Method for manufacturing a semiconductor device

Abstract

A method for manufacturing a semiconductor device (10), comprising: - a resin preparation step (S1) - for providing a tappet plate (32) in a hole (30a) formed in a recessed part (30A) of a lower mold (30), - for providing a first resin (20a) on the tappet plate (32), and - for providing a second resin (22a) having a lower thermal conductivity than the first resin (20a) on the first resin (20a); - a mounting step (S2) for placing a lead frame (12) on an upper surface of which a semiconductor chip (14) is mounted on an upper surface of the recessed part (30A); - a mold clamping step (S3) for placing an upper mold (40) on the lower mold (30), and for performing mold clamping in a state in which the semiconductor chip (14) is housed in a cavity formed by the lower mold (30) and the upper mold (40); - an injection step (S4) for lifting the plunger plate (32) after the first resin (20) and the second resin (22) have been melted to provide the second resin (22) in the cavity, and by subsequently introducing the first resin (20), the first resin (20) is brought into contact with a lower surface of the lead frame (12); and - a pressure maintaining step (S5, S7) for exerting a pressure on the first resin (20) and the second resin (22) through the plunger plate (32), and for maintaining the pressure.

Description

Area

[0001] The present invention relates to a semiconductor device in which a semiconductor chip is resin-sealed, and a method for manufacturing the semiconductor device. background

[0002] Patent Literature 1 discloses a technology for forming a molding resin on a workpiece. Specifically, after a resin for a pot is poured into a pot, a resin for a cavity is poured into a recessed portion of a cavity. By performing mold clamping of a mold, the resin for the pot and the resin for the cavity, which have both been melted, are pressed by a ram to mix them, and the recessed portion of the cavity is filled with the molten resin. Next, the molten resin in the recessed portion of the cavity is held at a predetermined resin pressure to cure under heating. State of the artPatent literature

[0003] Patent Literature 1: JP 2012- 166 432 A

[0004] JP H08-023005 A discloses a manufacturing method for a semiconductor device that enables a resin-sealed semiconductor element to be easily released from a mold without reducing the bonding strength by using a sealing resin film with different compounding agent distributions between one side and the other of the semiconductor element. An element bonded with a positive-side sealing resin film and a negative-side sealing resin film on the positive and negative sides is manufactured piece by piece in a mold. The sealing resin film contains laminated resin films with different compounding agent concentrations. The sealing resin film 2 contains laminated resin films also with different compounding agent concentrations. The resin films are brought into contact with the element while the resin films are brought into contact with the mold.A frame is clamped by external molds. The plate is pressed onto the element and hardened in a compression molding step.

[0005] JP H10-144827 A discloses a resin-sealed semiconductor device in which reflow resistance is improved while simultaneously reducing thermal resistance by applying a low-stress, high-thermal-conductivity sealing resin to the opposite sides of a lead frame connected to a semiconductor chip. Since the upper and lower transfer molding dies are each provided with gates and pots, a lead frame can be sealed on its opposite sides with different resins. Specifically, a resin-sealed semiconductor device with low stress and low thermal resistance can be obtained by sealing a semiconductor chip with a low-stress resin on the mounting side and a high-thermal-conductivity resin on the opposite side.Consequently, the stress at the interface between the semiconductor chip and the stress-relieving resin is suppressed at the time of heating the resin-sealed semiconductor device, and the reflow resistance can be improved while reducing the thermal resistance by efficiently dissipating the heat generated on the semiconductor chip during operation through the highly thermally conductive resin.

[0006] US 2001 / 0 042 913 A1 describes a manufacturing method for a semiconductor device, wherein at least one semiconductor element is arranged in a cavity of a resin molding die. A resin is supplied to a resin reservoir in direct contact with the cavity and then injected to fill the cavity. The resin filled into the cavity forms a resin seal for encapsulating the semiconductor element. The resin seal has a recess or protrusion as the remainder of the resin reservoir.

[0007] The document US 2017 / 0 004 981 A1 relates to a method for manufacturing a semiconductor device that can reduce deterioration in body strength and manufacturing costs and promotes miniaturization of a body. The method comprises steps of (a) providing a printed circuit board having a workpiece plate on which a semiconductor element is mounted, (b) disposing a first resin that is granular in a mold, (c) disposing the printed circuit board in the mold such that the first resin comes into contact with a bottom side of the workpiece plate, (d) filling the mold with a second resin at a top side of the first resin in the mold, and (e) curing the first resin and the second resin to mold the first resin and the second resin. SummaryTechnical problem

[0008] In a semiconductor device in which a semiconductor chip attached to a lead frame is resin-sealed, it is necessary to downsize the device to improve the thermal conductivity of the device and to improve the insulation property to protect the semiconductor chip from undesirable electrical influences. It is necessary to provide a semiconductor device with low cost and high quality.

[0009] The present invention has been devised to solve the above problems, and an object is to provide a semiconductor device with low cost and high quality, and a method for manufacturing the semiconductor device. Means to solve the problem

[0010] A semiconductor device related to the technical background of the present invention includes a lead frame, a semiconductor chip attached to an upper surface of the lead frame, a first resin in contact with a lower surface of the lead frame, a second resin provided on the first resin, the first resin having a higher thermal conductivity than the second resin, and the first resin and the second resin covering the semiconductor chip.

[0011] The object underlying the invention is achieved in a method for producing a semiconductor device according to the invention with the features of claim 1 and alternatively according to the invention with the features of claim 4. Advantageous further developments are the subject of the respective dependent claims.

[0012] According to one aspect of the present invention, a method for manufacturing a semiconductor device comprises a resin providing step of providing a plunger plate in a hole formed in a recessed part of a lower mold, wherein a first resin is provided on the plunger plate, and wherein a second resin, which has a lower thermal conductivity than the first resin, is provided on the first resin; a mounting step of placing a lead frame on an upper surface of which a semiconductor chip is mounted on an upper surface of the recessed part; a mold clamping step of placing an upper mold on the lower mold and performing mold clamping in a state in which the semiconductor chip is housed in a cavity provided by the lower mold and the upper mold; an injection step of lifting the plunger plate;after the first resin and the second resin are melted to provide the second resin in the cavity, and by subsequently providing the first resin, the first resin is brought into contact with a lower surface of the lead frame, and a pressure maintaining step of applying pressure to the first resin and the second resin through the plunger plate and maintaining the pressure.

[0013] A method for manufacturing a semiconductor device belonging to the technical background of the present invention comprises a resin providing step of providing a plunger plate in a hole formed in a recessed part of a lower mold, a resin being provided on the plunger plate, a mounting step of placing a lead frame on a lower surface from which a semiconductor chip is mounted on an upper surface of the recessed part, a mold clamping step of placing an upper mold on the lower mold while interposing a heat dissipation plate having a higher thermal conductivity than the resin between the lead frame and the upper mold, and performing mold clamping in a state in which the semiconductor chip is housed in a cavity provided by the lower mold and the upper mold,an injection step of raising the plunger plate after the resin has been melted, the plunger plate providing the resin in the cavity, and a pressure maintaining step of applying pressure to the resin from the plunger plate and maintaining the pressure.

[0014] According to another aspect of the present invention, a method for manufacturing a semiconductor device comprises a resin providing step of providing push plates in holes formed in a lower mold having a plurality of recessed portions and providing resins on the push plates, an assembling step of placing a lead frame to which a semiconductor chip is attached on an upper surface of the lower mold, a mold clamping step of placing an upper mold on the lower mold and performing mold clamping in a state in which a plurality of cavities are formed by the plurality of recessed portions and a runner connecting the plurality of cavities, an injection step of lifting the push plate to a predetermined position after the resin is melted to provide the resin in the plurality of cavities and the runner,and a pressure maintaining step for applying pressure to the resin through the ram plates and maintaining the pressure, wherein a pressure which the resin in the runner exerts on a movable block in the runner is detected when the ram plate is raised to the predefined position, wherein the movable block is moved in a direction in which it retreats from the runner when the pressure is higher than a predefined pressure, and wherein the movable block is moved in a direction in which it advances into the runner when the pressure is lower than the predefined pressure.

[0015] Other features of the present invention will be clarified below. Advantageous effects of the invention

[0016] According to this invention, for example, the first resin having a high thermal conductivity is provided on the lower surface of the lead frame, while the second resin having a lower thermal conductivity than the first resin is provided on the lead frame, and thereby a semiconductor device with low cost and high quality can be provided. Short description of the characters Fig. 1 is a cross-sectional view of a semiconductor device according to Embodiment 1. Fig. 2 is a flowchart illustrating a method for manufacturing a semiconductor device according to Embodiment 1. Fig. 3 is a cross-sectional view of a first resin and a second resin. Fig. 4 is a cross-sectional view of the lead frame and the like. Fig. 5 is a cross-sectional view illustrating the lower mold and the upper mold subjected to mold clamping. Fig. Figure 6 is a cross-sectional view illustrating the raised tappet plate. Fig. 7 is a cross-sectional view of ball plungers and the like. Fig. 8 is a plan view of the ball plungers and the like. Fig. 9 is a perspective view of a plurality of push rods and the like. Fig. 10 is a cross-sectional view of molds and the like which are provided with the ram device in Fig. 9 correspond. Fig. 11 is a cross-sectional view illustrating a method of manufacturing a semiconductor device according to Embodiment 2. Fig. 12 is a flowchart illustrating a method for manufacturing a semiconductor device according to Embodiment 3. Fig. 13 is a structure of an apparatus used for manufacturing a semiconductor device. Fig. 14 is a view illustrating the resin provided in the cavities and the runner. Fig. 15 is a diagram illustrating an example structure of the controller. Fig. 16 is a diagram illustrating another exemplary structure of the controller. Fig. 17 is a view illustrating a method of manufacturing a semiconductor device according to Embodiment 4. Fig. 18 is a view illustrating a method of manufacturing a semiconductor device according to a comparative example. Description of the embodiments

[0017] Semiconductor devices and methods for manufacturing a semiconductor device according to the technical background and embodiments of the present invention will be described with reference to the figures. The same or corresponding components are denoted by the same reference numerals, and repeated descriptions thereof will occasionally be omitted. Embodiment 1

[0018] Fig. 1 is a cross-sectional view of a semiconductor device 10 according to the technical background of the present invention. The semiconductor device 10 includes a lead frame 12. A semiconductor chip 14 is mounted on the upper surface of the lead frame 12. The semiconductor chip 14 is, for example, a switching device formed of Si or SiC. A first resin 20 is in contact with the lower surface of the lead frame 12. A second resin 22 is provided on the first resin 20. The first semiconductor chip 14 is covered by the first resin 20 and the second resin 22. The first resin 20 and the second resin 22 function as a package. The first resin 20 has a higher thermal conductivity than the second resin 22. The materials of the first resin 20 and the second resin 22 are not particularly limited as long as this condition is met. The first resin 20 is, for example, alumina, and the second resin 22 is, for example, silicon oxide.The thermal conductivity of the first resin 20 is preferably 2 W / m·K or more.

[0019] The lead frame 12 has a die pad portion to which the semiconductor chip 14 is attached, an inner lead portion provided in the resin, and an outer lead portion extending out of the resin. A control chip 24, which outputs a control signal to the semiconductor chip 14, is provided on the inner lead portion located in the second resin 22. The semiconductor chip 14 and the inner lead portion are connected to each other with a wire 26. The semiconductor chip 14 and the control chip 24 are connected to each other with a wire 28.

[0020] The first resin 20 is provided only below the lower surface of the lead frame 12. The first resin 20 contacts the lower surface of the semiconductor chip 14 via the lead frame 12, and the second resin 22 contacts the side surface and the upper surface of the semiconductor chip 14. The package is mainly composed of the second resin 22, and the volume occupied by the first resin 20 of the entire package is small. Accordingly, the second resin 22 has a larger volume than the first resin 20. The first resin 20 is exposed below the semiconductor chip 14, and the second resin 22 is exposed above the semiconductor chip 14.

[0021] Fig. 2 is a flowchart illustrating a method for manufacturing a semiconductor device according to Embodiment 1 of the present invention. This flowchart describes a method for manufacturing the semiconductor device 10. In step S1, first, a first resin and a second resin are provided on a plunger plate.

[0022] Fig. 3 is a diagram illustrating a first resin 20a and a second resin 22a. A lower mold 30 has a recessed portion 30A. A hole 30a is formed in the recessed portion 30A. A portion where the hole 30A is formed is referred to as a cup 30B. The pusher plate 32 is disposed in the hole 30a. The side surface of the pusher plate 32 is in contact with the cup 30B. The pusher plate 32 is supported by a push rod 34. When the push rod 34 moves in the positive and negative y-directions, the pusher plate 32 also moves in the positive and negative y-directions in an interlocking manner.

[0023] The first resin 20a is provided on such a tappet plate 32, and the second resin 22a, which has a lower thermal conductivity than the first resin 20a, is provided on the first resin 20a. The first resin 20a and the second resin 22a are granulated. For example, the first resin 20a is granular alumina, and the second resin 22a is granular silica. The above step of providing resin on the tappet plate 32 is referred to as a resin providing step.

[0024] Fig. Figure 3 also illustrates an upper mold 40. The upper mold 40 has a recessed portion 40A. Movable pins 42 are provided that penetrate the recessed portion 40A. The movable pins 42 penetrate the recessed portion 40A and can move in the positive and negative y-directions. Such movement can be realized by means of a motor.

[0025] Next, the process proceeds to step S2. In step S2, the lead frame 12 is placed on the lower mold 30. Fig. 4 illustrates the lead frame 12 placed on the lower mold 30. In step S2, the lead frame 12, to the upper surface of which the semiconductor chip 14 is attached, is placed on the upper surface of the recessed part 30A of the lower mold 30. This step is referred to as a mounting step.

[0026] Next, the process proceeds to step S3. In step S3, mold clamping is performed with the lower mold 30 and the upper mold 40. Fig. 5 is a view illustrating the lower mold 30 and the upper mold 40 that have undergone mold clamping. The lower mold 30 and the upper mold 40 are housed in a mold clamping device, the upper mold 40 is placed on the lower mold 30, and a predetermined mold clamping force is applied thereto. In this phase, the mold clamping is performed in the state where the semiconductor chip 14 is housed in a cavity 50 provided by the lower mold 30 and the upper mold 40. This step is referred to as the mold clamping step.

[0027] In the mold clamping step, the movable pins 42 are brought into contact with the upper surface of the lead frame 12. The movable pins 42 prevent the lead frame 12 from floating while the resin is injected into the cavity 50 and maintain pressure. To reliably prevent such floating, a plurality of movable pins 42 are preferably brought into contact with the upper surface of the lead frame 12.

[0028] Next, the process proceeds to step S4. After the first resin 20a and the second resin 22a are melted, the plunger plate 32 is raised in step S4. Fig. 6 is a view illustrating the lifted push plate 32. While the push plate 32 is being lifted, the second resin 22a is first supplied into the cavity 50, and then the first resin 20a is supplied. Therefore, the second resin 22 is supplied to an upper portion of the cavity 50, and the first resin 20a is supplied to a lower portion of the cavity 50. When the height of the upper surface of the push plate 32 coincides with the height of the lower surface of the recessed part 30A of the lower mold 30, the lifting of the push plate 32 is completed. By injecting the resin as above, the first resin 20 comes into contact with the lower surface of the lead frame 12. This step is referred to as an injection step.

[0029] Next, the process proceeds to step S5. In step S5, pressure maintenance and curing are carried out. Specifically, pressure is applied to the first resin 20 and the second resin 22 by the pusher plate 32, and the pressure is maintained. This step is referred to as the pressure maintenance step. Next, the process proceeds to step S6. In step S6, the pusher plate 32 is moved downward. A molded article is released from the molds, and thereby the Fig. 1 illustrated semiconductor device 10 is completed.

[0030] In Embodiment 1 of the present invention, the package including the first resin 20 and the second resin 22 is molded by the above-mentioned compression molding method. This causes less resin flow than in a transfer molding method in which resin is supplied into a cavity via a narrow runner. Accordingly, the first resin 20 and the second resin 22 are not significantly mixed, whereby a state in which the first resin 20 and the second resin 22 are substantially separated can be maintained. By utilizing such a characteristic of the compression molding method, the high thermal conductivity first resin 20 can be applied only to the underside of the lead frame 12. Heat generated by the semiconductor chip 14 is mainly dissipated to the outside via the lead frame 12 and the high thermal conductivity resin 20.Moreover, the second resin 22 having a lower thermal conductivity than the first resin 20 can be used for a portion which is not very important to improve thermal conductivity, whereby costs for semiconductor devices can be reduced.

[0031] The first resin 20 has a high electrical insulation property. When the first resin 20 is provided on the lower surface of the lead frame 12, a resin on the lower surface of the lead frame 12 can be formed thinner than in the case where the second resin, whose material is silicon oxide, is provided on the lower surface of the lead frame 12. The insulation property of 450 µm of the second resin formed on the lower surface of the lead frame 12 is equivalent to an insulation property of 150 µm of the first resin 20 formed on the lower surface of the lead frame 12. Accordingly, a semiconductor device can be downsized and a heat dissipation property can be improved without impairing the insulation property of the semiconductor device.

[0032] In the injection step and the pressure maintaining step in the method for manufacturing a semiconductor device according to Embodiment 1 of the present invention, the movable pins 42 are brought into contact with the upper surface of the lead frame 12 to prevent the lead frame 12 from floating. This can prevent the occurrence of a defective article due to the floating of the lead frame 12.

[0033] With Embodiment 1 of the present invention, resin molding can be performed using the plunger plate 32, which is identical to a plunger plate used in the transfer molding process. Thus, a common plunger mechanism can be shared by different types of articles.

[0034] Fig. 7 is a cross-sectional view of ball plungers 54 and the like that support the push rod 34. A support table 52 is fixed to the upper surface of a push rod block 51. The support table 52 has a recessed portion, and the lower end portion of the push rod 34 is housed in the recessed portion. The lower end portion of the push rod 34 can contact the support table 52 but is not fixed to the support table 52. The ball plungers 54, which can expand and contract in the lateral direction, are fixed to the support table 52. A ball or a pin is provided at a portion of the tip 54A of the ball plunger 54. A portion of the body 54B thereof is connected to the portion of the tip 54A. A spring is included in the portion of the body 54B.Therefore, when a load is applied to the tip portion 54A, the body portion 54B contracts, and when the load is released, the body portion 54B returns to its original length. A narrow-width portion 34a is preferably provided in the push rod 34 such that the tip portions 54A of the ball pushers 54 are brought into contact with the narrow-width portion 34a.

[0035] Fig. 8 is a plan view of the push rod 34 and the ball plungers 54. Four ball plungers 54 are in contact with the side surface of the push rod 34. When a force is applied from the push rod 34 to the ball plungers 54, the ball plungers 54 contract, which can shift the position of the push rod 34 by that amount. Therefore, the push rod 34 can be moved upwards, downwards, rightwards, and leftwards in the plan view, and can be rotated in the top view.

[0036] By moving the tappet block 51 in Fig. 7 in the positive and negative y-directions, the tappet plate 32 moves in the hole 30a in the positive and negative y-directions. In this phase, the tappet plate 32 preferably moves smoothly in the pot 30B, without the tappet plate 32 exerting a strong force on the pot 30B. As described with reference to the Fig. 7 and Fig. 8, the push rod 34 is therefore configured to move and rotate smoothly by supporting the push rod 34 by means of the ball plungers 54. As a result, the push plate 32 moves smoothly in the pot 30B without the push plate 32 exerting a strong force on the pot 30B. The above-mentioned method for manufacturing a semiconductor device is preferably implemented by using the push block 51, the support table 52, and the ball plungers 54, which are shown in Fig. 7 are illustrated.

[0037] For the method of manufacturing a semiconductor device according to Embodiment 1 of the present invention, the injection of resin into a cavity 50 has been described. However, a plurality of push rods may be attached to a push block to collectively inject resin into a plurality of cavities. Fig. 9 illustrates a plurality of pushrods 62 provided on a pushrod block 60. A pushrod plate 64 is connected to a pushrod 62. The pushrods 62 are preferably maintained in a displaceable state using the aforementioned ball pushrods 54.

[0038] Fig. 10 is a cross-sectional view of molds and the like which are provided with the ram device in Fig. 9 correspond. A plurality of recessed parts 70A are formed in a lower mold 70. A hole 70a is formed in a recessed part 70A. A plurality of recessed parts 72A are formed in an upper mold 72. Mold clamping of these forms a cavity from a recessed part 70A and a recessed part 72A, which provides a plurality of cavities. Using the Fig. 9 and Fig. The device illustrated in Figure 10 enables the injection step and the pressure maintenance step to be performed concurrently for the plurality of cavities. Since resin can be supplied to the individual cavities through the pusher plates 64, sprue portions do not need to be provided in the molds. Therefore, the lower mold 70 and the upper mold 72 can be reduced in size. By setting the area of ​​the pusher plate 64 in a plan view smaller than the area of ​​the lower surface of the recessed portion 70A, a larger hydrostatic pressure can be exerted on the resin than in the case where these areas are equivalent to each other.

[0039] An important feature of the semiconductor device and the method for manufacturing the semiconductor device according to Embodiment 1 is to form a package with two resins that have different thermal conductivities and that are not significantly mixed. The semiconductor device and the method for manufacturing a semiconductor device according to Embodiment 1 can be appropriately modified to an extent that does not impair this property. For example, the amount of the first resin 20 can be increased, and the first resin 20 can be provided above the lower surface of the die pad part of the lead frame 12. Furthermore, an intermediate resin having an intermediate thermal conductivity between those of the first resin 20 and the second resin 22 can be provided on the first resin 20, and the second resin 22 can be provided on the intermediate resin.In this case, the intermediate resin can promote heat dissipation in the right and left directions of the semiconductor device 10. Further, for example, the movable pins 42 can be omitted. If a pressure applied by the resin is small, the lead frame 12 is not necessarily fixed by the movable pins 42. The semiconductor chip 14 is not limited to a switching device. For example, a diode can be used as the semiconductor chip. A plurality of semiconductor chips can be housed in one package, and, for example, an inverter circuit can be composed of them.

[0040] The features and modifications described in Embodiment 1 can also be applied to semiconductor devices and methods for manufacturing a semiconductor device according to the following embodiments. In particular, since the semiconductor devices and methods for manufacturing a semiconductor device according to the following embodiments have many similarities to aspects in Embodiment 1, differences from the aspects of Embodiment 1 will be mainly described. Embodiment 2

[0041] Fig. 11 is a cross-sectional view illustrating a method for manufacturing a semiconductor device according to Embodiment 2. In the method for manufacturing a semiconductor device according to Embodiment 2, in the resin providing step, a resin 23 is first provided on the pusher plate 32. In the mounting step, the lead frame 12, to the lower surface of which the semiconductor chip 14 is attached, is placed on the upper surface of the recessed part 30A. The die pad part of the lead frame 12 is located above the semiconductor chip 14.

[0042] Next, the process proceeds to the mold clamping step. In the mold clamping step, the upper mold 40 is placed on the lower mold 30, while a heat sink 80 is interposed between the lead frame 12 and the upper mold 40, and the mold clamping is performed in the state where the semiconductor chip 14 is housed in the cavity 50 provided by the lower mold 30 and the upper mold 40. The heat sink 80 includes, for example, an insulating layer 80A and a heat sink 80B stacked on the insulating layer 80A. The insulating layer 80A is preferably a mold resin such as silicon dioxide and epoxy resin or a similar material. The material of the heat sink 80B is, for example, copper. The structure of the heat sink 80 is not specifically limited as long as its thermal conductivity can be higher than that of resin.During mold clamping, the upper surface of the heat dissipation plate 80 comes into contact with the lower surface of the recessed part 40A of the upper mold 40, and the lower surface of the heat dissipation plate 80 comes into contact with the upper surface of the lead frame 12.

[0043] Next, in the injection step, the push plate 32 is raised after the resin 23 is melted to supply the resin 23 into the cavity 50. In the injection step, the push plate 32 is raised, for example, until the upper surface of the push plate 32 has a height identical to the lower surface of the recessed part 30A of the lower mold 30. Next, in the pressure maintaining step, pressure is applied from the push plate 32 to the resin 23, and the pressure is maintained.

[0044] In Embodiment 1, since the first resin 20, which has high thermal conductivity, is brought into contact with the lower surface of the lead frame 12, and since the first resin 20 is exposed to the outside, a heat dissipation property of the device can be improved. However, if one attempts to further improve the heat dissipation property of the device, the first resin 20 will reach its limit. Therefore, in Embodiment 2, the heat dissipation plate 80 is provided to achieve better heat dissipation property of the device than in the case of using the first resin 20. Since the heat dissipation plate 80 can improve the heat dissipation property of the device, high thermal conductivity of the first resin 23 is not required. Therefore, the material of the resin 23 can be, for example, one such as silicon dioxide, which has lower thermal conductivity than alumina. Embodiment 3

[0045] Fig. 12 is a flowchart representing a method for manufacturing a semiconductor device according to Embodiment 3. Before the method for manufacturing a semiconductor device with Fig. 12, a structure of an apparatus with reference to Fig. 13, which is used for manufacturing a semiconductor device. At least two recessed portions 90A and 90B are formed in a lower mold 90. A pusher plate 32A is located in a hole provided in the recessed portion 90A. The pusher plate 32A is supported by a pusher rod 34A. A pusher plate 32B is located in a hole provided in the recessed portion 90B. The pusher plate 32B is supported by a pusher rod 34B. A motor 100 is connected to the pusher rods 34A and 34B. The motor 100 moves the pusher plates 32A and 32B in the positive and negative y-directions.

[0046] The upper mold 92 has at least two recessed portions 92A and 92B. A movable block 102 is provided between the recessed portions 92A and 92B. The movable block 102 is connected to a motor 106 via a spring 104. The motor 106 can move the movable block 102 in the positive and negative y-directions. In particular, the motors 100 and 106 are preferably servomotors. The motors 100 and 106 are connected to a controller 110.

[0047] In the method for manufacturing a semiconductor device according to Embodiment 3, the resin providing step is first performed in step S1. In the resin providing step, the pusher plates 32A and 32B are provided in the holes formed in the Fig. 13, and the resin 23 is provided on the push plates 32A and 32B. Next, the assembly step in step S2 is carried out. In the assembly step, the lead frames 12 and 13, to which the semiconductor chips 14 are mounted, as shown in Fig. 13, are placed on the upper surface of the lower mold 90. The lead frame 13 is placed on both recessed parts 90A and 90B.

[0048] Next, the mold clamping step is performed in step S3. In the mold clamping step, the upper mold 92 is placed on the lower mold 90. Fig. 13 is a cross-sectional view of the molds and the like after mold clamping. When the mold clamping is completed, a cavity 50A is formed by the recessed parts 90A and 92A, and a cavity 50B is formed by the recessed parts 90B and 92B. The two cavities 50A and 50B are connected to each other via a runner 50C. The volume of the runner 50C depends on the position of the movable block 102. The volume of the runner 50C is small when the movable block 102 is positioned low, and the volume of the runner 50C is large when the movable block 102 is positioned high.

[0049] Next, the injection step is performed in step S4. After the resin 23 is melted, the tappet plates 32A and 32B are raised to a predefined position in the injection step based on an instruction from the controller 110. For example, the tappet plates 32A and 32B are raised to a position where the upper surfaces of the tappet plates 32A and 32B coincide with the lower surfaces of the recessed portions 90A and 90B. This supplies the resin 23 to the cavities 50A and 50B and the runner 50C. In this phase, the two tappet plates 32A and 32B are preferably moved by means of a single tappet block. Such a tappet block may be provided in the engine 100.

[0050] Fig. 14 is a view illustrating the resin 23 provided in the cavities 50A and 50B and the runner 50C. When the push plates 32A and 32B are raised to a predetermined position, a pressure exerted by the resin 23 in the runner 50C on the movable block 102 is detected. This pressure can be detected, for example, by detecting a pressure that the movable block 102 exerts on the motor 106 via the spring 104. To detect such a pressure, a sensor is provided, for example, within the motor 106. Information about the detected pressure is transmitted to the controller 110.

[0051] In step S5, the controller 110 determines whether the pressure transmitted to the controller 110 is a predefined pressure. The "predefined pressure" can be any pressure range. If the detected pressure is greater than the predefined pressure, the controller 110 moves the movable block 102 in the direction in which it is retracted from the runner 50C. Specifically, the movable block 102 is moved upward. This adjusts the resin pressure in the cavities 50A and 50B to a predefined pressure.

[0052] If the detected pressure is lower than the predefined pressure, the controller 110 moves the movable block 102 in the direction that advances it into the runner 50C. Specifically, the movable block 102 is moved downward. This sets the resin pressure in the cavities 50A and 50B to a predefined pressure.

[0053] Moving the movable block 102 as above makes the pressing pressure and the thickness of the resin uniform. Step S6 is a step for adjusting the position of the movable block 102 as above. Specifically, resin thickness control can be achieved by feeding the positions of the push plates 32A and 32B back to the controller 110, and by raising the push plates 32A and 32B to the predefined position by the controller 110.

[0054] If it is determined in step S5 that the detected pressure corresponds to the predefined pressure, the process proceeds to step S7. The pressure maintenance step is executed in step S7. In the pressure maintenance step, pressure is applied to the resin 23 by the pusher plates 32A and 32B, and the pressure is maintained. Finally, in step S8, the pusher plates 32A and 32B are moved downward. As above, a product is formed by a single injection molding process in which a lead frame 13 is provided in a plurality of packages.

[0055] Fig. 15 is a diagram illustrating an exemplary configuration of the controller 110. The controller 110 includes a receiving device 110A, a processing circuit 110B, and a transmitting device 110C. Information about the pressure that the movable block 102 exerts on the motor 106 via the spring 104 is transmitted to the receiving device 110A. The above-mentioned individual functions performed in the controller 110 are realized by means of the processing circuit 110B. Namely, in the processing circuit 110B, it is determined whether the received pressure corresponds to the predefined pressure, and according to the determined result, an amount of movement of the movable block 102 is calculated.The processing circuit 110B may be dedicated hardware or a CPU (also referred to as a central processing unit, a central processing device, a processing device, a computing device, a microprocessor, a microcomputer, a processor, or a DSP) that executes a program stored in memory. When the processing circuit is dedicated hardware, the processing circuit corresponds to, for example, a single circuit, a composite circuit, a parallel-programmed processor, an ASIC, an FPGA, or a combination of these. Detecting the pressure and calculating the amount of movement of the movable block 102 may be realized by separate processing circuits, or they may be realized jointly by one processing circuit.

[0056] Fig. 16 illustrates an exemplary structure of the controller 110 in the case where the processing circuit is a CPU. In this case, the individual functions of the controller 110 can be implemented by software or by a combination of software and firmware. The software or firmware is referred to as programs and is stored in a memory 110E. The processor 110D implements the individual functions by reading and executing the programs stored in the memory 110E. Namely, the memory 110E, which stores the programs with which steps S4 to S8 in Fig. 12 are to be executed accordingly. These programs can also be regarded as programs that cause a computer to execute the procedures and methods of steps S4 to S8. The memory here corresponds to, for example, a non-volatile or volatile semiconductor memory such as a RAM, a ROM, a flash memory, an EPROM or an EEPROM, a magnetic disk, a flexible disk, an optical disk, a compact disk, a mini disk, a DVD, or the like. Of course, some of the above-mentioned individual functions may be realized by hardware, and some of them may be realized by software or firmware.

[0057] According to the method for manufacturing a semiconductor device according to Embodiment 3 of the present invention, the molding pressure and the thickness of the resin can be uniformed by controlling the position of the movable block 102 in accordance with the pressure of the resin 23 injected into the cavities 50A and 50B and the runner 50C. Accordingly, dispersion of insulation properties and external heat dissipation properties between products can be minimized. The method for manufacturing a semiconductor device according to Embodiment 3 can be modified in various ways within a scope that does not impair this feature. For example, the number of cavities formed in mold clamping is not limited to two, but three or more cavities may be formed. Embodiment 4

[0058] Fig. 17 is a view illustrating a method of manufacturing a semiconductor device according to Embodiment 4. Fig. 17 is a view illustrating the tappet plate 32 and the like in the injection step. The upper part thereof illustrates a cross-sectional view, and the lower part thereof illustrates a plan view. The plan view in the lower part illustrates that the tappet plate 32 is circular in plan view. Setting the tappet plate 32 circular in plan view can shorten its circumference more than a non-circular tappet plate with the same area. In other words, the circumference of the circular tappet plate 32 is the smallest among the circumferences of tappet plates of different shapes. By setting the circumference of the tappet plate 32 small, the amount of resin burrs that get between the tappet plate 32 and the pot 30B can be reduced. Thereby, the friction between the tappet plate 32 and the pot 30B can be minimized.

[0059] In addition, a lower surface 30C of the recessed part 30A is quadrangular in a plan view. As shown in the lower part of Fig. 17, the area of ​​the tappet plate 32 in a plan view is smaller than the area of ​​the lower surface 30C of the recessed part 30A. The area of ​​the tappet plate 32 in the plan view preferably corresponds to no more than half the area of ​​the lower surface 30C. Furthermore, the tappet plate 32 in the plan view is preferably located in the center of the lower surface 30C. By making the area of ​​the tappet plate 32 smaller than the area of ​​the lower surface 30C, the resin 23 injected into the cavity can be caused to spread slightly from directly below the die pad part to the right and left. The arrows in Fig. 17 illustrates the resin flow directions. Voids 22v are rarely formed above the semiconductor chip 14. Therefore, variation in heat dissipation characteristics between products can be prevented.

[0060] A resin ring 33 is provided along the circumference of the tappet plate 32 to prevent friction between the tappet plate 32 and the cup 30B due to lifting of the tappet plate 32 in the hole of the cup 30B. The tappet plate 32 can be protected by the resin 33, which is mainly in contact with the cup 30B when the tappet plate 32 is lifted.

[0061] Fig. 18 is a view illustrating a method for manufacturing a semiconductor device according to a comparative example. The upper part thereof illustrates a cross-sectional view, and the lower part thereof illustrates a plan view. The pusher plate 32 of the comparative example is quadrangular in plan view. Further, the area of ​​the pusher plate 32 in plan view is equivalent to the area of ​​the lower surface 30C of the recessed part 30A. As above, when the area of ​​the pusher plate 32 is large, the resin tends to remain between the pusher plate 32 and the pot 30B, and the lower mold 30 needs to be cleaned regularly.

[0062] The arrows in Fig.18 indicate resin flows. In the case of the comparative example, since the area of ​​the plunger plate 32 is large, upward flow of the resin 23 is predominant. Therefore, the flow of the resin 23 is disturbed by the die pad portion of the lead frame 12. This raises concerns that a void 22v will be formed directly above the die pad portion and that an insulation property of the device cannot be ensured.

[0063] Meanwhile, in the method for manufacturing a semiconductor device according to Embodiment 4, the area of ​​the pusher plate 32 is made sufficiently smaller than the area of ​​the lower surface 30C of the recessed part 30A of the lower mold 30. Therefore, in the injection step, rightward and leftward flows of the resin 23 are generated in addition to the upward flow of the resin 23. Accordingly, a void above the die pad part can be suppressed. Providing the pusher plate 32 at the center of the lower surface 30C of the recessed part 30A also contributes to the resin 23 spreading to the corners of the cavity.

[0064] In particular, the features of the semiconductor devices and the methods for manufacturing a semiconductor device according to the aforementioned embodiments can be combined. List of reference symbols

[0065] 10 semiconductor device, 12 lead frame, 14 semiconductor chip, 20 first resin, 22 second resin, 30 lower mold, 30A recessed part, 32 plunger plate, 40 upper mold, 40A recessed part

Claims

[1] A method for manufacturing a semiconductor device (10), comprising: - a resin preparation step (S1) - for providing a tappet plate (32) in a hole (30a) formed in a recessed part (30A) of a lower mold (30), - for providing a first resin (20a) on the tappet plate (32), and - for providing a second resin (22a) having a lower thermal conductivity than the first resin (20a) on the first resin (20a); - a mounting step (S2) for placing a lead frame (12) on an upper surface of which a semiconductor chip (14) is mounted on an upper surface of the recessed part (30A); - a mold clamping step (S3) for placing an upper mold (40) on the lower mold (30), and for performing mold clamping in a state in which the semiconductor chip (14) is housed in a cavity formed by the lower mold (30) and the upper mold (40); - an injection step (S4) for lifting the plunger plate (32) after the first resin (20) and the second resin (22) have been melted to provide the second resin (22) in the cavity, and by subsequently introducing the first resin (20), the first resin (20) is brought into contact with a lower surface of the lead frame (12); and - a pressure maintaining step (S5, S7) for exerting a pressure on the first resin (20) and the second resin (22) through the plunger plate (32), and for maintaining the pressure. [2] The method according to claim 1, wherein in the injection step (S4) and the pressure maintaining step (S5, S7), a movable pin (42) is brought into contact with the upper surface of the lead frame (12) to prevent the lead frame (12) from floating. [3] The method of claim 1 or 2, wherein the first resin (20) comprises aluminum oxide and the second resin (22) comprises silicon oxide. [4] A method for manufacturing a semiconductor device (10), comprising: - a resin preparation step (S1) - for providing tappet plates (32A, 32B) in holes formed in a lower mold (90) having a plurality of recessed parts (90A, 90B), and - for providing resins (23a) on the tappet plates (32A, 32B); - a mounting step (S2) for placing a lead frame (12, 13) to which a semiconductor chip (14) is attached on an upper surface of the lower mold (90); - a mold clamping step (S3) for placing an upper mold (92) on the lower mold (90), and for performing mold clamping in a state in which a plurality of cavities (50A, 50B) formed by the plurality of recessed parts (90A, 90B) and a runner (50C) connecting the plurality of cavities (50A, 50B) are formed; - an injection step (S4) for raising the tappet plates (32A, 32B) to a predefined position after the resin (23) has been melted to provide the resin (23) in the plurality of cavities (50A, 50B) and the runner (50C); and - a pressure maintaining step (S5, S7) for exerting pressure through the plunger plates (32A, 32B) on the resin (23) and maintaining the pressure, wherein: - a pressure exerted by the resin (23) in the runner (50C) on a movable block (102) in the runner (50C) is detected when the ram plate (32A, 32B) is raised to the predefined position, - the movable block (102) is moved in a direction in which it is withdrawn from the runner (50C) when the pressure is greater than a predefined pressure, and - the movable block (102) is moved in a direction in which it is advanced into the runner (50C) when the pressure is less than the predefined pressure. [5] A method according to any one of the preceding claims, wherein in a plan view, an area of ​​the tappet plate (32A, 32B) is smaller than an area of ​​a lower surface of the recessed part (90A, 90B). [6] The method according to any one of claims 1 to 4, wherein an area of ​​the tappet plate (32A, 32B) in a plan view corresponds to not more than one half of an area of ​​a lower surface of the recessed part (90A, 90B). [7] The method according to claim 5 or 6, wherein the tappet plate (32A, 32B) is located at a center of the lower surface of the recessed part (90A, 90B). [8] A method according to any one of the preceding claims, wherein the tappet plate (32A, 32B) is circular in plan view. [9] Method according to one of the preceding, wherein: - the tappet plate (32) is carried by a tappet rod (34), and - a ball tappet (54) is brought into contact with a lateral surface of the push rod (34). [10] A method according to any one of the preceding claims, wherein the injection step (S4) and the pressure maintaining step (S5, S7) are carried out jointly for a plurality of cavities (50A, 50B).

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