JPH11261204A - Circuit board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a circuit which can improve the adhesive property between its main body and a circuit pattern by mounting electronic parts on the circuit board by using a conductive adhesive and another circuit board which can improve the adhesive properties between its main body and a circuit pattern, between the circuit pattern and electronic parts, and between the main body and electronic parts by mounting the electronic parts on the circuit board by using the first-mentioned circuit board and conductive adhesive. SOLUTION: A circuit board, on the insulating main body 1 of which a conductive circuit pattern 2 is printed, is constituted of a circuit board provided with a notched portion 4 for exposing the mounting surface of the main body 1 at the terminal section 3 of the pattern 2 and another circuit board on which electronic parts 5 are fixed to the terminal section 3 of the first-mentioned circuit board with a conductive adhesive 6 stuck to the mounting surface of the main body 1 through the notched portion 4 of the terminal section 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a circuit board in which a circuit pattern made of a conductive metal, a conductive paint or a conductive paste is formed on an insulating substrate body.

[0002]

2. Description of the Related Art Recently, since lead is an environmentally hazardous substance, the use of solder has also been abolished in the field of circuit boards, and electronic components have been fixed to the terminal portions of circuit patterns with a lead-free conductive adhesive. The method has come to be used.
In addition, a circuit board using a conductive paste as a material of a circuit pattern, which has conventionally been impossible to solder by eliminating soldering, is being adopted.

[0003]

However, in general, it is difficult to say that the adhesion between the conductive metal constituting the circuit pattern and the organic conductive adhesive is good. The means had been stricken.
On the other hand, in the case of the conductive paint and the conductive paste, the resistance is firstly required to be low, and it is first required that screen printing is possible, and the adhesion to the substrate body is relatively neglected. That is the fact. Therefore, in a conventional circuit board, the adhesiveness between the substrate body and the circuit pattern is generally inferior to the adhesiveness between the circuit pattern and the conductive adhesive. This caused the problem of pattern peeling.

The present invention has been made in view of the above circumstances, and has been made in view of the above circumstances, and provides a circuit board capable of improving the adhesiveness between a board body and a circuit pattern by mounting an electronic component with a conductive adhesive. By performing mounting using a conductive adhesive using the circuit board, the circuit board with improved adhesion between the board body and the circuit pattern, between the circuit pattern and the electronic component, and between the board body and the electronic component is improved. An object of the present invention is to prevent peeling of a circuit pattern from a substrate body by providing.

[0005]

According to the present invention, there is provided a circuit board having a conductive circuit pattern printed on an insulating substrate body. The terminal portion is provided with a notch for exposing a mounting surface of the substrate body. The shape of the cutout is not particularly limited, but it is desirable that the portion exposing the mounting surface of the substrate main body is distributed evenly over the entire terminal portion. The material of the circuit pattern may be appropriately selected from existing materials such as a conductive metal, a conductive paint or a conductive paste. Note that the mounting surface is a surface on the side on which electronic components are mounted on the substrate main body.

Using the circuit board, an electronic component is fixed to a terminal portion thereof with a conductive adhesive that has been attached to a mounting surface of the board body through a cutout portion of the terminal portion, thereby forming a circuit pattern on the board body. The peel strength can be increased, and the peel strength can be further increased by selecting and combining materials made of materials having high mutual affinity as the substrate main body and the conductive adhesive.

[0007] As an example of a combination of the substrate main body and the conductive adhesive, if the substrate main body is made of an epoxy resin as a base material, a conductive adhesive mainly containing an epoxy resin is used. If the main body is made of a phenolic resin as a base material, the epoxy resin and the phenolic resin are mixed at a ratio of 3: 1.
It is also possible to use a mixed main material. As an example of the composition of the conductive adhesive, 50 to 55% of silver is blended with respect to 10 to 25% of the main material, and a solvent or other additives are added. Things are desirable.

[0008]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a circuit board according to an embodiment of the present invention. FIG. 1 shows the vicinity of a terminal portion 3 for mounting components on a circuit board according to the present invention. This circuit board is composed of a board body 1 made of an epoxy resin base material and a circuit pattern 2 made of copper foil.
The illustrated component mounting terminal portion 3 is a 1.2 mm × 1.2 mm rectangular terminal formed to surface mount an electronic component 5 having a lead wire 7 having a thickness of 0.65 mm. A rectangular notch 4 of 0.8 mm × 0.8 mm is formed at the center of the terminal 3, and the mounting surface of the board body 1 corresponding to the center of the terminal 3 is exposed.

In this example, the electronic component 5 is mounted on the circuit board.
In mounting, first, an epoxy-based conductive adhesive 6 is injected into the notch 4 of the component mounting terminal portion 3, the lead wire 7 of the electronic component 5 is placed thereon, and the conductive adhesive 6 is further removed. A process of attaching the lead wire 7 so as to wrap it and leaving the lead wire 7 to cure is performed. A comparison between the circuit board on which the electronic component 5 is mounted and the conventional circuit board on which the same electronic component 9 is mounted on the terminal portion 8 having no notch as shown in FIG. When a large external force is applied to the conventional circuit board, the circuit pattern peels off at the interface between the terminal portion 8 and the board body 10 to cause damage to the circuit pattern.
In the circuit board according to the above embodiment, the lead wire 7 was separated from the cured conductive adhesive 6, and the peeling as described above did not occur.

A comparison similar to the above is made up of a substrate main body 1 made of a phenolic resin as a base material and a circuit pattern 2 formed by printing a material containing 55% silver by using a phenolic resin as an organic component. The test was performed on a circuit board having a terminal portion 3 having a rectangular shape of 1.2 mm × 1.2 mm and having a rectangular cutout 4 of 0.8 mm × 0.8 mm formed in the center thereof. At that time, the conductive adhesive 6 was based on a mixture of an epoxy resin and a phenolic resin. As a result of the comparison, in the conventional circuit board, the interface between the circuit pattern 11 and the substrate main body 10 was peeled off by a force of about 3 kg, whereas in the case of the above embodiment, the interface between the circuit pattern 2 and the substrate main body 1 was separated. About 4 kg of force was required to peel.

[0011]

As described above, according to the present invention, the conductive adhesive comes into direct contact with the mounting surface of the substrate main body through the cutout of the terminal portion of the circuit pattern formed on the substrate main body. In general, in a conductive adhesive in which a conductive material such as silver is mixed with an organic material, the organic material plays a bonding function of the adhesive, and the bonding strength between the organic materials is determined by a circuit pattern. It is much stronger than the adhesive strength between the conductive metal or the like material and the organic material. In addition, the difference in the coefficient of thermal expansion at the interface between the two layers to be bonded to each other is smaller in the case of the organic material than in the case of the conductive metal or the like and the organic material, and the distortion at the bonding interface due to a temperature change is reduced.

According to the first aspect of the present invention, there is provided a circuit board having a terminal portion having a shape capable of deriving an effect of firmly fixing a circuit pattern to a board body by the above-described operation by mounting an electronic component with a conductive adhesive. Is provided,
By mounting the electronic component as in claim 2, the conductive adhesive that holds the electronic component, adheres to the substrate body, and is hardened causes the strong adhesive force between the organic materials through the cutouts to reduce the electronic component of the circuit pattern. It also plays the role of an anchor that supplements the peel strength of the component mounting terminals, and as a result, it is possible to increase the adhesiveness between the board body and the circuit pattern, between the circuit pattern and the electronic component, and between the board body and the electronic component. The bonding strength is not greatly affected by the temperature change of the electronic component mounting terminal. And the effect is claimed in claim 3
By selecting and combining materials composed of mutually compatible materials as the substrate main body and the conductive adhesive, as in the case of a circuit board, the above-described effect is further enhanced, and in particular,
A high practical effect can be achieved in a surface mount circuit board in which the component surface and the solder surface are on opposite sides and there is no such thing as a lead wire passing through a through hole and serving as an anchor. Furthermore, in addition to contributing to the reduction of the use of lead, which is an environmentally hazardous substance, in the field of circuit boards, it is possible to use a conductive paste or the like that could not be soldered in the past. The choices will be further expanded.

[Brief description of the drawings]

FIGS. 1A and 1B are a plan view and a cross-sectional view illustrating an example of the vicinity of a terminal portion of a circuit board according to the present invention.

FIG. 2 is a cross-sectional view showing an example of mounting an electronic component on a circuit board according to the present invention.

FIG. 3 is a cross-sectional view showing an example of mounting an electronic component on a circuit board according to the present invention.

FIGS. 4A and 4B are plan views showing an example of the vicinity of a terminal portion of a circuit board according to the present invention.

FIG. 5 is a cross-sectional view showing an example of mounting electronic components on a conventional circuit board.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Board main body 2 Circuit pattern 3 Terminal part 4 Notch part 5 Electronic component 6 Conductive adhesive

Claims (3)

[Claims] 1. A circuit board having a conductive circuit pattern (2) printed on an insulative substrate body (1), the terminal part (3) of the circuit pattern (2) being connected to the substrate body (1). A) a circuit board provided with a notch (4) for exposing the mounting surface. 2. An electronic component (5) is attached to said terminal portion (3).
Substrate body (1) through notch (4) of terminal portion (3)
2. The circuit board according to claim 1, wherein said circuit board is fixed with a conductive adhesive attached to said mounting surface. 3. The circuit board according to claim 2, wherein said board body (1) and said conductive adhesive (6) are made of a material having high mutual affinity and selected and combined.