JPH05175653A - Manufacture of printed wiring board - Google Patents

Abstract

PURPOSE:To accurately form a miniature circuit. CONSTITUTION:A through hole 3 is formed in a laminated board 2 to both side surfaces of which metal foils 1 are stuck. The board 2 is plated to form a through hole plated layer 4 on the inner periphery of the hole 3. Resin 5 is filled in the hole 3. Then, the surface of the board 2 is etched to etch a plated layer 6 adhered to the surface of the foil 1 by plating. When the layer 6 is removed in a state that the layer 4 is protected with the resin 5 to form a circuit, a thickness of metal to be etched is reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a printed wiring board having through holes.

[0002]

2. Description of the Related Art In manufacturing a printed wiring board having through holes 3, for example, a laminated plate 2 having a metal foil 1 such as a copper foil stretched on both sides is used. First, as shown in FIG. 2 is drilled to form a through hole 3, and then the laminated plate 2 is immersed in a plating bath to perform a plating treatment such as electroless copper plating to form a through hole plating layer on the inner periphery of the through hole 3. 4 is provided. Then, by etching the metal foil 1 to remove the portions other than the circuit pattern, it is possible to obtain a printed wiring board having the circuit 10 formed on the surface of the laminate 2 as shown in FIG. 2 (c). is there. In this printed wiring board, the circuits 10 on the front and back sides can be electrically connected by the through hole plating layer 4 provided on the inner periphery of the through hole 3.

[0003]

However, as shown in FIG. 2 (b), the plating layer 6 is formed on the surface of the metal foil 1 by the plating treatment when forming the through-hole plating layer 4 on the surface of the metal foil 1. In order to form a circuit, it is necessary to etch not only the metal foil 1 but also the plating layer 6, and the thickness of the metal to be etched is large. For example, even if the metal foil 1 having a thickness of 18 μm is used,
If the plating layer 6 is deposited to a thickness of 25 μm by the plating process, it is necessary to etch the metal having a total thickness of 43 μm. When the thickness of the metal to be etched is increased, the etching time becomes longer, and the side etching amount that the side surface of the circuit 10 receives the etching action increases. As a result, the resolution of the circuit formation deteriorates and the fine circuit is improved. There was a problem that it was difficult to form with high precision. As a countermeasure against this, it is conceivable to use an ultrathin metal foil such as a 9 μm copper foil, but such a thin metal foil is not practical because it is difficult to handle and the cost is high.

The present invention has been made in view of the above points, and it is an object of the present invention to provide a method for manufacturing a printed wiring board capable of forming a fine circuit with high accuracy.

[0005]

According to a method of manufacturing a printed wiring board according to the present invention, a through hole 3 is formed through a laminated plate 2 having metal foils 1 on both sides, and the laminated plate 2 is plated. Through hole plating layer 4 on the inner circumference of through hole 3
And filling the through hole 3 with the resin 5, and then etching the surface of the laminated plate 2 to etch the plating layer 6 attached to the surface of the metal foil 1 by the plating process. Is.

[0006]

Since the through hole 3 is filled with the resin 5, the surface of the laminated plate 2 is subjected to an etching treatment to etch the plating layer 6 attached to the surface of the metal foil 1 by the plating treatment. The plating layer 6 on the surface of the metal foil 1 can be removed with the resin 5 protecting the through-hole plating layer 4, and the thickness of the metal to be etched when forming a circuit can be reduced.

[0007]

EXAMPLES The present invention will be described in detail below with reference to examples. As the laminated plate 2 having the metal foil 1 stretched on both sides, for example, a double-sided copper-clad epoxy resin laminated plate having copper foils laminated on both sides can be used. First, a drilling process or a punching process is performed. Through holes 3 are formed in the laminated plate 2 as shown in FIG. Next, this laminated plate 2 is immersed in a plating bath to perform a plating treatment such as electroless copper plating to provide a through hole plating layer 4 on the inner circumference of the through hole 3. By performing the plating process in this way, the plating layer 6 is attached and provided on the surface of the metal foil 1 as shown in FIG. 1B.

Next, as shown in FIG. 1C, the through hole 3
The inside is filled with resin 5 to fill in the holes. The resin 5 is not particularly limited as long as it can withstand the etching liquid, and any resin can be used, but a thermosetting resin, an ultraviolet curing resin, or the like is preferable. In this way, after the resin 5 is filled in the through hole 3 to protect the through hole plating layer 4,
The surface of the laminated plate 2 is etched. This etching process is performed as so-called soft etching, and is performed by immersing the laminated plate 2 in a soft etching solution such as a copper chloride solution or an iron chloride solution or by spraying the soft etching solution on the surface of the laminated plate 2. Perform processing. By etching the surface of the laminated plate 2 in this manner, the plating layer 6 on the surface of the metal foil 1 can be removed as shown in FIG. It is preferable that the entire surface of the metal foil 1 is also etched so that the thickness of the metal foil 1 is reduced. Usually, it is preferable to perform etching until the thickness of the metal foil 1 becomes about 10 to 18 μm. Since the through-hole plating layer 4 is protected by the resin 5, it does not receive an etching action.

After the surface of the laminated plate 2 is thus etched, processing for forming a circuit is performed. The processing method for forming the circuit is not particularly limited as long as it includes an etching step. For example, first, a dry film photoetching resist is laminated on the surface of the metal foil 1 of the laminated plate 2, or an electrodeposition type photoetching resist is electrodeposition coated to cover the surface of the metal foil 1 with the photoetching resist, After exposing and developing the photoetching resist, the laminated plate 2 is immersed in an etching solution or the surface of the laminated plate 2 is sprayed with the etching solution to dissolve the portion of the metal foil 1 which is not covered with the photoetching resist. By this, Fig. 1
The circuit 10 can be formed by the remaining metal foil 1 as shown in (e). The resin 5 has a function of protecting the through-hole plating layer 4 even in this etching step, and the resin 5 is removed by dissolving it in an alkali such as caustic soda solution after the circuit is formed, if necessary. You can do it.

When the circuit 10 is formed by etching as described above, only the metal foil 1 is the object of etching, and the thickness of the metal to be etched is small.
Therefore, the etching time is short and the circuit 1
Since the side etching amount of the side surface of 0 is reduced, the resolution of circuit formation can be increased.
A fine circuit can be formed with high precision.
By the way, using a laminated plate 2 with a copper foil (metal foil 1) having a thickness of 18 μm, a plating layer 6 having a thickness of 25 μm was attached to the surface of the metal foil 1 during the plating process for forming the through-hole plating layer 4. In this case, the thickness of the metal to be etched during the circuit formation is 43 μm, the side etching amount generated when etching the metal having this thickness is about 30 μm, and the circuit 10 has a line width of about 60 μm.
The limit is to form the line interval to about 60 μm.
On the other hand, when the metal is removed to a thickness of 33 μm by half-etching as shown in FIG. 1D, the plating layer 6 is removed and the thickness of the metal foil 1 becomes 10 μm. The side etching amount generated when etching 1 is about 10 μm.
0 can be minutely formed with a line width of about 20 μm and a line interval of about 20 μm.

[0011]

As described above, according to the present invention, a through hole is formed through a laminated plate having metal foils on both sides, and the laminated plate is plated to form a through hole plating layer on the inner periphery of the through hole. After filling the resin in the through hole,
Since the plating layer attached to the surface of the metal foil by the above plating treatment is etched by etching the surface of the laminated plate, the plating layer on the surface of the metal foil is protected with the resin protecting the through-hole plating layer. Since it can be removed, it is possible to reduce the thickness of the metal to be etched without the need to etch the plating layer when forming a circuit, and it is possible to form a fine circuit with high accuracy. It is a thing.

[Brief description of drawings]

FIG. 1 shows an embodiment of the present invention (a),
(B), (c), (d), (e) is a partial sectional view, respectively.

FIG. 2 shows a conventional example, and includes (a), (b),
(C) is a partial cross-sectional view.

[Explanation of symbols]

 1 Metal Foil 2 Laminated Plate 3 Through Hole 4 Through Hole Plating Layer 5 Resin 6 Plating Layer

Claims (1)

[Claims] 1. A through hole is formed through a laminated plate having metal foils on both sides, and the laminated plate is plated to form a through hole plating layer on the inner periphery of the through hole, and the through hole is filled with resin. After that, the surface of the laminate is subjected to an etching treatment, and the plating layer adhered to the surface of the metal foil by the above-mentioned plating treatment is etched, thereby producing a printed wiring board.