JPH0813051A - Gold collecting method - Google Patents

Abstract

PURPOSE:To provide a gold collecting method for safely and inexpensively peeling and collecting the gold plated on electronic parts. CONSTITUTION:This method consists of a collecting stage for immersing the electronic parts 3 subjected to gold plating in an acid 1, dissolving conductors or substrate metals into an acid l, peeling the gold and collecting the peeled gold. The method may be provided with a refining stage for refining the collected gold. The gold plating is applied directly on the conduction of copper or copper alloy or on the substrate metals consisting of at least one kind of nickel, silver, tin or allays contg. these metals. A nitric acid 1 or hydrochloric acid is used for the acid. The nitric acid 1 is 10 to 60wt.% and is heated to a temp. above 50 deg.C and near the b.p. The gold of the gold plating is >=58.5% (14 gold). The electronic parts 3 are pulled up from the nitric acid 1 and thereafter the gold is filtered and collected from the nitric acid 1 in the collecting stage. Further, pulled up electronic parts 3 are washed in a washing liquid 13 and the gold peeled from the electronic parts 3 is filtered and collected from the inside of the washing liquid 13. The washing of the electronic parts 3 is executed by ultrasonic washing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention collects gold from an electronic component such as a printed wiring board or a scrap thereof (hereinafter referred to as "electronic component") in which a surface of a metal conductor is gold-plated through a base metal or directly. It concerns the method of collecting gold.

[0002]

2. Description of the Related Art In electronic parts such as printed wiring boards, conductors made of metal such as copper are provided on the surface for wiring inside the electronic parts or for connection with the outside.
The conductor is oxidized and loses conductivity when it comes into contact with air, and thus gold, which is difficult to be oxidized, is plated on the conductor.

In recent years, electronic devices such as facsimiles, personal computers, word processors, etc. have spread rapidly,
Along with this, the amount of gold-plated scrap that is generated when manufacturing electronic components such as printed wiring boards or electronic components of electronic devices (hereinafter referred to as “electronic components”) that are used and are no longer needed and discarded is enormous. Since it is a quantity, it is desired to recover gold from gold-plated electronic components.

Next, a method of collecting crude gold from a conventional gold-plated electronic component and collecting gold will be described with reference to FIG. The conventional method of collecting gold from the gold-plated electronic component is an application of the refining technique of gold ore.First, the gold-plated electronic component for collecting gold is crushed, sieved, or Collect metal scraps including gold by further incineration. Next, the metal scrap is immersed in aqua regia containing potassium cyanide to dissolve gold.
Then, after insoluble residues such as ceramics and glass are filtered off, the solution containing gold is neutralized and reduced to obtain crude gold.
The crude metal is further subjected to electrolytic refining and melting, processed into a gold ingot, and recovered.

According to the above-mentioned conventional gold collecting method, gold itself is dissolved, so that gold can be collected with high purity. However, because strong acids such as aqua regia and highly toxic substances such as potassium cyanide are used to dissolve gold, expensive wastewater treatment equipment and gas purification equipment are required, and the cost rise is inevitable. There is.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a gold collecting method for collecting gold from a gold-plated electronic component.

An object of the present invention is to eliminate the above-mentioned inconvenience,
(EN) Provided is a gold collecting method for safely and inexpensively collecting gold from a gold-plated electronic component.

[0008]

In order to achieve such an object, the gold collecting method of the present invention is a gold collecting method for collecting gold from an electronic component in which a metal conductor is gold-plated through a base metal or directly. The collecting method includes a collecting step of immersing the gold-plated electronic component in an acid, dissolving at least the base metal or the metal conductor in the acid, peeling the gold, and collecting the peeled gold. And

The gold collected in the collecting step may be reused as it is, but when it is desired to collect it as high-purity gold, the collected gold is further purified and recovered. You may provide a process.

The metal forming the conductor may be copper or an alloy thereof, and the base metal provided for plating the conductor with gold may include nickel, silver, tin or the like. Mention may be made of any one metal of the alloys.

The acid that dissolves the base metal or the metal conductor may be nitric acid or hydrochloric acid. Particularly, when nitric acid is used, a base metal made of nickel or the like is provided on a conductor made of copper or the like in the electronic component, and the base metal such as nickel is dissolved when gold is plated on the base metal. It is easy to do and the gold is easily peeled off.

The nitric acid preferably has a concentration in the range of 10 to 60% by weight in order to dissolve the base metal or the metal conductor. If the concentration of nitric acid is less than 10% by weight, the oxidizing power is weak and it is difficult to dissolve the base metal or the metal conductor. Further, since concentrated nitric acid is hygroscopic, it is difficult to make the concentration exceed 60% by weight.

Further, generally, when a metal is immersed in concentrated nitric acid, a passivity is formed on the surface of the metal, and the metal tends to be difficult to dissolve. However, heating the nitric acid enhances the oxidizing power, The metal dissolves in a short time. In the gold collecting method of the present invention, the nitric acid can be used at room temperature, but it is preferable to heat the nitric acid to a temperature of 50 ° C. or higher and a temperature around the boiling point in order to dissolve the base metal in a short time. If the temperature is lower than 50 ° C, it takes a long time to dissolve the base metal, and if heated to a temperature higher than the boiling point, nitric acid decomposes to generate harmful nitrogen oxide gas (NO _x ).

Further, the gold plated on the electronic parts is not dissolved in acid, and 58.5% or more (equivalent to 14 gold) in order to recover gold having a purity of 99% or more by repeating electric refining.
Is preferable, and the purity is more preferably 97% or more to facilitate purification.

In the gold collecting method of the present invention, in the collecting step, the electronic component is pulled up from the acid, and the gold separated from the acid is collected by filtration. At this time, some of the peeled gold and gold that has not been sufficiently peeled off are attached to the electronic component pulled up from the acid. Therefore, the electronic component pulled up from the acid is washed in a cleaning liquid, unpeeled gold adhering to the electronic component is peeled in the cleaning liquid, and the peeled gold is collected by filtration. Therefore, the gold collection rate can be improved. For cleaning the electronic parts, it is preferable to apply appropriate vibration to the electronic parts in order to facilitate peeling of the adhered gold, and a method such as ultrasonic cleaning is suitable for applying the vibration. .

[0016]

According to the gold collecting method of the present invention, at least the base metal is dissolved in the acid when the metal conductor provided on the electronic component is plated with the gold via the base metal. When gold is plated directly on the metal conductor, the metal conductor is dissolved in acid. As a result, the gold itself is separated from the electronic component as foil-shaped gold without melting, and the foil-shaped gold is collected. The gold collecting method of the present invention does not dissolve gold itself, and thus does not require aqua regia or potassium cyanide. Therefore,
Gold is cheaply collected because it is safe and does not require wastewater treatment or gas purification facilities for aqua regia or potassium cyanide. Further, in the gold collecting method of the present invention, gold having high purity is recovered by collecting the gold separated as described above and further refining it.

In the method of collecting gold according to the present invention, the metal conductor, which is copper or its alloy, or the base metal, which is any one of nickel, silver, tin, and alloys containing these, is nitric acid or hydrochloric acid. It is melted and the gold peels off. When the acid is nitric acid, the metal conductor such as copper or the base metal such as nickel is easily dissolved and gold is easily peeled off. When the nitric acid has a concentration in the range of 10 to 60% by weight or is heated to a temperature near the boiling point of 50 ° C. or higher, the base metal or the metal conductor is easily dissolved.

Since the gold plated on the electronic component has a purity of 58.5% (corresponding to 14 gold) or more, it is separated without being dissolved in nitric acid, and is refined to have a high purity.

In the method of collecting gold of the present invention, in the collecting step, the electronic component is pulled up from the nitric acid, and then gold is collected by filtering from the nitric acid. Further, the electronic component pulled up from the nitric acid is washed in a cleaning liquid, and unpeeled gold adhering to the electronic component is peeled in the cleaning liquid. Then, the gold separated from the cleaning liquid is collected by filtration. Therefore, the gold collection rate is improved. The cleaning of the electronic component is performed by ultrasonic cleaning so that appropriate vibration is applied to the electronic component to easily remove the attached gold.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The gold collecting method of the present invention will be described in more detail with reference to the accompanying drawings. FIG. 1 is an explanatory cross-sectional view of a gold plating collector used in this embodiment,
FIG. 2 is a flow chart showing a gold collecting method and a gold collecting method for purifying and collecting the collected gold according to the present embodiment.
FIG. 4 is an explanatory cross-sectional view of an electronic component used in this example, and FIGS. 4 and 5 are graphs showing the relationship between the concentration and temperature of nitric acid and the amount of base metal dissolved.

First, the structure of the electronic component used in this embodiment will be described. As shown in FIG. 3, the electronic component 3 has a conductor 3 made of copper on the surface of a substrate 31 made of ceramics or the like for wiring inside the electronic component 3 and for connection to the outside.
2 is formed, and gold plating 34 is applied on the conductor 32 with a base metal 33 made of nickel interposed therebetween. The base metal 33 made of nickel is provided because the crystal constants of copper and gold are different from each other, and even if the gold plating 34 is directly applied to the conductor 32 made of copper, good adhesion cannot be obtained. ing. Further, although gold having a purity of 97% or more is used for the gold plating 34 of the electronic component 3,
The method of the present invention can be applied as long as gold having a purity of 58.5% (corresponding to 14 gold) or more is used.

Next, the structure of the gold plating collecting apparatus used in the gold collecting method of this embodiment will be described. The device is
As shown in FIG. 1, a treatment tank 2 in which a base metal 33 made of nickel is dissolved in nitric acid 1 to remove a gold plating 34.
And the electronic component 3 from which the gold plating 34 has been peeled off in the processing tank 2.
And a washing tank 4 for washing.

A filter 5 and a heater 6 are provided at the bottom of the processing tank 2, and the filter 5 is provided with a removable filter 7 made of a material that is not attacked by nitric acid 1, and is closed by a drain pipe 8 to store a nitric acid storage tank. 9 is connected. A vacuum pump 10 is connected to the nitric acid storage tank 9, and an opening / closing valve 11 is provided in the pipe 8. Then, the electronic component 3 such as a printed wiring board is suspended by a suspending jig 12 provided above the processing tank 2 and immersed in the nitric acid 1.

Further, the cleaning liquid 4 is contained in the cleaning tank 4, and a filter 5 and an ultrasonic vibrator 14 driven by an ultrasonic oscillator (not shown) are provided at the bottom of the cleaning liquid 13. The filter 5 is connected to a drainage storage tank 16 that is closed by a drainage pipe 15, and the vacuum pump 10 is connected to the drainage storage tank 16 except that the filter 5 is the same as the filter 5 in the processing tank 2. Has become. And the electronic component 3 is the hanging jig 1.
When suspended by 2 and immersed in the cleaning liquid 13,
Ultrasonic waves are emitted from the ultrasonic oscillator 14 into the cleaning liquid 13 to clean the electronic component 3.

Next, a method of collecting gold according to this embodiment by the gold plating collecting device shown in FIG. 1 will be described with reference to FIG. In this embodiment, first, the gold-plated electronic component 3 having the above-described structure is immersed in nitric acid 1 in the processing bath 2.

When the electronic component 3 is dipped in nitric acid 1, the base metal (nickel) 33 is dissolved in nitric acid 1, but the gold plating 34 having a purity of 58.5% or more is dissolved in nitric acid 1 as described above. Since it does not, the gold plating 34 becomes a gold foil and peels off. Therefore, next, as shown in FIG. 2, the separated gold foil-shaped gold is collected.

In order to collect gold, first, the electronic component 3 is pulled up from the processing tank 2 shown in FIG. Next, the opening / closing valve 1 provided in the drainage pipe 8
1 is opened and the nitric acid 1 in the treatment tank 2 is discharged to the nitric acid storage tank 9, whereby the filter 7 provided in the filter 5 is opened.
The gold separated by is collected by filtration. At this time, nitric acid 1
At the beginning, it is discharged to the nitric acid storage tank 9 by its own weight, but when the filter 7 is clogged with the peeled gold, it becomes difficult to discharge. In such a case, the vacuum pump 10 is driven to provide a pressure difference between the outside air and the nitric acid storage tank 9, so that the nitric acid 1 can be quickly discharged to the nitric acid storage tank 9.

On the other hand, on the surface of the electronic component 3 pulled up from the processing bath 2, part of the gold stripped in the processing bath 2 together with the nitric acid 1 and the gold plating 34 that cannot be stripped sufficiently are left. Therefore, the nitric acid 1 is removed by ultrasonically cleaning the electronic component 3 in the cleaning tank 4, and the remaining unpeeled gold plating 34 is separated in the cleaning liquid 13 by the action of ultrasonic vibration. Then, in the same manner as when the nitric acid 1 is discharged from the processing tank 2, the cleaning liquid 13 is discharged from the cleaning tank 4, and the separated gold in the cleaning liquid 13 is collected by filtration with the filter 7.

Next, the gold collected as described above is refined. In the purification, first, the gold collected as described above is roasted at 1000 ° C. or lower using a degreasing furnace for ceramics or the like. Since the gold also contains an organic substance such as a brightener on the surface of the gold plating 34, the organic substance is removed by the roasting.

Next, the gold from which the organic substances have been removed is heated to a high temperature using a crucible to melt it, and is poured into a mold and cast into a flat plate shape which is easily electrorefined to obtain crude gold. Since the melting point of gold is 1064 ° C., the melting temperature is preferably about 1100 ° C. in consideration of work efficiency. The crucible is preferably made of a material that does not deteriorate even at the melting temperature or higher. For example, alumina, zirconia, magnesia, mullite, platinum or the like is used. A graphite mold is used as the mold.

The crude metal is treated in the same manner as in the conventional case, electrolytically refined and melted, and then recovered as a bare metal.

In the present invention, the nitric acid 1 is 15 to 6
Those having a concentration in the range of 0% by weight were used after being heated to 50 ° C. or higher and around the boiling point. The heating of the nitric acid 1 was performed by the heater 6 provided in the processing tank 2.

The dissolution amount (g) of nickel per hour in 100 cc of each concentration of nitric acid at room temperature is shown in Table 1 below.
And shown in FIG. Table 1 and FIG. 5 show the amount (g) of nickel dissolved per hour in 100 cc of nitric acid of each concentration at a temperature of 50 ° C. or higher and around the boiling point.

[0034]

[Table 1]

As is clear from Table 1 and FIG. 4, the amount of nickel dissolved in 100 cc of nitric acid at room temperature (g)
Is highest when the concentration of nitric acid is around 30% by weight, and is rather low when the concentration is 40% by weight or more. This is considered to be a result of formation of passivation on the surface of nickel by concentrated nitric acid. Further, the reason why the amount of nickel dissolved sharply decreases at 30% by weight or less is considered to be that the oxidizing power of nitric acid declines as the concentration decreases.

Further, as is clear from Table 1 and FIG.
By heating nitric acid, the amount of nickel dissolved in 100 cc of nitric acid has dramatically increased, and the effect is particularly remarkable when nitric acid is boiled.

Therefore, according to the gold collecting method of the present invention, 10
It is clear that the gold plating 34 can be rapidly peeled off from the electronic component 3 by heating nitric acid having a concentration in the range of ˜60 wt% to a temperature around the boiling point of 50 ° C. or higher, and especially 60 wt% nitric acid. It is clear that the gold plating 34 can be quickly peeled off by boiling the.

In this embodiment, the treatment tank 2 and the cleaning tank 4 are separately provided as shown in FIG. 1, but the ultrasonic transducer 14 is provided in the treatment tank 2 and gold plating with nitric acid 1 is performed. The peeling of 34 and the cleaning of the electronic component 3 may be performed in one tank. However, when doing so, a measure for protecting the ultrasonic vibrator 14 from nitric acid 1 and the discharged nitric acid 1
Also, it is necessary to take measures to prevent the cleaning liquid 13 from being mixed.

The gold plating 34 may be scratched in advance. By doing so, the base metal (nickel) 33 easily comes into contact with the nitric acid 1 and can be quickly dissolved.

In this embodiment, the case where the conductor 32 is copper and the base metal 33 is nickel has been described, but the conductor 32 may be a copper alloy and the base metal 33. May be an alloy containing the above metal such as nickel alloy, silver, tin or tin-lead. Further, the gold plating 34 is directly formed on the conductor 32 without providing the base metal 33.
May be given.

Although nitric acid is used as an acid for dissolving the base metal 33 in the above embodiment, hydrochloric acid may be used depending on the type of the base metal 33. By using the hydrochloric acid as hot hydrochloric acid, for example, metals such as aluminum and titanium are dissolved.

[0042]

As is apparent from the above, according to the method of collecting gold of the present invention, the gold or gold is dissolved by dissolving the conductor or the base metal interposed between the gold plating and the electronic component. It can be separated from the electronic component without melting itself, and the separated gold can be collected safely and at low cost. Further, by refining the collected gold, it can be recovered as high-purity gold.

The gold collecting method of the present invention is preferably used when the conductor is copper or a copper alloy and the base metal is any one of nickel, silver, tin or an alloy containing these. The base metal or metal conductor can be dissolved using nitric acid or hydrochloric acid.

When nitric acid is used as the acid, the nitric acid has a concentration in the range of 10 to 60% by weight, or is heated to a temperature near the boiling point of 50 ° C. or higher to facilitate the formation of the base metal or the metal conductor. Can be dissolved in.

Since the gold plated on the electronic component has a purity of 58.5% (14 gold) or more, it is not dissolved in an acid, so that the gold collection rate is high.

In the gold collecting method of the present invention, the gold can be easily collected by pulling up the electronic component from the acid and then collecting the gold by filtration from the acid in the collecting step. At this time, the electronic component pulled up from the acid is washed in a cleaning liquid, and gold separated in the cleaning liquid is collected by filtration, whereby the gold collection rate can be improved. The cleaning of the electronic component can be suitably performed by ultrasonic cleaning.

[Brief description of drawings]

FIG. 1 is an explanatory cross-sectional view of a gold plating collector used in this embodiment.

FIG. 2 is a flowchart showing a gold collecting method and a gold collecting method for purifying and collecting the collected gold according to the present embodiment.

FIG. 3 is an explanatory cross-sectional view of an electronic component used in this example.

FIG. 4 is a graph showing the relationship between the concentration and temperature of nitric acid and the amount of base metal dissolved.

FIG. 5 is a graph showing the relationship between the concentration and temperature of nitric acid and the amount of base metal dissolved.

FIG. 6 is a flowchart showing a conventional gold collecting method and a gold collecting method for purifying and collecting the collected gold.

[Explanation of symbols]

1 ... Acid, 3 ... Electronic component, 32 ... Metal conductor, 33
… Base metal, 34… gold plating.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kantaro Yamamoto 3-4 Kinugasa Sakae-cho, Yokosuka City, Kanagawa Prefecture No. 503 Yamada Mansion (72) Inventor Nobuhiro Yoshikawa 2-1367 Nisshin-cho, Omiya-shi, Saitama Hokkai Seiseki Co., Ltd. Company house 1-106 (72) Inventor Koichi Higashijima 2-12-15 Miyashirodai, Miyashiro-machi, Minami-Saitama-gun, Saitama Prefecture

Claims (11)

[Claims] 1. A gold collecting method for collecting gold from an electronic component in which a metal conductor is gold-plated through a base metal or directly, wherein the gold-plated electronic component is immersed in an acid, and at least the base metal or A method of collecting gold, comprising a collecting step of dissolving a metal conductor in an acid, peeling gold, and collecting the peeled gold. 2. A refining and collecting step of refining and collecting the gold collected in the collecting step.
How to collect the stated gold. 3. The method for collecting gold according to claim 1, wherein the conductor is copper or a copper alloy. 4. The collection of gold according to claim 1, wherein the base metal is one of nickel, silver, tin, and an alloy containing them. Method. 5. The method of collecting gold according to claim 1, wherein the acid that dissolves the base metal or the metal conductor is nitric acid or hydrochloric acid. 6. The method for collecting gold according to claim 5, wherein the concentration of the nitric acid is 10 to 60% by weight. 7. The method of collecting gold according to claim 5, wherein the nitric acid is heated at a temperature of 50 ° C. or higher and a boiling point or lower. 8. The method of collecting gold according to claim 1, wherein the purity of gold plated on the electronic component is 58.5% or more. 9. The method for collecting gold according to claim 1, wherein, in the collecting step, after pulling up the electronic component from the acid, the gold separated from the acid is collected by filtration. . 10. The electronic component pulled up from the acid is washed in a washing liquid, unpeeled gold adhering to the electronic component is peeled in the washing liquid, and the gold peeled from the washing liquid is collected by filtration. The method of collecting gold according to claim 1, wherein 11. The method for collecting gold according to claim 10, wherein the cleaning of the electronic component is performed by ultrasonic cleaning.