JP6591113B1 - Heat dissipation member and manufacturing method thereof - Google Patents

Abstract

In manufacturing a power module or the like by connecting a part to one side of a curved heat radiating member, the manufacturing stability (yield, etc.) is improved. A plate-like heat radiating member comprising a metal-silicon carbide composite containing aluminum or magnesium, wherein at least one main surface of two main surfaces of the heat radiating member is directed outwardly of the heat radiating member. It is curved in a convex shape, and the flatness of one main surface defined by JIS B 0621 is f1, and the other main surface, which is a main surface different from the one main surface, is JIS B 0621. A heat radiating member in which f2 is smaller than f1 by 10 μm or more when the specified flatness is f2. [Selection] Figure 1

Description

  The present invention relates to a heat radiating member and a manufacturing method thereof. More specifically, the present invention relates to a plate-like heat dissipation member provided with a metal-silicon carbide composite containing aluminum or magnesium and a method for manufacturing the same.

In recent years, a heat radiating member made of a metal-silicon carbide composite has been used as a heat radiating component for power modules in electric vehicles and electric railways, instead of conventional copper.
As the metal of the metal-silicon carbide composite, aluminum or an alloy thereof is often used.

The heat radiating member is often used by being joined to other parts (for example, a heat radiating fin or a heat radiating unit), and the property of the joint is important.
For example, when joining a heat radiating member to a heat radiating fin or a heat radiating unit, generally, the heat radiating member is screwed to the heat radiating fin, the heat radiating unit or the like using holes provided in the peripheral edge of the heat radiating member. However, if the surface of the heat radiating member that comes into contact with the heat radiating fins is concave or has a lot of minute irregularities, a gap is generated between the heat radiating member and the heat radiating fins and the heat transfer performance is lowered. There was a problem.

In view of the above problems, some heat radiating members have been proposed in which the surfaces to be joined to the heat radiating fins or the like are curved in a convex shape so that there is no gap between the heat radiating member and the heat radiating fins as much as possible.
This is because, as described above, the heat radiating member is usually fixed to a heat radiating fin or the like with a fixing member such as a screw, but the joint surface with the heat radiating fin or the like is curved in a convex shape. This is because, when fixed by the fixing member, the bonding surface becomes “moderately flat”, and the bonding property (adhesion) with the radiation fins and the like is increased.

  For example, Patent Document 1 discloses a plate-like composite formed by impregnating a porous silicon carbide molded body with a metal containing aluminum as a main component, and the plate is placed on another heat dissipation component within the plane of the plate-like composite. 4 or more holes for screwing with the convex surface of the cylindrical composite facing, the amount of warpage (Cx; μm) with respect to a length of 10 cm in the inter-hole direction (X direction), and the direction perpendicular to it (Y The relationship of the amount of warpage (Cy; μm) with respect to a length of 10 cm in the direction) is 50 ≦ Cx ≦ 250 and −50 ≦ Cy ≦ 200 (excluding Cy = 0). Is described.

  Patent Document 2 discloses a plate-like composite formed by impregnating a porous silicon carbide molded body with a metal whose main component is aluminum, and the amount of warpage of the main surface of the composite with respect to a length of 10 cm. Describes a silicon carbide composite having a warp of 250 μm or less.

Japanese Patent No. 3468358 International Publication No. 2015/115649

  As described above, (1) First, a curved heat dissipating member is manufactured, and (2) when joining it with heat dissipating fins, etc., the heat is dissipated from the heat dissipating member and the heat dissipated by “flattening” the curve by the force of screws It is known to improve the bondability with fins and the like, and thus improve the heat dissipation.

However, parts such as power elements are usually connected to the surface of the heat radiating member opposite to the surface in contact with the heat radiating fins, etc., and particularly in mass production, the component is connected to the curved heat radiating member. That is, it may be difficult to align the position, or it may be difficult to connect the components.
That is, when a power module or the like is manufactured by connecting components to one side of a curved heat radiating member, there is room for improvement in terms of manufacturing stability (yield and the like).

The present invention has been made in view of such circumstances.
One of the objects of the present invention is to improve the manufacturing stability (yield and the like) of a power module or the like by connecting components to one side of a curved heat radiating member.

  The present inventors diligently studied to solve the above problems. As a result, it was found that the flatness defined by JIS B 0621 of the two main surfaces of the plate-like heat radiating member seems to be closely related to the solution of the problem. Based on this knowledge, the invention provided below has been completed.

According to the present invention,
A plate-like heat dissipation member comprising a metal-silicon carbide composite containing aluminum or magnesium,
At least one main surface of the two main surfaces of the heat dissipation member is curved in a convex shape in the outer direction of the heat dissipation member,
Of the one main surface, JIS B flatness defined as _{f 1} in 0621, the other main surface is different from the main surface and said one main surface, a flatness defined by JIS B 0621 f _{2 where} f ₂ is 10 μm or less smaller than f ₁ ,
Is provided.

Moreover, according to the present invention,
A method of manufacturing the heat dissipation member,
Preparing a plate-like metal-silicon carbide composite containing aluminum or magnesium;
Including a step of machining at least a part of one surface of the composite to provide the one main surface,
Is provided.

  According to the present invention, it is possible to improve the manufacturing stability (yield and the like) of a power module or the like by connecting components to one side of a curved heat radiating member.

It is a schematic diagram for demonstrating the heat radiating member of this embodiment. FIG. 1A is an overhead view of the heat dissipating member of this embodiment, and FIG. 1B is a cross-sectional view of the heat dissipating member cut along a cross section α of FIG. It is a figure for demonstrating the at least one main surface of the heat radiating member of this embodiment especially 2 main surfaces. FIG. 2A is a diagram showing only one of the two principal surfaces of the heat dissipation member, and FIG. 2B is a cross-sectional view of FIG. 2A when one of the principal surfaces is cut. A cross-sectional view, FIG. 2C, is a cross-sectional view when one main surface is cut along the cross-section γ of FIG.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
In all the drawings, the same components are denoted by the same reference numerals, and description thereof will be omitted as appropriate.
In order to avoid complications, (i) when there are a plurality of identical components in the same drawing, only one of them is given a reference, and all are not attached, or (ii) 2 and later, the same components as in FIG. 1 may not be denoted again.
All drawings are for illustrative purposes only. The shape and dimensional ratio of each member in the drawings do not necessarily correspond to an actual article. In particular, the shape and dimensional ratio may be exaggerated for easy understanding. In particular, in each of the drawings, the size of the “curve” is exaggerated as compared with the actual article.

Unless otherwise specified, the term “abbreviated” in the present specification indicates that it includes a range that takes into account manufacturing tolerances, assembly variations, and the like.
As long as there is no notice in particular, the value in room temperature (23 degreeC) is employable about what can change a value with temperature among the various numerical values (especially measured value) in this specification.

<Heat dissipation member>
Fig.1 (a) is an overhead view of the heat radiating member (heat radiating member 1) of this embodiment.
The heat radiating member 1 is plate-shaped.
The main material of the heat radiating member 1 is a metal-silicon carbide composite containing aluminum or magnesium (details of the material will be described later together with the manufacturing method of the heat radiating member 1).

The heat radiating member 1 can usually be substantially rectangular. That is, when the heat radiating member 1 is viewed from above with one main surface of the heat radiating member 1 as an upper surface, the shape of the heat radiating member 1 is substantially rectangular.
Here, “substantially rectangular” means that at least one of the four corners of the heat radiating member 1 may be processed into a rounded shape instead of a right-angled shape (of course, the four corners are right-angled). It may be a shape).
In addition, when at least one of the four corners of the heat radiating member 1 is processed into a rounded shape, a point where the short side and the long side when the heat radiating member 1 is viewed from the top is crossed when the straight portion is extended. Can be defined as a rectangular “vertex”. At this time, the “short side length” and the “long side length” of the heat radiating member 1 can be defined by using the “vertex” as a start point or an end point.

The vertical and horizontal lengths of the heat radiating member 1 are, for example, about 40 mm × 90 mm to 250 mm × 140 mm.
The thickness of the heat radiating member 1 is 2 mm or more and 6 mm or less as an example, Preferably it is 3 mm or more and 5 mm or less. In addition, when the thickness of the thermal radiation member 1 is not uniform, it is preferable that the thickness in the gravity center part of the thermal radiation member 1 exists in the said range at least.

FIG.1 (b) is sectional drawing when the thermal radiation member 1 is cut | disconnected by the surface (alpha) of Fig.1 (a).
The plate-like heat radiating member 1 includes two main surfaces (one main surface is a main surface 2A and the other main surface is a main surface 2B). Typically, the main surface 2A is a surface that is joined to a heat radiation fin or the like, and the main surface 2B is a surface that is connected to a power element or the like.
In the heat radiating member 1, at least the main surface 2 </ b> A is curved in a convex shape not in the inner direction of the heat radiating member 1 but in the outer direction. Usually, the main surface 2A is curved in a convex shape in the outward direction, and does not have a portion that is partially concave.
Major surface 2A, a flatness defined by JIS B 0621 and _{f 1,} the main surface 2B, when the flatness defined by JIS B 0621 was _{f 2,} towards the _{f 2} is 10μm or more than _{f 1} small.

In the heat radiating member having a conventional curvature, there are many cases where the degree of curvature on the main surface 2A side and the degree of curvature on the main surface 2B side are substantially equal. Therefore, when connecting a component such as a power element to the main surface 2B side, alignment may be difficult, or connection of the component itself may be difficult.
On the other hand, in the heat radiating member 1 of FIG. 1, f ₁ (representing the degree of curvature of the main surface 2A) is relatively large and f ₂ (representing the degree of curvature of the main surface 2B) is relatively small. Thereby, on the side of the main surface 2A, it is possible to sufficiently obtain the joining property between the heat radiating member 1 and the heat radiating fins, and therefore, it is possible to obtain a sufficient heat radiating property. In addition, it is possible to easily align and connect components on the main surface 2B side as compared with the conventional heat dissipation member.

The flatness defined in JIS B 0621 is defined as the interval between two planes when the interval between the two parallel planes is minimized when the plane feature is sandwiched between the geometric parallel two planes.
Examples of the measuring device having the flatness f ₁ and the flatness f ₂ include a device VR-3000 manufactured by Keyence Corporation.
It is added that, the measurement of f ₁ is preferably performed for the entire main surface 2A. However, depending on the size of the heat dissipating member 1, the entire main surface 2A may not be within the observation field of view of the measuring apparatus. In that case, f ₁ is measured so that the center (geometric center of gravity) when the main surface 2A is viewed from above and the center of the observation field of view of the measuring device coincide. At this time, the long side of the main surface 2A which is substantially rectangular and the long side of the observation field (the observation field of the flatness measuring device is usually rectangular) are parallel to each other. preferable. The same applies to the measurement of f _2.

  More specific description of the heat radiating member 1 will be continued.

[Additional description of f ₁ , f ₂ , main surface 2B, etc.]
In the heat dissipating member 1, but rather of _{f 2} may be smaller 10μm or more than _{f 1,} preferably 50μm or smaller than the _{f 1} towards the _{f 2,} 100 [mu] m or more smaller than the _{f 1} towards the more preferably _{f 2.}
On the other hand, from the viewpoint of ease of manufacture of the heat radiating member 1 itself and an appropriate amount of bending, the difference between f ₁ and f ₂ (f ₁ −f ₂ ) is preferably 600 μm or less, and 500 μm or less. Is more preferably 400 μm or less.

The value of f ₁ itself is preferably 100μm or 700μm, more preferably 200μm or 600μm or less.
The value of f ₂ itself is preferably 300μm or less, more preferably 250μm or less, more preferably 200μm or less, particularly preferably 100μm or less. The lower limit of f ₂ may be 0 as an example. As another example, the lower limit of f ₂ may be of 50μm or more.

By appropriately designing the value of f ₁ itself, it is considered that the heat radiating member 1 can be fixed to the heat radiating fin or the like with a moderate (not too large) tightening force. This leads to further improvement in heat dissipation, reduction of cracks due to excessive force, and the like.
By appropriately designing the value of f ₂ itself, it is considered that alignment and connection of components connected to the main surface 2B can be further facilitated.

The main surface 2B may be curved in a convex shape toward the outer side of the heat radiating member 1, or vice versa, that is, may be curved in a concave shape toward the outer side of the heat radiating member 1. In consideration of the curvature of the heat radiating member 1 at the time of manufacturing the power device as the final product, the main surface 2B is preferably curved in a concave shape toward the outer side of the heat radiating member 1.
More specifically, the main surface 2B is concavely curved toward the outer side of the heat radiating member 1, and the degree of the curvature is expressed by flatness, as described above, preferably 300 μm or less, more preferably Is 250 μm or less, more preferably 200 μm or less, and particularly preferably 100 μm or less.

Of course, the main surface 2B may be curved in a convex shape toward the outer side of the heat radiating member 1. As long as the degree of curvature represented by f ₂ is 10 μm or more smaller than f ₁ , it is possible to make it difficult to cause a problem in connection with a power element or the like.

[Materials constituting main surfaces 2A, 2B, etc.]
As one aspect, main surface 2A and / or main surface 2B (that is, the surface of heat dissipation member 1) can be a metal-silicon carbide composite containing aluminum or magnesium.
As another aspect, main surface 2A and / or main surface 2B (surface of heat radiating member 1) may be a metal layer. For example, the main surface 2A and / or the main surface 2B preferably includes a surface metal layer containing aluminum or magnesium. In this case, the portion of the heat dissipation member 1 other than the surface metal layer can be a metal-silicon carbide composite or the like. The metal included in the metal surface layer is preferably the same as the metal included in the metal-silicon carbide composite. This is due to the reason for manufacturing the heat radiating member 1 (the method for manufacturing the heat radiating member 1 will be described later).

In addition, it is preferable that the plating layer is provided in the further outer side of the above-mentioned surface metal layer. In general, solder is used for connecting power elements and the like, but the plating layer can improve solder wettability.
The plating layer can be, for example, a Ni-containing plating layer.

When the heat radiating member 1 includes a metal surface layer, the average thickness of the surface metal layer is not particularly limited, but is, for example, 10 μm to 300 μm, preferably 30 μm to 150 μm.
When the heat radiating member 1 includes a plating layer, the average thickness of the plating layer is not particularly limited, but is, for example, 3 μm or more and 15 μm or less, preferably 4 μm or more and 10 μm or less.

Note that the values of f ₁ and f _2, in principle, to employ the values of the flatness of the outermost surface of the heat dissipating member 1.
For example, when the heat dissipating member 1 is composed only of a plate-like metal-silicon carbide composite, the flatness of both main surfaces of the plate-like metal-silicon carbide composite is measured, and f it can be set to a value of ₁ and _{f 2.}
In addition, when the outermost surface of the heat dissipating member 1 is a surface metal layer and the plated layer, that by measuring the flatness of the surface metal layer and the plated layer surface of the outermost surface, the value of f ₁ and f ₂ Can do.

[Indicators for surface roughness of main surfaces 2A and 2B]
As another viewpoint, by appropriately designing the “index for surface roughness” of the main surface 2A and the main surface 2B, performance such as heat dissipation can be further improved.
For example, the main surface 2A, the average length RS _m of roughness curve element, preferably be designed to 50μm or 250μm or less, and more preferably designed to 70μm or 160μm or less.
By setting the RS _m of the main surface 2A to an appropriate size, the bonding property with the heat radiating fins and the like can be further increased, and the heat radiating property can be further improved. Although detailed mechanism and the like of which is unknown, perhaps, by the RS _m and appropriate size, micro gap between the heat radiating member 1 radiation fins is reduced, it is believed that bonding is enhanced more.

Further, the main surface 2B, the average length RS _m of roughness curve element, preferably be designed to 50μm or 200μm or less, and more preferably designed to 70μm or 160μm or less.
By setting the RS _m of the main surface 2B to an appropriate size, for example, it is considered that the connectivity between the heat radiating member 1 and the power element can be improved.

[Curving Main Surface 2A]
FIG. 2 is a view for explaining the form of the main surface 2 </ b> A of the heat radiating member 1.
2A is a diagram showing only the main surface 2A of the heat radiating member 1, FIG. 2B is a cross-sectional view when the main surface 2A is cut along the cross section β of FIG. 2A, and FIG. FIG. 3 is a cross-sectional view of the main surface 2A cut along a cross-section γ in FIG. In these drawings, auxiliary lines and the like are described for the following explanation.

Here, the length of the long side of the rectangular heat radiating member 1 is a, the length of the short side is b, and the midpoints of the two short sides of the main surface 2A (indicated by M ₁ and M ₃ in the figure). ) Is defined as l ₁ , and a straight line connecting between the midpoints of the two long sides of the main surface 2A (indicated by M ₂ and M ₄ in the figure) is defined as l ₂ .

Further, when the heat radiating member 1 is viewed in cross section with a cross section β including l ₁ and substantially perpendicular to the main surface 2A, the maximum distance between a point on the curve formed by the main surface 2A and l ₁ is h _1, and l ₂ hints and when viewed in cross section the heat dissipating member 1 in the main surface 2A and cross section substantially perpendicular gamma, the maximum distance between a point and the l ₂ on the curve formed by the main surface 2A and h _2.

At this time, it is preferable to design the heat dissipation member 1 so that h ₁ / a ≧ h ₂ / b.
More specifically, the value of (h ₁ / a) / (h ₂ / b) is preferably 1.00 or more and 1.9 or less, and more preferably 1.07 or more and 1.6 or less. preferable.

The above inequality can be interpreted as follows.
It can be said that h ₁ / a means “curvature per unit length in the long side direction” in the heat radiating member 1.
Similarly, it can be said that h ₂ / b means “curvature per unit length in the short side direction” in the heat radiating member 1.
Then, “h ₁ / a ≧ h ₂ / b” means that the “degree of curvature” in the long side direction is the same as that in the short side direction even if the long side is longer than the short side. Can be interpreted as larger than that.

  Although details are unknown, when the heat radiating member 1 that is curved using screws or the like is pressed against other parts and joined, the rectangular (rectangular) heat radiating member 1 has a longer side than the short side direction. Easy to deform in the direction (easy to bend). Therefore, by making the “degree of bending” in the long side direction larger than that in the short side direction, it is easy to flatten the heat radiation member 1 as a whole without applying excessive force (even if the screwing force is relatively small). It is estimated to be. In addition, it is considered that cracking and the like around the screw can be suppressed because the screwing force may be relatively small.

[Screw holes]
The heat dissipating member 1 preferably includes a screw hole (not explicitly shown in FIGS. 1 and 2).
For example, when the heat radiating member 1 has a substantially rectangular shape, it is preferable that screw holes (through holes) are provided in the peripheral portions of the four corners of the heat radiating member 1. Further, depending on the length of the long side of the heat radiating member 1, for example, a hole may be provided near the midpoint of the long side in the peripheral portion of the heat radiating member 1.
The diameter of the hole can be, for example, about 5 mm to 9 mm.
In addition, the means for joining the heat radiating member 1 to other components is not limited to a screw. For example, joining may be performed with a dedicated jig that can be attached to other components.

[Manufacturing method / material]

The manufacturing method of the heat radiating member of this embodiment is not specifically limited, It can manufacture by applying a well-known method suitably.
Preferably, the heat dissipating member of this embodiment includes (i) preparing a plate-like metal-silicon carbide composite containing aluminum or magnesium, and (ii) at least one surface of the metal-silicon carbide composite. Can be manufactured through a process including a process of providing a main surface 2A as described above by machining (grinding, cutting, etc.) a part of the surface.

The heat dissipation member of the present embodiment includes a metal-silicon carbide composite containing aluminum or magnesium. A method preferably used for producing the metal-silicon carbide composite is a high-pressure forging method in which a porous body is impregnated with metal under high pressure. More specifically, a molten metal forging method or a die casting method can be employed. The high-pressure forging method is a method in which a porous body of silicon carbide (preform) is charged in a high-pressure vessel, and a metal melt containing aluminum or magnesium is impregnated at a high pressure to obtain a composite.
For manufacturing the heat radiating member of the present embodiment, a molten metal forging method is particularly preferable because it can be stably manufactured in a large amount. Hereinafter, the manufacturing method by the molten metal forging method is demonstrated.

As an example, the heat radiating member of this embodiment can be manufactured by the following processes.
(Step 1) A step of forming a planar silicon carbide porous body (SiC preform),
(Step 2) Machining at least one surface of the silicon carbide based porous body into a convex curved shape,
(Step 3) A metal comprising a silicon carbide based porous body impregnated with a metal (alloy) containing aluminum or magnesium, and a composite part containing silicon carbide and a metal, and a surface metal layer on the outer surface of the composite part. -Producing a silicon carbide composite; and
(Step 4) by machining at least convex surface metal layer of the processed surface side to the curved shape of the step of more of f ₂ to obtain a small heat radiating member or 10μm than f ₁

  The above (Step 1) to (Step 4) will be described more specifically.

There is no restriction | limiting in particular regarding the manufacturing method of the silicon carbide based porous material (SiC preform) in the said (process 1), It can manufacture by a well-known method. For example, it can be produced by adding silica, alumina, or the like as a binder to a raw material silicon carbide (SiC) powder, mixing, molding, and firing at 800 ° C. or higher.
There is no restriction | limiting in particular also about a shaping | molding method, Press molding, extrusion molding, cast molding etc. can be used, and the shape-retaining binder can be used together as needed.

The important characteristics of a metal-silicon carbide composite obtained by impregnating a silicon carbide based porous material with a metal containing aluminum or magnesium are thermal conductivity and thermal expansion coefficient. A higher SiC content in the silicon carbide based porous material is preferable because the thermal conductivity is high and the thermal expansion coefficient is small. However, if the content is too high, the aluminum alloy may not be sufficiently impregnated.
Practically, it is preferable to contain 40% by mass or more of coarse SiC particles having an average particle size of preferably 40 μm or more, and the relative density of the SiC preform is preferably in the range of 55% to 75%. The strength of the silicon carbide based porous material (SiC preform) is preferably 3 MPa or more in terms of bending strength in order to prevent cracking during handling and during impregnation. The average particle diameter is calculated by averaging the diameters obtained for 1000 particles using a scanning electron microscope (for example, “JSM-T200 type” manufactured by JEOL Ltd.) and an image analyzer (for example, manufactured by Nippon Avionics Co., Ltd.). Can be measured. The relative density can be measured by Archimedes method or the like.

About SiC powder which is a raw material of a silicon carbide based porous body (SiC preform), it is preferable to adjust the particle size by appropriately using coarse powder and fine powder together. By carrying out like this, it is easy to make compatible the intensity | strength of a silicon carbide based porous body (SiC preform), and the high heat conductivity of the heat radiating member finally obtained.
Specifically, a mixed powder obtained by mixing (i) SiC coarse powder having an average particle diameter of 40 μm or more and 150 μm or less and (ii) SiC fine powder having an average particle diameter of 5 μm or more and 15 μm or less is suitable. Here, the amount ratio of (i) and (ii) in the mixed powder is preferably (i) from 40% by mass to 80% by mass and (ii) from 20% by mass to 60% by mass.

A silicon carbide based porous material (SiC preform) is obtained by degreasing, firing, etc., a molded product of a mixture obtained by adding a binder to SiC powder. When the firing temperature is 800 ° C. or higher, it is easy to obtain a silicon carbide based porous material (SiC preform) having a bending strength of 3 MPa or more regardless of the atmosphere during firing.
However, in an oxidizing atmosphere, when firing at a temperature exceeding 1100 ° C., the oxidation of SiC is promoted, and the thermal conductivity of the metal-silicon carbide composite may be lowered. Therefore, it is preferable to bake at a temperature of 1100 ° C. or lower in an oxidizing atmosphere.
The firing time may be appropriately determined according to conditions such as the size of the silicon carbide based porous material (SiC preform), the amount charged into the firing furnace, and the firing atmosphere.

  When forming a silicon carbide porous body (SiC preform) into a predetermined shape at the time of molding, the silicon carbide porous body (SiC preform) is dried one by one or using a spacer such as carbon having a shape equal to the preform shape between the SiC preforms. Thus, it is possible to prevent a change in curvature due to drying. Moreover, regarding the firing, it is possible to prevent the shape change accompanying the change of the internal structure by performing the same treatment as that at the time of drying.

  In the above (step 2), at least one surface of the silicon carbide based porous material (SiC preform) is processed so as to have a convex curved shape toward the outside by a cutting / grinding tool such as a lathe. In this way, by performing machining (cutting) at the preform stage, there is no need to use special tools for cutting after metal impregnation, and the degree of curvature and flatness can be easily controlled. There is.

In the manufacture of the heat dissipation member of the present embodiment, processing may be performed not only on one side of the silicon carbide based porous body (SiC preform) but also on both sides. That is, in the finally obtained heat radiation member, as more of the f ₂ decreases 10μm or more than f _1, also, as in the respective values of f ₁ and f ₂ becomes a desired value, the silicon carbide-based porous body You may process on both surfaces of (SiC preform).

In the above (Step 3), a silicon carbide porous body (SiC preform) is impregnated with a metal containing aluminum or magnesium by a high-pressure forging method or the like, and a composite part containing silicon carbide and a metal, and a composite part A metal-silicon carbide composite comprising the outer surface metal layer can be produced.
Examples of a method for obtaining a metal-silicon carbide composite by impregnating a metal (alloy) containing aluminum or magnesium into a silicon carbide based porous material (SiC preform) include the following methods.

A silicon carbide porous body (SiC preform) is housed in a mold, and then one of a fiber, a spherical particle, and a crushed particle made of alumina or silica on both plate surfaces of the mold The above is arranged so as to be in direct contact with each other to form one block.
This block is preheated at 500 ° C. or more and 650 ° C. or less, and one or more blocks are placed in a high-pressure vessel. Thereafter, in order to prevent the temperature of the block from decreasing, as soon as possible, a molten metal containing aluminum or magnesium is pressurized at a pressure of 30 MPa or more, and the metal is impregnated in the voids of the silicon carbide based porous material (SiC preform).
As described above, a metal-silicon carbide composite including a composite part including silicon carbide and a metal and a surface metal layer on the outer surface of the composite part is obtained.

It is preferable that the metal (typically an alloy containing aluminum or magnesium) in the metal-silicon carbide composite has a melting point as low as possible in order to sufficiently penetrate into the voids of the preform when impregnated.
In this respect, for example, an aluminum alloy containing 7 mass% or more and 25 mass% or less of silicon is preferable. Furthermore, it is preferable that magnesium is contained in an amount of 0.2% by mass or more and 5% by mass or less because the bond between the silicon carbide grains and the metal portion becomes stronger. The metal components other than aluminum, silicon, and magnesium in the aluminum alloy are not particularly limited as long as the characteristics do not change extremely. For example, copper or the like may be included.

  As the aluminum alloy, AC4C, AC4CH, ADC12, etc., which are preferably alloys for casting, can also be used.

An annealing treatment may be performed after the metal-silicon carbide composite is produced for the purpose of removing strain generated during the impregnation. The annealing treatment performed for the purpose of strain removal is preferably performed at a temperature of 400 ° C. to 550 ° C. for 10 minutes to 5 hours.
If the annealing temperature is 400 ° C. or higher, the distortion inside the composite is sufficiently released, and it is possible to suppress a large change in curvature in the annealing process after machining. On the other hand, if the annealing temperature is 550 ° C. or lower, the aluminum alloy used in the impregnation can be prevented from melting.
If the annealing time is 10 minutes or more, the distortion inside the composite is sufficiently released, and it is possible to suppress a large change in curvature in the annealing process for removing the processing distortion after machining. On the other hand, the annealing time is preferably 5 hours or less from the viewpoint of mass productivity.

  In (Step 3), for example, one or more of fibers, spherical particles, and crushed particles made of alumina or silica are in direct contact with the surface of the silicon carbide porous body (SiC preform). Can be arranged. Thereby, a surface metal layer having a predetermined thickness can be formed. And there is almost no color unevenness after impregnation, and there is an advantage that workability is improved when adding a shape.

The content of the material consisting of one or more of fibers made of alumina or silica, spherical particles and crushed particles in the surface metal layer is preferably 0 with respect to the mass of the metal-silicon carbide composite. .1% by mass to 5% by mass, and more preferably 0.3% by mass to 2% by mass.
If this content is 0.1% by mass or more, it is easy to control the thickness of the aluminum layer, and it is possible to suppress a large change in the curved shape due to the annealing treatment after processing. Moreover, if this content is 5 mass% or less, an aluminum alloy layer will not become hard too much and it will become easy to give general machining.

When the thickness of the surface metal layer provided on the surface of the metal-silicon carbide composite is machined only on the heat radiating surface side (corresponding to the main surface 2A side of the heat radiating member 1) in (Step 4), double-side machining is performed. In any case, it is better to adjust appropriately so that the thickness difference between the front and back surface metal layers does not increase after processing. For the adjustment, the inorganic fibers described above can be used as appropriate.
Specifically, the average thickness of the metal layer on the circuit board mounting surface side (corresponding to the main surface 2B side in the heat dissipation member 1) is preferably 10 μm or more and 300 μm or less. Moreover, about the difference of the average thickness of the metal containing layer of both surfaces, it is preferable that the thinner average thickness is less than 50% with respect to the thicker average thickness.

  About the difference of the average thickness of the metal containing layer of both surfaces, it is more preferable to adjust within 40% of the average thickness of the metal containing layer of the heat radiation surface, and particularly preferably within 30%. This is because it is possible to suppress the bending state from being changed due to the difference in thermal expansion coefficient between the metal-containing layers on both sides.

In (Step 4), the surface metal layer on the surface side of the metal-silicon carbide composite that has been processed into at least a convex curved shape is machined, and in some cases, an annealing treatment or the like is further performed. _A heat radiating member with ₂ is smaller than f ₁ by 10 μm or more. Specifically, an appropriate curved shape is formed on the heat-radiating surface of the metal-silicon carbide composite with a tool capable of precise cutting (grinding, cutting, etc.) such as a lathe, and then, for example, 400 muffle furnace is used. Heating is performed at about 550 ° C. to about 550 ° C. and annealing is performed for about 2 to 6 hours.

In the present embodiment, it is possible to obtain a heat radiating member in which f ₁ , f _{2, and the} like have desired numerical values by precisely machining the surface layer on the surface of the metal-silicon carbide composite. In particular, not only the surface side processed into the convex curved shape of the metal-silicon carbide composite, but also the opposite side as needed, by appropriate machining (grinding, cutting, etc.), the desired f A heat dissipating member having ₁ , f ₂ , h ₁ / a, h ₂ / b, or the like can be obtained. That is, a heat radiating member having better heat radiating characteristics and reliability can be obtained.
In general, the metal-silicon carbide composite or the heat radiating member is deformed as a whole by a heat treatment such as “annealing” that can be performed in the above (Step 1) to (Step 4). In other words, even if only the heat dissipation surface of the metal-silicon carbide composite is curved by grinding, cutting, etc., a certain degree of curvature is usually formed on the opposite surface of the heat dissipation surface by heat treatment such as annealing. that (i.e., _{f 2} is the value not normal 0). Note that the degree of deformation due to heat treatment such as annealing can be estimated to some extent quantitatively by conducting several preliminary experiments.
In short, in the present embodiment, it is important to appropriately combine the machining conditions and the annealing conditions in order to obtain a desired heat radiating member.

The total average thickness of the metal-containing layers on both sides after the machining is preferably 500 μm or less, and particularly preferably 300 μm or less.
If the sum of the average thicknesses of the metal-containing layers on both sides is 500 μm or less, the thermal expansion of the entire heat radiating member can be kept relatively small, and when a thermal load is applied, the heat radiating member and the power element connected to the upper surface thereof It is possible to suppress the occurrence of cracks due to the difference in thermal expansion coefficient from the above.

Of course, the manufacturing method of the heat radiating member of this embodiment is not limited to the above.
For example, in the heat dissipation member of the present embodiment, the surface metal layer has an arbitrary configuration, and thus the surface metal layer does not necessarily have to be formed in the above (Step 3).

  As another example, it is also conceivable to omit (Step 2) among the above (Step 1) to (Step 4). In other words, the silicon carbide based porous body (SiC preform) before impregnation with the metal is not processed into a curved shape at the stage, and the desired machining or plane is performed at the stage of (Step 4). It is also conceivable to obtain a heat dissipation member having a degree. However, since machining before metal impregnation is easier to perform than after metal impregnation, it is preferable to form a certain curved shape at the stage of (Step 2) from the viewpoint of manufacturing cost reduction.

  As yet another example, it is conceivable to omit (Step 4) among the above (Step 1) to (Step 4). In other words, if the bending process is performed with sufficient accuracy at the stage of (Process 2) and a desired curve is provided in the mold used during the impregnation of (Process 3), machining in (Process 4) is unnecessary. There may be cases. However, in consideration of a change in dimensions due to heating and cooling due to metal impregnation, even if the bending process is performed with sufficient accuracy at the stage of (Step 2), the curved shape or plane can be obtained by performing (Step 4). It is preferable to adjust the degree.

The manufacturing method of the heat radiating member of the present embodiment may include other steps not described above.
For example, you may include the process of providing the hole for screwing. For example, between the above (Step 3) and (Step 4), holes for screwing for joining to other parts may be provided in the metal-silicon carbide composite by machining or the like. By providing a screwing hole between (Step 3) and (Step 4), the hole is used when fixing the metal-silicon carbide composite to the cutting / grinding tool in (Step 4). There is a merit that you can.

Further, after (Step 4), a step of polishing or blasting the surface of the heat dissipation member may be performed. Thus, it is possible to appropriately adjust for example the average length RS _m of the aforementioned roughness curve element. As a specific method of the polishing process or the blasting process, a known method can be appropriately applied.

  In addition, after (Step 4), a plating step may be performed to provide a plating layer. For example, a plating layer can be provided on the surface of the heat dissipation member by a known electroless Ni—P plating or Ni—B plating technique. The preferable thickness and the like of the plating layer are as described above.

  As mentioned above, although embodiment of this invention was described, these are illustrations of this invention and can employ | adopt various structures other than the above. Further, the present invention is not limited to the above-described embodiment, and modifications, improvements, and the like within the scope that can achieve the object of the present invention are included in the present invention.

Embodiments of the present invention will be described in detail based on examples and comparative examples. In addition, this invention is not limited to an Example.
In the following description, the “main surface 2A” is a surface joined to the heat radiating fins and the like, as described above, and is curved in a convex shape not in the inner direction but in the outer direction. The “main surface 2B” is a surface to which components such as a power element are connected.

<Manufacture of heat dissipation member>
[Example 1]
(Formation of silicon carbide based porous material)
First, the following silicon carbide powder A, silicon carbide powder B and silica sol were mixed with a stirring mixer for 30 minutes to obtain a mixture.
Silicon carbide powder A (manufactured by Taihei Random Co., Ltd .: NG-150, average particle size: 100 μm) 300 g
・ Silicon carbide powder B (manufactured by Yakushima Electric: GC-1000F, average particle size: 10 μm) 150 g
・ Silica sol (Nissan Chemical Industry Co., Ltd .: Snowtex) 30g

  The obtained mixture was put into a mold and press-molded at a pressure of 10 MPa. This obtained the flat molded object of the dimension of 185 mm x 135 mm x 5.5 mm. The obtained molded body was fired in the atmosphere at a temperature of 900 ° C. for 2 hours to obtain a silicon carbide based porous body having a relative density (bulk density) of 65 volume%.

The surface which becomes the main surface 2B of the heat dissipation member after completion of the silicon carbide based porous body was processed with a surface grinder. Thereafter, the surface to be the main surface 2A was machined into a convex curved shape with a lathe of R = 11 m. At this time, the thickness of the center of the silicon carbide based porous material was adjusted to be 4.8 mm.
In addition, 30 similar silicon carbide based porous bodies were prepared for the following steps.

(Metal impregnation)
210mm x 160mm x 0.8mm dimensions with alumina fiber (Tanaka Paper Industries Co., Ltd., purity 97%, sheet form) on the main surface 2A side of the machined silicon carbide porous body and carbon coated on both sides 30 sheets were laminated with a stainless steel plate.
Next, an iron plate having a thickness of 6 mm was arranged on both sides, connected with six M10 bolts, and tightened with a torque wrench so that the tightening torque in the surface direction was 3 Nm, thereby forming one block.
Thereafter, the integrated block was preheated to 620 ° C. in an electric furnace, and then stored in a preheated press mold having an inner diameter of 400 mmφ. A molten aluminum alloy containing 12% by mass of silicon and 1.0% by mass of magnesium was poured into the press mold, and pressed at a pressure of 100 MPa for 20 minutes. Thereby, the silicon carbide porous body was impregnated with the aluminum alloy.

After the impregnation, it was cooled to 25 ° C., then cut along the shape of the stainless steel plate with a wet band saw, and the sandwiched stainless steel plate was peeled off. Thereafter, annealing treatment was performed at a temperature of 500 ° C. for 3 hours in order to remove distortion during impregnation.
Thus, an aluminum-silicon carbide composite was obtained.

(Process after impregnation)
The outer periphery of the obtained aluminum-silicon carbide composite was processed with an NC lathe to make the vertical and horizontal dimensions 190 mm × 140 mm. Thereafter, through holes with a diameter of 7 mm were processed at 8 locations on the peripheral edge, and countersinks with a diameter of 10-4 mm were processed at 4 locations.

  Further, the side corresponding to the main surface 2A of the aluminum-silicon carbide composite was machined by a turning center so that R = 11 m. After machining, annealing was performed for 4 hours at a temperature of 500 ° C. using a muffle furnace. Thereby, the processing strain was removed.

  Further, the aluminum-silicon carbide composite is cleaned by blasting with alumina abrasive grains under conditions of a pressure of 0.4 MPa and a conveying speed of 1.0 m / min, and then electroless Ni-P and Ni-B plating Went. As a result, a plating layer having a thickness of 8 μm (Ni—P: 6 μm, Ni—B: 2 μm) was formed on the composite surface.

  Thus, a heat radiating member was obtained.

(Measurement of f ₁ and f ₂ )
The obtained heat radiation member, the main surface 2A and the main surface 2B, respectively, were measured flatness using a Keyence device VR-3000, was obtained _{f 1} and _{f 2.} At this time, since the main surface 2A and the main surface 2B did not fit in the apparatus observation field of view, the center (geometric center of gravity) when the main surface 2A / main surface 2B were viewed from above and the center of the observation field of view of the measurement apparatus Were measured, and a range of 190 mm × 100 mm was measured.

(Measurement of h ₁ and h ₂ )
Data on the shapes of the main surface 2A and the main surface 2B were obtained using a laser three-dimensional shape measuring machine, and h ₁ and h ₂ were obtained by analyzing the data.
Equipment: Laser three-dimensional shape measuring machine (the following four devices are integrated)
XYθ stage unit: K2-300 (manufactured by Kozu Seiki Co., Ltd.)
High precision laser displacement meter: LK-G500 (manufactured by Keyence Corporation)
Motor controller: SC-200K (manufactured by Kozu Seiki Co., Ltd.)
AD converter: DL-100 (manufactured by Kozu Seiki Co., Ltd.)

(Measurement of RSm)
The average length RSm of the roughness curve elements of the main surface 2A and the main surface 2B was measured according to ISO 4287-1997 using an apparatus SJ-310 manufactured by Mitutoyo Corporation.

[Examples 2 to 12]
In Examples 2 to 12, the length of the long side and the short side of the heat radiating member, the processing R in the above (formation of silicon carbide based porous material), the processing R in the above (processing after impregnation), and the like are changed. Produced the heat radiating member by the process similar to Example 1. FIG. Various values were measured in the same manner as in Example 1.

[Comparative Examples 1-3]
In the above (formation of the silicon carbide based porous material), the surface of the silicon carbide based porous material which is the main surface 2B of the heat dissipation member was not processed with a surface grinder, A heat radiating member was produced in the same manner as in Example 1 except that the processing R in the formation) and the processing R in the above (processing after impregnation) were changed. Various values were measured in the same manner as in Example 1.
In addition, since the surface used as the main surface 2B of the heat radiating member after completion was not processed with the surface grinder, the surface was curving somewhat naturally by baking and subsequent cooling.

Various numerical values are summarized in Table 1 and Table 2.
In the table, “E” in the columns of h ₁ / a and h ₂ / b is an exponential notation, and for example, 2.38E-03 means 2.38 × 10 ⁻³ .

<Evaluation of manufacturing stability of power modules>
Ten heat-dissipating members of each Example or Comparative Example were prepared, and a simulated power module substrate was manufactured by connecting a simulated power element to them.
As a specific procedure for manufacturing, using a device normally used for manufacturing a power module, among the two main surfaces of the heat radiating member of each example or comparative example, a specific 6 on the main surface 2B is used. A ceramic substrate (a substrate provided with a metal layer such as copper or aluminum on both sides of the ceramic plate) was soldered to the location. Thus, a simulated power module substrate was obtained.
Thereafter, in order to obtain a simulated power module, the simulated power module substrate was provided with a case, resin-sealed, and covered with a lid to obtain a simulated power module.

The obtained simulated power module was inspected for defects that could cause problems in mass production.
In all the simulated power modules manufactured using the heat radiation member of each example, there was no problem that could cause a problem in mass production.
On the other hand, in the simulated power module substrate manufactured using the heat radiating members of Comparative Examples 1 to 3, the jig for positioning the ceramic substrate does not fit well into one of the 10 pieces, the case after the ceramic substrate is connected There was a problem that could cause mass production problems.

  From the above results, it is shown that the manufacturing stability (yield, etc.) at the time of manufacturing the power module can be improved by using a plate-like heat radiating member having such a feature that the flatness of the two main surfaces satisfies a specific relationship. It was done.

In addition, when the heat radiating member of Examples 1-12 was joined to the heat radiating fin with a screw and the adhesion between the heat radiating member and the heat radiating fin, the heat radiating property, and the like were evaluated, the adhesion and the heat radiating property were good.
That is, it was shown that by using the heat radiating members of Examples 1 to 12, it is possible to manufacture a power module with good heat dissipation and to improve the yield when manufacturing such a power module.

1 Heat dissipation member 2A Main surface (one main surface)
2B Main surface (the other main surface)
5 Connection surface

Claims (9)

A plate-like heat dissipation member comprising a metal-silicon carbide composite containing aluminum or magnesium,
At least one main surface of the two main surfaces of the heat dissipation member is curved in a convex shape in the outer direction of the heat dissipation member,
Of the one main surface, JIS B flatness defined as _{f 1} in 0621, the other main surface is different from the main surface and said one main surface, a flatness defined by JIS B 0621 f when _two smaller radiating member should have 10μm or more than _{f 1} of _{f 2.} It is a heat radiating member of Claim 1, Comprising: A heat radiating member provided with the surface metal layer in which said one main surface and / or said other main surface contain aluminum or magnesium. Radiating member wherein _{f 1} is 100μm or more 700μm or less a heat radiating member according to claim 1 or 2. The heat dissipation member according to any one of claims 1 to 3,
Radiating member wherein _{f 2} is 300μm or less. The heat dissipation member according to any one of claims 1 to 4,
The heat dissipating member is substantially rectangular,
The length of the long side of the rectangle is a, the length of the short side is b,
A straight line connecting between the midpoints of the two short sides of the one main surface is l ₁ , and a straight line connecting between the midpoints of the two long sides of the one main surface is l ₂ ,
when the heat radiating member viewed in cross section with include l ₁ and the one main surface and cross section substantially perpendicular, said a point on the curve formed by the one major surface, the maximum distance between l ₁ and h _1,
The maximum distance between a point on the curve formed by the one main surface and l ₂ when the heat radiating member is viewed in a cross-section in a cross section that includes l ₂ and is substantially perpendicular to the one main surface is h ₂ . When
A heat radiating member satisfying h ₁ / a ≧ h ₂ / b. The heat dissipating member according to claim 5,
A heat dissipation member having a value of (h ₁ / a) / (h ₂ / b) of 1.00 or more and 1.9 or less. The heat dissipation member according to any one of claims 1 to 6,
It said one main surface, the average length RS _m of roughness curve element, the heat radiating member is 50μm or more 250μm or less. The heat dissipation member according to any one of claims 1 to 7,
It said other main surface, the average length RS _m of roughness curve element, the heat radiating member is 50μm or more 200μm or less. It is a manufacturing method of the heat radiating member given in any 1 paragraph of Claims 1-8,
Preparing a plate-like metal-silicon carbide composite containing aluminum or magnesium;
And a step of machining a part of at least one surface of the composite to provide the one main surface.

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