DD269635A1 - ELECTROLYTE FOR THE GALVANIC SEPARATION OF A PALLADIUM ALLOY - Google Patents

Abstract

The electrolyte is used for electrodepositing a palladium alloy with nickel or cobalt as an alloying component. According to the task he works in the neutral p H value range at p H 6.5 to 7.5 with very good p H value stability and tends only to a small extent to the salting. The electrolyte is prepared according to the invention from 5 to 25 g / l Pd in the form of a carbonate-based salt (palladium tetrammine bicarbonate, carbonate), 0.5 to 25 g / l Ni or 0.1 to 5 g / l Co (sulphate) and conductive salt (Ammonium sulfate, 30 to 100 g / l) and buffering salt (ammonium propanate, 1 to 100 g / l). The deposited layers are glossy up to 100 mm thick, free of pores and cracks, wear-resistant and meet the high requirements of electrical engineering / electronics and decorative applications.

Description

Field of application of the invention

The invention relates to an electrolyte for depositing a palladium-nickel or palladium-cobalt alloy, which is equally suitable for electrical engineering / electronics and decorative purposes.

Characteristic of the known technical solutions There are a variety of baths for the electrodeposition of Palladiumleoierungsschichten known. When Palladiumko.nponento be amino Komplexsaize in the form of chloride, nitrite, sulfite, sulfate, sulfamate or Carboxylic acid derivatives used 'DE-OS 3,147,823). As alloying components, nickel and cobalt have acquired special significance, almost exclusively as chloride or Sulfate are added to the electrolyte (DE-OS 3,443,420). Very numerous are also for an improvement of the Mixed crystal formation proposed additives, thereby increasing the corrosion resistance of the deposited Palladium alloy layer is to be achieved (DE-OS 3,108,466, DE-OS 3,108,467, DE-OS 3,108,508). It is also generally known that in order to achieve a good electrical Loitfähigkeit of the electrolyte of these ammonium salts

add. It is also known that palladium-doping electrolytes contain brighteners, which in particular have the task of increasing the leveling of the precipitates.

Palladium alloy electrolytes are, depending on the hydrodynamic conditions at current densities of 1 to 100 A / dm ² , im

pH range from pH 6.5 to pH 10 and at temperatures between 20 to 7O ⁰ C betriegen.

The known palladium ionizing electrolytes show at least partly the following disadvantages:

Because of the low solubility of the palladium component in chloride systems, such electrolytes must be operated at relatively high pHs. The pH value is adjusted with ammonia. Mostly a large part of the ammonia is expelled, especially at higher temperatures, which are necessary to obtain high deposition rates. This leads to a pH instability which adversely affects the technological regime and the quality of the screen.

- In chloride-containing baths, anodic chlorine rode up. On the one hand, this leads to stress on the working space or the environment and, on the other hand, requires correspondingly costly corrosion protection measures. In addition, material problems arise with respect to the anode material.

Sulfate based electrolytes have a low metal throughput because of the formation of the sparingly soluble nickel ammonium double salt. By increasing the pH, the service life of the electrolyte can indeed be increased, but this leads to the difficulties already mentioned.

- The use of organic additives generally complicates the bath management, as control and monitoring of bath compositions consuming and sometimes, because of lack of methods, are not possible. Also, these organic substances can form clogging products which adversely affect the deposition and, consequently, must be removed or, if purification is not possible, require a work-up of the baths when certain limits are reached.

- By the true! Operation of palladium baths, especially baths on sulphate chloride, required addition of palladium and nickel or cobalt salts. Accumulation of ammonium salts in the electrolyte, whereby the metal flow rate is limited and a relatively frequent change of electrolyte is required. This is associated with corresponding expenses for the processing of the spent electrolytes.

Aim of the EHIn

The object of the invention is to develop an electrolyte for the electrodeposition of a palladium alloy containing nickel or cobalt as an alloying component, the disadvantages of which are that both the expense of preparing the electrolyte and the difficulties in operating the electrolyte can be largely avoided and that under easily adjusted conditions high-gloss alloy layers are deposited, which are equally suitable for technical and decorative purposes.

Essence of the invention

The invention has for its object to develop an electrolyte for the electrodeposition of palladium alloy layers with nickel or cobalt cobalt as an alloy component, which works in the neutral pH range with very good pH stability and which tends only to a small extent to salinity. According to the invention, this object is achieved. daP for the batch of a palladium electrolyte 5 to 25g / l palladium in the form of a salt based on carbonate, preferably palladium tetrammine bicarbonate, 0.5 to 25g / l nickel or 0.1 to 5g / l cobalt, preferably as sulfates, and Leit- and Putfersalze vevwendet and the electrolyte is adjusted at operating temperature to a pH of pH 6.5 to 7fi . The buffer salts are ammonium salts of a simple carboxylic acid, in particular those of acetic acid, propionic acid, succinic acid and / or malonic acid. Preferably, from 1 to 100 g / l of ammonium propanate are used. As the conductive salt, ammonium sulfate is preferably used in an amount of 30 to 100 g / l.

The electrolyte is operated in the temperature range of 40 to 8O ⁰ C i: ⁿ d depending on the hydrodynamic conditions at the cathode at current densities of 0.1 to 100 A / dm ² .

embodiment

The invention will be explained in more detail with reference to exemplary embodiments:

Example 1: An electrolyte was prepared as follows: 10 g / l Pd as p-tetrammine hydroguan carbonate 5 g / l Ni as ι..SO "x 7H ₂ O 50 g / l (NH ₄ J ₂ SO ₄

3g / l NH ₄ C ₃ H ₅ O ₂ {ammonium propanate) The pH wu. Each set to pH 7.0.

In the current density range of 1-3A / drn ² and with a goods movement of 3 m / min bright bright, crack-free and pore-free alloy layers with 19% Ni were obtained at an operating temperature of 50 ° C. By increasing only the Ni content in the Electrolytes at 7.5 and 10 g / l were deposited 2 \ in the strong alloy layers with 22 and 26% Ni, respectively.

Example 2: An electrolyte was prepared from:

15 g / l Pd as Pd tetrammine bicarbonate

15g / l Ni as NiSO ₄ X 7H ₂ O

50 g / l (NH ₄ J ₂ SO ₄

60 g / l NH ₄ C ₃ H ₅ O ₂

pH - 7.2

In the current density range of 1-20 A / dm ² and onflow of the cathode brightly bright, crack and pore-free alloy layers were deposited with 30% Ni in a thickness of 100pm at 5O ⁰ C bath temperature.

Example 3: Electrolyte composition:

20 g / l Pd as Pd tetrammine carbonate

13 g / l Ni as NiSO ₄ X 7H ₂ O

20 g / l (NH ₄ I ₂ SO ₄

50 g / l (NH ₄ C ₃ H ₆ O ₂

pH = 6.8

in the current density range of 55-75A / dm ² using a rotating ring electrode high-gloss, crack and pore-free alloy layers were deposited with 24% Ni. By increasing the Ni content in the electrolyte to 20 g / l, the layers contain 30% Ni for the same quality. The achieved layer thicknesses Ι *? Βη at «ίΟμηι.

Example 4: Electrolyte composition:

10g / l Pd as 1 g / l Co as CoSO ₄ 50 g / l (NH ₄ J ₂ SO ₄ tetramminkarbonat Pd 50 g / l NH ₄ C ₃ H ₅ O ₂ pH = 7.0

At a current density of A / dm ² , a goods movement of 3 m / min and a bath temperature of 50 ° C, shiny Pd-Co alloy layers were deposited with 20% Co

 The electrolyte according to the invention has the following advantages:

- The susceptibility to salting is very low and is only partially due to the consumption of alloy component, whereby long Elektrolytstandzeiten and high metal throughputs ν'erden.

- The pH is in the neutral range and stable even at bath temperatures of £ 50 ⁰ C.

The achievable layer thicknesses can be varied within wide limits for the same, high quality of the layers. The layers are characterized by excellent mixed crystal formation.

- The deposited alloy layers are adherent, high gloss, pore and crack-free and show good wear resistance. They meet high standards as well as in the field of electrical engineering / electronics as well as for decorative applications.

By varying the metal concentration and the temperature, the electrolyte can be adapted to the given technical installation conditions in order to achieve the required deposition rates.

The content of alloying component nickel or cobalt in the deposited layer is independent of the current density and reproducibly controllable with the content of this component in the electrolyte and with the bath temperature.

- The high gloss of the deposited layers is achieved even at layer thicknesses a ΙΟΟμηι without the ZusaU of special brightener, whereby the risk of the formation of side reactions, as the Schichtqual did and / or the lifetime of the electrolyte adversely affect is avoided.

The electrolyte is characterized overall by a simple composition, easy handling and stable operation.

Claims (9)

1. electrolyte for the electrodeposition of a palladium alloy with nickel or cobalt as alloying component, characterized in that for its approach 5 to 25g / l palladium in the form of a salt based on carbonate, 0.5 to 25g / l nickel or 0.1 to bg / l cobalt and conductive and buffer salts are used and it is set at Arbaitstemperatur to a pH of pH 6.5 to 7.5. 2. An electrolyte according to claim 1, characterized in that palladium is used in the form of PallEdiumtetramminhydrogenkarbonat. 3. Electrolyte according to ^A .nspruch 1, characterized in that nickel or cobalt are contained in the form of their sulfates. 4. Elekirolyt according to claim 1, characterized in that the buffer salt used is an ammonium salt of a simple carboxylic acid. 5. Electrolyte na; h claim 1 and 4, characterized in that the ammonium salts of acetic acid, propionic acid, succinic acid and / or malonic acid are included. 6. An electrolyte according to claim 1,4 and 5, characterized in that 1 to 100g / l ammonium propanate are included. 7. An electrolyte according to claim 1, characterized in that it contains 30 to 100 g / l of an ammonium salt as conductive salt. 8. An electrolyte according to claim 1 and 7, characterized in that ammonium sulfate is borrowed as conductive salt. 9. An electrolyte according to claim 1 to 8, characterized in that it is operated in a temperature range of 4ö to 8O ⁰ C, at current densities of 0.1 to 100A / dm ² depending on the hydrodynamic conditions at the cathode.