally be termed "the metal ion". However it should be noted that the metal compound may be any compound containing a metal at a positive oxidation stage and which can be reduced to the metallic form with a suitable reductive agent. Thus further to soluble metal compounds forming metal ions in the metal component it is also possible to use insoluble or lesser soluble dis- persed metal compounds in the metal component.

Examples of non-conducting materials which have been metallized by means of the inventive method using the inkjet or tampon printing techniques are polymers such as acrylnifrile/butadiene/styrene-terpolymer (ABS), PC/ABS (polycarbonate/ ABS), polyacrylamide (PAA), polybutylene terephthalate (PBT) and polyethylene (PE), and other materials such as Al₂O₃, piezoelectric ceramics (PZT) and fibre-reinforced epoxy.

The inventive method based on a conventional printing process ensures a homoge- nous, pinhole-free and conducting surface layer, with good adhesion properties.

The adhesion of the metal layer deposited according to the invention has been tested by the ASTM B533-85(2004) Standard Test Method for Peel Strength of Metal Electroplated Plastics. This test is a quantitative determination of the adhesion of a galvanic metallization with the thickness 40 ± 4 μm on plastics. The metal is pulled off the plastic surface at a speed of 25 ± 3 mm/min and the necessary force is recorded. The metal surface having the dimensions 25 mm wide and 75 mm long. Values between 0,6-0,8 N/mm were measured by this test method, between selective metallized Cu and ABS polymer. Cf. example 1.

A very useful and simple printing technique to be used with the inventive method is tampon printing, which is also termed pad printing. By tampon printing a transfer pad or tampon picks up the image from an inked cliche and transfers it to the surface to be printed. A special advantage of the tampon printing is that prints can be made on complicated non-planar surfaces such as in recesses and on spherical surfaces. Examples of tampon printing are "open inkwell pad printing", "sealed ink cup pad printing" and "rotary gravure pad printing". A contemplated application of rotary gravure pad printing for carrying out the inventive method is the use of two cliche drums transferring the metal and reducer component, respectively, to the same trans- fer pad roller.

In an embodiment the inventive method is carried out by directing the metal component and the reducer component onto at least a part of the surface - simultaneously or within a short period of time - where after the substrate optionally is heated with microwaves.

The term "simultaneously or within a short period of time" indicates in the present description and claims that the two materials are directed to the surface in one operational step such as by moving two deposition nozzles in succession over the surface.

Alternatively, the surface to be provided with a metal deposit can first be covered by a coherent film formed by one of the reactants where after the other reactant is directed selectively in the desired pattern whereby the metal deposit only will be formed in the areas provided with both reactants.

Accordingly the method is either carried out by directing the metal component onto at least a part of the surface to form a coherent film of metal ions on the surface, followed by directing the reducer component selectively in a pre-selected pattern on the surface; or by directing the reducer component onto at least a part of the surface to form a coherent film thereof, followed by directing the metal component selectively in a pre-selected pattern on the surface.

In a further embodiment different patterns of deposits of different metals are available by directing a number of separate metal components each independently includ- ing a metal compound having the metal at a positive oxidation stage independently in patterns on the surface. Thus a first metal component containing metal ions of a first metal may be directed in a first pattern followed by a second metal component containing metal ions of a second metal in a second pattern and then a common reducer component is directed to the surface. The common reducer component may be directed to the surface in a combined pattern covering both the first and the second patterns or to the entire surface in which case non-reacted reductive agent is removed after the reduction. In the latter case the reducer component is preferably a reductive gas. If necessary, two different reductive agents are used between the deposition of the first and the second metal ion composition or if possible after the deposition of both.

A still further embodiment includes the steps of: step 1) directing the metal component and the reducer component onto at least a part of the surface, and step 2) coating at least a part of the surface with an insulating material. One ore more treatments with physical energy will be carried out according to the invention, for example as a following step 3) of heating the substrate with microwaves.

In this way it is possible to deposit electrical conducts in a desired pattern surrounded by a deposit of an insulating or non- conductive material, for example a polymer material. By a further development the steps (1) and (2) including appropri- ate treatment or treatments with physical energy can be repeated one or more times using the same or different patterns. This permits the preparation of a three dimensional article having a desired three dimensional pattern of electrical conducts embedded in an insulating material.

The present invention also relates to a device for depositing a metal layer on a nonconducting surface of a substrate. Such device has a) a means for directing a first component onto at least a part of the surface, b) a means for directing a second component onto at least a part of the surface, and c) a means for treatment with physical energy. This device is useable for carrying out the inventive method for depositing a metal layer on a non-conducting substrate but also for deposition of metal layers on electrically conducting substrates as well as semiconductors.

The means b) and c) can be combined to a means directing both a reducer component and physical energy onto at least a part of the surface.

In a particular embodiment the inventive device further comprises a means for directing a further component forming a layer of a non-conducting material onto at least a part of the surface.

Examples of the directing means are the above mentioned syringes, spray nozzles and conventional printing means for the first component which is always in the form of a liquid composition such as a solution or dispersion having suitable rheological and other physical and/or chemical properties depending on the direction method used.

The direction means for the second component may be of the same type as that for the first component when the second component is in a similar liquid state. How- ever, the second component may in some preferred embodiments be in a gaseous state in which case the direction means may be a shielded chamber, an oven or another device for the treatment of a surface with a gas.

Also in case of a liquid second component (the reducer component), more compli- cated printing means will not be necessary even in case of metallization in a selective pattern if the second component is easy to remove from the non reacted (non metallized) areas without damage of the substrate.

Combinations of the organic or inorganic metal compound to be reduced in the metal component and the reductive agent in the reducer component should be selected to ensure that the metal ion (or the metal being at a positive oxidation stage) will be reduced. Thus the equilibrium potential of the metal ion must be below the equilibrium potential of the reducing agent in the Pourbaix diagram (Potential-pH diagram) as exemplified in Fig. 10 showing the Pourbaix diagram for silver (Ag) and formaldehyde (dot line) as the reductive agent. Silver is a very noble metal and the potential of silver in the Pourbaix diagram shows that it is thermodynamically possible to use formaldehyde as reducing agent in electroless silver plating. However, it should be noted that the Pourbaix diagram is purely a thermodynamically consideration and does not reveal information concerning reaction kinetics. The diagram doesn't tell how fast the reaction is. In case the reaction velocity is low, the re- action can preferably be speeded up by a pre-treatment with physical energy.

For details on the Pourbaix diagram reference can be made to G. O. Mallory & J. B. Hajdu, Electroless Plating: fundamental and applications, ISBN 0-936569-07-7 and Marcel Pourbaix, Atlas of Electrochemical Equilibria, 1974.

Examples of suitable combinations of the organic or inorganic metal compound to be reduced in the first component and the reductive agent are the metal ion providing compounds: silver nitrate, nickel sulphate or copper sulphate, combined with one of the reducing agents: formaldehyde (CH₂O), glucose (C₆H₁₂O₆), hydrazine sulfate or dimethylaminobenzaldehyd (DMAB; Ehrlich's Reagent).

A suitable reductive agent is hydrogen, which can be either used as plasma activated hydrogen or as non-plasma-activated hydrogen for the reduction of metal ions. An example of reduction with non-plasma- activated hydrogen is an embodiment where gold is printed as an AuCl₃ containing composition on a ceramic substrate where after the substrate is treated in a hydrogen atmosphere for example in an oven. Preferred conditions are a hydrogen pressure of one atmosphere and a temperature of 180 - 250 °C. The reaction is: 2 AuCl₃ + 3 H₂ = 2 Au + 6 HC1 or more correct as the AuCl₃ is dissolved as AuCl₄ ^~:

2 AuCl₄ ^~ + 3 H₂ ± 2 Au + 6 HC1+ 2 CF

An example of plasma activated hydrogen as a reductive agent is the reduction of nickel chloride to nickel metal:

NiCl₂ + 2 H* = Ni + 2 HCl * activated

Treatment with plasma activated hydrogen may be carried out on the basis of the technique disclosed in US patent application publication No. US 2001/0001184 Al (Dommann et al.) wherein surfaces are subjected to a plasma discharge in an atmosphere containing hydrogen.

Use of hydrogen or plasma activated hydrogen as the reducer is advantageous when a deposit is to be made in a pre-selected pattern. In that case only the first component including the metal compound is to be directed to the surface in the desired pattern, and then the entire surface of the substrate can be treated with the reducer in a chamber or oven causing the reducer to react with the metal ion of the metal compound and doing no harm to the areas without the metal ion. In the same way any other reducer which can easily be removed from the metal ion free areas without any damage to the substrate can be directed to the entire surface in a non specific pattern. This will of course simplify the selective metallization in a desired pattern.

Plasma activated hydrogen can also be generated by a unit - which can be hold by hand — and produces atmospheric plasma. This unit can be a PlasmaPen available from TePla America, Corona, CA 92879, USA. Further units having nozzle diameters of 12 mm or 70 mm are available from JENOPTIK Automatisierungstechnik GmbH, D-07745 Jena, Germany. The term "atmospheric plasma" is used conventionally in the art for plasma at atmospheric pressure to distinguish it from vacuum plasma. Atmospheric plasma can often be more or less shielded form the surroundings but as an important advantage it is not necessary to make use of an air tight enclosure.

Such non selective treatment with the reducer is especially advantageous in an embodiment using two or more different metals. An example is the deposition of a first noble metal in a first pattern followed by a second noble metal in another pattern and then treatment of the entire surface with the reducer. An example is the prepara- tion of catalytic ceramic materials having multiple dots of Pd and Au in the order of 1 μm in diameter. Another example is the preparation of a biologically inhibiting material as disclosed in the PCT application PCT DK 03/00790 (Møller, Jensen and Hubert) having a surface with separated areas of anode material and cathode material where the distance between any point on the active surface and both the adjacent cathode material and the adjacent anode material does not exceed 200 μm and typically varies between 0.4 μm and 3 μm, where both the anode material and the cathode material have a positive galvanic potential, and where the potential of the cathode material is higher than the potential of the anode material.

The inventive method is also usable for the preparation of an EMI shield (Elecfro Magnetic Interference shield). EMI shields are used to shield against ordinary electromagnetic interference and are normally made of a copper, nickel or silver.

The invention also relates to an article obtainable by the inventive method. Useful examples of the inventive article are articles in a form selected among an electrode pattern printed on a polymer surface, such as of PC/ ABS or fibre reinforced epoxy; a three dimensional contact pattern imbedded in a non-conductive material; an electrode pattern printed on a ceramic surface such as of Al₂O₃ or PZT; a printed pattern consisting of more metals, such as Cu, Pt and Au, foπning a multi-metal catalyst on a ceramic surface; an electrode pattern printed on cellulose fibres, such as paper; an electrode pattern printed on a conductive metal, such as stainless steel or carbon fi- bres; an electrode pattern printed on Si, Al semiconductors, such as for applications as capacitors, waveguides, field effect transistors and other MEMS applications; and a printed pattern of metals, such as Pd and Au, on a conducting surface forming a biological inhibiting surface.

In a preferred embodiment the substrate is - subsequent to the deposition of a catalytic activator component or a metal to be deposited on the non-conducting surface - treated with a physical form of energy defined as corona discharge, atmospheric plasma, flame treatment, microwave, infrared light or UN light. Such treatment can improve the adhesion and support the bonding between the catalytic activator or the metal and the non-conducting surface. The treatment can also support, initiate and/or activate a chemical reaction preferably a chemical reduction of the metal to be deposited. The reduction of the metal can be released by a reducer component in the form of a solid reductive agent, a solution of a reductive agent or a reductive gas.

In some embodiments the substrate is treated with physical energy before the deposition of the metal component. Such energy treatment may be the only energy treatment but preferably such energy treatment is a supplementary energy treatment. To improve the adhesion of the metal to the substrate the treatment with physical en- ergy before the deposition of the metal component can be carried out together with an active agent, for example an oxidizing or reducing agent.

To achieve a higher adhesion between the metal and substrate the energy transmitting process can optionally be performed in a protecting and/or a reactive gas to form acid or alkaline groups. The gas is preferably at about atmospheric pressure. The conditions used depends on the type of chemical bond desired between the metal and the non conducting substrate.

By using a SO₂ gas, SO₃ gas, SO₂ containing gas, a sulfonic acid, or sodiumhydro- gensulfite as a reactive agent it is possible to form -SO₃H groups on the surface.

These sulfonic acid groups can act as adhesion promoters based on an ion exchange effect. By using other gases in the physical treatment step, carboxyl acid groups can be developed by using: O₂(g), CO₂(g), air, H₂O +ozone and other sources of oxygen.

The adhesion between the metal and the substrate can be achieved by forming inter- facial forces which may consist of valence forces or interlocking action or both. The mechanism for establishing such adhesion of the metal layer to the substrate depends on the energy transmitting process, the present gas, and the metal compound in question.

The valence forces are caused by chemical interaction between molecules and can be classified as ionic bonds, covalent bonds or weaker bonds such as hydrogen bonds. Ionic and hydrogen bonds are the most common types of chemical bonds in the present case.

By repeating the energy transmitting process such as a corona or flame treatment after the deposition of the metal ions or the reaction mixture it is possible to establish stronger bonds.

Using a freatment with corona or atmospheric plasma it is possible to decompose PdCl₂:

PdCl₂ = Pd + Cl₂ at l200 °C

Using an atmospheric plasma containing hydrogen it is possible to reduce PdCl₂:

PdCl₂ + H₂ = Pd + 2HC1

Alternatives to PdCl₂ are Pd(NH₃)₄Cl₂, Pd(NO₂)₄ ^"2 or Pd(CH₃COO)₂ The adhesion of the Pd clusters can be improved by mixing the palladium compound with an adhesion promoter such as a manganese or iron compound for formation of carbides or oxides in the surface.

By treating the surface with KMn0 a thin layer of MnO₂ is formed - Thereafter the Mn0₂ is reduced by a hydrogen containing corona gas at atmospheric pressure

2H₂(g) + MnO₂ = Mn + 2H₂O(l)

(g) = gas, (1) = liquid.

By further treating the surface in an inert atmosphere the Mn forms carbides with the carbon in the polymer illustrated by CH₄ 7Mn + 3 CH₄(g) = Mn₇C₃ + 6H₂(g)

Other carbide building metals such as iron can similarly react with the carboxylic group. 6Fe + CH₃COOH = 2Fe₃C + 2H₂O

In both cases the use of the Pd compound mixed with the metal (Mn or Fe) reacting chemically on the surface can provide a good basis for plating of electroless copper or electroless nickel on the surface.

Using a corona or atmospheric plasma containing hydrogen it is also possible to reduce NiCl₂ directly by hydrogen.

NiCl₂ + H₂(g) = Ni + 2HC1 at 430 °C

Or perhaps by formation of activated hydrogen: NiCl₂ + 2H* = Ni + 2HCl 2H* is a very strong reducing agent.

Under similar conditions Ni(CH₃COO)₂ is reduced directly with hydrogen:

Ni(CH₃COO)₂ + H₂(g) = Ni + 2CH₃COOH at 200 °C

The various chemical reactions between metal compounds and polymeric substrates appear to be important for the surprisingly good adhesion obtained by the present invention. Thus it is believed that formation of carbides by reaction between metal and polymeric substrates improve the adhesion significantly. More generally, primarily chemical bonds between the deposited metal, carbon, oxygen, nitrogen or perhaps other atoms will be formed on the polymer surface. The bond can be increased over time or by a moderate heat treatment.

In some cases it is assumed that strong bond between carbide, nitride or oxide forming metals and the respective groups takes place under the corona discharge treatment in a suitable gas. Examples of relevant carbides are Fe₃C, Ni₃C and Mn₇C₃.

By treating a polymer surface with an energy transmitting process a lot of chemical reactions can take place.

Use of a corona in an O₂ containing gas will reduce a gold tetrachloride ion (tetra- chloroaurate(III)) to metallic gold:

4AuCl₄- + 2H⁺ + O₂ = 4Au + 2OH^" + 8C1₂

Using a reducing gas in an atmospheric plasma or in a flame treatment it is possible to reduce copper ions and copper oxides on a non-conducting surface.

Cu⁺² + H₂ = Cu + 2H⁺ CuO + CH₄ = Cu + CO + 2H₂ from 180 °C

Cu(OH)₂ + H₂(g) = Cu + 2H₂O

Using microwaves together with a solution of nickel ions in contact with an reducing agent on a ABS polymer surface will as the first reaction step cause a chemical reduction of nickel followed by a new reaction stimulating the adhesion of nickel to chemical groups containing -COOH.

The reaction between nickel and the carboxylic group is here illusfrated by acetic acid. The type of reaction may be:

6Ni + CH₃COOH = 2Ni₃C + 2H₂O at 330°C

As appears from the above the various reactions are supported by one or more treatments with physical energy. It further appears that such treatments may be carried out before, simultaneously with and/or after the treatments with the metal component and/or the reducer component.

In a preferred embodiment the inventive method may be used for the preparation of a printed circuit board of two or more layers from a non-conducting subsfrate having a first side A and an opposite second side B. This embodiment includes the steps of: step 1) drilling one ore more holes through the subsfrate from side A to side B, step 2) a first corona treatment of side A with a reducing or oxidizing gas, step 3) printing side A with a catalyst material in pre-selected pattern, step 4) a second corona treatment of side A with a reducing gas, step 5) turning the substrate, step 6) a first corona freatment of side B with a reducing or oxidizing gas, step 7) printing side B with a catalyst material in pre-selected pattern, step 8) a second corona freatment of side B with a reducing gas, step 9) immersing the substrate in an electroless Cu plating bath step 10) immersing the substrate in an electroplating bath to obtain a layer thickness of 15 - 40 μm, typically approximately 30μm, and through hole plating.

By use of this embodiment of the inventive method all masking, etching, CND/PND and photolithography process steps are eliminated. It can be utilized on rigid substrates, flexible substrates and combinations thereof and for 3D MID.

Useful examples of the inventive article are articles in a form selected among printed circuit boards (PCBs), flexible PCBs, rigid-flexible PCBs, polyimide articles, epoxy articles, three dimensional molded interconnected devices (3D MID), resistors (i.e printed conductive tracks, combined with isolating layers), capacitors (printed conductive tracks, with an isolating layer in between), diodes, transistors, inductors (a printed conductive track printed in the form of a spiral having centre co- incident with contact and an end), sensor devices (for mechanical or chemical sen- soring e.g. flexible plastic sheet with printed metal layers), solar cells (consisting of semiconductor material, insulating materials and conductive materials printed in a pattern), displays (pixel display made of light emitting materials printed on a conductive pattern in dots), lenses (printed multiple layers of conductive printed mate- rial and modified polymer), batteries (a printed conductive metallic negative electrode, a printed electrolyte and a printed metallic positive electrode), quantum dots (formed in an array enabling logic gates), electrical and optical cables (conductive lines printed on flexible substrates), planar flat panel displays, and selective area doping materials (different conductive and nonconductive materials with different properties printed in specific patterns).

According to a preferred embodiment the inventive device for manufacturing of planar or flexible PCB articles includes of the following stations, a) a hole drilling machine and cleaning means, b) a 2D corona machine with supply of reducing or oxidizing gas, c) a means for direct printing of catalyst material in pre selected pattern by use of ink-jet printing, d) a 2D corona machine with supply of reducing gas, e) means for direct printing of alignment marks and legend with UN-curable ink by use of ink-j et printing, f) means for UN-curing of ink by UN light source, g) an electroless Cu plating bath, h) an air knife and a rinsing station, i) an electroplating bath to obtain a layer thickness of 15 - 40 μm, typically ap- proximately 30μm, and through hole plating, j) an air knife and a rinsing station, k) a means for drying and heating, 1) a means for solder mask printing.

Other equipments required may be conveyors and automated handling equipment for transporting the PCB from each station to next one. By the use of this device the Cu lamination onto the PCB substrate is eliminated. In stead of a hole drilling machine a CO₂ laser can be used for making holes. Hole drilling machines, CO₂ lasers, legend and solder mask printer is prior art known to the skilled person.

According to a further preferred embodiment the inventive device for manufacturing of three dimensional molded interconnected devices (3D MID) includes of the following stations, a) a hole drilling machine and cleaning means, b) a 3D corona machine with supply of reducing or oxidizing gas, c) a means for direct printing of catalyst material in pre selected pattern by use of pad printing or robot handled ink-jet printer, d) a 3D corona machine with supply of reducing gas, e) means for direct printing of alignment marks and legend with UN-curable ink by use of pad printing or robot handled ink-jet printer, f) means for UN-curing of ink by UN light source, g) an electroless Cu plating bath, h) an air knife and a rinsing station, i) an electroplating bath to obtain a layer thickness of 15 - 40 μm, typically approximately 30μm, and through hole plating, j) an air knife and a rinsing station, k) a means for drying and heating,

1) a means for solder mask printing.

Other equipment required may include conveyors and automated handling equip- ment for fransporting the 3D MID from each station to next one. By the use of this device the use of masks, PND, laser ablation and expensive fillers in the polymer is eliminated.

2D and 3D corona machines are available from NETAPHOΝE A/S, DK-6000 Kold- ing, Denmark .

In connection with the inventive method one or more useful steps can involve further directing onto at least a part of the surface a component selected from conductive polymers, pastes containing nano-metal particles, sol-gel compounds, semicon- ductors, silane and/or polysilane compounds, organo-metallics and/or metallo organ- ics, electrolytes and/or ceramic pastes.

Brief Description of the Drawings

Fig. 1 is a schematic side view illustrating the dispensation of a first metal composi- tion containing metal ions and a second reducer composition containing a reductive agent from two print heads to a subsfrate based on the inkjet printing technique,

Fig. 2 is a top view of the two print heads shown in Fig. 1,

Fig. 3 is a schematic side view illustrating the treatment of non-conductive substrate according to a preferred embodiment of the inventive method. Fig. 4 is a schematic side view illustrating another preferred embodiment including a first corona treatment with an oxidizing or reducing gas, dispensation of a metal component from a print head by inkjet printing and a second corona treatment with a reducing gas.

Fig. 5 is a schematic side view illustrating the treatment of non-conductive substrate according to a preferred embodiment of the inventive method followed by conventional electroless plating and high-speed electroplating.

Fig. 6 - 9 show the result of a peel test on a metal layer deposited according to the invention.

Fig. 10 is a Pourbaix diagram (potential-pH diagram) for silver (Ag) and formalde- hyde (dot line),

Fig. 11 shows schematically a multi-metal catalyst of Ag, Au and Pt,

Figs. 12 - 13 show schematically two steps of the preparation of a three dimensional article having a desired three dimensional pattern of electrical conducts embedded in an insulating material,

Figs. 14 a and b show a PC/ ABS substrate with a copper pattern obtained by tampon print technique,

Fig. 15 shows a fibre reinforced epoxy substrate with a nickel pattern obtained by inkjet print technique, and

Fig. 16 shows an aluminiumoxide substrate with a nickel pattern obtained by inkjet print technique. The principle of the present method is further illustrated below with reference to an embodiment based on an inkjet printing technique.

Referring to Fig. 1 and 2 a first print head 1 is supplied from a not shown source or reservoir with a first metal composition 2 containing a metal compound with the metal at a positive oxidation stage, and a second print head 3 is supplied from a not shown source or reservoir with a second reducer composition 4 containing or consisting of a reductive agent.

Fig. 1 is a side view of the two print heads 1 and 3 during a printing process. The print heads are moved in succession in the direction shown with an arrow 5 over a substrate 6, which has a non-conducting surface to be plated by the inventive method. As shown in Fig. 2 the first print head 1 is provided with a number of nozzles 7 and similarly the second print head 3 is provided with a number of nozzles 8. Each set of nozzles 7 and 8 are equidistantly distributed perpendicular with the moving direction 5.

Each one of the nozzles in the two sets of nozzles 7 and 8 is provided with a micro pump individually controlled over the time to dispense droplets of the first and sec- ond compositions, respectively, in a pre-selected pattern on the substrate 6. In this way spots 9 of the compositions 2 and 4, respectively are printed on the substrate 6.

During the printing the print heads move synchronously in the direction of the arrow 5 and print the two compositions 2 and 4 within a short period of time whereby the two compositions are mixed on the surface of the substrate 6.

This creates a chemical reaction were metal ions (oxidation stage 1; Me⁺ (liquid)) from the first metal composition 2 are reduced to the metallic form (oxidation stage 0; Me⁰ (solid)). In this way a solid metal layer is formed on the surface of the sub- sfrate. The quality of the formed layer depends on several factors e.g. composition, concentration, spreading on the surface, viscosity, density and surface tension of the two compositions. The two compositions can be modified to adjust the desired properties by means of conventional adjuvants and/or additives. If the surface is catalytic, this also affects the formed layer because the catalysis will support the reaction.

As shown in Fig. 3 a substrate 5 of a non-conducting material is moved in the direction shown with an arrow 7 under a number of freatment stations: A corona treatment with atmospheric plasma 1; deposition of metal ions for example by inkjet printing 2; treatment with a reducer component to reduce the metal ions into the me- tallic form 3; a further corona treatment with an atmospheric gas plasma of e.g. Ar/H or He 4; and further treatments such as electroless plating and/or electrochemical plating on one or more plating baths 6.

Fig. 4 shows a principle according to a preferred embodiment using a first corona freatment 51 with an oxidizing or reducing gas before the deposition of the metal component exemplified as a deposition by inkjet printing 52. Then follows a second corona freatment 53 with a reducing gas. The substrate (not shown) is moved in the direction shown with an arrow 54 supported by a conveyor belt 55.

Fig. 5 shows a plant 56 for incorporating the inventive treatments shown in Fig. 4 and conventional after treatment of electroless plating and electrolytic plating. The subsfrate (not shown) is moved in the direction shown with an arrow 54 supported by a conveyor belt 55. In a typical embodiment the process includes successively a cleaning 57 in 5 seconds, a first corona freatment 51 in 5 - 20 seconds, deposition of the metal component by inkjet printing 52 in 15 seconds, a second corona treatment 53 with a reducing gas in 5 - 20 seconds, a conventional electroless plating 58 in 20 - 40 seconds, a rinse 59 in 1 - 5 seconds, a high-speed electrolytic plating 60 in 120 seconds providing a metal layer of about 20 μm and finally a rinse 61 and drying 62 in 20 - 180 seconds. Thus a total process time of 121 - 335 seconds (2 - 6 minutes) is possible. Figs. 6 - 9 show results from peel tests. The figures, especially Fig. 9, show clearly a roughness of the polymer surface after the peel test. This indicates a strong adhesion between metal and polymer.

Figs. 12 and 13 show the preparation of a three dimensional article having a three dimensional pattern of electrical conducts embedded in an insulating material. The two print heads 1 and 3 are similar to those in Figs. 1 and 2. In succession after these print heads comes a further print head 10 having a number of nozzles dispensing a non-conduction material such as a polymer material. After this comes a further de- vice 11 which in case of a polymer is delivered from the print head 10 can be a source of UN light causing polymerisation (hardening) of the polymer material. A microwave gun or another source of physical energy can be provided (not shown) to support the metallization.

The print heads 1, 3, 10 and the device 11 are moved over the substrate 6 in the direction of the arrow 5 by a first movement delivering a first layer 15, which in the cross sections shown is a metal layer 12. Thereafter in a second movement a second layer 16 is delivered. As shown on Fig. 12 the layer 16 has small metal spots 14 and the remaining layer is a non-conducting material 13. Fig. 13 shows the situation af- ter eight movements for forming eight layers 15 - 22 in the desired three dimensional pattern of metal imbedded in the non-conducting material. The metal in this pattern can be used as conducts. Thus the spots 14 in the layer 16 will serve as an elecfrical contact between the metal layers 15 and 17. This embodiment of the inventive method has a number of possible applications. Examples are the conducts in an electrical device such as the conducts and/or the antenna of a mobile telephone and polymer toy bricks having an integrated circuit.

The print head 10 may alternatively provide a ceramic forming material. Thus it may deliver a liquid ceramic slurry which may be sintered by microwaves. In this way the microwaves may simultaneously both sinter the ceramic and support the reduc- tion. Furthermore interaction between the metal and the ceramic may support the adhesion of the metal to the ceramic.

The embodiment shown in Figs. 12 and 13 can be modified according to the princi- pie shown in Fig. 4 by use of a first corona treatment with an oxidizing or reducing gas before the deposition of the metal component by inkjet printing, which then is followed by a second corona treatment 53 with a reducing gas. Alternatively to the movement of the different treatment devices, such as print heads, corona freatment devices and the device 11, it is possible and often preferred that these devices are stationary whereas the subsfrate is moved relative to the devices for example supported by a conveyor belt as shown in Figs. 4 and 5.

Examples

Some preferred embodiments of the inventive method exemplified with metal depo- sition on a planar ABS substrate follows one of the processes 1 - 3 including the steps as described below. The conventional formulation and/or etching of the ABS substrate prior to the metallization is omitted.

Process 1 1. Clean in alcohol 2. Corona freatment with Ar/H₂(g) 10 sec. 1000W 3. Print with Pd/KMnO4 (1) 4. Corona treatment with Ar/H₂(g) 10 sec. 1000W 5. Immersing in electroless Cu bath in 15 sec. 6. Rinse in water 7. Electroplating to layer thickness 20-40 μm 8. Rinse in water 9. Heat treatment in oven 60 °C 6-12 hours.

Process 2 1. Clean in alcohol Corona treatment with SO₂(g) 10 sec. 1000W Print with PdCl₂(l) (12 g/1) Corona treatment with Ar/H₂(g) 10 sec. 1000W Immersing in elecfroless Cu bath in 15 sec. Rinse in water Electroplating to layer thickness 20-40 μm Rinse in water Heat treatment in oven 60 °C 6-12 hours

Process 3 1. Clean in alcohol 2. Corona freatment with SO₂(g) 10 sec. 1000W 3. Print with Cu⁺⁺(1) 4. Corona treatment with Ar/H₂ (g) 10 sec. 1000W 5. Immersing in electroless Cu bath in 15 sec. 6. Electroplating to layer thickness 20-40 μm 7. Heat freatment in oven 60 °C 6-12 hours

Example 1 (process 1-2) A planar subsfrate of ABS having a surface of 100 x 60 mm was selective metallized by use of an ink-jet printer. This was done by printing a catalytic compound consisting of PdCl₂+KMnO (l) in a pattern with the dimensions 25 x 75 mm on the substrate followed by corona discharge, simultaneously applying Ar/H₂ (g) into the corona field. The substrate was corona treated by a discharge power of 1000 W with the frequency in the range of 20-30 kHz. A roll with a diameter of 100 mm and with a dielectric 5 mm silicone rubber isolation was used as an electrode, and a metal plate was used as a ground. The discharge gap was 2 ± 0.6 mm and ambient temperature 23 ± 4°C.

The ABS subsfrate was then immersed in an electroless Cu bath based on formaldehyde as a reducing agent in approximately 30 -t 10 sec and subsequently followed by copper electroplating to a layer thickness of 40 ± 10 μm. The final metal pattern was tested by the ASTM B533-85 method, showing a peel force of approximately 0,8 ± 0.4 N/mm. The result of the peel-off test is shown in Fig. 8.

Fig. 9 shows a SEM picture of the surface after the peel test. The surface topography clearly shows cohesive fracture both within the polymer as well as in the metal. The picture evidences that the deposited metal layer, does bond the polymer surface.

Example 2 (process 1-2) A planar substrate of PBT having a surface of 100 x 60 mm was selective metallized by use of an ink-jet printer. This was done by printing a catalytic compound consisting of PdCl₂+FeCl₂(l) in a pattern with the dimensions 25 x 75 mm on the substrate followed by corona discharge, simultaneously applying Ar/H₂ (g) into the corona field. The catalytic pattern was treated with the same corona properties as in exam- pie 1.

The PBT substrate was then immersed in an elecfroless Ni bath based on sodium hypophosphite as a reducing agent in approximately 30 ± 10 sec and subsequently followed by copper electroplating to a layer thickness of 40 ± 10 μm. The final metal pattern was tested by the ASTM B533-85 method, showing a peel-off force of approximately 0,8 ± 0.4 N/mm. The result of the peel test is shown in Fig. 6.

Example 3 (Process 3)

A planar substrate of ABS having a surface of 100 x 60 mm was selective metallized by use of an ink-jet printer. This was done by treating the subsfrate with a corona discharge, simultaneously applying SO₂(g) into the corona field, subsequently printed with a solution of Cu⁺⁺(1) in a pattern with the dimensions 25 x 75 mm on the substrate followed by corona discharge, simultaneously applying Ar/H₂(g) into the corona field. The catalytic pattern was treated with the same corona properties as in example 1. The ABS subsfrate was then immersed in an electroless Ni bath based on sodium hypophosphite as a reducing agent in approximately 30 ± 10 sec and subsequently followed by copper electroplating to a layer thickness of 40 --- 10 μm. The final metal pattern was tested by the ASTM B533-85 method, showing a peel force of approximately 0,8 ± 0.4 N/mm. The result of the peel test is shown in Fig. 7.

Example 4

Using the inkjet printing technique the inventive method was carried out based on the formaldehyde method.

The first metal composition is a silver ion solution A:

A. To an aqueous solution of 20 g silver nitrate an ammonia solution was added as a complex forming agent until a clear solution was obtained and made up to 1 lifre with water. The chemical reaction can be described by following equation:

2Ag⁺ + 2NH₃ + H₂O = Ag₂O + 2NH₄ ⁺

Where Ag₂O is a brown precipitate. The silver ions are complex bound with ammo- nia according to:

Ag⁺ + 2NH₃ = [Ag(NH₃)₂]⁺

Note: This solution is rather unstable as it is capable of forming AgNH₂ and Ag₃N, (which is extremely explosive) and thus the solution should not be stored too long.

The second reducer composition is a formaldehyde solution B:

B. Formaldehyde 40 ml, water 200 ml. The solutions A and B were used in the ratio 1:1. After printing formation of silver crystals appeared in the first 1-2 minutes and thereafter the water evaporated from the surface during the next 3-10 minutes.

After the two solutions had been mixed during the printing process, the silver ions in the form of a diamine complex in the solution were reduced by the formaldehyde according to:

2Ag [(NH₃)₂]⁺ + HCHO + H₂O = 2Ag + HCOO^" + 3H⁺ + 4NH₃

A ceramic substrate was provided with a printed silver pattern using the above printing method. To improve the adhesion the subsfrate was treated in a 2450 MHz microwave oven in 10 — 30 seconds.

Example 5

A substrate of PC/ ABS having a surface of 60 x 60 mm was selectively metallized by use of a tampon printing technique. This was done by printing a catalytic PdCl₂ pattern on the substrate followed by immersing in an elecfroless Cu bath based on formaldehyde in a beaker. The bath with the substrate in the beaker was treated in a 2450 MHz microwave oven in following way: The bath was heated until it was boiling. After boiling in 2 seconds the heat was turned off to avoid over boiling. Then after 1 to 2 seconds, when boiling had ended, the heat was turned on and again boiling was allowed for 2 seconds. In this way the bath was subjected to totally 4 boiling periods each time in about 2 seconds. The resulting PC/ ABS subsfrate with copper print is shown in Fig. 14 a and b.

Example 6

A substrate of fibre reinforced epoxy having a surface of 30 x 30 mm was selectively metallized by use of an inkjet printing technique. This was done by printing a catalytic PdCl₂ pattern on the subsfrate followed by immersing in an elecfroless Ni bath based on sodium hypophosphite as a reducing agent. The Ni bath with the im- mersed subsfrate was then treated in a 2450 MHz microwave as described in example 4. The resulting fibre reinforced epoxy substrate with nickel print is shown in Fig. 15. Letter size 5 mm.

Example 7

A subsfrate of aluminiumoxide, Al₂O₃, having a surface of 50 x 30 mm was selectively metallized by use of an inkjet printing technique. This was done by printing a catalytic PdCl₂ pattern on the substrate followed by immersing in an electroless Ni bath based on sodium hypophosphite as a reducing agent. The Ni bath with the im- mersed substrate was then treated in a 2450 MHz microwave as described in example 4. The resulting aluminiumoxide substrate with nickel print is shown in Fig. 16. Letter size 5 mm.

The metal deposits obtained in examples 4 - 7 all showed excellent adhesion by the above described Tape Test ASTM D3359-02 Method B.

Example 8

A multi-metal catalyst is prepared by the deposition of three different metal salts in individual patterns as shown in fig. 11. The substrate may be of any heat resistant material able to resist the temperatures used for the reduction reaction, such as 200 °C. As an example the subsfrate may be of a ceramic material. A first, second and third metal component containing an Au ion, such as AuCl , an Ag ion, such as [Ag(NH₃)₂]⁺, and a Pt complex, such as [Pt(NH₃)₄]Cl₂, respectively, are printed on the subsfrate in the individual patterns, and then the substrate can be treated with hydrogen and microwaves at 200 °C. Alternatively each printing step with a metal component may be followed by an individual reduction step. However, in that case treatment with microwaves should be avoided between the metal printing steps as the previously deposited metal will give raise to disturbing electrical currents. Thus the microwave treatment should only be used when all metal and reducer compo- nents have been deposited on the surface of the subsfrate. In fig. 11 the diameter of the individual metal spots may be down to approximately 10 μm and the distance between the spots may be down to approximately 10 μm.

Example 9 Piezoelectric actuators are solid state (ceramic) actuators that directly convert elecfrical energy into motion (mechanical energy). They can be provided with external electrodes by selective metallization of the piezoelectric ceramic (PZT) by the use of a printing technique, such as inkjet or tampon printing. The tampon printing technique can be carried out with two cliche rolls for the metal component A and the re- ducer component B according to example 4, respectively. As examples metals like Au, Ag, Pt, Cu, Ni or Ru may be used as the external electrode material.

Example 10

Microfluid systems can be obtained by selective metallization of polymers using inkjet printing, tampon printing or another conventional printing teclinique or a combination thereof. A microfluid system is a microsystem with a complete integration of different basic elements like pumps, valves and reaction chambers made possible by the use of microtechnologies. An example is a micro mixer element having a size of for example 500 μm x 500 μm x 720 μm.

Example 11

Semiconductors, semi conducting surfaces (wafers) are selectively metallized using inkjet printing, tampon printing or another conventional printing technique or a combination thereof. The metallized semiconductors can be usable as solar cells and various MEMS devices (MEMS: Microelectromechanical Systems).

Example 12

Biological inhibiting surfaces can be obtained on a stainless steel subsfrate by providing the stainless steel surface with small patterns of silver and palladium using inkjet printing, tampon printing or another conventional printing technique or a combination thereof. The obtained biological inhibiting surfaces can have a structure corresponding to the material disclosed in PCT DK 03/00790.

The above description of the invention reveals that it is obvious that it can be varied in many ways. Such variations are not to be considered a deviation from the scope of the invention, and all such modifications which are obvious to persons skilled in the art are also to be considered comprised by the scope of the succeeding claims.

Claims

1. A method for depositing a metal layer on a non-conducting surface of a subsfrate, characterized by directing onto at least a part of the surface a) a metal component which is a liquid composition including an organic or inorganic metal compound with the metal at a positive oxidation stage and optionally one or more adjuvants and/or additives stabilizing a metal ion solution and/or controlling the rheological and other properties of the composition, and b) a reducer component including a reductive agent being able to reduce the metal of the metal compound into the metallic form in situ on said part of the surface, and optionally one or more adjuvants and/or additives controlling the rheological and other properties, whereby the deposition process is supported by a freatment with physical energy.

2. A method according to claim 1, characterized in that the freatment with physical energy is a treatment with corona discharge, atmospheric plasma, flame treatment, microwave, infrared light and/or UN light.

3. A method according to claim 1 or 2, characterized in that the treatment with physical energy is carried out in 2 separate steps.

4. A method according to claim 3, characterized in that the first step of treatment with physical energy is carried out before the treatment with the metal component according to step a).

5. A method according to claim 3, characterized in that the second step of freatment with physical energy is carried out after the treatments with the metal component according to step a) and with the reducer component according to step b) or simultaneously with the freatment with the reducer component according to step b).

6. A method according to claim 1, characterized in that the treatment with physical energy is combined with the direction of the reducer component onto the surface.

7. A method according to one of the preceding claims, characterized in that the metal to be deposited is a catalytic and/or activating metal.

8. A method according to claim 7, characterized in that the metal to be deposited is selected among Au, Ag, Pd, Pt, Mn, W, Ni, Ru, Rli, Se, Te, Si, and/or Cr.

9. A method according to claim 7, characterized in that the surface provided with a deposit of a catalytic and/or activating metal is further treated for depositing a further metal layer according to the method of claim 1 , whereby the further metal layer is of the same or a different metal.

10. A method according to claim 7, characterized in that the surface provided with a deposit of a catalytic and/or activating metal is further treated for depositing a further metal layer by a conventional electroless or electrolytic plating technique.

11. A method according to claim 1 , characterized by the steps of a) a first corona freatment with a gas containing at least one agent with oxidizing properties and at least one (inert) earner gas, b) treating the surface with a liquid containing a permanganate salt and a salt of Pd, Ru or Cu, and c) a second corona treatment with a gas containing at least one agent with reducing properties and at least one (inert) gas.

12. A method according to claim 1, characterized by the steps of a) a corona freatment with a SO₂ gas, SO₃ gas, SO₂ containing gas, a sulfonic acid, or sodiumhydrogensulfite, and b) treating the surface with a liquid containing a salt of Pd , Ru or Cu and c) a second corona freatment with a hydrogen containing gas.

13. A method according to claim 1, characterized in that the method further comprises the steps of - elecfroless plating on the obtained metal layer, electroplating on the obtained elecfroless plating layer, and heating in an oven at 40 - 75 °C in 1 to 20 hours.

14. A method according to claim 1, characterized by pre-treatment of the surface by directing a catalytic activator component onto at least a part of the surface before the treatment with the metal component and the reducer component.

15. A method according to claim 1, characterized by directing an activator component, the metal component and/or the reducer component selectively on the non- conducting surface in a pre-selected pattern.

16. A method according to claim 15, characterized by directing the activator component, the metal component and/or the reducer component selectively on the non-conducting surface by means of a conventional printing technique.

17. A method according to claim 16, characterized by directing an activator component, the metal component and/or the reducer component selectively on the non-conducting surface by means of digital printing, inkjet printing, screen-printing (serigraphic printing), tampon printing, gravure printing (intaglio printing), letter- press printing, relief printing and/or plain printing

18. A method according to claim 1, characterized by directing an activator component, the metal component and/or the reducer component selectively on the nonconducting surface by means of a syringe.

19. A method according to any one of the preceding claims, characterized by directing the metal component and the reducer component onto at least a part of the surface simultaneously or within a short period of time.

20. A method according to claim 1, characterized by directing the reducer component or the metal component onto at least a part of the surface to form a coherent film thereof on the surface, and thereafter directing the other component selectively in a pre-selected pattern on the surface.

21. A method according to any one of the preceding claims, characterized in that a number of separate metal components each including independently a metal compound having the metal at a positive oxidation stage are directed independently in patterns on the surface.

22. A method according to any one of the preceding claims, characterized by the steps of: step 1) treating the surface with physical energy, step 2) directing the metal component and the reducer component onto at least a part of the surface, step 3) treating the surface with physical energy, step 4) coating at least a part of the surface with an insulating material, and step 5) optionally repeating the steps 1 to 4 one or more times.

23. A method according to claim 1 for the preparation of a printed circuit board of two or more layers from a non-conducting subsfrate having a first side A and an opposite second side B, characterized by the steps of: step 1) drilling one ore more holes through the subsfrate from side A to side B, step 2) a first corona treatment of side A with a reducing or oxidizing gas, step 3) printing side A with a catalyst material in pre-selected pattern, step 4) a second corona freatment of side A with a reducing gas, step 5) turning the substrate, step 6) a first corona treatment of side B with a reducing or oxidizing gas, step 7) printing side B with a catalyst material in pre-selected pattern, step 8) a second corona freatment of side B with a reducing gas, step 9) immersing the substrate in an electroless Cu plating bath step 10) immersing the substrate in an electroplating bath to obtain a layer thiclmess of 15 - 40 μm and tlirough hole plating.

24. A method according to claim 23, characterized in that the pre-selected pattern printed in step 3) includes one or more alignment marks and that the pre-selected pattern in step 7) is printed in register with the alignment marks.

25. A method according to claim 1, characterized in that the freatment with physical energy includes a first corona treatment with an oxidizing agent and a second corona freatment with a reducing agent.

26. A method according to claim 25, characterized in that the treatment with physical energy includes a first corona freatment with a SO₂ or SO₃ containing gas and a second corona treatment with a H₂ containing gas.

27. A method according to claim 1, characterized in that the treatment with physical energy includes a first corona freatment with a reducing agent and a second corona treatment with a reducing agent.

28. A method according to claim 27, characterized in that the treatment with physical energy includes a first corona freatment with a H₂ containing gas and a second corona treatment with a H₂ containing gas.

29. A method according to claim 1, characterized in that the metal component is deposited on a subsfrate by pad printing where after the substrate is treated with at- mospheric hydrogen plasma in a 3D corona.

30. A method according to claim 1, characterized by further directing onto at least a part of the surface a component selected from conductive polymers, pastes containing nano-metal particles, sol-gel compounds, semiconductors, silane and/or polysilane compounds, organo-metallics and/or metallo organics, electrolytes and/or ceramic pastes.

31. A device for depositing a metal layer on a surface of a subsfrate, characterized by a) a means for directing onto at least a part of the surface a metal component which is a liquid composition including an organic or inorganic metal compound with the metal at a positive oxidation stage and optionally one or more additives stabilizing a metal ion solution and/or controlling the rheological and other properties of the composition, b) a means for directing onto at least a part of the surface a reducer component including a reductive agent being able to reduce the metal of the metal compound into the metallic form in situ on said part of the surface, and c) a means for treating the surface with physical energy.

32. A device according to claim 31, characterized in that the means (c) for treat- ing the surface with physical energy is a means for freatment with atmospheric plasma, corona discharge, flame, microwave, infrared light, or UV-light.

33. A device according to claim 31 for manufacturing of planar or flexible print circuit boards, characterized by including of the following stations, a) a hole drilling machine and cleaning means, b) a 2D corona machine with supply of reducing or oxidizing gas, c) a means for direct printing of catalyst material in pre selected pattern by use of ink-jet printing, d) a 2D corona machine with supply of reducing gas, e) means for direct printing of alignment marks and legend with UN-curable ink by use of ink-jet printing, f) means for UN-curing of ink by UN light source, g) an elecfroless Cu plating bath, h) an air knife and a rinsing station, i) an electroplating bath to obtain 15 - 40 μm layer thickness and through hole plating, j) an air knife and a rinsing station, k) a means for drying and heating,

1) a means for solder mask printing.

34. A device according to claim 31 for manufacturing of a three dimensional molded interconnected device (3D MID), characterized by including of the following stations, a) a hole drilling machine and cleaning means, b) a 3D corona machine with supply of reducing or oxidizing gas, c) a means for direct printing of catalyst material in pre selected pattern by use of pad printing or robot handled ink-jet printer, d) a 3D corona machine with supply of reducing gas, e) means for direct printing of alignment marks and legend with UN-curable ink by use of pad printing or robot handled ink-jet printer, f) means for UN-curing of ink by UN light source, g) an electroless Cu plating bath, h) an air knife and a rinsing station, i) an electroplating bath to obtain 15 - 40 μm layer thickness and through hole plating, j) an air knife and a rinsing station, k) a means for drying and heating,

1) a means for solder mask printing.

35. An article having a non- conductive surface with a metal layer deposited on the surface obtainable by the method according to claim 1.

36. An article according to claim 35 in a form selected among an electrode pattern printed on a polymer surface, preferably of PC/ ABS or fibre reinforced epoxy; a three dimensional contact pattern imbedded in a non- conductive material; an electrode pattern printed on a ceramic surface, preferably of Al₂O₃ or PZT; a printed pat- tern consisting of more metals, preferably Cu, Pt and Au, forming a multi-metal catalyst on a ceramic surface; an electrode pattern printed on cellulose fibres, preferably paper; an electrode pattern printed on a conductive metal, preferably stainless steel or carbon fibres; an electrode pattern printed on Si, Al semiconductors, preferably for applications as capacitors, waveguides, field effect transistors and other MEMS applications; and a printed pattern of metals, preferably Pd and Ag, on a conducting surface forming a biological inhibiting surface.

37. An article according to claim 35 in a form selected among printed circuit boards (PCBs), flexible PCBs, rigid-flexible PCBs, polyimide articles, epoxy arti- cles, three dimensional molded interconnected devices (3D MID), resistors, capacitors, diodes, transistors, inductors, sensor devices, solar cells, displays, lenses, batteries, quantum dots, electrical and optical cables, planar flat panel displays, and selective area doping materials.