JPH10135591A - Heat conductive substrate and wiring substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat conductive substrate capable of securing the heat conductivity, while sustaining the electric insulation required for mounting an electronic part at low cost. SOLUTION: Mn-Zn ferrite particles (2) making the 87wt.% to the total wt of the particles (2) plus PPS resin pellet (1) are mixed with each other using a kneader. Next, this mixture is fed to a two axle extruder for melting down the PPS resin pellet (1) at the temperature of 200-250 deg.C, while for kneading the ferrite particles (2) into the PPS resin (1) to be linearly extruded from a discharge nozzle for solidifying by cooling down in water. Next, the cooled down solid matter is cut off in pellets using a pelletizer into mixed pellets, so that they may be fed to an in-line screw injection molding machine to be thermally melted down at about 350 deg.C for pressure-injection into a metallic mold at the pressure of about 1000kg/cm<2> to cool down the metallic mold at about 200 deg.C in the pressure-reduced state down to 500kg/cm<2> .

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat conductive substrate and a heat conductive wiring substrate used in the field of electronic equipment, and more particularly to a method for efficiently dissipating heat generated from mounted electronic components to the outside. The present invention relates to a heat conductive substrate and a heat conductive wiring substrate that can be made.

[0002]

2. Description of the Related Art In recent years, electronic devices, both industrial and consumer, have been further reduced in size and thickness, and as a result, the various components that make up the electronic devices have been rapidly reduced in size and innovation in mounting technology has been rapidly progressing. ing. For example, various technologies have been developed to enable high-density mounting even on a printed wiring board that is a mounting base for electronic components that have been reduced in size and thickness.
Examples of such technology development include miniaturization of mounting wiring patterns, high multilayer wiring, and reduction in diameter of via holes connecting wiring patterns between multilayer wiring boards. In particular, the progress of high integration (high density) in recent electronic devices (such as large-scale LSIs) has been remarkable, and has been spurred by the development of technology for high density surface mounting. From such a background, the present applicant has developed a multilayer substrate in which all layers suitable for high-density surface mounting have an IVH (inner via hole) structure. However, in such a multilayer substrate, the influence of heat generated from electronic components such as mounted LSIs, power ICs, and power supply circuit components on peripheral components (other mounted electronic components) becomes a serious problem. I have.

[0003]

As a measure for dissipating the heat generated by the electronic component, a heat radiating fin made of aluminum is mounted on the electronic component side, and the heat is dissipated by utilizing the large surface area, or the heat dissipating fan is mounted. It is common to install and thereby forcibly cool. On the other hand, on the wiring board side on which electronic components are mounted, since the base material is phenol resin or epoxy resin, which is originally an insulating material, the thermal conductivity of the board is extremely low, and the heat generated by the electronic components is sufficiently dissipated. It is difficult to let. Therefore, a printed wiring board (hereinafter, referred to as a heat conductive board) having a wiring pattern formed on an upper surface of a heat conductive board obtained by forming an electrically insulating coating film on the surface of a metal substrate such as aluminum having excellent heat conductivity. In addition, a measure is taken in which a power IC, a power supply circuit component, and the like are mounted on the thermally conductive wiring board, and heat generated from these components is dissipated to the outside via the board. However, the above-mentioned heat conductive substrate requires an insulating film or an insulating layer to be formed on the surface of the metal substrate, which naturally inevitably increases the cost. On the other hand, reports or products have been reported on examples of using a ceramic substrate or a ferrite plate-like molded body containing alumina or beryllium oxide as a thermally conductive substrate as it is,
The cost problem has not been solved.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and can secure thermal conductivity while maintaining electrical insulation required for mounting electronic components. It is an object of the present invention to provide a heat conductive substrate and a heat conductive wiring board which can be manufactured in a low temperature.

[0005]

Means for Solving the Problems In order to achieve the above object, the heat conductive substrate of the present invention is a substrate obtained by mixing ferrite powder in a synthetic resin substrate. In such a heat conductive substrate of the present invention, the synthetic resin constituting the base ensures the necessary electrical insulation as a mounting substrate, and the ferrite powder dispersed in the synthetic resin base provides excellent heat conduction. The efficiency and the effect of shielding electromagnetic waves can be obtained. Therefore, when an electronic component is mounted, heat generated from the electronic component is efficiently radiated to the outside via the substrate. Also, since the electromagnetic waves generated from the electronic components are shielded by the substrate, the electromagnetic waves generated from the electronic components mounted on one main surface of the substrate adversely affect the operation of the electronic components mounted on the other main surface. Can be prevented. Also,
The amount of ferrite powder used as a heat conductive material is smaller than the amount of heat conductive material used in a conventional substrate of this type, and it can be manufactured in a simple process. As a result, the product cost can be reduced.

In the heat conductive substrate of the present invention, the content of the ferrite powder per substrate is 70 to 98 wt.
%, And the substrate resistance required for the mounting substrate (generally, the surface resistance is 1 × 10 ¹⁰ Ω / cm) without impairing the form of the substrate.
² or more), and extremely excellent thermal conductivity can be obtained.

Further, in the heat conductive substrate of the present invention, at least one selected from the group consisting of alumina powder, magnesia powder, aluminum nitride powder, silicon carbide powder, beryllium oxide powder and silica glass powder together with ferrite powder. It is preferable that one powder is mixed. With such a configuration, the mechanical strength of the substrate is improved and the moldability of the substrate during manufacturing is improved.

Further, in the heat conductive substrate of the present invention having the above preferred configuration, the ferrite powder, alumina powder, magnesia powder, aluminum nitride powder, silicon carbide powder, beryllium oxide powder and silica It is more preferable that the total content with at least one powder selected from glass powder is 70 to 98 wt%. With such a configuration, the form as a substrate is not impaired, and the While maintaining high substrate resistance (generally, surface resistance is 1 × 10 ¹⁰ Ω / cm ² or more)
Extremely good thermal conductivity can be obtained.

Further, in the heat conductive substrate of the present invention having a more preferable configuration, a ferrite powder, an alumina powder, a magnesia powder, an aluminum nitride powder, a silicon carbide powder, a beryllium oxide powder and a silica glass powder are provided. Compounding ratio with at least one powder selected from powder (ferrite powder: at least one powder selected from alumina powder, magnesia powder, aluminum nitride powder, silicon carbide powder, and beryllium oxide powder) Is 2: 1 to 2 by weight
The ratio is more preferably 0: 1. With such a configuration, extremely excellent thermal conductivity and mechanical strength can be obtained without impairing the electromagnetic wave shielding effect.

In the heat conductive substrate of the present invention, the synthetic resin is preferably a thermoplastic resin. With such a structure, a highly reliable product can be easily manufactured by an injection molding method. . Further, by arranging a wiring pattern such as a copper foil pattern in an injection molding die and performing insert molding, a heat conductive wiring board described later can be easily manufactured.

Further, in the heat conductive substrate of the present invention, the synthetic resin is preferably an elastic resin, and with such a structure, a bendable flexible substrate can be obtained.

In the heat conductive substrate of the present invention, the synthetic resin is preferably a thermosetting resin. With such a structure, a highly reliable product can be easily obtained by a compression molding method or a transfer molding method. Can be manufactured. Also, a heat conductive wiring board described later can be easily manufactured by insert-molding a wiring pattern such as a copper foil pattern using a transfer molding method.

In the heat conductive substrate of the present invention, the synthetic resin substrate is preferably a substrate obtained by impregnating a thermosetting resin into a core material made of an inorganic fiber or organic fiber cloth and curing the core material. With such a configuration, the mechanical strength of the substrate can be improved.

Another heat conductive substrate according to the present invention is a heat conductive substrate having a multilayer structure, wherein at least one of the heat conductive substrates comprises the heat conductive substrate according to the present invention. In such another heat conductive substrate of the present invention, as a substrate other than the heat conductive substrate of the present invention, for example, a synthetic resin substrate, a thermosetting resin to a core material made of inorganic fiber or organic fiber cloth. By using a resin substrate that does not contain a heat conductive material such as a substrate that is impregnated and cured, the mechanical strength of the entire heat conductive substrate having a multilayer structure can be kept high. Therefore, it is possible to reduce the thickness of the heat conductive substrate alone, and it is selected from ferrite powder, alumina powder, magnesia powder, aluminum nitride powder, silicon carbide powder, beryllium oxide powder and silica glass powder. The amount of at least one powder used can be reduced.

Further, the heat conductive wiring board of the present invention has a wiring pattern formed on at least one main surface of the heat conductive substrate having a single-layer structure or the heat conductive substrate having a multilayer structure of the present invention. . In such a heat conductive wiring board of the present invention, electronic components can be mounted on the main surface of the board at high density. Further, when the heat conductive wiring board is formed by using a flexible heat conductive board using a synthetic resin base made of an elastic resin, the plurality of heat conductive wiring boards are electrically connected by this. By doing so, it is possible to create a mounting board having an enlarged heat radiation area.

In the heat conductive wiring board of the present invention, it is preferable that a wiring pattern is formed on both main surfaces of the front and back surfaces of the heat conductive substrate, and the wiring patterns on both front and back surfaces are connected via through holes. With such a configuration, the electronic components can be mounted on the wiring patterns on both the front and back main surfaces of the board at a high density. Further, since the wiring patterns on the front and back main surfaces are connected by through holes, heat of the electronic components mounted on the front and back main surfaces of the board is efficiently dissipated from the front and back main surfaces of the board.

Further, another heat conductive wiring board of the present invention comprises:
A heat conductive wiring board having a multilayer structure, wherein at least a wiring pattern is formed on both front and back main surfaces of the heat conductive substrate having a single layer structure or the heat conductive substrate having a multilayer structure according to the present invention; It is characterized by including a heat conductive wiring board formed by connecting the wiring patterns on the surface through through holes, and a wiring board formed by connecting the wiring patterns formed on both front and back main surfaces through the through holes. And In such another heat conductive wiring board of the present invention, as the wiring board, for example, a wiring pattern is formed on both front and back main surfaces of a synthetic resin substrate, and the wiring pattern on both front and back main surfaces is inserted through a through hole. A wiring pattern is formed on both front and back main surfaces of a wiring board formed by connecting and connecting a thermosetting resin to a core material made of an inorganic fiber or an organic fiber cloth and curing the resin. By using a wiring board or the like formed by connecting the wiring patterns on the surface through through holes, by changing the number of layers and the order of stacking these wiring boards and the heat conductive wiring board, heat dissipation, electromagnetic wave shielding It is possible to adjust various characteristics of the wiring board, such as performance and board strength.

In the heat conductive wiring board of the present invention, it is preferable that an electric insulating film is formed between the wiring pattern and the heat conductive substrate.
A thermally conductive wiring board having excellent thermal conductivity and high surface electrical resistance can be obtained.

[0019]

Embodiments of the present invention will be described below. (First Embodiment) FIG. 1 is a sectional view of a heat conductive substrate according to a first embodiment of the present invention. In the figure, reference numeral 3 denotes a heat conductive substrate, which is constituted by mixing a ferrite powder 2 into a synthetic resin substrate 1.

Examples of the synthetic resin constituting the synthetic resin base 1 of the heat conductive substrate 3 of the present embodiment include polybutylene terephthalate (PBT), polyphenylene sulfide (PPS), and polytetrafluoroethylene (PTF).
E), thermoplastic resins such as liquid crystal polymer (LCP) and polyphenylene oxide (PPO), and thermosetting resins such as phenolic resin, epoxy resin, polyimide resin, unsaturated polyester resin, polyurethane resin, and diallyl phthalate resin. used. Regardless of whether a thermoplastic resin or a thermosetting resin is used, one or more of the above-described resins can be used.

The ferrite powder 2 mixed in the synthetic resin substrate 1 is, for example, a Mn-Zn type, Cu-Z
Various ferrites such as n-based, Ni-Zn-based, and Cu-Zn-Mg-based can be used, and one or more selected from these are used. The particle size of the ferrite powder 2 is generally 0.1 to 10 μm, preferably 0.5 to 3 μm in volume average particle size.
μm. The shape of the ferrite powder is not particularly limited,
Although various shapes such as a spherical shape and a needle shape can be used, it is preferable to use a spherical powder from the viewpoint of moldability and heat conductivity. In general, it is preferable that the amount of ferrite powder 2 mixed in the synthetic resin substrate 1 (mixing amount) be 70 wt% or more based on the entire substrate 3. This is because if the content is less than 70 wt%, it becomes difficult to provide the substrate 3 with sufficient thermal conductivity (thermal conductivity indicating a thermal conductivity of 3.5 W / m · ° C. or more). On the other hand, if the amount of the ferrite powder 2 mixed into the synthetic resin base 1 is too large, the electric resistance (surface electric resistance) of the substrate 3 is reduced to a resistance value (generally 1 × 1) required as a mounting substrate.
0 ¹⁰ Ω / cm ² or more), and it becomes difficult to maintain the form as a substrate. For this reason, it is preferable that the upper limit of the amount of the ferrite powder 2 to be mixed into the synthetic resin substrate 1 (blending amount) is 98 wt% or less based on the entire substrate 3. The ferrite powder 2 varies depending on the type of the synthetic resin constituting the synthetic resin base 1 and the like.
80-95 wt% of the total amount of the substrate 3
, The thermal conductivity of the substrate 3 becomes extremely good (4.5 W / m · ° C. or more) and the electric resistance (surface electric resistance) of the substrate 3 is extremely high (1 × 10 ^11). Ω / c
m ² or more). The heat conductive substrate 3 of the present embodiment
Is not particularly limited, but is generally 0.1 to 3 mm.

Although the method of manufacturing the heat conductive substrate 3 of the present embodiment is not particularly limited, one specific example thereof will be briefly described. First, a method of manufacturing the heat conductive substrate 3 in which the synthetic resin base 1 is made of a thermoplastic resin (PPS resin) will be described. First, the Mn-Zn ferrite powder was added to a PPS resin pellet by adding Mn-Zn to the total weight of both.
The ferrite powder is added so as to have a weight ratio of 87% by weight, and sufficiently mixed by a kneader. If the ferrite powder is surface-treated with a fatty acid such as stearic acid or linoleic acid in this mixing step, the dispersibility of the ferrite powder on the surface of the PPS resin pellet is improved, and the heat conductive substrate obtained after molding is obtained. The mechanical properties of are improved. In particular, excellent elasticity can be provided. Next, the PPS resin pellets having the ferrite powder adhered to the surface thereof are charged into a twin-screw extruder, and heated to a temperature of 200 to 250 ° C.
Dissolve S-resin and ferrite powder sufficiently
The mixture is kneaded into a PS resin, extruded linearly from a discharge nozzle at the tip of a twin-screw extruder, and cooled and solidified in water. next,
This cooled solidified product is cut into pellets by a pelletizer, and this is used as mixed pellets. Next, the mixed pellets were charged into an in-line screw injection molding machine,
Heated and melted at 50 ° C and put in a mold to about 1000 kg / cm ²
Injection at a pressure of 500 kg / cm ²
The mold is cooled to about 200 ° C. while the pressure is once reduced. Thereafter, the completed heat conductive substrate is taken out of the mold. In addition, when a wiring pattern (insert) made of, for example, a copper foil is arranged in a mold at the time of injection molding and insert molding is performed, a heat conductive wiring substrate having a wiring pattern formed on a surface can be obtained. .

Next, a method for manufacturing the heat conductive substrate 3 in which the synthetic resin substrate 1 is made of a thermosetting resin (heat curable epoxy resin) will be described. First, after mixing an epoxy resin main material and a polyamide curing agent, a Cu-Zn ferrite powder is added to this mixture with Cu based on the total weight of both.
-Add the Zn ferrite powder so that the weight ratio is 95 wt%, and knead the mixture with a three-roll mill until the mixture becomes homogeneous. Next, this kneaded material is pre-cured to make a tablet,
The tablet is transferred into a molding die having a predetermined shape, and is compression-molded in a state where the tablet is heated and pressurized to be completely cured to obtain a heat conductive substrate. The transfer molding method may be used instead of the compression molding method. In particular, by using the transfer molding method, it is possible to perform the insert molding without damaging the wiring pattern (insert) arranged in the mold. It is possible to manufacture a heat conductive wiring substrate having a wiring pattern formed on a surface thereof at a high yield.

The heat conductive substrate 3 formed by using the synthetic resin substrate 1 made of a thermoplastic resin or a thermosetting resin as described above is a hard substrate, but the synthetic resin substrate 1 is made of polybutadiene, ethylene propylene rubber or the like. By using the above-mentioned elastomer (a resin having rubber-like elasticity at around normal temperature), the thermally conductive substrate 3 can be a flexible substrate that can be bent.

In the heat conductive substrate 3 according to the present embodiment, the synthetic resin substrate 1 provides the electrical insulation required for a mounting substrate, and the ferrite powder 2 dispersed in the substrate 1 provides excellent heat insulation. Heat conduction efficiency and electromagnetic wave shielding effect can be obtained. Therefore, when an electronic component is mounted thereon, heat generated from the electronic component is efficiently radiated to the outside via the substrate 3. In addition, since the electromagnetic wave generated from the electronic component is shielded by the substrate 3, one main surface (front surface)
The electronic component mounted on the other main surface (back surface) can be prevented from being adversely affected by the electromagnetic wave generated from the electronic component mounted on the other main surface. In addition, the amount of heat conductive material (ferrite powder) used is smaller than that of a conventional substrate of this type, and the manufacturing process is simple.
Product costs can be greatly reduced.

The thermal conductive substrate 3 according to the present embodiment is often used alone as a mounting substrate. For example, a substrate (synthetic resin substrate) formed of only one synthetic resin on one main surface thereof is used. Or a substrate made of glass fiber, metal fiber, wood fiber, or synthetic resin fiber cloth impregnated with a thermosetting resin and cured (core-containing thermosetting resin substrate), By mounting the synthetic resin substrate or the core-containing thermosetting resin substrate between two heat conductive substrates 3, a mounting substrate having a multilayer structure can be formed. In this case, since the strength of the entire substrate having the multilayer structure is reinforced by the synthetic resin substrate or the core material-containing thermosetting resin substrate, the thickness of the heat conductive substrate can be reduced (for example, 0.1 mm or less), and ferrite can be reduced. The amount of powder used can be reduced. Further, when the heat conductive substrate 3 is a flexible substrate that can be bent, if the synthetic resin substrate is made of the above-mentioned elastomer, the multilayer substrate can be a flexible substrate.

(Second Embodiment) FIG. 2 is a sectional view of a heat conductive substrate according to a second embodiment of the present invention. In the figure, the same reference numerals as those in FIG. 1 indicate the same or corresponding parts,
Reference numeral 4 denotes a heat conductive substrate, which is a ferrite powder 2, Al ₂ O ₃ (alumina) powder, MgO (magnesia) powder, AlN (aluminum nitride) powder, S
At least one powder (auxiliary heat conductive powder) 5 selected from iC (silicon carbide) powder, BeO (beryllium oxide) powder and silica glass powder is mixed therein.

That is, the heat conductive substrate 4 of the present embodiment
Is an Al ₂ O ₃ powder as an auxiliary heat conductive powder 5 in the synthetic resin substrate 1 of the heat conductive substrate 3 of the first embodiment;
It contains at least one powder selected from MgO powder, AlN powder, SiC powder, BeO powder and silica glass powder. The manufacturing method is basically the same as that of the heat conductive substrate 3 of the first embodiment except that the auxiliary heat conductive powder 5 is used together with the ferrite powder 2. Although the reason is not clear, the heat conductive substrate 4 of the present embodiment is compared with the heat conductive substrate 3 of the first embodiment in which only the ferrite powder 2 is mixed in the synthetic resin base 1. The mechanical strength is improved, and the moldability when molding the mixture of the synthetic resin and the powder into a plate at the time of production is improved.

In the heat conductive substrate 4 of the present embodiment, the particle size of the auxiliary heat conductive powder 5 is generally 0.1 by volume average particle size.
10 to 10 μm, preferably 0.5 to 3 μm. The shape of the auxiliary heat conductive powder 5 is not particularly limited, but it is preferable to use a spherical powder from the viewpoint of moldability and heat conductivity. The mixing amount of the ferrite powder 2 and the auxiliary thermal conductive powder 5 into the synthetic substrate 1 (total blending amount of the ferrite powder 2 and the auxiliary thermal conductive powder 5) is generally 70% by weight or more based on the entire substrate 4. Is preferred. This is for the same reason as the preferable amount of the ferrite powder 2 mixed in the heat conductive substrate 3 of the first embodiment is 70 wt% or more based on the entire substrate 3. Further, for the same reason as the heat conductive substrate 3 of the first embodiment, the ferrite powder 2 and the auxiliary heat conductive powder 5 (Al ₂ O ₃ powder, MgO powder, AlN powder,
It is preferable that the upper limit of the mixing amount (blending amount) of the SiC powder, BeO powder and silica glass powder) into the synthetic substrate 1 is 98 wt% or less based on the entire substrate 4. Also in the heat conductive substrate 4 of the present embodiment, the amount of the ferrite powder 2 and the auxiliary heat conductive powder 5 mixed into the synthetic resin base 1 (the amount of the ferrite powder 2 and the auxiliary heat conductive powder 5 The total amount is 8 per substrate 3
When the content is in the range of 0 to 95 wt%, the thermal conductivity and electric resistance (surface electric resistance) of the substrate 4 become extremely good. The mixing ratio of the ferrite powder 2 and the auxiliary heat conductive powder 5 (ferrite powder 2: auxiliary heat conductive powder 5) is generally 2: 1 to 50: 1, preferably 2: 1 to 20: 1. It is. This is because, when the compounding amount of the auxiliary heat conductive powder 5 increases beyond the mixing ratio, the effect of shielding the electromagnetic wave in the entire substrate 4 decreases, and when the mixing amount decreases beyond the mixing ratio, only the ferrite powder 2 is used. This is because it hardly changes from the mechanical strength and moldability of the substrate when used. Although the thickness of the heat conductive substrate 4 of the present embodiment is not particularly limited, it is generally 0.1 to 3.0 mm. In addition, it is needless to say that the multilayered substrate can also be formed by laminating the above-described synthetic resin substrate or the core-containing thermosetting resin substrate on the thermally conductive substrate 4 of the present embodiment.

(Third Embodiment) FIGS. 3A and 3
FIG. 4B is a sectional view illustrating a step of manufacturing the heat conductive substrate according to the third embodiment of the present invention, in which FIG.
The same reference numerals indicate the same or corresponding parts. Hereinafter, the manufacturing process will be described with reference to FIG.

First, a core material 7 made of two glass fiber cloths is prepared, and each is impregnated with an epoxy resin 6 in which a ferrite powder 2 is dispersed, and is dried to prepare a prepreg 8.
After forming a and 8b, these prepregs 8a and 8b are overlapped. Then, the prepregs 8a and 8b are heated and pressed by a hot press molding machine (not shown) (FIG. 3).
(A): Reference numeral 50 in the figure indicates a pressing force. ) To compress and harden the epoxy resin 6, the ferrite powder 2 is mixed into the synthetic resin base 1,
A heat conductive substrate 8 in which a core material 7 made of a piece of glass fiber cloth is inserted is obtained (FIG. 3B: prepreg 8a)
And the resin layer on the front side of the prepreg 8b are integrated by compression molding. ). In the above, a glass fiber cloth is used for the core material 7, but a cloth made of metal fiber such as stainless steel fiber or titanium alloy fiber, a cloth made of wood fiber, a cloth made of synthetic resin fiber such as aramid fiber, or the like. Can also be used. The form of the fabric is not particularly limited, but is preferably a nonwoven fabric from the viewpoint of strength. Although the epoxy resin 1 is used as the thermosetting resin, other thermosetting resins such as a phenol resin and a polyimide resin may be used. Further, similarly to the second embodiment, the auxiliary heat conductive powder (Al ₂ O ₃ powder, MgO powder, AlN powder,
At least one powder selected from SiC powder, BeO powder and silica glass powder) 5 can also be used.
Although two prepregs 8a and 8b are stacked and heated and pressed to obtain a substrate, one prepreg may be heated and pressed to form a substrate.

In the heat conductive substrate 8 of the present embodiment, the amount of the ferrite powder 2 mixed into the substrate (blending amount) or
The total amount (mixing amount) of the ferrite powder 2 and the auxiliary heat conductive powder 5 mixed into the substrate is 70 wt% per substrate as in the case of the heat conductive substrates 3 and 4 of the first and second embodiments.
% Is preferable. This corresponds to the first and second
The reason is the same as the reason for the heat conductive substrates 3 and 4 of the embodiment. Also, the upper limit is 98 watts per substrate as in the case of the heat conductive substrates 3 and 4 of the first and second embodiments.
It is preferably set to t% or less. Further, similarly to the heat conductive substrates 3 and 4 of the first and second embodiments, the amount of the ferrite powder 2 mixed into the substrate (blending amount), or the ferrite powder 2 and the auxiliary heat conductive powder When the total amount (mixing amount) of the No. 5 in the substrate is within the range of 80 to 95 wt% based on the entire substrate, the thermal conductivity and the electrical resistance (surface electrical resistance) of the thermally conductive substrate 8 are extremely excellent. Become.

The heat conductive substrate 8 of this embodiment as described above
Since the synthetic resin substrate 1 includes the core material 7 made of fiber cloth, the substrate has extremely improved mechanical strength. In addition, a heat conductive wiring board can be manufactured by arranging a wiring pattern made of, for example, a copper foil pattern on the surface of the prepregs 8a and 8b during the hot press molding step of the prepregs 8a and 8b. In addition, it is needless to say that the multilayered substrate can also be formed by laminating the above-described synthetic resin substrate or the core-containing thermosetting resin substrate on the thermally conductive substrate 8 of the present embodiment.

(Fourth Embodiment) FIG. 4 is a sectional view of a heat conductive wiring board according to a fourth embodiment of the present invention. In the figure, the same reference numerals as those in FIG. 1 denote the same or corresponding parts, and 11 denotes a heat conductive wiring board, which is provided on both front and back main surfaces of the heat conductive substrate 3 of the first embodiment, for example, a copper foil or the like. A wiring pattern 10 made of a conductor is formed, and the wiring patterns 10 on both front and back main surfaces are connected by through holes 9 formed at required positions of the heat conductive substrate 3. In the drawing, the wiring pattern 10 is provided on both the front and back main surfaces of the substrate.
However, when the wiring pattern 10 is formed only on one main surface of the substrate, the through hole 9 is naturally unnecessary. Further, the formation of the through hole 9 is based on the wiring pattern 1.
It may be before the formation of 0 or after the formation of the wiring pattern 10.
The through hole 9 is formed by forming a through hole in the substrate by, for example, drilling or irradiating a laser beam, and then forming a copper electrode by plating on the inner wall of the through hole, or forming a silver paste or a copper paste in the through hole. For example, a method of printing and filling a conductive paste such as the above is used.

In the heat conductive wiring board 11 of this embodiment, when heat-generating electronic components such as a power IC and a power transformer are mounted on the wiring pattern 10, the heat can be effectively dissipated. it can. Further, when electronic components are mounted on both the front and back surfaces of the wiring board 11, it is possible to prevent the electronic components mounted on the other surface from being adversely affected by electromagnetic waves generated from the electronic components mounted on one surface. it can.

The heat conductive wiring board 11 of this embodiment
Then, the heat conductive substrate is replaced with the heat conductive substrate 3 of the first embodiment.
However, the heat conductive substrate may be the heat conductive substrate 4 of the second embodiment or the heat conductive substrate 8 of the third embodiment. When the heat conductive substrate 8 of the third embodiment is used, the heat conductive wiring board is manufactured as follows. First, the prepreg described in the third embodiment is prepared, a laser beam is applied to the prepreg to form a through hole at a desired position, and a conductive paste such as a silver paste or a copper paste is printed and filled to form a through-hole. After forming the hole,
A copper foil is placed on both front and back main surfaces of the prepreg, and the prepreg is compression-hardened by heating and pressing. Next, a copper foil is patterned by photolithography to form a wiring pattern, thereby completing a heat conductive wiring board.

(Fifth Embodiment) FIG. 5 is a sectional view of a thermally conductive multilayer wiring board according to a fifth embodiment of the present invention.
4, the same reference numerals as those in FIG. 4 denote the same or corresponding parts, and 19 denotes a heat conductive multilayer wiring board, which includes the heat conductive wiring board 11 of the fourth embodiment and a ferrite powder. A double-sided wiring board 16 and an intermediate connector 18 are laminated. The double-sided wiring board 16 forms wiring patterns 13 and 14 on both front and back main surfaces of an epoxy resin base material 12 containing a nonwoven fabric of aramid fiber as a core material,
The wiring patterns 13 and 14 on the front and back main surfaces are connected by through holes (via holes) 15 formed at required positions on the epoxy resin base material 12. The intermediate connector 18 has a through hole (via hole) 17 at a predetermined position of an epoxy resin base material containing a nonwoven fabric of aramid fiber as a core material.
Is formed.

Hereinafter, a method of manufacturing the thermally conductive multilayer wiring board of the present embodiment will be briefly described. A core material is prepared from a nonwoven fabric of aramid fiber, impregnated with an epoxy resin, and dried to obtain a prepreg. Next, a through hole is formed at a required position of the prepreg by irradiating a laser beam, and the through hole is filled with a conductive paste such as a copper paste or a silver paste to form a through hole (via hole) 15. Next, a copper foil is adhered to both front and back main surfaces of the prepreg, and the prepreg is compressed and cured by pressing and heating the prepreg, and then the copper foil is patterned into a predetermined pattern by a photolithographic method, and wiring is performed. When the patterns 13 and 14 are formed, a double-sided wiring board 16 in which the wiring patterns 13 and the wiring patterns 14 are electrically connected through through holes (via holes) 15 is completed. Here, the density of the conductive material (powder) of the conductive paste in the through hole (via hole) 15 increases when the prepreg is compression-hardened.

Next, a porous prepreg prepared by impregnating an aramid fiber non-woven fabric with a core material of epoxy resin and drying is prepared, a through-hole is formed at a predetermined position of the prepreg by irradiating a laser beam, and the through-hole is formed. Is filled with a conductive paste such as a copper paste or a silver paste to form a through hole (via hole) 17 to form an intermediate connector 18.

Finally, the obtained double-sided wiring board 16,
The heat conductive wiring board 11 and the intermediate connector 18 of the fourth embodiment are arranged such that the intermediate connector 18 is arranged between the double-sided wiring board 16 and the heat conductive wiring board 11 of the fourth embodiment. The conductive paste in the through-holes (via holes) 17 of the intermediate connector 18 is hardened by heating and pressurizing these from above and below, thereby compressing the intermediate connector 18, and the back surface (lower surface) of the heat conductive wiring board 11 is hardened. The wiring pattern 10) is connected to the wiring pattern 13 on the front surface (upper surface) of the double-sided wiring substrate 16 to obtain a heat conductive multilayer wiring substrate 19 having the heat conductive wiring substrate 11 on the uppermost layer (surface layer).

In the heat conductive multilayer wiring board 19 of the present embodiment, when heat-generating electronic components such as a power IC and a power transformer are mounted on the wiring pattern 10, the heat can be effectively dissipated. Can be. When a heat-generating electronic component is mounted on the wiring pattern 14 on the back surface of the multilayer wiring board 19, the heat generated from the electronic component causes the wiring patterns 13 and 10 and the through holes (via holes) in the multilayer wiring board 19 to be formed. The heat is transmitted to the uppermost layer (surface layer) of the thermally conductive wiring board 11 through the layers 15 and 17 and is radiated from the uppermost layer (surface layer) of the thermally conductive wiring board 11. In addition, when electronic components are mounted on both the front and back surfaces of the multilayer wiring board 19, the electronic components mounted on the other surface are prevented from being adversely affected by electromagnetic waves generated from the electronic components mounted on one surface. Can be.

In the heat conductive multilayer wiring board 19, the double-sided wiring board 16 is used as the lowermost layer (backside layer), but the same heat conductive wiring as the uppermost layer (surface layer) is used as the lowermost layer (backside layer). The substrate 11 can also be used. The heat conductive multilayer wiring board 19 has a three-layer structure,
It is also possible to further increase the number of the heat conductive wiring boards 11 and to further laminate them via the intermediate connector 18. Further, the double-sided wiring board 16 forms a through-hole by irradiating a laser beam on a porous prepreg obtained by impregnating a nonwoven fabric of aramid fiber with an epoxy resin in a core material, and drying the through-hole with a copper paste or a silver paste. This is a double-sided wiring board in which a conductive paste is filled to form through-holes (via holes) 17. Wiring patterns are formed on both front and back main surfaces of a glass-epoxy substrate conventionally used in this field. It is also possible to use a double-sided wiring board on which wiring patterns on both front and back main surfaces are formed.

(Embodiment 6) FIG. 6 is a sectional view of a heat conductive wiring board according to a sixth embodiment of the present invention. In the figure, the same reference numerals as those in FIG. Is a heat conductive wiring board, which is provided on one main surface (front surface) of the heat conductive substrate 3 of the first embodiment.
1 is formed, and a wiring pattern 10 is formed on the front surface of the electric insulating film 51 and the other main surface (back surface) of the heat conductive substrate 3.
And the electrical insulating film 51 is connected by a through hole 9 formed at a required position. That is,
The heat conductive wiring board 20 of the present embodiment includes a heat conductive board 3
An electric insulating film 51 is provided between the substrate and the wiring pattern 10 to increase the surface resistance of the substrate to 1 × 10 ¹³ Ω / cm ² or more (preferably 1 × 10 ¹³ to 1 × 10 ¹⁸ Ω / cm ² ). It is. The electric insulating film 51 here is, for example, an epoxy resin,
It is made of a material such as a polyimide resin, and is formed by a method such as coating or attaching a film. The thickness of the electric insulating film 51 is generally set to 10 μm or less. It has a thickness of 10 μm
This is because when it is larger, the heat dissipation of the substrate tends to decrease. If the thickness of the electric insulating film 51 becomes too small, the surface resistance of the substrate is sufficiently increased (10 ¹³ / c).
m ² or more), it is difficult to increase the
It is necessary to do above.

In the heat conductive wiring board 20 of the present embodiment, the electric insulating film 51 is provided on the main surface of the heat conductive substrate 3 so that the heat dissipation of the substrate is not hindered.
The electric resistance of the surface of the substrate can be increased, and the reliability as a mounting substrate can be increased. It is needless to say that the same effect can be obtained by forming such an electric insulating film 51 on the main surface of the heat conductive substrate 3 in the heat conductive multilayer wiring board 19 of the fifth embodiment.

(Seventh Embodiment) FIG. 7A is a plan view of a heat conductive wiring board according to a seventh embodiment of the present invention.
7B is a side view of a specific example of an electronic device using the heat conductive wiring board shown in FIG. 7A, and FIG. 7C uses the heat conductive wiring board shown in FIG. It is a side view of other specific examples of electronic equipment.

In FIG. 7A, reference numeral 40 denotes a heat conductive wiring board, which runs parallel to the main surface of a heat conductive board 21 made by mixing ferrite powder in a synthetic resin base made of polybutadiene. A plurality of wiring patterns 22 are formed, and connection pads 23 are formed at both ends of the wiring pattern 22, thereby forming a bendable flexible substrate.

In FIG. 7 (b), reference numeral 24 denotes, for example, the heat conductive wiring board 11 of the fourth embodiment, on which electronic components 25 having a small heat generation amount such as capacitors are mounted on the main surface.
A connection terminal 26 is provided at an end of the main surface. Reference numeral 27 denotes, for example, the heat conductive wiring board 11 of the fourth embodiment, on which a plurality of heat-generating electronic components 28 such as a power transformer and a power IC are mounted on the main surface at a high density. Is provided with a connection terminal 29. Thermal conductive wiring board 24
And connection terminals 26, 2 of heat conductive wiring board 27, respectively.
9 shows a flexible heat conductive wiring board 40 shown in FIG.
Connection pads 23 are connected using solder or metal bumps, so that two wiring boards (a heat conductive wiring board 24 and a heat conductive wiring board 27) are formed in an electric circuit.
Is connected. In the electronic device configured as described above, a power transformer and a power I
When a module formed by mounting a plurality of heat-generating electronic components 28 such as C at a high density operates to generate heat, the heat is not only dissipated from the heat conductive wiring board 27 but also dissipated. The heat is transmitted to the heat conductive wiring board 24 via the flexible heat conductive wiring board 40, and is also radiated from the flexible heat conductive wiring board 40 and the heat conductive wiring board 24. As a result, the heat generated from the electronic component 28 is very efficiently dissipated, and the electronic component 28 operates stably. On the other hand, in FIG. 7 (c), the same reference numerals as those in FIG. 7 (b) denote the same or corresponding parts, and 30 denotes a casing 30 made of a metal having excellent heat conductivity such as aluminum. A connector 31 made of a metal having thermal conductivity, such as aluminum or copper, is attached to the inner surface of the connector 30. The connection pad 23 at one end of the flexible heat conductive wiring board 40 is connected to the connection terminal 29 of the heat conductive wiring board 27 using solder or a metal bump, and the other end is connected to the connector by screwing or the like. 31. In the electronic device configured as described above, the heat generated from the heat generating component 28 is dissipated from the heat conductive wiring board 27 and the flexible heat conductive wiring board 40 and the connector 31 are connected.
The heat generated from the electronic component 28 can be very efficiently dissipated, and the electronic component 28 operates stably. Although the casing 30 for accommodating the heat conductive wiring board 27 and the electronic components 28 is used as a heat dissipating means here, the connector 31 is simply provided on a metal plate having excellent heat conductivity such as aluminum. It is also possible to use the attached one as heat dissipating means.

[0048]

As described above, according to the heat conductive substrate of the present invention, since the substrate is made by mixing ferrite powder into the synthetic resin substrate, the electrical insulation required for the mounting substrate is secured. In addition, excellent heat conduction efficiency and an electromagnetic wave shielding effect can be obtained. Therefore, when an electronic device is configured using this heat conductive substrate as a mounting substrate, even if the electronic component generates heat, the heat is efficiently radiated to the outside via the substrate, and the heated electronic component itself and other electronic components are generated. The components operate stably, and the electromagnetic waves generated from the electronic components mounted on one main surface of the board do not reach the electronic components mounted on the other main surface, and the electronic components are protected from interference noise. Thus, a highly reliable electronic device can be obtained. Also,
Since the amount of ferrite powder used as a heat conductive material is smaller than the amount of heat conductive material used in a conventional substrate of this type, the product cost can be reduced compared to the conventional substrate of this type. be able to.

According to the heat conductive wiring board of the present invention, a wiring pattern is formed on at least one principal surface of the heat conductive substrate obtained by mixing ferrite powder in the synthetic resin base of the present invention. So, for example, power IC
Even if heat-generating electronic components such as a power supply and a power transformer are densely mounted on the wiring pattern, heat can be dissipated extremely efficiently, and a highly reliable electronic device can be obtained.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a heat conductive substrate according to a first embodiment of the present invention.

FIG. 2 is a sectional view of a heat conductive substrate according to a second embodiment of the present invention.

FIG. 3 is a cross-sectional view illustrating a process of manufacturing a thermally conductive substrate according to a third embodiment of the present invention.

FIG. 4 is a sectional view of a heat conductive wiring board according to a fourth embodiment of the present invention.

FIG. 5 is a sectional view of a heat conductive wiring board according to a fifth embodiment of the present invention.

FIG. 6 is a sectional view of a heat conductive wiring board according to a sixth embodiment of the present invention.

FIG. 7A is a plan view of a heat conductive wiring board according to a seventh embodiment of the present invention, and FIG. 7B is an electron using the heat conductive wiring board shown in FIG. 7A. FIG. 7C is a side view of another specific example of the electronic device using the heat conductive wiring board shown in FIG. 7A.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Synthetic resin base 2 Ferrite powder 3 Thermal conductive substrate

Continued on the front page (51) Int.Cl. ⁶ Identification code FI C08K 3/36 C08K 3/36 C08L 101/00 C08L 101/00 H05K 1/02 H05K 1/02 A 3/46 3/46 UT 7 / 20 7/20 C

Claims (14)

[Claims] 1. A thermally conductive substrate obtained by mixing ferrite powder in a synthetic resin substrate. 2. The thermally conductive substrate according to claim 1, wherein the content of the ferrite powder is 70 to 98 wt% based on the whole substrate. 3. A ferrite powder is mixed with at least one powder selected from alumina powder, magnesia powder, aluminum nitride powder, silicon carbide powder, beryllium oxide powder and silica glass powder. The heat conductive substrate according to claim 1. 4. A ferrite powder, an alumina powder, a magnesia powder, an aluminum nitride powder,
The heat conductive substrate according to claim 3, wherein the total content of at least one powder selected from a silicon carbide powder, a beryllium oxide powder, and a silica glass powder is 70 to 98 wt%. 5. A ferrite powder, an alumina powder, a magnesia powder, an aluminum nitride powder, a silicon carbide powder,
Compounding ratio with at least one powder selected from beryllium oxide powder and silica glass powder (ferrite powder: alumina powder, magnesia powder, aluminum nitride powder,
The thermally conductive substrate according to claim 4, wherein the weight ratio of at least one powder selected from silicon carbide powder, beryllium oxide powder, and silica glass powder) is 2: 1 to 20: 1. 6. The method according to claim 1, wherein the synthetic resin is a thermoplastic resin.
6. The heat conductive substrate according to any one of items 1 to 5, 7. The synthetic resin is an elastic resin.
6. The heat conductive substrate according to any one of 5. 8. The method according to claim 1, wherein the synthetic resin is a thermosetting resin.
6. The heat conductive substrate according to any one of items 1 to 5, 9. The heat conduction according to claim 1, wherein the synthetic resin substrate is a substrate formed by impregnating a thermosetting resin into a core material made of an inorganic fiber or an organic fiber cloth and curing the resin. Substrate. 10. A heat conductive substrate having a multilayer structure, at least one of which comprises the heat conductive substrate according to claim 1. 11. A heat conductive wiring board formed by forming a wiring pattern on at least one main surface of the heat conductive board according to claim 1. 12. The heat conductive wiring board according to claim 11, wherein wiring patterns are formed on both front and back main surfaces of the heat conductive substrate, and the wiring patterns on the front and back main surfaces are connected via through holes. . 13. A heat conductive wiring board having a multilayer structure, wherein a wiring pattern is formed on at least both main surfaces of the heat conductive substrate according to claim 1; It is characterized by including a heat conductive wiring board formed by connecting the wiring patterns on the surface through through holes, and a wiring board formed by connecting the wiring patterns formed on both front and back main surfaces through the through holes. Thermal conductive wiring board. 14. The heat conductive film according to claim 11, wherein an electric insulating film is formed between the heat conductive substrate and the wiring pattern of the heat conductive wiring substrate provided in the outermost layer. Wiring board.