Electrodeposition from multiple electrolytes

Abstract

EL The present invention provides a system for electrodepositing a plurality of electrolytes onto a substrate in a single deposition chamber to form an article, in which the system comprises a removable substrate; a deposition chamber containing the substrate in which the chamber has an inlet and an outlet and in which the chamber comprises at least one anode with connection to a source of electrical current; a plurality of electrolyte reservoirs for an electrolyte solution connected to the deposition chamber through the inlet; and a rinse medium reservoir connected to the deposition chamber through the inlet. Also provided is a system comprising a cradle to form an article, methods using the systems of the invention, and composite materials and devices prepared by the methods of the invention.

Claims

1. A system for electrodepositing different metals onto a substrate from a plurality of electrolytes to form an article, in which the system comprises (i) a removable substrate that is removable from the article to be formed via electrodeposition; (ii) a cradle containing the substrate in which the cradle comprises a plurality of anodes with connection to a source of electrical current, wherein each anode is located at a different position relative to the substrate; (iii) a plurality of electrolyte solution baths, wherein each electrolyte bath is configured to electrodeposit a different metal onto the substrate; and (iv) a rinse medium bath, wherein the system is configured such that each anode of the plurality of anodes is configured so as be able to receive a different electrical current from another anode of the plurality of anodes.

2. A system as claimed in claim 1, wherein the system comprises a robotic arm configured to move the cradle between electrolyte solution baths.

3. A system as claimed in claim 1, wherein the system comprises a plurality of cradles.

4. A system as claimed in claim 1, wherein the system comprises a non-conducting field modifier positioned between the substrate and an anode.

5. A system as claimed in claim 1, wherein the substrate is thermolabile, cryosensitive or soluble.

6. A system as claimed in claim 1, wherein at least one anode is an insoluble anode.

7. A system as claimed in claim 1, in which each electrolyte solution includes one or more transition metal ions.

8. A system as claimed in claim 7, in which the one more transition metal ions is selected from the group consisting of vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), and combinations thereof.

9. A system as claimed in claim 1, in which at least one electrolyte solution includes one or more noble metal ions selected from the group consisting of ruthenium (Ru), rhodium (Rh), palladium (Pd), silver (Ag), osmium (Os), iridium (Ir), platinum (Pt) and gold (Au), and combinations thereof.

10. A system as claimed in claim 1, in which at least one electrolyte solution includes one more metal ions selected from the group consisting of silver (Ag), gold (Au), palladium (Pd), copper (Cu), iron (Fe), cobalt (Co), nickel (Ni), zinc, (Zn) and tin (Sn), or combinations thereof.

11. A system as claimed in claim 10, in which at least one electrolyte solution comprises nickel and cobalt.

12. A system as claimed in claim 1, wherein each of the plurality of electrolyte solution baths includes one or more metal ions is selected from the group consisting of vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), ruthenium (Ru), rhodium (Rh), palladium (Pd), silver (Ag), osmium (Os), iridium (Ir), platinum (Pt) and gold (Au), zinc, (Zn) and tin (Sn), and combinations thereof.

13. A method for electrodeposition of different metals from a plurality of electrolytes on a substrate to form an article, in which the substrate is held in a cradle, comprising using a system as claimed in claim 1, said method comprising forming an article by electrodeposition of different metals from a plurality of electrolytes on a removable substrate.

14. The method of claim 13, further comprising the step of removing the substrate from the article.

Description

(1) The invention will now be further described in the following Examples which are present for the purposes of illustration only and should not be construed as being limitations on the invention. Reference is made in the Examples to the following drawings in which:

(2) FIG. 1 shows a schematic diagram of the arrangement for depositing more than one electrolyte in a deposition chamber.

(3) FIGS. 2 and 3 show schematic diagrams of example deposition chambers.

(4) FIG. 4 shows a schematic diagram of the arrangement for depositing a work piece cradle into a series of electrolytic baths and rinsing baths. The electrolytic baths may be independently heated, stirrer and monitored for ion concentration, pH and temperature.

(5) FIGS. 5 and 6 shows schematic diagrams of an example work piece cradle.

(6) FIG. 7 shows a flow diagram of essential and optional process steps to form an object by the process described herein. Steps highlighted in double lines are the path taken in the Example 1 described herein.

(7) In FIG. 1, a deposition chamber (“deposition vessel”) (1) is shown in fluid connection via a control valve (3) to an electrolyte reservoir (5) containing “Electrolyte 1”, a rinse reservoir (7) and an electrolyte reservoir (9) containing “Electrolyte 2”. Each of electrolyte reservoirs (5) and (9) are under the control of optional concentration monitors (11) and (13) respectively. The feeds of fresh electrolyte via separate fluid connection circuits into electrolyte reservoirs (5) and (9) are provided with optional filters (15) and (17) respectively. The feed of fresh electrolyte and waste spent electrolyte is controlled by three-way valve (19) which is in fluid connection with a suitable waste receptacle (21).

(8) In use the system of the invention can therefore be operated to provide flows of electrolyte into the deposition chamber. The concentration of the electrolyte in the electrolyte reservoirs can be independently monitored and controlled.

(9) In some embodiments, the electrolyte can be recycled from the deposition chamber back into the electrolyte reservoirs. Alternatively, the electrolyte solution from the deposition chamber can be removed after use.

(10) In FIG. 2, a deposition chamber (100) is shown in which a substrate (or work piece) (102) is shown.

(11) The chamber is formed from a sidewall (101) and end caps (103, 105). The chamber is provided with an electrolyte outlet (104) and a rinsing medium (water purge) inlet (106) in end cap (103). Electrode connections (108, 110) are shown in end cap (103) for the electrodes (anodes) (112, 114). The chamber is provided with an external heater (116, 118), an internal agitation device (120), an internal temperature sensor (122) and a pH sensor (124). The internal agitation device (120) is not shown in detail. In end cap (105), there is provided an electrolyte inlet and drain (outlet) (126) and a rinsing medium (water purge) outlet (drain) (128). Electrode connections (130, 132) are shown in end cap (105).

(12) FIG. 3 shows a deposition chamber (100) with the features of FIG. 2, but with the addition of non-conducting field modifiers (133) positioned between the electrodes (anodes) (112, 114) and the work piece (102).

(13) In FIG. 4, a cradle (10) is shown attached to a robotic arm (12). Three solution baths are shown, containing “Electrolyte 1” in bath (5), “Electrolyte 2” in bath (9), and rinse medium in bath (7). Each solution bath is under the control of optional concentration monitors (11) and (13) respectively.

(14) In use the system of the invention can therefore be operated such that the robotic arm brings the cradle (10) to each solution bath and lowers and raises the cradle into and out of the solution bath. The concentration of the electrolyte in the solution baths can be independently monitored and controlled.

(15) In FIG. 5, a cradle (107) is shown in which a substrate (or work piece) (102) is shown. The cradle is formed from a connecting frame (134) and end caps (103, 105). The cradle is provided with electrode connections (108, 110) in end cap (103) for the electrodes (anodes) (112, 114). Electrode connections (130, 132) are shown in end cap (105).

(16) FIG. 6 shows a cradle (107) with the features of FIG. 5, but with the addition of non-conducting field modifiers (133) positioned between the electrodes (anodes) (112, 114) and the work piece (102).

(17) In FIG. 7, the outline of a work-flow is described using a system of the invention. The process may comprise (i) drawing the device to be prepared, for example using CAD system; (ii) preparing the pre-form or mandrel, e.g. using 3D-printing, or extruded tube or injection moulded part, or wax casting; (iii) preparation of the initial electrode, e.g. using silver Electrodag™ spray, or silver mirror or electroless metal deposition, followed by addition of sacrificial metal layer; (iv) internal finish—inner surface deposition; (v) main structure to control strength, for example single layer deposition, or multilayer deposition with a bilayer structure, or multilayers of immiscible metals, or multilayers of pure metal and metal including particles, or metal alloy co-deposition; (vi) external finish—outer surface deposition; (vii) remove mandrel, for example using hot caustic, solvent vapour, heating, or cooling; and (viii) remove sacrificial layer, for example by selective etch. The process may alternatively comprise preparing a stainless steel former from the drawing.

Example 1: Deposition of High Strength Obround Beam

(18) An obround beam was prepared according to a method of the invention as follows: 1. A polystyrene extrusion with the interior dimensions of the obround beam (16 mm×10 mm) and a length of 300 mm was sprayed with silver Electrodag™ to produce a thin even coating and the solvent allowed to evaporate. Total surface area=1.3 dm.sup.2. 2. The coated extrusion was placed in the deposition vessel so that it was in contact with the end-cap central electrodes and the circuit checked for good electrical contact. 3. The deposition vessel was then assembled and with pipes and electrical connections made. Non-consuming anodes were positioned to provide an even deposition over the entire surface area of the mandrel. 4. Holding tanks containing the electrolytes to be used were continually agitated through a filter pump and maintained at the desired temperature. These were: (i) Nickel sulphamate (Ni(NH.sub.2SO.sub.3).sub.2,4H.sub.2O) at a concentration of 80-100 g/L+nickel chloride (NiCl.sub.2)+HCl, T=30° C. pH<3. Anode material was pure nickel. Ethylenediaminetetraacetic acid (EDTA) was used as a complexing agent and surfactants added as required ˜5 mL/L to prevent gas bubbles forming at the cathode. (ii) Copper sulphate at a concentration of 80-100 g/L+12-15% H.sub.2SO.sub.4, T=30° C., pH 1.5-2. Copper alloyed with 3% phosphorous (Cu3% P) used as an anode material in the holding tank. Ethylenediaminetetraacetic acid (EDTA) was used as a complexing agent and surfactants added as required to prevent gas bubbles forming at the cathode. 5. Internal surface deposition: The nickel electrolyte was pumped into the deposition vessel and Ni deposited at a current density of 2 A/dm.sup.2 for 30 minutes (5 μm). 6. Multi-layer deposition: The deposition vessel was first flushed with a water air mixture and then filled with the copper electrolyte. The current was connected in the reverse polarity and energized for 5 seconds, then in the normal polarity at a current density of 1.5 A/dm.sup.2 for 3 minutes. The vessel was then flushed with the water air mixture and filled with the nickel electrolyte and Ni deposited at a current density of 2 A/dm.sup.2 for 3 minutes. This sequence was repeated 100 times. 7. External surface deposition: The nickel electrolyte was pumped into the deposition vessel and Ni deposited at a current density of 2 A/dm.sup.2 for 30 minutes (5 μm). 8. The deposition vessel was flushed with a water air mixture, drained and dried. The part was removed from the deposition vessel and placed in a vapour degreasing apparatus. Butyl acetate solvent was passed through the inside of the part until all of the polystyrene mandrel had been removed.

(19) The material making up the resulting part has a tensile yield strength (0.2% plastic strain) of 750 MPa, an ultimate tensile strength of 1500 MPa and strain to failure of 2%.

Example 2: Deposition of Bellows Integrated Couplings

(20) A flexible bellows with integral flanges and fixing holes is prepared according to a method of the invention as follows: 1. A 3 dimensional printed hollow mandrel is generated from a computer aided design drawing of the interior surface of the bellows (internal diameter 15 mm and an overall length of 100 mm) that consists of a corrugated region and flanges at each end extending to a diameter of 35 mm. The mandrel is coated with silver using the silver mirror process. Silver is removed from the areas of the mandrel that will form the fixing holes. Total surface area=0.65 dm.sup.2. 2. The silvered mandrel is placed in the deposition vessel so that it is in contact with the end-cap central electrodes and the circuit checked for good electrical contact. 3. The deposition vessel is then assembled and with pipes and electrical connections made. Non-consuming anodes are positioned to provide different deposition conditions at the corrugated section of the bellows and the flanged areas at each end of the mandrel. Non-conductive field modifiers may be positioned between the anodes and work piece as required. 4. Electrolytes to be used are as described in Example 1. 5. Internal surface deposition: The nickel electrolyte is pumped into the deposition vessel and Ni deposited at a current density of 2 A/dm.sup.2 for 15 minutes (5 μm) over the whole surface area. 6. Multi-layer deposition: The deposition vessel is first flushed with a water air mixture and then filled with the copper electrolyte. The current is connected in the reverse polarity and energized for 5 seconds, then in the normal polarity at a current density of 1.5 A/dm.sup.2 for 1.5 minutes across the whole surface area and then a further 3 minutes at the flange area only. The vessel is then flushed with the water air mixture and filled with the nickel electrolyte and Ni deposited at a current density of 2 A/dm.sup.2 for 1.5 minutes only in the area of the corrugations. This sequence is repeated 100 times. 7. External surface deposition: The nickel electrolyte is pumped into the deposition vessel and Ni deposited over the whole work piece at a current density of 2 A/dm.sup.2 for 15 minutes (5 μm). 8. The deposition vessel is flushed with a water air mixture, drained and dried. The part is removed from the deposition vessel and flushed internally with caustic soda at 90° C. until the mandrel has been removed, followed by vapour degreasing.

Example 3: Deposition of Heat Exchanger with the Couplings Joined into the Part

(21) A heat-exchange vessel with integral pipe couplings is prepared according to a method of the invention as follows: 1. A computer aided design drawing of the interior surface of the heat-exchanger is created so that it can be wrapped around the component to be cooled to maximise the cooling efficiency. The shape may be a hollow form with approximate dimensions of, for example, 50 mm×50 mm×3 mm and include pipe runs to allow fluid in and out of the vessel. The shape may include mesas positioned to maintain the 3 mm thickness of the hollow form. An aluminium mould is created by computer aided machining from which wax casts can be made. The wax cast is sprayed with silver Electrodag™ to produce a thin even coating and the solvent allowed to evaporate. Total surface area of approximately 0.65 dm.sup.2. 2. The silver coated wax is placed in a cradle so that it is in contact with the end-cap central electrodes and the circuit checked for good electrical contact. 3. The cradle is then assembled and electrical connections made. Non-consuming anodes are positioned to provide different deposition conditions at the edges of the heat-exchanger to those of the flat areas. 4. Electrolytes to be used are as described in Example 1. 5. Internal surface deposition: The cradle is lowered into the nickel electrolyte and Ni deposited at a current density of 2 A/dm.sup.2 for 15 minutes (5 μm) over the whole surface area. 6. Multi-layer deposition: The cradle is removed from the nickel electrolyte tank and lowered into a rinsing bath. The cradle is then removed from the rinsing bath and lowered into the copper electrolyte. The current is connected in the reverse polarity and energized for 5 seconds, then in the normal polarity at a current density of 1.5 A/dm.sup.2 for 1.5 minutes across the whole surface area. The cradle is then removed from the copper electrolyte tank and lowered into a rinsing bath. The cradle is then lowered into the nickel electrolyte and Ni deposited at a current density of 2 A/dm.sup.2 for 30 seconds only around the edges of the heat exchanger. This sequence is repeated 100 times. 7. Addition of pipe couplings: The part is then removed from the cradle and proprietary pipe couplings placed onto the pipe ends. 8. External surface deposition: The cradle is lowered into the copper electrolyte and Cu deposited at a current density of 1.5 A/dm.sup.2 for 150 minutes (50 μm) over the whole part including the couplings so that they become integrated into the part. 8. The cradle is then removed from the copper electrolyte tank and lowered into a rinsing bath. The part is removed from the cradle and placed in an oven at a temperature 30° C. above the melting temperature of the wax until the wax has been drained from the part, followed by vapour degreasing.

Example 4: Deposition of Concentric Spiral Tube Heat Exchanger

(22) A heat-exchanger consisting of 3 concentric pipes, each separated from each other in the shape of a spiral is prepared according to a method of the invention as follows: 1. A 3 dimensional printed wax spiral is generated from a computer aided design drawing of the interior of the inner most pipe of the heat exchanger, for example, with dimensions of 5 mm diameter solid, in a helical shape 25 mm in diameter and 100 mm in length. The resulting wax mandrel is coated with silver using the silver mirror process. Total surface area of approximately 0.45 dm.sup.2. 2. The silvered coated wax mandrel is placed in a cradle so that it is in contact with the end-cap central electrodes and the circuit checked for good electrical contact. 3. The cradle is then assembled and electrical connections made. Non-consuming anodes are positioned to provide an even deposition over the entire surface area of the mandrel. 4. Electrolytes to be used are as described in Example 1. 5. First pipe deposition: The cradle is lowered into the copper electrolyte and Cu deposited at a current density of 1.5 A/dm.sup.2 for 100 minutes (50 μm). 6. The cradle is then removed from the copper electrolyte tank and lowered into a rinsing bath. The part is removed from the cradle and dipped in molten wax to build up an even 2.5 mm wax deposit on the part. Pipe inlets and outlets are created by attaching polystyrene tube to the ends of the part, embedded in the wax. The resulting wax mandrel is coated with silver using the silver mirror process. 7. Second pipe deposition: The cradle is lowered into the copper electrolyte and Cu deposited at a current density of 1.5 A/dm.sup.2 for 200 minutes (50 μm). 8. The cradle is then removed from the copper electrolyte tank and lowered into a rinsing bath. The part is removed from the cradle and dipped in molten wax to build up an even 2.5 mm wax deposit on the part. Pipe inlets and outlets are created by attaching polystyrene tube to the ends of the part, embedded in the wax. The resulting wax mandrel is coated with silver using the silver mirror process. 9. Third pipe deposition: The cradle is lowered into the copper electrolyte and Cu deposited at a current density of 1.5 A/dm.sup.2 for 15 minutes. 10. Multilayer deposition: The cradle is then removed from the copper electrolyte tank and lowered into a rinsing bath. The cradle is then lowered into the nickel electrolyte and Ni deposited at a current density of 2 A/dm.sup.2 for 5 minutes. The cradle is then removed from the nickel electrolyte tank and lowered into a rinsing bath. The cradle is then lowered into the copper electrolyte. The current is connected in the reverse polarity and energized for 5 seconds, then in the normal polarity at a current density of 1.5 A/dm.sup.2 for 15 minutes. This sequence is repeated 50 times. 11. External surface deposition: The nickel electrolyte is pumped into the deposition vessel and Ni deposited at a current density of 2 A/dm.sup.2 for 15 minutes (5 μm). 12. The cradle is then removed from the nickel electrolyte tank and lowered into a rinsing bath. The part is removed from the cradle and placed in an oven at a temperature 30° C. above the melting temperature of the wax until the wax has been drained from the part. The part is then placed in a vapour degreasing apparatus. Butyl acetate solvent is passed through the inside of the part until all of the polystyrene tubes and traces of wax have been removed.

Example 5: Deposition of Concave Mirror

(23) A concave mirror is prepared according to a method of the invention as follows: 1. A convex stainless steel mandrel with the curvature and dimensions of the mirror to be formed is constructed by computer aided machining with, for example, a diameter of 100 mm. The mandrel may include flanges around the edges of the mirror that provide structural rigidity and fixing points for attachment to a supporting structure. The part of the mandrel corresponding to the mirror surface may be polished to a high surface finish. 2. The mandrel is placed in the deposition vessel so that it is in contact with the end-cap central electrodes and the circuit checked for good electrical contact. 3. The deposition vessel is then assembled and with pipes and electrical connections made. Non-consuming anodes are positioned to provide different deposition conditions at the convex section of the mandrel and the flanged areas at edge of the mandrel. 4. Silver deposition: A silver electrolyte (typically, silver cyanide) is pumped into the deposition vessel and Ag deposited on the convex section only at a current density of 2 A/dm.sup.2 for 150 minutes (25 μm). 5. The deposition vessel is flushed with a water air mixture and then filled with the copper cyanide electrolyte. Cu is deposited on the convex section only at a current density of 1.5 A/dm.sup.2 for 1 minutes (0.5 μm). 6. The deposition vessel is flushed with a water air mixture and then filled with the copper electrolyte of Example 1. Cu is deposited over the whole surface area at a current density of 1.5 A/dm.sup.2 for 100 minutes (50 μm). 7. Multilayer deposition: The vessel is flushed with a water air mixture and then filled with the nickel electrolyte of Example 1 and Ni deposited at a current density of 2 A/dm.sup.2 for 5 minutes. The vessel is flushed with a water air mixture and then filled with the copper electrolyte of Example 1. The current is connected in the reverse polarity and energized for 5 seconds, then in the normal polarity at a current density of 1.5 A/dm.sup.2 for 15 minutes. This sequence is repeated 50 times. 8. External surface deposition: The deposition vessel is flushed with a water air mixture and the nickel electrolyte is pumped into the deposition vessel and Ni deposited at a current density of 2 A/dm.sup.2 for 30 minutes (5 μm). 9. The deposition vessel is flushed with a water air mixture, drained and dried. The part is removed from the deposition vessel and gentle heated on a hot plate until the part comes away from the mandrel. The mandrel may then be reused.