JPH09187751A - Method for treating printed circuit board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for treating a printed circuit board which is easy of treatment in disposal. SOLUTION: A printed circuit board containing at least a phenol resin is immersed in an alkaline aqueous solution to swell the resin so that metal foil such as copper foil can be peeled off easily from the board. Not only the metal foil but also mounted parts can be separated easily from the board. By immersing the board in water after the immersion in an alkaline aqueous solution, the swelling of the resin is promoted by utilizing osmotic pressure difference to facilitate the separation and removal of metal foil and parts.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of immersing a printed circuit board containing at least a phenol resin in an alkaline aqueous solution, or a process of immersing a printed circuit board in an alkaline aqueous solution and then immersing it in water at least once. It is about the method.

[0002]

2. Description of the Related Art Paper-based phenolic resin laminates and cloth-based phenolic resin laminates are widely used as printed circuit boards for general electric appliances and the like. It is common to crush it together with or after it is separated from the product, or to reclaim it in the soil as it is.

[0003]

Copper-clad laminates provided with copper wiring are often used for printed circuit boards such as paper-based phenolic resin laminates and cloth-based phenolic resin laminates.
C chips, capacitors, resistors, switches, connectors and the like are mounted mainly by using solder. Under the current circumstances, crushing and landfilling are performed as is, and the elution of lead from solder is becoming an environmental issue, and valuable metals such as copper are also collected. This is a problem from the viewpoint of effective use of resources because it is not denied.

However, such a printed circuit board cannot sufficiently separate the metal and the resin by simply crushing it, and is difficult to recycle.

Therefore, an object of the present invention is to provide a method of treating a printed circuit board, which is easy to dispose of at the time of disposal.

[0006]

The present invention is a method of treating a printed circuit board, wherein the printed circuit board containing at least a phenol resin is immersed in an alkaline aqueous solution.

Further, in the method of treating a printed circuit board, the immersion treatment step of immersing the printed circuit board containing at least a phenol resin in an alkaline aqueous solution and then in water is performed at least once.

Further, regarding a printed circuit board containing a phenol resin in which one or more parts are mounted on the metal wiring part, after removing at least a part of the parts,
It is a method for treating a printed circuit board, which comprises immersing in an alkaline aqueous solution and peeling off the metal wiring portion.

[0009]

The printed circuit board used in the present invention may be any printed circuit board containing a phenol resin, for example, a paper-based phenol resin laminated plate, a cloth-based phenol resin laminated plate, a glass cloth. Examples include base material phenol resin laminates, asbestos base phenol resin laminates, synthetic fiber base phenol resin laminates, and the like.

Of course, components such as IC chips, capacitors, resistors, switches, and connectors may be mounted on these printed boards, and resists such as photoresists and screen printing resists and adhesive tapes. It doesn't matter if it is marked with.

Furthermore, these printed circuit boards may be coated with a coating material which is attacked by alkali. Examples of the coating material that is attacked by the alkali include polyurethane, silicone, acrylic, butyl rubber and the like.

Most of copper wiring is used for the wiring of the printed circuit board, but other than that, for example, a conductive metal foil such as silver, aluminum or nickel may be used.

The adhesive for bonding the metal foil and the substrate may be a commonly used adhesive, and examples of the thermosetting resin include phenol resin,
Epoxy resins, resilicinol resins and the like are available, and thermoplastic resins include polyvinyl butyral and nitrile rubber. More specifically, for example, polyvinyl butyral modified phenol resin, acrylonitrile rubber modified phenol resin, modified epoxy resin and the like can be mentioned.

The alkaline aqueous solution used in the present invention is an aqueous solution containing an alkaline alkali metal compound or an alkaline alkaline earth metal compound. Examples of the alkaline alkali metal compound or alkaline alkaline earth metal compound include sodium hydroxide, potassium hydroxide, barium hydroxide, sodium ethoxide, potassium butoxide and the like. The higher the concentration of the solution of the alkaline alkali metal compound or the alkaline alkaline earth metal compound, the more it will attack the phenol resin, the resist, the adhesive bonding the wiring metal foil and the substrate together, but sodium ions, potassium ions, etc. As a result, the viscosity of the solution also increases and the permeability of the solution into the printed circuit board decreases. Therefore, the concentration is preferably such that the resin or the like is sufficiently attacked and the liquid permeability is not lowered. Therefore, the solution concentration of the alkaline alkali metal compound or the alkaline alkaline earth metal compound is preferably 10 N or less, and more preferably 2 to 7 N.

The alkaline alkali metal compound or alkaline alkaline earth metal compound may be contained not only as a single component but also as a plurality of components.

In order to improve the permeability of the solution into the printed circuit board, for example, alcohols such as methyl alcohol and ethyl alcohol, acetone, tetrahydrofuran, ethylene glycol, ethylene glycol monoethyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl. Ether, diethylene glycol, diethylene glycol diethyl ether,
Diethylene glycol dimethyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, dimethylformamide, dimethylamine and the like may be added.

Further, the treatment temperature is higher than the boiling point of water (100 ° C. at normal pressure) because a higher permeation rate can be obtained at a higher temperature.
It is preferable to heat within the range of the following), but when alcohols are contained, the temperature is preferably below their boiling point.
In the case of immersing in water after immersing in the alkaline aqueous solution, the temperature of the water is preferably as high as possible below the boiling point.

In the treatment method of immersing in the alkaline aqueous solution of the present invention, the phenol resin, the resist, the adhesive of the wiring metal foil and the substrate, the coating and the like are invaded by the alkali and decomposed, dissolved or swelled. Therefore, swelling and softening of the printed board, peeling of the laminated plate, peeling of the metal foil for wiring, peeling of the coating, etc. are promoted, and the printed board and the metal foil for wiring can be easily separated. As a result, the component mounted on the printed board can be easily removed, and the mounted component, the wiring metal foil, and the phenol resin substrate can be separated. Since the separated individual items can be processed separately, they can be appropriately processed, recycled, and reused. In particular, most of the solder is attached to the metal foil, and therefore, by properly treating it, the load on the environment can be reduced, and the metal foil such as copper can be recycled.

Further, among the treatment methods of the present invention, in the treatment method in which the immersion treatment step of immersing in an alkaline aqueous solution and then in water is performed at least once, the alkaline aqueous solution is permeated into the printed circuit board, Immersion in water causes an osmotic pressure difference between the inside and outside of the printed circuit board, and a large amount of water enters the printed circuit board in an attempt to eliminate the osmotic pressure difference, causing swelling, softening of the printed circuit board, and Peeling or the like is further promoted, and it becomes possible to peel and remove the wiring metal foil from the printed circuit board more easily.

Since the hardness of the treated phenol resin substrate is greatly reduced, it can be easily pulverized and a finely pulverized product can be produced with low energy. For this pulverization, for example, in a grinding mill such as a grinder or an impact pulverizer such as a hammer mill, a ball mill, a mixer, etc., the phenol resin substrate in a wet state after treatment is put,
Can be easily crushed. In addition, it is preferable to use a spray dryer in order to avoid coagulation during drying of the finely pulverized product. The finely pulverized product thus produced can be reused as a filler or the like.

The present invention will be described in more detail with reference to specific examples. (Example 1) In this example, a paper-based phenol resin laminate (30 x 30 x thickness 1.5 mm), a cloth-based phenol resin laminate (30 x 30 x thickness 1.5 mm), a glass substrate as a printed circuit board A phenol resin laminate (30 × 30 × 1.5 mm thick) was used. A copper foil having a thickness of 35 μm was adhered to one surface of each of these substrates using a polyvinyl butyral modified phenolic resin to form a comb-shaped electrode having a pitch of 0.3 mm, and eutectic solder was adhered to several places thereof.

These three types of printed circuit boards were immersed in a 5N aqueous sodium hydroxide solution at 80 ° C. for 20 hours.
The thickness and weight of the substrate before and after the immersion treatment were measured. Table 1 shows the rate of change in thickness and the rate of change in weight of the substrate after the immersion treatment with respect to the substrate before the immersion treatment.

[0023]

[Table 1]

From these results, the thickness and weight of all the substrates were increased, swelled, and slightly deformed. Moreover, since a part of the copper foil was peeled off and turned up on any of the substrates, the copper foil could be easily peeled off by pulling it with tweezers, and the solder could be removed while being attached to the copper foil. In particular, the paper-based phenolic resin laminate and the cloth-based phenolic resin laminate were able to peel and remove the copper foil more easily than the glass-based phenolic resin laminate.

As a result, the printed board can be easily separated into the laminate and the conductive metal foil. (Embodiment 2) In this embodiment, an appropriate wiring is formed on the paper-based phenolic resin laminate (50 × 50 × thickness 1.5 mm) with the copper foil used in Embodiment 1, and one IC chip, 10 resistors,
A printed circuit board was prepared by mounting three capacitors and one connector on one surface of the board by soldering.

This printed board was immersed in a 5N aqueous sodium hydroxide solution at 80 ° C. for 20 hours.

As a result, the printed board swelled, the resist was completely peeled off, and a part of the laminate was peeled off. Also, a part of the copper foil was peeled off, and when the peeled part was pulled with tweezers, the copper foil could be peeled off together with the solder. Therefore, the mounted component can be easily removed by pulling it with tweezers, and the laminated plate, the component, and the copper foil to which the solder is attached can be separated.

By treating the printed circuit board on which the components are mounted with the treatment method of the present invention, it is possible to easily remove the components and collect metals such as copper foil.

(Embodiment 3) In this embodiment, the same component-mounted printed circuit board as in Embodiment 2 was processed as follows. First, among the mounted components, the wire portion of the resistor and the capacitor, which are connected by a wire, and the connecting foot portion of the IC chip and the connector were cut to separate and remove the component from the printed board. Then, the substrate from which the parts were removed was immersed in a 5N aqueous sodium hydroxide solution at 80 ° C. for 20 hours.

As a result, the printed board swelled, the resist was completely peeled off, and a part of the laminate was peeled off. Also, part of the copper foil was about to be peeled off, so if you rub the surface with a polypropylene brush, you can peel off the copper foil, solder, and wire parts and legs of the component together, and remove the metal parts such as the phenol resin board and copper foil. I was able to separate it.

By removing the mounting components in advance before the treatment with the alkaline aqueous solution, the subsequent peeling process can be facilitated.

Example 4 In this example, the same three types of printed circuit boards as in Example 1 were used, and these were immersed in a 5N aqueous sodium hydroxide solution at 80 ° C. for 15 hours, and then at 80 ° C. It was immersed in water and treated for 3 hours.

The thickness and weight of the substrate after each immersion treatment were measured. Table 2 shows the rate of change in thickness and the rate of change in weight of the substrate after the immersion treatment with respect to the substrate before the immersion treatment.

[0034]

[Table 2]

By comparing this result with the result of Example 1, a larger swelling and a larger weight increase are obtained when the immersion treatment is carried out by transferring it to water after the immersion treatment in the alkaline aqueous solution, rather than the immersion treatment in the alkaline aqueous solution for a long time. I understand that
Due to such a large change in the substrate, the peeled-off portion of the copper foil is increased and the separation of the copper foil becomes easier. The copper foil on each substrate could be easily separated using tweezers.

(Embodiment 5) In the present embodiment, the same component mounting printed circuit board as in Embodiment 2 is used and immersed in a 5N sodium hydroxide aqueous solution at 80 ° C. for 15 hours and then transferred to 80 ° C. water. Immersion treatment was performed for 3 hours.

As a result, the printed board swelled, the resist was completely peeled off, and a part of the laminated plate was peeled off. In addition, a part of the copper foil was peeled off, and the copper foil could be easily peeled off together with the solder from the peeled part. Therefore, the mounted component can be easily removed, and the laminated plate, the component, and the copper foil to which the solder is attached can be separated. The ease of peeling the copper foil was easier than in Example 2, and the treatment could be performed in a shorter time.

(Embodiment 6) In this embodiment, a component-mounted printed circuit board similar to that in Embodiment 2 is first prepared in the same manner as in Embodiment 3.
The mounted parts were separated and removed from the printed circuit board. After that, the substrate from which the parts have been removed is placed in a 5N sodium hydroxide aqueous solution to give
After immersion treatment at 0 ℃ for 15 hours, transfer to 80 ℃ water for 3
It was immersed for a period of time.

As a result, the printed circuit board swelled, the resist was completely peeled off, and a part of the laminated plate was about to be peeled off. Also, part of the copper foil was about to be peeled off, so if you rub the surface with a polypropylene brush, you can peel off the copper foil, solder, and wire parts and legs of the component together, and remove the metal parts such as the phenol resin board and copper foil. I was able to separate it.

This peeling and removal was easier than that in Example 3 because there were more peeled portions. (Embodiment 7) In this embodiment, a component-mounted printed board similar to that of Embodiment 2 is coated with a urethane coating material (trade name:
By Humisil (Bokusui Brown Co., Ltd.)
The surface was coated. This printed board was immersed in a 5N sodium hydroxide aqueous solution at 80 ° C. for 20 hours, then transferred to 80 ° C. water and immersed for 3 hours.

As a result, the coating material was peeled off during the immersion treatment in the alkaline aqueous solution, and swelling of the printed board, peeling of the resist, peeling of a part of the laminated plate and the like were observed. In addition, a part of the copper foil was peeled off, and the copper foil could be easily peeled off together with the solder from the peeled part. Therefore, the mounted component can be easily removed, and the laminated plate, the component, and the copper foil to which the solder is attached can be separated. A printed circuit board coated in this way could be treated in the same manner.

In the above examples, the sodium hydroxide aqueous solution was used as the alkaline aqueous solution, but it is not limited to this, and the potassium hydroxide aqueous solution or sodium ethoxide aqueous solution as described above may be used. Good.

Further, in the above embodiment, the printed circuit board was allowed to stand while being immersed in the alkaline aqueous solution or water, but the method is not limited to this method. The resist or coating may be peeled off and removed by brushing with. In addition, improve the permeability of the liquid by applying ultrasonic waves or pressure,
You may promote removal of mounted parts.

Further, in the case of a printed circuit board on which components are mounted, as a method for removing the mounted components before the treatment with the alkaline aqueous solution, for example, a method of applying heat to melt the solder may be used. .

Further, when processing a printed circuit board on which the component is surface-mounted, the component is removed together with the metal foil from the printed circuit board unless the component is removed in advance by applying heat to the printed circuit board. Can be separated into metal foil with parts attached.

[0046]

INDUSTRIAL APPLICABILITY As described above, according to the present invention, a printed circuit board containing at least a phenol resin is immersed in an alkaline aqueous solution so that the phenol resin is swollen and the copper foil is easily peeled from the board. Can be easily separated.

By immersing in an alkaline aqueous solution and then in water, the swelling of the phenol resin is promoted by utilizing the osmotic pressure difference, and the copper foil and parts can be separated and removed more easily.

According to this processing method, the metal foil can be easily recovered from the substrate and reused without generating noise unlike the conventional crushing processing.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Hiroshi Onishi Hiroshi Onishi 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Nobuo Sonoda 1006 Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd.

Claims (3)

[Claims] 1. A method of treating a printed circuit board, which comprises a step of immersing a printed circuit board containing at least a phenol resin in an alkaline aqueous solution. 2. A method for treating a printed circuit board, which comprises performing an immersion treatment step of immersing a printed circuit board containing at least a phenolic resin in an alkaline aqueous solution and then in water at least once. 3. A printed circuit board containing a phenolic resin, in which one or more parts are mounted on a metal wiring part, is immersed in an alkaline aqueous solution after at least a part of the parts is removed, and the metal wiring part is peeled off. A method for treating a printed circuit board, comprising: