JP2006196927A - Semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor device of chip-size in which the reliability of packaging is improved by improving soldering in packaging. <P>SOLUTION: The semiconductor device comprises a base portion 11 composed of a rectangular metal plate, a metal base 10 provided with connection electrodes 15 arranged in both sides portions 12 formed in the both sides of the base portion 11, and a semiconductor chip 1 mounted on the base portion 11 of the metal base 10, wherein the packaging is performed using electrodes 7 and 8 which are formed on the surface of the semiconductor chip 1 and connection electrodes 15. The surface height of the connection electrodes 15 are made higher than that of the electrodes 7 and 8 of the semiconductor chip 1 by a given dimension. When mounted in the packaging substrate face down, the semiconductor chip 1 does not touch the packaging substrate preventing the semiconductor chip 1 to be mechanically damaged, and further a soldering layer is formed with configured minute spacing between the electrodes 7 and 8 and the packaging substrate, thereby the reliability of the soldering is enhanced. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a package of a semiconductor device, and more particularly to a semiconductor device having a package structure having a chip size and excellent heat dissipation.

  In recent years, due to the demand for higher integration of electronic circuits mounted with semiconductor devices, it has been required to further downsize the packages of individual semiconductor devices. As described above, a chip size package (CSP) has been proposed as a semiconductor device in which the package is miniaturized. FIG. 12 shows a semiconductor device described in Patent Document 1. A metal plate having a size slightly larger than that of a semiconductor chip is processed into a dish shape, and this dish-shaped metal plate (hereinafter referred to as a metal base) 110 is formed. The semiconductor chip 101 is mounted in the recess 111. The semiconductor chip 101 is an example of a MOS transistor chip. A drain electrode that does not appear in the figure is formed on the back surface of the semiconductor chip 101, and the drain electrode is directly fixed to the bottom surface of the recess 111, and the periphery of the semiconductor chip 101. The recess 113 is filled with a resin 113 and sealed. Further, a gate electrode 107 and a source electrode 108 are formed on the surface of the semiconductor chip 101 and are formed so as to be flush with the surface of the metal base 110. A plurality of regions in the peripheral portion 112 on the surface of the metal base 110 are configured as the drain connection electrode 115. By mounting this semiconductor device on a mounting substrate (not shown) by face-down, the drain connection electrode 115 of the peripheral portion 112 of the metal base 110 is connected to the pad portion for the drain connection electrode provided on the mounting substrate, and at the same time the gate The electrode and the source electrode are connected to the pad portions for the gate electrode and the source electrode, respectively.

  Here, in Patent Document 1, as shown in FIG. 13A, the concave portion 121 is formed leaving both sides 122 of the metal base 120, and the surface of both sides 122 is configured as the drain connection electrode 125. Further, as shown in FIG. 13 (b), not only both sides of the metal base 130, but only one side 132 is left to form the recess 131, and then on the plurality of locations in the length direction of the one side 132. There has also been proposed a structure in which a groove 133 extending over the entire thickness is formed, and the surface of the region separated by the groove 133 is configured as the drain connection electrode 135, respectively. As a technique similar to that shown in FIG. 13A, although not shown in Patent Document 2, a recess is formed leaving both sides, a semiconductor chip is mounted in the recess, and the electrodes on the surface of the semiconductor chip are formed. A technique for mounting by face-down on the same surface as the surfaces of both sides is described.

  Further, Patent Document 3 proposes a semiconductor device as shown in FIG. 14 which is almost the same as the semiconductor device of FIG. 12, but here the peripheral portion 142 is left on the metal base 140 by press working or the like. A recess 141 is formed, and the semiconductor chip 101 is fixed in the recess 141. Here, the surface of the peripheral portion 142 of the metal base 140 is formed in substantially the same plane as the electrode 102 provided on the surface of the semiconductor chip 101, and each electrode 102 on the surface of the peripheral portion 142 and the surface of the semiconductor chip 101 is formed. A solder ball 103 is formed on the surface and mounting is performed by face-down.

In these conventional semiconductor devices, the metal base has a slightly larger planar dimension than the semiconductor chip, and is a thickness dimension obtained by adding the thickness of the metal base to the thickness of the semiconductor chip. Since there is no need to bond wires or the like, and there is little need to seal with resin, the semiconductor device can be made smaller and thinner, and the structure is simple, so that it can be manufactured at a low cost. Moreover, since the metal base functions as a heat sink in the mounted state, there is also an advantage that heat dissipation is excellent.
US Patent Application Publication No. 2001/0048116 JP-A-8-78657 US Pat. No. 6,133,634

  As a result of studies made by the present inventors on these semiconductor devices, it has become clear that the following problems are latent. As shown in FIGS. 12 and 14, in the semiconductor device in which the recess is formed except for the peripheral portion of the metal base, the metal base needs to be pressed or etched to form the recess. Machining is complicated and difficult to process with high precision, resulting in an obstacle to cost reduction. In this respect, in the semiconductor device shown in FIGS. 13A and 13B, both sides or one side of the metal base can be formed by bending or cutting, and relatively high accuracy can be obtained. Therefore, it is advantageous in reducing the size and price. It is also advantageous in that heat dissipation can be improved, and mechanical strength can be improved even if it is small and thin.

  However, in the semiconductor device shown in FIG. 13A, the surface of both sides 122 of the metal base 120 is formed as a flat surface, and the entire surface or a part thereof is formed as the drain connection electrode 125. The area of the drain connection electrode 125 is larger than the areas of the gate electrode 107 and the source electrode 108, and the heat capacity of the drain connection electrode 125 is larger than that of the gate electrode and the source electrode when mounted by face down. Therefore, when mounting on the mounting board with solder, it is necessary to supply a larger amount of solder at the drain connection electrode 125 than the amount of solder of the gate electrode 107 and the source electrode 108, and the solder density on the mounting board is not uniform. Also, the heat capacity of the solder becomes non-uniform. Therefore, the drain connection electrode 125 must be heated to a high temperature during solder reflow, and the high temperature causes thermal damage to a part of the semiconductor device, particularly a connection portion between the semiconductor chip and the metal base, and at the same time, the gate electrode 107 with a small amount of solder. In addition, there is a problem in that the connection reliability of the source electrode 108 due to the solder is lowered, and the mounting reliability is lowered. In addition, since the surface of the drain connection electrode 125 and the surface of the gate electrode 107 and the source electrode 108 are substantially the same surface, when mounting on the mounting substrate by face-down during mounting, the gate electrode 107 and the source electrode 108 are mounted on the mounting substrate. There is also a problem that the semiconductor chip 101 including the electrodes is mechanically damaged by colliding with the surface. Such a problem also occurs in the semiconductor device shown in FIGS. 12 and 14 because the drain connection electrode is formed over a wide area of the metal base.

  Also in the semiconductor device shown in FIG. 13B, since the area of the drain connection electrode 135 is larger than the areas of the gate electrode and the source electrode, the difference in the amount of solder due to the difference in heat capacity, This causes a problem of thermal damage to the semiconductor chip and a problem of connection reliability due to solder. In this case, if the area of the drain connection electrode 135 is reduced, the heat capacity of each drain connection electrode 135 at the time of mounting can be reduced, which is effective in solving the above-described problem. The grooves 133 formed by cutting are divided into a plurality of regions, and in particular, the grooves 133 are formed over the entire thickness of the metal base 130 in order to separate the drain connection electrodes 135. Therefore, the individual drain connection electrodes 135 are separated. Has a cantilever structure with respect to the metal base 130, the mechanical strength of the drain connection electrode 135 is lowered, and the support strength of the metal base is lowered when mounted on the mounting board. There is a problem that reliability decreases. Also in this semiconductor device, since the drain connection electrode 135, the gate electrode 107, and the source electrode 108 have the same surface, there is a problem of mechanical damage to the semiconductor chip during mounting.

  An object of the present invention is to provide a semiconductor device in which soldering at the time of mounting is particularly good and mounting reliability is improved.

  The present invention is mounted on a metal base including a bottom portion made of a rectangular metal plate and a plurality of connection electrodes each formed of a convex portion provided on at least two opposite sides of the bottom portion, and mounted on the bottom portion of the metal base. The surface mount type semiconductor device is configured to be mounted on the surface of the semiconductor chip by using the plurality of connection electrodes and the surface height of the plurality of connection electrodes. It is characterized by being made higher by a required dimension than the surface height of the electrode of the semiconductor chip.

  Here, the plurality of connection electrodes are formed in a portion where the thickness of the metal plate is partially thick in a partial region of the surface of the bottom portion. For example, the metal base is formed by etching or forging a metal plate. Further, the surface height of the connection electrode is set to about 0 to 0.1 mm higher than the surface height of the electrode of the semiconductor chip. The area of the connection electrode is smaller than the area of the electrode of the semiconductor chip. The connection electrode is disposed so as to be symmetric with respect to at least one of the length direction of both sides and the direction orthogonal thereto. Further, the connection electrode has a trapezoidal cross section in which the surface area is smaller than the lower area. The connection electrodes are formed at positions that are symmetric with respect to at least one of the length direction of the semiconductor chip and the width direction across the semiconductor chip. One connection electrode is formed on each of both sides of the bottom chip. It is preferable that a solder ball is formed on at least one of the electrode of the semiconductor chip or the connection electrode.

  In the semiconductor device of the present invention, for example, the semiconductor chip is a transistor chip of a MOS transistor, the drain electrode is formed on the back surface of the semiconductor chip and mounted in a state of being in direct contact with the bottom side, and the connection electrode is configured as the drain connection electrode. This is realized by a configuration in which a gate electrode and a source electrode are formed on the surface of the semiconductor chip.

  According to the present invention, similar to the semiconductor device shown in FIGS. 13A and 13B, there are obtained advantages that heat dissipation, downsizing, cost reduction, and mechanical strength are increased. Of course, since the height of the surface of the connection electrode is higher than the gate electrode and the source electrode of the semiconductor chip, mechanical damage to the semiconductor chip is prevented when mounting on the mounting substrate by face-down during mounting. In addition, by securing an appropriate gap between the electrode of the semiconductor chip and the pad part of the mounting substrate, the solder supplied to this part is crushed and leaks to the outer peripheral part, and the adjacent pad part is short-circuited To prevent problems such as Further, the solder interposed between the electrode and the pad portion of the semiconductor chip improves the connection reliability against mechanical stress with an appropriate thickness. This increases the reliability of soldering.

  Further, according to the present invention, the metal base is partially increased in thickness by etching or forging the metal plate in a partial region of the surface of the bottom portion, and a plurality of connection electrodes are formed in this portion. Therefore, a metal base with high dimensional accuracy can be obtained. In addition, since the area of the connection electrode is smaller than the area of the electrode of the semiconductor chip, the reliability of soldering in the electrode of the semiconductor chip can be improved and the heat capacity of the connection electrode can be reduced, so that the solder during mounting can be reduced. In soldering, the amount of solder with the electrode of the semiconductor chip can be made substantially equal, and suitable soldering is possible for each of the electrode and the connection electrode. In particular, the connection electrode can be formed with a trapezoidal cross section whose surface area is smaller than the area of the lower part, so that the mechanical strength of the connection electrode can be increased, and the reliability of soldering to the mounting substrate can be improved. it can. Furthermore, the connection electrodes are arranged symmetrically with respect to at least one of the length direction of the semiconductor chip and the direction orthogonal thereto, or arranged at positions where the electrodes and the connection electrodes are symmetric, so that the connection electrodes are mounted on the mounting substrate at the time of mounting. It is possible to perform soldering by placing it in a stable state with respect to the soldering, and evenly distributing the heat conduction and contact force during soldering to each connection electrode or semiconductor chip electrode. Reliability can be increased. Furthermore, since the solder balls are provided on the connection electrodes, it is possible to easily perform soldering during mounting.

  Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a perspective view of a first embodiment in which the present invention is applied to a semiconductor device D using a MOSFET semiconductor chip, and FIG. 2 is a partially exploded perspective view thereof. 3A, 3B, and 3C are a plan view, a front view, and a right side view. The metal base 10 is formed of a metal plate such as copper or white and white, and a flat bottom portion 11 and a bottom portion 11 are formed by bending both sides of a substantially rectangular plate material to 90 degrees with a required width dimension. And both sides 12 standing upright along both sides. A shallow narrow groove 13 is formed on the surface along the boundary between the base 11 and the both sides 12, and the side 12 can be bent with high dimensional accuracy by the narrow groove 13. ing. The both side portions 12 have a center portion with a required interval in the length direction and a notch groove 14 in which both end portions are notched to a depth of about ½ of the height dimension, and are sandwiched between these notch grooves 14. Each of the two side portions 12 is provided with a convex portion 15 in which the both side portions 12 are left over the entire height, and these convex portions 15 are formed as drain connection electrodes. Here, the length in the length direction of the drain connection electrode 15 is equal to or smaller than the diameter of the circular gate electrode 7 and the source electrode 8 provided in the semiconductor chip 1 to be described later, that is, the same as these electrodes. Or it is formed in a slightly short dimension.

  On the other hand, the semiconductor chip 1 is mounted on the upper surface of the base 11 by a die bonding material 20 such as silver paste. The semiconductor chip 1 has a MOSFET element 3 formed on the main surface of a chip 2 cut out of a semiconductor wafer such as silicon as shown in FIG. A metal layer is formed on the entire back surface of the side to form the drain electrode 4. An insulating layer 5 is formed on the upper surface of the chip 2 so as to cover the element 3, and a metal layer connected to the element is embedded in a contact hole 6 opened in the insulating layer 5 to form a gate electrode 7. And one source electrode 8 are formed. The gate electrode 7 and the source electrode 8 are each formed in a circular shape and aligned along the length direction of the both side portions 12. Here, the gate electrode 7 and the source electrode 8 have the same shape and area. Is formed.

  The drain electrode 4 on the back surface of the semiconductor chip 1 is mounted in contact with the upper surface of the bottom portion 11 of the metal base 10. In this mounted state, the position of the gate electrode 7 and the source electrode 8 in the length direction is a position corresponding to the drain connection electrode 15 formed on the both side portions 12. 1 and 3C, when the semiconductor chip 1 is mounted on the metal base 10, the surface height of the drain connection electrode 15 formed on the metal base 10 is the gate electrode. 7 and the surface of the source electrode 8 are formed so that the height difference is d = 0 to 0.1 mm, preferably 0.05 mm or less, and here 0.03 mm.

  A method for manufacturing the semiconductor device D having the above configuration will be described. FIG. 4 is a conceptual diagram for explaining the manufacturing method. A punching device S1 sequentially punches at a predetermined length interval while feeding a metal strip M, which is a long metal plate of copper, white, etc., of a required thickness in the length direction, and forms one metal base. A notch M1 is formed in the corresponding length position, the metal bases are connected to each other by a narrow connecting piece M2 along the length direction, and the connecting piece M2 is cut in a later process, thereby forming the semiconductor device. Make it easy to separate into pieces. At this time, as shown in FIG. 2, shallow narrow grooves 13 are formed on the surface along a portion corresponding to the boundary between the bottom piece portion 11 and both side portions 12 of the metal base 10 of the metal band M. Further, a portion corresponding to both sides 12 of the metal base 10 is punched with a notch groove 14 having a required length with a width approximately half the width of both sides at the center and both ends in the length direction. .

  Next, bending is performed by bending the outer portions of the metal strip M by 90 degrees with respect to the narrow groove 13 in the bending apparatus S2, and the bottom portion 11 of the region sandwiched between the narrow grooves 13 and both sides thereof are subjected to bending. Both sides 12 bent up are formed. At this time, since the bending of the both side portions 12 is guided by the narrow groove 13, both the side portions 12 can be easily bent to accurate dimensions. Further, as can be seen from a partially enlarged view of FIG. 3 (c), since the bending can be performed without generating an R (curved surface) on the inner side of the bent portion, the semiconductor chip 1 that mounts the bending position in a later step. Thus, the semiconductor device D can be downsized by reducing the size of the metal base 10. Furthermore, in this case, the position can be regulated by bending the side surface 13a of the narrow groove 13 so as to contact the upper surface of the bottom side portion 11 of the metal base 10, and the height dimension of both side portions 12 can be made with extremely high accuracy. Can be managed. In addition, even when mechanical stress is applied to both sides 12 during the post-process mounting, it is possible to suppress the deformation in the drain connection electrode 15 including both sides 12. Then, the upright sides 12 are formed as drain connection electrodes 15 whose upper edges are left by the notch grooves 14 formed by the punching device S1 in the lengthwise direction at two places in the full width dimension of the sides 12. Will be.

  Next, a die bond material 20 such as a silver paste is applied or printed on the surface of the base 11 in the die bond material supply device S3. Then, the semiconductor chip 1 cut out from the wafer W in the mounting device S4 is positioned on the surface of the bottom portion 11 in a state where the drain electrode 4 on the back surface is pressed against the surface of the bottom portion 11. At this time, the gate electrode 7 and the source electrode 8 are positioned so as to be substantially at the center position in the width direction of the bottom portion 11 and at positions substantially coincident with the two drain connection electrodes 15 of both sides 12 in the length direction. I do. While maintaining this state, heat treatment is performed in the curing device S5 to cure (reflow) the die bond material 20, and the semiconductor chip 1 is mounted on the bottom portion 11. At this time, the height of the drain connection electrode 15 on both sides 12 of the metal base 10 is adjusted by appropriately adjusting the force pressing the semiconductor chip 1 or by adjusting the thickness of the die bond material 20. The dimension d = 0 to 0.1 mm, here, about 0.03 mm higher than the surface height of the gate electrode 7 and the source electrode 8. Then, the connecting piece M2 of the metal band M connecting the metal bases 10 in the length direction is cut and separated by the separating device S6, thereby manufacturing the individual semiconductor device D shown in FIG. Is completed.

  In the semiconductor device D of this embodiment, as shown in FIG. 5, the mounting substrate 30 on which the circuit pattern 32 corresponding to the gate electrode 7, the source electrode 8, and the drain connection electrode 15 is formed is face-down. Implemented. The mounting substrate 30 is formed by patterning a copper foil or the like on the surface of the insulating plate 31 to form the circuit pattern 32, and a gate pad portion 33, a source pad portion 34, and a drain pad portion 35 are formed thereon. In mounting, for example, solder that does not appear in the drawing is printed on the surface of each of the pad portions 33, 34, and 35 of the mounting substrate 30, and the upper surface of the semiconductor device is opposed to the surface of the mounting substrate 30. Each electrode 7, 8, 15 is positioned so as to face the corresponding wiring pad portion 33, 34, 35, and the solder is reflowed in this state, whereby each electrode of the semiconductor device is soldered to the pad, Implementation will be done.

  As described above, in the semiconductor device D of the present embodiment, the metal base 10 has a slightly larger planar dimension than the semiconductor chip 1, and the thickness dimension is substantially equal to the thickness of the semiconductor chip 1. It is an added dimension, and it is not necessary to bond a metal wire or the like to the semiconductor chip 1 and is not sealed with resin, so that the semiconductor device can be reduced in size and thickness and mounted. Then, since the metal base 10 functions as a heat sink, heat dissipation is excellent.

  Further, when the semiconductor device D of the present embodiment is mounted on the mounting substrate 30, the height of the surface of the drain connection electrode 15 is higher than the gate electrode 7 and the source electrode 8 of the semiconductor chip 1. When the semiconductor device D is mounted on the mounting substrate 30 by face down, only the drain connection electrode 15 is brought into contact with the mounting substrate 30, so that an excessive impact or contact force is applied to the gate electrode 7 and the source electrode 8. This prevents the semiconductor chip 1 from being mechanically damaged. Further, by securing an appropriate gap between the gate electrode 7 and the source electrode 8 and the pad portions 33 and 34 of the mounting substrate 30, the solder supplied to this portion is crushed and leaks to the outer peripheral portion. Thus, problems such as short-circuiting adjacent pad portions 33 and 34 and adjacent pads 35 are prevented. Further, the solder interposed between the gate electrode 7 and the source electrode 8 and the pad portions 33 and 34 improves the connection reliability against mechanical stress with an appropriate thickness. This increases the reliability of soldering.

  In this embodiment, the drain connection electrode 15 on both sides 12 has a length in the length direction that is very short compared to the length of the metal base 10. In this embodiment, the drain connection electrode 15 has the same length as the gate electrode 7 and the source electrode 8. Therefore, the area of the drain connection electrode 15 is smaller than the areas of the gate electrode 7 and the source electrode 8. As a result, the heat capacity of the drain connection electrode 15 can be reduced, and the amount of solder between the gate electrode 7 and the source electrode 8 of the semiconductor chip 1 can be made substantially equal in soldering during mounting. Therefore, it is not necessary to unnecessarily set the drain connection electrode 15 at the time of soldering at the time of mounting, thereby preventing the semiconductor chip 1 from being thermally damaged and preventing the solder from being sucked up along the electrode. 7 and 8 and the drain connection electrode 15 can be suitably soldered. By uniformizing the amount of solder in each electrode, it is possible to facilitate the design of a solder supply mask on the mounting substrate 30, mainly to facilitate inspection of the solder paste printing state, etc., and to further uniform the heat capacity during mounting. This is also effective in preventing misalignment by aligning the timing of solder melting and solidification. Further, while the length of the drain connection electrode 15 is shortened in this way to reduce the area, the lower region of the two drain connection electrodes 15 arranged in the length direction exists over the entire length of the metal base 10. Since it is integral with both side portions 12, the mechanical strength of the drain connection electrode 15 does not decrease.

  Further, since the drain connection electrode 15 is disposed symmetrically with respect to each of the length direction of both side portions 12 and the width direction of the semiconductor chip 1 orthogonal thereto, the metal base 10 is face-down during mounting so that the surface of the mounting substrate 30 Since the drain connection electrodes 15 are in contact with the surface of the mounting board 30 in a state where they are evenly arranged, the semiconductor device D is placed on the mounting board 30 in a stable state and soldered. It is possible to perform soldering, and it is possible to increase the reliability of connection by uniformizing heat conduction during soldering and uniformly distributing the contact force to each connection electrode. In particular, in this embodiment, since the four drain connection electrodes 15 are arranged symmetrically with respect to each of the length direction and the width direction of the metal base 10, the stability can be made extremely high. .

  Further, when manufacturing the semiconductor device D of the present embodiment, as shown in FIG. 4, both sides 12 are bent by the narrow grooves 13 formed in the metal band M, and are formed on both sides 12. Since the drain connection electrode 15 is formed by punching, as described above, the drain connection electrode 15 can be formed with high dimensional accuracy, and the reliability of the metal base 10 can be improved. Furthermore, since the processing only involves punching, bending, and press cutting with respect to the metal band M, manufacturing is easy, which is advantageous in reducing the cost of the semiconductor device.

  FIG. 6A is a perspective view of a semiconductor device according to a second embodiment of the present invention, and FIG. 6B is an enlarged sectional view of a part thereof. Here, as in the first embodiment, the present invention is applied to a semiconductor device as a MOSFET, and parts equivalent to those in the first embodiment are denoted by the same reference numerals. In this embodiment, the shape of the drain connection electrode of the metal base 10A is modified, and one drain connection electrode 15A is formed at each of the side portions 12 of the metal base 10A at substantially the center position in the length direction. That is, the drain connection electrode 15A is formed in a state in which the height of the substantially central portion in the length direction of the upper edge of both sides 12 is larger than the height dimension of both sides 12 to form the projecting piece 16. The protruding piece is bent 90 degrees so as to be horizontal toward the outside at a predetermined position. And the part bent horizontally of this protrusion 16 is comprised as the drain connection electrode 15A.

  Here, the horizontal portion of the projecting piece 16 as the drain connection electrode 15A is formed in a square, and the length of one side thereof is the inscribed square of the gate electrode 7 and the source electrode 8 which are the circular shape of the semiconductor chip 1. The dimensions are close to. Furthermore, also in this embodiment, the semiconductor chip 1 is mounted on the surface of the bottom 11 of the metal base 10A. The semiconductor chip 1 is the same as that of the first embodiment, and the drain electrode 4 on the back surface is mounted with a die bond material. A circular gate electrode 7 and a source electrode 8 are provided on the surface of the semiconductor chip 1. When the semiconductor chip 1 is mounted, the height of the surface of the drain connection electrode 15A is 0 to 0.1 mm, preferably about 0.03 mm, than the height of the gate electrode 7 and the source electrode 8 of the semiconductor chip 1. It is formed to be higher.

  In the semiconductor device according to the present embodiment, the metal base 10A has a slightly larger planar dimension than the semiconductor chip 1 as in the first embodiment, and the thickness dimension is the same as the thickness of the semiconductor chip 1 and the thickness of the metal base 10A. In addition, there is no need to bond a metal wire or the like to the semiconductor chip 1 and it is not sealed with resin, so that the semiconductor device can be reduced in size and thickness and mounted. In this state, since the metal base 10A functions as a heat sink, the heat dissipation is excellent.

  Further, when the semiconductor device of the present embodiment is mounted on the mounting substrate 30 as shown in FIG. 5, the drain connection electrode 15A on both sides 12 has a length dimension compared to the length of the metal base 10A. In addition, since the square with a very short side dimension is formed in an area smaller than the area of the gate electrode 7 and the source electrode 8, the heat capacity of the drain connection electrode 15A when the solder is reflowed can be reduced, and the drain connection electrode 15A. It is possible to easily perform soldering at Further, since the dimension of one side of the drain connection electrode 15A is a dimension included in the circle of the gate electrode 7 and the source electrode 8, the pad part 35 for the drain connection electrode formed on the mounting substrate 30 is temporarily used for the gate electrode. Even when the drain electrode 15 is formed to have the same dimensions as the pad portions 33 and 34 for the source electrode, the drain connection electrode 15 hardly protrudes from the pad portion 35. Further, the area of the drain connection electrode 15A is made smaller than that of the gate electrode 7 and the source electrode 8 in this way, while the lower region of the drain connection electrode 15A is integrated with both side portions 12 existing over the entire length of the metal base 10A. Therefore, the mechanical strength of the drain connection electrode 15A can be increased. Furthermore, since the surface of the drain connection electrode 15A is higher than the gate electrode 7 and the source electrode 8, mechanical damage to the semiconductor chip 1 during mounting is prevented, and the gate electrode 7 and the source electrode 8 are soldered. Can be suitably performed, and the reliability of soldering is increased. In this embodiment, the area of the drain connection electrode 15A can be made larger than that in the first embodiment even though the metal plate is processed in the same manner as in the first embodiment, so that the heat capacity of the drain connection electrode 15A is reduced. Although this is disadvantageous, the contact area of the mounting substrate 30 with the pad portion 35 is increased, which is advantageous in reducing the drain connection resistance. As a result, the mounting reliability of the drain connection electrode can be remarkably improved as compared with the conventional semiconductor device.

  FIG. 7A is a perspective view of a third embodiment of a modification of the second embodiment, and FIG. 7B is an enlarged sectional view of a part thereof. The metal base of the second embodiment is formed by bending, but here the metal base 10B is formed by etching or forging. That is, the rectangular mesa-shaped convex portions 17 are integrally formed on both sides of the surface of the bottom portion 11B of the rectangular metal base 10B, which is somewhat larger in width than the semiconductor chip 1, and these convex portions are connected to the drain. It is configured as an electrode 15B. Similar to the drain connection electrode of the second embodiment, the drain connection electrode 15B is formed at a substantially intermediate position in the length direction of the bottom portion 11B. The drain connection electrode 15A of the second embodiment is formed to have almost the same area, but the cross section in the thickness direction is formed to be a trapezoid whose area below the surface is somewhat larger. . Further, when the semiconductor chip 1 is mounted, the height of the surface of the drain connection electrode 15B is 0 to 0.1 mm, preferably about 0.03 mm, than the height of the gate electrode 7 and the source electrode 8 of the semiconductor chip 1. It is formed to be higher.

  The semiconductor device of this embodiment has the same thickness dimension as the first and second embodiments, and the semiconductor device can be thinned. Further, the area of the bottom portion 11B of the metal base 10B is almost the same as that of the first and second embodiments, and it is possible to achieve miniaturization. Furthermore, since the metal base 10B functions as a heat sink, it is possible to ensure heat dissipation.

  Moreover, when mounting the semiconductor device of this embodiment on a mounting board, it can carry out similarly to the 1st and 2nd embodiment. However, since the drain connection electrode 15B is integral with the bottom portion 11B of the metal base 10B, the heat capacity is larger than that of the gate electrode 7 and the source electrode 8, but the drain connection electrode 15B is not limited to the gate electrode 7 and the source electrode 8. Since the area is smaller than that of the trapezoidal cross section, the heat capacity is reduced, the amount of solder does not increase unnecessarily, the solder between the gate electrode 7 and the source electrode 8 is made uniform, and the solder connection is reliable. Improves. Furthermore, since the surface of the drain connection electrode 15B is located higher than the gate electrode 7 and the source electrode 8, mechanical damage to the semiconductor chip 1 during mounting is prevented, and the gate electrode 7 and the source electrode 8 The reliability of soldering can be improved. Furthermore, since the drain connection electrode 15B has a trapezoidal cross section and is integrated with the bottom portion 11B of the metal base 10B in the periphery of the lower portion, sufficient mechanical strength can be obtained, and the mounting reliability can be improved also from this surface. .

  Here, in the first to third embodiments, solder balls or the like are formed on the gate electrode, the source electrode, and the drain connection electrode, and mounting on the mounting board is performed using the solder balls. Is also possible. The use of solder balls has the advantage that mounting is easier than pad-shaped electrodes and mounting defects are reduced. Further, since the distance from the mounting substrate surface can be secured by the height of the solder ball, there is an advantage that the flux component at the time of mounting is difficult to adhere to the surface of the semiconductor chip and the deterioration of reliability due to corrosion is prevented. For example, FIG. 8 shows an example applied to the semiconductor device D of the first embodiment. The height of both sides 12A of the metal base 10 is lengthened so that the drain connection electrode 15 is formed of the gate electrode 7 and the source electrode 8. The height of the solder ball 21 is made higher than that of the solder ball 21 by the size close to the surface, and the solder ball 21 is formed on the gate electrode 7 and the source electrode 8, and the height of the drain electrode 15 is 0 than the height of the solder ball 21. It is formed to be about 0.03 mm high. By using the solder ball 21 and the drain connection electrode 15 for mounting on the mounting board, advantageous mounting by the solder ball described above becomes possible. FIG. 9A shows an example in which a solder ball is applied to the second embodiment, and FIG. 9B shows an example in which the solder ball is applied to the third embodiment, and each of the electrodes 7, 8, 15A. , 15B, solder balls 21 are formed, and the solder balls 21 are used to mount the mounting substrate by thermocompression bonding. In the case of the first and second embodiments, the height of the surface of the solder ball 21 formed on the drain connection electrode is made higher than the height of the surface of the solder ball 21 formed on the gate electrode and the source electrode.

  Further, by using the solder balls, for example, as shown in FIG. 10A, when the semiconductor chip 1A having a large thickness is mounted on the metal base 10B of the third embodiment, the gate electrode 7 and the source When there is a large difference in the surface height between the electrode 8 and the drain connection electrode 15B, the solder ball having a diameter corresponding to the difference in the surface height is only applied to the lower electrode, here the drain connection electrode 15B. By forming 21, it is possible to mount face down on the mounting substrate. Conversely, as shown in FIG. 10B, when the height of the drain connection electrode 15B ′ is larger than the thickness of the semiconductor chip 1, the difference in height between the gate electrode 7 and the source electrode 8 of the semiconductor chip 1 is caused. A solder ball 21 having a corresponding diameter is formed. In this case, a difference is provided between the surface height of the electrode and the surface height of the solder ball. When the solder ball 21 is mounted, in the process shown in FIG. 4, the solder ball mounting device S7 is disposed at a subsequent process position of the mounting device S4, and the semiconductor chip 1 is mounted on the metal base 10. Thereafter, the solder ball 21 can be mounted on each electrode by placing the solder ball 21 on a predetermined electrode in the solder ball mounting device S7 and reflowing in the curing device S5 simultaneously with the semiconductor chip.

  FIG. 11A is a perspective view of a semiconductor device according to a reference example of the present invention, and FIG. 11B is a partially enlarged sectional view thereof. Here, as in the first embodiment, the present invention is applied to a semiconductor device as a MOSFET. In this reference example, the metal base 10C is formed of a rectangular metal plate having an area approximately twice that of the semiconductor chip 1, and the semiconductor chip 1 is located in a region near one side of the surface of the bottom 11C of the metal base 10C. Is mounted. In addition, two drain connection electrodes 15C are integrally formed in a region near the other side of the bottom portion 11C. The semiconductor chip 1 is the same as the semiconductor chip of the first embodiment, and the drain electrode 4 on the back surface of the semiconductor chip 1 is mounted on the surface of the bottom portion 11C of the metal base 10C with a die bond material. A circular gate electrode 7 and a source electrode 8 are provided on the surface.

  The two drain connection electrodes 15C are each formed in a mesa shape having a circular shape in a region near the other side of the bottom portion 11C of the metal base 10C. That is, each drain connection electrode 15C is formed by etching or forging a metal plate constituting the bottom portion 11C of the metal base 10C, and is a circular mesa having a slightly smaller diameter than the gate electrode 7 and the source electrode 8. Further, each drain connection electrode 15A is formed so that the diameter dimension of the lower region is slightly larger than the surface so that the cross-sectional shape in the plate thickness direction is a trapezoid. Further, as shown in FIG. 11 (c), both drain connection electrodes 15A are arranged at positions symmetrical to each other so that their distances are equal to the other side and both ends of the adjacent bottom portion 11C. Has been. When the semiconductor chip 1 is mounted in a region closer to one side of the base 11C, each of the centers of the gate electrode 7, the source electrode 8, and the two drain connection electrodes 15C is slightly smaller than the metal base 10C. These two drain connection electrodes 15C, the gate electrode 7 and the source electrode 8 are arranged symmetrically so as to be positioned in the square. In the case of this reference example, the drain connection electrode 15C, the gate electrode 7 and the source electrode 8 are configured to have the same surface height, that is, the difference between both surfaces is 0 mm.

  The semiconductor device of this reference example can be formed with a thickness dimension substantially the same as that of the first to third embodiments, and the semiconductor device can be made thinner. On the other hand, compared with the first to third embodiments, the area of the metal base 10C is almost twice that of the semiconductor chip 1, so that it is slightly disadvantageous in terms of miniaturization. Since the area of the functioning metal base 10C is large, it is possible to improve heat dissipation.

  Further, when the semiconductor device of this reference example is mounted on the mounting substrate, the two drain connection electrodes 15C have the same circular shape as the gate electrode 7 and the source electrode 8 of the semiconductor chip 1, and thus soldering at each electrode is performed. The attachment can be performed under almost the same conditions. However, since the drain connection electrode 15C is integral with the metal base 10C, the heat capacity is larger than that of the gate electrode 7 and the source electrode 8, but the drain connection electrode 15C is slightly smaller in diameter than the gate electrode 7 and the source electrode 8. Since the area is small and has a trapezoidal cross section, the amount of solder in each electrode is equalized at the time of mounting, and the drain is not unnecessarily high, as in the above embodiments. The reliability of soldering in the connection electrode 15C and the reliability of soldering in the gate electrode 7 and the source electrode 8 are improved.

  Further, since the two drain connection electrodes 15C are arranged at equal distances from the respective sides of the metal base 10C, the heat capacities of both drain connection electrodes 15C can be made equal. This is effective in improving the uniformity of solder reflow in the drain connection electrode 15C. Further, since each drain connection electrode 15C exists in a region inside the side of the metal base 10C, solder is not sucked along the side surface of the metal base 10C during mounting. Furthermore, since the drain connection electrode 15C, the gate electrode 7 and the source electrode 8 are arranged at symmetrical positions, the stability of the metal base 10C at the time of mounting is improved, and the soldering conditions for each electrode are equalized. This is advantageous in increasing the reliability of soldering at each electrode described above. In this case, since the surface heights of the drain connection electrode 15C, the gate electrode 7 and the source electrode 8 are equal, it goes without saying that the semiconductor device can be mounted on the mounting substrate in a stable state and soldered. . Furthermore, since both drain connection electrodes 15C are integral with the metal base 10C at the lower part, sufficient mechanical strength can be obtained, and the mounting reliability can be improved also from this aspect.

  Although illustration is omitted here, solder balls may be formed on the drain connection electrode 15C, the gate electrode 7 and the source electrode 8 also in the reference example. In the third embodiment and the reference example, the cross-sectional shape of the drain connection electrode is trapezoidal, but it may be formed in a prismatic shape or a cylindrical shape. However, it is necessary that the lower region is formed integrally with the metal base, and is not formed with a groove or the like between the metal base and is continuous. Furthermore, in the reference example, the drain connection electrode and each electrode of the semiconductor chip are not necessarily arranged in a square shape, and it is possible to obtain the same operational effect only by arranging in a grid shape.

  In the first to third embodiments, the drain connection electrode is shown to be higher than the gate electrode and the source electrode of the semiconductor chip by a required dimension. Such a feature of the present invention is the first to the third. The present invention is not limited to the configuration described in the third embodiment, and is similarly applied to a semiconductor device having a known configuration described in the related art, thereby preventing mechanical damage of the semiconductor chip and each of the drain connection electrode and the electrode of the semiconductor chip. Thus, the effect of improving the reliability of soldering can be obtained. Further, in the third embodiment, when the metal base is formed by etching, it is disadvantageous in terms of the manufacturing process as compared with the bending process, but even in this case, the drain connection electrode having a simple shape is formed. Since the metal plate is only etched in the thickness direction so as to be left, it can be realized relatively easily. Of course, if it is formed by forging, it can be manufactured as easily as bending.

  In each of the above embodiments, an example in which the present invention is applied to a MOSFET is shown. However, the present invention can be similarly applied to a semiconductor device on which another semiconductor chip such as a bipolar transistor, a diode, or an IC is mounted. Is possible.

1 is a perspective view of a semiconductor device according to a first embodiment of the present invention. FIG. 2 is an exploded perspective view in which a part of the semiconductor device of FIG. 1 is broken. FIG. 2 is a plan view, a front view, and a right side view of the semiconductor device of FIG. 1. It is a conceptual diagram for demonstrating the manufacturing method of the semiconductor device of FIG. FIG. 2 is a perspective view for explaining a mounting structure of the semiconductor device of FIG. 1. It is the perspective view and partial expanded sectional view of the semiconductor device of the 2nd Embodiment of this invention. It is the perspective view and partial expanded sectional view of the semiconductor device of the 3rd Embodiment of this invention. It is a perspective view of the semiconductor device of the modification of the 1st Embodiment of this invention. It is a perspective view of the semiconductor device of the modification of the 2nd and 3rd embodiment of this invention. It is a perspective view of the semiconductor device of the further modification of the 3rd Embodiment of this invention. It is the perspective view of the semiconductor device of the reference example of this invention, a partial expanded sectional view, and a top view which shows arrangement | positioning of each electrode. It is a perspective view of an example of the conventional semiconductor device. It is a perspective view of the other example of the conventional semiconductor device. It is a perspective view of the other example of the conventional semiconductor device.

Explanation of symbols

D Semiconductor device 1 Semiconductor chip 4 Drain electrode 7 Gate electrode 8 Source electrodes 10, 10A, 10B, 10C Metal base 11, 11B, 11C Bottom side 12 Both sides 13 Narrow grooves 15, 15A, 15B, 15C Drain connection electrode 20 Mounting material 21 Solder balls 30 Mounting substrate 31 Insulating substrate 32 Circuit pattern 33 Gate electrode pad portion 34 Source electrode pad portion 35 Drain connection electrode pad portion

Claims (11)

  A metal base comprising a bottom portion made of a rectangular metal plate, and a plurality of connection electrodes each made of a convex portion provided on at least two opposing sides of the bottom portion, and a semiconductor mounted on the bottom portion of the metal base A surface mount type semiconductor device configured to be mounted on the surface of the semiconductor chip by using the plurality of connection electrodes and the surface height of the plurality of connection electrodes. A semiconductor device characterized in that it is higher than the surface height of the electrode of the semiconductor chip by a required dimension.   2. The semiconductor device according to claim 1, wherein the plurality of connection electrodes are formed in a portion where the thickness of the metal plate is partially thick in a partial region of the surface of the bottom side portion.   The semiconductor device according to claim 2, wherein the metal base is formed by etching or forging the metal plate.   4. The semiconductor device according to claim 1, wherein a surface height of the connection electrode is higher by about 0 to 0.1 mm than a surface height of the electrode of the semiconductor chip.   5. The semiconductor device according to claim 1, wherein the area of the connection electrode is smaller than the area of the electrode of the semiconductor chip.   6. The semiconductor device according to claim 1, wherein the connection electrodes are arranged so as to be symmetric with respect to at least one of a length direction of the both side portions and a direction orthogonal thereto.   7. The semiconductor device according to claim 1, wherein the connection electrode has a trapezoidal cross section in which a surface area is smaller than a lower area. 8.   8. The connection electrode according to claim 1, wherein the connection electrode is formed at a position that is symmetric with respect to at least one of a length direction of the semiconductor chip and a width direction sandwiching the semiconductor chip. Semiconductor device.   9. The semiconductor device according to claim 8, wherein one connection electrode is formed on each of both sides of the bottom portion chip.   10. The semiconductor device according to claim 1, wherein a solder ball is formed on at least one of the electrode of the semiconductor chip or the connection electrode. The semiconductor chip is a transistor chip of a MOS transistor, and a drain electrode is formed on a back surface of the semiconductor chip and mounted in a state of being in direct contact with the bottom portion, and the connection electrode is configured as a drain connection electrode. 11. The semiconductor device according to claim 1, wherein a gate electrode and a source electrode are respectively formed on the surface.

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