JP2006156930A - Flexible board having inter-layer junction, and manufacturing method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method for a flexible board the method of which does not include processes of through-hole formation and conductive paste filling. <P>SOLUTION: The manufacturing method for the flexible board includes a step of (a) providing a sheet base material which has a film, insulating resin layers formed on the front surface of the film and the back surface opposite to the front surface, respectively, and wiring patterns embedded respectively in the insulating layers; and a step of (b) jointing a part of the wiring pattern in the front surface to a part of the wiring pattern in the back surface, by pushing a part of either of the wiring patterns in the front and back surfaces into the interior of the sheet base material. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a flexible substrate and a method for manufacturing the same. More specifically, the present invention relates to a flexible substrate and a multilayer flexible substrate in which parts of wiring patterns located on the front surface side and the back surface side are bonded to each other through a film, and methods for manufacturing the same.

  In recent years, not only miniaturization, weight reduction, and thinning of electronic devices but also miniaturization and high frequency of electronic components have been strongly demanded along with high-speed processing of electronic circuits. For example, in portable electronic devices such as mobile phones, miniaturization, weight reduction, and thickness reduction are regarded as one of the biggest problems (see, for example, Patent Document 1). Therefore, it is necessary to cope with downsizing or high frequency by mounting various mounting parts with a high wiring density with a short wiring length.

  In such a situation, a flexible substrate has attracted attention as a thin printed circuit board that can realize high-density mounting (for example, see Patent Document 2). Hereinafter, a conventional method for manufacturing a flexible substrate will be described with reference to FIG.

  First, as shown in FIG. 1A, a hole 502 for interlayer connection is formed in an insulating sheet 501 having a thickness of about 50 to 100 μm by drilling or laser processing. Next, as shown in FIG. 1B, the conductive paste 503 is filled into the holes 502 by using a printing method. And as shown in FIG.1 (c), metal foil (copper foil) 504 is arrange | positioned on both surfaces of the insulating sheet 501, and as shown in FIG.1 (d), the metal foil 504 is laminated | stacked by press. Thereafter, as shown in FIG. 1E, a resist film 505 having the same pattern as the conductor circuit is formed on the metal foil 504. Next, after etching the metal foil 504 using the resist film 505 as a mask and then removing the resist film 505, a flexible substrate 500 having a conductor circuit 506 is obtained as shown in FIG.

  Subsequently, a method of manufacturing the multilayer flexible substrate 550 will be described with reference to FIG.

  First, as shown in FIG. 2A, the flexible substrate 500 shown in FIG. 1F is used as a core substrate, and an insulating sheet 501a in which a conductive paste is filled in a hole 502 on the substrate 500 and a metal. The foil 504a is laminated by pressing. Next, as shown in FIG. 2B, a resist film 505 is selectively formed on the metal foils 504a on both sides of the laminate. Next, the metal foil 504a is etched using the resist film 505 as a mask, and then the resist film 505 is removed to obtain a multilayer flexible substrate 550 composed of four layers of conductor circuits as shown in FIG.

Thus, in the conventional manufacturing method, etching, which is a wet process, is used to form the wiring pattern. Therefore, not only is the influence of the etching solution exerted on the insulating sheet, but also cleaning / It was necessary to perform drying and the like, and it took time and effort. In addition, the wiring pattern formed by etching is exposed on the substrate surface, and micro-cracks are easily generated in the wiring pattern due to the bending of the flexible substrate, which is not always satisfactory in terms of the bending life. It was.
JP 2003-163422 A JP 2001-1111189 A

  The conventional manufacturing method is basically the same as the manufacturing method of a rigid substrate (typical printed circuit board) in that it includes a step of forming a through hole and filling a conductive paste. Such a process is complicated (for example, takes about 3 hours), and it has been desired to simplify or omit it. On the other hand, the process of forming a through hole and then filling with a conductive paste is an indispensable process for manufacturing a flexible substrate and a multilayer flexible substrate, and it is basically difficult to omit such a step. I came. Moreover, since it was essential, it was often not recognized as a problem. Therefore, the manufacturing method of the flexible substrate and multilayer flexible substrate which can solve such a subject has not been realized yet.

  SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a flexible substrate and a method for manufacturing a multilayer flexible substrate that do not form a through hole and do not fill with a conductive paste. Moreover, the further objective is to provide the flexible substrate and multilayer flexible substrate which are obtained with such a manufacturing method.

(I) The present invention
(A) (i) film,
(Ii) a sheet having a film surface (that is, a “front” surface) and an insulating resin layer formed on the back surface facing the surface, and (iii) a wiring pattern embedded in the insulating resin layer A step of preparing a base material, and (b) a part of at least one of the front and back wiring patterns is pushed into the sheet base material to penetrate the insulating resin layer and the film, and a part of the front wiring pattern and the back wiring Provided is a method of manufacturing a flexible substrate (referred to herein as “manufacturing method I”) including a step of bonding a part of a pattern, and a flexible substrate obtained thereby.

  In the step (b) of the flexible manufacturing method (I) of the present invention, “a part of the wiring pattern on the front surface and the back surface” is in a positional relationship facing each other. A part of the wiring pattern is bonded to each other.

(II) The present invention also provides:
(A ₁ ) (i) film,
(Ii) having an insulating resin layer formed on the surface of the film (that is, the “front” surface) and the back surface facing the surface, and (iii) a wiring pattern embedded in the insulating resin layer on the surface Preparing a sheet substrate comprising:
(A ₂ ) a step of preparing a flexible substrate (preferably a substrate having a wiring pattern on the surface); and (b) the insulating resin layer on the back surface of the sheet base material and the surface of the substrate are in contact with each other After the sheet base material is aligned and overlaid, a part of the wiring pattern of the sheet base material is pushed into the substrate side to penetrate the insulating resin layer and the film, and a part of the wiring pattern of the sheet base material is placed on the substrate (preferably A flexible substrate manufacturing method (referred to herein as “manufacturing method II”) including a step of bonding to a part of a wiring pattern of a substrate is provided, and a flexible substrate obtained therefrom is provided.

  Furthermore, the present invention provides a method for producing a multilayer flexible substrate comprising the steps of the production methods (I) and / or (II), and additionally comprising the step of laminating further flexible substrates, A multilayer flexible substrate obtained therefrom is also provided.

  The “joining part” formed by joining has a function of electrically connecting the wiring pattern layer on the front surface and the wiring pattern layer on the back surface, and is also referred to as “interlayer connection part” in this specification.

  In the manufacturing methods (I) and (II) of the present invention, it is not necessary to form through holes and fill with conductive paste to connect the wiring patterns. In the manufacturing method of this invention, wiring patterns can be connected by pressing a part of wiring pattern using the roll member which has a needle-shaped member or a projection part, for example. For example, when a roll member having a plurality of protrusions is used, a plurality of interlayer connection sites can be continuously formed by passing a sheet base material between the pair of roll members. Therefore, in the production methods (I) and (II) of the present invention, a roll-to-roll method can be used. As a result, productivity is improved and mass production is possible. In addition, the roll-to-roll method has an advantage that the sheet base material can be easily held when the flexible substrate is manufactured.

  Unlike the case of using an electrically conductive paste, the interlayer connection part is formed seamlessly with the same material as the wiring pattern, so the impedance between the via (corresponding to the interlayer connection part of the present invention) and the wiring pattern. Can be avoided. Further, since the wiring pattern and the interlayer connection part are formed of the same material, the thermal expansion coefficients of the wiring pattern and the interlayer connection part are equal, and the connection reliability is excellent.

  Furthermore, the sheet base material used in the production methods (I) and (II) of the present invention can be obtained by transferring a wiring pattern previously formed on a carrier sheet to an insulating resin layer on the film. Therefore, a sheet base material can be prepared by a dry process without performing wet etching. In addition, a dry process is performed for forming the interlayer connection portion in order to use the needle-shaped member or the roll member. Accordingly, the production methods (I) and (II) of the present invention are all simple processes that can be carried out by a dry process and are easy to handle.

BEST MODE FOR CARRYING OUT THE INVENTION

  Hereinafter, the flexible substrate and multilayer flexible substrate manufacturing method of the present invention, and the resulting flexible substrate and multilayer flexible substrate will be specifically described.

  First, the flexible substrate manufacturing method (I) of the present invention and the flexible substrate obtained therefrom will be mainly described. In FIG. 3, the structure of the sheet | seat base material 10 used at a process (a) is shown with sectional drawing. 4 and 5 show a configuration of the obtained flexible substrate 100 in a sectional view and a perspective view, respectively.

First, in step (a), as shown in FIG.
(I) Film 11
(Ii) an insulating resin layer 12 formed on the front surface of the film 11 and the back surface facing the surface, and (iii) a wiring pattern 20 embedded in the insulating resin layer 12
A sheet base material 10 is prepared.

In this sheet base material 10, the film 11 is preferably thinner than the insulating resin layer 12. For example, the thickness ratio of the insulating resin layer 12 / the thickness of the film 11 is preferably 1.1 to 8, and more preferably 1.2 to 6. Here, “the thickness of the insulating resin layer” means the thickness of the insulating resin layer formed on one surface of the film 11. As a specific thickness, for example, the thickness T _i of the insulating resin layer 12 is 3 to 80 μm, and the thickness T _f of the film 11 is 2 to 16 μm. Thus, since the film 11 is thin, it is easy to break through it and form an interlayer connection site. Furthermore, since the wiring pattern 20 (20a, 20b) is embedded in the insulating resin layer, the distance between the wiring pattern 20a on the front surface and the wiring pattern 20b on the back surface is narrow, and it becomes easy to join the two in the pressing process. ing. For example, the distance between the wiring pattern 20a on the front surface and the wiring pattern 20b on the back surface is preferably 2 to 15 μm, and more preferably 2 to 9 μm. Further, in this way, the flexible substrate configured so that the insulating resin layer 12 is thicker than the film 11 has good sliding flexibility or flex life. This is because when the flexible substrate is bent, the stress applied to the film and the embedded wiring pattern is relaxed by the insulating resin layer having a low elastic modulus.

  The film 11 is generally a resin film having insulating properties, and preferably a heat resistant film. Examples of the film 11 include a resin film made of aramid or polyimide. More preferably, an aramid film is used as the film 11. This is because an aramid film has excellent surface smoothness, low water absorption and dimensional stability, and has a predetermined strength even when it is thinner than a polyimide film (a film usually used for flexible substrates). It is because it is easy to implement | achieve and it is cheaper than a polyimide film. Furthermore, an aramid film is preferable because it has high elastic strength and is suitable for thinning, and the thickness of the aramid film corresponding to the strength of a polyimide film having a thickness of about 12.5 μm is about 4 μm.

  The insulating resin layers 12 formed on both surfaces of the film 11 have a function of accommodating the wiring pattern 20. In order to improve the adhesiveness with the wiring pattern 20 or to improve the adhesiveness between the substrates in multilayering, it is preferable that the insulating resin layer 12 has adhesiveness. Therefore, the insulating resin layer is preferably formed of at least one resin selected from the group consisting of epoxy resins, polyimide resins, acrylic resins, and resins obtained by modifying them.

  The sheet base material 10 used in the manufacturing method of the present invention is characterized in that the wiring pattern 20 is embedded in the insulating resin layer 12. In order to obtain such a wiring pattern, first, as shown in FIG. 6A, a base material 80 having an insulating resin layer 12 formed on the front surface and the back surface of a film 11 is prepared. Next, as shown in FIG. 6B, the wiring patterns 20 a and 20 b are embedded in the insulating resin layer 12. For embedding the wiring patterns 20a and 20b, a transfer method as shown in FIG. 7 is preferably used. In this transfer method, first, a carrier sheet 32 provided with wiring patterns 20a and 20b in advance, and a film 11 having an insulating resin layer 12 on both surfaces are prepared. Subsequently, the carrier sheet 32 and the film 11 are pressed by the nip pressure of the pair of roll members 31 by passing the carrier sheet 32 and the film 11 between the pair of roll members 31 rotating in a certain direction. By this pressing, the wiring patterns 20a, 20b on the carrier sheet 32 are embedded in the insulating resin layer 12 of the film 11, so that by finally removing the carrier sheet 32, the wiring patterns 20a, 20b are formed in the insulating resin layer 12. Can be obtained. In the case where the insulating resin layer 12 is made of a thermosetting resin, it is preferable that the insulating resin layer 12 be in a semi-cured state at the time of embedding. The wiring patterns 20a and 20b are preferably embedded in the insulating resin layer 12 so as to be flush with or substantially flush with the insulating resin layer 12. Thereby, the flatness of the sheet base material 10 and the flexible substrate 100 obtained from the sheet base material 10 is excellent, which is advantageous when multilayered. Such a transfer method can form a wiring pattern with a finer pitch than a wiring pattern formed by wet etching. For example, the line / space (L / S) of the wiring pattern formed by wet etching is about 40 μm / 40 μm, whereas the L / S of the wiring pattern using the transfer method is 15 μm / 15 μm (30 μm pitch). ).

  The wiring pattern 20 may be formed of any material as long as it has conductivity. For example, the wiring pattern 20 may be formed of a metal material selected from the group consisting of copper, nickel, gold, and silver. preferable. The carrier sheet used in the transfer method is preferably a sheet material made of an organic film such as PET or a metal foil such as a copper foil and having a thickness of about 25 to 200 μm.

  Next, the step (b) will be described. In step (b), a part of at least one of the front and back wiring patterns is pushed into the sheet base material, and the insulating resin layer and the film are broken through to join a part of the front wiring pattern and a part of the back wiring pattern. To do. As a result, a part of the wiring pattern on the front surface and a part of the wiring pattern on the back surface are in pressure contact (therefore, in this specification, the step (b) is also referred to as a pressure contact process). However, in the step (b), it is only necessary that a part of the wiring pattern on the front surface and a part of the wiring pattern on the back surface are electrically connected. Note that it does not. The pushing direction is preferably substantially perpendicular to the sheet substrate surface. In FIG. 4 or FIG. 5, a joint part (that is, an interlayer connection part) formed by joining is indicated by reference numeral 25.

  As a tool used for pressing, a needle-like member may be used, or a roll member 33 having a protrusion 35 as shown in FIG. 8 may be used. When using a roll member, it is preferable to use it as a pair of roll members in order to utilize the nip pressure. FIG. 9 shows a mode in which the flexible substrate 100 is manufactured by the needle-like member 50. The needle-like member 50 has a pressing surface (that is, a tip portion) preferably having a hemispherical surface. Note that the pressing portion of the needle-like member 50 may be planar. Similarly, the tip of the protrusion 35 of the roll member 33 preferably has a hemispherical surface. The tip of the projection 35 of the roll member 33 may also be planar. The needle-like member and the roll member are preferably made of SUS, nickel, aluminum, or the like.

  When both a part of the front side wiring pattern and a part of the back side wiring pattern are pushed in, as shown in FIG. 4, a cross section of the wiring pattern composed of a part of the front side wiring pattern and a part of the back side wiring pattern. Becomes substantially X-shaped. However, when one wiring pattern is maintained flat and a part of the other wiring pattern is pushed in, the cross section of a part of the pushed wiring pattern becomes substantially U-shaped.

  When both a part of the wiring pattern on the front side and a part of the wiring pattern on the back side are pushed in, it is possible that a part of both wiring patterns are joined together in the film, but only a part of one wiring pattern is It is also possible to adopt a mode in which the films are bonded to each other in the insulating resin layer while penetrating the film. Further, when only a part of one of the wiring patterns is pushed in, only a part of the pushed wiring pattern penetrates the film, and a part of both the wiring patterns is bonded to each other in the insulating resin layer. .

  The pushing operation in the step (b) can be performed at room temperature, for example, at a temperature of 20 to 80 ° C. The pushing force applied per interlayer connection site is preferably 100 to 1200 gf, more preferably 500 to 1000 gf.

  In addition, in step (b), when the pressing operation is performed with the roll member having the protrusions in a state where the sheet base material is moved in a certain direction, the interlayer connection sites can be continuously formed. Therefore, in the manufacturing method (I) of the present invention, a roll-to-roll method can be used, and mass production of flexible substrates becomes possible.

  In a preferred embodiment, in the step (b), as shown in FIG. 10, a conductive material 27 is provided in a protruding shape on the wiring pattern 20 on at least one of the front surface and the back surface (in the present invention, this conductive material is “ (Also referred to as “conductive protrusions”), by pushing in the conductive protrusions 27, at least one of the portion 22 a of the wiring pattern 20 a on the front surface and the portion 22 b of the wiring pattern 20 b on the back surface is indirectly introduced into the sheet substrate 10. You may push in. In FIG. 10, conductive protrusions 27 are provided on both the front wiring pattern 20a and the rear wiring pattern 20b.

  In such an embodiment, as shown in FIG. 11 (a) or 11 (b), the conductive material 27 is filled in the recesses formed on the surface of the wiring pattern by pressing, and the surface of the wiring pattern is flattened. Become. Therefore, the flatness of the flexible substrate 100 is excellent, and a structure suitable for lamination is provided. In the obtained flexible substrate 100, the interlayer connection is made with a low resistance due to the filled conductive material 27, and a large current can flow as required.

  When a part of the wiring pattern on the front surface or a part of the wiring pattern on the back surface is pushed in using the conductive protrusion, a needle-like member or a roll member can be used. FIG. 12 shows a mode in which a portion 22a of the front wiring pattern 20a and a portion 22b of the rear wiring pattern 20b are pushed in using the needle-like member 50. In addition, when using a roll member, it is preferable to use the cylindrical roll member 34 as shown in FIG. The roll member 34 is preferably formed of a material such as styrene or rubber.

  The conductive protrusion 27 is preferably made of a metal, for example, preferably made of a metal-based alloy selected from the group consisting of copper, nickel, aluminum, gold, silver and a mixture containing these metals. . Note that a resin having electrical conductivity, such as a conductive paste containing such metal powder or carbon powder as conductive particles, can also be used as the material of the conductive protrusion 27.

  In order to form the conductive protrusion 27 on the wiring pattern 20, a paste printing method, a bump forming method, a ball mounting method, an electrophotographic method, or the like can be used. That is, in the paste printing method, the conductive material is paste-printed and then dried to form the protruding conductive material. In the bump formation method or the ball mounting method, the conductive protrusion is formed by forming a bump on the metal layer or mounting a metal ball. Further, in the electrophotographic method, as shown in FIG. 14, after charging the photosensitive drum 51 with a charger (charging roll) 52, the surface of the photosensitive drum is subjected to light writing using a light source (LED, laser, etc.) 53. An electrostatic latent image is formed at a predetermined position. Next, after the conductive material 27 is attached to the photosensitive drum 51, the conductive material 27 is transferred onto the wiring pattern 20 to form the conductive protrusions 27 on the sheet base material.

  When the conductive protrusion is not provided on both the wiring pattern on the front surface and the wiring pattern on the back surface, but the conductive protrusion is provided only on the wiring pattern on either the front surface or the back surface, the roll member 34 is provided. By performing the pushing step (b) used, a cross section of a part of the wiring pattern becomes substantially U-shaped. Instead of forming the conductive protrusions prior to the pressing step (b), a conductive material may be used after the pressing step (b). That is, the conductive material is filled in the recess formed in the pressing step (b) in order to flatten the wiring pattern surface or reduce the resistance of the interlayer connection portion.

  As a preferred embodiment, in the step (b), a part of the wiring pattern on the front surface and a part of the wiring pattern on the back surface are joined to each other through solder to form an interlayer connection part. For example, as shown in FIG. 15, the sheet base material 92 in which the solder 15 is inserted between the film 11 and the wiring pattern 20 is pressed by the roll member 33 to form the interlayer connection portion 25 including the solder 15. . The sheet base material 93 on which the interlayer connection portion 25 is formed is preferably subjected to a reflow process using a furnace 70. The flexible substrate 100 manufactured in this way has good connection reliability because it additionally includes solder 15 at the joint portion between the portion 22a of the wiring pattern 20a on the front surface and the portion 22b of the wiring pattern 20b on the back surface. It becomes.

  Note that, as shown in FIG. 16, the interlayer connection portion including the solder 15 may be formed also when the pressing is performed through the conductive protrusion 27. In such an embodiment, the sheet base material 92 in which the solder 15 is inserted between the film 11 and the wiring pattern 20 is used, and the conductive protrusions 27 are formed on the sheet base material 92. . The obtained flexible substrate 100 is excellent not only in flatness but also in connection reliability.

  As a preferred embodiment, after the joining portion is formed in the step (b), the joining surface may be heat-treated to improve the joining state. For example, as shown in FIG. 17, the welding apparatus 60 is moved in the vertical direction (directions indicated by arrows 62 and 64) with respect to the flexible substrate 100 moving in the horizontal direction (direction indicated by arrows 40). The bonding surface 22c of the part 25 can be continuously heat-treated. As such treatment, various methods such as a laser machining method or an electric discharge machining method can be used as well as a welding method.

  In particular, as shown in FIG. 18, it is preferable to apply ultrasonic waves to the bonding portion 25 formed in the step (b). In the embodiment shown in FIG. 18, the ultrasonic application tool 60 is reciprocated in a direction substantially perpendicular to the moving direction of the flexible substrate 100 (directions indicated by arrows 62 and 64). Thereby, the contact / non-contact between the ultrasonic application tool 60 and the flexible substrate 100 is repeated, and the application of ultrasonic waves is repeatedly turned on / off. By applying ultrasonic waves, the interlayer connection part (that is, the bonding part 25) is ultrasonically bonded, so that the strength of the interlayer connection part 25 is improved and the connection reliability is further improved. Further, the contact surface or the bonding surface (interface) 22c is melted by ultrasonic bonding, and as a result, the resistance value of the interlayer connection portion 25 is reduced (for example, 1 of the resistance value of the interlayer connection portion before application of ultrasonic waves). Not only can flow a large current, but also leads to a reduction in power consumption. The frequency of the ultrasonic vibration is preferably about 15 kHz to 150 kHz. The output power is preferably about 10 W to several thousand W. The application time is preferably 0.1 to 10 seconds (typically about 1 second), and the corresponding applied energy is 1 kJ to several kJ.

  Not only a mode in which ultrasonic waves are applied after the formation of the interlayer connection sites, but also a mode in which ultrasonic waves are applied when forming the interlayer connection sites. Preferably, ultrasonic waves are applied during the formation of the interlayer connection portion by pressing using a roll member or a needle-like member having a protrusion. That is, the pushing step (b) is performed using a roll member or a needle-like member to which a function of applying ultrasonic waves is added. For example, when a needle-like member is used, an embodiment in which ultrasonic waves can be applied from the tip of the needle-like member is preferable.

  As a further aspect, it is preferable to heat the interlayer connection site before or during application of ultrasonic waves. As a result, the vicinity of the interlayer connection site is softened, the interlayer connection site is easily deformed, and the connection area is increased, so that ultrasonic bonding can be performed better. Heating the sheet base material itself leads to warming of the interlayer connection site, so that the sheet base material or the flexible substrate may be disposed on a heated roll member or a conveyor, for example. The temperature of the sheet base material or flexible substrate achieved by heating is, for example, 50 to 400 ° C, preferably 100 to 300 ° C.

  The application of ultrasonic waves is preferably performed while measuring the physical characteristics of a part of the wiring pattern. Examples of such physical characteristics include a resistance value of a part of the wiring pattern or a dent amount of the wiring pattern. For example, when ultrasonic bonding is performed while measuring physical properties such as resistance value, the strength of the interlayer connection part can be known in real time, and it is possible to apply ultrasonic waves until the strength reaches a desired value. Become. In addition, the application of ultrasonic waves while measuring physical properties may be performed only once or several times. After that, the application time or the amount of ultrasonic energy, etc. can be determined using the results obtained therefrom. Can be adjusted.

  In addition, in the aspect which applies an ultrasonic wave, as FIG. 19 shows, the sheet | seat base material 94 which has arrange | positioned the conductive layer 15 inside the wiring pattern 20 may be used. The conductive layer 15 preferably comprises a metal selected from the group consisting of aluminum, gold, silver, platinum, vanadium, and the like. In addition, you may include solder in this conductive layer 15 as needed.

  In the embodiment shown in FIG. 19, when the sheet base 94 is passed through the roll member 33, the front and back wiring patterns 20 are pushed into the sheet base, and the front wiring pattern 20a and the conductive layer 15 inside thereof. Then, the wiring pattern 20b on the back surface and the conductive layer 15 on the inner side are bonded to each other, so that an interlayer connection portion 25 including the conductive layer 15 is formed. Subsequently, an ultrasonic wave is applied to the sheet base material 95 having such an interlayer connection part 25 by the ultrasonic application tool 60 to ultrasonically bond the interlayer connection part 25. In the obtained flexible substrate 100, an alloy formed by melting a plurality of types of metals is not included in the same kind of metal (for example, copper and copper), but is included in the joint part of the interlayer connection part 25. Is further improved. Therefore, a flexible substrate with better connection reliability can be obtained.

Although the manufacturing method (I) has been mainly described above, the flexible substrate obtained from the manufacturing method (I) is as shown in FIG. 4 or FIG.
Film 11,
Insulating resin layer 12 formed on the front surface of film 11 and the back surface facing the surface, and wiring pattern 20 embedded in insulating resin layer 12
Comprising
With a part of at least one of the front and back wiring patterns 20 penetrating through the insulating resin layer 12 and the film 11, the part 22a of the front wiring pattern 20a and the part 22b of the back wiring pattern 20b are bonded to each other. A junction site 25 is formed.

  By using such a flexible substrate 100, a multilayer flexible substrate 150 as shown in FIG. 20 can be manufactured. In the multilayer flexible substrate 150 shown in FIG. 20, the solid substrate 110 including the metal layer 21 is used as a core substrate, and the flexible substrate 100 obtained by the manufacturing method (I) of the present invention is laminated on both surfaces of the core substrate 110. . Further, for example, a flexible substrate 100 obtained by the manufacturing method (I) of the present invention is used as a core substrate, and a typical flexible substrate (for example, the flexible substrate 500 obtained in FIG. 1F) is laminated thereon. Is also possible. The characteristic of such a multilayer flexible substrate is that its thickness is very thin. For example, when the thickness of one flexible substrate obtained by the production method (I) of the present invention is 24 μm, the thickness is less than 100 μm even if four layers are laminated, and the thickness is not less than six layers. Is less than 150 μm, and an extremely thin multilayer flexible substrate is realized.

  Next, with reference to FIG. 21, the manufacturing process of the flexible substrate 100 of this invention is demonstrated including the transfer process of a wiring pattern.

  First, as shown in FIG. 21, the base material 80 on which the insulating resin layers 12 are formed on both surfaces of the film 11 is advanced in the direction of the arrow 40. When the substrate 80 is passed between a pair of roll members (that is, nip rolls) 31, the wiring pattern 20 (20 a and 20 b) is transferred to the insulating resin layer 12.

  The wiring pattern 20 before being transferred (that is, the wiring patterns 20a and 20b) is disposed on the carrier sheet 32, and the carrier sheet 32 moves in the direction of the arrow 42 by the rotation of the roll member 31, and the roll member. The carrier sheet 32 is pressed in the direction of the insulating resin layer 12 of the substrate 80 by the nip pressure of 31, and the wiring patterns 20 (20a, 20b) are embedded in the insulating resin layer 12.

  After the wiring pattern 20 (that is, the wiring patterns 20 a and 20 b) is embedded, the sheet base material 90 that proceeds in the direction of the arrow 41 is passed between the pair of roll members 33. As shown in FIG. 21, the roll member 33 includes a plurality of protrusions 35, and the protrusions 35 are provided corresponding to the pattern of interlayer connection sites (so-called vias) to be formed. . When the protrusion 35 of the roll member 33 comes into contact with the portion 22a of the wiring pattern 20a and the portion 22b of the wiring pattern 20b due to the rotation of the pair of roll members 33 (rotation in the direction of the arrow 44), the wiring pattern 20a. The portion 22a of the wiring pattern and the portion 22b of the wiring pattern 20b are pushed into the inside of the sheet base material 90, so that both are bonded to each other through the thin film 11.

  In addition, the aspect which pushes a part of wiring pattern through a conductive protrusion becomes as FIG. 22 shows. In the embodiment shown in FIG. 22, the conductive protrusions 27 are provided between the wiring pattern transfer process and the pressure contact process. The sheet base material 90 on which the conductive protrusions 27 are formed is passed between the pair of roll members 34. The pair of roll members 34 rotate in the direction of the arrow 44, and when the roll member 34 comes into contact with the conductive protrusions 27, a portion 22a of the wiring pattern 20a on the front surface and a portion 22b of the wiring pattern 20b on the back surface are It is pushed into the inside of the film substrate 90 through the conductive protrusions 27 and breaks through the thin film 11 to be bonded to each other. In addition, since the conductive protrusions 27 pushed into the sheet base material 90 by the pair of roll members 34 are filled in the concave portions formed on the surface of the wiring pattern, the surface of the obtained flexible substrate 100 is It becomes flat.

  As a preferred embodiment, as shown in FIG. 23, when a roll member 36 having a recess 35 ′ is used, a convex portion 26 is formed on the wiring pattern 20 by using a repulsive force at the time of roll pressure contact instead of a pressing force due to roll pressure contact. Can be formed. If this method is used, it becomes possible to make the convex part 26 function as a bump, for example, and to form an interlayer connection part. In addition, as shown in FIG. 24, it is also possible to use the roll member 37 provided with both the projection part 35 and the recessed part 35 '. In the embodiment shown in FIG. 24, the protrusion 26 and the interlayer connection portion 25 are formed by the roll member 37 after the transfer process.

  Next, the roll-to-roll method will be briefly described. FIG. 25 shows a manufacturing process of the flexible substrate 100 using the roll-to-roll method. In this method, a roll process is applied from the beginning to the end. As shown in FIG. 25, the base material 80 before the wiring pattern 20 is formed is wound around a roll 30a and sent out in the direction of the arrow 40 when the wiring pattern 20 and the interlayer connection part 25 are formed. And after the wiring pattern 20 and the interlayer connection part 25 are formed, the flexible substrate 100 is finally wound up by the roll 30d. The roll-to-roll method is suitable for mass production because the sheet substrate and the flexible substrate can be easily held and the flexible substrate can be continuously produced. The reason why such a roll-to-roll method can be used is that all the production methods of the present invention can be carried out by a dry process.

  In addition, when manufacturing a multilayer flexible substrate from the flexible substrate 100 by a roll-to-roll method, it becomes an aspect as shown in FIG. Here, the film member 110 in which the insulating resin layer 12 is formed on both surfaces of a solid metal layer 21 (solid copper foil) that can function as a shield layer is used as a core substrate. The film member 110 is sent out in the direction of the arrow 40 from the roll 30a. The flexible substrate 100 is sent to both sides of the film member 110 from the roll 30b. The film member 110 and the flexible substrate 100 are stacked between the roll members 38. The roll member 38 rotates in the direction of the arrow 45, and the flexible substrate 100 and the film member 110 are pressed against each other by the nip pressure. The manufactured multilayer flexible substrate 150 proceeds in the direction of the arrow 40 as it is, and is finally wound around the roll 30d. Thereafter, the multilayer flexible substrate 150 may be cut into a predetermined dimension or may be subjected to a multilayering process.

  As a preferred embodiment, when the roll member 33 is used in a manner as shown in FIG. 27, the transfer process and the pressure contact process of the wiring pattern 20 can be performed substantially simultaneously. Thereby, the manufacturing process can be made more efficient. In the illustrated embodiment, the base material 80 and the carrier sheet 32 on which the wiring pattern 20 is formed are passed between a pair of roll members 33, and the wiring pattern 20 on the carrier sheet 32 is an insulating resin layer of the base material 80. 12 and a part (22a, 22b) of the wiring pattern 20 is pressed to form an interlayer connection portion 25.

The production method (I) of the present invention and the flexible substrate obtained therefrom have been described above. Next, the manufacturing method (II) of the flexible substrate of this invention and the flexible substrate obtained from it are demonstrated. Production method (II) is:
(A ₁ ) (i) film,
(Ii) preparing an insulating resin layer formed on the surface of the film and the back surface facing the surface, and (iii) a sheet substrate having a wiring pattern embedded in the insulating resin layer on the surface;
(A ₂ ) a step of preparing a substrate having a wiring pattern on the surface; and (b) the sheet base material is aligned on the substrate so that the insulating resin layer on the back surface of the sheet base material is in contact with the surface of the substrate. And a step of pressing a part of the wiring pattern of the sheet base material toward the substrate side through the insulating resin layer and the film, and joining a part of the wiring pattern of the sheet base material to a part of the wiring pattern of the substrate. .

In FIG. 28, the structure of the flexible substrate 200 obtained with the manufacturing method (II) of this invention is shown with sectional drawing. The illustrated flexible substrate 200 includes:
A flexible substrate 200 in which a substrate 215 and a sheet base 210 are overlaid,
The substrate 215 has a wiring pattern 17 on its surface, and
Sheet base 210 is film 11,
Insulating resin layer 12 formed on the front surface of film 11 and the back surface facing the surface, and wiring pattern 20 embedded in insulating resin layer 12 on the surface
Consists of
The sheet base 210 and the substrate 215 are stacked so that the insulating resin layer 12 on the back surface of the sheet base 210 and the surface of the substrate 215 are in contact with each other.
The portion 22 of the wiring pattern 20 of the sheet base 210 is pushed into the substrate 215 side, and the portion 22 of the wiring pattern 20 of the sheet base 210 and the portion 17a of the wiring pattern 17 of the substrate 215 mutually. It is characterized in that a bonded portion is formed by bonding.

  28, the insulating resin layer 12 is formed not only on the front surface of the film 11 but also on the back surface. Here, the insulating resin layer 12 on the front surface has a function of accommodating the wiring pattern 20, and the insulating resin layer 12 on the back surface has a function of improving the adhesiveness with the substrate 215. Accordingly, it is sufficient to form the insulating resin layer 12 only on one side of the film 11 from the viewpoint of accommodating the wiring pattern 20, but considering both the adhesiveness with the substrate, both surfaces of the film 11 as shown in FIG. It is necessary to form the insulating resin layer 12 on the surface.

  As shown in FIG. 28, in the flexible substrate 200 obtained by the manufacturing method (II) of the present invention, the portion 22 of the wiring pattern 20 of the sheet base 210 and the portion 17a of the wiring pattern 17 on the surface of the substrate 215 are pressed against each other. It is joined by. The joining portion 25 formed by joining functions as a so-called “interlayer connection portion”.

  The sheet base material 210 used in the manufacturing method (II) is different from the sheet base material 10 used in the manufacturing method (I) in which the wiring pattern is formed on both sides of the film, and is wired only on one side of the film. Note that no pattern is formed. Note that the sheet substrate 210 can be regarded as a layer composed of a flexible wiring pattern, and can also be referred to as a “flexible wiring layer”.

The sheet base 210 is preferably such that the film 11 is thinner than the insulating resin layer 12. For example, the ratio of the thickness of the insulating resin layer 12 to the thickness 11 of the film is preferably 1.1 to 8, more preferably 1.2 to 6. The “thickness of the insulating resin layer” here means the thickness of the insulating resin layer formed on one surface of the film 11 as in the case of the manufacturing method (I). As a specific thickness, for example, the thickness T _i of the insulating resin layer 12 is 3 to 80 μm, and the thickness T _f of the film 11 is 2 to 16 μm. Thus, since the sheet | seat 11 is thin, it is easy to break through and form the interlayer connection part 25. FIG. Furthermore, since the wiring pattern 20 is embedded in the insulating resin layer 12, the distance between the wiring pattern 20 and the wiring pattern 17 on the surface of the substrate 215 is narrow, and it is easy to join both in the pressing process. For example, the distance between the wiring pattern 20 of the sheet base 210 and the wiring pattern 17 of the substrate 215 is preferably 2 to 15 μm, more preferably 2 to 9 μm. Note that the flexible substrate of the present invention having a configuration in which the wiring pattern is embedded in the insulating resin layer 12 thicker than the film 11 has good sliding flexibility or the same reason for the manufacturing method (I). Has a flex life.

  The film 11 is generally a resin film having insulating properties, and preferably a heat resistant film. Examples of the film 11 include a resin film made of aramid or polyimide. Preferably, an aramid film is used as the film 11 for the same reason as in the manufacturing method (I).

  The insulating resin layer 12 not only stores the wiring pattern 20 but also has a function of improving the adhesion between the substrates when the number of layers is increased. Therefore, it is preferable that the insulating resin layer 12 has adhesiveness as in the case of the production method (I). Therefore, the insulating resin layer 12 is preferably formed from at least one resin selected from the group consisting of epoxy resins, polyimide resins, acrylic resins, and resins obtained by modifying them.

  In the sheet substrate 210 used in the manufacturing method of the present invention, the wiring pattern 20 is embedded in the insulating resin layer 12 on the surface. In order to obtain such a wiring pattern 20, it is preferable to use the same transfer technique as in the manufacturing method (I). The wiring pattern 20 is preferably formed from the same material as in the manufacturing method (I).

The “substrate 215 having a wiring pattern on the surface” prepared in the step (a ₂ ) has flexibility. As the substrate 215, for example, a typical flexible substrate 500 as shown in FIG. 1 (f) may be used, but any substrate may be used as long as it has flexibility. . In the substrate 215 shown in FIG. 28, the wiring pattern 17 is formed only on one surface, but the wiring pattern 17 may be formed on the back surface thereof. When a multilayer flexible substrate is formed, various substrates are stacked using such a substrate 215 as a base, so that the substrate 215 can function as a core substrate.

  Next, step (b) of production method (II) will be described. In the step (b), a portion 22 of the wiring pattern 20 of the sheet base 210 is pushed into the substrate 215 side to break through the insulating resin layer 12 and the film 11, and the wiring 22 between the portion 22 of the wiring pattern 20 of the sheet base 210 and the substrate 215. The part 17a of the pattern 17 is joined. Prior to the pressing, the sheet base 210 and the substrate 215 are overlapped so that the insulating resin layer 12 on the back surface of the sheet base 210 and the surface of the substrate 215 are in contact with each other. And the wiring pattern 17 of the substrate 215 are aligned so as to face each other.

  The tool used for pressing is the same as in the manufacturing method (I), and a needle-like member may be used, or a roll member 33 having a projection 35 as shown in FIG. 8 may be used.

  When a part of the wiring pattern is pushed in the step (b) of the manufacturing method (II), the section of the wiring pattern at that part becomes substantially U-shaped as shown in FIG. As shown in FIG. 29, the recess formed by pressing may be filled with a conductive material 27 to flatten the outer surface of the wiring pattern 20. The conductive material 27 used is preferably made of the same material as the conductive material used in the manufacturing method (I).

  In the example shown in FIGS. 28 and 29, the sheet base 210 is disposed only on one side of the substrate 215, but the sheet base 210 may be similarly disposed on both sides of the substrate 215. Furthermore, another additional sheet substrate 210 may be laminated on such a sheet substrate 210. In addition, since the surface of the flexible substrate 200 obtained by the manufacturing method (II) is excellent in flatness, the possibility that the wiring pattern is misaligned is reduced, which is suitable for further stacking of the sheet base material 210. Note that the multilayer flexible substrate obtained from the flexible substrate 200 is extremely thin as in the case of the manufacturing method (I).

  FIG. 30 is a perspective view showing an example of a multilayer flexible substrate 205 using the flexible substrate 200 obtained by the production method (II) of the present invention. In the multilayer flexible substrate 205 shown in FIG. 30, the sheet base material 210 is formed on both surfaces of the substrate 215. An interlayer connection portion 25 is formed from a part 17 a of the wiring pattern 17 formed on the surface of the substrate 215 and a part 22 of the wiring pattern 20 of the sheet base 210. In the illustrated embodiment, the conductive material 27 is filled in the recesses formed on the surface of the wiring pattern by pressing, but a configuration in which the conductive material 27 is not filled is also possible.

  In the multilayer flexible substrate 205, a U-shaped or B-shaped region (that is, a substantially closed region or a closed region) 29 as shown in FIG. 30 is formed using the interlayer connection portion 25. Such a closed region 29 (or substantially closed region 29) formed by the interlayer connection portion 25 is extremely difficult to manufacture because the central portion falls off in the conventional method of forming a via hole. It can be said to be a peculiar structure. For example, the wiring pattern 20 connected to the interlayer connection portion 25 constituting the closed region 29 (or the substantially closed region 29) is used for the ground, and the signal interlayer connection portion (so-called via) 25 is formed in the region 29. When formed, a multilayer flexible substrate 205 having a structure resistant to noise is obtained.

  Next, the manufacturing method (II) of the flexible substrate 200 of the present invention will be described with reference to FIG. FIG. 31 schematically shows a process for manufacturing the multilayer flexible substrate 220 including the flexible substrate 200 of the present invention.

  First, a sheet substrate 210 in which the wiring pattern 20 is embedded in the insulating resin layer 12 on the film 11 is prepared, and a flexible substrate 215 is prepared. In the substrate 215, wiring patterns 17 are formed on both surfaces, and the wiring patterns 17 on each surface (front surface and back surface) are electrically connected by vias (for example, conductive paste portions) 18. In the illustrated embodiment, a thermosetting adhesive layer 12 ′ is provided on an organic film 11 ′ made of polyimide, and a wiring pattern 17 made of copper foil is formed thereon. The substrate 215 is sent out in the direction of the arrow 40 from the roll 30a. On the other hand, the sheet | seat base material 210 is arrange | positioned on the carrier sheet 32, and is sent out from the roll 30b. In addition, what is necessary is just to produce the sheet | seat base material 210 previously using the transfer process similar to manufacturing method (I), as shown in FIG.

  As illustrated in FIG. 31, the substrate 215 and the sheet base 210 pass between a pair of roll members (that is, nip rolls) 38, whereby the sheet base 210 is stacked on the substrate 215. At that time, the wiring pattern 17 of the substrate 215 is embedded in the insulating resin layer 12 of the sheet base 210. The carrier sheet 32 that has conveyed the sheet substrate 210 is wound around the roll 30c.

  Subsequently, the conductive material 27 is arranged on the laminated base material 90 in the form of a protrusion. That is, the conductive protrusion 27 is provided. The conductive protrusion 27 is formed on a part of the wiring pattern 20 corresponding to the pattern of the interlayer connection site (so-called via). The conductive protrusion 27 can be formed using a technique such as a paste printing method, a bump forming method, a ball mounting method, or an electrophotographic method, as in the manufacturing method (I).

  Thereafter, the laminated base material 90 on which the conductive protrusions 27 are formed is passed between the pair of roll members 34. When pressing is performed between the pair of roll members 34 via the conductive protrusions 27, the interlayer connection portions 25 are formed, and at the same time, the concave portions formed on the surface of the wiring pattern are filled with the conductive material 27. . Specifically, when the roll member 34 comes into contact with the conductive protrusions 27, the conductive protrusions 27 are pushed into the laminated base material 90, and a part 22 of the wiring pattern 20 of the sheet base material 210 is formed on the laminated base material 90. As a result, the thin film 11 (and the insulating resin layer 12) is pierced and the portion 22 of the wiring pattern 20 is joined to the portion 17a of the wiring pattern 17 of the substrate 215. Since the conductive protrusions 27 pushed into the laminated base material 90 by the pair of roll members 34 remain as they are in the recessed area on the surface of the wiring pattern, the flatness of the multilayer flexible substrate 220 is maintained. The multilayer flexible substrate 220 in which the interlayer connection part 25 is formed proceeds in the direction of the arrow 40 as it is, and after being wound around the roll 30d, is finally cut into a predetermined dimension. In addition, when making it multilayer further, it will be sent to the further lamination process.

  In the embodiment shown in FIG. 31, the sheet base 210 is laminated on one side of the substrate 215, but the sheet base 210 may be laminated on both sides of the substrate 215 as shown in FIG.

  Further, in the embodiment shown in FIG. 31, the conductive protrusion 27 is used to perform the pressure contact process with the roll member 34 having no protrusion, but the conductive protrusion 27 is not attached as shown in FIG. 34. You may implement a press-contact process with the roll member 33 which has the projection part 35, without using.

  Further, as shown in FIG. 35 (a), a convex portion 26 is formed on the wiring pattern 17 using a roll member 37 having a concave portion 35 ′ in addition to the protruding portion 35, and then as shown in FIG. 35 (b). In addition, it is possible to form the interlayer connection portion 25a by causing the convex portions 26 to function as bumps.

  In the production method (II) of the present invention, the flexible substrate 100 obtained by the production method (I) of the present invention can be used as the flexible substrate 215. The mode in that case is shown in FIG. A substrate 215 shown in FIG. 36 has a configuration in which a wiring pattern is embedded in insulating resin layers 12 ′ formed on both surfaces of a film 11 ′, and a part of the front surface wiring pattern 20a and a back surface wiring pattern 20b. An interlayer connection portion 25b is formed from a part of the substrate. In the embodiment shown in FIG. 36, the conductive material 27 is filled in the recess formed due to the interlayer connection portion 25b. When such a substrate 215 is used, it is not necessary to form through holes not only on the sheet base material 210 but also on the substrate 215. Therefore, the manufacturing methods (I) and (II) of the present invention The benefits will be better utilized. FIG. 37 shows the configuration of the multilayer flexible substrate 260 obtained in the manufacturing process of FIG. The multilayer flexible substrate 260 shown in FIG. 37 corresponds to a configuration in which the configuration of the substrate 215 portion of the multilayer flexible substrate 205 shown in FIG. 30 is changed. In the embodiment shown in FIG. 37, the wiring pattern on the right side of the region filled with the conductive material 27 is mainly used for the ground (20G), while the wiring pattern on the left side is mainly used for the signal (20S). can do.

  When the configuration of the flexible substrate 200 obtained by the manufacturing method (II) is suitably used, a three-dimensional coil (inductor) 155 can be constructed in the multilayer flexible substrate 270 as shown in FIGS. . FIG. 38 is a perspective view showing a cross-sectional structure of the multilayer flexible substrate 270, and FIG. 39 is a perspective view showing only the wiring patterns 17 and 20. A cross section taken along line A-A ′ in FIG. 39 corresponds to the cross section in FIG. 38. In the illustrated embodiment, a three-dimensional coil (inductor) 155 is formed in the thin multilayer flexible substrate 270 by the wiring patterns 17 and 20 and the interlayer connection portions 19 and 25 instead of a planar coil. This coil 155 can be used as an inductor of an ultrathin sheet-like device. Further, since the interlayer connection part is formed of the same material as the wiring (wiring pattern), an inductor having a low DC resistance component can be formed. Further, in the case of the coil 155 arranged three-dimensionally, the number of turns of the coil can be increased even if the occupied area in the plane is small, compared with the coil arranged two-dimensionally. It has the advantage that an inductance value can be obtained.

  According to the production method (II) of the present invention, similarly to the production method (I), it is not necessary to form through holes and fill with a conductive paste, and an interlayer connection site can be easily formed. A flexible substrate can be manufactured easily. Further, since the production method (II) can be carried out by a dry process as in the production method (I), a so-called roll process such as a roll-to-roll method can be applied. Therefore, a flexible substrate can be continuously manufactured, and mass production becomes possible.

  In the production method (II) of the present invention, as in the production method (I), an aramid having a higher elastic strength than polyimide and suitable for thinning can be used as a film material. A substrate is realized.

  Here, in the manufacturing method (II) of the present invention, since the transfer step can be used in the same manner as in the manufacturing method (I), the wiring pattern 20 and the sheet substrate 210 are flush (or substantially flush). Thus, the wiring pattern 20 can be embedded in the insulating resin layer 12. Therefore, the flexible substrate 200 (or sheet base material) obtained by the production method (II) is excellent in flatness and can be easily laminated.

  Heretofore, the flexible substrate manufacturing methods (I) and (II) of the present invention and the flexible substrates 100 and 200 obtained therefrom have been described.

  Next, an embodiment in which a multilayer flexible substrate is constructed from the flexible substrates 100 and 200 obtained from the production method (I) or (II) of the present invention will be described.

  FIG. 40 exemplarily shows a multilayer flexible substrate 180 in which six layers of flexible substrates 120 are stacked. At least one of the flexible substrates 120 is the flexible substrate 100 or 200 obtained by the production method (I) or the production method (II) of the present invention.

For thickness _{T 1} is to realize a thin multilayer flexible substrate 180, the thickness it is preferred to use flexible substrates 100 and 200 of 10 to 25 [mu] m. In addition to the flexible substrates 100 and 200, for example, a typical flexible substrate (for example, the flexible substrate 500 in FIG. 1F) or a flexible substrate 130 having the solid metal layer 28 (see FIG. 41) may be used. More preferably, in the flexible substrate 120 of the multilayer flexible substrate 180, the number of the flexible substrates 100 and 200 obtained by the manufacturing method (I) or the manufacturing method (II) of the present invention is more than half. In addition, between two adjacent flexible substrates which comprise the multilayer flexible substrate 180, the insulating resin layer of one flexible substrate may combine the function of the insulating resin layer of the other flexible substrate. That is, one insulating resin layer may exist between the film of one flexible substrate and the film of the other flexible substrate.

  Since the electronic component 81 (semiconductor chip in FIG. 40) can be mounted on the multilayer flexible substrate 180 as shown in FIG. 40, the flexible device 300 can be constructed. In the illustrated embodiment, the semiconductor chip 81 is connected to a wiring pattern (not shown) formed on the surface of the multilayer flexible substrate 180 via connection members 82 (for example, bumps or solder). An underfill 83 is formed around the connection portion of the semiconductor chip 81.

When the thickness T ₂ of the semiconductor chip 81 is, for example, 50 to 130 μm, and the thickness T _{1 of} the six-layer multilayer flexible substrate 180 is, for example, 75 to 150 μm, the thickness of the flexible device 300 (= T ₁ + T ₂ ) is only 125 to 280 μm. Thus, the ultra-thin (300 μm or less) flexible device 300 has high utility value.

  The mounting portion of the semiconductor chip 81 of the flexible device 300 as shown in FIG. 40 can be flat as shown in FIG. In the embodiment shown in FIG. 42, the composite sheet 84 made of an inorganic filler and a resin is formed to be at the same level (or the same height) as the upper surface of the semiconductor chip 81. The reason why such a composite sheet 84 is used is that heat dissipation from the semiconductor chip 81 is improved by the inorganic filler contained therein, and the composite sheet has the same thermal expansion coefficient as that of the semiconductor chip 81. This is because the sheet 84 can be prepared.

  If the composite sheet 84 having the wiring pattern formed on the surface is transferred onto the multilayer flexible substrate 180, the flexible device 300 having the wiring pattern (not shown) formed on the surface 84a can be obtained. Since the flatness of the surface 84a is good, an electronic component can be further mounted on the surface.

  As shown in FIG. 43, a flexible device 300 in which electronic components (in this case, passive components 85a and 85b) are built in a multilayer flexible substrate 180 can also be constructed. In order to incorporate the passive components 85a and 85b, for example, a transfer method may be used as shown in FIGS. 44 (a) and 44 (b). Specifically, first, as shown in FIG. 44 (a), not only the wiring pattern 20, but also a passive component 85a (for example, a sheet-like capacitor formed by printing or thin film sputtering) or a passive component 85b (for example, A sheet-like resistor formed by printing or thin film sputtering) is arranged on the carrier sheet 32 in advance. Next, as shown in FIG. 44B, if the passive components 85a and 85b are transferred to the insulating resin layer 12 of the substrate 80 together with the wiring pattern 20, a flexible substrate with built-in passive components can be obtained. As the built-in passive components 85a and 85b, for example, an inductor, a capacitor, or a resistor can be considered. Even if the base material 80 is thin, the insulating resin layer 12 is thicker than the film 11, so that electronic components can be built in relatively easily.

  The flexible substrate 100, 200, the multilayer flexible substrate 180, or the flexible device 300 of the present invention is preferably mounted on a thin or small electronic device whose mounting area is extremely limited by taking advantage of the characteristics of them. The electronic device (for example, a mobile phone) 400 as shown in FIG.

  A thin mobile phone 400 shown in FIG. 45 (preferably ultrathin and T = 2 to 6 mm or less) uses a flexible substrate 100 as a circuit board. However, the flexible substrate 200, the multilayer flexible substrate 180, or the flexible device 300 may be used as the circuit board of the mobile phone 400.

  A casing 499 of the mobile phone 400 has a display unit (for example, an LCD panel) 491, a key unit 496 (mounted with an antenna 492, a battery 493, and a button 496a), and a camera unit (for example, a CCD or CMOS image sensor). 497 is installed. Since the mounting area in the housing 499 is limited, it is possible to effectively use the flexible substrates 100 and 200 having excellent bending life obtained by the manufacturing method (I) or (II) of the present invention. For the flexible substrate 100 used as a circuit board, it is relatively free to provide the curved portion or the bent portion 100a or the folded portion 100b, so that high-density mounting is realized.

  The preferred embodiments of the present invention have been described above. However, such embodiments are not limited and, of course, various modifications can be made. For example, in order to reduce the manufacturing cost, a flexible substrate is manufactured by using a relatively large number of laminates with metal layers, preferably single-sided copper-clad laminates, in the production method (I) or (II) of the present invention. It is also possible.

  Although it is essentially different from the technical idea of the present invention, JP-A-3-2014498, JP-A-49-27866, JP-A-55-102291, JP-A-9-283881, Further, a remark is made on JP-A-52-71677.

  In JP-A-3-2014498 and JP-A-49-27866, a part of a wiring pattern is used without using a screw in order to ensure electrical connection with a metal substrate (for example, an aluminum substrate). A technique for breaking through an insulating layer and connecting to a metal substrate is disclosed. In such a technique, a connection tool is used to connect to a metal substrate. Since the surface of the relatively soft aluminum substrate is deeply depressed by this connecting tool until it is completely deformed, such a technique is not applied to the use of the double-sided flexible substrate via. In the first place, no wiring pattern is formed on a metal plate (aluminum plate) that functions as a heat sink. Further, what is disclosed in the publication is basically an alternative technology for connection by screws, and thus is essentially different from the present invention.

  Japanese Patent Laid-Open No. 55-102291 discloses a through-hole conduction structure of a flexible circuit board. The technique disclosed in this publication is an alternative technique for a normal plated through hole, and such a technique is essentially different from the present invention. Furthermore, in the through-hole conduction structure disclosed in the publication, connection reliability may not be good from a structural viewpoint. That is, the circuit wiring pattern of one surface and the other surface is in contact with the so-called shoulder portion of the through hole, but it is a point contact when viewed in cross section, and only a circular line contact when viewed from the whole. The connection reliability remains uneasy. On the other hand, the interlayer connection part of the present invention has a stable line contact when viewed in cross section, and is in surface contact when viewed from the whole, and in that respect is the technique disclosed in the publication It is very different. In the case of a plated through hole, wiring cracks are likely to occur at the shoulder portion of the through hole, and it is necessary to take measures against such wiring cracks. It is also different in that the stress corresponding to the shoulder is small.

  Japanese Patent Application Laid-Open No. 9-283881 discloses a circuit board including a pressure contact via. In this circuit board, a part of the wiring on the surface of the base material is abutted inside the base material to form a pressure contact via. When forming the press-contact via, thermal softening is used. For example, as shown in FIG. 2 of the publication, the press-contact via is formed in a state where the pressure plate is heated using a heater. Therefore, the base material is limited to being made of a thermoplastic resin, and the heat resistance of the resulting circuit board may not be preferable. Japanese Laid-Open Patent Publication No. 52-71677 discloses a method of electrically connecting circuit conductors formed on both sides of a printed circuit board. The printed circuit board used has circuit conductors formed on both sides of an insulating substrate made of thermoplastic resin. Accordingly, the insulating substrate at the location to be connected is thermally softened and the circuit conductors on both sides are pressed, and then both are brought into close contact and spot welding is performed. Therefore, the method disclosed in the publication is limited to that the insulating base material is made of a thermoplastic resin, and the heat resistance of the obtained circuit board may be unfavorable, as in JP-A-9-283881. There is sex. On the other hand, the flexible substrate of this invention is comprised from the film and thermosetting resin which have heat resistance, and has high heat resistance as a whole. Moreover, the structure of the flexible substrate of the present invention is such that the wiring pattern is embedded in the insulating resin layer, the distance between the wiring patterns on the front surface and the back surface is substantially narrow, and a thin film (preferably a thin layer) Since a film made of aramid suitable for conversion is used, an interlayer connection site can be formed without thermal softening. Thus, the structure of the flexible substrate of the present invention is different from the structure of the circuit board and the printed circuit board disclosed in JP-A-9-283881 and JP-A-52-71677. The technical idea is different from the disclosed invention.

  Based on Examples 1-3, it tested about the flexible substrate of this invention, and its manufacturing method.

  First, in Example 1 and Example 2, a test was performed on the flex life of the flexible substrate of the present invention.

[Example 1]
(Film material)
The film (organic film) used in Example 1 is shown in Table 1.

(Preparation of substrate used for flex life measurement)
A thermosetting epoxy resin was applied to both sides of the film by a roll coater method to form an insulating resin layer. Next, a wiring pattern was embedded in this insulating resin layer.

  Prior to embedding the wiring pattern, first, a thin release layer made of a nickel-phosphorus alloy is formed on the surface of an electrolytic copper foil having a thickness of 70 μm, which serves as a support substrate for the wiring pattern, and the thickness is electrolytically plated on the release layer. A 12 μm copper foil was formed. Then, a dry film resist was attached to the copper foil, and a wiring pattern was formed by sequentially performing exposure, development, etching, and resist film removal.

  Next, the supporting base material provided with the wiring pattern is aligned and overlapped with the insulating resin layers formed on the front surface side and the back surface side of the film, and then heated to 60 ° C., and a pressure of 3 MPa is applied for 5 minutes. In addition, the wiring pattern of the support substrate was embedded in the insulating resin layer. Subsequently, after cooling, only the supporting base material was peeled off, and heated for 1 hour under conditions of 140 ° C. and 5 MPa to fully cure the insulating resin layer. The board | substrate used as the base of a flexible substrate was obtained by the above method. Table 2 shows the specifications of the substrate.

(Measurement of bending life)
The bending life of each of the obtained sample substrates was measured by a method based on IPC-240C and JIS-C5016.

  In measuring the bending life, first, the sample substrate was fixed between two flat plates facing each other at a constant interval in a state where the sample substrate was bent at 180 ° so as to have a constant curvature. By moving the flat plates in parallel at a determined speed and stroke, the sample substrate was slid and repeatedly reciprocated. At this time, the direct current resistance value of the wiring pattern located on the inner curved surface of the sample substrate was monitored, and the number of reciprocating motions when the initial resistance value was increased by 80% was defined as the flex life. As a comparative example, the bending life of a copper foil used for the wiring pattern (that is, a 12 μm copper foil formed by electrolytic plating) was examined by the same method.

(result)
The results of this example are shown in FIG. FIG. 46 is a graph of the number of bendings (= bending life) versus the film tensile modulus at room temperature. In the comparative example, breakage was observed after 800 reciprocations. In view of this, referring to FIG. 46, it can be seen that the substrate serving as the base of the flexible substrate of the present invention has a good flex life regardless of the elastic modulus of the film. The reason why the substrate has a good bending life is that the wiring pattern is embedded in the insulating resin layer, so that the wiring stress is dispersed by the insulating resin layer fixing the wiring surface, and the wiring pattern is caused by bending. This is probably because the progress of the obtained microcracks is suppressed.

[Example 2]
(Preparation of substrate used for flex life measurement)
In Example 2, by using the same method as in Example 1, the ratio of the insulating resin layer thickness to the film thickness was variously changed to prepare a substrate. Table 3 shows the specifications of the prepared substrate.

(Test conditions)
All films used were aramid films (“Mictron” manufactured by Toray Industries, Inc.). The sample substrates 2a to 2e have the same substrate thickness, and the sample substrates 2c, 2f, and 2g have substantially the same film thickness. Using such a sample substrate, the bending life was measured using the same method as in Example 1. The test conditions were a test speed of 25 Hz, a stroke of 25 mm, and a curvature radius of 2 mm, 4 mm, and 8 mm.

(result)
The results are shown in FIGS. 47 and 48. FIG. 47 is a graph of the number of bendings (= bending life) with respect to the bending radius. FIG. 48 is a graph of the ratio of the thickness of the insulating resin layer to the film thickness (= insulating resin layer thickness / film thickness) and the number of bendings (= flexing life). Referring to these graphs, it can be seen that the sample substrate having a thicker insulating resin layer than the film shows a better bending life, and the effect becomes particularly remarkable as the bending radius decreases. The reason why the flex life is improved in this way is considered to be that the stress applied to the wiring pattern and the film can be more relaxed by the insulating resin layer having a low elastic modulus.

[Example 3]
In Example 3, while confirming the effect of the pressure welding performed with the manufacturing method of this invention, the ultrasonic wave was applied to the interlayer connection part, and the effect was also confirmed.

(Production of substrate used in this example)
In the same manner as in Example 1, a film having an insulating resin layer formed on both surfaces and two carrier sheets (70 μm copper foil) provided with a wiring pattern were prepared. The film used was an aramid film having a thickness of 4 μm (“Mikutron” manufactured by Toray Industries, Inc.), and the thickness of the insulating resin layer (that is, the adhesive resin layer) formed on both surfaces thereof was 10 μm. Further, the wiring pattern on the carrier sheet was formed to have a thickness of 9 μm by an electrolytic plating method. The carrier sheet on which the wiring pattern is formed in this way is aligned with and superposed on the insulating resin layers formed on the front surface side and the back surface side of the film, and then heated to 60 ° C., and a pressure of 3 MPa is applied for 5 minutes. In addition, the wiring pattern was embedded in the insulating resin layer. Subsequently, after cooling, only the carrier sheet was peeled off. Thus, an uncured sheet base material in which the wiring pattern was formed on the front surface side and the back surface side was obtained. Here, a wiring pattern was used in which the connection parts are connected to form a chain via by connecting electrodes on both sides determined to form the connection parts inside the substrate. The diameter of the electrode on which this interlayer connection site is formed was 600 μm.

(Formation of interlayer connection part)
Next, using the pushing tool, the electrodes defined above were pushed into one of the surfaces of the uncured sheet base material to join the opposing electrodes inside the sheet base material, thereby forming an interlayer connection site. In this method, a wiring pattern in which 100 interlayer connection sites were connected was formed. The pushing tool used was a SUS needle-like member (the tip of the needle has a hemispherical shape) having a cylindrical shape with a cross section of 100 μm in diameter. Then, the flexible substrate in which the chain via was formed was able to be obtained by heating this for 1 hour under the conditions of a temperature of 140 ° C. and a pressure of 5 MPa.

(Fabrication of ultrasonically treated flexible substrates)
Using an ultrasonic application tool (Ultrasonic Industry Co., Ltd., model USW-610Z20S), ultrasonic vibration (vibration frequency is 28 KHz, 200 W) from the electrode of the interlayer connection part (that is, chain via) to the interlayer connection part. By applying (output power), a flexible substrate subjected to ultrasonic treatment was obtained.

(Measurement of resistance value)
The resistance values of the chain vias of these two types of flexible substrates were measured by the four-terminal method, and the resistance value per interlayer connection site was calculated by subtracting the separately measured wiring resistance value. In addition, 10 samples were prepared, and the average value was obtained. The wiring resistance value was measured by forming a wiring pattern having the same wiring length and wiring width as the portion where the interlayer connection site does not exist, and measuring the resistance value of this wiring pattern by the four-terminal method.

(result)
FIG. 49 shows the resistance value per interlayer connection site when the pressure (ie, load) at the time of pushing is changed. Referring to FIG. 49, it was found that the resistance value converged to a certain value by being pushed in while applying a certain pressure or more. In addition, it was found that by applying ultrasonic waves, the resistance value per interlayer connection site was ½ or less (about 1/5 in this example), and the resistance was extremely low.

(Liquid tank thermal shock test)
Subsequently, a liquid tank thermal shock test was performed on sample substrates (10 each) prepared by fixing the pressure at the time of pressing to 750 gf. In the liquid tank thermal shock test, one cycle of exposing the sample substrate to each liquid tank having a temperature of −55 ° C. and 125 ° C. for 5 minutes was defined as one cycle, and was performed up to 2000 cycles. The resistance value was measured after the test, and the measured resistance value change was 10% or more. The test results show that the failure rate for 1000 cycles of the flexible substrate to which no ultrasonic wave is applied is 0%, the failure rate for 2000 cycles is 20%, and the failure rate for 1000 cycles of the flexible substrate to which ultrasonic waves are applied is 0%. The defect rate for 2000 cycles was 0%. From this, the advantageous effect of the flexible substrate of this invention was confirmed.

(Summary)
Although depending on the design conditions of the flexible substrate, the following was found in Example 3. The frequency of the ultrasonic vibration is preferably about 15 kHz to 150 kHz. This is because if this range is exceeded, the output tends to be too large and unsuitable for precision machining.On the other hand, if it falls below this range, the output is too small to cause melting due to application of ultrasonic waves. This is because a tendency to become insufficient occurs. The output power is preferably 10 W to several thousand W. Similarly, if this range is exceeded, it tends to be unsuitable for precision processing, and if it falls below this range, melting tends to be insufficient. The application time is 0.1 to 10 seconds (typically about 1 second), and the corresponding applied energy is 1 kilojoule to several kilojoules (kJ).

  The flexible substrate, the multilayer flexible substrate, or the flexible device obtained by the manufacturing method of the present invention can be used for a cellular phone as a circuit substrate. Moreover, it can be used not only for mobile phones but also for PDAs or notebook computers. Furthermore, it can also be used for other applications such as a digital still camera or a wall-mounted flat panel display (FPD). As described above, it is considered that the technical value of the flexible substrate of the present invention, particularly the multilayer flexible substrate, becomes higher as the flexible substrate is used in various regions.

Cross-reference of related applications

  This application is Japanese Patent Application No. 2004-79848 (Application Date: March 19, 2004, Title of Invention: “Flexible Substrate, Multilayer Flexible Substrate, Flexible Device, Electronic Apparatus, and Flexible Substrate Manufacturing Method”), Japanese Patent Application No. 2004-088853 (filing date: March 25, 2004, title of invention: “flexible substrate, multilayer flexible substrate, flexible device and method for producing flexible substrate”), Japanese Patent Application No. 2004-2004 No. 088854 (filing date: March 25, 2004, title of invention: “flexible substrate, flexible device and method for producing flexible substrate”), Japanese Patent Application No. 2004-318887 (filing date: November 2, 2004) Japan, title of invention: “Manufacturing method of flexible substrate, flexible Sibling substrate, flexible device and circuit board module "), and Japanese Patent Application No. 2004-318888 (filing date: November 2, 2004, title of invention:" Method for manufacturing flexible substrate, flexible substrate and flexible device ") ) Claiming priority under the Paris Convention. All the contents disclosed in the application are incorporated herein by this reference.

FIG. 1A to FIG. 1F are cross-sectional views showing a manufacturing process of a conventional flexible substrate. 2 (a) to 2 (c) are cross-sectional views showing a manufacturing process of a conventional flexible substrate. FIG. 3 is a cross-sectional view showing the configuration of the sheet substrate 10 used in the production method (I) of the present invention. FIG. 4 is a cross-sectional view showing the configuration of the flexible substrate 100 obtained by the production method (I) of the present invention. FIG. 5 is a perspective view showing a flexible substrate 100 obtained by the production method (I) of the present invention. 6 (a) and 6 (b) are cross-sectional views showing a manufacturing process of the sheet base material 10. FIG. FIG. 7 is a cross-sectional view schematically showing a transfer method. FIG. 8 is a perspective view of the roll member 33 having the protrusions 35. FIG. 9 is a cross-sectional view showing an aspect of manufacturing the flexible substrate 100 using the needle-like member 50. FIG. 10 is a cross-sectional view showing a mode of manufacturing the flexible substrate 100 using the conductive protrusions 27. FIGS. 11A and 11B are cross-sectional views showing a mode in which the conductive material 27 is filled in the recesses formed on the surface of the wiring pattern. FIG. 12 is a cross-sectional view showing an aspect in which the flexible substrate 100 is manufactured using the needle-like member 50 and the conductive protrusion 27. FIG. 13 is a perspective view of the roll member 34 having no protrusions. FIG. 14 is a cross-sectional view showing a mode in which the conductive protrusion 27 is formed by electrophotography. FIG. 15 is a cross-sectional view showing a mode in which the flexible substrate 100 is manufactured by disposing the solder 15 between the film 11 and the wiring pattern 20. FIG. 16 is a cross-sectional view showing an aspect in which the flexible substrate 100 is manufactured using the conductive protrusions 27 and the solder 15. FIG. 17 is a cross-sectional view showing an aspect in which the welding instrument 60 is used. FIG. 18 is a cross-sectional view showing a mode in which ultrasonic waves are applied to the bonding site 25. FIG. 19 is a cross-sectional view showing a mode in which the flexible substrate 100 is manufactured by disposing the conductive layer 15 inside the wiring pattern 20. FIG. 20 is a cross-sectional view showing the configuration of the multilayer flexible substrate 150 including the flexible substrate 100. FIG. 21 is a cross-sectional view showing the manufacturing process of the flexible substrate 100. FIG. 22 is a cross-sectional view illustrating a process of manufacturing the flexible substrate 100 using the conductive protrusions 27. FIG. 23 is a cross-sectional view showing a mode in which the convex portion 26 is formed in the wiring pattern 20 by the roll member 36 having the concave portion 35 ′. FIG. 24 is a cross-sectional view showing a mode in which the flexible substrate 100 is manufactured using a roll member 37 having a protrusion 35 and a recess 35 '. FIG. 25 is a cross-sectional view showing an aspect of manufacturing the flexible substrate 100 by a roll-to-roll method. FIG. 26 is a cross-sectional view showing a process of manufacturing the multilayer flexible substrate 150 by a roll-to-roll method. FIG. 27 is a cross-sectional view showing a mode in which the transfer process and the press-contact process of the wiring pattern 20 are performed simultaneously. FIG. 28 is a cross-sectional view showing the configuration of the flexible substrate 200 obtained by the production method (II) of the present invention. FIG. 29 is a cross-sectional view showing the configuration of the flexible substrate 200 in which the concave portions are filled with the conductive material 27. FIG. 30 is a perspective view showing an example of the multilayer flexible substrate 205. FIG. 31 is a cross-sectional view showing a process for manufacturing a multilayer flexible substrate 220 including the flexible substrate 200 of the present invention. FIG. 32 is a cross-sectional view showing a transfer method. FIG. 33 is a cross-sectional view illustrating a process of manufacturing the multilayer flexible substrate 230 by laminating the sheet base 210 on both sides of the substrate 215. FIG. 34 is a cross-sectional view showing a mode in which the pressure contact process is performed by the roll member 33 having the protrusions 35. FIGS. 35A and 35B are cross-sectional views illustrating a process of manufacturing the multilayer flexible substrate 250 by forming the convex portions 26 in the wiring pattern 17. FIG. 36 is a cross-sectional view showing a process of manufacturing the multilayer flexible substrate 260 from the flexible substrate 100. FIG. 37 is a perspective view showing the configuration of the multilayer flexible substrate 260 obtained in the manufacturing process of FIG. FIG. 38 is a perspective view showing the configuration of the multilayer flexible substrate 270 obtained from the manufacturing method (II). FIG. 39 is a perspective view showing the configuration of the multilayer flexible substrate 270 through which only the wiring patterns 17 and 20 are seen. FIG. 40 is a cross-sectional view showing the configuration of the flexible device 300. FIG. 41 is a cross-sectional view showing the configuration of the flexible substrate 130 having a solid metal layer. FIG. 42 is a cross-sectional view showing the configuration of the flexible device 300 having the composite sheet 84. FIG. 43 is a cross-sectional view showing a configuration of a flexible device 300 incorporating an electronic component. 44 (a) and 44 (b) are cross-sectional views showing a process of incorporating passive components 85a and 85b. FIG. 45 is a perspective view showing a configuration of an electronic device 400 on which the flexible substrate 100 is mounted as a circuit board. FIG. 46 is a graph showing the relationship between the film elastic modulus and the number of bendings. FIG. 47 is a graph showing the relationship between the radius of curvature and the number of bends. FIG. 48 is a graph showing the relationship between the ratio of insulating resin layer thickness / film thickness and the number of bendings. FIG. 49 is a graph showing the relationship between the indentation load and the resistance value.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Sheet base material used by manufacturing method (I) 11,11 'Film 12,12', 13 Insulating resin layer 15 Solder or conductive layer 17 Substrate wiring pattern 17a Substrate wiring pattern 18 Via 19 Interlayer connection part 20 Wiring Pattern 20a Front side wiring pattern 20b Back side wiring pattern 20G Ground wiring pattern 20S Signal wiring pattern 21 Solid metal layer 22 Part of wiring pattern 22a Part of wiring pattern on front side 22b Part of wiring pattern on back side 22c Bonding surface 25, 25a 25b, 25c Interlayer connection part or joint part 26 Convex part formed in wiring pattern 27 Conductive material or conductive projection 28 Solid metal layer 29 Closed region 30a, 30b, 30c, 30d Roll 31 Roll member used for transfer method 32 Carrier sheet 33 Roll member having a raised portion 34 Roll member having no projection portion 35 Projection portion 35 ′ Concavity 36 Roll member having a recess portion 37 Roll member having a recess portion and a projection portion 38 Roll member 40, 41 Movement of sheet base material or flexible substrate or the like Direction 42 Movement direction of carrier sheet 43, 44, 45 Roll member rotation direction 50 Needle-like member 51 Photosensitive drum 52 Charger 53 Light source 54 Conductive material supply device 55 Photoconductive drum rotation direction 56 Electric discharger 60 Welding tool 62,64 Welding Direction of movement of instrument or ultrasonic application tool 70 Furnace 80 Base material 81 Electronic component (semiconductor chip)
82 connecting member 83 underfill 84 composite sheet 84a surface of composite sheet 85a, 85b passive component 90, 92, 93, 94, 95 sheet base material 100 flexible substrate 100a, 100b bent portion 110 solid layer 120 including metal layer 120 Flexible substrate 130 Flexible substrate having a solid metal layer 150 Multilayer flexible substrate 152,154 Movement direction of needle-like member 155 Coil (inductor)
180 multilayer flexible substrate 200 flexible substrate of the present invention 205 multilayer flexible substrate 210 sheet base material used in manufacturing method (II) 215 substrate (core substrate)
220,230,240 Flexible substrate (Multilayer flexible substrate)
250, 260, 270 Multilayer flexible substrate 300 Flexible device 400 Electronic equipment (mobile phone)
491 Display unit 492 Antenna 493 Battery 496 Key unit 496a Button 497 Camera unit 499 Housing 500 Conventional flexible substrate 501 501a Insulation sheet 502 Hole 503 Conductive paste 504,504a Metal foil 505 Resist film 506 Conductor circuit 550 Conventional multilayer flexible substrate

Claims (29)

A method for producing a flexible substrate comprising a film, an insulating resin layer and a wiring pattern,
(A) (i) film,
(Ii) a step of preparing a sheet substrate having an insulating resin layer formed on the front surface of the film and a back surface opposite to the surface; and (iii) a wiring pattern embedded in the insulating resin layer; (B) pressing a part of the wiring pattern on at least one of the front surface and the back surface into the sheet base material, and joining the part of the wiring pattern on the front surface and a part of the wiring pattern on the back surface. A manufacturing method of a flexible substrate.   2. The method of manufacturing a flexible substrate according to claim 1, wherein in the step (b), a part of the wiring pattern is pushed in by a needle-shaped member or a roll member having a protrusion.   In the step (b), a conductive material is provided on a part of at least one wiring pattern on the front surface and the back surface, and a part of at least one wiring pattern on the front surface and the back surface is formed by pressing the conductive material. The method for manufacturing a flexible substrate according to claim 1, wherein a part of the wiring pattern on the front surface and a part of the wiring pattern on the back surface are bonded by being pushed into the sheet base material.   The manufacturing method of the flexible substrate in any one of Claims 1-3 which further includes the process of applying an ultrasonic wave to the joining site | part formed by the said process (b).   The flexible substrate according to any one of claims 1 to 4, wherein in the step (a), a sheet base material is prepared by transferring a previously formed wiring pattern to the insulating resin layer. Method. the film,
An insulating resin layer formed on the surface of the film and the back surface facing the surface, and a flexible substrate having a wiring pattern embedded in the insulating resin layer,
A part of the wiring pattern on at least one of the front surface and the back surface is pressed into the flexible substrate, and a part of the wiring pattern on the front surface and a part of the wiring pattern on the back surface are bonded to each other. A flexible substrate in which a portion is formed.   The flexible substrate according to claim 6, wherein a cross section of a wiring portion constituted by a part of the wiring pattern on the front surface and a part of the wiring pattern on the back surface is an X shape or a U shape.   The flexible substrate according to claim 6, wherein the film is thinner than the insulating resin layer.   The flexible substrate according to claim 8, wherein a ratio of thickness of the insulating resin layer / thickness of the film is 1.2 to 6.   The flexible substrate according to claim 6, wherein the film is made of aramid.   The flexible substrate according to claim 6, wherein a conductive material is filled in a recess formed on the surface of the wiring pattern by pressing, and the surface of the wiring pattern is flattened.   The flexible substrate according to any one of claims 6 to 11, wherein the bonding portion is subjected to ultrasonic treatment. A multilayer flexible substrate in which a plurality of flexible substrates are laminated,
A multilayer flexible substrate, wherein at least one of the flexible substrates is a flexible substrate according to any one of claims 6 to 12. A method for producing a flexible substrate comprising a sheet base material and a substrate,
(A ₁ ) (i) film,
(Ii) a step of preparing a sheet base material having an insulating resin layer formed on the surface of the film and a back surface facing the surface, and (iii) a wiring pattern embedded in the insulating resin layer on the surface ,
(A ₂ ) a step of preparing a substrate having a wiring pattern on the surface; and (b) the sheet base material and the substrate are overlapped so that the insulating resin layer on the back surface of the sheet base material is in contact with the surface of the substrate. Thereafter, a part of the wiring pattern of the sheet base material is pushed into the substrate side, and a part of the wiring pattern of the sheet base material is joined to a part of the wiring pattern of the substrate. .   The method for manufacturing a flexible substrate according to claim 14, wherein in the step (b), a part of the wiring pattern of the sheet base material is pushed in by a needle-shaped member or a roll member having a protrusion.   In the step (b), a conductive material is provided on a part of the wiring pattern of the sheet base material, and by pushing the conductive material, a part of the wiring pattern of the sheet base material is pushed to the substrate side, The method for manufacturing a flexible substrate according to claim 14, wherein a part of the wiring pattern of the sheet base material is bonded to a part of the wiring pattern of the substrate.   The manufacturing method of the flexible substrate in any one of Claims 14-16 which further includes the process of applying an ultrasonic wave to the joining site | part formed by the said process (b). A flexible substrate composed of a sheet base material and a substrate having a wiring pattern on the surface,
The sheet substrate is a film,
An insulating resin layer formed on the surface of the film and the back surface facing the surface, and a wiring pattern embedded in the insulating resin layer on the surface,
The sheet base material and the substrate are stacked so that the insulating resin layer on the back surface of the sheet base material is in contact with the surface of the substrate,
A part of the wiring pattern of the sheet base material is pushed into the substrate side, and a part of the wiring pattern of the sheet base material and a part of the wiring pattern of the substrate are joined to each other to form a joining portion. A flexible substrate that is formed.   The flexible substrate according to claim 18, wherein a cross section of a part of the wiring pattern of the sheet base material has a U shape. The substrate has a wiring pattern on the back surface facing the front surface,
The sheet base material is disposed on the front surface and the back surface of the substrate, and a part of the wiring pattern of the sheet base material on the front surface and the back surface is pushed into the substrate side. The flexible substrate according to claim 18 or 19, wherein a part of the wiring pattern of the material and a part of the wiring pattern on the front surface and the back surface of the substrate are bonded to each other to form a bonding portion.   The flexible substrate according to any one of claims 18 to 20, wherein the film is thinner than the insulating resin layer.   The flexible substrate according to claim 21, wherein a ratio of thickness of the insulating resin layer / thickness of the film is 1.2-6.   The flexible substrate according to any one of claims 18 to 22, wherein the film is made of aramid.   The flexible substrate according to any one of claims 18 to 23, wherein a conductive material is filled in a recess formed on the surface of the wiring pattern by pressing, and the surface of the wiring pattern is flattened.   The flexible substrate according to any one of claims 18 to 24, wherein the bonding portion is subjected to ultrasonic treatment. A multilayer flexible substrate in which a plurality of flexible substrates are laminated,
A multilayer flexible substrate, wherein at least one of the flexible substrates is a flexible substrate according to any one of claims 18 to 25. 27. A flexible device comprising: the multilayer flexible substrate according to claim 13 or 26; and a semiconductor chip mounted on a wiring pattern on a surface of the multilayer flexible substrate. 27. A flexible device comprising the multilayer flexible substrate according to claim 13 or 26, and an electronic component incorporated in at least one flexible substrate constituting the multilayer flexible substrate. An electronic apparatus comprising the multilayer flexible substrate according to claim 13 or 26 as a circuit substrate.

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