WO2013027542A1 - Flexible printed circuit board and method for producing flexible printed circuit board - Google Patents

Abstract

This flexible printed circuit board (10), which comprises a substrate layer (11), a wiring circuit (12a), and an insulating layer (13) comprising a photosensitive resin, is provided with an insulating layer covered region (Q1), which is covered by the insulating layer (13), and an insulating layer non-covered region (Q2), which is not covered by the insulating layer (13). When viewed from the direction perpendicular to the surface (H) of the flexible printed circuit board (10), the intersection angles (A1-A4) of the intersections of the boundary line (K1) between the insulating layer covered region (Q1) and the insulating layer non-covered region (Q2) and the line (T2) representing the side surface (12a-1) of the wiring circuit (12a) covered by the insulating layer covered region (Q1) are formed into acute angles.

Description

Flexible printed wiring board and method for manufacturing the flexible printed wiring board

The present invention relates to a flexible printed wiring board having an insulating layer made of a photosensitive resin, and a method for manufacturing the flexible printed wiring board.

In recent years, a flexible printed wiring board having characteristics such as flexibility and flexibility is preferably used in a printed wiring board disposed inside an electronic device that is becoming smaller in size.
Such a flexible printed wiring board includes a base material layer made of an insulating resin, a wiring circuit made of a conductive metal formed on the base material layer, and an insulating resin covering the base material layer and the wiring circuit. It is generally formed of an insulating layer made of
Moreover, in such a flexible printed wiring board, after covering the base material layer and the wiring circuit with a photosensitive resin, an insulating layer is formed through an exposure process, a development process, and a curing process.
As a prior art showing such a flexible printed wiring board, for example, there is Patent Document 1 below.

Japanese Patent Laid-Open No. 10-321993

However, in the flexible printed wiring board in which the insulating layer is formed of a photosensitive resin as shown in Patent Document 1, the end face of the insulating layer is considered without considering the relationship with the circuit direction of the wiring circuit (laying direction of the wiring circuit). What designs the shape is common.
Therefore, depending on the shape of the end face of the insulating layer, there is a coating defect such as a crack in the region where the insulating layer is formed in the manufacturing stage of the flexible printed wiring board (specifically, in the development process and the curing process for forming the insulating layer). There was a problem that occurred.

Therefore, the present invention solves the above-described conventional problems and designs the end face shape of the insulating layer made of a photosensitive resin in consideration of the relationship with the circuit direction of the wiring circuit (laying direction of the wiring circuit). Accordingly, the flexible printed wiring board and the method for manufacturing the flexible printed wiring board can effectively prevent the occurrence of coating defects such as cracks in the region where the insulating layer is formed in the manufacturing stage of the flexible printed wiring board. Offering is an issue.

The flexible printed wiring board of the present invention is a flexible print comprising a base material layer, a wiring circuit formed on the base material layer, and an insulating layer made of a photosensitive resin covering the base material layer and the wiring circuit. It is a wiring board. In addition, an insulating layer covering region covered with the insulating layer and an insulating layer non-covering region not covered with the insulating layer are provided. And in that, the boundary line of the said insulating layer coating area | region and the said insulating layer non-coating area | region seen from the orthogonal | vertical direction with respect to the surface of a flexible printed wiring board, and the said wiring circuit covered with the said insulating layer coating area | region The first feature is that the intersection angle intersecting with the line representing the side surface is formed as an acute angle.

According to the first aspect of the present invention, the flexible printed wiring board includes a base material layer, a wiring circuit formed on the base material layer, and a photosensitive resin that covers the base material layer and the wiring circuit. It is a flexible printed wiring board which consists of an insulating layer which consists of. And what comprises the insulating layer coating area | region coat | covered with the said insulating layer, and the insulating layer non-coating area | region which is not coat | covered with the said insulating layer, The said insulating layer coating | cover seen from the perpendicular | vertical direction with respect to the surface of a flexible printed wiring board A crossing angle at which a boundary line between the region and the insulating layer non-covering region intersects with a line representing a side surface of the wiring circuit covered by the insulating layer covering region is formed at an acute angle. Thereby, it is possible to effectively prevent the occurrence of coating defects such as cracks in the region where the insulating layer is formed in the manufacturing stage of the flexible printed wiring board. Therefore, it is possible to obtain a flexible printed wiring board with good manufacturing efficiency and good yield.

Further, in addition to the first feature of the present invention, the flexible printed wiring board of the present invention has a second feature that the crossing angle is 15 degrees or more and less than 90 degrees.

According to the second feature of the present invention, in addition to the function and effect of the first feature of the present invention, the intersection angle is not less than 15 degrees and less than 90 degrees. It is possible to effectively prevent the occurrence of coating defects such as cracks in the region where the insulating layer is formed. Therefore, it is possible to obtain a flexible printed wiring board with higher production efficiency and better yield.

In addition to the first or second feature of the present invention, the flexible printed wiring board of the present invention has a third feature that the crossing angle is 30 degrees or more and less than 60 degrees.

According to the third feature of the present invention, in addition to the operational effects of the first or second feature of the present invention, the intersection angle is 30 degrees or more and less than 60 degrees. In the manufacturing stage, it is possible to more effectively prevent the occurrence of coating defects such as cracks in the region where the insulating layer is formed. Therefore, it is possible to obtain a flexible printed wiring board with higher production efficiency and better yield.

The flexible printed wiring board according to the present invention has a plurality of wiring circuits in addition to any one of the first to third features of the present invention described above, and a width between the wiring circuits and adjacent wiring circuits. A fourth feature is that at least one of the intervals is 20 μm or less.

According to the fourth aspect of the present invention, in addition to the operation and effect of any one of the first to third aspects of the present invention, the wiring circuit includes a plurality of wiring circuits and the width of the wiring circuit. Since at least one of the distances between the adjacent wiring circuits is 20 μm or less, the flexible printed wiring board can be miniaturized and the wiring density can be increased.

In the flexible printed wiring board of the present invention, in addition to any one of the first to fourth features of the present invention, a boundary line between the insulating layer covering region and the insulating layer non-covering region is a waveform. This is the fifth feature.

According to the fifth aspect of the present invention, in addition to the function and effect of any one of the first to fourth aspects of the present invention, a boundary line between the insulating layer covered region and the insulating layer non-covered region Is a waveform. As a result, the angle at which the boundary line between the insulating layer covering region and the insulating layer non-covering region intersects with the side surface of the wiring circuit covered with the insulating layer covering region can be effectively sharpened on both side surfaces of the wiring circuit. can do. Therefore, it is possible to obtain a flexible printed wiring board with higher production efficiency and better yield.

The method for producing a flexible printed wiring board of the present invention is a method for producing a flexible printed wiring board having the first feature of the present invention. Then, a base material layer forming step for forming the base material layer, a wiring circuit forming step for forming a wiring circuit on the base material layer, a photosensitive resin on the base material layer and the wiring circuit, and exposure At least an insulating layer forming step of forming an insulating layer coating region covered with the insulating layer and an insulating layer non-covering region not covered with the insulating layer through processing, development processing, and curing treatment. At the same time, a crack is prevented from occurring at a boundary portion between the insulating layer covering region and the insulating layer non-covering region. As the means, in the insulating layer forming step, the boundary line between the insulating layer covering region and the insulating layer non-covering region, as viewed from the direction perpendicular to the surface of the flexible printed wiring board, and the insulating layer covering region A sixth feature is that the insulating layer is formed with an acute angle of crossing with the line representing the side surface of the wiring circuit covered by the wire.

According to the sixth feature of the present invention, the method for manufacturing a flexible printed wiring board is the method for manufacturing a flexible printed wiring board having the first feature of the present invention. Then, a base material layer forming step for forming the base material layer, a wiring circuit forming step for forming a wiring circuit on the base material layer, a photosensitive resin on the base material layer and the wiring circuit, and exposure At least an insulating layer forming step of forming an insulating layer coating region covered with the insulating layer and an insulating layer non-covering region not covered with the insulating layer through processing, development processing, and curing treatment. At the same time, in the insulating layer forming step, as a means for preventing the boundary portion between the insulating layer covering region and the insulating layer non-covering region from being cracked, from the direction perpendicular to the surface of the flexible printed wiring board. The insulating layer having an acute crossing angle at which the boundary line between the insulating layer coating region and the insulating layer non-covering region and the line representing the side surface of the wiring circuit covered by the insulating layer coating region intersect Form. Thereby, in an insulating layer formation process, it can prevent effectively that coating defects, such as a crack, generate | occur | produce in an insulating layer coating area | region. Therefore, it can be set as the manufacturing method of a flexible printed wiring board with good manufacturing efficiency and a good yield.

According to the flexible printed wiring board of the present invention, it is possible to effectively prevent the occurrence of coating defects such as cracks in the region where the insulating layer made of the photosensitive resin is formed in the manufacturing stage of the flexible printed wiring board. . Therefore, it is possible to obtain a flexible printed wiring board with good manufacturing efficiency and good yield. Moreover, it can be set as the flexible printed wiring board in which wiring circuit miniaturization and high-density wiring are possible.
Further, according to the method for manufacturing a flexible printed wiring board of the present invention, in the insulating layer forming step, it is possible to effectively prevent the occurrence of coating defects such as cracks in the region where the insulating layer made of the photosensitive resin is formed. it can. Therefore, it can be set as the manufacturing method of a flexible printed wiring board with good manufacturing efficiency and a good yield.

It is a figure which shows the flexible printed wiring board which concerns on embodiment of this invention, and is a top view which shows the whole flexible printed wiring board. It is a figure which shows the flexible printed wiring board concerning embodiment of this invention, and is sectional drawing of the principal part in the aa line direction of FIG. 4A. It is sectional drawing which simplifies and shows the manufacturing method of the flexible printed wiring board which concerns on embodiment of this invention. It is sectional drawing which simplifies and shows the manufacturing method of the flexible printed wiring board which concerns on embodiment of this invention. It is a figure which simplifies and shows the manufacturing method of the flexible printed wiring board concerning embodiment of this invention, and is a top view of the principal part which shows the state by which the pattern mask 20 was arrange | positioned above the resin layer 13a in exposure processing. It is a figure which simplifies and shows the manufacturing method of the flexible printed wiring board concerning the embodiment of the present invention, and is a top view of the important section showing base material layer 11, wiring circuit 12a, and resin layer 13a after being developed by development processing. is there. FIG. 4B is a simplified view illustrating the method for manufacturing the flexible printed wiring board according to the embodiment of the present invention, and is a cross-sectional view in the direction of the line bb of FIG. 4B. It is a top view which shows the principal part of the flexible printed wiring board which concerns on embodiment of this invention. It is a figure which simplifies and shows the manufacturing method of the conventional flexible printed wiring board and the conventional flexible printed wiring board, and is a top view which shows the principal part of the conventional flexible printed wiring board. FIG. 6B is a simplified view of the conventional flexible printed wiring board and the conventional flexible printed wiring board manufacturing method, showing a cross-sectional view in the direction of the line cc of FIG. 6A, and development in the manufacturing stage of the conventional flexible printed wiring board It is a figure which shows typically the state in which a crack (crack) arises in the resin layer 130a by a process and a hardening process.

DESCRIPTION OF SYMBOLS 10 Flexible printed wiring board 11 Base material layer 12 Conductive layer 12a Wiring circuit 12a-1 Side surface 13 Insulating layer 13-1 End surface 13a Resin layer 20 Pattern mask 30 Exposure means 40 Thermosetting means 100 Flexible printed wiring board 110 Base material layer 120 Conductivity Layer 120a Wiring circuit 120a-1 Side surface 130 Insulating layer 130-1 End surface 130a Resin layer A1 Crossing angle A2 Crossing angle A3 Crossing angle A4 Crossing angle B1 Crossing angle B2 Crossing angle B3 Crossing angle B4 Crossing angle C1 Cracking D1 Base layer forming process E Wiring circuit forming process F Insulating layer forming process F1 Resin layer forming process F2 Exposure process F3 Curing process K1 Boundary line K2 Boundary part L Width M Height Q1 Insulation Covered region Q2 insulating layer uncovered regions R wiring circuit exposed area S interval T1 line T2 line

Referring to the following drawings, a flexible printed wiring board 10 according to an embodiment of the present invention and a method for manufacturing the flexible printed wiring board 10 will be described for understanding of the present invention. However, the following description is an embodiment of the present invention, and does not limit the contents described in the claims.

The flexible printed wiring board 10 which concerns on embodiment of this invention is what is called a single-sided flexible printed wiring board which provides the wiring circuit 12a only on the single side | surface of the base material layer 11, as shown to FIG. 1B.
Moreover, as shown to FIG. 1A, it is a flexible printed wiring board provided with the wiring circuit exposure area | region R formed by exposing the wiring circuit 12a from the insulating layer 13. FIG. The wiring circuit exposed region R is used as a terminal portion or the like.

Next, the flexible printed wiring board 10 will be described in more detail with reference to FIGS. 2 to 5 while explaining the method for manufacturing the flexible printed wiring board 10 according to the embodiment of the present invention.

With reference to A of FIG. 2, the base material layer 11 which consists of insulating resin is formed by the base material layer formation process D1.
Any insulating resin may be used as long as it is normally used as the insulating resin for forming the base layer of the flexible printed wiring board, such as polyimide and polyester.
In particular, those having high heat resistance in addition to flexibility are desirable. For example, polyamide resins, polyimide resins such as polyimide and polyamideimide, and polyethylene naphthalate can be preferably used.
As the heat resistant resin, any resin may be used as long as it is usually used as a heat resistant resin for forming the base layer of the flexible printed wiring board, such as a polyimide resin or an epoxy resin.
The thickness of the base material layer 11 is desirably about 5 μm to 50 μm.

Next, referring to FIG. 2B, a conductive layer 12 is formed by first laminating a conductive metal on the base material layer 11 in the wiring circuit forming step E.
The conductive layer 12 can be formed using a known forming method. For example, it can form by plating electroconductive metal foil on the base material layer 11 (so-called additive method).
Note that copper (Cu) can be used as the conductive metal foil. Of course, it is not limited to copper (Cu), and any material can be used as long as it is normally used as a conductive metal foil for forming a conductive layer of a flexible printed wiring board.
Next, referring to FIG. 2C, a plurality of wiring circuits 12 a are formed in the conductive layer 12 by a wiring circuit forming step E.
More specifically, the wiring circuit 12a is formed by removing a predetermined region (a region where no wiring circuit is formed) of the conductive layer 12 by etching.
Note that the width L of the wiring circuit 12a shown in FIG. 1B is preferably about 5 μm to 150 μm. The interval S between the adjacent wiring circuits 12a is preferably about 5 μm to 150 μm. More preferably, at least one of the width L of the wiring circuit 12a and the interval S between the adjacent wiring circuits 12a is preferably 5 μm to 20 μm. By setting it as such a structure, it can be set as the flexible printed wiring board in which the miniaturization of the wiring circuit 12a and high-density wiring are possible.
The height M of the wiring circuit 12a is preferably about 5 μm to 35 μm.
In the present embodiment, although not shown in detail, the width L and the interval S are the same length.

Next, referring to FIG. 2D, the resin layer 13a is formed by coating the surface of the base material layer 11 and the wiring circuit 12a with a photosensitive resin by the resin layer forming process F1 in the insulating layer forming step F.
More specifically, in this embodiment, the resin layer 13a is formed by applying liquid photosensitive polyimide to the surface of the base material layer 11 and the wiring circuit 12a.
Note that the liquid photosensitive resin is not limited to the photosensitive polyimide, and a photosensitive epoxy resin, a photosensitive acrylic resin, or the like can be used.

Next, the solvent of the resin layer 13a is evaporated by a drying process (not shown) in the insulating layer forming step F.
Thereafter, referring to FIG. 3A, the resin layer 13 a is exposed through the pattern mask 20 using the exposure means 30 by the exposure processing F <b> 2 in the insulating layer forming step F.
More specifically, as shown in FIG. 4A, in the flexible printed wiring board 10, the insulating layer covering region Q1 (shown by one-dotted diagonal line) covered with the insulating layer 13 and the insulating layer non-covered with the insulating layer 13 are not covered. The resin layer 13a is exposed using a pattern mask 20 having a pattern corresponding to the covering region Q2 (mainly a region where the wiring circuit 12a is exposed to form the wiring circuit exposed region R).
In the present embodiment, as shown in FIG. 4A, the pattern shape of the pattern mask 20 is such that the boundary line K1 between the insulating layer covering region Q1 and the insulating layer non-covering region Q2 has a waveform.
More specifically, as shown in FIG. 4B, the following configuration is used as a means for preventing the boundary portion K2 between the insulating layer covering region Q1 and the insulating layer non-covering region Q2 from cracking. That is, the boundary line K1 between the insulating layer covering region Q1 and the insulating layer non-covering region Q2 (a line representing the end surface 13-1 of the insulating layer 13 to be formed later) viewed from the direction perpendicular to the surface H of the flexible printed wiring board. T1) and a pattern having a waveform such that an intersection angle A1 to an intersection angle A4 intersecting the line T2 representing the side surface 12a-1 on both sides of the wiring circuit 12a covered by the insulating layer covering region Q1 are acute angles. The exposure is performed using the pattern mask 20.
Here, the “boundary portion K2” means “the boundary line K1 and the side surface 12a− of the wiring circuit 12a covered with the insulating layer covering region Q1 as viewed from the direction perpendicular to the surface H of the flexible printed wiring board”. It means a region within a range of about 5 μm on the outer side in the width direction of the wiring circuit 12a from the intersection with the line T2 representing 1.
Further, the “surface H of the flexible printed wiring board” means “the surface on which the wiring circuit 12a is disposed in the flexible printed wiring board 10” as shown in FIGS. 1A, 1B, and 5. Shall.
Further, the intersection angle A1 to the intersection angle A4 can be appropriately changed according to the width L of the wiring circuit 12a and the interval S between the adjacent wiring circuits 12a if they are acute angles. However, it is preferably 15 degrees or more and less than 90 degrees, and more preferably 30 degrees or more and 60 degrees or less. Further, the intersection angle A1 and the intersection angle A2 formed on both sides in the width direction of the wiring circuit 12a (the intersection angle A3 and the intersection angle A4) may be the same angle or different angles. .
Further, the exposure amount and the exposure time in the exposure process F2 can be changed as appropriate. But preferably the exposure amount is ^{200mj / cm 2 ~ 1500mj / cm} 2 or so, the exposure time is preferably set to 20 seconds to 90 seconds or so.
The pattern mask 20 may be configured to use either a positive type or a negative type.
The shape of the wave, more specifically, the amplitude, period, etc. of the wave can be appropriately changed according to the width L of the wiring circuit 12a and the interval S between the adjacent wiring circuits 12a. In this embodiment, as shown in a simplified manner in FIG. 4B, a sine wave whose amplitude is vertically symmetrical is used, and one wave crest is formed in one wiring circuit 12a (width L of one wiring circuit 12a). Is configured such that one wave trough is arranged between adjacent wiring circuits 12a (interval S between adjacent wiring circuits 12a).

Next, in a development process (not shown) in the insulating layer forming process F, the resin layer 13a exposed in the exposure process F2 is developed.
More specifically, a region corresponding to the insulating layer non-covering region Q2 in the resin layer 13a is dissolved and removed with a developer.
By this process, as shown in FIG. 4B, an insulating layer covering region Q1 and an insulating layer non-covering region Q2 are formed.
The developer may be any one as long as it is usually used for developing a photosensitive resin for forming an insulating layer of a flexible printed wiring board, such as an organic solvent or an alkaline aqueous solution. However, it is preferable to use an organic solvent and set the development time to about 5 to 15 minutes.

Next, referring to FIG. 3B and FIG. 3C, the resin layer 13a developed by the development process is cured by the curing process F3 in the insulating layer forming process F, thereby forming the insulating layer 13.
More specifically, the resin layer 13a that forms the insulating layer coating region Q1 that has not been dissolved and removed in the development process is thermally cured by the thermosetting means 40.
The thermosetting conditions can be changed as appropriate. However, it is preferable to perform heat treatment for about 30 minutes to 10 hours in a temperature atmosphere of about 150 ° C. to 350 ° C.
The thickness of the insulating layer 13 is desirably about 3 μm to 25 μm.

By passing through the above process, the flexible printed wiring board 10 which concerns on embodiment of this invention shown to C of FIG. 3 is formed. More specifically, as shown in FIG. 5, the boundary K1 between the insulating layer covering region Q1 and the insulating layer non-covering region Q2 as viewed from the direction perpendicular to the surface H of the flexible printed wiring board 10 is insulated. Crossing angles A1 to A4 intersecting with the line T2 representing the side surface 12a-1 of the wiring circuit 12a covered by the layer covering region Q1 are formed at acute angles. At the same time, the flexible printed wiring board 10 including the insulating layer 13 having the corrugated end face 13-1 is formed.
The flexible printed wiring board 10 thus formed is disposed inside various electronic devices such as a mobile phone.

The flexible printed wiring board 10 and the manufacturing method of the flexible printed wiring board 10 according to the embodiment of the present invention having such a configuration have the following effects.
When the pattern mask 20 used in the exposure processing F2 is viewed from the direction perpendicular to the surface H of the flexible printed wiring board 10, the boundary line K1 between the insulating layer covering region Q1 and the insulating layer non-covering region Q2 (insulating formed later) A crossing angle A1 to a crossing angle A4 at which the line T1) representing the end face 13-1 of the layer 13 and the line T2 representing the side face 12a-1 on both sides of the wiring circuit 12a covered by the insulating layer covering region Q1 intersect. It is assumed that the pattern mask includes a waveform boundary line K1 having an acute angle. As a result, in the development process (not shown) and the curing process F3, a crack (crack) or the like is generated at the boundary portion K2 between the insulating layer coating region Q1 and the insulating layer non-covering region Q2 shown in FIGS. 4B and 4C. Generation | occurrence | production of the coating defect can be prevented effectively.
That is, in the development process and the curing process F3, the resin layer 13a is swollen due to sucking the developer and contracted due to subsequent drying. By designing the crossing angle A1 to the crossing angle A4 to be acute with respect to such a phenomenon, it is particularly effective that shrinkage due to drying occurs in multiple directions at the boundary portion K2 of the resin layer 13a in the insulating layer coating region Q1. Therefore, stress concentration can be prevented from occurring at the boundary portion K2 of the resin layer 13a. Therefore, it is possible to effectively prevent the occurrence of coating defects such as cracks at the boundary portion K2 of the resin layer 13a in the insulating layer coating region Q1 in the development processing.
Furthermore, in the curing treatment F3, volume shrinkage occurs when the imide precursor is heated and imidized in the resin layer 13a. By designing the crossing angle A1 to the crossing angle A4 to be acute with respect to such a phenomenon, it is effective that shrinkage due to heating occurs in multiple directions particularly at the boundary portion K2 of the resin layer 13a in the insulating layer coating region Q1. Therefore, stress concentration can be prevented from occurring at the boundary portion K2 of the resin layer 13a. Therefore, in the curing process F3, it is possible to effectively prevent the occurrence of coating defects such as cracks at the boundary portion K2 of the resin layer 13a in the insulating layer coating region Q1.
Therefore, it is possible to effectively prevent the occurrence of coating defects such as cracks in the resin layer 13a in the insulating layer coating region Q1 in the manufacturing stage, and to achieve a flexible printed wiring board and a flexible printed wiring board with high manufacturing efficiency and high yield. It can be set as the manufacturing method of this.
In addition, in this way, the pattern design of the pattern mask 20 (the end face of the insulating layer 13) in consideration of the circuit direction of the wiring circuit 12a (laying direction of the wiring circuit 12a) and the behavior of the resin layer 13a in the development process and the curing process F3. (Design of shape). By doing so, the boundary portion K2 of the resin layer 13a in the insulating layer covering region Q1 is poorly covered only by changing the pattern design without changing the material of the photosensitive resin forming the resin layer 13a (insulating layer 13). Can be prevented. Therefore, it is possible to realize a flexible printed wiring board having a high manufacturing efficiency and a high yield and a manufacturing method of the flexible printed wiring board at a low cost.
Further, as shown in FIG. 4A, the pattern shape of the pattern mask 20 is set such that the boundary line K1 between the insulating layer coating region Q1 and the insulating layer non-covering region Q2 has a waveform. By doing so, the line T2 representing the boundary line K1 and the side surfaces 12a-1 on both sides of the wiring circuit 12a covered with the insulating layer covering region Q1 when viewed from the direction perpendicular to the surface H of the flexible printed wiring board 10 is obtained. The crossing angle A1 to the crossing angle A4 at which the crossing can be easily made acute. Therefore, it can be set as the manufacturing method of the flexible printed wiring board and flexible printed wiring board with much higher manufacturing efficiency.
Furthermore, the width L and the interval S are the same length, and the wave shape is a sine wave whose amplitude is vertically symmetrical, and one wave crest is formed in one wiring circuit 12a (width L of one wiring circuit 12a). Is configured such that one wave trough is arranged between the adjacent wiring circuits 12a (interval S between the adjacent wiring circuits 12a), so that the intersection angle A1 to the intersection angle A4 can be the same angle. Therefore, the stress applied to the plurality of boundary portions K2 of the resin layer 13a in the insulating layer covering region Q1 can be made uniform. Therefore, even when high-density wiring is applied, it is possible to effectively prevent the occurrence of coating defects such as cracks at the plurality of boundary portions K2 of the resin layer 13a. Therefore, it can be set as the manufacturing method of the flexible printed wiring board which can implement | achieve the high density wiring with a good yield, and a flexible printed wiring board. Moreover, pattern formation of the pattern mask 20 can be facilitated, and a flexible printed wiring board and a manufacturing method of the flexible printed wiring board can be obtained with higher manufacturing efficiency.

On the other hand, in the conventional flexible printed wiring board and the method for manufacturing the flexible printed wiring board, the circuit direction of the wiring circuit (laying direction of the wiring circuit) and the behavior of the resin layer in the development process and the curing process are considered. In general, the design of the pattern mask (design of the end face shape of the insulating layer) is performed without any pattern mask.
For example, as shown in FIG. 6A, the boundary line K1 between the insulating layer covering region Q1 and the insulating layer non-covering region Q2 (end surface 130− of the insulating layer 130− when viewed from the direction perpendicular to the surface H of the flexible printed wiring board 100). There is a flexible printed wiring board 100 in which a line T1) indicating 1 is inclined to a linear shape.
In such a configuration, as shown in FIG. 6A, the intersection angle B1 and the intersection angle B3 can be acute angles, but the intersection angle B2 and the intersection angle B4 are obtuse.
Therefore, in development processing and curing processing, shrinkage due to drying occurs in multiple directions at the boundary portion K2 of the resin layer 130a corresponding to the intersection angle B2 and the intersection angle B4. Therefore, stress concentration occurs at the boundary portion K2 of the resin layer 130a corresponding to the intersection angle B2 and the intersection angle B4. Therefore, as shown in FIG. 6B, there has been a problem that a coating failure such as a crack occurs in the boundary portion K2 of the resin layer 130a corresponding to the intersection angle B2 and the intersection angle B4 in the development processing.
Further, in the curing process, shrinkage due to imidization occurs in multiple directions at the boundary portion K2 of the resin layer 130a corresponding to the intersection angle B2 and the intersection angle B4. Therefore, stress concentration occurs at the boundary portion K2 of the resin layer 130a corresponding to the intersection angle B2 and the intersection angle B4. Therefore, as shown in FIG. 6B, there has been a problem that a coating failure such as a crack occurs at the boundary portion K2 of the resin layer 130a corresponding to the intersection angle B2 and the intersection angle B4 in the curing process.
In the conventional flexible printed wiring board 100, the same members and the same functions as those of the flexible printed wiring board 10 described above are given the same two-digit number and alphabet, and detailed description is omitted. It shall be.

Therefore, by adopting the configuration of the flexible printed wiring board 10 and the manufacturing method of the flexible printed wiring board 10 according to the embodiment of the present invention, the boundary portion K2 of the resin layer 13a in the insulating layer covering region Q1 in the development processing and the curing processing F3. It is possible to effectively prevent the occurrence of coating defects such as cracks.
Therefore, it is possible to provide a flexible printed wiring board and a method for manufacturing a flexible printed wiring board with high manufacturing efficiency and high yield.

In the present embodiment, the flexible printed wiring board 10 is configured as a so-called single-sided flexible printed wiring board that includes the wiring circuit 12a only on one side of the base material layer 11, but is not necessarily limited to such a configuration. Alternatively, a so-called double-sided flexible printed wiring board having wiring circuits 12a on both surfaces of the base material layer 11 may be used.
In the present embodiment, the resin layer 13a is formed of a liquid photosensitive resin. However, the resin layer 13a is not necessarily limited to such a configuration, and a film-like photosensitive resin is formed on the substrate layer 11 and the wiring circuit 12a. It is good also as a structure which pastes.
In this embodiment, the boundary line K1 between the insulating layer covering region Q1 and the insulating layer non-covering region Q2 is configured to have a waveform. However, the present invention is not necessarily limited to such a configuration, and side surfaces on both sides of the wiring circuit 12a covered with the boundary line K1 and the insulating layer coating region Q1 as viewed from the direction perpendicular to the surface H of the flexible printed wiring board 100. Any shape can be used as long as the intersecting angle with the line T2 representing 12a-1 can be an acute angle.
In the present embodiment, the flexible printed wiring board 10 is formed by the base material layer 11, the conductive layer 12, and the insulating layer 13. It is good also as a structure set as the flexible printed wiring board which adds a board and comprises a flexure.
In the present embodiment, the width L of the wiring circuit 12a and the interval S between the adjacent wiring circuits 12a have the same length. However, the present invention is not limited to such a configuration. It is good also as a structure which makes S different length.
Further, the shape of the flexible printed wiring board 10, the number of wiring circuits 12a, the formation position of the wiring circuit exposure region R, etc. are not limited to those of the present embodiment, and can be changed as appropriate.

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

The value of the width L of the wiring circuit 12a, the value of the distance S between the adjacent wiring circuits 12a, and the insulating layer covering region Q1 and the insulating layer non-covering region Q2 as viewed from the direction perpendicular to the surface H of the flexible printed wiring board 10 And changing the value of the crossing angle A1 at which the boundary line K1 and the line T2 representing the side surface 12a-1 of the wiring circuit 12a covered by the insulating layer covering region Q1 intersect to form a flexible printed wiring board, It was observed whether or not a crack (crack) occurred in the boundary portion K2 of the resin layer 13a in the insulating layer covering region Q1. The results are shown in Table 1.

From the results in Table 1, by making the crossing angle A1 an acute angle (30 degrees or more and 60 degrees or less), it is possible to effectively prevent cracks from occurring in the boundary portion K2 of the resin layer 13a in the insulating layer coating region Q1. You can see that you can. In particular, when the width L of the wiring circuit 12a and the interval S between the adjacent wiring circuits 12a are fine (18 μm or more and 20 μm or less), the insulating layer covering region Q1 is cracked at the boundary portion K2 of the resin layer 13a (cracking). It can be seen that the occurrence of) can be effectively prevented.

According to the present invention, in the insulating layer forming step, it is possible to effectively prevent the occurrence of coating defects such as cracks in the region where the insulating layer made of the photosensitive resin is formed. Industrial applicability in the field of flexible printed wiring boards having layers is high.

Claims (6)

1. A flexible printed wiring board comprising: a base material layer; a wiring circuit formed on the base material layer; and an insulating layer made of a photosensitive resin that covers the base material layer and the wiring circuit, wherein the insulating layer The insulating layer covering region and the insulating layer as viewed from the direction perpendicular to the surface of the flexible printed wiring board, comprising the insulating layer covering region covered with the insulating layer and the insulating layer non-covering region not covered with the insulating layer A flexible printed wiring board, wherein a crossing angle between a boundary line with an uncovered region and a line representing a side surface of the wiring circuit covered with the insulating layer covering region is formed at an acute angle.
2. The flexible printed wiring board according to claim 1, wherein the crossing angle is 15 degrees or more and less than 90 degrees.
3. The flexible printed wiring board according to claim 1 or 2, wherein the crossing angle is 30 degrees or more and less than 60 degrees.
4. 4. The wiring circuit according to claim 1, wherein the wiring circuit includes a plurality of wiring circuits, and at least one of a width of the wiring circuit and an interval between adjacent wiring circuits is 20 μm or less. The flexible printed wiring board as described.
5. 5. The flexible printed wiring board according to claim 1, wherein a boundary line between the insulating layer covering region and the insulating layer non-covering region is a waveform.
6. It is the manufacturing method of the flexible printed wiring board of Claim 1, Comprising: The base material layer formation process which forms a base material layer, The wiring circuit formation process which forms a wiring circuit on the said base material layer, The said base material After coating the photosensitive resin on the layer and the wiring circuit, an insulating layer coating region covered with the insulating layer and an insulating layer non-covering region not covered with the insulating layer are formed through an exposure process, a development process, and a curing process. An insulating layer forming step, and as a means for preventing the boundary portion between the insulating layer covering region and the insulating layer non-covering region from being cracked, in the insulating layer forming step, the flexible printed wiring board A boundary line between the insulating layer covering region and the insulating layer non-covering region and a line representing a side surface of the wiring circuit covered with the insulating layer covering region, viewed from a direction perpendicular to the surface, intersect. Method of manufacturing a flexible printed wiring board, characterized in that the crossing angle and an acute angle to form an insulating layer.

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