JPH07150363A - Electroless ni-based plating solution for aln substrate - Google Patents

Abstract

PURPOSE:To provide the plating solution with which a plated coating film having excellent properties such as film adhesion, hardness, can be formed selectively on only the wiring provided on the AlN substrate by specifying the Ni ion source, complexing agent, second complexing agent and reducing agent used as the components of the plating solution. CONSTITUTION:The composition of this plating solution consists of nickel sulfate (or that contg. water of crystallization), nickel chloride or nickel acetate as the Ni ion source, ethylene diamine as the complexing agent, lactic acid as the second complexing agent and sodium hypophosphite as the reducing agent. An appropriate combination of these components is prepared and an acid is added to the resulting composition to adjust its pH and the solution thus obtained is used as the objective plating solution. At the time of performing the plating, the temp. of the plating solution is preferably within the range of 60 to 80 deg.C and the concn. of the Ni ion source in the plating solution is preferably about 0.01 to 0.10 mol/l and also, the concn. of the complexing agent and the second complexing agent in the plating solution are preferably about 0.05 to 0. 20mol/l and about 0. 15 to 0. 30mol/l respectively and further, the concn. of the reducing agent in the plating solution is preferably about 0. 05 to 0. 30mol/l.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to electroless Ni for AlN substrates.
More specifically, the present invention relates to an electroless Ni-based plating solution for AlN substrates, which is useful, for example, when Ni-plating 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 an electric current is applied from the outside to reduce and deposit metal ions in a solution on a cathode, metal ions in a solution are reduced and deposited on the surface of an object to be plated without using an external current. The method is generally called chemical plating. The chemical plating is roughly classified into immersion plating based on ion substitution and electroless plating using a chemical reducing agent.

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

On the other hand, in the electroless plating, a salt of a metal to be 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, a solution. The material to be plated is mixed in a solution in which a pH buffering agent for suppressing fluctuations in the pH, a pH adjusting agent for keeping the pH value constant, and a stabilizing agent for stabilizing the solution are mixed. It is a method of dipping and reducing and depositing a metal on the surface of the object to be plated.

A problem with this method is that the metal is reduced and deposited by a reducing agent instead of an electric current, so that the cost is higher than that of electrolytic plating, and when an attempt is made to increase the plating speed, a powder state in the plating bath is used. There is a possibility that the metal may be deposited, so that the plating speed cannot be increased too much.

[0006] On the other hand, on the other hand, a power source, electrodes, etc. are not required, and by simply immersing the object to be plated in a plating solution, it is possible to obtain a coating having a uniform thickness excellent in adhesion, homogeneity, etc. It is easy to control the properties of the sheath by changing the plating conditions such as the composition of the plating solution, and it is possible to form a coating that meets the required characteristics. It is widely used industrially because of its excellent features such as that it is possible to perform direct plating on non-conductive substances such as plastic, glass, ceramics and the like.

[0007] When the electroless plating treatment is applied to the object to be plated, the mechanism of what reaction proceeds in the solution to form the plating film is not completely understood. Absent.

However, for example, when hypophosphite is used as the reducing agent and electroless Ni plating treatment is applied to a ceramic substrate or the like, the chemical reaction shown in the following chemical formulas 1 to 3 is performed in the solution. It is said to proceed.

[0009]

## STR1 ## _{^{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]

Embedded image H ₂ PO ₂ ⁻ + H → P + H ₂ O + OH ⁻ As shown in the above formula 1, oxidation of phosphorus in hypophosphite ions progresses, Ni is reduced, and the surface of the object to be plated is reduced. To deposit. At this time, the reaction of Chemical formula 2 also proceeds at the same time, water is reduced and hydrogen is generated. Hydrogen is actually involved in the reductive precipitation of Ni shown in Chemical formula 1, and Ni is reduced by transferring electrons to the Ni ions by the hydrogen atom once reduced in the reaction of Chemical formula 2 above. It is said to be. Further, with respect to hypophosphorous acid, a disproportionation reaction progresses, and a part of phosphorus is oxidized as shown in Chemical formula 2, and at the same time, a part of other phosphorus is changed as shown in Chemical formula 3. It is reduced and phosphorus is deposited. That is, the hydrogen atom once reduced by the reaction of Chemical formula 2 releases an electron also to the phosphorus in the hypophosphite ion, whereby the phosphorus in the hypophosphite ion is also reduced. Therefore, the deposited film usually becomes an alloy of Ni and phosphorus. This Ni alloy brings about the 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 electroless Ni plating, it is considered that the deposition reaction of the plated coating proceeds due to the above-mentioned reaction, but this deposition reaction forms a coating having excellent wear resistance and heat resistance, so that it is industrially used. It has been used for a long time and has been studied for a long time, and its reaction mechanism is gradually becoming clear.

[0013]

Thus, although electroless plating is widely used, this electroless N
The objects to be plated that were subjected to i-plating processing were 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 corrodes the substrate even when immersed in a high temperature solution for a long time. Most of them do not occur. Therefore, in the past, 90 to 1 has been used for the above-mentioned object to be plated.
It was possible to perform the plating treatment in a high temperature range of about 00 ° C.

In recent years, it has come to be used for plating of printed wiring boards and the like, and in this case, it is desirable that the temperature for forming the coating is low, so that 3
A low-temperature Ni-based plating solution that can be plated at a low temperature of 0 to 60 ° C. has also been developed. However, these Ni-based plating solutions are also intended for the object to be plated having a relatively high corrosion resistance, and are not intended for chemically unstable substrates such as AlN substrates. Table 1 shows the composition of a Ni-based plating solution that has been conventionally used for plating in a high temperature range, and Table 2 below shows the composition of a Ni-based plating solution that performs plating in a low temperature range.

[0015]

[Table 1]

[0016]

[Table 2]

Let us perform electroless plating on the wiring formed by co-firing with Cu or W paste or on the AlN substrate having the wiring formed by a method such as the sputtering method on the surface. If so, Table 1 and Table 2
When any of the conventionally used Ni-based plating solutions such as those shown in Fig. 3 is used, a bleeding phenomenon occurs in which a plating film is formed in a place other than the metal wiring part, or Al
The N substrate itself was dissolved, or an autolysis 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. Especially, when a metal such as W is contained in the AlN substrate as a coloring agent or the like. It is difficult to prevent the bleeding phenomenon because a plating film is formed on a portion where the metal is exposed and the plating film spreads starting from this portion. The colorant such as W existing in the AlN substrate is usually added in order to prevent ultraviolet rays and the like from passing through the AlN substrate and deteriorating the Si substrate and the like.

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

[0020]

[Chemical formula 4] AlN + 3H ⁺ → Al ³⁺ + NH ₃

[0021]

Embedded image AlN + OH ⁻ + H ₂ O → AlO ₂ ⁻ + NH _{3 When the} pH approaches neutrality, the concentration of protons and hydroxyl groups decreases, so the reaction does not proceed easily, but slightly as a sintering aid in AlN. Dissolution of the added CaO was observed,
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 reactions shown in the following chemical formulas 6 to 7 proceed.

[0022]

Embedded image 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 Therefore, when Al ions dissolved from the AlN substrate are present in the solution, the ethylenediamine of the ligand leaves the Ni ion and is coordinated to the Al ion, and the ligand is stripped off. The resulting Ni ions become unstable, and the self-decomposition reaction proceeds in the solution, and powdery Ni and foil-like Ni are reduced and precipitated in the solution. Therefore, 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 above-mentioned reasons, when it is attempted to plate the wiring formed on the AlN substrate by the electroless plating method using the Ni-based plating solution which has been conventionally used, the above-mentioned various inconveniences are caused. However, there is a problem that it is very difficult to stably plate the wiring on the AlN substrate.

The present invention has been made in view of the above problems, and does not corrode the AlN substrate, and only the wiring formed on the AlN substrate by the electroless plating method has characteristics such as film adhesion and hardness. It is an object of the present invention to provide an electroless Ni-based plating solution for AlN substrates, which can form an excellent plating film selectively and quickly.

[0026]

In order to achieve the above object, an electroless Ni-based plating solution for an AlN substrate according to the present invention comprises:
(Crystalline water) nickel sulfate, (Crystalline water) nickel chloride or (Crystalline water) nickel acetate as Ni ion source, (Crystalline water) ethylenediamine as complexing agent, lactic acid as second complexing agent, and reducing agent As (containing water of crystallization), it is characterized by containing sodium hypophosphite.

The concentration of (crystal water containing) nickel sulfate, (crystal water containing) nickel chloride, or (crystal water containing) nickel acetate used as the Ni ion source in the present invention in the Ni-based plating solution is 0.01. It is preferably about 0.10 mol / liter. Here, for example, the description that nickel sulfate is (crystal water containing) nickel sulfate means that the nickel sulfate may contain crystal water or may be an anhydride. This also applies to other compounds. In the following, a compound to which (water of crystallization) is added will be represented by omitting (water of crystallization), but in reality, a compound containing water of crystallization is also included.

When 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 film is formed. If the concentration of the nickel sulfate or nickel chloride in the Ni-based plating solution exceeds 0.10 mol / liter, powder or foil pieces in the solution become difficult. -Like Ni tends to precipitate, and the precipitation rate decreases on the contrary.

The concentration of ethylenediamine used as a complexing agent in the Ni-based plating solution is 0.05 to 0.20.
About mol / liter is preferable. N of ethylenediamine
If the concentration in the i-based plating solution is less than 0.05 mol / liter, it cannot form a complex with Ni ²⁺ completely,
On the other hand, when the concentration of ethylenediamine in the Ni-based plating solution exceeds 0.20 mol / liter, the amount of the complexing agent becomes too large.
A stable complex of i is formed and Ni is less likely to precipitate.

The concentration of lactic acid, which is the second complexing agent used together with ethylenediamine as the 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 / liter, the deposition rate of Ni is high, but the pH of the Ni-based plating solution becomes unstable and a plated film is formed at a stable rate. In addition, the bleeding phenomenon is likely to occur, while the concentration of lactic acid in the Ni-based plating solution is 0.
When it exceeds 30 mol / liter, the amount of the complexing agent becomes too large as a whole, so that the amount of Ni deposited is suppressed. Here, lactic acid acts as a complexing agent with ethylenediamine, but since ethylenediamine is the main complexing agent,
It is customary to call it the second complexing agent. Furthermore, this lactic acid also serves as a pH adjuster. Since the lactic acid has a chiral center, there are two optical isomers,
In the present invention, any one may be used, and a commonly used racemate 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 / liter is preferred. If the concentration of sodium hypophosphite in the Ni-based plating solution is less than 0.05 mol / liter, the reducing power is weak and Ni is not precipitated, while the sodium hypophosphite is used in the Ni-based plating solution. If the concentration in the medium exceeds 0.30 mol / liter, the oxidation reaction of the hypophosphite ion shown in Chemical formula 1 proceeds, and the amount of free Ni ion also increases. Decrease.

In the electroless Ni-based plating solution for AlN substrate according to the present invention, usually, the Ni ion source, the complexing agent, the second complexing agent, and the reducing agent are mixed in an appropriate combination to obtain an acid. Although it can be used as a plating solution by adjusting the pH by adding, depending on the 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. When sulfuric acid or nitric acid is used, SO ₄ ²⁻ ion in sulfuric acid or NO ₃ ⁻ ion in nitric acid adversely affects the stability of the formed Ni complex, which is not preferable. In particular, NO ₃ ^- in the case of ions,
Ni (NO ₃ ) ₂ forms a stable salt, which is not preferable. Examples of the additives include organic acid salts that function as pH buffers and organic acids that function as pH adjusters. Further, specifically, examples of the organic acid salt include sodium succinate, sodium citrate, and sodium acetate, and examples of the organic acid include malic acid and malonic acid.

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

Usually, the liquid temperature for the plating treatment is 60 to
A range of 80 ° C is preferred. In order to form a uniform coating having excellent properties, the N
It is preferable to keep the temperature of the i-based plating solution within ± 1 ° C and the pH within ± 0.05, and to stir the Ni-based plating solution and
It is necessary to perform sufficient rotation of the 1N substrate so that the AlN substrate is constantly supplied with a fresh solution. It is also necessary to remove dissolved oxygen by blowing nitrogen or argon gas into the Ni-based plating solution.

[0035]

According to the electroless Ni plating solution for AlN substrates according to the present invention, nickel sulfate (containing crystal water), nickel chloride (containing crystal water) or nickel acetate (containing crystal water) as a Ni ion source, complexing It contains (crystal-containing water) ethylenediamine as an agent, lactic acid as a second complexing agent, and (crystal-containing water) sodium hypophosphite as a reducing agent.
The N substrate is not melted and corroded, and a phosphorus-containing Ni plating film excellent in characteristics such as adhesion to the wiring and hardness of the film itself is rapidly formed only on the wiring formed on the AlN substrate. It

FIG. 7 is a graph showing the relationship between the buffer capacity of organic acid and the precipitation amount of Ni. As shown in FIG.
There is a strong correlation between the amount of i deposited and the buffer capacity of the organic acid, and the larger the buffer capacity, the greater the amount of Ni deposited. Therefore, the electroless Ni plating solution for AlN substrates according to the present invention, which uses lactic acid having a large buffer capacity, can quickly form a plating film. However, it is considered that the buffer capacity and the amount of deposited Ni do not completely correspond to each other because there are other factors related to the amount of deposited Ni.

[0037]

EXAMPLES AND COMPARATIVE EXAMPLES Hereinafter, Al according to the examples of the present invention
A case where an AlN substrate is plated with 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 by using an electroless Ni-based plating solution having a composition different from that of the electroless Ni-based plating solution according to the present invention will be described.

As the AlN substrate, A manufactured by Sumitomo Metal Ceramics Co., Ltd., which has calcium aluminum oxide, calcium yttrium aluminum oxide or the like at the grain boundary, is used.
An IN substrate was used. Then, the AlN substrate is sequentially sputtered by a T method so that a predetermined wiring pattern is formed.
i, Mo, Cu coatings of 0.05 μm and 0.5, respectively
The base metal layer was formed to a thickness of 0.5 μm and 0.5 μm to form a plating film. The minimum line width of this wiring is 50 μm
It is a degree.

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

As the organic acid and the organic acid salt, those shown in Table 3 were used, and the concentration was 0.01 mol / liter only for EDTA.2Na, and the other organic acids and organic acid salts were all 0.0
It was set to 8 mol / liter. The reason for setting this concentration is
Similarly, since the suitable concentrations of the pH buffering agent and the second complexing agent in the Ni-Rochelle salt complex solution were 0.075 mol / liter, the effects were compared and examined by adjusting them to almost the same concentration. As a method for preparing the Ni-based plating solution according to the example, the basic components were added to a 500 ml beaker. The added 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 the pH was adjusted to be in the range of 6.4 to 6.6 using dilute hydrochloric acid. After that, Table 3
After adding the organic acid and the organic acid salt shown in 1 and measuring up to a 1-liter measuring flask,
Adjusted to. This is because if all reagents are prepared at the same time and the pH is adjusted and the pH is adjusted, a strong buffer action acts on the solution and pH adjustment becomes difficult, which may change the liquidity of the plating solution. Because.

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

Next, 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.) were mixed with a mixed acid solution on the AlN substrate on which a plating film was formed by the plating treatment. (Reagent) 25 ml and then diluted with pure water to make a 100 ml solution 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) The concentration of dissolved Ni ions and P ions was determined by emission spectroscopic analysis, and the content of P ions was determined.

By dipping the AlN substrate in a mixed acid solution, Mo, Cu, etc. of the underlying metal layer and the AlN substrate itself were corroded and dissolved, but this 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 above, P ions were detected in the solution in which the plated coating was dissolved. The reason why sodium hypophosphite was deposited at the same time when the Ni plated coating was formed was This is because it forms an alloy with.

As can be seen from Table 3, the precipitation amount of Ni was large when lactic acid was used as the second complexing agent, and particularly when lactic acid alone was added to the basic component, the precipitation amount was the largest. ing. From this result, the electroless Ni-based plating solution having a composition in which lactic acid was added as the second complexing agent to the three types of basic components according to the example has a large amount of N deposition.
It can be seen that the i-based plating solution has excellent properties.
No bleeding occurred when the Ni-based plating solution according to this example was used.

It is considered that the above-mentioned plating solution has good characteristics as a Ni-based plating solution because of the buffer capacity of the plating solution.

On the other hand, Comparative Example 32 using only the basic components
In the case of the Ni-based plating solution according to (1), the amount of deposition of the plating film was the largest, but since no pH buffering agent or pH adjusting agent such as organic acid or organic salt salt was used, it took about 45 minutes during the plating process. When the plating treatment was performed for a long time, the pH fluctuated significantly, and bleeding occurred due to the self-decomposition reaction of the Ni-based plating solution.

As a result, it was found that the system in which lactic acid was added to the basic components had an excellent effect on the formation of the plating film. Therefore, the preferred range of these components was examined as yet another example. FIGS. 1 to 4 use four components 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. 6 is a graph showing the weight of Ni deposited when the concentration of the remaining one component is changed while keeping the value constant. The changed components are nickel chloride hexahydrate (Examples 9 to 15) in FIG.
In FIG. 2, ethylenediamine (Examples 16 to 25), FIG.
Sodium hypophosphite monohydrate (Examples 26 to 3)
4), and in FIG. 4, DL-lactic acid (Examples 35 to 40, Comparative Example 32).

From FIGS. 1 to 4, the concentration of nickel chloride hexahydrate in the Ni-based plating solution according to the embodiment is 0.01 to
0.10 mol / liter, the concentration of ethylenediamine is 0.05 to 0.20 mol / liter, and the concentration of sodium hypophosphite is 0.05 to 0.30 mol / liter.
In the liter range, the amount of precipitation of Ni is large, and it can be seen that the concentration range of each component is within the preferable range.
When the concentration of lactic acid exceeds 0.30 mol / liter, the amount of Ni deposited increases, but in the range where the concentration is lower than that, the amount of Ni ion deposited hardly changes. However, when the concentration was lower than 0.15 mol / liter, the pH was likely to change during precipitation.

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

FIG. 5 shows Al plated with the above electroless Ni-based plating solution for AlN substrates according to Example 1.
FIG. 7 is an enlarged plan view showing a plating state of a part of the N substrate, while FIG. 6 shows a plating state of a part of the AlN substrate subjected to the plating treatment using the Ni-based plating solution according to Comparative Example 33. It is an enlarged plan view showing a state.

As is clear from FIGS. 5 and 6, Example 1
In the case where the plating treatment is performed using the electroless Ni-based plating solution for the AlN substrate according to the present invention, the Ni plating film 10 is selectively formed only on the wiring formed on the AlN substrate 11, whereas the comparative example In the case of performing the plating treatment using the Ni-based plating solution according to No. 33, the Ni plating film 10 is also formed on the portion other than the wiring formed on the AlN substrate 11, and the bleeding phenomenon described above is clearly recognized. .

Next, the adhesion strength of the formed plating film was examined by using the electroless Ni-based plating solution for the AlN substrate according to Example 1. The film adhesion strength is measured by soldering a Ni lead wire with 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 plated coating broke 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 having the same composition as in the case of Example 1 was used.
When an AlN substrate having a base metal layer having a length and width of 50 mm was plated using a system plating solution, it was examined whether or not the AlN substrate was dissolved. The investigation of the solubility of the AlN substrate was carried out by examining the Al ³⁺ ion, which is the main component of the AlN substrate, and Ca ²⁺ and Y ^{3+, which} were added as an auxiliary agent during the firing of the AlN substrate, after the plating treatment. The presence or absence in the solution was examined by ICP emission spectroscopy.
Further, the concentrations of Ni and P, which are film forming components, were measured at the same time. The plating treatment was continuously performed five times using the same Ni-based plating liquid, and after each plating treatment, the Ni-based plating liquid was sampled to measure the concentration of each metal described above. The results are shown in Table 5.

[0057]

[Table 5]

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

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

[0060]

As described above in detail, the AlN according to the present invention is
In the electroless Ni-based plating solution for substrates, nickel sulfate (containing crystal water), nickel crystal (containing crystal water) or nickel acetate (containing crystal water) as a Ni ion source, and (crystal water containing) as a complexing agent Since it contains ethylenediamine, lactic acid as a second complexing agent, and sodium hypophosphite (as water containing crystallization) as a reducing agent, a wiring formed on an AlN substrate at a low temperature without dissolving and corroding the AlN substrate. Only in this case, a phosphorus-containing Ni plating film having excellent characteristics such as adhesion to wiring and hardness of the film itself can be rapidly formed.

[Brief description of drawings]

FIG. 1 is an electroless Ni for AlN substrate according to an embodiment of the present invention.
6 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 is changed and the other three components are kept at constant concentrations in the system plating solution.

FIG. 2 is an electroless Ni for AlN substrate according to an embodiment of the present invention.
6 is a graph showing the relationship between the amount of Ni deposition 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 plating solution.

FIG. 3 is an electroless Ni for AlN substrate according to an embodiment of the present invention.
N in the case where the concentration of sodium hypophosphite monohydrate was changed and the other three components were kept at constant concentrations in the plating solution
2 is a graph showing the relationship between the amount of precipitation and the concentration of sodium hypophosphite.

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

FIG. 5 is an electroless N for AlN substrate according to Example 1 of the present invention.
FIG. 4 is an enlarged plan view showing a plating state of a part of an AlN substrate that has been plated 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 Ni deposition amount.

[Explanation of symbols]

 11 AlN substrate 10 Ni plating film

Claims (1)

[Claims] 1. A (crystal water containing) nickel sulfate, a (crystal water containing) nickel chloride or a (crystal water containing) nickel acetate as a Ni ion source, a (crystal water containing) ethylenediamine as a complexing agent, and a second complexing agent. An electroless Ni-based plating solution for an AlN substrate, which contains lactic acid and sodium hypophosphite as a reducing agent (water containing crystallization).