Semiconductor module and semiconductor device

A semiconductor module includes a semiconductor chip, base frame, a circuit board, and a screw. The base frame has a main surface having a concave portion in which the semiconductor chip is mounted. The base frame is thermally and electrically connected with the semiconductor chip through a die bonding material. The circuit board has a grounding pattern and is arranged above the main surface of the base frame. The screw electrically connects the main surface of the base frame and the outer peripheral portion of the concave portion to the grounding pattern of the circuit board and mechanically connects the base frame to the circuit board.

This nonprovisional application is based on Japanese Patent Application No. 2010-131158 filed on Jun. 8, 2010 with the Japan Patent Office, the entire contents of which are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a semiconductor module and a semiconductor device. More particularly, the present invention relates to a structure for separating dissipation of heat generated in a semiconductor device from grounding of a circuit.

2. Description of the Background Art

In semiconductor devices, in order to stabilize operation, it is required to efficiently release heat generated by semiconductor elements.

For example, Japanese Patent Laying-Open No. 4-174547 discloses a structure of a lead frame for a power semiconductor device. According to Japanese Patent Laying-Open No. 4-174547, a die pad of a lead frame is formed thicker than an outer lead of the lead frame. Heat generated in a semiconductor chip is absorbed in the die pad. The increased thickness of the die pad facilitates heat dissipation from the semiconductor chip. The surface of the die pad that is opposite to the surface provided with the semiconductor chip is exposed without being covered with resin. The exposed surface is brought into contact, for example, with a heat radiation fin, thereby facilitating dissipation of heat generated by the semiconductor chip.

Japanese Patent Laying-Open No. 6-61396 discloses a lead frame for improving a heat dissipation effect while the characteristics of a semiconductor device are maintained. This lead frame includes a stage on which a semiconductor chip is mounted. A heat sink plate is attached on the back surface of the stage.

Japanese Patent Laying-Open No. 2007-165442 discloses a mold package capable of improving heat dissipation and high-frequency characteristics. This mold package has a thick lead electrode connected with a semiconductor chip, and a thin lead electrode thinner than the thick lead electrode. The lower surface of the thick lead electrode is exposed on the lower surface of the package and is used as a heat dissipation electrode. On the other hand, part of the upper surface of the thick lead electrode is exposed on the upper surface of the package and is used as a grounding electrode.

For semiconductor devices operating at high frequency or high power, in particular, grounding of a semiconductor chip is important. In many cases, the back surface electrode of the semiconductor chip is used as a grounding electrode and is electrically connected with a lead frame via a die bonding pad. The potential of the grounding electrode can be stabilized more as the number of paths of ground current output from the back surface of the semiconductor chip is increased. However, Japanese Patent Laying-Open Nos. 4-174547 and 6-61396 do not disclose a specific structure for securing a path of ground current.

On the other hand, size reduction is required in a module including a circuit board and a semiconductor device operating at high frequency or higher power. According to the structure disclosed in Japanese Patent Laying-Open No. 2007-165442, the grounding electrode and the heat dissipation electrode are arranged on the upper surface and the lower surface of the package, respectively, so that ground current and thermal flow can be separated from each other such that the direction of ground current and the direction of thermal flow are opposite to each other. Thus, the module can be reduced in size. However, according to the structure disclosed in Japanese Patent Laying-Open No. 2007-165442, the path of ground current is limited to the path formed by the thick lead electrode. In view of stable operation of semiconductor devices, a larger number of ground paths is preferable.

SUMMARY OF THE INVENTION

The present invention is made to solve the aforementioned problem. An object of the present invention is to achieve size reduction of a semiconductor module, efficient heat dissipation, and reliable grounding.

A semiconductor module according to an aspect of the present invention includes at least one semiconductor chip, a base frame, a circuit board, a first lead terminal, and a connection member. The base frame has a main surface having a concave portion in which at least one semiconductor chip is mounted. The base frame is thermally and electrically connected with at least one semiconductor chip. The circuit board has a first grounding pattern and is arranged on the main surface of the base frame. The first lead terminal is integrally formed with the base frame and is connected to the first grounding pattern of the circuit board. The connection member electrically connects an outer peripheral portion of the concave portion that is a part of the main surface of the base frame, to the first grounding pattern of the circuit board. The connection member mechanically connects the base frame to the circuit board.

According to the structure described above, the circuit board is arranged on the main surface of the base frame. Ground current output from the semiconductor chip flows toward the first grounding pattern of the circuit board. Therefore, ground current flows upward from the semiconductor chip. On the other hand, heat produced in the semiconductor chip is dissipated via the base frame. Therefore, the direction of current and the direction of thermal flow can be separated from each other, thereby achieving efficient heat dissipation and size reduction of the semiconductor module. Furthermore, each of the first lead terminal and the connection member forms a path through which ground current flows. Accordingly, reliable grounding of the semiconductor chip can be achieved.

Preferably, the base frame includes a protrusion portion formed to extend from a bottom surface of the concave portion toward the main surface. The circuit board further has a second grounding pattern being connected to the protrusion portion and having a potential equal to a potential of the first grounding pattern. At least one semiconductor chip includes first and second semiconductor chips arranged in the concave portion such that the protrusion portion is sandwiched between the first and second semiconductor chips.

According to the structure described above, the protrusion portion sandwiched between the first and semiconductor chips forms a path of ground current. Accordingly, reliable grounding of the semiconductor chips can be achieved.

Preferably, the base frame further includes a heat dissipating surface being located opposite to the main surface and having a convex portion. The semiconductor module further includes a resin. The resin covers a part of the main surface of the base frame so as to fill the concave portion and covers a periphery of the convex portion.

According to the structure described above, the semiconductor chip can be protected against moisture or shocks. In addition, since the heat dissipating surface can be prevented from being entirely covered with resin, heat can be dissipated efficiently.

Preferably, a length of a part of the first lead terminal that protrudes from a surface of the resin is 0.15 mm or more.

According to the structure described above, the first lead terminal can be connected to the electrode pattern of the circuit board, for example, by solder.

Preferably, when a length in a direction vertical to the main surface of the base frame is defined as a height, the height of the first lead terminal with reference to a region of part of the main surface that is exposed from the resin is 0.3 mm or less.

According to the structure described above, the first lead terminal can be connected to the electrode pattern of the circuit board, for example, by solder.

Preferably, the connection member is a screw. A hole through which the screw is passed is formed in each of an outer peripheral portion of the main surface and the first grounding pattern of the circuit board. The semiconductor module further includes a heat sink. The heat sink is in contact with the convex portion of the heat dissipating surface and fixes the base frame and the circuit board by the screw. The outer peripheral portion of the main surface is brought into contact with the first grounding pattern by the screw.

According to the structure described above, the base frame can be electrically connected with the circuit board by the screw. Furthermore, the heat sink and the base frame can be brought into intimate contact with each other.

Preferably, a diameter of the hole is 2 mm or more.

According to the structure described above, a general screw can be used.

Preferably, the semiconductor module further includes a second lead terminal electrically connected with at least one semiconductor chip. A through hole is formed in the second lead terminal.

According to the structure described above, when the second lead terminal is connected to the circuit board by solder, the solder can easily spread over the surface of the second lead terminal. Another advantage is in that the second lead terminal can be shortened by cutting the second lead terminal at the location of the through hole.

A semiconductor device according to another aspect of the invention includes at least one semiconductor chip, a base frame, and a lead terminal. The base frame has a main surface having a concave portion in which at least one semiconductor chip is mounted. The base frame is thermally and electrically connected with at least one semiconductor chip. The lead terminal is integrally formed with the base frame and is connected to a grounding pattern of a circuit board arranged on the main surface of the base frame. A hole through which a connection member for mechanically and electrically connecting the base frame to the circuit board is passed is formed in an outer peripheral portion of the concave portion that is part of the main surface of the base frame.

According to the structure described above, the circuit board can be arranged on the main surface of the base frame. Thus, ground current can flow upward from the semiconductor chip. On the other hand, heat produced in the semiconductor chip is dissipated via the base frame. Therefore, the direction of current and the direction of thermal flow can be separated from each other, thereby achieving efficient heat dissipation and size reduction of the semiconductor module. Furthermore, each of the first lead terminal and the connection member forms a path through which ground current flows. Thus, reliable grounding of the semiconductor chip can be achieved.

In accordance with the present invention, the direction of thermal flow and the direction of flow of ground current can be separated from each other, and in addition, the number of paths of ground current can be increased. Therefore, in accordance with the present invention, size reduction of a semiconductor module, efficient heat dissipation, and reliable grounding can be achieved.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the following, embodiments of the present invention will be described in detail with reference to the figures. It is noted that in the figures the same or corresponding parts are denoted with the same reference signs and a description thereof will not be repeated.

A high-frequency amplifier will be described below as a semiconductor module in accordance with an embodiment of the present invention. However, the present invention is applicable to a module having a circuit board and a semiconductor device. Therefore, the present invention is not limited only to the application of high-frequency amplifiers.

First Embodiment

FIG. 1is a top view of a semiconductor module in accordance with a first embodiment of the present invention.FIG. 2is a front view of the semiconductor module shown inFIG. 1. In the following description, the height direction of a high-frequency amplifier101is defined as the y-axis direction and the horizontal direction of high-frequency amplifier101is defined as the x-axis direction.

Referring toFIG. 1andFIG. 2, high-frequency amplifier101is a semiconductor module in accordance with the first embodiment of the present invention. High-frequency amplifier101includes a semiconductor device1, a circuit board2, a heat sink3, and screws4,4A,4B. Semiconductor device1has a base frame5, a sealing resin8, and lead terminals9A,9B,10,11.

Circuit board2is arranged on the upper side of semiconductor device1. Circuit board2has main surfaces2A and2B located opposite to each other. Main surface2A faces upward in high-frequency amplifier101.

Heat sink3is arranged on the lower side of semiconductor device1. Semiconductor device1is sandwiched between circuit board2and heat sink3and is fixed by screws4A,4B. Circuit board2is fixed to heat sink3by screws4A,4B and a plurality of screws4. The number of screws4is not specifically limited.

FIG. 3is a plan view for illustrating the circuit board and the semiconductor device in accordance with the first embodiment. Referring toFIG. 3andFIG. 1, semiconductor device1is fixed to main surface2B of circuit board2by a method such as reflow soldering. Through holes12A and12B through which screws4A and4B are passed, respectively, are formed in base frame5. Two through holes corresponding to through holes12A and12B are formed in circuit board2.

Diameter d shows the diameter of each of through holes12A and12B. Diameter d is preferably 2 mm or more. Thus, a general screw can be used in high-frequency amplifier101. Therefore, the cost of high-frequency amplifier101can be reduced.

Circuit board2has an input matching circuit and an output matching circuit. Circuit board2has grounding patterns2C,2D having a ground potential. Grounding patterns2C,2D are electrode patterns for grounding of the input matching circuit and the output matching circuit.

Semiconductor device1has lead terminals9A,9B,10,11. Lead terminals9A,9B are integrated with base frame5. Accordingly, lead terminals9A,9B are electrically connected with base frame5. Lead terminals9A,9B protrude from sealing resin8. Lead terminals9A and9B are electrically connected to grounding patterns2C and2D of circuit board2, for example, by solder. As will be described in detail later, lead terminals9A,9B are electrically connected with the grounding electrode of the semiconductor element via base frame5.

Let the length of lead terminals9A,9B each be L with respect to the side surface of sealing resin8. Length L is preferably 0.15 mm or more. When length L is 0.15 mm or more, lead terminals9A,9B can be reliably connected to grounding patterns2D,2C of circuit board2.

Circuit board2is fixed to heat sink3by screws4,4A,4B, so that the dissipating surface of base frame5is in contact with heat sink3. The heat dissipating surface is the surface of base frame5shown inFIG. 3. The heat dissipating surface of base frame5is in contact with heat sink3, so that semiconductor device1is thermally connected to heat sink3.

Lead terminal10is in contact with main surface2B of circuit board2and is electrically connected to the input matching circuit of circuit board2, for example, by solder. Lead terminal11is in contact with main surface2B of circuit board2and is electrically connected to the output matching circuit of circuit board2, for example, by solder.

Through holes10A,10B are formed in lead terminal10. Similarly, through holes11A,11B are formed in lead terminal11. Since the through holes are formed in each of lead terminal10and11, solder can easily spread over the surface of each lead terminal. The shape of through holes10A,10B,11A,11B is rectangular in an embodiment, although any shape may be employed.

FIG. 4is a cross-sectional view taken along IV-IV inFIG. 1. Referring toFIG. 4, semiconductor device1includes conductive base frame5, a semiconductor chip6, a die bonding material7, and sealing resin8. The main component of base frame5is a metal (for example, copper). Base frame5has a main surface5A. A concave portion5C is formed in main surface5A. The bottom surface of concave portion5C is located lower than lead terminals9A,9B.

Base frame5further has a main surface5B. Main surface5B is located opposite to main surface5A. Main surface5B is in contact with a main surface20of heat sink3. In other words, main surface5B functions as a heat dissipating surface.

Semiconductor chip6is arranged in concave portion5C of base frame5. In the embodiment of the present invention, semiconductor chip6is a transistor device, more specifically, a FET (field-effect transistor). However, the kind of the semiconductor chip is not specifically limited. Die bonding material7electrically and mechanically connects semiconductor chip6to base frame5. Die bonding material7is, for example, solder.

A grounding electrode is formed on the back surface of semiconductor chip6. Semiconductor chip6is electrically and thermally connected with base frame5through die bonding material7. Lead terminals9A,9B are connected with base frame5and connected with the grounding pattern of circuit board2.

Sealing resin8fills concave portion5C of base frame5. Circuit board2is arranged on semiconductor device1.

Main surface5B of base frame5has a central portion15and a peripheral portion16. Central portion15protrudes downward in high-frequency amplifier101below peripheral portion16. In other words, main surface5B has a convex portion. Sealing resin8covers the periphery of the convex portion (central portion15) of main surface5B. The surface of sealing resin8is formed at a location recessed from central portion15of main surface5B. If the surface of sealing resin8and main surface5B of base frame5are at approximately the same level, the contact between main surface5B of base frame5and main surface20of heat sink3may be insufficient due to the roughness of main surface20of heat sink3. Since central portion15of main surface5B protrudes from sealing resin8, base frame5can be reliably brought into contact with main surface20of heat sink3.

Step height T1is a height difference between the surface of sealing resin8and central portion15of main surface5B of base frame5. Step height T1is preferably 10 μm or more. Step height T1of 10 μm can reduce the possibility that the contact between central portion15of main surface5B of base frame5and main surface20of heat sink3is hindered by sealing resin8.

Lead terminals9A,9B are connected with grounding patterns2D,2C of circuit board2to form two paths of ground current. In the following, the path of ground current is also referred to as “ground path.” One path is a path from the back surface electrode of semiconductor chip6to grounding pattern2D of circuit board2and is formed of die bonding material7, base frame5, and lead terminal9A. The other path is a path from the back surface electrode of semiconductor chip6to grounding pattern2C of circuit board2and is formed of die bonding material7, base frame5, and lead terminal9B.

In accordance with an embodiment of the present invention, additional two ground paths are formed by screws4A and4B. One path is a path from the back surface electrode of semiconductor chip6to grounding pattern2C and is formed of die bonding material7, base frame5, and screw4A. The other path is a path from the back surface electrode of semiconductor chip6to grounding pattern2D and is formed of die bonding material7, base frame5, and screw4B.

FIG. 6is an equivalent circuit modeling high-frequency amplifier101in accordance with the first embodiment of the present invention. Referring toFIG. 6, semiconductor chip6is a FET. The gate of semiconductor chip6is connected to the input matching circuit formed of a capacitor C11and an inductor L11. The drain of semiconductor chip6is connected to the output matching circuit formed of a capacitor C21and an inductor L21. The source of semiconductor chip6is connected to inductors L1to L4for grounding at a node J1.

The gate of semiconductor chip6is connected to lead terminal10via wire13. The drain of semiconductor chip6is connected to lead terminal11via wire14. The source of semiconductor chip6corresponds to the back surface electrode of the semiconductor chip. The source of semiconductor chip6is connected to base frame5via die bonding material7.

Node J1corresponds to the interface between semiconductor chip6(including die bonding material7) and base frame5. Inductor L1equivalently shows the path of ground current from semiconductor chip6to lead terminal9A. Inductor L2equivalently shows the path of ground current from semiconductor chip6to lead terminal9B. Inductor L3equivalently shows the path of ground current from semiconductor chip6to screw4A. Inductor L4equivalently shows the path of ground current from semiconductor chip6to screw4B. A node J2corresponds to one end of inductor L3. A node J3corresponds to one end of inductor L4.

Lead terminal9A is connected to a ground node Gnd1of circuit board2. Lead terminal9B is connected to a ground node Gnd2of circuit board2. Screw4A is connected to a ground node Gnd3of circuit board2. Screw4B is connected to a ground node Gnd4of circuit board2. Ground nodes Gnd1, Gnd4correspond to grounding pattern2D of circuit board2. Ground nodes Gnd2, Gnd3correspond to grounding pattern2C of circuit board2.

In operation of semiconductor chip6, electric current flows from the drain of semiconductor chip6to the source of semiconductor chip6. The electric current flowing out of the source of semiconductor chip6, that is, ground current flows through each of inductors L1to L4to the ground nodes (Gnd1to Gnd4) of circuit board2. In the first embodiment, ground current passes through each of the above-noted four paths and flows upward from semiconductor device1.

On the other hand, when semiconductor chip6is operated, power Pd is consumed and semiconductor chip6generates heat. The heat generated by semiconductor chip6is dissipated into the air40through base frame5and heat sink3. The thermal equivalent circuit of high-frequency amplifier101is represented by air40, temperatures Tj, Tc, power consumption Pd, and thermal resistances Rth[j−c], Rthf.

Temperature Tj shows a junction temperature of semiconductor chip6. Temperature Tc shows a temperature at a contact point between main surface5B (central portion15) of base frame5and main surface20of heat sink3. Thermal resistance Rth[j−c] shows junction-to-case thermal resistance from the connection portion between semiconductor chip6and base frame5to main surface5B (central portion15) of base frame5. Rthf shows thermal resistance from the upper surface (main surface20) of heat sink3to the lower surface of heat sink3. The lower surface of heat sink3is in contact with air40. Heat generated in semiconductor chip6flows through base frame5and heat sink3downward from heat sink3. In other words, in accordance with the first embodiment, both ground current and thermal flow along the y-axis direction. However, the direction of ground current and the direction of thermal flow are separated from each other such that the direction of ground current and the direction of thermal flow are opposite to each other. Thus, the size of the semiconductor module can be reduced.

Furthermore, in accordance with the first embodiment, in addition to lead terminals9A,9B, screws4A,4B form the paths of ground current, thereby increasing the number of paths of ground current. Accordingly, the back surface electrode (grounding electrode) of semiconductor chip6can be reliably grounded.

Therefore, in accordance with the first embodiment, a semiconductor module capable of efficient heat dissipation and reliable grounding with a reduced size can be obtained. In this respect, comparisons between the first embodiment and comparative examples will be described below.

Comparative Examples

FIG. 7is a top view showing a first comparative example of the high-frequency amplifier in accordance with an embodiment of the present invention.FIG. 8is a front view of the comparative example shown inFIG. 7.

Referring toFIG. 7andFIG. 8, a high-frequency amplifier201has a semiconductor device51, circuit boards52A,52B, heat sink3, and lead terminals59A,59B,60,61. Lead terminals59A,59B are provided independently from semiconductor device51. Lead terminals59A and59B are terminals for grounding, and lead terminals60and61are an output terminal and an input terminal, respectively.

Circuit boards52A and52B are an input matching circuit and an output matching circuit, respectively. Semiconductor device51is arranged on a surface of heat sink3. Semiconductor device51is electrically connected to circuit boards52A,52B via lead terminals60,61. Semiconductor device51is fixed to heat sink3by screws54A,54B and connected to lead terminals59A,59B. Lead terminals59A,59B are electrically connected to a grounding pattern (not shown) of each of circuit boards52A and52B.

FIG. 9is a cross-sectional view taken along IX-IX inFIG. 7. Referring toFIG. 9, semiconductor device51includes a base frame55, semiconductor chip6, die bonding material7, and a cover58. The main component of base frame55is a metal (for example, copper). Unlike the first embodiment of the present invention, a concave portion is not formed in the main surface of base frame55. Die bonding material7electrically and thermally connects semiconductor chip6to base frame55. Cover58covers semiconductor chip6. Lead terminals59A,59B are brought into intimate contact with base frame55by screws54A,54B. Lead terminals59A,59B are connected to circuit boards52A,52B, for example, by a method such as soldering.

Thermal grease63is interposed in a gap between base frame55and heat sink3so that heat produced by semiconductor chip6easily escapes to heat sink3. If thermal grease63is an insulating material, electrical connection between base frame55and heat sink3is inhibited. However, the back surface electrode of semiconductor chip6is connected to the grounding pattern of each of circuit boards52A,52B through die bonding material7, base frame55, and lead terminals59A,59B. Thus, paths of ground current output from the back surface electrode of semiconductor chip6are formed.

FIG. 10is a diagram showing an equivalent circuit modeling components of high-frequency amplifier201shown inFIG. 7toFIG. 9. Referring toFIG. 10, a node J1is a connection point between semiconductor chip6and inductors L10, L20for grounding. Node J1shows the interface between semiconductor chip6(including die bonding material7) and base frame55.

Inductor L10for grounding corresponds to a part that connects each of lead terminals59A,59B to circuit board52A. Inductor L20for grounding corresponds to a part that connects each of lead terminals59A,59B to circuit board52B. Inductor L10for grounding is connected with ground node Gnd1of circuit board52A at a node J11. Inductor L20for grounding is connected with ground node Gnd2of circuit board52B at a node J12. Circuit board52A has an inductor L21and a capacitor C21connected to the drain of semiconductor chip6. Circuit board52B has an inductor L11and a capacitor C11connected to the gate of semiconductor chip6.

Circuit boards52A,52B and semiconductor device51are arranged on heat sink3and arranged along the x-axis direction. Electric current output from the source of semiconductor chip6flows into ground node Gnd2of circuit board52A through inductor L20for grounding and also flows into ground node Gnd1of circuit board52B through inductor L10for grounding. Therefore, ground current flows in the horizontal direction (x-axis direction).

On the other hand, junction temperature Tj of semiconductor chip6is thermally connected with air40through thermal resistance Rth[j−c] and thermal resistance Rthf. Thermal resistance Rth[j−c] shows junction-to-case thermal resistance from the junction portion between semiconductor chip6and base frame55to the lower surface of base frame55. Thermal resistance Rthf shows thermal resistance between heat sink and air, that is, thermal resistance from the upper surface (including thermal grease63) of heat sink3to the lower surface of heat sink3that is thermally connected with the air. Similarly to the first embodiment, heat produced in semiconductor chip6flows downward from semiconductor device51.

In the first comparative example, semiconductor device51is arranged between circuit boards52A and52B. Therefore, electric current output from the back surface electrode of semiconductor chip6flows in the horizontal direction. Therefore, the horizontal length of the high-frequency amplifier is increased.

FIG. 11is an equivalent circuit diagram illustrating a second comparative example of the high-frequency amplifier in accordance with an embodiment of the present invention. Referring toFIG. 11andFIG. 6, a high-frequency amplifier202differs from high-frequency amplifier101in that screws4A,4B are omitted. More specifically, high-frequency amplifier202has a path formed of inductor L3for grounding and screw4A and a path formed of inductor L4for grounding and screw4B.

Electric current output from the source of semiconductor chip6flows along the y-axis direction upward from semiconductor device1. Heat generated by semiconductor chip6flows along the y-axis direction downward from semiconductor device1. Similar to the first embodiment, in accordance with the second comparative example, the direction of electric current and the direction of thermal flow are separated from each other such that the direction of electric current and the direction of thermal flow are opposite to each other. However, in the second comparative example, two screws for fixing semiconductor device1to the circuit board are omitted. Therefore, in accordance with the second comparative example, the number of paths of ground current is two.

It is noted that when semiconductor device1shown inFIG. 11is replaced with a mold package shown in Japanese Patent Laying-Open No. 2007-165442, the mold package cannot be fixed to the circuit board by screws. Therefore, the number of paths of ground current cannot be increased.

On the other hand, in the first embodiment, circuit board2is arranged above semiconductor device1. In addition, each of lead terminals9A,9B and screws4A,4B forms a path of ground current. In accordance with the first embodiment, the direction of ground current and the direction of thermal flow can be separated from each other. Yet, the number of paths of ground current can be increased. Therefore, in accordance with the first embodiment, the semiconductor chip can be grounded reliably, and in addition, heat generated in the semiconductor chip can be dissipated efficiently. Furthermore, ground current flows above the semiconductor device, thereby preventing an increase in horizontal length of the high-frequency amplifier.

It is noted that coplanarity of lead terminals9A,9B is preferably 300 μm or less in order to facilitate reflow soldering for connecting lead terminals9A,9B of semiconductor device1to circuit board2.

FIG. 12is a diagram for illustrating coplanarity of lead terminals9A,9B. Referring toFIG. 12, a plane C is a reference plane for defining coplanarity of lead terminals9A,9B. Reference plane C is a plane extending from the surface of base frame5that is exposed from sealing resin8, that is, main surface5A. In the following description, the length in the direction vertical to reference plane C is defined as the height, and the location of reference plane C is defined as the reference location in height. Coplanarity of lead terminals9A,9B is the height from the reference location of the main surface of lead terminals9A,9B (the surface connected to the grounding pattern of circuit board2). Specifically, heights H1, H2shown inFIG. 12show coplanarity of lead terminal9A (or9B). When coplanarity of lead terminals9A,9B is limited to 300 μm or less, lead terminals9A,9B can be reliably connected to the grounding pattern of circuit board2by solder.

Second Embodiment

FIG. 13is a top view of a high-frequency amplifier102in accordance with a second embodiment of the present invention.FIG. 14is a plan view showing a semiconductor device included in high-frequency amplifier102.FIG. 15is a cross-sectional view of high-frequency amplifier102taken along XV-XV inFIG. 13.

In the second embodiment, concave portion5C is divided into concave portions5C1and5C2by a grounding portion17. Semiconductor chips6A and6B are arranged in concave portions5C1and5C2, respectively. Semiconductor chip6A is joined to base frame5through die bonding material7A. Semiconductor chip6B is joined to base frame5through die bonding material7B.

Grounding portion17is a part of base frame5. Grounding portion17is a protrusion portion formed to extend upward from the bottom surface of concave portion5C. Grounding portion17has a surface exposed on the surface of sealing resin8. This exposed surface is used as a soldering surface. Thus, grounding portion17is electrically connected with a grounding pattern2E provided in circuit board2. Like grounding patterns2C,2D, grounding pattern2E has a ground potential.

Semiconductor device21has lead terminals10C,10D and lead terminals11C,11D. Lead terminal10C and lead terminal11C are electrically connected to the input terminal and the output terminal, respectively, of one of semiconductor chips6A and6B. Lead terminal10D and lead terminal11D are electrically connected to the input terminal and the output terminal, respectively, of the other of semiconductor chips6A and6B. Similar to the first embodiment, lead terminals9A and9B are connected to grounding patterns2D and2C of circuit board2, respectively.

It is noted that the configuration of the other part of high-frequency amplifier102is similar to the configuration of the corresponding part of high-frequency amplifier101in accordance with the first embodiment, and therefore, a detailed description thereof will not be repeated hereinafter. Like the first embodiment, length L of each of lead terminals9A and9B with respect to the side surface of sealing resin8is preferably 0.15 mm or more. Furthermore, coplanarity of lead terminals9A,9B is preferably 300 μm or less. Diameter d of each of through holes12A and12B is preferably 2 mm or more.

Grounding portion17strengthens the grounding of the region interposed between semiconductor chips6A and6B. Therefore, at least three ground paths can be secured for each semiconductor chip. The location of grounding portion17is preferably in the middle of the region between semiconductor chips6A and6B. Thus, the length of the path of ground current from semiconductor chip6A to grounding portion17and the length of the path of ground current from semiconductor chip6B to grounding portion17can be made equal to each other. Therefore, the effect of strengthening the grounding of semiconductor chips6A,6B is further enhanced.

FIG. 16is a diagram showing an equivalent circuit modeling high-frequency amplifier102in accordance with the second embodiment. Referring toFIG. 16, the gate of each semiconductor chip6A,6B is connected to an input matching circuit formed of capacitor C11and inductor L11. The drain of each semiconductor chip6A,6B is connected to an output matching circuit formed of capacitor C21and inductor L21. The source of semiconductor chip6A is connected to inductors L1to L5for grounding at a node J1. The source of semiconductor chip6B is connected to inductors L1to L5for grounding at a node14.

Node J1corresponds to the interface between semiconductor chip6A (including die bonding material7A) and base frame5. Node J4corresponds to the interface between semiconductor chip6B (including die bonding material7B) and base frame5. A node J5is located between nodes J1and J4.

Inductor L5equivalently shows a current path from semiconductor chips6A,6B to the exposed surface of grounding portion17. The exposed surface is connected to a ground node Gnd6of circuit board2. Ground node Gnd6corresponds to grounding pattern2E. Grounding portion17(inductor L5) forms a path through which ground current flows upward from semiconductor device21.

In accordance with the second embodiment, the number of paths through which ground current flows upward from semiconductor device21can be increased, as compared with the first embodiment. Furthermore, in accordance with the second embodiment, a path of ground current can be formed between two semiconductor chips, so that the path of ground current can be shortened. Therefore, in accordance with the second embodiment, the grounding of each semiconductor chip can be further strengthened.

In the second embodiment, the number of semiconductor chips is not limited to two as long as it is two or more. If the semiconductor device includes (n+1) semiconductor chips (where n is an integer equal to or larger than 1), n grounding portions are formed to extend upward from the middle location between two semiconductor chips adjacent to each other. The surface of each of n grounding portions is exposed on the surface of sealing resin8. Their exposed surfaces are connected to the grounding patterns (corresponding to grounding pattern2E) of circuit board2by solder.

Third Embodiment

FIG. 17is a top view of a high-frequency amplifier103in accordance with a third embodiment of the present invention.FIG. 18is a plan view showing a semiconductor device included in high-frequency amplifier103.

As can be understood from the comparison betweenFIG. 17andFIG. 13or the comparison betweenFIG. 18andFIG. 14, semiconductor device31in accordance with the third embodiment differs from semiconductor device21in accordance with the second embodiment in the shape of the input terminal and the output terminal. Specifically, the length of lead terminals10E,10F from the surface of sealing resin8is shorter than the length of lead terminals10C,10D from the surface of sealing resin8. This is applicable to lead terminals11E,11F.

Lead terminals10E,10F,11E,11F can be formed by cutting lead terminals10C,10D at the locations of through holes10A,10B by tie bar cutting. It is noted that lead terminal10and lead terminal11of semiconductor device1in accordance with the first embodiment can be shortened, similarly to the third embodiment.