JP2002314229A - Method for manufacturing flexible printed circuit board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve a wiring density, to improve an opening positional accuracy, to improve reliability and to improve the yield of a pattern plating step in manufacture of a flexible printed circuit board of a double access type having a one-side conductor circuit. SOLUTION: A method for manufacturing the flexible printed circuit board comprises the steps of forming a resist layer 13 of a reverse pattern on the surface of an insulating film 12 with a copper foil, and executing copper plating 14. The method further comprises the steps of laminating an insulating film 8 on the surface, irradiating the part of accessing holes of the films 8 and 11 with a laser beam to form openings 3. The method also comprises the steps of pattern forming the conductor layer part exposed from the opening 3 and the plated layer part by etching, and executing the copper plating 10. The method also comprises the steps of removing the resist layer, and then removing the conductor layer 1 retained between the circuit patterns and the plated layer 14 by etching.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a flexible printed circuit board (FP) on which an integrated circuit such as an IC or an LSI is mounted.
The present invention relates to the production method C). In particular, it facilitates the manufacture of high-definition double-access type FPCs that contribute to miniaturization and weight reduction in electronic devices such as portable information terminal devices, mobile phones, small video devices, and small electronic cameras, and improves production yield. FPC that can improve productivity
And a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, an insulating film has a circuit pattern made of a conductor on one surface, and each of the insulating layer and the insulating film provided on the surface of the circuit pattern opposite to the insulating film has a circuit pattern. FPCs having an access hole reaching up to a maximum are known.

As described above, the double access type FPC having the access holes on both sides of the conductor layer makes it possible to use the component mounting space more effectively than the single access type which has the access holes on one side. This can contribute to miniaturization and thinning. In addition, in the configuration in which the circuit pattern is formed on one surface of the insulating film (single-sided conductor circuit), the material cost and material cost are lower than in the configuration in which the circuit pattern made of a conductor is formed on both surfaces of the insulating film (double-sided conductor circuit). The manufacturing cost is low, and the bending resistance is good.

Hereinafter, as a first prior art, a process of manufacturing a double access type FPC having a single-sided conductor circuit by a pre-opening method will be described with reference to FIG.

FIG. 2A shows a copper foil 1 serving as a circuit pattern.
Is shown. With copper foil alone, handling is very poor,
Since wrinkles are likely to occur, a material having a thickness of about 35 μm is usually used. As shown in FIG. 2 (b),
An insulating film (polyimide film or the like) 2 having a portion (portion to be an access hole) 3 necessary for connection, component mounting, contact and the like is opened. This insulating film 2
Is composed of an adhesive layer 2b for lamination and an insulating layer 2a.

Next, as shown in FIG. 2C, an etching resist layer 4 for forming a circuit pattern and an etching resist layer 5 for protecting the opening 3 are formed. Then, as shown in FIG. 2D, a circuit pattern (circuit) is formed by a known etching method or the like.
6 is formed. After that, as shown in FIG. 2E, the etching resists 4 and 5 are removed.

Subsequently, as shown in FIG.
An insulating film (polyimide film or the like) 8 having another portion (a portion serving as an access hole) 7 necessary for component mounting and a contact is opened. The insulating film 8 includes an adhesive layer 8b for lamination and an insulating layer 8a. At this time, the portion where the insulating film 8 is laminated is the uneven portion 9 on which the circuit pattern 6 is formed,
Since the embedding property of the adhesive layer 8b is poor, bubbles are easily generated.

Thereafter, as shown in FIG. 2 (g), a pattern plating 10 is applied to an exposed portion of the circuit pattern (a portion to be an access hole).

Next, as a second prior art, a process of manufacturing a double access type FPC having a single-sided conductor circuit by a laser aperture processing method will be described with reference to FIG.

FIG. 3A shows an insulating film 12 with a copper foil provided with a copper foil 1 serving as a circuit pattern on an insulating film (polyimide film or the like) 11. The copper foil 1 needs to have strength so that only the copper foil is used in a later laser processing step, and needs to have a thickness of at least about 18 μm.

Next, as shown in FIG. 3B, an etching resist layer 4 for forming a circuit pattern is formed. Then, as shown in FIG. 3C, a circuit pattern (circuit) 6 is formed by a known etching method or the like. Thereafter, as shown in FIG. 3D, the etching resist 4 is removed.

Subsequently, as shown in FIG.
In order to open a part (a part to be an access hole) 3 necessary for component mounting, a contact and the like, the insulating film 11 is removed by irradiating a laser beam.

Next, as shown in FIG. 3 (f), an insulating film (polyimide film or the like) in which another portion (access hole portion) 7 necessary for connection, component mounting, contact and the like is opened. 8 is laminated. This insulating film 8
Is composed of an adhesive layer 8b for lamination and an insulating layer 8a. At this time, the portion where the insulating film 8 is laminated is the uneven portion 9 on which the circuit pattern 6 is formed, and since the embedding property of the adhesive layer 8b is poor, bubbles are likely to be generated.

Thereafter, as shown in FIG. 3G, a pattern plating 10 is applied to an exposed portion of the circuit pattern (a portion to be an access hole).

[0015]

However, the prior art 1 described with reference to FIG. 2 has the following problems. (1) Since the copper foil is thick (about 35 μm), there is a limit in forming a fine wire. Generally, the limit is a line width of 50 μm (pitch: 100 μm). (2) In consideration of the opening shape accuracy and the laminating position accuracy of the insulating film to be laminated on both surfaces, the positional accuracy of the insulating film with respect to the circuit pattern needs to be ± 0.3 mm or more, so that precise component mounting can be performed. Can not. Further, (3) the film laminated portion is an uneven portion on which a circuit pattern is formed, and the adhesive for laminating the insulating film cannot be sufficiently embedded, and bubbles are easily generated. This causes a reduction in insulation resistance, firing due to heating when mounting components, and the like. Also,
(4) When pattern plating is performed by a normal electroplating method, plating leads are required. Further, a hole for cutting a lead connected to an independent circuit portion through which no current flows for plating after plating is required. To cope with these, extra design time is required, and providing a cut hole increases the product area and leads to an increase in cost. Furthermore, there is also a method of using (5) an electroless plating method that does not require plating leads, but short circuits are apt to occur when the distance between the circuits is narrow, and the limit is generally 50 μm.

On the other hand, the prior art 2 described with reference to FIG. 3 has the following problems. (1) The insulating film is removed by laser processing, but this portion is only a copper foil and has poor strength, and tends to wrinkle, so that a fine wire cannot be maintained. Generally, the limit is a line width of 50 μm (pitch: 100 μm). Also, (2)
In consideration of the accuracy of the opening shape of the insulating film laminated on one side and the positional accuracy of the lamination, the positional accuracy of the insulating film with respect to the circuit pattern needs to be ± 0.3 mm or more, so that precise component mounting cannot be performed. Further, (3) the film laminated portion is an uneven portion on which a circuit pattern is formed,
The adhesive for laminating the insulating film cannot be sufficiently embedded, and bubbles are easily generated. This causes a reduction in insulation resistance, firing due to heating when mounting components, and the like. (4) When performing pattern plating by a normal electroplating method, a plating lead is required. Further, a hole for cutting a lead connected to an independent circuit portion through which no current flows for plating after plating is required.
To cope with these, extra design time is required, and providing a cut hole increases the product area and leads to an increase in cost. Further, there is a method using (5) an electroless plating method that does not require plating leads. However, when a circuit is narrow, a short circuit easily occurs.
The μm interval is the limit.

The present invention has been made to solve such problems of the prior art, and has improved wiring density by forming a high-definition circuit, improved opening position accuracy to enable mounting of precision components, and improved lamination. An object of the present invention is to provide a method for manufacturing a flexible printed wiring board, which can improve the reliability of an insulating film or an insulating layer and the yield of a pattern plating step.

[0018]

According to the flexible printed wiring board of the present invention, a circuit pattern composed of a conductor is sandwiched between a pair of insulating layers, and an access hole reaching the circuit pattern is provided in each of the two insulating layers. A method for manufacturing a flexible printed wiring board having a circuit pattern portion on the conductor layer side surface of a first insulating layer comprising an insulating film provided with a circuit pattern conductor layer on one surface. A first step of forming a resist layer having the removed reverse pattern, a second step of plating over the resist layer surface and the conductor layer surface, and a third step of laminating and forming a second insulating layer on the plating layer surface Step: irradiating a portion of the first insulating layer and the second insulating layer which will be an access hole with a laser beam, removing the insulating layer at the portion, and opening the portion. Forming a resist layer by etching the conductor layer portion exposed from the opening of the first insulating layer and the plating layer portion exposed from the opening of the second insulating layer. A fifth step of removing the surface until the surface is exposed, and a surface of the conductor layer portion exposed from the opening of the first insulating layer and a plating layer portion exposed from the opening of the second insulating layer. A sixth step of further plating the surface of the substrate, and a seventh step of removing the conductor layer portion and the plating layer portion remaining between the circuit patterns by etching after removing the resist layer, whereby The above object is achieved.

In the second step, it is preferable that the thickness of the plating layer is larger than the thickness of the resist layer, plating is performed so as to cover the resist layer, and the surface of the plating layer is smoothed.

In the third step, a second insulating layer is preferably formed on the smoothed plating layer surface.

[0021] In the fourth step, the laser beam is reflected by the conductor layer or the plating layer, and only the first insulating layer and the second insulating layer are removed.

In the fifth step, the conductor layer portion exposed from the opening of the first insulating layer and the plating layer portion exposed from the opening of the second insulating layer are simultaneously etched. Can be.

In the seventh step, the conductor layer portion and the plating layer portion remaining between the circuit patterns can be simultaneously etched.

[0024] In the fifth step, it is preferable that the etching is performed so that the conductor layer portion and the plating layer portion are thinner than the resist layer.

In the sixth step, electroplating can be performed without separately providing a plating lead for connecting between circuit patterns and a hole for cutting the plating lead.

The operation of the present invention will be described below.

According to the present invention, in the manufacture of a double access type FPC having a single-sided conductor circuit, an insulating film having a conductor layer for a circuit pattern on one surface is used, as in the prior art 1. It is not necessary to use a thick conductor layer. When the insulating layer is removed by laser processing, a resist layer or the other insulating layer is present on the back surface of the conductor layer or the plating layer. Therefore, from 0.1 μm
An ultra-thin copper foil of about 2 μm can be used, and the wiring can be thinned.

The opening of the insulating layer is provided by laser processing, and the laser beam is reflected by the conductor layer or plating layer thereunder to remove only the insulating layer, so that the opening position accuracy is excellent. Prior art 1 and prior art 2
As described above, the component mounting accuracy does not decrease due to the opening shape accuracy and the laminating position accuracy of the insulating film, and accurate component mounting becomes possible.

When forming the second insulating layer by printing or film lamination, the portion where the insulating layer is printed or the portion where the insulating film is laminated is the surface of the plating layer. It is not an uneven portion where a circuit pattern is formed. Therefore, the insulating layer or the adhesive for laminating the insulating film is sufficiently embedded, and the deterioration of the insulation resistance does not occur. Further, the plating layer is made thicker than the resist layer and is plated so as to cover the resist layer, whereby the surface of the plating layer can be smoothed. In this case, since the second insulating layer can be laminated on the smoothed plating layer surface, there is no occurrence of firing or the like due to heating at the time of mounting components, and the reliability can be further improved. In addition, by reducing the thickness of the plating layer to about 10 μm to 20 μm, the thickness of the finally obtained circuit pattern is reduced, and the flexibility is improved.

When the surface of the conductor layer or the pattern plating is performed, the conductor layer or the plating layer remains between the circuit patterns. Therefore, electroplating can be performed without providing a separate hole after plating for plating leads for connecting between circuit patterns and leads for connecting to independent circuit portions as in the prior arts 1 and 2. is there.

The conductor layer and the plating layer exposed from the openings of the first insulating layer and the second insulating layer can be simultaneously etched. At this time, by etching so that the conductor layer and the plating layer are thinner than the resist layer thickness, when performing pattern plating, the resist layer in the reverse pattern portion becomes a dam between adjacent circuits, and the pattern plating is short-circuited with the adjacent circuit. Not done. After the pattern plating, the conductor layer and the plating layer remaining between the circuit patterns can be simultaneously etched.

[0032]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a double-access type FP having a single-sided conductor circuit according to the present embodiment.
It is sectional drawing for demonstrating the process of manufacturing C.

FIG. 1A shows an insulating film 12 with a copper foil provided with a copper foil 1 serving as a circuit pattern on an insulating film (polyimide film or the like) 11. Copper foil 1
The thickness is preferably about 0.1 μm to 2 μm.
The one having a thickness of about μm is used. As the insulating film 12 with a copper foil, a so-called plating-type two-layer base material that is generally commercially available (a plating layer formed on a base material made of an insulating film) can be used.

Next, as shown in FIG. 1B, in order to form a circuit pattern, a resist layer 13 is formed in a reverse pattern excluding the circuit pattern portion. This resist layer 13
Can be formed by a general additive method.

Subsequently, as shown in FIG. 1C, a copper plating 14 is applied. At this time, by making the thickness of the plating layer 14 larger than the thickness of the resist layer 13 by, for example, about 1 μm, a smooth copper plating surface can be obtained. It is preferable that the thickness of the plating layer is thin, specifically, 10 μm to
It is preferably about 20 μm.

Thereafter, as shown in FIG. 1D, an insulating film (polyimide film or the like) is formed on the plating layer 14.
8 is laminated. The insulating film 8 includes an adhesive layer 8b for lamination and an insulating layer 8a. At this time, the portion where the insulating film 8 is laminated is a smooth copper plated surface, and no bubbles are generated. Further, since the insulating layer can be formed on the smooth copper plating surface, the insulating layer can be formed by a printing method in addition to the lamination of the insulating films.

Next, as shown in FIG. 1E, in order to open a portion (a portion to be an access hole) 3 necessary for connection, component mounting, contact, etc., a laser beam is irradiated to insulate the portion. The conductive films 11 and 2b are removed. At this time,
Because it is reflected by laser light or copper foil or copper plating layer,
Only the insulating film (insulating resin) is removed, and the opening accuracy can be reduced to ± 50 μm or less.

Subsequently, as shown in FIG. 1 (f), primary etching for etching the copper foil 1 portion and the copper plating layer 14 exposed from the opening 3 more by about 1 μm on each side than the resist layer 13. I do. The etching at this time can be handled by a so-called soft etching, such as a hydrogen peroxide-based or organic acid-based etchant.

Thereafter, as shown in FIG. 1 (g), pattern plating is applied to an exposed portion (a portion to be an access hole) of the circuit pattern. At this time, since the copper foil 1 and the copper plating layer 14 partially remain between the circuit patterns, there is no independent circuit pattern, and all circuits can be plated by electroplating. Therefore, there is no need to provide a plating lead or a lead cutting hole after plating.
Further, the resist layer 13 in the reverse pattern portion does not serve as a dam between adjacent circuits, and the pattern plating layer 10 does not short-circuit with the adjacent circuit.

Next, as shown in FIG. 1H, the resist layer 13 is removed. Then, as shown in FIG.
The portion of the copper foil 1 and the portion of the copper plating layer 14 remaining between the circuit patterns are etched to complete the FPC of the present embodiment. At this time, each side is etched by about 1 μm more than the thickness of the resist layer 13, but can be dealt with by a so-called soft etching, such as a hydrogen peroxide-based or organic acid-based etchant.

[0041]

As described in detail above, according to the present invention,
(1) Wiring can be formed with a line width of 50 μm or less (pitch: 100 μm). Further, (2) the opening position accuracy of the double access portion required for connection, component mounting, contact, and the like is excellent, and precise component mounting can be performed. Further, (3) the film lamination portion and the insulating layer printing portion can be smoothed portions, so that reliability such as insulation and heat resistance can be improved. Also, (4)
Pattern plating can also be performed on a circuit that eventually becomes an independent pattern by a normal electroplating method. Further, a plating lead or a hole for cutting the lead after plating is not required, and the manufacturing cost can be reduced. Further, (5) since the pattern plating can be performed so as not to connect to the adjacent circuit, the production yield can be improved.

[Brief description of the drawings]

FIGS. 1A to 1I are cross-sectional views for explaining a manufacturing process of an FPC according to an embodiment of the present invention.

FIGS. 2A to 2G are cross-sectional views for describing a manufacturing process of an FPC according to Conventional Technique 1. FIGS.

FIGS. 3A to 3G are cross-sectional views for explaining a manufacturing process of an FPC according to Conventional Technique 2. FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Copper foil 2 Insulating film 2a Insulating layer 2b Laminating adhesive 3 Opening part (access hole) 4 Resist layer 5 Protective resist layer 6 Circuit pattern 7 Opening part (access hole) 8 Insulating film 8a Insulating layer 8b For laminating Adhesive 9 Uneven portion 10 Pattern plating layer 11 Insulating resin film 12 Insulating resin film with copper foil 13 Resist layer formed in reverse pattern portion 14 Copper plating layer

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5E338 AA12 BB19 EE23 EE31 5E339 AA02 AB02 AC01 AC10 AD03 AE01 BD06 BD08 BE11 BE13 CE12 GG02 5E343 AA02 AA12 AA33 BB12 BB14 BB24 BB67 BB71 CC61 DD21 DD43 DD76 GG06 GG06

Claims (8)

[Claims] 1. A method for manufacturing a flexible printed wiring board having a circuit pattern comprising a conductor sandwiched between a pair of insulating layers, and having an access hole reaching each of the circuit patterns in each of the two insulating layers. Forming a resist layer having a reverse pattern excluding a circuit pattern portion on a surface of a first insulating layer formed of an insulating film having a conductor layer for a circuit pattern provided on one surface thereof on a side of the conductor layer; A second step of plating over the surface of the resist layer and the surface of the conductor layer; a third step of laminating and forming a second insulating layer on the surface of the plating layer; and the first insulating layer and the second A fourth step of irradiating a portion of the insulating layer to be an access hole with a laser beam and removing the insulating layer at that portion to form an opening; and forming an opening in the first insulating layer. A fifth step of removing the conductor layer portion exposed from the substrate and the plating layer portion exposed from the opening of the second insulating layer until the resist layer surface is exposed by etching; A sixth step of further plating the surface of the conductor layer portion exposed from the opening of the layer and the surface of the plating layer portion exposed from the opening of the second insulating layer; and removing the resist layer. And removing the conductive layer portion and the plating layer portion remaining between the circuit patterns by etching after etching. 7. A method for manufacturing a flexible printed wiring board, comprising: 2. The method according to claim 1, wherein, in the second step, the thickness of the plating layer is made larger than the thickness of the resist layer, plating is performed so as to cover the resist layer, and the surface of the plating layer is smoothed. The method for producing a flexible printed wiring board according to the above. 3. The method for manufacturing a flexible printed wiring board according to claim 2, wherein in the third step, a second insulating layer is formed on the smoothed plating layer surface. 4. In the fourth step, a laser beam is reflected by the conductor layer or the plating layer, and only the first insulating layer and the second insulating layer are removed. 3. The method for manufacturing a flexible printed wiring board according to any one of the above items 3. 5. The method according to claim 5, wherein in the fifth step, the first
The flexible part according to any one of claims 1 to 4, wherein the conductor layer part exposed from the opening of the insulating layer and the plating layer part exposed from the opening of the second insulating layer are simultaneously etched. Manufacturing method of printed wiring board. 6. The method for manufacturing a flexible printed wiring board according to claim 1, wherein in the seventh step, the conductor layer portion and the plating layer portion remaining between the circuit patterns are simultaneously etched. . 7. The flexible print according to claim 1, wherein, in the fifth step, the conductive layer portion and the plating layer portion are etched so as to be thinner than the thickness of the resist layer. Manufacturing method of wiring board. 8. The flexible device according to claim 1, wherein in the sixth step, electroplating is performed without separately providing a plating lead for connecting between circuit patterns and a hole for cutting the plating lead. Manufacturing method of printed wiring board.