JP5413067B2 - Circuit board - Google Patents

Description

  The present invention relates to a circuit board.

  An example of a circuit board based on the prior art is disclosed in JP-T-2002-503033 (Patent Document 1). Patent Document 1 discloses a connection element for making an electrical connection between a large circuit board and a chip disposed on the surface of the circuit board. This connecting element includes a strip-shaped plastic sheet having a constant width and three strip-shaped conductor patterns formed on the upper surface thereof. These three conductor patterns are composed of one signal conductor provided in the center and a total of two ground planes arranged one on each side. These conductor patterns are formed so as to extend in the longitudinal direction of the plastic sheet in parallel with being separated from each other. For these conductor patterns, the plastic sheet serves as a base material. These three conductor patterns constitute a coplanar waveguide. Patent Document 1 discloses a configuration in which three conductor patterns have a constant width and are parallel to each other except for an end portion, and also shows a configuration in which the width of each conductor pattern gradually changes. ing.

Japanese translation of PCT publication No. 2002-503033

  There is a structure including two substrates having rigidity and a flexible substrate that connects between the two substrates. A portion of the two substrates having rigidity in the structure is referred to as a “rigid portion”, and a portion of the flexible substrate that connects between the two rigid portions is referred to as a “flexible portion”. The whole structure is also called a “rigid flexible substrate”. A rigid flexible board is a type of circuit board.

  A side view of an example of a rigid flexible substrate is shown in FIG. A flexible portion 53 is connected between the rigid portions 51 and 52. A cross section of the flexible portion 53 is shown in FIG. The flexible part 53 includes a resin base 53e and metal patterns 53a, 53b, 53c formed on the upper surface thereof.

  Regardless of the location of the metal patterns 53a, 53b, 53c of the flexible portion 53, the resin base 53e always exists below the metal pattern. When current flows through the metal patterns 53a, 53b, and 53c of the flexible portion 53, the electrical characteristics may vary due to the presence of the resin base material 53e in contact with the metal pattern. For example, if the resin used for the base material 53e has a high dielectric constant, stray capacitance is generated in the metal pattern when bent, and the electrical characteristics are likely to fluctuate.

  Rigid flexible boards are usually used by being incorporated into some equipment, but when the equipment is used, when the flexible part is used in a form that bends greatly, or when the flexible part repeatedly bends frequently. In this case, the metal pattern may be peeled off from the resin portion as the base material. When peeling off during use, the characteristics change undesirably.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a circuit board in which there is little variation in electrical characteristics due to the material of the base material in the flexible part and there is no fear of peeling of the base material.

  To achieve the above object, a circuit board according to the present invention includes a first rigid portion including a first insulating base and a first circuit pattern, a second insulating base and a second circuit pattern. And a flexible metal thin plate portion that connects the first rigid portion and the second rigid portion without a base material, wherein the metal thin plate portion includes the first and second rigid portions. 2 is electrically connected to the circuit pattern.

  According to the present invention, since the base material for physically supporting the metal thin plate portion is not provided around the metal thin plate portion constituting the line, the electric characteristics are less likely to fluctuate with respect to the bending. In addition, since the base material does not exist in the metal thin plate portion from the beginning, there is no possibility of characteristic fluctuation due to peeling.

It is a perspective view of the circuit board in Embodiment 1 based on this invention. It is sectional drawing of the circuit board in Embodiment 1 based on this invention. It is sectional drawing of the flexible part of the circuit board in Embodiment 1 based on this invention. It is a perspective view of the 1st modification of the circuit board in Embodiment 1 based on this invention. It is sectional drawing of the flexible part of the 2nd modification of the circuit board in Embodiment 1 based on this invention. It is sectional drawing of the flexible part of the 3rd modification of the circuit board in Embodiment 1 based on this invention. It is sectional drawing of the flexible part of the 4th modification of the circuit board in Embodiment 1 based on this invention. It is a side view of the 5th modification of the circuit board in Embodiment 1 based on this invention. It is a side view of the circuit board based on a prior art. It is sectional drawing of the flexible part contained in the circuit board based on a prior art.

(Embodiment 1)
(Constitution)
With reference to FIGS. 1-3, the circuit board in Embodiment 1 based on this invention is demonstrated. A perspective view of a circuit board 101 in this embodiment is shown in FIG. 1, and a cross-sectional view is shown in FIG. The circuit board 101 according to the present embodiment includes a first rigid portion 1 including a first insulating base material 11 and a first circuit pattern 12, a second insulating base material 21, and a second circuit pattern 22. The 2nd rigid part 2 containing 1 and the flexible metal thin plate part 3 which connects the 1st rigid part 1 and the 2nd rigid part 2 without a base material are provided. The metal thin plate portion 3 is electrically connected to the first and second circuit patterns 12 and 22.

  The metal thin plate portion 3 includes three strip-shaped metal films arranged in parallel at the same height. In the metal thin plate portion 3, these three strip-shaped metal films constitute a line. The central one of the metal thin plate portions 3 is a signal line portion 3a, and a total of two on both sides is a ground portion 3b, which constitute a coplanar type high-frequency line. The metal thin plate portion 3 is formed of a metal foil such as a copper foil. FIG. 3 shows a cross-sectional view taken along the line III-III in FIG.

  The metal film of the metal thin plate part 3 connects two rigid parts without a base material for physically supporting the metal film. That is, these metal films directly and electrically connect the two rigid parts without using a base material. Such a configuration in which the metal film directly passes through the air without using the base material is also referred to as “base material-less”.

(Action / Effect)
In the present embodiment, since the metal thin plate part 3 constituting the line connects the first rigid part 1 and the second rigid part 2 without a base material, only the air around the line is not resin. Will exist. Since air has a dielectric constant ε = 1, stray capacitance is less likely to occur than any resin. In the present embodiment, the portion connecting the rigid portions, that is, the flexible portion is basically composed of only a metal film, and has a structure without the resin portion, so the material cost of the resin portion is not required for the flexible portion. Yes, cost can be reduced.

  In general, a metal foil such as a copper foil is fixed to a base material by an anchor effect, and therefore the surface roughness of the metal film must be increased. In this embodiment, the surface of the metal film Since it is not necessary to increase the roughness, a circuit board having excellent high-frequency characteristics can be obtained. Specifically, the surface roughness Ra of both main surfaces of the metal film can be set to several μm or less.

  Since the flexible part is a part where stress is most generated by bending deformation, if the structure is a structure in which the resin and the metal are superposed, peeling is likely to occur at the interface between the resin and the metal. However, in the present embodiment, since the flexible portion is basically made only of metal, there is no possibility that peeling will occur, and undesired characteristic changes due to peeling will not occur.

  Therefore, the circuit board in this embodiment can be a circuit board that is particularly suitable for high-frequency applications without much fluctuation in electrical characteristics such as impedance and without fear of peeling of the base material.

  In the present embodiment, preferably, the first and second rigid portions 1 and 2 include via-hole conductors 31 and 32 provided in the first and second circuit patterns 12 and 22, respectively, The part 3 is joined to the via-hole conductors 31 and 32 by solid phase diffusion bonding. As to whether or not solid phase diffusion bonding is performed, when solid phase diffusion bonding is performed, the connection portion between the metal thin plate portion 3 and the via-hole conductors 31 and 32 is integrated, and an intermetallic compound is locally generated. So it can be identified. If it is joined by solid phase diffusion bonding in this way, the metal thin plate portion 3 as the flexible portion and the first and second circuit patterns 12 and 22 included in the rigid portion can be securely and firmly connected. The bonding strength between the rigid portion and the metal thin plate portion can be increased, which is preferable.

  Furthermore, as shown in FIG. 4, the metal thin plate portion 3 can include a connection portion 4 for making an electrical connection to the outside. The connection portion 4 is a partial region in the middle of the thin metal plate portion 3, and external wiring 5 is connected to the connection portion 4. Thus, if the connection part 4 is provided, the electrical connection with the exterior can be performed easily.

  It is preferable that the 1st and 2nd rigid parts 1 and 2 include the laminated structure which laminated | stacked the some flexible sheet. If it is this structure, the rigid part which contains a circuit pattern inside can be formed easily.

  It is preferable that the metal thin plate part 3 as a flexible part is pulled out from the interlayer of the flexible sheet as a rigid part. If it is this structure, when it laminates | stacks a flexible sheet, it will be set as the structure which extended a part of circuit pattern, and a flexible part can be easily formed by making it protrude from a flexible sheet. Further, the bonding strength between the rigid portion and the metal thin plate portion can be further increased. In this respect, it is preferable that the thin metal plate portion is solid phase diffusion bonded to the via-hole conductor on both main surfaces in the rigid portion.

  The surface of the metal thin plate portion 3 is preferably covered with a rust preventive film. If it is this structure, it can prevent that the metal thin plate part 3 rusts and a characteristic deteriorates. The rust-proofing film may be a resin. The rust preventive film may have a thickness of 1 μm or less. FIG. 5 shows a cross section of the flexible portion when the surface of the metal thin plate portion 3 is covered with a rust-proofing film. In this example, the antirust treatment film is a resin film 6. As shown in FIG. 5, the resin film may cover one surface of each metal film of the thin metal plate portion 3. Moreover, as shown in FIG. 6, the structure which the resin film covers both surfaces of each metal film and the side surface is exposed may be sufficient. Moreover, as shown in FIG. 7, the structure which a resin film covers the both surfaces and side surface of each metal film may be sufficient. As shown in FIGS. 5 to 7, even if any resin film is attached to the metal film of the flexible part, these resin films are only for protecting the surface of the metal film, and support the metal film. Is not. Therefore, these do not fall under the “base material”. Each metal film of the thin metal plate portion 3 maintains its own posture by its own rigidity.

  As shown in FIGS. 1 and 2, the metal thin plate portion 3 preferably includes a plurality of strip-shaped metal foils arranged at the same height. With such a configuration, when the rigid portion is formed by stacking, a plurality of wires can be arranged in the same layer to form a connection to the metal thin plate portion.

  The metal thin plate portion 3 preferably includes a plurality of strip-shaped metal foils arranged at different heights. This is, for example, a rigid flexible substrate configured as shown in FIG. This rigid flexible substrate includes a thin metal plate portion 3h. With such a configuration, the wiring included in the metal thin plate portion 3h can be distributed in the vertical direction, so that the degree of freedom of wiring is increased and the width required for the flexible portion can be reduced.

  In the said embodiment, although it showed that it may form with copper foil as an example of a metal thin plate part, you may form with metals other than copper. Further, the thin metal plate portion may be formed by a combination of a plurality of types of metal films. In addition, in the case of copper foil, since it must have a certain intensity | strength and rigidity, it is preferable that the thickness is 10-40 micrometers.

  In the circuit board according to the present invention, the metal thin plate portion as the flexible portion is basically formed only of metal, but a film other than metal, such as a resin film, is attached to the surface of the metal film. As long as it does not correspond to the substrate. The “base material” is used to physically support a metal film or the like formed on the surface, and plays a role like a foundation. Therefore, the member plays a dominant role in maintaining the posture of the flexible portion. When some other member is attached to the surface of the metal film, and the posture of the flexible part is almost determined by the rigidity of the metal film itself, the other member attached to the surface of the metal film is the base. Not applicable to the material.

  In addition, the said embodiment disclosed this time is an illustration in all the points, Comprising: It is not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and includes all modifications within the scope and meaning equivalent to the terms of the claims.

  DESCRIPTION OF SYMBOLS 1 1st rigid part, 2nd 2nd rigid part, 3 metal thin plate part, 3a signal line part, 3b ground part, 4 connection part, 5 external wiring, 6 resin film, 11 1st insulating base material, 12 1st 1 circuit pattern, 21 second insulating base material, 22 second circuit pattern, 31, 32 via-hole conductor, 51, 52 rigid portion, 53 flexible portion, 53a, 53b, 53c metal pattern, 53e base material, 101 circuit substrate.

Claims (7)

A first rigid portion including a first insulating substrate and a first circuit pattern;
A second rigid portion including a second insulating substrate and a second circuit pattern;
A flexible thin metal plate portion that connects the first rigid portion and the second rigid portion without a base material;
The metal thin plate portion is electrically connected to the first and second circuit patterns ,
The first and second rigid portions include via hole conductors provided in the first and second circuit patterns, respectively, and the metal thin plate portion is bonded to the via hole conductors by solid phase diffusion bonding. A circuit board. The circuit board according to claim 1, wherein the thin metal plate portion includes a connection portion for electrical connection to the outside. It said first and second rigid part comprises a layered structure formed by stacking a plurality of flexible sheets, the circuit board according to claim 1 or 2. The circuit board according to claim 3 , wherein the metal thin plate portion is drawn from an interlayer of the flexible sheet having the laminated structure. Surface of the sheet metal part is covered with rust-proofing membrane, circuit board according to any one of claims 1 to 3. The sheet metal part includes a plurality of strip-shaped metal foil disposed at the same height, the circuit board according to any one of claims 1 to 5. The sheet metal part includes a plurality of strip-shaped metal foil arranged at a height different circuit board according to any one of claims 1 to 5.

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