JP2010212520A - Electronic device and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electronic device having an electronic element mounted on a heat sink, having anisotropic thermal conductivity, with good heat dissipation. <P>SOLUTION: The electronic device includes the heat sink with the anisotropic thermal conductivity, and the electronic element mounted on the heat sink and having a quadrilateral plane shape projected on a mounting surface of the heat sink. The electronic element is disposed on the heat sink such that the heat dissipation is higher in one diagonal direction of the plane shape than in a side direction. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an electronic device on which an electronic element is mounted and a method for manufacturing the same. For example, the present invention relates to a semiconductor device in which a semiconductor element is mounted on a heat sink and a manufacturing method thereof.

  High output power amplifiers using semiconductors such as silicon (Si), gallium arsenide (GaAs), and gallium nitride (GaN) are widely applied to mobile phone base station power amplifiers, satellite mounted power amplifiers, and the like. In these applications, there is a strong demand for small size and high output, and high output power density is required. As the output power density increases, the channel temperature of a field effect transistor (FET) constituting the amplifier increases, which adversely affects the long-term reliability of the FET. Therefore, in order to dissipate the heat generated in the FET, the chip on which the FET serving as the heat source is formed is mounted on a package including a metal heat sink formed of a metal material having good thermal conductivity.

  Generally, copper (Cu) that is inexpensive and has good thermal conductivity is used as the metal heat sink. However, since the thermal expansion coefficient of Cu is as large as about 17 ppm / K, Cu and a semiconductor substrate such as silicon and gallium arsenide differ in thermal expansion coefficient by about 3 to 6 times. Therefore, when Cu is used as a heat sink, there is a problem that due to the difference in thermal expansion coefficient, thermal stress is applied to the semiconductor substrate in the assembly process, thereby impairing reliability.

  Therefore, generally, a material having a small thermal expansion coefficient such as tungsten (W) or molybdenum (Mo) is mixed with Cu to reduce the thermal expansion coefficient of the metal heat sink. However, in the heat sink of CuW or CuMo, the thermal conductivity is lowered as the content of W or Mo is increased in order to reduce the thermal expansion coefficient. Therefore, in recent power amplifiers with high power density, the heat sink material such as CuW or CuMo, the channel temperature of the FET should be lower than the guaranteed temperature (for example, about 120 ° C. to 150 ° C. for GaAs and Si). There is a problem that is becoming difficult. As described above, it is difficult for a metal heat sink to achieve both high thermal conductivity suitable for a semiconductor device and small thermal stress.

  Therefore, in order to achieve both high thermal conductivity and small thermal stress, for example, a graphite material is used as a heat sink (see, for example, Patent Document 1). On the other hand, carbon-based materials such as graphite materials have great anisotropy with respect to thermal conductivity. For this reason, the heat radiation performance varies greatly depending on the shape and arrangement direction of a heat source such as a semiconductor element with respect to the carbon-based heat sink. Therefore, in order to improve heat dissipation, a three-dimensional orientation relationship between the heat source and the heat sink is defined (for example, see Patent Document 2). The semiconductor device described in Patent Literature 2 includes a semiconductor element that has a rectangular planar shape and serves as a heat generation source, and a heat sink portion on which the semiconductor element is mounted. In the semiconductor device described in Patent Document 2, the long side direction of the semiconductor element is the X direction, the short side direction is the Y direction, the thickness direction is the Z direction, and the heat conductivities in the X, Y, and Z directions of the heat sink are respectively shown. When Kxx, Kyy and Kzz are set, the thermal conductivity is Kzz ≧ Kyy> Kxx.

JP 2005-200239 A International Publication No. 2008/053586

  The following analysis is given from the perspective of the present invention.

  In the semiconductor device described in Patent Document 2, the heat dissipation is improved by arranging the semiconductor element so that the long side (one side) of the semiconductor element faces the direction of high heat conductivity of the heat sink. . However, according to this arrangement, the other side faces the direction with low thermal conductivity, so when the difference between one side and the other side is small, for example, in the case of a square or a rectangle close to a square, The heat dissipation from the other side may be reduced.

  An object of the present invention is to provide an electronic device in which an electronic element is mounted on a heat sink having an anisotropic thermal conductivity with good heat dissipation and a method for manufacturing the same.

  According to a first aspect of the present invention, a first heat sink having an anisotropic thermal conductivity, and an electronic element mounted on the first heat sink and having a quadrangular planar shape projected onto the mounting surface of the first heat sink, An electronic device is provided. The electronic device has a first heat radiation direction in which the heat radiation direction in the direction perpendicular to the extending direction of one diagonal line in the planar shape or the diagonal line extending direction is higher than the heat radiation characteristic in the side direction on the mounting surface. Located on the heat sink.

  According to a second aspect of the present invention, there are provided a first heat sink having anisotropic thermal conductivity, and an electronic element mounted on the first heat sink and having a quadrangular planar shape projected on the mounting surface of the first heat sink. An electronic device is provided. The thermal conductivity in the extending direction of one diagonal line of the planar shape on the mounting surface of the first heat sink or the thermal conductivity in the direction perpendicular to the extending direction of the diagonal line is one side of the planar shape on the mounting surface of the first heat sink. It is higher than the thermal conductivity in the extending direction.

  According to a third aspect of the present invention, there are provided a first heat sink having an anisotropic thermal conductivity, and an electronic element mounted on the first heat sink and having a quadrangular planar shape projected on the mounting surface of the first heat sink. An electronic device is provided. On the mounting surface, an angle formed between the direction in which the first heat sink has the highest thermal conductivity and the angle formed by one of the diagonal lines extending in the plane or the direction perpendicular to the diagonal line extending direction is −30 °. ~ 30 °.

  According to a fourth aspect of the present invention, there are provided a first heat sink having anisotropic thermal conductivity, and an electronic element mounted on the first heat sink and having a quadrangular planar shape projected on the mounting surface of the first heat sink. An electronic device is provided. In the first heat sink, the three orthogonal directions are the first direction, the second direction, and the third direction, the thermal conductivity in the first direction is Ka, the thermal conductivity in the second direction is Kb, and the thermal conductivity in the third direction. Is the angle between one direction of the first direction or the second direction and the direction perpendicular to the mounting surface of the first heat sink when K ≧ Kb> Kc or Kb ≧ Ka> Kc Is −30 ° to 30 °. Of the first direction and the second direction, an angle formed between the other direction and one of the diagonal lines extending in the plane shape or a direction perpendicular to the diagonal line extending direction is −30 ° to 30 °.

  According to the fifth aspect of the present invention, on the mounting surface of the first heat sink having an anisotropic thermal conductivity, the electronic element having a quadrilateral planar shape is extended in one diagonal line of the planar shape on the mounting surface. There is provided a method for manufacturing an electronic device that is mounted such that the heat dissipation property in the direction perpendicular to the direction in which the diagonal lines extend is higher than the heat dissipation property in the side direction.

  According to the sixth aspect of the present invention, on the mounting surface of the first heat sink having an anisotropic thermal conductivity, the electronic element having a quadrilateral planar shape is arranged on one diagonal line of the planar shape on the mounting surface of the first heat sink. So that the thermal conductivity in the direction perpendicular to the extending direction of the diagonal line or the extending direction of the diagonal line is higher than the thermal conductivity in the extending direction of one side of the planar shape on the mounting surface of the first heat sink. A method for manufacturing an electronic device to be mounted is provided.

  According to the seventh aspect of the present invention, an electronic element having a quadrilateral planar shape is formed on the mounting surface of the first heat sink with anisotropic thermal conductivity, and the first heat sink has the highest thermal conductivity on the mounting surface. Manufacture of an electronic device to be mounted so that an angle formed between the high direction and the extending direction of one diagonal line of the planar shape or an angle formed between the vertical direction and the extending direction of the diagonal line is −30 ° to 30 ° A method is provided.

  According to the eighth aspect of the present invention, in the first heat sink with anisotropic thermal conductivity, the three orthogonal directions are defined as the first direction, the second direction, and the third direction, and the thermal conductivity in the first direction is Ka. When the thermal conductivity in the second direction is Kb, the thermal conductivity in the third direction is Kc, and Ka ≧ Kb> Kc or Kb ≧ Ka> Kc, the planar shape is formed on the mounting surface of the first heat sink. Is an angle formed between one direction of the first direction and the second direction and a direction perpendicular to the mounting surface of the first heat sink between −30 ° and 30 °, and the first direction and Electrons to be mounted so that an angle formed between the other direction of the second direction and the direction in which one of the diagonal lines in the planar shape extends or the direction perpendicular to the direction in which the diagonal lines extend is −30 ° to 30 °. A method of manufacturing a device is provided.

  According to the present invention, the direction of high thermal conductivity of the heat sink having thermal anisotropy is set in a direction parallel to or approximating the diagonal extension direction or the diagonal extension direction in the planar projection of the electronic device to be mounted. On the other hand, each side of the electronic element can be faced in a direction having a high thermal conductivity by being directed in a vertical direction or an approximate direction. Thereby, in an electronic device, the heat dissipation of the heat | fever which the electronic element emitted can be improved.

The schematic perspective view of the electronic device which concerns on the 1st-3rd embodiment of this invention. The schematic plan view for demonstrating the electronic device which concerns on the 1st-3rd embodiment of this invention. The schematic plan view for demonstrating the electronic device which concerns on the 1st-3rd embodiment of this invention. The schematic plan view for demonstrating the electronic device which concerns on the 1st-3rd embodiment of this invention. The schematic perspective view for demonstrating the electronic device which concerns on 4th Embodiment of this invention. The schematic plan view for demonstrating the electronic device which concerns on 4th Embodiment of this invention. The schematic plan view for demonstrating the electronic device which concerns on 4th Embodiment of this invention. The schematic perspective view for demonstrating the electronic device which concerns on 5th Embodiment of this invention. The schematic plan view for demonstrating the electronic device which concerns on 5th Embodiment of this invention. The schematic plan view for demonstrating the electronic device which concerns on 5th Embodiment of this invention. The schematic plan view for demonstrating the electronic device which concerns on 5th Embodiment of this invention. The schematic plan view for demonstrating the electronic device which concerns on 5th Embodiment of this invention. 1 is a schematic cross-sectional view of a semiconductor device according to Example 1. FIG. 1 is a schematic cross-sectional view of a semiconductor device according to Example 1. FIG. FIG. 6 is a schematic cross-sectional view of a semiconductor device according to a second embodiment. FIG. 6 is a schematic cross-sectional view of a semiconductor device according to a second embodiment.

  Hereinafter, preferred forms of the first to fourth viewpoints will be described.

  According to a preferred form of the first aspect, when the planar shape is a rectangle other than a square, the electronic element has a heat dissipation property in a direction perpendicular to the diagonal direction on the mounting surface, and a heat dissipation property in the side direction. It arrange | positions at a 1st heat sink so that it may become higher.

  According to a preferred form of the second viewpoint, when the planar shape is a rectangle other than a square, the thermal conductivity in the direction perpendicular to the direction in which the diagonal line extends on the mounting surface of the first heat sink is mounted on the first heat sink. It is higher than the thermal conductivity in the extending direction of one side of the planar shape on the surface.

  According to a preferred embodiment of the third aspect, when the planar shape is a rectangle other than a square, the mounting surface has a direction in which the first heat sink has the highest thermal conductivity and a direction perpendicular to the diagonal extension direction. Is an angle of −30 ° to 30 °.

  According to a preferred form of the fourth viewpoint, when the planar shape is a rectangle other than a square, the angle formed between the other direction and the direction perpendicular to the diagonal direction is −30 ° to 30 °. .

  According to a preferred form of the fourth aspect, Ka and Kb are 10 times or more of Kc.

  According to the preferable form of the fourth viewpoint, Ka and Kb are 600 W / mK or more.

  According to a preferred form of the fourth aspect, the electronic device further includes a second heat sink that is at least partially in contact with the first heat sink and has an anisotropic thermal conductivity. In the second heat sink, the three orthogonal directions are the fourth direction, the fifth direction, and the sixth direction, the thermal conductivity in the fourth direction is Kd, the thermal conductivity in the fifth direction is Ke, and the thermal conductivity in the sixth direction. Is Kf, and when Kd ≧ Ke> Kf or Ke ≧ Kd> Kf, the angle formed between the fourth direction or the fifth direction of the second heat sink and the third direction of the first heat sink is −30 °. ~ 30 °.

  According to the preferable form of the fourth viewpoint, Kd and Ke are 10 times or more of Kf.

  According to the preferable form of the fourth aspect, the second heat sink has a recess or a through hole. The first heat sink is disposed in the recess or the through hole.

  According to the preferable form of the fourth viewpoint, the angle formed by the sixth direction of the second heat sink and the third direction of the first heat sink is −30 ° to 30 °.

  According to the preferable form of the fourth viewpoint, Kd and Ke are 600 W / mK or more.

  According to the preferable form of the said 1st-4th viewpoint, the planar shape in the mounting surface of an electronic element is a rectangle. The ratio of the length of one side of the rectangle in the planar shape to the length of the other side is 0.65 to 1.5.

  According to the preferable form of the said 1st-4th viewpoint, a 1st heat sink or a 1st heat sink, and a 2nd heat sink have a metal layer in the surface on the opposite side to the mounting surface and mounting surface of a 1st heat sink. The electronic element is mounted on the metal layer.

  According to the preferred form of the eighth aspect, in the second heat sink with anisotropic heat conductivity, the three orthogonal directions are the fourth direction, the fifth direction, and the sixth direction, and the thermal conductivity in the fourth direction is When Kd, the thermal conductivity in the fifth direction is Ke, and the thermal conductivity in the sixth direction is Kf, and Kd ≧ Ke> Kf or Ke ≧ Kd> Kf, the first heat sink is at least partially in contact with it. The second heat sink is arranged so that an angle formed between the fourth direction or the fifth direction of the second heat sink and the third direction of the first heat sink is −30 ° to 30 °.

  An electronic device according to a first embodiment of the present invention will be described. FIG. 1 is a schematic perspective view of an electronic device according to the first embodiment of the present invention. FIG. 2 is a schematic plan view of the electronic device according to the first embodiment of the present invention. The electronic device 1 includes a heat sink 2 having an anisotropic thermal conductivity and an electronic element 3 serving as a heat source. The electronic element 3 is mounted on the heat sink 2.

  The heat sink 2 only needs to have an anisotropic thermal conductivity, and for example, a heat sink formed of a carbon-based material can be used. As the carbon-based heat sink, for example, a composite material obtained by impregnating a carbon-based composite material having carbon and carbon fibers with a metal such as Cu or Al can be used. As the carbon material, for example, graphite, carbon fiber, carbon nanotube, carbon nanowire, silicon carbide (SiC) single crystal, or the like may be used. In such a carbon-based heat sink, for example, the thermal conductivity is higher in a certain plane direction, and the thermal conductivity is lower in the direction perpendicular to the plane than in the plane direction. For example, in the carbon-based composite material, the ratio of thermal conductivity in three orthogonal directions is 500 to 750: 400 to 700: 1 to 150.

  The thermal conductivity of the heat sink 2 can be measured using a laser flash method. When the heat sink 2 is ceramic, the thermal conductivity of the heat sink 2 is preferably measured in accordance with JISR1611. When the heat sink 2 is metal, the thermal conductivity of the heat sink 2 is preferably measured in accordance with JISH7801.

  A metal layer (not shown) such as a Cu thin layer may be interposed between the electronic element 3 and the heat sink 2. Also, a metal layer may be formed on the surface of the heat sink 2 opposite to the mounting surface 2a. The surface of the heat sink 2 can be flattened by the metal layer.

The planar shape of the electronic element 3 projected onto the mounting surface 2a of the heat sink 2 is preferably a quadrilateral (a quadrangle OPQR in FIG. 2), and more preferably a rectangle. In the present invention, the length of one side 3a, the ratio of the length of the other side 3b which intersects the one side 3a (e.g., in FIG. 2, the length of the length L ₁ and the side PQ side OP L ₂ ratio) is preferably 0.5 to 2, more preferably 0.65 to 1.5, and even more preferably closer to 1. Thereby, according to this invention, heat dissipation can be improved more. The electronic element 3 applicable to the electronic device 1 of the present invention is not particularly limited, and various electronic elements can be used. For example, a semiconductor element can be used as the electronic element.

  In the first embodiment, on the mounting surface 2a, the angle formed between the direction of the lowest thermal conductivity of the heat sink 2 and the extending direction of one side of the electronic element 3 on the mounting surface 2a is not −10 ° to 10 °. preferable. For example, in FIG. 2, the angle formed between the direction 5 (black arrow) of the lowest thermal conductivity of the heat sink 2 and the side 3 b (for example, side AB) of the electronic element 3 is not −10 ° to 10 °.

  If the quadrangle OPQR is rectangular and the direction 5 of the lowest thermal conductivity and the extending direction of the side OP are the same, the side PQ and the side RO face the direction of low thermal conductivity. In this case, heat cannot be efficiently radiated from the side PQ and the side RO, and the heat dissipation from the electronic element 3 is reduced. According to the first embodiment, such a decrease in heat dissipation can be suppressed.

  Next, an electronic device according to a second embodiment of the present invention will be described with reference to FIGS. 3 and 4 are schematic plan views of the electronic device 1 shown in FIG. In the second embodiment, on the mounting surface 2a, the direction of the highest thermal conductivity of the heat sink 2 and the extension direction of one diagonal line or the extension of one diagonal line of the planar shape OPQR of the electronic element 3 on the mounting surface 2a. The angle formed by the direction perpendicular to the direction is preferably −30 ° to 30 °, more preferably −10 ° to 10 °, and 0 ° (that is, parallel to the diagonal extending direction 4a). Further preferred. For example, as shown in FIG. 3, the angle formed between the direction 6 (the white arrow) having the highest thermal conductivity and the extending direction 4a of the diagonal line (for example, the diagonal line PR) of the electronic element 3 is −30 ° to 30 °. More preferably, it is −10 ° to 10 °, and more preferably 0 °. Alternatively, as shown in FIG. 4, the angle formed between the direction 6 (the white arrow) having the highest thermal conductivity and the vertical direction 4 b with respect to the extending direction 4 a of the diagonal line (for example, the diagonal line PR) of the electronic element 3 is It is set to −30 ° to 30 °, more preferably −10 ° to 10 °, and still more preferably 0 ° (that is, parallel to the direction perpendicular to the diagonal extension direction 4a).

Moreover, when the planar shape of the electronic element 3 is a rectangle other than a square, the form shown in FIG. 4 is more preferable than the form shown in FIG. In order to improve the heat dissipation, it is better to improve the heat dissipation from the longer side than the heat dissipation from the shorter side in the planar shape of the electronic element 3. Therefore, in order to enhance the heat dissipation from the long side, the direction 6 with the highest thermal conductivity should be closer to the longer side than the shorter side. For example, in the embodiment shown in FIG. 3, when the length L ₂ of the side PQ is longer than the length L ₁ of the side OP, the angle between the short side OP and direction 6 of the highest thermal conductivity, highest thermal Comparing the angle formed between the conductivity direction 6 and the long side PQ, the angle formed between the direction 6 having the highest thermal conductivity and the side OP is closer to the vertical. On the other hand, in the embodiment shown in FIG. 4, when the angle formed between the direction 6 of the highest thermal conductivity and the short side OP is compared with the angle formed between the direction 6 of the highest thermal conductivity and the long side PQ, the highest heat conductivity is obtained. The angle formed by the conductivity direction 6 and the side PQ is closer to the vertical. In this case, the form shown in FIG. 4 can improve the heat dissipation from the side PQ more than the heat dissipation from the side OP. Therefore, when the planar shape of the electronic element 3 is a rectangle other than a square, the direction 6 of the highest thermal conductivity and the direction 4b perpendicular to the extending direction 4a of the diagonal line (for example, the diagonal line PR) of the electronic element 3 It is preferable that the angle formed is −30 ° to 30 °, more preferably −10 ° to 10 °, and still more preferably 0 ° (that is, parallel to the direction perpendicular to the diagonal direction 4a).

  According to this embodiment, each side of the electronic element 3 faces in a direction with high heat dissipation. Thereby, for example, in FIG. 3, heat generated in the electronic element 3 can be released from each side in a direction with high thermal conductivity, and heat dissipation can be improved.

  Except for the above embodiment, the second embodiment is the same as the first embodiment. This embodiment can also be combined with the first embodiment.

  Next, an electronic device according to a third embodiment of the present invention will be described with reference to FIGS. In the third embodiment, on the mounting surface 2a, the thermal conductivity in the extending direction 4a of one diagonal of the planar shape of the electronic element 3 or the extending direction 4a of one diagonal of the planar shape of the electronic element 3 is compared. The thermal conductivity in the vertical direction 4 b is higher than the thermal conductivity in the extending direction of the sides 3 a and 3 b of the electronic element 3.

  For example, in FIG. 3, the thermal conductivity in the diagonal PR direction is preferably higher than the thermal conductivity in the side OP direction and the thermal conductivity in the side PQ direction of the planar shape of the electronic element 3. Alternatively, in FIG. 4, the thermal conductivity in the direction perpendicular to the diagonal PR direction is preferably higher than the thermal conductivity in the side OP direction and the thermal conductivity in the side PQ direction of the planar shape of the electronic element 3.

Further, when the planar shape of the electronic element 3 is a rectangle other than a square, the thermal conductivity in the direction 4b perpendicular to the diagonal extension direction 4a is greater than the thermal conductivity in the diagonal extension direction 4a. It is preferable that the electronic element 3 has a higher thermal conductivity in the direction of the sides 3a and 3b of the planar shape. For example, in FIG. 4, the length L ₂ of the side PQ is time longer than the length L ₁ of the side OP, diagonal PR extending direction of the diagonal PR than the thermal conductivity of the extending direction with respect to the vertical direction The heat conductivity from the long side PQ direction can be improved by setting the thermal conductivity higher than the thermal conductivity in the side OP direction and the thermal conductivity in the side PQ direction of the planar shape of the electronic element 3. Thereby, as described in the second embodiment, the heat dissipation can be further improved.

  According to the present embodiment, the four sides of the electronic element 3 face more widely in the direction of high heat dissipation. Thereby, compared with the case where the heat conductivity of the extension direction of one diagonal of the electronic element 3 is lower than the heat conductivity of the extension direction of one side of the electronic element 2, heat dissipation can be improved more.

  Except for the above embodiment, the second embodiment is the same as the first embodiment. This embodiment can also be combined with at least one of the first embodiment and the second embodiment.

  Next, an electronic device according to a fourth embodiment of the invention will be described. FIG. 5 is a schematic perspective view for explaining an electronic apparatus according to the fourth embodiment of the present invention. 6 and 7 are schematic plan views for explaining an electronic device according to the fourth embodiment of the present invention. In addition, the arrow directions of directions A, B, and C shown in FIGS. 5 to 7 are examples, and are not limited thereto.

  In the fourth embodiment, three orthogonal directions of the heat sink 2 are defined as a first direction A, a second direction B, and a third direction C, and the thermal conductivities in the first direction A, the second direction B, and the third direction C are set. Let Ka, Kb, and Kc respectively. Further, Ka, Kb, and Kc are in a relationship of Ka ≧ Kb> Kc or Kb ≧ Ka> Kc. Ka and Kb are preferably 10 times or more of Kc. Further, Ka and Kb are preferably 600 W / mK or more.

  The first direction A having a high thermal conductivity Ka is preferably the same as the direction perpendicular to the mounting surface 2a of the electronic element 3 (the thickness direction of the electronic element 3). The first direction A is preferably ± 30 ° with respect to the direction perpendicular to the mounting surface 2a of the electronic element 3, more preferably ± 10 °, and 0 ° (that is, parallel to the direction perpendicular to the mounting surface 2a). ). By making the first direction A having high thermal conductivity substantially perpendicular to the contact surface between the electronic element 3 and the heat sink 2, the heat of the electronic element 3 can be efficiently radiated.

  When the first direction A is substantially perpendicular to the mounting surface 2 a of the electronic element 3, the first direction X and the second direction Y are substantially parallel to the mounting surface 2 a of the electronic element 3. At this time, as shown in FIG. 6, the second direction B having a higher thermal conductivity is in the extension direction 4 a of one diagonal line of the electronic element 3 than the extension direction of the sides 3 a and 3 b of the electronic element 3. It is preferable to turn it (closer). Alternatively, as shown in FIG. 7, it is preferable that the one of the sides 3a and 3b of the electronic element 3 is oriented in the direction 4b perpendicular to the extending direction 4a of one diagonal line of the electronic element 3 (is closer). . Preferably, in the planar projection of the electronic element 3 on the mounting surface 2a, the second direction B is perpendicular to the extending direction 4a of the diagonal line (for example, the diagonal line PR in FIG. 6) of the electronic element 3 or the extending direction 4a of the diagonal line. It is preferably ± 30 ° with respect to the direction 4b, more preferably −10 ° to 10 °, and 0 ° (that is, parallel to the perpendicular direction 4b with respect to the diagonal direction 4a or the diagonal direction 4a). ). As a result, on the mounting surface 2a, all four sides of the electronic element 3 face the second direction B, which has higher thermal conductivity, and heat generated by the electronic element 3 is directed in a direction parallel to the mounting surface. Can also escape efficiently.

Further, when the planar shape of the electronic element 3 is a rectangle other than a square, the form shown in FIG. 7 is preferable to the form shown in FIG. That is, it is preferable that the second direction B is more parallel to the direction 4b perpendicular to the diagonal direction 4a than to the diagonal direction 4a. For example, in FIG. 6, when the length _{L 2} of the side PQ is longer than the length _{L 1} of the side OP, the second direction B is, with respect to the extending direction 4a of the diagonal PR than extending direction 4a of the diagonal PR Therefore, the heat radiation from the long side PQ direction can be improved by being more parallel to the vertical direction 4b. Thereby, as described in the second embodiment, the heat dissipation can be further improved.

  Except for the above embodiment, the second embodiment is the same as the first embodiment. This embodiment can also be combined with at least one of the first to third embodiments.

  Next, an electronic device according to a fifth embodiment of the invention will be described. FIG. 8 is a schematic perspective view for explaining an electronic apparatus according to the fifth embodiment of the present invention. 9 and 12 are schematic plan views for explaining an electronic apparatus according to the fifth embodiment of the present invention. 8-12, the same code | symbol is attached | subjected to the same element shown in FIGS. 1-6. In addition, the arrow directions of directions A, B, C, D, E, and F shown in FIGS. 8 to 12 are examples, and are not limited thereto.

  The electronic device 21 according to this embodiment includes an electronic element 3, a first heat sink 2, and a second heat sink 22. The first heat sink 2 and the electronic element 3 are the same as the heat sink and the electronic element 3 in the first to fourth embodiments. Hereinafter, the second heat sink 22 will be mainly described.

  Similar to the first heat sink 2, the second heat sink 22 has thermal anisotropy. The second heat sink 22 is arranged in contact with at least a part of the first heat sink 2. For example, the second heat sink 22 is in contact with the surface of the first heat sink 2 perpendicular to the mounting surface 2a. 8 and 9, the second heat sink 2 is disposed so as to be fitted into the recess or the through hole of the second heat sink 22. Further, the contact area between the first heat sink 2 and the second heat sink 22 is made larger so that the heat of the first heat sink 2 can be efficiently conducted by the second heat sink 22.

  It is preferable that the direction in which the thermal conductivity of the second heat sink 22 is low and the direction in which the thermal conductivity of the first heat sink 2 is low are not the same direction. The direction in which the heat conductivity of the second heat sink 22 is high and the direction in which the heat conductivity of the first heat sink 2 is low are preferably the same direction.

  The three orthogonal directions of the second heat sink 22 are the fourth direction D, the fifth direction E, and the sixth direction F, and the thermal conductivities in the fourth direction D, the fifth direction E, and the sixth direction F are Kd, Ke, Let it be Kf. Further, it is assumed that Kd, Ke, and Kf have a relationship of Kd ≧ Ke> Kf or Ke ≧ Kd> Kf. At this time, Kd and Ke are preferably 10 times or more of Kf. Further, Kd and Ke are preferably 600 W / mK or more.

  The sixth direction F having a low thermal conductivity Kf is preferably the same direction as the direction perpendicular to the mounting surface 2a (the thickness direction of the electronic element 3). The sixth direction F is preferably ± 30 ° with respect to the direction perpendicular to the mounting surface 2a of the electronic element 3, more preferably ± 10 °, and even more preferably 0 °. Accordingly, the fourth direction D and the fifth direction E having high thermal conductivity are directed to the extending direction of the mounting surface 2a, so that the heat conducted to the first heat sink 2 can be efficiently diffused. Become.

  As shown in FIGS. 9 to 12, at least one of the fourth direction D and the fifth direction E with high thermal conductivity is in the third direction C with low thermal conductivity of the first heat sink 2. , Preferably ± 30 °, more preferably ± 10 °, and even more preferably 0 °. Thereby, the heat dissipation in the direction where the thermal conductivity of the first heat sink 2 is low can be supplemented by the second heat sink 22, and the heat dissipation can be enhanced.

  Except for the above embodiment, the second embodiment is the same as the first embodiment. The fifth embodiment can be combined with at least one of the first to fourth embodiments.

  The content shown in FIGS. 1 to 12 is an example, and the present invention is not limited to this. For example, in the above embodiment, the present invention has been described using the diagonal line PR, but it goes without saying that the diagonal line OQ may be used.

  An example of the electronic device of the present invention will be described. An electronic device is a semiconductor device in which a semiconductor element is mounted as an electronic element. 13 and 14 are schematic cross-sectional views of the semiconductor device according to the first embodiment. FIG. 13 and FIG. 14 show different forms. Example 1 is an example of the first to fourth embodiments.

  The semiconductor devices 100 and 200 include a heat sink 101 having an anisotropic thermal conductivity, a semiconductor element 102 mounted on the heat sink 101, a matching circuit board 103 mounted on the heat sink 101, the semiconductor element 102, and the matching circuit board 103. The sealing resin 105 and the sealing lid 106 to be sealed, the input terminal 107 and the output terminal 108, and each element (for example, between the semiconductor element 102 and the matching circuit substrate 103, between the semiconductor element 102 and the input terminal 107) are electrically connected. A bonding wire 104 is provided for connection. At least the mounting surface of the semiconductor element 102 of the heat sink 101 is plated (for example, Au plating) in order to fuse the semiconductor element 102 and the heat sink 101.

  In the semiconductor devices 100 and 200, the relative arrangement relationship between the semiconductor element 102 that is a heat source and the heat sink 101 satisfies at least one of the first to fourth embodiments. Thereby, the heat generated in the semiconductor element 102 can be efficiently released.

  A semiconductor device 200 shown in FIG. 14 has a metal layer (for example, a Cu thin layer) 109 on at least both surfaces of the heat sink 101 in order to flatten the surface of the heat sink 101. The metal layer 109 can be attached by using, for example, a bonding layer (not shown) made of metal. The metal layer 109 can be, for example, 100 μm to 150 μm.

  Next, a method for manufacturing the semiconductor devices 100 and 200 will be described. First, surface processes such as electrodes and wiring on semiconductor devices such as FETs formed of semiconductor materials such as silicon (Si), gallium arsenide (GaAs), gallium nitride (GaN), and silicon carbide (SiC) in the pre-process. Is done. Subsequently, a PHS (Plated Heat Sink) plating process is performed on the back surface of the wafer in the back surface process, and after etching or the like, the chips are individually formed by dicing. Thereby, the semiconductor element 102 is obtained. Since these pre-processes are the same as known techniques, their description is omitted. Subsequently, a post-process for packaging the manufactured semiconductor element 102 is performed. The semiconductor element 102 and the matching circuit substrate 103 are fused by, for example, AuSn solder (containing 20% Sn) on the heat sink 101 held on a mounting device maintained at 300 ° C., for example. The semiconductor element 102 is mounted on the heat sink 101 so as to satisfy at least one of the first to fourth embodiments. When the semiconductor device 200 is manufactured, the metal layer 109 is formed on the heat sink 101 in advance. Subsequently, the bonding wire 104 is used to electrically connect the input-side pad electrode of the semiconductor element 102 and the pad electrode of the matching circuit board 103, and the matching circuit board 103 and the input terminal 107 of the package. Is done. Similarly, on the output side, the output-side electrode pad of the semiconductor element 102 and the output terminal 108 of the package are electrically connected using the bonding wire 104. Finally, the semiconductor lid 102 is covered and the semiconductor element 102 is sealed, and the semiconductor devices 100 and 200 including the heat sink 101 on which the semiconductor element 102 is mounted are manufactured.

  An example of the electronic device of the present invention will be described. 15 and 16 are schematic cross-sectional views of the semiconductor device according to the second embodiment. FIG. 13 and FIG. 14 show different forms. Example 2 is an example of the fifth embodiment.

  The semiconductor device 300 shown in FIG. 15 is the same as the semiconductor device 100 shown in FIG. 13 except that the second heat sink is provided as in the fifth embodiment shown in FIGS. Also, the semiconductor device 400 shown in FIG. 16 is the same as the semiconductor device 200 shown in FIG. 14 except that the second heat sink is provided as in the fifth embodiment shown in FIGS.

  In the following Examples 1-4 and Comparative Examples 1-4, it tested about the influence which the relative positional relationship of a heat sink and an electronic element exerts on heat dissipation. In the examples, the two directions (1) where the heat conductivity of the heat sink is high are oriented in the direction perpendicular to the thickness direction of the electronic element and the diagonal direction of the planar shape of the electronic element. On the other hand, in the comparative example, the two directions in which the heat conductivity of the (first) heat sink is high are directed to the thickness direction and the short side direction of the electronic element.

  A GaN FET was used as a semiconductor element which is an electronic element. As the heat sink, a composite material obtained by impregnating a carbon-based composite material made of carbon and carbon fibers with Cu was used. Table 1 below shows the values of the thermal conductivities Ka to Kf in each direction of the heat sink and the direction with respect to the semiconductor element in each example and comparative example. Ka to Kf are the same as those described in the above embodiment. In the (first) heat sink, the thermal conductivities in the three orthogonal directions are Ka, Kb, and Kc, respectively, and in the second heat sink, the orthogonal three-directional heat conduction is performed. The rates were Kd, Ke, and Kf, respectively. In Table 1, “thickness” means parallel to the thickness direction of the semiconductor element (direction perpendicular to the mounting surface of the semiconductor element), and “pair” means the semiconductor in the planar projection of the semiconductor element with respect to the mounting surface. It means that it is parallel to the vertical direction with respect to the diagonal direction of the element. In addition, “long” is parallel to the long side direction of the semiconductor element in the planar projection of the semiconductor element with respect to the mounting surface, “short” is parallel to the short side direction, and “side” is parallel to the side direction. It means that there is. At this time, the thermal conductivity Kb in the second direction was the maximum value on the mounting surface of the first heat sink, and the thermal conductivity Kc in the third direction was the minimum value on the mounting surface of the first heat sink.

  In each of the following examples and comparative examples, the difference in channel temperature before and after driving the semiconductor element when the power consumption of the semiconductor element was 5 W was measured. Channel temperature was measured directly using an infrared thermal analysis method. The emissivity of the surface of the semiconductor element was determined from the amount of infrared rays radiated from the surface of the semiconductor element placed on the stage that had been previously heated to a predetermined temperature and the surface temperature = stage temperature. Thereafter, the amount of infrared rays was measured in a state where the semiconductor element was energized (in a state where the surface temperature of the semiconductor element was increased), and the surface temperature of the semiconductor element was determined using this and the pre-measured emissivity, and used as the channel temperature. The temperature rise of the channel is shown in Table 1 below.

[Example 1 and Comparative Example 1]
In Example 1 and Comparative Example 1, a semiconductor device as shown in FIG. 13 was tested. The planar shape of the semiconductor element was a rectangle of 1.0 mm (short side) × 1.2 mm (long side), and the thickness of the heat sink was 1.3 mm.

[Example 2 and Comparative Example 2]
In Example 2 and Comparative Example 2, a semiconductor device as shown in FIG. 14 was tested. The planar shape of the semiconductor element was a square of 1.0 mm × 1.0 mm, and the thickness of the heat sink was 1.3 mm. Further, a thin copper layer having a thickness of 100 μm was attached to both surfaces of the heat sink.

[Example 3 and Comparative Example 3]
In Example 3 and Comparative Example 3, a semiconductor device as shown in FIG. 15 was tested. The planar shape of the semiconductor element was a rectangle of 1.0 mm (short side) × 2.0 mm (long side), and the thickness of the heat sink was 1.3 mm.

[Example 4 and Comparative Example 4]
In Example 4 and Comparative Example 4, a semiconductor device as shown in FIG. 16 was tested. The planar shape of the semiconductor element was a rectangle of 1.0 mm (short side) × 1.2 mm (long side), and the thickness of the heat sink was 1.5 mm. Further, a thin copper layer having a thickness of 100 μm was attached to both surfaces of the heat sink.

  According to the examples to which the present invention is applied, the temperature rise is lower than that of the comparative example, and it can be seen that the present invention is more excellent in heat dissipation. Further, by comparing Example 3 with Comparative Example 3, according to the present invention, the ratio of the short side to the long side in the planar shape is 1: 2 (the length of one side and the length of the other side. It has been found that even a rectangular electronic device having a ratio of 0.5 to 2) can improve heat dissipation.

  The electronic element in the present invention may be an active element such as a semiconductor element or a passive element as long as it serves as a heating element. Examples of the electronic element include GaN FET, Si LDMOS, GaAs FET, insulated gate bipolar transistor (IGBT) using Si and SiC, and the like. Moreover, the present invention can be applied to an MMIC (Microwave Monolithic Integrated Circuit) as well as a single element. In this case, unlike the case of a single element, the planar shape of the entire semiconductor chip and the shape of each semiconductor element included in the semiconductor chip do not necessarily match, but the present invention is based on the planar shape of the semiconductor element having the largest amount of heat generation. The direction should be determined.

  The electronic device of the present invention has been described based on the above-described embodiment, but is not limited to the above-described embodiment, and the above-described implementation is within the scope of the present invention and based on the basic technical idea of the present invention. It cannot be overemphasized that various deformation | transformation, a change, and improvement with respect to a form can be included. Further, various combinations, substitutions, or selections of various disclosed elements are possible within the scope of the claims of the present invention.

  Further problems, objects, and developments of the present invention will become apparent from the entire disclosure of the present invention including the claims.

  The present invention can be applied to, for example, high frequency / high output power amplifiers, in particular, mobile phone base station power amplifiers and various radar power amplifiers.

DESCRIPTION OF SYMBOLS 1,21 Electronic device 2 (1st) Heat sink 2a Electronic element mounting surface 3 Electronic element 3a, 3b Side 4a Diagonal extension direction 4b Direction perpendicular to diagonal extension direction 5 Low thermal conductivity 6 Thermal conductivity Higher rate 22 Second heat sink 100, 200, 300, 400 Semiconductor device 101 (First) heat sink 102 Semiconductor element 103 Matching circuit board 104 Bonding wire 105 Sealing resin 106 Sealing lid 107 Input terminal 108 Output terminal 109 Metal layer 110 Second heat sink

Claims (22)

A first heat sink with anisotropic thermal conductivity;
An electronic element mounted on the first heat sink and having a quadrilateral planar shape projected onto the mounting surface of the first heat sink;
The electronic element has higher heat dissipation in the direction of extension of one diagonal of the planar shape or heat dissipation in the direction perpendicular to the direction of extension of the diagonal on the mounting surface than heat dissipation in the side direction. As described above, the electronic device is arranged on the first heat sink. When the planar shape is a rectangle other than a square,
The electronic element is disposed on the first heat sink so that heat dissipation in a direction perpendicular to an extending direction of the diagonal line is higher than heat dissipation in a side direction on the mounting surface. The electronic device according to claim 1. A first heat sink with anisotropic thermal conductivity;
An electronic element mounted on the first heat sink and having a quadrilateral planar shape projected onto the mounting surface of the first heat sink;
The mounting surface of the first heat sink has a thermal conductivity in the direction in which one of the diagonal lines of the planar shape on the mounting surface of the first heat sink is perpendicular to the direction in which the diagonal extends. An electronic device having a higher thermal conductivity in the extending direction of one side of the planar shape. When the planar shape is a rectangle other than a square,
The thermal conductivity in the direction perpendicular to the extending direction of the diagonal line in the first heat sink on the mounting surface of the first heat sink is the extending direction of one side of the planar shape on the mounting surface of the first heat sink. The electronic device according to claim 3, wherein the electronic device has a higher thermal conductivity. A first heat sink with anisotropic thermal conductivity;
An electronic element mounted on the first heat sink and having a quadrilateral planar shape projected onto the mounting surface of the first heat sink;
In the mounting surface, an angle formed by a direction in which the first heat sink has the highest thermal conductivity and an extension direction of one of the diagonal lines of the planar shape, or an angle formed by a direction perpendicular to the extension direction of the diagonal line. Is an electronic device characterized by being -30 ° to 30 °. When the planar shape is a rectangle other than a square,
The angle between the direction in which the thermal conductivity of the first heat sink is highest and the direction perpendicular to the extending direction of the diagonal line is -30 ° to 30 ° on the mounting surface. 5. The electronic device according to 5. A first heat sink with anisotropic thermal conductivity;
An electronic element mounted on the first heat sink and having a quadrilateral planar shape projected onto the mounting surface of the first heat sink;
In the first heat sink, three orthogonal directions are defined as a first direction, a second direction, and a third direction, the thermal conductivity in the first direction is Ka, the thermal conductivity in the second direction is Kb, and the thermal conductivity in the third direction. When the rate is Kc and Ka ≧ Kb> Kc or Kb ≧ Ka> Kc,
An angle formed between one direction of the first direction and the second direction and a direction perpendicular to the mounting surface of the first heat sink is −30 ° to 30 °.
Of the first direction and the second direction, an angle formed between the other direction and the extending direction of one diagonal line of the planar shape or a direction perpendicular to the extending direction of the diagonal line is -30 ° to 30 °. An electronic device characterized in that it is °. When the planar shape is a rectangle other than a square,
The electronic device according to claim 7, wherein an angle formed between the other direction and a direction perpendicular to the extending direction of the diagonal line is −30 ° to 30 °.   9. The electronic device according to claim 7, wherein Ka and Kb are 10 times or more of Kc.   The electronic device according to claim 7, wherein Ka and Kb are 600 W / mK or more. A second heat sink that is at least partially in contact with the first heat sink and has an anisotropic thermal conductivity;
In the second heat sink, the three orthogonal directions are the fourth direction, the fifth direction, and the sixth direction, the thermal conductivity in the fourth direction is Kd, the thermal conductivity in the fifth direction is Ke, and the thermal conductivity in the sixth direction. When the rate is Kf and Kd ≧ Ke> Kf or Ke ≧ Kd> Kf,
The angle formed between the fourth direction or the fifth direction of the second heat sink and the third direction of the first heat sink is -30 ° to 30 °. The electronic device as described in any one.   12. The electronic device according to claim 11, wherein Kd and Ke are 10 times or more of Kf. The second heat sink has a recess or a through hole,
The electronic device according to claim 11, wherein the first heat sink is disposed in the recess or the through hole.   The angle formed by the sixth direction of the second heat sink and the third direction of the first heat sink is -30 ° to 30 °. The electronic device described.   Kd and Ke are 600 W / mK or more, The electronic device as described in any one of Claims 11-14 characterized by the above-mentioned. The planar shape of the mounting surface of the electronic element is a rectangle,
The ratio of the length of one side and the length of the other side of the rectangle in the planar shape is 0.65 to 1.5, according to any one of claims 1 to 15. Electronic equipment. The first heat sink or the first heat sink and the second heat sink have a metal layer on at least a surface of the first heat sink opposite to the mounting surface and the mounting surface,
The electronic device according to claim 1, wherein the electronic element is mounted on the metal layer.   On the mounting surface of the first heat sink having an anisotropic thermal conductivity, an electronic element having a quadrilateral planar shape is arranged to dissipate heat in the extending direction of one diagonal line of the planar shape on the mounting surface or to extend the diagonal line. A method of manufacturing an electronic device, wherein mounting is performed such that heat dissipation in a direction perpendicular to a current direction is higher than heat dissipation in a side direction.   On the mounting surface of the first heat sink having an anisotropic thermal conductivity, an electronic element having a quadrilateral planar shape is transferred in the extending direction of one diagonal line of the planar shape on the mounting surface of the first heat sink. Or mounting so that the thermal conductivity in the direction perpendicular to the extending direction of the diagonal line is higher than the thermal conductivity in the extending direction of one side of the planar shape on the mounting surface of the first heat sink. A method for manufacturing an electronic device.   On the mounting surface of the first heat sink having an anisotropic thermal conductivity, an electronic element having a quadrangular planar shape is formed on the mounting surface. The direction in which the thermal conductivity of the first heat sink is the highest on the mounting surface, A method of manufacturing an electronic device, characterized in that mounting is performed such that an angle formed with one diagonal line extending direction or an angle formed with a direction perpendicular to the diagonal line extending direction is -30 ° to 30 °. . In the first heat sink with anisotropic thermal conductivity, the three orthogonal directions are defined as the first direction, the second direction, and the third direction, the thermal conductivity in the first direction is Ka, and the thermal conductivity in the second direction is Kb. And when the thermal conductivity in the third direction is Kc, and Ka ≧ Kb> Kc or Kb ≧ Ka> Kc,
On the mounting surface of the first heat sink, an electronic element having a quadrilateral planar shape is provided.
Of the first direction and the second direction, an angle between one direction and a direction perpendicular to the mounting surface of the first heat sink is −30 ° to 30 °,
Of the first direction and the second direction, an angle formed between the other direction and the extending direction of one diagonal line of the planar shape or a direction perpendicular to the extending direction of the diagonal line is -30 ° to 30 °. A method of manufacturing an electronic device, wherein the electronic device is mounted so as to be at an angle. In the second heat sink with anisotropic thermal conductivity, the three orthogonal directions are the fourth direction, the fifth direction, and the sixth direction, the thermal conductivity in the fourth direction is Kd, and the thermal conductivity in the fifth direction is Ke. And when the thermal conductivity in the sixth direction is Kf and Kd ≧ Ke> Kf or Ke ≧ Kd> Kf,
The first heat sink is at least partially in contact, and an angle between the fourth direction or the fifth direction of the second heat sink and the third direction of the first heat sink is −30 ° to 30 °. The method of manufacturing an electronic device according to claim 21, wherein the second heat sink is arranged as described above.

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