JPH09326542A - Method of fabricating circuit board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a circuit board whose efficiency in use is improved by performing a second process for jointing a lead wire of a part to a hardenable conductive member which is formed in a first process before the hardenable conductive member is hardened. SOLUTION: After forming a plating layer on a copper foil formed on each of the surface and the back face of a circuit board 1, an etching resist is laminated on the surface of the plating layer, and is exposed and developed, thereby forming a resist pattern. After that, the etching resist is etched and removed with a ferric chloride etching solution, thereby forming a wiring pattern 2. A through hole 5 for connecting the surface and the back face of the circuit board 1 is opened and filled with a copper paste 6 as a hardenable conductive member. Before the copper paste 6 is hardened, a lead wire 11 of a part 10 is jointed to the copper paste 6. Consequently, an efficiency in use of the circuit board 1 can be improved.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method of manufacturing a circuit board. Conventionally, when a component is mounted on a printed circuit board, it has been usual to place the circuit component on the surface of the component, insert the lead of the circuit component into the through hole, and solder it. However, in recent years, the packaging density of circuit components has been improved, the wiring patterns have been miniaturized accordingly, and the number of pins of the circuit components has increased significantly. With the increase in the density of such circuit boards, printed circuit boards having three or more layers have been used, and multilayer circuit boards that are easy to manufacture are required.

[0002]

2. Description of the Related Art FIG. 4 is a sectional view showing an example of the structure of a conventional circuit board. In the figure, reference numeral 1 denotes a circuit board, which is composed of a laminated body of three insulating substrates. Two
Is a wiring pattern (circuit pattern) formed on the front and back surfaces of the circuit board 1, 3 is a wiring pattern provided on an inner layer of the circuit board 1, and 4 is for electrical connection between the front surface and the back surface of the circuit board 1. It is a cured body of a copper paste as a curable conductive member that is filled and cured in the through hole opened in the. The hardened body 4 of the copper paste electrically connects the front and back surfaces of the circuit board 1 and the wiring patterns 2 and 3 of the outer and inner layers to each other.

[0003]

In the above-mentioned conventional circuit board, a through hole is opened to make an electrical connection between the front surface and the back surface of the circuit board, and the through hole is filled with copper paste. , This copper paste was used only for making electrical connection between two or more different points.

The present invention has been made in view of the above problems, and a curable conductive member for making an electrical connection between two or more different points is also used for bonding components. It is an object of the present invention to provide a method for manufacturing a circuit board that improves the utilization efficiency of the board.

[0005]

DISCLOSURE OF THE INVENTION The present invention for solving the above-mentioned problems is a curable material for a portion of a circuit board made of an insulating substrate having a wiring pattern, which requires electrical connection between two or more different points. A first step of forming a conductive member,
It is characterized by a second step of adhering the lead wire of the component to the curable conductive member before the curable conductive member formed in the first step is cured.

According to the configuration of the present invention, the lead wire of the component is adhered before the curable conductive member formed between two or more different points is cured, thereby improving the utilization efficiency of the circuit board. Can be made.

In this case, when it is necessary to electrically connect the front surface and the back surface of the circuit board, a through hole is opened, and the curable conductive member is filled in the through hole.
The lead wire of the component is bonded to the through hole filled with the curable conductive member.

According to the structure of the present invention, the lead wire of the component is adhered before the curable conductive member filled in the through hole is cured, so that the through hole can be used for electrical connection and component mounting. Can also be used as, and the utilization efficiency of the circuit board can be improved.

Further, the curable conductive member is characterized in that it is obtained by kneading dendritic copper powder, epoxy resin and a curing agent. According to the configuration of the present invention, it is possible to improve the electrical connection when the lead wires of the components are bonded.

[0010]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a flowchart showing an embodiment of the method of the present invention. The present invention relates to a first step of forming a curable conductive member at a place where electrical connection between two or more different points is required in a circuit board made of an insulating substrate having a wiring pattern formed thereon, and the first step. Before the curable conductive member formed in the process is cured, it is constituted by a second process of adhering the lead wire of the component to the curable conductive member. By taking such steps, the lead wires of the components are bonded before the curable conductive member formed between two or more different points is cured, thereby improving the utilization efficiency of the circuit board. Can be made.

FIG. 2 is a view showing an embodiment of a process for manufacturing a circuit board according to the method of the present invention, each showing a cross section. The same parts as those in FIG. 4 are designated by the same reference numerals. (A) Drill through holes on the front and back surfaces of the circuit board where electrical connection is required.

In the figure, 1 is a circuit board, and 2 is a wiring pattern (circuit pattern) formed on the front and back surfaces of the circuit board 1. The circuit board 1 has, for example, a thickness of 1.2.
A glass epoxy substrate, which is an insulator of about mm, is used. The wiring pattern 2 is formed as follows.
After forming a plating layer on the copper foil formed on the front surface and the back surface of the circuit board 1, an etching resist is laminated on the surface of the plating layer, exposed and developed to form a resist pattern, and a ferric chloride etching solution is formed. After etching is performed, the etching resist is peeled off to form the wiring pattern 2. The thickness of the wiring pattern 2 is about 35 μm. Although the circuit board 1 has two layers, it may be composed of a plurality of insulating substrate layers each having a wiring pattern in the inner layer.

Reference numeral 5 is a through hole penetrating the front surface and the back surface of the circuit board 1. As the diameter of the through hole 5,
For example, about 0.9 mm is used. (B) A curable conductive member is filled in the through hole 5.

Specifically, the through holes 5 are filled with a copper paste by a screen printing method. As the curable conductive member, a copper paste having the following composition is used. That is, as a binder component, 35 equivalents of bisphenol A diglycidyl ether having an epoxy equivalent of 173 g / equivalent and 100 parts by weight of the bisphenol A diglycidyl ether are used.
100 parts by weight of decyl glycidyl ether, 39 parts by weight of novolac-type phenol resin as a curing agent, and dendritic copper powder having an average particle size of 10.5 μm as copper powder, 100 parts by weight of a binder.
Add 360 parts by weight to parts by weight, and add 2-ethyl-4.
-Methylimidazole added to 2.8 parts by weight with respect to 100 parts by weight of binder is kneaded with a three-roll for 45 minutes to prepare a copper paste. 6 in the figure is a copper paste. By using the above-mentioned components as the copper paste, it is possible to improve the electrical connection when the lead wires of the components are bonded.

(C) Before the copper paste 6 is hardened,
The lead wire of the component is adhered to the copper paste 6. In the figure, 10 is a component, and 11 is a lead wire of the component 10. This lead wire 11 is inserted into the copper paste 6. And
When the copper paste 6 hardens, the copper paste 6 and the lead wire 1
1 and 1 are electrically adhered to each other so that conduction can be established. To cure the copper paste 6, use an air oven at 50 ° C-30.
And 180 ° C.-60 minutes. The lead wire cannot be inserted due to the increase in viscosity due to the hardening of the copper paste at room temperature for about one day after the start of hardening. In order to improve conduction between the lead wire 11 and the copper paste 6,
The surface of the lead wire 11 is treated in advance so that the surface of the lead wire 11 is not oxidized or dirt is attached, and then the lead wire 11 is inserted into the copper paste 6. As the component 10, for example, a resistor,
Capacitors, transistors, ICs, LSIs, etc. can be considered. Specifically, a lead-through resistor that is a mounting component (Matsushita Electronics Co., Ltd .: metal oxide film fixed resistor ERG-
1AN) is used.

According to this embodiment, the copper paste 6 filled in the through holes is used also as an adhesive for the component 10 in order to electrically connect the front surface and the back surface of the circuit board 1, which is different. Before the curable conductive member filled between two points is cured, the lead wires of the parts are adhered to
The curable conductive member for establishing the electrical connection between the points is also used for bonding the components, so that the utilization efficiency of the circuit board can be improved.

FIG. 3 is a diagram showing another embodiment of the present invention. The same components as those in FIG. 2 are denoted by the same reference numerals. The embodiment shown in the drawing shows a case where the locations where electrical connection is required are not the front surface and the back surface of the circuit board 1 but two points on the same surface. Two different through holes on the same surface are filled with the copper paste 6. Then, before the copper paste 6 is cured, the lead wire 11 of the component 10 is bent into an L shape and inserted into the copper paste 6. Then, when the copper paste 6 is hardened, the lead wire 11 of the component 10 and the copper paste 6 are adhered to each other and electrical continuity is established. Also in this embodiment, in order to improve the electrical connection between the lead wire 11 and the copper paste 6, it is desirable to perform the surface treatment of the lead wire 11 as described above.

According to this embodiment, the curable conductive member for making an electrical connection between two or more different points is also used for adhering components to improve the utilization efficiency of the circuit board. You can

The curable conductive member used in the present invention is
The present invention is not limited to the copper paste shown in the embodiment, and other types of curable conductive members having equivalent performance can be used.

The lead wire 11 of the component 10 may be bent at its tip end into an L-shape or a U-shape to prevent the lead wire 11 from coming off from the copper paste.

[0021]

[Embodiments] In the obtained multilayer circuit board, the through-hole resistances formed on the front and back of the circuit board are all 100 mΩ or less, and the connection strength (pull-out strength) between the lead wire of the component and the cured body of the copper paste is It was 3 Kgf, and it was confirmed that all were well connected.

[0022]

As described above in detail, according to the present invention, in a circuit board made of an insulating substrate on which a wiring pattern is formed, curing is performed at a place where electrical connection between two or more different points is required. And a second step of adhering a lead wire of a component to the curable conductive member before the curable conductive member formed in the first step is cured. By doing so, the lead wire of the component is adhered before the curable conductive member formed between two or more different points is cured, so that the utilization efficiency of the circuit board can be improved.

In this case, when it is necessary to electrically connect the front surface and the back surface of the circuit board, a through hole is opened, and the curable conductive member is filled in the through hole.
By bonding the lead wire of the component to the through hole filled with the curable conductive member, by bonding the lead wire of the component before the curable conductive member filled in the through hole is cured, It can be used for both electrical connection and component mounting,
The utilization efficiency of the circuit board can be improved.

Furthermore, by using a material obtained by kneading dendritic copper powder, an epoxy resin and a curing agent as the curable conductive member, electrical connection is achieved when the lead wires of the components are bonded. Can be good.

[Brief description of drawings]

FIG. 1 is a flowchart showing an embodiment of the method of the present invention.

FIG. 2 is a diagram showing an example of an embodiment of a manufacturing process of a circuit board according to the method of the present invention.

FIG. 3 is a diagram showing another embodiment of the present invention.

FIG. 4 is a diagram showing a configuration example of a conventional circuit board.

[Explanation of symbols]

 1 circuit board 2 wiring pattern 5 through hole 6 copper paste 10 parts 11 lead wire

Claims (3)

[Claims] 1. A first step of forming a curable conductive member at a location where electrical connection between two or more different points is required in a circuit board made of an insulating substrate on which a wiring pattern is formed, and the first step. The method for producing a circuit board, which comprises the second step of adhering the lead wire of the component to the curable conductive member before the curable conductive member formed in the step of 1. 2. When a front surface and a back surface of the circuit board need to be electrically connected, a through hole is opened, the curable conductive member is filled in the through hole, and the curable conductive member is filled. 2. The method for manufacturing a circuit board according to claim 1, wherein lead wires of components are adhered to the through holes. 3. The circuit according to claim 1, wherein the curable conductive member is obtained by kneading dendritic copper powder, epoxy resin and a curing agent. Substrate manufacturing method.