JP2011159663A - Semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor device uniforming temperatures at respective regions of a semiconductor element. <P>SOLUTION: The semiconductor device 10 includes a semiconductor element 11 and a cooler 20. A thickness d1 of an upper sidewall member 21 positioned between the semiconductor element 11 and a cooling water channel 30 is thin in a range corresponding to a center region of the semiconductor element 11 and thick in a range corresponding to a peripheral region. The center region easy to rise in temperature is efficiently cooled, so that the temperatures in the respective regions of the semiconductor element 11 get uniform. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a semiconductor device including a semiconductor element and a cooler that cools the semiconductor element.

The semiconductor device disclosed in Patent Document 1 includes a semiconductor element and a cooler that cools the semiconductor element. The cooler includes a wall member that defines a cooling water flow path, and fins extend from the wall member toward the cooling water flow path. The fin is formed long in the range corresponding to the central region of the semiconductor element, and the fin is formed short in the range corresponding to the peripheral region of the semiconductor element.
When the semiconductor element operates, the semiconductor element generates heat. Since the central region of the semiconductor element is less likely to dissipate heat than the peripheral region, the central region of the semiconductor element tends to be locally hot. In the semiconductor device of Patent Document 1, since the fins formed in the range corresponding to the central region that is likely to be high in temperature are formed long, the cooling efficiency is high in the range corresponding to the central region of the semiconductor element. . The technique of Patent Document 1 intends to equalize the temperature of each part of the semiconductor element.

JP 2003-008264 A

However, in reality, the cooling water flows more easily in the portion where the fin is short than in the portion where the fin is long. For this reason, in the semiconductor device of Patent Document 1, the amount of cooling water flowing in the range corresponding to the central region of the semiconductor element is smaller than the amount of cooling water flowing in the range corresponding to the peripheral region. In the semiconductor device of Patent Document 1, it is difficult to say that the relationship that the heat dissipation in the central region of the semiconductor element is higher than the heat dissipation in the peripheral region is realized. The semiconductor device disclosed in Patent Document 1 still leaves room for problems in that the temperature of each part of the semiconductor element is made uniform. If the temperature of each part of the semiconductor element is not uniform, thermal stress acts on a joint part that fixes the semiconductor element to the substrate, such as solder, and the life of the joint part is reduced.
The technology disclosed in the present specification has been made in view of such circumstances, and an object thereof is to provide a semiconductor device capable of making the temperature of each part of a semiconductor element more uniform.

A semiconductor device disclosed in this specification includes a semiconductor element and a cooler. The cooler includes a wall member that defines a refrigerant flow path. When observed in a cross section orthogonal to the refrigerant flow path, the thickness of the wall member located between the semiconductor element and the refrigerant flow path is thin in the range corresponding to the central region of the semiconductor element, and corresponds to the peripheral region of the semiconductor element. Thick in the range.
The “thin and thick” relationship mentioned above may be either a thin or thick relationship, or a relationship in which the thickness changes in multiple stages from the thinnest part to the thickest part. Sometimes.

  According to the above configuration, since the distance between the semiconductor element and the coolant channel is closer in the central region than in the peripheral region of the semiconductor element, the heat dissipation in the central region of the semiconductor element is improved more than the heat dissipation in the peripheral region. Can do. As a result, the temperature difference between the central region and the peripheral region of the semiconductor element can be reduced, and the temperature of each part of the semiconductor element can be made more uniform.

A partition wall that divides the coolant channel into a plurality of channels is formed along the direction from the peripheral region on one side of the semiconductor element to the peripheral region on the other side when observed in a cross section orthogonal to the coolant channel. It is preferable that
The partition wall can secure a contact area between the wall member and the refrigerant, and can improve the cooling efficiency. Further, the distribution of the refrigerant flow rate in the direction can be made uniform.

The thickness of the wall member located between the semiconductor element and the refrigerant flow path is thin in the range corresponding to the central area of the semiconductor element, and corresponds to the peripheral area of the semiconductor element when observed in a cross section along the refrigerant flow path. It is preferable that the thickness is as large as possible.
According to the above configuration, since the distance between the semiconductor element and the refrigerant flow path is close in the central region of the semiconductor element when observed along the direction in which the refrigerant flows, heat dissipation in the central region of the semiconductor element is reduced in the peripheral region. It is possible to improve the performance. As a result, the temperature distribution of the semiconductor element when observed along the direction in which the refrigerant flows can be made uniform.

When observed in a cross-section along the refrigerant flow path, the thickness of the wall member located between the semiconductor element and the refrigerant flow path is thick in a range corresponding to the upstream side of the refrigerant flow path, and on the downstream side of the refrigerant flow path. It is also preferable that it is thin in the corresponding range.
As the refrigerant flows from the upstream side toward the downstream side, the refrigerant is heated under the influence of heat generated in the semiconductor element. Since the refrigerant temperature rises more downstream than the upstream side of the refrigerant flow path, there is a possibility that the cooling capacity of the semiconductor element may be reduced more downstream than the upstream side.
In the above configuration, since the distance between the semiconductor element and the coolant channel can be made closer to the downstream side than the upstream side, the cooling capacity of the semiconductor element can be prevented from decreasing on the downstream side of the channel. As a result, the temperature distribution of the semiconductor element when observed along the direction in which the refrigerant flows can be made uniform.

  When observed in a cross section along the refrigerant flow path, the wall member is thinned in a range corresponding to the central region of the semiconductor element, the wall member is thickened on the upstream side, and the wall member is thinned on the downstream side. Can also be combined. By using in combination, the temperature distribution of the semiconductor element when observed along the direction in which the refrigerant flows can be made more uniform.

  A high thermal conductivity portion having a thermal conductivity in the direction from the central region to the peripheral region of the semiconductor element that is higher than the thermal conductivity of the base material constituting the wall member in the wall member located between the semiconductor element and the refrigerant flow path Can be formed.

  According to the above configuration, when the cross section perpendicular to the refrigerant flow path is observed, the heat generated in the central region that is easily heated is first transferred to the central region of the wall member, and then to the peripheral region of the wall member through the high heat conducting portion. Heat transfer. Even when the semiconductor element is stacked only in the central region of the wall member forming the cooler, the heat generated in the semiconductor element can be transferred to the entire wall member. Therefore, it can suppress that the center area | region of a semiconductor element becomes high temperature locally. The temperature distribution when observed in a cross section orthogonal to the refrigerant flow path can be homogenized. Moreover, the heat conducted from the semiconductor element to the entire wall member can be dissipated to the refrigerant in a wide range, and the semiconductor element can be cooled more appropriately. Thereby, the temperature of each part of a semiconductor element can be equalized more appropriately.

  Forming a high thermal conductivity portion in the wall member located between the semiconductor element and the refrigerant flow path, the heat conductivity in the direction along the refrigerant flow path being higher than the thermal conductivity of the base material constituting the wall member; You can also.

  According to the above configuration, when the cross section along the refrigerant flow path is observed, the heat generated in the central region that is easily heated is first transferred to the central region of the wall member, and then to the peripheral region of the wall member through the high heat conduction portion. Heat transfer. Even when the semiconductor element is stacked only in the central region of the wall member forming the cooler, the heat generated in the semiconductor element can be transferred to the entire wall member. Therefore, it can suppress that the center area | region of a semiconductor element becomes high temperature locally. The temperature distribution can be homogenized when observed in a cross section along the refrigerant flow path. Moreover, the heat conducted from the semiconductor element to the entire wall member can be radiated to the refrigerant in a wide range, and the semiconductor element can be cooled more appropriately. Thereby, the temperature of each part of a semiconductor element can be equalized more appropriately.

When using a high thermal conductivity part that has a high thermal conductivity in the direction crossing the refrigerant channel or in the direction along the refrigerant channel, use the high thermal conductivity part that has a high thermal conductivity in the direction connecting the semiconductor element and the refrigerant channel. It is preferable. In that case, it is preferable that the thermal conductivity in the direction connecting the semiconductor element and the refrigerant flow path is higher than the thermal conductivity of the base material constituting the wall member.
In this case, both the phenomenon of heat transfer to a wide range of the wall member and the heat transfer phenomenon with respect to the refrigerant are activated, and the temperature of each part of the semiconductor element can be more appropriately uniformized.

  According to the semiconductor device disclosed in this specification, the temperature difference between the central region and the peripheral region of the semiconductor element can be reduced, and the temperature of each part of the semiconductor element can be made uniform.

1 is a plan view showing a semiconductor device of Example 1. FIG. Sectional drawing in the II-II line of FIG. Sectional drawing in the III-III line of FIG. FIG. 4 is a cross-sectional view corresponding to FIG. 3 of a semiconductor device according to a modification of Example 1; FIG. 6 is a plan view showing a semiconductor device of Example 2. The perspective view which shows the cross-section in the VI-VI line of FIG. FIG. 6 is a plan view showing a semiconductor device of Example 3. The perspective view which shows the cross-section in the VIII-VIII line of FIG. FIG. 6 is a plan view showing a semiconductor device of Example 4; The perspective view which shows the cross-section in the XX line of FIG. FIG. 10 is a plan view showing a semiconductor device according to Example 5; Sectional drawing in the XII-XII line | wire of FIG. Sectional drawing in the XIII-XIII line | wire of FIG. FIG. 14 is a cross-sectional view of a semiconductor device according to Modification 1 of Embodiment 5 corresponding to FIG. 13. FIG. 13 is a cross-sectional view of a semiconductor device according to a second modification of the fifth embodiment corresponding to FIG. 12.

The features of the embodiments of the technology disclosed in this specification will be described below.
(Feature 1) A flow path is formed between the upper wall member and the lower wall member of the cooler, and the partition wall extends from the upper wall member toward the lower wall member. Thereby, the heat conducted from the semiconductor element to the wall member is radiated to the cooling water flowing through the flow path through the partition wall.
(Characteristic 2) The flow path of the cooler includes a plurality of branch channels divided by an upper wall member and a partition wall adjacent to the lower wall member, and the cross-sectional area of each branch channel is the same. Thereby, a refrigerant | coolant flows equally through each flow path.

Example 1
A semiconductor device according to a first embodiment of the technology disclosed in this specification will be described with reference to FIGS. FIG. 1 is a plan view of the semiconductor device 10 according to the first embodiment. As shown in FIG. 1, in the semiconductor device 10, the semiconductor element 11 and the cooler 20 are stacked. As will be described later, a plurality of layers are actually interposed between the semiconductor element 11 and the cooler 20, but these layers are not shown in FIG. In the plan view of the semiconductor device according to another embodiment, the layer between the semiconductor element and the cooler is not shown. As shown in FIG. 1, the cooler 20 has a substantially square shape in a plan view of the semiconductor device 10. The semiconductor element 11 has a substantially square shape smaller than the cooler 20, but is large enough to cover most of the cooler 20. In plan view, the center of the semiconductor element 11 and the center of the cooler 20 coincide.

  2 is a cross-sectional view taken along line II-II in FIG. 1, and FIG. 3 is a cross-sectional view taken along line III-III. In the semiconductor device 10, actually, as shown in FIGS. 2 and 3, a plurality of layers are interposed between the semiconductor element 11 and the cooler 20. That is, as shown in FIGS. 2 and 3, the semiconductor device 10 includes a semiconductor element 11, a mounting substrate 13, a base plate 18, and a cooler 20 that are stacked in order. Between the semiconductor element 11 and the mounting substrate 13, a first bonding portion 12 for bonding them is interposed, and between the mounting substrate 13 and the base plate 18, a second bonding portion 17 for bonding them is interposed. is doing. Further, a third joint portion 19 that joins the base plate 18 and the cooler 20 is interposed. In each figure, the direction in which these layers are stacked is the z-axis direction, and the directions orthogonal to the z-axis are the x-axis and the y-axis.

  In this embodiment, the semiconductor element 11 is made of a silicon semiconductor and is composed of a plurality of IGBTs. The semiconductor element 11 is not limited to the IGBT, and may be a thyristor, a MOSFET, a diode, or the like. The semiconductor element 11 may be made of a semiconductor such as silicon nitride, gallium arsenide, or gallium nitride. The mounting substrate 13 has a three-layer structure including a first layer 14, a second layer 15, and a third layer 16. The first layer 14 and the third layer 16 are made of a metal such as aluminum or copper, and the second layer 15 is made of an insulator of aluminum nitride or aluminum oxide. In this embodiment, the base plate 18 is made of copper. The base plate 18 may be made of aluminum or an alloy of aluminum or copper and molybdenum. The 1st junction part 12 and the 2nd junction part 17 are comprised with the solder. Moreover, the 3rd junction part 19 between the baseplate 18 and the cooler 20 is comprised by brazing or grease joining.

  As shown in FIGS. 2 and 3, the cooler 20 includes an upper wall member 21 on which the semiconductor elements 11 and the like are stacked, a lower wall member 22 that faces the upper wall member 21, and four side plates 23. I have. In the cooler 20, a cooling water flow path 30 is defined by an upper wall member 21, a lower wall member 22, and a side plate 23. As shown in FIG. 2, the cooler 20 includes a plurality of partition walls 24 extending from the upper wall member 21 to the lower wall member 22. As shown in FIG. 3, the cooling water passage 30 includes an inlet portion 31 located at the upstream end and an outlet portion 32 located at the downstream end. As shown in FIG. 2, the cooling water flow path 30 includes a plurality of branch flow paths 33 surrounded by an upper wall member 21, a lower wall member 22 and a partition wall 24 adjacent to each other. As shown in FIG. 3, the y-axis direction extends from the inlet portion 31 to the outlet portion 32. An inflow pipe 35 into which cooling water as a refrigerant flows is connected to the inlet 31 of the cooler 20, and an outflow pipe 36 from which the cooling water flows out is connected to the outlet 32 of the cooler 20. . In addition, you may make it use substances other than water as a refrigerant | coolant. In the cooling water flow path 30 of the cooler 20, the cooling water flows in the y-axis direction. Specifically, as shown by the arrows in FIG. 3, the cooling water flows into the inlet portion 31 through the inflow pipe 35 and then branches to the branch channel 33 and flows. The cooling water that has flowed through the branch channel 33 joins at the outlet 32 and flows out through the outflow pipe 36. When the semiconductor element 11 operates and generates heat, this heat is transferred to the cooler 20 through the layers 12, 13, 17, 18, and 19. The heat transferred to the cooler 20 is radiated to the cooling water flowing through the cooling water flow path 30. In this way, the heat generated in the semiconductor element 11 is radiated to the cooling water, and the semiconductor element 11 is cooled.

  As shown in FIG. 2, when observed in a cross section orthogonal to the cooling water flow path 30, the thickness d <b> 1 of the upper wall member 21 is thin in a range corresponding to the central region of the semiconductor element 11, and corresponds to the peripheral region of the semiconductor element 11. Thick in the range. More precisely, the thickness d1 of the upper side wall member 21 changes in multiple steps from the thinnest thickness at the central position to the thickest thickness at the outermost peripheral position. In addition, the thickness d2 of the lower wall member 22 is thicker in the range corresponding to the central region of the semiconductor element 11 than in the range corresponding to the peripheral region of the semiconductor element 11. The space | interval of the upper wall member 21 and the lower wall member 22 is the same space | interval over the whole x-axis direction, and each partition wall 24 is the same length. Moreover, the partition walls 24 are arranged at equal intervals in the x-axis direction. Therefore, the cross-sectional areas of the respective diversion channels 33 defined by the upper wall member 21, the lower wall member 22, and the partition wall 24 are the same size. As a result, the cooling water flows through the branch flow path 33 evenly. In addition, since the thickness d1 of the upper side wall member 21 is configured as described above, the distance to the cooling water channel 30 (the branch channel 33) is closer to the central region of the semiconductor element 11. The heat dissipation in the central region of the semiconductor element 11 can be improved more than the heat dissipation in the peripheral region, and the heat dissipation in the central region that tends to become high temperature can be enhanced. As a result, the temperature difference between the central region and the peripheral region of the semiconductor element 11 can be reduced in the direction orthogonal to the cooling water flow path 30, and the temperature of each part of the semiconductor element 11 can be made uniform.

  Further, as shown in FIG. 3, when observed in a cross section along the cooling water flow path 30, the cooling water flow path 30 (dividing flow path 33) is formed in an arc shape, and the thickness d1 of the upper side wall member 21 is determined by the semiconductor element. It is thinner in the range corresponding to the central region of the semiconductor element 11 than in the range corresponding to the peripheral region 11. Further, the thickness d <b> 2 of the lower wall member 22 is thicker in the range corresponding to the central region of the semiconductor element 11 than in the range corresponding to the peripheral region of the semiconductor element 11. Further, the thickness d1 of the upper wall member 21 at the entrance 31 and the thickness d1 of the upper wall 21 at the exit 32 are the same, and the entrance 31 and the exit 32 have the same height (z-axis). The same position in the direction). Therefore, in a cross-sectional view along the direction in which the cooling water flows, the distance to the cooling water flow path 30 (the branch flow path 33) is closer to the central region of the semiconductor element 11. Thereby, the heat dissipation in the center area | region of the semiconductor element 11 can be improved rather than the heat dissipation in a peripheral area | region, and the heat dissipation in the center area | region which tends to become high temperature can be improved. As a result, the temperature difference between the central region and the peripheral region of the semiconductor element 11 in the direction along the cooling water flow path 30 can be reduced, and the temperature of each part of the semiconductor element 11 can be made uniform.

  In the present embodiment, the temperature of each part of the semiconductor element 11 can be made uniform, so that it is possible to suppress degradation caused by a crack or the like in the central region of the first joint portion 12. As a result, an increase in the thermal resistance from the semiconductor element 11 to the cooler 20 can be suppressed, and the heat radiation performance in the central region of the semiconductor element 11 can be improved over the long term. Obtainable.

  The effect of suppressing the deterioration of the central region of the first joint portion 12 can also be explained from a cooling cycle test and a power cycle test conducted by the inventors of the present application. In this experiment, a semiconductor device in which the thickness of the upper wall member of the cooler was the same throughout was used instead of the semiconductor device of the present example. That is, a semiconductor device in which the distance from the semiconductor element to the cooling water flow path of the cooler is uniform in each part of the semiconductor element was used. The semiconductor device used in the test is the same as the present embodiment except for cooling.

The thermal cycle test is a test in which a semiconductor device is repeatedly left in two constant temperature baths, a high-temperature bath and a low-temperature bath, and repeated every time the temperature of the semiconductor device is long (several hours or every day). This test assumes a state in which the temperature of each part of the semiconductor element changes and changes uniformly. As a result of this test, although a crack occurred at the end of the first joint, this crack did not propagate to the central region of the first joint.
On the other hand, the power cycle test is a test in which a temperature cycle stress is generated by intermittent energization of a semiconductor element and assumes a state in which the temperature of the semiconductor device changes in a short time (less than 1 second or in units of several seconds). . As a result of this test, the first joint portion was deteriorated such as a crack at a portion corresponding to the central region of the semiconductor element, and the thermal resistance in heat conduction from the semiconductor element to the cooler was increased.

In the power cycle test, the part corresponding to the central region of the semiconductor element in the first joint portion deteriorated because the semiconductor device in which the thickness of each part of the upper side wall member is uniform causes the semiconductor element to be intermittently energized. This is presumably because the temperature of each part of the element (and hence the first joint) becomes non-uniform. That is, in the first joint portion, the portion corresponding to the central region of the semiconductor element is locally high in temperature and the thermal expansion is large, whereas the portion corresponding to the peripheral region of the semiconductor element is not so large in thermal expansion. It is considered that distortion caused by the difference in thermal expansion occurred in the central region. If the semiconductor element is intermittently energized and a strain in the central region of the first joint is repeatedly generated, a crack occurs in the central region of the first joint. Thereby, the heat dissipation in the central region of the semiconductor element is lowered, and the temperature of the central region of the semiconductor element is further increased, so that the deterioration in the central region of the first junction further proceeds.
In this regard, in the present embodiment, the thickness d1 of the upper wall member 21 of the cooler 20 is set as described above, so that the temperature of each part of the semiconductor element 11 can be made uniform. As a result, it is possible to prevent the thermal resistance from the semiconductor element 11 to the cooler 20 from increasing due to the deterioration of the central region of the first joint 12.

(Modification of Example 1)
A modification of the first embodiment will be described with reference to FIG. As shown in FIG. 4, in the semiconductor device 40 of this modification, the configuration of the cooler 41 is different from that of the first embodiment. In addition, since the other structure is the same as Example 1, the member of the same structure is shown with the same code | symbol as Example 1, and the description is abbreviate | omitted.
As shown in FIG. 4, in the cooler 41, the cooling water flow path 45 (dividing flow path 48) is formed in an arc shape in a cross-sectional view along the direction in which the cooling water flows. It is close to the water channel 45. In this modification, the outlet 47 side of the cooling water channel 45 is formed at a higher position than the inlet 46 side, and the arc drawn by the cooling water channel 45 extends from the inlet 46 side as indicated by the broken line. It inclines upwards toward the exit 47 side. Therefore, in a cross-sectional view along the direction in which the cooling water flows, the thickness d1 of the upper side wall member 42 is thinner at a portion corresponding to the downstream side of the cooling water flow channel 45 than at a portion corresponding to the upstream side of the cooling water flow channel 45. The thickness d2 of the lower wall member 43 is thicker at the portion corresponding to the downstream side of the cooling water flow path 45 than at the portion corresponding to the upstream side of the cooling water flow path 45.

  The cooling water is heated by the heat from the semiconductor element 11 as it flows from the upstream side to the downstream side of the cooling water channel 45. Since the temperature of the cooling water is higher on the downstream side than the upstream side of the cooling water flow path 45, in the semiconductor element 11, the part corresponding to the downstream side of the cooling water flow path 45 rather than the part corresponding to the upstream side of the cooling water flow path 45. There is a possibility that the heat dissipation is lower. In the present modification, the distance between the semiconductor element 11 and the cooling water channel 45 can be made closer to the downstream side than the upstream side, so that the heat dissipation of the semiconductor element 11 is lowered on the downstream side of the cooling water channel 45. Can be suppressed. As a result, in the semiconductor element 11, the temperature difference between the portion corresponding to the upstream side of the cooling water passage 45 of the cooler 41 and the portion corresponding to the downstream side is reduced, and the temperature of each portion of the semiconductor element 11 is further appropriately set. It can be made uniform. Other functions and effects are the same as those of the first embodiment.

(Example 2)
Next, a semiconductor device 50 according to the second embodiment will be described with reference to FIGS. FIG. 5 is a plan view of the semiconductor device 50 of this embodiment. The semiconductor device 50 of the present embodiment is different from the first embodiment in the plan view of the semiconductor element 51. The semiconductor element 51 is composed of a plurality of IGBTs, and is formed in a substantially rectangular shape that is long in the y-axis direction of FIG. 5 in a plan view. In plan view of the semiconductor device 50, the center of the semiconductor element 51 and the center of the cooler 60 coincide with each other, and the semiconductor element 51 is stacked on the cooler 60 only in the central region in the x-axis direction.

FIG. 6 shows a cross-sectional structure taken along line VI-VI in FIG. In the semiconductor device 50, the semiconductor element 51, the first bonding portion 52, the mounting substrate 53, the second bonding portion 54, the base plate 55, the third bonding portion 56, and the cooler 60 are stacked in this order.
The cooling water flow path 63 formed in the cooler 60 includes a plurality of branch flow paths 64 having the same cross-sectional area, and has the same configuration as the cooling water flow path 30 of the first embodiment. As described above, the semiconductor element 51 is stacked only in the central region of the cooler 60 in the x-axis direction (the right end in FIG. 6). In other words, when observed in a cross section (xz plane) orthogonal to the cooling water flow path 63, the semiconductor element 51 is stacked only in the central region of the upper side wall member 61. In other words, the upper wall member 61 extends to the left side from the left peripheral portion of the semiconductor element 51 and extends to the right side from the right peripheral portion of the semiconductor element 51.

  The base material of the cooler 60 is copper. In the present embodiment, a first high heat conduction portion 62 is formed on the upper wall member 61 of the cooler 60. The first high heat conducting portion 62 is formed on substantially the entire upper wall member 61, and the portion where the upper wall member 61 is thicker is formed thicker. The entire surface of the first high heat conduction unit 62 is covered with copper which is a base material of the cooler 60. The first high thermal conductivity portion 62 is made of hexagonal graphite. In hexagonal graphite, a layer in which carbon atoms are covalently bonded in the shape of a turtle shell in the a-axis and b-axis directions extends, and a plurality of layers overlap in the c-axis direction. In the c-axis direction, they are connected by van der Waals force. Hereinafter, a layer of carbon atoms covalently bonded in a turtle shell shape is referred to as an ab plane. In this graphite, the thermal conductivity in the direction along the ab plane is 1000 [W / mK], which is higher than the thermal conductivity 394 [W / mK] of copper which is the base material of the cooler 60. On the other hand, in this graphite, the thermal conductivity in the c-axis direction is 10 [W / mK], which is lower than the thermal conductivity of copper which is the base material of the cooler 60.

  In FIG. 6, a broken line and a solid line inside the first high heat conducting portion 62 schematically show the ab plane of graphite. In the present embodiment, the ab planes of graphite of the first high heat conducting section 62 are arranged in parallel with the xz plane, and the c-axis of graphite is aligned in the y-axis direction. Therefore, the first high heat conduction unit 62 is configured to perform heat in the stacking direction (z-axis direction) of the semiconductor element 51 and the upper side wall member 61 and in the direction from the central region of the semiconductor element 51 to the left and right peripheral regions (x-axis direction). The conductivity is higher than the thermal conductivity of the base material of the upper side wall member 61. Therefore, when observed in a cross section orthogonal to the cooling water flow path, the heat generated in the semiconductor element 51 is first conducted to the central range of the upper side wall member 61 in the x-axis direction, and then, as shown by the broken line arrow in FIG. 1 Conducted from the central range of the upper side wall member 61 in the x-axis direction to the left and right peripheral regions (peripheral regions in the x-axis direction) through the high heat conduction part 62 Even when the semiconductor element 51 is stacked only in the central range in the left-right direction of the upper wall member 61, the heat generated in the semiconductor element 51 is conducted to the entire upper wall member 61. Therefore, it can suppress that the center range of the upper side wall member 61 becomes high temperature locally. Further, since the heat conducted from the semiconductor element 51 to the upper wall member 61 is radiated to the cooling water flowing through the flow path 63 through the entire upper wall member 61, the semiconductor element 51 can be cooled more appropriately. As described above, the temperature of each part of the semiconductor element 51 can be made more appropriate and uniform.

In the present embodiment, the semiconductor element 51 extends in the y-axis direction on the cooler 60. In light of the purpose of cooling using the entire upper side wall member 61, it is less necessary to conduct in the y-axis direction than the need to transfer heat in the x-axis direction. In the first high thermal conductivity portion 62, the thermal conductivity in the x-axis direction is higher than the thermal conductivity in the y-axis direction. Therefore, the heat conducted from the semiconductor element 51 is conducted with high thermal conductivity in the x-axis direction, and the heat can be more appropriately diffused throughout the upper side wall member 61.
Furthermore, in this embodiment, the thermal conductivity in the stacking direction (z-axis direction) of the semiconductor element 51 and the upper side wall member 61 is higher than the thermal conductivity of the base material of the upper side wall member 61. Therefore, the heat conducted to the upper wall member 61 of the cooler 60 is efficiently conducted also to the flow path side (z-axis direction) through the first high heat conduction portion 62 as shown by the solid line arrow in FIG. Therefore, the heat generated in the semiconductor element 51 can be efficiently radiated to the cooling water through the first high heat conduction portion 62 of the upper side wall member 61. Other configurations and operational effects are the same as those of the first embodiment.

  Even when the base material of the cooler 60 is made of aluminum, the thermal conductivity in the direction along the ab plane of graphite is higher than the thermal conductivity 237 [W / mK] of aluminum, and the thermal conductivity in the c-axis direction. Since the rate is lower than the thermal conductivity of aluminum, the same effect can be achieved.

(Modification of Example 2)
In Example 2 described above, the first high thermal conductivity portion 62 is made of hexagonal graphite. However, you may make it comprise a 1st high heat conductive part with the material which impregnated the metal to the carbon nanotube. In this case, the first high thermal conductivity portion is arranged so that the carbon nanotubes extend in the x-axis direction. For example, a material obtained by impregnating carbon nanotubes with aluminum has a thermal conductivity of about 700 [W / mK], and can be improved to 3 to 4 times the thermal conductivity of aluminum. Therefore, when the base material of the upper wall member is made of aluminum, the thermal conductivity in the x-axis direction of the first high thermal conductivity portion can be made 3 to 4 times higher than the thermal conductivity of the base material. Even when the heat generated in the semiconductor element is likely to be transmitted only to the central range in the x-axis direction of the upper wall member, the central range of the upper wall member is locally raised to a high temperature by the first high thermal conductivity portion including carbon nanotubes. It can be suppressed. Further, heat generated in the semiconductor element can be radiated to the cooling water through the entire upper wall member.

(Example 3)
Next, a semiconductor device 70 of Example 3 will be described with reference to FIGS. FIG. 7 is a plan view of the semiconductor device 70 of this embodiment. The semiconductor device 70 of this embodiment is different from the above embodiments in the plan view of the semiconductor element 71. The semiconductor element 71 is composed of a plurality of IGBTs, and is formed in a substantially rectangular shape that is long in the x-axis direction of FIG. 7 in plan view. In the plan view of the semiconductor device 70, the center of the semiconductor element 71 and the center of the cooler 80 coincide with each other, and the semiconductor element 71 is stacked on the cooler 80 only in the central region in the y-axis direction.

FIG. 8 shows a cross-sectional structure taken along line VIII-VIII in FIG. In the semiconductor device 70, the semiconductor element 71, the first bonding portion 72, the mounting substrate 73, the second bonding portion 74, the base plate 75, the third bonding portion 76, and the cooler 80 are stacked in this order.
The cooling water channel 83 formed in the cooler 80 includes a plurality of branch channels 84 having the same cross-sectional area, and has the same configuration as the cooling water channel 30 of the first embodiment. As described above, the semiconductor element 71 is stacked only in the central region of the cooler 80 in the y-axis direction (the end on the near side in FIG. 8). In other words, when observed in a cross section (yz plane) along the cooling water flow path 83, the semiconductor element 71 is stacked only in the central region of the upper side wall member 81. In other words, the cooler 80 extends upstream from the upstream end of the semiconductor element 71 and extends downstream from the downstream end.

The base material of the cooler 80 is copper. In the present embodiment, the second high heat conducting portion 82 is formed on the upper wall member 81 of the cooler 80. The second high heat conduction portion 82 is formed on substantially the entire upper wall member 81, and the portion where the upper wall member 81 is thicker is formed thicker. The entire surface of the second high heat conduction portion 82 is covered with copper which is a base material of the cooler 80. The second high heat conducting portion 82 is made of hexagonal graphite.
In FIG. 8, a broken line and a solid line inside the second high heat conducting portion 82 schematically show the ab plane of graphite. In the present embodiment, the ab plane of graphite of the second high thermal conductivity portion 82 is arranged in parallel with the yz plane, and the c-axis of graphite is aligned in the x-axis direction. Accordingly, the thermal conductivity in the direction in which the cooling water flows (y-axis direction) is higher than the thermal conductivity of the base material of the upper wall member 81. Therefore, in a cross-sectional view along the direction in which the cooling water flows, the heat generated in the semiconductor element 71 is first conducted to the central region of the upper side wall member 81, and the heat is shown in the broken line arrow in FIG. 2 Conducted from the central region of the upper side wall member 81 to the peripheral region (peripheral region in the y-axis direction, upstream peripheral region and downstream peripheral region) through the high thermal conductivity portion 82. Even when the semiconductor element 71 is stacked only in the central region of the upper wall member 81, heat generated in the semiconductor element 71 is conducted to the entire upper wall member 81. Thereby, it can suppress that the center area | region of the upper side wall member 81 becomes high temperature locally. Moreover, since the heat conducted from the semiconductor element 71 to the upper wall member 81 is dissipated to the cooling water flowing through the cooling water channel 83 through the entire upper wall member 81, the semiconductor element 71 can be cooled more appropriately. As described above, the temperature of each part of the semiconductor element 71 can be made more uniform.

In the present embodiment, the semiconductor element 71 extends in the x-axis direction on the cooler 80. Therefore, in light of the purpose of transferring heat to the entire range of the upper side wall member 81, it is necessary to conduct heat in the y-axis direction, but it is not necessary to conduct heat in the x-axis direction. In the second high thermal conductivity portion 82, the thermal conductivity in the y-axis direction is higher than the thermal conductivity in the x-axis direction. Therefore, the heat of the semiconductor element 71 is conducted as shown by the broken line arrows in FIG. The entire upper wall member 81 can be diffused.
Furthermore, in this embodiment, the thermal conductivity in the stacking direction (z-axis direction) of the semiconductor element 71 and the upper side wall member 81 is higher than the thermal conductivity of the base material of the upper side wall member 81. Therefore, the heat conducted to the upper wall member 81 of the cooler 80 is efficiently conducted to the cooling water channel side (z-axis direction) through the second high heat conduction portion 82 as shown by the solid line arrow in FIG. Therefore, the heat generated in the semiconductor element 71 can be efficiently radiated to the cooling water through the second high heat conduction portion 82 of the upper side wall member 81. Other configurations and operational effects are the same as those of the first embodiment.

Example 4
Next, a semiconductor device 90 of Example 4 will be described with reference to FIGS. FIG. 9 is a plan view of the semiconductor device 90 of this embodiment. The semiconductor device 90 of this embodiment is different from the above embodiments in the plan view of the semiconductor element 91. The semiconductor element 91 is composed of a plurality of IGBTs, and is formed in a substantially square shape in plan view. In plan view, the center of the semiconductor element 91 and the center of the cooler 100 coincide with each other, and the semiconductor element 91 is stacked on the cooler 100 only in the central regions in the x-axis direction and the y-axis direction.

FIG. 10 shows a cross-sectional structure taken along line XX of FIG. In the semiconductor device 90, the semiconductor element 91, the first bonding portion 92, the mounting substrate 93, the second bonding portion 94, the base plate 95, the third bonding portion 96, and the cooler 100 are stacked in this order.
The cooling water flow path 103 formed in the cooler 100 includes a plurality of branch flow paths 104 having the same cross-sectional area, and is the same as the cooling water flow path 30 of the first embodiment. As described above, the semiconductor element 91 is the central region (right end portion in FIG. 10) of the cooler 100, and the central region (end portion on the near side in FIG. 10) also in the y axis direction. It is laminated only on. In other words, the semiconductor element 91 is stacked only in the central region of the upper side wall member 101 in both a cross-sectional view along the cooling water flow path 103 and a cross-sectional view orthogonal to the cooling water flow path 103.

The base material of the cooler 100 is copper. In the present embodiment, the third high thermal conductivity portion 102 is formed on the upper wall member 101 of the cooler 100. The third high thermal conductive portion 102 is formed on substantially the entire upper wall member 101, and the portion where the thickness of the upper wall member 101 is thicker is formed thicker. The entire surface of the third high heat conduction unit 102 is covered with copper which is the base material of the cooler 100. The third high thermal conductivity portion 102 is made of hexagonal graphite.
In FIG. 10, the solid line inside the third high thermal conductivity portion 102 schematically shows the ab plane of graphite. In the present embodiment, the ab plane of graphite of the third high heat conducting section 102 is arranged in parallel with the xy plane, and the c axis of graphite is aligned in the z axis direction. Therefore, in the third high thermal conductivity portion 102, the thermal conductivity in the x-axis direction is higher than the thermal conductivity of the base material, and the thermal conductivity in the y-axis direction is higher than the thermal conductivity of the base material. Therefore, the heat generated in the semiconductor element 91 is first conducted to the central range of the upper wall member 101, and the heat is transmitted to the center of the upper wall member 101 through the third high heat conducting portion 102 as shown by the solid line arrow in FIG. Conduction from the region to the peripheral region (x-axis direction and y-axis direction). Even when the semiconductor element 91 is stacked only in the central region of the upper wall member 101, heat generated in the semiconductor element 91 is conducted to the entire upper wall member 101. Therefore, it can suppress that the center area | region of the upper side wall member 101 becomes high temperature locally. The heat conducted from the semiconductor element 91 to the upper wall member 101 is radiated to the cooling water flowing through the cooling water channel 103 through the entire upper wall member 101. Therefore, the semiconductor element 91 can be cooled more appropriately. As described above, the temperature of each part of the semiconductor element 91 can be more appropriately uniformized. Other configurations and operational effects are the same as those of the first embodiment.

(Example 5)
Next, a semiconductor device 110 according to the fifth embodiment will be described with reference to FIGS. FIG. 11 is a plan view of the semiconductor device 110 of this embodiment. The semiconductor device 110 of this embodiment is different from the above embodiments in the plan view of the semiconductor element 111. In the present embodiment, a plurality of (four in this embodiment) semiconductor elements 111 are stacked on one cooler 120. Each semiconductor element 111 is composed of a plurality of IGBTs. In plan view of the semiconductor device 110, the length of one side of the semiconductor element 111 is shorter than ½ of the length of one side of the cooler 120 and is arranged in two rows on the cooler 120 in the x-axis direction. In addition, they are arranged in two rows in the y-axis direction.

12 is a cross-sectional view taken along line XII-XII in FIG. 11, and FIG. 13 is a cross-sectional view taken along line XIII-XIII in FIG. In the semiconductor device 110, the semiconductor element 111, the first joint 112, the mounting substrate 113, the second joint 114, the base plate 115, the third joint 116, and the cooler 120 are stacked in this order.
As shown in FIGS. 12 and 13, the cooler 120 includes a cooling water flow path 130 between an upper wall member 121 in which the semiconductor elements 111 and the like are stacked and a lower wall member 122 that faces the upper wall member 121. Is formed. As shown in FIG. 12, in the cooling water channel 130, a plurality of partition walls 124 extending from the upper wall member 121 to the lower wall member 122 extend. As shown in FIG. 13, the cooling water channel 130 includes an upstream inlet portion 131 and a downstream outlet portion 132. The inlet portion 131 and the outlet portion 132 have the same height. As shown in FIG. 12, the cooling water channel 130 includes a plurality of branch channels 133 surrounded by a plurality of partition walls 124 extending from the upper wall member 121 to the lower wall member 122. It extends in the y-axis direction from the inlet portion 131 to the outlet portion 132. An inflow pipe 135 into which cooling water flows is connected to the inlet part 131 of the cooler 120, and an outflow pipe 136 from which cooling water flows out is connected to the outlet part 132 of the cooler 120. Also in the present embodiment, the cooling water flows in the y-axis direction through the cooling water channel 130 as shown by the arrows in FIG.

  As shown in FIG. 12, the semiconductor elements 111 are arranged in two rows on the cooler 120 in a cross-sectional view orthogonal to the flowing direction of the cooling water. In this cross-sectional view, the thickness d1 of the upper wall member 121 is thinner at the part corresponding to the central region of each of the two semiconductor elements 111 than at the part corresponding to the peripheral region. Further, the thickness d2 of the lower side wall member 122 is thicker at the part corresponding to the central region of each of the two semiconductor elements 111 than at the part corresponding to the peripheral region. Therefore, in each semiconductor element 111, the distance to the cooling water flow path 130 (dividing flow path 133) is closer to the center area. The heat dissipation of the central region of the semiconductor element 111 can be improved more than the heat dissipation of the peripheral region, and the heat dissipation can be further increased in the central region that tends to be high temperature. As a result, the temperature difference between the central region and the peripheral region of the semiconductor element 111 can be reduced in the direction orthogonal to the cooling water flow path 130, and the temperature of each part of the semiconductor element 111 can be made uniform. Also in this embodiment, the cross-sectional areas of the respective diversion channels 133 are the same size, and the cooling water flows through the diversion channels 133 evenly.

  Further, as shown in FIG. 13, the semiconductor elements 111 are arranged in two rows on the cooler 120 in a cross-sectional view along the direction in which the cooling water flows. In this cross-sectional view, the cooling water channel 130 (dividing channel 133) is formed in a shape in which two arcs protruding corresponding to the central regions of the two semiconductor elements 111 are continuous. That is, the thickness d1 of the upper side wall member 121 is thinner at the part corresponding to the central region of each of the two semiconductor elements 111 than at the part corresponding to the peripheral region. Further, the thickness d2 of the lower side wall member 122 is thicker at the part corresponding to the central region of each of the two semiconductor elements 111 than at the part corresponding to the peripheral region. In the present embodiment, the inlet 131 and the outlet 132 have the same thickness d1 of the upper wall member 121 and the same thickness d2 of the lower wall member 22. Therefore, the inlet 131 and the outlet 132 are formed at the same height (the same position in the z-axis direction).

  In the present embodiment, in a cross-sectional view along the direction in which the cooling water flows, the distance to the cooling water flow path 130 (dividing flow path 133) is closer to the central region of each semiconductor element 111. The heat dissipation of the central region of the semiconductor element 111 can be improved more than the heat dissipation of the peripheral region, and the heat dissipation can be further increased in the central region that tends to be high temperature. As a result, the temperature difference between the central region and the peripheral region of the semiconductor element 111 in the flowing direction of the cooling water can be reduced, and the temperature of each part of the semiconductor element 111 can be made uniform. Moreover, since the temperature of each part of the semiconductor element 111 can be made uniform, the heat in the heat conduction from the semiconductor element 111 to the cooler 120 due to the occurrence of a crack in the central region of the first joint 112. It can also suppress that resistance falls. Other configurations and operational effects are the same as those of the first embodiment.

(Modification 1 of Example 5)
A first modification of the fifth embodiment will be described with reference to FIG. As shown in FIG. 14, in the semiconductor device 140 of this modification, the configuration of the cooler 141 is different from that of the fifth embodiment.
In a cross-sectional view along the flow direction of the cooling water (y-axis direction) shown in FIG. 14, the cooling water flow path 150 (dividing flow path 153) of the cooler 141 corresponds to each central region of the two semiconductor elements 111. Two protruding arcs are formed in a continuous shape. In the present embodiment, the outlet portion 152 is formed at a position higher than the inlet portion 151. That is, in the cross-sectional view shown in FIG. 14, the thickness d1 of the upper wall member 142 is thinner at the part corresponding to the downstream side of the cooling water flow path 150 than the part corresponding to the upstream side of the cooling water flow path 150.
Thereby, also in this modification, it can suppress that the heat dissipation of the semiconductor element 111 becomes low in the downstream of the cooling water flow path 150 where the temperature of cooling water becomes high similarly to the modification of Example 1. Therefore, in the semiconductor element 111, the temperature difference between the part corresponding to the upstream side and the part corresponding to the downstream side of the cooling water channel 145 of the cooler 141 is further reduced, and the temperature of each part of the semiconductor element 111 is further increased. It can be made uniform properly. Other configurations and operational effects are the same as those of the fifth embodiment.

(Modification 2 of Example 5)
A second modification of the fifth embodiment will be described with reference to FIG. As shown in FIG. 15, in the semiconductor device 160 of this modification, the configuration of the cooler 161 is different from that of the fifth embodiment and the modification 1.
In a cross-sectional view orthogonal to the flowing direction of the cooling water (y-axis direction) shown in FIG. 15, the flow path 163 of the cooler 161 is a single flow path having a shape in which two arcs are continuous. That is, the cooler 161 does not include a partition wall, and the cooling water channel 163 is not branched into the branch channel. The thickness d1 of the upper wall member 162 is a portion corresponding to the central region of each of the two semiconductor elements 111 and is thinner than a portion corresponding to the peripheral region. Even in such a configuration, since the distance to the cooling water flow path 163 is closer to the central region of the semiconductor element 111 in a cross-sectional view orthogonal to the direction in which the cooling water flows, the heat dissipation of the central region of the semiconductor element 111 It can be higher than heat dissipation. As a result, the temperature difference between the central region and the peripheral region of the semiconductor element 111 can be reduced, and the temperature of each part of the semiconductor element 111 can be more appropriately uniformized.
In Examples 1 to 4, the cooler may not be provided with a partition wall, and the flow path may not be branched.

(Other examples)
In each of the embodiments described above, when the cooler includes a partition wall, a branch channel is formed by the wall member and the partition wall adjacent to the lower wall member. However, the partition wall may extend from the wall member toward the lower wall member and may have a length that does not reach the lower wall member. Further, the interval between adjacent partition walls may not be equal.
In the modified example of the first embodiment and the modified example 1 of the fifth embodiment, the thickness of the wall member is larger than the portion corresponding to the upstream side of the flow channel in a cross-sectional view along the direction in which the cooling water flows in the flow channel. Is thinner at the part corresponding to the downstream side of the flow path and thinner at the part corresponding to the central area of the semiconductor element than the part corresponding to the peripheral area of the semiconductor element, and the wall member has a thickness in the middle of the flow path. It is the thinnest at the corresponding site. However, in a cross-sectional view along the direction in which the cooling water flows in the flow path, the thickness of the wall member is simply thinner at the site corresponding to the downstream side of the flow channel than the site corresponding to the upstream side of the flow channel. Alternatively, the wall member may be configured such that the thickness corresponding to the downstream side of the flow path becomes thinner (the part corresponding to the downstream side than the position corresponding to the midstream of the flow path).
Further, the cooler is a section corresponding to the central region of the semiconductor element rather than the thickness of the portion corresponding to the peripheral region of the semiconductor element in a cross-sectional view orthogonal to the direction in which the cooling water flows in the flow path. It is thin, and the thickness of the wall member may be constant at each part in a cross-sectional view along the direction in which the cooling water flows in the flow path.

As mentioned above, although the specific example of the technique disclosed by this specification was demonstrated in detail, these are only illustrations and do not limit a claim. The technology described in the claims includes various modifications and changes of the specific examples illustrated above.
In addition, the technical elements described in the present specification or the drawings exhibit technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technology exemplified in this specification or the drawings achieves a plurality of objects at the same time, and has technical utility by achieving one of the objects.

10, 40, 50, 70, 90, 110, 140, 160: Semiconductor devices 11, 51, 71, 91, 111: Semiconductor elements 12, 52, 72, 92, 112: First junctions 13, 53, 73, 93, 113: mounting substrate 14: first layer 15: second layer 16: third layer 17, 54, 74, 94, 114: second joint portions 18, 55, 75, 95, 115: base plates 19, 56, 76, 96, 116: third joint portions 20, 41, 60, 80, 100, 120, 141, 161: coolers 21, 42, 61, 81, 101, 121, 142, 162: upper side wall members 22, 43 122: Lower side wall member 23: Side plate 24, 124: Partition walls 30, 45, 63, 83, 103, 130, 145, 150, 163: Cooling water flow paths 31, 46, 131, 151 1: Inlet portions 32, 47, 13 , 152: outlet portions 33, 48, 64, 84, 104, 133, 153: branch passages 35, 135: inflow pipe 36, 136: outflow pipe 62: first high heat conduction section 82: second high heat conduction section 102: first 3 High heat conduction part

Claims (7)

It has a semiconductor element and a cooler,
The cooler includes a wall member that defines a refrigerant flow path,
In the cross section orthogonal to the coolant channel, the thickness of the wall member located between the semiconductor element and the coolant channel is thin in a range corresponding to the central region of the semiconductor element, and in the peripheral region of the semiconductor element. A semiconductor device characterized by being thick in a corresponding range.   A partition wall that divides the coolant channel into a plurality of channels is formed along a direction from the peripheral region on one side of the semiconductor element to the peripheral region on the other side in a cross section orthogonal to the coolant channel. The semiconductor device according to claim 1, wherein:   In the cross section along the refrigerant flow path, the thickness of the wall member located between the semiconductor element and the refrigerant flow path is thin in a range corresponding to the central area of the semiconductor element, and in the peripheral area of the semiconductor element. The semiconductor device according to claim 1, wherein the semiconductor device is thick in a corresponding range.   In the cross section along the refrigerant flow path, the wall member positioned between the semiconductor element and the refrigerant flow path is thick in a range corresponding to the upstream side of the refrigerant flow path, and is downstream of the refrigerant flow path. The semiconductor device according to claim 1, wherein the semiconductor device is thin in a range corresponding to the side.   The wall member located between the semiconductor element and the refrigerant flow path has a thermal conductivity in a direction from a central region to a peripheral region of the semiconductor element from a thermal conductivity of a base material constituting the wall member. The semiconductor device according to claim 1, wherein a high heat conduction portion is formed.   The wall member located between the semiconductor element and the coolant channel has a high thermal conductivity in which the thermal conductivity in the direction along the coolant channel is higher than the thermal conductivity of the base material constituting the wall member. The semiconductor device according to claim 1, wherein a portion is formed.   The thermal conductivity of the high thermal conductivity portion in a direction connecting the semiconductor element and the refrigerant flow path is higher than the thermal conductivity of a base material constituting the wall member. Semiconductor device.

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