JPH0229758B2 - METSUKIGOKINSOSEIOANTEISASERUDENKIMETSUKYOKUOYOBIMETSUKIHOHO - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to electroplated palladium-nickel alloy coatings, and in particular to a plating bath and its coating that control the stability of the alloy composition of the coating over a wide range of varying current densities. Regarding the method. [Prior Art and Its Problems] Historically, gold has been considered a particularly suitable plating material for electrical contacts, due to its corrosion resistance, solderability, and low electrical contact at low loads. Resistance and, due to. However, since gold plating is expensive, research has been conducted into cheaper materials to replace it. Palladium-nickel alloy has shown excellent properties as a substitute for gold for plating electrical contacts.
One of the most successful of these palladium-nickel coatings is U.S. Pat.
, and is disclosed here for reference. The palladium-nickel electroplated surface coatings described in this patent effectively protect the substrate against corrosion, have unaltered solderability, and exhibit reduced electrical contact resistance at low loads. The coatings according to the above-mentioned patents are produced by electroplating in a plating bath containing palladium ()ammine chloride, nickel ammine sulfate, a small amount of brightener, and a conductive salt. Electroplating is about 5 to 25 amps/sq.dm., i.e. 50 to 250 amps/sq.dm.
It is carried out at a current density in the range of ft. (hereinafter referred to as asf). The current density in the high part of this range, i.e. approximately
At 100 asf or more, the Pd-Ni composition of the plating film can be easily and accurately controlled. When the current density falls below this level, it becomes increasingly difficult to control the alloy composition. Control of Pd-Ni composition during electroplating is very important. The properties of this Pd-Ni alloy film are important for the specifications of electronic contacts, such as solderability, toughness, hardness, thermal stability of contact resistance, and corrosion resistance in the atmosphere. It changes drastically depending on the composition of the plating alloy. By precisely controlling this level and keeping the composition of the plated Pd-Ni alloy constant, it is possible to stably impart the desired properties to the contact product. Other manufacturing criteria of plated contacts, such as bubble-freeness, service life, etc., are primarily determined by the thickness of the expensive metal alloy. Standardize widely used non-destructive manufacturing techniques, such as electron backscatter spectroscopy and X-ray fluorescence techniques, to measure coating thickness on high-value metal alloys for specific alloy compositions. You have to try to measure things. Therefore, when manufacturing contact products plated with Pd-Ni alloy, stabilizing the alloy composition is also necessary to control the thickness and thickness-dependent properties of the alloy coating as desired. be. The stability of alloy composition is particularly related to current density. In a typical plating method for formed terminals, the current density changes by as much as four times depending on the position of the contact. The width of the change in current density depends on the geometry of the part, the design of the plating cell, and other factors. The range of current density variation in many formed terminals is 25 to 100 asf. Depending on the location, terminals may be plated at less than 10 asf or more than 150 asf. The effect of changes in current density on alloy composition stability is well illustrated in FIG. 1 and Examples 1-3.
For the purpose of this invention, the stability parameters for evaluating the performance of the Pd-Ni alloy plating method are the Pd content, weight %, of the alloy deposited at 100 asf and the content in the case of 25 asf. It is expressed as a difference. In curve A in Figure 1, this difference has the sign △weight%Pd
(100−25). The △wt% Pd (100−25) of a plating bath made from a commonly commercially available formulation of palladium chloride/ammine salt and an organic brightener is:
As shown in Examples 1-3, it ranges from about 12 to 22.
In Example 1, plating tests were conducted on six commercially available palladium dichloride ammine salts using the same bath chemical composition and plating conditions. The Δwt% Pd(100-25) in this test was between 13.0 and 18.7, all of which resulted in instability with respect to the desired alloy composition consistency. [Means for Solving the Problems] In the embodiment of the present invention, the range of △wt%Pd(100-25) of the Pd-Ni alloy plating bath is from 0 to 6.
It is. This shows that when iodide ions are intentionally added to the Pd-Ni alloy plating bath, the stability of the operation is clearly demonstrated by the significant decrease in the parameter △wt% Pd(100−25). This is due to the discovery that this can be improved. It is important to purify palladium salts to remove chemical species that may promote instability;
This is also necessary to achieve the final stability [Δwt% Pd(100-25)=0]. [Example] As mentioned above, the addition of iodide to the Pd-Ni alloy plating bath has a clear effect on controlling the composition of the plating alloy, and this is due to the parameter △wt% Pd (100
−25). For a Pd-Ni alloy plating bath that does not contain organic brighteners,
When a small amount of iodide, about 15 ppm, is added, as shown in Example 4, Δwt%Pd(100-25) becomes less than 2.0.
The relationship between alloy composition and current density in the 15 ppm test of Example 4 is shown by curve B in FIG. Curve A in Figure 1 is the result of a test conducted with the same plating bath chemistry and test conditions, except that a sodium vinyl sulfonate brightener was used in place of iodide ions (Example 1). (See plating test number V). As a result of using sodium vinyl sulfonate instead of iodide ion, △wt%Pd(100−25)
Increased to 18.7. When added to a Pd-Ni alloy plating bath without organic additives, iodide ions act as brighteners. The addition of iodide ions not only provides a coating with a mirror-like luster, but also increases the maximum current density,
Allows the deposition of smooth, dense, bubble-free coatings. For Pd-Ni alloy plating processes based on organic brighteners such as aliphatic sulfonic acids, the addition of small amounts of iodide ions is very effective in promoting the stability of the process. This fact is illustrated in Example 5, where the addition of iodide ions was reduced from 6 to 100 ppm.
The consistency of the alloy composition plated by the sodium vinyl sulfonate brightener-based method is demonstrated as the temperature rises to FIG. 2 shows the stability parameters in Example 5 in relation to the iodide ion concentration. This data shows that adding only 25 ppm of iodide ion can reach a leveling off of Δwt% Pd(100-25) from 18.7 to about 5. In the Pd-Ni alloy delivery method based on other organic brighteners, such as quaternized pyridine,
Unless a large amount of iodide ions are added, the stability of the process cannot be improved. This situation is illustrated in Example 6, which describes a process based on industrial grade N-benzyl nicotine inner salts as brighteners with addition of iodide ions in the range 23 to 300 ppm. The effect on the consistency of the plated alloy is shown. This salt is CAS registration number 15990-43-3 - pyridinium 3-carboxy 1-(methylphenyl) hydroxide inner salt,
It is essentially a type of pyridinium salt.
By adding 300 ppm of iodide ions, the Δwt% Pd(100-25) of this method was reduced from 16.9 to 11.7. An additional improvement in the consistency of the alloy composition plated by this method is achieved by lowering the concentration of the pyridinium salt and by removing impurities that may promote instability in the brightener.
achieved. Examples 7, 8 and 9 show the effect of purifying palladium salts.
Shown below. The palladium salts used in Examples 7, 8 and 9 were purified using the following facts:
Namely, palladium diamine chloride, Pd
(NH ₃ ) ₂ Cl ₂ is insoluble in water, and palladium chloride.
When a solution of tetraammine is treated with excess hydrochloric acid, the following reaction forms a precipitate. Pd(NH ₃ ) ₄ Cl ₂ +HCl → 1/2Pd(NH ₃ ) ₂ Cl ₂ +1/2H ₂ PdCl ₄ +3NH ₃ That is, ammonia is separated and palladium chloride () acid is formed. However, palladium diamine chloride can be made soluble by treatment with ammonia (dissolved in NH ₄ OH). That is, Pd(NH ₃ ) ₂ Cl ₂ +2NH ₃ →Pd(NH ₃ ) _{4 Cl} Palladium dichloride tetraammine salt easily dissolves in water. Therefore, to further purify the purchased palladium chloride tetraammine salt, the following method is used: (a) Palladium chloride tetraammine salt, Pd
Dissolve (NH ₃ ) ₄ Cl ₂ , in deionized water; (b) Precipitate palladium diamine chloride, Pd(NH) ₂ Cl ₂ , by adding excess hydrochloric acid; (c) Precipitate palladium chloride dianmine
Redissolve in NH ₄ OH to again form a palladium chloride tetraamine solution. Further, to purify the purchased palladium chloride diamine salt, the following method is used: (a) Palladium chloride diamine salt is purified with NH ₄ OH
(b) add excess hydrochloric acid to precipitate the palladium chloride diamine; (c) filter the precipitated palladium chloride diamine from the mother liquor and deionize it. Rinse several times with cold water. Based on the above procedure, one cycle of purification is defined as a series of repeated steps to return the original components to the same chemical composition (i.e. palladium diamine chloride is converted into the same palladium diamine chloride). ). From the above, the palladium balance performed in this series of procedures was verified based on the above-mentioned stoichiometry. It is well known among chemical synthesis experts that precipitation (recrystallization) removes impurities from the supernatant mother liquor and purifies the precipitated product. Besides this purification method, there are other methods such as, for example, reacting an aqueous solution of palladium salt with hydrogen peroxide (especially in the case of organic impurities), or passing the palladium solution through a head of palladium powder, or carbon treatment. This should be obvious to the engineer concerned. It should be noted that in many purification methods, iodide can also be lost, along with undesirable impurities that increase instability;
Iodide ions must be added to achieve the required concentration. The impurity content of other components of the Pd--Ni plating bath also needs to be precisely controlled. Examples 8 and 9 also demonstrate the remarkable effectiveness of precipitation purification as described above in combination with the addition of iodide to the Pd--Ni plating bath. As a result of conducting one cycle of refining palladium chloride tetraammine and testing with a formulation in which 31 ppm of iodide ions were added to the plating bath, △wt% Pd (100-25) was 4.2
It became. When using palladium chloride tetraamine purified in two purification cycles in the same plating bath (35 ppm iodide added), △wt% Pd
(100−25) becomes 0.4, and from the current density 25 asf
A virtually constant alloy composition was obtained between 100 asf. The present invention can be widely used for all Pd--Ni alloy plating methods. Current density from 25
In the range of 100 amps/sq.ft., a test to confirm the effect of adding iodide to ensure consistency of the composition of the plating alloy was carried out using various nickel salts (see Example 10),
Various salts with different conductivities (see Example 11), a wide range of agitation levels (see Example 12), and a wide range of
Pd/Ni molar concentration ratios, which resulted in the deposition of alloys with a wide range of compositions (see Examples 13, 14, 15), were performed. In the pH range 7-9 commonly used in industrial plating baths, iodide addition is equally effective. The principle of the generation mechanism explaining the effect of making the alloy composition constant is shown in FIG. During electroplating, the contact terminal acts as a solid negative electrode,
This is then electroplated with a Pd-Ni alloy. Adsorbed monolayer of added iodide ions
monolayer) forms an effective bridge for the palladium ions, possibly Pd(NH ₃ ) ₄ ⁺⁺ ions, in the plating bath and carries the charge to the electrode. However, iodide ions do not provide an effective bridge to nickel ion species. This ligand-bridge effect has already been described in the literature. In essence, this bridge facilitates the transfer of charge to or from the target ion (in this case a palladium ion) by adsorbing to the electrode and inserting itself into the coordination sphere of the target ion. As mentioned above, this effect is discriminatory in this case and does not provide a bridge as effective against the nickel species as it does against the palladium species, but this effect can be written as: 1 M+X ^- → M(X ^- ) ads. 2 M(X ^- ) ads+Pd(NH ₃ ) ₄ ⁺⁺ → [M...X...Pd(NH ₃ ) ₃ ] ⁺ +NH ₃ 3 [M... ₃ ) ₃ ] ⁺ +2e ^- →Pd ⁰ +3NH ₃ +M(X ^- ) ads. The overall reaction is Pd(NH ₃ ) ₄ ⁺⁺ 2e ^- →Pd ⁰ +4NH ₃ In the above equation, M is the metal electrode , X ^- is an additive used to obtain a compositional consistency effect, and
The one in parentheses represents the bridge formed between the metal and the palladium species. Note that ads. is an abbreviation for adsorption. The type of coordination presented here is often related to the structure of the “inner sphere,” which means that at least one ligand is shared, i.e., that both coordination shells This is because they belong to the same time. Adsorption of iodide ions takes place when the potential of the cathode is more positive than the point of zero charge (PZC). At a more positive potential than PZC, the entire surface of the electrode is positively charged, and at a more negative potential than PZC, the entire surface is negatively charged. The mechanism described above is consistent with the observation that purification enhances this effect (see Examples 7, 8, 9). Purification, such as that carried out in the examples of the present invention, removes adsorbed substances from the plating bath (by removing them from the palladium source), but this substance is removed from the iodide (i.e. surfactant) at the electrode. Although it competes with
We do not offer bridges to palladium. Of course, different materials compete with iodide at the surface to different extents. Therefore, according to the currently accepted theory of surfactant action, more lyophobic materials compete more effectively and maintain compositional constancy at the surface of an electrode immersed in an aqueous solution. It tends to reduce the effect of iodide. This is reflected in the test results for "pyridinium salts", where the amount of this type of material in the plating bath is lower on a mass basis than the typical amount of sodium vinyl sulfonate added.
It reduces the effect of iodide, although it is much less (see Example 6). In fact, this deleterious effect cannot be practically overcome by increasing the amount of iodide. This finding also includes surface effects,
That is, if this effect is a dose effect, the instability caused by quaternized pyridine should be "neutralized" by the addition of a large amount of iodide. Generally, the degree of hydrophobicity is correlated to the relative amount of organic character of the molecule in question. Where competition with intentionally added substances is not desirable,
Iodide ions maintain compositional consistency more effectively than in the presence of sodium vinyl sulfonate (see Example 4). Apart from its degree of hydrophobicity, the other key property of a surfactant that has a major influence on its competition with iodide is the charge of the surface active moiety, i.e. the positively charged active moiety. neutralizes the effect of iodide by creating competition between itself and palladium ions for iodide. Since this model assumes that at least a monomolecular layer of iodide is coated on the electrode surface, the optimum concentration of iodide in the bath solution varies depending on differences in conditions such as plating and moving mass. EXAMPLES The invention will now be explained in detail by means of specific examples. All of these examples were performed on copper alloy disks, which were subjected to a pre-plating process common in the art. The disks were then electroplated with a pure nickel coating using a common nickel sulfate plating process. This nickel undercoat prevents copper contamination of the Pd--Ni plating bath, but it is not necessary for the practice of this invention.
The nickel plated surface was activated by immersion in a 20% by volume solution of sulfuric acid prior to Pd-Ni alloy plating. This nickel plating and Pd-Ni
Both stages with alloy plating are 100 to 500 rpm.
It was carried out in a rotary-disc-electrode plating apparatus at rotational speeds in the range of . The thickness of the Pd-Ni alloy coating is 60 μin, and this thickness is determined by using energy-dispersive X-ray analysis (EDXA) technology and applying an accelerating voltage of 20 kV to emit electrons for accurate compositional analysis. is sufficient. Example 1 This example illustrates the typical instability of the composition of Pd--Ni alloys deposited with formulated palladium salts obtained from various commercially available materials.
Plating baths with the same composition were formulated with palladium salts from the six materials listed in Table 1.

[Table] The composition of the plating bath and plating conditions are as follows. Chemical composition of the plating bath Pd concentration: Table salt 20g / Ni concentration: Nickel sulfate/ammine 10g / Sodium vinyl sulfonate: 2.8g / Ammonium sulfate: 50g / Ammonium hydroxide: Required amount for specified pH Plating conditions temperature: 48℃ PH: 8.5 (adjusted by addition of NH ₄ OH or HCl) Rotation speed of disc: 500 rpm Six types of plating baths with the compositions described above, each containing one of the six types of palladium salts listed in the table. The disks were plated with a Pd-Ni alloy coating using a modified Pd-Ni alloy coating at current densities ranging from 25 to 200 amp/sq.ft. The results of the analysis of the coating composition of the alloy can be seen in the table. The stability parameters of the alloy composition for six types of plating baths [△wt%Pd(100-25)] are
It ranged from 13.0 to 18.7.

[Table] Example 2 A Pd--Ni alloy film was electrically deposited on a disk at a current density of 25 to 200 asf with the chemical composition of the plating bath and the plating conditions as shown below, i.e., the chemical composition of the plating bath Pd Concentration: as palladium tetraammine dichloride, 17.0g/Ni concentration: as nickel ammine chloride
11.0g/ Sodium vinyl sulfonate: 2.8g/ Ammonium sulfate: 50g/ Ammonium hydroxide:
Required amount plating conditions to achieve the specified PH Temperature: 48°C PH: 8.0 Rotation speed: 500 rpm The results of the analysis of the coating composition as a function of current density are shown in the table. In this test, the parameter [Δwt%Pd(100-25)] was 21.4.

[Table] Example 3 A Pd-Ni alloy film was electrically deposited on a disk at a current density of 25 to 200 asf with the chemical composition of the plating bath and the plating conditions as shown below, i.e., the chemical composition of the plating bath Pd Concentration: 15.0g as palladium tetraammine dichloride / Ni concentration: 7.5g as nickel chloride / “Pyridinium salt”: 0.6g / Ammonium chloride: 30g / Ammonium hydroxide:
Required amount plating conditions to achieve the specified PH Temperature: 48°C PH: 8.5 Rotation speed: 500 rpm The results of the analysis of this coating composition as a function of current density are shown in the table. The parameter [Δwt% Pd (100-25)] in this test was 16.9.

[Table] Example 4 This example shows the beneficial effect of adding iodide ions to a Pd--Ni alloy plating bath, which dramatically improves the consistency of the alloy composition. from 15
In a plating bath containing 50 ppm iodide ions, from 25
A Pd-Ni alloy coating was electrically deposited on the disk at a current density of 200 asf. The chemical composition of the plating bath and the plating conditions are as follows: Chemical composition of the plating bath Pd concentration: as palladium dichloride tetraammine 20g/Ni concentration: as nickel chloride ammine
10g/ammonium sulfate: 50g/ammonium hydroxide:
Required amount plating conditions to achieve the specified PH Temperature: 48°C PH: 8.5 Rotation speed: 500 rpm The results of the analysis of the coating composition as a function of current density and iodide ion concentration are shown in the table.
[△wt% of a plating bath containing 15 ppm iodide ions
Pd(100−25)] was 2.0.

[Table] Note: *The rest are Nickel examples 5 This example includes sodium vinyl sulfonate.
The results show that the addition of iodide ions to the Pd--Ni alloy plating bath significantly improves the consistency of the alloy composition. 0, 6, 15, 25,
In a plating bath containing 50 and 100 ppm iodide ions,
Pd--Ni alloy coatings were electrically deposited on the discs at current densities from 25 to 100 asf. The chemical composition of the plating bath and the plating conditions are as follows: Chemical composition of the plating bath Pd concentration: as palladium dichloride tetraammine 20.g/Ni concentration: as nickel chloride ammine
10g/ Sodium vinyl sulfonate: 2.8g/ Ammonium hydroxide:
Required amount plating conditions to achieve the specified PH Temperature: 48℃ PH: 8.5 Rotation speed: 500rpm Stability parameters [△wt% Pd (100−25)] determined as a function of iodide ion concentration are shown in the table. It is shown. Addition of 25 ppm iodide ions reduced Δwt%Pd(100-25) from 18.7 to 5.2. Surface iodide ion concentration ppm △wt% Pd (100-25) 0 18.7 6 12.8 15 7.6 25 5.2 50 5.0 100 5.9 Example 6 This example shows Pd-Ni containing quaternized pyridine.
The addition of iodide ions to the alloy plating bath shows the beneficial effect of significantly improving the consistency of the alloy composition. 0, 23, 100 and 300ppm
Pd--Ni alloy coatings were electrically deposited onto the discs at current densities from 25 to 100 asf in a plating bath containing iodide ions of . The chemical composition of the plating bath and the plating conditions are as follows: Chemical composition of the plating bath Pd concentration: 15.0 g as palladium tetraamine dichloride / Ni concentration: 7.5 g as nickel chloride / "Viridinium salt": 0.6 g / Ammonium hydroxide:
Required amount plating conditions to achieve the specified PH Temperature: 48℃ PH: 8.5 Rotation speed: 500rpm Stability parameters [△wt% Pd (100−25)] determined as a function of iodide ion concentration are shown in the table. It is shown. Addition of 300 ppm iodide ions reduced Δwt%Pd(100-25) from 16.9 to 11.7. Surface iodide ion concentration ppm △wt% Pd (100-25) 0 16.9 23 15.5 100 13.9 300 11.7 Example 7 This example demonstrates the use of palladium salts to improve the compositional consistency of electro-deposited Pd-Ni alloys. This shows the remarkable effect of purification. A portion of one lot of commercially available palladium dichloride tetraammine salt was purified by one cycle of recrystallization as described above. A plating bath in which the Pd-Ni alloy coating is standard treated with palladium salt as received.
and electroplating baths with the same chemical composition standard treated with purified palladium salts and electrolytically deposited onto disks under the same plating conditions at current densities of 25 to 100 asf. The basic chemical composition of the plating bath and plating conditions are shown in Example 1.
is the same as The iodide ion concentration in the plating bath is <
It was 1ppm. When standard treatment is performed with palladium salt as received, the parameter is 18.7;
On the other hand, the stability parameter when subjected to standard treatment with purified palladium salt was 14.5. Example 8 This example demonstrates the remarkable effect that iodide ion addition and palladium salt purification have on the compositional consistency of an electro-deposited Pd--Ni alloy. One sample of palladium chloride tetraammine salt was purified by the recrystallization cycle described above. At current densities ranging from 25 to 100 asf, Pd—
Ni alloy was plated on the disk, and the chemical composition of the plating bath and the plating conditions were as follows. That is, chemical composition of the plating bath Pd concentration: 20.g/Ni concentration: as nickel ammine sulfate
10g/ Sodium vinyl sulfonate: 2.8g/ Iodide ion: 31ppm Ammonium sulfate: 50g/ Ammonium hydroxide:
Required amount plating conditions to achieve the specified PH Temperature: 48°C PH: 8.5 Rotation speed: 500 rpm The △weight% Pd (100−25) of this method was 4.2. Example 9 This example demonstrates the remarkable effect that iodide ion addition and palladium salt purification have on the compositional consistency of an electro-deposited Pd--Ni alloy. One sample of palladium chloride tetraammine salt was purified by the two recrystallization cycles described above. Pd--Ni alloy was plated on the disk at a current density ranging from 25 to 100 asf, and the chemical composition of the plating bath and plating conditions were as follows. That is, chemical composition of the plating bath Pd concentration: 20g/Ni concentration: as nickel ammine sulfate
10g/ Sodium vinyl sulfonate: 2.8g/ Iodide ion: 35ppm Ammonium sulfate: 50g/ Ammonium hydroxide:
Required amount plating conditions to achieve the specified PH Temperature: 48°C PH: 8.5 Rotation speed: 500 rpm The △weight% Pd (100−25) of this method was 0.4. Example 10 A Pd--Ni alloy coating was electrically deposited on a disk at current densities between 25 and 100 asf under the same test conditions. The plating bath in this case consists of three different types of nickel salts: ammine sulfate; sulfate;
and standard treatment with chloride. The palladium salt, other chemical parameters, and plating conditions were the same as in Example 8. The constancy of palladium alloy composition for the three different types of nickel salts is shown in the table. Table Type of Nickel Salt △wt% Pd (100-25) Ammine Sulfate 4.2 Sulfate 2.8 Chloride 2.3 Example 11 Pd-Ni alloy coatings were deposited on disks at current densities between 25 and 100 asf under the same test conditions. was deposited electrically. The plating bath in this case was standard processed under two different types of conductive salts. Palladium salts and other basic chemical composition parameters,
The plating conditions were the same as in Example 8. The constancy of the palladium alloy composition for the two different conductivity salts is shown in the table. Surface Conductive Salt △wt% Pd (100-25) Ammonium Sulfate 4.2 Ammonium Chloride 0.8 Example 12 This example shows the remarkable effect of the addition of iodide ions for consistency of Pd-Ni alloy composition in the agitation level range. is shown as a function of current density. Current density ranges from 25 to 100asf, 100 and
A Pd--Ni alloy was plated on a disk rotating at a speed of 500 rpm, and the chemical composition of the plating bath and the plating conditions were as follows. That is, the chemical composition of the plating bath: Pd concentration: as palladium diamine dichloride 20g/Ni concentration: as nickel diamine sulfate
10g/ Sodium vinyl sulfonate: 2.8g/ Iodide ion concentration: 31ppm Ammonium sulfate: 50g/ Ammonium hydroxide:
Required amount plating conditions to achieve the specified PH Temperature: 48℃ PH: 8.6 Rotation speed: 100 and 500rpm When the rotation speed is 100rpm, △weight%Pd (100-
25) was 3.2. When the rotation speed is 500 rpm, △
The weight percent Pd (100-25) was 2.8. Example 13 This example shows the remarkable effect of iodide ion addition on Pd-Ni alloy composition consistency when performed in a plating bath with a palladium to nickel molar concentration ratio of 0.86. There is. Pd—Ni on the disk at current densities ranging from 25 to 100 asf.
The alloy was plated, and the chemical composition of the plating bath and the plating conditions were as follows. That is, the chemical composition of the plating bath: Pd concentration: as palladium diamine dichloride 17.0 g/Ni concentration: as nickel diamine sulfate
11.0g/ Sodium vinyl sulfonate: 2.8g/ Ammonium sulfate: 50g/ Ammonium hydroxide:
Required amount plating conditions to achieve the specified PH Temperature: 48℃ PH: 8.5 Rotation speed: 500rpm When the first plating test was completed, 100ppm iodide ions were added to the plating bath and the disk set for the second time. was plated with Pd-Ni alloy at the same current density setting. Table X shows the analysis results of the composition of the coating alloy in the tests before and after the addition of iodide ions.

[Table] Note: * The rest is nickel When 100 ppm of iodide ions were added to the plating bath, △wt% Pd (100-25) decreased from 21.4 to 1.5. Example 14 This example shows the remarkable effect of iodide ion addition on Pd-Ni alloy composition consistency when performed in a plating bath with a palladium to nickel molar concentration ratio of 0.55. There is. Pd—Ni on the disk at current densities ranging from 25 to 100 asf.
The alloy was plated, and the chemical composition of the plating bath and the plating conditions were as follows. That is, the chemical composition of the plating bath: Pd concentration: as palladium diamine dichloride 15.6 g/Ni concentration: as nickel diamine sulfate
15.4g/ Sodium vinyl sulfonate: 2.8g/ Ammonium sulfate: 50g/ Ammonium hydroxide:
Required amount plating conditions to achieve the specified PH Temperature: 48℃ PH: 8.5 Rotation speed: 500rpm When the first plating test was completed, 100ppm iodide ions were added to the plating bath and the disk set for the second time. was plated with Pd-Ni alloy at the same current density setting. The analysis results of the composition of the coating alloy in the tests before and after the addition of iodide ions are shown in Table XI.

[Table] Note: * The rest is nickel When 100 ppm of iodide ions were added to the plating bath, △wt% Pd (100-25) decreased from 18.1 to 2.5. Example 15 This example shows the remarkable effect of iodide ion addition on Pd-Ni alloy composition consistency when performed in a plating bath with a palladium to nickel molar concentration ratio of 0.24. . Current density from 25
A Pd--Ni alloy was plated on the disk at a current density in the range of 100 asf, and the chemical composition of the plating bath and the plating conditions were as follows. That is, the chemical composition of the plating bath: Pd concentration: as palladium diamine dichloride 7.4 g/Ni concentration: as nickel diamine sulfate
17.0g/ Sodium vinyl sulfonate: 2.8g/ Iodide ion concentration: 11ppm Ammonium sulfate: 50g/ Ammonium hydroxide:
Required amount plating conditions to achieve the specified PH Temperature: 48℃ PH: 8.0 Rotation speed: 500rpm When the first plating test was completed, 89ppm of iodide ions were added to the plating bath and the disk set for the second time. was plated with Pd-Ni alloy at the same current density setting. The analysis results of the composition of the coating alloy in the tests before and after the addition of iodide ions are shown in Table XII.

[Table] Note: * The rest is nickel When 89 ppm of iodide ions were added to the plating bath, △wt% Pd (100-25) decreased from 17.9 to 9.4. Although the above description and attached drawings relate to some embodiments of the present invention, it will be obvious to those skilled in the art that other embodiments and modifications equivalent to these can be considered. Will.

[Brief explanation of drawings]

Figure 1 shows the influence of current density on the compositional stability of Pd--Ni alloy, in which curve A represents plating test number V of Example 1, curve B represents
Figure 2 shows the superior effect of the 15 ppm iodide addition according to the present invention as shown in Example 4. The figure shown in FIG. 3 is a conceptual diagram illustrating the mechanism that influences the constant Pd--Ni alloy composition at the electrode interface.

Claims (1)

[Scope of Claims] 1. Plating a film of palladium-nickel alloy on a conductive substrate in an electroplating bath capable of maintaining the palladium content of the plating alloy substantially constant at a predetermined value. An electroplating bath for stabilizing a plating alloy composition, characterized in that the plating bath contains a palladium salt, a nickel salt, and at least 15 ppm of iodide ions. 2. The palladium salt is palladium()ammine chloride, the nickel salt is a salt selected from the group consisting of nickel sulfate/ammine, nickel sulfate, and nickel chloride, and the nickel salt is a conductive salt. the conductive salt has a pH in the range of 7 to 9, the conductive salt is either ammonium sulfate or ammonium chloride, and the organic brightener is vinyl sulfone. The electroplating bath according to claim 1, wherein the electroplating bath is one of sodium chloride and quaternized pyridinium. 3. In a plating method in which a conductive substrate is plated with a film of palladium-nickel alloy, and the palladium content of the alloy is kept substantially constant at a predetermined value, the above method comprises: (a) palladium salt and nickel; with salt and at least
(b) passing a plating current through the plating bath, in which case the current density on the conductive substrate is about 10 amps/sq; ft. to about 150 amps/sq.ft.; (c) depositing a coating of palladium-nickel alloy on the conductive substrate and applying current densities within the range of current densities used; The difference in palladium content is 10
A method for plating a palladium-nickel alloy film on a conductive substrate, the method comprising: