JP2013149808A - Metal core flexible wiring board and manufacturing method of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a metal core flexible wiring board which has a metal core as a core material and is excellent in flexibility, and provide a manufacturing method of the same.SOLUTION: A first insulator layer 12 and a second insulator layer 13, which are made of a liquid crystal polymer, are joined to both surfaces of a soft flat plate like metal substrate 11. On an upper surface of the first insulator layer 12, signal wiring 14, ground wiring 15, etc. are disposed as a conductor pattern. The ground wiring 15 connects with the metal substrate 11 through first conductor bumps 16. Further, circuit lines 17, a die land 18 for element mounting, etc. are disposed on a lower surface of the second insulator layer 13 as a conductor pattern. The die land 18 connects with the metal substrate 11 through second conductor bumps 19. As necessary, a through hole 20 is provided for connecting the conductor patterns on the upper surface and the lower surface with each other, or an opening 22 is provided for heat radiation.

Description

  The present invention relates to a metal core flexible wiring board having heat dissipation and electromagnetic shielding properties and excellent flexibility, and a method for manufacturing the same.

  Flexible wiring boards (hereinafter also referred to as FPCs) are used in electronic devices such as network devices, servers, and testers. For example, in the use of a high-speed digital signal in the range of several GHz to several tens of GHz, high-speed transmission is required without impairing the high-frequency characteristics. In particular, in mobile electronic devices such as portable devices, with the miniaturization or thinning of the FPC, high-density wiring and lightening of the FPC are being promoted in various ways. Then, the density of wiring is increased by miniaturization and multilayering of conductor patterns that become circuit wiring and the like. As described above, FPCs are required to have high-speed transmission of electric signals, high density, and thin film, and their sophistication is being advanced.

  The application of FPC is expanding as a composite part to which an electronic circuit function is added in addition to a cable to an electronic device, a connector function, and the like. In order to enable downsizing and higher functionality of electronic devices, finer, higher integration, higher speed, or multi-functionalization of semiconductor elements (hereinafter referred to as higher performance of semiconductor elements) that are electronic components mounted on FPCs. (Also called) is remarkable.

  However, the density of electronic components mounted on the FPC increases, and the heat generation density of the electronic components increases. In addition, when a high-speed digital signal is used, heat generated by the dielectric loss increases. Since the generated heat cannot be sufficiently radiated by the component itself, a structure capable of effectively diffusing heat is required for the FPC.

  Up to now, as printed wiring boards having a function of heat diffusion, various metal core printed wiring boards having a metal core excellent in heat dissipation and thermal uniformity, for example, in the core material have been developed and used in part ( For example, see Patent Documents 1 and 2). However, the conventional metal core printed wiring board is mainly a rigid substrate that uses the mechanical strength of the metal core as it is, and disclosure of application of the metal core to so-called FPC having flexibility or flexibility is apparent. I can't.

JP 2007-294932 A JP 2009-21627 A

  By the way, if an attempt is made to apply, for example, a flat metal core as a core material to an advanced flexible wiring board as described above, the softness of the metal core is ensured and the main surface of the metal core has flexibility. For example, an insulating layer made of resin is essential. In addition, these insulator layers are required to have excellent flexibility with high resistance to repeated bending. In order to enable this excellent bendability, it is necessary to have a high adhesive strength between the insulator layer and the metal core, and in particular, an excellent stretchability of the insulator layer in these interface regions.

  However, a metal core flexible wiring board (hereinafter also referred to as a metal core FPC) in which the above-described insulating layer having excellent flexibility and a metal core is formed as a core material has not been described so far. For example, a metal core FPC excellent in transmission characteristics that does not impair high-frequency characteristics of electrical signals such as high-speed digital signals is not disclosed.

  The present invention has been made in view of the above circumstances, and provides a metal core flexible wiring board having a metal core as a core material, having heat dissipation or electromagnetic shielding properties and excellent flexibility, and a method for manufacturing the same. Objective. Furthermore, it aims at providing the metal core FPC excellent in the transmission characteristic of electrical signals, such as a high frequency.

  In order to achieve the above object, a metal core flexible wiring board according to the present invention has a soft flat metal substrate and a flexible insulator layer bonded to the metal substrate. It is characterized by that. Here, the insulator layer is made of a liquid crystal polymer. Alternatively, it is made of a synthetic resin containing an oligophenylene ether and a styrene butadiene elastomer.

  And the manufacturing method of the metal core flexible wiring board concerning this invention WHEREIN: The 1st protrusion-form conductor is provided in the predetermined conductor pattern arrange | positioned on the inner surface of the 1st interlayer insulation layer. Either the laminated plate or the first metal foil provided with the first projecting conductor in a predetermined region is placed on one main surface of the flat metal substrate via the first resin film. And a second laminated plate in which a second protruding conductor is provided in a predetermined conductor pattern disposed on the inner surface of the second interlayer insulating layer, or a predetermined region. Laminating any one of the second metal foils provided with the second protruding conductors on the other main surface of the metal substrate via the second resin film; The laminated body formed by laminating the main surface is heated and pressed to form the first protrusion The first protruding conductor is connected to one main surface of the metal base by inserting the first resin film into the electric body, and the second resin film is inserted into the second protruding conductor. Connecting the second projecting conductor to the other main surface of the metal base and joining and integrating the laminate.

  According to the present invention, it is possible to provide a metal core flexible wiring board having a metal core as a core material, having flexibility, heat dissipation, or electromagnetic shielding properties and excellent in flexibility, and a method for manufacturing the same. Further, it is possible to provide a metal core FPC excellent in transmission characteristics of electric signals such as high frequencies.

The partial expanded sectional view which shows an example of the metal core flexible wiring board concerning the 1st Embodiment of this invention. Sectional drawing according to manufacturing process which shows an example of the manufacturing method of the metal core flexible wiring board concerning the 1st Embodiment of this invention. Sectional drawing according to the manufacturing process following the process of FIG. The partial expanded sectional view which shows an example of the metal core flexible wiring board concerning the 2nd Embodiment of this invention. Sectional drawing according to manufacturing process which shows an example of the manufacturing method of the metal core flexible wiring board concerning the 2nd Embodiment of this invention. Sectional drawing according to manufacturing process following the process of FIG.

  Several preferred embodiments of the present invention will be described below with reference to the drawings. Here, the drawings are schematic, and ratios of dimensions and the like are different from actual ones.

(First embodiment)
A metal core flexible wiring board and a manufacturing method thereof according to a first embodiment of the present invention will be described with reference to FIGS. In this embodiment, a metal core FPC in which transmission wiring for transmitting a high-frequency signal is formed will be described.

  As shown in FIG. 1, in the metal core flexible wiring board 10, a first insulator layer 12 excellent in flexibility is formed on one main surface which is an upper surface of a soft and flat metal base 11. . Further, a second insulator layer 13 having excellent flexibility is bonded to the other main surface which is the lower surface of the metal substrate 11.

  A plurality of signal lines 14 and ground lines 15 serving as strip lines are disposed on the surface of the first insulator layer 12 in a conductor pattern. Here, the signal wirings 14 are shown as two pairs of transmission wirings that can cope with LVDS (Low Voltage Differential Signaling). The ground wiring 15 is connected to one main surface of the metal substrate 11 through the first conductor bumps 16 serving as conductive members.

  Similarly, a plurality of circuit lines 17 are arranged in a required conductor pattern on the surface of the second insulator layer 13. Further, for example, a die land 18 which is mounted with a bare chip semiconductor element mounted thereon is formed in the conductor pattern. The die land 18 is connected to the other main surface of the metal substrate 11 through the second conductor bump 19 serving as a conductive member. The second conductor bumps 19 are provided in an appropriate number, and for example, heat generated from the semiconductor element can be effectively diffused to the metal substrate 11 through the second conductor bumps 19.

  Further, in the metal core flexible wiring board 10, a through hole 20 is provided in the first insulator layer 12, the metal base 11, and the second insulator layer 13 as necessary. A conductor pattern (not shown) formed on the surface of the first insulator layer 12 and a conductor pattern (not shown) formed on the surface of the second insulator layer 13 by the through-hole conductor 20a in the through-hole 20 (Not shown) are electrically connected. An inner wall insulating layer 21 is formed in the through hole 20 so as to insulate and separate the metal base 11 and the through hole conductor 20a.

  In the metal core flexible wiring board 10, a part of the first insulator layer 12 is removed and an opening 22 is provided as necessary. The opening 22 is provided when increasing heat radiation from the metal substrate 11. Although not shown, it is preferable that a solder resist is formed between the conductor patterns formed on the surfaces of the first insulator layer 12 and the second insulator layer 13. A plating layer is preferably formed on the surface of these conductor patterns. Alternatively, a resin cover lay film may protect the front and back surfaces of the metal core flexible wiring board 10.

  Here, the metal substrate 11 is made of a material that can be elastically deformed or plastically deformed, that is, has flexibility and can be bent freely. Examples of suitable materials include aluminum (Al), copper (Cu), and alloys thereof. In addition, a conductive organic metal may be used. And the thickness is appropriately determined, for example, by about 200 μm to 1 mm.

  As the 1st insulator layer 12 and the 2nd insulator layer 13, the liquid crystal polymer which is a thermoplastic resin is used, and each liquid crystal polymer does not ask | require the same kind or a different kind. And the film thicknesses thereof are appropriately set to about 15 μm to 100 μm, for example. The liquid crystal polymer can have a thermal expansion coefficient substantially equal to that of the metal substrate 11. For this reason, although the details will be described later, when the first insulator layer 12 and the second insulator layer 13 are joined to the metal substrate 11 by a heating and pressurizing process (hot pressing), they are generated at their interfaces. Thermal stress is reduced. In addition, it is possible to perform excellent bonding with small residual strain when the temperature is lowered by hot pressing. At the same time, the stretchability of the liquid crystal polymer at the interface becomes excellent, and the adhesive strength between the liquid crystal polymer and the metal substrate 11 increases. Thus, the insulating layer of the liquid crystal polymer is directly bonded to the metal substrate without an adhesive to form a strong laminate. For this reason, even if the wiring board is bent, the insulator layer does not peel off from the metal substrate or cause a crack.

  Examples of the liquid crystal polymer include multiaxially oriented thermoplastic polymers represented by xidar (trade name, manufactured by Dartco) and Vectra (trade name, manufactured by Clanese). Further, it may be modified by adding and blending another insulating resin. Examples thereof include Bexter FA type, Bexter CT type, and BIAC film.

  Liquid crystal polymers are generally flexible and have low dielectric properties. For example, the relative dielectric constant at a frequency of 1 GHz to 25 GHz is about 2.85, and the dielectric loss tangent is 0.0025 or less, which is extremely small compared to other resins. Further, its water absorption and hygroscopicity are stable and low. For this reason, for example, high-speed transmission in high-speed digital signal transmission of several GHz to several tens GHz band becomes easy. Further, the dielectric loss is small in the high-speed digital signal in the high frequency band, and it is possible to transmit a stable and high-quality electric signal without impairing the high-frequency characteristics.

  The conductor pattern such as the signal wiring 14, the ground wiring 15, the circuit wiring 17 or the die land 19 is made of commonly used Cu or Cu alloy. The plating layer formed on the surface of these conductor patterns is composed of a single layer of gold (Au), silver (Ag), nickel (Ni), or a composite layer of Ni / Au, Ni / Ag or the like.

  The first conductor bump 16 and the second conductor bump 19 include, for example, conductive particles such as Ag, Au, Cu, tin (Sn), lead (Pb), and conductive carbon, and epoxy resin, phenol resin, acrylic resin, and the like. It is a mixture.

  The through-hole conductor 20a is formed by an electroless plating method or an electrolytic plating method, and is, for example, Cu. Alternatively, it may be formed by filling the through hole 20 with a conductive paste such as Cu paste, for example. In any case, the through-hole conductor 20a makes the inside of the through-hole 20 conductive.

  The inner wall insulating layer 21 will be described later with reference to a method for manufacturing the metal core flexible wiring board 10, and for example, a thermosetting resin such as an epoxy resin or a polyimide resin may be used. And the material which is excellent in crack resistance after thermosetting and has sufficient flexibility is preferable. Therefore, a material obtained by mixing a filler such as alumina or glass fiber into the thermosetting resin is preferably used.

  Next, an example of the manufacturing method of the metal core flexible wiring board concerning the 1st Embodiment of this invention is demonstrated. As shown in FIG. 2A, for example, a flat metal substrate 11 (for example, a Cu plate) having a thickness of 200 μm to 1 mm is prepared. Here, the surface of the metal substrate 11 is preferably cleaned by treatment with a chemical solution or the like, or appropriately roughened.

  Further, as shown in FIG. 2B, a first conical conductive paste 24 which is a required number of protruding conductors on the inner surface of the first metal foil 23 made of Cu having a thickness of about 10 μm to 30 μm, for example. Prepare with bumps. Similarly, a second conical conductive paste 26, which is a required number of protruding conductors, is bumped onto the inner surface of the second metal foil 25 and prepared. Here, the first conical conductive paste 24 and the second conical conductive paste 26 are bumped by repeating screen printing and drying of the conductive paste using, for example, a stainless steel screen plate. Here, as described above, the conductive paste is a mixture of conductive particles such as Ag, Au, Cu, Sn, Pb, and carbon and an epoxy resin, a phenol resin, an acrylic resin, and the like.

  Next, as shown in FIG. 2C, the first metal foil 23 is turned upside down and positioned with respect to, for example, the metal substrate 11 together with the first resin film 27 made of a liquid crystal polymer having a thickness of, for example, about 15 μm to 100 μm. Laminate and stack. Similarly, for example, the second metal foil 25 is positioned with respect to the metal substrate 11 together with the second resin film 28 made of a liquid crystal polymer having a thickness of about 15 μm to 100 μm and set up by laminating and laminating.

  And the laminated body which consists of the said 1st metal foil 23, the 1st resin film 27, the metal base | substrate 11, the 2nd metal foil 25, and the 2nd resin film 28 is thermocompression-bonded and integrated by hot press. After this hot pressing, as shown in FIG. 2D, the composition of the first conical conductive paste 24 is changed to the first conductor bump 16 along with the plastic deformation in which the head is crushed. Further, the first resin film 27 becomes the first insulator layer 12. Here, the first conductor bump 16 penetrates the first insulator layer 12 and is connected to the metal substrate 11. Similarly, the composition of the second conical conductive paste 26 is changed along with the plastic deformation in which the head is crushed to become the second conductor bump 19. The second resin film 28 becomes the second insulator layer 13. Here, the second conductor bump 19 penetrates through the second insulator layer 13 and is connected to the metal substrate 11.

In the hot press, the atmospheric gas is preferably in a reduced pressure state, for example, and the heating temperature at that time is a temperature at which a resin film made of a thermoplastic liquid crystal polymer is thermally softened. For example, the temperature is set to about 180 ° C to 320 ° C. Moreover, pressurization is about 30-100 kgf / cm < ² >, for example.

  Next, as shown in FIG. 3A, for the metal base 11, the first insulator layer 12, the first metal foil 23, the second insulator layer 13, and the second metal foil 25 that are joined and integrated, Drill a predetermined area. In this drilling, the through hole 29 is formed by drilling or laser processing. Thereafter, the exposed surfaces of the metal substrate 11, the first insulator layer 12, the first metal foil 23, the second insulator layer 13, the second metal foil 25 and the inner walls of the through holes 29 are cleaned.

  Subsequently, as shown in FIG. 3B, the through hole 29 is filled with an embedded resin 30 made of a thermosetting resin using, for example, a squeegee. And it heat-hardens by performing the heat processing of predetermined temperature. Then, the through hole 20 is formed by re-piercing the thermally cured embedded resin 30 by, for example, laser processing. Here, the inner diameter of the through hole 20 is, for example, 0.2 mm or more smaller than that of the through hole 30, and an inner wall insulating layer 21 is formed in the through hole 20 as shown in FIG. . Then, mechanical polishing and desmear treatment are performed to clean the exposed surfaces of the first metal foil 23, the second metal foil 25, and the inner wall insulating layer 21.

Next, a plating outer layer is formed by depositing on the outer surfaces of the first metal foil 23 and the second metal foil 25 and the inner wall insulating layer 21 in the through hole 20 by, for example, electroless plating of Cu. Here, the film thickness of the plating outer layer is set to about 5 μm to 25 μm.
Then, as shown in FIG. 3D, selective etching using photolithography is performed on the first metal foil 23 and the second metal foil 25 on which the plating outer layers are laminated. Thus, the 1st metal foil 23 and the 2nd metal foil 25 with which the plating outer layer was laminated are patterned.

  Then, as shown in FIG. 3E, a ground wiring 15 connected to the metal substrate 11 through the signal wiring 14 and the first conductor bump 16 is formed on the surface of the first insulator layer 12 in a predetermined conductor pattern. Similarly, a die land 18 connected to the surface of the second insulator layer 13 through the circuit line 17 and the second conductor bump 19 is formed in a predetermined conductor pattern. Further, in the through hole 20, a through hole conductor 20 a is formed to be conductive and formed on the surface of the second insulator layer 13 and a conductor pattern (not shown) formed on the surface of the first insulator layer 12. A conductive pattern (not shown) is electrically connected.

  Thereafter, if necessary, a part of the first insulator layer 12 is removed, and the opening 22 described in FIG. 1 is provided. Then, a plating layer may be formed on the surface of the metal substrate 11 exposed at the conductor pattern or the opening 22 formed on the surfaces of the first insulator layer 12 and the second insulator layer 13 described above. Alternatively, the through hole 20 in which the through hole conductor 20a is formed may be filled with a resin or the like. Thus, the metal core flexible wiring board 10 as shown in FIG. 1 is produced.

  In the metal core flexible wiring board of the present embodiment, for example, a soft flat metal substrate 11 such as Al or Cu is used as a metal core, and a first insulator layer 12 made of a flexible liquid crystal polymer on both sides thereof. The second insulator layer 13 is joined. Here, these insulator layers are bonded so that the adhesive strength with the metal substrate 11 is high and the thermal expansion coefficient thereof is approximately the same as that of the metal substrate 11. And the metal core FPC comes to exhibit excellent flexibility.

  Further, when the metal base 11 is a metal core that is plastically deformed or elastically deformed, the metal core FPC can be arranged or arranged between components in the electronic device or between the devices. This is because even if there is an obstacle between parts or devices, the metal core FPC that bypasses the obstacle can be bent very easily.

  Moreover, in the metal core flexible wiring board of this embodiment, sufficient heat dissipation or electromagnetic shielding properties by the metal core can be obtained. At the same time, since the insulator layer has excellent low dielectric characteristics, the signal wiring or circuit wiring of the metal core FPC seems to exhibit extremely excellent transmission / conduction characteristics of high-speed digital signals in the range of several GHz to several tens of GHz. become. In addition, high-density mounting of high-performance semiconductor elements becomes possible.

  In the manufacturing method of the metal core flexible wiring board according to the present embodiment, a flexible flat metal substrate 11 is used as a metal core, and the first insulator layer 12 and the second insulator layer 13 are laminated from both sides by hot pressing. Join and integrate. For this reason, the adhesive strength is uniform and stable on both surfaces of the metal core. Further, by forming conductor bumps as vias connecting the conductor pattern disposed on the surface of the first insulator layer 12 or the surface of the second insulator layer 13 and the metal core, the productivity of the metal core FPC is increased. . And even if the density of the conductor pattern is increased and the via density is increased, the flexibility of the metal core FPC is not impaired. This is because the conductor bump is a mixture of resin and metal particles having a hardness lower than that of metal.

  Further, the through hole 20 for electrically connecting the conductor patterns disposed on the surface of the first insulator layer 12 and the surface of the second insulator layer 13 is formed by joining the metal substrate 11 and the first insulation after being joined and integrated. The through hole 29 is formed in the body layer 12 and the second insulator layer 13. For this reason, the stability of the high adhesive strength of the metal substrate 11, the first insulator layer 12, and the second insulator layer 13 is not impaired at all by the formation of the through hole 20.

(Second Embodiment)
Next, a metal core flexible wiring board according to a second embodiment of the present invention will be described with reference to FIGS. This embodiment will be described in the case of a metal core FPC that facilitates multilayering.

  As shown in FIG. 4, in the metal core flexible wiring board 40, the first insulator layer 41 and the second insulator layer 42 having excellent flexibility on both surfaces of the metal base 11 similar to that described in the first embodiment. Are integrally joined.

  And the 1st circuit wiring 43 and the ground wiring 44 are arrange | positioned at the surface of the 1st insulator layer 41 at the conductor pattern. The ground wiring 44 is connected to the main surface of the metal base 11 through the first conductor bump 45. Similarly, a plurality of second circuit lines 46 are arranged in a required conductor pattern on the surface of the second insulator layer 42. Further, connection lands 47 for semiconductor elements to be mounted are formed in the conductor pattern. The connection land 47 is connected to the other main surface of the metal base 11 through the second conductor bump 48. The second conductor bumps 48 are provided in an appropriate number.

  Further, a first interlayer insulator layer 49 is laminated on the first insulator layer 41, and a third circuit wiring 50 is disposed on the surface of the first interlayer insulator layer 49. Further, for example, a first die land 51 on which a semiconductor element is mounted is formed and connected to the ground wiring 44 through the third conductor bump 52. Here, for example, heat generated from the semiconductor element mounted on the first die land 51 is thermally diffused to the metal substrate 11 through the third conductor bump 52, the ground wiring 44, and the first conductor bump 45.

  Similarly, a second interlayer insulator layer 53 is laminated on the second insulator layer 42, and a fourth circuit wiring 54 is disposed on the surface of the second interlayer insulator layer 53. Further, for example, a second die land 55 on which a semiconductor element is mounted is formed and connected to the connection land 47 through a fourth conductor bump 56. Then, the heat generated from the semiconductor element is thermally diffused to the metal substrate 11 through the fourth conductor bumps 48, the connection lands 47 and the second conductor bumps 48.

  In the metal core flexible wiring board 40, through holes 57 are formed in the first interlayer insulator layer 49, the first insulator layer 41, the metal base 11, the second insulator layer 42, and the second interlayer insulator layer 53 as necessary. Is provided. The inside of the through hole 57 is formed by the through hole conductor 57a on the surface of the conductor pattern (not shown) formed on the surface of the first interlayer insulator layer 49 and the surface of the second interlayer insulator layer 53. A conductor pattern (not shown) is electrically connected. In the through hole 57, an inner wall insulating layer 58 is formed so as to insulate and separate the metal substrate 11 and the through hole conductor 57a. The structure of the through hole 57 is the same as that described in the first embodiment.

  In the metal core flexible wiring board 40, a heat radiating plate 59 made of, for example, an Al substrate is provided as necessary. The heat radiating plate 59 is connected to the edge of the metal base 11 from which the first insulator layer 41 or a part of the first insulator layer 41 is removed, and dissipates heat diffusing to the metal base 11 to the outside. To do. As described in the first embodiment, although not shown, a solder resist is formed between the conductor patterns formed on the surfaces of the first interlayer insulator layer 49 and the second interlayer insulator layer 53. Also good. Alternatively, a resin cover lay film may protect the front and back surfaces of the metal core flexible wiring board 40.

  In the metal core flexible wiring board 40, the first insulator layer 41 and the second insulator layer 42 are made of a thermosetting synthetic resin containing oligophenylene ether and a styrene-butadiene elastomer. As such a synthetic resin, for example, ADFLEMA OPE system (trade name, manufactured by NAMICS) is exemplified. And the film thickness is set to about 15 micrometers-100 micrometers, for example. The thermosetting synthetic resin has a relative dielectric constant of 3 or less and a dielectric loss tangent of 0.003 or less. Further, its water absorption or hygroscopicity is low, and it exhibits extremely excellent and stable transmission / conduction characteristics of high-speed digital signals in the range of several GHz to several tens of GHz.

  The oligophenylene ether is also called, for example, OPE (bifunctional polyphenylene ether oligomer) and has a polymer structure in which polyphenylene ether is added to both ends of the bifunctional core. Here, the average molecular weight of OPE is about 500 to 5000, preferably 1000 to 3000. Examples of such commercially available products include OPE2St-1200 and OPE2St-2200 manufactured by Mitsubishi Gas Chemical Company, Inc. The OPE is produced by using, for example, a vinyl compound described in JP-A Nos. 2009-161725 and 2011-68713 as a composition. OPE derivatives may also be used, such as epoxy derivatives and styrene derivatives.

  Here, the synthetic resin may contain other components. For example, in order to adjust the curing temperature of the synthetic resin, a maleimide curing agent, a phenol curing agent, an amine curing agent and the like are appropriately mixed. Alternatively, for example, an epoxy resin and its curing catalyst are added in order to adjust the adhesion with the metal substrate 11. Here, as the curing catalyst, for example, an amine-based curing catalyst or an imidazole-based curing catalyst for shortening heat curing is used.

  This synthetic resin preferably has a curing temperature lower than the glass transition point Tg or melting point Tm of the first interlayer insulating layer 49 and the second interlayer insulating layer 53 made of resin. Here, the curing temperature is a temperature at which the synthetic resin is polymerized or crosslinked to be cured. The resin of the first interlayer insulator layer 49 and the second interlayer insulator layer 53 may have a glass transition point and may not show a clear Tg, but the thermosetting temperature does not show a clear Tg. Is preferably lower than the melting point Tm of the thermoplastic resin. The elastic modulus of the first insulator layer 41 and the second insulator layer 42 after thermosetting is smaller than the elastic modulus of the first interlayer insulator layer 49 and the second interlayer insulator layer 53.

  The elastic modulus in the first insulator layer 41 and the second insulator layer 42 can be adjusted as appropriate depending on the amount of the elastomer component. For such an elastomer component, a resin having a small dielectric loss tangent, such as polyester resin, nitrile rubber (NBR), styrene butadiene rubber (SBR), is preferable. Then, for example, the tensile elastic modulus of the first insulator layer 41 and the second insulator layer 42 after thermosetting is set to be in a range of 100 MPa to 1 GPa. In contrast, the tensile elastic modulus of the first interlayer insulator layer 49 and the second interlayer insulator layer 53 is about 2 GPa to 20 GPa, which is larger than that of the first insulator layer 41 and the second insulator layer 42. Become.

  In addition, a glass transition point is normally calculated | required by two methods, TMA method and DMA method, by the glass transition temperature measuring method (it applies to JISC6493). Here, in the TMA method, the test piece is heated from room temperature at a rate of 10 ° C./min, the amount of thermal expansion in the thickness direction is measured with a thermal analyzer, and a tangent line is drawn on the curves before and after the glass transition point. Tg is obtained from the intersection of the tangent lines. In the DMA method (tensile method), the test piece is heated from room temperature at a rate of 2 ° C./min, the dynamic viscoelasticity and loss tangent of the test piece are measured with a viscoelasticity measuring device, and the peak temperature of the loss tangent is measured. Obtain Tg. As the elastic modulus, the tensile elastic modulus or bending elastic modulus of the resin film is used. The elastic modulus is measured according to JIS K 7127 or ASTM D882.

  And as the 1st interlayer insulation layer 49 and the 2nd interlayer insulation layer 53, resin which has a low dielectric property is preferable. Examples of the resin forming the low dielectric resin layer include liquid crystal polymers, polyimide resins, polyethylene naphthalate resins, and composite resins thereof. Alternatively, a thermosetting resin such as bismaleimide-triazine resin (BT resin) may be used. And the film thicknesses thereof are appropriately set to about 15 μm to 100 μm, for example.

  Here, the same liquid crystal polymer as that described in the first embodiment is used. Examples of the polyimide resin include polyimide film “Kapton” (trade name, manufactured by Toray DuPont) and Aurum (trade name, manufactured by Mitsui Chemicals). And as a polyethylene naphthalate type-resin, the thermoplastic resin of Teonex (brand name. Product made by Teijin DuPont) is illustrated as a suitable thing, for example.

  In the low dielectric resin layer, the relative dielectric constant at a frequency of 1 MHz is preferably 3.5 or less. Such a relative permittivity facilitates high-speed transmission in high-speed digital signal transmission of, for example, several GHz to several tens GHz band. The dielectric loss tangent in the high frequency band is preferably 0.005 or less. With such a dielectric loss tangent, in combination with the low dielectric properties of the first insulator layer 41 and the second insulator layer 42 described above, in a high-speed digital signal in a high frequency band of several GHz to several tens GHz. The dielectric loss is small, and high-quality electrical signals can be transmitted without damaging the high-frequency characteristics.

  Conductor patterns such as the first circuit wiring 43, the ground wiring 45, the second circuit wiring 46, the connection land 47, the third circuit wiring 50, the first die land 51, the fourth circuit wiring 54, and the second die land 55 are the first It consists of Cu or Cu alloy similarly to having demonstrated in embodiment. A plating layer similar to that described in the first embodiment may be formed on the surface of these conductor patterns.

  The conductor bumps used in the metal core flexible wiring board 40 are, for example, metal particles such as Ag, Au, Cu, Sn, Pb, conductive carbon, and epoxy resin, as described in the first embodiment. It is a mixture of phenol resin, acrylic resin and the like.

  Next, an example of the manufacturing method of the metal core flexible wiring board concerning the 2nd Embodiment of this invention is demonstrated. As shown in FIG. 5A, a first conical conductive paste 61, which is a required number of protruding conductors, is applied to the inner surface of a first metal foil 60 made of Cu having a thickness of about 10 μm to 30 μm, for example. Bumping is performed in the same manner as described in the embodiment. Further, for example, a required number of fourth conical conductive pastes 63, which are protruding conductors, are bumped onto the inner surface of the second metal foil 62 made of Cu having a thickness of about 5 μm to 20 μm.

  Then, as shown in FIG. 5B, for example, a first interlayer resin film 64 made of, for example, a liquid crystal polymer having a thickness of about 15 μm to 100 μm and the third metal foil 65 are laminated on the first metal foil 60 and set up. . Similarly, a second interlayer resin film 66 made of, for example, a liquid crystal polymer having a thickness of, for example, about 15 μm to 100 μm and a fourth metal foil 67 are laminated on the second metal foil 62 and set up. Subsequently, the first metal foil 60, the first interlayer resin film 64, and the third metal foil 65 are thermocompression-bonded and integrated with a hot press. Similarly, the second metal foil 62, the second interlayer resin film 66, and the fourth metal foil 67 are bonded by thermocompression with a hot press.

  In this way, as shown in FIG. 5 (c), the third conical conductive paste 61 is crushed in the same manner as described in the first embodiment to become the third conductor bumps 52, The first metal foil 60 and the third metal foil 65 are electrically connected. The first interlayer resin film 64 becomes the first interlayer insulator layer 49. Similarly, the fourth conical conductive paste 63 becomes the fourth conductor bump 56 and electrically connects the second metal foil 62 and the fourth metal foil 67. The second interlayer resin film 66 becomes the second interlayer insulator layer 53. Then, two double-sided metal-clad laminates are produced.

  Next, the first metal foil 60 and the fourth metal foil 67 are each selectively etched using photolithography. Then, as shown in FIG. 6A, the first metal foil 60 is patterned into an inner layer conductor pattern such as the first circuit wiring 43 and the ground wiring 44 to form a first laminated board. The fourth metal foil 67 is patterned into an inner layer conductor pattern such as the second circuit wiring 46 and the connection land 47 to form a second laminate. Further, in the first laminated plate, the first conical conductive paste 68 is bumped on the surface of, for example, the ground wiring 44 of the conductor pattern disposed on the inner surface of the first interlayer insulating layer 49. Similarly, in the second laminate, the second conical conductive paste 69 is bumped on, for example, the connection land 47 of the conductor pattern provided on the inner surface of the second interlayer insulator layer 53.

  And as shown to Fig.6 (a), the 1st laminated board is turned over, and the 1st resin film 70 and the 1st metal foil 60 which consist of the said uncured synthetic resin whose thickness is about 15 micrometers-100 micrometers, for example are made. The metal substrate 11 is positioned and overlapped with the upper surface of the metal substrate 11 and laminated. Similarly, for example, the second resin film 71 made of the uncured synthetic resin having a thickness of about 15 μm to 100 μm and the second metal foil 62 are positioned with respect to the lower surface of the metal substrate 11 and stacked and laminated.

  And the laminated body of the 1st laminated board mentioned above, the 1st resin film 70, the metal base | substrate 11, the 2nd laminated board, and the 2nd resin film 71 is thermocompression-bonded and integrated by hot press. After this hot pressing, as shown in FIG. 6B, the head of the first conical conductive paste 68 is crushed to become the first conductor bump 45. The first resin film 70 becomes the first insulator layer 41. At the same time, the second conical conductive paste 69 becomes the second conductor bump 48, and the second resin film 71 becomes the second insulator layer 42.

  Thereafter, in the same manner as described in the first embodiment, the metal base 11, the first insulator layer 41, the second insulator layer 42, the first interlayer insulator layer 49, the first insulator layer 49, and the like, which are joined and integrated. A through hole 72 is formed in the second interlayer insulator layer 53, the third metal foil 65, and the second metal foil 62. Then, as shown in FIG. 6C, the embedded resin 73 is filled in the through hole 72.

  Then, a through hole 57 is formed in the embedded resin 73. Further, after mechanical polishing and desmear treatment, an outer plating layer that adheres to the outer surface of the third metal foil 65, the second metal foil 62, and the surface of the inner wall insulating layer 58 in the through hole 57, for example, by electroless plating of Cu. Form. Then, selective etching using photolithography is performed on the third metal foil 65 and the second metal foil 62 on which the plating outer layers are laminated. In this way, as shown in FIG. 6D, the third circuit wiring 50, the first die land 51, the fourth circuit wiring 54, and the second die land 55 are formed as outer layers of the conductor pattern. Then, a through-hole conductor 57a is formed.

  Thereafter, the first insulator layer 41 and the first interlayer insulator layer 49 or the second insulator layer 42 and part of the second interlayer insulator layer 53 are removed as necessary, for example, the heat sink described in FIG. 59 is attached so as to stick to the edge of the metal substrate 11. In this way, the metal core flexible wiring board 40 as shown in FIG. 4 is produced.

  In the manufacture of the metal core flexible wiring board 40 according to the second embodiment, a method that partially uses the manufacturing method of the metal core flexible wiring board 10 according to the first embodiment may be used. In this case, as the first insulator layer 12 and the second insulator layer 13, a thermosetting synthetic resin containing an oligophenylene ether and a styrene-butadiene elastomer is applied instead of the liquid crystal polymer. Then, an outer layer of the conductor pattern is formed by so-called build-up. Further, by repeating such build-up, further multilayering becomes easy.

  In the second embodiment, the same effect as described in the first embodiment is obtained. Furthermore, a thermosetting synthetic resin containing an oligophenylene ether and a styrene butadiene elastomer has a smaller elastic modulus than the resin constituting the interlayer insulator layer laminated thereon, and is excellent in stretchability. For this reason, it exists between the interlayer insulation layer laminated | stacked with a comparatively big elasticity modulus, and a metal core, and functions effectively as a buffer material of the bending stress produced in the bending of the metal core FPC. And, for example, multilayering by building up a metal core FPC becomes easy.

  For convenience, the description has been made using the terms “upper surface” and “lower surface”. The “upper surface” and the “lower surface” mean that they are in a relationship of front and back, and do not mean spatial top and bottom.

  Although the preferred embodiments of the present invention have been described above, the above-described embodiments do not limit the present invention. Those skilled in the art can make various modifications and changes in specific embodiments without departing from the technical idea and technical scope of the present invention.

  It may be a metal core flexible wiring board in which the structure of the first embodiment and the structure of the second embodiment are combined. That is, the first insulator layer 12 made of a liquid crystal polymer is formed on one main surface of the metal substrate 11, and the second main surface made of a thermosetting synthetic resin containing an oligophenylene ether and a styrene-butadiene elastomer on the other main surface. The insulator layer 13 may be formed.

  In addition, the metal core flexible wiring board may have a structure in which an insulator layer and a conductor pattern are formed on one main surface of the metal substrate 11 and an insulator layer or a conductor pattern is not formed on the other main surface. . That is, the conductor pattern may be formed on only one side of the metal substrate 11.

  The metal core flexible wiring board has the conductor pattern on the surface of the first insulator layer 12 or the second insulator layer 13 shown in the first embodiment as an inner layer, and an outer layer conductor pattern is formed by lay-up or build-up. It may be a multilayer structure.

  The metal core flexible wiring board has a structure in which the ground layer covers the signal wiring 14 and the ground wiring 15 on the surface of the first insulating layer 12 shown in the first embodiment via an interlayer insulating layer. May be.

  Further, the first insulator layer 12 and the first insulator layer 13 shown in the first embodiment are replaced with a liquid crystal polymer in a metal core flexible wiring board made of a synthetic resin containing an oligophenylene ether and a styrene butadiene elastomer. It may be.

  In the metal core flexible wiring board, a single-sided metal-clad laminate may be used instead of the double-sided metal-clad laminate as shown in the second embodiment. In this case, the metal core flexible wiring board does not have the first metal foil 60 or the second metal foil 62 as described in the second embodiment on the surface thereof, and an outer layer conductor pattern is disposed on the front surface or the back surface. It becomes a structure that is not installed. Further, the formed through hole may be used to connect between the inner-layer conductor patterns or between the inner-layer and outer-layer conductor patterns.

  The metal core flexible wiring board is formed between the first insulator layer 41 and the first interlayer insulator layer 49 or between the second insulator layer 42 and the second interlayer insulator layer 53 shown in the second embodiment. A structure in which no conductor pattern is disposed may be used. In this case, the first insulator layer 41 or the second insulator layer 42 is used as an adhesive layer between the metal substrate 11 and the second insulator layer 42 or the second interlayer insulator layer 53.

  DESCRIPTION OF SYMBOLS 10, 40 ... Metal core flexible wiring board, 11 ... Metal base | substrate (metal core), 12, 41 ... 1st insulator layer, 13, 42 ... 2nd insulator layer, 14 ... Signal wiring, 15, 44 ... Ground wiring, 16, 45 ... first conductor bump, 17 ... circuit wiring, 18 ... die land, 19, 48 ... second conductor bump, 20, 57 ... through hole, 20a, 57a ... through hole conductor, 21, 58 ... inner wall insulating layer , 22 ... opening, 23, 60 ... first metal foil, 24, 68 ... first conical conductive paste (first projecting conductor), 25, 62 ... second metal foil, 26, 69 ... second cone Conductive paste (second projecting conductor), 27, 70 ... first resin film, 28, 71 ... second resin film, 29, 72 ... through hole, 30, 73 ... embedded resin, 43 ... first circuit Wiring 46 ... second circuit wiring 47 Connection land 49 ... first interlayer insulator layer 50 ... third circuit wiring 51 ... first die land 52 ... third conductor bump 53 ... second interlayer insulator layer 54 ... fourth circuit wiring 55 ... Second die land, 56, fourth conductive bump, 59, heat radiating plate, 61, third conical conductive paste, 63, fourth conical conductive paste, 64, first interlayer resin film, 65, third metal foil, 66 ... second interlayer resin film, 67 ... fourth metal foil

Claims (6)

A flat metal substrate having flexibility, and a flexible insulator layer bonded to both main surfaces of the metal substrate;
The metal core flexible wiring board, wherein the insulator layer is made of a synthetic resin or a liquid crystal polymer containing oligophenylene ether and a styrene-butadiene elastomer.   The metal core flexible wiring board according to claim 1, wherein a low dielectric resin layer having a relative dielectric constant of 3.5 or less at a frequency of 1 GHz is formed by being laminated on the insulator layer. The insulator layer is made of a synthetic resin containing an oligophenylene ether and a styrene butadiene elastomer,
The metal core flexible wiring board according to claim 2, wherein the low dielectric resin layer is made of a liquid crystal polymer, a polyimide resin, a polyethylene naphthalate resin, or a composite resin thereof.   A conductor pattern is formed on the surface of the insulator layer or the low dielectric resin layer, and the conductor pattern is connected to the metal substrate via a conductor bump penetrating the insulator layer or the low dielectric resin layer. The metal core flexible wiring board according to claim 2, wherein the metal core flexible wiring board is provided. A first laminated plate in which a first protruding conductor is provided in a predetermined conductor pattern disposed on the inner surface of the first interlayer insulating layer, or a first protruding conductor in a predetermined region Laminating any one of the first metal foils provided with a body on one main surface of a flat metal substrate via a first resin film;
A second laminated plate in which a second protruding conductor is provided in a predetermined conductor pattern disposed on the inner surface of the second interlayer insulator layer, or a second protruding conductor in a predetermined region Laminating one of the second metal foils provided with a body on the other main surface of the metal substrate via a second resin film;
The first projecting conductor is formed by inserting the first resin film into the first projecting conductor by heating and pressurizing the laminate formed on both main surfaces of the metal base. Is connected to one main surface of the metal substrate, and the second protruding conductor is connected to the other main surface of the metal substrate by inserting the second resin film of the second protruding conductor. The step of joining and integrating the laminates;
A method for producing a metal core flexible wiring board, comprising: A step of forming a through-hole penetrating the laminate after the laminate is joined and integrated;
Filling the through hole with a thermosetting resin and thermosetting,
Forming a through hole in the thermoset resin;
The method for producing a metal core flexible wiring board according to claim 5, further comprising a step of making the inside of the through hole conductive.

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