Method for electroless nickel deposition onto copper without activation with palladium

Abstract

The invention relates to selective deposition of a nickel layer on a copper surface. The invention may be used in the production of electrically conductive areas for electronic circuits. Method for nickel deposition on the surface of copper comprises immersing an item, which surface is to be deposited with the nickel layer, into one or more baths, of which at least one contains a reducing agent and of which at least one is adapted for (electroless) plating of nickel. In order to extend the field of application and to obtain practically pure nickel coatings, said reducing agent comprises boronic or phosphoric compounds, comprising morpholine borane (C.sub.4H.sub.9BNO), or dimethylamine borane (C.sub.2H.sub.7BN), or sodium tetrahydroborate (NaBH.sub.4), or sodium hypophosphite (NaH.sub.2PO.sub.2) and said reducing agent directly or indirectly reduces insoluble copper (I) or copper (II) compounds on the copper surface. At least one of the mention baths comprises a ligand or mixture thereof.

Claims

1. A method for nickel deposition on a surface of an item which is produced from copper or has a copper layer on the item comprising: immersing said item into an electroless nickel plating bath comprising: a reducing agent and a ligand or mixture of ligands; wherein: said reducing agent directly or indirectly reduces insoluble copper (I) or copper (II) compounds on the surface of the item or on the copper layer of the item; and at least one of said ligand in the bath facilitates dissolution of incompletely reduced insoluble copper compounds by binding the incompletely reduced insoluble copper compounds to soluble complexes, such that a substantially pure copper surface is present where nickel is deposited.

2. The method of claim 1, wherein at least one of said ligand in the bath or mixture thereof consists of any water-soluble chemical compound capable of forming sufficiently stable complexes with copper ions selected from a group consisting of: ethylenediamine (C.sub.2H.sub.8N.sub.2), diethylenetriamine (C.sub.4H.sub.13N.sub.3), and N,N,N′,N′-tetrakis(2-hydroxypropyl)ethylenediamine(C.sub.14H.sub.32N.sub.2O.sub.4).

3. The method of claim 1, wherein said method further comprises: initially immersing said item in an activation bath, which comprises said reducer and said ligand or the mixture therefor and subsequently immersing said item into the electroless nickel plating bath in which nickel is electrolessly deposited on the copper surface; wherein in the activation bath, an electron which appears after an anodic oxidation reaction of said reducing agent from the activation bath activates the copper surface by reducing Cu(I) and Cu(II) oxides and/or oxy-hydroxy compounds on the surface, and at a same time, anodic catalytic or thermal decomposition reactions occur, releasing hydrogen, and the hydrogen is reacting as an active reducing agent with the Cu(I) and Cu (II) compounds on the copper surface, leaving the substantially pure copper surface and where nickel is then deposited without any intermediate step in the electroless nickel bath.

4. The method of claim 1, wherein said reducing agent contains boronic or phosphoric compounds to reduce the insoluble copper (I) and copper (II) compounds present on the surface of the item produced from copper or has a copper layer; and the at least one ligand or a ligand from the mixture of ligands is selected from a group of chemical compounds of: ethylenediamine (C.sub.2H.sub.8N.sub.2), diethylenetriamine (C.sub.4H.sub.13N.sub.3), and N,N,N′,N′-tetrakis(2-hydroxypropyl) ethylenediamine(C.sub.14H.sub.32N.sub.2O.sub.4), selecting concentrations of said chemical compounds of said ligand, such that said chemical compounds dissolves the incompletely reduced insoluble copper compounds by binding the incompletely reduced insoluble copper compounds to the soluble complexes so that substantially pure copper surface is produced on which the nickel is deposited.

5. The method of claim 3, wherein said activation bath consists of a sodium hypophosphite (NaH.sub.2PO.sub.2) solution with a concentration from 0.5 M up to the limit of solubility and said at least one ligand of: N,N,N′,N′-tetrakis (2-hydroxypropyl) ethylenediamine(C.sub.14H.sub.32N.sub.2O.sub.4) in a concentration from 0.001 M to the solubility limit and an immersion time ranges from 1 to 15 min at a temperature of 80-96° C.

6. The method of claim 3, wherein said activation bath consists of a morpholine borane (C.sub.4H.sub.9BNO) solution with a concentration from 0.01 M up to the limit of solubility and said mixture of ligands of: N,N,N′,N′-tetrakis(2-hydroxypropyl) ethylenediamine (C.sub.14H.sub.32N.sub.2O.sub.4) and amino acetic acid (C.sub.2H.sub.5NO.sub.2) in a concentration from 0.001 M to the solubility limit and an immersion time ranges from 1 to 15 min at a temperature of 18-50° C.

7. The method of claim 3, wherein said activation bath consists of a dimethylamine borane (C.sub.2H.sub.7BN) solution with a concentration from 0.01 M up to the limit of solubility and said mixtures of ligands: nitrilotriacetic acid (C.sub.6H.sub.9NO.sub.6) and ethylenediamine (C.sub.2H.sub.8N.sub.2) in a concentration from 0.001 M to the solubility limit and an immersion time ranges from 1 to 15 min at a temperature of 18-50° C.

8. The method of claim 3, wherein said activation bath consists of a sodium tetrahydroborate (NaBH.sub.4) solution with a concentration from 0.01 M up to the limit of solubility and said mixtures of ligands of: diethylenetriamine (C.sub.4H.sub.13N.sub.3) and ethylenediaminetetraacetic acid (C.sub.10H.sub.16N.sub.2O.sub.8) in a concentration from 0.001 M to the solubility limit and an immersion time ranges from 1 to 15 min at a temperature of 18-50° C.

9. The method of claim 1, wherein said electroless plating bath of nickel consists of nickel sulphate (NiSO.sub.4) at a concentration of 0.05-0.5 M; reducing agent of sodium hypophosphite (NaH.sub.2PO.sub.2) at a concentration of 0.25-3 M; N,N,N′, N′-tetrakis (2-hydroxypropyl) ethylenediamine (C.sub.14H.sub.32N.sub.2O.sub.4) at a concentration of 0.25-1 M; and sodium hydroxide (NaOH) at a concentration sufficient for required pH adjustment.

10. The method of claim 1, wherein said surface of said item which is produced by copper is plated by nickel using a sequence of two different nickel plating baths, a first nickel plating bath containing sodium hypophosphite (NaH.sub.2PO.sub.2) as the reducing agent, metalizing the first nickel plating bath which is an alkaline electroless nickel plating bath with pH in a range of 8.5-10.0, and later said item is immersed in a second nickel plating bath which is an acidic electroless nickel plating bath with pH in a range of 4.0-6.0.

11. The method of claim 1, wherein said bath is adapted for electroless plating of nickel consists of nickel sulphate (NiSO.sub.4) at a concentration of 0.05-0.5 M; a reducing agent of morpholine borane (C.sub.4H.sub.9BNO) at a concentration of 0.01-1 M; a mixture of ligands of diethylenetriamine (C.sub.4H.sub.13N.sub.3) at a concentration of 0.001-0.5 M; and N,N,N′,N′-tetrakis(2-hydroxypropyl)ethylenediamine (C.sub.14H.sub.32N.sub.2O.sub.4) at a concentration of 0.001-0.2 M: sodium hydroxide (NaOH) at a concentration sufficient for pH adjustment to pH 5.0-7.8; and plating at a temperature of 18-35° C.

12. The method of claim 1, wherein said bath is adapted for electroless plating of nickel consists of nickel sulphate (NiSO.sub.4) at a concentration of 0.05-0.5 M; a reducing agent of dimethylamine borane (C.sub.2H.sub.7BN) at a concentration of 0.01-1 M; ligands of: diethylenetriamine (C.sub.4H.sub.13N.sub.3) at a concentration of 0.001-0.5 M; and N,N,N′,N′-tetrakis(2-hydroxypropyl)ethylenediamine(C.sub.14H.sub.32N.sub.2O.sub.4) at a concentration of 0.001-0.2 M: sodium hydroxide (NaOH) at a concentration sufficient for pH adjustment to pH 5.0-7.8; and plating at a temperature 18-35° C.

13. The method of claim 1, wherein said bath is adapted for electroless plating of nickel consists of nickel sulphate (NiSO.sub.4) at a concentration of 0.05-0.5 M; a reducing agent of sodium tetrahydroborane (NaBH.sub.4) at a concentration of 0.01-0.5 M; a ligand of N,N,N′,N′-tetrakis(2-hydroxypropyl)ethylenediamine (C.sub.14H.sub.32N.sub.2O.sub.4) at a concentration of 0.001-0.2 M; a ligand of potassium sodium tartrate (KNaC.sub.4H.sub.4O.sub.6) at a concentration of 0.05-0.2 M; disodium thiosulphate (Na.sub.2S.sub.2O.sub.3) at a concentration of 0.001-0.01 M; sodium hydroxide (NaOH) at a concentration sufficient for pH adjustment to pH 12.0-13.0; and plating at a temperature of 18-35° C.

14. The method of claim 4, wherein said bath is adapted for electroless plating of nickel consists of nickel sulphate (NiSO.sub.4); sodium hydroxide (NaOH); a ligand of amino acetic acid (C.sub.2H.sub.5NO.sub.2), and a ligand of N,N,N′,N′-tetrakis (2-hydroxypropyl) ethylenediamine (C.sub.14H.sub.32N.sub.2O.sub.4) at a concentration of 0.001-0.2 M; and a reducing agent of sodium hypophosphite (NaH.sub.2PO.sub.2) at a concentration exceeding 0.8 M.

15. The method of claim 14, wherein said bath is adapted for electroless plating of nickel consists of nickel sulphate (NiSO.sub.4) at a concentration of 0.05-0.5 M; the reducing agent of sodium hypophosphite (NaH.sub.2PO.sub.2) at a concentration of 0.8-3 M; the ligand of amino acetic acid (C.sub.2H.sub.5NO.sub.2) at a concentration of 0.25-1 M; and a ligand of N,N,N′,N′-tetrakis(2-hydroxypropyl)ethylenediamine (C.sub.14H.sub.32N.sub.2O.sub.4) at a concentration of 0.001-0.2 M; sodium hydroxide (NaOH) at a concentration sufficient for pH adjustment to pH 4.0-6.0; and plating at a temperature of 80-96° C.

16. The method of claim 4, wherein said bath is adapted for electroless plating of nickel consists of nickel sulphate (NiSO.sub.4) at a concentration of 0.05-0.5 M; a reducing agent of morpholine borane (C.sub.4H.sub.9BNO) at a concentration of 0.1-1 M; a ligand of diethylenetriamine (C.sub.4H.sub.13N.sub.3) at a concentration of 0.001-0.5 M; and a ligand of N,N,N′,N′-tetrakis(2-hydroxypropyl)ethylenediamine(C.sub.14H.sub.32N.sub.2O.sub.4) at a concentration of 0.001-0.2 M: sodium hydroxide (NaOH) at a concentration sufficient for pH adjustment to pH 5.0-7.8; and plating at a temperature of 18-35° C.

17. The method of claim 4, wherein said bath is adapted for electroless plating of nickel consists of nickel sulphate (NiSO.sub.4) at a concentration of 0.05-0.5 M; a reducing agent of dimethylamine borane (C.sub.2H.sub.7BN) at a concentration of 0.1-1 M; a ligand of diethylenetriamine (C.sub.4H.sub.13N.sub.3) at a concentration of 0.001-02 M and a ligand of N,N,N′,N′-tetrakis(2-hydroxypropyl)ethylenediamine (C.sub.14H.sub.32N.sub.2O.sub.4) at a concentration of 0.001-0.2 M; sodium hydroxide (NaOH) at a concentration sufficient for pH adjustment to pH 5.0-7.8; and plating at a temperature of 18-35° C.

18. The method of claim 4, wherein said bath is adapted for electroless plating of nickel consists of nickel sulphate (NiSO.sub.4) at a concentration of 0.05-0.5 M; a reducing agent of sodium tetrahydroborane (NaBH.sub.4) at a concentration of 0.02-0.5 M; a ligand of ethylenediamine (C.sub.2H.sub.8N.sub.2) at a concentration of 0.001-0.5 M; a ligand of potassium sodium tartrate (KNaC.sub.4H.sub.4O.sub.6) at a concentration of 0.05-0.2 M; and a ligand of N,N,N′,N′-tetrakis(2-hydroxypropyl)ethylenediamine(C.sub.14H.sub.32N.sub.2O.sub.4) at a concentration of 0.001-0.2 M; disodium thiosulphate (Na.sub.2S.sub.2O.sub.3) at a concentration of 0.001-0.01 M; sodium hydroxide (NaOH) at a concentration sufficient for pH adjustment to pH 12.0-13.0; and plating at a temperature of 18-35° C.

19. (canceled)

20. The method of claim 3, further comprising immersing said item with the activated copper surface into a second electroless nickel plating bath, in which nickel is electrolessly deposited on the copper surface, wherein the immersing said item into the second electroless nickel plating bath occurs after immersing said item in the activation bath without any intermediate step.

Description

DESCRIPTION OF THE INVENTION AND EXAMPLES

[0052] Electrically conductive areas in electronic devices are mainly formed from copper, as copper has one of the highest electrical conductivity (higher than that of gold), is relatively inexpensive, and can be easily deposited on a dielectric substrate such as fibre-reinforced resins, polymers, or even ceramics. However, copper atoms diffuse into other materials such as solder, which cause degradation of the copper layer. Moreover, copper tends to oxidise easily. For these reasons, a barrier layer is deposited. The most convenient is to form a barrier layer of nickel into which no diffusion of copper atoms takes place, and a thin oxide-protective and electrically conductive layer of gold or platinum can be easily deposited on this layer by immersion method. Electroless deposition of nickel on a copper surface using electroless nickel-plating baths containing phosphorus compounds is practically impossible, or a prolonged process without additional activation or sensitisation, and, therefore, a surface activation step is introduced. Activation is usually carried out with palladium, but the process is expensive and difficult to control the spatial selectivity of the deposition.

[0053] The present invention is intended for the activation of a copper surface for electroless deposition of nickel from a bath. The process can be implemented in two ways. First, by activation of the intended metallised areas with an activation solution (bath) consisting of reducing agents containing boron or phosphorus and comprising copper ion ligands or mixtures thereof, followed by immersion of the activated copper surface in an electroless nickel plating bath in which a nickel layer is selectively formed directly on the copper surface to be coated. Another option: Nickel can be deposited directly on the copper surface without additional surface activation step, using morpholine borane (C.sub.4H.sub.9BNO) or dimethylamine borane (C.sub.2H.sub.7BN) or sodium tetraborane (NaBH.sub.4) or higher (over 0.8 M) concentration of sodium hypophosphate (NaH.sub.2PO.sub.2) as a reducing agent in electroless nickel plating baths.

[0054] Initially, the surface is washed or wiped with sulfuric acid H.sub.2SO.sub.4, concentration: 0.5-4 M for 3-15 minutes. This step is performed if the surface is strongly oxidized. This step can be omitted if all other multilayer coating steps are performed immediately (within 5 minutes) after chemical deposition of copper. The activation of the surface by an activation bath follows, optionally using one of the following activation processes by dipping in:

[0055] a) sodium hypophosphite (NaH.sub.2PO.sub.2) solution with a concentration from 0.5 M up to the limit of solubility and which contains one or more copper ions ligand, which concentration is from 0.01 M up to the limit of solubility and the immersion time ranges from 1 to 15 minutes at 80-96° C. temperature. After the activation, the surface is washed with 0.5 M NaH.sub.2PO.sub.2 solution at 80-90° C. for 1 second.

[0056] b) morpholine borane solution with a concentration from 0.01 M up to the limit of solubility and which contains one or more copper ions ligands, which concentration is from 0.01 M up to the limit of solubility and the immersion time ranges from 1 to 15 minutes at 18-50° C. temperature. After activation, the surface is washed with water at 80-96° C. for 1 second.

[0057] c) dimethylamine borane solution with a concentration from 0.01 M up to the limit of solubility and which contains one or more copper ions ligands and the immersion time ranges from 1 to 15 minutes at 18-50° C. temperature. After activation, the surface is washed with water at 80-96° C. for 1 second.

[0058] d) with sodium tetrahydroborate (NaBH.sub.4) at a concentration of 0.01 M to the solubility limit and one or more copper ions ligands at a concentration of 0.01 M to the solubility limit; process time 1-15 minutes at 18-50° C.; after activation, the surface is washed with deionized water at 80-96° C. for 1 second.

[0059] Examples of activation baths:

[0060] Bath no. 1 composition and coating conditions: [0061] 0.5 M—sodium hypophosphite (NaH.sub.2PO.sub.2); [0062] 0.01 M—N,N,N′,N′-tetrakis(2-hydroxypropyl)ethylenediamine; [0063] sodium hydroxide (NaOH) in a concentration sufficient to adjust the pH of the solution to 9.2; [0064] at 88° C. for 5 min.

[0065] Bath no. 2 composition and coating conditions: [0066] 0.5 M—morpholino borane (C.sub.4H.sub.9BNO); [0067] 0.01 M—diethylenetriaminepentaacetic acid (C.sub.14H.sub.23N.sub.3O.sub.10); [0068] sodium hydroxide (NaOH) in a concentration sufficient to adjust the pH of the solution to 7; [0069] at 30° C. for 5 min.

[0070] Further, it follows the chemical electroless deposition of nickel by immersing the article in chemical metallisation bath No. 3 (deposition rate ˜9.2 μm/h), which is alkaline to initiate the deposition process, the coating process is performed for 1-10 minutes, after that, the article is immersed in bath No. 4 (acidic), in which the nickel layer is thickened, deposition rate ˜3.7 μm/h.

[0071] Bath No. 3 composition and conditions: [0072] 0.1 M nickel sulphate (NiSO.sub.4); [0073] 0.5 M sodium hypophosphite (NaH.sub.2PO.sub.2); [0074] 0.6 M amino acetic acid (C.sub.2H.sub.5NO.sub.2); [0075] add sodium hydroxide (NaOH) for pH adjusting to pH 9.2; [0076] plating at 85-95° C. temperature.

[0077] Bath No. 4 composition and conditions: [0078] 0.1 M nickel sulphate (NiSO.sub.4); [0079] 0.25 M sodium hypophosphite (NaH.sub.2PO.sub.2); [0080] 0.4 M amino acetic acid (C.sub.2H.sub.5NO.sub.2); [0081] Add sodium hydroxide (NaOH) for pH adjusting to pH 5.2; [0082] plating at 85-95° C. temperature.

[0083] Activation route a). Advantage: after the activation, there is no need to wash the part; it can be immersed directly in a nickel-plating bath containing the same reducing agent-sodium hypophosphite.

[0084] Activation routes b), c), and d). Advantage: the process takes place at the room temperature; low reagent concentrations are used; can be plated in a phosphorus-free electroless nickel-plating bath using morpholine borane or dimethylamine borane as reducing agents; practically pure nickel coatings are deposited.

[0085] The advantage of described baths is that the activation can be performed in any of the described baths, and then the nickel plating can also be performed in any of the described ones.

[0086] Another advantage is that pure nickel coatings without phosphorus impurities can be deposited using baths in which the reducing agents are boron compounds.

[0087] Principle of operation: the electrons which formed during the anodic oxidation of the reducing agent in solution activate the copper surface by reducing copper (I) and copper (II) oxides and oxy/hydroxy compounds on the surface to metallic copper. At the same time as the thermal and/or catalytic decomposition (dehydrogenation) of the reducing agent takes place, the atomic hydrogen formed during the release (in statu nascendi-Latin) is adsorbed on the surface. It is known that the hydrogen formed during the release is a very active reducing agent and thus further cleans the surface of the copper, giving it catalytic properties. In addition, an added ligand helps to dissolve incompletely reduced insoluble copper compounds by binding them to soluble complexes. When the activated item is immersed in the electroless nickel plating bath, the electroless nickel plating process on the pure copper surface easily begins.

[0088] Reactions during copper surface activation:

[0089] with sodium hypophosphite

2H.sub.2PO.sub.2.sup.−+2OH.sup.−.fwdarw.2H.sub.2PO.sub.3.sup.−+H.sub.2↑+2e.sup.−

Cu.sup.2++2e.sup.−.fwdarw.Cu.sup.0

Cu.sup.2++e.sup.−.fwdarw.Cu.sup.0

H.sub.2PO.sub.2.sup.−+H.sub.2O.fwdarw.H.sub.2PO.sub.3.sup.−+2H.sub.(ads)

Cu.sup.2++2H.sub.(ads).fwdarw.Cu.sup.0+2H.sup.+

Cu.sup.+H.sub.(ads).fwdarw.Cu.sup.0+H.sup.+

with morpholine borane

2C.sub.4H.sub.8O—NH.BH.sub.3+8OH.sup.−.fwdarw.2BO.sub.2.sup.−+2C.sub.4H.sub.8O—NH+4H.sub.2O+3H.sub.2↑+6e.sup.−

##STR00001##
Cu.sup.2++2e.sup.−.fwdarw.Cu.sup.0

Cu.sup.++e.sup.−.fwdarw.Cu.sup.0

C.sub.4H.sub.8O—NH.BH.sub.3+4OH.sup.−.fwdarw.BO.sub.2.sup.−+C.sub.4H.sub.8O—NH+2H.sub.2O+3H.sub.(ads)+3e.sup.−

Cu.sup.2++2H.sub.(ads).fwdarw.Cu.sup.0+2H.sup.+

Cu.sup.++H.sub.(ads).fwdarw.Cu.sup.0+H.sup.+

with dimethylamine borane

2(CH.sub.3).sub.2NH.BH.sub.3+8OH.sup.−.fwdarw.2BO.sub.2.sup.−+2(CH.sub.3).sub.2NH+4H.sub.2O+3H.sub.2↑+6e.sup.−

##STR00002##
Cu.sup.2++2e.sup.−.fwdarw.Cu.sup.0

Cu.sup.++e.sup.−.fwdarw.Cu.sup.0

(CH.sub.3).sub.2NH.BH.sub.3+4OH.sup.−.fwdarw.BO.sub.2.sup.−+(CH.sub.3).sub.2NH+2H.sub.2O+3H.sub.(ads)+3e.sup.−

Cu.sup.2++2H.sub.(ads).fwdarw.Cu.sup.0+2H.sup.+

Cu.sup.++H.sub.(ads).fwdarw.Cu.sup.0+H.sup.+

with tetra hydroborate

BH.sub.4.sup.−+4OH.sup.−.fwdarw.BO.sub.2.sup.−+2H.sub.2O+2H.sub.2↑+4e.sup.−

Cu.sup.2++2e.sup.−.fwdarw.Cu.sup.0

Cu.sup.++e.sup.−.fwdarw.Cu.sup.0

BH.sub.4.sup.−+3OH.sup.−.fwdarw.BO.sub.2.sup.−+H.sub.2O+5H.sub.(ads)+3e.sup.−

Cu.sup.2+2H.sub.(ads).fwdarw.Cu.sup.0+2H.sup.+

Cu.sup.++H.sub.(ads).fwdarw.Cu.sup.0+H.sup.+

[0090] Advantages compared to other activation baths: only copper surfaces are activated and later is nickel-plated while using classic activation solutions with Pd (II) salts, the entire surface of the part is activated, and nickel is deposited not only on copper but also on a plastic surface.

[0091] In one of the methods, a nickel coating can be deposited on a copper surface by skipping treatment with an activating bath. If a chemical nickel-plating solution containing at least one of the following reducing agents is used: morpholine borane (C.sub.4H.sub.9BNO), dimethylamino borane (C.sub.2H.sub.7BN), sodium tetrahydroborate (NaBH.sub.4) or sodium hypophosphite (NaH.sub.2PO.sub.2) in higher concentrations (more than 0.8 M), copper may be coated with nickel or its alloys without additional activation and washing steps.

[0092] Initially, the surface is washed or wiped with sulfuric acid H.sub.2SO.sub.4 with a concentration of 0.5-4 M for 3-15 minutes. This step is performed if the surface is strongly oxidised.

[0093] This step can be omitted if all other multilayer coating steps are performed immediately (within 5 minutes) after step by step. This is followed by electroless deposition of nickel by immersing the item into electroless metallization baths No. 5 or No. 6, or No. 7.

[0094] Bath No. 5 composition and conditions: [0095] 0.05 M nickel sulphate (NiSO.sub.4); [0096] 0.1 M morpholine borane (C.sub.4H.sub.9BNO); [0097] 0.015 M diethylenetriamine (C.sub.4H.sub.13N.sub.3); [0098] Add sodium hydroxide (NaOH) for pH adjusting to pH 7.0; [0099] platting at 30° C. temperature.

[0100] Bath No. 6 composition and conditions: [0101] 0.05 M nickel sulphate (NiSO.sub.4); [0102] 0.1 M dimethylamine borane (C.sub.2H.sub.7BN); [0103] 0.015 M diethylenetriamine (C.sub.4H.sub.13N.sub.3); [0104] Add sodium hydroxide (NaOH) for pH adjusting to pH 7.0; [0105] platting at 30° C. temperature.

[0106] Bath No. 7 composition and conditions: [0107] 0.125 M nickel sulphate (NiSO.sub.4); [0108] 0.125 M sodium tetrahydroborane (NaBH.sub.4); [0109] 0.25 M ethylenediamine (C.sub.2H.sub.8N.sub.2); [0110] 0.15 M potassium sodium tartrate (KNaC.sub.4H.sub.4O.sub.6); [0111] 0.008 M disodium thiosulphate (Na.sub.2S.sub.2O.sub.3); [0112] Add sodium hydroxide (NaOH) for pH adjusting to pH 12.5; [0113] platting at 30° C. temperature.

[0114] Another example with no activation step can be given for electroless nickel bath where sodium hypophosphite is used as a reducing agent, and activation step can be skipped if the concentration of NaH.sub.2PO.sub.2 exceeds 0.8 M in the nickel electroless plating bath which consists of nickel sulphate (NiSO.sub.4); sodium hydroxide (NaOH); amino acetic acid (C.sub.2H.sub.5NO.sub.2), and sodium hypophosphite (NaH.sub.2PO.sub.2).

[0115] Bath No. 8 composition and conditions: [0116] 0.1 M nickel sulphate (NiSO.sub.4); [0117] 1 M sodium hypophosphite (NaOH); [0118] 0.4 M amino acetic acid (C.sub.2H.sub.5NO.sub.2); [0119] Add sodium hydroxide NaOH for pH adjusting to pH 5.2; [0120] platting at 92° C. temperature.

[0121] In this type of chemical nickel plating baths (No. 5-8), no additional chemical activation is required, because the concentration of the reducing agent already in the solution is sufficient for the preparation and activation of the copper surface. Ni.sup.2+ ions in chemical nickel plating bath do not interfere with the copper activation process, and diethylenetriamine (C.sub.4H.sub.13N.sub.3), ethylenediamine (C.sub.2H.sub.8N.sub.2), amino ethanoic acid (C.sub.2H.sub.5NO.sub.2) and potassium sodium tartrate (KNaC.sub.4H.sub.4O)) may also be involved in the transfer of copper (dissolution) as Cu (II) ligands, for example, for copper oxide (CuO) and amino acetic acid (C.sub.2H.sub.5NO.sub.2):

CuO+2H.sub.2NCH.sub.2COOH.fwdarw.Cu(H.sub.2NCH.sub.2COO.sup.−).sub.2+H.sub.2O

[0122] Optimal concentrations of reagents in the baths and process durations can be determined experimentally or using an automated method for determining solution concentrations and/or process durations, using equipment that indicates and loads the information about the surface of the item and condition of the bath to a computer, and calculates concentrations of the baths and/or chemical process data in situ based on the loaded information. Optimization by iterations (cycles) can be performed in this way.

[0123] As final consideration it is worth emphasizing that the invention described a method for nickel deposition on a surface of an item which is produced from copper or has a copper layer on it comprising steps of reducing, dissolving; and plating.

[0124] In one embodiment of the invention, these steps can be performed one after another in a sequential way and possibly such order is enforced by changing the baths between the steps.

[0125] However, in an alternative embodiment of the invention, these steps can happen in parallel or substantially simultaneously also. While the chemistry, of course, demands that at least some reduction has to happen before the solving can take place, it is the reduction of insoluble copper compounds and dissolution of such insoluble compounds by the formation of soluble complex compounds occur actually preferably simultaneously because the reduction reaction rate is much higher (preferably at least two or more orders in magnitude), compared with that of dissolution reaction. The advantage of this embodiment is that all the processes appear in a single bath (single step) because the electroless nickel plating bath contains every mentioned compound: reducer and ligand (hence a suitable mixture of all required components).

[0126] The invention has been described in terms of specific embodiments, which should be considered as examples only and not limiting the practical scope of the invention. Therefore, any changes and modifications to the technological processes, materials and reactions are possible provided that the changes and modifications do not depart from the definition of the patent invention.