NL8400049A - BATH AND METHOD FOR FAST ELECTROPLATING PALLADIUM. - Google Patents

Description

VO 5344

Title: Bath and method for quickly electroplating palladium.

The invention relates to electroplating baths and methods for quickly depositing flexible palladium metal on bath backers with a specific combination of components.

Much patent literature exists over many years 5 regarding the electrical deposition of palladium metal. This prior art includes, for example, the following U.S. Patents. 330,149 1,921,941 1,993,623 10 2,207,358 2,451,340 3,150,065 3,206,382 3,458,409 15 3,480,523 3,530,050 3,544,435 3,580,820 3,933,602 20 4,076,599 _ 4,092,225 '> \ 4,098,656 and 4,144,141

The problems commonly encountered with known palladium-25 electroplating baths, including slow deposition and brittleness by hydrogen, have recently been detailed in various articles for The Second AES Symposium On Economics Use of And Substitution For Precious -Metals in The Electronics Industry of October 5 and 6, 1982 in Danvers, Mass.

The articles were from J.A. Abys "a Unique Palladium Electrochemistry 30 Characteristics and Film Properties" and from H.S. Trop and A.V. Siaweleski "Application of BTL Pd Technology to Barrel Plating."

Thus, there appears to be a need for technical palladium baths that operate effectively at high speeds over a wide range of current-tight Kéden to produce a smooth palladium deposit on a variety of substrates.

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The invention now relates to measures to overcome the problems associated with past palladium metal electroplating baths.

To this end, baths are provided with the correct combination of components for effective deposition of palladium metal on various substrates.

These baths contain palladium-amine complexes allowing for a quick deposition of flexible palladium metal. easily achieved. Thus, a flexible palladium metal can be deposited on a series of undercoats 10 with a high tolerance to metal impurities such as copper if. these specific electroplating baths are used. This is explained in more detail below.

According to the invention, it has now been found that an effective and rapid deposition of flexible and ductile palladium metal can be achieved when used as a source of palladium in the bath of a palladium amine complex in combination with at least four other bath components.

These other bath components include ammonium sulfate, an ammonium halide salt, an alkali metal pyrophosphate, and a stress reducing agent. The present electroplating baths will usually be operated under weakly basic conditions, preferably at a pH between 7 and 9. The bath temperatures will usually be between 50 and 80 ° C, while current densities up to at least 3000 ASP are effective in the invention can be applied. According to a further feature of the invention, the electroplating bath may also contain a wetting agent, preferably an alkali metal fluorosulfonate, to reduce or avoid the pitting problem which may otherwise occur.

As mentioned, one of the main components of the electroplating bath is the palladium amine complex, which may be in the form of a halogen, nitrite, nitrate, sulfate or sulfamate.

Characteristic complexes are the following: • Pd (NH3) 2Cl2

Pd (NH3) 2 (NO2) 2 Pd (NH3) 4 (NO3) 2 and Pd (NH3) 2 SO4. The chloride and dinitrite complexes are preferred for the present purpose.

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Other palladium salts that can be used are dichloro-diamine palladium and the like.

The palladium metal in the bath is used in amounts of 10-80 g / l, preferably 40-70 g / l.

The other four essential electroplating bath components are anionic sulfate, ammonium halide, an alkali metal pyrophosphate, and a stress reducer. While the amounts of these components in the baths can vary over a wide range, the presence of any of these components is essential to achieve the desired results. It will be understood that these three components are known conductive salts or electrolytes.

Ammonium sulfate is usually used in amounts of 20-60 g / 1 and preferably 30 to 50 g / 1.

The ammonium halide can be ammonium chloride, ammonium bromide, or ammonium fluoride. However, the use of ammonium chloride is preferred. The amount of ammonium halide in the bath can vary from 10-80 g / l, and most preferably 20-30 g / l.

Tetra potassium pyrophosphate is the preferred alkali metal pyrophosphate that can be used in electroplating in the instant baths. Nevertheless, other tetra-alkali metal pyrophosphates such as tetrasodium pyrophosphate, ammonium pyrophosphate and the like can also be used. The tetra-alkali metal pyrophosphate is usually used in amounts between 20 and 150 g / l, most preferably about 80-100 g / l, calculated as a trihydrate salt. The use of electroplating baths 25 with palladium diamine dinitrite and tetrapotassium pyrophosphate is disclosed in U.S. Patent 4,092,225, but the current density is limited to about 50 ASF.

The fifth essential component of the present baths is a anti-spawning agent. Preferably, this stress relieving agent is a derivative of benzenesulfonic acid and the use of o-formyl benzenesulfonic acid (OFB) has been found to be particularly suitable for various applications.

Other stress relievers that can be used include, for example, saccharin and 2-butene-1,4-dione. Generally, the strain reducing agent will be used in an amount of 1-10 g / l, most preferably 3-5 g / l.

The electroplating baths of the invention also contain 8400049-4-further ingredients common in this technique, provided that they do not adversely affect the production of ductile or flexible palladium or the rapid deposition achievable with the invention. As mentioned previously, one of these further ingredients is a surfactant which can minimize or completely eliminate the metal wick problem, which otherwise may occur in the present invention. Minor amounts of an anionic fluorinated wetting agent, such as a mixture of potassium perfluoroalkyl sulfonates, for example, the brands FC-98 and FC-95 of Minnesota Mining and Manufacturing Company, can be used to combat the pitting phenomenon. The amount of wetting agent 3 can usually be between 5 and 20 cm / 1, most preferably between 7 and 15 cm / V 1 for the present purposes.

FC-95 and FC-98 are potassium perfluoroalkyl sulfonates, the use of which is preferred. Decompose both FC-95 and FC-98 at 390 ° C.

In a 0.1% aqueous solution, FC-95 has a pH of 7-8, and FC-98 has a pH of 6-8. FC-98, potassium perfluorocyclohexyl sulfonate is slightly less surfactant but creates a foam that is less dense and less stable. Both types have excellent chemical and thermal stability, especially in acidic and oxidative systems. A method of preparing these perfluoroalkyl sulfonates is shown in U.S. Patent 2,519,983, while use of surfactants in electroplating baths is shown in U.S. Patent 2,750,334.

The pH of the present baths will be between about 7 and 9, preferably between 7 and 8; and one will work at temperatures between about 30 and 80 ° C, preferably between 60 and 70 ° C. Although the tank current densities that can be effectively used with the present baths can range from about 10 to 200 ASF, slightly higher current densities are preferred, for example from about 180-200 ASF. On the other hand, however, a current density range of about 200-3,000 ASF can be used in the invention in fast plating systems. Under the preferred conditions of the invention, the rate of deposition of flexible palladium metal on the substrate can be about 6 microns per minute, while ranges from 1 to 25 can be easily achieved.

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The present baths can be used in combination with insoluble platinum, coated platinum, tantalum or columbium anodes.

Generally, rack or grid plating is applied to workpieces, such as box and pin contacts, printed circuit boards on board, sie-5 boards, etc. with metal surfaces such as copper, brass, bronze, nickel, silver, steel, etc. with palladium metal or if Desirably, palladius metal alloys are deposited in the form of high quality flexible coatings.

Electroplating baths according to the invention have the following composition:

Ingredient Concentration in q / 1 (a) Pd metalaL complex 40 to 80 (b) (NH4) 2 SO4 30 to 60 (c) NH4Cl 10 to 80 15 (d) OFB 1 to 10 (e) Ρ4Ρ20? 20 to 150 (f) FC-98 5 to 20 ml (g) NH4OH to pH 8 (h) water residue 20 The invention is further illustrated by the following examples, the concentrations being given in grams per liter unless otherwise indicated .

EXAMPLE I

A series of tests were performed with electroplating baths 25 of the composition according to Table A. All plating operations were carried out in a tank with a current density of 200 ASF, a temperature of 70 ° C and a pH of 8, with good stirring and a constant anode / cathode ratio. . The substrate used was copper, and the palladium metal complex consisted of Pd (NH3) 2Cl2. The pH was adjusted with ammonia.

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The data shows that in addition to the palladium metal complex and ammonia, the electroplating bath must contain ammonium sulfate, a stress relieving agent® tetrapotassium pyrophosphate to achieve the desired result. Run A according to the invention provided excellent results: high speed and deposition of ductile palladium metal. In contrast, the other tests outside the scope of the invention did not provide the desired satisfactory results.

EXAMPLE II

A palladium electroplating bath was prepared by dissolving the following 10 components in water: components concentration, g / 1

Pd, as Pd (NH3) 2Cl2 70 (NH4) 2S04 50 NH.C1 30 4 15 K4P2 ° 7 · 3 H2 * 100 OFB 10 FC-98 (1 g / 1 dissolved) 10 ml

This bath was operated at a pH 9, at 70-75 ° C and a current density of about 195 ASF reached. Rapidly deposited palladium layers of about 75 microns were applied to a copper substrate at a rate of 6 microns per minute. These film layers could be rolled up to cylinders and deformed into a square.

EXAMPLE III

A further electroplating bath was prepared by dissolving the following components in water: components concentration, g / l

Pd, as Pd (NH3) 2Cl2 60 (NH4) 2S04 50 NH4Cl 30 30 K4P207.3H20 100 OFB 5 FC-98 (1 g / 1) dissolved 10 ml

This bath was operated at a pH of 8 and a temperature of about 70-75 ° C. Cell tests were performed with this bath, reaching current densities up to 3000 ASF. Good and smooth deposits were achieved with a deposition rate of up to 25 microns per minute.

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EXAMPLE IV

Components Concentration q / 1

Pd, as Pd (NH3) 2Cl2 6Q

(HB4> 2S04 50 ™ 4C1 30 5 ΚΛ07. 3H2o 100 OPB 5 PC-98 (1 g / 1 dissolved)

Cu, as CuSO4. 5 H20 2

This bath was operated at a pH of 7.5 and a temperature of 70 ° C and a current density of 200 ASF. A 25 micron thick ductile film was obtained without any co-deposition of the copper.

The above data reveal that the present palladium electroplating baths allow rapid deposition of ductile palladium metal at high current densities, i.e. up to 200 ASF in a tank and 3000 ASF or more in a cell. In addition, the data show that the bath is tolerant to copper, nickel, iron and gold.

For the sake of completeness, it is pointed out that the above examples are illustrative only and that various variations and modifications are possible without departing from the scope of the invention.

8400049

Claims (19)

1. Rapid electrical deposition bath of ductile palladium metal containing 40-80 g / l palladium metal in the form of palladium-amine complex; about 20-90 g / l ammonium sulfate; about 10-70 g / l ammonium halide, about 20-150 g / l of an alkali metal pyrophosphate and a stress relieving agent. Rapid deposition bath according to claim 1, characterized in that it also contains a minor amount of an anionic fluorine-containing surfactant. Rapid deposition bath according to claim 2, characterized in that the surfactant is an alkali metal perfluoroalkyl sulfonate. Rapid deposition bath according to claim 1, characterized in that the ammonium halide is in the form of ammonium chloride. Rapid deposition bath according to claim 1, characterized in that the palladium amine complex is the palladium diamine chloride. Rapid deposition bath according to claim 1, characterized in that the stress relieving agent is a derivative of benzenesulfonic acid. Rapid deposition bath according to claim 6, characterized in that the benzenesulfonic acid derivative is the o-formylbenzenesulfonic acid. 8. Method for the electrical and rapid deposition of ductile palladium on a metal substrate, characterized in that the substrate is immersed in an electroplating bath, which operates at a pH of 7-9, a temperature of 50-80 ° C and a current density between 10 and 3000 ASF, the electroplating bath being formed by an aqueous solution of the following ingredients: Ingredients Concentration, q / 1 (a) palladium metal, as palladium amino complex 40-60 (b) (NH4) 2S04 30 " 50 30 (c) NH4Cl 20 - 30 (d) alkali metal pyrophosphate 80 - 100 (e) stress reducer 3-5 Method according to claim 8, characterized in that the pH of the electroplating bath is 7-9. 8400049 1 ^ · Η -10- Method according to claim 8, characterized in that the temperature of the bath is between 60 and 70 ° C. Method according to claim 8, characterized in that the current density is between 180 and 3000 ASF. Method according to claims 8-11, characterized in that the substrate is made of copper, nickel, brass, iron, gold or alloys thereof. Process according to claim 8, characterized in that the palladium amine complex is formed by palladium amine chloride. Method according to claim 8, characterized in that the palladium amine complex is formed by palladium amine nitrite. Method according to claim 8, characterized in that the stress-reducing agent is a derivative of benzenesulfonic acid. 16. A method according to claim 15, characterized in that the benzene-15 sulfonic acid derivative is o-formyl benzenesulfonic acid. A method according to claim 8, characterized in that the bath also contains a minor amount of an anitogenic fluorine-containing moisturizing anti-pit content. 18. A method according to claim 17, characterized in that the wetting agent is an alkali metal perfluoroalkyl sulfonate. A method according to claim 8, characterized in that the alkali metal pyrophosphate is the tetrapotassium pyrophosphate. 1400049