JPH0892753A - Recycling of electroless plating solution - Google Patents

Abstract

PURPOSE: To increase the frequency of recyclings of electroless plating soln. CONSTITUTION: When a plating soln. is recycled, a plating soln. prepared by adding an alkali agent to a plating soln. to be recycled so that the alkali agent concn. in the original plating soln. is increased by 1-20% is used. Consequently, the plating soln. is activated, the reactivity of plating deteriorated due to the impurities eluted into the plating soln. from a material to be treated is restored, the frequency of recyclings is increased, the plating soln. is efficiently used to reduce the amt. of the soln. to be discarded, and further the productivity of electroless plating is enhanced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for recycling and using an electroless plating solution such that an electroless plating solution such as an electroless copper plating solution can be recycled more frequently.

[0002]

2. Description of the Related Art Electroless plating is a plating method in which a metal is deposited on the surface of an object to be treated by a chemical reaction. For example, external electrodes of ceramic electronic parts such as porcelain capacitors,
It is used as a means for covering the conductor portion of a printed wiring board and the surface of plastic with a metal such as copper. For example, electroless copper plating is one in which an object to be treated is immersed in an electroless copper plating solution containing copper ions, a reducing agent and a complexing agent as main components, and a pH adjusting agent, a stabilizing agent, etc. In Although,
When an electroless plating solution of sodium hydroxide solution using copper sulfate as a copper ion source, formalin as a reducing agent, and tartrate as a complexing agent is used, copper ions are reduced by the following reaction to form metallic copper. Are deposited on the surface of the object to be treated.

CuSO ₄ + 2HCHO + 4NaOH = C
u + H ₂ + 2H ₂ O + 2HCOONa + Na ₂ SO ₄ At this time, the complexing agent serves as a catalyst for reducing the reduction potential of reducing Cu ²⁺ to Cu, which, conversely, promotes the anodic oxidation reaction of formalin (reducing agent). It carries out the function of the catalyst. Since Cu ²⁺ , HCHO and NaOH are consumed by the plating treatment by this reaction,
The plating process is repeatedly performed while supplementing the plating solution with copper sulfate, formalin and sodium hydroxide. However, when the plating process progresses and the composition in the plating bath changes, a side reaction product is generated by the next side reaction, and the stability of the plating bath deteriorates. 2Cu ²⁺ + HCHO + 5OH → Cu ₂ O + HCOO ⁻ + 3H ₂ O a Cu ₂ O + H ₂ O → Cu + 2OH ⁻ b Cu ₂ O + 2HCHO + 2OH ⁻ → 2Cu + H ₂ + 2HCOO ⁻ + H ₂ O ca cuprous oxide (Cu ₂ O) is generated. Then, in the disproportionation reaction of the formula b or the reaction of the formula c, metallic copper is deposited on the suspended matter in the solution which is the nucleus, and when this occurs, the plating bath becomes extremely unstable. In the extreme case, in the plating bath. The metal continues to deposit, causing so-called self-decomposition. A stabilizer is used in order to suppress the destabilization of the plating bath.
This stabilizer is adsorbed on metallic copper generated by the side reaction of the above formulas a to c and has a catalyst poisoning action, or a cuprous ion (C
It forms a stable complex with u ⁺ ) and suppresses the formation of cuprous oxide. However, when the number of times the plating bath is used repeatedly (the number of times of recycling use) is increased, sodium formate (HCOONa) and Powe glass (Na ₂ SO ₄ ) are accumulated in the plating solution. In addition, a conductive paste containing zinc (Zn) powder or nickel (Ni) powder is applied to both end surfaces of a ceramic body such as a porcelain capacitor of an object to be processed, and electroless copper plating is applied thereon. However, Zn and Ni are eluted in the plating solution at this time, and silicon (S
When i) is included, this silicon also elutes and mixes in the plating solution, so-called contamination from the object to be processed occurs. Then, not only pollutants of sodium formate and Pau-silver accumulated in these plating solutions, eluates of Zn and Si, but also copper particles that may be generated in the plating solution float in the plating solution, Precipitation of metallic copper due to the above-mentioned side reaction easily occurs on the surface of these particularly pollutants as nuclei, and therefore the deposition rate of copper on the object to be treated is decreased, and a predetermined copper plating film cannot be obtained. However, the stability of the plating solution is impaired, and if it is left as it is, the copper deposition reaction with respect to the suspended matter in the plating bath proceeds synergistically, causing so-called self-decomposition, making it impossible to form a plated film on the object to be treated.

[0004]

In order to solve these problems, a method of periodically replacing a part of the plating solution in use with a fresh plating solution has been used, but in that case, it is replaced. Since the so-called aged plating solution is discarded, a large amount of waste solution is generated, and the disposal thereof causes an environmental problem, so that the treatment method becomes a new problem. In addition, even if sodium formate or Pau-silver is accumulated, the accumulated amount thereof is not so large as to hinder the predetermined plating, but the eluate from the object to be treated such as Zn or Si is generated. If the plating solution does not fulfill its intended function due to the accumulation of the contaminants, the contaminated plating solution is electrodialyzed using an ion exchange membrane in order to remove these contaminants from the plating solution and reuse the plating solution. It was also considered to be regenerated by. In this method, a pair of facing cation exchange membranes are arranged on each electrode side in an electrodialysis tank equipped with an anode and a cathode, and a contaminated plating solution is put between the cation exchange membranes to place both electrodes. Voltage is applied to move the cation components such as Zn and Si ions to the cathode side and take them out to the outside, the solution of the anion components between the cation exchange membranes is returned to the plating tank, and the formalin and copper sulfate are plated in the plating tank. It is to be replenished and reused, but as described above, pipes and ions for returning the plating solution regenerated from the accumulated formic acid and Pour-silver, and the plating film deposited with this as the nucleus to the plating tank. Since it adheres to the exchange membrane, it is necessary to remove the adhered matter and replace these members with new ones, and there is a problem that the maintenance is not easy.

A first object of the present invention is to increase the number of times the electroless plating solution is recycled and used. Second of the present invention
It is an object of the present invention to provide a method for recycling and using an electroless plating solution, which can maintain a stable deposition rate of a plating metal on an object to be processed even if the number of times of recycling is increased. A third object of the present invention is to provide a method for recycling and using an electroless plating solution which can reduce the amount of waste solution generated from the electroless plating solution. A fourth object of the present invention is to provide a method for recycling and using an electroless plating solution which has high productivity and can perform low cost electroless plating.

[0006]

In order to solve the above-mentioned problems, the present invention provides (1), a metal ion for plating, a reducing agent,
What is claimed is: 1. A method for recycling an electroless plating solution, which comprises repeatedly using an electroless plating solution containing at least a complexing agent and an alkaline agent, and replenishing the necessary components that have been consumed. Recycling is the use of non-circulating electroless plating solution, and at least every time the electroless plating solution falls below a predetermined plating capacity within the number of times of recycling use, the alkaline agent originally blended in the electroless plating solution It is intended to provide a method for recycling and using an electroless plating solution, which has a step of adding an alkaline agent in a concentration increase of 1 to 20% with respect to the concentration. In addition, the present invention uses the electroless plating solution containing (2), a metal ion for plating, a reducing agent, a complexing agent, and an alkaline agent repeatedly to replenish necessary components that have been consumed, while performing the electroless plating treatment. A method of recycling and using the electroless plating solution, wherein recycling of the electroless plating solution is a circulating use of the electroless plating solution, and the time is set so that the electroless plating solution does not fall below a predetermined plating capacity. A method for recycling and using an electroless plating solution, which comprises a step of adding an alkali agent having a concentration increase of 1 to 20% to the concentration of the alkali agent initially mixed to the electroless plating solution at intervals.
The present invention provides a method for recycling and using the electroless plating solution according to (1) or (2) above, wherein 1 to 20% is 3 to 15%.

In the present invention, an alkaline agent is added to the electroless plating solution, but in the case of the original electroless plating solution, it is preferably added to adjust the pH to 11.80 to 13.00, The alkaline agent added when the plating ability is reduced (in the case of (1) above) or before it is reduced (in the case of (2) above) is an increase in the concentration with respect to the concentration of the alkaline agent originally contained in the electroless plating solution. Minute ratio (concentration increase ratio with respect to the initial concentration of the alkaline agent) is 1 to 20
%, Preferably 3 to 10 is added. If the amount is too small or too large, the predetermined plating ability cannot be maintained. The alkaline agent added to maintain the plating ability may have a constant addition amount as long as the concentration increase ratio with respect to the initially mixed alkaline agent concentration is 1 to 20%. You can use as many as you like. In the former case, for example, if the initial concentration of the alkaline agent in the electroless plating solution is 100, and the concentration increase fraction is 5% with respect to the initial concentration of the alkaline agent, the amount of the alkaline agent added in the second cycle is consumed. It is the sum of the amount of alkaline agent replenished and 5 (for example, if 20 out of 100 is consumed, 5 is added on top of that 20 replenishment, so a total of 25 is added.
The density is 105 relative to 00. ) The amount of the alkaline agent added in the third cycle is the sum of the amount of the alkaline agent consumed and 5 (the concentration is 110 relative to the initial concentration of 100). In addition to the amount of replenishing the consumed alkaline agent by 5, it increases by 5, for example, in the 30th cycle, 150 times of the amount of the replenished amount of the alkaline agent, which is 1.5 times the original 100, was added. It will be. By increasing the concentration of the alkaline agent in this way, it is possible to restore the plating reactivity lowered by the eluted impurities such as Zn. The addition of the alkaline agent may be carried out each time the object to be treated is charged, but the addition may be omitted if the electroless plating solution does not fall below a predetermined plating capacity during the charging. If the plating solution is circulated and used, it may be added at a time interval, in which case the electroless plating solution will fall below the prescribed plating capacity even when trying to add it at regular intervals. If not, it may be postponed to be added. As an alkaline agent, NaOH,
Hydroxides of alcal metals such as KOH and LiOH are preferred.

In the present invention, the complexing agent refers to a substance capable of forming a complex, and specifically, for example, tartrate, EDTA (ethylenediaminetetraacetic acid), NTA.
(Nitrilotriacetic acid), HEDTA (oxyethylethylenediaminetriacetic acid), DHEDDA (dihydroxyethylethylenediaminediacetic acid), 1,3PDTA (1,3
-Propenediaminetetraacetic acid), DTPA (diethylenetriaminepentaacetic acid), TTHA (triethylenetetraminehexaacetic acid), HIMDA (hydroxyethyliminodiacetic acid), ammonia and the like compounds, which are metals, especially Cu.
And a compound capable of forming a complex with a transition metal.

In the present invention, "metal ions for plating"
Is an ion of the metal to be plated on the object to be processed, for example, copper ion in the case of copper plating,
Not limited to this, electroless plating of gold (Au), platinum (P
Electroless metal plating such as electroless plating of t) can also be performed, and in these cases, metal ions such as Au ions and Pt ions are referred to. Examples of counter ions of these metal ions include sulfate ions, nitrate ions, and mineral acid ions such as chloride ions. To supply them, for example, in the case of Cu ions, copper sulfate, copper nitrate, copper chloride salt, etc. Etc., and a cupric salt is particularly preferable, but other copper compounds such as metallic copper and copper oxide may be dissolved in a mineral acid solution such as sulfuric acid and supplied. In the case of, it can be performed according to this. The concentration of metal ions in the electroless plating solution is preferably 5 g / liter to 10 g / liter. If it is more than this, the metal precipitation reaction in the plating solution is likely to occur, and if it is less than this, the plating metal precipitation reaction on the object to be treated tends to be low.

In the present invention, the "reducing agent" means a compound capable of forming a metal film by reducing the metal ions to be plated by the electroless plating solution and depositing the metal on the surface of the object to be treated. Specific examples include formalin, paraformaldehyde, dimethylamine borane, hypophosphite, hydrazine, glyoxylic acid, KBH ₄ , NaBH ₄ , and Rochelle salt. These can be used alone or in combination. The concentration of the reducing agent in the electroless plating solution is preferably 0.1 g / liter to 20 g / liter. If it is more than this, the metal precipitation reaction in the plating solution is likely to occur, and if it is less than this, the plating metal precipitation reaction on the object to be treated tends to be low.

In the present invention, it is also preferable to use a stabilizer for the plating solution, which is DDCN.
(Sodium diethyldithiocarbamate), KSCN
(Potassium thiocyanate), 2,2′-bipyridyl,
2,2'-dipyridine, nicotinic acid, thiourea, tetramethylthiourea, cupron, cuperone, thiazole, 2
-Mercaptobenzothiazole, potassium ferrocyanide, potassium ferricyanide, sodium cyanide, pyrrole, pyrazole, imidazole, 1,2,4-triazole, 1,2,4-benzotriazole, thiophene, thiomelide, rhodanin, rubeanic acid, pyridine,
Triazine, methyl orange, benzoquinoline, 2,
2'-biquinoline, dithizone, diphenylcarbazide,
Nerocuproine, 2 (2-viridyl) imidazoline,
It is preferable to add a cyano compound such as 1,10-phenanthroline, a nitrogen-based organic compound, a sulfur-based compound and the like, and these may be used alone or in combination. The concentration of the stabilizer in the electroless plating solution is 0.01 to 100 ppm
Is preferred. If it is more than this, the plating reaction on the object to be treated is likely to stop, and if it is less than this, the plating reaction is less likely to occur.

The use conditions of the electroless plating solution are, for example, 30 to 55 ° C. and several tens of minutes (for example, 15 minutes) in the case of the initially mixed electroless plating solution. The conditions may be the same, but may be different.

The above-mentioned method of recycling and using the electroless plating solution of the present invention is also used for forming electrodes and conductors in the production of electronic parts. Examples of electronic parts are ceramic capacitors and laminated ceramic capacitors. , Hybrid IC, laminated LC filter, multilayer substrate,
Examples thereof include laminated ceramic electronic components such as composite electronic components having other circuits formed on the surface of the laminated component.

[0014]

For example, the electroless copper plating solution becomes more active as the pH increases, and the plating reaction to form a plating film on the object to be treated is more likely to occur. It is possible to reduce the influence of this deterioration of the plating reaction due to contaminants from the processed material.

[0015]

EXAMPLES Examples of the present invention will be described below. Example 1 A mixture obtained by weighing the following components was placed in a 1-liter polyethylene pot and wet mixed by a ball mill method at 60 rpm for 15 hours to obtain a slurry. Ceramic powder 88.65 parts by weight Binder resin (polyvinyl butyral resin) 9.85 parts by weight (glass transition point 65 ° C.) Di-n-phthalate 1.50 parts by weight Ethanol 100 parts by weight Toluene 100 parts by weight

After defoaming the obtained slurry, the slurry is supplied on a long polyester (PET) having a width of 1 m and having a surface treated with a silicone type release agent, and a green layer having a thickness of 200 μm is obtained by a doctor blade method. A sheet was formed, dried, peeled and cut into a size of 100 mm × 100 mm to obtain a ceramic insulator green sheet. A large number of circular plates for ceramic bodies were cut from this ceramic insulator green sheet, heated to 500 ° C. for de-pinder treatment, and further fired at 1000 ° C. for firing each ceramic disc body (diameter 8 mm. , Thickness 0.5m
m) was obtained.

Next, a baking type conductive paste is obtained by the following composition. Zinc powder (particle size distribution 0.1 to 30 μ) 100 parts by weight Lead borosilicate glass powder 3 parts by weight (particle size 44 μ or less, 325 mesh pass) Epoxy acrylate 30 parts by weight (85% 2-ethylhexyl acrylate solution of epoxy acrylate) 1 part by weight of benzoin Epoxy acrylate is a 30% acrylic acid modified product. The above-mentioned composition was stirred and mixed for 15 hours to prepare a baking type conductive paste. This baking-type conductive paste was screen-printed with 200 mesh to apply a circular shape having a diameter of 7 mm to the central portions of both front and back surfaces of the ceramic disk element, and then an ultraviolet irradiation device (2500-4500).
Å, strength of 80w-cm) to the coating film from the light source 20c
Ultraviolet rays were irradiated for 20 seconds at a distance of m. Next, it was heated and baked at 850 ° C. for 10 minutes in a furnace with an air circulating atmosphere. In this way, 20,000 pieces of ceramic disc element bodies with baking type zinc electrodes (elements for ceramic capacitors) were prepared.

Pretreatment was carried out by immersing these bake-type ceramic disk elements with zinc electrodes in a solution of 3% sodium hypophosphite, and the following electroless plating solutions were prepared for electroless copper plating. Copper sulfate pentahydrate 8.5 g / liter Roussel salt (potassium sodium tartrate) 40.0 g / liter formalin (37% aqueous formaldehyde solution) 8 ml / liter sodium hydroxide (NaOH) 11.5 g / liter Reinecke salt (tetraisothiocyanatodiene) Ami 5.0 ppm Chromium (III) ammonium 2,2-dipyridine 0.5 ppm This electroless copper plating solution (30 liters) was placed in a barrel plating tank and the temperature was maintained at 50 ° C. Barrel electroless copper plating was carried out for 15 minutes by inserting 20,000 plate elements, and it was confirmed by the color that a copper plating film was formed on the baked zinc electrode of the obtained processed product. Then, after taking out the processed material,
C ²⁺ by copper ion concentration detector (emission spectrophotometer)
Cu ₂ SO ₄ is supplemented as a shortage from the initial C ²⁺ concentration of the plating solution based on the measured value, and formaldehyde is measured by a titration method using reagents Na ₂ SO ₃ and H ₂ O. Was measured and based on the measured value, 35% HCHO solution was replenished as a shortage from the formaldehyde concentration of the original plating solution.

Then, after replenishing the consumed amount of NaOH so that the concentration of the initial composition is 11.5 g / l, stirring is performed while further adding 0.345 g / l, which is about 3% higher, for recycling. A plating solution for was prepared. Thereafter, in the same manner as above, 20,000 pre-fabricated ceramic disc element bodies with baking type electrodes were subjected to pretreatment, and electroless copper plating treatment was performed in the same manner as above. Similarly, the treated product is taken out, the copper ion concentration and the formaldehyde concentration are measured to supplement the deficiency from the initial blending amount, and the consumed amount is supplemented with 0.345 g / liter of NaOH. In addition, 20,000 pre-prepared baking type electrode-equipped ceramic disk elements were pre-treated and then electroless copper plated, which was repeated 28 times for a total of 30 cycles. Electroless copper plating treatment was performed. Since 0.345 g / liter of NaOH was added in each cycle after the second cycle, it means that about 10 g / liter of NaOH was added in addition to the amount replenished to the initial concentration. Every time the plating process of each cycle is performed, 50 processed products are randomly extracted and the thickness of the copper plating film on the baking type electrode is measured by the fluorescent X-ray film thickness meter (the plating formed in 15 minutes. The film thickness, that is, the plating deposition rate (μm / 15 minutes) was measured. The average value is shown in Table 1.

Fraction of increasing concentration of NaOH (concentration increasing ratio to initial concentration of NaOH (g / liter), hereinafter referred to as Na
OH concentration increase fraction), as shown in the Example column of Table 1, 5.0, 7.0, 10.0, 1.0, 1
The electroless copper plating process for each addition amount step was performed in the same manner as above except that the addition amount was changed to 6 steps of 5.0 and 20.0%, and the addition amount of each step was used. The thickness of the copper-plated film on the baking type electrode of the product was measured, and the average value of 50 values for each addition amount step is shown in Table 1. In the table,
"Stop" indicates that the plating reaction on the object to be treated has stopped, and "decomposition" indicates that the plating solution self-decomposed. The same applies to Table 2 below.

Comparative Example 1 In Example 1, the electroless copper plating treatment was carried out in the same manner as in Example 1 except that the NaOH concentration increasing rate was set to 0 as shown in the column of Comparative Example 1 in Table 1. As shown in 1, the deposition of copper on the baking type electrode of the ceramic disk element body with the baking type electrode of the object to be treated was stopped at the third cycle, and electroless copper plating treatment of 4 cycles or more could not be performed.

[0022]

[Table 1]

Example 2 In Example 1, electroless copper plating was performed for 30 cycles in the same manner as in Example 1 except that a nickel powder paste having the following composition was used as the baking type conductive paste, and each cycle was the same as Example 1. Then, the thickness of the copper plating film was measured, and the average value of the 50 is shown in Table 2. Nickel powder (particle size distribution 0.1 to 30 μ) 100 parts by weight Lead borosilicate glass powder 3 parts by weight (particle size 44 μ or less, 325 mesh pass) Epoxy acrylate 30 parts by weight (85% 2-ethylhexyl acrylate solution of epoxy acrylate) 1 part by weight of benzoin Epoxy acrylate is a 30% acrylic acid modified product.

Comparative Example 2 An electroless copper plating process was carried out in the same manner as in Example 2 except that the NaOH concentration increasing rate was set to 0 as shown in the column of Comparative Example 2 in Table 2. In the 2nd and 3rd cycles, the deposition rate of copper on the baking type electrode of the ceramic disk element body with the baking type electrode of the object to be treated was stopped, and electroless copper plating treatment of 4 cycles or more could not be performed.

[0025]

[Table 2]

From the results shown in Tables 1 and 2, when the concentration increase rate of NaOH is 3 to 10%, the plating reaction on the object to be treated is not impaired even when the number of recycles is 30, while the increase rate of NaOH concentration is 15%. In%, the number of cycles is 1/3 of that,
When the rate of increase is 1% or 20%, the plating reaction of the number of cycles less than half is not impaired, but both are superior to the case where the rate of increase is 0, that is, not increasing. It is clear that the former case is significantly improved. If the electroless plating solution can be repeatedly used for 10 cycles or more, it can be said to be practical in terms of productivity and cost.

Example 3 In Example 1, the electroless copper plating solution was circulated through a filter, and the performance of the plating solution was checked every 10 to 20 minutes, and the plating capacity was likely to fall below a predetermined level. Occasionally (the rate of formation of a plating film on an object to be treated can be judged by the color of copper), after replenishing the consumed NaOH, a fixed amount of NaOH is added to the plating solution so that the rate of increase in concentration is 5 to 10%, Electroless copper plating was carried out in the same manner as above except that the plating solution was continuously used, and any one of the fixed amounts within the range of 5 to 10% was added, and the preparation of the treatment object was repeated 30 times. Even when the treatment was performed, good results were obtained, which was almost the same as in the case of the NaOH concentration increasing fractions of Example 1, 5, 7, and 10%.

[0028]

According to the present invention, since the concentration of the alkaline agent is increased when the electroless plating solution is repeatedly used, the plating reaction of the electroless plating solution on the surface of the object to be treated is prevented from being lowered. It is possible to increase the number of cycles of repeated use thereof, whereby the plating liquid can be effectively used and the amount of waste can be reduced. Also,
Even if the electroless plating solution is repeatedly used, the deposition rate of the metal on the surface of the object to be processed can be kept unchanged, so that the plating solution can be used without causing insufficient plating on the object to be processed. Even if the number of cycles is increased, it is possible to form a plated film having a uniform material and a uniform thickness. In this way, the performance of plating on the object to be processed can be improved and its productivity can be increased.

Claims (3)

[Claims] 1. An electroless plating solution for repeatedly performing an electroless plating process by repeatedly using an electroless plating solution containing at least a metal ion for plating, a reducing agent, a complexing agent and an alkaline agent, and replenishing the necessary components consumed. The recycling use of the electroless plating solution is the use of a non-circulating electroless plating solution, and at least the electroless plating solution is reduced to a predetermined plating capacity or less in the number of times of recycling use. A method of recycling and using an electroless plating solution, which comprises a step of adding to each of the electroless plating solution an alkali agent having a concentration increase of 1 to 20% with respect to the initially blended alkali agent concentration. 2. An electroless plating solution for repeatedly performing an electroless plating treatment by repeatedly using an electroless plating solution containing at least a metal ion for plating, a reducing agent, a complexing agent and an alkaline agent, and replenishing the consumed necessary components. The method of recycling the electroless plating solution is a circulating use of the electroless plating solution, wherein the electroless plating solution is provided with a time interval so as not to drop below a predetermined plating capacity. A method for recycling and using an electroless plating solution, which comprises a step of adding to the electroless plating solution an alkaline agent having a concentration increase of 1 to 20% with respect to an initially blended alkaline agent concentration. 3. 1 to 20% is 3 to 10%.
Alternatively, the method for recycling the electroless plating solution according to 2 is used.