EP0225422A1 - Alkaline baths and methods for electrodeposition of palladium and palladium alloys - Google Patents
Alkaline baths and methods for electrodeposition of palladium and palladium alloys Download PDFInfo
- Publication number
- EP0225422A1 EP0225422A1 EP86107737A EP86107737A EP0225422A1 EP 0225422 A1 EP0225422 A1 EP 0225422A1 EP 86107737 A EP86107737 A EP 86107737A EP 86107737 A EP86107737 A EP 86107737A EP 0225422 A1 EP0225422 A1 EP 0225422A1
- Authority
- EP
- European Patent Office
- Prior art keywords
- electrolyte
- palladium
- complexing agent
- substrate
- compound
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Ceased
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Classifications
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
- C25D3/00—Electroplating: Baths therefor
- C25D3/02—Electroplating: Baths therefor from solutions
- C25D3/50—Electroplating: Baths therefor from solutions of platinum group metals
- C25D3/52—Electroplating: Baths therefor from solutions of platinum group metals characterised by the organic bath constituents used
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
- C25D3/00—Electroplating: Baths therefor
- C25D3/02—Electroplating: Baths therefor from solutions
- C25D3/56—Electroplating: Baths therefor from solutions of alloys
- C25D3/567—Electroplating: Baths therefor from solutions of alloys containing more than 50% by weight of platinum group metals
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Electroplating And Plating Baths Therefor (AREA)
Abstract
Description
- The invention relates to the electrodeposition of pure palladium or palladium alloys and to alkaline electrolytic plating solutions containing palladium metal, a complexing agent, and, when desired, one or more alloying metals.
- Electrical contacts and connectors, as used in the electronics field, are generally fabricated from copper alloys onto which is electrodeposited a thin layer of a precious metal such as gold or palladium. The electrodeposit must possess certain metallurgical properties such as corrosion resistance, freedom from porosity, wear resistance, low and stable contact resistance, ductility, etc. In most cases, gold which has been hardened with a small amount of nickel or cobalt is used as the electrodeposit.
- The industry initially began to substitute palladium or palladium alloys in place of gold in an attempt to lower the cost of these contacts. Thus, the industry is continually searching for better electroplating baths and processes for depositing these metals.
- Numerous electroplating solutions for pure palladium have been disclosed by the prior art. Although these solutions may contain various palladium species, a wide range of additives, and pHs ranging virtually from 0 to 14, the most commonly employed palladium plating solutions contain inorganic amine complexes of palladium. Two preferred complexes are palladosamine chloride Pd(NH3)4C12 or palladium diaminodinitrite Pd(NH3)2(N02)2 and baths containing these complexes are usually operable over a pH range of between about 8 and 10. It is also common to utilize a slight excess of ammonia or ammonium hydroxide to stabilize these complexes in the bath.
- Such prior art plating baths have several disadvantages, including evolution of ammonia fumes, frequent replenishment of the ammonium stabilizing compound and the required use of strike baths for certain basis metals.
- The present invention proposes electrolytes and methods for the electrodeposition of pure palladium or palladium alloys that present an improvement over the prior art electrolytes and their deposits.
- An objective of this invention is to provide an alkaline electrolyte for the electrodeposition of palladium or palladium alloys. This electrolyte has a minimum attack on the basis metals being plated, and is stable so that it will not deteriorate with extended use. In this regard, the electrolyte formulation is commercially feasible and able to operate satisfactorily in modern electroplating equipment.
- Another objective of this invention is to electroplate a palladium or palladium alloy by utilizing these novel electrolytes. Such palladium or palladium-alloy electrodeposits are lustrous, semi-bright to bright deposits having suitable ductility, freedom of porosity, wearability, corrosion resistance and low contact resistance. These are the physical and metallurgical characteristics which are necessary for applications involving electrical contacts and connectors.
- The invention relates to an alkaline electrolyte for the electrodeposition of palladium or palladium alloys which comprises at least one soluble palladium compound, at least one complexing agent and, when desired, one or more soluble alloying metal compounds. When palladium alloy plating is desired the amount and type of the complexing agent should be sufficient to provide electrodeposition potentials of palladium and the alloying metals sufficiently close to obtain the desired palladium alloy deposits. Preferably, these deposits should have a palladium content of at least about 20%.
- The complexing agent should be present in an amount sufficient to maintain the palladium and the alloying metal compounds in solution in the electrolyte. Also, the electrolyte must have a sufficiently alkaline pH to solubilize the complexing agent and metal complexes. The pH of these electrolytes normally ranges from about 8 to 14, with 12 to 14 being preferred.
- The complexing agents of the invention include any organic compound which is soluble in the electrolyte and which contains at least one heterocyclic ring having at least one nitrogen atom in the ring, with at least one of the ring carbons containing a hydroxyl or carbonyl oxygen group, and the ring being substituted with at least one carboxyl group. A single four, five, six or seven member heterocyclic ring or groups of such rings may be utilized in the invention. Specifically preferred complexing agents include chelidamic acid, orotic acid, or 2-pyrrolidone-5-carboxylic acid.
- The invention also relates to methods for formulating electrolytes which can be used for electroplating palladium or palladium alloys. The electrolytes are formulated by adding the palladium compound, the complexing agent, and, optionally, an alloying metal compound, to water and adjusting the amount of complexing agent as well as the pH of the solution to solubilize these compounds. The electroplating methods include immersing a suitable anode and a substrate to be plated into these electrolytes and electroplating palladium or a palladium alloy thereupon by passing an electric current through the electrolyte.
- The invention achieves substantial improvements over prior art palladium and palladium alloy baths and plating methods by supplying an electrolyte that contains palladium and, when used, the alloying metal, in an alkaline bath. These metals are complexed by chelating or complexing agents so that their electrodeposition potentials are close enough to permit the electroplating of palladium alloys having the desired palladium content. All metal compounds in the electrolyte are complexed by the complexing agent provided. "Complexing agents. or "chelating agents" are equivalent for purposes of this invention.
- The complexing agents which are suitable for this invention include any organic compound which is soluble in the electrolyte and which contains at least one heterocyclic ring having one or more nitrogen atoms in the ring, at least one carboxyl group substituted on a ring carbon and/or at least one hydroxyl or carbonyl oxygen attached to a ring carbon. When a single heterocyclic ring is utilized as a complexing agent, it preferably should contain between four and seven members. Multiple-rings are also contemplated by the invention.
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- R is a carboxyl group attached to the ring and W is 1, 2, or 3;
- R 2 is a carbonyl oxygen or its hydroxyl tautomer attached to the ring and X is 0, 1, 2, or 3;
- R 3 is a substituent which may include hydroxyl, carbonyl, carboxyl, aldehyde, H, Cl, S, HSO3, phenyl, NH2, NO- or any other substituent which will not adversely affect the solubility of the compound in the bath, its stability or its chelation or complexing ability and Y is 0, 1, 2, or 3;
- Z is 1, 2, or 3; and
- A indicates an additional substituent that may be the same or similar to the presently described heterocyclic ring which will form a di or tricyclic ring system therewith.
- The carboxyl group of R1 is preferably attached directly to a ring carbon. However, it may also be indirectly attached to a ring carbon through another substituent as long as the solubility, stability, and complexing ability of the compound is not adversely affected. Similarly, the carbonyl oxygen and its hydroxyl tautomer may also be directly or indirectly attached to a ring carbon.
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- Preferred compounds include those described above which have at least 1 carboxyl group substituted on a ring carbon and at least 1 hydroxyl or carbonyl oxygen attached to a ring carbon, singly or in combination.
- Other preferred compounds are those having at least two carboxyl groups attached to ring carbons. Optionally, these compounds may also have a hydroxyl or carbonyl oxygen attached to a ring carbon.
- For any of these compounds to be successful in the present invention, the compound must be soluble in the electrolyte. Thus, solubilizing groups may be added to these compounds to increase their ability to remain soluble in the electrolyte. Also, the pH of the solution can be adjusted to increase the solubility of the compound in the electrolyte.
- The heterocyclic ring compound must be capable of complexing the palladium compound as well as the alloying metal compounds, over an alkaline pH range of 8-14 in order the plating potentials of the metals can be brought sufficiently close so that the desired alloy can be plated. A pH range of about 12 to 14 is usually optimum.
- Examples of the preferred heterocyclic ring compounds are those that are substituted with at least one carbonyl group and at least one carboxyl group. These compounds, which must be stable and form soluble metal complexes at the operating pH of the bath, include:
- chelidamic acid
- orotic acid
- hydantoin carboxylic acid
- succinimide carboxylic acid
- 2-pyrrolidone-5-carboxylic acid
- carboxy hydroxy pyridine
- carboxy caprolactam
- picolinic or dipicolinic acid
- carboxy xanthine
- quinoline carboxylic acid or dicarboxylic acid
- α-imidazilidone-4-carboxylic acid
- The compound of choice should be readily soluble in the bath at the operating pH and should be capable of complexing the selected metals. Also, the metal complexes should likewise be bath soluble. The term ™complexing ability. as used herein includes both the complexing and/or chelating functions of the compound.
- The pH of the bath can be varied by adding a base such as lithium, sodium, ammonium, or potassium hydroxide (for raising the pH) or by adding a suitable acid to reduce the pH. When using any specific compound that is disclosed herein, the pH range to be used is that which maintains all metals in solution so that the proper alloy can be deposited containing the desired metallurgical characteristics.
- The most advantageous compounds within the scope of this invention can be readily determined by those skilled in the art by routine experimentation.
- Plating tests are run at the pH values which produce homogeneous solutions. The metallurgical characteristics of the deposits are then examined for suitability for the intended application, i.e., such as for use on electrical contacts or connectors.
- Not all compounds within the scope of the groups disclosed herein are capable of achieving all of the objectives of this invention. Some compounds do not achieve sufficient solubility and some of the resultant electrolytes are not stable. Some of the deposits may not have sufficient brightness, some may be too brittle and crack, others may be non-uniform, etc. All of these compounds, however, achieve some of the objectives of the invention. Those skilled in the art can readily determine which compounds or combinations of compounds are most suitable for the intended uses.
- The most desirable compounds for complexing palladium from those disclosed in this invention are, as mentioned above, those heterocyclic ring compounds that contain one or more carboxyl groups attached to one or more carbons in the ring, along with one or more carbonyl or hydroxyl groups each attached to one or more carbons in the ring. Specific examples of preferred compounds are chelidamic acid, orotic acid and 2-pyrrolidone-5-carboxylic acid. These compounds are illustrated below.
- For alloy plating, two or more complexing agents can be used. In certain situations, when the preferred palladium complexing compounds are utilized, the second complexing agent can be a lesser substituted compound (i.e., an organic compound having a nitrogen heterocycle wherein the ring is substituted with one carboxyl, carbonyl or hydroxyl group. This is because alloying metals in general, will not form the same strength of complexation as palladium.
- Other, secondary complexing agents may be added. These agents include ammonia, amines, amino acids, phosphonates and the like. For certain situations, bases such as ammonium hydroxide or other hydroxide compounds (i.e., alkali hydroxides and the like) are also suitable as secondary complexing agents.
- If the pH of the electrolyte is high (i.e. above about 12), there may be substantial amounts of hydroxyl ion present which can also form complexes certain with metal in the electrolyte. Such metals which are capable of being complexed by hydroxyl ions include palladium (which forms palladite, PdO2 =), zinc (zincate, ZnO2 =), gold (aurate, AuO3 ≡) and tin (stannate, SnO3 =).
- When secondary complexing agents are used and/or the solution pH is above 12, the metals may be present in the solution as an equilibrium mixture of the organic metal complex, the metal complex of the secondary complexing agent and/or the hydroxyl complex, depending upon the strength and amounts of the various metal complexes formed in the electrolyte.
- The concentrations of complexing compounds or mixtures of complexing compounds used in these electrolytes can vary from 10-200 g/1 or more depending on the metal concentrations and solubility. In general, the higher the metal concentration, the higher the concentration of the complexing compounds required. The minimum amount of complexing compound is that which is required to complex the metals sufficiently in solution to produce the desired electrodeposited alloy. The maximum amount of such agent is controlled by its solubility in the bath. If the concentration is too high, there will be a lack of solubility and crystallization or precipitation will take place.
-
- Operating temperatures can vary from ambient (i.e., 70°F) to about 170°F, with 120-150°F preferred. Current densities can vary from 1-200 ASF or higher depending upon degree of agitation, temperature and metal concentration. The pH can vary from 8-14 depending upon compounds chosen, solubility and ability to complex the metals, with a range of 12 to 14 being especially advantageous.
- When silver chloride is used as a source of silver metal, the strength of the complexing agent used must be such that it can complex silver in the presence of chloride ion. If this is not the case, then silver must be supplied as another metal salt such as silver nitrate or silver hydroxide, and the solution should be free of substantial amounts of chloride ions.
- Palladium can be supplied in a salt form such as palladium sulphate, palladium nitrate, palladium hydroxide, or palladium chloride, if chloride does not cause precipitation. It may also be possible to separately form the palladium and or other metal complexes of the desired compound and then add the metal to the electrolyte in the form of the metal complex which is soluble in the electrolyte at the operating pH.
- Having thus described the invention, the following non-limiting examples are further illustrative of the invention. In each example, a plating bath was prepared by adding the disclosed components into water.
-
- Example 1 Pure palladium was plated from the above stock solution and a sound, uniform, bright to semibright deposit was obtained.
- Example 2 1.8 grams/liter of tin metal as tin sulfate was added to the stock solution. The deposit obtained contained 54.7% palladium and 45.3 tin. The deposit was sound, and bright to semi-bright.
- Example 3 0.3 grams/liter of indium as indium sulfate was added to the stock solution and the deposit obtained contained 90.4% palladium and 9.6% indium. The deposit was sound and bright to semi-bright.
- Example 4 1.0 g/1 of nickel as nickel sulfate was added to the stock solution and the deposit contained 87.6% palladium and 12.4% nickel. The deposit was sound and bright to semi- bright.
- Example 5 0.9 g/l of copper as copper sulfate was added to the stock solution and the deposit which was obtained contained 64.2% palladium and 35.8% copper. The deposit was sound and bright to semi-bright.
- Example 6 1.1 g/l of gold as gold chloride was added to the stock solution and a deposit was obtained that contained 68.6% palladium and 31.4% gold. The deposit was sound and bright to semi-bright.
- As noted above, predetermined amounts of cobalt, zinc, or cadmium metal can also be added to the stock solution to provide the desired alloy. The only limitation on the alloying metal is that it should be soluble in the electrolyte.
- If more than one alloying metal is used, then a ternary, rather than binary, alloy can be electrodeposited. The following example illustrates a ternary alloy according to the invention.
- Example 7 1 g/l silver metal (as silver nitrate) and 1 g/l gold metal (as gold chloride) were added to the stock solution. The deposit was sound and bright and analyzed 43.8% palladium, 55.4% silver, and 0.6% gold.
- The remaining examples illustrate various palladium-silver baths and electrodeposits.
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- Examples 10 through 17 produce palladium-silver alloy deposits ranging from about 70:30 to 50:50 composition.
- Although the examples illustrate the use of a single complexing agent in each bath, it is understood that two or more of such agents can be combined to obtain equal or better results. Also, secondary complexing agents, as described above, may be added to the electrolyte to complex the alloying metals.
- While it is apparent that the invention herein disclosed is well calculated to fulfill the objects above stated, it will be appreciated that numerous modifications and embodiments may be devised by those skilled in the art,and it is intended that the appended claims cover all such modifications and embodiments as fall within the true spirit and scope of the present invention.
Claims (40)
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US80813185A | 1985-12-12 | 1985-12-12 | |
US808131 | 1985-12-12 |
Publications (1)
Publication Number | Publication Date |
---|---|
EP0225422A1 true EP0225422A1 (en) | 1987-06-16 |
Family
ID=25197950
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP86107737A Ceased EP0225422A1 (en) | 1985-12-12 | 1986-06-06 | Alkaline baths and methods for electrodeposition of palladium and palladium alloys |
Country Status (2)
Country | Link |
---|---|
EP (1) | EP0225422A1 (en) |
JP (1) | JPS62139893A (en) |
Cited By (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB2283498A (en) * | 1993-08-16 | 1995-05-10 | Enthone Omi Inc | Metallic additive-free white palladium electroplating bath |
GB2287717A (en) * | 1994-02-26 | 1995-09-27 | Sung Soo Moon | Palladium-gold alloy electroplating compositions |
WO2000035259A2 (en) * | 1998-12-10 | 2000-06-15 | Gerhard Naundorf | Method for producing printed conductor structures |
WO2017210728A1 (en) * | 2016-06-06 | 2017-12-14 | Commonwealth Scientific And Industrial Research Organisation | Method of forming a pd-au alloy layer on a substrate |
DE102018120357A1 (en) * | 2018-08-21 | 2020-02-27 | Umicore Galvanotechnik Gmbh | Electrolyte for the deposition of silver and silver alloy coatings |
US11846036B2 (en) | 2018-08-21 | 2023-12-19 | Umicore Galvanotechnik Gmbh | Electrolyte for the cyanide-free deposition of silver |
Families Citing this family (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPH06146058A (en) * | 1992-11-04 | 1994-05-27 | Bisou Japan:Kk | Palladium-indium alloy plating bath |
JPH06146059A (en) * | 1992-11-12 | 1994-05-27 | Bisou Japan:Kk | Palladium-cobalt-indium alloy plating bath |
JP2008081765A (en) * | 2006-09-26 | 2008-04-10 | Tanaka Kikinzoku Kogyo Kk | Palladium alloy plating solution and method for plating using the same |
JP5758361B2 (en) * | 2012-08-31 | 2015-08-05 | 日本エレクトロプレイテイング・エンジニヤース株式会社 | Non-cyanide gold-palladium alloy plating solution and plating method |
Citations (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3458409A (en) * | 1964-10-12 | 1969-07-29 | Shinichi Hayashi | Method and electrolyte for thick,brilliant plating of palladium |
US3972787A (en) * | 1974-06-14 | 1976-08-03 | Lea-Ronal, Inc. | Palladium electrolyte baths utilizing quaternized pyridine compounds as brighteners |
US4278514A (en) * | 1980-02-12 | 1981-07-14 | Technic, Inc. | Bright palladium electrodeposition solution |
DE3317493A1 (en) * | 1983-05-13 | 1984-11-15 | W.C. Heraeus Gmbh, 6450 Hanau | GALVANIC DEPOSITION OF PALLADIUM COVERS |
EP0149029A1 (en) * | 1983-12-29 | 1985-07-24 | INOVAN-Stroebe GmbH & Co. KG | Palladium bath |
-
1986
- 1986-06-06 EP EP86107737A patent/EP0225422A1/en not_active Ceased
- 1986-06-06 JP JP13044186A patent/JPS62139893A/en active Pending
Patent Citations (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3458409A (en) * | 1964-10-12 | 1969-07-29 | Shinichi Hayashi | Method and electrolyte for thick,brilliant plating of palladium |
US3972787A (en) * | 1974-06-14 | 1976-08-03 | Lea-Ronal, Inc. | Palladium electrolyte baths utilizing quaternized pyridine compounds as brighteners |
US4278514A (en) * | 1980-02-12 | 1981-07-14 | Technic, Inc. | Bright palladium electrodeposition solution |
DE3317493A1 (en) * | 1983-05-13 | 1984-11-15 | W.C. Heraeus Gmbh, 6450 Hanau | GALVANIC DEPOSITION OF PALLADIUM COVERS |
EP0149029A1 (en) * | 1983-12-29 | 1985-07-24 | INOVAN-Stroebe GmbH & Co. KG | Palladium bath |
Cited By (10)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB2283498A (en) * | 1993-08-16 | 1995-05-10 | Enthone Omi Inc | Metallic additive-free white palladium electroplating bath |
GB2283498B (en) * | 1993-08-16 | 1997-06-25 | Enthone Omi Inc | Electroplating bath and process for white palladium |
GB2287717A (en) * | 1994-02-26 | 1995-09-27 | Sung Soo Moon | Palladium-gold alloy electroplating compositions |
US5552031A (en) * | 1994-02-26 | 1996-09-03 | Hanyang Chemical Ind., Co. | Palladium alloy plating compositions |
GB2287717B (en) * | 1994-02-26 | 1997-09-24 | Sung Soo Moon | Palladium-gold alloy plating compositions |
WO2000035259A2 (en) * | 1998-12-10 | 2000-06-15 | Gerhard Naundorf | Method for producing printed conductor structures |
WO2000035259A3 (en) * | 1998-12-10 | 2000-10-19 | Gerhard Naundorf | Method for producing printed conductor structures |
WO2017210728A1 (en) * | 2016-06-06 | 2017-12-14 | Commonwealth Scientific And Industrial Research Organisation | Method of forming a pd-au alloy layer on a substrate |
DE102018120357A1 (en) * | 2018-08-21 | 2020-02-27 | Umicore Galvanotechnik Gmbh | Electrolyte for the deposition of silver and silver alloy coatings |
US11846036B2 (en) | 2018-08-21 | 2023-12-19 | Umicore Galvanotechnik Gmbh | Electrolyte for the cyanide-free deposition of silver |
Also Published As
Publication number | Publication date |
---|---|
JPS62139893A (en) | 1987-06-23 |
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