JPH06296083A - Manufacture of wiring board - Google Patents

Abstract

PURPOSE:To provide a method of manufacturing a wiring board which is excellent in wiring density and connection efficiency. CONSTITUTION:Two wiring boards each mounted with a circuit conductor are arranged confronting each other, an insulating adhesive agent is interposed between them, and the boards are thermocompressed into one piece for the formation of a laminated wiring board, wherein holes are previously provided to the insulating adhesive agent layer at prescribed spots through which the circuit conductors provided to the boards are connected together, the connecting parts of the circuit conductors are plated with solder, and the solder plating is heated to electrically connect the circuit conductors together after the boards are laminated into one piece.

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 wiring board.

[0002]

2. Description of the Related Art In a printed wiring board, as the wiring density increases, the number of conductive holes used to electrically connect the wiring of one layer and the wiring of another layer increases. Conventionally, the conduction hole is formed by forming a through hole and plating the inner wall of the through hole in a laminated plate in which a prepreg is laminated on a copper-clad laminated plate or an inner layer circuit board to be laminated in multiple layers.

By the way, even in the case of a simple double-sided circuit board,
A hole is drilled in a double-sided copper-clad laminate and electroless plating is performed.Usually, electrolytic plating is performed to secure the thickness of the conductor in the through hole, an etching resist is formed, and unnecessary copper is chemically etched. Therefore, there is a problem that the process must be removed to form a circuit, the process is complicated, and each processing solution must be managed. As a method for solving such a problem, a method is known in which, after making a hole, the hole is filled with silver paste to make electrical connection.

Further, in the case of a multilayer wiring board, it is necessary to avoid the through hole portion and form wiring in a layer unrelated to the connection between layers. Therefore, the interlayer connection method using the through holes is an obstacle to increasing the wiring density. Therefore, a method has been developed in which, when manufacturing a multilayer wiring board, not only the holes penetrating the entire wiring board are used but only the adjacent layers are used for interlayer connection. There are basically two methods for this method, depending on how to make the through holes. The first method is to use a photosensitive material as the interlayer insulating material. After forming the wiring of the first layer by a usual method, a photosensitive insulating material is applied or laminated in the shape of a sheet. Next, a photomask is applied, and ultraviolet rays are irradiated, followed by development to form holes only in the conductive holes. Next, the surface of this insulating layer is immersed in a liquid containing CrO ₃ and H ₂ SO ₄ , for example, to chemically form a rough surface. Next, electroless plating or electroless plating and electroplating are used together to form a necessary wiring conductor. If necessary, this process is repeated in sequence to form a required wiring layer to form a multilayer structure. The second method is
This is a method of using a laser to form a conduction hole. Since an inorganic material such as glass fiber is difficult to be laser-processed, generally, an insulating layer not using the inorganic fiber is laid on the surface of the first layer, and further copper foil is laid on the surface and laminated and bonded. next,
Etch the copper foil in the part of the conduction hole. A laser is irradiated to the etched portion to remove the insulating layer and form a conductive hole. Next, plating is performed to form a necessary wiring conductor. If necessary, this method is repeated to form the required wiring layer, and the multilayer printed wiring board is manufactured.

Further, when the wiring board is made to have a high density, if the wiring board is large in size, even if there is a defective portion, it cannot be used as a product and there is a problem that the yield is reduced. To solve this problem, separate the wiring board into smaller wiring boards, and use a card cage or the like to integrate them when mounting. It is designed to stand up, insert it into a large-sized wiring board, and solder it to integrate it.

Furthermore, in the case of a flexible wiring board,
When simply used to connect the wiring board and the wiring board or the wiring board and the electronic components, the wiring pattern is also simple, and there is no particular problem, but when mounting the electronic components on the flexible wiring board, After making the wiring high density,
The demand for use as a cable is also increasing, and it has been difficult to realize without using a flexible wiring board substrate in which copper foil is attached to both surfaces. Such a flexible wiring board substrate may be high in cost, but as described above, it requires the same steps as when manufacturing a double-sided wiring board, and protects the circuit on the surface of the wiring board. The insulating coating is usually made of the same material as the base material of the substrate for flexible wiring board and is bonded with an adhesive, which further increases the cost. In addition, the adhesive used for bonding the base material of such a flexible wiring board substrate or the insulating coating and the circuit copper is weak against a strong alkaline solution such as an electroless plating solution, and also polyimide or the like. Since the flexible film is also vulnerable to such an alkaline solution, there is a problem that it is difficult to perform plating for a long time. Therefore, at present, a flexible wiring board having two or more layers is efficiently connected, or a hard wiring board using a normal epoxy resin or phenol resin (hereinafter referred to as a rigid wiring board) and a flexible wiring board are connected. Has devised and put into practical use the following method. At the connection point, a connection land is provided on the lower wiring board, and at a corresponding location on the upper wiring board, a land larger than the connection land is provided, and a hole is formed at the center of the land.
A method of soldering the lands to each other after overlapping is disclosed in Japanese Utility Model Publication No. 49-116565, and a wiring board having a circuit conductor formed on one side thereof and a flexible wiring board having a circuit conductor formed on one side thereof are faced to each other and at least connected. A method of applying solder to one of the circuit conductors at a location and heating it for electrical connection is disclosed in JP-B-51-42742.
Disclosed in Japanese Patent Publication, a wiring board having a circuit conductor formed on one surface and a flexible wiring board having a circuit conductor formed on one surface are faced back, holes are made at connection points, connection pins are inserted, and soldering is performed from both sides. The method is disclosed in Japanese Utility Model Publication No. 62-3895.

[0007]

Among the above-mentioned conventional techniques, the double-sided substrate technique is one in which when the solder paste filling the holes is heated, the solvent contained in the paste evaporates,
Air bubbles called blowers may be generated, making it impossible to connect circuits on both sides.In addition, when mounting electronic components on the wiring board manufactured in this way by soldering, heat the solder in the holes. Therefore, there is a problem that the reliability of the connection decreases.

In the case of a multilayer wiring board, a method of not providing a hole penetrating the whole is provided, and the problem of the first method is that of a photosensitive insulating material. This material undergoes the above-mentioned chemical surface roughening in order to obtain adhesion with plating, but there are few materials that simultaneously satisfy the photosensitivity and this characteristic, and the adhesion of the plating film is not sufficient. The problem with the second method is
There is a drawback in that the equipment is large due to the use of the laser.

Further, the high-density wiring is used as another wiring board,
In the method of integrating by soldering, the high-density wiring board and the wiring board connected to the wiring board cannot be connected at high density, and the high-density wiring board is not fixed. Therefore, there is a problem that components cannot be mounted at the same time.

In the case of a flexible wiring board, a connection land is provided on the lower wiring board at a connection point, and a land larger than the connection land is provided at a corresponding location on the upper wiring board, and a hole is formed at the center thereof. The method of soldering the lands after opening and stacking is that the area required for the connection land is large and the wiring cannot be made high density, and the wiring board with the circuit conductor formed on one side and the flexible circuit with the circuit conductor formed on one side The wiring boards are opposed to each other, at least one of the circuit conductors at the connection point is soldered, and the method of heating and electrical connection is as it is, because the circuit conductors are short-circuited at the other points facing each other. 2 when facing each other
Arrange so that the circuit conductors do not overlap on one wiring board, or
Alternatively, another insulating layer must be formed between the two wiring boards, and a high-density circuit cannot be formed, or an insulating layer and an adhesive for bonding the insulating layer are used,
There is a problem that the process becomes complicated, with the wiring board with the circuit conductor formed on one side and the flexible wiring board with the circuit conductor formed on one side facing back, making holes at the connection points and inserting the connection pins The method of soldering from requires the formation of holes for inserting connection pins and the formation of solder lands for connection, and it is difficult to perform high-density wiring.

It is an object of the present invention to provide a method of manufacturing a wiring board which is excellent in wiring density and which can be connected with high efficiency.

[0012]

According to the method of manufacturing a wiring board of the present invention, two wiring boards having circuit conductors are faced to each other,
A method of sandwiching an insulating adhesive between them, heating and pressurizing them to laminate and integrate them, wherein a hole is previously made in the insulating adhesive to connect the circuit conductors of two wiring boards, and the circuit is formed. It is characterized in that the connection points of the conductors are plated with solder in advance, and after the layers are integrated, the solder plating is heated to make electrical connection.

At this time, as a method of heating the solder plating at the connecting point, use a solder whose melting point is lower than the heating temperature at the time of stacking and integrating, and at the same time when stacking and integrating, heat the solder plating. Electrical connection.

If an insulating adhesive that can be temporarily fixed by heating for a short time is used, if it is temporarily fixed before being laminated by heating and pressurizing, it can be integrated before lamination. Alternatively, the solder plating may be heated in advance to make the electrical connection.

Also, two wiring boards having circuit conductors formed on one surface are faced to each other, and an insulating adhesive is sandwiched between only the areas where the two wiring boards need to be connected to heat and heat the wiring board.
After pressurizing and laminating, the insulating adhesive is preliminarily provided with a hole at a place where two circuit conductors are connected, and a solder plating is performed at a connecting place of the circuit conductors. If the solder plating is heated to make an electrical connection, the wiring boards can be partially connected.
For example, it is possible to create only a high-density required part as a separate wiring board and connect it to a large-sized wiring board. Also, connect a flexible wiring board and a rigid wiring board, and even a part of the flexible wiring board. Can also be used as a cable. It is also possible to connect a part of the two flexible wiring boards and use the other parts for connection for different purposes.

As described above, also in the method of connecting only the areas where the two wiring boards need to be connected, the above-mentioned lamination and integration are performed, and at the same time, the solder plating is heated to make the electrical connection, and the lamination is performed. It goes without saying that the solder plating can be heated in advance to make the electrical connection before the integration.

As a method of heating the solder plating at the connecting point, one wiring board having a thickness of 0.1 mm or less can be heated from the back surface of the wiring board. For example, it is also possible to use heating means such as a soldering iron or various energy radiation sources such as infrared rays and laser light. In this case, if the thickness is 0.1 mm or more, heat transfer is delayed, and the insulating base material may be damaged before the solder is heated and melted.

As a method for heating the solder plating at the connecting point, it is also possible to use a heat generation due to contact resistance by passing an electric current between the circuits which are electrically connected to the circuit where the solder plating to be connected is formed. . In this case, the contact resistance decreases as the solder starts melting, the solder melts, and the contact area increases, so when a constant voltage source is used as the power supply, heat generation should be limited by the decrease in contact resistance. When a constant current source is used, a constant current can be flowed regardless of contact resistance, and in order to confirm the connection, the contact resistance decreases because the voltage of the power supply decreases. The termination of the connection can be monitored.

The wiring board having the circuit conductor used in the present invention may be any wiring board that is normally used. For example, as the base material, epoxy resin,
Phenolic resin, polyimide resin, polyester resin,
Fluororesin, glass cloth impregnated with these, paper, or a mixture of these resins with glass fiber, talc, kaolin, an inorganic filler carrying an electroless plating catalyst, an organic filler, or the like, There is a film of these resins.

As the insulating adhesive, polyimide-based, epoxy-based or acryl-modified epoxy-based adhesives can be used. Epoxy-based adhesives are particularly high-molecular ones in terms of heat resistance and electrical characteristics. .

The method of heating and pressurizing to laminate and integrate is not particularly limited as long as it is used under conditions suitable for the base material and the insulating adhesive.

As a method of making holes in the insulating adhesive in advance where the circuit conductors of two wiring boards are to be connected, the adhesive is formed into a sheet shape, and a peelable protective film is stuck on both sides and stacked, It can be performed by drilling or punching, and can also be performed by using laser, plasma or the like.

The method of performing the solder plating on the connection portion of the circuit conductor may be the usual solder plating, and may be the electroless plating or the electrolytic plating. It is preferable that the thickness of the solder plating is set to a thickness such that the two wiring boards can be brought into contact with each other after they are stacked. It is necessary to select the type of solder in consideration of the temperature when mounting the electronic component on the wiring board and the melting point in particular. In consideration of this, as a method of heating the solder plating at the connection point, it is possible to simultaneously heat the electronic components on the wiring board by soldering.

[0024]

[Function] Since the insulating adhesive has the functions of both interlayer adhesion and interlayer insulation and the connection between the circuit layers is made by soldering, it can be efficiently manufactured and a hole for connection can be provided. Since it is provided only on the insulating adhesive, the wiring can be easily densified.

[0025]

[Example] MCL-E-67 which is a single-sided copper-clad laminate
An etching resist was formed on a copper foil (trade name, manufactured by Hitachi Chemical Co., Ltd.), and unnecessary copper foil was removed by etching to form two single-sided wiring boards. Next, a hole having a diameter of 0.5 mm was drilled at a location where Pyralux (product name, manufactured by DuPont) as an adhesive sheet 8 was connected, the protective film was removed, and then the sheet was placed between the single-sided wiring boards and the pressure was 20 kg. Multilayer adhesion was performed at a temperature of 170 ° C./cm ^{2 for} 1 hour. As a method for heating the solder plating at the connection point, a current was supplied from a constant voltage power source of 0.5 V between the circuits that were electrically connected to the circuit where the solder plating to be connected was formed, and the heat generated by the contact resistance was used. As a result, the connection state was good without an air blower as a result of observing the cross section with a microscope.

Example 2 A multi-wire wiring board was prepared as a high-density wiring board,
Only a necessary portion was formed as a four-layered multilayer wiring board having a glass cloth-epoxy resin as a base material in a size of 500 mm × 500 mm and connected. In the multi-wire wiring board, glass cloth-epoxy prepreg GEA-168 (manufactured by Hitachi Chemical Co., Ltd., trade name) is overlaid on the surface of the inner layer circuit board having a power / ground layer, and an adhesive AS for wiring is attached on the surface.
102 (Hitachi Chemical Industry Co., Ltd., trade name) is laminated, and the insulated electric wire 0HAW-1IMW-0.1 (Hitachi Cable Co., Ltd. trade name) is fixed in a required shape by a numerical control wiring machine, Glass cloth mixed with a catalyst for electroless plating as an insulating coating-epoxy prepreg GEA-68
(Hitachi Chemical Co., Ltd., trade name), pressure, 20
Under the conditions of kg / cm ² , temperature 170 ° C., 1 hour, heat and pressure are applied to laminate and integrate, and a resist for electroless plating is laminated on the surface, and only the necessary circuit shape is applied using a photo mask. After exposing, developing and removing, make holes at the necessary connection points and expose the cut parts of the insulated wires to be connected in the holes, and perform electroless plating to remove surface circuits and hole inner walls. A metal layer was formed. After that, electroless solder plating was performed on the surface to be connected to the other wiring board. A glass cloth-epoxy resin-based four-layer multilayer base wiring board is formed with a solder resist after forming a circuit by a known method, except for a portion to be connected to the multi-wire wiring board. Only the solder was plated. Then, AS-10 which is an epoxy adhesive sheet
2 (manufactured by Hitachi Chemical Co., Ltd., trade name) was cut into the size of the multi-wire wiring board, and a hole of 0.5 mm was punched at a place where the two wiring boards were connected to remove the protective film. After that, stack it between the two wiring boards and apply pressure 20
Multilayer adhesion was performed at kg / cm ² and a temperature of 170 ° C. for 1 hour.
Since the solder used at this time was a low melting point solder (160 ° C.) containing antimony / bismuth, all the connections could be made simultaneously after the lamination adhesion. In addition, when electronic components were mounted on the composite wiring board thus created using reflow solder, the low melting point solder did not seep out, and the two wiring boards and the cured insulating adhesive It is speculated that the well-melted solder was trapped in the area surrounded by the holes. Furthermore, as a result of using a low melting point solder having a melting point of 190 ° C. containing only antimony, some parts were not connected after lamination, but after the reflow soldering, all the connections were good. Was done in.

Example 3 One-sided flexible wiring board made of polyimide base material and Example 2
Connecting the four-layered multilayer wiring board used in, using normal 6/4 solder as the solder, and heating it with a soldering iron from the back surface of the flexible wiring board as a heating means.
It was prepared in the same manner as in Example 1 except that it was irradiated with laser light. The connection was good in all connection methods.

Example 4 In Example 3, before laminating and adhering, laminating with a heating roll and temporarily fixing, heating with a soldering iron for connection, and laminating and adhering.

[0029]

Industrial Applicability According to the present invention, it is possible to provide a method for producing a wiring board which is excellent in wiring density and is highly efficient in connection, and can be applied to various wiring boards having various application ranges.

Claims (10)

[Claims] 1. A method in which two wiring boards on which circuit conductors are formed are faced to each other, an insulating adhesive is sandwiched between them, and heating and pressing are performed to laminate and integrate them. A hole is made in the place where the circuit conductors of the two wiring boards are connected, a solder layer is formed at the place where the circuit conductors are connected, and after the layers are integrated, the solder layers are heated for electrical connection. A method of manufacturing a wiring board, characterized by: 2. A method in which two wiring boards on which circuit conductors are formed are opposed to each other, an insulating adhesive is sandwiched therebetween, and heat and pressure are applied to laminate and integrate them. A hole is made in the place where the circuit conductors of the two wiring boards are connected, a solder layer is formed at the place where the circuit conductors are connected, and the solder layers are heated at the same time to make an electrical connection. A method of manufacturing a wiring board, characterized by: 3. A method in which two wiring boards on which circuit conductors are formed are opposed to each other, an insulating adhesive is sandwiched therebetween, and heat and pressure are applied to laminate and integrate the insulating boards in advance. A hole is made in the place where the circuit conductors of the two wiring boards are connected, a solder layer is formed at the place where the circuit conductors are connected, and the solder layers are heated in advance to make an electrical connection before they are laminated and integrated. A method of manufacturing a wiring board, which is characterized by carrying out. 4. The two wiring boards having circuit conductors are faced to each other, and an insulating adhesive is sandwiched between only the areas where the two wiring boards need to be connected, and heated and pressed to form a laminated body. And the insulating adhesive is preliminarily used in advance.
A feature is that a hole is formed at a place where two circuit conductors are connected, a solder layer is formed at a place where the circuit conductors are connected, and after the laminated layers are integrated, the solder layer is heated to make an electrical connection. Wiring board manufacturing method. 5. The two wiring boards on which circuit conductors are formed are opposed to each other, and an insulating adhesive is sandwiched between only the areas where the two wiring boards need to be connected, and heated and pressed to form a laminated body. And the insulating adhesive is preliminarily used in advance.
A feature is that a hole is formed at a place where two circuit conductors are connected, a solder layer is formed at the connection place of the circuit conductors, and at the same time when the layers are integrated, the solder layer is heated to make an electrical connection. Wiring board manufacturing method. 6. The two wiring boards on which circuit conductors are formed are faced to each other, and an insulating adhesive is sandwiched between only the areas where the two wiring boards need to be connected, and heated and pressed to form a laminated body. And the insulating adhesive is preliminarily used in advance.
A feature is that a hole is made at the place where two circuit conductors are connected, a solder layer is formed at the place where the circuit conductors are connected, and the solder layers are heated in advance to make an electrical connection before they are laminated and integrated. Manufacturing method of wiring board. 7. A method for heating a solder layer at a connection point is to heat one wiring board to a thickness of 0.1 mm or less and to heat from the back surface of the wiring board.
Or the method for manufacturing a wiring board according to any one of 6 above. 8. As a method of heating a solder layer at a connecting point, an electric current is caused to flow between circuits that are electrically connected to a circuit in which a solder layer to be connected is formed, and heat generated by contact resistance is used. Item 7. A method for manufacturing a wiring board according to any one of items 1, 3, 4 and 6. 9. The wiring board according to claim 2, wherein a method of heating a solder layer at a connecting point is one having a melting point of solder lower than a heating temperature at the time of stacking and integrating. Manufacturing method. 10. The method for heating a solder layer at a connecting point is performed by simultaneously heating an electronic component on a wiring board when the electronic component is soldered. Manufacturing method.