Classifications

• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
  • H05K1/00—Printed circuits
  • H05K1/02—Details
• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
  • H05K3/00—Apparatus or processes for manufacturing printed circuits
  • H05K3/46—Manufacturing multilayer circuits

Definitions

• the present invention relates to a flexible multilayer circuit board.
• the flexible multilayer circuit board of Patent Document 1 has a wide portion in the longitudinal direction perpendicular to the thickness direction, which is wider in the short direction of the conductor, and a narrow portion in the short direction of the conductor, which is narrower, so that it can be bent in the thickness direction at the narrow portion.
• the flexible multilayer circuit board in Patent Document 1 achieves a certain degree of flexibility by changing the width of the conductor in the short direction, but it is designed to be used in a nearly straight line, and has the disadvantage that the stress when bending cannot be sufficiently reduced.
• the present invention aims to provide a flexible multilayer circuit board with excellent flexibility.
• the present invention is a flexible multilayer circuit board comprising an insulating layer, a first conductor layer disposed on one side of the insulating layer in the thickness direction, a second conductor layer disposed on the other side of the insulating layer in the thickness direction, and a wiring portion embedded in the insulating layer, wherein the first conductor layer has a first ground conductor portion, the second conductor layer has a second ground conductor portion, and the flexible multilayer circuit board has a folded portion in a longitudinal intermediate portion perpendicular to the thickness direction, the first ground conductor portion and the second ground conductor portion have a first thickness other than the folded portion, and at least one of the first ground conductor portion and the second ground conductor portion has a second thickness in the folded portion, and the second thickness is thinner than the first thickness.
• At least one of the first ground conductor portion and the second ground conductor portion has a second thickness that is thinner than the first thickness at the bent portion. Therefore, the bent portion has excellent flexibility in the thickness direction.
• the present invention [2] includes the flexible multilayer circuit board described in [1], in which the first ground conductor portion and the second ground conductor portion each have the second thickness in the folded portion.
• the first ground conductor portion and the second ground conductor portion each have the second thickness at the bent portion. Therefore, the bent portion has excellent flexibility in both thickness directions.
• the present invention [3] includes the flexible multilayer circuit board described in [2], in which at least one of the first ground conductor portion and the second ground conductor portion further has the first thickness in the folded portion.
• At the bent portion at least one of the first ground conductor portion and the second ground conductor portion further has a first thickness. Therefore, at the bent portion, appropriate rigidity is ensured and the board can be bent at a larger angle in the thickness direction.
• the present invention [4] includes the flexible multilayer circuit board described in [3], in which, in the folded portion, each of the first ground conductor portion and the second ground conductor portion further has the first thickness.
• the first ground conductor and the second ground conductor each further have a first thickness at the bent portion. Therefore, the bent portion can be bent at a larger angle to both sides in the thickness direction while ensuring a suitable rigidity.
• the present invention [5] includes the flexible multilayer circuit board described in [4], in which the first ground conductor portion and the second ground conductor portion each have the first thickness and the second thickness alternately along the longitudinal direction in the bent portion.
• the first ground conductor and the second ground conductor each have a first thickness and a second thickness alternately along the longitudinal direction at the bent portion. This provides the bent portion with even better flexibility in both thickness directions.
• the present invention [6] includes the flexible multilayer circuit board described in [5], in which the first thickness of the first ground conductor is located on the opposite side of the insulating layer to the first thickness of the second ground conductor in the thickness direction, and the second thickness of the first ground conductor is located on the opposite side of the insulating layer to the second thickness of the second ground conductor in the thickness direction.
• the first thickness of the first ground conductor portion overlaps with the first thickness of the second ground conductor portion in the thickness direction, and the second thickness of the first ground conductor portion overlaps with the second thickness of the second ground conductor portion. This provides even better flexibility in both directions in the thickness direction at the bent portion.
• the present invention [7] includes a flexible multilayer circuit board according to any one of [1] to [6], in which the insulating layer comprises a bonding layer, a first porous resin layer disposed on one side of the bonding layer in the thickness direction, and a second porous resin layer disposed on the other side of the bonding layer in the thickness direction, and the wiring portion is embedded in the bonding layer.
• the insulating layer includes a bonding layer, a first porous resin layer, a first base resin layer, a second porous resin layer, and a second base resin layer, in that order toward the other side in the thickness direction. This results in excellent adhesion between the first conductor layer and the insulating layer, and between the insulating layer and the second conductor layer, and also allows for a low dielectric constant.
• the flexible multilayer circuit board of the present invention has a bent portion in the middle of the longitudinal direction perpendicular to the thickness direction, and at the bent portion, at least one of the first ground conductor portion and the second ground conductor portion has a second thickness that is thinner than the first thickness. Therefore, it has excellent flexibility.
• FIG. 1 shows a longitudinal cross-sectional view of one embodiment of a flexible multilayer circuit board of the present invention.
• FIG. 2 shows a cross-sectional view of the flexible multilayer circuit board shown in FIG. 1 taken along line A-A' in the width direction.
• FIG. 3 shows a cross-sectional view of the flexible multilayer circuit board shown in FIG. 1 taken along line B-B' in the width direction.
• FIG. 4 shows a cross-sectional view taken along line C-C' in the width direction of the flexible multilayer circuit board shown in FIG.
• Figures 5A to 5D show a method for manufacturing the flexible multilayer circuit board shown in Figure 1.
• Figure 5A shows a step of preparing a first porous laminate
• Figure 5B shows a step of forming a first via
• Figure 5C shows a step of patterning a third conductor layer
• Figure 5D shows a step of preparing a second porous laminate.
• 6A to 6D are successive to Fig. 5D and show the manufacturing method of the flexible multilayer circuit board shown in Fig. 1.
• Fig. 6A shows the step of laminating the second porous laminate to the first porous laminate
• Fig. 6B shows the step of forming the second via
• Fig. 6C shows the step of forming the plating layer
• Fig. 6D shows the step of forming the ground conductor portion and the terminal portion.
• 7A to 7C are subsequent to Fig.
• FIG. 6D shows the method for manufacturing the flexible multilayer circuit board shown in Fig. 1.
• Fig. 7A shows the step of forming the second thickness
• Fig. 7B shows the step of bonding the cover insulating layer
• Fig. 7C shows the step of bonding the reinforcing base material.
• FIG. 8 shows a longitudinal cross-sectional view of a first modified example of the flexible multilayer circuit board shown in FIG.
• Flexible Multilayer Circuit Board A flexible multilayer circuit board 1 according to one embodiment of the present invention will be described with reference to FIGS.
• the vertical direction of the paper indicates the thickness direction of the flexible multilayer circuit board 1.
• the horizontal direction of the paper indicates the longitudinal direction of the flexible multilayer circuit board 1.
• the depth direction of the paper indicates the width direction (short side direction) of the flexible multilayer circuit board 1.
• the vertical direction of the paper indicates the thickness direction of the flexible multilayer circuit board 1.
• the horizontal direction of the paper indicates the width direction (short side direction) of the flexible multilayer circuit board 1.
• the depth direction of the paper indicates the longitudinal direction of the flexible multilayer circuit board 1.
• the flexible multilayer circuit board 1 has a thickness.
• the flexible multilayer circuit board 1 extends in a planar direction perpendicular to the thickness direction.
• the flexible multilayer circuit board 1 has a generally flat plate shape that is long in the longitudinal direction.
• the longitudinal direction is perpendicular to both the thickness direction and the width direction.
• the flexible multilayer circuit board 1 includes an insulating layer 2, a first conductor layer 10 disposed on one side of the insulating layer 2 in the thickness direction, a second conductor layer 20 disposed on the other side of the insulating layer 2 in the thickness direction, and a wiring section 30 embedded in the insulating layer 2.
• the flexible multilayer circuit board 1 includes an insulating layer 2, a first conductor layer 10 disposed on one side of the insulating layer 2 in the thickness direction, a second conductor layer 20 disposed on the other side of the insulating layer 2 in the thickness direction, and a wiring section 30 embedded in the insulating layer 2.
• the flexible multilayer circuit board 1 also includes a bent section F in the middle part in the longitudinal direction.
• the first conductor layer 10 has a first ground conductor portion 11, and if necessary, a first terminal portion 12.
• the first conductor layer 10 has the first ground conductor portion 11 and the first terminal portion 12.
• the second conductor layer 20 has a second ground conductor portion 21, and if necessary, a second terminal portion 22.
• the second conductor layer 20 has the second ground conductor portion 21 and the second terminal portion 22.
• the first terminal portion 12 and the second terminal portion 22 may be collectively referred to as the terminal portion.
• the first ground conductor portion 11 and the second ground conductor portion 21 have a first thickness T1.
• at least one of the first ground conductor portion 11 and the second ground conductor portion 21 has a second thickness T2.
• the second thickness T2 is thinner than the first thickness T1.
• the flexible multilayer circuit board 1 may include a first via connection portion 51, a second via connection portion 52, a cover insulating layer 60, and a reinforcing substrate 70, as necessary.
• FIGS. 2 to 4 show a portion of each cross-sectional view of the flexible multilayer circuit board 1.
• the flexible multilayer circuit board 1 has multiple configurations shown in FIGS. 2 to 4 in the width direction.
• the insulating layer 2 includes a bonding layer 3, a first porous resin layer 4a disposed on one side of the bonding layer 3 in the thickness direction, and a second porous resin layer 4b disposed on the other side of the bonding layer 3 in the thickness direction.
• the insulating layer 2 may further include a first base resin layer 5a disposed on one side of the first porous resin layer 4a in the thickness direction, and a second base resin layer 5b disposed on the other side of the second porous resin layer 4b in the thickness direction. Specifically, as shown in FIG.
• the insulating layer 2 includes a bonding layer 3, a first porous resin layer 4a disposed on one surface in the thickness direction of the bonding layer 3, a first base resin layer 5a disposed on one surface in the thickness direction of the first porous resin layer 4a, a second porous resin layer 4b disposed on the other surface in the thickness direction of the bonding layer 3, and a second base resin layer 5b disposed on the other surface in the thickness direction of the second porous resin layer 4b.
• the insulating layer 2 also embeds the wiring section 30, which will be described in more detail later.
• the insulating layer 2 has a plurality of first through holes 41 that penetrate in the thickness direction between the first ground conductor portion 11 and the second ground conductor portion 21.
• the insulating layer 2 also has a second through hole 42 at each of its longitudinal ends that penetrates in the thickness direction between the terminal portion and the wiring portion 30.
• the insulating layer 2 does not have a first through hole 41 or a second through hole 42 at the bent portion F.
• the bonding layer 3 has a thickness.
• the bonding layer 3 has a substantially flat plate shape.
• the bonding layer 3 is an adhesive layer that bonds between layers, specifically, the bonding layer 3 bonds the first porous resin layer 4 a and the second porous resin layer 4 b.
• the bonding layer 3 is disposed on the other thickness-wise side of the first porous resin layer 4a and on one thickness-wise side of the second porous resin layer 4b.
• the bonding layer 3 is disposed between the first porous resin layer 4a and the second porous resin layer 4b. More specifically, the bonding layer 3 is in contact with the other thickness-wise side of the first porous resin layer 4a and in contact with one thickness-wise side of the second porous resin layer 4b.
• the bonding layer 3 also embeds the wiring section 30, which will be described in more detail later.
• the material (or raw material) of the bonding layer 3 is not particularly limited as long as it is used as an insulating material in a wiring circuit board.
• a preferable example of the material of the bonding layer 3 is a low dielectric material.
• An example of the material of the bonding layer 3 is a resin.
• the resin include polycarbonate resin, polyimide resin, fluorinated polyimide resin, epoxy resin, phenol resin, urea resin, melamine resin, diallyl phthalate resin, silicone resin, thermosetting urethane resin, fluororesin, polyolefin resin (e.g., cycloolefin polymer), and liquid crystal polymer.
• a preferable example is polyimide resin.
• the bonding layer 3 is preferably a non-porous, solid, dense film in order to improve adhesion between layers.
• the bonding layer 3 is preferably a non-porous polyimide resin layer.
• the porosity of the bonding layer 3 is, for example, 0.5% or less, preferably 0.1% or less, and more preferably 0%.
• the dielectric constant of the bonding layer 3 at a frequency of 100 GHz is, for example, 1.0 to 3.5, preferably 1.0 to 3.2, more preferably 1.0 to 3.0, even more preferably 1.0 to 2.7, and especially preferably 1.0 to 2.5.
• the dielectric constant of the bonding layer 3 at a frequency of 100 GHz is, for example, more than 1.0 and, for example, 3.5 or less, preferably 3.2 or less, more preferably 3.0 or less, even more preferably 2.7 or less, and particularly preferably 2.5 or less.
• the dielectric constant of bonding layer 3 is measured using a resonator method with a frequency of 100 GHz.
• the dielectric tangent of the bonding layer 3 at a frequency of 100 GHz is, for example, 0 to 0.005, preferably 0 to 0.004, more preferably 0 to 0.003, and even more preferably 0 to 0.002.
• the dielectric tangent of the bonding layer 3 at a frequency of 100 GHz is, for example, greater than 0 and, for example, 0.005 or less, preferably 0.004 or less, more preferably 0.003 or less, even more preferably 0.002 or less, and particularly preferably less than 0.002.
• the dielectric tangent of bonding layer 3 is measured using a resonator method with a frequency of 100 GHz.
• the thickness of the bonding layer 3 is, for example, 1 ⁇ m to 300 ⁇ m, preferably 10 ⁇ m to 200 ⁇ m, more preferably 20 ⁇ m to 150 ⁇ m, even more preferably 30 ⁇ m to 100 ⁇ m, and particularly preferably 40 ⁇ m to 80 ⁇ m.
• the thickness of the bonding layer 3 is, for example, 1 ⁇ m or more, preferably 10 ⁇ m or more, more preferably 20 ⁇ m or more, even more preferably 30 ⁇ m or more, particularly preferably 40 ⁇ m or more, and, for example, 300 ⁇ m or less, preferably 200 ⁇ m or less, more preferably 150 ⁇ m or less, even more preferably 100 ⁇ m or less, particularly preferably 80 ⁇ m or less.
• the thickness of the bonding layer 3 is the total thickness including the thickness of the wiring portion 30 to be embedded.
• the thickness of the bonding layer 3 on one side of the wiring portion 30 in the thickness direction and the thickness of the bonding layer 3 on the other side of the wiring portion 30 in the thickness direction are not particularly limited and may be the same or different. Considering the manufacturing method, the thickness of the bonding layer 3 on one side of the wiring portion 30 in the thickness direction and the thickness of the bonding layer 3 on the other side of the wiring portion 30 in the thickness direction are preferably different.
• the thickness of the bonding layer 3 on one side of the wiring portion 30 in the thickness direction is the distance from one side of the wiring portion 30 in the thickness direction to one side of the bonding layer 3 in the thickness direction
• the thickness of the bonding layer 3 on the other side of the wiring portion 30 in the thickness direction is the distance from the other side of the wiring portion 30 in the thickness direction to the other side of the bonding layer 3 in the thickness direction.
• the thickness of the bonding layer 3 on one side of the wiring portion 30 in the thickness direction is, for example, 1 ⁇ m to 100 ⁇ m, preferably 3 ⁇ m to 70 ⁇ m, more preferably 5 ⁇ m to 50 ⁇ m, even more preferably 7 ⁇ m to 30 ⁇ m, and particularly preferably 8 ⁇ m to 20 ⁇ m.
• the thickness of the bonding layer 3 on the other side of the wiring portion 30 in the thickness direction is, for example, 5 ⁇ m to 200 ⁇ m, preferably 10 ⁇ m to 100 ⁇ m, more preferably 15 ⁇ m to 70 ⁇ m, even more preferably 18 ⁇ m to 50 ⁇ m, and particularly preferably 20 ⁇ m to 40 ⁇ m.
• the ratio of the thickness of the bonding layer 3 on one side of the wiring section 30 in the thickness direction to the thickness of the bonding layer 3 on the other side of the wiring section 30 in the thickness direction is, for example, 1.0 to 10, preferably 1.3 to 8.0, more preferably 1.5 to 6.0, even more preferably 1.8 to 4.0, and particularly preferably 2.0 to 3.0.
• the thickness of the bonding layer 3 on one side of the wiring part 30 in the thickness direction is preferably thinner than the thickness of the bonding layer 3 on the other side of the wiring part 30 in the thickness direction.
• the first porous resin layer 4a has a thickness.
• the first porous resin layer 4a has a substantially flat plate shape.
• the first porous resin layer 4a is a layer that reduces the dielectric constant of the flexible multilayer circuit board 1.
• the first porous resin layer 4a is disposed on one thickness-wise side of the bonding layer 3 and on the other thickness-wise side of the first base resin layer 5a.
• the first porous resin layer 4a is disposed between the bonding layer 3 and the first base resin layer 5a. More specifically, the first porous resin layer 4a is in contact with one thickness-wise surface of the bonding layer 3 and in contact with the other thickness-wise surface of the first base resin layer 5a.
• the thickness of the first porous resin layer 4a is, for example, 1 ⁇ m to 200 ⁇ m, preferably 5 ⁇ m to 100 ⁇ m, more preferably 10 ⁇ m to 70 ⁇ m, even more preferably 15 ⁇ m to 50 ⁇ m, and particularly preferably 20 ⁇ m to 40 ⁇ m.
• the thickness of the first porous resin layer 4a is, for example, 1 ⁇ m or more, preferably 5 ⁇ m or more, more preferably 10 ⁇ m or more, even more preferably 15 ⁇ m or more, particularly preferably 20 ⁇ m or more, and, for example, 200 ⁇ m or less, preferably 100 ⁇ m or less, more preferably 70 ⁇ m or less, even more preferably 50 ⁇ m or less, particularly preferably 40 ⁇ m or less.
• the second porous resin layer 4b has a thickness.
• the second porous resin layer 4b has a substantially flat plate shape.
• the second porous resin layer 4b is a layer that reduces the dielectric constant of the flexible multilayer circuit board 1.
• the second porous resin layer 4b is disposed on the other thickness-wise side of the bonding layer 3 and on one thickness-wise side of the second base resin layer 5b.
• the second porous resin layer 4b is disposed between the bonding layer 3 and the second base resin layer 5b. More specifically, the second porous resin layer 4b is in contact with the other thickness-wise side of the bonding layer 3 and in contact with one thickness-wise side of the second base resin layer 5b.
• the thickness of the second porous resin layer 4b is adjusted to be within the same range as the thickness of the first porous resin layer 4a.
• the first porous resin layer 4a and the second porous resin layer 4b are collectively referred to as the porous resin layer 4.
• the materials and physical properties of the first porous resin layer 4a and the second porous resin layer 4b described below may be the same or different. Preferably, they are the same.
• the material (or raw material) of the porous resin layer 4 can be a resin.
• the resin include polycarbonate resin, polyimide resin, fluorinated polyimide resin, epoxy resin, phenolic resin, urea resin, melamine resin, diallyl phthalate resin, silicone resin, thermosetting urethane resin, fluororesin, and liquid crystal polymer, preferably polyimide resin and liquid crystal polymer, and more preferably polyimide resin.
• the porous resin layer 4 is porous in order to reduce the dielectric constant.
• the porous resin layer 4 has, for example, closed cells and/or open cells.
• the porous resin layer 4 is preferably a porous polyimide resin layer.
• the porosity of the porous resin layer 4 is, for example, 50% to 100%, preferably 60% to 99%, more preferably 70% to 99%, and even more preferably 80% to 99%.
• the porosity of the porous resin layer 4 is, for example, 50% or more, preferably 60% or more, more preferably 70% or more, and even more preferably 80% or more, and is, for example, less than 100%, preferably 99% or less.
• the dielectric constant can be reduced. Furthermore, if the porosity of the porous resin layer 4 is equal to or less than the upper limit, the strength of the porous resin layer 4 can be ensured.
• dielectric constant of air 1 and the dielectric constant of polyimide resin is 3.5, so by applying the above formula, the following can be expressed.
• Dielectric constant of porous polyimide resin layer porosity+3.5(1-porosity)
• Porosity (%) [(3.5 ⁇ dielectric constant of porous polyimide resin layer)/2.5] ⁇ 100
• the dielectric constant of the porous resin layer 4 at a frequency of 100 GHz is, for example, more than 1.0 and, for example, 3.0 or less, preferably 2.5 or less, more preferably 2.2 or less, and even more preferably 2.0 or less.
• the dielectric constant of the porous resin layer 4 is measured using a resonator method with a frequency of 100 GHz.
• the dielectric tangent of the porous resin layer 4 at a frequency of 100 GHz is, for example, greater than 0 and, for example, 0.0050 or less, preferably 0.0040 or less, more preferably 0.0030 or less, even more preferably 0.0025 or less, and particularly preferably 0.002 or less.
• the dielectric tangent of the porous resin layer 4 is measured by the resonator method using a frequency of 100 GHz.
• the porous resin layer 4 has a low dielectric constant at a frequency of 100 GHz, and furthermore, the dielectric tangent of the porous resin layer 4 at a frequency of 100 GHz is low. Therefore, transmission loss can be suppressed in high frequency regions such as a frequency of 100 GHz. More specifically, if the dielectric constant of the porous resin layer 4 at a frequency of 100 GHz is equal to or less than the upper limit value, and furthermore, if the dielectric tangent of the porous resin layer 4 at a frequency of 100 GHz is equal to or less than the upper limit value, transmission loss can be suppressed in high frequency regions such as a frequency of 100 GHz.
• the total thickness of the porous resin layer 4 (total thickness of the first porous resin layer 4a and the second porous resin layer 4b) is, for example, 2 ⁇ m to 1000 ⁇ m, preferably 10 ⁇ m to 600 ⁇ m, more preferably 20 ⁇ m to 300 ⁇ m, even more preferably 30 ⁇ m to 100 ⁇ m, and particularly preferably 40 ⁇ m to 80 ⁇ m.
• the total thickness of the porous resin layer 4 (total thickness of the first porous resin layer 4a and the second porous resin layer 4b) is, for example, 2 ⁇ m or more, preferably 10 ⁇ m or more, more preferably 20 ⁇ m or more, even more preferably 30 ⁇ m or more, particularly preferably 40 ⁇ m or more, and, for example, 1000 ⁇ m or less, preferably 600 ⁇ m or less, more preferably 300 ⁇ m or less, even more preferably 100 ⁇ m or less, particularly preferably 80 ⁇ m or less.
• the first base resin layer 5a has a thickness.
• the first base resin layer 5a has a substantially flat plate shape.
• the first base resin layer 5a is a layer that enhances the adhesion between the first porous resin layer 4a and the first conductor layer 10.
• the first base resin layer 5a is disposed on one thickness-wise side of the first porous resin layer 4a and on the other thickness-wise side of the first conductor layer 10.
• the first base resin layer 5a is disposed between the first porous resin layer 4a and the first conductor layer 10. More specifically, the first base resin layer 5a is in contact with one thickness-wise surface of the first porous resin layer 4a and in contact with the other thickness-wise surface of the first conductor layer 10.
• the first base resin layer 5a is disposed as necessary.
• the thickness of the first base resin layer 5a is, for example, 0.1 ⁇ m to 50 ⁇ m, preferably 0.5 ⁇ m to 20 ⁇ m, more preferably 1.0 ⁇ m to 10 ⁇ m, even more preferably 1.5 ⁇ m to 7.0 ⁇ m, and particularly preferably 2.0 ⁇ m to 5.0 ⁇ m.
• the thickness of the first base resin layer 5a is, for example, 0.1 ⁇ m or more, preferably 0.5 ⁇ m or more, more preferably 1.0 ⁇ m or more, even more preferably 1.5 ⁇ m or more, particularly preferably 2.0 ⁇ m or more, and for example, 50 ⁇ m or less, preferably 20 ⁇ m or less, more preferably 10 ⁇ m or less, even more preferably 7.0 ⁇ m or less, particularly preferably 5.0 ⁇ m or less.
• the ratio of the thickness of the first base resin layer 5a to the thickness of the first porous resin layer 4a is, for example, 0.01 to 0.5, preferably 0.05 to 0.3, and more preferably 0.08 to 0.2.
• the ratio of the thickness of the first base resin layer 5a to the thickness of the first porous resin layer 4a is, for example, 0.01 or more, preferably 0.05 or more, more preferably 0.08 or more, and for example, 0.5 or less, preferably 0.3 or less, more preferably 0.2 or less.
• the first base resin layer 5a is thinner than the first porous resin layer 4a.
• the ratio of the thickness of the first base resin layer 5a to the thickness of the first porous resin layer 4a is equal to or greater than the above lower limit, the adhesion between the first porous resin layer 4a and the first conductor layer 10 can be sufficiently ensured. Also, if the ratio of the thickness of the first base resin layer 5a to the thickness of the first porous resin layer 4a is equal to or less than the above upper limit, the total thickness of the flexible multilayer circuit board 1 can be made thin while the dielectric constant is reduced.
• the second base resin layer 5b has a thickness.
• the second base resin layer 5b has a substantially flat plate shape.
• the second base resin layer 5b is a layer that enhances the adhesion between the second porous resin layer 4b and the second conductor layer 20.
• the second base resin layer 5b is disposed on the other thickness-wise side of the second porous resin layer 4b and on one thickness-wise side of the second conductor layer 20.
• the second base resin layer 5b is disposed between the second porous resin layer 4b and the second conductor layer 20. More specifically, the second base resin layer 5b is in contact with the other thickness-wise side of the second porous resin layer 4b and in contact with one thickness-wise side of the second conductor layer 20.
• the second base resin layer 5b is disposed as necessary.
• the thickness of the second base resin layer 5b is, for example, 0.1 ⁇ m to 50 ⁇ m, preferably 0.5 ⁇ m to 20 ⁇ m, more preferably 1.0 ⁇ m to 10 ⁇ m, even more preferably 1.5 ⁇ m to 7.0 ⁇ m, and particularly preferably 2.0 ⁇ m to 5.0 ⁇ m.
• the thickness of the second base resin layer 5b is, for example, 0.1 ⁇ m or more, preferably 0.5 ⁇ m or more, more preferably 1.0 ⁇ m or more, even more preferably 1.5 ⁇ m or more, particularly preferably 2.0 ⁇ m or more, and for example, 50 ⁇ m or less, preferably 20 ⁇ m or less, more preferably 10 ⁇ m or less, even more preferably 7.0 ⁇ m or less, particularly preferably 5.0 ⁇ m or less.
• the ratio of the thickness of the second base resin layer 5b to the thickness of the second porous resin layer 4b is, for example, 0.01 to 0.5, preferably 0.05 to 0.3, and more preferably 0.08 to 0.2.
• the ratio of the thickness of the second base resin layer 5b to the thickness of the second porous resin layer 4b is, for example, 0.01 or more, preferably 0.05 or more, more preferably 0.08 or more, and for example, 0.5 or less, preferably 0.3 or less, more preferably 0.2 or less.
• the second base resin layer 5b is thinner than the second porous resin layer 4b.
• the ratio of the thickness of the second base resin layer 5b to the thickness of the second porous resin layer 4b is equal to or greater than the above lower limit, the adhesion between the second porous resin layer 4b and the second conductor layer 20 can be sufficiently ensured. Also, if the ratio of the thickness of the second base resin layer 5b to the thickness of the second porous resin layer 4b is equal to or less than the above upper limit, the total thickness of the flexible multilayer circuit board 1 can be made thin while the dielectric constant is reduced.
• the first base resin layer 5a and the second base resin layer 5b are collectively referred to as the base resin layer 5.
• the materials and physical properties of the first base resin layer 5a and the second base resin layer 5b described below may be the same or different. Preferably, they are the same.
• the material (or raw material) of the base resin layer 5 can be a resin.
• resins include polycarbonate resin, polyimide resin, fluorinated polyimide resin, epoxy resin, phenolic resin, urea resin, melamine resin, diallyl phthalate resin, silicone resin, thermosetting urethane resin, fluororesin, and liquid crystal polymer, preferably polyimide resin and liquid crystal polymer, and more preferably polyimide resin.
• the base resin layer 5 is preferably a non-porous, solid, dense film in order to improve adhesion between layers.
• the base resin layer 5 is preferably a non-porous polyimide resin layer.
• the porosity of the base resin layer 5 is, for example, 0.5% or less, preferably 0.1% or less, and more preferably 0%.
• the dielectric constant of the base resin layer 5 at a frequency of 100 GHz is, for example, 1.0 to 4.5, preferably 1.0 to 4.0, more preferably 1.0 to 3.5, and even more preferably 1.0 to 3.3.
• the dielectric constant of the base resin layer 5 at a frequency of 100 GHz is, for example, more than 1.0 and, for example, 4.5 or less, preferably 4.0 or less, more preferably 3.5 or less, and even more preferably 3.3 or less.
• the dielectric constant of the base resin layer 5 is measured using a resonator method with a frequency of 100 GHz.
• the dielectric tangent of the base resin layer 5 at a frequency of 100 GHz is, for example, 0 to 0.0050, preferably 0 to 0.0040, more preferably 0 to 0.0030, even more preferably 0 to 0.0025, and particularly preferably 0 to 0.0020.
• the dielectric tangent of the base resin layer 5 at a frequency of 100 GHz is, for example, greater than 0 and, for example, 0.0050 or less, preferably 0.0040 or less, more preferably 0.0030 or less, even more preferably 0.0025 or less, and particularly preferably 0.002 or less.
• the dielectric tangent of the base resin layer 5 is measured using a resonator method with a frequency of 100 GHz.
• the total thickness of the base resin layer 5 (the total thickness of the first base resin layer 5a and the second base resin layer 5b) is, for example, 0.2 ⁇ m to 100 ⁇ m, preferably 1.0 ⁇ m to 40 ⁇ m, more preferably 2.0 ⁇ m to 20 ⁇ m, even more preferably 3.0 ⁇ m to 14 ⁇ m, and particularly preferably 4.0 ⁇ m to 10 ⁇ m.
• the total thickness of the base resin layer 5 (total thickness of the first base resin layer 5a and the second base resin layer 5b) is, for example, 0.2 ⁇ m or more, preferably 1.0 ⁇ m or more, more preferably 2.0 ⁇ m or more, even more preferably 3.0 ⁇ m or more, particularly preferably 4.0 ⁇ m or more, and for example, 100 ⁇ m or less, preferably 40 ⁇ m or less, more preferably 20 ⁇ m or less, even more preferably 14 ⁇ m or less, particularly preferably 10 ⁇ m or less.
• the first conductor layer 10 has a thickness.
• the first conductor layer 10 extends in the longitudinal direction.
• the first conductor layer 10 is disposed on one side in the thickness direction of the first base resin layer 5a. Specifically, the first conductor layer 10 is disposed on one surface in the thickness direction of the first base resin layer 5a. In other words, the first conductor layer 10 is in contact with one surface in the thickness direction of the first base resin layer 5a.
• the first conductor layer 10 is disposed opposite the second conductor layer 20 so as to overlap the wiring section 30 when projected in the thickness direction.
• the first conductor layer 10 and the second conductor layer 20 are disposed opposite each other so as to overlap the wiring section 30 when projected in the thickness direction.
• the first conductor layer 10 has a first ground conductor portion 11 and, if necessary, a first terminal portion 12. Preferably, it has a first ground conductor portion 11 and a first terminal portion 12. Specifically, as shown in FIG. 1, the first conductor layer 10 has a first ground conductor portion 11, and further has a first terminal portion 12 at one end in the longitudinal direction.
• the material of the first conductor layer 10 is not particularly limited as long as it is a conductor material that is typically used in wired circuit boards.
• Examples of materials for the first conductor layer 10 include copper, iron, silver, gold, aluminum, nickel, and alloys thereof (e.g., stainless steel and bronze). Copper is preferred.
• the first ground conductor portion 11 earths a weak current that affects the first terminal portion 12.
• the weak current includes a current of less than 1 A, for example.
• the first ground conductor portion 11 is disposed on one side in the thickness direction of the first base resin layer 5a. Specifically, the first ground conductor portion 11 is disposed on one surface in the thickness direction of the first base resin layer 5a. In other words, the first ground conductor portion 11 is in contact with one surface in the thickness direction of the first base resin layer 5a.
• the first ground conductor portion 11 extends across the entire width of the flexible multilayer circuit board 1.
• the center in the width direction of the first ground conductor portion 11 is cut out toward the other longitudinal end side so that the first terminal portion 12 can be disposed therein.
• the first ground conductor portion 11 has a plurality of the above-mentioned cutouts spaced apart in the width direction.
• an earth member is connected to the first ground conductor portion 11.
• the first terminal 12 receives and transmits signals via a signal terminal (not shown).
• An example of the signal is a differential signal.
• the signal includes a small current of less than 1 A.
• the first terminal portion 12 is disposed on one side in the thickness direction of the first base resin layer 5a. Specifically, the first terminal portion 12 is disposed on one surface in the thickness direction of the first base resin layer 5a. In other words, the first terminal portion 12 is in contact with one surface in the thickness direction of the first base resin layer 5a.
• the first terminal portion 12 is disposed, for example, at one end in the longitudinal direction. Note that the first terminal portion 12 does not have to be disposed at the other end in the longitudinal direction where the second terminal portion 22 is disposed.
• the first terminal portion 12 is disposed opposite the wiring portion 30.
• the first terminal portion 12 is disposed in the notched portion of the first ground conductor portion 11 in the width direction. In other words, the first terminal portion 12 is disposed between the two first ground conductor portions 11 at a distance in the width direction.
• first terminal portions 12 are arranged at one end in the longitudinal direction and spaced apart in the width direction. Specifically, at one end in the longitudinal direction, the first ground conductor portions 11 and the first terminal portions 12 are arranged alternately and spaced apart in the width direction.
• the thickness of the first terminal portion 12 may be the same as or different from the first thickness T1 of the first ground conductor portion 11 described below. Preferably, they are the same.
• the second conductor layer 20 has a thickness.
• the second conductor layer 20 extends in the longitudinal direction.
• the second conductor layer 20 is disposed on the other side in the thickness direction of the second base resin layer 5b. Specifically, the second conductor layer 20 is disposed on the other surface in the thickness direction of the second base resin layer 5b. In other words, the second conductor layer 20 is in contact with the other surface in the thickness direction of the second base resin layer 5b.
• the second conductor layer 20 is disposed opposite the first conductor layer 10 so as to overlap the wiring section 30 when projected in the thickness direction.
• the first conductor layer 10 and the second conductor layer 20 are disposed opposite each other so as to overlap the wiring section 30 when projected in the thickness direction.
• the second conductor layer 20 has a second ground conductor portion 21 and, if necessary, a second terminal portion 22. Preferably, it has a second ground conductor portion 21 and a second terminal portion 22. Specifically, as shown in FIG. 1, the second conductor layer 20 has a second ground conductor portion 21 and further has a second terminal portion 22 at the other end in the longitudinal direction.
• the material for the second conductor layer 20 can be the same as the material for the first conductor layer 10 described above.
• the second ground conductor 21 earths a weak current that affects the second terminal 22.
• the weak current includes a current of less than 1 A, for example.
• the second ground conductor portion 21 is disposed on the other side in the thickness direction of the second base resin layer 5b. Specifically, the second ground conductor portion 21 is disposed on the other surface in the thickness direction of the second base resin layer 5b. In other words, the second ground conductor portion 21 is in contact with the other surface in the thickness direction of the second base resin layer 5b.
• the second ground conductor portion 21 extends across the entire width of the flexible multilayer circuit board 1.
• the center in the width direction of the second ground conductor 21 is cut out toward the one longitudinal end so that the second terminal 22 can be positioned.
• the second ground conductor 21 has a plurality of the above-mentioned cutouts spaced apart in the width direction.
• an earth member is connected to the second ground conductor portion 21.
• the second terminal 22 receives and transmits signals, etc., via a signal terminal (not shown).
• a signal terminal (not shown).
• An example of the signal is a differential signal.
• the signal includes a small current, for example, less than 1 A.
• the second terminal portion 22 is disposed on the other side in the thickness direction of the second base resin layer 5b. Specifically, the second terminal portion 22 is disposed on the other surface in the thickness direction of the second base resin layer 5b. In other words, the second terminal portion 22 is in contact with the other surface in the thickness direction of the second base resin layer 5b.
• the second terminal portion 22 is disposed, for example, at the other end in the longitudinal direction. Note that the second terminal portion 22 does not have to be disposed at the end in the longitudinal direction where the first terminal portion 12 is disposed.
• the second terminal portion 22 is disposed opposite the wiring portion 30.
• the second terminal portion 22 is disposed in the notched portion of the second ground conductor portion 21 in the width direction. In other words, the second terminal portion 22 is disposed between the two second ground conductor portions 21 at a distance in the width direction.
• multiple second terminal portions 22 are arranged at the other end in the longitudinal direction, spaced apart in the width direction.
• the second ground conductor portions 21 and the second terminal portions 22 are arranged alternately at the other end in the longitudinal direction, spaced apart in the width direction.
• the thickness of the second terminal portion 22 may be the same as or different from the first thickness T1 of the second ground conductor portion 21 described below. Preferably, they are the same.
• the flexible multilayer circuit board 1 has a bent portion F in a longitudinal intermediate portion perpendicular to the thickness direction.
• the bent portion F is a portion where at least one of the first ground conductor portion 11 and the second ground conductor portion 21 has a different thickness from the first ground conductor portion 11 and the second ground conductor portion 21 other than the bent portion F in order to make it easier to bend the flexible multilayer circuit board 1.
• the first ground conductor portion 11 and the second ground conductor portion 21 have a first thickness T1.
• the first thickness T1 and second thickness T2 of the first ground conductor portion 11 are the thickness-wise distance between one thickness-wise surface of the first base resin layer 5a and one thickness-wise surface of the first ground conductor portion 11, and the first thickness T1 and second thickness T2 of the second ground conductor portion 21 are the thickness-wise distance between the other thickness-wise surface of the second base resin layer 5b and the other thickness-wise surface of the second ground conductor portion 21.
• one longitudinal end of the bent portion F is the side surface of one longitudinal end of the portion having the second thickness T2 that is located at the furthest end in the longitudinal direction among the portions having the second thickness T2 of the first ground conductor portion 11 and the second ground conductor portion 21.
• the other longitudinal end of the bent portion F is the side surface of the other longitudinal end of the portion having the second thickness T2 that is located at the furthest end in the longitudinal direction among the portions having the second thickness T2 of the first ground conductor portion 11 and the second ground conductor portion 21.
• the flexibility in the thickness direction can be improved at the bent portion F.
• each of the first ground conductor portion 11 and the second ground conductor portion 21 preferably has a second thickness T2.
• the bending portion F has excellent flexibility in both directions in the thickness direction.
• each of the first ground conductor portion 11 and the second ground conductor portion 21 has a second thickness T2, and at least one of the first ground conductor portion 11 and the second ground conductor portion 21 further has a first thickness T1. Even more preferably, each of the first ground conductor portion 11 and the second ground conductor portion 21 has a first thickness T1 and a second thickness T2.
• first ground conductor portion 11 and the second ground conductor portion 21 have the first thickness T1 and the second thickness T2, respectively, appropriate rigidity is ensured at the bending portion F, and the bending can be performed at a larger angle to both sides in the thickness direction.
• each of the first ground conductor portion 11 and the second ground conductor portion 21 has a first thickness T1 and a second thickness T2 alternately along the longitudinal direction.
• first ground conductor portion 11 and the second ground conductor portion 21 each have the first thickness T1 and the second thickness T2 alternating along the longitudinal direction, the bending portion F has even better flexibility on both sides in the thickness direction.
• the first thickness T1 of the first ground conductor portion 11 overlaps with the first thickness T1 of the second ground conductor portion 21, and the second thickness T2 of the first ground conductor portion 11 overlaps with the second thickness T2 of the second ground conductor portion 21.
• the first thickness T1 of the first ground conductor portion 11 is located on the opposite side of the insulating layer 2 to the first thickness T1 of the second ground conductor portion 21 in the thickness direction
• the second thickness T2 of the first ground conductor portion 11 is located on the opposite side of the insulating layer 2 to the second thickness T2 of the second ground conductor portion 21 in the thickness direction.
• the rigidity of the flexible multilayer circuit board 1 can be reduced at the bent portion F, and the flexibility to both sides in the thickness direction is further improved.
• the first thickness T1 is, for example, 1 ⁇ m to 300 ⁇ m, preferably 5 ⁇ m to 200 ⁇ m, more preferably 10 ⁇ m to 100 ⁇ m, even more preferably 15 ⁇ m to 70 ⁇ m, particularly preferably 20 ⁇ m to 50 ⁇ m, and most preferably 25 ⁇ m to 35 ⁇ m.
• the first thickness T1 is, for example, 1 ⁇ m or more, preferably 5 ⁇ m or more, more preferably 10 ⁇ m or more, even more preferably 15 ⁇ m or more, particularly preferably 20 ⁇ m or more, and most preferably 25 ⁇ m or more, and, for example, 300 ⁇ m or less, preferably 200 ⁇ m or less, more preferably 100 ⁇ m or less, even more preferably 70 ⁇ m or less, particularly preferably 50 ⁇ m or less, and most preferably 35 ⁇ m or less.
• the second thickness T2 is, for example, 0.5 ⁇ m to 100 ⁇ m, preferably 1 ⁇ m to 50 ⁇ m, more preferably 3 ⁇ m to 30 ⁇ m, even more preferably 5 ⁇ m to 20 ⁇ m, and particularly preferably 7 ⁇ m to 15 ⁇ m.
• the second thickness T2 is, for example, 0.5 ⁇ m or more, preferably 1 ⁇ m or more, more preferably 3 ⁇ m or more, even more preferably 5 ⁇ m or more, particularly preferably 7 ⁇ m or more, and, for example, 100 ⁇ m or less, preferably 50 ⁇ m or less, more preferably 30 ⁇ m or less, even more preferably 20 ⁇ m or less, particularly preferably 15 ⁇ m or less.
• the ratio (T1/T2) of the first thickness T1 to the second thickness T2 is, for example, 1.0 to 10, preferably 1.2 to 8.0, more preferably 1.5 to 6.0, even more preferably 1.8 to 5.0, and particularly preferably 2.0 to 4.0.
• the ratio of T1 to the second thickness T2 is, for example, more than 1.0, preferably 1.2 or more, more preferably 1.5 or more, even more preferably 1.8 or more, particularly preferably 2.0 or more, and, for example, 10 or less, preferably 8.0 or less, more preferably 6.0 or less, even more preferably 5.0 or less, particularly preferably 4.0 or less.
• the difference (T1-T2) between the first thickness T1 and the second thickness T2 is, for example, 1 ⁇ m to 100 ⁇ m, preferably 5 ⁇ m to 70 ⁇ m, more preferably 10 ⁇ m to 50 ⁇ m, even more preferably 13 ⁇ m to 40 ⁇ m, and particularly preferably 15 ⁇ m to 30 ⁇ m.
• the difference (T1-T2) between the first thickness T1 and the second thickness T2 is, for example, 1 ⁇ m or more, preferably 5 ⁇ m or more, more preferably 10 ⁇ m or more, even more preferably 13 ⁇ m or more, particularly preferably 15 ⁇ m or more, and for example, 100 ⁇ m or less, preferably 70 ⁇ m or less, more preferably 50 ⁇ m or less, even more preferably 40 ⁇ m or less, particularly preferably 30 ⁇ m or less.
• the second thickness T2 is thinner than the first thickness T1.
• the flexibility in the thickness direction is excellent. Specifically, if the ratio of the first thickness T1 to the second thickness T2 (T1/T2) is equal to or greater than the lower limit (exceeds), the flexibility in the thickness direction is excellent. In addition, if the difference between the first thickness T1 and the second thickness T2 (T1-T2) is equal to or greater than the lower limit, the flexibility in the thickness direction is excellent.
• first thickness T1 of the first ground conductor portion 11 and the second thickness T1 of the second ground conductor portion 21 may be the same as each other or may be different as long as they are within the above range. Preferably, they are the same as each other.
• second thickness T2 of the first ground conductor portion 11 and the second thickness T2 of the second ground conductor portion 21 may be the same as each other or may be different as long as they are within the above range. Preferably, they are the same as each other.
• the respective pitches are, for example, 1 ⁇ m to 200 ⁇ m, preferably 10 ⁇ m to 100 ⁇ m, more preferably 20 ⁇ m to 80 ⁇ m, and even more preferably 30 ⁇ m to 60 ⁇ m.
• each of the above pitches may be uniform or irregular.
• the proportion of the folded portion F in the overall length of the flexible multilayer circuit board 1 in the longitudinal direction is, for example, 5% to 30%.
• the wiring section 30 is electrically connected to the terminal section and transmits signals from the terminal section.
• the wiring section 30 has a thickness.
• the wiring section 30 extends in the longitudinal direction.
• multiple wiring sections 30 are arranged at intervals in the width direction.
• the wiring section 30 is embedded in the insulating layer 2 (specifically, the bonding layer 3). Specifically, both surfaces in the thickness direction and the side surface (in other words, the entire outer peripheral surface) of the wiring section 30 are in contact with the bonding layer 3.
• the material of the wiring portion 30 can be the same as the material of the first conductor layer 10.
• the thickness of the wiring portion 30 is, for example, 1 ⁇ m to 100 ⁇ m, preferably 5 ⁇ m to 70 ⁇ m, more preferably 10 ⁇ m to 50 ⁇ m, even more preferably 13 ⁇ m to 30 ⁇ m, and particularly preferably 15 ⁇ m to 20 ⁇ m.
• the thickness of the wiring portion 30 is, for example, 1 ⁇ m or more, preferably 5 ⁇ m or more, more preferably 10 ⁇ m or more, even more preferably 13 ⁇ m or more, particularly preferably 15 ⁇ m or more, and, for example, 100 ⁇ m or less, preferably 70 ⁇ m or less, more preferably 50 ⁇ m or less, even more preferably 30 ⁇ m or less, particularly preferably 20 ⁇ m or less.
• the first via connection portion 51 is filled into the plurality of first through holes 41. That is, a plurality of first via connection portions 51 are provided.
• the multiple first via connection parts 51 contact the first ground conductor part 11 and the second ground conductor part 21 so as to electrically connect the first ground conductor part 11 and the second ground conductor part 21.
• one thickness direction end of the multiple first via connection parts 51 contacts the other thickness direction surface of the first ground conductor part 11, and the other thickness direction end of the multiple first via connection parts 51 contacts one thickness direction surface of the second ground conductor part 21.
• the peripheral side surface of the multiple first via connection parts 51 contacts the insulating layer 2.
• the first ground conductor part 11 and the second ground conductor part 21 are electrically connected via the multiple first via connection parts 51.
• the first via connection portions 51 are arranged in a pair, side by side in the width direction, with the wiring portion located between them.
• the first ground conductor portion 11, the second ground conductor portion 21, and the first via connection portion 51 form a roughly square-shaped ground path.
• the first conductor layer 10 and the second conductor layer 20 are arranged opposite each other so as to overlap the wiring section 30 when projected in the thickness direction, and the pair of first via connection sections 51 are arranged so that the wiring section 30 is located between them, thereby suppressing the occurrence of dielectric loss in the wiring section 30.
• the first ground conductor portion 11, the second ground conductor portion 21, and the first via connection portion 51 form a roughly U-shaped ground path at one end in the longitudinal direction.
• the ground path opens toward one side in the thickness direction.
• the first ground conductor portion 11, the second ground conductor portion 21, and the first via connection portion 51 form a roughly inverted U-shaped ground path. In that case, when viewed in cross section from the width direction, the ground path opens toward the other side in the thickness direction.
• multiple first via connection portions 51 are arranged at intervals in the width direction. Specifically, multiple wiring portions 30 and multiple first via connection portions 51 are arranged alternately at intervals in the width direction.
• first via connection portions 51 are arranged at intervals in the longitudinal direction.
• the first via connection portion 51 is not arranged at the bent portion F.
• the first via connection portion 51 is not positioned at the bending portion F, it can be easily bent in the thickness direction.
• the first via connection portion 51 is formed by filling the first through hole 41 with the material for the first via connection portion 51.
• the material of the first via connection portion 51 can be the same as the material of the first conductor layer 10.
• the second via connection portion 52 is filled in the second through hole 42 .
• the second via connection portion 52 contacts the terminal portion and the wiring portion 30 so as to electrically connect the terminal portion and the wiring portion 30. Specifically, as shown in FIG. 1, the second via connection portion 52 contacts the first terminal portion 12 and the wiring portion 30 at one end in the longitudinal direction, and contacts the second terminal portion 22 and the wiring portion 30 at the other end in the longitudinal direction. More specifically, at one end in the longitudinal direction, one end in the thickness direction of the second via connection portion 52 contacts the other thickness direction surface of the first terminal portion 12, and the other end in the thickness direction of the second via connection portion 52 contacts one thickness direction surface of the wiring portion 30.
• the other end in the thickness direction of the second via connection portion 52 contacts one thickness direction surface of the second terminal portion 22, and the one end in the thickness direction of the second via connection portion 52 contacts the other thickness direction surface of the wiring portion 30. Furthermore, the peripheral side surface of the second via connection portion 52 contacts the insulating layer 2. As a result, the terminal portion and the wiring portion 30 are electrically connected via the second via connection portion 52.
• the second via connection parts 52 are arranged at both ends in the longitudinal direction. In addition, the second via connection parts 52 are not arranged at any other places than both ends in the longitudinal direction.
• one second via connection portion 52 is disposed between a pair of first via connection portions 51 in the width direction.
• the terminal portion, the wiring portion 30, and the second via connection portion 52 form a roughly I-shaped signal path at each end in the longitudinal direction.
• multiple second via connection portions 52 are arranged at intervals in the width direction at each of both ends in the longitudinal direction. Specifically, one second via connection portion 52 is arranged corresponding to one wiring portion 30 at each of both ends in the longitudinal direction.
• the second via connection portion 52 is formed by filling the second through hole 42 with the material of the second via connection portion 52.
• the material of the second via connection portion 52 can be the same as the material of the first conductor layer 10.
• the cover insulating layer 60 is a layer for protecting the surface of the flexible multilayer circuit board 1 .
• the cover insulating layer 60 is disposed on one thickness-wise side of the first conductor layer 10 and on the other thickness-wise side of the second conductor layer 20. That is, the cover insulating layer has a first cover insulating layer 61 disposed on one thickness-wise side of the first conductor layer 10 and a second cover insulating layer 62 disposed on the other thickness-wise side of the second conductor layer 20.
• the first cover insulating layer 61 contacts one thickness-wise surface of the first conductor layer 10.
• the second cover insulating layer 62 contacts the other thickness-wise surface of the second conductor layer 20.
• the cover insulating layer 60 covers at least the first conductor layer 10 and the second conductor layer 20 other than the terminal portion.
• the material of the cover insulating layer 60 can be, for example, the same resin as the material of the first porous resin layer 4a.
• the thickness of the cover insulating layer 60 is, for example, 1 ⁇ m to 100 ⁇ m, preferably 3 ⁇ m to 70 ⁇ m, more preferably 5 ⁇ m to 50 ⁇ m, even more preferably 7 ⁇ m to 40 ⁇ m, and particularly preferably 9 ⁇ m to 30 ⁇ m.
• the thickness of the cover insulating layer 60 is, for example, 1 ⁇ m or more, preferably 3 ⁇ m or more, more preferably 5 ⁇ m or more, even more preferably 7 ⁇ m or more, particularly preferably 9 ⁇ m or more, and, for example, 100 ⁇ m or less, preferably 70 ⁇ m or less, more preferably 50 ⁇ m or less, even more preferably 40 ⁇ m or less, particularly preferably 30 ⁇ m or less.
• the reinforcing substrate 70 is a substrate that reinforces the flexible multilayer circuit board 1.
• the reinforcing substrate 70 has a generally flat plate shape.
• the reinforcing substrate 70 is disposed on each of both ends in the longitudinal direction.
• the reinforcing substrate 70 is arranged at each of both ends in the longitudinal direction on one thickness-wise side of the first conductor layer 10 that does not have a terminal portion, or on the other thickness-wise side of the second conductor layer 20 that does not have a terminal portion.
• the reinforcing substrate 70 has a first reinforcing substrate 71 arranged at the other longitudinal end on one thickness-wise side of the first cover insulating layer 61, and a second reinforcing substrate 72 arranged at one longitudinal end on the other thickness-wise side of the second cover insulating layer 62.
• the first reinforcing substrate 71 contacts one thickness-wise surface of the first cover insulating layer 61 at the other longitudinal end.
• the second reinforcing substrate 72 contacts the other thickness-wise surface of the second cover insulating layer 62 at one longitudinal end.
• the material of the reinforcing substrate 70 is not particularly limited.
• Examples of the material of the reinforcing substrate 70 include metals and hard resins. Metals are preferable. Examples of metals include stainless steel, copper, iron, and aluminum.
• the thickness of the reinforcing substrate 70 is not particularly limited.
• the flexible multilayer circuit board 1 may have an adhesive layer between each of the above-mentioned layers. Specifically, adhesive layers may be provided between the first conductor layer 10 and the first cover insulating layer 61, between the second conductor layer 20 and the second cover insulating layer 62, between the first cover insulating layer 61 and the first reinforcing substrate 71, and between the second cover insulating layer 62 and the second reinforcing substrate 72.
• the material (or raw material) of the adhesive layer there are no particular limitations on the material (or raw material) of the adhesive layer, so long as it is a material that is commonly used for adhesive layers in printed circuit boards.
• materials (or raw materials) for the adhesive layer include resins.
• the thickness of the adhesive layer is not particularly limited.
• a Method for Manufacturing a Flexible Multilayer Circuit Board A method for manufacturing a flexible multilayer circuit board 1 will be described with reference to FIGS. 5A to 7C.
• First porous laminate preparation step As shown in FIG. 5A, first, a first porous laminate 100a is prepared.
• the first porous laminate 100a has conductor layers on both sides in the thickness direction. Specifically, the first porous laminate 100a has a first base conductor layer 101a, a first insulating layer 102a, and a third conductor layer 106, in that order, toward the other side in the thickness direction.
• the first insulating layer 102a has a first porous resin layer 104a and a first bonding layer 103a, in that order, toward the other side in the thickness direction, and further has a first base resin layer 105a, as necessary, arranged on one side in the thickness direction of the first porous resin layer 104a.
• the first underlying conductor layer 101a and the third conductor layer 106 in the first porous laminate 100a are before patterning, and are not the first conductor layer 10 and the wiring section 30 in the flexible multilayer circuit board 1 shown in Figures 1 to 4.
• the method for preparing the first porous laminate 100a is described, for example, in JP 2019-123851 A.
• a second through hole 142 is then formed. Specifically, the second through hole 142 is formed so as to penetrate the first base conductor layer 101a and the first insulating layer 102a. The second through hole 142 exposes one surface of the third conductor layer 106 in the thickness direction.
• the second through hole 142 can be formed, for example, by drilling.
• drilling methods include laser processing, drilling, and blasting. Laser processing is preferred.
• the third conductor layer 106 is then patterned to form the wiring portion 130 and the interlayer connection portion 131.
• the above-mentioned second through hole 142 is formed on one thickness direction side of the wiring portion 130. In other words, one thickness direction surface of the wiring portion 130 is exposed.
• Examples of patterning the third conductor layer 106 include wet etching and dry etching, and preferably includes wet etching.
• a second porous laminate 100b is prepared on the other side in the thickness direction of the wiring portion 130 and the interlayer connection portion 131 of the first porous laminate 100a.
• the second porous laminate 100b has a conductor layer only on the other side in the thickness direction.
• the second porous laminate 100b has a second base conductor layer 101b and a second insulating layer 102b, in that order, toward one side in the thickness direction.
• the second insulating layer 102b has a second porous resin layer 104b and a second bonding layer 103b, in that order, toward one side in the thickness direction, and further has a second base resin layer 105b, if necessary, arranged on the other side in the thickness direction of the second porous resin layer 104b.
• the method for preparing the second porous laminate 100b is described, for example, in JP 2019-123851 A.
• one thickness direction surface of the second bonding layer 103b of the second porous laminate 100b is bonded toward the other thickness direction side of the wiring portion 130 and the interlayer connection portion 131 of the first porous laminate 100a.
• a press machine (not shown) capable of pressing in the thickness direction is used.
• the pressing pressure is not limited and is, for example, 0.5 MPa to 10 MPa, preferably 3 MPa to 10 MPa.
• the pressing time is, for example, 1 minute to 120 minutes, preferably 10 minutes to 120 minutes.
• the pressing may be a heat press.
• the pressing temperature is, for example, 80°C to 300°C, preferably 120°C to 300°C.
• the second bonding layer 103b contacts the other thickness-wise surface of the first bonding layer 103a while covering the other thickness-wise surface and the entire outer peripheral surface of the wiring portion 130 and the interlayer connection portion 131.
• the first bonding layer 103a and the second bonding layer 103b deform and enter between the adjacent wiring portion 130 and the interlayer connection portion 131.
• the first bonding layer 103a and the second bonding layer 103b may be integrated to form the bonding layer 103.
• the interface between the first bonding layer 103a and the second bonding layer 103b does not need to be observed.
• the wiring portion 130 and the interlayer connection portion 131 are embedded in the first bonding layer 103a of the first porous laminate 100a and the second bonding layer 103b of the second porous laminate 100b.
• the porous laminate includes, in order toward one side in the thickness direction, a second underlying conductor layer 101b, a second underlying resin layer 105b, a second porous resin layer 104b, a bonding layer 103, a first porous resin layer 104a, a first underlying resin layer 105a, and a first underlying conductor layer 101a, and the bonding layer 103 embeds a wiring portion 130 and an interlayer connection portion 131.
• a first through hole 141 is formed. Specifically, a first through hole 141 penetrating the first underlying conductor layer 101a and the first insulating layer 102a is formed on one thickness direction side of the interlayer connection portion 131, and a first through hole 141 penetrating the second underlying conductor layer 101b and the second insulating layer 102b is formed on the other thickness direction side of the interlayer connection portion 131.
• the method for forming the first through hole 141 can be the same as the method for forming the second through hole 142 described above.
• the first plating layer 107a is formed on the inner peripheral surface of the first through hole 141, the inner peripheral surface of the second through hole 142, and one thickness direction surface of the first base conductor layer 101a
• the second plating layer 107b is formed on the inner peripheral surface of the first through hole 141 and the other thickness direction surface of the second base conductor layer 101b.
• the combination of the first base conductor layer 101a and the first plating layer 107a formed on one thickness direction surface of the first insulating layer 102a corresponds to the first conductor layer 110.
• the combination of the second base conductor layer 101b and the second plating layer 107b formed on one thickness direction surface of the second insulating layer 102b corresponds to the second conductor layer 120.
• the thickness of the first conductor layer 110 is the total thickness of the first underlying conductor layer 101a and the first plating layer 107a.
• the thickness of the second conductor layer 120 is the total thickness of the second underlying conductor layer 101b and the second plating layer 107b.
• the first plating layer 107a formed on the inner circumferential surface of the second through hole 142 on one thickness-wise side of the wiring portion 130 corresponds to the second via connection portion 152.
• the first plating layer 107a formed on the inner circumferential surface of the first through hole 141 on one thickness-wise side of the interlayer connection portion 131, the interlayer connection portion 131, and the second plating layer 107b formed on the inner circumferential surface of the first through hole 141 on the other thickness-wise side of the interlayer connection portion 131 together correspond to the first via connection portion 151.
• the first conductor layer 110 and the second conductor layer 120 are patterned.
• Examples of the patterning of the first conductor layer 110 and the second conductor layer 120 include wet etching and dry etching, and preferably, wet etching.
• the first conductor layer 110 is patterned to form the first ground conductor portion 111 and the first terminal portion 112.
• the second conductor layer 120 is patterned to form the second ground conductor portion 121 and the second terminal portion (not shown).
• the total thickness of the first underlying conductor layer 101a and the first plating layer 107a is the first thickness T1 of the first ground conductor portion 111, and is also the thickness of the first terminal portion 112.
• the total thickness of the second underlying conductor layer 101b and the second plating layer 107b is the first thickness T1 of the second ground conductor portion 121, and is also the thickness of the second terminal portion.
• At least one of the first ground conductor part 111 and the second ground conductor part 121 is patterned at the bent part F.
• the patterning of the first ground conductor part 111 and the second ground conductor part 121 include wet etching and dry etching, and preferably wet etching. Note that the etching of the first ground conductor part 111 and the second ground conductor part 121 is light etching (soft etching), and only a portion of the first ground conductor part 111 and the second ground conductor part 121 is removed in the thickness direction, rather than being entirely removed.
• the second thickness T2 is the total thickness of the first underlying conductor layer 101a and the first plating layer 107a or the total thickness of the second underlying conductor layer 101b and the second plating layer 107b after etching.
• the second thickness T2 is the thickness of the first underlying conductor layer 101a or the thickness of the second underlying conductor layer 101b after etching.
• the cover insulating layer 160 is attached to one surface in the thickness direction of the first conductor layer 110 and the other surface in the thickness direction of the second conductor layer 120 .
• first cover insulating layer 161 is bonded to one surface in the thickness direction of the first conductor layer 110.
• the second cover insulating layer 162 is bonded to the other surface in the thickness direction of the second conductor layer 120.
• the pressing machine described above is used for bonding.
• the pressing conditions are the same as above.
• the first cover insulating layer 161 enters between the adjacent first ground conductor portion 111 and first terminal portion 112.
• the first cover insulating layer 161 contacts one thickness-wise surface of the first base resin layer 105a exposed from the first ground conductor portion 111 and the first terminal portion 112.
• the second cover insulating layer 162 enters between the adjacent second ground conductor portion 121 and the second terminal portion 122.
• the second cover insulating layer 162 contacts the other thickness-wise surface of the second base resin layer 105b exposed from the second ground conductor portion 121 and the second terminal portion 122.
• the flexible multilayer circuit board 1 is manufactured in this way.
• the flexible multilayer circuit board 1 of the present invention has a bent portion F in a longitudinal intermediate portion, and at least one of the first ground conductor portion 11 and the second ground conductor portion 21 has a second thickness T2 that is thinner than the first thickness T1 at the bent portion F. Therefore, the flexible multilayer circuit board 1 has excellent flexibility.
• the first ground conductor 11 and the second ground conductor 21 each have a first thickness T1 and a second thickness T2 alternately along the longitudinal direction at the bent portion F, but the present invention is not limited to this. It is sufficient that at least one of the first ground conductor 11 and the second ground conductor 21 has the second thickness T2 at the bent portion F of the flexible multilayer circuit board 1. Specifically, as shown in FIG. 8, at the bent portion F, only the first ground conductor 11 may have only the second thickness T2.
• the bent portion F coincides with the portion of the first ground conductor portion 11 having the second thickness T2 in the longitudinal direction.
• the second ground conductor portion 21 has a uniform thickness at the bend portion F and other than the bend portion F. Specifically, the second ground conductor portion 21 has only the first thickness T1 at the bend portion F and other than the bend portion F. Note that, at the bend portion F, the second ground conductor portion 21 may be formed with a second thickness T2 similar to that of the first ground conductor portion 11.
• the flexible multilayer circuit board 1 includes only one bent portion F, but is not limited to this.
• the flexible multilayer circuit board 1 may include a plurality of bent portions F. The number of bent portions F is appropriately selected according to the electronic device to which the flexible multilayer circuit board 1 is applied.
• the proportion of each bent portion F in the total length of the flexible multilayer circuit board 1 in the longitudinal direction is, for example, 5% to 30%.
• the proportion of all bent portions F in the total length of the flexible multilayer circuit board 1 in the longitudinal direction is, for example, 5% to 30%.
• the first conductor layer 10 has a first terminal portion 12 and the second conductor layer 20 has a second terminal portion 22, and at the other end in the longitudinal direction, the first conductor layer 10 does not have the first terminal portion 12 and the second conductor layer 20 has the second terminal portion 22.
• the flexible multilayer circuit board 1 is not limited to this.
• either the first conductor layer 10 or the second conductor layer 20 may have a terminal portion.
• the first conductor layer 10 may have the first terminal portion 12, and the second conductor layer 20 may not have the second terminal portion 22.
• the first conductor layer 10 may not have the first terminal portion 12, and the second conductor layer 20 may have the second terminal portion 22.
• the first conductor layer 10 may not have the first terminal portion 12, and the second conductor layer 20 may have the second terminal portion 22, and at the other longitudinal end, the first conductor layer 10 may have the first terminal portion 12, and the second conductor layer 20 may not have the second terminal portion 22.
• the position of the terminals on the flexible multilayer circuit board 1 can be selected to suit the electronic device to which it is applied.
• the second via connection portion 52 electrically connects the terminal portion and the wiring portion 30, and therefore its arrangement is changed depending on the arrangement of the first terminal portion 12 and the second terminal portion 22. Furthermore, the arrangement of the reinforcing substrate 70 is also changed depending on the arrangement of the first terminal portion 12 and the second terminal portion 22.
• the first thickness T1 and the second thickness T2 may be formed by forming an additional plating layer on at least one of the first ground conductor portion 111 and the second ground conductor portion 121, in addition to the portion corresponding to the second thickness T2 (additive method).
• the first through hole 141 and the second through hole 142 are formed in separate steps, but the method is not limited to this.
• the second through hole forming process may not be performed, and the first through hole 141 and the second through hole 142 may be formed together during the first through hole forming process, or a portion of the first through hole 141 (the first through hole 141 on the first porous laminate 100a side) may be formed during the second through hole forming process.
• the flexible multilayer circuit board 1 of the present invention is suitable for use in electronic devices such as mobile phones, smartphones, tablet terminals, and digital cameras.

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• Engineering & Computer Science (AREA)
• Microelectronics & Electronic Packaging (AREA)
• Manufacturing & Machinery (AREA)
• Structure Of Printed Boards (AREA)

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Citations (4)

• 2024
  • 2024-11-13 WO PCT/JP2024/040303 patent/WO2025121093A1/ja active Pending
  • 2024-11-13 JP JP2025539946A patent/JP7775535B2/ja active Active
  • 2024-11-18 TW TW113144301A patent/TW202529489A/zh unknown

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