JP7329370B2 - Heat sink and its manufacturing method - Google Patents

Description

The present invention relates to a radiator plate used to efficiently dissipate heat generated from a heating element such as a semiconductor element, and a manufacturing method thereof.

2. Description of the Related Art A heat sink is used to efficiently dissipate heat generated from a semiconductor device from a semiconductor device. The heat sink is required to have a high thermal conductivity for its function, and is joined to semiconductors, ceramic circuit boards, metal package members, etc. by soldering or brazing. expansion rate).

Since SiC and GaN have a wide bandgap, research and development have been advanced in recent years to apply them to high-voltage, high-frequency power semiconductor devices. Power semiconductor devices using SiC or GaN are expected to have low loss characteristics, high temperature operability, and environmental stability, and are also expected to realize miniaturization of semiconductor equipment. However, since a semiconductor using SiC or GaN is harder than a Si semiconductor, there is a problem that when a heat sink is soldered, the joint is easily cracked. For this reason, the heat sink to be applied is required to have a lower coefficient of thermal expansion and higher thermal conductivity than the conventional heat sink. is less than 11 ppm/K, preferably 10 ppm/K or less, and the thermal conductivity in the plate thickness direction is 230 W/m·K or more, preferably 250 W/m·K or more.

Conventionally, in order to realize a heat sink with a low coefficient of thermal expansion and high thermal conductivity, a Cu material with a high thermal conductivity but a high coefficient of thermal expansion and a Mo material with a low coefficient of thermal expansion but with a low thermal conductivity are laminated. A heat sink made of a /Mo clad material is known.
Regarding such a heat sink made of a Cu/Mo clad material, Patent Document 1 describes a multilayer clad material in which Cu layers and Mo layers are alternately laminated, and the total number of layers of Cu layers and Mo layers is five. It shows a radiator plate composed of a clad material with a Cu layer as the outermost layer, each Mo layer having a thickness of 200 μm or less, and a Mo volume ratio of 2.78 to 10%. Further, as the thermal properties of this radiator plate, the thermal conductivity at room temperature is 200 W/m·K or more, and the thermal expansion coefficient (average thermal expansion coefficient from 30° C. to 850° C.) is 14 ppm/K or less.

Further, in Patent Document 2, a clad material in which Mo layers and Cu layers are alternately laminated, the total number of layers of the Cu layers and the Mo layers is five, the outermost layer is the Mo layer, and each Mo A heat sink made of a clad material having a layer thickness of 50 μm and a Mo volume ratio of 15.8% (Example 8), similarly, the total number of layers of the Cu layer and the Mo layer is 7 layers, and the outermost layer is the Mo layer. A radiator plate (Example 9) made of a clad material with a thickness of each Mo layer of 50 μm and a volume ratio of Mo of 20%, and the total number of layers of the Cu layer and the Mo layer is 11 layers, and the outermost layer is composed of Mo layers, each Mo layer has a thickness of 50 μm, and a heat sink (Example 10) composed of a clad material with a Mo volume ratio of 30% is shown. Further, as the thermal characteristics of this radiator plate, the thermal conductivity at room temperature is 200 W/m·K or more, and the thermal expansion coefficient is 14 ppm/K or less.

Further, Patent Document 3 discloses a heat sink made of a three-layer clad material of Mo/Cu/Mo, in which the layer ratio is Mo/Cu/Mo=2:1:2 (the volume ratio of Mo is about 80%). A heat sink (Example 1) with a thermal expansion coefficient of 6 ppm/K and a thermal conductivity of 170 W/m·K, and a layer ratio of Mo/Cu/Mo=5:1:5 (the volume ratio of Mo is about 91 %), a thermal expansion coefficient of 5.5 ppm/K, a heat sink with a thermal conductivity of 155 W/m·K (Example 2), and a layer ratio of Mo/Cu/Mo = 1:1:1 (Mo volume ratio of about 67%), a thermal expansion coefficient of 7 ppm/K, and a thermal conductivity of 185 W/m·K (Example 3).

Japanese Patent No. 3862737 JP-A-2010-56148 JP-A-2000-323632

According to the studies of the present inventors, the heat dissipation plate has a coefficient of thermal expansion in a low temperature region (for example, an average coefficient of thermal expansion within the plate surface from 50 ° C. to 100 ° C.) and a coefficient of thermal expansion in a high temperature region (for example, from 50 ° C. It has been found that a large difference in plate in-plane average thermal expansion coefficient up to 800° C. causes the following practical problems. In other words, semiconductor packages, to which heat sinks are mainly applied, repeat operation and rest of the semiconductor. The temperature is repeatedly raised and lowered. Therefore, when a heat sink is joined to a semiconductor element or a package member, even if a sound joint is obtained by soldering or brazing, if there is a large difference in the coefficient of thermal expansion between the low temperature region and the high temperature region, the above-mentioned problems may occur. Due to the difference in thermal expansion coefficient, strain is generated in the joint due to repeated temperature rise and fall, and this strain causes fatigue cracks in the joint, which may cause problems in the reliability of the semiconductor device.
Furthermore, another problem with heat sinks made of clad materials is that if there is a large amount of heat flow loss in the plate thickness direction due to interfacial thermal resistance between layers (Cu layers and Mo layers), the desired high thermal conductivity cannot be stably obtained. Turns out there was a problem. It was also found that the degree of such heat flow loss can be evaluated by the difference (ratio) between the measured value and the calculated value of thermal conductivity in the plate thickness direction.

According to studies by the present inventors, the heat sink made of a multi-layer (five or more layers) clad material described in Patent Document 1 and Patent Document 2 has a low coefficient of thermal expansion in a high temperature region, but has a low coefficient of thermal expansion. Since the coefficient of thermal expansion is high in the region, the difference in coefficient of thermal expansion between the low temperature region and the high temperature region is large, and it has been found that the above problems tend to occur. In addition, for the clad material with a large total number of Mo layers and Cu layers, the difference between the measured value and the calculated value of thermal conductivity in the plate thickness direction is large. It has been found that the desired high thermal conductivity may not be stably obtained due to the large heat flow loss in the .
Moreover, the heat sink made of the three-layer clad material of Mo/Cu/Mo described in Patent Document 3 has a problem of low thermal conductivity in the plate thickness direction.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve the problems of the prior art as described above, and to provide a heat sink having a clad structure in which Mo layers and Cu layers are alternately laminated, which has high thermal conductivity and a wide temperature range from low to high temperatures. The coefficient of thermal expansion is low in the region, the difference in the coefficient of thermal expansion between the low temperature region and the high temperature region is small, and the heat flow loss in the plate thickness direction due to interfacial thermal resistance between layers is small, and the desired high thermal conductivity can be stably obtained. To provide a heat sink that can be
Another object of the present invention is to provide a manufacturing method capable of stably manufacturing a heat sink having such excellent thermal properties at low cost.

As a result of repeated studies by the present inventors to solve the above problems, a heat sink having a clad structure in which Mo layers and Cu layers are alternately laminated has a three- to seven-layer clad structure in which the Mo layer is the outermost layer. In addition, by optimizing the volume ratio of Mo, it has high thermal conductivity and low thermal expansion coefficient in a wide temperature range from low temperature to high temperature, and the difference in thermal expansion coefficient between low temperature region and high temperature region is small, and , There is little heat flow loss in the plate thickness direction due to interfacial thermal resistance between layers, and the desired high thermal conductivity is stably obtained (that is, the difference between the measured value and the calculated value of thermal conductivity in the plate thickness direction is small). It has been found that a plate is obtained.

The present invention has been made based on the above findings, and has the following gist.
[1] A radiator plate having a clad structure in which Mo layers and Cu layers are alternately laminated, wherein the total number of Mo layers and Cu layers is 3 to 7 layers, and the outermost layers on both sides are Mo layers. A heat sink, characterized in that the volume ratio of Mo is 21 to 60%.
[2] In the radiator plate of [1] above, [average coefficient of thermal expansion within plate surface from 50°C to 100°C]/[average coefficient of thermal expansion within plate surface from 50°C to 800°C] < 1.5 A heat sink, characterized by:
[3] In the radiator plate of [1] above, [average coefficient of thermal expansion within plate surface from 50°C to 100°C]/[average coefficient of thermal expansion within plate surface from 50°C to 800°C] ≤ 1.3 A heat sink, characterized by:

[4] In the heat sink of any one of [1] to [3] above, the average in-plane thermal expansion coefficient from 50°C to 100°C, the average in-plane thermal expansion coefficient from 50°C to 200°C, 50 The plate in-plane average thermal expansion coefficient from ° C. to 400 ° C. and the plate in-plane average thermal expansion coefficient from 50 ° C. to 800 ° C. are both less than 11.0 ppm / K, and the thermal conductivity λ _m in the plate thickness direction is 230 W / A heat sink, characterized by being m·K or more.
[5] In the radiator plate of any one of [1] to [4] above, the ratio λ _m /λ _c of the thermal conductivity λ _m in the plate thickness direction and the calculated thermal conductivity λ _c in the plate thickness direction by the simple rule of combination is 0.88 or more.
[6] In the radiator plate of any one of [1] to [4] above, the ratio λ _m /λ _c of the thermal conductivity λ _m in the plate thickness direction and the calculated thermal conductivity λ _c in the plate thickness direction by the simple rule of combination is 0.90 or more.

[7] In the radiator plate of any one of [1] to [4] above, the ratio λ _m /λ _c of the thermal conductivity λ _m in the thickness direction and the calculated thermal conductivity λ _c in the thickness direction by the simple rule of combination is 0.95 or more.
[8] In the radiator plate of any one of [1] to [7] above, Mo Layers (y1) and (y2) exist, and the ratio (x)/(y1)+(y2) of the total layer thickness of the Cu layer (x) and the Mo layers (y1) and (y2) is 3. 0 or less.
[9] In the radiator plate of any one of [1] to [7] above, Mo Layers (y1) and (y2) exist, and the ratio (x)/(y1)+(y2) of the total layer thickness of the Cu layer (x) and the Mo layers (y1) and (y2) is 2. 6 or less.
[10] In the heat sink of any one of [1] to [9] above, a plated film having a thickness of 20 μm or less is formed on one or both sides of the heat sink main body composed of the laminated Mo layer and Cu layer. A radiator plate characterized by:

[11] The method for manufacturing a heat sink according to any one of [1] to [9] above, wherein the Mo material and the Cu material are laminated, and the laminated body is hot pressure-bonded to obtain the A method for manufacturing a heat sink, comprising: obtaining a heat sink in which a Mo layer made of Mo material and a Cu layer made of Cu material are laminated.
[12] A radiator plate characterized by forming a plating film with a thickness of 20 μm or less on one or both sides of a radiator plate body composed of a laminated Mo layer and a Cu layer in the manufacturing method of the above [11]. Production method.
[13] A semiconductor package comprising the radiator plate according to any one of [1] to [10] above.
[14] A semiconductor module comprising the semiconductor package according to [13] above.

The heat sink of the present invention has a high thermal conductivity and a low coefficient of thermal expansion in a wide temperature range from low to high temperatures. The heat flow loss in the plate thickness direction is small, and the desired high thermal conductivity is stably obtained (that is, the difference between the measured value and the calculated value of the thermal conductivity in the plate thickness direction is small).
This heat sink can be securely joined to semiconductor elements and package members by soldering or brazing. Even if a large temperature change occurs due to repeated operation and stop of the heat sink, strain due to the difference in thermal expansion coefficient between the low temperature area and the high temperature area of the heat sink is unlikely to occur, and fatigue cracks are unlikely to occur. Obtainable.
Moreover, according to the manufacturing method of the present invention, a heat sink having such excellent thermal properties can be stably manufactured at low cost.

A graph showing the thermal properties of the heat sink of the example in terms of the thermal conductivity in the plate thickness direction (thermal conductivity at room temperature) and the average coefficient of thermal expansion within the plate surface from 50°C to 800°C. A graph showing the thermal properties of the heat sink of the example in terms of the thermal conductivity in the plate thickness direction (thermal conductivity at room temperature) and the average coefficient of thermal expansion within the plate surface from 50°C to 100°C. Graph summarizing the plate in-plane average thermal expansion coefficients from 50° C. to 100° C. to 800° C. (100° C., 200° C., 400° C., 800° C.) for the heat sinks of the examples. Graph showing the thermal properties of the heat sink of the example (invention example) arranged in terms of the relationship between the volume ratio of Mo and the thermal conductivity in the plate thickness direction (thermal conductivity at room temperature)

The heat sink of the present invention has a clad structure in which Mo layers and Cu layers are alternately laminated, the total number of Mo layers and Cu layers is 3 to 7 layers, and the outermost layers on both sides are Mo It is characterized by a layer and a Mo volume ratio of 21 to 60%. Therefore, this heat sink can be "Mo/Cu/Mo" (three layers), "Mo/Cu/Mo/Cu/Mo" (five layers) or "Mo/Cu/Mo/Cu/Mo/Cu/Mo" ( 7 layers) clad structure.

Such a heat sink of the present invention (here, a heat sink having a Mo/Cu/Mo clad structure will be described as an example) is a Cu/Mo/Cu clad as shown as a comparative example in Patent Document 1, for example. It has a high thermal conductivity compared to structural heat sinks. This is considered to be due to the following difference in action and effect. That is, in the case of the Cu/Mo/Cu structure as shown in Patent Document 1, the thermal conductivity is outer layer (Cu layer) > inner layer (Mo layer), so the outer layer (Cu layer) with high thermal conductivity When the heat flow enters the inner layer (Mo layer), which has low thermal conductivity, it is reflected and scattered at the interface between the outer layer and the inner layer, disturbing the heat flow. Therefore, it is considered that the thermal conductivity in the plate thickness direction is reduced accordingly. On the other hand, in the case of the Mo/Cu/Mo structure of the present invention, since the thermal conductivity of the outer layer (Mo layer)<the inner layer (Cu layer), the turbulence of the heat flow at the interface between the outer layer and the inner layer (interface There is almost no heat resistance), and the heat that enters the outer layer (Mo layer) is transmitted to the inner layer (Cu layer) side as it is. When the heat flow enters from the inner layer (Cu layer) to the other outer layer (Mo layer), the heat flow is disturbed at the interface between the layers, but the material of each layer is already flowing between the Mo layer and the Cu layer. Since the heat flow is restricted by the inherent heat transfer resistance, the interfacial thermal resistance at the interface between the layers is different from that at the interface between the outer layer (Cu layer) and the inner layer (Mo layer) as in the above comparative example of Patent Document 1. The interfacial thermal resistance due to reflection/scattering is remarkably reduced. As a result, it is considered that high thermal conductivity in the plate thickness direction is obtained.

Further, in the heat sink of the present invention having a clad structure in which the outermost layer is a Mo layer, the total number of layers of Mo layers and Cu layers is 3 to 7 layers (preferably 3 layers or 5 layers). is due to the following reasons. That is, when the total number of layers of the Mo layer and the Cu layer increases, the layer thickness of the Mo layer becomes relatively small, so even if the coefficient of thermal expansion in the high temperature region is low, the coefficient of thermal expansion in the low temperature region does not decrease. Therefore, the difference in thermal expansion coefficient between the low temperature region and the high temperature region becomes large, and the problem described above due to this difference in thermal expansion coefficient, that is, the strain caused by the difference in thermal expansion coefficient This tends to cause problems such as fatigue cracks occurring in the joints. The reason why the coefficient of thermal expansion in the low-temperature region is not lower than that in the high-temperature region as described above is that in the high-temperature region, the stiffness of Cu decreases while the stiffness of Mo remains high. Although it can be suppressed with a layer, the stiffness of Cu is high in the low temperature region, and it is considered that the thin Mo layer cannot suppress the expansion of Cu. Furthermore, when the total number of layers of the Mo layer and the Cu layer increases, the number of heat flows from the Cu layer, which has a high interfacial thermal resistance, to the Mo layer increases, and heat flow loss in the plate thickness direction due to the interfacial thermal resistance between layers increases. Therefore, it becomes difficult to stably obtain a desired high thermal conductivity. The extent of such heat flow loss can be evaluated by the difference (ratio between the two) between the measured value and the calculated value of thermal conductivity in the plate thickness direction. For the above reasons, in the present invention, the total number of Mo layers and Cu layers is 3 to 7 layers, preferably 3 or 5 layers.

When the volume ratio of Mo (the volume ratio of Mo in the clad material in which the Mo layers and the Cu layers are alternately laminated) is low, the thickness of the Mo layer becomes relatively small. When the volume ratio of Mo is less than 21%, the tendency becomes remarkable. On the other hand, when the volume ratio of Mo increases, the thermal conductivity decreases, and especially when the volume ratio of Mo exceeds 60%, desired high thermal conductivity cannot be obtained. For the above reasons, the volume ratio of Mo is set to 21 to 60% in the present invention. From the viewpoint of achieving higher thermal conductivity and further reducing the difference in thermal expansion coefficient between the low temperature region and the high temperature region, the lower limit of the volume ratio of Mo is preferably 23%, more preferably 29%. Similarly, the upper limit of the volume ratio of Mo is preferably 55%, more preferably 50%.

For the reasons described above, the heat sink of the present invention has high thermal conductivity, low thermal expansion coefficient in a wide temperature range from low temperature to high temperature, small difference in thermal expansion coefficient between low temperature region and high temperature region, and Excellent thermal performance with little heat flow loss in the plate thickness direction due to interfacial thermal resistance, etc., and the desired high thermal conductivity can be stably obtained (that is, the difference between the measured value and the calculated value of thermal conductivity in the plate thickness direction is small). have characteristics. For this reason, if (i) the coefficient of thermal expansion is high in the low-temperature region and the difference in the coefficient of thermal expansion between the low-temperature region and the high-temperature region is large, when the heat sink is bonded to the semiconductor element or package member, the semiconductor (ii) Heat flow in the plate thickness direction due to interfacial thermal resistance between layers, etc. It is possible to solve two major practical problems: high loss (large difference between the measured and calculated values of thermal conductivity in the plate thickness direction) and the inability to stably obtain the desired high thermal conductivity. can.

Here, specifically, the radiator plate of the present invention preferably has the following thermal characteristics.
First, regarding the coefficient of thermal expansion and thermal conductivity, the average coefficient of thermal expansion within the plate surface from 50 ° C. to 100 ° C., the average coefficient of thermal expansion within the plate surface from 50 ° C. to 200 ° C., and the average coefficient of thermal expansion Both the in-plane average thermal expansion coefficient and the plate in-plane average thermal expansion coefficient from 50 ° C. to 800 ° C. are less than 11.0 ppm / K, preferably 10.0 ppm / K or less, and the thermal conductivity in the plate thickness direction λ It is preferable that _m is 230 W/m·K or more, desirably 250 W/m·K or more.

In addition, regarding the difference in thermal expansion coefficient between the low temperature region and the high temperature region, [plate in-plane average thermal expansion coefficient from 50 ° C. to 100 ° C.] / [plate in-plane average thermal expansion coefficient from 50 ° C. to 800 ° C.] < 1.5, preferably [average coefficient of thermal expansion in the plate surface from 50° C. to 100° C.]/[average coefficient of thermal expansion in the plate surface from 50° C. to 800° C.]≦1.3. Due to the small difference in thermal expansion coefficient between the low temperature region and the high temperature region, when the heat sink is joined to a semiconductor element or package member by soldering or brazing, the semiconductor is repeatedly operated and stopped at the joint. Even if a large temperature change occurs due to the heat sink, strain due to the difference in thermal expansion coefficient between the low temperature region and the high temperature region of the heat sink is unlikely to occur, and a highly durable joint that is less likely to cause fatigue cracks can be obtained.

Furthermore, regarding the fact that a high thermal conductivity can be _stably obtained, the ratio _{λ m} /λ _c is preferably 0.88 or more, preferably 0.90 or more, more preferably 0.95 or more. Here, the ratio λ _m /λ _c between the thermal conductivity λ _m in the plate thickness direction and the calculated thermal conductivity λ _c is such that the higher the value, the smaller the heat flow loss in the plate thickness direction due to interfacial thermal resistance between layers. It means that a _desired high thermal _conductivity can be stably obtained. can be stably obtained.
The calculated thermal conductivity λ _c in the plate thickness direction according to the simple rule of composition is calculated by the following formula.
Calculated thermal conductivity λ _c = V _Mo × λ _Mo + V _Cu × λ _Cu
where V _Mo : Volume fraction of Mo layer
V _Cu : Volume fraction of Cu layer
λ _Mo : Thermal conductivity of pure Mo (= 138 W/m K)
λ _Cu : thermal conductivity of pure Cu (= 405 W/m K)

In a semiconductor package to which the heat sink of the present invention is mainly applied, the heat sink is bonded to a semiconductor or a ceramic such as an alumina substrate. has been used. On the other hand, since the heat sink of the present invention is compatible with high-power semiconductors such as SiC semiconductors and GaN semiconductors, the thermal conductivity in the plate thickness direction (at room temperature) is more excellent as described above. Thermal conductivity) is 230 W/m·K or more, preferably 250 W/m·K or more, plate surface average thermal expansion coefficient from 50°C to 100°C, plate surface average thermal expansion coefficient from 50°C to 200°C , the plate in-plane average thermal expansion coefficient from 50 ° C. to 400 ° C. and the plate in-plane average thermal expansion coefficient from 50 ° C. to 800 ° C. are all less than 11.0 ppm / K, preferably 10.0 ppm / K or less properties are particularly preferred.

FIG. 1 and FIG. 2 show the thermal characteristics of heat sinks of Examples described later in order, and FIG. Figure 2 shows the average coefficient of thermal expansion in the sheet surface from 50°C to 800°C. each shown. Here, the plate in-plane thermal expansion coefficient is measured by a push rod type displacement detection method, and the difference between each elongation amount at 50 ° C.-800 ° C. and 50 ° C.-100 ° C. is divided by the temperature difference to obtain 50 ° C. to 800° C. and the average in-plane thermal expansion coefficient from 50° C. to 100° C. were obtained. Also, the thermal conductivity in the plate thickness direction (thermal conductivity at room temperature) was measured by the flash method. The method of measuring and calculating the thermal characteristics is the same for the thermal characteristics shown in FIGS. 3 and 4, which will be described later.

1 and 2 show a heat sink made of 5-layer and 7-layer clad materials with a low Mo volume ratio (comparative example), a heat sink made of an 11-layer clad material (comparative example), and 5 layers with a Cu layer as the outermost layer. The thermal characteristics of a radiator plate made of a clad material (comparative example) and a radiator plate made of a three-layer to seven-layer clad material of the present invention (examples of the invention) are shown.
According to FIGS. 1 and 2, the desired high thermal conductivity was obtained for all the heat sinks of the invention examples, and high heat conductivity was also obtained for the heat sinks of the comparative examples, except for a part (Comparative Example 5). It is On the other hand, regarding the plate in-plane average thermal expansion coefficient, the “plate in-plane average thermal expansion coefficient from 50 ° C. to 800 ° C.” in FIG. However, the "average coefficient of thermal expansion within the plate surface from 50 ° C. to 100 ° C." in FIG. Low Comparative Examples 1, 2 and 4 are 11.0 ppm/K or more. In Comparative Example 5, the thermal conductivity λ _m was less than 230 W/m·K, and high thermal conductivity was not obtained.

Furthermore, "[Average coefficient of thermal expansion within the plate surface from 50°C to 100°C]/[Average coefficient of thermal expansion within the plate surface from 50°C to 800°C]" indicating the difference in coefficient of thermal expansion between the low temperature region and the high temperature region tends to increase as the volume ratio of Mo decreases, and tends to increase as the number of layers of the clad material increases. In particular, invention examples 1 to 5 and 9 to 16 are 1.3 or less), while comparative examples 1 to 4 and 6 are 1.5 or more, and the difference in thermal expansion coefficient between the low temperature region and the high temperature region is It turns out to be big. Here, since Comparative Examples 1, 2, 4, and 6 have a small volume ratio of Mo, and Comparative Example 3 has a volume ratio of Mo equivalent to that of Invention Example 1, the total of the Mo layer and the Cu layer is Since the multi-layer clad material has 11 layers, the difference in coefficient of thermal expansion between the low temperature region and the high temperature region is large. Also, among the invention examples, the higher the volume ratio of Mo, the smaller the difference in thermal expansion coefficient between the low temperature region and the high temperature region.

In addition, there is little heat flow loss in the plate thickness direction due to interfacial thermal resistance between layers, and the "thermal conductivity λ _m (measured value) and calculated thermal conductivity The ratio λ _m /λ _c ″ to the ratio λ _c (calculated value) tends to decrease as the number of layers of the clad material increases. 0.88 or more (especially 0.90 or more in Invention Examples 1 to 11 and 13 to 16, 0.95 or more in Invention Examples 1 to 4, 6, 7, 9 to 11, and 16), whereas 11 In Comparative Example 3, which is a layer clad material, it is less than 0.88, and it is understood that the desired high thermal conductivity cannot be stably obtained due to the large heat flow loss in the plate thickness direction due to interfacial thermal resistance between layers. Comparative Examples 4 and 5, in which the outermost layer is a Cu layer, also have a ratio λ _m /λ _c of less than 0.88.

FIG. 3 summarizes the plate in-plane average thermal expansion coefficients from 50° C. to 100° C. to 800° C. (100° C., 200° C., 400° C., 800° C.) for the radiator plates of the above-described examples. As a whole, it can be seen that the inventive examples have a lower coefficient of thermal expansion in a wide temperature range from low temperature to high temperature than the comparative examples, and the difference in thermal expansion coefficient between the low temperature range and the high temperature range is small. In addition, as described above, Comparative Examples 1 to 4 and 6 show the difference in thermal expansion coefficient between the low temperature region and the high temperature region "[average coefficient of thermal expansion in the plate surface from 50 ° C. to 100 ° C.] / [from 50 ° C. The plate surface average thermal expansion coefficient up to 800° C.]” is 1.5 or more, and the difference in thermal expansion coefficient between the low temperature region and the high temperature region is large.
FIG. 4 shows the thermal characteristics of the radiator plate of the above-described example (invention example) arranged in terms of the relationship between the volume ratio of Mo and the thermal conductivity in the plate thickness direction (thermal conductivity at room temperature). is.

In the heat sink of the present invention, each thickness of the Mo layer and the Cu layer, the layer thickness ratio of the Mo layer and the Cu layer, and the plate thickness of the heat sink are not particularly limited, but among them, the layer thickness is the largest. Mo layers (y1) and (y2) are present on both sides of the Cu layer (x) (however, if there is only one Cu layer, the Cu layer), and the thickness of the Cu layer (x) and the Mo layer ( The ratio (x)/(y1)+(y2) of the total layer thickness of y1) and (y2) is preferably 3.0 or less, particularly preferably 2.6 or less. When the ratio (x)/(y1) + (y2) > 2.6, especially the ratio (x)/(y1) + (y2) > 3.0, the binding force of the Cu layer by the Mo layer in the low temperature region is Therefore, the difference in coefficient of thermal expansion between the low temperature region and the high temperature region tends to increase.

In addition, in order to ensure thermal characteristics and prevent warping and distortion during practical use, the heat sink has a symmetrical structure (Mo It is preferred that the thickness of the layer and the thickness of the Cu layer be symmetrical). Also, the plate thickness of the radiator plate is often about 1 mm, but there is no particular limitation. Also, the density of the heat sink is determined by the volume ratio of Mo.

The surface of the heat sink of the present invention may be plated with Ni plating or the like for the purpose of anticorrosion or bonding with other members (brazing or soldering). In this case, the thickness of the plating film is preferably 20 μm or less so that the plating film does not greatly affect the thermal properties of the heat sink. The type of plating is not particularly limited, and for example, Ni plating, Cu plating, Au plating, Ag plating, etc. can be applied, and plating selected from these can be applied singly or in combination of two or more layers. The plated film may be provided only on one side of the heat sink body composed of the laminated Mo layer and the Cu layer, or may be provided on both sides of the heat sink body. In addition, in order to improve the plating properties when plating such as Ni plating on the surface of the heat sink, the surface of the heat sink (the surface of the Mo layer, which is the outermost layer) should have a thickness that does not affect the thermal characteristics (for example, several A Cu film (plated film or the like) having a thickness of about μm to ten and several μm may be formed.

The manufacturing method of the heat sink of the present invention is not particularly limited, but in the case of the heat sink of the present invention, it is possible to obtain better thermal properties by applying a hot pressure bonding method than by a hot rolling method. found out. For this reason, it is preferable to apply a hot pressure bonding method to the production of the heat sink of the present invention. In this method, the Mo material (a) and the Cu material (b) are laminated, and this laminate is hot-bonded under pressure to form a Mo layer of the Mo material (a) and the Cu material (b). A radiator plate with a laminated Cu layer is obtained. Although there is no particular limitation on the method for joining the laminate, hot pressure joining by spark plasma sintering (SPS) and hot press is preferred. General conditions may be used for this hot pressure bonding.

The thicknesses of the Mo material (a) and the Cu material (b) are selected according to the thicknesses of the Mo layer and the Cu layer of the heat sink to be manufactured. In addition, it may be composed of a plurality of thin Mo materials in which the Mo material (a) is laminated, or may be composed of a plurality of thin Cu materials in which the Cu material (b) is laminated. Therefore, in that case, (1) the Mo material (a) made of a plurality of Mo materials and the single Cu material (b) are laminated, (2) the single Mo material (a) and the multiple Cu materials (3) Laminate a Mo material (a) made of a plurality of Mo materials and a Cu material (b) made of a plurality of Cu materials. , hot pressure bonding the laminate.
In addition, if necessary, the heat sink main body obtained by hot pressure bonding can be plated to form a plating film as described above on one or both sides of the heat sink main body.

INDUSTRIAL APPLICABILITY The heat sink of the present invention can be suitably used for semiconductor packages such as ceramic packages and metal packages provided in various semiconductor modules, and high heat dissipation and durability can be obtained. In particular, despite its high thermal conductivity, the low coefficient of thermal expansion is maintained even after exposure to high temperatures exceeding 800°C, so there is no problem in applications such as brazing where the joining temperature is as high as 750°C or higher. Applicable.

A laminate of 3 to 11 layers is formed by alternately laminating Mo material and Cu material having a predetermined thickness, and this laminate is subjected to a spark plasma sintering (SPS) device (manufactured by Sumitomo Coal Mining Co., Ltd. "DR. SINTER SPS-1050") was used to perform hot pressure bonding at 950° C. for 18 minutes and a pressure of 20 MPa to produce heat sinks of invention examples and comparative examples. In Invention Example 16, a plated layer consisting of Cu plating (lower layer, plating thickness 10 μm) + Ni plating (upper layer, plating thickness 3 μm) was formed on the surface (both sides) of the heat sink main body obtained as described above. .
For each specimen, the in-plane thermal expansion coefficient was measured by a push rod displacement detection method, and each elongation amount at 50 ° C.-100 ° C., 50 ° C.-200 ° C., 50 ° C.-400 ° C., and 50 ° C.-800 ° C. Divide the difference by the temperature difference to find the average coefficient of thermal expansion within the plate surface from 50°C to 100°C, the average coefficient of thermal expansion within the plate surface from 50°C to 200°C, and the average coefficient of thermal expansion within the plate surface from 50°C to 400°C. An average thermal expansion coefficient and an in-plane average thermal expansion coefficient from 50° C. to 800° C. were determined. Also, the thermal conductivity in the plate thickness direction (thermal conductivity at room temperature) was measured by the flash method.

Tables 1 to 4 show the thermal properties of each specimen together with the manufacturing conditions. According to this, compared with the comparative example, the inventive example has a high thermal conductivity, a low coefficient of thermal expansion in a wide temperature range from low temperature to high temperature, a small difference in thermal expansion coefficient between the low temperature region and the high temperature region, and The heat flow loss in the plate thickness direction due to interfacial thermal resistance between layers is small, and the desired high thermal conductivity is stably obtained (that is, the difference between the measured value and the calculated value of the thermal conductivity in the plate thickness direction is small). It can be seen that the thermal characteristics of the Specifically, (i) the plate surface average thermal expansion coefficient from 50 ° C. to 100 ° C., the plate surface average thermal expansion coefficient from 50 ° C. to 200 ° C., the plate surface average thermal expansion from 50 ° C. to 400 ° C. Both the expansion coefficient and the plate in-plane average thermal expansion coefficient from 50 ° C. to 800 ° C. are less than 11.0 ppm / K (10.0 ppm / K or less in a particularly preferable configuration), (ii) the thermal conductivity in the plate thickness direction λ _m is 230 W/m K or more (250 W/m K or more in a particularly preferable configuration), (iii) showing the difference in thermal expansion coefficient between the low temperature region and the high temperature region [average heat in the plate surface from 50 ° C to 100 ° C expansion coefficient]/[plate in-plane average thermal expansion coefficient from 50 ° C. to 800 ° C.] is less than 1.5 (1.3 or less in a particularly preferable configuration), (iv) high thermal conductivity can be stably obtained The ratio λ m /λ _c of the thermal conductivity λ _m (measured value) in the plate thickness direction and the calculated thermal conductivity λ _c (calculated value) in the plate thickness direction according to the simple combination rule is _0.88 or more (especially 0.90 or more, more preferably 0.95 or more), which is an excellent thermal property. Therefore, it can be expected to have high heat dissipation and durability as a heat sink for semiconductor packages and the like.

Claims (14)

In a heat sink having a clad structure in which Mo layers and Cu layers are alternately laminated,
The total number of layers of Mo layers and Cu layers is 3 to 7 layers, the outermost layers on both sides are Mo layers, and the volume ratio of Mo is 21 to 36 % ,
Mo layers (y1) and (y2) are present on both sides of the Cu layer (x) having the largest layer thickness (however, if there is only one Cu layer, the Cu layer), and the layer of the Cu layer (x) The ratio (x)/(y1)+(y2) of the thickness and the total layer thickness of the Mo layers (y1) and (y2) is 1.75 or more and 3.0 or less,
1. A radiator plate characterized by satisfying [plate in-plane average thermal expansion coefficient from 50° C. to 100° C.]/[plate in-plane average thermal expansion coefficient from 50° C. to 800° C.]<1.5. 2. The radiator plate according to claim 1, wherein the total number of layers of Mo layers and Cu layers is three, and the volume ratio of Mo is 25 to 36%. [Average coefficient of thermal expansion within the plate surface from 50°C to 100°C]/[Average coefficient of thermal expansion within the plate surface from 50°C to 800°C] ≤ 1.3. The heat sink described. In-plane average thermal expansion coefficient from 50°C to 100°C, In-plane average thermal expansion coefficient from 50°C to 200°C, In-plane average thermal expansion coefficient from 50°C to 400°C, 50°C to 800°C Any one of claims 1 to 3, wherein the plate in-plane average thermal expansion coefficient is less than 11.0 ppm/K, and the thermal conductivity λ _m in the plate thickness direction is 230 W/m K or more. The heat sink described in . The ratio λ _m /λ _c between the thermal conductivity λ _m in the plate thickness direction and the calculated thermal conductivity λ _c in the plate thickness direction according to the simple rule of combination is 0.88 or more. The radiator plate according to any one of the above. The ratio λ _m /λ _c between the thermal conductivity λ _m in the plate thickness direction and the calculated thermal conductivity λ _c in the plate thickness direction according to the simple combination rule is 0.90 or more. The radiator plate according to any one of the above. The ratio λ _m /λ _c between the thermal conductivity λ _m in the plate thickness direction and the calculated thermal conductivity λ _c in the plate thickness direction according to the simple rule of combination is 0.95 or more. The radiator plate according to any one of the above. Thermal conductivity in thickness direction λ _m and the calculated thermal conductivity in the plate thickness direction λ _c ratio λ _m /λ _c 5. The heat sink according to any one of claims 1 to 4, wherein the is 1.01 or more. Mo layers (y1) and (y2) are present on both sides of the Cu layer (x) having the largest layer thickness (however, if there is only one Cu layer, the Cu layer), and the layer of the Cu layer (x) The ratio (x)/(y1)+(y2) of the thickness and the total layer thickness of the Mo layers (y1) and (y2) is 2.6 or less, according to any one of claims 1 to 8 . heatsink. The heat sink according to any one of claims 1 to 9, wherein a plated film having a thickness of 20 µm or less is formed on one or both sides of the heat sink main body composed of laminated Mo layers and Cu layers. A method for manufacturing a heat sink according to any one of claims 1 to 9,
A radiator plate characterized by laminating a Mo material and a Cu material and hot-pressing and bonding the laminate to obtain a radiator plate in which a Mo layer made of the Mo material and a Cu layer made of the Cu material are laminated. manufacturing method. 12. The method for manufacturing a heat sink according to claim 11, wherein a plating film having a thickness of 20 [mu]m or less is formed on one or both sides of the heat sink main body composed of the laminated Mo layer and Cu layer. A semiconductor package comprising the radiator plate according to any one of claims 1 to 10. A semiconductor module comprising the semiconductor package according to claim 13 .

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