JPS6324072A - Electroless palladium-nickel alloy plating liquid - Google Patents

Abstract

PURPOSE:To develop an excellent electroless plating liquid for a Pd-Ni alloy by using at least one kind of ammonia and amide compd. as a stabilizer and an org. compd. contg. bivalent sulfur in combination with an aq. soln. contg. compd. of Pd and Ni and using a specific reducing agent. CONSTITUTION:0.001-8mol/l at least one kind of the ammonia or amine compd. as the plating stabilizer and 1-500mg/l org. compd. contg. bivalent S such as mercaptane are used in combination with the aq. soln. prepd. by dissolving 0.0001-0.5mol/l soluble Pd compd. such as chloride of Pd and 0.001-1.0mol/l soluble Ni compd. such as Ni chloride, and 0.005-1mol/l at least one kind of a hypophosphoric acid compd. and hydrogenated boron compd. such as dimethylamine borane is used as the reducing agent for Pd ions and Ni ions to prepair the electroless plating liquid for the Pd-Ni alloy as substitutive plating for Au plating to be used for electrical contact parts of electronic parts. Such liquid of 5-11pH is used at 10-90 deg.C liquid temp. The electroless plating liquid for the Pd-Ni alloy having small porosity and high adhesiveness is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an electroless palladium-nickel alloy plating solution.

Conventional technology and its problems Electrical contact parts of electronic components are required to be surface-coated with noble metals that have good corrosion resistance and excellent electrical properties, and industrially, gold electroplating is mainly used. It has been adopted.

In recent years, various surface treatments of other noble metals have been investigated as substitutes for gold, and palladium in particular is expected to have a wide range of industrial applications because it is the cheapest among the platinum group metals.

However, although palladium has satisfactory performance in various aspects as a substitute for gold, in the presence of organic gas,
Due to the catalytic action of palladium itself, a polymer is formed on the plating surface, causing contact failure. Therefore, research has been carried out on various Pd alloy platings that do not have such drawbacks, and Pd alloy plating containing more than a certain amount of Ni
-Ni alloys do not form polymers on their surfaces even in the presence of organic gases, and have therefore come to be known to be preferable as a material to replace gold.

Most of the current research on Pc1-Ni alloy plating is based on electroplating methods.
As is well known, in electroplating, it is difficult to form a plating film of uniform thickness on electrical components having minute and complicated shapes. According to the electroless plating method, these problems are solved, and the plating solution can be easily managed automatically, and the deposited film becomes bore-free and has good corrosion resistance. There have been few reports on electroless Pd-Ni alloy plating solutions that can be put to practical use industrially. For example, Electroch em.

Technology, 6.427 (1968
), nickel sulfate 0.11 mol/l, palladium chloride 0.011 mol/l, 38% hydrochloric acid 4 mQ/l, 2
An electroless Pd-Ni alloy plating solution consisting of 160 mf2/l of 5% ammonia water and 0.094 mol/l of sodium hypophosphite has been reported, but this plating solution has extremely poor stability and cannot be used during the plating process. A rapid precipitation phenomenon of metal in the plating solution, so-called decomposition of the plating solution occurs, and therefore it is unsuitable for practical use.

Means for Solving the Problems In view of the problems of the prior art as described above, the inventor of the present invention
We have carried out extensive research in order to obtain an electroless Pd-Ni alloy plating solution that is practical even on an industrial scale. the result,
By adding at least one of ammonia and amine compounds and an organic compound containing divalent sulfur as a stabilizer to an aqueous solution containing Pd and Ni compounds, the stability of the solution becomes extremely excellent. It has been shown that when at least one compound selected from hypophosphorous acid compounds and boron hydride compounds is used as a reducing agent, an electroless palladium-nickel alloy plating film that is practical even on an industrial scale can be obtained. This finding led to the completion of the present invention.

That is, the present invention provides: a) Palladium compound 0.0001-0.5 mol/l b) Nickel compound 0.001-1 mol/l C) At least one of ammonia and amine compound 0.001-8
mol/l d) 1 to 500 mg/l of organic compound containing divalent sulfur
f2. and e) an electroless palladium-nickel alloy plating solution comprising an aqueous solution containing 0.005 to 1 mol/l of at least one of a hypophosphorous acid compound and a boron hydride compound.

In the plating solution of the present invention, a palladium compound such as palladium chloride, sodium palladium chloride, potassium palladium chloride, palladium ammonium chloride, palladium sulfate, palladium nitrate, palladium acetate, palladium oxide, etc. is used as a Pd source. The concentration of palladium compound is 0
．． 0001 to about 0.5 mol/l, preferably 0.0001 to 0.5 mol/l.
The amount should be approximately 0.001 to 0.1 mol/l. If the concentration is less than 0.0001 mol/l, the deposition rate of the plating film will be slow (so it is not practical), while if the concentration is more than 0.5 mol/l, the deposition rate will not be further improved and the plating will be worse. This is not preferable because it will impede the stability of the liquid.

Sources of Ni include nickel chloride, nickel ammonium chloride, nickel bromide, nickel iodide, nickel sulfate, nickel ammonium sulfate, nickel nitrate, nickel carbonate, nickel sulfamate, nickel acetate, nickel benzoate, nickel citrate, Nickel compounds such as nickel formate, nickel tartrate, and nickel oxalate can be used. The concentration of nickel compound is 0.001 to 1
About mol/l, preferably 0.01 to 0.5 mol/l
It should be about l. At a concentration of less than 0.001 mol/l, nickel becomes difficult to eutectoid, while at a concentration of more than 1 mol/l,
The stability of the plating solution decreases, and multiple ammonia and/or amine compounds are required to dissolve the nickel compound, which is uneconomical. In particular, when ammonia is used, it is not preferable because it creates a bad working environment due to odor and the like.

In the plating solution of the present invention, by changing the concentration ratio of palladium compounds and nickel compounds in the plating solution, the ratio of palladium to nickel in the deposited film can be adjusted, and a plating film of any composition can be easily obtained. .

In the plating solution of the present invention, in order to maintain the stability of the solution, it is necessary to use a combination of at least one of ammonia and amine compounds and an organic compound containing divalent sulfur. Ammonia and amine compounds form complexes with Pd and Ni in the plating solution, function to stably hold these components in the solution, and contribute to stabilization of the solution. The concentration of ammonia and/or amine compound is 0.001 to 8
The amount is about mol/l, preferably about 0.01 to 5 mol/l. When ammonia is used alone, 0.0% is used to improve the stability of the plating solution. More preferably, it is about 0.075 mol/l or more. The higher the concentration of ammonia and/or amine compounds, the better the stability of the liquid.
Concentrations exceeding the above range are uneconomical, and especially when ammonia is used, the working environment becomes poor due to odor, which is not preferred. Further, a concentration lower than the above range is not preferable because the stability of the liquid decreases and it becomes easy to decompose.

In the present invention, the amine compound includes amino acids. Amine compounds suitable for use in the present invention include specifically monoamines such as methylamine,
Ethylamine, propylamine, dimethylamine, trimethylamine, dimethylethylamine, benzylamine, 2-naphthylamine, isobutylamine, isoamylamine, etc. Diamines include methylenediamine, ethylenediamine, tetramethylenediamine, pentamethylenediamine, hexamethylenediamine, etc., polyamines Examples include diethylenetriamine, tetraethylenepentamine, pentaethylenehexamine, hexaethylenehebutamine, etc. Amino acids include ethylenediaminetetraacetic acid or its sodium salt, N-hydroxyethylenediaminetriacetic acid or its sodium salt, glycine, N-methylglycine , dimethylglycine, iminodiacetic acid, hydantoic acid, glycocyamine, etc., imidacillins such as imidacillin, 2-methyl-2-imidacillin, 2-phenyl-2-imidacillin, 2-benzyl-2-imidacillin, 1,2-diphenyl-2 -Imidacillin, 2,4
．． 5-triphenyl-2-imidacillin, 2,2'-
Examples include bis(2-imidacillin) and 2-chloromethyl-2-imidacillin.

In the present invention, at least one of the above-mentioned amine compound and ammonia may be used. However, when ammonia is used alone, the time until the initial plating occurs, that is, after the object to be plated is immersed in the plating solution. , it may take a long time for the plating to start adhering. In such a case, the initial generation time can be shortened by using ammonia and the above-mentioned amine compound in combination. Amine compound conversion is 0.00 when used in combination with ammonia.
When the amount is about 0.05 mol/l or more, it is effective in shortening the initial generation time. In addition, in a plating solution containing an amine compound as a complexing agent, the appearance of the plating film becomes particularly good when the plating film is thickened.

Specifically, as the organic compound containing divalent sulfur suitable for use in the plating solution of the present invention, (CH3) 3 C
SH, CH3(CH2) s CH(CH3) SH.

CH3(Cl3) I + SH, HSCH2C0O
H.

H3CH2CH2C0OH.

isomerkabutans; (C2Hs) 2S.

c6H5-s-c6H5, CH3-3-C6H5゜HO
OCCH2SCH2COOH.

Nosulfides such as HOOCCH2CH2SCH2CH2coOH; (CH3)2 S2. (C2H5)2
S2゜(C3H7)2 S2. C6H5S2-C6H
An example is 5°. These sulfur-containing organic compounds can be used alone or in appropriate combinations. The amount of the sulfur-containing organic compound used is 1 to 500 mg/(two degrees, preferably about 5 to 100 mg/l). If the amount of the sulfur-containing organic compound used exceeds the above range, the precipitation rate of the plating film will decrease. This is not preferable because the appearance of the precipitated plating film will deteriorate.Also, if the concentration is below the above range,
This is unsuitable because the stability of the plating solution will be insufficient.

As mentioned above, the plating solution of the present invention requires the combined use of ammonia and/or amine compounds and sulfur-containing organic compounds, and is extremely stable and suitable for use on an industrial scale. It is a plating solution. Furthermore, as described above, the range of amounts of ammonia and/or amine compounds used is wide, and even if the amount used is small, the stability of the solution is not impaired, so the plating solution can be easily managed. Particularly when using a low amount of ammonia, the amount of ammonia volatilized is extremely small, resulting in a favorable working environment and long-term storage of the liquid.

In the plating solution of the present invention, at least one of a hypophosphorous acid compound and a boron hydride compound is used as a reducing agent for reducing Pd ions and Ni ions to metal. As the hypophosphorous acid compound, hypophosphorous acid or its ammonium, lithium, sodium, potassium, calcium salt, etc. can be used, and as the borohydride compound, dimethylamine borane, trimethylamine borane, isopropylamine borane, morpholine borane, etc. can be used. Amineboranes, sodium borohydride, potassium borohydride, etc. can be used. The amount of the reducing agent used is about 0.005 to 1 mol/l, preferably about 0.01 to 0.5 mol/l. If the amount used is less than 0.005 mol/l, the plating will not be sufficiently deposited, while if it exceeds 1 mol/l, the plating solution will become unstable, which is not preferable.

As mentioned above, the plating solution of the present invention has extremely excellent stability due to the combination of ammonia and/or amine compounds and a specific sulfur-containing organic compound, and therefore, as mentioned above, it has excellent stability. agent can be used.

The plating solution of the present invention is an aqueous solution containing the above-mentioned components as essential components, and is extremely stable and capable of forming a good plating film.

When the pH of the plating solution of the present invention having the above composition is further adjusted to 5 to 11, the stress of the deposited film is reduced, and a plating film with almost no cracks can be formed. A plating film with almost no cracks formed from a plating solution whose pH is adjusted to 5 to 11 in this way has good solder wettability and good solderability. To adjust the pH of the plating solution, use an acid such as HCQ or H2S04 or Na.
This may be carried out using an alkali compound such as OH.

The plating solution of the present invention is capable of plating at a wide temperature range of 10 to 90°C, and in particular, the best smooth and glossy plating film can be obtained at a solution temperature of about 25 to 70°C. In this way, plating can be performed at a relatively low temperature, making it easier to manage the plating solution, and especially when using ammonia, it is possible to suppress the volatilization of ammonia, thus maintaining a good working environment. be able to. Furthermore, in the plating solution of the present invention, the higher the temperature of the solution, the faster the deposition rate of the plating film tends to be, and by appropriately setting the temperature within the above-mentioned temperature range, any deposition rate can be achieved.

In addition, in the plating solution of the present invention, the deposition rate of the plating film is
Since it depends not only on the liquid temperature but also on the Pd and N 1418 degrees, the deposition rate of the plating film can also be adjusted by appropriately setting the Pd concentration. As described above, the deposition rate of the plating solution of the present invention depends on the solution temperature and metal concentration, but is almost unaffected by changes in the concentration of other components or the pH of the plating solution. Easy to control.

In order to carry out plating treatment using the plating solution of the present invention, a substrate having catalytic properties for the reduction and precipitation of the Pd--Ni alloy film may be immersed in the solution within the temperature range described above. Examples of catalytic substrates include Fe5CoSNi, Cu,
SnSAg, Au.

Examples include Pt, Pd, and alloys thereof. In addition, even if the substrate does not have catalytic properties such as resin, glass, ceramics, W, etc., the above-mentioned method can be applied by imparting catalytic properties using known methods such as the sensitizing-activator method and the catalyst-accelerator method. The plating process can be performed by immersing it in a plating solution in the same manner as in the above method.

The deposition of the palladium-nickel alloy film by the plating solution of the present invention proceeds in an autocatalytic manner, resulting in a film with low porosity and high adhesion.

Effects of the Invention The electroless palladium-nickel alloy plating solution of the present invention has the following excellent properties.

(a) It is a plating solution with extremely high stability.

(b) The resulting plating film has a good appearance, and even when the film thickness is increased, the plating film has a good appearance.

(c) Since the precipitation is self-catalytic, the porosity of the deposited film is small, the corrosion resistance is good, and the adhesion to the substrate is good.

(iv) Since the stability of the plating solution is good even with a low amount of ammonia, volatilization of ammonia can be suppressed by setting a low amount of ammonia. Furthermore, in a plating solution that uses an amine compound, the amine compound does not volatilize during plating work or storage.

Therefore, the storage stability of the plating solution is good, and the working environment is also good.

(e) Since precipitation can be performed at low temperatures, workability is good, and even in the case of an ammonia bath, there is little volatilization of ammonia.
It is easy to manage the plating solution.

(f) Since the film is an alloy film of Pd and Ni, no polymer is formed on the surface of the deposited film even in an organic gas atmosphere, making it ideal for application to electrical contact parts that require reliability.

(g) By changing the ratio of Pd and Ni in the liquid,
Pd-Ni alloy plating with any composition depending on the application can be easily obtained. Since it is hardly affected, the plating film thickness can be easily controlled.

(S) By adjusting the pH to 5 to 11, a plated film with very few cracks can be obtained.

Such a plating film has good solderability and is suitable for application to electronic parts.

(v) By setting the pH to around neutrality, a wide variety of objects to be treated, resist inks, etc. can be used, and a wide variety of materials can be used for plating equipment.

The plating bath of the present invention has excellent properties as described above, and can be applied to contact parts that require high reliability in electronic components, and as a base plating film to extend the life of gold plating films. It is extremely useful for applications, etc., and furthermore,
In addition, it can be widely used for parts that particularly require corrosion resistance.

EXAMPLES The present invention will be explained in more detail by way of examples below.

Example 1 A plating solution having the following composition was prepared.

PdCQ2 o, 01 mol/lN i
CQ 2 ・6H20 The following variables 828% ammonia water 200mQ/l Thiodiglycolic acid 20
mg/lN a N2 P 02 ・N20 0.
08 mol/l* N1CQ2 War 6H20 is 0°005
．． 0.01.0, 02.0.05.0. 1 and 0.2
It was changed in 6 ways in mol/l.

Using the obtained plating solution, a copper plate was plated for 1 hour at a solution temperature of 40°C. FIG. 1 shows the relationship between the ratio of Ni to Pd in the plating solution and the amount of Ni in the precipitate. As is clear from FIG. 1, by adjusting the ratio of Ni to Pd in the plating solution, a precipitate with an arbitrary composition can be obtained. In addition, the appearance of the obtained precipitate was good, and J I
As a result of conducting a bending test according to 5-Z-2248, no abnormality occurred in any of the samples, and the adhesion was good.

Furthermore, in order to investigate the stability of the above plating solution,
Table 1 shows the results of heating to 25°C, closed storage at 25°C, and open storage at 25°C.

Table 1 Also, for comparison, a plating solution (N i
CQ 2 ・6H20ha0. As a result of a storage test using 1 mol/Q), the solution decomposed in about 1 hour when stored at 25°C, and within 5 minutes at 40'C.

From the above results, it is clear that the plating solution of the present invention has excellent stability at high temperatures and long-term storage stability at room temperature. Note that when stored in the open, the solution decomposed within 4 to 7 days, which is an extremely superior result compared to conventional plating solutions.

Further, the decomposition of the plating solution due to this open storage is caused by the volatilization of ammonia, and by appropriately replenishing ammonia, open storage for a long time is also possible.

Example 2 A plating solution having the following composition was prepared.

PdC1220,01 mol/l Ni CQ2 ・6H200,1 mol/l 28% ammonia water 200 mf2/l Thiodiglycolic acid 20 mg/l NaH2PO211H20 or NaBH40,08 mol/l Using this plating solution, plate a copper plate at a solution temperature of 40°C. Figure 2 shows the relationship between plating time and amount of precipitation when plating is performed. In the figure, the ◯ marks indicate the results when NaH2PO2.H20 was used, and the Δ marks indicate the results when NaBH was used. From Figure 2, when NaH2PO2・H2O is used, the precipitation rate is 1.4 mg/cm2・hr, and NaH2PO2・H2O is used.
When BH4 is used, the precipitation rate is 1.7 mg/
cm 2 ·hr, and in all cases, a linear relationship was observed between plating time and the amount of precipitation, indicating that the precipitation was autocatalytic. In addition, Niff1 in the precipitate is
When NaH2PO, L-H2O was used, it was about 30% by weight, and when NaBH was used, it was about 35% by weight.

Example 3 A plating solution having the following composition was prepared.

PdC920, 01 mol/l NiCQ2 ・6H200, 1 mol/l 28% ammonia water 200 mfl/l sulfur-containing organic compound x
20ffIg/lN a H2P 02 ・H2
00.08 mol/l* As a sulfur-containing organic compound,
Three types were used: thiodiglycolic acid, thiodipropionic acid, and 2-mercaptobenzothiazole.

FIG. 3 shows the relationship between the solution temperature and the deposition rate when plating was performed on a copper plate for 1 hour using this plating solution while changing the solution temperature. Moreover, the relationship between the liquid temperature and Nift in the precipitate is shown in FIG. In the figure, the O mark indicates the result when thiodiglycolic acid was used, the Δ mark indicates the result when thiodipropionic acid was used, and the mouth mark indicates the result when 2-mercaptobenzothiazole was used. From the above results, it can be seen that the higher the liquid temperature, the higher the plating rate, and the more Niff1 in the precipitate tends to increase. In addition, the obtained plating film is
A good appearance was obtained when any of thiodiglycolic acid, thiodipropionic acid, and 2-mercaptobenzothiazole was used.

Example 4 A plating solution having the following composition was prepared.

PdC (1!2 0.01 mol/lN
iCQ2 ・6H200, 1 mol/lNH2CH2C
H2NH20,'08 mol/l thiodiglycolic acid
20 mg/9NaH2PO2.H200.08 mol/l Using this plating solution, a copper plate was plated for 1 hour at a solution temperature of 40.degree. As a result, the amount of Ni in the precipitate was approximately 3
0% by weight, and both the appearance and adhesion of the obtained precipitate were good. In addition, even if the above plating solution is heated to 90°C, the plating solution does not decompose, and at 25°C it does not decompose.
No decomposition of the plating solution occurred even when it was stored open for several months.

Example 5 The plating solution shown in Example 4 was prepared with HCQ and NaOH to each pH value shown in Table 2 below, and a plating film with a thickness of 1 μm was formed on a copper plate at a solution temperature of 40°C. It was measured. Next, the state of the obtained plating film was observed with a scanning electron microscope (3000x magnification), and then a solderability test was conducted using the method described below. The results are shown in Table 2.

0 soldering is a sample (25mm x 25mm x
Q.3 [1111] is used as rosin flux (rosin 2
After pretreatment by immersion in 5% isopropyl alcohol solution), using a meniscograph (manufactured by Philips),
6/4 solder (tin: lead = 6:
4) The sample was immersed perpendicularly to the solder surface to a depth of 12 mm, and the time until the contact angle between the solder and the sample surface reached 90 degrees was measured, and the zero cross time was determined as 0viILL.
5TD-883B). It can be said that the shorter the zero cross time, the better the wettability of the solder to the plating film.

Next, after measuring the zero cross time, the state of the adhered solder was observed on the sample, and the adhesion of the solder was investigated. The results are shown with the following symbols.

○...Solder adheres uniformly △...Solder adheres to 98% or more of the immersed surface although it is partially uneven ×...Solder adheres to less than 98% of the surface and the adhesion is uneven It is.

Table 2 Example 6 A plating solution having the following composition was prepared.

PdCC! 2 0.01 mol/lNiC9
2・6H200, 1 mol/l Amine compound” 0.08 mol/l Thiodiglycolic acid 20mg/9NaH2PO2・H2
00,06 mol/l*Amine compounds include dimethylamine, dimethylethylamine, methylenediamine,
Tetramethylenediamine, diethylenetriamine, pentaethylenehexamine, N-hydroxyethylenediaminetriacetic acid, glycine, imidacilline, and 2-benzyl-2-imidacyline were each used alone.

These plating solutions were adjusted to pH 8 with hydrochloric acid, and the solution temperature was 60°.
Plating was performed on a copper plate using C. As a result, a film with good adhesion and appearance was formed.

Furthermore, the obtained plating film had no cracks and had good soldering properties. Furthermore, the stability during heating and storage stability of each of the above plating solutions was investigated and showed good stability.

Example 7 A plating solution having the following composition was prepared.

PdCl22 0.01 mol/lN
i CQ 2 ・6H200, 1 mol/lNH2CH
2CH2NH20.08 mol/l sulfur-containing organic compound”
20mg/(!NaH2PO2・H200,0
6 mol/l* As a sulfur-containing organic compound, H3CH
2 COOH.

were used alone.

These plating solutions were adjusted to pH 8 with hydrochloric acid, and the solution temperature was 60°.
Metsusen was performed on the copper plate at C. As a result, a film with good adhesion and appearance was formed.

Furthermore, the obtained plating film had no cracks and had good soldering properties. Furthermore, the stability during heating and storage stability of each of the above plating solutions was investigated and showed good stability.

Example 8 A plating solution having the following composition was prepared.

PdCQ2 0.01 mol/lN i
CQ 2 ・6H200, 1 mol/l NH2CH2C
H2NH20.08 mol/l thiodiglycolic acid
20mg/l reducing agent” 0.
06 mol/l* As reducing agents, dimethylamine borane, isopropylamine borane, morpholine borane, and sodium borohydride were each used alone.

These plating solutions were adjusted to pH 8 with hydrochloric acid, and the solution temperature was 60°C.
Plating was performed on a copper plate. As a result, a film with good adhesion and appearance was formed.

Furthermore, the obtained plating film had no cracks and had good soldering properties. Furthermore, the stability during heating and storage stability of each of the above plating solutions was investigated and showed good stability.

[Brief explanation of drawings]

Figure 1 is a graph showing the relationship between the Ni and PdO ratio in the solution and the amount of Ni in the precipitate, Figure 2 is a graph showing the relationship between plating time and amount of precipitation, and Figure 3 is a graph showing the relationship between the liquid temperature and the amount of Ni deposited. A graph showing the relationship between speed and FIG. 4 is a graph showing the relationship between liquid temperature and the amount of Ni in the precipitate. (That's all) Figure 1: 5N"rnNi/(Ni+pd) (wtz) Figure 2: Time (h") Figure 3: Figure 4

Claims (2)

[Claims] (1) a) Palladium compound 0.0001-0.5 mol/l b) Nickel compound 0.001-1 mol/lc) At least one of ammonia and amine compound 0.001-8
mol/l d) 1 to 500 mg/l of organic compound containing divalent sulfur
and e) an aqueous solution containing 0.005 to 1 mol/l of at least one of a hypophosphorous acid compound and a boron hydride compound. (2) The electroless palladium-nickel alloy plating solution according to claim 1, which has a pH of 5 to 11.