JP2993336B2 - Electroless Ni plating solution for AlN substrate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an electroless Ni for an AlN substrate.
More particularly, the present invention relates to an electroless Ni-based plating solution for an AlN substrate, which is useful when, for example, performing an Ni plating process on an AlN substrate in a manufacturing process of an IC package or the like.

[0002]

2. Description of the Related Art In contrast to electroplating, in which a current is externally applied to reduce and precipitate metal ions in a solution on a cathode, metal ions in a solution are reduced and deposited on the surface of a body to be plated without using an external current. The method is generally called chemical plating. This chemical plating is further roughly classified into immersion plating based on ion substitution and electroless plating using a chemical reducing agent.

In the immersion plating, for example, a metal such as Ni is immersed in a solution containing ions of a noble metal such as gold,
This is a method in which gold is deposited on Ni by a so-called substitution reaction, and once the Ni surface is covered with gold, the growth of plating stops, and there is a problem that thick plating is difficult.

On the other hand, the electroless plating comprises a salt of a metal deposited in a solution, a complexing agent for forming a complex with the metal, a reducing agent for reducing a metal complex to reduce and deposit a simple metal, The object to be plated is placed in a solution in which a pH buffering agent for suppressing fluctuations in pH during the process, a pH adjusting agent for keeping the pH value at a constant value, and a stabilizer for stabilizing the solution are mixed. In this method, the metal is immersed to reduce and deposit a metal on the surface of the object to be plated.

[0005] The problems of this method are that the metal is reduced and precipitated with a reducing agent instead of an electric current, so that the cost is higher than that of electrolytic plating. For example, there is a possibility that the metal may be deposited, so that the plating rate cannot be too high.

On the other hand, a power source, electrodes, etc. are not required, and a coating having a uniform thickness excellent in adhesion, homogeneity, etc. can be obtained only by immersing the object to be plated in a plating solution. It is easy to control the physical properties of pods by changing the plating process conditions such as the plating solution composition, and it is possible to form a film that meets the required characteristics. It is widely used industrially because of its excellent features such as being able to perform plating directly on non-conductive substances such as plastics, glass, and ceramics.

[0007] When the above-mentioned electroless plating treatment is applied to the object to be plated, the mechanism of what kind of reaction proceeds in the solution to form a plating film has not been completely elucidated. Absent.

However, for example, when hypophosphite is used as a reducing agent and a ceramic substrate or the like is subjected to electroless Ni plating, a chemical reaction represented by the following chemical formulas (1) to (3) occurs in a solution. It is said to progress.

[0009]

^{Embedded image} Ni ²⁺ + H ₂ PO ₂ ⁻ + H ₂ O → Ni + H ₂ PO ₃ ⁻ + 2H ⁺

[0010]

Embedded image H ₂ PO ₂ ⁻ + H ₂ O → H ₂ PO ₃ ⁻ + H ₂

[0011]

H ₂ PO ₂ ⁻ + H → P + H ₂ O + OH ^- As shown in the above formula 1, the oxidation of phosphorus in hypophosphite ions progresses, Ni is reduced, and Precipitates. At this time, the reaction of Chemical Formula 2 also proceeds simultaneously, and water is reduced to generate hydrogen. Hydrogen is actually involved in the reduction precipitation of Ni shown in the chemical formula (1), and the hydrogen atoms once reduced in the reaction of the chemical formula (2) transfer electrons to the Ni ions to reduce the Ni. It is said that Further, as for hypophosphorous acid, the disproportionation reaction proceeds, and some phosphorus is oxidized as shown in the chemical formula 2, and at the same time, as shown in the chemical formula 3, some other phosphorus is It is reduced to precipitate phosphorus. That is, the hydrogen atom once reduced by the reaction of the chemical formula 2 also emits an electron to phosphorus in hypophosphite ion, whereby phosphorus in hypophosphite ion is also reduced. For this reason, the deposited film is usually an alloy of Ni and phosphorus. This Ni alloy has an effect of being superior in hardness of the coating, adhesion to the substrate, and the like, as compared with the coating of Ni alone.

In the electroless Ni plating, it is considered that the deposition reaction of the plating film proceeds by the above-described reaction. However, since the deposition reaction forms a film having excellent wear resistance and heat resistance, it is industrially necessary. At the same time, it has been studied for a long time, and its reaction mechanism is gradually being clarified.

[0013]

As described above, although electroless plating is widely used, this electroless N
The plating target to be subjected to the i-plating treatment is limited. That is, the object to be plated is relatively stable to acids and bases, such as Al ₂ O ₃ plate, Cu plate, and Au plate, and corrosion of the substrate even when immersed in a high-temperature solution for a long time. In most cases, this is unlikely to occur. Therefore, conventionally, 90 to 1
The plating process could be performed in a high temperature range of about 00 ° C.

In recent years, it has also been used for plating of printed wiring boards and the like. In this case, it is desirable that the temperature for forming a film is low,
Low-temperature Ni-based plating solutions capable of performing plating at a low temperature of about 0 to 60 ° C. have been developed. However, these Ni-based plating liquids are also intended for a plated body having relatively corrosion resistance, and are not intended for a chemically unstable substrate such as an AlN substrate. Table 1 shows the composition of a Ni-based plating solution that is conventionally used for plating in a high temperature range, and Table 2 below shows the composition of a Ni-based plating solution that is used for plating in a low temperature range.

[0015]

[Table 1]

[0016]

[Table 2]

An electroless plating process is performed on wiring formed by simultaneous firing using Cu or W paste, or wiring on an AlN substrate having wiring formed on the surface using a method such as sputtering. Table 1 and Table 2
In the case of using any of the Ni-based plating solutions conventionally used as shown in FIG.
The N substrate itself dissolved or a self-decomposition reaction of the solution occurred.

As described above, it is difficult to find a condition in which only the metal wiring on the surface of the AlN substrate is plated. Particularly, when a metal such as W is contained in the AlN substrate as a coloring agent or the like. Since a plating film is formed on a portion where the metal is exposed, and the plating film spreads from this portion as a starting point, it has been difficult to prevent the bleeding phenomenon. The coloring agent such as W present in the AlN substrate is usually added in order to prevent ultraviolet rays and the like from transmitting through the AlN substrate to deteriorate the Si substrate and the like.

With respect to the dissolution of the AlN substrate by the Ni-based plating solution, AlN itself is not stable to acid or alkali, and in an acidic or alkaline solution, the decomposition as shown in the following formulas (4) to (5) is performed. Since the reaction proceeds, Al
The N substrate will be corroded. Since Al is amphoteric, it dissolves in the solution as ions both in acidic and alkaline conditions.

[0020]

Embedded image AlN + 3H ⁺ → Al ³⁺ + NH ₃

[0021]

AlN + OH ⁻ + H ₂ O → AlO ₂ ⁻ + NH _{3 When the} pH approaches neutrality, the concentration of protons and hydroxyl groups decreases, so that the reaction does not easily proceed, but slightly as a sintering aid in AlN. Dissolution of the added CaO was observed, and A
It is considered that the substance existing at the grain boundary containing 1N is dissolved. When Al ions are present in the solution by such a reaction, the reaction represented by the following formulas (6) to (7) proceeds.

[0022]

## STR00006 ## ^{_{3Ni (en) 2 2+ + 2Al}} 3+ → 2Al (en) 3 3+ + 3Ni 2+

[0023]

## STR00008 ## ^{_{2Ni (en) 3 2+ + 2Al}} 3+ → 2Al (en) 3 3+ + 2Ni 2+ ie, skip ethylene diamine is a ligand of the Ni complex ion (en) is coordinated to the people of Al ion When Al ions dissolved from the AlN substrate are present in the solution, the ligand ethylenediamine separates from the Ni ions and coordinates toward the Al ions, and the ligand is peeled off. The obtained Ni ions become unstable and the self-decomposition reaction proceeds in the solution, so that powdered Ni or foil-shaped Ni is reduced and precipitated in the solution. For this reason, the deposited powder adheres to the substrate, or the Ni concentration in the solution changes, so that the conditions for forming the film change.

For the reasons described above, when the wiring formed on the AlN substrate is to be plated by the electroless plating method using the conventionally used Ni-based plating solution, the above-mentioned various disadvantages occur. Therefore, there is a problem that it is very difficult to stably perform plating on the wiring on the AlN substrate.

The present invention has been made in view of the above-mentioned problems, and it is possible to improve the characteristics such as film adhesion and hardness only on wiring formed on an AlN substrate by electroless plating without corroding the AlN substrate. An object of the present invention is to provide an electroless Ni-based plating solution for an AlN substrate that can form an excellent plating film selectively and quickly.

[0026]

Means for Solving the Problems] for AlN substrate according to the present invention in order to achieve the above object electroless Ni-based plating solution, sulfuric acid nickel as a Ni ion source, salts of nickel or acetic acid nickel, complex lactate, and as a reducing agent is characterized by comprising the following phosphite sodium as agent and to d ethylenediamine, second complexing agent.

The concentration of the Ni-based plating solution of the present invention in which Ru sulfate nickel used as a Ni ion source, inorganic nickel or acetic acid nickel, preferably about 0.01 to 0.10 mol / liter. Here, nickel sulfate, nickel chloride,
Kernels contain water of crystallization, but are anhydrous
Is also good.

If the concentration of the nickel sulfate, nickel chloride or nickel acetate in the Ni-based plating solution is less than 0.01 mol / liter, the Ni ion concentration in the Ni-based plating solution decreases, so that the Ni coating When the concentration of the nickel sulfate or nickel chloride in the Ni-based plating solution exceeds 0.10 mol / L, the formation of powder or foil pieces in the solution becomes difficult. Ni in the form of a crystal is easily precipitated, and the deposition rate is rather lowered.

The concentration of ethylenediamine used as a complexing agent in the Ni-based plating solution is preferably about 0.05 to 0.20 mol / liter. Here, ethylenediamine is crystalline
It may contain water or may be anhydrous. If the concentration of ethylenediamine in the Ni-based plating solution is less than 0.05 mol / liter, a complex cannot be completely formed with Ni2 ^+, and self-decomposition of Ni ions easily occurs. If the concentration in the plating solution exceeds 0.20 mol / l, the amount of complexing agent becomes too large,
Is formed, and Ni is hardly precipitated.

The concentration of lactic acid as a second complexing agent used together with ethylenediamine as a complexing agent in the Ni-based plating solution is preferably about 0.15 to 0.30 mol / liter. When the concentration of lactic acid in the Ni-based plating solution is less than 0.15 mol / L, the deposition rate of Ni is high, but the pH of the Ni-based plating solution becomes unstable, and a plating film is formed at a stable rate. And the bleeding phenomenon easily occurs. On the other hand, when the concentration of lactic acid in the Ni-based plating solution is 0.1%.
When the amount exceeds 30 mol / liter, the amount of the complexing agent becomes too large as a whole, so that the amount of Ni precipitated is suppressed. Here, lactic acid acts as a complexing agent together with ethylenediamine, but since ethylenediamine is the main complexing agent,
It is customary to refer to the second complexing agent. The lactic acid also serves as a pH adjuster. Since the lactic acid has a chiral center, there are two types of optical isomers,
In the present invention, any of them may be used, and a commonly used racemic body may be used.

The concentration of sodium hypophosphite used as a reducing agent in the Ni-based plating solution is 0.05 to 0.30 mol / mol.
Liters are preferred. Where sodium hypophosphite is
It may contain water of crystallization or may be anhydrous.
The concentration of sodium hypophosphite in the Ni-based plating solution is 0.
When the concentration is less than 05 mol / l, the reducing power is weak and Ni does not precipitate. On the other hand, when the concentration of sodium hypophosphite in the Ni-based plating solution exceeds 0.30 mol / l,
Since the oxidation reaction of hypophosphite ions shown in the formula proceeds and the amount of free Ni ions also increases, the amount of precipitated Ni also decreases.

In the electroless Ni-based plating solution for an AlN substrate according to the present invention, the Ni ion source, the complexing agent, the second complexing agent, and the reducing agent are usually mixed in an appropriate combination, and then mixed with an acid. Can be used as a plating solution by adjusting the pH by adding, but depending on conditions such as the type of the underlying metal and the thickness of the plating layer, a plating solution containing other additives may be used. Good. Here, the acid used for adjusting the pH is preferably hydrochloric acid. The use of sulfuric acid or nitric acid is not preferred because SO ₄ ^2- ions in sulfuric acid and NO ₃ ⁻ ions in nitric acid adversely affect the stability of the formed Ni complex. In particular, in the case of NO ₃ ^- ion,
Ni (NO ₃ ) ₂ is not preferred because it forms a stable salt. Examples of the additive include an organic acid salt serving as a pH buffer and an organic acid serving as a pH adjuster. More specifically, examples of the organic acid salt include sodium succinate, sodium citrate, sodium acetate, and the like, and examples of the organic acid include malic acid, malonic acid, and the like.

Next, a method of plating a AlN substrate using the electroless Ni-based plating solution for an AlN substrate will be described.

Usually, the liquid temperature at the time of performing the plating treatment is 60 to
A range of 80 ° C. is preferred. In order to form a uniform film having excellent characteristics, the above N
Preferably, the temperature of the i-based plating solution is kept within ± 1 ° C. and the pH is kept within ± 0.05.
It is necessary to sufficiently rotate the 1N substrate so that a fresh solution is always supplied to the AlN substrate. It is also necessary to remove dissolved oxygen by blowing nitrogen or argon gas into the Ni-based plating solution.

[0035]

According to electroless Ni-based plating solution for AlN substrate according to the present invention, e and sulfate nickel as a Ni ion source, salts of nickel <br/> or acetic acid nickel, a complexing agent ethylenediamine , lactic acid as a second complexing agent, and is a reducing agent include the following phosphite sodium, at low temperatures, without AlN substrate is melted corrosion selectively only to the wiring formed on the AlN substrate In addition, a phosphorus-containing Ni plating film having excellent properties such as adhesion to wiring and hardness of the film itself is quickly formed.

FIG. 7 is a graph showing the relationship between the buffer capacity of the organic acid and the amount of Ni deposited. As shown in FIG.
There is a large correlation between the amount of i deposited and the buffer capacity of the organic acid, and the larger the buffer capacity, the larger the amount of Ni deposited. Therefore, the electroless Ni plating solution for an AlN substrate according to the present invention using lactic acid having a large buffer capacity can quickly form a plating film. However, it is considered that the reason why the buffer capacity does not completely correspond to the amount of Ni deposited is that there are other factors related to the amount of Ni deposited.

[0037]

EXAMPLES AND COMPARATIVE EXAMPLES Hereinafter, Al according to examples of the present invention will be described.
A case in which an AlN substrate is plated using an electroless Ni-based plating solution for an N substrate will be described. As a comparative example, a case where a plating film is formed using an electroless Ni-based plating solution having a composition different from the composition of the electroless Ni-based plating solution according to the present invention will be described.

As the AlN substrate, an AN manufactured by Sumitomo Metal Ceramics Co., Ltd. having calcium aluminum oxide, calcium yttrium aluminum oxide, etc. at the grain boundaries.
An 1N substrate was used. Then, TN is sequentially formed on the AlN substrate by a sputtering method so as to form a predetermined wiring pattern.
i, Mo, and Cu coatings were respectively 0.05 μm and 0.5 μm.
It was formed to a thickness of 0.5 μm or 0.5 μm, and was used as a base metal layer for forming a plating film. The minimum line width of this wiring is 50 μm
It is about.

A plating film is formed on the base metal layer using an electroless Ni-based plating solution having the composition shown in Table 1. First, basic components (Ni ion source, complexing agent,
Nickel chloride hexahydrate (NiC) as a reducing agent)
l ₂ · 6H ₂ O), sodium hypophosphite monohydrate (Na
H ₂ PO ₂ .H ₂ O) and ethylenediamine (en) were adjusted to the concentrations shown in Table 3. This concentration is Ni-
When chemically reducing Ni from a Rochelle salt complex,
The value that maximizes the film deposition amount is selected.

The organic acids and organic acid salts shown in Table 3 were used, and the concentration was 0.01 mol / L for EDTA · 2Na only, and the other organic acids and organic acid salts were 0.0 mol / L.
It was 8 mol / l. The reason for setting this concentration is
Similarly, since the appropriate concentrations of the pH buffering agent and the second complexing agent in the Ni-Rochelle salt solution were 0.075 mol / liter, respectively, the concentrations were adjusted to substantially the same concentration to compare and examine the effects. As a method of preparing a Ni-based plating solution according to the example, basic components were added to a 500 ml beaker. The addition amount is such that the concentration shown in Table 1 is obtained when the total amount is 1 liter. These components were well stirred and mixed, and adjusted with dilute hydrochloric acid so that the pH was in the range of 6.4 to 6.6. Then, Table 3
After adding the organic acid and the organic acid salt shown in the above, and making up a 1-liter volumetric flask, a predetermined pH described later
Was adjusted. This is because if all the reagents are prepared at once and then the volume is adjusted and the pH is adjusted, a strong buffer action acts on the solution, making it difficult to adjust the pH, which may change the liquid property of the plating solution. Because.

An AlN substrate having a metal thin film obtained by the above method was immersed in this Ni-based plating solution to perform plating. At this time, the temperature of the Ni-based plating solution was set to 60
The pH was maintained within ± 1 ° C. and the pH was within 6.00 ± 0.01, and the Ni-based plating solution was sufficiently stirred and the AlN substrate was sufficiently rotated so that a fresh solution was always supplied to the AlN substrate. . During the plating process, nitrogen was blown into the Ni-based plating solution to remove dissolved oxygen. The plating time is 15 minutes.

Then, 25 ml of concentrated nitric acid (special grade reagent manufactured by Kishida Chemical Co., Ltd.) and concentrated sulfuric acid (special grade manufactured by Kishida Chemical Co., Ltd.) (Reagent) and mixed with 25 ml, and then immersed in a solution diluted to 100 ml with pure water to dissolve the plating film. Then, the metal ion concentration in the solution in which the plating film is dissolved is determined by ICP (Inductively Coupled).
Plasma) was measured by emission spectroscopy to determine the dissolved Ni ion and P ion concentrations, and the P ion content.

By dipping the AlN substrate in the mixed acid solution, Mo, Cu, etc. of the underlying metal layer and the AlN substrate itself were corroded and dissolved, but did not particularly affect the quantitative analysis of Ni ions and P ions. . The results are shown in Tables 3 and 4 below.

[0044]

[Table 3]

[0045]

[Table 4]

In Tables 3 and 4, P ions were detected in the solution in which the plating film was dissolved, because sodium hypophosphite was simultaneously precipitated when the Ni plating film was formed, This is because they form an alloy with

As can be seen from Table 3, when lactic acid was used as the second complexing agent, the amount of Ni precipitated was large, especially when lactic acid was added alone to the basic component. ing. From this result, the electroless Ni-based plating solution having the basic composition of the three basic components according to the example and lactic acid added as the second complexing agent has a large amount of N
It can be seen that the i-type plating solution has excellent characteristics.
When the Ni-based plating solution according to this example was used, no bleeding occurred.

The reason why the plating solution has good characteristics as a Ni-based plating solution is considered to be due to the buffer capacity of the plating solution.

On the other hand, Comparative Example 32 using only basic components
In the case of the Ni-based plating solution according to the above, the deposition amount of the plating film was the largest, but since a pH buffering agent or a pH adjusting agent such as an organic acid or an organic salt was not used, it took about 45 minutes during the plating process. When the plating treatment was performed for a long time, the pH greatly changed, and bleeding occurred due to the self-decomposition reaction of the Ni-based plating solution.

As a result, it was found that a system in which lactic acid was added to the basic component had an excellent effect on the formation of a plating film. As another example, the preferable ranges of these components were examined. FIGS. 1 to 4 show four concentrations of nickel chloride hexahydrate as a Ni ion source, ethylenediamine as a complexing agent, lactic acid as a second complexing agent, and sodium hypophosphite as a reducing agent. 5 is a graph showing the weight of Ni precipitated when the concentration of the remaining one component was changed while keeping constant. In FIG. 1, the changed components are nickel chloride hexahydrate (Examples 9 to 15),
In FIG. 2, ethylenediamine (Examples 16 to 25), FIG.
Then, sodium hypophosphite monohydrate (Examples 26 to 3)
4) and FIG. 4 shows DL-lactic acid (Examples 35 to 40, Comparative Example 32).

From FIG. 1 to FIG. 4, the concentration of nickel chloride hexahydrate in the Ni-based plating solution according to the example was 0.01 to 0.01.
0.10 mol / l, the concentration of ethylenediamine is 0.05 to 0.20 mol / l, and the concentration of sodium hypophosphite is 0.05 to 0.30 mol / l.
It can be seen that the Ni precipitation amount is large in the range of 1 liter, which is a preferable range of the concentration of each component.
When the concentration of lactic acid exceeds 0.30 mol / liter, the amount of Ni precipitation increases, but in the lower concentration range, the amount of Ni ion precipitation hardly changes. However, when the concentration is lower than 0.15 mol / liter, the pH tends to fluctuate during precipitation.

Further, as Comparative Example 33, a commercially available Ni-based plating solution (Linden SA pH, manufactured by World Metal Co., Ltd.)
6.8-7.2), and the temperature of the Ni-based plating solution is 9
A plating film was formed under the same conditions as in the example except that the temperature was adjusted to 0 ° C. and the pH was set to 7.0.

FIG. 5 shows Al plated by the above-described plating process using the electroless Ni-based plating solution for an AlN substrate according to the first embodiment.
FIG. 6 is an enlarged plan view showing the plating state of a part of the N substrate, while FIG. 6 is a plan view showing the plating state of a part of the AlN substrate which has been subjected to the above plating treatment using the Ni-based plating solution according to Comparative Example 33. It is the enlarged plan view which showed the state.

Embodiment 1 As is clear from FIGS.
In the case where the plating treatment was performed using the electroless Ni-based plating solution for an AlN substrate according to (1), the Ni plating film 10 was selectively formed only on the wiring formed on the AlN substrate 11, whereas the comparative example In the case where the plating treatment was performed using the Ni-based plating solution according to No. 33, the Ni plating film 10 was also formed on portions other than the wiring formed on the AlN substrate 11, and the bleeding phenomenon described above was clearly recognized. .

Next, the adhesion strength of the plating film formed by using the electroless Ni-based plating solution for an AlN substrate according to Example 1 was examined. The measurement of the film adhesion strength was performed by soldering a Ni lead wire having a diameter of 1 mm to the plating film and pulling it vertically at a speed of 10 mm per minute.
The strength when the plating film was broken was defined as the film adhesion strength. As a result, a value of 2.48 kg / mm ² or more was obtained, and it was confirmed that the film had sufficient film adhesion strength.

Next, Ni of the same composition as in Example 1 was used.
When plating was performed on an AlN substrate having a base metal layer having a length of 50 mm and a width of 50 mm using a system plating solution, it was examined whether or not the AlN substrate was dissolved. In this investigation of the solubility of the AlN substrate, Al ³⁺ ions, which are the main components of the AlN substrate, and Ca ²⁺ and Y ³⁺ added as auxiliaries at the time of firing the AlN substrate have finished plating. The presence or absence of the solution was examined by ICP emission spectroscopy.
The concentrations of Ni and P, which are film forming components, were also measured at the same time. The plating process was performed 5 times continuously using the same Ni-based plating solution. After each plating process, the Ni-based plating solution was sampled, and the concentration of each metal described above was measured. Table 5 shows the results.

[0057]

[Table 5]

As is clear from Table 5, Al ³⁺ , C
Each ion of a ²⁺ and Y ³⁺ was 0.1 ppm or less, and no dissolution from the AlN substrate was observed. on the other hand,
The Ni ²⁺ ions and P decrease by a substantially constant amount at each measurement, and it can be seen that a fixed amount of plating film is formed on the wiring of the AlN substrate with good reproducibility.

As described above, A according to the embodiment is
When the AlN substrate was plated using an electroless Ni-based plating solution for an 1N substrate, the AlN substrate was not dissolved, and only the wiring on the AlN substrate was selectively excellent in characteristics such as film adhesion strength. The plating film could be formed quickly.

[0060]

As described in detail above there for AlN substrate electroless Ni-based plating solution according to the present invention, as a Ni ion source
Sulfate nickel salt nickel or acetic acid nickel, et as a complexing agent <br/> ethylenediamine, lactate as a second complexing agent, and a reducing agent because it contains the following phosphite sodium,
At low temperatures, a phosphorus-containing Ni plating film having excellent properties such as adhesion to the wiring and hardness of the film itself can be quickly formed selectively on the wiring only without dissolving and corroding the AlN substrate.

[Brief description of the drawings]

FIG. 1 shows an electroless Ni for an AlN substrate according to an embodiment of the present invention.
5 is a graph showing the relationship between the amount of Ni deposited and the concentration of nickel chloride hexahydrate when the concentration of nickel chloride hexahydrate was changed and the other three components were kept at a constant concentration in the system plating solution.

FIG. 2 shows an electroless Ni for an AlN substrate according to an embodiment of the present invention.
5 is a graph showing the relationship between the amount of Ni deposited and the concentration of ethylenediamine when the concentration of ethylenediamine is changed and the other three components are kept at a constant concentration in the system plating solution.

FIG. 3 shows an electroless Ni for an AlN substrate according to an embodiment of the present invention.
In the base plating solution, the concentration of sodium hypophosphite monohydrate was changed to maintain the other three components at a constant concentration.
3 is a graph showing the relationship between the amount of i precipitation and the concentration of sodium hypophosphite.

FIG. 4 shows an electroless Ni for an AlN substrate according to an embodiment of the present invention.
In the system plating solution, the concentration of DL-lactic acid was changed, and the amount of Ni deposition and DL-lactic acid when the other three components were kept at a constant concentration.
It is the graph which showed the relationship with the concentration of lactic acid.

FIG. 5 is an electroless N for an AlN substrate according to the first embodiment of the present invention.
FIG. 3 is an enlarged plan view showing a plating state of a part of an AlN substrate that has been subjected to a plating process using an i-based plating solution.

FIG. 6 is an enlarged plan view showing a plating state of a part of an AlN substrate plated with an electroless Ni-based plating solution for an AlN substrate according to Comparative Example 33.

FIG. 7 is a graph showing the relationship between the buffer capacity of an organic acid added to a Ni-based plating solution and the amount of Ni deposited.

[Explanation of symbols]

 11 AlN substrate 10 Ni plating film

Claims (1)

(57) [Claims] 1. It is characterized in that it contains nickel sulfate, nickel chloride or nickel acetate as a Ni ion source, ethylenediamine as a complexing agent, lactic acid as a second complexing agent, and sodium hypophosphite as a reducing agent. Electroless Ni-based plating solution for AlN substrates.