Abstract:
In a case of a semiconductor chip having an electrode pad to be wire-bonded to a header, securing of a fixing region is difficult since the spread of an Ag paste cannot be controlled, therefore, there has existed a problem such that stable manufacturing could not be carried out. Also, there existed a problem such that realization of stable manufacturing resulted in an excessively large external package form. A projection part is provided in a header, and a fixing region of a bonding wire is secured by arranging a chip at a position shifted in a direction to become distant from the projection part. An electrode pad to be connected to the header is arranged closer to the chip center than the other electrode pads of the identical chip side, and a wire is extended therefrom to the projection part or in the vicinity thereof so as to cross the chip and is fixed. Thereby, downsizing of the package and stable manufacturing are realized.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention:  
           [0002]    The invention relates to a semiconductor device and, specifically to a semiconductor device with a reduced package size.  
           [0003]    1. Description of the Related Art  
           [0004]    Mobile communication devices such as mobile telephones often utilize microwaves in the GHz range, and commonly use switching devices for high frequency signals which are used in switching circuits for changing antennas and switching circuits for transmitting and receiving such signals (for example, Japanese Laid-Open Patent Application No. Hei 9-181642). Such a device often uses a field effect transistor (hereinafter referred to as an FET) based on gallium arsenide (GaAs) as high frequencies are used with the device. Accordingly, efforts have been made in developing a monolithic microwave integrated circuit (MMIC) by integrating the aforementioned switching circuits and in developing an integrated circuit for a mixer use which realizes low distortion and a broadband operation.  
           [0005]    [0005]FIG. 1 is a top view of a conventional semiconductor device that includes a semiconductor chip  41  mounted on a frame, which features two switching FETs and two shunt FETs. In this configuration, the chip size has been reduced to its minimum (0.55 mm×0.5 mm) that is allowed by current engineering capabilities. The semiconductor chip  41  is mounted on a header  80  of the frame using a conductive adhesive such as a Ag paste  85  or a non-conductive adhesive. Pad electrodes on the chip  41  are connected to corresponding leads, respectively, by bonding wires  80  radially extending from the chip  41 . In particular, a capacity terminal electrode pad CP is wire-bonded to the header and is thereby connected to the capacity terminal C.  
           [0006]    In this configuration, however, the spread of the Ag paste for mounting the chip cannot be easily controlled. Although the spread of the Ag paste in FIG. 1 is under good control, it is likely that some portion of the paste extend toward the edge of the header. Because it is difficult to fix a bonding wire to a header surface covered by the paste, a large margin should be created around the chip for stable wire bonding to the header. Accordingly, even though the ship size has been reduced to the minimum, the package size has not been reduced accordingly because of the large margin necessary for wire bonding.  
         SUMMARY OF THE INVENTION  
         [0007]    The invention provides a semiconductor device that includes a frame having a header and a plurality of leads, and a projection part extending from the header and penetrating into a space between two of the leads. The device also includes a semiconductor chip mounted on the header and having a plurality of electrode pads, and a bonding wire, one end of which is fixed to one of the electrode pads, another end of which is fixed to the projection part or the header adjacent the projection part.  
           [0008]    The invention also provides a semiconductor device that includes a frame having a header and a plurality of leads, and a projection part extending from the header and penetrating into a space between two of the leads. The device also includes a semiconductor chip having a switch circuit that includes two field effect transistors, one input terminal electrode pad, one control terminal electrode pad, two output terminal electrode pads and one of a ground terminal electrode pad and a capacity terminal electrode pad. The semiconductor chip also has a plurality of electrode pads. The device also includes a bonding wire, one end of which is fixed to the ground terminal electrode pad or the capacity terminal electrode pad, another end of which is fixed to the projection part or the header adjacent the projection part.  
           [0009]    The invention further provides a semiconductor device that includes a frame having a header and two leads, and a projection part extending from the header and penetrating into a space between the leads. The header and the projection part substantially receive a DC voltage. The device also includes a semiconductor chip mounted on the header and having an electrode pad. One of the two leads communicates a high frequency signal. The device further includes a bonding wire, one end of which is fixed to the electrode pad, another end of which is fixed to the projection part or the header adjacent the projection part. The projection part is configured to shield the lead communicating the high frequency signal from other portion of the semiconductor device. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]    [0010]FIG. 1 is a top view of a conventional semiconductor device that includes a semiconductor chip mounted on a frame.  
         [0011]    [0011]FIG. 2A is a circuit diagram of a semiconductor switch of a first embodiment of the invention, and FIG. 2B is a semiconductor chip of the first embodiment based on the circuit of FIG. 2A.  
         [0012]    [0012]FIG. 3 is a semiconductor device of the first embodiment in which the chip of FIG. 2A is mounted on a frame.  
         [0013]    [0013]FIG. 4A is a top view of a packaging of the first embodiment, and FIGS. 4B and 4C are side views of the packaging of FIG. 4A.  
         [0014]    [0014]FIG. 5A is a semiconductor chip of a second embodiment of the invention, and FIG. 5B is a semiconductor device of the second embodiment in which the chip of FIG. 5A is mounted on a frame.  
         [0015]    [0015]FIG. 6A is a circuit diagram of a semiconductor mixer of a third embodiment of the invention, and FIG. 6B is a semiconductor chip of the third embodiment based on the circuit of FIG. 6A.  
         [0016]    [0016]FIG. 7A is a semiconductor device of the third embodiment in which the chip of FIG. 6B is mounted on a frame, and FIG. 7B is a side view of a packaging of the third embodiment. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0017]    The invention will be described with reference to FIGS. 2A through 7B.  
         [0018]    [0018]FIG. 2A is a circuit diagram of a compound semiconductor switching circuit device of a first embodiment of the invention. In this circuit, between two output terminals, OUT 1  and OUT 2 , of two FETs, FET 1  and FET 2 , and a ground, shunt FETs, FET 3  and FET 4 , are connected. A pair of complementary signals are applied to gates of these shunt FETs, FET 3  and FET 4 , through control terminals, Ctl- 2  and Ctl- 1 , that also applies the complementary signals to the gates of switch FETs, FET 1  and FET 2 . As a result, when FET 1  is on, the shunt FET 4  is also on, and FET 2  and the shunt FET 3  are off.  
         [0019]    In this circuit, when a signal path from the common input terminal IN to the output terminal OUT 1  is turned on and a signal path from the common input terminal IN to the output terminal OUT 2  is turned off, the input signals leaking into the output terminal OUT 2  is released to the ground via a grounded capacitor (not shown), as the shunt FET 4  is on. Accordingly the signal leakage is prevented and isolation characteristics of the device is improved.  
         [0020]    In this embodiment, the ground capacitor is external to the semiconductor chip. A capacitor terminal electrode pad CP of the chip, shown in FIG. 2B, is connected to the external ground capacitor through a capacitor terminal C shown in FIG. 3. The semiconductor chip may include the ground capacitor and in this case the capacitor terminal pad CP may serve as a ground terminal electrode pad.  
         [0021]    [0021]FIG. 2B shows an example of a compound semiconductor chip based on the circuit design of FIG. 2A. On a GaAs substrate that is semi-insulating, the switching FETs, FET 1  and FET 2 , are arranged in right and left at the central portion of the device, and shunt FETs, FET 3  and FET 4 , are arranged in the vicinities of the right and left lower corners. Resisters R 1 , R 2 , R 3 , and R 4  are connected to gate electrodes of the respective FETs. In addition, electrode pads I,  01 ,  02 , C 1 , C 2 , and CP, which correspond to a common input terminal IN, output terminals OUT 1  and OUT 2 , control terminals Ctl- 1  and Ctl- 2 , and the capacitor terminal C, are provided near the edges of the substrate. Furthermore, source electrodes of the shunt FETs, FET 3  and FET 4 , are connected to each other and are connected to the capacitor terminal C, which is further connected to the ground through the ground capacitor.  
         [0022]    [0022]FIG. 3 shows a compound semiconductor device of the first embodiment, in which the semiconductor chip of FIG. 2B is mounted on a frame. As shown in FIG. 3, this embodiment uses a six-pin frame. A header  50  is located in the center of the frame to receive the compound semiconductor chip  51 . Three leads  52 ,  53 , and  54  aligned along one end of the chip are connected to electrode pads C 2 , I, and C 1  for a control terminal Ctl- 2 , a common input terminal IN, and a control terminal Ctl- 1  via bonding wires  80 , respectively. Two leads  55  and  57  aligned along the other end are connected to electrode pads  2  and  1  for an output terminal OUT 2  and an output terminal OUT 1  via bonding wires, respectively. Furthermore, a central lead  56  extends to the header  50  and is connected to a capacity terminal electrode pad CP of the compound semiconductor chip  51  via a bonding wire.  
         [0023]    Projection parts extends from a header  50  and penetrate into a space between two leads. The capacity terminal electrode pad CP is connected via a bonding wire to the projection part  100  extending from the header  50 . The bonding wire may also be fixed on the header at a vicinity of the projection part  100 . Such a connection of the bonding wire to the header is possible because the projection part provides extra support for wire bonding at the edge of the header.  
         [0024]    Furthermore, the compound semiconductor chip  51  is mounted off the center of the header  50  and is located at a position shifted away from the projection part  100  that receives the bonding wire so that a space between the bonding wire connected to the header  50  and bonding wires on both sides thereof can be sufficiently secured.  
         [0025]    In the conventional device of FIG. 1, all the bonding wires extend radially from the respective electrode pads to the corresponding leads located outside the chip. However, in this embodiment, the bonding wire connected to the capacity terminal electrode pad CP travels over the chip to reach the projection part  100 .  
         [0026]    Accordingly, the above configuration provides stable wire bonding at the projection part even though the width (X direction) of the header is smaller than the with of the conventional header of FIG. 1. In this configuration, the projection part itself provides a space and margin for stable wire bonding, and the header does not have to provide the margin for bonding as in the case of the conventional device of FIG. 1. That is, even if an Ag paste  85  spreads on the header, wire bonding can be provided on the projection part or in the vicinity of the projection part where a stable bonding is secured. Therefore, the header is reduced in size and package size reduction is realized. Thus, stable manufacturing of the semiconductor device is achieved.  
         [0027]    In this embodiment, a plurality of projection parts are configured to penetrate into a space between respective leads. The lead  56 , which serves as a capacity terminal C, and projection parts are grounded via an external ground capacitor. The leads  54  and  52  connected to the control terminals Ctl- 1  and Ctl- 2  receive DC voltages which serve as a ground voltage for high frequency signals. By arranging the leads and the projection parts, which are at substantially at a ground level (reference level) for high frequency signals, between the lead  53  of the common input terminal IN, the lead  57  of the output terminal OUT 1 , and the lead  55  of the output terminal OUT 2 , isolation characteristics between the respective high-frequency signal terminals IN, OUT 1 , and OUT 2  are improved. Although the device of this embodiment has four projection portions, the device may have just one projection part to secure a stable wire bonding connection.  
         [0028]    [0028]FIG. 4A is a plan view of the device of FIG. 3 after molding process for packaging, and FIGS. 4B and 4C show cross-sectional views of molded device of FIG. 4A. The chip  51  is fixed to the header by a conductive paste  85  or a non-conductive paste, and is covered by a resin layer  81  formed by transfer molding with the far ends of the respective leads  52 ,  53 ,  54 ,  55 ,  56 , and  57  exposed. This package is called MCP 6  and is smaller in size at 2.0 mm ×2.1 mm×0.9 mm than the conventional packaging of FIG. 1 which houses the same chip of FIG. 2B and is as large as 2.9 mm×2.8 mm×1.1 mm.  
         [0029]    Furthermore, since the wire connected to the projection part requires a certain length, by arranging the wire as an M-shaped loop as shown in FIGS. 4B and 4C, the height can be suppressed even with a long wire, thus contributing to a reduction in the thickness of the packaging.  
         [0030]    In addition, as shown in FIG. 4C, the chip may be mounted on the frame so as to face the opposite direction. This is called MCPH 6  and is identical to MCP 6  in terms of size including the front-end leads, although its resin mold is wider than that of MCP 6 .  
         [0031]    In this embodiment, the chip is mounted off the center of the header However, the chip may be mounted on any position including the center as long as a sufficient surface can be secured for wire bonding. In addition, the electrode pad to be fixed to the header is not limited to a capacity terminal electrode pad and may be any electrode pad. For example, in the circuit diagram of FIG. 2A, the external capacity terminal C may be directly grounded without fitting an external capacity thereto so that the terminal becomes a ground terminal. In this case the control signals should be 0/−3V while control signals applied to the switch FETs with an external ground capacitor should be 0/+3V.  
         [0032]    [0032]FIGS. 5A and 5B show a second embodiment of this invention. In this configuration, the electrode pad connected to the projection portion is not aligned with other two electrode pads along a chip side, but is located closer to the chip center than other electrode pads on the same side. The semiconductor chip of FIG. 5A is substantially identical in the structure to the chip of FIG. 2A except that the capacity terminal electrode pad CP is closer to the chip center. Thereby, as in FIG. 5B, since a longer range of angle is available for wire bonding between the electrode pad CP and the projection part, bonding positioning is more flexible. Thus failures during wire bonding can be considerably reduced.  
         [0033]    Furthermore, because the distance between the bonding wire and the terminal electrode pads  02 , which is adjacent the capacity terminal electrode pad CP, the insertion loss is suppressed.  
         [0034]    A third embodiment of the invention includes a device for uses as a mixer employing GaAs FETs. FIG. 6A shows a circuit diagram of a mixer integrated circuit device. Gate electrodes of the first FET 1  and fourth FET 4  are connected to a gate terminal Gate 1 , and gate electrodes of the second FET 2  and third FET 3  are connected to a gate terminal Gate 2 . In addition, source electrodes (or drain electrodes) of the first FET 1  and second FET 2  are connected to a source terminal Source 2 , and source electrodes (or drain electrodes) of the third FET 3  and fourth FET 4  are connected to a source terminal Sourcel. Furthermore, drain electrodes (or source electrodes) of the first FET 1  and third FET 3  are connected to a drain terminal Drain 1 , and drain electrodes (or source electrodes) of the second FET 2  and fourth FET 4  are connected to a drain terminal Drain 2 .  
         [0035]    This mixer integrated circuit device carries out frequency conversion, and the mixer IC of this circuit configuration is called a double balanced mixer. RF signals, LO signals, and IF signals are respectively provided as a pair of signals with phases having 180° difference created by an external balun. Therefore, an even-order harmonics is suppressed. In particular, this is best suited for high-frequency digital radio communications by a mobile communications apparatus where low distortion is required. Furthermore, since the device can be used in a broad frequency band, this is best suited for use as a CATV tuner mixer. In the operation, RF signals are inputted into a source terminal Sourcel and a source terminal Source 2 , LO signals are inputted into a gate terminal Gate 1  and a gate terminal Gate 2 , and IF signals are taken out from a drain terminal Drain 1  and a drain terminal Drain 2 .  
         [0036]    [0036]FIG. 6B shows an example of a compound semiconductor chip in which the compound semiconductor mixer circuit shown in FIG. 6A is integrated.  
         [0037]    FET 1 , FET 2 , FET 3 , and FET 4  are arranged in the central part of a GaAs substrate. In addition, electrode pads G 2  and S 2  which respectively correspond to a gate terminal Gate 2  and a source terminal Source 2  are aligned along one side of the chip, and a source terminal Source  1  electrode pad S 1  to be connected to a header is arranged closer to the chip center than these two electrode pads. Electrode pads G 1 , D 1 , and D 2  which correspond to a Gate terminal Gate 1 , drain terminal Drain 1 , and a drain terminal Drain 2  are aligned along the opposed side of the chip.  
         [0038]    As shown in FIG. 6B, two of the four FETs share one source electrode, one drain electrode and one gate electrode, respectively. The FETs are connected to two gate terminal electrode pads, G 1  and G 2 , two source terminal electrode pads, S 1  and S 2 , and two drain terminal electrode pads, D 1  and D 2 .  
         [0039]    [0039]FIGS. 7A and 7B show the chip of FIG. 6B is mounted on a frame. As shown in FIG. 7A, the frame has six-pins leads, and a header  150  is located in the central portion of the frame. A compound semiconductor chip  151  is mounted on the header  150 . Three leads  152 ,  153 , and  154  aligned along one end of the chip are connected to a gate terminal electrode pad G 1 , a drain terminal electrode pad D 1 , and a drain terminal electrode pad D 2  of the compound semiconductor chip  151  via bonding wires, respectively. In addition, two leads  155  and  157  aligned along the other end are connected to a gate terminal electrode pad G 2  and a source terminal electrode pad S 2  of the compound semiconductor chip  151  via bonding wires, respectively. Furthermore, a central lead  156  extends from the header  150  and is connected to a capacity terminal electrode pad S 1  of the compound semiconductor chip  151 .  
         [0040]    A projection part  200  extends from the header and penetrates into a space between the leads. A bonding wire connected to the source terminal electrode pad S 1  is fixed to this projection part or in the vicinity of the projection part.  
         [0041]    The compound semiconductor chip is mounted away from the center of the header and away from the projection part so that a space enough for wire bonding to the projection part is secured between the bonding wires fixed adjacent the bonding wires connected to the projection part. As is the case with the first embodiment, in this configuration the projection part provides a space and margin for stable wire bonding without having to provide the large margin space in the header for securing stable wire bonding. Accordingly, the width of the header is reduced and thus the packaging size is reduced as well. Furthermore, as is the with the second embodiment, the wire bonding to the projection part is flexible because of the positioning of the source terminal electrode pad S 1 .  
         [0042]    In addition, as shown in FIG. 7B, the chip is covered by a resin layer  81  formed by transfer molding with the far ends of the respective leads  152 ,  153 ,  154 ,  155 ,  156 , and  157  exposed. This package is called MCP 6  and is smaller in size at 2.0 mm×2.1 mm×0.9 mm. Furthermore, as is the case with the first embodiment, the long bonding wires take the form of the M-shaped loop and contributes to the height reduction of the packaging.  
         [0043]    The above mixer integrated circuit device has a chip size of 0.45×0.45 mm, which requires a packaging size as large as 2.9 mm×2.8 mm×1.1 mm according to the conventional packaging. Based on this invention, however, a frame identical to that of the switch circuit device of the first or second embodiment can be utilized for the mixer device. In other words, the device can be mounted in a small package such as MCP 6  or MCPH 6 . Therefore, this can meet demands for use in a mobile-phone unit and a CATV tuner. Furthermore, the same frame may be used for the switch circuit device as well as the mixer circuit device to reduce overall production cost.  
         [0044]    In the embodiments, a compound semiconductor device is described as an example. However, the invention also applies to a silicon semiconductor device as well.