阅读说明：本技术 柔性基板 (Flexible substrate ) 是由 西津新司郎 于 2018-08-23 设计创作，主要内容包括：本发明涉及柔性基板,在将在表面和背面以层状印刷有电路的柔性基板折弯,并将该柔性基板锡焊于封装体时,为了减轻对该柔性基板施加的应力,而具有将在该柔性基板的厚度方向上构成该柔性基板的基底基板层(2、9)、和从上下夹着该基底基板层的两个印刷有电路的图案层(1、3、8、10)作为一体,在厚度方向上变形为凹状的变形部(7、14)。另外,在该柔性基板表面,在以长度方向为横、以宽度方向为纵的情况下的纵横的尺寸中,使长度方向的两端的纵尺寸变得大于中央部分的纵尺寸。另外,在该柔性基板面中的靠上侧以及靠下侧的部分设置有空孔(21a、22a)。(The present invention relates to a flexible substrate, which is bent to form a flexible substrate with circuits printed on the front surface and the back surface in layers, and is soldered to a package, and which is provided with deformation portions (7, 14) which are integrated with base substrate layers (2, 9) which form the flexible substrate in the thickness direction of the flexible substrate and two pattern layers (1, 3, 8, 10) with circuits printed on the base substrate layers from the upper and lower sides and are deformed into a concave shape in the thickness direction, in order to reduce stress applied to the flexible substrate. In addition, on the surface of the flexible substrate, in the longitudinal and transverse dimensions in the case where the longitudinal direction is the transverse direction and the width direction is the longitudinal direction, the longitudinal dimension at both ends in the longitudinal direction is made larger than the longitudinal dimension at the central portion. Further, the flexible substrate surface is provided with holes (21a, 22a) at portions thereof located above and below the flexible substrate surface.)

1. A flexible substrate is characterized by comprising:

a base substrate layer composed of an insulator;

a surface pattern layer on which a circuit is printed on a surface of the base substrate layer; and

a back pattern layer printed with a circuit on a back surface of the base substrate layer,

the flexible substrate has a deformation portion that integrates the base substrate layer, the front surface pattern layer, and the back surface pattern layer and deforms into a concave shape in a thickness direction of the flexible substrate.

2. The flexible substrate of claim 1,

the deformed shape of the deformed portion is cylindrical, and when the width of the deformed portion is B and the depth is H, the value of H/B is set to be less than 0.46.

3. The flexible substrate of claim 1,

the deformed shape of the deformed portion is cylindrical, and when the curvature radius of the deformed shape in the thickness direction of the surface pattern layer in the deformed portion is R and the thickness of the flexible substrate is d, the value of d/R is set to be less than 0.26.

4. The flexible substrate according to any one of claims 1 to 3,

the flexible substrate has a front surface, a rear surface, and a longitudinal direction extending from the front surface to the rear surface.

5. The flexible substrate according to any one of claims 1 to 4,

the surface pattern layer has at least one hole in each of positions on the upper side and the lower side of the surface of the flexible substrate.

Technical Field

The present invention relates to a flexible substrate.

Background

A conventional flexible substrate (also referred to as a flexible Printed circuit board or an fpc) (flexible Printed circuits)) used for optical communication has a flat and linear shape when viewed in cross section in a thickness direction thereof. However, in actual use, a flexible substrate for optical communication is generally used in a bent state due to restrictions in packaging products and the like. That is, the flexible substrate is bent for use in a process such as soldering the package to the flexible substrate.

Patent document 1: japanese patent laid-open publication No. 2015-138476

As described above, since the flexible substrate used for optical communication is bent when soldered to the package, a bending stress is generated in the flexible substrate depending on the result of the bending. In addition, the bending stress generated causes a problem that the function to be exerted by the flexible substrate is not exerted.

Here, a conventional flexible substrate for optical communication is composed of at least one base substrate layer, at least one surface pattern layer on which a circuit is printed, and at least one pattern layer on which a circuit is printed.

When the flexible substrate having such a structure is bent, the pattern portion of the surface pattern layer of the flexible substrate is damaged, and a break or a pinhole is generated in the pattern portion of the printed circuit. Further, there is a problem that the circuit is electrically disconnected and cannot function due to disconnection or pin holes in the pattern portion of the circuit.

Disclosure of Invention

The present application discloses a technique for solving the above-described problems, and an object of the present application is to prevent a flexible substrate from being electrically disconnected from a circuit and failing to function due to a disconnection or a pinhole in a pattern portion of a circuit printed on the substrate.

The flexible substrate disclosed in the present application includes:

a base substrate layer, which is composed of an insulator,

a surface pattern layer on which a circuit is printed on a surface of the base substrate layer; and

a back pattern layer printed with a circuit on a back surface of the base substrate layer,

the flexible substrate has a deformation portion that integrates the base substrate layer, the front surface pattern layer, and the back surface pattern layer and deforms into a concave shape in a thickness direction of the flexible substrate.

According to the flexible substrate disclosed in the present application, it is possible to prevent the circuit of the flexible substrate from being electrically disconnected and failing to function due to disconnection or pin holes in the pattern portion of the circuit printed on the substrate.

Drawings

Fig. 1 is a schematic view showing an example of a cross section in the thickness direction of a flexible substrate according to embodiment 1.

Fig. 2 is a schematic diagram showing an example of a cross section in the thickness direction of the flexible substrate according to embodiment 2.

Fig. 3 is a schematic view showing an example of the surface of the flexible substrate according to embodiment 3.

Fig. 4 is a schematic diagram showing an example of the surface of the flexible substrate according to embodiment 4.

Fig. 5 is a schematic view showing another example of the surface of the flexible substrate according to embodiment 4.

Detailed Description

Embodiment 1.

Hereinafter, an embodiment of the present application will be described with reference to the drawings.

Fig. 1 is a schematic view of a cross section in the thickness direction of an example of a flexible substrate for optical communication used in embodiment 1. The flexible substrate generally has flexibility, can be repeatedly deformed with a relatively weak force, and has a property of maintaining its electrical characteristics even when deformed, and these characteristics can be maintained here.

In fig. 1, a base substrate layer 2, which is a film-shaped insulator made of, for example, polyimide, and is formed of at least 1 layer, is provided at the center in the thickness direction, at least 1 circuit-printed front pattern layer 1 made of normal copper is provided on the adjacent upper side, and at least 1 circuit-printed back pattern layer 3 made of normal copper is provided on the adjacent lower side of the base substrate layer 2, and the flexible substrate is formed of the 3 layers. In the figure, the three layers are separated from each other and drawn so that a gap is present between adjacent layers for the convenience of explanation, but actually adjacent layers are bonded to each other with an adhesive and no gap is present. The thickness d of the three-layer flexible substrate is set to 0.210 ± 0.034mm, including a tolerance.

As a flexible substrate to be actually used, as shown in fig. 1, a flexible substrate having a deformed portion 7 is used, and the deformed portion 7 includes a front surface pattern layer deformed portion 4 on which a circuit is printed (a portion of the front surface pattern layer 1 where the height position in the thickness direction starts to change in the back surface direction and which is formed in an arc shape (a portion located on the left side in fig. 1), the same applies to the other embodiments), a front surface pattern layer deformed portion 5 (a portion of the front surface pattern layer 1 where the height position in the thickness direction starts to change in the back surface direction and which is formed in an arc shape (a portion located on the right side in fig. 1), the same applies to the other embodiments), and a back surface pattern layer deformed portion 6 on which a circuit is printed (a portion of the back surface pattern layer 3 where the height position in the thickness direction changes in the back surface direction and which is recessed, the same applies to the other embodiments) The entire central portion of the substrate is deformed into a concave shape. Among representative values representing the deformed state of the deformed portion 7, the width B shown in the figure is 0.55mm, and the depth H is 0.25 mm. Here, the width B is defined by the minimum value of the distance between the surface pattern layer deformed portion 4 and the surface pattern layer deformed portion 5 in the longitudinal direction of the flexible substrate, and the depth H is defined by the maximum value of the values of the amount of positional change in the thickness direction between the surface of the surface pattern layer 1 and the concave deformed portion of the surface pattern layer 1. Further, the H/B ratio of the deformed portion 7 is set to a (positive) value smaller than 0.46. The flexible substrate having the concave portion in advance is used for the following reason.

That is, when packaging a product, an end portion (hereinafter, described in detail as "end portion") of the flexible substrate for optical communication is mounted to a package by soldering, but when mounting, the flexible substrate is bent at a central portion in a longitudinal direction thereof and then mounted.

This is because, during bending, stress is generated in the flexible substrate due to bending stress of bending, but by using the flexible substrate for optical communication in which the deformation portion is formed in advance, the magnitude of the stress can be reduced as compared with the case where the flexible substrate without the deformation portion is bent.

In this way, when the flexible substrate for optical communication is bent and soldered to the package, the broken line or pinhole is generated in the pattern portion on which the circuit is printed on the flexible substrate due to the stress applied to the flexible substrate, but as described above, in the flexible substrate of the present embodiment, the stress can be reduced, and therefore, it is possible to prevent the circuit of the flexible substrate from being electrically disconnected and not functioning due to the broken line or pinhole generated in the pattern portion on which the circuit is printed.

Embodiment 2.

Fig. 2 is a schematic view of a cross section in the thickness direction of an example of the flexible substrate for optical communication used in embodiment 2.

As shown in fig. 2, the flexible substrate is provided with at least 1 base substrate layer 29, at least 1 surface pattern layer 8 printed with a circuit on the adjacent upper side, and at least 1 back pattern layer 10 on the adjacent lower side of the base substrate layer 2, and the flexible substrate is composed of the three layers. The thickness d of the flexible substrate in which the three layers are added is set to 0.210 ± 0.034mm including a tolerance, as in the case of embodiment 1.

As a flexible substrate to be actually used, as shown in fig. 2, a flexible substrate provided with a deforming portion 14 in advance is used in a central portion in a thickness direction of the flexible substrate, and the deforming portion 14 deforms the entire portion located at the center in a longitudinal direction of the flexible substrate, including the front surface pattern layer deforming portions 11 and 12 of the front surface pattern layer, which are deformed into a concave shape, and the rear surface pattern layer deforming portion 13 of the rear surface pattern layer, which is deformed into a concave shape.

In this case, a portion including at least 1 circuit-printed surface pattern layer-deformed portion 11 and surface pattern layer-deformed portion 12 is formed in a cylindrical shape (hereinafter, this portion is referred to as a cylindrical body 15). When the curvature radius of the cross-sectional shape (circular arc shape) of the cylindrical body 15 in the thickness direction of the printed circuit board is R, R is set to satisfy R > 0.822 mm.

In the flexible substrate of fig. 2, the maximum strain amount ∈ max is expressed as ∈ max ═ d/(2 × R) in accordance with the curvature radius R and the thickness d. Therefore, it is found that the radius of curvature R can be increased in order to reduce the maximum strain amount.

In fig. 2, the thickness d of the sum of the front surface pattern layer 8, the base substrate layer 9, and the back surface pattern layer 10 is 0.210 ± 0.034 mm. Therefore, the curvature radius R of the circular arc-shaped portion of the cross section of the cylindrical body 15 including the surface pattern layer deformed portions 11 and 12 is set to satisfy R > 0.822mm as described above. That is, the curvature radius R of the arc-shaped portion, which is the deformed shape of the cross section in the thickness direction of the deformed portion, is determined so that d/R becomes a (positive) value smaller than 0.26 with respect to the thickness d of the flexible substrate.

By setting the radius of curvature R of the cylindrical body 15 in this way, even when the flexible substrate is bent and soldered to a package for packaging the product in actual use, stress applied to the flexible substrate for optical communication is reduced by the cylindrical body 15 having the set radius of curvature R.

As described above, when the flexible substrate is bent and the end portion of the flexible substrate is soldered to the package body at the time of packaging the product, the stress generated in the flexible substrate can be reduced by the cylindrical body 15 provided in the flexible substrate. Therefore, it is possible to prevent the occurrence of disconnection or pin holes in the pattern portion on which the circuit is printed on the flexible substrate. That is, it is possible to prevent the flexible substrate from being unable to function because the circuit is electrically disconnected due to disconnection or pin holes in the pattern portion on which the circuit is printed.

Embodiment 3.

Fig. 3 is a schematic view (plan view) of an example of the flexible substrate for optical communication used in embodiment 3, as viewed from the front surface (direction orthogonal to the thickness direction) of the flexible substrate described in fig. 1 and 2.

In this figure, the flexible substrate for optical communication is also configured by (not shown) at least 1 surface pattern layer on which a circuit is printed, at least 1 base substrate layer, and at least 1 back pattern layer on which a circuit is printed in the thickness direction, and includes the following three main components in a plan view: a front left-side constituent 16 (constituting a distance a between points 16a, 16 b), a front right-side constituent 18 (constituting a distance b between points 18a, 18 b), and a front center constituent 17 (constituting a distance c between ends 17a, 17 b).

In addition, the surface connecting portion 19 (a portion formed of the individual connecting portions 19a and 19 b) which is a portion connecting the surface left-side constituent portion 16 and the surface right-side constituent portion 18 to the surface center constituent portion 17 has a linearly decreasing size between upper and lower constituent ends (constituent points) as shown in the drawing.

As described above, the distance c between the end portions 17a and 17b of the front central component 17 is shorter than the distance a between the points 16a and 16b of the front left component 16 and the distance b between the points 18a and 18b of the front right component 18, whereby the flexible substrate is easily bent at the central portion in the longitudinal direction of the surface. In this case, specifically, for example, a ≈ b is set, and 1/2a < c < 2/3 a.

Therefore, in actual use, when the flexible substrate is bent and the end portion of the flexible substrate (specifically, for example, the entire range including the left end of the front-left side constituent portion 16 including the constituent points 16a and 16b and the distance of mm from the left end in the longitudinal direction) is soldered to the package body at the time of packaging the product, the stress generated in the flexible substrate can be reduced by providing the front-center constituent portion 17 of the flexible substrate.

Therefore, it is possible to prevent the occurrence of a broken line or a pinhole in the pattern portion having the circuit printed thereon. That is, even if the flexible substrate is bent at the time of packaging the product, the flexible substrate is not broken or pin holes are not generated in the pattern portion on which the circuit is printed, and thus the circuit can be prevented from being electrically disconnected and failing to function. In the above description, the case where the upper and lower contour lines of the surface connecting portion 19 are straight lines has been described as an example, but the present invention is not limited to this, and may be a curved contour line such as a circular arc. Even in this case, the same effects as those in the above-described case are obtained.

Embodiment 4.

Fig. 4 is a schematic view (plan view) of an example of the flexible substrate for optical communication used in embodiment 4, as viewed from the front surface of the flexible substrate described in fig. 3.

As shown in the drawing, in the flexible substrate for optical communication according to embodiment 4, in the flexible substrate having at least 1 uppermost pattern circuit 20 (consisting of 20a, 20b, 20c, 20d, and 4 circuits in order from the upper side) of the surface pattern layer on which the circuits are printed, the upper side and the lower side of the surface of the uppermost pattern layer of the surface pattern layer are provided with the via portions 21 and 22 (see the via portions 21a and 22a and the like in fig. 4) in which a plurality of through vias having a diameter of 10 μm or more and less than 100 μm are formed.

That is, since the through holes are provided in the upper portion and the lower portion of the hole arrangement portion 23 surrounded by the dotted frame, the rigidity of the hole arrangement portion 23 of the flexible substrate is relatively low compared to other portions, and therefore, in actual use, the flexible substrate is easily bent at the time of packaging of a product, and stress generated in the flexible substrate is reduced by bending.

Therefore, the flexible substrate does not have a broken line or a pinhole in the pattern portion on which the circuit is printed, and the circuit can be prevented from being broken and not functioning due to the broken line or the pinhole in the pattern portion on which the circuit is printed.

Fig. 5 is a schematic view (plan view) of another example of the flexible substrate for optical communication used in embodiment 4, as viewed from the front surface of the flexible substrate.

As shown in the drawing, in another example of the flexible substrate for optical communication according to embodiment 4, only the uppermost pattern circuit 24 of the surface pattern layer shown in fig. 4 is different from the uppermost pattern circuit 20 of the surface pattern layer described above. That is, in another example of the flexible substrate shown in fig. 4, the uppermost pattern circuit 24 of the surface pattern layer is formed linearly along the longitudinal direction of the flexible substrate without being bent halfway. As a result, the arrangement of the holes on the surface of the flexible substrate did not change, and the 4 uppermost pattern circuits were disposed on the inner side farther from the surface outline as a whole.

In this case, since the circuit pattern before bending is not bent in the middle, it is assumed that the circuit pattern is formed so as to be less likely to be damaged even if originally subjected to stress, and therefore, it is considered that the occurrence of disconnection or pin holes in the circuit pattern portion of the flexible substrate can be more effectively prevented than in the case of the flexible substrate shown in fig. 4.

In addition, although various exemplary embodiments and examples have been described in the present application, the various features, modes, and functions described in one or more embodiments are not limited to the application to the specific embodiments, and can be applied to the embodiments alone or in various combinations. Therefore, a myriad of modifications not illustrated are assumed to be within the scope of the technology disclosed in the present specification. For example, the present invention includes a case where at least one component is modified, added, or omitted, and a case where at least one component is extracted and combined with the components of the other embodiments.

Specifically, in embodiment 3, it is not necessary to set the respective constituent ends to be equidistant from each other from the center line of the shape in the width direction of the flexible substrate, and the same effect as in the case of the equidistant configuration can be obtained even if the equidistant configuration is not set. Similarly, even when the shape center line is set to be equidistant from each other in the width direction, it is not necessary to set the shape center line to be equidistant from each other in the longitudinal direction.

In embodiment 4, a case where a plurality of holes are present in each of hole 21 and hole 22 has been described as an example, but the present invention is not limited to this, and similar effects can be produced even when there is only one hole in each of hole 21 and hole 22.

Description of the reference numerals

1. A surface pattern layer; 2. a base substrate layer; 3. a back pattern layer; 4. 5, 11, 12.. surface pattern layer deformation; 6. a back pattern layer deformation; 7. a deformation; a cylindrical body; a surface left formation; 16a, 16b, 18a, 18b.. forming points; forming an end; a surface central formation; a right-side formation of the surface; a surface connection; 19a, 19b.. the individual connections; 20. an uppermost pattern circuit of the surface pattern layer; 21. a void portion; 21a, 22a.. blank hole; a void arrangement portion.