JP2833393B2 - Electroless copper plating method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to electroless copper plating used in the field of surface treatment.
The present invention relates to an electroless copper plating method using an electroless copper plating solution containing a copper ion complexing agent, a copper ion reducing agent, and a pH adjuster.

[0002]

2. Description of the Related Art Electroless plating is capable of forming a film without being limited by the shape and material of a body to be plated, and is increasingly being spotlighted as a surface treatment technique which is rich in mass productivity. However, in order to increase the mass productivity, supply of the plating solution becomes a problem. That is, with the progress of the electroless plating reaction, the replenishment of the metal ions that are insufficient in the plating solution has conventionally been performed by replenishing the metal compound. However, the replenished metal compound is reduced to hydrogen generated by a plating reaction and metallized before forming a complex with a complexing agent present in the plating solution, and the metallized particles precipitate in the plating solution.
In addition, the replenished metal compound forms a precipitate as a metal hydroxide in an alkaline plating solution, and the precipitate co-deposits with the metal on the object to be plated to form a metal coating formed on the surface of the object to be plated. Produces a zaratsuki phenomenon. Further, the above phenomenon increases the bath load, resulting in an increase in the consumption rate of metal ions, and shortens the pot life in which the plating solution can be used stably.

[0003]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and has as its object to prevent the replenished metal ions from depositing in the plating solution and to maintain the metal ions free for a long time. An object of the present invention is to provide an electroless copper plating method that maintains the activity of an electrolytic plating solution.

[0004]

According to the present invention, there is provided an electroless copper plating method comprising a copper ion, a copper ion complexing agent, a copper ion reducing agent, and a pH adjuster in an electroless copper plating tank. When replenishing the above copper ions to the electrolytic copper plating solution,
Sulfuric acid is added to the electroless copper plating solution partially removed from the electroless copper plating bath to adjust the pH to a pH range where the complexing agent of copper ions and copper ions can quickly form a copper complex.
In this step, a copper compound is newly added to the electroless copper plating solution in this state, and a copper complex solution is prepared.
The method is characterized by comprising a step of storing in the complex replenishing tank and a step of replenishing the copper complex solution stored in the copper complex replenishing tank in accordance with the measurement of the electroless copper plating solution.

[0005]

According to the present invention, no precipitation of copper particles since replenishing chemically stable state copper complex solution in an electroless copper main <br/> Tsu key solution in the plating solution tank, copper hydroxide Does not form.

Hereinafter, an electroless copper plating method according to the present invention will be described with reference to the drawings. FIG. 1 is a block diagram of an electroless copper plating apparatus according to one embodiment of the present invention.

As shown in FIG. 1, an electroless copper plating solution tank 1 is filled with an electroless copper plating solution 12 for plating an object 2 to be plated. As the electroless copper plating solution composed mainly complexing agent of copper ions, copper ions, a reducing agent of the copper ions, and contains a pH adjusting agent, other optionally added such as a surfactant and a stabilizer Agent. The temperature of the plating solution is generally maintained at 50 ° C to 90 ° C.

[0008] In the present invention, the copper complex replenishing tank 21, copper ions <br/> ting and copper complex solution 7 comprising a complexing agent of the copper ions are stored, in an electroless copper plating solution 12 As the copper ions are consumed, the electroless copper plating solution tank 1 is replenished. Line supply is intermittent for the electroless copper plating solution tank 1 of the copper <br/> complex solution 7
Will be The copper complex solution 7 is appropriately determined depending on the composition of the electroless copper plating solution 12.

With the progress of the electroless copper plating reaction,
The copper ion reducing agent 8 and the pH adjusting agent 9 are appropriately replenished to the electroless copper plating solution tank 1.

The above-mentioned copper complex solution 7, pH adjuster 9, and copper ion reducing agent 8 are sampled by a pump 11 from an electroless copper plating solution 12 in an electroless copper plating solution tank 1. A pump 4 for each copper complex solution 7, a pump 5 for a copper ion reducing agent 8, and a pH adjusting agent 9 based on instructions from the controller 3 including detectors such as a copper ion concentration, a reducing agent concentration, and a pH. The pump 6 operates, and replenishment is performed automatically.

In the present invention, as the plating reaction progresses, the plating solution in which the complexing agent which has formed a complex with copper ions returns to the complexing agent present alone is transferred to the electroless copper plating solution tank 1.
Extraction part by operating the pump 11 from, sends the extraction liquid to the complexing tank 13, the copper complex solution 7 newly adding copper of <br/> compound 17 in the complexation bath 13 . Note that the complexing tank 13 is provided with a spare complexing tank 13a, and is sequentially switched as necessary.

To prepare the copper complex solution 7, sulfuric acid 16 is supplied, and a copper compound 17 and a reducing agent are added to adjust the concentration of the metal component and the concentration of the reducing agent. The reason why the pH is first adjusted with sulfuric acid is that the supplied copper ions can quickly form a copper complex with the complexing agent, so that the pH range is in a chemically stable state . For example, in the case of an electroless copper plating solution using ethylenediaminetetraacetic acid as a complexing agent, copper ions quickly form a copper complex with the complexing agent in a pH range of 4 to 10.
Moreover, a complexing agent 18 and additives 19 of copper ions added as needed, perform these density adjustment, the copper complex solution 7
And

[0013] Upon addition of the copper compound 17 to an electroless copper plating solution 12 in the electroless copper plating solution tank 1 taken out above is suitably mixed with new copper complex solution 7, electroless copper plating <br/> key It is preferable that the amount of the accumulated salt, which is a reaction by-product, in the liquid 12 is not increased. In addition, it is preferable to remove using an electrodialysis method or a reverse osmosis method because it is possible to prevent the concentration of the inert metal salt of the electroless copper plating solution 12 from increasing.

The complexing tank 13 and a spare complexing tank 13a
Air is supplied as a gas containing oxygen from a blower 15 to the copper complex solution 7 to which the copper compound 17 has been added.
3 and the supply and dissolution of finely divided air from the diffuser 14 provided in the spare complexing tank 13a is effective for preventing copper precipitation and stirring.

The copper complex solution 7 modified as described above is sent to a copper complex replenishing tank 21 by a pump 20, and is appropriately replenished to the electroless copper plating solution tank 1. This replenished copper complex solution 7
The temperature to be effective to reduce electroless the copper keep the temperature range up to the plating solution temperature of the plating liquid tank 1, the temperature distribution of the electroless copper plating solution tank 1 from 20 ° C. or higher. Therefore,
When replenishing the copper complex solution 7 into an electroless copper plating solution tank 1, to the copper <br/> complex solution 7 may be heated by the heater 10 may be provided with a heat insulating device to the copper complex replenishing tank 21 .

[0016]

Example 1 Electroless copper plating was performed using the electroless copper plating apparatus shown in FIG. The electroless copper plating solution 12 in the electroless copper plating tank 1 used under the following conditions. In addition, NaOH was added as a pH adjuster 9 to the electroless copper plating solution 12, and the pH was measured. As a result, the pH was 12.0.

Conditions for electroless copper plating solution CuSO ₄ 5H ₂ O (for metal ions) 10 g / l EDTA ₂ Na ₂ H ₂ O (complexing agent) 30 g / l HCHO (reducing agent) 1.8 g / l Cyanide additive (additive) 10 mg / l Polyethylene glycol (additive) 200 mg / l 1 liter ・ Liquid temperature------------------------60 ° C. A glass with a processing area of ² dm ² / l in which a nucleation treatment is applied to a 360-liter electroless copper plating bath 1 The epoxy substrate was used as the plating object 2, which was immersed and subjected to electroless copper plating. Feed from an electroless copper plating solution tank 1 a sample of the plating solution 12 to the controller 3 via the pump 11, the copper Lee <br/> on concentration, the concentration of the reducing agent, to measure the pH, depending on the respective consumption , Pump 4 is activated to supply copper complex solution 7
And HCH, which is a replenishing reducing agent 8 by operating the pump 5
O was supplied with NaOH as a pH adjuster 9 for supply by operating the pump 6. The copper complex solution 7 was supplied at a liquid temperature of 40 ° C. by providing a heater 10 in the middle of the liquid sending pipe.

The pump 11 is operated in accordance with the progress of the plating reaction, and the electroless copper plating 12 in the electroless copper plating solution tank 1 is operated.
Was partially taken out and sent to a complexing tank 13 having a capacity of 150 liters. It is to be noted that a spare tank 13a is provided, and switching is sequentially performed as necessary.

The removed liquid is first p-pulped with sulfuric acid 16
After adjusting H to 10.5, copper compound 1 containing a reducing agent
An aqueous solution of No. 7 and a mixed solution of copper sulfate at 250 g / L and HCHO at 48 g / L were added to adjust the copper concentration to 20 g / L. pH 10.5
As a result, a metal complex of copper and EDTA was quickly formed. Thereafter, an alkali solution of EDTA was added as a complexing agent 18 for copper ions, and a cyanide additive and polyethylene glycol were added as additives 19, and a copper complex solution 7 shown in the following composition table was added.
Was prepared.

Composition of copper complex solution CuSO ₄ 5H ₂ O (for metal ions) 20 g / liter EDTA ₂ Na ₂ H ₂ O (complexing agent) 30 g / liter HCHO (reducing agent) −−−−−−−−− 3.6 g / l ・ Cyanide-based additive (additive) -10-mg / l ・ Polyethylene glycol (additive) ----- 200 mg / l ・pH ------------------- 10.5 the complexing tank 13, and the spare complexing tank 13a, adding copper of <br/> compound 17 Air was supplied from the blower 15 to the copper complex solution 7 as a gas containing oxygen, and finely divided air was supplied from the diffuser 14 provided in the complexing bath 13 and the spare complexing bath 13a. The copper compound 17 copper complexing <br/> body solution 7 was added through the pump 20 feeding to the copper complex replenishing tank 21, was utilized as the copper complex solution 7 for supplementation.

Although the electroless copper plating was continued up to 5 turns by the above operation, the copper plating film formed on the surface of the plating object 2 without copper being deposited in the plating solution tank 1 was good without any roughness phenomenon. Met.

COMPARATIVE EXAMPLE Plating was performed using the same electroless copper plating solution as in Example 1 except that a copper ion replenishing solution under the following conditions was used in place of the copper complex solution of Example 1 and replenished to the plating solution tank. Was.

Conditions for the copper ion replenishing liquid ・ CuSO ₄ 5H ₂ O --- 125 g / liter ・ HCHO -------------------------- 27 g / 1 liter ・ pH -------------------------------- Amount to adjust the pH to 3 -Temperature of the liquid --40--40 ℃ After one turn, copper was deposited on the bottom of the plating solution tank, and after 8 hours, the plating solution had to be replaced.

[0024]

Electroless copper plating method of the present invention exhibits, chemically stable, by using copper <br/> complex solution consisting of a complexing agent of copper ions and the copper ions, supplemented with copper ions Does not precipitate in the plating solution. And this copper complex solution
It is in an electroless copper plating solution taken out from the electroless plating solution bath, was added sulfuric acid, complexing agent of the copper ions and copper ions
Promptly adjusted to pH region capable of forming a copper complex, since the addition of copper reduction <br/> compound is prepared to hold the electroless copper main <br/> Tsu liquid activity over time.

[Brief description of the drawings]

FIG. 1 is a block diagram of an electroless copper plating apparatus according to one embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Electroless copper plating liquid tank 2 Plated object 3 Controller 4 Pump 5 Pump 6 Pump 7 Copper complex solution 8 Reducing agent 9 pH adjuster 10 Heater 11 Pump 12 Electroless copper plating liquid 13 Complexing tank 13a Complexing tank 14 Dispersion Trachea 15 Blower 16 Sulfate 17 Copper compound 18 Complexing agent 19 Additive 20 Pump 21 Copper complex supply tank

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hiromasa Hattori 1048 Kadoma Kadoma, Osaka Prefecture Matsushita Electric Works, Ltd. References JP-A-3-75378 (JP, A) JP-A-2-298273 (JP, A) JP-A-1-49787 (JP, B2) (58) Fields investigated (Int. Cl. ⁶ , DB name ) C23C 18/40 C23C 18/31

Claims (1)

(57) [Claims] 1. A copper ions electroless copper plating bath, a complexing agent of copper ions <br/> down, the copper ion reducing agent, and the copper ion in an electroless copper plating solution containing a pH adjusting agent When replenishing, sulfuric acid is added to the electroless copper plating solution partially removed from the electroless copper plating tank, and adjusted to a pH range where the above-mentioned complexing agent of copper ions and copper ions can quickly form a copper complex. Work
In this state, a copper compound is newly added to the electroless copper plating solution in this state , a copper complex solution is prepared, a copper complex solution is stored in a copper complex replenishing tank, and the above electroless copper plating solution is measured. If necessary, replenish the above copper complex
An electroless copper plating method comprising a step of replenishing a copper complex solution stored in a tank .