JPH0740624B2 - Low pitch printed wiring board and manufacturing method thereof - Google Patents

Abstract

PURPOSE:To provide a low-pitch printed wiring board which is equipped with a stable conductive line even if a wire pattern is highly reduced in pitch in the printed wiring board used for connecting between electric and electronic parts and a method for fabricating the same. CONSTITUTION:A fine groove 2 is provided along a position to be a conductive line 3 on a surface of an insulating base 1 at least on a part where a wire pattern is to be formed and conductive paste is printed to form a low-pitch printed wiring board, and a method for fabricating the board is provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a low pitch printed wiring board used for wiring electric and electronic parts to each other and a method for manufacturing the same.

[0002]

2. Description of the Related Art Printed wiring boards are used for wiring between electric and electronic parts, and their manufacture has hitherto been carried out by printing conductive lines on the surface of an insulating base material with an ink made of a conductive paste. There is.

[0003]

However, in recent years, with the miniaturization and refinement of electric and electronic devices, the wiring pitch has become finer. Generally, a paste having conductivity is poor in transferability, and the printing pitch has a limit of about 0.2 to 0.3 mm. Even if the paste is above this limit, ink drips at a pitch of about 0.4 mm or less. When the viscosity of the ink is increased in order to prevent the leak and to cause the leak, there is a defect that the ink is worn out and the wire is broken and the yield is extremely deteriorated. As another method, there is a method of forming a wiring pattern by adhering a metal foil to an insulating base material and performing etching, but this has a disadvantage in that the number of steps is large and the material is expensive.

[0004]

The inventor of the present invention has found that the phenomenon of sagging or scraping of the conductive paste, which has made it difficult to form a low-pitched wiring pattern, is due to the wetting property of the conductive paste with respect to the base material. Focusing on this phenomenon, in order to prevent such a phenomenon, the conductive line has a good wetting property, and in order to prevent a leak, if the wetting property is deteriorated in the direction perpendicular to the conductive line, a low pitch wiring pattern is formed. The present invention has been completed with the idea that it can be easily formed by printing, and the first invention is a printed wiring board in which a conductive pattern is printed on a surface of an insulating base material with a conductive paste to form a wiring pattern, A low-pitch printed wiring board, characterized in that at least a surface on which a wiring pattern is formed is provided with fine grooves along the conductive lines.
According to the invention, a fine groove is provided along a predetermined position of the conductive line on at least a portion of the surface of the insulating base material where the wiring pattern is to be formed, and the conductive line is printed with a conductive paste to form a desired wiring pattern. And a method of manufacturing a low-pitch printed wiring board.

As the insulating base material used in the present invention, conventionally known ones can be used. As the rigid base material, glass epoxy, glass or phenol resin can be used, and as the flexible base material, a polyester film such as PFT, PEN or PBT can be used. Examples include polyimide film and phenol resin-impregnated paper. If the width of the fine grooves formed on the surface of the base material is larger than the pitch of the wiring pattern, that is, the distance between the conductive lines, it is meaningless to prevent leakage. / 10
The following is desirable.

Further, the closer the distance between the grooves is, the better, but the upper limit is preferably less than the distance between the conductive lines, and more preferably less than 1/10 of the distance between the conductive lines. It is not necessary that the grooves communicate with each other along the conductive lines, and it is sufficient that the grooves are oriented along the conductive lines, and the degree of orientation is such that the deviation from the conductive lines at both ends of one groove is 1/10 of the distance between the conductive lines. The following is recommended. If the depth of the groove is too shallow, the wetting of the conductive paste cannot be controlled, and if it is too deep, the strength of the base material is weakened. Therefore, it is preferably 0.1 μm or more and 1/2 or less of the thickness of the base material. Further, regarding the control of wetting, the angle of the side surface of the groove is important, and the closer to 90 ° to the substrate surface direction, the better.

In order to form such a groove, it is preferable to process it in a certain direction with a laser beam, but in addition to this, a method of sandblasting by sanding the surface of the base material with sand for polishing, sandpaper, wire brush, etc. A method of rubbing in a certain direction so that the angle with the surface of the substrate is 30 ° or more,
Examples include a method of transferring the pattern of the groove formed in the mold to a film by pressing. 1 (a), b),
The shapes of various grooves 2 provided on the surface of the insulating base material 1 are shown in (c), (d), and (e).

To print the conductive paste on the groove, a method using a roll such as screen printing or gravure printing is used. Conductive paste, carbon, gold, conductivity imparting powder such as silver, polyester resins, polyurethane resins, the binder such as epoxy resin, is contained 40 to 95 wt%, the specific resistance and 10 ⁴ ~10 ⁰ Ω · cm It is sufficient that the insulating base material has a good wetting property. The wetting property of the conductive paste by the above-mentioned insulating base material is almost controlled by the viscosity of the conductive paste, and specifically, it is preferable to be 50 to 500 poise. FIG. 2 shows a printed wiring board according to the present invention.

The printed wiring board according to the present invention is shown in FIGS.
As shown in FIG. 2, by providing an anisotropic conductive adhesive layer 5 in which conductive particles 4 are dispersed in an insulating adhesive on the surface on which the conductive line 3 is formed, it can be used as a heat seal connector. , PCB, FPC, etc. are used for connection between electric circuits.

[0010]

EXAMPLE A surface of a PET film having a thickness of 25 μm was
Rubbing a No. 000 paper file with a pressure of about 5 kg / cm ² in one direction, width 0.5-3 μm, depth 0.1-2 μm
A large number of grooves were formed. After cleaning this surface while applying an electrostatic discharge blow, a silver-carbon conductive paste having a viscosity of 200 poise was printed on a screen having a conductive line width of 0.1 mm and a line pitch of 0.2 mm, and then dried to obtain a length. A low pitch printed wiring board having a width of 40 mm and a width of 20 mm and consisting of 100 conductive lines was obtained. When the width of each conductive line was measured, the minimum value was 80 μm and the maximum value was 11
6 μm, resistance is 25.6 Ω on average, 31.0 at maximum
There was no leak between the conductive lines at Ω.

[0011]

As described above, according to the present invention, the number of disconnection of the conductive lines is small, the resistance value is stable, and there is no leak between the conductive lines. Therefore, a printed wiring board having a finer pitch can be easily produced with a high yield. Since the conductive paste can be produced and printed with fine grooves formed thereon, the adhesion of the base material and the conductive line is good due to the anchor effect, the bending resistance is improved, and the printed wiring board of the present invention can be manufactured. By using it, it has become possible to highly miniaturize and refine electric and electronic equipment.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of various grooves according to the present invention.

FIG. 2 is a partially enlarged perspective view of an embodiment of a low pitch printed wiring board according to the present invention.

FIG. 3 is a plan view of an embodiment of a low pitch printed wiring board according to the present invention.

FIG. 4 is an enlarged cross-sectional view taken along the line AA ′ of FIG.

[Explanation of symbols]

 1 Insulating Substrate 2 Groove 3 Conductive Line 4 Conductive Particle 5 Anisotropic Conductive Adhesive Layer

Claims (2)

[Claims] 1. A printed wiring board in which a wiring pattern is formed by printing a conductive line on a surface of an insulating base material with a conductive paste, and at least a surface on which the wiring pattern is formed is provided with fine grooves along the conductive line. A low pitch printed wiring board characterized by being provided. 2. A fine groove is provided along a predetermined position of the conductive line on at least a portion of the surface of the insulating base material where the wiring pattern is to be formed, and the conductive line is printed with a conductive paste to form a desired wiring pattern. A method for manufacturing a low-pitch printed wiring board, comprising: