JP4326366B2 - Metal base circuit board - Google Patents

Description

The present invention relates to a metal base circuit board suitable for use in a hybrid integrated circuit in which an output semiconductor and a control semiconductor are mounted together.

A circuit for mounting highly exothermic electronic components because a metal base circuit board with an insulating layer made of an epoxy resin filled with an inorganic filler on a metal plate and a circuit on it is excellent in heat dissipation. Used as a substrate.

Regarding circuit boards on which hybrid integrated circuits are mounted, semiconductor elements for output and the like are miniaturized due to the high integration of semiconductor elements, and in addition to various types of semiconductor elements, resistor chips and the like are also provided on the same substrate. The method of mounting has become mainstream. Since the required substrate characteristics are different for each semiconductor element and electronic component, a circuit board having characteristics partially corresponding to each semiconductor element and electronic component is required.

For this reason, for example, a circuit board in which different types of insulating layers are combined has been proposed as disclosed in Patent Document 1. However, in such a composite insulating substrate, the manufacturing process thereof is complicated, and thus the cost is increased, and it is not technically easy to combine different insulating layers in a small area in a complicated manner. There has been a problem that a significant reduction in size cannot be achieved.
JP-A-6-90071.

Usually, in a hybrid integrated circuit using a metal base circuit board, an output semiconductor and a control semiconductor for controlling the operation of the output semiconductor are both mounted on the circuit of the metal base circuit board. As the characteristics required for the substrate, the former requires slightly higher capacitance but excellent thermal conductivity, and the latter requires extremely low capacitance even at the expense of thermal conductivity. Is done.

However, when the control semiconductor is placed on a circuit designed to have a very low capacitance, in some cases, the supplementary heat dissipation from the control semiconductor is not sufficient, and sufficient operating time can be secured. It turns out that there may not be.

As a result of various studies to solve the above problems, the present inventor has sufficiently provided heat from the control semiconductor when providing a low dielectric constant portion at least below the circuit portion that is directly electrically connected to the control semiconductor. The inventor has obtained the knowledge that a hybrid integrated circuit that can dissipate, has excellent noise characteristics, and can sufficiently handle high-frequency operation is obtained.

That is, the present invention makes it possible to mount various types of semiconductor elements and electronic components by partially changing the substrate characteristics on the same circuit board. An object of the present invention is to provide a metal base circuit board suitable for a hybrid integrated circuit having an output semiconductor.

The present invention is used for a hybrid integrated circuit including a metal plate, an insulating layer provided on the metal plate, a circuit provided on the insulating layer, and a plurality of semiconductors mounted on the circuit. a metal base circuit board, some of the semiconductor mounting is not a portion of the circuit, only setting the low dielectric portion in the lower portion of the metal plate of the partial, yet low dielectric portion is, the surface of the metal plate a recess portion provided, a metal base circuit board characterized by being filled with a resin containing an inorganic filler in the recess portion, is favored properly, the inclination of the side wall of the recessed portion 35 to 65 ° The metal-based circuit board as described above.

In the present invention, the inorganic filler is made of fused silica , and the fused silica has an average particle size of 0.3 to 5.0 μm, 3.5 to 45.0% by volume, and an average particle size of 6 to The metal base circuit board is characterized by containing 18.0 to 80.0% by volume of 30 μm.

The metal base circuit board of the present invention is a metal base circuit board used in a hybrid integrated circuit having a plurality of semiconductors including a control semiconductor having a large amount of heat generation. By adopting the above structure, that is, a control semiconductor. The heat generated in the control semiconductor is immediately dissipated to the metal plate through the circuit and the insulation layer, while ensuring the operating characteristics of the control semiconductor by having a low dielectric part under the circuit directly connected to the circuit. Therefore, for example, it can be applied to hybrid integrated circuits such as high frequency filters such as macrostrip lines, high frequency power supplies, and digital amplifiers for audio, which could not be applied to conventional metal base circuit boards. Has the effect of being able to.

In addition to the above structure, the metal base circuit board of the present invention has a low dielectric portion having a specific shape, and a specific fused silica is used as an inorganic filler. Therefore, the semiconductor element can operate with high reliability, and the operation reliability of the hybrid integrated circuit can be improved.

Hereinafter, the present invention will be described with reference to the drawings.

FIG. 1 is an example of a hybrid integrated circuit using a metal base circuit board according to the present invention. In the hybrid integrated circuit, a plurality of semiconductors, that is, an output semiconductor 7 and a control semiconductor, are provided on the circuit 5 of a metal base circuit board including a metal plate 1, an insulating layer 2, and a circuit 5. 8 is installed. The output semiconductor 7 is often connected to the circuit 5 via a heat spreader 6 for the purpose of promoting heat dissipation, but this may not be used. In addition, the control semiconductor 8 is usually joined to the circuit 5 without using a heat spreader because it does not generate a large amount of heat. Further, in FIG. 1, a signal from the control semiconductor 8 is electrically joined to the output semiconductor 7 through the circuit 5 and the bonding wire 4. The present invention is characterized in that the low dielectric constant portion 3 is provided at least under a circuit directly electrically connected to the control semiconductor 8. By adopting such a structure, a conventional metal is provided. The present invention is characterized in that it can be applied to a hybrid integrated circuit for a purpose in which the base circuit board cannot be applied, the supplementary heat dissipation from the control semiconductor is insufficient, and the operation time cannot be sufficiently secured.

In the present invention, instead of the metal plate 1, a part of the metal plate 1 may be replaced with a material having a dielectric constant lower than that of the metal plate, and the material is not particularly limited. It is possible to obtain a conventionally known method for manufacturing a metal base circuit board without making a major process change, by providing a recess in the substrate and filling the recess with a resin containing an inorganic filler. Moreover, since it is easy to select a material having excellent bonding properties with the insulating layer 2 and the metal plate 1, it is particularly preferable.

Further, with respect to the recessed portion, it is preferable that the side wall thereof has an inclination of 35 to 65 ° according to the study of the present inventor. If the angle is less than 35 °, the area of the side wall portion becomes large, and it is necessary to sufficiently increase the recessed portion in order to ensure the capacitance. In the case where there is a corner with the bottom surface, a gap is likely to remain in the corner portion, and in any case, the electrical characteristics of the obtained metal base circuit board are likely to deteriorate. Furthermore, although it is not necessary to specifically define the bottom surface shape of the hollow portion, the flat shape is a mechanical method such as pressing or cutting, or a chemical as a method for forming the hollow on the metal plate. This is preferable because a manufacturing method excellent in mass productivity such as a chemical method such as etching can be applied.

Furthermore, as for the shape of the recess, when the metal base circuit board is viewed from above, the recess is wider than the circuit on which the control semiconductor is mounted and the circuit for transmitting a signal such as a high frequency when used as a hybrid integrated circuit. What is necessary is just to be large, and although thickness (depth) changes with materials of the insulating adhesive which forms an insulating layer, etc., it should usually be 50-800 micrometers. Further, the depth of the dent may vary depending on the individual dent, but it is preferable because all can be processed at the same depth.

Furthermore, in the present invention, the resin containing the inorganic filler that fills the hollow portion may be any resin having a low dielectric constant, but preferably has high thermal conductivity.

Examples of the inorganic filler include aluminum oxide, silicon oxide, aluminum nitride, boron nitride, etc. Among them, aluminum oxide, silicon oxide, boron nitride has a low dielectric constant portion with a good balance between low dielectric constant and high thermal conductivity. Since it is obtained, it is preferable. There are no particular restrictions on the shape of the constituent particles of the inorganic filler, but spherical particles are preferable for improving fluidity, and the use of an inorganic filler having cavities is more preferable because the dielectric constant of the low dielectric constant portion is further lowered. In particular, according to the results of the study of the present inventors, those having an average particle size of 0.3 to 5.0 μm are 3.5 to 45.0% by volume, and those having an average particle size of 6 to 30 μm are 18.0 to 80. The fused silica containing 0.0% by volume is excellent in high filling property, and as a result, a low dielectric constant portion having a good balance between low dielectric constant and high thermal conductivity can be obtained stably and reliably. preferable.

Regarding the resin, thermosetting resins such as epoxy resin, phenol resin, polyimide resin, various engineer plastics, thermoplastic resins such as polyethylene, polypropylene, vinylidene chloride, polyethylene terephthalate, ABS resin, AS resin, and acrylic resin Silicone resin, urethane resin, and the like can be used. Of these, it is preferable to use the same resin as the insulating layer, and epoxy resin is preferably used because of its good adhesion to the metal plate.

In the present invention, the metal plate may be any material as long as it has excellent thermal conductivity, but aluminum, aluminum alloy, copper and copper alloy have high thermal conductivity. Are preferably selected. Moreover, there is no restriction | limiting in particular as thickness of a metal plate, but 0.3 mm-4.0 mm are generally used.

In the present invention, the composition and characteristics of the insulating layer are also extremely important. The insulating layer is made of a resin containing an inorganic filler. Examples of the inorganic filler include alumina (aluminum oxide), boron nitride, magnesia (magnesium oxide), barium sulfate, zinc oxide, silica, silicon nitride, and aluminum nitride. An electrically insulating inorganic compound such as Alumina, Boron Nitride, Aluminum Nitride and Silica are preferably used because they are inexpensive and readily available. Among these, alumina and aluminum nitride are more preferably selected because they can be spherical and highly filled, and an insulating layer with extremely high thermal conductivity can be easily obtained.

Examples of the resin include thermosetting resins such as epoxy resins, phenol resins, polyimide resins, various engineer plastics, thermoplastic resins such as polyethylene, polypropylene, vinylidene chloride, polyethylene terephthalate, ABS resins, AS resins, acrylic resins, Silicone resin, urethane resin, fluororesin, and the like are used. In particular, epoxy resin is preferably selected because of its excellent bondability with a metal plate.

That is, in the present invention, regarding the combination of an inorganic filler and a resin, an epoxy resin containing at least one of alumina, boron nitride, aluminum nitride, and silica is used as a metal plate or a metal foil forming a circuit. This is a preferable combination because an insulating layer having a high adhesive force and having a high thermal conductivity after curing and an insulating layer having a small capacitance can be easily obtained. The same applies to the resin containing the inorganic filler constituting the low dielectric constant portion.

Generally, a roll coater, a gravure coater, a donation coater, screen printing, or the like is used as a method of applying a resin containing an uncured inorganic filler (hereinafter simply referred to as “insulating adhesive”) to a predetermined portion. be able to. Further, the insulating adhesive is a single layer or a plurality of layers. In the case of a plurality of layers, the cost is increased due to the length of the process, but there is a feature that the dielectric breakdown resistance is improved and the thickness accuracy of the insulating layer can be improved.

In the present invention, the material of the circuit and the metal foil for forming the circuit is any one of copper, aluminum, nickel, iron, tin, silver, titanium, an alloy containing two or more of these metals, or the above A clad foil using a metal or an alloy can be used. In addition, the method for producing the metal foil may be one produced by an electrolytic method or a rolling method, and metal plating such as Ni plating, Ni-Au plating, or solder plating may be applied on the metal foil. From the viewpoint of adhesiveness with the insulating adhesive, it is more preferable that the surface of the metal foil (circuit) on the side in contact with the insulating adhesive is roughened in advance by etching, plating, or the like.

Some of the circuits of the metal base circuit board of the present invention are in contact with a metal plate through an insulating layer, and others are in contact with the metal plate through an insulating layer and a low dielectric constant portion. When a hybrid integrated circuit is manufactured using the metal base circuit board of the present invention, a control electronic component such as a resistor chip and a capacitor chip is mounted on the latter circuit, so that signal distortion from the control semiconductor is reduced. In addition, by mounting an output semiconductor, control semiconductor, etc. on the former circuit, it is possible to prevent an excessive temperature rise of the semiconductor and a malfunction caused thereby, and as a result, hybrid integration The effect that a highly reliable operation can be ensured for the entire circuit can be obtained.

A thermosetting resist ink is applied to a desired position on an aluminum plate of 150 mm x 150 mm x 1.5 mm, etched to form a depth of 300 µm, and the inclination of the side wall of the depression is 43 °, and then the resist ink is removed. did.

Then, blended into bisphenol A type liquid epoxy resin (Japan Epoxy Resin, EP828) so as to contain 45% by volume of alumina (Nippon Light Metal Co., Ltd., LS-20) with an average particle size of 2 μm, and mixed to insulate Agent A was prepared.

Moreover, bisphenol A type liquid epoxy resin (Japan Epoxy Resin, EP828) fused spherical silica (FB-1SDX, manufactured by Denki Kagaku Kogyo Co., Ltd.) with an average particle size of 1.7 μm and an average particle size of 11.3. An insulating adhesive B was prepared by blending so as to contain 40% by volume of fused spherical silica (manufactured by Denki Kagaku Kogyo Co., Ltd., FB-550).

Insulating adhesive B was applied on the aluminum plate having the recesses, and then the insulating adhesive A was applied so that the insulating layer in a portion other than the recesses had a thickness of 50 μm. Further, a copper foil was laminated on the insulating adhesive A to obtain a metal base substrate.

With respect to the metal base substrate, a copper foil was etched by masking a desired position with an etching resist, and then the etching resist was removed, followed by washing and drying, thereby forming a circuit to obtain a metal base circuit substrate. When forming a circuit, a circuit is formed in which a resistor chip or a capacitor that is directly electrically connected from the control semiconductor is mounted at a position where the recess is present, and an output semiconductor or control is provided where there is no recess. A circuit for mounting semiconductors was formed.

About the metal base circuit board obtained by the said operation, the dielectric breakdown voltage and the electrostatic capacitance per unit area were measured. The breakdown voltage was measured according to JIS C2110. In measuring the electrostatic capacity per unit area, the electrostatic capacity at a measurement frequency of 1 MHz is obtained by an LCR meter, and the area of the measurement part in contact with the insulating adhesive is obtained. The capacitance was obtained by dividing by the circuit area. Table 1 shows main production conditions and measurement results of the metal base circuit board.

Next, a hybrid integrated circuit illustrated in FIG. 1 was prepared using the metal base circuit board. The hybrid integrated circuit is a digital amplifier equipped with a digital signal IC as a control semiconductor and a MOS-FET as an output semiconductor. When this hybrid integrated circuit was operated at an operating frequency of 1.2 MHz, it was confirmed that it operated normally.

(Comparative example) In Example 1, the same procedure as in Example 1 was used except that a flat aluminum plate having no depression was used, and that the insulating adhesive A was applied to the aluminum plate in a thickness of 50 μm. A metal base substrate and a metal base circuit board were produced. The measurement results of this metal base circuit board are also shown in Table 1. Further, a digital amplifier was manufactured in the same manner as in Example 1, and the operation was confirmed.

Since the metal base circuit board of the present invention has a small electrostatic capacity, a circuit portion suitable for mounting electronic components such as a resistor chip and a capacitor for controlling an output semiconductor, and a thermal conductivity having a slightly large electrostatic capacity. It has excellent circuit performance and a circuit portion suitable for mounting an output semiconductor and a control semiconductor that require heat dissipation, and can provide a hybrid integrated circuit with high operational reliability, which is very useful in the industry.

The figure which shows an example of the hybrid integrated circuit using the metal base circuit board of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Metal plate 2 Insulating layer 3 Low dielectric constant part 4 Bonding wire 5 Circuit 6 Heat spreader 7 Semiconductor for output 8 Semiconductor for control

Claims (3)

Metal base circuit board used for a hybrid integrated circuit comprising a metal plate, an insulating layer provided on the metal plate, a circuit provided on the insulating layer, and a plurality of semiconductors mounted on the circuit And, for a part of the circuit that is not a semiconductor mounting portion, a low dielectric constant portion is provided on a metal plate below the circuit portion , and the low dielectric constant portion has a depression on the surface of the metal plate. A metal-based circuit board, characterized in that the recess is filled with a resin containing an inorganic filler . Metal base circuit board according to claim 1, wherein the side wall of the recessed portion, characterized in that it has an inclination of 35 to 65 °. The inorganic filler is made of fused silica , and the fused silica has an average particle size of 0.3 to 5.0 μm, 3.5 to 45.0% by volume, and an average particle size of 6 to 30 μm. 3. The metal base circuit board according to claim 1, wherein the metal base circuit board contains 0 to 80.0% by volume.

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