JPH09199830A - Manufacture of flexible wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solderable and flexible wiring board having small dimensional change by heat. SOLUTION: First, an epoxy-based, polyester-based or acryl-based bonding agent is applied to an insulating film using a comma-coater, and the bonding agent is semicured under a suitable travelling and heating condition. Then, the metal foil such as copper foil, aluminum foil and the like is joined to the adhesive surface of the above-mentioned insulating film using a roll laminator and the like, the bonding agent is cured, and a metal clad board is formed. Then, a prescribed circuit pattern is formed by etching the metal foil. A cover lay is formed on the circuit pattern, a surface treatment is conducted on the exposed circuit pattern, solder plating, nickel plating and gold plating are conducted, and a flexible wiring board is manufactured.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for manufacturing a flexible wiring board. More specifically, the present invention relates to a flexible wiring board having a small dimensional change.

[0002]

2. Description of the Related Art A flexible printed circuit (FPC) is an insulating film on which a metal foil such as a conductive copper foil is attached, and a predetermined circuit pattern is formed on the metal foil by etching or the like. To be done. A coverlay made of an insulating resin film is formed on the circuit pattern surface to prevent bridges during soldering.
This flexible wiring board has flexibility, and due to the flexibility, it has been widely used in various electronic devices and the like.

As the insulating film, a resin film having an insulating property such as polyimide or polyester is used. Such a flexible wiring board can be manufactured as follows. First, an adhesive is applied on the insulating film and heated to volatilize the solvent to make it a semi-cured state. After that, a metal foil such as a copper foil is attached.
Furthermore, the adhesive is cured by heating to produce a metal foil bonded substrate.

The metal foil bonded substrate is etched to form a predetermined circuit pattern. After that, the connection portion of the circuit pattern with the electronic component is exposed, and a coverlay is formed by screen printing or the like. Finally, solder or Ni / Au is adhered on the exposed circuit pattern and surface treatment of the exposed circuit pattern is performed to manufacture a flexible wiring board.

Various electronic components can be soldered to the flexible wiring board thus manufactured to mount the electronic components.

[0006]

However, when a PET film is used in the above production, for example, when a cover lay or the like is screen-printed, it is heat-cured.
Further, even when components are mounted by soldering, a high temperature higher than the melting point of the solder is applied.

For this reason, the dimensions of the PET film may change, and the flexible wiring board may largely sag or wrinkle, which may impair the reliability of the flexible wiring board.

The present invention has been made in view of the drawbacks of the above conventional examples, and an object of the present invention is to provide a flexible wiring board which has a small dimensional change due to heat and can be soldered. .

[0009]

A method for manufacturing a flexible wiring board according to the present invention is a method for manufacturing a flexible wiring board having an insulating film and a metal foil to be a circuit pattern bonded on the insulating film to form a circuit pattern. The method is characterized in that an adhesive is applied to at least one surface of the insulating film, and a semi-cured state is finished under appropriate running conditions and heating conditions, and the metal foil is bonded to the semi-cured state and heat-cured. .

The flexible wiring board of the present invention comprises PE
Although a T film is used, the smaller the dimensional change rate after heating is, the better. For example, the dimensional change rate after heating at 150 ° C. for 30 minutes is preferably 0.1% or less.

Various thicknesses can be used, and for example, an insulating film having a thickness of 25 μm, 50 μm, 75 μm or the like can be used.

An adhesive is applied to at least one surface of the insulating film and finished in a semi-cured state under appropriate running and heating conditions.

The heating temperature for finishing to a semi-cured state is as follows:
It may be set according to the heat-resistant grade of the insulating film so as to minimize the dimensional change rate. For example, a PET film having a dimensional change rate of 0.1% or less after heating at 150 ° C. for 30 minutes is used. 110 if used
The range of ℃ -160 ℃ is desirable. In addition, when using a PET film of general grade,
It is preferable to perform heat treatment at 0 ° C. for 10 minutes.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The flexible wiring board of the present invention is manufactured as follows. First, by using a comma coater or the like on the insulating film, epoxy type, polyester type,
Apply an acrylic adhesive or the like, for example 110 ° C to 1
The adhesive is semi-cured by heating at 60 ° C. for 10 minutes to evaporate the solvent.

Next, while heating, a metal foil such as a copper foil or an aluminum foil is attached to the adhesive surface of the insulating film by using a roll laminator or the like.

After that, the adhesive is cured by heating at 70 ° C. for 48 hours, for example, to prepare a metal foil bonded substrate.

Next, the metal foil is etched to form a predetermined circuit pattern. Thereafter, a cover lay is formed in the same manner as in the conventional example, surface treatment is performed on the exposed circuit pattern, and solder or the like is attached thereto to manufacture the flexible wiring board of the present invention.

The flexible wiring board manufactured in this manner has less slack and wrinkles, and electronic components can be soldered by a reflow curve as shown in FIG. 1, for example. The reflow curve shown in FIG. 1 shows conditions for mounting electronic components on a flexible wiring board by low-temperature soldering. In this case, first, the flexible board is gradually heated to 80 ° C. to 130 ° C.
Preheating is performed by heating in the range of ° C for at least 60 seconds from the start of heating. Next, the flexible substrate is heated within 80 seconds by 5 ° C lower than the maximum heating temperature, that is, 150 ° C.
~ 185 ° C range, then 155 ° C ~ 1
It is advisable to raise the maximum heating temperature of 90 ° C. and complete the soldering of electronic components within 20 seconds.

[0019]

EXAMPLES Next, as an example, a circuit pattern was formed by subjecting the above-mentioned metal foil laminated substrate to an etching treatment, and the effect of the present invention was confirmed.

[Example] An insulating film having a thickness of 7
5 μm low heat shrinkable polyester film [SLA manufactured by Teijin Limited, 150 ° C., dimensional change rate after heating for 30 minutes:
0.1%], and an epoxy resin-based adhesive is applied so that the thickness after drying is about 25 μm.
Dry at 60 ° C for 10 minutes. Next, a copper foil having a thickness of 35 μm was attached at 70 ° C. using a roll laminator, and then an etching process was performed to form a predetermined circuit pattern.

Next, using those having these circuit patterns formed thereon, the dimensional change rate after heating at 150 ° C. for 30 minutes was measured.

[0022]

[Table 1]

As can be seen from Table 1, 140 ° C., 140 ° C.
In each of the examples bonded with the semi-cured adhesive heated to 0 ° C., the dimensional change rate was about 0.1% in both the length direction and the width direction, and no bending or wrinkling was observed. There was almost no impact on the implementation.

Also, in Example 1 which was bonded at 160 ° C., the shrinkage was 0.2% in the length direction, slight bending and wrinkling were observed, and there was a slight effect on the mounting of electronic parts. Met.

Comparative Example Next, using PET films having different dimensional change rates after heating, a circuit pattern was formed in the same manner as in the example, and the dimensional change rate after heating at 150 ° C. for 30 minutes was measured.

As an insulating film, the dimensional change rates after heating at 150 ° C. for 30 minutes are 0.4% and 1.3%, respectively.
Types of PET film [thickness 75 μm, manufactured by Toray Industries, Inc.]
Using, the adhesive is applied so that the thickness after drying is about 25 μm, and dried at 140 ° C. for 10 minutes. Next, a copper foil having a thickness of 35 μm was attached at 70 ° C. by using a laminator, and then an etching process was performed to form a predetermined circuit pattern, thereby producing a substrate of a comparative example.

For the substrates of these comparative examples, 150
The dimensional change rate (longitudinal direction in which the change was large) was measured after heating at 30 ° C. for 30 minutes. Table 2 shows the results.

[0028]

[Table 2]

As can be seen from Table 2, the dimensional change rate of the substrate of the example was 0.1%, whereas the dimensional change rate of the comparative substrate was 0.5% and 1. 5%
Met.

When a PET film having a dimensional change rate after heating of 0.1% is used in the substrate of the embodiment, almost no wrinkles or sagging are observed, and there is no influence on the mounting of electronic parts. There wasn't. PE with a dimensional change rate of 0.4%
When the T film was used, wrinkles and sagging were observed, which was not suitable for mounting electronic parts. Dimensional change rate is 1.3%
When the PET film of No. 3 was used, many wrinkles and sagging were observed, and it was completely unsuitable for mounting electronic parts.

In this way, an adhesive is applied to at least one surface of the insulating film, finished in a semi-cured state under appropriate running conditions and heating conditions, and bonded to the metal foil,
If the dimensional change rate after heating is set to about 0.2%, wrinkles and slack are less likely to occur even when the circuit pattern is surface-treated,
In addition, it is possible to manufacture a flexible wiring board having good mountability of mounted components. Therefore, a reliable flexible wiring board can be provided.

[0032]

The flexible wiring board of the present invention is a method for manufacturing a flexible wiring board having an insulating film and a metal foil to be a circuit pattern laminated on the insulating film. Applying an adhesive to at least one surface of the conductive film, finishing the applied adhesive to a semi-cured state under appropriate running conditions and heating conditions, bonding it to the metal foil, and thermally curing the adhesive. Therefore, it is possible to manufacture a flexible wiring board with less wrinkles and slack.

At this time, if an insulating film having a dimensional change rate of 0.1% or less after heating at 150 ° C. for 30 minutes is used, the dimensional change rate of the flexible wiring board can be suppressed to about 0.2%. The occurrence of wrinkles and slack during mounting can be reduced.

When the adhesive is semi-cured in the temperature range of 110 ° C. to 160 ° C. under appropriate running and heating conditions, the dimensional change rate of the flexible wiring board can be minimized.

[Brief description of drawings]

FIG. 1 is an example of a reflow curve when an electronic component is mounted on a flexible wiring board of the present invention.

Continuation of front page (51) Int.Cl. ⁶ Identification number Internal reference number FI Technical display location B29L 31:34 (72) Inventor Kenkichi Hirai 1-5 Minamihonmachi, Joetsu City, Niigata Prefecture Arisawa Manufacturing Co., Ltd.

Claims (3)

[Claims] 1. A method for manufacturing a flexible wiring board, comprising: an insulating film; and a metal foil, which is laminated on the insulating film to form a circuit pattern, wherein an adhesive is applied to at least one surface of the insulating film. Is applied, and the metal foil is pasted on the applied adhesive under heating, the adhesive is finished in a semi-cured state under appropriate running conditions and heating conditions, and the adhesive is applied to the metal foil, and then adhered. A method for manufacturing a flexible wiring board, which comprises thermally curing an agent. 2. The flexible wiring board comprises 150
The method for manufacturing a flexible wiring board according to claim 1, wherein the dimensional change rate after heating at 30 ° C. for 30 minutes is 0.2% or less. 3. The flexible wiring board manufacturing substrate according to claim 1, wherein the heat treatment of the adhesive applied to the insulating film is performed in a temperature range of 110 ° C. to 160 ° C.