JPS60170995A - Circuit board - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] Industrial Application Field The present invention is applicable to television, stereo, video (!l'(ID
This invention relates to wiring boards mainly used in general electrical products.

Conventional configurations and their problems In recent years, as devices have become smaller and lighter, the wiring boards installed inside them have also been required to be smaller, and together with the miniaturization of components, high-density packaging has begun to be attempted. .

Conventionally, most of the methods for connecting small chip components such as resistors and transistors to printed wiring boards have been done by soldering.

To give an example, first, adhesive for fixing the components is supplied to the position on the wiring board where the components are to be mounted, then the components are mounted, the adhesive is solidified, and the components do not move or fall off. There is a method of soldering a wiring board by immersing it in a solder bath containing molten solder, or by placing its surface in contact with a jet zone where molten solder is flowing.

According to such a method, it is first necessary to drop the adhesive onto a predetermined location, and then the adhesive must be solidified after the parts are mounted, which increases the number of production steps. Also, if the amount of adhesive is too large, the adhesive will leak,
If the soldering penetrates into the electrode, the soldering becomes a cause of failure. Furthermore, since the parts are directly exposed to the high heat of the molten solder, there is a problem that the performance of the parts deteriorates due to the heat.

On the other hand, since molten solder is soldered by a mechanism in which the solder is brought into contact with the electrode and the solder is supplied, the surface tension of the solder is large on the electrode located in a place where the distance between parts is narrow. There is no solder intrusion and therefore no soldering.

Some of the shredded chip components have electrodes formed on the bottom surface of the component body, and it is virtually impossible to solder such components by the method described above. When the pitch of the twisted component terminals and the pattern interval become narrower, solder bridging occurs and high-density packaging cannot be accommodated.

Another example of soldering of components on a board is to supply the required amount of cream solder to the electrodes using screen printing or a dispenser in advance, then mount the components, and solder them using an atmospheric furnace or infrared rays. There is a method in which the solder cream is melted and solidified by heating it in a furnace or the like and then soldering the parts.

According to this method, since cream solder is supplied by screen printing, it is possible to place the solder Mk relatively accurately and finely in the N degree position, so it is compatible with higher-density component mounting than the above-mentioned method. can. However, after the cream solder is placed in a designated place, ``sag'' and ``bleeding'' of the cream solder always occur, so when the mounting density becomes high and the electrode spacing becomes narrow, the cream solder ``sag'' and ``bleeding'' will cause the cream solder to sag. A phenomenon occurs in which the gap between the cream solder becomes extremely narrow or crosslinks between the electrodes, and when such a state is heated and the cream solder is melted and solidified, solder bridges occur between the electrodes.Therefore, the packaging density is Even if the cream solder sag, it is limited to a density that ensures a safe distance.

In addition, no special adhesive is used to fix the parts, but the adhesiveness of the cream solder is used to hold them in place, so when the cream solder melts and fluidizes due to heating, the parts move due to the movement of the cream solder.
There are problems such as deviation from the electrode, resulting in poor soldering, and short circuit with the @9 electrode.

OBJECTS OF THE INVENTION The present invention eliminates the drawbacks of the prior art as described above and provides a wiring board that enables high-density and highly reliable component mounting.

Structure of the Invention The wiring board of the present invention includes a wiring board having a wiring pattern formed on the surface of the board, an anisotropic conductive film having conductivity in the film thickness direction on the wiring pattern, and further comprising: Electronic components are mounted and fixed on a conductive film to provide electrical continuity between the wiring pattern and the electronic components. Furthermore, since electronic components are not exposed to high temperatures like soldering, it is possible to achieve highly reliable and high-density component mounting with extremely simple work without introducing deterioration of component performance due to heat. This is the conflict that made it possible.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is an exploded configuration diagram of an embodiment of the present invention. Reference numeral 1 is a wiring board, and 2 is a wiring pattern formed on the surface of the wiring board 1. 3 is an anisotropic conductive film, and 4 is a chip-shaped electronic component. Electrodes 4a are formed at both ends of the chip component 4. FIG. 2 shows the state after the components are mounted. An anisotropic conductive film 3 is attached so as to cover the wiring pattern 2 formed on the surface of the wiring board 10 without being separated, and a chip component 4 is mounted on the anisotropic conductive film 3 at a position corresponding to the wiring pattern 2. The anisotropic conductive film 3 is made to contain a thermosetting adhesive and/or both that are cured by ultraviolet irradiation to provide adhesive properties at room temperature. Press to temporarily fix. The wiring board 1 on which the chip components 4 are temporarily fixed in this manner is subjected to force, heat or ultraviolet irradiation to harden the adhesive and permanently fix the mounted components. Since the anisotropic conductive film 3 is electrically connected only in the film thickness direction, by mounting and pressing the chip component 4, the electrical connection between the wiring pattern 2 and the electrode 4a of the chip component 4 is already established. Completed.

Effects of the Invention As is clear from the above explanation, the present invention uses an anisotropic conductive film and imparts adhesive properties to it, thereby eliminating the need for electrical and mechanical connections of parts using solder as in the past. It is said that Therefore, short circuits due to solder bridges and conduction defects due to insufficient solder are completely eliminated, and packaging density can be dramatically improved. In addition, since the mounted components are temporarily fixed, there is no distortion or lifting of the mounted components, which sometimes occurs during soldering, and components can be mounted extremely easily on both sides of the board, making it possible to easily mount components on both sides of the board. It won't fall off. Since the parts are not exposed to high temperatures as in the case of soldering, there is no deterioration of the parts' characteristics due to heat, and the structure is extremely simple, and it is possible to produce highly reliable, high-density parts in a short process. The present invention provides a wiring board that can be mounted.

[Brief explanation of drawings]

FIG. 1 is an exploded configuration diagram showing one embodiment of the wiring board of the present invention, and FIG. 2 is a sectional view showing the state after components are mounted on the wiring board. 1... Wiring board, 2... Wiring pattern, 3...
...Anisotropic conductive film, 4...Chip parts,
4a... Electrode.

Claims (1)

[Scope of Claims] (1) An anisotropic conductive film having conductivity in the film thickness direction is pasted on the wiring pattern of a wiring board having a wiring pattern formed on the surface of the board, and A wiring board characterized in that electronic components are mounted and fixed on an electrical film, and electrical conductivity is provided only in the film thickness direction between the wiring pattern and the electronic components. (2) The wiring board according to claim 1, wherein the anisotropic conductive film has adhesive properties. (i) The wiring board according to claim 1, wherein the anisotropic conductive film contains a thermosetting resin. (4) The wiring board according to claim 1, wherein the anisotropic conductive film contains a photocurable resin.