JP2012144767A - Composite member, heat radiation member, semiconductor device, and method of manufacturing composite member - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide: a composite member superior in adhesion with solder; a heat radiation member comprising the composite members; a semiconductor device including the heat radiation member; and a method of manufacturing the composite member.SOLUTION: A composite member 1 includes a substrate 20 made of a composite material in which magnesium or magnesium alloy is combined with SiC, and a metal covered layer 10 having multilayer structure that is formed on the surface of the substrate 20. The metal covered layer 10 includes, in order from the side of the substrate 20: an underlayer 11 having the same composition as a matrix metal of the substrate 20; a zinc layer 12 formed by zincate treatment; a copper plating layer 13; and a nickel plating layer 14. The copper plating layer 13 is comparatively thick, exceeding 1 μm in thickness. Due to such a structure, peeling strength between the composite member 1 and solder is high, and semiconductor elements or the like are hard to be peeled off from the composite member 1 when they are bonded thereto.

Description

  The present invention relates to a composite member in which magnesium (so-called pure magnesium) or a magnesium alloy and SiC are combined, a heat radiating member composed of the composite member, a semiconductor device including the heat radiating member, and a method for manufacturing the composite member It is. In particular, the present invention relates to a composite member having excellent adhesion with solder.

  As a constituent material of a heat radiating member (heat spreader) of a semiconductor element, a composite material of a metal and a non-metallic inorganic material (typically ceramics) such as Al—SiC is used. In recent years, a magnesium-based composite material using magnesium (Mg), which is lighter than aluminum (Al), or an alloy thereof as a matrix metal has been studied mainly for the purpose of reducing the weight of a heat dissipation member (see Patent Document 1).

  When it is desired to sufficiently cool the semiconductor element, the heat radiating member and the semiconductor element may be joined by solder. Patent Document 1 proposes to provide a metal layer such as magnesium on the surface of a substrate made of a composite material in order to uniformly apply nickel plating in order to improve wettability with solder.

JP 2010-106362 A

  It is desired to improve the adhesion between the heat dissipation member and the solder. By increasing the adhesion, the reliability of the joint between the heat dissipation member and the solder can be increased. In order to increase the adhesion, it is effective to increase the adhesion between the nickel plating and the substrate. Although nickel plating can be applied uniformly by forming a metal layer such as magnesium on a substrate made of the above-described magnesium-based composite material, the adhesion between the nickel plating and the substrate is further enhanced with only the metal layer. It is difficult. As a result, it is difficult to further improve the adhesion between the heat dissipation member and the solder. Conventionally, a structure for further improving the adhesion has not been sufficiently studied.

  Then, one of the objectives of this invention is providing the composite member excellent in adhesiveness with a solder. Another object of the present invention is to provide a heat radiating member composed of the above composite member and a semiconductor device including the heat radiating member. Furthermore, the other object of this invention is to provide the manufacturing method of the said composite member.

  In order to improve the adhesiveness with the solder, the present inventors studied to perform a zincate treatment, which is widely used as a pretreatment for plating, before nickel plating. As a result, although the adhesion was improved, it was not sufficient. Then, in addition to the zincate process, when copper plating was examined, the adhesiveness was improved. In particular, although the detailed mechanism is not clear, a substrate made of a composite material by using a thin plating such as general strike plating, more specifically, a relatively thick copper plating rather than a nano-order plating. It was found that the adhesion between aluminum and plating can be greatly improved. The present invention is based on the above findings.

  The composite member of the present invention comprises a substrate made of a composite material in which magnesium or a magnesium alloy and SiC are composited. The composite material contains 50% by volume or more of SiC, and the thermal expansion coefficient of the composite member is 4 ppm / K or more. 15 ppm / K or less. A metal coating layer covering at least a part of at least one of the pair of opposing surfaces of the substrate is provided. The metal coating layer includes, in order from the substrate side, a base layer, a zinc layer, a copper plating layer, and a nickel plating layer serving as an outermost surface layer, and the thickness of the copper plating layer is more than 1 μm.

  The composite member of the present invention has a smooth surface by providing an underlayer. Here, when the surface of the composite member is not smooth and has unevenness, the unevenness on the surface of the composite member remains even after plating. As a result, the gas (mainly air) present in the recessed portion is blown out as bubbles from the recessed portion during soldering, causing defective soldering. On the other hand, the composite member of the present invention has a smooth surface as described above, so that the bubbles are difficult to blow out, poor soldering is difficult to occur, and is excellent in surface properties and appearance. In addition, since the base layer is made of metal, electroplating can be used with the base layer as a conductive portion in forming the plating layer, and the plating layer can be formed with high productivity.

  And although a detailed mechanism is unknown about this invention composite member, a board | substrate and a nickel plating layer closely_contact | adhere firmly because a copper plating layer is comparatively thick. Therefore, when a solder is applied on the nickel plating layer and a desired member is joined, the member is hardly peeled off from the solder or the nickel plating layer, and the reliability of the joint portion with the solder can be improved. In addition, since the adhesion between the substrate and the nickel plating layer is high, even when the plating layer is used as a corrosion-resistant layer without applying solder, the plating layer is difficult to peel off, so that the corrosion resistance and the like are also improved. Excellent.

  In addition, the composite member of the present invention has a thermal expansion coefficient that is about the same as that of the semiconductor element and its peripheral parts (about 4 ppm / K to 8 ppm / K), or a small difference in thermal expansion coefficient. In such a case, even when subjected to a heat cycle, the semiconductor element and its peripheral parts are difficult to peel off due to thermal expansion and contraction. Therefore, the heat radiating member using the composite member of the present invention can efficiently release the heat of the semiconductor element and can be suitably used for the heat radiating member of the semiconductor element.

  As one form of this invention, the form by which the said base layer was comprised from magnesium is mentioned.

  Although various metals can be used as the constituent material of the base layer, the adhesion between the base layer and the substrate is excellent by using magnesium which is the same as the main component of the metal component of the substrate. Therefore, it is expected to contribute to an improvement in peel strength between the substrate and the nickel plating layer.

  As one form of this invention, the form comprised from the structure | tissue where the constituent metal of the said base layer and the metal component of the said composite material continue is mentioned.

  The composite member of the above form can be obtained, for example, by forming a base layer simultaneously with the manufacture of a substrate when a substrate made of a composite material is manufactured by an infiltration method. That is, according to the above embodiment, the manufacturing process of the substrate and the manufacturing process of the base layer can be made into one process, and the manufacturing process is excellent, and the structure material of the substrate and the constituent material of the base layer are continuous. And it is excellent also in the adhesiveness of both. Therefore, it is expected to contribute to an improvement in peel strength between the substrate and the nickel plating layer. Also, in this embodiment, when the metal component is magnesium, compared to the case of a magnesium alloy, (1) the thermal conductivity of the substrate and the underlayer can be increased, and (2) crystal precipitates are nonuniform during solidification. Since it is difficult to generate, it has an advantage that it is easy to form a uniform structure.

  As one form of the present invention, a form in which the thermal conductivity of the composite member is 180 W / m · K or more can be mentioned.

  According to the said form, it can utilize suitably for the heat radiating member of a semiconductor element because a thermal expansion coefficient is a value comparable as or near the value of a semiconductor element and its peripheral device, and thermal conductivity is high enough.

  A utilization form of the composite member of the present invention includes a heat radiating member constituted by the composite member, a semiconductor device including the heat radiating member, and a semiconductor element mounted on the heat radiating member.

  As described above, according to the composite member of the present invention, it has a thermal expansion coefficient suitable for the thermal expansion coefficient of the semiconductor element and its peripheral devices, and is excellent in heat dissipation. Available to:

The composite member of the present invention comprising the substrate made of the magnesium-based composite material and the metal coating layer having a multilayer structure can be manufactured by, for example, the following manufacturing method of the present invention. The manufacturing method of the composite member of the present invention relates to a method of manufacturing a plate-shaped composite member made of a composite material by combining magnesium or a magnesium alloy and SiC, and the following material preparation step, zincate processing step And a copper plating step and a nickel plating step, and through these steps in the above order, a composite member having a thermal expansion coefficient of 4 ppm / K or more and 15 ppm / K or less is manufactured.
Material preparation step: A substrate made of a magnesium-based composite material with a SiC content of 50% by volume or more and a base layer made of metal on at least a part of at least one of a pair of opposing surfaces of the substrate. The process of preparing materials that can be obtained.
Zincate treatment step: A step of forming a zinc layer by performing a zincate treatment on the base layer.
Copper plating step: A step of forming a copper plating layer having a thickness of more than 1 μm by performing copper plating on the zinc layer.
Nickel plating step: a step of forming a nickel plating layer by performing nickel plating on the copper plating layer.

  As one form of the production method of the present invention, before performing the zincate treatment, the material is subjected to heat treatment under the conditions of a heating temperature of 200 ° C. or more, a melting point of magnesium or a magnesium alloy in the substrate, a heating time of 5 minutes or more. The form which comprises the process to give is mentioned.

  By making the copper plating layer relatively thick as described above, a composite member having high adhesion between the substrate and the metal coating layer (particularly the nickel plating layer) can be obtained. Furthermore, as a result of investigations by the present inventors, it was found that swelling (local peeling) may occur in the metal coating layer when solder is applied. As a result of various studies to reduce the local peeling, it was found that it is effective to perform heat treatment before the zincate treatment as described above. Although this detailed reason is not certain, it estimates as follows. When the underlayer is etched as a pretreatment for the zincate process, the swelling is uneven in the degree of erosion due to etching, and the deeply eroded portion becomes a groove or a hole (hereinafter simply referred to as a groove). By applying zincate treatment or plating so as to cover the air, the air in the groove portion expands due to the heat at the time of applying the solder, and this expansion causes peeling at the interface between the base layer and the zinc layer by the zincate treatment. It is thought that it occurred. This variation in the degree of erosion due to etching is considered to be caused by defects that may exist locally in the underlayer. Then, it is considered that this defect was corrected by the heat treatment, so that variation in the degree of erosion during etching could be reduced, and swelling was reduced by suppressing the formation of the groove. The specific conditions are proposed as the heat treatment conditions.

  In the composite member of the present invention, the heat dissipation member of the present invention, and the semiconductor device of the present invention, the nickel plating layer is hardly peeled off and is excellent in adhesiveness with the solder.

FIG. 1 is a schematic cross-sectional view of a composite member according to an embodiment. FIG. 2 is a micrograph of a metal coating layer portion in the composite member (sample No. 5) of the embodiment. FIG. 3 is a photomicrograph of the metal coating layer portion in the swollen composite member.

Hereinafter, the present invention will be described in more detail.
≪Composite material≫
First, a substrate made of a composite material of a matrix metal and a nonmetallic inorganic material, which is a main component of the composite member, will be described.
〔substrate〕
[Matrix metal: Magnesium or magnesium alloy]
The metal component of the substrate is so-called pure magnesium composed of 99.8% by mass or more of Mg and impurities, or a magnesium alloy composed of additive elements and the balance Mg and impurities. When the metal component is pure magnesium, it has the advantages of improving the thermal conductivity and the uniformity of the structure as described above. When the metal component is a magnesium alloy, the melting temperature is lowered due to the lowering of the liquidus temperature, and the corrosion resistance of the substrate. And an improvement in mechanical properties (strength, etc.). The additive element includes at least one of Li, Ag, Ni, Ca, Al, Zn, Mn, Si, Cu, Zr, Be, Sr, Y, Sn, Ce, and rare earth elements (excluding Y and Ce). . Since these elements cause a decrease in thermal conductivity when the content increases, the total content is preferably 20% by mass or less (the total alloy is 100% by mass; the same applies to the content of additive elements). In particular, Al is preferably 3% by mass or less, Zn is 5% by mass or less, and other elements are each preferably 10% by mass or less. Addition of Li has the effect of reducing the weight of the composite member and improving the workability. Known magnesium alloys such as AZ, AS, AM, ZK, ZC, LA, and WE may be used. A matrix metal raw material is prepared so as to have a desired composition.

[Non-metallic inorganic material: SiC]
<Composition>
SiC (1) has a thermal expansion coefficient of about 3 ppm / K to 4 ppm / K and is close to the thermal expansion coefficient of semiconductor devices and peripheral components. (2) Among non-metallic inorganic materials, it has a particularly high thermal conductivity. (Crystal: about 390W / m · K to 490W / m · K), (3) Various shapes and sizes of powders and sintered bodies are commercially available, and (4) High mechanical strength. Play. Therefore, in the composite member of the present invention, SiC is a constituent element. Other non-metallic inorganic materials having a thermal expansion coefficient smaller than that of Mg, excellent thermal conductivity, and difficult to react with Mg, such as Si ₃ N ₄ , Si, MgO, Mg ₂ Si, MgB ₂ , Al ₂ O ₃ At least one of AlN, diamond, and graphite can be contained.

<Presence state>
The presence state of the SiC is typically a dispersed form in a matrix metal (hereinafter referred to as a dispersed form), a form connected by a network unit that bonds SiC (hereinafter referred to as a bonded form). Is mentioned. In the dispersion form, powder can be typically used, and the formation of the network part is unnecessary, the productivity is excellent, and the cost can be reduced. In the bonded form, since SiC is continuous, the heat conduction path is continuous, so that the substrate is likely to have a high thermal conductivity. In particular, the entire SiC is connected by the network part, and the matrix metal is filled between the SiC, and there are few closed pores in addition to this configuration (the closed pore is 10 volumes with respect to the total volume of SiC in the substrate). % Or less, preferably 3% by volume or less), since the matrix metal is sufficiently present, the thermal conductivity is further improved. A typical example of the network unit is a configuration composed of SiC. In addition, the network part may be configured by a non-metallic inorganic material other than SiC described above. The presence of the network portion and the ratio of closed pores in the substrate can be confirmed or measured by observing the cross section of the substrate with an optical microscope or a scanning electron microscope (SEM), for example.

<Content>
The content of SiC in the substrate is 50% by volume or more when the substrate is 100% by volume. When SiC is 50 volume% or more, the thermal expansion coefficient of the substrate is about 3.5 ppm to about 15 ppm, and the thermal expansion coefficient of the composite member including the metal coating layer described later is 4 ppm / K or more and 15 ppm / K or less. It can be a composite member. The higher the SiC content, the higher the thermal conductivity and the smaller the thermal expansion coefficient. In consideration of the thermal characteristics, it is preferably 60% by volume or more, and more preferably 65% by volume or more. In particular, when it is 60% by volume or more and 90% by volume or less, and further 65% by volume or more and 85% by volume or less, the thermal characteristics are excellent as described above, and the industrial productivity of the substrate is also excellent.

[Thickness of substrate]
The thickness of the substrate can be selected as appropriate, but is preferably 10 mm or less, particularly 6 mm or less when used as a heat dissipation member for a semiconductor element.

[Thermal characteristics of the substrate]
Since the substrate contains 50% by volume or more of SiC, the thermal expansion coefficient is small with the substrate alone as described above. Further, the substrate has a high thermal conductivity, for example, 180 W / m · K or more, 200 W / m · K or more, particularly 220 W / m · K or more.

(Metal coating layer)
Next, the metal coating layer provided on the substrate will be described.
One of the features of the composite member of the present invention is that at least part of at least one of the pair of opposing surfaces of the substrate is provided with a metal coating layer having a multilayer structure made of a specific metal. By providing this metal coating layer, the wettability with solder can be improved when solder is applied. Moreover, by setting it as a specific composition and thickness so that it may mention later, the peeling strength of a board | substrate and the nickel plating layer mentioned later is high, As a result, this invention composite member and solder can adhere | attach firmly. In addition, the provision of a metal coating layer can also be expected to have effects such as (1) excellent appearance and surface properties and (2) improved corrosion resistance.

[Underlayer]
The lowermost layer of the metal coating layer, that is, the foundation layer provided immediately above the substrate, smoothes the surface of the substrate made of a composite material and forms a copper plating layer and a nickel plating layer, which will be described later, with a uniform thickness. It can be made easier, or can be used as a conduction point when the plating layer is formed by electroplating. The underlayer is made of an appropriate metal capable of having such a function. For example, it is possible to adopt a form composed of the same composition as the matrix metal or a form composed of the same composition as the main component (magnesium) of the matrix metal. In particular, it is preferable that the underlayer is formed of a structure continuous with the matrix metal because of excellent productivity. The form in which the underlayer is composed of the above continuous structure (in this case, the underlayer has a cast structure similar to that of the matrix metal) forms the underlayer simultaneously with the composite of SiC and the matrix metal as described above. It is obtained by doing. Therefore, in this embodiment, the substrate made of the composite material and the base layer can be manufactured in one process, and the productivity is excellent. Alternatively, the underlayer can be formed from a composition different from that of the matrix metal. Specifically, for example, from the group consisting of Al, Cu, Ni having a purity of 99% or more and alloys containing Al, Cu, Ni as the main component (alloys containing more than 50% by mass of Al, Cu, Ni) A form in which the base layer is composed of one selected metal is exemplified.

  The thickness of the underlayer is preferably 1 μm or more, and if it is too thick, it causes an increase in the thermal expansion coefficient of the entire composite member including the metal coating layer and a decrease in the thermal conductivity of the composite member. It is preferably 1 mm or less, more preferably 0.5 mm (500 μm) or less.

[Zinc layer]
The zinc layer provided on the base layer is a layer formed by a zincate process described later, and has a function of easily forming a copper plating layer described later. The zinc layer formed by the zincate treatment is a very thin layer on the order of 1 nm to 100 nm. Such a thin layer is one of the indicators showing that the thin layer is formed by the zincate process.

[Copper plating layer]
The greatest feature of the composite member of the present invention is that a copper plating layer is provided on the zinc layer, and the thickness thereof is relatively thick, more than 1 μm. Since the copper plating layer is relatively thick as described above, the composite member of the present invention particularly increases the peeling strength of the nickel plating layer, and the zinc layer, the copper plating layer, and the nickel plating layer are difficult to peel off when bonded to solder. . If the thickness of the copper plating layer is too thick, it causes an increase in the coefficient of thermal expansion of the composite member, an increase in weight, and a decrease in productivity. Therefore, it is preferably 50 μm or less, particularly preferably 10 μm or less, and more preferably 1 μm or more and 10 μm or less. . In addition, the copper plating layer can be expected to have the same effect even in the form of a copper alloy. In addition, the presence of a very thin zinc layer such as a nano-order in the lower layer as described above in the above range is an index indicating that the copper layer on the zinc layer has been formed by plating. Become one.

[Nickel plating layer]
The nickel plating layer provided on the copper plating layer is a layer that forms the outermost surface of the metal coating layer. In a typical form of the composite member of the present invention, at least a part of the outermost surface of the composite member is nickel. It is formed by a plating layer. The nickel plating layer mainly has a function of improving the wettability with the solder and contributes to an improvement in appearance and corrosion resistance. If the thickness of the nickel plating layer is too thick, it causes an increase in the coefficient of thermal expansion of the composite member, a decrease in thermal conductivity, and a decrease in productivity, so 50 μm or less, particularly 10 μm or less is preferable, and 1 μm or more and 10 μm or less. More preferred. In addition, the nickel plating layer can be expected to have the same effect even when the nickel plating layer is formed of a nickel alloy.

[Metal coating layer formation area]
The formation region of the metal coating layer on the substrate can be appropriately selected. For example, when the composite member of the present invention is used as a heat radiating member for a semiconductor element, one of the opposing surfaces of the substrate is a mounting surface on which the semiconductor element is mounted, and the other surface is a cooling surface that contacts the cooling device. Used. Usually, since solder is applied to the mounting surface, it is preferable to provide a metal coating layer at least on the mounting surface of the mounting surface. A metal coating layer may be provided on the entire mounting surface, and both the mounting surface and the cooling surface. The total thickness of the metal coating layer is preferably 10 μm or more and 1000 μm or less.

[Thermal characteristics of heat dissipation member]
Although the composite member of the present invention has the metal coating layer, the thermal expansion coefficient tends to be larger than that of the substrate made of the magnesium-based composite material, but it is 4 ppm / K or more and 15 ppm / K or less. The thermal expansion coefficient consistency with the semiconductor element and its peripheral devices is excellent. In addition, the composite member of the present invention contains a specific amount of SiC, so that the thermal conductivity is high, and satisfies, for example, 180 W / m · K or more. As mentioned above, by increasing the filling rate of SiC, having a network part, or by reducing the thickness of the metal coating layer (thickness of each layer), the thermal expansion coefficient is smaller and the thermal conductivity is lower. A higher composite member can be obtained. For example, a composite member having a thermal conductivity of 200 W / m · K or more, particularly 250 W / m · K or more, and further 300 W / m · K or more can be obtained. By using the composite member having excellent thermal conductivity as the heat radiating member in this manner, the reliability of the heat radiating member can be improved, and the heat radiating member can be made smaller, which can contribute to the miniaturization of the semiconductor device. . In addition, in a composite member having a metal coating layer, the thermal expansion coefficient and thermal conductivity can be measured by a commercially available device, and the thermal expansion coefficient is determined by a composite law in consideration of the rigidity of each material constituting the composite member. It can be calculated.

≪Heat dissipation material≫
As described above, the composite member of the present invention, which has excellent thermal expansion coefficient matching with the semiconductor element and its peripheral devices and excellent heat dissipation, can be used as it is as a heat dissipation member for semiconductor elements. In addition, the heat dissipating member can be provided with a through-hole through which a fixing member such as a bolt for fixing to the cooling device is inserted at an appropriate location (typically near the corner or periphery of the substrate). . The through-hole can be formed in the composite material portion by using, for example, laser or electric discharge machining. However, if the through-hole portion is made of a metal, it is easy to perform drilling. For example, when manufacturing a substrate so that the metal portion is provided at an appropriate place on the substrate, the metal piece is placed in a mold, and the metal piece is cast simultaneously at the time of compounding, and the metal piece portion of the obtained substrate is punched. Or by preparing an appropriate metal tube and casting the metal tube at the same time during compounding, a composite member having a through hole can be obtained. The metal piece may be the same metal as the metal component of the substrate, i.e., magnesium or a magnesium alloy, or at least a part of a different metal, for example, stainless steel, non-metallic high-strength material such as carbon (including fibrous materials). May be included). At least a part of the through-hole made of the high-strength material is less likely to loosen due to a decrease in the axial force of the bolt even when subjected to a heat cycle, and the heat radiating member of the present invention is firmly fixed to the fixing target. The state can be maintained stably. The through hole may be either a threaded screw hole or a form that is not threaded, and may be a form that is countersunk.

≪Manufacturing method≫
Next, the manufacturing method of the composite member provided with the said metal coating layer is demonstrated in order of a process.
[Material preparation process]
In this step, a material including an underlayer is produced on a substrate made of a magnesium-based composite material containing SiC. An infiltration method can be suitably used for manufacturing the substrate. The infiltration method is a method in which molten magnesium or a magnesium alloy is infiltrated into a SiC aggregate housed in a mold and combined. In addition, a powder metallurgy method, a melting method, etc. can be utilized. When the infiltration method is used for manufacturing the substrate, the underlayer can be formed simultaneously with the composite as described above. In addition, a metal plate for forming vapor deposition and an underlayer is appropriately prepared. This metal plate is brazed, ultrasonic bonded, cast-in, rolled (clad rolling), hot press, oxide solder method, inorganic adhesive. The base layer can be formed by bonding to the substrate using at least one technique of bonding by the above. When the composition of the underlayer is different from that of the matrix metal, a technique using the metal plate may be used.

[material]
As the matrix metal, an ingot of pure magnesium or a magnesium alloy can be suitably used. As a raw material for the SiC aggregate, typically, SiC powder can be used. In particular, it is a particulate or fibrous SiC powder, and the average particle diameter (in the case of a fiber, the average short diameter) is 1 μm or more and 3000 μm or less, particularly 5 μm or more and 200 μm or less, and it is easy to produce a powder aggregate. . When a plurality of types of powders having different average particle sizes are used in combination, it is easy to increase the filling rate of SiC.

  Since non-metallic inorganic materials such as SiC used as a raw material exist almost as they are in the substrate made of composite material, the volume ratio of SiC and pores in the substrate and the existence state of the network part depend on the raw material used. Depending on and substantially equal to the raw material. Therefore, the material and amount of the raw material are appropriately selected so that the substrate has desired thermal characteristics. Also, the shape and size of the mold that forms the SiC aggregate by filling the raw material powder so that the substrate has a predetermined shape and size, and the shape and size of the mold that combines the SiC aggregate and the matrix metal The size is appropriately selected.

[SiC aggregate]
In the form of the SiC aggregate, there are forms that are difficult to handle (for example, those formed by tapping) and forms that can be handled (typically powder compacts, and sintered compacts obtained by sintering powder compacts) ). The powder compact is, for example, slip cast (slurry using raw material powder and water and a dispersion material and then dried), pressure molding (dry press, wet press, uniaxial pressure molding, CIP (hydrostatic pressure). Press), extrusion molding, etc.) and doctor blade method (flowing slurry using raw material powder and solvent, antifoaming agent, resin, etc. to doctor blade, then evaporating solvent) And a sintered body (typically, a SiC porous body having a network portion) obtained by further sintering the above-described forms, or these forms or forms by tapping. When the content of SiC in the substrate is increased to, for example, 70% by volume or more, slip casting, pressure molding, and a doctor blade method can be suitably used for forming a powder compact. When the SiC content in the substrate is low, a SiC aggregate can be easily obtained by using tapping. In this case, the raw material SiC is directly filled in the mold used for the composite.

  The sintered body is (1) higher in strength than the powder molded body, is less likely to be chipped when stored in a mold and is easy to handle, (2) a porous body can be easily manufactured, (3) sintered By adjusting the temperature and holding time, there is an advantage that the sintered body can be densified and the filling rate of SiC can be easily improved. The sintering conditions are, for example, (1) vacuum atmosphere, heating temperature: 800 ° C. to less than 1300 ° C., holding time: about 10 minutes to 2 hours, (2) air atmosphere, heating temperature: 800 ° C. to 1500 ° C., holding time : About 10 minutes to 2 hours. Under conditions (1) and (2), an SiC aggregate having no network part tends to be obtained. On the other hand, when sintered in a vacuum atmosphere, heating temperature: 1300 ° C or higher and 2500 ° C or lower, holding time: 2 hours to 100 hours, SiC is directly bonded to each other, and the SiC porous body in which the network part is formed of SiC is formed. can get. By using a SiC aggregate having a network part (typically, a SiC porous body) as a raw material, a substrate having a network part can be easily obtained. A commercially available SiC sintered body (having open pores) may be used as the SiC aggregate. When using a SiC aggregate having a network part, if a porous body having few closed pores (10% by volume or less, preferably 3% by volume or less with respect to the total volume of the SiC aggregate) and having open pores is used as a raw material The molten metal of the matrix metal can be sufficiently infiltrated into the porous body, and a composite member having excellent thermal characteristics can be obtained.

[Formation of oxide film]
Further, when the SiC aggregate having an oxide film on its surface is used, the wettability between the SiC aggregate and the matrix metal is enhanced, and even if the gap between SiC is very small, the capillary Due to the phenomenon, the matrix metal melt easily penetrates. The oxide film may be formed on SiC powder, or may be formed on the above-described powder molded body or sintered body. The conditions for forming the oxide film are the same for powders and sintered bodies, and the heating temperature is preferably 700 ° C. or higher, particularly preferably 750 ° C. or higher, more preferably 800 ° C. or higher, especially 850 ° C. or higher, and further 875 It is preferably at least 1000 ° C.

[composite]
When using the infiltration method, a substrate made of a magnesium-based composite material is obtained by housing the SiC aggregate in a mold, infiltrating the matrix metal melt, and then solidifying the matrix metal. When the compounding is performed in an atmosphere of 0.1 × 10 ⁻⁵ MPa or more and atmospheric pressure (generally 0.1 MPa (1 atm)), the molten metal is easy to handle and pores due to gas uptake in the atmosphere hardly occur. Further, when compounding is performed in an inert atmosphere such as Ar, the reaction between the Mg component and the atmospheric gas can be prevented, and the deterioration of the thermal characteristics due to the presence of the reaction product can be suppressed. When the matrix metal is magnesium (pure Mg), the infiltration temperature is preferably 650 ° C. or higher, and the higher the infiltration temperature, the higher the wettability. Therefore, 700 ° C. or higher, particularly 800 ° C. or higher, and further 850 ° C. or higher is preferable. However, if the temperature exceeds 1000 ° C., defects such as shrinkage cavities and gas holes may occur, and Mg may boil. Therefore, the infiltration temperature is preferably 1000 ° C. or less. Moreover, 900 degrees C or less is more preferable in order to suppress excessive oxidation and the production | generation of a crystallization thing. Furthermore, it is expected that a substrate or an underlayer with few internal defects and surface defects can be obtained by controlling the cooling direction and cooling rate of the composite during solidification. Specifically, in the SiC aggregate, cooling is performed in one direction from the side opposite to the side where the molten metal is supplied, that is, when the molten metal is cooled from the side where the molten metal is already supplied toward the side where the molten metal is supplied, it has already solidified. Since the cooling proceeds while the volume decrease of the portion is compensated by the unsolidified molten metal, it is easy to reduce the occurrence of the defects. The cooling rate is preferably adjusted so as to provide a temperature gradient of, for example, 0.1 ° C./mm or more, particularly 0.5 ° C./mm or more. Alternatively, the cooling rate (difference between the temperature T _H at a certain point in the composite and the predetermined temperature T _L (<T _H ): required to decrease T _H −T _L from the temperature T _H to the temperature T _L. Value divided by time t: (T _H −T _L ) / t) is 0.5 ° C / min or more, more preferably 3 ° C / min or more, especially 10 ° C / min or more, and further 50 ° C / min or more. It is easy to reduce the above-mentioned defects even by cooling with.

  When the base layer is formed at the same time as the above composite, for example, a composite that uses the metal plate as the base layer by placing and casting a metal plate for forming the base layer between the mold and the SiC aggregate. A member is obtained. Alternatively, if a spacer or the like is disposed so that a predetermined gap is provided between the mold and the SiC aggregate, and the molten metal of the matrix metal flows into the gap, the molten matrix flows into the matrix of the substrate. An underlayer having the same composition as the metal and a structure continuous with the matrix metal can be formed. In the case of using a SiC aggregate having such a strength that it can stand on its own in the mold, such as the above-described sintered body, a predetermined gap can be maintained without using the spacer. However, the size of the SiC aggregate and the mold is selected so that a predetermined gap is provided.

  As the spacer, naphthalene or the like that can be removed by sublimation with heat at the time of compounding, or a material having excellent heat resistance such as carbon, iron, or stainless steel (for example, SUS430) can be used. This spacer may be left embedded in the underlayer, or the spacer portion may be removed by cutting or the like. The shape of the spacer is not particularly limited. For example, a linear body or a thin plate-like body having a slightly smaller diameter than the base layer to be formed can be used. When using a sintered body as described above, a gap corresponding to the diameter of the linear body is provided between the SiC aggregate and the mold by fixing the SiC aggregate to the mold with the linear body. And most of the said linear body can be embed | buried underlayer. Adjust the size of the metal piece or metal tube for providing the above-described bolt hole (for example, use a material longer than the thickness of the sintered body by the thickness of the base layer) so that a gap is provided. Also good.

[Preprocessing]
When the zincate treatment is performed on the substrate (material) having the obtained underlayer, it is preferable to perform pretreatment such as polishing and etching to clean and smooth the surface of the underlayer. The underlayer does not substantially contain a high-hardness material such as SiC, and is easily polished by being made of metal.

[Heat treatment process]
By subjecting the material to a specific heat treatment as described above, the adhesion between the substrate and, in particular, the zinc layer to the nickel plating layer can be increased. As described above, the heating temperature is preferably 200 ° C. or higher, preferably not higher than the melting point of the matrix metal, and more preferably 300 ° C. or higher and 450 ° C. or lower so that the matrix metal of the substrate does not melt. When the temperature is 450 ° C. or lower, the matrix metal (magnesium component) is difficult to burn, so the heating atmosphere can be an air atmosphere, and workability and economy are excellent. As described above, the heating time is preferably 5 minutes or more, more preferably 60 minutes or more and 3000 minutes or less. When this heat treatment is performed, the heat treatment is preferably performed before the pretreatment.

[Jincate treatment process]
Zincate treatment is applied to the material to form a zinc layer. A commercially available zincate treatment solution can be used for the zincate treatment. By this zincate treatment, zinc is deposited on the surface of the base layer to form a zinc layer.

[Copper plating process / Nickel plating process]
A copper plating layer is formed on the zinc layer to form a copper plating layer, and a nickel plating layer is formed thereon to form a nickel plating layer. For the formation of these plating layers, plating methods and conditions used for general copper plating and nickel plating can be used, and both electroplating and electroless plating can be used. It is preferable that both the copper plating layer and the nickel plating layer are continuously formed by electroplating because of excellent productivity. When using electroplating, the thickness of each plating layer can be adjusted by adjusting the energization time and the like. Moreover, when utilizing electroplating, a base layer can be utilized for a conduction | electrical_connection location.

[Other processes]
In addition, you may heat-process after forming a nickel plating layer. As for this heat processing, heating temperature: 150 degreeC-450 degreeC, heating time: 5 minutes-240 minutes are mentioned. This heat treatment can increase the peel strength and hardness.

[Test example]
A composite member including a metal coating layer having a multilayer structure was fabricated on a substrate made of a composite material in which pure magnesium and SiC were combined, and peel strength and thermal characteristics were examined.

Each sample was produced as follows.
Pure magnesium ingot (commercially available) consisting of 99.8% by mass or more of Mg and impurities as raw materials, and a commercially available plate-like SiC sintered body (SiC porous body in which the network part is composed of SiC. Density 80%) was prepared. Here, the prepared SiC aggregate was subjected to an oxidation treatment at 875 ° C. for 2 hours to form an oxide film.

  The SiC aggregate is housed in a mold, molten pure magnesium is infiltrated into the SiC aggregate, and then the pure magnesium is solidified.

  Here, the mold was made of carbon and was a rectangular parallelepiped box having one opened. The internal space of this mold is used as a storage space for the SiC aggregate. The mold may be integrally molded, but if a mold that is integrally formed by combining a plurality of divided pieces is used, it is easy to take out the casting (here, the substrate (material) including the underlayer). . In addition, here, a pair of carbon sheets with a thickness of 0.5 mm are prepared as spacers (those having an area sufficiently smaller than the two opposite surfaces of the SiC aggregate), and the above-mentioned mold is used between the SiC aggregate and the mold. And having an internal space large enough to arrange the spacer.

  Then, the SiC aggregate is housed in the mold, and the carbon sheet is disposed so as to sandwich two opposing surfaces of the plate-like SiC aggregate. Then, a gap corresponding to the thickness of the carbon sheet (here, a gap of 0.5 mm) is provided between a portion where the carbon sheet is not in contact with each other on each of a pair of opposed surfaces of the SiC aggregate. When using a spacer such as a carbon sheet, the spacer is bonded to the SiC aggregate with low melting point glass, low melting point salt, water glass, etc. in order to prevent the spacer from being displaced with respect to the SiC aggregate. Also good.

  Here, the SiC aggregate was stored in the mold after a commercially available release agent was applied to a location where the SiC aggregate was in contact with the inner peripheral surface of the mold. By applying a release agent, the material can be easily taken out. This step of applying the release agent may be omitted.

  The mold has an ingot mounting part connected to the periphery of the opening, the ingot prepared in the ingot mounting part is disposed, and the ingot is heated by heating the mold to a predetermined temperature. Melt. The mold is heated by inserting the mold into a heatable atmosphere furnace.

  Here, the atmosphere furnace is adjusted so that the infiltration temperature is 875 ° C., the Ar atmosphere, and the atmosphere pressure is atmospheric pressure. The molten pure magnesium flows into the inner space of the mold from the opening of the mold and is infiltrated into the SiC aggregate arranged in the inner space, and between the mold provided by the spacer and the SiC aggregate. Flows into the gap. While maintaining the heating state (here, 2 hours), the SiC aggregate and the molten pure magnesium were combined, and then cooled in an Ar atmosphere (water cooling here) to solidify the pure magnesium.

  By the above process, a material (total thickness: 5 mm) having an underlayer made of pure magnesium is obtained on each of two opposing surfaces of the substrate 20 made of Mg—SiC composite material. Note that depending on the arrangement of the spacers, at least one of the four side surfaces connecting the two surfaces of the substrate may be covered with a metal (here, magnesium) similar to the matrix metal of the substrate.

The following steps were sequentially performed on the obtained material.
Sample No.1 (No heat treatment, no copper plating)
Polishing → Etching → Zincate treatment → Nickel plating Sample No. 2 to 4 (No heat treatment, with copper plating)
Polishing → Etching → Zincate treatment → Copper plating → Nickel plating Sample No. (with heat treatment, with copper plating)
Heat treatment → Polishing → Etching → Zincate treatment → Copper plating → Nickel plating

  The heat treatment was performed at 450 ° C. × 540 minutes (air atmosphere). The polishing was wet polishing, and the etching / zincate treatment was performed using a commercially available etching solution and a commercially available zincate treatment solution. Moreover, all the said plating was performed by electroplating using the base layer which consists of magnesium for a conduction | electrical_connection location. The plating conditions were those used for general copper plating and nickel plating. In electroplating, the thickness of the copper plating layer was changed by adjusting the energization time and the amount of current.

  Through the above steps, as shown in FIG. 1, a substrate 20 made of a SiC-Mg composite material and a metal coating layer 10 having a multilayer structure that substantially covers the entire surface of each of a pair of opposing surfaces of the substrate 20 and A magnesium-based composite member 1 having the above (samples Nos. 3 to 5) is obtained. The metal coating layer 10 includes a base layer 11, a zinc layer 12, a copper plating layer 13, and a nickel plating layer 14 in this order from the substrate 20 side. The composite member of Sample No. 2 has a copper plating layer thinner than Samples Nos. 3 to 5, and the composite member of Sample No. 1 does not have a copper plating layer.

  About the obtained composite member of each sample No. 1-5, the thickness of copper plating layer and nickel plating layer, peel strength (MPa), thermal expansion coefficient (ppm / K), thermal conductivity (W / m ) Was investigated. The results are shown in Table 1.

  For the thickness of each plating layer, each sample is subjected to CP (Cross-section Polisher) processing to obtain a cross-section in the thickness direction, and this cross-section is observed with a scanning electron microscope (2000x), and image processing is performed on the micrograph. Each plating layer was extracted by applying, and the thickness of a plurality of points in the photograph was measured, and the average thickness is shown in Table 1. When the thickness of the underlayer was measured in the same manner, it was about 0.5 mm (500 μm), and it was confirmed that it substantially coincided with the spacer thickness described above.

  Peel strength is the strength when solder is peeled off by applying molten solder on the nickel plating layer of each sample and solidifying it, then pulling the solder vertically with a tweezers using a commercially available bump pull test device. Are measured and the strength is shown in Table 1.

  The thermal expansion coefficient and the thermal conductivity were measured using a commercially available measuring device after cutting a test piece from each sample. The thermal expansion coefficient was measured in the range of 30 ° C to 150 ° C.

  As shown in Table 1, it can be seen that the peel strength is improved by forming the copper plating layer after the zincate treatment. In particular, Sample Nos. 3 to 5 with a copper plating layer of more than 1 μm have a peel strength of 20 MPa or more, much higher than the practically required 10 MPa or more, and the reliability of the joint location between the composite member and solder It is expected to improve the sex. Furthermore, it turns out that peeling strength can be raised more by performing heat processing before a zincate process. In addition, it can be seen that Sample Nos. 3 to 5 all have a thermal expansion coefficient of 4 ppm / K or more and 15 ppm / K or less, and the thermal conductivity is as high as 250 W / m · K or more.

  FIG. 2 is a photomicrograph of Sample No. 5. As shown in FIG. 2, in sample No. 5, the zinc layer 12 is uniformly formed on the surface of the base layer 11, and the copper plating layer 13 and the nickel plating layer 14 formed on the zinc layer 12 have a uniform thickness. It can be seen that it is formed. In Sample No. 5, it can be seen that the surface of the underlayer 11 is smooth and substantially free of defects.

  FIG. 3 is a photomicrograph of a sample produced in the same manner as Sample No. 4. As shown in FIG. 3, this sample has a plurality of large grooves on the surface of the base layer 11, and it can be seen that the zinc layer 12 formed on each groove is peeled off from the base layer 11. As described above, when there is a defect on the surface of the underlayer 11, the zinc layer 12 to the plating layers 13 and 14 are locally peeled off at the interface between the underlayer 11 and the zinc layer 12 by heating at the time of applying the solder. There is a fear. On the other hand, it can be seen that by performing the specific heat treatment before the zincate treatment, the surface defects of the base layer 11 can be corrected as shown in FIG.

  Furthermore, when the components of the composite members of the obtained sample Nos. 3 to 5 were examined with an EDX apparatus, the substrate 20: Mg and SiC, the remainder: impurities, and the metal coating layer 10 were Mg and impurities sequentially from the substrate 20 side. A layer made of Zn (underlayer 11), a layer made of Zn and impurities (zinc layer 12), a layer made of Cu and impurities (copper plating layer 13), and a layer made of Ni and impurities (nickel plating layer 14). In addition, CP processing was performed on the composite members of sample Nos. 3 to 5, and a cross section in the thickness direction was taken. When this cross section was examined by SEM observation, the SiC in the substrate 20 was network-like, and the SiCs were SiC. The porous body bonded by the above, that is, a porous body in which the network portion is composed of SiC, was the same as the sintered material used. Furthermore, when the cross section was observed with an optical microscope, pure magnesium was infiltrated into the gaps between the SiC, and the underlying layer 11 formed on the surface of the substrate 20 was a structure continuous with the matrix metal of the substrate 20. I was able to confirm.

  Further, when the content of SiC in the substrate 20 part of the obtained composite members of Sample Nos. 3 to 5 was measured, it was 80% by volume. The content of SiC is CP processed as described above to take a cross-section in the thickness direction of the composite member, and the substrate portion is observed with an optical microscope (50x) in this cross-section, and this observation image is analyzed by commercial image analysis. The total area of SiC in this substrate part is obtained by image processing with an apparatus, and the value obtained by converting this total area into a volume ratio is defined as a volume ratio based on this cross section (area ratio ≒ volume ratio), and n = 3 cross section The volume ratio was determined and used as the average value.

  From the above, the obtained composite members of Sample Nos. 3 to 5 are excellent in consistency with semiconductor elements having a thermal expansion coefficient of about 4 ppm / K and its peripheral parts, and also have high thermal conductivity and thermal characteristics. It turns out that it is excellent. And these composite members are excellent in adhesiveness with a solder, when applying a solder on a nickel plating layer. Therefore, when these composite members are used as a heat radiating member of a semiconductor element, it is expected that the heat radiating property is excellent and the reliability of the joint portion with the solder can be improved.

  In this test example, a commercially available SiC sintered body was used as the SiC aggregate, but a powder compact that was not sintered (such as a slip cast compact), or a SiC aggregate that was filled with SiC powder by tapping or the like. The body can be used.

  Moreover, in this test example, although the form which provides a metal coating layer on both surfaces of a board | substrate was demonstrated, it can be set as the form which provides a metal coating layer only on the single side | surface of a board | substrate.

  A magnesium-based composite member having a multilayered metal coating layer on both sides of the substrate was prepared in the same manner as Sample No. 5 in the above test example by changing the SiC content in the range of 50% to 78% by volume. Produced. Here, SiC content, thermal expansion coefficient, and thermal conductivity are (78%, 6.0ppm / K, 240W / mK), (73%, 7.0ppm / K, 235W / mK), (63%, 8.0ppm, respectively) / K, 225 W / mK), (55%, 9.0 ppm / K, 220 W / mK), (50%, 9.3 ppm / K, 210 W / mK) composite members were produced. The obtained composite members were examined for peel strength in the same manner as in the above test examples. As a result, all were 20 MPa or more, and the adhesiveness to the solder was excellent. Moreover, each obtained composite member was excellent also in thermal conductivity.

  The present invention is not limited to the above-described embodiment, and can be appropriately changed without departing from the gist of the present invention. For example, the content of SiC in the substrate, the presence form of SiC, the composition of the matrix metal (for example, magnesium alloy), the size and thickness of the composite member, the thickness of each layer constituting the metal coating layer, the material of the underlayer -Thickness, the formation area of a metal coating layer, and the conditions at the time of a composite can be changed suitably.

  The composite member of the present invention can be suitably used for a heat spreader of the semiconductor element (the heat dissipation member of the present invention). The semiconductor device of the present invention can be suitably used for parts of various electronic devices. The manufacturing method of this invention composite member can be utilized suitably for manufacture of the said this invention composite member.

1 Composite material 20 Substrate 10 Metal coating layer
11 Underlayer 12 Zinc layer 13 Copper plating layer 14 Nickel plating layer

Claims (8)

A composite member comprising a substrate made of a composite material in which magnesium or a magnesium alloy and SiC are combined,
The composite material contains 50% by volume or more of SiC,
The thermal expansion coefficient of the composite member is 4 ppm / K or more and 15 ppm / K or less,
Of the pair of opposing surfaces of the substrate, at least one surface comprises a metal coating layer covering at least a part thereof,
The metal coating layer comprises, in order from the substrate side, a base layer, a zinc layer, a copper plating layer, a nickel plating layer that becomes an outermost surface layer,
A composite member, wherein the copper plating layer has a thickness of more than 1 μm.   2. The composite member according to claim 1, wherein the base layer is made of magnesium.   3. The composite member according to claim 1, wherein the composite member is composed of a structure in which a constituent metal of the base layer and a metal component of the composite material are continuous.   The composite member according to any one of claims 1 to 3, wherein the composite member has a thermal conductivity of 180 W / m · K or more.   A heat radiating member comprising the composite member according to any one of claims 1 to 4.   6. A semiconductor device comprising: the heat radiating member according to claim 5; and a semiconductor element mounted on the heat radiating member. A composite member manufacturing method for manufacturing a plate-shaped composite member made of a composite material by combining magnesium or a magnesium alloy and SiC,
Preparing a material comprising a substrate made of a magnesium-based composite material with an SiC content of 50% by volume or more and a base layer made of metal on at least a part of at least one of a pair of opposing surfaces of the substrate And a process of
Forming a zinc layer by applying a zincate treatment on the underlayer;
Applying copper plating on the zinc layer to form a copper plating layer having a thickness of more than 1 μm;
Providing nickel plating on the copper plating layer, and forming a nickel plating layer,
A method for producing a composite member, comprising producing a composite member having a coefficient of thermal expansion of 4 ppm / K or more and 15 ppm / K or less. Before applying the zincate treatment,
8. The composite according to claim 7, comprising a step of performing a heat treatment on the material at a heating temperature of 200 ° C. or more, a melting point of magnesium or a magnesium alloy in the substrate or less, and a heating time of 5 minutes or more. Manufacturing method of member.