JP2000013017A - Manufacture of flexible wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a flexible wiring board wherein a conductive paste through a through hole is prevented from sticking to a print table or stopping a sucking hole, for improved productivity. SOLUTION: At through hole printing, a gas-permeable sheet 5 is tight-fitted to the rear surface of a flexible insulating film substrate 1, a wiring pattern 8 is printed on a specified position of the surface with a conductive paste 9 while sucked and fixed to a print table 6, and after the conductive paste 9 is allowed to flow in a through hole 3 so that wring patterns 8 and 2 on front and rear surfaces are connected, the gas-permeable sheet 5 is separated, thus the conductive paste 9 infiltrating into the rear surface of the flexible insulating film substrate 1 from the through hole 3 is absorbed in the gas-permeable sheet 5 without reaching the print table 6, resulting in no conductive paste sticking to the print table.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a flexible wiring board used for assembling an electronic device on which electronic elements are mounted.

[0002]

2. Description of the Related Art A circuit board constituting an electronic device is a circuit board in which a wiring pattern is formed on an insulating substrate by using a conductive paste by printing or the like, and electronic elements such as a transistor, a resistor, a capacitor, and an IC circuit are attached thereto. However, in recent years, electronic devices have become smaller and more sophisticated, and liquid crystal display panels (LC
D) As display devices such as plasma displays (PDPs) have become larger and more colorized, the pitch of wiring patterns formed on the substrate has been on the order of 0.3 mm to 0.2 m.
m, and even 0.1 mm. Along with this, a flexible wiring board in which a wiring pattern is formed on both sides of a flexible insulating film with a conductive paste on the both sides of a flexible insulating film, and the wiring patterns on the front and back are electrically connected by through-hole printing has been frequently used. .

A conventional method for manufacturing a flexible wiring board is to form a wiring pattern on the back surface of the substrate by screen printing or the like using a conductive paste, and to provide a through hole in a conductive portion with the wiring pattern formed on the front surface. An insulating film substrate is placed on a printing table of a printing machine, and is sucked and fixed on a printing table by a vacuum pump or the like from a suction hole of the table, and a flexible insulating film substrate is formed with a conductive paste by screen printing or the like. Print the wiring pattern on the surface, let the conductive paste flow into the through-holes, electrically connect the wiring patterns on the front and back, so-called through-hole printing, then put in the dryer, the conductive paste that became the wiring pattern Has been dried.

[0004]

However, in the above-described conventional through-hole printing, the conductive paste that has wrapped around the through-hole blocks the suction holes on the printing table,
Each time before printing starts, conductive paste that has closed the suction hole or conductive paste that has adhered to the table has to be transferred to the back side of the flexible insulating film of the sheet to be printed next and then printed to cause printing failure. Sex paste had to be removed.

If the conductive paste is left on the printing table, it is transferred to the back surface of the flexible insulating film. If there is a wiring pattern in the transferred portion, the wiring board becomes defective. I will. The object of the present invention has been made in view of the above points, and it is possible to prevent adhesion of a conductive paste from a through hole to a printing table and to block a suction hole, thereby improving production efficiency. An object of the present invention is to provide a method for manufacturing a wiring board.

[0006]

According to the present invention, at the time of the above-mentioned printing of a through hole, a permeable sheet is brought into close contact with the back surface of a flexible insulating film substrate, and is adsorbed and fixed on a printing table while being fixed at a predetermined position on the front surface. Then, a wiring pattern is printed with a conductive paste, the conductive paste is caused to flow into the through holes, the wiring patterns on the front surface and the back surface are connected, and then the sheet is separated. When printing through-holes, the air-permeable sheet is adhered to the back surface of the flexible insulating film substrate, and placed on the printing table, so that the conductive paste wrapped around the back surface of the flexible insulating film substrate from the through-holes Is absorbed by the air-permeable sheet and does not reach the printing table, so that the conductive paste does not adhere to the printing table, and the problem of the present invention is solved.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic partial cross-sectional view after completion of through-hole printing by the method for manufacturing a flexible wiring board according to the present invention. In FIG. 1, reference numeral 1 denotes a flexible insulating film substrate, on the back surface of which a wiring pattern 2 is formed by a conductive paste by screen printing or the like, and the conductive paste flows into a through-hole 3 provided at a place where the surface is electrically connected to the front surface. Have been. In the manufacturing method of the present invention, the flexible insulating film substrate 1 is placed on a printing table 6 of a printing machine in a state where a breathable sheet 5 having a large number of ventilation holes 4 is adhered to the back surface of the flexible insulating film substrate 1, The flexible insulating film substrate 1 is sucked and fixed on the printing table 6 by suction from the suction hole 7 by means such as a vacuum pump.

In this state, when the wiring pattern 8 is printed at a predetermined position on the surface of the flexible insulating film substrate 1 with a conductive paste by screen printing or the like, the conductive paste flows into the through-hole 3 and becomes flexible. The conductive paste 9 connected to the wiring pattern 2 on the back surface of the insulating film 1 and further wrapping around the back surface of the flexible insulating film 1 is adsorbed on the air-permeable sheet 5. The conductive paste 9 adsorbed on the air permeable sheet 5 is absorbed inside even if it enters the air holes 4, and does not reach the back surface of the air permeable sheet 5. After the wiring pattern 8 is printed, the air permeable sheet 5 is separated from the flexible insulating film substrate 1, the flexible insulating film substrate 1 is conveyed to a dryer, and the conductive paste serving as the wiring pattern is dried. A flexible wiring board is manufactured.

In the conventional through-hole printing, the conductive paste adheres to the printing table, and the time required for removing the conductive paste is not always constant. It is not possible to perform the through-hole printing on the flexible wiring board at regular intervals. Although it was possible, according to the present invention, since the conductive paste does not adhere to the printing table, there is no need to remove the conductive paste, and printing can be performed at regular intervals, so that the production efficiency is greatly improved.

Examples of the flexible insulating film used in the present invention include polyesters such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT) and polyethylene naphthalate (PEN), polyimide, polycarbonate, polyphenylene sulfide and the like. However, a polyester film is preferable in terms of bending resistance, temperature change, dimensional stability against external force, and adhesion of the conductive paste, and the thickness is preferably 10 to 50 μm.

As the conductive paste, 40 to 95% by weight of a conventionally known conductive powder such as carbon, gold, silver, copper or nickel is added to a binder such as polyester resin, polyurethane resin, epoxy resin or acrylic resin. be contained, the volume resistivity of ¹⁰ × 10 -3 ~10 × 10 ⁰
Ω · cm is preferable. The conductive paste used for the wiring pattern on the front and back of the flexible insulating film is
The same or different conductive paste may be used, but the conductive paste flowing into the through-hole is preferably the same component as the binder of the conductive paste on the front and back sides from the viewpoint of conduction stability due to compatibility.

The air-permeable sheet has a large number of air holes, is air-permeable, needs to be smooth so as not to adversely affect printing, preferably has a retention particle diameter of 1 to 5 μm, and has a thickness of: If it is too thick, handling will be troublesome.If it is too thin, the conductive paste transferred to the paper will wrap around the back of the paper,
0.2 to 1.0 mm is preferred. Sheets satisfying such conditions are preferably paper, particularly filter paper, but are not limited thereto, and any sheet, such as a nonwoven fabric, may be used as long as it satisfies the above conditions. good.
The through hole provided in the wiring board has a diameter of 0.5 m
When the diameter is smaller than m, the needle for opening the through hole is liable to be bent due to insufficient strength, and when the diameter is larger than 2.0 mm, it is too large from the viewpoint of wiring density.

The flexible wiring board obtained by the present invention is obtained by dispersing conductive particles on both sides of an insulating binder made of an anisotropic conductive adhesive, for example, a thermoplastic component or a thermosetting component. By applying such a material, it can be used as a heat seal connector between substrates. In this case, as the conductive particles, furnace black, channel black, carbon particles such as carbon black such as acetylene black or graphite, gold,
Metal particles such as silver, copper, nickel, and aluminum, and plastic particles whose surfaces are plated with metal are used.

[0014]

EXAMPLE The present invention was carried out using the apparatus shown in FIG. For the long flexible insulating film to be the flexible wiring board, PET having a thickness of 25 μm was used, and for the conductive paste, the conductive powder was silver and the binder was polyester resin. The breathable sheet has a retention particle diameter of 4 μm.
m, a long filter paper having a thickness of 0.23 μm was used.

First, a wiring pattern is continuously printed on the back surface with a conductive paste by screen printing, and a through hole having a diameter of 1.0 mm is provided by a needle at a predetermined conduction point with the front surface. A roll body 12 on which a film was wound was prepared. The roll body 12 is fixed to a rotating shaft 14 attached to a delivery unit 13, and the flexible insulating film 11 unwound from the roll body 12 is sandwiched between a driving roller 15 and a rotating roller 16 and transported to a screen printing machine 17. did.

On the other hand, a roll body 19 on which a long permeable sheet 18 is wound is prepared, and the roll body 19 is fixed to a rotating shaft 21 attached to a delivery section 20, and the permeable sheet 18 unwound therefrom is prepared. Then, the flexible insulating film 11 was sandwiched between the driving roller 15 and the rotating roller 16, and was brought into close contact with the back surface of the flexible insulating film 11. The flexible insulating film 11 is conveyed to the screen printing machine 17 in a state in which the flexible insulating film 11 is in close contact with the air permeable sheet 18, and the air permeable sheet 18 is placed on the print table 22 with the air permeable sheet 18 facing downward, and the suction of the print table 22 is performed. It was sucked and fixed by a vacuum pump through a hole (not shown).

Next, a wiring pattern is printed with a conductive paste on a predetermined position on the surface of the flexible insulating film 11 by a screen printing machine 17 and the wiring patterns on the front and back sides are connected. The permeable film 11 and the air permeable sheet 18 were passed between the tension roller 23 and the drive roller 25. Thereafter, the breathable sheet 18 is separated from the flexible insulating film 11, and the breathable sheet 18 is
The flexible insulating film 11 is wound around a rotary shaft 26 attached to the flexible wiring board 4, passes through a buffer section 27, is conveyed to a dryer 28, and is dried by a conductive paste serving as a wiring pattern. A substrate was prepared.

In the present invention, through-hole printing was performed 100 times continuously. As a result, the cycle time was constant at 20 seconds / sheet, but the same thickness was obtained by the conventional method for manufacturing a flexible wiring board. When the PET sheet was subjected to through-hole printing 100 times, the cycle time was not constant as is clear from the graph shown in FIG. 3, and the average cycle time was 34.5 seconds / sheet, and the breathable sheet was used. The value was worse than in the case of the present invention. That is, when through-hole printing was performed by the method for manufacturing a flexible wiring board according to the present embodiment, productivity was improved by about 70% as compared with the conventional method.

[0019]

According to the present invention, continuous printing can be performed at a constant interval, and the conductive paste does not adhere to the print table. Therefore, there is no need for the operator to remove the conductive paste adhered to the print table. Thus, the productivity is improved and the burden on the worker is reduced.

[Brief description of the drawings]

FIG. 1 is a schematic partial cross-sectional view after completion of through-hole printing according to the present invention.

FIG. 2 is a schematic explanatory view showing an embodiment of the present invention.

FIG. 3 is a graph showing a cycle time of a conventional through-hole printing.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Flexible insulating film 20 Sending part 2, 8 Wiring pattern 21 Rotating shaft 3 Through hole 22 Printing table 4 Vent hole 23 Pulling roller 5 Breathable sheet 24 Winding part 6 Printing table 25 Drive roller 7 Suction hole 26 Rotating shaft REFERENCE SIGNS LIST 9 conductive paste 27 buffer unit 11 flexible insulating film 28 dryer 12 roll body 13 delivery unit 14 rotation shaft 15 drive roller 16 rotation roller 17 screen printer 18 breathable sheet 19 roll body

Claims (2)

[Claims] 1. A flexible insulating film substrate having a wiring pattern and a through hole formed on a back surface thereof is fixed on a printing table by adhering a gas permeable sheet to the back surface of the substrate, and is fixed to a predetermined position on the front surface. A flexible wiring board, comprising: printing a wiring pattern with a conductive paste, flowing the conductive paste into the through holes, connecting the wiring patterns on the front surface and the back surface, and separating the breathable sheet. Manufacturing method. 2. The method according to claim 1, wherein the air-permeable sheet is paper or nonwoven fabric.