JP7820105B2 - Printed circuit board - Google Patents

Description

The present invention relates to a printed circuit board.

The printed circuit board described in Patent Document 1 includes a conductor pattern (referred to as a wiring pattern in the document), and a portion of the conductor pattern in the extension direction is a fuse portion (referred to as a pattern fuse in the document), and is configured so that when a current greater than or equal to the fusing current flows through the printed circuit board, the fuse portion will melt within the fusing time.

Japanese Patent Application Laid-Open No. 2007-311467

It is desirable for the fuse section to be structured so that it dissipates heat well while a current within the rated current flows, and reliably melts within the melting time when a current greater than the melting current flows. However, the technology in Patent Document 1 leaves room for improvement in this regard.

The present invention was made in consideration of the above-mentioned problems, and relates to a printed circuit board structured so that the fuse portion dissipates heat well while a current within the rated current flows, and the fuse portion more reliably melts within the melting time when a current greater than the fusing current flows.

According to the present invention, a flexible film-like base substrate;
a conductive pattern formed on one main surface of the base material;
a cover film covering the one main surface of the base substrate;
a lid member covering a surface of the cover film opposite to the base substrate side;
an adhesive layer that bonds the cover film and the lid member to each other;
Equipped with
a portion of the conductor pattern in an extending direction thereof is a fuse portion;
the cover film has a film opening that corresponds to at least a portion of the fuse portion, and the lid member covers the film opening;
the lid member is a plate-shaped member having a recess that opens toward the base substrate,
a surface of the lid member on which the recess is formed is bonded to the opposite surface of the cover film via the adhesive layer ;
the film opening and the recess are in communication with each other,
There is provided a printed circuit board in which a common air layer exists inside the film opening and inside the recess.

This invention provides a printed circuit board with a structure in which the fuse portion dissipates heat well while a current within the rated current flows, and the fuse portion melts more reliably within the melting time when a current greater than the melting current flows.

1(a) and 1(b) are diagrams showing a fuse portion of a conductor pattern and its surrounding structure in the first embodiment, with FIG. 1(a) being a perspective view and FIG. 1(b) being a plan view. FIG. 2 is a cross-sectional view taken along line AA shown in FIG. FIG. 3A is a cross-sectional view of a printed circuit board according to a first modification of the first embodiment, and FIG. 3B is a cross-sectional view of a printed circuit board according to a second modification of the first embodiment. FIG. 10 is a cross-sectional view of a printed circuit board according to a third modified example of the first embodiment. 5(a) and 5(b) are diagrams showing the fuse portion of the conductor pattern and its surrounding structure in the second embodiment, where FIG. 5(a) is a plan view and FIG. 5(b) is a cross-sectional view taken along line A-A in FIG. 5(a). 6(a) and 6(b) are diagrams showing the fuse portion of the conductor pattern and its surrounding structure in the third embodiment, with FIG. 6(a) being a perspective view and FIG. 6(b) being a plan view. 7A is a cross-sectional view taken along line AA shown in FIG. 6B, and FIG. 7B is a partially enlarged view of part A shown in FIG. 7A. FIG. 11 is a plan view of a printed circuit board according to a modified example of the third embodiment. FIG. 9 is a cross-sectional view taken along line AA shown in FIG. 8.

Embodiments of the present invention will be described below with reference to the drawings. Note that in all drawings, similar components will be designated by the same reference numerals, and descriptions will be omitted where appropriate.

First Embodiment
First, the first embodiment will be described with reference to FIGS.

As shown in Figures 1(a), 1(b), and 2, the printed circuit board 100 of this embodiment includes a flexible film-like base substrate 10, a conductor pattern 20 formed on one main surface 10a of the base substrate 10, a cover film 71 covering one main surface 10a of the base substrate 10, and a lid member 61 covering the surface of the cover film 71 opposite to the base substrate side (one surface 71a in this embodiment).
A portion of the conductor pattern 20 in the extending direction is the fuse portion 31, the cover film 71 has a film opening 73 that is an opening corresponding to at least a portion of the fuse portion 31, and the lid member 61 covers the film opening 73.
The cover film 71 covering one main surface 10 a of the base substrate 10 also covers the conductive patterns 20 .

The width and thickness of the fuse portion 31 are set so that when a current equal to or greater than a preset fusing current flows, it will melt before the non-fuse portion 36 in the conductor pattern 20 within the melting time. Meanwhile, while a current equal to or less than the rated current flows, the heat dissipation properties of the fuse portion 31 are ensured to prevent fires or short circuits caused by heat generation in the fuse portion 31, as well as unintended melting of the fuse portion 31.

According to this embodiment, a film opening 73 is formed in the cover film 71 in a portion corresponding to at least a part of the fuse portion 31, and the film opening 73 is covered by the lid member 61. This makes it easy to form an air layer 95 with high thermal insulation properties (low thermal conductivity) within the film opening 73. This ensures sufficient thermal insulation around the fuse portion 31, regardless of the structure and configuration around the fuse portion 31 on the printed circuit board 100, compared to a case in which the film opening 73 is not formed. Therefore, while the fuse portion 31 maintains a configuration that allows good heat dissipation while a current within the rated current flows, the fuse portion 31 can be melted in a shorter time when a current equal to or greater than the melting current flows.
Thus, according to this embodiment, it is possible to easily realize a printed circuit board 100 having a structure in which the fuse portion 31 dissipates heat well while a current within the rated current flows, and when a current greater than the fusing current flows, the fuse portion 31 more reliably melts within the fusing time.
In the present invention, the air layer 95 may be present throughout the entire film opening 73, or may be present in only a portion of the film opening 73, or even a large number of air bubbles may be dispersed within the film opening 73.
Furthermore, in the present invention, for example, the air layer 95 does not have to exist within the film opening 73. In this case, the film opening 73 is filled with a material that has higher thermal insulation properties than the cover film 71 and the first adhesive layer 74. This ensures sufficient thermal insulation around the fuse portion 31 compared to when the film opening 73 is not formed.

As an example, the printed circuit board 100 is incorporated into a voltage monitoring module (not shown) and is used to monitor voltage by connecting the conductor pattern 20 to a bus bar (not shown) that connects multiple battery cells (not shown).
More specifically, the printed circuit board 100 is equipped with, for example, a connector (not shown), and is connected via the connector to a measuring device that performs various controls, enabling voltage monitoring. Furthermore, each conductor pattern 20 connected to a bus bar is provided with a fuse portion 31. Typically, the fuse portion 31 is disposed near the corresponding bus bar, but the location of the fuse portion 31 is not limited to this example. The printed circuit board 100 may also include, for example, a conductor pattern 20 that is connected to a thermistor (not shown) that senses temperature. In this case, the conductor pattern 20 does not have a fuse portion 31.

In the following, when explaining the positional relationships between the components of the printed circuit board 100, the upper side in Figure 2 will be referred to as the upper side or upper portion, and the opposite side will be referred to as the lower side or lower portion. However, these directional specifications are for convenience only and do not limit the orientation of the printed circuit board 100 during manufacture or use.

2, the printed circuit board 100 is a laminate formed in a plate or sheet shape. More specifically, in addition to the base substrate 10, the conductive pattern 20, the cover film 71, and the lid member 61, the printed circuit board 100 further includes, for example, a first adhesive layer 74 that bonds the cover film 71 to the base substrate 10, a second adhesive layer 63 that bonds the cover film 71 to the lid member 61, and a third adhesive layer 15 that bonds the conductive pattern 20 to the base substrate 10.
In the present embodiment, a first adhesive layer 74 is laminated on the base substrate 10 via a conductive pattern 20, and a cover film 71 is laminated directly on the first adhesive layer 74. Furthermore, a second adhesive layer 63 is laminated directly on the cover film 71, and a lid member 61 is laminated directly on the second adhesive layer 63. Furthermore, a third adhesive layer 15 is laminated directly on the base substrate 10, and a conductive pattern 20 is laminated directly on the third adhesive layer 15.
However, in the present invention, the conductive pattern 20 may be provided directly on the base substrate 10, for example.
It should be noted that the lid member 61 and the second adhesive layer 63 are omitted from illustration in FIGS.

The base substrate 10 is a thin film-like substrate having two main surfaces.
The base substrate 10 may be any substrate as long as it contains a thermoplastic resin layer and exhibits thermoplastic properties as a whole.
Here, thermoplasticity refers to the property of softening when heated and hardening again when cooled.
The base substrate 10 is made of a thermoplastic resin, and in this embodiment, polyimide is used as the material. However, the material of the base substrate 10 is not limited to this example, and it is possible to use, for example, polyethylene naphthalate (Polyethylene Naphthalate: PEN), polyethylene terephthalate (Polyethylene Terephthalate: PET), liquid crystal polymer (Liquid Crystal Polymer: LCP), fluorine-based resin (Polytetra Fluoroethylene: PTFE), or a resin containing any of these.

The printed circuit board 100 includes, for example, a plurality of conductor patterns 20 extending in parallel with one another. Each conductor pattern 20 is formed by processing copper foil, for example.
1(a) and 1(b), each conductor pattern 20 includes linear portions 21 extending linearly along a first direction (the left-right direction in FIGS. 1(b) and 2) among directions along one main surface 10a of the base substrate 10. The linear portions 21 are spaced apart (e.g., equally spaced) from one another in a second direction (the up-down direction in FIG. 1(b)) perpendicular to the first direction. A first adhesive layer 74 fills at least a portion of the gaps between the linear portions 21. The fuse portion 31 is also spaced apart from other conductor patterns 20 in a predetermined manner, for example, so that it will blow out reliably under predetermined conditions.
The width dimension of the straight portion 21 of each conductor pattern 20 is substantially constant regardless of the position in the extending direction of the conductor pattern 20, except for the tapered portion 33 described later.
In the following, when describing the positional relationship between the components of the printed circuit board 100, the left side in FIG. 1B may be referred to as the left side, and the opposite side may be referred to as the right side.

In the example shown in FIGS. 1A and 1B, a fuse portion 31 is located in the center of the linear portion 21 in the extending direction, and non-fuse portions 36 are located on both ends of the fuse portion 31.
In this embodiment, the fuse portion 31 is formed in a meandering shape in plan view. This ensures a sufficient length of the fuse portion 31, increases the electrical resistance of the fuse portion 31, and allows heat to be trapped around the fuse portion 31 in the conductor pattern 20. However, in the present invention, the fuse portion 31 may also be formed in a substantially linear shape in plan view, as in a third embodiment described later.

2 , in this embodiment, the film thickness of the fuse portion 31 is thinner than, for example, the film thickness of the non-fuse portion 36 in the conductor pattern 20. This makes it possible to ensure a larger surface area of the fuse portion 31 while maintaining a desired cross-sectional area of the fuse portion 31, compared to when the film thickness of the fuse portion 31 is the same as the film thickness of the non-fuse portion 36. Therefore, the heat dissipation properties of the fuse portion 31 can be improved while maintaining a structure that allows the fuse portion 31 to generate heat well.
More specifically, as an example, at the boundary 32 between the non-fuse portion 36 and the fuse portion 31, the film thickness of the conductor pattern 20 can be configured to gradually become thinner from the non-fuse portion 36 toward the fuse portion 31.
This allows the conductor pattern 20 to be configured so that it smoothly switches from the non-fuse portion 36 to the fuse portion 31. Therefore, for example, when the printed circuit board 100 is bent, it is possible to prevent stress from concentrating on the boundary portion 32 between the non-fuse portion 36 and the fuse portion 31, and therefore the structural strength of the printed circuit board 100 can be sufficiently ensured.
The present invention is not limited to this example, and the film thickness of the conductive pattern 20 in the boundary portion 32 may be gradually reduced from the non-fuse portion 36 toward the fuse portion 31, for example.
Furthermore, the present invention is not limited to this example, and the film thickness of the conductive pattern 20 and the film thickness of the non-fuse portion 36 at the boundary portion 32 may be the same.

The method for making the film thickness of the fuse portion 31 thinner than the film thickness of the non-fuse portion 36 is not particularly limited. For example, a method of locally etching the portion of the conductor pattern 20 that will become the fuse portion 31 may be used, or a method of selectively forming a plating layer (not shown) on the portion of the conductor pattern 20 that will become the non-fuse portion 36 may be used.

In this embodiment, for example, the width of the fuse portion 31 may be narrower than the width of the non-fuse portion 36 .
This makes it easier for the fuse portion 31 to generate heat locally when a current greater than or equal to the fusing current flows through the conductor pattern 20, thereby ensuring that the fuse portion 31 melts within the melting time.
More specifically, in the case of this embodiment, as an example, each boundary portion 32 includes a tapered portion 33 in which the width dimension of the conductor pattern 20 gradually narrows from the non-fuse portion 36 toward the fuse portion 31 .
In a tapered portion 33 of the boundary portion 32 at one end (hereinafter, referred to as the left side) in the extension direction of the fuse portion 31 (left-right direction in FIG. 1B ), the width dimension of the conductor pattern 20 gradually narrows, for example, in a plan view, toward the other end (hereinafter, referred to as the right side) in the extension direction of the fuse portion 31. The right end of the tapered portion 33 of the left boundary portion 32 is connected to the left end of the fuse portion 31.
Similarly, in a tapered portion 33 of the boundary portion 32 at the other end (right end) in the extension direction of the fuse portion 31 (left-right direction in FIG. 1B ), the width dimension of the conductor pattern 20 gradually narrows, for example, in a plan view, toward one end (left side) in the extension direction of the fuse portion 31. The left end of the tapered portion 33 of the right boundary portion 32 is connected to the right end of the fuse portion 31.
However, the present invention is not limited to this example, and the width of the fuse portion 31 and the width of the non-fuse portion 36 may be set to be the same.

As described above, the cover film 71 covers the conductive pattern 20 from the side opposite the base substrate 10. In this embodiment, the cover film 71 contains a thermoplastic resin, just like the base substrate 10, and may be a layer formed solely from a thermoplastic resin, or a layer containing a resin other than a thermoplastic resin. In this embodiment, as an example, the cover film 71 is made of polyimide, which is the same type of material as the base substrate 10.

1B, in the present embodiment, the film opening 73 is disposed in a region corresponding to at least a portion of the fuse portion 31 of one conductor pattern 20 (in the present embodiment, the conductor pattern 20a) in plan view. The outline of the film opening 73 is located between the one conductor pattern 20a and another conductor pattern 20 adjacent to the one conductor pattern 20, and the first adhesive layer 74 is present at least in the region between the other conductor pattern 20 and the film opening 73 (for example, regions 26 and 27 described below).
This ensures good insulation between one conductor pattern 20a and another conductor pattern 20.
1(a) and 1(b), conductor patterns 20b and 20c are arranged in the second direction with conductor pattern 20a sandwiched therebetween. A first adhesive layer 74 is present in a region 26 between conductor patterns 20a and 20b and in a region 27 between conductor patterns 20a and 20c. The first adhesive layer 74 is also present in regions between conductor patterns 20 that are arranged outside the range shown in FIGS. 1(a) and 1(b).

It is preferable that the film opening 73 is set to a shape and size such that, when viewed in a plane, the entire outline of the fuse portion 31 is located in an area inside the outline of the film opening 73.
In this embodiment, the film opening 73 is formed in a generally oval shape (a generally rounded rectangular shape) that is elongated in the first direction in a plan view. More specifically, the outline of the film opening 73 includes, for example, a pair of straight lines that extend parallel to each other in the left-right direction (first direction), and a semicircle that is convex toward the left and a semicircle that is convex toward the right (hereinafter, referred to as a pair of semicircles).
One of the pair of straight lines of the film opening 73 is located in region 26 between conductor pattern 20a and conductor pattern 20b, which are arranged side by side in the second direction, and the other of the pair of straight lines is located in region 27 between conductor pattern 20a and conductor pattern 20c, which are arranged side by side in the second direction.
In a plan view, one of the pair of semicircles of the film opening 73 is located, for example, near the left end of the left tapered portion 33, and the other semicircle is located, for example, near the right end of the right tapered portion 33.
This results in a structure in which, in a plan view, the entire outline of the fuse portion 31 is located in an area inside the outline of the film opening 73, thereby ensuring better thermal insulation around the entire fuse portion 31. Therefore, when a current greater than the fusing current flows, the fuse portion 31 can be more reliably melted within the fusing time.
In the present invention, the planar shape of the film opening 73 is not particularly limited, and may be, for example, a substantially rectangular shape, a circular shape, or other shapes.
In addition, in the present invention, the timing of forming the film opening 73 in the cover film 71 is not particularly limited, and may be, for example, after or before laminating the cover film 71 onto the first adhesive layer 74.

The lid member 61 is, for example, a reinforcing film. The lid member 61 (reinforcing film) is arranged in a region that overlaps at least a portion of the fuse portion 31 in a plan view. In the present embodiment, the lid member 61 is arranged so as to cover the entire cover film 71 from above.
The lid member 61 is made of, for example, polyimide, which is the same material as the base substrate 10 and the cover film 71 .
However, in the present invention, as in a third embodiment described later, the cover member 61 is not necessarily limited to a reinforcing film, and the material constituting the cover member 61 is not limited to this example either.

The first adhesive layer 74 is provided on the upper surface of the conductive pattern 20 and on an area of one main surface 10 a of the base substrate 10 where the conductive pattern 20 is not formed.
The second adhesive layer 63 is provided, for example, over substantially the entire upper surface of the cover film 71 .
The third adhesive layer 15 is provided, for example, in an area on one main surface 10 a of the base substrate 10 where the conductive pattern 20 is arranged.
Each of the first adhesive layer 74, the second adhesive layer 63 and the third adhesive layer 15 is made of an adhesive or prepreg made of, for example, an epoxy resin, an acrylic resin or a PI resin.

In this embodiment, as shown in FIG. 2, an opening 75 is formed in the first adhesive layer 74 in an area corresponding to the film opening 73, and an air layer 95 present in the opening 75 is in contact with the fuse portion 31.
As a result, the air layer 95, which has high thermal insulation properties (low thermal conductivity), ensures sufficient thermal insulation around the fuse portion 31. Therefore, when a current greater than the fusing current flows, the fuse portion 31 generates heat well and melts within the fusing time.
Furthermore, in this embodiment, as shown in FIG. 2, an opening (hereinafter, second opening 64 ) is formed in the second adhesive layer 63 in an area corresponding to the film opening 73 .
This allows the air layer 95 to exist even within the second opening 64. Therefore, the volume of the air layer 95 can be sufficiently secured, and the thermal insulation around the fuse portion 31 can be further improved.
1(b), in plan view, the outline of the opening 75 is, for example, shaped and positioned to match the outline of the film opening 73. Therefore, in plan view, the region inside the film opening 73 (opening 75) is a region where the first adhesive layer 74 is not formed. Similarly, in plan view, the outline of the second opening 64 is, for example, shaped and positioned to match the outline of the film opening 73. Therefore, in plan view, the region inside the film opening 73 (second opening 64) is a region where the second adhesive layer 63 is not formed.

The method for forming the opening 75 and the second opening 64 is not particularly limited, but as an example, in the manufacturing process of the printed circuit board 100, the opening 75 and the second opening 64 can be formed by applying the adhesive constituting the first adhesive layer 74 to an area on the other surface 71 b of the cover film 71 where the film opening 73 is not formed, and applying the adhesive constituting the second adhesive layer 63 to an area on one surface 71 a of the cover film 71 where the film opening 73 is not formed. In this case, from the viewpoint of preventing the adhesive from flowing into the film opening 73, it is preferable that the thicknesses of the first adhesive layer 74 and the second adhesive layer 63 are thin.
However, the method for forming the opening 75 and the second opening 64 is not limited to this example. For example, a cover film 71 on which the first adhesive layer 74 and the second adhesive layer 63 have been formed in advance may be prepared, and the film opening 73, opening 75, and second opening 64 may be formed simultaneously by die-cutting the cover film 71.

The thickness of the first adhesive layer 74 is not particularly limited, but is preferably, for example, 8 μm or more and 50 μm or less.
The thickness of the second adhesive layer 63 is not particularly limited, but is preferably, for example, 8 μm or more and 50 μm or less.
The thickness of the third adhesive layer 15 is not particularly limited, but is preferably, for example, 0 μm or more and 50 μm or less.

The thickness of the cover film 71 is not particularly limited, but is preferably, for example, 12.5 μm or more and 50 μm or less.
The thickness of the lid member 61 is not particularly limited, but is preferably, for example, 12.5 μm or more and 50 μm or less.

The thickness of the base substrate 10 is not particularly limited, but is preferably, for example, 12.5 μm or more and 50 μm or less.
The thickness of the conductor pattern 20 is not particularly limited, but is preferably, for example, 5 μm to 35 μm. Note that the thickness of the conductor pattern 20 here refers to the average thickness of the entire conductor pattern 20.

In this embodiment, as in the modified example of the third embodiment described later, each conductor pattern 20 of the printed circuit board 100 may have a fuse portion 31, and the cover film 71 may have film openings 73 formed in areas corresponding to at least a portion of the fuse portion 31 of each conductor pattern 20.
In this case, the cover member 61 may cover, for example, a plurality of film openings 73 or only one film opening 73 .
Furthermore, when multiple film openings 73 are formed, the printed circuit board 100 may be provided with, for example, multiple cover members 61, each of which individually covers a corresponding film opening 73.

<Modifications 1 and 2 of the First Embodiment>
Next, first and second modifications of the first embodiment will be described with reference to FIGS.
The printed circuit board 100 of this modified example differs from the printed circuit board 100 of the first embodiment described above in the points described below, but is otherwise configured in the same way as the printed circuit board 100 of the first embodiment described above.
3A and 3B are cross-sectional views taken along the first direction (left-right direction).

In the first embodiment, an example was described in which, during the manufacturing process of the printed circuit board 100, the adhesive constituting the second adhesive layer 63 is applied to a region of the cover film 71 where the film opening 73 is not formed. However, in the present invention, when the adhesive constituting the second adhesive layer 63 is applied to the cover film 71, a portion of the adhesive may penetrate into the film opening 73. In this case, the adhesive may selectively penetrate into the upper portion of the film opening 73, as in Variation 1 shown in FIG. 3( a). In this case, an air layer 95 is present in the lower portion of the film opening 73, thereby ensuring sufficient thermal insulation around the fuse portion 31. Alternatively, the adhesive constituting the second adhesive layer 63 may penetrate into the entire film opening 73, as in Variation 2 shown in FIG. 3( b). In this case, the adhesive penetrates into the film opening 73, which is an air gap, and the adhesive that has penetrated into the film opening 73 is expected to contain air bubbles 92. These air bubbles 92 then ensure sufficient thermal insulation around the fuse portion 31.

<Modification 3 of First Embodiment>
Next, a modification of the first embodiment will be described with reference to FIG.
The printed circuit board 100 of this modified example differs from the printed circuit board 100 of the first embodiment described above in the points described below, but is otherwise configured in the same way as the printed circuit board 100 of the first embodiment described above.
FIG. 4 is a cross-sectional view taken along the first direction (left-right direction).

In this modification, as shown in Fig. 4, the film opening 73 is filled with an arc-extinguishing agent 91. This prevents arc current from occurring between the blown fuse portions 31, even if a voltage equal to or greater than the rated voltage is applied to the fuse portions 31 after they have blown. This prevents fires and short circuits caused by heat generated by the fuse portions 31.
The arc-extinguishing agent 91 is preferably evenly filled, for example, in the gap between the cover member 61 and the fuse portion 31. In this manner, the arc-extinguishing agent 91 can more reliably suppress ignition or short circuit caused by heat generation in the fuse portion 31.
The arc-extinguishing agent 91 is not particularly limited, but may be formed into a large number of particles and made of quartz, alumina, or the like.

In the present invention, instead of the arc-extinguishing agent 91, for example, a resin material with high thermal insulation properties may be applied to the entire surface of the fuse portion 31. This configuration also makes it possible to suppress fires and short circuits caused by heat generation from the fuse portion 31.

Second Embodiment
Next, a second embodiment will be described with reference to FIGS. 5(a) and 5(b).
The printed circuit board 100 of this embodiment differs from the printed circuit board 100 of the first embodiment and each of its modified examples in the points described below, but is otherwise configured in the same way as the printed circuit board 100 of the first embodiment and each of its modified examples.

Furthermore, the printed circuit board 100 includes, for example, a second conductor pattern 40 formed on a different layer of the printed circuit board 100 from the conductor pattern 20, and a second cover film 76 covering the second conductor pattern 40.
The second cover film 76 has a second film opening 77 which is an opening located in a region corresponding to the film opening 73 in a plan view.
This results in a configuration in which an air layer 96 is also formed below the fuse portion 31, thereby further improving the heat insulation around the fuse portion 31.
More specifically, in this embodiment, the printed circuit board 100 includes a second conductor pattern 40 formed on the other main surface 10b of the base substrate 10, and a second cover film 76 covering the other main surface 10b of the base substrate 10.
5( a) and 5(b), the second film opening 77 is set to, for example, the same shape and dimensions as the film opening 73, and in a plan view, the outline of the second film opening 77 substantially coincides with the outline of the film opening 73. Therefore, the entire outline of the fuse portion 31 is located in an area more inward than the outline of the second film opening 77.
In the present invention, the printed circuit board 100 may be, for example, a multi-layer FPC in which three or more conductor patterns are laminated via a plurality of base materials (not shown), a plurality of adhesive layers (not shown), etc. In this case, the number and arrangement of the film openings 73 can be appropriately set depending on the number of conductive patterns included in the printed circuit board 100 and the structure of each layer.

In this embodiment, the second cover film 76 contains, for example, a thermoplastic resin, just like the cover film 71, and may be a layer formed solely from a thermoplastic resin, or may be a layer containing a resin other than a thermoplastic resin. In this embodiment, as an example, the second cover film 76 is made of polyimide, which is the same type of material as the cover film 71.

Furthermore, in this embodiment, the printed circuit board 100 is provided with a second cover member 66 that covers the other main surface 10b of the base substrate 10, and the second cover member 66 covers the second film opening 77 from below.
This prevents the fuse portion 31 from being exposed to the outside of the printed circuit board 100 through the second film opening 77, even if the base substrate 10 is damaged, for example. Therefore, the safety of the printed circuit board 100 can be improved.
The second cover member 66 is set to have, for example, the same shape and dimensions as the cover member 61 .

As an example, second lid member 66 is a reinforcing film, similar to lid member 61. Second lid member 66 (reinforcing film) is disposed in a region that overlaps at least a portion of fuse portion 31 in a plan view. In the present embodiment, second lid member 66 is disposed so as to cover the entire second cover film 76 from below.
The second lid member 66 is made of, for example, polyimide, which is the same material as the lid member 61 .
However, in the present invention, the second lid member 66, like the lid member 61, is not necessarily limited to a reinforcing film, and the material constituting the second lid member 66 is not limited to this example either.
In FIG. 5A, the cover member 61 and the second adhesive layer 63 are omitted.

The printed circuit board 100 also includes, for example, a fourth adhesive layer 78 that bonds the base substrate 10 and the second conductor pattern 40 together, a fifth adhesive layer 68 that bonds the second cover film 76 and the second lid member 66 together, and a sixth adhesive layer 81 that bonds the second conductor pattern 40 and the second cover film 76 together.
In the present embodiment, a fifth adhesive layer 68 is laminated directly on the second lid member 66, and a second cover film 76 is laminated directly on the fifth adhesive layer 68. Furthermore, a sixth adhesive layer 81 is laminated directly on the second cover film 76, and a second conductor pattern 40 is laminated directly on the sixth adhesive layer 81. Furthermore, a fourth adhesive layer 78 is laminated directly on the second conductor pattern 40, and a base substrate 10 is laminated directly on the fourth adhesive layer 78.

The fourth adhesive layer 78 is provided, for example, over substantially the entire area of one main surface 10 b of the base substrate 10 .
The fifth adhesive layer 68 is provided, for example, over substantially the entire lower surface of the second cover film 76 .
The sixth adhesive layer 81 is provided, for example, over substantially the entire upper surface of the second cover film 76 .
Each of the fourth adhesive layer 78 to the sixth adhesive layer 81 is made of, for example, an adhesive or prepreg made from an epoxy-based resin, an acrylic-based resin, or a PI-based resin, similar to the first adhesive layer 74 to the third adhesive layer 15.
Here, for example, a second opening 79 is formed in the fifth adhesive layer 68 in a region corresponding to the second film opening 77. This ensures a sufficient volume for the air layer 96 disposed below the fuse portion 31, thereby further improving the thermal insulation around the fuse portion 31.

In addition, in this embodiment, a through hole (not shown) is formed in the base substrate 10, and a plating layer (not shown) is also formed within the through hole, and the conductor pattern 20 and the second conductor pattern 40 are electrically connected to each other via the plating layer within the through hole.
This ensures a sufficient heat dissipation area for the heat generated in the fuse portion 31, so that even if the resistance value of the fuse portion 31 is increased, a configuration can be realized in which the fuse portion 31 will not melt as long as a current within the rated current flows.
However, in the present invention, for example, the base substrate 10 may not have through holes or plating layers formed therein, and the conductive pattern 20 and the second conductive pattern 40 may not be electrically connected to each other.

5B, the second conductor pattern 40 is disposed, for example, in a position that does not overlap the fuse portion 31 (a position that avoids the fuse portion 31) in a plan view. This ensures a sufficient heat dissipation area for the heat generated in the fuse portion 31, while also ensuring that the fuse portion 31 will melt when a current equal to or greater than the fusing current flows.
More specifically, in this embodiment, the second conductor pattern 40 is disposed in an area outside the outline of the film opening 73 in plan view.
As another example, the second conductor pattern 40 may be formed in a mesh shape in a plan view, which can ensure a sufficient radiation area for the heat generated in the fuse portion 31.

The thickness of the fourth adhesive layer 78 is not particularly limited, but is preferably, for example, not less than 0 μm and not more than 50 μm.
The thickness of the fifth adhesive layer 68 is not particularly limited, but is preferably, for example, 8 μm or more and 50 μm or less.

The thickness of the second cover film 76 is not particularly limited, but is preferably, for example, 12.5 μm or more and 50 μm or less.
The thickness of the second lid member 66 is not particularly limited, but is preferably, for example, 12.5 μm or more and 50 μm or less.

The thickness dimension of the second conductor pattern 40 is not particularly limited, but is preferably, for example, 5 μm or more and 35 μm or less. Note that the thickness dimension of the second conductor pattern 40 here refers to the average thickness dimension of the entire second conductor pattern 40.

Third Embodiment
Next, a third embodiment will be described with reference to FIGS. 6(a) to 7(b).
The printed circuit board 100 of this embodiment differs from the printed circuit board 100 of the first and second embodiments described above in the points described below, but is otherwise configured in the same way as the printed circuit board 100 of the first and second embodiments described above.

In this embodiment, similarly to the second embodiment, the printed circuit board 100 includes a lid member 61, a cover film 71, a second lid member 66, and a second cover film 76.
However, as shown in FIGS. 6( a ) to 7 ( b ), in this embodiment, a recess 62 corresponding to the film opening 73 is formed on the surface of the cover member 61 facing the base substrate 10 .
This results in a configuration in which an air layer 95 is present within the recess 62, which allows the volume of the air layer 95 to be more effectively secured, thereby ensuring even better insulation around the fuse portion 31.
Similarly, a recess (recess 67 in this embodiment) corresponding to the film opening is formed on the surface of the second lid member 66 facing the base substrate 10 .
This results in a configuration in which an air layer 96 is present within the recess 67, making it possible to better secure the volume of the air layer 96, and therefore to further ensure the thermal insulation around the fuse portion 31.

In this embodiment, the cover member 61 is formed in the shape of a flat rectangular parallelepiped whose top-to-bottom dimension is smaller than its left-to-right and front-to-back dimensions. The interior of the recess 62 and the film opening 73 are in communication with each other.
6(b), in plan view, the outline of the recess 62 is formed, for example, in the same shape as the outline of the film opening 73, and is set to a size slightly larger than the outline of the film opening 73. More specifically, in plan view, the entire outline of the film opening 73 is located in an area more inward than the outline of the recess 62.
The second lid member 66 is set, for example, to have a shape and dimensions that are vertically symmetrical to those of the lid member 61. Therefore, the recess 67 of the second lid member 66 is set to a size that is slightly larger than the outline of the film opening 73, and the entire outline of the film opening 73 is located in an area inside the outline of the recess 67 in a plan view.
As a result, the entire outline of the fuse portion 31 is positioned in an area inside the outlines of each of the recesses 62 and 67, so that when a current greater than the fusing current flows, the insulating properties of the air layers within the recesses 62 and 67 allow the fuse portion 31 to generate heat well and melt within the fusing time.
In the present invention, the lid member 61 and the second lid member 66 are not limited to this example, and may have different shapes and dimensions. Therefore, the recess 62 and the recess 67 may have different shapes and dimensions.

In this embodiment, the cover member 61 and the second cover member 66 are each formed of, for example, a flame-retardant material, which can prevent ignition due to heat generation from the fuse portion 31. The flame-retardant material is not particularly limited, but may be, for example, FR4.
However, in the present invention, the material for forming the cover member 61 and the second cover member 66 is not limited to a flame-retardant material such as FR4, and can be appropriately selected depending on the configuration and use of the printed circuit board 100.
In addition, in the present invention, each of the cover member 61 and the second cover member 66, which are formed from a flame-retardant material such as FR4, may be formed, for example, in the shape of a flat plate and may have no recesses 62, 67.

<Modification of the third embodiment>
Next, a modification of the third embodiment will be described with reference to FIGS.
The printed circuit board 100 of this embodiment differs from the printed circuit board 100 of the first to third embodiments described above in the points described below, but is otherwise configured in the same way as the printed circuit board 100 of the first to third embodiments described above.

8 , each conductor pattern 20 has a fuse portion 31. The cover film 71 has film openings 73 formed in areas corresponding to at least a portion of the fuse portion 31 of each conductor pattern 20.
In plan view, a plurality of film openings 73 are arranged in one recess 62 of the cover member 61 .
This allows the air layer 95 in each recess 62 to improve the thermal insulation around each fuse portion 31. In other words, since only one cover member 61 is required, the manufacturing cost and number of steps for the printed circuit board 100 can be reduced.
In this modified example, as in the third embodiment, the lid member 61 formed from a flame-retardant material such as FR4 may be, for example, formed in the shape of a flat plate without any recesses 62, and such a lid member 61 may cover multiple film openings 73.

Furthermore, the fuse portions 31 of adjacent conductor patterns 20 among the plurality of conductor patterns 20 are arranged at positions shifted from each other in the extending direction of the plurality of conductor patterns 20 .
With this configuration, even if multiple fuse portions 31 are arranged closely together, heat generation or melting of the fuse portion 31 of one conductor pattern 20 can be prevented from affecting the fuse portions 31 of other adjacent conductor patterns 20.
More specifically, in this modification, each fuse portion 31 includes, for example, a fuse portion 31a disposed on the right side and a fuse portion 31b disposed on the left side of a reference line 110 shown in Fig. 8. The conductor patterns 20 having the fuse portion 31a disposed on the right side and the conductor patterns 20 having the fuse portion 31b disposed on the left side are alternately and repeatedly arranged in the second direction.
In this modified example, one film opening 73 is provided for each fuse portion 31. Therefore, with reference to the reference line 110, the film openings 73 located on the right side and the film openings 73 located on the left side are alternately arranged in the second direction. In plan view, the entire outline of each fuse portion 31 is located in an area inside the outline of the corresponding film opening 73.
In addition, in plan view, the entire outline of each film opening 73 is located in an area inside the outline of one of the recesses 62 of the lid member 61 .
In this modified example, each fuse portion 31 is formed in a substantially linear shape in a plan view.

Each embodiment has been described above with reference to the drawings, but these are merely examples of the present invention, and various other configurations may also be adopted.

The above embodiment encompasses the following technical ideas.
(1) a flexible film-like base material;
a conductive pattern formed on one main surface of the base material;
a cover film covering the one main surface of the base substrate;
a lid member covering a surface of the cover film opposite to the base substrate side;
Equipped with
a portion of the conductor pattern in an extending direction thereof is a fuse portion;
The cover film has a film opening that corresponds to at least a part of the fuse portion, and the lid member covers the film opening.
(2) The printed circuit board according to (1), further comprising a first adhesive layer that bonds the cover film and the base material together.
(3) A printed circuit board as described in (2), in which an opening is formed in the first adhesive layer in an area corresponding to the film opening, and an air layer present in the opening is in contact with the fuse portion.
(4) A plurality of the conductor patterns are provided, the conductor patterns extending in parallel with each other;
The printed circuit board according to (2) or (3), wherein, in a plan view, the film opening is disposed in an area corresponding to at least a portion of the fuse portion of one of the conductor patterns, the outline of the film opening is located between the one conductor pattern and another conductor pattern adjacent to the one conductor pattern, and the first adhesive layer is present at least in the area between the other conductor pattern and the film opening.
(5) The printed circuit board according to any one of (1) to (4), further comprising a second adhesive layer that bonds the cover film and the lid member together.
(6) The printed circuit board according to (5), wherein an opening is formed in the second adhesive layer in an area corresponding to the film opening.
(7) a second conductor pattern formed on a layer different from the conductor pattern on the printed circuit board;
a second cover film covering the second conductor pattern;
Equipped with
The printed circuit board according to any one of (1) to (6), wherein the second cover film has a second film opening that is an opening located in a region corresponding to the film opening in a plan view.
(8) A plurality of the conductor patterns are provided, the conductor patterns extending in parallel with each other.
Each conductor pattern has the fuse portion,
the cover film has film openings formed in areas corresponding to at least a portion of the fuse portion of each conductor pattern;
The printed circuit board according to any one of (1) to (7), wherein the cover member covers a plurality of the film openings.
(9) The printed circuit board according to any one of (1) to (8), wherein the cover member is a reinforcing film.
(10) A printed circuit board according to any one of (1) to (8), in which a recess corresponding to the film opening is formed on the surface of the cover member facing the base substrate.
(11) A plurality of the conductor patterns are provided, the conductor patterns extending in parallel with each other.
Each conductor pattern has the fuse portion,
the cover film has film openings formed in areas corresponding to at least a portion of the fuse portion of each conductor pattern;
The printed circuit board according to (10), wherein a plurality of the film openings are arranged in one of the recesses of the cover member in a plan view.
(12) A second cover member covering the other main surface of the base material is provided,
The printed circuit board according to any one of (1) to (11), wherein a recess corresponding to the film opening is formed on the surface of the second cover member facing the base substrate.
(13) The printed circuit board according to any one of (1) to (12), wherein the film opening is filled with an arc-extinguishing agent.
(14) A plurality of the conductor patterns are provided, the conductor patterns extending in parallel with each other.
The printed circuit board according to any one of (1) to (13), wherein the fuse portions of adjacent conductor patterns among the plurality of conductor patterns are arranged at positions shifted from each other in the extension direction of the plurality of conductor patterns.

10 Base substrate 10a One principal surface 10b Other principal surface 15 Third adhesive layer 20 Conductive pattern 21 Linear portions 26, 27 Region 31 Fuse portion 32 Boundary portion 33 Tapered portion 36 Non-fuse portion 40 Second conductive pattern 61 Lid member (first lid member)
62 Recess 63 Second adhesive layer 64 Second opening 66 Second cover member 67 Recess 68 Fifth adhesive layer 71 Cover film 71a One surface 71b Other surface 73 Film opening 74 First adhesive layer 75 Opening 76 Second cover film 77 Second film opening 78 Fourth adhesive layer 79 Second opening 81 Sixth adhesive layer 91 Arc-extinguishing agent 92 Air bubbles 95, 96 Air layer 100 Printed circuit board

Claims (13)

a flexible film-like base material;
a conductive pattern formed on one main surface of the base material;
a cover film covering the one main surface of the base substrate;
a lid member covering a surface of the cover film opposite to the base substrate side;
an adhesive layer that bonds the cover film and the lid member to each other;
Equipped with
a portion of the conductor pattern in an extending direction thereof is a fuse portion;
the cover film has a film opening that corresponds to at least a portion of the fuse portion, and the lid member covers the film opening;
the lid member is a plate-shaped member having a recess that opens toward the base substrate,
a surface of the lid member on which the recess is formed is bonded to the opposite surface of the cover film via the adhesive layer ;
the film opening and the recess are in communication with each other,
The printed circuit board has a common air layer present inside the film opening and inside the recess. The printed circuit board according to claim 1, wherein the depth of the recess is greater than the thickness of the cover film. The printed circuit board according to claim 1 or 2, wherein, in a plan view, the entire outline of the film opening is located inside the opening of the recess in the lid member. The printed circuit board described in any one of claims 1 to 3, comprising a first adhesive layer that bonds the cover film and the base substrate to each other. The printed circuit board described in claim 4, wherein an opening is formed in the first adhesive layer in an area corresponding to the film opening, and an air layer present in the opening contacts the fuse portion. a plurality of the conductor patterns extending in parallel to one another;
6. The printed circuit board according to claim 4 or 5, wherein, in a plan view, the film opening is arranged in an area corresponding to at least a portion of the fuse portion of one of the conductor patterns, the outline of the film opening is located between the one conductor pattern and another conductor pattern adjacent to the one conductor pattern, and the first adhesive layer is present at least in the area between the other conductor pattern and the film opening. 3. The printed circuit board according to claim 1, wherein an opening is formed in the adhesive layer in a region corresponding to the film opening. a second conductor pattern formed on a layer different from the conductor pattern on the printed circuit board;
a second cover film covering the second conductor pattern;
Equipped with
The printed circuit board according to claim 1 , wherein the second cover film has a second film opening that is an opening located in a region corresponding to the film opening in a plan view. a plurality of the conductor patterns extending in parallel to one another;
Each conductor pattern has the fuse portion,
the cover film has film openings formed in areas corresponding to at least a portion of the fuse portion of each conductor pattern;
The printed circuit board according to claim 1 , wherein the cover member covers a plurality of the film openings. The printed circuit board according to claim 1 , wherein the cover member is a reinforcing film. a plurality of the conductor patterns extending in parallel to one another;
Each conductor pattern has the fuse portion,
the cover film has film openings formed in areas corresponding to at least a portion of the fuse portion of each conductor pattern;
The printed circuit board according to claim 10 , wherein a plurality of the film openings are arranged in one of the recesses of the cover member in a plan view. a second cover member covering the other main surface of the base material;
The printed circuit board according to claim 1 , wherein a recess corresponding to the film opening is formed on a surface of the second cover member facing the base substrate. a plurality of the conductor patterns extending in parallel to one another;
The printed circuit board according to claim 1 , wherein the fuse portions of adjacent conductor patterns among the plurality of conductor patterns are arranged at positions shifted from each other in the extending direction of the plurality of conductor patterns.