JPH0424859B2 - - Google Patents

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a connection method for electronic components that connects a wiring pattern formed on a circuit board and a connecting portion of an electronic component using an anisotropic conductive adhesive. Regarding the method.

(Prior Art) Conventionally, there are devices that improve the reliability of contacts and connection terminals of wiring patterns formed on circuit boards by applying surface treatments such as Au plating or Sn plating. Recently, as shown in FIGS. 3 and 4, a conductive ink film (overcoat layer) c is printed on the wiring pattern b formed on the circuit board a to form the wiring pattern b. By overcoating, there are some cases in which the same effect as the plating treatment described above can be obtained. Then, an anisotropic conductive adhesive d is applied onto the circuit board a on which the ink film c is printed, and an electronic component e is mounted on the anisotropic conductive adhesive d. It is connected to lead terminal f.

(Problems to be Solved by the Invention) However, in the above-described connection method, resistance increases at the interface between the wiring pattern b and the overcoat layer c, resulting in an electrical connection between the wiring pattern b and the lead terminal f of the electronic component e. There was a problem that the reliability of the system decreased.

(Means for Solving the Problems) A method for connecting electronic components according to the present invention includes forming a wiring pattern on a circuit board, forming a conductive overcoat layer on the wiring pattern, and forming a conductive overcoat layer on the wiring pattern. An anisotropic conductive adhesive is applied to the upper surface of the circuit board that covers the circuit board, and electronic components are mounted on the anisotropic conductive adhesive by thermocompression bonding, and the connection parts of the electronic components and the wiring pattern are electrically connected. In this connection method, an anisotropic conductive adhesive to which a solvent for melting the overcoat layer is added is used as the anisotropic conductive adhesive.

(Function) When an anisotropic conductive adhesive is applied to the top surface of the circuit board including the wiring pattern and overcoat layer,
The overcoat layer is melted and softened by the solvent added to the anisotropic conductive adhesive, and the anisotropic conductive filler in the anisotropic conductive adhesive penetrates into the overcoat layer. When the electronic component is mounted by thermocompression bonding in this state, the overcoat layer is softened and the connecting portion of the electronic component and the wiring pattern are directly connected by the anisotropically conductive filler.

(Example) An example of the present invention will be described below with reference to FIGS. 1 and 2.

In Fig. 1, 1 is a solid or flexible circuit board, and Cu,
A wiring pattern 2 made of a metal such as Al or Ag is formed, and a conductive overcoat layer 3 that is easily melted in an acetate-based or ketone-based solvent is formed on the wiring pattern 2.

The overcoat layer 3 is formed using a paste-like material in which a conductive filler such as carbon is dispersed in a binder and contains a solvent in advance. Further, it is desirable that the binder is made of thermoplastic resin. This conductive paste is applied onto the wiring pattern 2 by a method such as printing, and then dried to volatilize the solvent to form an overcoat layer 3.

Next, an anisotropic conductive adhesive 4 is applied onto the circuit board 1 including the wiring pattern 2 and the overcoat layer 3. Here, the anisotropic conductive adhesive 4 is a material that has a property of having no conductivity in the horizontal direction but is conductive only in the vertical direction, and is generally a material that is bonded by thermocompression bonding.

The anisotropic conductive adhesive 4 includes an overcoat layer 3
A solvent that easily melts the overcoat layer 3, for example,
30 to 60% of the same type of solvent as that contained in the product is added. Therefore, this anisotropic conductive adhesive 4
can be applied onto the circuit board 1 by a method such as printing. Note that the anisotropic conductive adhesive 4 may be either a thermoplastic type or a thermosetting type.

In this way, when the anisotropic conductive adhesive 4 is applied, the overcoat layer 3, which has been evaporated once, will come into contact with the solvent again, and the overcoat layer 3 will melt and soften, causing the anisotropic The anisotropic conductive filler in the conductive adhesive 4 has penetrated into the overcoat layer 3. By drying in this state, the solvent unnecessary for adhesion is volatilized and removed, and the circuit board 1 having the structure shown in FIG. 2 is formed.

On this circuit board 1, various electronic components 5 such as a liquid crystal display element, a flat package LSI, an LED, a capacitor, etc. are mounted. That is, the circuit board 1
The upper wiring pattern 2 and the connection terminal 6 of the electronic component 5 are aligned and bonded by thermocompression bonding.

In this way, the overcoat layer 3 into which the anisotropic conductive filler in the anisotropic conductive adhesive 4 has penetrated is bonded to the electronic component 5 because the binder is softened by thermocompression bonding and pressure is applied thereto. The terminal 6 is compressed to penetrate into this overcoat layer 3,
The structure is such that the connection terminal 6 and the wiring pattern 2 are directly connected via an anisotropic conductive filler. This structure is shown in FIG.

The electrical connection structure obtained by this method is
It has low resistance and high reliability. Furthermore, since soldering is not required to mount the electronic component 5 on the circuit board 1, it is also possible to mount the electronic component on a circuit board with low heat resistance such as a polyester base material or a carbon printed board. , it is possible to reduce costs.

(Effects of the Invention) As described above, according to the method for connecting electronic components according to the present invention, it is possible to obtain a low resistance and highly reliable electrical connection structure for electronic components.

[Brief explanation of drawings]

1 and 2 show an example of the method for connecting electronic components according to the present invention, FIG. 1 is a vertical cross-sectional view of electronic components mounted on a circuit board by this method, and FIG. FIGS. 3 and 4 are longitudinal cross-sectional views of a circuit board on which a wiring pattern and an overcoat layer are formed with an anisotropic conductive adhesive applied thereto, showing an example of a conventional method for connecting electronic components. The figure is a vertical cross-sectional view of an anisotropic conductive adhesive coated on a circuit board on which wiring patterns and overcoat layers have been formed, and Figure 4 is a vertical cross-sectional view of electronic components mounted on this circuit board. be. 1... Circuit board, 2... Wiring pattern, 3...
Overcoat layer, 4... Anisotropic conductive adhesive, 5
...Electronic components, 6...Connection terminals.

Claims (1)

[Claims] 1. A wiring pattern is formed on a circuit board, an overcoat layer of conductive pillars is formed on the wiring pattern, and an anisotropic conductive adhesive is applied to the upper surface of the circuit board covering the overcoat layer. and mounting an electronic component on the anisotropic conductive adhesive by thermocompression bonding to electrically connect a connecting portion of the electronic component and the wiring pattern, the method comprising: A method for connecting electronic components, characterized in that an anisotropic conductive adhesive to which a solvent for melting the overcoat layer is added is used.