Electronic device

Provided is an electronic device capable of simultaneously achieving heat dissipation, electromagnetic wave suppression effect and ESD protection at a high level. The device includes: an electronic component 30 provided on a substrate 31; an electrically conductive shielding can 20 having an opening 21 and provided so as to surround the electronic component 30 and connected to a ground 32; an electrically conductive cooling member 40 provided on the top of the electrically conductive shielding can 20; a thermally and electrically conductive sheet 10 provided between the electronic component 30 and the electrically conductive cooling member 40; and an insulating member 50 provided between the thermally and electrically conductive sheet 10 and the electrically conductive cooling member 40 and facing the electronic component 30 through the opening 21, wherein the insulating member 50 has a size equal to or larger than the region of the electronic component 30 facing through the opening 21, and the electrically conductive shielding can 20 and the electrically conductive cooling member 40 are electrically connected through the thermally and electrically conductive sheet 10.

TECHNICAL FIELD

The present technology relates to an electronic device having excellent heat dissipation, electromagnetic wave suppression, and electrostatic discharge properties and is particularly suitable for use in a semiconductor device. This application is a National Stage Patent Application of PCT International Patent Application No. PCT/JP2019/024173 filed on Jun. 18, 2019 under 35 U.S.C. § 371, which claims priority on the basis of Japanese Patent Application No. 2018-121354, filed on Jun. 26, 2018, in Japan, which is incorporated by reference herein.

BACKGROUND ART

In recent years, while electronic devices tends to be miniaturized, since the power consumption cannot be changed so much due to the diversity of applications, measures for heat dissipation in the equipment have become more important.

As measures for heat dissipation in the electronic devices, a heat radiator plate made of a metal material having a high thermal conductivity such as copper or aluminum, a heat pipe, a heat sink, and the like are widely used. These heat dissipating components having excellent thermal conductivity are arranged so as to be close to electronic components such as a semiconductor package which is a heat generating component in the electronic device in order to achieve a heat dissipating effect or temperature relaxation in the device. These heat dissipating components having excellent thermal conductivity are disposed from the electronic components which are heat generating components to a place of low temperature.

However, the heat generating component in the electronic device is an electronic component such as a semiconductor device having a high current density; the fact that the current density is high implies that the electric field strength or the magnetic field strength, which can be a component of unwanted radiation, is large. Therefore, a heat dissipating component made of metal disposed in the vicinity of the electronic component not only absorbs heat, but also causes a problem by picking up a harmonic component of the electric signal flowing in the electronic component. Specifically, since the heat dissipating component is made of a metal material, the heat dissipating component itself functions as an antenna for a harmonic component or as a transmission path for a harmonic noise component.

Therefore, it is desired to develop a technology that achieves both heat dissipation and electromagnetic wave suppression effects. For example, Patent Document 1 discloses a technology in which a shielding case for covering an electronic component mounted on a printed board having a hole for a fin and a heat dissipation fin are provided, and a part of the heat dissipation fin is exposed to the outside of the shielding case via the hole for the fin.

However, although the technology disclosed in Patent Document 1 can secure a certain level of heat dissipation, because the hole for the fin is provided in the shielding case, it is considered that the electromagnetic wave suppression effect cannot be sufficiently obtained and both of the heat dissipation and the electromagnetic wave suppression effect cannot be achieved simultaneously.

Furthermore, when a charged human body touches an electronic device, the accumulated static electricity might be discharged into the electronic device, which causes malfunction or damage to electronic components such as semiconductor devices, so that ESD (electro-static discharge) protection measures are also required in addition to the above measures for heat dissipation and electromagnetic wave suppression.

PRIOR ART REFERENCE

Patent Reference

SUMMARY OF THE INVENTION

Problem to be Solved by the Invention

In view of the above, it is an object of the present invention to provide an electronic device having excellent heat dissipation properties and electromagnetic wave suppression effects and provided with ESD protection properties.

Means of Solving the Problem

The present inventors have studied the above problem repeatedly, and have found the fact that heat dissipation properties can be improved by providing an electrically conductive shielding can connected to a ground so as to cover the electronic component, and that excellent electromagnetic wave absorption performance can also be achieved without degrading the electromagnetic wave absorption performance by providing an opening in the electrically conductive shielding can and forming a thermally and electrically conductive sheet at least through the opening to connect the electronic component and the cooling member. Furthermore, present inventors also found that ESD protection can be simultaneously realized in addition to heat dissipation and electromagnetic wave suppression by arranging an insulating member at a predetermined position in order to provide effective ESD protection. As a result, the electronic device according to the present technology can simultaneously realize heat dissipation, electromagnetic wave suppression effect, and ESD protection at a high level.

The present technology is based on the above findings and an electronic device according to the present technology includes: an electronic component provided on a substrate; an electrically conductive shielding can having an opening and provided so as to surround the electronic component and connected to a ground; an electrically conductive cooling member provided on an upper portion of the electrically conductive shielding can; a thermally and electrically conductive sheet provided between the electronic component and the electrically conductive cooling member; and an insulating member provided between the thermally and electrically conductive sheet and the electrically conductive cooling member and facing the electronic component through the opening, wherein the insulating member has a size equal to or larger than a region of the electronic component facing the insulating member through the opening, and wherein the electrically conductive shielding can is electrically connected to the electrically conductive cooling member through the thermally and electrically conductive sheet.

Effects of the Invention

According to the present technology, it is possible to provide an electronic device capable of simultaneously achieving heat dissipation, electromagnetic wave suppression, and ESD protection measures at a high level.

MODE FOR CARRYING OUT THE INVENTION

Hereinafter, an electronic device according to the present technology will be described in detail with reference to the drawings. It should be noted that the present technology is not limited to the following embodiments and various modifications can be made without departing from the scope of the present technology. Moreover, the features illustrated in the drawings are shown schematically and are not intended to be drawn to scale. Actual dimensions should be determined in consideration of the following description. Furthermore, those skilled in the art will appreciate that dimensional relations and proportions may be different among the drawings in certain parts.

In the following, an example of an electronic device according to the present technology will be described with reference to a semiconductor device using a semiconductor element as an electronic component. As shown inFIG. 1, a semiconductor device1according to the present technology includes a semiconductor element30, an electrically conductive shielding can20, an electrically conductive cooling member40, an insulating member50, and a thermally and electrically conductive sheet10.

The semiconductor device1includes the electrically conductive shielding can20having an opening21and provided so as to surround the semiconductor element30, and the thermally and electrically conductive sheet10is formed between the semiconductor element30and the electrically conductive cooling member40.

The semiconductor element30can be a source of heat and electromagnetic waves; however, by providing the electrically conductive shielding can20so as to surround the semiconductor element30, connecting the electrically conductive shielding can20to a ground32, providing the thermally and electrically conductive sheet10around the opening21of the electrically conductive shielding can20, and connecting the electrically conductive cooling member40through the thermally and electrically conductive sheet10, the ground32, the electrically conductive shielding can20, the thermally and electrically conductive sheet10, and the electrically conductive cooling member40forms a virtual shielding can for shielding the semiconductor element30, so that electromagnetic waves are shielded, thereby achieving an excellent electromagnetic wave suppressing effect.

Further, by forming the opening21in the electrically conductive shielding can20and providing the thermally and electrically conductive sheet10having high thermal conductivity between the semiconductor element30and the electrically conductive cooling member40, thermal conduction to the electrically conductive cooling member40is greatly improved, and as a result, excellent heat dissipation can also be realized.

The semiconductor device1is characterized in that the insulating member50is provided between the semiconductor element30and the electrically conductive cooling member40, so that the semiconductor element30and the insulating member50face each other through the opening21.

The thermally and electrically conductive sheet10efficiently transmits heat generated by the semiconductor element30to the electrically conductive cooling member40, while there is a possibility that static electricity discharged to the electrically conductive cooling member40flows into the semiconductor element30. However, in the semiconductor device1, the insulating member50is provided between the thermally and electrically conductive sheet10and the electrically conductive cooling member40so that the insulating member50faces the semiconductor element30through the opening21of the electrically conductive shielding can20. Further, in the semiconductor device1, the electrically conductive shielding can20and the electrically conductive cooling member40are electrically connected to each other via the thermally and electrically conductive sheet10. As a result, in the semiconductor device1, the static electricity S discharged to the electrically conductive cooling member40flows through the thermally and electrically conductive sheet10while avoiding the insulating member50, and can flow to the ground32through the electrically conductive shielding can20. Therefore, the semiconductor device1can prevent the static electricity discharged to the electrically conductive cooling member40from being transmitted to electronic components such as the semiconductor element30, and can prevent malfunction and damage.

Here, the state in which the semiconductor element30and the insulating member50face each other through the opening21includes a case where the insulating member50faces the entire region of the semiconductor element30exposed to the side of the electrically conductive cooling member40from the opening21, and other cases where the insulating member50is overlapped with a part of the semiconductor element30exposed to the electrically conductive cooling member40side from the opening21as long as the effect of protection against electro-static discharge (ESD) is achieved.

Next, each member constituting the semiconductor device1will be described.

Semiconductor Device

As shown inFIG. 1, the semiconductor device1includes the semiconductor element30formed on a substrate31. The semiconductor element30is not particularly limited as long as it is an electronic component made of a semiconductor. Examples include integrated circuits such as ICs and LSIs, CPUs, MPUs, graphic processing elements, and image sensors, among others.

Also, the substrate31on which the semiconductor element30is formed is not particularly limited, and an appropriate substrate can be used according to the type of the semiconductor device. The substrate31is provided with the ground (GND)32. The ground32may be formed on the inner layer of the substrate31or on the back surface of the substrate31as shown inFIG. 1.

InFIG. 1, for convenience of illustration, the electrically conductive shielding can20is shown penetrating the substrate31and directly connecting to the ground32. However, in a general practical use, as shown inFIG. 2, a land33is provided on the surface of the substrate31so as to surround the semiconductor element30in the whole or in part, and the electrically conductive shielding can20is connected to this part by solder or the like. The land33is electrically connected to the ground32by a through hole (not shown) formed in the substrate31, whereby the electrically conductive shielding can20is electrically connected to the ground32.

The substrate31is provided with a microstrip line35at a position where the semiconductor element30is mounted.

Shielding Can

As shown inFIG. 1, the semiconductor device1includes the opening21through which at least a part of the semiconductor element30is exposed to the side of the electrically conductive cooling member40, and the electrically conductive shielding can20connected to the ground32. In the semiconductor device1, the electrically conductive shielding can20connected to the ground32shields the semiconductor element30together with the thermally and electrically conductive sheet10and the electrically conductive cooling member40, thereby shielding electromagnetic waves and exhibiting an electromagnetic wave suppressing effect. As will be described later, the semiconductor device1can efficiently dissipate heat of the semiconductor element30to the electrically conductive cooling member40by thermally connecting the semiconductor element30exposed from the opening21and the electrically conductive cooling member40through the thermally and electrically conductive sheet10.

The material constituting the electrically conductive shielding can20is not particularly limited as long as it has a high electrical conductivity and a high shielding effect of electromagnetic waves. For example, a metal having a high electrical conductivity such as aluminum, copper, stainless steel, or a magnetic material having a high electrical conductivity can be used. Examples of the magnetic material having high electrical conductivity include permalloy, Sendust, Fe or Co amorphous materials, and microcrystalline materials. When the above-mentioned magnetic material is used as the material constituting the shielding can20, the magnetic shielding effect and the magnetic absorption effect can be expected in addition to the electric shielding effect.

The opening21provided in the electrically conductive shielding can20is a through hole provided in the electrically conductive shielding can20. In the electrically conductive shielding can20, the semiconductor element30faces the insulating member50and the electrically conductive cooling member40through the opening21, and the thermally and electrically conductive sheet10, which will be described later, is provided between the semiconductor element30and the cooling member40. That is, as shown inFIG. 1, the thermally and electrically conductive sheet10is formed in a direction connecting the semiconductor element30and the electrically conductive cooling member40(inFIG. 1, the stacking direction of each member).

The size of the opening21is not particularly limited, and can be appropriately changed according to the size of the semiconductor element30or other factors. The smaller the opening area of the opening21, the smaller the emission of electromagnetic waves and the smaller the radiation electromagnetic field. However, from the viewpoint of releasing heat from the semiconductor element30, it is preferable to use a large thermally and electrically conductive sheet10with the opening21enlarged. Therefore, the size of the opening21is appropriately adjusted according to the thermal conductivity and the electromagnetic noise suppression effect required for the semiconductor device1.

Electrically Conductive Cooling Member

As shown inFIG. 1, the electrically conductive cooling member40of the semiconductor device1is provided on an upper portion of the electrically conductive shielding can20. The electrically conductive cooling member40is a member for absorbing heat generated by the semiconductor element30acting as a heat source and dissipating the heat to the outside. The electrically conductive cooling member40is connected to the semiconductor element30via the thermally and electrically conductive sheet10, which will be described later, so that heat generated by the semiconductor element30can be diffused to the outside, thereby ensuring heat dissipation of the semiconductor device1.

The type of the electrically conductive cooling member40is not particularly limited, and can be appropriately selected according to the type of the semiconductor device1. Examples include a radiator, a cooler, a heat sink, a heat spreader, a die pad, a cooling fan, a heat pipe, a metal cover, and an electronic device housing. Among these heat dissipating members, a radiator, a cooler, or a heat sink is preferably used in view of achieving more excellent heat dissipating properties.

It should be noted that, as shown inFIG. 1, the electrically conductive cooling member40is provided at an upper portion of the electrically conductive shielding can20, but is not in contact with the electrically conductive shielding can20and is provided at a certain distance. This is because the thermally and electrically conductive sheet10, which will be described later, is provided between a top surface20aof the electrically conductive shielding can20and the electrically conductive cooling member40, and electrically connects the electrically conductive shielding can20and the electrically conductive cooling member40through the thermally and electrically conductive sheet10.

Thermally and Electrically Conductive Sheet

As shown inFIG. 1, the semiconductor device1includes the thermally and electrically conductive sheet10which is sandwiched between the electrically conductive shielding can20and the electrically conductive cooling member40and is in contact with the semiconductor element30and the electrically conductive cooling member40. In the semiconductor device1, the electrically conductive shielding can20and the electrically conductive cooling member40are electrically connected to each other via the thermally and electrically conductive sheet10, and the semiconductor element30and the electrically conductive cooling member40are thermally connected to each other via the thermally and electrically conductive sheet10.

Since the thermally and electrically conductive sheet10having electrical conductivity and high thermal conductivity is provided between the semiconductor element30and the electrically conductive cooling member40, heat of the semiconductor element30can be transmitted to the electrically conductive cooling member40through the thermally and electrically conductive sheet10to improve heat dissipation. In addition, since the electrically conductive shielding can20and the electrically conductive cooling member40are electrically connected to each other through the thermally and electrically conductive sheet10, static electricity discharged to the electrically conductive cooling member40can flow to the electrically conductive shielding can20connected to the ground32.

The thermally and electrically conductive sheet10preferably has flexibility and tackiness. The flexibility facilitates handling and improves adhesiveness to the semiconductor element30, the electrically conductive shielding can20, and the electrically conductive cooling member40, thereby achieving excellent thermal conductivity and electrical conductivity. Further, the flexibility enables pressurization by the electrically conductive cooling member40, thereby ensuring more adhesiveness, and maintaining adhesiveness even when expansion or contraction occurs.

The material constituting the thermally and electrically conductive sheet10is not particularly limited as long as it has excellent electrical conductivity and thermal conductivity. For example, in view of the high level of electrical conductivity and thermal conductivity, a thermally conductive sheet including a binder resin, a thermally conductive filler, and an electrically conductive filler can be used as the thermally and electrically conductive sheet10. The material constituting the thermally and electrically conductive sheet10will be described below.

Binder Resin

The binder resin constituting the thermally and electrically conductive sheet10is a resin component to be a base material of the thermally and electrically conductive sheet10. The type is not particularly limited, and a known binder resin can be appropriately selected. For example, one of the binder resins is a thermosetting resin.

Among the above-mentioned thermosetting resins, silicone is preferably used in view of excellent molding processability and weather resistance, as well as adhesiveness and followability to electronic components. The silicone is not particularly limited, and the type of silicone can be appropriately selected according to the purpose.

From the viewpoint of obtaining the molding processability, weather resistance, and adhesiveness, among others, it is preferable that the silicone is composed of a main agent of a liquid silicone gel and a curing agent. Such silicones include, for example, addition reaction type liquid silicones and thermal vulcanization type millable silicones using peroxides for vulcanization.

A preferable example of the addition reaction type liquid silicones is a two-part addition reaction type silicone containing a polyorganosiloxane having a vinyl group as a main agent and a polyorganosiloxane having a Si—H group as a curing agent. In the combination of the main agent of the liquid silicone gel and the curing agent, the blending ratio of the main agent and the curing agent is preferably 35:65 to 65:35 by mass ratio.

The content of the binder resin in the thermally and electrically conductive sheet10is not particularly limited, and can be appropriately selected according to the purpose. For example, from the viewpoint of ensuring the formability of the sheet and the adhesiveness of the sheet, it is preferably about 20 to 50 vol %, more preferably about 30 to 40 vol %, of the thermally and electrically conductive sheet10.

Thermally Conductive Filler

The thermally and electrically conductive sheet10contains a thermally conductive filler in a binder resin. The thermally conductive filler is a component for improving the thermal conductivity of the sheet. The type of the thermally conductive filler is not particularly limited, but it is preferable to use a fibrous thermally conductive filler in view of achieving higher thermal conductivity.

The “fibrous” of the fibrous thermally conductive filler refers to a shape having a high aspect ratio (approximately 6 or more). Therefore, in the present invention, not only thermally conductive fillers such as fibrous and rod-like fillers but also granular fillers and flake-like thermally conductive fillers having a high aspect ratio are included in the fibrous thermally conductive fillers.

The type of the fibrous thermally conductive filler is not particularly limited as long as it is a fibrous material having high thermal conductivity, and examples thereof include metals such as silver, copper, and aluminum, ceramics such as alumina, aluminum nitride, silicon carbide, and graphite, and carbon fibers, among others. Among these fibrous thermally conductive fillers, it is preferable to use carbon fibers in view of achieving higher thermal conductivity.

The thermally conductive filler may be used alone or in combination by mixing two or more fillers. When two or more types of thermally conductive fillers are used, all of them may be fibrous thermally conductive fillers, or a fibrous thermally conductive filler may be mixed with a thermally conductive filler of different shapes.

The type of the carbon fiber is not particularly limited, and can be appropriately selected according to the purpose. For example, a material obtained by graphitizing pitch-based fiber, PAN-based fiber, and PBO fiber, or a material synthesized by arc discharge method, laser evaporation method, CVD (chemical vapor deposition) method, or CCVD (catalytic chemical vapor deposition) method, among others, can be used. Among them, carbon fibers obtained by graphitizing PBO fibers and pitch-based carbon fibers are more preferable from the viewpoint of obtaining high thermal conductivity.

The carbon fiber may be processed by surface treatment of a part or the whole of the carbon fiber as required. Examples of the surface treatment include an oxidation treatment, a nitriding treatment, a nitration treatment, a sulfonation treatment, and a treatment for attaching or bonding a metal, a metal compound, an organic compound to the functional group introduced to the surface by these treatments or the surface of the carbon fiber. Examples of the functional group include a hydroxyl group, a carboxyl group, a carbonyl group, a nitro group, and an amino group.

Further, the average fiber length (average long axis length) of the fibrous thermally conductive filler can be appropriately selected without any particular limitation, and from the viewpoint of reliably obtaining high thermal conductivity, it is preferably in the range of 50 to 300 μm, more preferably in the range of 75 to 275 μm, and particularly preferably in the range of 90 to 250 μm. Further, the average fiber diameter (average short axis length) of the fibrous thermally conductive filler can be appropriately selected without any particular limitation, and from the viewpoint of reliably obtaining high thermal conductivity, it is preferably in the range of 4 to 20 μm, and more preferably in the range of 5 to 14 μm.

The aspect ratio (average long axis length/average short axis length) of the fibrous thermally conductive filler is 6 or more and preferably 7 to 30 from the viewpoint of reliably obtaining high thermal conductivity. Even when the aspect ratio is small, an improvement effect of thermal conductivity or the like is observed, but since a large characteristic improvement effect cannot be obtained, for example, due to a decrease in orientation, the aspect ratio is preferably set to 6 or more. On the other hand, when the value exceeds 30, the dispersibility in the thermally and electrically conductive sheet10decreases, so that the thermal conductivity might be insufficient.

Here, the average long axis length and the average short axis length of the fibrous thermally conductive filler can be measured by, for example, a microscope, a scanning electron microscope (SEM) or the like, and the average can be calculated from a plurality of samples.

The content of the fibrous thermally conductive filler in the thermally and electrically conductive sheet10is not particularly limited and can be appropriately selected according to the purpose, but is preferably from 4 to 40 vol %, more preferably from 5 to 30 vol %, and particularly preferably from 6 to 20 vol %. If the content is less than 4 vol %, it may be difficult to obtain a sufficiently low thermal resistance, and if the content is more than 40 vol %, it may affect the formability of the thermally and electrically conductive sheet10and the orientation of the fibrous thermally conductive filler.

Further, in the thermally and electrically conductive sheet10, the thermally conductive filler is preferably oriented in one or more directions. By orienting the thermally conductive filler, higher thermal conductivity and electromagnetic wave absorption can be realized.

For example, when it is desired to improve the thermal conductivity of the thermally and electrically conductive sheet10and the heat dissipation of the semiconductor device, the thermally conductive filler can be oriented substantially perpendicular to the sheet surface. On the contrary, when it is desired to improve the electromagnetic wave shielding performance of the thermally and electrically conductive sheet10and improve the electromagnetic wave suppressing effect of the semiconductor device, the thermally conductive filler can be oriented substantially parallel to the sheet surface.

Here, a direction substantially perpendicular to or substantially parallel to the sheet surface means a direction substantially perpendicular to or substantially parallel to the sheet surface direction. However, since the orientation direction of the thermally conductive filler varies slightly during manufacturing, the present invention allows a deviation of about ±20° from the direction perpendicular to or parallel to the sheet surface.

The method of adjusting the orientation angle of the thermally conductive filler is not particularly limited. For example, the orientation angle can be adjusted by preparing a molded body for a sheet which is a base of the thermally and electrically conductive sheet10and adjusting the cutting angle in a state where the fibrous thermally conductive filler is oriented.

Electrically Conductive Filler

The thermally and electrically conductive sheet10contains an electrically conductive filler in a binder resin. The electrically conductive filler is a component for improving the conductivity of the sheet. The type of the electrically conductive filler is not particularly limited, but it is preferable to use a fibrous electrically conductive filler in view of achieving higher conductivity and having conductive anisotropy easily conducting in the thickness direction of the sheet and hardly conducting in the surface direction of the sheet.

This type of electrically conductive filler can be made of a material having electrical conductivity among the above-described thermally conductive fillers. Among them, the carbon fiber can be suitably used because it has high thermal conductivity and electrical conductivity.

By orienting the fibrous electrically conductive filler substantially perpendicular to the sheet surface, the thermally and electrically conductive sheet10is preferably provided with a conductive anisotropy which is easily conductive in the thickness direction of the sheet and hardly conductive in the surface direction of the sheet. The thermally and electrically conductive sheet10is sandwiched between the electrically conductive shielding can20and the electrically conductive cooling member40, whereby the static electricity discharged to the electrically conductive cooling member40is allowed to flow to the electrically conductive shielding can20, and the static electricity which flows into the thermally and electrically conductive sheet10while avoiding the insulating member50to be described later basically flows to the electrically conductive shielding can20having a relatively low electric resistance, and by providing the conductive anisotropy, the static electricity hardly flows under the insulating member50and can be prevented from being transmitted to the semiconductor element30more reliably. The electric resistance ratio of the thermally and electrically conductive sheet10in the in-plane direction with respect to the thickness direction is preferably high and for example, 100 times or more.

Inorganic Filler

The thermally and electrically conductive sheet10may further contain an inorganic filler in addition to the binder resin, the thermally conductive filler, and the electrically conductive filler described above. This is because the thermal conductivity of the thermally and electrically conductive sheet10can be further enhanced to improve the strength of the sheet.

The inorganic filler is not particularly limited in terms of shape, material, and average particle diameter, and can be appropriately selected according to the purpose. Examples of the shape include spherical, elliptical, massive, granular, flat, and needle-like shapes. Among them, the spherical shape and the elliptical shape are preferable from the viewpoint of the fillability, and the spherical shape is particularly preferable.

Examples of the material of the inorganic filler include aluminum nitride (AlN), silica, alumina (aluminium oxide), boron nitride, titania, glass, zinc oxide, silicon carbide, silicon, silicon oxide, and metal particles, among others. One or more of these may be used alone or in combination. Among them, alumina, boron nitride, aluminum nitride, zinc oxide, and silica are preferable, and alumina and aluminum nitride are particularly preferable from the viewpoint of thermal conductivity.

The inorganic filler may be surface treated. When the inorganic filler is treated with a coupling agent as the surface treatment, the dispersibility of the inorganic filler is improved and the flexibility of the thermally and electrically conductive sheet10is improved.

The average particle diameter of the inorganic filler can be appropriately selected according to the type of inorganic substance or the like. When the inorganic filler is alumina, the average particle diameter thereof is preferably from 1 to 10 μm, more preferably from 1 to 5 μm, and particularly preferably from 4 to 5 μm. If the average particle diameter is less than 1 μm, the viscosity may be increased and the mixing may become difficult. On the other hand, when the average particle diameter exceeds 10 μm, there is a possibility that the thermal resistance of the thermally and electrically conductive sheet10increases.

When the inorganic filler is aluminum nitride, the average particle diameter thereof is preferably 0.3 to 6.0 μm, more preferably 0.3 to 2.0 μm, and particularly preferably 0.5 to 1.5 μm. If the average particle diameter is less than 0.3 μm, the viscosity may be increased and the mixing may become difficult, and if the average particle diameter exceeds 6.0 μm, the thermal resistance of the thermally and electrically conductive sheet10may be increased.

The average particle size of the inorganic filler can be measured by, for example, a particle size distribution meter or a scanning electron microscope (SEM).

Magnetic Metal Powder

Further, the thermally and electrically conductive sheet10preferably further contains magnetic metal powder in addition to the binder resin, fibrous thermally conductive fibers, and inorganic filler described above. By including the magnetic metal powder, electromagnetic wave absorbency can be imparted to the thermally and electrically conductive sheet10.

The type of the magnetic metal powder is not particularly limited as long as it has electromagnetic wave absorbability, and a known magnetic metal powder can be appropriately selected. For example, amorphous metal powder or crystalline metal powder can be used. Examples of the amorphous metal powder include Fe—Si—B—Cr type, Fe—Si—B type, Co—Si—B type, Co—Zr type, Co—Nb type, and Co—Ta type, and examples of the crystalline metal powder include pure iron, Fe type, Co type, Ni type, Fe—Ni type, Fe—Co type, Fe—Al type, Fe—Si type, Fe—Si—Al type, and Fe—Ni—Si—Al type. Further, as the crystalline metal powder, refined microcrystalline metal powder obtained by adding a small amount of N (nitrogen), C (carbon), O (oxygen), B (boron) or the like to the crystalline metal powder may be used.

The magnetic metal powder may be a mixture of two or more different materials or different average particle sizes.

The shape of the magnetic metal powder is preferably adjusted to be spherical, flat, or the like. For example, in the case of increasing the fillability, it is preferable to use a magnetic metal powder having a spherical particle diameter of several μm to several tens μm. Such a magnetic metal powder can be produced by, for example, an atomizing method or a method for thermally decomposing a metal carbonyl. The atomizing method has an advantage that a spherical powder can be easily formed, and is a method in which a molten metal is made to flow out from a nozzle, and a jet stream of air, water, an inert gas, or the like is blown onto the molten metal which has flowed out to solidify the molten metal as droplets. When the amorphous magnetic metal powder is produced by the atomizing method, the cooling rate is preferably set to about 1×106(K/s) in order to prevent the molten metal from crystallizing.

When the amorphous alloy powder is produced by the atomizing method described above, the surface of the amorphous alloy powder can be made smooth. By using the amorphous alloy powder having a small surface unevenness and a small specific surface area as the magnetic metal powder, the fillability with respect to the binder resin can be enhanced. Further, by performing the coupling treatment, the fillability can be further improved.

In addition to the binder resin, the thermally conductive filler, the electrically conductive filler, the inorganic filler, and the magnetic metal powder described above, the thermally and electrically conductive sheet10may optionally contain other components according to the purpose. Other components include, for example, thixotropy-imparting agents, dispersants, curing accelerators, retarders, slight tackifiers, plasticizers, flame retardants, antioxidants, stabilizers, and colorants, among others.

FIG. 3is a schematic view illustrating an example of a manufacturing process of the thermally and electrically conductive sheet10. As shown inFIG. 3, the thermally and electrically conductive sheet10is manufactured through a series of steps such as extrusion, molding, curing, and cutting (slicing). First, a binder resin, a filler, an inorganic filler, and a magnetic metal powder are mixed and stirred to prepare a thermally conductive resin composition. Next, the prepared thermally conductive resin composition is extruded into a predetermined shape such as a rectangular parallelepiped and cured to obtain a molded body of the thermally conductive resin composition. When the prepared thermally conductive resin composition is extruded, the filler such as carbon fiber blended in the thermally conductive resin composition can be oriented in the extrusion direction by passing through a plurality of slits. Next, after the obtained molded body is cured, the cured molded body is cut to a predetermined thickness by an ultrasonic cutter in a direction perpendicular to the extrusion direction, thereby producing the thermally and electrically conductive sheet10. Because the filler such as carbon fiber is oriented in the thickness direction, the thermally and electrically conductive sheet10has thermal and electrical anisotropy in which thermal and electrical conductivity in the thickness direction is high and thermal and electrical conductivity in the surface direction is low.

The size of the thermally and electrically conductive sheet10is not particularly limited, but it is provided between the semiconductor element30and the cooling member40facing each other through the opening21of the shielding can20, electrically connects the electrically conductive shielding can20and the electrically conductive cooling member40, and therefore has a covering area at least larger than the area of the opening21as shown inFIG. 1. Although the upper limit of the covering area of the thermally and electrically conductive sheet10is not particularly limited, since it is provided on the top surface20aof the electrically conductive shielding can20, the area of the top surface20aof the electrically conductive shielding can20is substantially the upper limit.

Here,FIG. 4is a view illustrating a state where the thermally and electrically conductive sheet10and the electrically conductive shielding can20are viewed from above. As shown inFIG. 4, the covering area of the thermally and electrically conductive sheet10is the area of the electrically conductive shielding can20(including the opening21) covered by the thermally and electrically conductive sheet10(area S of the shaded portion inFIG. 4).

As shown inFIG. 4, the thermally and electrically conductive sheet10is provided on the top surface20aincluding the opening21of the electrically conductive shielding can20. The thermally and electrically conductive sheet10may cover the top surface20aincluding the opening21and the back surface20bof the electrically conductive shielding can20. The top surface20aof the electrically conductive shielding can20refers to the surface of the electrically conductive shielding can20on the side of the electrically conductive cooling member40, and the back surface20bof the electrically conductive shielding can20refers to a surface of the electrically conductive shielding can20on the side of the semiconductor element30. When the thermally and electrically conductive sheet10covers both the top surface20aand the back surface20bof the electrically conductive shielding can20, the covering area is not the sum of the covering areas on the top surface20aand the back surface20b, but the covering area on each surface. This is because the thermally and electrically conductive sheet10can achieve superior heat dissipation properties by covering a part of the top surface20aand a part of the back surface20bof the electrically conductive shielding can20.

The thermally and electrically conductive sheet10can be constituted by laminating and integrating a plurality of sheets. For example, as shown inFIG. 1, when the thermally and electrically conductive sheet10is provided between the semiconductor element30and the cooling member40facing each other through the opening21of the electrically conductive shielding can20and covers the top surface20aof the electrically conductive shielding can20(that is, when the covering area of the thermally and electrically conductive sheet10is larger than the area of the opening21of the shielding can20), the thermally and electrically conductive sheet10is preferably formed of a plurality of sheets having different sizes. By combining sheets of different sizes, the thermally and electrically conductive sheet10can have a desired shape. As shown inFIG. 1, for example, the thermally and electrically conductive sheet10can be formed with a projection10athat enters the opening21and contacts with the semiconductor element30, and a body portion10bthat contacts with the top surface20aof the electrically conductive shielding can20and the electrically conductive cooling member40.

The thermally and electrically conductive sheet10may be composed of one sheet. In this case, the thermally and electrically conductive sheet10is sandwiched between the semiconductor element30and the electrically conductive cooling member40and pressed to cover a part of the top surface20aof the shielding can20, and the part of the sheet is pushed out into the electrically conductive shielding can20through the opening21to be brought into contact with the semiconductor element30.

However, when the thermally and electrically conductive sheet10is formed of a plurality of sheets having different sizes, no step such as pressing is required, so that the thermally and electrically conductive sheet10can be formed in a state in which a fibrous thermally conductive filler described later is oriented, and as a result, superior heat dissipation can be achieved.

The thickness of the thermally and electrically conductive sheet10is not particularly limited, and can be appropriately changed according to the distance between the semiconductor element30and the electrically conductive cooling member40, the size of the shielding can20, and the like. However, in view of the fact that heat dissipation, electromagnetic wave suppression effect, and conductivity between the electrically conductive cooling member40and the electrically conductive shielding can20can be realized at a higher level, the thickness of the thermally and electrically conductive sheet10is preferably from 50 μm to 4 mm, more preferably from 100 μm to 4 mm, and particularly preferably from 200 μm to 3 mm, If the thickness of the thermally and electrically conductive sheet10exceeds 4 mm, the distance between the semiconductor element30and the electrically conductive cooling member40becomes longer, and thus the heat transfer characteristic may be degraded, whereas if the thickness of the thermally and electrically conductive sheet10is less than 50 μm, the electromagnetic wave suppressing effect may be reduced.

Here, the thickness of the thermally and electrically conductive sheet10means the thickness of the thickest portion of the thermally and electrically conductive sheet10, as shown inFIG. 1, regardless of whether the thermally and electrically conductive sheet10is formed of one sheet or a plurality of sheets.

The thermally and electrically conductive sheet10preferably has tackiness on the surface. This is because the adhesion between the thermally and electrically conductive sheet10and other members can be improved, and the sheet can be prevented from being deviated from the initially disposed position of the sheet on the electrically conductive shielding can20or the semiconductor element30. Further, in the case where the thermally and electrically conductive sheet10is composed of a plurality of sheets, the adhesion between the sheets can also be improved. The method of imparting tackiness to the surface of the thermally and electrically conductive sheet10is not particularly limited. For example, the binder resin constituting the thermally and electrically conductive sheet10may be optimized to provide tackiness, or an adhesive layer having tackiness may be separately provided on the surface of the thermally and electrically conductive sheet10.

Further, the thermal conductivity of the portion in contact with the semiconductor element30can be enhanced by making the thermal conductivity of the central portion of the thermally and electrically conductive sheet10to be larger than the thermal conductivity of the outer peripheral portion of the sheet. On the other hand, with respect to the outer periphery of the sheet having a small area in contact with the semiconductor element30, electromagnetic wave absorption performance can be prioritized over thermal conductivity. As a result, the semiconductor device1can achieve more excellent heat dissipation properties and electromagnetic wave suppression effects.

Here, the sheet center portion of the thermally and electrically conductive sheet10refers to a portion where the thermally and electrically conductive sheet10contacts the semiconductor element30, and particularly a portion corresponding to a portion having a large amount of heat generation (a portion commonly referred to as a hot spot). The outer peripheral portion of the sheet refers to a portion other than the center portion.

The method of changing the thermal conductivity of the thermally and electrically conductive sheet10is not particularly limited, but it is possible to change the thermal conductivity by changing the material, the blending ratio, and the orientation direction, among others, of the fibrous thermally conductive filler in the central portion of the sheet and the outer peripheral portion of the sheet.

Insulating Member

The insulating member50is provided between the semiconductor element30exposed on the electrically conductive cooling member40side from the opening21of the electrically conductive shielding can20and the electrically conductive cooling member40, and faces the semiconductor element30through the opening21. Thus, the insulating member50prevents the static electricity discharged to the electrically conductive cooling member40from flowing into the semiconductor element30.

The insulating member50is not particularly limited as long as it is made of a material having an electric resistance higher than that of the thermally and electrically conductive sheet10, and can be made of any known material. Since the insulating member50is provided between the semiconductor element30and the electrically conductive cooling member40, it is preferable to be formed of a material having excellent thermal conductivity from the viewpoint of efficiently transferring heat of the semiconductor element30to the electrically conductive cooling member40in addition to high electrical resistivity. Examples of such a material having high thermal conductivity and high electrical resistivity include thermally conductive ceramics such as aluminum nitride (AlN).

The insulating member50is provided on one surface40aof the electrically conductive cooling member40facing the semiconductor element30by adhesion or the like. Here, as shown inFIG. 1, it is preferable that the insulating member50has an area smaller than the area of the thermally and electrically conductive sheet10and is entirely covered with the thermally and electrically conductive sheet10provided on the one surface40a. As described above, in the semiconductor device1, the thermally and electrically conductive sheet10covers the insulating member50facing the semiconductor element30through the opening21, so that the electrically conductive shielding can20and the electrically conductive cooling member40are electrically connected to each other through the thermally and electrically conductive sheet10around the opening21on the top surface20aof the electrically conductive shielding can20.

As a result, the static electricity discharged to the electrically conductive cooling member40of the semiconductor device1is guided to the outer edge portion of the thermally and electrically conductive sheet10covering the insulating member50by the insulating member50, and flows to the ground32through the top surface20aof the electrically conductive shielding can20provided around the opening21connected to the outer edge portion of the thermally and electrically conductive sheet10. Since the electrically conductive shielding can20has a low electrical resistance and is connected to the ground32, static electricity flowing to the outer edge portion of the thermally and electrically conductive sheet10can be forcedly guided to the electrically conductive shielding can20and the ground32. Thus, by overlapping the semiconductor element30with the insulating member50, static electricity can be avoided from the semiconductor element30and can be guided to the top surface20aaround the opening21of the electrically conductive shielding can20having a high conductivity, so that it is possible to prevent static electricity from being transmitted to the semiconductor element30and to prevent malfunction and damage from occurring.

Further, by providing the thermally and electrically conductive sheet10with an electrical anisotropy in which electricity easily flows in the thickness direction, in this case, in the direction extending between the electrically conductive cooling member40and the top surface20aof the electrically conductive shielding can20, and hardly flows in the surface direction, in this case, in the direction crossing the top surface20aof the electrically conductive shielding can20and the opening21, static electricity is hardly transmitted from the outer edge of the thermally and electrically conductive sheet10to the side of the semiconductor element30, and malfunction and damage can be further prevented.

In the semiconductor device1shown inFIG. 1, the opening21is formed smaller than the size of the semiconductor element30, and a part of the semiconductor element30faces the insulating member50through the opening21.

As shown inFIG. 1, it is preferable that the insulating member50has an area equal to or larger than the area of the opening21, and is overlapped with the entire area of the semiconductor element30facing the insulating member through the opening21. Since static electricity hardly flows in the region overlapped with the insulating member50, the insulating member50has an area equal to or larger than the area of the opening21and is overlapped with the entire region of the semiconductor element30exposed from the opening21to the side of the electrically conductive cooling member40, whereby the static electricity hardly flows into the semiconductor element30.

Manufacturing Process of the Semiconductor Device1

The semiconductor device1can be formed by mounting the semiconductor element30on the substrate31on which the microstrip line35and the ground32are formed, arranging the electrically conductive shielding can20, the thermally and electrically conductive sheet10, and the electrically conductive cooling member40in this order, and then pressurizing the electrically conductive cooling member40.

The electrically conductive cooling member40is previously provided with the insulating member50at a predetermined position facing the opening21of the electrically conductive shielding can20. Therefore, by arranging the electrically conductive cooling member40on the substrate31, the insulating member50is provided between the semiconductor element30and the electrically conductive cooling member40and faces the semiconductor element30through the opening21.

As described above, the electrically conductive shielding can20is connected by solder or the like to the land33provided on the entire circumference or partially so as to surround the semiconductor element30. The land33is electrically connected to the ground32by a through hole (not shown) formed in the substrate31, whereby the electrically conductive shielding can20is electrically connected to the ground32.

The thermally and electrically conductive sheet10is sandwiched between the electrically conductive cooling member40and the top surface20aof the electrically conductive shielding can20by pressurizing the electrically conductive cooling member40. As a result, the electrically conductive shielding can20connected to the ground32is electrically connected to the electrically conductive cooling member40via the thermally and electrically conductive sheet10.

Next, a modified embodiment of the semiconductor device according to the present technology will be described. In the following description, the same members as those of the semiconductor device1are denoted by the same reference numerals, and their details are omitted. As shown inFIG. 5, in a semiconductor device2according to the present technology, the opening21may be formed larger than the semiconductor element30, and the entire semiconductor element30may face the electrically conductive cooling member40. In the semiconductor device2shown inFIG. 5, it is preferable that the insulating member50has an area equal to or larger than the area of the semiconductor element30and is overlapped with the entire area of the semiconductor element30facing via the opening21. Thus, in the semiconductor device2as well, since the insulating member50is overlapped with the entire region of the semiconductor element30, it is possible to make it more difficult for static electricity to flow through the semiconductor element30.

Further, in the semiconductor device2, since the opening21of the electrically conductive shielding can20is formed to be larger than the semiconductor element30, the top surface20aof the electrically conductive shielding can20can be flush with the semiconductor element30, and the height of the electrically conductive shielding can20can be suppressed to be equal to the height of the semiconductor element30while maintaining the electromagnetic wave suppression effect. Further, the thermally and electrically conductive sheet10does not need to enter the opening21, and the height of the semiconductor device2can be reduced as a whole.

As shown inFIG. 6, a ground pattern60having an opening61provided around the semiconductor element30may be provided in place of the electrically conductive shielding can20. In a semiconductor device3shown inFIG. 6, the ground pattern60is formed on the substrate31so as to surround the semiconductor element30. That is, in the semiconductor device3, the opening61surrounding the semiconductor element30is provided in the ground pattern60, and the semiconductor element30faces the insulating member50through the opening61. The ground pattern60is connected to the ground32formed on the back surface of the substrate31through a through hole. The ground32may be formed in the inner layer of the substrate31.

In the semiconductor device3, the thermally and electrically conductive sheet10provided between the semiconductor element30and the electrically conductive cooling member40is connected to the ground pattern60formed on the surface of the substrate31, whereby the ground pattern60and the electrically conductive cooling member40are electrically connected through the thermally and electrically conductive sheet10.

In the semiconductor device3, similarly to the semiconductor device2described above, it is preferable that the insulating member50has an area equal to or larger than the area of the semiconductor element30and is overlapped with the entire area of the semiconductor element30facing the semiconductor element via the opening21. Thus, in the semiconductor device3as well, since the insulating member50is overlapped with the entire region of the semiconductor element30, it is possible to make it more difficult for static electricity to flow through the semiconductor element30.

Since the semiconductor device3is provided with the ground pattern60having the opening61provided around the semiconductor element30instead of the electrically conductive shielding can20, the height of the semiconductor device3as a whole can be reduced while maintaining the electromagnetic wave suppression effect.

EXAMPLES

Next, examples of the present technology will be described. It should be noted that the present technology is not limited to the configuration of the examples described below. The semiconductor devices according to the following Examples 1, 2, and Reference Examples 1 to 3 were prepared, and heat dissipation, noise, ESD, thickness of the semiconductor device, and thermal resistance of the thermally conductive sheet were evaluated. Further, a semiconductor device according to Reference Example 4 was prepared, and the noise suppression effect of Example 1 was examined with reference to Reference Example 4.

In the description of Examples 1 and 2 and Reference Examples 1 to 4, the same members are denoted by the same reference numerals, and their details are omitted. In Examples 1 and 2 and Reference Examples 1 to 4, the measurement methods of thermal resistance and electric field strength are common.

The configuration of Example 1 is the same as the configuration of the semiconductor device1shown inFIG. 1, and the arrangement and dimensions of the respective components are as follows.

Thermally and electrically conductive sheet10: 18 mm×18 mm×0.27 mm thick on the electrically conductive shielding can20; 16 mm×16 mm×0.95 mm thick on the semiconductor device

The distance between the electrically conductive cooling member40and the substrate31is 1.7 mm.

In the thermally and electrically conductive sheet10, a two-part addition reaction type liquid silicone was used as a resin binder, Fe—Si—B—Cr amorphous magnetic particles having an average particle diameter of 5 μm was used as magnetic metal powders, pitch carbon fibers (“thermally conductive fiber” available from Nippon Graphite Fiber Co., Ltd.) having an average fiber length of 200 μm was used as fibrous thermally conductive fillers, and these were dispersed at a volume ratio of the two-part addition reaction type liquid silicone:amorphous magnetic particles:pitch carbon fibers=35 vol %:53 vol %:12 vol % to prepare a silicone composition (composition for the sheet) (bulk thermal conductivity: 5 W/mk). The resulting thermally and electrically conductive sheet10was measured for vertical thermal resistance (calculated by combining the thermal resistance of the interface and the internal thermal resistance) in accordance with ASTM D 5470.

The electrically conductive cooling member40is made of an aluminum plate. The electrically conductive shielding can20is made of stainless steel. The ground32and the microstrip line35are both copper wires. The signal line of the semiconductor element30is simplified by the microstrip line35, and both ends are set as input/output ends of signals. The main body (portion molded with resin) of the semiconductor element30is a dielectric having a relative dielectric constant of 4 and a dielectric loss tangent of 0.01.

The electromagnetic wave suppression effect was evaluated by calculating the maximum electric field strength at a position3maway from the semiconductor device using the three-dimensional electromagnetic field simulator ANSYS HFSS (manufactured by ANSYS), and expressed as the electric field strength with respect to the frequency (dBμV/m).

The configuration of Example 2 is the same as the configuration of the semiconductor device2shown inFIG. 5, and the arrangement and dimensions of the respective components are as follows.

Thermally and electrically conductive sheet10: 18 mm×18 mm×0.27 mm thick on the semiconductor element and the electrically conductive shielding can20

The distance between the electrically conductive cooling member40and the substrate31is 0.32 mm.

Reference Example 1

As Reference Example 1, a semiconductor device70is shown inFIG. 7. In the semiconductor device70, the microstrip line35is formed on the surface of the substrate31having the ground32provided on the rear surface, and the semiconductor element30is mounted thereon. The semiconductor element30is connected to the electrically conductive cooling member40through a noise-suppressing thermally conductive sheet75(bulk thermal conductivity: 3 W/mk, permeability μr″=5). The noise-suppressing thermally conductive sheet75has the same structure as the thermally and electrically conductive sheet10except that the carbon fibers (electrically conductive filler) are not blended and the magnetic metal powder is mainly blended.

The arrangement and dimensions of respective components of the semiconductor device70are as follows.

Noise-suppressing thermally conductive sheet75: 16 mm×16 mm×1.0 mm thick on the semiconductor element and the electrically conductive shielding can20

The distance between the electrically conductive cooling member40and the substrate71is 1.7 mm.

Reference Example 2

As Reference Example 2, a semiconductor device80is shown inFIG. 8. In the semiconductor device80, the microstrip line35is formed on the surface of the substrate31having the ground32provided on the rear surface, and the semiconductor element30is mounted thereon. In the semiconductor device80, the semiconductor element30is covered with an electrically conductive shielding can86having no opening. The electrically conductive shielding can86has the same structure as the electrically conductive shielding can20except that no opening is provided, and is connected to the ground32. In the semiconductor device80, an insulating thermally conductive sheet76(bulk thermal conductivity: 3 W/mk) is provided between the semiconductor element30and the electrically conductive shielding can86, and between the electrically conductive shielding can86and the electrically conductive cooling member40. The insulating thermally conductive sheet76has the same structure as the thermally and electrically conductive sheet10except that the carbon fiber (electrically conductive filler) is not blended and an inorganic filler is mainly blended.

The arrangement and dimensions of respective components of the semiconductor device80are as follows.

Insulating thermally conductive sheet76: 16 mm×16 mm×0.4 mm thick on the semiconductor element and on the electrically conductive shielding can, respectively

The distance between the electrically conductive cooling member40and the substrate31is 1.7 mm.

Reference Example 3

As Reference Example 3, a semiconductor device90is shown inFIG. 9. In the semiconductor device90, the microstrip line35is formed on the surface of the substrate31having the ground32provided on the rear surface, and the semiconductor element30is mounted thereon. In the semiconductor device90, the semiconductor element30is covered with an electrically conductive shielding can86having no opening. The electrically conductive shielding can86is connected to the ground32. In the semiconductor device90, the insulating member50is provided over the entire surface of the electrically conductive cooling member40facing the electrically conductive shielding can86. In the semiconductor device90, the thermally and electrically conductive sheet10(bulk thermal conductivity: 5 W/mk) is provided between the semiconductor element30and the electrically conductive shielding can86, and between the electrically conductive shielding can86and the insulating member50.

The arrangement and dimensions of respective components of the semiconductor device90are as follows.

Thermally and electrically conductive sheet10: 16 mm×16 mm×0.35 mm thick on the electrically conductive shielding can; 16 mm×16 mm×0.4 mm thick on the semiconductor device

The distance between the electrically conductive cooling member40and the substrate31is 1.7 mm.

Reference Example 4

As Reference Example 4, a semiconductor device100is shown inFIG. 10. The semiconductor device100has the same structure as that of Example 1 except that the insulating member50is not provided, and the microstrip line35is formed on the front surface of the substrate31having the ground32provided on the back surface, and the semiconductor element30is mounted thereon. In the semiconductor device100, the semiconductor element30is covered with the electrically conductive shielding can20provided with the opening21. The electrically conductive shielding can20is connected to the ground32. In the semiconductor device100, the thermally and electrically conductive sheet10is provided between the semiconductor element30and the electrically conductive cooling member40, and between the electrically conductive shielding can20and the electrically conductive cooling member40.

The arrangement and dimensions of respective components of the semiconductor device100are as follows.

Thermally and electrically conductive sheet10: 18 mm×18 mm×0.27 mm thick on the electrically conductive shielding can20; 16 mm×16 mm×1.0 mm thick on the semiconductor device

The distance between the electrically conductive cooling member40and the substrate31is 1.7 mm.

As shown in Table 1, in Examples 1 and 2, the heat dissipation, noise, and ESD protection measures were all good (hereinafter, denoted as “G”). That is, in Examples 1 and 2, since the opening21is formed in the electrically conductive shielding can20, the thermally and electrically conductive sheet10having high thermal conductivity is provided between the semiconductor element30and the electrically conductive cooling member40, and the insulating member50is also made of a material having high thermal conductivity, the thermal conduction to the electrically conductive cooling member40is greatly improved, so that excellent heat dissipation properties can be achieved.

Further, in Examples 1 and 2, a virtual shielding can for shielding the semiconductor element30is formed by the ground32, the electrically conductive shielding can20, the thermally and electrically conductive sheet10, and the electrically conductive cooling member40, so that electromagnetic wave shielding can be performed, thereby achieving an excellent electromagnetic wave suppressing effect.

Further, in Examples 1 and 2, since the electrically conductive shielding can20and the electrically conductive cooling member40are electrically connected through the thermally and electrically conductive sheet10, the static electricity discharged to the electrically conductive cooling member40flows through the thermally and electrically conductive sheet10avoiding the insulating member50and flows to the ground32through the electrically conductive shielding can20. Therefore, in Examples 1 and 2, it is possible to prevent the static electricity discharged to the electrically conductive cooling member40from being transmitted to electronic components such as the semiconductor element30, and an excellent ESD protection is implemented.

Further, when considering the minimum thickness T from the semiconductor element30to the electrically conductive cooling member40, Example 1 has at least a total thickness of 0.32 mm constituted by the thickness of the thermally and electrically conductive sheet10(0.27 mm) on the top surface20aof the electrically conductive shielding can20and the thickness of the electrically conductive shielding can20(0.05 mm) and the height (h) between the opening21of the electrically conductive shielding can20plus the semiconductor element30(0.32 mm+h). In this case, the thermal resistance between the semiconductor element30and the electrically conductive cooling member40is 10.58° C./W plus the thermal resistance value α of the thickness h component (10.58+α° C./W). In Example 2, since the semiconductor element30and the top surface20aof the electrically conductive shielding can20are flush with each other, the total thickness is 0.32 mm constituted by the thickness of the thermally and electrically conductive sheet10(0.27 mm) on the top surface20aof the electrically conductive shielding can20and the thickness of the electrically conductive shielding can20(0.05 mm). In this case, the thermal resistance between the semiconductor element30and the electrically conductive cooling member40was 10.58° C./W.

In Reference Example 1, since the heat of the semiconductor element30can be radiated to the electrically conductive cooling member40by the noise-suppressing thermally conductive sheet75, heat dissipation measures are implemented. However, since the electrically conductive shielding can20is not provided and the noise-suppressing thermally conductive sheet75is thin, the electromagnetic wave suppressing effect is degraded and thus the electromagnetic wave suppressing measures are not sufficient (BAD, hereinafter denoted as “B”). Further, since the static electricity discharged to the electrically conductive cooling member40is transmitted to the semiconductor element30through the noise-suppressing thermally conductive sheet75, a necessary ESD protection is not implemented (B). The minimum thickness T is equal to the thickness of the noise-suppressing thermally conductive sheet75(0.27 mm). In this case, the thermal resistance between the semiconductor element30and the electrically conductive cooling member40was 12.74° C./W.

Further, in Reference Example 2, the electrically conductive shielding can20is not provided with the opening, so that the contact area between the insulating thermally conductive sheet76and the electrically conductive shielding can20is increased, and the thermal conductivity is inhibited. The insulating thermally conductive sheet76has a lower thermal conductivity than the thermally and electrically conductive sheet10. Therefore, the heat generated by the semiconductor element30is hardly transmitted to the electrically conductive cooling member40, and necessary heat dissipation measures are not implemented (B). It should be noted that Reference Example 2 has sufficient electromagnetic wave suppression measures by providing the electrically conductive shielding can20(G), and ESD protection measures are also implemented by using the insulating thermally conductive sheet76(G). However, in Reference Example 2, since the insulating thermally conductive sheets76are disposed above and below the electrically conductive shielding can20, the minimum thickness T is 0.59 mm in total, which is the sum of thickness of the two thermally and electrically conductive sheets10(0.27 mm×2) and the thickness of the electrically conductive shielding can20(0.05 mm). In this case, the thermal resistance between the semiconductor element30and the electrically conductive cooling member40was 15.12° C./W.

In Reference Example 3, the electrically conductive shielding can20is not provided with the opening, so that the contact area between the insulating thermally conductive sheet76and the electrically conductive shielding can20is increased, and the thermal conductivity is inhibited. Therefore, although the thermally and electrically conductive sheet10having a thermal conductivity higher than that of the insulating thermally conductive sheet76is used, it is insufficient (denoted as “I”) as heat dissipation measures. Further, in Reference Example 3, since the electrically conductive shielding can20connected to the ground32and the electrically conductive cooling member40are insulated from each other by the insulating member50provided on the entire surface of the electrically conductive cooling member40, the electrically conductive cooling member40itself can function as an antenna. Therefore, it can be said to be insufficient (I) as electromagnetic wave control measures. It should be noted that, in Reference Example 3, since the insulating member50is provided on the entire surface of the electrically conductive cooling member40, ESD protection measures are implemented (G). However, in Reference Example 3, since the insulating thermally conductive sheets76are disposed above and below the electrically conductive shielding can20, and the insulating member50is arranged over the entire surface of the electrically conductive cooling member40, the minimum thickness T is 0.64 mm in total, which is the sum of thickness of the two thermally and electrically conductive sheets10(0.27 mm×2), the thickness of the electrically conductive shielding can20(0.05 mm), and the thickness of the insulating member50(0.05 mm). In this case, the thermal resistance between the semiconductor element30and the electrically conductive cooling member40was 14.90° C./W.

Since the semiconductor device100shown in Reference Example 4 has the same structure as that of Example 1 except that the insulating member50is not provided, heat dissipation measures and electromagnetic wave suppression measures other than ESD protection measures are implemented (G).

Next, the electric field characteristics of the semiconductor device according to Examples and Reference Examples will be described with reference toFIGS. 11 to 13.

FIG. 11is a graph showing simulation results of electric field strength characteristics measured by setting the magnetic permeability μr″ of the noise-suppressing thermally conductive sheet75of Reference Example 1 to 5 (500 MHz) and the volume resistivity of the thermally and electrically conductive sheet10of Reference Example 3 to 0.015 [Ω*m]. As described above, in Reference Example 1, measures for suppressing electromagnetic waves are insufficient, and it is understood that a high electric field strength is measured and noise is not suppressed. In Reference Example 3, although the shielding can20is provided, because the electrically conductive cooling member40itself functions as an antenna, although the electric field strength decreases in some frequency bands, a high electric field strength is consistently measured, and it is understood that noise suppression is insufficient.

FIG. 12is a graph showing simulation results of electric field strength characteristics measured by setting the volume resistivity of the thermally and electrically conductive sheet10of the Reference Example 4 to 0.15 [Ω*m], 0.015 [Ω*m], and 0.0015 [Ω*m]. It can be seen that the electric field strength is lower than in Reference Examples 1 and 3 and noise is suppressed. Further, as the volume resistivity of the thermally and electrically conductive sheet10decreases, the electric field strength also decreases and noise can be suppressed.

FIG. 13is a graph showing simulation results of electric field strength characteristics measured by setting the volume resistivity of the thermally and electrically conductive sheet10of Example 1 to 0.15 [Ω*m], 0.015 [Ω*m], and 0.0015 [Ω*m]. It can be seen that Example 1 also has the same electric field strength/frequency characteristic as that of Reference Example 4 shown inFIG. 12, and exhibits a particularly good electromagnetic wave suppression effect when the volume resistivity of the thermally and electrically conductive sheet10is 0.15 Ω*m or less.

DESCRIPTION OF REFERENCE CHARACTERS