JP2006114578A - Manufacturing method of printed circuit board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To easily form a plated layer within a blind via hole with the electric plating method, and to connect different conductor layers with the plated layer formed with the electric plating within the blind via hole. <P>SOLUTION: The printed circuit board manufacturing apparatus 1 is constituted with an original board 10' of a printed circuit board 10, a plating vessel 20 for reserving the plating solution L, a circulating apparatus 30 for circulating the plating solution L within th plating vessel 20, and a power feeding apparatus 40 for applying voltage for the electric plating on the original board 10' of the printed circuit board 10 and an anode plate 50. The negative electrode 41 of the power feeding apparatus 40 is connected only with the second conductor layer 11B of the original board 10' projected from the solution level of the plating solution L. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for manufacturing a printed wiring board, and more particularly to a method for manufacturing a printed wiring board in which conductor layers are connected to each other by a plating layer formed by electroplating inside a blind via hole.

  Conventionally, through wiring holes or blind via holes having a very small diameter of about 0.1 mm to 0.2 mm are formed on a multilayer printed wiring board, and plating is deposited on the inner wall surface of these via holes to connect circuit wirings of each layer. Things have been done. These platings are exclusively performed by electroless plating in order to enhance adhesion with the insulating layer interposed between the circuit wirings. As a method for plating through via holes (through holes) by electroless plating, for example, there is a method disclosed in Patent Document 1.

According to the method of Patent Document 1, first, a copper compound is attached to the inner wall surface of the through via hole, and the through via hole is immersed in a reducing liquid in this state to reduce the copper compound, thereby reducing the inner wall surface of the through via hole. A layer of particulate metallic copper is formed. Then, a plating layer is formed on the inner wall surface of the through via hole by electroless plating using the particulate metal copper as a catalyst for electroless plating. Thus, the use of the catalyst improves adhesion between the insulating layer exposed on the inner wall surface of the through via hole and the plating layer.
Japanese Patent Laid-Open No. 6-256961 (paragraphs 0006 to 0013)

  In order to deposit a plating layer inside the blind via hole using the above-described plating method of the inner wall surface of the through via hole by electroless plating, a pretreatment for attaching a catalyst to the inside of the blind via hole is necessary, which is troublesome. Take it. Therefore, the inventors tried to deposit a plating layer inside the blind via hole by electroplating. Hereinafter, description will be given with reference to the drawings.

FIG. 5 is a cross-sectional view of a blind via hole.
As shown in FIG. 5, the printed wiring board 100 includes an insulating layer 102 and conductor layers 101 a and 101 b stacked via the insulating layer 102. The printed wiring board 100 is formed with a blind via hole 103 that penetrates the conductor layer 101a and the insulating layer 102 and reaches the conductor layer 101b. That is, the conductor layer 101b is exposed on the bottom surface of the blind via hole 103, and the conductor layer 101a is exposed on the inner wall surface. A resist layer 104 is printed on the surfaces of the conductor layers 101a and 101b in order to prevent deposition of plating.

  In order to shorten the plating time, the inventors tried to connect the both by depositing plating in the blind via hole 103 from both the conductor layers 101a and 101b. Specifically, a negative electrode of a power feeding device (not shown) is connected to both the conductor layer 101a and the conductor layer 101b, the printed wiring board 100 is immersed in the plating solution L, and is opposed to the opening of the blind via hole 103. The anode plate 105 was disposed at the position, and electroplating was performed.

  However, after a predetermined time has passed, the printed wiring board 100 was taken out and a continuity test of the conductor layers 101a and 101b was performed. As a result, it was found that the two were not connected.

The cause of the failure is estimated as follows.
That is, when the plating layer 106a deposited on the surface of the conductor layer 101a and the plating layer 106b deposited on the surface of the conductor layer 101b grow to each other, a gap 107 as shown in FIG. It is formed. The gap 107 is formed in a deeply intricate shape and gradually narrows. If the gap 107 becomes narrow, it is considered that the plating solution L in this gap cannot be replaced well and the growth of plating is hindered. In particular, the blind via hole 103 has a bag hole shape, and its diameter is as small as about 0.1 mm to 0.2 mm. Therefore, it is estimated that the replacement of the plating solution L in the blind via hole 103 is deteriorated. The

The present invention has been made in view of these problems, and an object of the present invention is to provide a method of manufacturing a printed wiring board that can easily form a plating layer in a blind via hole by electroplating.
Another object of the present invention is to provide a method of manufacturing a printed wiring board in which different conductor layers are connected by a plating layer formed by electroplating in a blind via hole.

  The method for manufacturing a printed wiring board according to claim 1, wherein a plurality of conductor layers stacked via an insulating layer, at least one conductor layer and the insulating layer are penetrated to reach another conductor layer. A printed wiring board having a blind via hole and a plating layer formed in the blind via hole and connecting the conductive layer and the other conductive layer, the printed wiring board having the penetrating hole. Electroplating is performed using only as a cathode.

  According to this method, since electroplating is performed using only the other conductor layer exposed on the bottom surface of the blind via hole as a cathode, the plating layer is deposited only on the surface of the other conductor layer. Therefore, the conventional gap 107 (see FIG. 5) is not formed, and the growth of the plating layer is not hindered. Then, when the plating layer grown from the bottom surface of the blind via hole reaches the conductor layer exposed on the inner wall surface of the blind via hole, both are connected.

  Here, the insulating layer is, for example, a polyimide film or a polyester film in the case of a flexible printed wiring board, and in the case of a rigid printed wiring board, a paper base material, a glass cloth paper composite base material, or a synthetic fiber cloth base material. Such as a base material such as a phenol resin, an epoxy resin, a polyimide resin, or a polyester resin is impregnated. An adhesive layer may be interposed between the insulating layer and the conductor layer.

  The conductor layer is, for example, a conductor pattern formed of a conductive material such as copper, a stainless plate as a ground layer, or the like. The conductor pattern may be plated with gold.

  The plating layer is preferably formed of a material such as gold, copper, or nickel. In particular, when the other conductor layer is made of a stainless material, it is most preferable to use nickel plating.

  In addition, this invention is applicable to the printed wiring board whose diameter of a blind via hole is about 0.1 mm-0.2 mm, for example.

  A method for manufacturing a printed wiring board according to claim 2 is the method for manufacturing a printed wiring board according to claim 1, wherein a plating solution is applied to a surface of the printed wiring board on which the blind via hole is formed in a plating bath. Electroplating is performed while spraying.

  According to such a method, in the plating bath, electroplating is performed while spraying the plating solution onto the surface of the printed wiring board on which the blind via hole is formed. It will be replaced with liquid. Therefore, the plating layer can be grown well.

  According to the present invention, since the growth of the plating layer is not hindered, the plating layer can be easily formed in the blind via hole by electroplating. Therefore, it is possible to connect different conductor layers using blind via holes.

  The best mode for carrying out the present invention will be described in detail with reference to the drawings. In the description, the same elements are denoted by the same reference numerals, and redundant description is omitted. In the drawings to be referred to, FIG. 1 is a schematic sectional view showing a printed wiring board manufacturing apparatus. FIG. 2 is an enlarged cross-sectional view of a portion A in FIG. FIGS. 3A and 3B are enlarged views of the BB cross section of FIG. 1. FIG. 3A shows a state in which the plating layer is being formed, and FIG. 3B shows a state in which the plating layer formation is completed. FIG. 4 is an explanatory diagram showing the state of spraying the plating solution onto the surface of the printed wiring board and the flow of the plating solution.

  In the present embodiment, a printed wiring board capable of discharging static electricity charged in the conductive pattern to the ground layer by connecting the conductive pattern of the printed wiring board and the ground layer by a plating layer formed in the blind via hole. This will be described as an example.

<Printed wiring board manufacturing equipment>
First, the printed wiring board manufacturing apparatus 1 will be described.

  As shown in FIG. 1, a printed wiring board manufacturing apparatus 1 according to the present embodiment includes an original plate 10 ′ of a printed wiring board 10, a plating tank 20 that stores a plating solution L, and a plating solution L in the plating tank 20. And a power feeding device 40 that applies a voltage for electroplating to the original plate 10 ′ and the anode plate 50 of the printed wiring board 10.

(Printed wiring board 10)
The printed wiring board 10 is a board in a state immediately before mounting an electronic component (not shown), and as shown in FIG. 2, the first conductor layer 11A, the second conductor layer 11B, and the gap between them. An insulating layer 12 that interposes and insulates the blind via hole 13 that reaches the surface 11Ba of the second conductor layer 11B from the surface 11Aa of the first conductor layer 11A through the first conductor layer 11A and the insulating layer 12; The plating layer 15 is formed inside the blind via hole 13 and connects the first conductor layer 11A and the second conductor layer 11B. Resist layers 14 and 14 are formed on the front surface 11Aa of the first conductor layer 11A and the back surface 11Bb of the second conductor layer 11B.

  Here, since FIG. 2 is a diagram showing the state of the printed wiring board 10 before the plating layer 15 is formed, the plating layer 15 is indicated by a broken line in FIG. For convenience of explanation, the printed wiring board 10 in a state immediately before forming the plating layer 15 is referred to as “original plate 10 ′”. Further, in the present embodiment, the original plate 10 ′ includes only one blind via hole 13, but it goes without saying that a plurality of blind via holes 13 may be included.

11 A of 1st conductor layers are the conductor patterns formed by etching copper foil etc., for example, and connect between the electronic components (not shown) mounted in the printed wiring board 10. FIG.
Here, if static electricity is charged in the first conductor layer 11A, it may cause a failure when an electronic component is mounted later, and thus it is necessary to discharge (ground) this static electricity. In the present embodiment, the thickness t ₁ of the first conductor layer 11A is about 8 to 12 μm.

The second conductor layer 11B is a layer made of, for example, a stainless material, and serves as a ground layer for discharging static electricity charged in the first conductor layer 11A. The second conductor layer 11B is laminated on the first conductor layer 11A via an insulating layer 12 to be described later. The second conductor layer 11B corresponds to “another conductor layer” in the claims. In the present embodiment, the thickness t ₂ of the second conductor layer 11B is about 15 to 20 μm.

The insulating layer 12 is a layer made of, for example, a polyimide film, and is laminated by coating a polyimide resin on the copper foil constituting the first conductor layer 11A. In the present embodiment, the thickness t ₃ of the insulating layer 12 is about 10 μm.

  As shown in FIG. 2, the blind via hole 13 is a so-called bag hole recessed through the first conductor layer 11A and the insulating layer 12 so as to reach the surface 11Ba of the second conductor layer 11B. Therefore, the surface 11Ba of the second conductor layer 11B is exposed on the bottom surface of the blind via hole 13, and the cut surface 11Ab of the first conductor layer 11A is exposed on the inner wall surface of the blind via hole 13. In the present embodiment, the blind via hole 13 is formed so that its diameter D is about 0.1 mm to 0.2 mm. Moreover, the blind via hole 13 is formed using a very small diameter drill or laser.

The resist layer 14 is a layer that covers and protects a portion where electroplating is not desired to be deposited, and is formed, for example, by a method such as dry film processing or solder resist printing. In the present embodiment, the resist layer 14 is laminated on the front surface 11Aa of the first conductor layer 11A and the back surface 11Bb of the second conductor layer 11B, and the inside of the blind via hole 13 is exposed. In the present embodiment, the thickness t ₄ of the resist layer 14 is about 38 μm.

  The plating layer 15 connects the first conductor layer 11A and the second conductor layer 11B. In the present embodiment, the static electricity charged in the first conductor layer 11A is applied to the second conductor layer 11B, which is a ground layer. It plays the role of energizing. The plating layer 15 is formed in the blind via hole 13 by electroplating (see FIG. 3). In the present embodiment, the plating layer 15 is formed by nickel plating with relatively good adhesion to the stainless steel material. The formation of the plating layer 15 will be described in detail later.

(Plating tank 20)
As shown in FIG. 1, the plating tank 20 is a water tank for storing the plating solution L, and can immerse the original plate 10 ′ of the printed wiring board 10 and the anode plate 50 described later.
Moreover, although illustration is abbreviate | omitted, the plating tank 20 is equipped with the support means which can support original plate 10 'and the anode plate 50 in the state which mutually faced. The original plate 10 ′ is supported by the supporting means in a state where one end protrudes from the plating solution L.
The plating solution L stored in the plating tank 20 is selected according to the material of the plating layer 15 that is to be formed in the blind via hole 13. In the present embodiment, a nickel plating solution is employed as the plating solution L.

(Circulating device 30)
The circulation device 30 is a device for circulating the plating solution L stored in the plating tank 20, and as shown in FIG. 1, a pump 31, an injection nozzle 32, a suction port 33, and a hose 34 connecting them. It is composed of
The circulation device 30 can spray the plating solution L sucked from the suction port 33 from the spray nozzle 32. Further, the spray nozzle 32 is directed to the surface of the original plate 10 ′ immersed in the plating tank 20, and can spray the plating solution L onto the original plate 10 ′.

Further, the plating solution L sprayed on the original plate 10 ′ is refluxed in the plating tank 20, sucked into the pump 31 from the suction port 33, and sprayed again from the spray nozzle 32. Thereby, the plating solution L in the plating tank 20 is circulated and stirred. Furthermore, the fresh plating solution L enters the inside of the blind via hole 13 formed on the surface of the original plate 10 ′ and replaces the old plating solution L.
The circulation device 30 may be configured to include a plurality of injection nozzles 32.

(Power supply device 40)
The power feeding device 40 is a device that applies a voltage for performing electroplating between an anode and a cathode, and includes a negative electrode 41 and a positive electrode 42. The negative electrode 41 is connected only to the second conductor layer 11B of the original plate 10 ′ protruding from the liquid surface of the plating solution L (see FIG. 3). The positive electrode 42 is connected to an anode plate 50 described later.
In addition, the electric power feeder 40 is provided with the control apparatus (illustration omitted) for adjusting the applied voltage and energization time, and can adjust these suitably according to the magnitude | size and thickness of the plating layer 15 to form. It has become.

(Anode plate 50)
The anode plate 50 is, for example, a metal strip-shaped member, and is disposed at a position facing the opening of the blind via hole 13 of the original plate 10 ′ immersed in the plating tank 20. That is, when a voltage is applied to the second conductor layer 11 </ b> B and the anode plate 50 by the power feeding device 40, a current flows between the surface 11 </ b> Ba of the second conductor layer 11 </ b> B exposed on the bottom surface of the blind via hole 13 and the anode plate 50. The nickel plating is deposited on the surface 11Ba of the second conductor layer 11B, which is the cathode (see FIG. 3).

<Method for Manufacturing Printed Wiring Board 10>
It continues and the manufacturing method of the printed wiring board 10 is demonstrated.

  First, as shown in FIG. 1, the negative electrode 41 of the power feeding device 40 and the second conductor layer 11B of the original plate 10 'are connected, and the positive electrode 42 and the anode plate 50 are connected. Then, the opening of the blind via hole 13 formed in the original plate 10 ′ and the anode plate 50 face each other so that they are immersed in the plating solution L stored in the plating tank 20.

Then, the operation of the circulation device 30 is started, and the plating solution L is sprayed from the spray nozzle 32 onto the surface of the original plate 10 ′ (surface on which the blind via hole 13 is formed), and the operation of the power feeding device 40 is started. Then, the plating layer 15 is deposited in the blind via hole 13.
Hereinafter, the formation process of the plating layer 15 will be described with reference to FIG.

  When a voltage is applied to the second conductor layer 11B and the anode plate 50 by the power feeding device 40, a current flows between the surface 11Ba of the second conductor layer 11B exposed on the bottom surface of the blind via hole 13 and the anode plate 50, and the cathode Then, nickel plating is deposited on the surface 11Ba of the second conductor layer 11B, and the plating layer 15 starts to be formed (see FIG. 3A). And as time passes, the plating layer 15 grows toward the opening of the blind via hole 13.

  At this time, since the negative electrode 41 of the power feeding device 40 is connected only to the second conductor layer 11B, nickel plating is deposited on the cut surface 11Ab of the first conductor layer 11A exposed on the inner wall surface of the blind via hole 13. Never do. Therefore, the plating layer 15 deposited on the surface 11Ba of the second conductor layer 11B grows to the first conductor layer 11A without being inhibited from growing.

When the thickness of the plating layer 15 grown from the bottom surface of the blind via hole 13 becomes larger than the thickness t ₃ of the insulating layer 12, the plating layer 15 and the cut surface 11Ab of the first conductor layer 11A come into contact with each other. Thereby, the first conductor layer 11A also becomes a cathode, and thereafter, as shown in FIG. 3B, nickel plating is also deposited from the cut surface 11Ab of the first conductor layer 11A. And as the thickness of the plating layer 15 deposited on the cut surface 11Ab of the first conductor layer 11A increases, the first conductor layer 11A and the second conductor layer 11B are firmly connected by the plating layer 15. Become.

When the formation of the plating layer 15 is completed, the printed wiring board 10 is taken out from the plating tank 20 and the resist layer 14 is removed as necessary.
Thus, the production of the printed wiring board 10 is completed.

  Here, replacement of the plating solution L in the blind via hole 13 will be described with reference to FIG.

  As shown in FIG. 4, the injection nozzle 32 of the circulation device 30 is directed to the surface 14 a of the original plate 10 ′ in which the blind via hole 13 is recessed, and from the injection nozzle 32 toward the surface 14 a of the original plate 10 ′. The plating solution L is sprayed.

  When the flow S1 of the plating solution L sprayed from the spray nozzle 32 toward the surface 14a of the original plate 10 ′ reaches the surface 14a, it changes its direction and starts to flow along the surface 14a of the original plate 10 ′ (see S2). ). Here, since the blind via hole 13 is formed on the surface 14a of the original plate 10 ', the flow S2 along the surface 14a of the original plate 10' is disturbed by the opening of the blind via hole 13, and a part of the blind via hole 13 is formed. (See symbol S3). And by this flow S3, replacement | exchange of the plating solution L in the blind via hole 13 will be performed.

  Although illustration is omitted, when the flow S1 of the plating solution L ejected from the injection nozzle 32 directly enters the blind via hole 13, the replacement of the plating solution L in the blind via hole 13 is directly performed by the flow S1. To be done.

According to the method for manufacturing a printed wiring board according to the present embodiment, the following operational effects are obtained.
That is, the connection between different conductor layers in the via hole, which has been conventionally performed by electroless plating, can be reliably and easily performed by electroplating. As a result, the degree of freedom of the manufacturing method is improved and the technology can be diversified.

  The best mode for carrying out the present invention has been described in detail with reference to the drawings. However, the present invention is not limited to the embodiment, and may be changed as appropriate without departing from the spirit of the present invention. Is possible.

  For example, in the present embodiment, the printed wiring board 10 is configured to connect the first conductor layer 11 </ b> A and the second conductor layer 11 </ b> B by the plating layer 15 formed in the blind via hole 13. However, the present invention may be applied to a printed wiring board having more conductor layers. In such a case, a blind via hole is recessed so as to reach one conductor layer through a plurality of conductor layers and insulating layers, and a plating layer is formed in the blind via hole to connect each conductor layer. can do.

  In the present embodiment, the second conductor layer 11B is a ground layer. However, the present invention is not limited to this, and the second conductor layer 11B may be a conductor pattern and the printed wiring board 10 may be a multilayer printed wiring board. .

  In the present embodiment, the first conductor layer 11A is made of copper foil, but is not limited to this, and may be made of other materials, for example, to prevent corrosion. Further, gold plating or the like may be applied to the surface of the copper foil. Moreover, although the 2nd conductor layer 11B decided to consist of stainless steel materials, it is not restricted to this.

  Needless to say, the printed wiring board 10 may be either a flexible printed wiring board or a rigid printed wiring board.

  In the present embodiment, nickel plating is used as the plating solution L. However, the present invention is not limited to this, and other plating such as copper plating or gold plating may be used. In order to assist the formation of the plating layer 15 in the blind via hole 13, degreasing, acid treatment, and strike plating in the blind via hole 13 may be performed in advance.

It is a schematic sectional drawing which shows the manufacturing apparatus of a printed wiring board. It is sectional drawing which expanded and showed the A section of FIG. It is the figure which expanded and showed the BB cross section of FIG. 1, (a) shows the state during plating layer formation, (b) shows the state of completion of plating layer formation. It is explanatory drawing which shows the injection state of the plating solution to the surface of a printed wiring board, and the flow of a plating solution. It is sectional drawing of a blind via hole.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Printed wiring board manufacturing apparatus 10 Printed wiring board 10 'Original board 11A 1st conductor layer 11B 2nd conductor layer 12 Insulating layer 13 Blind via hole 14 Resist layer 15 Plating layer 20 Plating tank 30 Circulating device 40 Power supply apparatus 50 Anode plate L Plating liquid

Claims (2)

A plurality of conductor layers stacked via an insulating layer;
A blind via hole penetrating at least one conductor layer and the insulating layer to reach another conductor layer;
A printed wiring board having a plating layer formed in the blind via hole and connecting the conductor layer and the other conductor layer that are penetrated,
A method for producing a printed wiring board, wherein electroplating is performed using only the other conductor layer as a cathode.   2. The method of manufacturing a printed wiring board according to claim 1, wherein electroplating is performed in a plating bath while spraying a plating solution onto the surface of the printed wiring board on which the blind via hole is formed.

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