JP2000151039A - Flexible wiring board and electronic circuit device using the sme - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable reliable joint when metal bumps at a periphery of a flexible wiring board are joined to wiring lines of a package by heating them under pressure by using a bonding tool. SOLUTION: In the flexible wiring board of a grounded coplanar line structure wherein a first grounding wiring part 2 is formed on a first major surface of an insulating flexible substrate and second grounding wiring parts 3 and a wiring parts 4 for high frequency signals are formed on a second major surface thereof. In this case, a first metallic bump 5 is provided in an external terminal connection area 'a' of each wiring part 4, and island-like wiring pads 7 having the same thickness as the first grounding wiring parts 2 and not connected with the first grounding wiring part are provided on the first major surface at positions corresponding to the first metallic bumps 5.

Description

DETAILED DESCRIPTION OF THE INVENTION TECHNICAL FIELD OF THE INVENTION

The present invention relates to a double-sided wiring type flexible wiring for connecting to a circuit element such as a bare chip semiconductor element, a package, or an electrode terminal or a wiring of a wiring board, and an electronic circuit device using the same.

[0002]

2. Description of the Related Art FIG. 8 is a perspective view showing the structure of a double-sided wiring type flexible wiring board according to a first conventional example. FIG. (B) shows the second main surface side (front surface side) on which the high-frequency signal wiring pattern is formed.

In this flexible wiring board, a first ground wiring 22 is formed on a first main surface of an insulating flexible substrate 21, and a second ground wiring 23 and a high-frequency signal wiring are formed on a second main surface. 24, the ground wiring 22 on the first main surface and the ground wiring 2 on the second main surface.
3 is electrically connected by a through via (not shown). On the second main surface side, a first metal bump 25 for connecting to an electrode terminal or a wiring of a package or a wiring board is provided at an outer edge portion facing the second main surface side, and near the center for connecting to an electrode terminal of a semiconductor element. A second metal bump 26 is provided. 27 is a semiconductor element mounting part.

The high-frequency signal wiring 24 has a structure of a grounded coplanar line portion b from the position of the second metal bump 26 to the vicinity of the outer edge of the flexible wiring board. As a result, the wiring width is increased. This is because the electrode terminal of the semiconductor element has a terminal width:
The electrode terminals and wiring of packages and wiring boards are as large as 70 to 100 μm and the minimum terminal pitch: about 120 to 150 μm, while the terminal / wiring width is about 200 to 300 μm and the minimum terminal / wiring pitch is about 250 to 350 μm. This is because dimensional matching is considered.

For the reason described later, in the external terminal connection region a in which the wiring width of the high-frequency signal wiring 24 is widened, the first terminal is formed so as not to have a grounded coplanar line structure, that is, a coplanar line. A cutout portion 22a is formed in the first grounding wiring 22 on the main surface of (1).

In the grounded coplanar line, a high-frequency signal wiring 24, a ground wiring 22, and a ground wiring 23
The characteristic impedance of the line is determined by the electromagnetic coupling with the line, and when the electromagnetic coupling increases, the characteristic impedance decreases. That is, when the relative permittivity, the plate thickness, and the wiring film thickness of the insulating flexible substrate 21 are constant, the gap (G) between the high-frequency signal wiring 24 and the ground wiring 23 is obtained.
Is smaller, or the wiring width (W) of the high-frequency signal wiring 24 is wider, the characteristic impedance is lower.
Incidentally, the relative permittivity of the insulating flexible substrate 21 is 3.
5.Grounded coplanar line configuration with characteristic impedance of 50Ω when the thickness is 50μm and wiring thickness is 10μm,
According to the circuit analysis simulator (Series IV of HP), when the wiring width (W) = 90 μm, the gap (G) = 45
μm When the wiring cap (W) = 140 μm, the gap (G) = 6000
μm is calculated.

[0007] The wiring pattern of the grounded coplanar line structure can match both the terminal width and the minimum terminal pitch to the electrode terminals of the semiconductor element without any problem as shown in the above calculation results. In contrast, when the wiring width (W) is widened, the gap (G) becomes extremely wide, so that it is difficult to match the terminal pitch.

Therefore, as exemplified in the structure of the flexible wiring board of FIG. 8, in the external terminal connection region a of the high-frequency signal wiring 24, the first ground wiring 22 on the first main surface is formed.
The notch 22a is formed in the groove to weaken the electromagnetic coupling, thereby suppressing the expansion of the gap (G) due to the widening of the wiring width (W), and reducing the terminal width and terminal pitch of the electrode terminals of the package or wiring board. The dimensions are matched.

FIG. 9 is a perspective view showing a state in which the first conventional flexible wiring board illustrated in FIG.

In order to connect the flexible wiring board to the package 28, first, the flexible wiring board is positioned and mounted on the package 28, and then is pressurized and heated from above by a bonding tool 32 to form a high frequency signal. The first metal bump 25 on the wiring 24 is bonded to the high-frequency signal wiring 29 of the package, and the first metal bump 25 on the grounding wiring 23 is bonded to the ground wiring 30 of the package. Reference numeral 31 denotes a semiconductor element housing cavity.

FIG. 10 is a vertical cross-sectional view taken along the line CC ′ shown in FIG. 8 and shows a state where pressure and heat are applied by the bonding tool 32.

As described with reference to FIG. 8, in the first ground wiring 22 of the flexible wiring board, a position corresponding to the external terminal connection area a of the high-frequency signal wiring 24 is formed in the cutout portion 22a. Therefore, as shown in FIG.
On the first main surface side of the back surface of the first metal bump 25 on the high-frequency signal wiring 24, a gap 34 is formed between the bonding pad 32 and the bonding tool 32 by the thickness of the first ground wiring 22.

For this reason, in the structure of the first conventional flexible wiring board, the bonding tool 32 presses and presses.
Even if it is heated, the first metal bump 25 provided on the high-frequency signal wiring 24 is not sufficiently pressurized and heat-transferred, so that the first metal bump 25 and the high-frequency signal wiring 2
9 becomes uncertain.

[Second Conventional Example] FIGS. 11A and 11B are perspective views showing the structure of a double-sided wiring type flexible wiring board according to a second conventional example. FIG. 11A shows the first main surface side, and FIG. Shows the second main surface side on which the high-frequency signal wiring pattern is formed.

In the flexible wiring board of the second conventional example, a first ground wiring 22 is formed on a first main surface of an insulating flexible substrate 21 in the same manner as in the first conventional example. The second ground wiring 23 and the high-frequency signal wiring 24 are formed on the main surface of the first ground wiring 2.
The formation pattern of the notch 2 is different from that of the first conventional example. That is, in the second conventional example, the notch 22 is formed over the entire area of the external terminal connection area a near both ends on the first main surface side of the insulating flexible substrate 21.
b is formed. That is, the first ground wiring 22 is not formed at all in the external terminal connection region a.

When such a flexible wiring board of the second conventional example is mounted on a package and the metal bumps 25 are to be joined to the wiring of the package, the D-D 'line shown in FIG. As shown in FIG. 12 showing a vertical cross section at the position shown in FIG. 12, a gap 34 corresponding to the thickness of the ground wiring 22 is provided between the bonding tool 32 and the first main surface of the back surface of all the first metal bumps 25. Is formed, and the problem that the joining of all the first metal bumps 25 becomes more uncertain than in the first conventional example occurs. 33 is a semiconductor element mounting portion 27
Semiconductor device mounted on a semiconductor device.

Therefore, in the case of the structure of the external terminal connection area a of the flexible wiring board according to the second conventional example, the center of the bonding tool 32 is so arranged that the bonding tool 32 contacts only the external terminal connection area a. Although it is conceivable that the external terminal connection area a is usually narrow, about 300 to 400 μm, the contact area of the bonding tool 32 is insufficiently secured. The bonding state of the first metal bump 25 cannot be sufficiently improved.

In the first and second conventional examples, the flexible wiring board having the grounded coplanar line structure for the high-frequency signal wiring has been described as an example. Even in this case, the ground wiring on the first main surface of the external terminal connection region a is formed by the cutout portions 22a and 22b of the ground wiring 22.
In the case of a wiring pattern having the following, the same problem as described above occurs.

[0019]

As described above, in the structure of the external terminal connection area a of the conventional flexible wiring board, even if the bonding tool 32 is used to apply pressure and heat, the first metal bump 25 can be sufficiently applied. Pressure and heat transfer are not performed, and there is a disadvantage that the bonding between the first metal bump 25 and the electrode terminal or wiring of the package or another wiring board becomes uncertain.

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a bonding tool on a surface opposite to a metal bump for connecting to an electrode terminal or a wiring of a package or a wiring board. An object of the present invention is to provide a flexible wiring board and an electronic circuit device having a structure that solves the above-described problem by preventing a void from being formed therein when setting.

[0021]

In order to achieve the object of the present invention, a flexible wiring board of the first invention is connected to a circuit element such as a bare chip semiconductor element, a package, or an electrode terminal or wiring of a wiring board. A flexible wiring board of a double-sided wiring type, wherein a first grounding wiring is formed on a first main surface of an insulative flexible substrate, and a second main wiring opposite to the first main surface is provided. In a flexible wiring board having a grounded coplanar line structure or a microstrip line structure in which a second ground wiring and a high-frequency signal wiring are formed on a surface, a metal bump is provided in an external terminal connection region of the high-frequency signal wiring. At a position on the first main surface corresponding to the metal bump, having the same thickness as the first ground wiring and electrically unconnected to the first ground wiring. Which is configured by providing the Jo interconnect pad.

The flexible wiring board of the second invention is a double-sided wiring type flexible wiring board for connecting to a circuit element such as a bare chip semiconductor element, a package, or an electrode terminal or a wiring of a wiring board. A first ground wire is formed on a first main surface of the substrate, and a second ground wire and a high-frequency signal wire are formed on a second main surface opposite to the first main surface. In a flexible wiring board having a grounded coplanar line structure or a microstrip line structure, metal bumps are individually provided in external terminal connection regions of the high-frequency signal wiring and the second grounding wiring, and the first main surface is provided. At an upper position corresponding to each of the metal bumps, an island-shaped wiring pad having the same thickness as the first grounding wiring and not electrically connected to the first grounding wiring. It was constructed by providing.

A flexible wiring board according to a third aspect of the present invention is a flexible wiring board of a double-sided wiring type for connecting to a circuit element such as a bare chip semiconductor element, a package, or an electrode terminal or wiring of a wiring board. A flexible microstrip line structure in which a first ground wiring is formed on a first main surface of a substrate, and a high-frequency signal wiring is formed on a second main surface opposite to the first main surface. In the wiring board, a metal bump is provided in an external terminal connection region of the high-frequency signal wiring, and the first bump is provided on the first main surface at a position corresponding to the metal bump.
And an island-shaped wiring pad having the same thickness as that of the ground wiring and electrically disconnected from the first ground wiring.

An electronic circuit device according to a fourth aspect of the invention is configured by applying a circuit element such as a bare chip semiconductor element, a package, or a wiring board to the flexible wiring board according to the first to third aspects of the invention.

[0025]

DESCRIPTION OF THE PREFERRED EMBODIMENTS [First Embodiment] FIG.
FIGS. 2A and 2B are perspective views showing a structure of the flexible wiring board according to the first embodiment of the present invention, wherein FIG. 1A is a first main surface side, and FIG. 1B is a second main surface on which a high-frequency signal wiring pattern is formed; The side is shown.

In this flexible wiring board, a first ground wiring 2 is formed on a first main surface of an insulating flexible substrate 1, while a second ground wiring 3 and a high-frequency signal are formed on a second main surface. And the first and second ground wirings 2 and 3 are formed.
Between them, continuity is achieved by through vias (not shown).

An opposing outer edge of the second main surface is provided with a first terminal for connection to an electrode terminal or a wiring of a package or a wiring board.
And a second metal bump 6 for connection to an electrode terminal of the semiconductor element is provided near the center of the second main surface.

The high-frequency signal wiring 4 has a grounded coplanar line structure. The width of the wiring is widened in the external terminal connection area a so as to be dimensionally matched to the terminal width and the wiring width of a package or a wiring board.

The first ground wiring 2 on the first main surface is formed as shown in FIG.
As in the case of the conventional flexible wiring board shown in FIG. 1, the notch 2a is provided at a portion corresponding to the widened wiring pattern in the external terminal connection region a of the high-frequency signal wiring 4, but in the present invention, Newly, at the corresponding position on the back surface of the first metal bump 5 on the first main surface, the thickness is the same as that of the first grounding wiring 2 and is not electrically connected to the first grounding wiring 2. Are provided. Although the island-shaped wiring pad 7 is illustrated in the case of a rectangle in FIG. 1, other shapes such as a circle and a triangle may be used. Reference numeral 8 denotes a semiconductor element mounting portion.

FIG. 2 is a perspective view showing a state in which the flexible wiring board of FIG.

The procedure for connecting the flexible wiring board to the package 9 is as follows. First, the flexible wiring board is positioned and mounted on the package 9, and then pressed and heated by the bonding tool 13 from above to apply a high frequency signal. Wiring 4
The upper first metal bump 5 is bonded to the high-frequency signal wiring 10 of the package 9, and the first metal bump 5 on the ground wiring 3 is bonded to the ground wiring 11 of the package 9. Reference numeral 12 denotes a semiconductor element housing cavity.

FIG. 3 is a vertical cross-sectional view taken along the line AA ′ shown in FIG. 2 and shows a state in which the bonding tool 13 is pressurizing and heating.

In the conventional flexible wiring board shown in FIG. 8, the first main surface of the back surface of the first metal bump 25 on the high-frequency signal wiring 24 and the bonding tool 32 are connected as shown in FIG. Since a gap 34 is generated between the first and second wires 24 on the high-frequency signal wiring 24 by the bonding tool 32,
However, in the flexible wiring board of the present invention, as shown in FIG. 3, the position of the back surface of the first metal bump 5 on the first main surface is insufficient. Since the island-shaped wiring pads 7 are provided so that no void is formed in the bonding tool 13, the bonding tool 13 can be in close contact.

Thus, the pressurizing force generated by the bonding tool 13 is applied to the high-frequency signal wiring 4 and the second ground wiring 3.
And the heat from the bonding tool 13 is transmitted to the metal bumps 5 of the high-frequency signal wiring 4 via the island-shaped wiring pads 7 at the shortest distance.

FIG. 4 shows the upper plane of an analysis model used for simulating the transmission characteristics when the flexible wiring board of the present invention is connected to the package 9 by the finite element method, which is one of the three-dimensional electromagnetic field analysis techniques. FIG. 5 is a view showing a longitudinal section, and FIG. 5 is a line insertion loss (S21) obtained by comparing and analyzing the case where the island-shaped wiring pad 7 exists (the present invention) and the case where the island-like wiring pad 7 does not exist (the prior art) by the analysis model of FIG. It is a figure which shows the characteristic of reflection loss (S22).

As shown in FIG. 4, the analysis range is from the port P1 of the wiring portion of the package 9 immediately before the junction of the first metal bump 5 to the grounded coplanar line immediately before the junction of the second metal bump 6. This is the range up to the port P2 of the part b.

The insertion loss (S21) and the reflection loss (S
The characteristic of 22) is not so different from the characteristic of the wiring pattern of the prior art even with the wiring pattern of the present invention having the island-shaped wiring pad 7, Is not deteriorated.

As described above, the flexible wiring board according to the present invention can be used with the first metal bump 5 on the high-frequency signal wiring 4 and the high-frequency signal for the package without impairing the high-frequency performance of the conventional flexible wiring board. Since the bonding with the wiring 10 can be reliably performed, an electronic circuit device having excellent connection reliability and high-frequency performance can be realized by using the flexible wiring board of the present invention.

In the first embodiment, a flexible wiring board in which the high-frequency signal wiring has a grounded coplanar line structure has been described as an example, but the high-frequency signal wiring has a microstrip line structure. Even in the case of a plate, the same advantages and effects as described above can be obtained by providing electrically disconnected island-shaped wiring pads in the external terminal connection region a. In this microstrip line structure, the second ground wiring 3 is arranged or eliminated such that electromagnetic coupling with the high-frequency signal wiring 4 is weakened.

[Second Embodiment] FIGS. 6A and 6B are perspective views showing the structure of a flexible wiring board according to a second embodiment, wherein FIG. 6A shows the first main surface side, and FIG. FIG. 3 shows a second main surface side on which a signal wiring pattern is formed.

In the illustrated flexible wiring board, as in the first embodiment shown in FIG. 1, a first ground wiring 2 is formed on a first main surface of an insulating flexible substrate 1 and a second ground wiring 2 is formed.
The second ground wiring 3 and the high-frequency signal wiring 4 are formed on the main surface of the first embodiment, but the formation pattern of the first ground wiring 2 is different from that of the first embodiment. That is, in the second embodiment, the notch 2b is formed over the entire area of the external terminal connection area a near the both ends on the first main surface side of the insulating flexible substrate 2, and At the corresponding position on the back surface of the first metal bump 5 on the first main surface, an island-shaped wiring having the same thickness as the first grounding wiring 2 and electrically disconnected from the first grounding wiring 2. A package 7 'is provided.

As described above, the flexible wiring board is placed on the package 9 and the metal bumps 5 are connected to the wiring 1 of the package 9.
At the time of bonding to the first metal bumps 0 and 11, as shown in FIG. 7, the space between the first main surface side above the first metal bumps 5 and the bonding tool 13 is tightly connected via the island-shaped wiring pads 7 '. As a result, the pressure from the bonding tool 13 is evenly applied to the metal bumps 5 of the high-frequency signal wiring 4 and the second grounding wiring 3, and the heat from the bonding tool 13 is released from the island. The shortest distance is transmitted to each metal bump 5 via the wiring pad 7 '.
Accordingly, between the first metal bump 5 on the second ground wiring 3 of the flexible wiring board and the ground wiring 11 of the package 9, the high-frequency signal wiring 4 of the flexible wiring board and the high-frequency signal wiring of the package 9 are provided. The connection between the first and the second 10 is ensured.

In the flexible wiring board of this embodiment,
The results of the transmission characteristic simulation by the finite element method show that the provision of the island-shaped wiring pads 7 'has no adverse effect on the insertion loss and reflection loss characteristics of the high-frequency line, and impairs the high-frequency performance of the conventional flexible wiring board. In addition, the first metal bump 5 and the high-frequency signal wiring 10 of the package 9 can be reliably joined, and the use of the flexible wiring board of the present invention makes it possible to provide an electronic circuit having excellent connection reliability and high-frequency performance. The device can be realized.

Incidentally, also in the second embodiment,
The high-frequency signal wiring has been described as an example of a flexible wiring board having a grounded coplanar line structure. However, even when the high-frequency signal wiring is a flexible wiring board having a microstrip line structure, the external terminal connection area a By providing the electrically disconnected island-shaped wiring pads, the same advantages and effects as described above can be obtained. In this microstrip line structure, similarly to the above, the second ground wiring 3 is arranged or eliminated so that electromagnetic coupling with the high-frequency signal wiring 4 is weakened. In addition, although the island-shaped wiring pad 7 'is illustrated in FIG. 6 as being rectangular, other shapes such as a circle and a triangle may be used.

[0045]

As described above, according to the flexible wiring board of the present invention, the correspondence of the back surface of the metal bump formed on the external connection terminal region on the second main surface side of the insulating flexible substrate on the first main surface is provided. At the same position as the first grounding wiring, the island-shaped wiring pad electrically disconnected from the first grounding wiring is provided, so that the pressure and heat transfer from the bonding tool to the metal bumps are provided. It is intended to be performed efficiently.

For this reason, the connection between the metal bumps and the electrode terminals and the wiring of the package or the wiring board can be ensured, and the use of the flexible wiring board of the present invention provides excellent connection reliability. There is an advantage that an electronic circuit device can be realized. That is, in the production of an electronic circuit device for a high frequency application to which a flexible wiring board is applied, the production yield can be improved, so that the industrial value is extremely high.

[Brief description of the drawings]

FIGS. 1A and 1B are views showing a flexible wiring board according to a first embodiment of the present invention, wherein FIG. 1A is a perspective view showing a first main surface side, and FIG.
FIG. 4 is a perspective view showing a second main surface side.

FIG. 2 is a perspective view showing a state where the flexible wiring board of FIG. 1 is mounted on a package and connected.

FIG. 3 is a longitudinal sectional view showing a state where the flexible wiring board of FIG. 1 is placed on a package and pressed and heated by a bonding tool.

FIG. 4 is an explanatory diagram of a transmission characteristic analysis model when the flexible wiring board of FIG. 1 is mounted on a package and connected.

FIG. 5 is a characteristic diagram of a transmission characteristic simulation result by a finite element method for the analysis model of FIG. 4;

FIGS. 6A and 6B are views showing a flexible wiring board according to a second embodiment of the present invention, wherein FIG. 6A is a perspective view showing a first main surface side, and FIG.
FIG. 4 is a perspective view showing a second main surface side.

7 is a longitudinal sectional view showing a state in which the flexible wiring board of FIG. 6 is placed on a package and pressed and heated by a bonding tool.

FIGS. 8A and 8B are diagrams showing a first conventional flexible wiring board, wherein FIG. 8A is a perspective view showing a first main surface side, and FIG. 8B is a perspective view showing a second main surface side.

9 is a perspective view showing a state in which the flexible wiring board of FIG. 8 is mounted on a package and connected.

10 is a longitudinal sectional view showing a state in which the flexible wiring board of FIG. 8 is placed on a package and pressed and heated by a bonding tool.

11A and 11B are diagrams showing a second conventional flexible wiring board, wherein FIG. 11A is a perspective view showing a first main surface side, and FIG. 11B is a perspective view showing a second main surface side.

12 is a longitudinal sectional view showing a state where the flexible wiring board of FIG. 11 is placed on a package and pressed and heated by a bonding tool.

[Explanation of symbols]

 1, 21... Insulating flexible substrate 2, 22... First ground wiring 3, 23... Second ground wiring 4, 24. ... First metal bumps 6, 26... Second metal bumps 7, 7 ′..., Island-shaped wiring pads 8, 27. Element mounting section 9, 28 ... Package 10, 29 ... Package high-frequency signal wiring 11, 30 ... Package ground wiring 12, 31 ... Semiconductor element housing Cavities 13, 32 ... Bonding tools 14, 33 ... Semiconductor elements 34, 34 '... gaps

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5E336 BB12 BC34 BC37 CC32 CC55 EE01 GG11 5E338 AA02 AA12 AA16 BB63 BB71 BB75 CC01 CC02 CC06 CD23 CD24 CD33 EE01 EE11 5F044 KK03 KK10 KK16

Claims (4)

[Claims] 1. A double-sided wiring type flexible wiring board for connecting to a circuit element such as a bare chip semiconductor element, a package, or an electrode terminal or a wiring of a wiring board, on a first main surface of an insulating flexible board. A grounded coplanar line structure in which a first grounding wire is formed on the second main surface opposite to the first main surface and a second grounding wire and a high-frequency signal wiring are formed on the second main surface. In the flexible wiring board having a strip line structure, a metal bump is provided in an external terminal connection region of the high-frequency signal wiring, and the first ground wiring is provided on a position corresponding to the metal bump on the first main surface. A flexible wiring board provided with island-shaped wiring pads having the same thickness as that of the first grounding wiring and electrically disconnected from the first grounding wiring. 2. A double-sided wiring type flexible wiring board for connecting to a circuit element such as a bare chip semiconductor element or the like, a package, or an electrode terminal or wiring of a wiring board, wherein the flexible wiring board is provided on a first main surface of an insulating flexible board. A grounded coplanar line structure in which a first grounding wire is formed on the second main surface opposite to the first main surface and a second grounding wire and a high-frequency signal wiring are formed on the second main surface. In a flexible wiring board having a strip line structure, metal bumps are individually provided in external terminal connection regions of the high-frequency signal wiring and the second grounding wiring,
Island wiring pads having the same thickness as the first ground wiring and electrically unconnected to the first ground wiring are provided at positions on the first main surface corresponding to the individual metal bumps. A flexible wiring board characterized by the following. 3. A double-sided wiring type flexible wiring board for connecting to a circuit element such as a bare chip semiconductor element, a package, or an electrode terminal or wiring of a wiring board, wherein the flexible wiring board is provided on a first main surface of an insulating flexible board. A flexible wiring board having a microstrip line structure in which a first ground wire is formed on a second main surface opposite to the first main surface, and a high-frequency signal wire is formed on the second main surface. A metal bump is provided in an external terminal connection region of the wiring, and the first ground wiring and the first ground wiring have the same thickness as the first ground wiring at a position corresponding to the metal bump on the first main surface. A flexible wiring board, wherein island-shaped wiring pads are provided which are not connected to each other. 4. An electronic circuit device comprising a circuit element such as a bare chip semiconductor element, a package, or a wiring substrate applied to the flexible wiring board according to claim 1.