JP4969147B2 - Manufacturing method of flexible printed wiring board - Google Patents

Description

  The present invention relates to a method for manufacturing a flexible printed wiring board with sharp edges of circuit lines, and more particularly to a method for manufacturing a flexible printed wiring board used as an antenna coil of an IC card or an IC tag.

  Conventionally, flexible printed wiring boards have been used as components of various electronic devices and surface heating elements. In recent years, this flexible printed wiring board has been used as an antenna coil for IC cards and IC tags.

  Conventionally, a flexible printed wiring board is manufactured by the following method. That is, a resist treatment is performed on the surface of the metal foil of the laminate on which the metal foil and the synthetic resin film are bonded to form a resist portion and a non-resist portion, and then an etching treatment is performed to expose the non-resist portion. It is manufactured by a method of dissolving and removing a non-resist portion of a metal foil (Patent Document 1). In the flexible printed wiring board thus obtained, the metal foil remains in the resist portion, and the portion of the metal foil becomes a circuit.

  When a flexible printed wiring board is used as an antenna coil for an IC card or IC tag, it is necessary to form circuit lines with high density in a small area due to the miniaturization of the IC card or IC tag, and the circuit line interval is narrowed. There is a need to. When the circuit line interval is narrowed, short circuiting easily occurs unless the edge of the circuit line formed by etching is sharpened. That is, if the circuit line edge is not sharp and has irregularities, adjacent convex portions of the circuit line edge come into contact with each other, causing a short circuit.

  In order to sharpen the edge of the circuit line, it is known that the dissolution and removal rate of the metal foil by the etching process may be increased. This is because if the dissolution / removal rate is increased, non-resist sites remain less dissolved in the etching process. In order to increase the dissolution and removal rate, a metal foil that is easily dissolved by an etching solution may be used, and the composition of the etching solution may be examined, or the composition of the metal foil may be examined. However, when used for an antenna coil, the metal foil is preferably a copper foil or an aluminum foil from the viewpoint of durability, and an etching solution that dissolves the copper foil or the aluminum foil satisfactorily must be used. There is not much room for consideration.

  Under such circumstances, it has been proposed to use an aluminum foil to which a certain amount of iron has been added to increase the dissolution and removal rate (Patent Document 2). However, even with such a method, it has been difficult to universally increase the dissolution removal rate.

Japanese Patent Publication No. 5-61794 JP 2002-368523 A

The present inventor has examined why it is not possible to universally increase the dissolution and removal rate even if the alloy composition of the aluminum foil is changed so as to be easily dissolved in the etching solution. The present inventor first investigated the dissolution behavior of an aluminum foil by the following method when etching the aluminum foil. That is, the mass (g) before etching and the mass (g) after etching were measured every 10 seconds from the start of etching. Then, this mass difference is converted per unit square meter, and the dissolution loss (g / m ² ) with respect to the etching time is plotted as the dissolution loss, as shown in FIG. As can be seen from FIG. 1, it has been found that there is a latent period in which dissolution hardly occurs for a certain time from the start of etching.

  As a result of various investigations regarding this incubation period, since rolled aluminum foil was used as the aluminum foil, rolling oil adhered to the surface, and it was thought that the time during which this rolling oil was removed would be the incubation period. . Further, since an oxide film having a certain thickness was formed on the surface of the rolled aluminum foil, it was thought that the time for removing this oxide film might be a latent period. Since the amount of rolling oil deposited and the thickness of the oxide film differ depending on the individual rolled aluminum foil, there are those with a long incubation period and those with a short incubation period. I thought it was impossible.

  Then, when this inventor performed the etching process after removing rolling oil and an oxide film, it became clear that the melt | dissolution removal rate became very quick irrespective of the synthetic composition of aluminum foil. This invention is made | formed by selecting a processing liquid suitable for removing rolling oil and an oxide film based on such knowledge.

That is, the present invention performs a resist treatment on the surface of the rolled aluminum foil of the laminate in which the rolled aluminum foil and the synthetic resin film are bonded to form a resist portion and a non-resist portion, and then an etching treatment. In the method of manufacturing a flexible printed wiring board for dissolving and removing the non-resist portion of the rolled aluminum foil exposed in the non-resist portion, the non-resist portion is washed with water after the resist treatment and before the etching treatment. The present invention relates to a method for producing a flexible printed wiring board, wherein the substrate is treated with an alkaline aqueous solution selected from the group consisting of a sodium oxide aqueous solution, a sodium carbonate aqueous solution and a sodium phosphate aqueous solution, and the etching treatment is performed with a hydrochloric acid aqueous solution .

  In the present invention, first, a laminate in which a rolled aluminum foil and a synthetic resin film are bonded is prepared. The rolled aluminum foil is obtained by subjecting an aluminum ingot to homogenization, hot rolling, cold rolling, and the like. The thickness is preferably about 10 to 60 μm for an antenna coil of an IC card or IC tag. Further, in many cases, an oxide film having a thickness of about 3.0 to 10.0 nm is generally formed on the rolled aluminum foil thus obtained. The alloy composition of the aluminum ingot used for obtaining the rolled aluminum foil is arbitrary in the present invention. Generally, a synthetic composition such as 1N30, 8021, 8079 defined in JIS H 4160 (1992) is used.

  As the synthetic resin film, a film made of polyethylene, polypropylene, polyethylene terephthalate, polyethylene naphthalate, or the like is used. In particular, the synthetic resin film used for the flexible printed wiring board is preferably one that hardly shrinks and does not deteriorate due to heat. Therefore, a polyethylene terephthalate (polyester) film or a polyethylene naphthalate film is preferably used. The thickness of the synthetic resin film is preferably about 10 to 70 μm.

  The rolled aluminum foil and the synthetic resin film are laminated with an adhesive or the like to form a laminate. For example, with a polyurethane adhesive or the like, a rolled aluminum foil and a synthetic resin film are bonded to form a laminate. In addition, heat-resistant adhesives such as epoxy adhesives, polyamideimide adhesives, polyimide adhesives, and polyetherimide adhesives are applied to the rolled aluminum foil side, and polyurethane-based adhesives are applied to the synthetic resin film side. It is good also as a laminated body by apply | coating an adhesive agent so that both adhesives may contact | abut and bonding a rolled aluminum foil and a synthetic resin film.

  The rolled aluminum foil may be bonded to only one surface of the synthetic resin film, or may be bonded to both surfaces. For the antenna coil of an IC card or IC tag, it is preferable that circuits are formed on both sides in order to increase the sensitivity of the antenna. Therefore, it is preferable to use the laminated body which bonded the rolled aluminum foil on both surfaces of the synthetic resin film.

  A resist treatment is performed on the surface of the rolled aluminum foil of the laminate. The resist treatment is performed by printing a resist ink on a portion that becomes a circuit line of the rolled aluminum foil and curing the ink. Conventionally known resist inks are used as the resist ink. For example, resist inks containing acrylic resins or epoxy resins can be used. By the resist treatment, a resist portion in which a cured film (resist film) of resist ink is formed on the surface of the rolled aluminum foil and a non-resist portion in which no resist film exists are formed. The resist portion on which the resist film is formed becomes a portion constituting the circuit.

After the resist portion and the non-resist portion are formed, the non-resist portion is etched, and the non-resist portion of the rolled aluminum foil exposed in the non-resist portion is dissolved and removed. Is that the non-resist region is treated with a specific aqueous alkali solution after the resist treatment and before the etching treatment. That is, after the resist treatment and before the etching treatment, the treatment is performed with an alkaline aqueous solution selected from the group consisting of a sodium hydroxide aqueous solution, a sodium carbonate aqueous solution and a sodium phosphate aqueous solution. Then, by treating the non-resist region with this specific aqueous alkali solution, the rolling oil adhering to the exposed rolled aluminum foil surface and the oxide film formed on the surface can be removed. As a result, the dissolution removal rate of the non-resist region becomes extremely fast.

When a sodium hydroxide aqueous solution is used as the specific aqueous alkali solution, the concentration is preferably 0.1 to 45% by mass. When such an aqueous solution is used, the rolling oil and the oxide film are quickly removed. Specifically, the rolling oil and the oxide film can be satisfactorily removed by treatment for 5 to 60 seconds with an aqueous solution having a liquid temperature of 40 to 60 ° C.

After pre-treatment with a specific aqueous alkali solution, etching is performed. Etching process intends line using aqueous hydrochloric acid. By etching with an aqueous hydrochloric acid solution, the rolled aluminum foil in the non-resist region is dissolved and removed, and a circuit is formed by the rolled aluminum foil in which the resist portion remains, whereby a flexible printed wiring board is obtained.

  Although a resist film is formed on the surface of the resist portion, this resist film may or may not be removed. In the case of removing the resist film, a resist ink containing an alkali-soluble acrylic resin or the like may be used, and the resist film may be dissolved in an alkaline aqueous solution after the etching treatment.

  The flexible printed wiring board manufactured as described above is used for conventionally known applications. For example, it is used by being incorporated in an electronic device or a surface heating element. In the present invention, since the flexible printed wiring board can be reduced in size, it is preferably used as an antenna coil of an IC card or an IC tag.

The method for producing a flexible printed wiring board according to the present invention comprises a rolling oil that is treated with a specific aqueous alkali solution after the resist treatment and before the etching treatment, and adheres to the rolled aluminum foil surface of the non-resist portion, And the oxide film currently formed in the surface of rolled aluminum foil is removed. Therefore, since the rolled aluminum foil can be immediately dissolved and removed during the etching process using the hydrochloric acid aqueous solution , there is an effect that the dissolution and removal speed can be extremely increased.

  As a result of exhibiting such effects, the edge of the circuit line of the obtained flexible printed wiring board can be sharpened, and even if the circuit line interval is narrowed, it is difficult to short-circuit. Therefore, the obtained flexible printed wiring board can be reduced in size and can be suitably used as an antenna for an IC card or an IC tag.

  EXAMPLES Hereinafter, although this invention is demonstrated based on an Example, this invention is not limited to an Example.

Example 1
Si: 0.3% by mass, Fe: 0.4% by mass, Cu, Mn, Mg, Zn, Ti, Ga and other inevitable impurity elements: 0.05% by mass or less, Al: balance of aluminum casting with elemental composition The lump was homogenized at 540 ° C. for 4 hours and immediately hot-rolled to obtain an aluminum plate having a thickness of 2.5 mm. The aluminum plate was cold-rolled to obtain an aluminum thin plate having a thickness of 0.65 mm, and then subjected to intermediate annealing at 380 ° C. for 5 hours. Then, after the intermediate annealing, cold rolling was performed to obtain a thickness of 220 to 250 μm, and then cold rolling was further performed using a rolling oil to obtain a hard rolled aluminum foil having a thickness of 35 μm. The thickness of the oxide film formed on the surface of the rolled aluminum foil was 4.5 ± 0.5 nm.

    One side of this rolled aluminum foil is coated with a heat-resistant adhesive containing polyamide-imide resin (trade name “Bridinol AI-03”, manufactured by Dainichi Seika Kogyo Co., Ltd.), and the thickness is 2 ± 0.5 μm. A heat resistant adhesive layer was formed. After applying an adhesive containing polyurethane resin (trade name “Adcoat 76P1” manufactured by Toyo Morton Co., Ltd.) to the surface of the heat-resistant adhesive layer, a 25 μm thick polyester film (Toray Industries, Inc.) is applied to the surface. Manufactured and sold under the trade name "Lumirror"). As described above, a laminate in which a synthetic resin film (polyester film) was bonded to one side of a rolled aluminum foil was obtained.

  After printing on this rolled aluminum foil side surface with a resist ink containing an epoxy resin (trade name “NW8800 Blue 1.75” manufactured by Tanaka Chemical Co., Ltd.), the epoxy resin is used at 160 ° C. Was cured to form a resist portion and a non-resist portion. The thickness of the resist film printed on the resist portion was 1.5 ± 0.5 μm.

  After that, the resist-printed laminate was pretreated by immersing it in a sodium hydroxide aqueous solution (liquid temperature 60 ° C.) having a concentration of 0.1% by mass for 30 seconds. After the pretreatment, the substrate was immersed in an aqueous hydrochloric acid solution having a concentration of 10% by mass (liquid temperature: 50 ° C.) to carry out etching treatment. The etching treatment time was performed until it was observed that the rolled aluminum foil in the non-resist region was completely dissolved and removed. A flexible printed wiring board was obtained as described above.

Example 2
The resist-printed laminate was flexible in the same manner as in Example 1 except that it was immersed in a 0.5% by weight sodium hydroxide aqueous solution (liquid temperature 55 ° C.) for 15 seconds and pretreated. A printed wiring board was obtained.

Example 3
The resist-printed laminate was flexible in the same manner as in Example 1 except that it was pretreated by immersing it in an aqueous solution of sodium hydroxide (liquid temperature 53 ° C.) having a concentration of 1.0% by mass for 30 seconds. A printed wiring board was obtained.

Example 4
The resist-printed laminate was flexible in the same manner as in Example 1 except that it was immersed in a 5.0% by weight sodium hydroxide aqueous solution (liquid temperature 50 ° C.) for 15 seconds and pretreated. A printed wiring board was obtained.

Example 5
The resist-printed laminate was flexible in the same manner as in Example 1 except that it was immersed in a 5.0% by weight sodium hydroxide aqueous solution (liquid temperature 50 ° C.) for 30 seconds and pretreated. A printed wiring board was obtained.

Example 6
The resist-printed laminate was flexible in the same manner as in Example 1 except that it was immersed in a 5.0% by weight sodium hydroxide aqueous solution (liquid temperature 53 ° C.) for 30 seconds and pretreated. A printed wiring board was obtained.

Example 7
The flexible printed wiring is the same as in Example 1 except that the resist-printed laminate is immersed in an aqueous sodium hydroxide solution (solution temperature: 50 ° C.) having a concentration of 40% by mass for 5 seconds and pretreated. I got a plate.

Example 8
The flexible print was made in the same manner as in Example 1 except that the resist-printed laminate was immersed in an aqueous solution of sodium carbonate (liquid temperature 50 ° C.) having a concentration of 5.0% by mass for 30 seconds and pretreated. A wiring board was obtained.

Example 9
The flexible printed material was printed in the same manner as in Example 1 except that the resist-printed laminate was immersed in an aqueous solution of sodium phosphate (liquid temperature: 50 ° C.) having a concentration of 1.0% by mass for 30 seconds. A wiring board was obtained.

Comparative Example 1
A flexible printed wiring board was obtained by the same method as in Example 1 except that no pretreatment with an aqueous solution was performed.

Comparative Example 2
A flexible printed wiring board was obtained by the same method as in Comparative Example 1 except that the etching treatment was performed using a ferric chloride aqueous solution (liquid temperature 50 ° C.) having a concentration of 40% by mass.

Example 10
Si: 0.2% by mass, Fe: 0.8% by mass, Cu, Mn, Mg, Zn, Ti, Ga and other unavoidable impurity elements: 0.05% by mass or less, Al: balance of elemental aluminum casting A rolled aluminum foil was obtained by the same method as in Example 1 except that the lump was used. The thickness of the oxide film formed on the surface of the rolled aluminum foil was also 4.5 ± 0.5 nm. A flexible printed wiring board was obtained by the same method as in Example 3 except that this rolled aluminum foil was used.

Example 11
A flexible printed wiring board was obtained in the same manner as in Example 8 , except that the rolled aluminum foil used in Example 10 was used.

In the production methods according to Examples 1 to 11 and Comparative Examples 1 and 2 , the dissolution removal time of the non-resist region was measured. The dissolution removal time was measured by measuring the time required until it was observed that the rolled aluminum foil in the non-resist region was completely dissolved and removed. The results were as shown in Table 1.

Further, the sharpness of the edge of Examples 1 11 and Comparative Examples 1, 2 formed on the flexible printed wiring board obtained by the manufacturing method according to the circuit line, and evaluated by the following method. That is, using a microscope VHX-500 manufactured by Keyence Corporation, the surface of the flexible printed wiring board was observed using a 100 × objective lens. Then, as shown in FIG. 2, when the maximum width between the edges of adjacent circuit lines is L and the minimum width is S, the sharpness was evaluated by the value of L−S. The smaller the value, the sharper the edge of the circuit line. The maximum width and the minimum width were measured in the range where the length W of the circuit line was 2 mm. The results are also shown in Table 1.

[Table 1]
━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
Dissolution removal time Sharpness of edge of circuit line
(Sec.) (Μm)
━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
Example 1 47 35
Example 2 43 39
Example 3 39 43
Example 4 33 37
Example 5 30 28
Example 6 54 59
Example 7 57 76
Example 8 38 62
Example 9 40 58
Example 10 48 35
Example 11 28 53
Comparative Example 1 194 241
Comparative Example 2 194 238
━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  As is clear from the results in Table 1, it can be seen that when the method according to the example is adopted, the dissolution removal rate of the non-resist region is remarkably increased as compared with the method according to the comparative example. It can also be seen that the sharpness of the edge of the circuit line is remarkably improved in the flexible printed wiring board obtained by the method according to the example. Therefore, if the method according to the embodiment is adopted, the etching processing time can be shortened, the edge of the circuit line of the obtained flexible printed wiring board can be remarkably sharpened, and a short circuit is less likely to occur. I understand.

It is the graph which showed the relationship between the etching process time and melt | dissolution loss in the case of etching by the conventional method. It is the figure which showed the meaning of the maximum width and minimum width used when evaluating the sharpness of the circuit line edge of a flexible printed wiring board.

Claims (6)

Resist treatment is performed on the surface of the rolled aluminum foil of the laminate in which the rolled aluminum foil and the synthetic resin film are bonded to form a resist portion and a non-resist portion, and then etching treatment is performed to expose the non-resist portion. In the manufacturing method of a flexible printed wiring board for dissolving and removing the non-resist portion of the rolled aluminum foil,
After the resist treatment and before the etching treatment, the non-resist site is treated with an alkaline aqueous solution selected from the group consisting of a sodium hydroxide aqueous solution, a sodium carbonate aqueous solution and a sodium phosphate aqueous solution ,
A method for producing a flexible printed wiring board, characterized in that the etching treatment is performed with an aqueous hydrochloric acid solution . The method for producing a flexible printed wiring board according to claim 1, wherein the alkaline aqueous solution is a sodium hydroxide aqueous solution having a concentration of 0.1 to 45% by mass.   The method for manufacturing a flexible printed wiring board according to claim 1, wherein the resist film present in the resist portion is removed after the etching process.   The method for producing a flexible printed wiring board according to claim 1, wherein the rolled aluminum foil has a thickness of 10 to 60 µm, and the rolled aluminum foil has a surface oxide film thickness of 3.0 to 10.0 nm.   A flexible printed wiring board obtained by the method according to claim 1.   An IC card or IC tag comprising an IC chip connected to the flexible printed wiring board according to claim 5.

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