SU819228A1 - Palladium-plating electrolyte - Google Patents

Description

one

The invention relates to electroplating, in particular to electrolytic deposition of palladium coatings on electrical contacts, printed circuit boards and other current-carrying parts, mainly working for wear.

The palladium electrolyte containing palladium chloride, ammonium sulphate, urea, saccharin and 2,2-dipyridyl is known {.

High quality coatings are precipitated from this electrolyte. However, the presence of a large amount of organic additives complicates the preparation, operation and correction of the electrolyte.

Closest to the invention is the known palladium electrolyte containing palladium tetraaminochloride, ammonium chloride, am.miac, and ammonia 2.

However, the known electrolyte is not sufficiently effective (see table). In addition, the presence of ammonium boron, which is not commercially available but is synthesized in the electrolyte preparation process, complicates the process of electrolyte preparation and correction. Coatings obtained in a known electrolyte are susceptible to being gripped by hands.

which requires additional processing, such as kratsavani.

The aim of the invention is to improve the stability of the electrolyte and the quality of the coating.

The goal is achieved by the fact that the electrolyte additionally contains ammonium sulfosalicylate and magnesium sulfate in the following ratio of components, g / l:

Palladium tetraaminochloride

(in terms of metal) |

Ammonium sulfosalicylate (in terms of sulfosylcyl acid) 20-40

Magnesium sulfate 30-50

The electrolyte is prepared as follows.

Palladium chloride in the form of a suspension is dissolved in a 25% ammonia solution heated to 50-60 ° C while gradually adding and re-mixing the suspension, then ammonium sulfosalicylate, previously prepared by neutralizing sulfosalicylic acid with ammonia, is added, then magnesium sulfate is added, tested pH of electrolyte.

The deposition process is recommended to be carried out at pH 8.5-9.5, room temperature (8-25 ° C) and current density

0.8-1.2 A / dm using insoluble carbon anodes.

The coating is applied to brass samples and parts (electrodes of microphones and printed circuit boards) in baths of both stationary and bell or drum type.

When parts are coated with copper and its metals, copper accumulates in the electrolyte, which leads to a deterioration in the quality of the coating — it becomes fragile and stained with copper layers.

fine. The coating is deposited even, smooth, shiny, without cracks, with strong adhesion to the substrate.

The electrolyte according to the invention has a high dispersing and covering ability (when coating complexly shaped parts, the thickness of the coating on the outer and inner sides of the part differs by only 5-10%).

The invention can be illustrated by several examples presented in the table.

Table

Sulfosalicylate ions have an inhibitory effect on copper ions, binding them to complex compounds, therefore contamination of the electrolyte with copper, which adversely affects the stability of the electrolyte and the quality of the coating, is much slower than in the amino chloride electrolyte.

Magnesium sulfate contributes to the formation of elastic coatings without cracks.

Introduced additives are non-toxic, chemically stable and do not decompose during electrolysis.

Since the palladating process occurs with insoluble carbon anodes, the consumption of palladium salts in the elec- tric and iron is compensated for by adjustments. Repeated correction of the electrolyte (50-60 times) does not degrade the quality of the coating and does not reduce the technological parameters. This is indicative of the stability of the operation of the palladium bath. When covering forty batches of electrodes of the microphone MK-16, the electrolyte after 50-60 adjustments works normally. After long-term storage of the electrolyte, about six months, the coating of printed circuit boards was carried out, the bath continued to work

The table below shows that the electrolyte according to the invention works

4Q at room temperature, gives a high current efficiency, has a high stability, and consequently, a high service life.

Microhardness and wear resistance

45 coatings obtained in this electrolyte, higher than those obtained in a known electrolyte.

The coatings obtained in the electrolyte according to the invention are free from microcracks, which is reflected in the corrosion resistance and mechanical properties of the coatings. The coatings are deposited brilliant and do not require additional mechanical processing, which reduces the complexity of the process (coatings are not susceptible to being gripped by hands).

Claims (2)

Invention Formula Palladium electrolyte containing palladium tetraaminochloride, differing in that.m., In order to increase the electrolyte stability and quality of the coating, it additionally contains ammonium fosalicylate ammonium sulphate and magnesium sulfate 5 Gl-i, the following ratio of components, in terms of metal) 15–25 ammopi sulfosalicylate 5 (in: recalculation of sulfosalicylic acid) 20–40 (Sulfate lmagin 30–50 b Sources of information taken into account during the examination 1. USSR Author's Certificate No. 572539, C. 25 D 3/50, published in 1977. 2. USSR author's certificate number 377430, cl. From 25 D 3/50, published. 1973.