JPS586793B2 - Bright palladium electroplating bath - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the technique of electroplating palladium; a number of plating baths have been proposed for this purpose.

Representative baths are disclosed, for example, in US Pat. Nos. 3,580,820, 3,933,602, and 3,972,787.

Said patents describe, for example, systems comprising palladium di- or tetraamine halides, palladium-urea sulfite complexes, palladium dinitrite complexes, palladium tetramine nitrite or sulfate complexes or palladium amine sulfite complexes. ing.

What is desirable is to improve the gloss of palladium.

It is also desirable to utilize palladium electroplating baths which can be used for bright plating on normally passivated iron, cobalt or nickel substrates, usually under alkaline conditions.

In this case, by adjusting the temperature value of the bath to 4.5 to 12, a bright plating layer of palladium can be obtained from an aqueous bath containing palladium in the form of a soluble palladium salt, a type 1 brightener, and a type 2 organic brightener. It has been discovered that it can be obtained.

Palladium is provided in some electrodepositable form to the electroplating bath of the present invention.

Bath stability is improved by using divalent palladium complexes such as urea or amine complexes.

Suitable examples are palladium amine complexes with chlorides, nitrites or sulfites.

The palladium content of the plating bath is in the range 0.1-50 g/l.

To obtain strike plating, a concentration of 1 to 5 g/l is preferably about 10 g/l.

The first type and second type nickel brighteners are F. A. Lowe
Written by nheim: Modern Electroplat
ing 2nd edition, published 1963, 272 pages and M
etal Finishing Guidebook &
Directory 42 edition published in 1974, page 358.

This type 1 brightener is generally an unsaturated sulfonated compound in which the unsaturated bond is in the α- or β-position with respect to the sulfone group.

These compounds have the formula: A. -SO3-B, where A4 is a substituted or unsubstituted allyl or alkyl group, and B is an alkali metal, ammonium, or amine, or R is an alkyl group having up to 6 carbon atoms. -OH, -OR, -OM, -NH2,>
They are NH, -H, and -R.

Type 2 organic brighteners are generally unsaturated or carbonyl organic compounds.

Examples are >C=O, >C=C<, -C≡N, >C=N-,
It is a compound containing 1C≡C1, >N-C=S, -N=N1.

This kind of compound is the above-mentioned Metal Finishing compound.
It is displayed on page 360 of gGnindebook.

The individual brightener concentrations range from 0.001 to 25 g/l.

Several compounds are found in the description of both Type 1 and Type 2 brighteners.

Although these compounds can be used alone, particularly improved results are obtained when a second, heterogeneous compound of either type is used.

The pH of the electroplating solution must be kept at a value between 4.5 and 12 to avoid stability problems.

For strike plating, where a value of about 6.5 is particularly desirable, a value of about 4.5 to 7.0 is selected.

About 7-10 is preferred for normal electroplating, and about 8.
Values between 0 and 9.0 are currently optimal.

Adjustment of the pH value is carried out by adding non-reactive acids or bases commonly used for this purpose, such as ammonium hydroxide or hydrochloric acid.

The use of ammonium hydroxide helps promote stability of the palladium amine complex, while hydrochloric acid increases solution conductivity, thereby minimizing hydrogen evolution at the cathode.

Although other commonly used non-toxic pH adjusting agents are also available, the former is preferred because of its dual function.

To further reduce the potential for hydrogen formation at the cathode, it is generally desirable to include an additional amount of conductive salt.

Although any of the commonly used conductive salts normally used in palladium electroplating may be used in the baths of the present invention, the currently preferred conductive salt is ammonium chloride.

The chloride anion also improves the conductivity of the solution, while the presence of ammonium increases the stability of the palladium amine complex.

As adjunct compounds, such as partially neutralized phosphate compounds can be used for their conductive and buffering properties.

One compound that has been found to be particularly effective is ammonium 1
Hydrogen phosphate.

The baths of this invention can also be modified to include additives such as metal brighteners and chelating elements.

Suitable metal brighteners are cadmium, copper, gallium, indium, tellurium, arsenic, and zinc.

Suitable chelating or sequestering agents include EDTA, NTA
．． and carboxylic acid chelators such as succinic acid and phosphoric acid chelators.

Polyalkyl polyamines such as diethylene triamine can be added as well.

The temperature of the palladium bath ranges from room temperature to about 160°F.
7°C).

The preferred temperature would typically be 130'F (54.4C) to avoid excess ammonia escaping from the solution.

The current density is 0.1 to 50 Amps/sqft (0.0
1 to 5.37 A/dm2) is appropriate.

Current densities of 5 to 15 amps per square foot (about 0.55 to 1.65 A/dm2), preferably 10 amps per square foot (about 1.1 A./dm2) can be used for hook plating.

For barrel plating, a suitable range is 0.5 to 3 amps per square foot (about 0.05 to 0.33 A/dm2).

If a low stress plating layer is desired, conventional stress reducing agents such as sulfamic acid, its salts or derivatives can be used.

Concentrations up to 100 g/l are suitable, but preferred concentrations are between 25 and 75 g/l.

The following examples will serve to more fully illustrate the advantages of the invention.

Example 1 A palladium electroplating bath is prepared as follows.

Ingredients Concentration (g/l) EDTA.
20(NH4)2HP
O4s o Na2S03 28Pd,
As Pd(NH3)2C12 10 1st class brightener 0005→2 2nd class 1/
The temperature of the 0.005 → 2 bath was maintained between 8.5 and 9, and the plating was performed on the brass panel at a temperature of 120°C (approximately 48°C).
．． 9°C), current density 5 amps/sq ft (approximately 0.5
5A. /dm2).

In the absence of either brightener, only a slightly hazy plating layer was obtained.

The first class brightener used was methylene bis (naphthalene,
The second brightener was benzaldehyde-O-sodium sulfonate.

The type 1 brightener was added first and was much less effective at concentrations up to 2 g/l.

With 2 g/l of the first type brightener, a plated layer with improved semi-gloss properties can be obtained with the coexistence of 0.02 g/l of the second brightener, and a bright plated layer with a brightness of 0.37 to 2.0 g/l obtained between.

Similar results were obtained using 2-butene-1,4 as the second brightener.
-obtained when using diols.

Example 2 The next palladium plating bath was made as follows.

Ingredients Concentration (g/l) EDTA.
30Pd, Pd(NH
3) As 2Cl2 10 Class 1 brightener
0.05 2nd class brightener 0
．． 0005-0.04 Under the conditions of Example 1, a bright plated layer was again obtained by adding both brighteners.

The first type brightener was the same as in Example 1, but
2-butyne-1,4 diol was used as the second type brightener.

Similar results were obtained when allyl sulfonate and ethoxylated butyne diol were replaced with 2-butyne-1,4-diol.

Example 3 Another palladium plating bath was prepared as follows.

Ingredients Concentration (g/l) EDTA
30(NH4)2HPO4
75Pd, Pd(NH3)2C
12 as 10 Class 1 brightener
0.05 2nd type tt 0.00
04-0.05 The first type brightener was the same as in Example 1, and the second type brightener was 2-butene-1,4-diol.

Under the conditions of Example 1, a bright plating layer was obtained, but without the brightener a hazy plating layer was obtained.

In further examples, Type 1 brighteners such as sodium benzene sulfonate, benzene sulfamide and phenolsulfonic acid were used with generally similar results.

In Examples 1, 2 and 3, EDTA. Experiments were also conducted on each palladium plating bath without the addition of .

EDTA. Other components and experimental methods were the same as in each example.

The results of these experiments are based on EDTA. The above Example 1 with the addition of
, 2 and 3, a bright plating layer was obtained.

Claims (1)

[Claims] 1 Palladium as a soluble palladium salt from 0.1 to
50g/l and methylene bis(naphthalene sodium)
0.00 of a Class 1 brightener selected from the group consisting of sodium benzene sulfonate, benzene sulfonamide, and phenol-sulfonic acid.
01 to 25 g/l and a second type organic brightener selected from the group consisting of benzaldehyde-O-sodium sulfonate, 2-butyne-1,4-diol, 2-butene-1,4-diol and allylsulfonate. 0.0001～
consisting essentially of 25 g/l and between 4.5 and 12 p.
Stable aqueous electroplating bath with H value. 2 0.1~ of palladium as soluble palladium salt
50g/l and methylene bis(naphthalene sodium)
0.00 of a Class 1 brightener selected from the group consisting of sodium benzene sulfonate, benzene sulfonamide, and phenol-sulfonic acid.
01 to 25 g/l and a second type organic brightener selected from the group consisting of benzaldehyde-O-sodium sulfonate, 2-butyne-1,4-diol, 2-butene-1,4-diol and allylsulfonate. 0.0001～
consisting essentially of 25 g/l and between 4.5 and 12 p.
A stable aqueous electroplating bath exhibiting an H value, the bath containing:
An electroplating bath in which at least one chelating or complexing agent selected from the group consisting of carboxylic acid or phosphoric acid chelating agents is present between 5 g/l and the solubility limit of the solution. 3. An electroplating bath according to claim 1, comprising at least one conductive salt or buffer salt. 4 Palladium as a soluble palladium salt is chloride,
Claim 1 Present in divalent form as an amine complex selected from bromide, nitrite or sulfite complexes
The electroplating bath described in .