JP2017028018A - Heat dissipation substrate, device and manufacturing method for heat dissipation substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat dissipation substrate excellent in heat dissipation as a result of reduction of warpage, and to provide a device including the heat dissipation substrate, and a manufacturing method for the heat dissipation substrate.SOLUTION: In a heat dissipation substrate including a base material mainly composed of aluminum or an aluminum alloy, and an insulating heat conduction layer laminated on one surface of the base material, the heat conduction layer includes an inorganic layer containing a binder mainly composed of phosphate glass, and the ratio of the maximum thickness of the inorganic layer to the maximum width is 0.6% or less. The average thickness of the inorganic layer is preferably 10-200 μm. Preferably, the inorganic layer further contains a filler mainly composed of alumina. The median size of the filler in the heat conduction layer is preferably 5-100 μm, and the content of the filler is preferably 30-65 mass%.SELECTED DRAWING: None

Description

  The present invention relates to a heat dissipation substrate, a device, and a heat dissipation component.

  In recent years, heat generated from electronic components has increased with the increase in power of electronic components. For example, in a high-brightness LED, a high temperature is locally generated, which causes a decrease in light emission efficiency, a change in light emission color, deterioration of the element, and the like. For this reason, it is required to efficiently dissipate this heat. In response to the above request, a coating film having insulating properties and thermal conductivity is formed on the surface of a substrate having excellent thermal conductivity by containing a binder and a filler, and the substrate side is brought into contact with a cooling material such as a cooling fin. In addition, a heat dissipation substrate that improves heat dissipation efficiency by bringing the coating side into contact with an electronic component or the like is widely known.

  Examples of the substrate include a ceramic substrate such as alumina and a metal substrate such as aluminum. Of these, alumina has a high thermal conductivity of 25 W / mK and excellent heat dissipation efficiency, but is expensive and inferior in workability and difficult to manufacture in a thin shape. On the other hand, the metal substrate is less expensive than alumina. In particular, aluminum is often used as such a base material because of its excellent thermal conductivity, light weight, and excellent workability.

  Moreover, as said film, it is requested | required that a binder and a filler are excellent in thermal conductivity, and the addition amount of a filler is enough much. In addition, when the average thickness of the film is large, the heat dissipation efficiency of the heat dissipation substrate may be reduced by the film. Therefore, it is necessary to reduce the average thickness of the film to such an extent that insulation can be ensured.

  As the binder, resins such as epoxy and polyimide are widely known. The thermal conductivity of such a resin is generally about 0.1 W / mk. Examples of the filler include silica, alumina, silicon nitride, and boron nitride. The thermal conductivity of this silica is about 1 W / mK, and the thermal conductivity of alumina is about 25 W / mK. Moreover, the thermal conductivity of silicon nitride and boron nitride is even higher. Since the thermal conductivity of these fillers is higher than the thermal conductivity of the binder, the thermal conductivity of the coating can be improved by mixing with a resin. Of these, alumina is often used because of its excellent thermal conductivity and low cost.

  Specific examples of such a heat dissipation board include, for example, a circuit board (see Japanese Patent Laid-Open No. 6-44824) in which a mixture of a bisphenol A type epoxy resin and an inorganic filler is laminated on a metal base, and an inorganic hollow powder. And a metal base circuit board (see JP 2009-129801 A) obtained by laminating an epoxy resin or the like to be laminated on a metal base material.

  However, since such a heat dissipation substrate uses an organic coating such as an epoxy resin, it has low heat resistance, and is not suitable for use in a high temperature environment exceeding 200 ° C., for example. Has a disadvantage that it is easy to pass water and is used for a long time in a humid environment, and the film is easily deteriorated by energizing and carbonizing the resin of the film.

  For this reason, a heat dissipation substrate has been devised in which a glassy inorganic layer such as enamel is laminated on a metal plate. Examples of such a heat radiating substrate include a heat radiating substrate in which a hollow layer is formed on the surface of a metal core (see Japanese Patent Application Laid-Open Nos. 1-110789 and 2006-344893).

  However, in the conventional heat dissipation substrate, since an inorganic layer such as enamel is formed by firing, the heat dissipation substrate warps due to a difference in thermal expansion coefficient between the metal substrate and the inorganic layer, shrinkage due to firing of the inorganic layer, or the like. Occurs. This warpage is particularly remarkable in a relatively soft aluminum substrate. As a result, it is difficult for the cooling material such as the cooling fins and the heating element such as the electronic component and the heat radiating board to be in close contact with each other.

  The above inconvenience can be solved by reducing the warpage of the heat dissipation substrate, but no indicator has been established as to how much the heat dissipation efficiency can be obtained by reducing the warpage. Therefore, excessive processing to reduce the warpage of the heat dissipation substrate increases the manufacturing cost of the heat dissipation substrate, and on the other hand, the heat dissipation efficiency becomes insufficient as a result of insufficient warpage reduction. .

JP-A-6-44824 JP 2009-129801 A Japanese Patent Laid-Open No. 1-110789 JP 2006-344893 A

  The present invention has been made on the basis of the above-described circumstances, and aims to provide a heat dissipation substrate that is excellent in heat dissipation as a result of reducing warpage, a device including the heat dissipation substrate, and a method for manufacturing the heat dissipation substrate. To do.

  The invention made in order to solve the above-mentioned problems is a heat dissipation board comprising a base material mainly composed of aluminum or an aluminum alloy, and a heat conductive layer that is laminated on one surface of the base material and has an insulating property. The heat conductive layer includes an inorganic layer containing a binder mainly composed of phosphate glass, and the ratio of the maximum thickness difference of the inorganic layer to the maximum width is 0.6% or less. It is a heat dissipation board.

  In the heat dissipation substrate, the base material and the heat conductive layer are excellent in thermal conductivity because the base material contains aluminum or a binder containing aluminum as a main component and the inorganic layer contains phosphate glass as a main component. Moreover, compared with the conventional heat conductive layer containing resin, it is excellent in the heat resistance of a heat conductive layer. Further, the ratio of the maximum thickness difference to the maximum width is used as an index representing the amount of warpage, and when this ratio is equal to or less than the above upper limit, the base material side of the heat dissipation substrate is brought into contact with the coolant, and the inorganic layer side is set to the electronic component. The heat transfer efficiency from the heat generating element to the heat radiating board and from the heat radiating board to the coolant can be effectively increased. As a result, it is possible to greatly improve the heat dissipation performance of the heat dissipation substrate by the necessary minimum warp reduction processing.

  The average thickness of the inorganic layer is preferably 10 μm or more and 200 μm or less. By setting the thickness of the inorganic layer within the above range, both the thermal conductivity and the insulating property of the inorganic layer can be made high.

  The inorganic layer may contain a filler mainly composed of alumina. Thus, high thermal conductivity and cost reduction can be made compatible by containing the filler which has an inorganic substance as a main component containing an alumina. Moreover, since alumina is excellent in adhesiveness with phosphate glass, the strength of the inorganic layer can be improved.

  The median diameter of the heat conductive filler is preferably 5 μm to 100 μm, and the content ratio of the heat conductive filler in the inorganic layer is preferably 30% by mass to 65% by mass. Thus, the thermal conductivity and intensity | strength of an inorganic substance layer can be made compatible easily by making the average particle diameter and content rate of the said heat conductive filler into the said range.

  It is preferable to further include a coating layer which is laminated on one surface of the inorganic layer and mainly contains silicon oxide, silicon nitride, epoxy resin, or acrylic resin. Thus, when the said heat dissipation board is provided with the said coating layer, the unevenness | corrugation in an inorganic material layer is filled, and the uniformity of the surface of the said heat dissipation board improves. As a result, the insulating property of the heat dissipation substrate is improved.

  Another invention made to solve the above problems is a device including the heat dissipation substrate.

  Since the device includes the heat dissipation substrate, the device has excellent heat dissipation.

  Yet another invention made to solve the above problems is a heat dissipation comprising a base material mainly composed of aluminum or an aluminum alloy, and a thermally conductive layer laminated on one surface of the base material and having an insulating property. A method for producing a substrate, comprising: a step of coating and baking an inorganic layer composition containing binder particles mainly composed of phosphate glass on one surface of the base material, The ratio of the maximum thickness difference of the inorganic layer formed after the firing step to the maximum width is 0.6% or less.

  According to the manufacturing method, it is possible to easily and reliably obtain a heat dissipation substrate in which the ratio of the maximum thickness difference to the maximum width is 0.6% or less.

Here, the “main component” means that which is the most abundant component (for example, 50% by mass or more) on a mass basis. “Maximum width” means the longest axis when the heat dissipation substrate is circular or elliptical in plan view, and the longest diagonal line when the base material or heat dissipation substrate is polygonal in plan view. “Maximum thickness difference” means a difference in thickness between the thickest part and the thinnest part. The “ratio of the maximum thickness difference to the maximum width” is the following formula when the maximum width of the heat dissipation board is L (mm), the maximum thickness difference is X (mm), and the relative warpage is B (%): This is a value obtained based on 1). The “median diameter” means a particle diameter at which the volume integrated value is 50% in the particle size distribution obtained by the laser diffraction scattering method.
B = (X / L) × 100 (1)

  As described above, the heat dissipation substrate of the present invention is excellent in heat dissipation efficiency as a result of reducing warpage. Moreover, since the device of this invention is equipped with the said thermal radiation board | substrate, it is excellent in thermal radiation efficiency. Furthermore, the method for manufacturing a heat dissipation board of the present invention can easily and reliably obtain the heat dissipation board. Therefore, the heat dissipation board and the heat dissipation component can be suitably used for electronic components that are becoming smaller.

  Hereinafter, the manufacturing method of the heat sink, the device, and the heat sink according to the present invention will be described.

[Heat dissipation board]
The said heat dissipation board is mainly provided with the base material and the heat conductive layer laminated | stacked on one surface of this base material, and having insulation.

<Base material>
A base material has aluminum or an aluminum alloy as a main component, and a heat conductive layer is laminated on one surface.

  When the main component of the base material is an aluminum alloy, the magnesium content in the aluminum alloy is preferably small. Specifically, an aluminum alloy other than the 5000s or 6000s specified in JIS-H4000 (2014) is preferable. Thus, peeling of the inorganic layer from the base material can be reduced by using an aluminum alloy having a low magnesium content as the base material.

  Moreover, as this aluminum or aluminum alloy, 3000 series aluminum alloy prescribed | regulated to JIS-H4000 (2014) is more preferable.

  Further, the base material may further contain, for example, copper, iron, an alloy thereof other than aluminum and aluminum alloy. Here, the thermal conductivity of aluminum is about 200 to 250 W / mK, the thermal conductivity of copper is about 350 to 400 W / mK, and the thermal conductivity of iron is about 80 W / mK. Therefore, the thermal conductivity of the substrate can be improved by adding copper. Moreover, since copper and iron are harder than aluminum, the strength of the base material can be improved by adding copper, iron, or an alloy thereof.

  As a minimum of the average thickness of a substrate, 0.1 mm is preferred and 0.5 mm is more preferred. On the other hand, the upper limit of the average thickness is preferably 5 mm, and more preferably 4 mm. When the average thickness is smaller than the lower limit, the strength of the heat dissipation substrate may be reduced. On the other hand, when the average thickness exceeds the upper limit, it may be difficult to use the heat dissipation board in a downsized electronic device.

<Heat conduction layer>
A heat conductive layer is directly laminated | stacked on one surface of a base material, and is mainly equipped with an inorganic substance layer. The heat conductive layer may further include a coating layer.

  The heat conductive layer may be laminated on only one surface of the base material, or may be laminated on both surfaces, but is preferably laminated only on one surface. Usually, aluminum has better thermal conductivity than phosphate glass. Therefore, the heat dissipation efficiency of the heat dissipation board is further improved by bringing the surface of the heat dissipation board on which the heat conductive layer is not laminated into contact with the coolant.

(Inorganic layer)
The inorganic layer is a layer directly laminated on one surface of the substrate, and contains a binder mainly composed of phosphate glass. This inorganic layer can provide insulation to the heat dissipation substrate. The inorganic layer may further contain a filler mainly composed of alumina.

  As a minimum of the average thickness of an inorganic layer, 10 micrometers is preferred, 20 micrometers is more preferred, 30 micrometers is still more preferred, and 50 micrometers is especially preferred. On the other hand, the upper limit of the average thickness is preferably 500 μm, more preferably 400 μm, further preferably 300 μm, and particularly preferably 250 μm. When the average thickness is smaller than the lower limit, defects such as pinholes in the inorganic layer are likely to occur, and the insulating properties of the inorganic layer may be reduced. On the other hand, when the average thickness exceeds the upper limit, the thermal resistance of the inorganic layer increases, and the heat dissipation property of the heat dissipation substrate may be reduced.

  Moreover, when the inorganic layer contains a filler described later, the average thickness of the inorganic layer is preferably 1.5 times or more and 10 times or less the median diameter of the filler. As described above, by setting the average thickness of the inorganic layer and the median diameter of the filler in the above range, both the insulating property and the thermal conductivity of the inorganic layer can be achieved at a high level.

(binder)
A binder has phosphate glass as a main component. Moreover, when the inorganic layer contains a filler to be described later, the filler voids are filled.

  This phosphate glass preferably has a lower melting point than the metal that is the main component of the substrate. Thus, an inorganic substance layer can be easily formed by the method mentioned later because the melting point of phosphate glass is lower than the melting point of the metal. Specifically, for example, when the main component of the substrate is aluminum, the melting point of aluminum is about 660 ° C., and therefore the melting point of phosphate glass is preferably 450 ° C. or higher and 580 ° C. or lower.

  Further, this phosphate glass generally has a higher thermal conductivity than an epoxy resin or the like. For this reason, the inorganic layer is excellent in heat dissipation efficiency as compared with the resin layer of the conventional heat dissipation substrate. Specifically, the thermal conductivity of a general resin is about 0.1 W / mK, and the thermal conductivity of phosphate glass is about 1.0 W / mK.

(Filler)
The filler is dispersed in the inorganic layer and improves the thermal conductivity in the inorganic layer. If each particle of the filler is dispersed in the inorganic layer without coming into contact with other particles, the thermal conductivity of the inorganic layer may be difficult to improve. Therefore, the particles of the filler are in contact with each other. It is preferable.

  The filler contains alumina as a main component. Thus, the filler cost can be reduced because the main component of the filler is alumina. Moreover, the thermal conductivity of an inorganic layer improves because the main component of a filler is an alumina, and also the intensity | strength of an inorganic layer improves due to the adhesive improvement of a binder and a filler.

  The filler may further contain amorphous silicon oxide, crystalline silicon dioxide, aluminum nitride, silicon nitride and the like in addition to alumina.

  Moreover, as a filler, a thing with higher heat conductivity than the said binder is preferable. When the thermal conductivity of the filler is equal to or lower than that of the binder, the thermal conductivity of the inorganic layer is not improved even if the filler is added.

  The lower limit of the median diameter of the filler is preferably 5 μm and more preferably 10 μm. On the other hand, the upper limit of the median diameter is preferably 100 μm, more preferably 50 μm, and even more preferably 30 μm. When the median diameter is smaller than the lower limit, it is difficult for the filler particles to come into contact with each other, and it is difficult to improve the thermal conductivity of the inorganic layer. On the contrary, when the median diameter exceeds the upper limit, it may be difficult to form the inorganic layer by a coating method described later, or the inorganic layer may be excessively thick.

  As a minimum of the content rate of the above-mentioned filler in the above-mentioned inorganic layer, 30 mass% is preferred, 35 mass% is more preferred, and 40 mass% is still more preferred. On the other hand, as an upper limit of the said content rate, 85 mass% is preferable, 80 mass% is more preferable, and 75 mass% is further more preferable. When the said content rate is smaller than the said minimum, there exists a possibility that the heat conductivity of an inorganic substance layer may become difficult to improve. On the other hand, if the content ratio exceeds the upper limit, it may be difficult to form the inorganic layer due to the low adhesion between the fillers.

<Coating layer>
The coating layer is laminated on one surface of the inorganic layer, and fills the unevenness of the inorganic layer caused by the filler, thereby improving the uniformity of the thickness of the inorganic layer, and as a result, improves the insulation of the heat dissipation substrate.

  In addition, the heat dissipation substrate is usually used by bringing the surface on the inorganic layer side into contact with a heating element such as an electronic device and the surface on the base material side in contact with a coolant. In this case, the outermost surface of the inorganic layer is directly exposed to a high-temperature heating element, the temperature decreases toward the substrate side of the inorganic layer, and the temperature becomes the lowest on the contact side of the substrate with the coolant. As described above, the highest temperature in the heat dissipation substrate is in the vicinity of the outermost surface on the inorganic layer side. Therefore, by forming the coating layer on the outermost surface of the inorganic layer, the coating layer with high heat resistance becomes the inorganic layer. The outermost surface is covered, and the heat resistance of the heat dissipation substrate is improved.

  In addition, the phosphate glass, which is the main component of the binder in the inorganic layer, is slightly inferior in water resistance, and there is a possibility that an alkali component flows out from the phosphate glass, but the coating layer covers the inorganic layer, The outflow of this alkali component can be suppressed.

  Examples of the main component of the coating layer include silicon oxide, silicon nitride, epoxy resin, and acrylic resin. Among these, silicon oxide and silicon nitride are preferable, and amorphous silicon oxide and silicon nitride having a polysilazane structure are more preferable.

  The lower limit of the average thickness of the coating layer is preferably 0.5 μm, more preferably 5 μm, and even more preferably 10 μm. On the other hand, the upper limit of the average thickness is preferably 50 μm, more preferably 40 μm, still more preferably 35 μm, and particularly preferably 30 μm. When the average thickness is smaller than the lower limit, the voids in the inorganic layer are not sufficiently filled, and the insulating property of the heat dissipation substrate may be insufficient. On the other hand, when the average thickness exceeds the upper limit, the coating layer functions as a heat insulating layer, and there is a possibility that the heat dissipation property of the heat dissipation substrate is lowered, or that the coating layer is cracked.

  The upper limit of the ratio of the maximum thickness difference of the inorganic layer to the maximum width of the heat dissipation substrate is 0.6%, preferably 0.4%, more preferably 0.35%, and further preferably 0.25%. . When the said ratio exceeds the said upper limit, there exists a possibility that the adhesiveness of the said heat sink and a heat generating body and a coolant may fall, and it becomes difficult to improve the heat dissipation of the said heat sink.

  The lower limit of the maximum width is preferably 1.5 cm, and more preferably 2 cm. On the other hand, the upper limit of the maximum width is preferably 30 cm, more preferably 25 cm, and even more preferably 20 cm. If the maximum width is smaller than the lower limit, the heat dissipation substrate may be excessively small, and heat dissipation may be difficult to improve. On the other hand, if the maximum width exceeds the upper limit, the absolute value of warpage of the heat radiating substrate is increased, and there is a possibility that the contact area with the heating element and the coolant is difficult to increase.

<Advantages>
In the heat dissipation substrate, the base material and the heat conductive layer are excellent in thermal conductivity because the base material contains aluminum or a binder containing aluminum as a main component and the inorganic layer contains phosphate glass as a main component. Moreover, compared with the conventional heat conductive layer containing resin, it is excellent in the heat resistance of a heat conductive layer. Further, the ratio of the maximum thickness difference to the maximum width is used as an index representing the amount of warpage, and when this ratio is equal to or less than the above upper limit, the base material side of the heat dissipation substrate is brought into contact with the coolant, and the inorganic layer side is set to the electronic component. The heat transfer efficiency from the heat generating element to the heat radiating board and from the heat radiating board to the coolant can be effectively increased. As a result, it is possible to greatly improve the heat dissipation performance of the heat dissipation substrate by the necessary minimum warp reduction processing.

[device]
The device includes the heat dissipation substrate. Specifically, a heating element such as an electronic device is disposed on the inorganic layer side of the heat dissipation substrate, and a coolant is disposed on the base material side of the heat dissipation substrate. Examples of the coolant include a water-cooling device, an air-cooling device, and a heat conduction member such as a cooling fin.

<Advantages>
Since the device includes the heat dissipation substrate, the device has excellent heat dissipation.

[Manufacturing method of heat dissipation substrate]
The heat dissipation substrate manufacturing method is a method for manufacturing a heat dissipation substrate comprising a base material mainly composed of aluminum or an aluminum alloy, and a heat conductive layer laminated on one surface of the base material and having an insulating property. One surface of the substrate mainly includes a step of applying and baking an inorganic layer composition containing binder particles mainly composed of phosphate glass (inorganic layer forming step).

  Moreover, it is preferable that the said manufacturing method is equipped with the process (correction process) of correcting the curvature of a thermal radiation board after the said inorganic substance layer formation process in addition to the said process. Furthermore, the said manufacturing method is a process (coating layer formation process) which coats and dries the composition for coating layers which has a siloxane compound as a main component on one surface of the inorganic substance layer formed after the said coating and baking process. May be further provided.

  In the heat dissipation substrate obtained by the manufacturing method, the ratio of the maximum thickness difference of the inorganic layer to the maximum width is 0.6% or less.

<Inorganic layer forming step>
In the inorganic layer forming step, an inorganic layer is formed on one surface of the substrate. In this step, for example, a step of preparing binder particles by pulverization of phosphate glass (binder particle preparation step), and a step of preparing a composition for inorganic layer containing the binder particles (composition step for inorganic layer composition) And a step of coating the inorganic layer composition (coating step) and a step of firing the coated inorganic layer composition (firing step).

(Binder particle preparation process)
In the binder particle preparation step, for example, using a pulverizer such as a pot mill or a jet mill, the phosphate glass is pulverized to a desired size to obtain binder particles.

  The lower limit of the median diameter of the binder particles is preferably 2.5 μm, more preferably 3 μm, and particularly preferably 5 μm. On the other hand, the upper limit of the median diameter is preferably 100 μm, more preferably 80 μm, and further preferably 50 μm. If the median diameter is smaller than the lower limit, the phosphate glass melted by heating after coating may not be sufficiently spread, and the uniformity of the inorganic layer may be reduced. On the contrary, when the median diameter exceeds the upper limit, the binder particles and the filler are not sufficiently mixed, and the uniformity of the inorganic layer may be lowered.

(Inorganic layer composition preparation process)
In the inorganic layer composition preparation step, the binder particles may be used directly as the inorganic layer composition, or the inorganic binder layer composition may be prepared by mixing the binder particles with a filler, water, or an aqueous solvent.

Examples of the aqueous solvent include linear or branched aliphatic lower alcohols such as methanol, ethanol, n-propanol, 2-propanol, and t-butyl alcohol;
Aromatic alcohols such as benzyl alcohol or 2-phenylethanol;
Polyethylene glycols such as propylene glycol, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, PEG200, PEG400;
Polypropylene glycols such as dipropylene glycol and tripropylene glycol;
Polyhydric alcohols such as 1,3-butanediol, 2,3-butanediol, 1,4-butanediol, 1,5-pentanediol, hexylene glycol;
Ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, 3-methyl-3-methoxybutanol, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, triethylene glycol monomethyl ether , Triethylene glycol monoethyl ether, triethylene glycol dimethyl ether, triethylene glycol diethyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether Alkyl ether derivatives of polyhydric alcohols such as ether acetate;
Examples include lower ketones such as acetone.

  When the said composition for inorganic layers contains water or an aqueous solvent, as a minimum of solid content concentration of the composition for inorganic layers, 40 mass% is preferable and 50 mass% is more preferable. On the other hand, the upper limit of the solid content concentration is preferably 70% by mass, and more preferably 65% by mass. If the solid content concentration is lower than the lower limit, the thickness of the inorganic layer is greatly reduced by baking after coating, and it may be difficult to obtain an inorganic layer having a desired thickness, and it takes time for the heat dissipation substrate. There is a risk that the production efficiency of the product will be reduced. Conversely, if the solid content concentration exceeds the upper limit, uniform application of the inorganic layer composition may be difficult.

(Coating process)
In the coating step, the inorganic layer composition is applied to one surface of the substrate to form a coating film. Examples of the coating method include coater coating, spray coating, and printing coating. Among these, spray coating and printing coating are preferable from the viewpoint that the inorganic layer composition can be easily and uniformly applied.

  When the said composition for inorganic layers contains water or an aqueous solvent, after coating the said composition for inorganic layers and forming a coating film, it is good to dry this coating film and to remove a solvent. As a minimum of the above-mentioned drying temperature, 15 ° C is preferred and 20 ° C is more preferred. On the other hand, the upper limit of the drying temperature is preferably 100 ° C, more preferably 90 ° C. When the said drying temperature is smaller than the said minimum, drying requires time and there exists a possibility that the manufacturing efficiency of the said heat sink may fall. On the other hand, when the drying temperature exceeds the upper limit, the binder particles in the inorganic layer composition are melted, and it may be difficult to form a uniform inorganic layer.

  As a minimum of the above-mentioned drying time, 10 minutes are preferred and 30 minutes are more preferred. On the other hand, the upper limit of the drying time is preferably 600 minutes, and more preferably 300 minutes. When the drying time is smaller than the lower limit, water or an aqueous solvent is not sufficiently removed from the coating film of the inorganic layer composition, and it may be difficult to form a uniform inorganic layer due to the remaining solvent. Conversely, when the drying time exceeds the upper limit, the manufacturing efficiency of the heat dissipation substrate may be reduced.

(Baking process)
In the baking step, the binder film in the coating film is melted by baking the coating film, and an inorganic layer is formed.

  As a minimum of the said calcination temperature, 300 degreeC is preferable and 350 degreeC is more preferable. On the other hand, the upper limit of the firing temperature is preferably 580 ° C, more preferably 550 ° C. If the baking temperature is lower than the lower limit, the binder particles in the coating film may not be sufficiently melted. On the contrary, when the baking temperature exceeds the upper limit, the filler in the coating film is melted, and there is a possibility that an inorganic layer having sufficient thermal conductivity cannot be formed.

  As a minimum of the above-mentioned calcination time, 15 minutes are preferred and 20 minutes are more preferred. On the other hand, the upper limit of the firing time is preferably 1 hour, and more preferably 50 minutes. If the baking time is smaller than the lower limit, the binder particles in the coating film may not be sufficiently melted. On the contrary, when the baking time exceeds the upper limit, the manufacturing efficiency of the heat dissipation substrate may be reduced.

<Coating layer formation process>
In the coating layer forming step, a coating layer is formed on one surface of the inorganic layer formed in the inorganic layer forming step. This step mainly includes, for example, a step of coating the coating layer composition on one surface of the inorganic layer (coating step) and a step of drying the coating layer composition after coating (drying step). Have.

(Coating process)
In the coating process, a coating film is formed by coating the coating layer composition on one surface of the inorganic layer. When the coating layer contains silicon oxide as a main component, the coating layer composition mainly contains a siloxane compound.

  The siloxane compound is a compound having a siloxane bond, and may have a substituent such as an alkyl group. As this siloxane compound, alkoxysiloxane, its oligomer or polysiloxane using it is preferable. Examples of the alkoxysiloxane include alkoxysiloxane oligomers such as alkoxydisiloxane, and alkoxy-containing polysiloxanes having a three-dimensional network structure. Among these, alkoxysiloxane oligomers are preferable from the viewpoint of improving the strength of the coating layer. Here, the “siloxane oligomer” means a polymer in which about 2 to 100 siloxane monomers are polymerized.

  The coating layer composition usually further contains a solvent. Examples of the solvent include nonpolar solvents in addition to the above water and aqueous solvents.

  Examples of the nonpolar solvent include chain hydrocarbon solvents such as hexane, heptane, octane and pentane, alicyclic hydrocarbon solvents such as cyclohexane, and aromatic hydrocarbon solvents such as benzene, toluene and xylene. Of these, aromatic hydrocarbon solvents are preferred, and toluene and xylene are more preferred.

  Examples of the method for applying the coating layer composition to the inorganic layer include a coating method using a brush, a coater, or the like. According to these methods, the unevenness of the inorganic layer can be efficiently filled. On the other hand, in the vacuum deposition method or the sputtering method, there is a possibility that the coating layer composition may not sufficiently penetrate into the gaps such as irregularities caused by the filler and pinholes in the inorganic layer. Therefore, a coating method is used in the manufacturing method of the heat dissipation substrate.

(Drying process)
In the drying step, the coating film formed in the coating step is dried. The drying temperature and time can be appropriately changed according to the composition of the coating layer composition.

<Correction process>
In the correction process, warpage of the heat dissipation substrate is reduced.

  An example of the correction device used in this step is a press device. As this pressing device, for example, a known method such as a flat plate pressing device, a hot pressing device, a star-working processing device or the like can be used, but there is a possibility that the warping of the heat dissipation substrate cannot be sufficiently reduced, and the inorganic layer and the substrate are deformed. Since there exists a possibility of damaging, it is preferable to use an exclusive flatness correction apparatus.

  Here, the inventors have found that the ratio of the maximum thickness difference with respect to the maximum width of the heat dissipation substrate can be used as an index of the warp. For example, in the case of an aluminum substrate having a length of 50 mm, a width of 50 mm, and an average thickness of 2 mm, the maximum width is 50 × 1.41 = 70.5 mm. Here, when an inorganic layer having an average thickness of 100 μm is formed on one surface of the substrate and the maximum thickness difference between the inorganic layers is 1.2 mm, the warpage is 1.2 ÷ 70.5 × 100 = 1. 7%. Since this heat dissipation substrate is inferior in heat dissipation efficiency and requires a warp reduction process, various warp reduction processes were verified using various correction devices.

  First, when the processing device provided with a plurality of rollers and passing the heat dissipation substrate between them was used as the correction device, the inorganic layer was cracked.

  In addition, when the flat plate press device that holds the heat dissipation board from above and below is used as the straightening device, the warp seems to be reduced during pressurization, but the warp may be restored when the pressure is lowered. Is expensive. For example, when the heat dissipation substrate having the above-mentioned size and warpage was flat pressed, the maximum thickness difference of the inorganic layer after pressing was 1.0 mm, the warpage was 1.4%, and the reduction of warpage was insufficient.

  Furthermore, even when using a hot press device that is heated to 200 ° C. with pressurization and held by a carbon flat plate as the straightening device, the maximum thickness difference of the inorganic layer after pressing is similar to the flat plate press. The warpage was 1.0 mm and the warpage was 1.4%, and the reduction of warpage was insufficient.

  In addition, when the staring device that forms a large number of small convex portions on at least one of the upper surface plate and the lower surface plate and presses the convex portions against the heat dissipation substrate is used as the correction device, the portion that comes into contact with the convex portions The inorganic material layer was cracked or a large dent was formed on the substrate surface.

  On the other hand, when a dedicated flatness correcting device, which will be described later, is used as the correcting device, the inorganic layer is hardly cracked and the warpage is sufficiently reduced.

  As said flatness correction apparatus, the apparatus provided with the press part and press stand which can press-process a metal plate, for example is mentioned. In this apparatus, the press table has an annular region in which the metal plate abuts on the opposing surface, and the press part has a plurality of hemispherical tips at the inside of the annular region at least on the opposing surface side. Has protrusions.

  Further, in the flatness correcting device, the press portion includes a base on which the plurality of protrusions are implanted, and a mechanism that adjusts the protrusion height of the plurality of protrusions, and thereby, within the annular region. It is preferable that the protrusion height of the protrusion be larger. As described above, the height of the protrusion increases toward the center portion of the press portion, so that a stronger pressure can be applied to the center portion of the heat radiating substrate that is more warped, and the warpage of the heat radiating substrate can be efficiently reduced. .

  Furthermore, it is preferable that a buffer sheet such as a resin sheet is disposed between the press portion and the heat dissipation substrate during pressing. Thereby, damage to the inorganic layer of the heat dissipation substrate can be prevented more reliably. The resin sheet is preferably made of silicone or Teflon (registered trademark). Furthermore, in addition to the buffer sheet or instead of the buffer sheet, a resin layer may be laminated on the outer surface of the tip of the protrusion. The presence of such a resin layer can more reliably prevent the inorganic layer of the heat dissipation substrate from being damaged.

  Moreover, it is preferable that the flatness correction device is formed with a spot according to the size of the heat dissipation substrate to be pressed on the press stand. Specifically, a concave step is formed in accordance with the size and thickness of the heat dissipation substrate to be pressed at the center of the press table, and a hole that is slightly smaller than this step is formed in the step. Things. Thereby, damage to the inorganic layer and the like due to excessive pressing of the heat dissipation substrate can be further reduced.

<Advantages>
According to the manufacturing method, it is possible to easily and reliably obtain a heat dissipation substrate in which the ratio of the maximum thickness difference to the maximum width is 0.6% or less.

[Other Embodiments]
The said heat dissipation board | substrate is not limited to the said embodiment. The heat dissipation substrate may be manufactured while adjusting the thickness of the inorganic layer so as to reduce the warpage, in addition to correcting the warpage by performing a correction step after formation as in the above embodiment. In this case, it is not necessary to adjust the warp after manufacture.

  Moreover, you may laminate | stack the said coating layer after the said correction process. Thus, by laminating the coating layer after correcting the warp, minute cracks generated in the inorganic layer can be filled with the coating layer, and the insulation of the heat dissipation substrate can be improved efficiently.

  The heat dissipation substrate may include a plurality of base materials and inorganic layers in the thickness direction. In this case, the composition of the plurality of base materials and inorganic layers may be different. By providing a plurality of base materials and inorganic layers having different compositions as described above, various characteristics of the heat dissipation substrate can be appropriately adjusted.

  Similarly, the heat dissipation substrate may include a plurality of coating layers in the thickness direction. However, since the coating layer is preferably thin as described above, it is preferable that only one layer is provided.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to these Examples.

[Manufacture of heat sink]
An aluminum plate (industrial pure aluminum 1050, average thickness 2 mm) as a substrate was cut into 50 mm length and 50 mm width by a shearing machine, and the surface was washed with a neutral detergent.

  Next, low melting point phosphate glass flakes (“VQ0028” manufactured by Nippon Frit Co., Ltd.) were pulverized using a jet mill to a median diameter of 5 μm to obtain binder particles. Water was added to the binder particles and stirred to prepare an inorganic layer composition. The solid content concentration of the inorganic layer composition was 60% by mass.

  The prepared inorganic layer composition was sprayed on the surface of the substrate for 5 seconds using a spray gun (Anest Iwata “G151”), heated in a drying furnace at 60 ° C. and dried for 30 minutes. Then, it baked at 450 degreeC for 30 minutes in the electric furnace, and obtained the thermal radiation board | substrate with which the inorganic substance layer with an average thickness of 100 micrometers was formed.

The center of the surface of the heat dissipation substrate swells and warps, and the difference between the thickness of the central portion and the thickness of the peripheral portion is 1.2 mm. For this heat dissipation board, the maximum width of the heat dissipation board was L (mm), the maximum thickness difference was X (mm), and the relative warpage amount B (%) was determined based on the following formula (1).
B = (X / L) × 100 (1)
Here, since L is 50 × 1.41 = 70.5 mm and X is 1.2 mm, B is 1.7%.

  Here, the average thickness of the inorganic layer was measured using an eddy current film thickness meter (“MMS 3AM” manufactured by Fischer Instrument Co., Ltd.), and the cross-sectional shape of the heat dissipation substrate was measured using a scanning electron microscope (“S4000” manufactured by Hitachi Power Solutions). )).

[Example 1]
Warpage was corrected by the following procedure using a dedicated flatness correction device for the heat dissipation substrate.

  As the flatness straightening device, a flatness straightening device including a flat plate-like press part and a press stand was used. At the center of the press portion, 7 × 7 projections having a hemispherical tip with a radius of 2.6 mm were arranged in a grid pattern at intervals of 7 mm. Of these projections, one of the most central portions is 0.5 mm higher than the projection of the peripheral portion, and eight of the 3 × 3 central portions excluding one of the central portion are 0.2 mm higher than the peripheral portion. Increased by 3 mm.

  In addition, a hole with a diameter of 46 mm is formed in the center of the press table, and by placing the heat dissipation substrate on the hole, the peripheral edge of the heat dissipation substrate is brought into contact with the press table, whereby the heat dissipation substrate is Retained.

  The heat radiating board was held between the press portion and the press stand, and the heat radiating board was warped by pressing from both sides of the heat radiating board. Here, the relative curvature amount B was calculated | required based on the said Formula (1) about the heat sink board after correction. Since L is 70.5 mm, which is the same as before correction, and X in Example 1 is 0.095 mm, B in Example 1 is 0.13%.

[Examples 2 to 5 and Comparative Examples 4 and 5]
The warping of the heat dissipation substrate was corrected in the same manner as in Example 1 except that the pressing means and the pressure during pressing were set to the values shown in Table 1. Table 1 shows the amount of warpage after correction and the amount of relative warpage obtained based on the above formula (1).

  Here, in Example 5 and Comparative Example 5, since the thickness of the central portion of the heat dissipation substrate is smaller than the thickness of the peripheral portion, X is “the thickness of the peripheral portion−the thickness of the central portion”.

[Comparative Example 1]
As a correction means, instead of the above-described flatness correction device, a flat plate hand press (“Hand Press 1-312-01” manufactured by ASONE) was used to press the heat dissipation substrate under a press pressure of 15 kg. After pressing, the relative warpage amount was determined based on the above formula (1).

[Comparative Example 2]
As a correction means, a hot press machine (“Hi-Multi 5000” manufactured by Fuji Denpa Kogyo Co., Ltd.) is used in place of the dedicated flatness correction device, and the conditions are atmospheric pressure 0.2 MPa, press temperature 300 ° C., press pressure 1 t. The heat dissipation board was pressed. After the pressing, the heat dissipation substrate was cooled, and the relative warpage was determined based on the above formula (1).

[Comparative Example 3]
In Comparative Example 3, correction was not performed and the warp during the formation of the inorganic layer was kept.

<Evaluation>
About the heat sink of the said Example and comparative example, the thermal resistance was measured with the following procedures. First, an aluminum block having a side of 100 mm was prepared and immersed in water that was circulated so as to maintain 18 ° C. to a depth of 75 mm. Next, heat conduction grease (“G747” from Shin-Etsu Chemical Co., Ltd., heat conductivity 0.9 W / mK) is applied to the base material side surface of the heat dissipation substrate so that the average thickness is 0.08 mm. Then, the heat dissipation substrate was attached to the aluminum block. Thereafter, the heat conductive grease is pasted on the surface of the heat radiating substrate on the inorganic layer side so that the average thickness is 0.08 mm. The heat conductive grease and the heat radiating substrate and heater , 25 mm in length, 25 mm in width, and 2.5 mm in height). A load of 5 N was applied from the heater side to the laminate of the heater, the heat dissipation substrate and the aluminum block to fix the components together, and a thermocouple was attached to the aluminum block to obtain a laminate with a heat dissipation substrate.

The heater was heated by energizing the heater of the laminate with the heat dissipation substrate. When the temperature inside the heater reaches 50 ° C., the aluminum block surface temperature A (° C.), the heater internal temperature H (° C.), and the heater output P (W) are measured. Thermal resistance R (° C./W) was calculated. Table 1 shows the thermal resistance of the heat dissipation substrates of the examples and comparative examples.
R = (HA) / P (2)

  As shown in Table 1, the thermal resistance of the heat dissipation substrate decreases in proportion to the relative warpage, and in an example in which the relative warpage is 0.6% or less, the thermal resistance is 1 ° C./W or less. It was. In particular, in Examples 1 and 2 in which the relative warpage amount was 0.25% or less, the thermal resistance was 0.5 ° C./W or less, and the heat dissipation property of the heat dissipation substrate was excellent.

  On the other hand, in the comparative examples in which the relative warpage amount exceeds 0.6%, the thermal resistance is high, and the heat dissipation performance of the heat dissipation board is insufficient. In particular, in Comparative Examples 1 and 2 using a conventional press machine and in Comparative Example 4 using a dedicated correction tool, but the press pressure is low, the amount of relative warpage is large, which is as high as Comparative Example 3 with no correction. Thermal resistance was shown.

  As described above, the heat dissipation substrate of the present invention is excellent in heat dissipation as a result of reducing warpage. Moreover, since the device of this invention is equipped with the said thermal radiation board | substrate, it is excellent in heat dissipation. Furthermore, the method for manufacturing a heat dissipation board of the present invention can easily and reliably obtain the heat dissipation board. Therefore, the heat dissipation board and the heat dissipation component can be suitably used for electronic components that are becoming smaller.

Claims (7)

A base material mainly composed of aluminum or an aluminum alloy;
A heat dissipation board that is laminated on one surface of the base material and has a heat conductive layer having insulation properties,
The heat conductive layer includes an inorganic layer containing a binder mainly composed of phosphate glass,
A ratio of the maximum thickness difference of the inorganic layer to the maximum width is 0.6% or less.   The heat dissipation substrate according to claim 1, wherein the average thickness of the inorganic layer is 10 μm or more and 200 μm or less.   The heat dissipation substrate according to claim 1, wherein the inorganic layer further contains a filler mainly composed of alumina.   The heat dissipation substrate according to claim 3, wherein the median diameter of the filler in the heat conductive layer is 5 µm or more and 100 µm or less, and the filler content is 30 mass% or more and 65 mass% or less.   The heat dissipation according to any one of claims 1 to 4, further comprising a coating layer which is laminated on one surface of the inorganic layer and mainly contains silicon oxide, silicon nitride, epoxy resin, or acrylic resin. substrate.   A device comprising the heat dissipation substrate according to any one of claims 1 to 5. A base material mainly composed of aluminum or an aluminum alloy;
A method of manufacturing a heat dissipation board comprising: a heat conductive layer laminated on one surface of the base material and having an insulating property,
On one surface of the substrate, a step of coating and baking a composition for an inorganic layer containing binder particles mainly composed of phosphate glass,
The manufacturing method of the heat dissipation board | substrate characterized by the ratio with respect to the maximum width of the largest thickness difference of the inorganic substance layer formed after this coating and baking process being 0.6% or less.