JP2008066375A - Excellent heat radiating substrate and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an excellent heat radiating substrate reduced in weight, and excellent in heat radiating property and insulation reliability, and also to provide a method for manufacturing the same. <P>SOLUTION: The excellent heat radiating substrate 100 using CFRP plate 1 as a core material includes: a copper film 8 which covers surrounding and internal wall surface of a through-hole 1a provided with the CFRP plate 1; insulated layers 50a, 50b formed of preplegs 4a, 4b sequentially holding preplegs 2a, 2b and glass cloths 3a, 3b which cover both surfaces of the CFRP plate 1 covered with the copper film 8 and the internal wall of the through-hole 1a; wiring layers 51a, 51b formed of preplegs 5a, 5b, 6a, 6b provided on both surfaces of the preplegs 4a, 4b; and a through-hole 9 which connects wiring layers 7a, 7b, 7c, and 7d provided to the circuit layers 51a, 51b. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a high heat dissipation substrate that is lightweight and excellent in heat dissipation and a method for manufacturing the same, and more particularly to a high heat dissipation substrate excellent in insulation reliability and a method for manufacturing the same.

  In recent years, printed circuit boards have come to be desired to have a substrate with good heat dissipation as the density of electronic components increases. A metal core substrate is known as a printed wiring board excellent in heat dissipation and has already been put into practical use. By using a metal such as aluminum or copper having high thermal conductivity as the core material, the metal core substrate can disperse heat from the heat-generating component over the entire substrate and suppress the temperature rise of the heat-generating component.

  Recently, carbon fiber reinforced plastic (Carbon Fiber Reinforced Plastics: hereinafter abbreviated as CFRP) may be used as a core material (see, for example, Patent Document 1). CFRP is a composite material composed of carbon fiber and resin, and the coefficient of thermal expansion, thermal conductivity, strength, and specific gravity can be adjusted by the carbon fiber content and structure (cross material, unidirectional material). (For example, refer to Patent Document 2). If carbon fiber with high thermal conductivity is used, a core material that has the same heat dissipation as aluminum and is lighter than aluminum can be made. If a CFRP core substrate can be produced using this core material, In addition, a lightweight high thermal conductive substrate can be obtained.

  Since CFRP is conductive like other metal cores, it is necessary to insulate the through holes connecting the wirings above and below the CFRP core with a filling resin. In a conventional CFRP core substrate manufacturing method, first, through holes are provided in a CFRP core material, and a prepreg (a thermosetting resin is impregnated into a glass cloth in a semi-cured state above and below the CFRP core material provided with the through holes. And stacking press under vacuum. At this time, the semi-cured resin is melted by heat and filled into the through hole. A through hole having a smaller diameter than that of the through hole and plated with copper is formed in the through hole filled with the resin.

Japanese Patent Laid-Open No. 11-40902 (stages 0008 to 0015, FIG. 9) JP 2003-273482 A (stages 0034 to 0049, FIG. 16)

  However, when CFRP is used for the core material, unlike the case of aluminum, in the conventional manufacturing method, when the through hole is formed, carbon powder is generated from the carbon fiber exposed on the hole wall surface, and the resin is filled in the next process. In addition, the carbon powder is mixed into the resin, so that the insulation between the CFRP core and the through hole is lowered, and in some cases, there is a short circuit.

  In addition, when the counterbore part is provided as a heat dissipation hole in the metal core substrate, the generated carbon powder may be scattered between the wirings, causing a short circuit, or entering the substrate manufacturing apparatus and scattering to other substrates. There was also the problem of causing a short circuit.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a high heat dissipation substrate having excellent insulation reliability in a high heat dissipation substrate and a method for manufacturing the same.

  The high heat dissipation substrate according to the present invention includes a protective film covering both surfaces of the CFRP core layer provided with through holes and the inner wall of the through hole, both surfaces of the CFRP core layer covered with this protective film, and an inner wall of the through hole. A prepreg layer that covers the wiring, wiring provided on both surfaces of the prepreg layer, and a through hole that conducts both wirings through the inner wall surface of the prepreg layer that covers the through hole.

  The manufacturing method of the high heat dissipation substrate according to the present invention includes a step of forming a protective film on both surfaces of the CFRP core layer provided with the through hole and on the inner wall of the through hole.

  According to the present invention, by covering the wall surface of the through hole provided in the CFRP core layer with the protective film, the generation of carbon powder can be prevented, and the insulation reliability between the CFRP core and the through hole is improved. be able to. Moreover, mixing of carbon powder into the substrate manufacturing apparatus, scattering to other substrates, and short circuit can be prevented.

Hereinafter, embodiments of the present invention will be described in detail.
Embodiment 1 FIG.
FIG. 1 is a cross-sectional view showing the configuration of the high heat dissipation substrate 100 according to the first embodiment. As shown in FIG. 1, in the high heat dissipation substrate 100, insulating layers 50a and 50b are respectively formed on both front and back surfaces of a CFRP plate 1 as a CFRP core layer, and circuit layers 51a are respectively formed on the surfaces of the insulating layers 50a and 50b. , 51b are formed.

  The insulating layers 50a and 50b are configured by sequentially stacking prepregs 2a and 2b, glass cloths 3a and 3b, and prepregs 4a and 4b, respectively. The circuit layers 51a and 51b have a structure in which prepregs 5a and 5b and prepregs 6a and 6b are sequentially stacked. The prepregs 6a and 6b have wiring patterns 7a, 7b, Wiring layers 7c and 7d are formed inside.

  The CFRP plate 1 is provided with a through hole 1a, and the hole wall surface and the periphery of the through hole 1a are covered with a metal film as a protective film. Here, the copper film 8 was used as the metal film. Further, a through hole 9 penetrating the high heat dissipation substrate 100 is provided so as to pass through the center of the through hole 1a.

  The through hole 9 connects the respective wiring layers 7a, 7b, 7c, and 7d formed in the circuit layers 51a and 51b by the wiring layer 7e, and is electrically connected. The diameter of the through hole 9 is smaller than that of the through hole 1a, and the surface of the CFRP plate 1 and the surface covered with the copper film 8 are electrically insulated by the hole filling resin portion 2c filled with the prepregs 2a and 2b. Yes.

  As long as the CFRP plate 1 is a composite material composed of carbon fiber and resin, the carbon fiber content, structure (unidirectional material, cloth material) and the like are not particularly limited, but the thermal conductivity is 500 W / m. -If a prepreg made of K carbon fiber (cross material) is used, a core material that is lighter than aluminum while having the same heat dissipation as aluminum can be obtained.

  The prepregs 2a and 2b, the hole filling portion 2c, and the prepregs 4a and 4b use a thermosetting resin containing an inorganic filler and an elastomer. As the prepregs 5a and 5b and the prepregs 6a and 6b, prepregs in which a glass cloth is impregnated with a thermosetting resin are used.

  Examples of the inorganic filler include alumina, silica, magnesia, aluminum nitride, boron nitride, and silicon nitride, and at least one is used. Examples of the elastomer include CTBN (Carboxy-terminated butadiene-acrylonitrile), ATBN (Amine-terminated buta-ylene) and the like from the viewpoint of compatibility. Examples of the thermosetting resin include epoxy, bismaleimide, cyanate ester, and polyimide.

  Next, a manufacturing method will be described. 2 to 4 are cross-sectional views showing manufacturing steps of the high heat dissipation substrate 100 in the first embodiment. FIGS. 2A to 2D are steps for coating the copper film 8, FIGS. 3A to 3D are steps for forming the insulating layers 50a and 50b, and FIGS. 4A to 4D are circuit layers 51a. , 51b are shown.

  First, in the coating process of the copper film 8, as shown in FIG. 2A, a CFRP plate 1 that is copper-clad on both sides is prepared, and soft etching is performed to reduce the thickness of the copper film 8. Next, as shown in FIG. 2B, a through hole 1a is formed. Subsequently, as shown in FIG. 2C, copper plating is performed on the front surface of the CFRP plate 1 to form an inner wall portion 8a of the copper film on the hole wall surface of the through hole 1a. Further, as shown in FIG. 2D, the copper film 8 is patterned to form lands 8b.

  Next, in the formation process of the insulating layers 50a and 50b, first, as shown in FIG. 3A, resin sheets 52a and 52b in which release films 10a and 10b are respectively attached to one side of the prepregs 2a and 2b are prepared. The prepregs 2a and 2b are arranged so that the exposed surfaces of the CFRP plate 1 on which the inner wall 8a and the land 8b are formed overlap each other. The prepregs 2a and 2b are used in a semi-cured state (B stage). For the release film, for example, a PET (polyethylene terephthalate) film is used.

  Subsequently, the resin sheets 52a and 52b arranged in this way are heated and pressurized in a vacuum state. As shown in FIG. 3B, the prepregs 2a and 2b are melted, the through holes 1a are filled without voids or dents, and the CFRP plate 1 is laminated. After lamination, the release films 10a and 10b are peeled off.

  Next, as shown in FIG. 2 (c), resin sheets 53a and 53b having release films 11a and 11b attached to one side of the prepregs 4a and 4b are prepared, and the CFRP plate 1 laminated with the prepregs 2a and 2b. The glass cloths 3a and 3b are respectively sandwiched between the front and back surfaces of the glass cloth 3a and 3b so that the exposed surfaces of the prepregs 4a and 4b overlap the glass cloths 3a and 3b, respectively. The prepregs 4a and 4b are used in a semi-cured state (B stage).

  Subsequently, the resin sheets 53a and 53b arranged in this way are heated and pressurized in a vacuum state. As shown in FIG. 2E, the prepregs 4a and 4b and the prepregs 2a and 2b are melted, and the prepreg 2a and the prepreg 4a, and the prepregs 2b and 4b are laminated with the glass cloths 3a and 3b interposed therebetween, respectively. Further, heating and pressurization is continued to completely cure the prepregs 2a, 2b, 4a, and 4b, whereby the insulating layers 50a and 50b are formed on the CFRP plate 1.

  Next, in the step of forming the circuit layers 51a and 51b, first, as shown in FIG. 4A, the release films 11a and 11b are peeled off from the CFRP plate 1 on which the insulating layers 50a and 50b are formed. Next, as shown in FIG. 4B, prepregs 6a and 6b on which wiring layers 7a and 7c and wiring layers 7b and 7d are formed are prepared, and prepregs 5a and 5b are formed on both surfaces of the insulating layers 50a and 50b. The prepregs 5a and 5b are arranged so that the surfaces of the prepregs 6a and 6b on which the wiring layers 7c and 7d are formed overlap each other.

  The prepregs 5a and 5b are each in a semi-cured state (B stage). The prepregs 6a and 6b are formed by laminating copper foils on both sides and completely curing, and then forming wiring layers 7c and 7d in a predetermined pattern only on one side. Here, as the prepregs 5a, 5b, 6a, and 6b, ordinary prepregs in which a glass cloth was impregnated with a thermosetting resin were used.

  Subsequently, the prepregs 6a and 6b arranged in this way are heated and pressurized in a vacuum state. As shown in FIG. 4C, the prepregs 5a and 5b are melted, and the prepregs 6a and 6b are bonded to both surfaces of the insulating layers 50a and 50b while filling the steps with the respective wiring layers 7c and 7d. Further, heating and pressurization are continued to completely cure the prepregs 5a, 5b, 6a, and 6b, whereby circuit layers 51a and 51b are formed on both surfaces of the insulating layers 50a and 50b.

  Next, as shown in FIG. 4D, a through hole 9a for the through hole 9 having a smaller diameter than the through hole 1a is provided coaxially with the through hole 1a filled with the prepregs 2a and 2b. After the through-hole 9 is formed by performing copper plating on the inner wall surface of the through-hole 9a, predetermined patterning is performed on the wiring layers 7a and 7b, and soldering by external processing, solder resist coating, and gas leveler processing is performed as subsequent processes. By performing the coating, a high heat dissipation substrate as shown in FIG. 1 is obtained.

  As described above, in the first embodiment, by covering the hole wall surface of the through hole 1a provided in the CFRP plate 1 with the copper film 8, it is possible to prevent the generation of carbon powder, and between the CFRP plate and the through hole. Therefore, the insulation reliability can be improved. Moreover, mixing of carbon powder into the substrate manufacturing apparatus, scattering to other substrates, and short circuit can be prevented.

  Further, by providing the land 8b in the through hole 1a, the hole provided in the CFRP plate can be easily recognized as the reference hole by X-ray, and the through hole and the CFRP plate can be prevented from being short-circuited.

  In the first embodiment, the hole wall surface of the through hole provided in the CFRP plate 1 is covered with the copper film, but at the position where the counterbore portion 12 is provided as the heat dissipation hole of the CFRP plate 1 as shown in FIG. A copper film 8c may be provided.

  In this case, when forming the counterbore, if laser processing is used, the counterbore can be stopped by the copper film 6c, and unlike mechanical processing such as milling, the generation of carbon powder is prevented without damaging the CFRP plate 1. be able to.

Embodiment 2. FIG.
In the high heat dissipation substrate of the first embodiment, the copper film 8 is used as the protective film, but in the second embodiment, a case where a resin film is used will be described.

  FIG. 6 is a cross-sectional view showing the configuration of the high heat dissipation substrate 102 in the second embodiment. As shown in FIG. 6, in the high heat dissipation substrate 102, the hole wall surface and the periphery of the through hole 1 a of the CFRP plate 1 are covered with a resin film 13 as a protective film. Other configurations are the same as those in the first embodiment, and the same reference numerals as those in FIG.

  FIG. 7 is a cross-sectional view showing a manufacturing process of the high heat dissipation substrate 102 in the second embodiment. 7A to 7D show the coating process of the resin film 13. As shown in FIG. 7A, a CFRP plate 1 is prepared, and then a through hole 1a is formed as shown in FIG. 7B.

  Subsequently, as shown in FIG. 7 (c), an uncured thermosetting resin diluted with a solvent is applied to the CFRP plate 1 in which the through holes 1a are formed, and then cured, whereby the front and back sides of the CFRP plate 1 are obtained. The resin film 13 is formed on both sides and the hole wall surface of the through hole 1a. Other manufacturing steps are the same as those in the first embodiment, and the description thereof is omitted.

  As described above, in the second embodiment, the hole wall surface of the through hole 1a provided in the CFRP plate 1 is covered with the resin film 13, thereby not only preventing the generation of carbon powder but also forming a protective film. Even so, the increase in weight can be kept to a minimum.

  In the present embodiment, the insulating layers 50a and 50b are formed by laminating a glass cloth with a prepreg containing an inorganic filler and an elastomer, but the normal layers used when forming the circuit layers 51a and 51b are used. Alternatively, the prepregs 5a and 5b which are prepregs may be used.

  As shown in FIG. 8, the prepregs 5a and 5b cover the CFRP plate 1 by filling the through holes 1a with the hole filling resin portion 2c, insulate the through holes 9 and the CFRP plate 1, and adhere the prepregs 6a and 6b. In this case, the formation process of the insulating layers 50a and 50b can be omitted, and the manufacturing process can be simplified.

  Next, examples of the present invention will be shown and described in more detail. In addition, the evaluation used in the Example and the measurement of the physical property were performed by the method shown below.

(1) Insulation resistance A high heat dissipation substrate having a counterbore part 12 is prepared, and an insulation resistance measurement device (Moving Probe Tester EMMA880, manufactured by Microcraft) is used to measure the insulation resistance between the CFRP plate 1 and the through hole 9 from the counterbore part 12. Measured with The criteria for determination was acceptable if the applied voltage was 250 V and the insulation resistance was 65 MΩ or more.

(2) Cross-sectional observation After implementing the heat cycle test of the produced high heat dissipation board | substrate, the cross section was observed with the microscope and through-hole reliability, adhesiveness, hole filling property, etc. were evaluated visually. The heat cycle test was allowed to stand at −65 ° C. for 15 minutes, then left at 125 ° C. for 15 minutes, and this was repeated for 500 cycles.

Example 1
First, a CFRP plate 1 (thickness 0.5 mm, size 405 mm × 340 mm) in which carbon fibers (cross material) with a thermal conductivity of 500 W / m · K are laminated and copper-coated on both sides is prepared, and the surface of the CFRP plate 1 is softened. Etching was performed to reduce the thickness of the copper film 8 to about 6 μm (see FIG. 2A).

  Next, a through hole 1a having a diameter of 1.5 mm was provided in the CFRP plate 1 by a drill (see FIG. 2B). Subsequently, copper plating was performed to form a copper film of about 10 μm on the wall surface of the through hole 1 a and about 15 μm on both surfaces of the CFRP plate 1 (see FIG. 2C). Next, patterning was performed to form a land 8b having an outer diameter of 1.8 mm (see FIG. 2D).

  Next, resin sheets 52a and 52b made of prepregs 2a and 2b and release films 10a and 10b, and resin sheets 52a and 52b made of prepregs 4a and 4b and release films 11a and 11b were prepared. The resin sheets 52a and 52b are made of an epoxy resin in a semi-cured state (B stage) in which an alumina filler and CTBN (Carboxy-terminated butadiene-acrylonitrile) are mixed, and those having a thermal conductivity of 3 W / m · K are used. Alumina filler having a particle size of 0.1 to 50 μm was used, and prepregs 2a and 2b and prepregs 4a and 4b were made of semi-cured epoxy resin (B stage) having thicknesses of 240 μm and 120 μm, respectively.

Next, resin sheets 52a and 52b were placed on the CFRP plate 1 on which the lands 8b and the inner wall portion 8a were formed (see FIG. 3A), and the prepregs 2a and 2b were vacuum-laminated (see FIG. 3B). In this vacuum lamination, vacuuming was performed at 150 ° C. for 1 minute, and then heating and pressing were further performed at 10 kg / cm ² for 2 minutes.

Next, the release films 10a and 10b are peeled off, the resin sheets 52a and 52b are arranged with the glass cloths 3a and 3b having a thickness of 55 μm interposed therebetween (see FIG. 3C), and the prepregs 4a and 4b are vacuum-laminated ( (Refer FIG.3 (d)). In this vacuum lamination, vacuuming was performed at 150 ° C. for 20 seconds, followed by further heating and pressing at 10 kg / cm ² for 20 seconds. Subsequently, the temperature was raised at a rate of temperature rise of 3 ° C./min, and heat-pressed at 190 ° C. and 30 kg / cm ² for 1 hour to obtain completely cured insulating layers 50a and 50b.

Next, the CFRP plate 1 on which the insulating layers 50a and 50b are formed (see FIG. 4A) is sandwiched between the prepregs 5a and 5b in a semi-cured state (B stage) having a thickness of 60 μm, and the thickness is 70 μm. , 7c and prepregs 6a and 6b having a thickness of 200 μm provided with wiring layers 7b and 7d (see FIG. 4B), the temperature is raised at a rate of temperature rise of 3 ° C./min, 180 ° C., 30 kg / cm ^By heating and pressing at ² for 1 hour to laminate, fully cured circuit layers 51a and 51b were obtained (see FIG. 4C). As the prepregs 5a, 5b, 6a, and 6b, ordinary prepregs in which a glass cloth was impregnated with an epoxy resin were used.

  Next, a through hole 9a for a through hole 9 having a diameter of 0.9 mm was provided coaxially with the through hole 1a in the CFRP plate 1 formed up to the circuit layers 51a and 51b (see FIG. 4D). Subsequently, the inner wall surface of the through-hole 9a is plated with copper to form the through-hole 9, and then the wiring layers 7a and 7b are subjected to predetermined patterning, and as subsequent processes, external processing, solder resist coating, gas leveler processing A high heat dissipation substrate was obtained by performing solder coating according to (see FIG. 1).

  When the insulation test between the CFRP plate 1 and the through hole 9 was performed on the obtained high heat dissipation substrate, an insulation resistance of 65 MΩ or more was obtained at 250V. Further, when the cross section of the obtained high heat dissipation substrate was observed, no abnormality such as peeling or cracking was observed. Moreover, although the cross-sectional observation was performed after implementing the heat cycle test of a high thermal radiation board | substrate, abnormality was not seen especially.

Example 2
First, a CFRP plate 1 (thickness 0.5 mm, size 405 mm × 340 mm) laminated with carbon fibers (cross material) having a thermal conductivity of 500 W / m · K is prepared (see FIG. 7A), and the diameter is measured by a drill. A 1.5 mm through hole 1a was provided (see FIG. 7B).

  Next, about 10 μm of uncured epoxy resin diluted with methyl ethyl ketone was applied to both the front and back surfaces of the CFRP plate 1 and the wall surface of the through hole 1a, dried at 50 ° C., and then cured by heating at 180 ° C. for 1 hour (see FIG. 7 (c)).

  The insulating layers 50a and 50b, the circuit layers 51a and 51b, and the post-process were formed using the same method as in Example 1 to obtain a high heat dissipation substrate (see FIG. 6).

  When the insulation test between the CFRP plate 1 and the through hole 9 was performed on the obtained high heat dissipation substrate, an insulation resistance of 65 MΩ or more was obtained at 250V. Further, when the cross section of the obtained high heat dissipation substrate was observed, no abnormality such as peeling or cracking was observed. Moreover, although the cross-sectional observation was performed after implementing the heat cycle test of a high thermal radiation board | substrate, abnormality was not seen especially.

It is sectional drawing which shows the structure of Embodiment 1 of the high thermal radiation board | substrate which concerns on this invention. It is process drawing which shows the manufacturing method of Embodiment 1 of the high thermal radiation board | substrate which concerns on this invention. It is process drawing which shows the manufacturing method of Embodiment 1 of the high thermal radiation board | substrate which concerns on this invention. It is process drawing which shows the manufacturing method of Embodiment 1 of the high thermal radiation board | substrate which concerns on this invention. It is sectional drawing which shows other embodiment of Embodiment 1 of the high thermal radiation board | substrate which concerns on this invention. It is sectional drawing which shows the structure of Embodiment 2 of the high thermal radiation board | substrate which concerns on this invention. It is process drawing which shows the manufacturing method of Embodiment 2 of the high thermal radiation board | substrate which concerns on this invention. It is sectional drawing which shows the structure of other embodiment of the high thermal radiation board | substrate which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 CFRP board 1a Through-hole 2a, 2b, 2c, 4a, 4b, Prepreg 3a, 3b Glass cloth 5a, 5b, 6a, 6b Prepreg including glass cloth 7a, 7b, 7c, 7d, 7e Wiring layer 8, 8c Copper film 8a Inner wall portion 8b Land 9 Through hole 12 Counterbore portion 13 Resin films 100, 101, 102, 103 High heat dissipation substrate

Claims (7)

  A CFRP core layer provided with a through hole, a protective film covering both surfaces of the CFRP core layer and the inner wall of the through hole, and both surfaces of the CFRP core layer covered with the protective film and an inner wall of the through hole A high heat dissipation substrate comprising a covering prepreg layer, wiring provided on both surfaces of the prepreg layer, and a through hole that conducts the wiring through an inner wall surface of the prepreg layer covering the through hole.   The high heat dissipation substrate according to claim 1, wherein the protective film is made of copper.   The high heat dissipation substrate according to claim 1, wherein the protective film is made of a resin.   The high heat dissipation substrate according to claim 2, wherein the protective film is provided in a predetermined pattern.   The high heat dissipation substrate according to claim 4, further comprising a counterbore part, and a protective layer provided on a surface of the CFRP core layer of the counterbore part.   A method for manufacturing a high heat dissipation substrate, comprising: forming a protective film on both surfaces of a CFRP core layer provided with a through hole and on an inner wall of the through hole.   Furthermore, the manufacturing method of the high thermal radiation board | substrate of Claim 6 which has the process of forming a protective film in a predetermined pattern.

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