Semiconductor device and heat sink assembly and method for assembling a semiconductor device and a heat sink

Abstract

To suppress the occurrence of a damage in a semiconductor device when external force is applied.SOLUTION: A semiconductor device is provided by the present invention. A first lead frame includes a first reinforcement part extending in a second terminal direction over a sealing member center line and connecting a plurality of first fixing parts and a first terminal, A second lead frame includes a second reinforcement part extending in a first terminal direction over the sealing member center line and connecting a plurality of second fixing parts and a second terminal. The first reinforcement part and the second reinforcement part overlap by a width W expanding horizontally from each sealing member center line.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a semiconductor device having a structure in which a substrate is sealed with a sealing member. [Background technology]

[0002] Known examples of conventional inventions relating to semiconductor devices include the semiconductor device described in Patent Document 1. In this semiconductor device, a substrate on which elements and the like are mounted is sealed in a resin package with screw holes formed on both sides, and screws are passed through the screw holes of the semiconductor device and screwed to a heat sink, thereby attaching the semiconductor device in close contact with the heat sink and improving heat dissipation. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2006-237305 A Summary of the Invention [Problem to be solved by the invention]

[0004] FIG. 1 shows the structure of a conventional semiconductor device.

[0005] As shown in Fig. 1(A), lead terminals 101 are soldered and fixed to a substrate 100 on which electronic components such as semiconductor elements are mounted, and then the whole is sealed in a resin package 102 to form a semiconductor device 103. Next, as shown in Fig. 1(B), the semiconductor device 103 is fixed to a heat sink 105 with screws 104.

[0006] Incidentally, in a semiconductor device using a power semiconductor, it is required that the heat sink 105 and the semiconductor device 103 are completely in close contact with each other in order to improve the heat dissipation effect. If the heat sink 105 and the semiconductor device 103 are completely flat, they can be screwed together with the screw 104 to make them in close contact with each other. However, it is difficult to manufacture the mounting surfaces completely flat in this way. Therefore, as shown in FIG. 1(A), it is common to form the mounting surface of the semiconductor device 103 to be slightly convex downward and the mounting surface of the heat sink 105 to be slightly convex upward, and then screw the semiconductor device 103 and the heat sink 105 together to make them in close contact with each other. FIG. 1(B) shows the state in which the semiconductor device 103 and the heat sink 105 are in close contact with each other after screwing. In FIG. 1(B), the hardness of the semiconductor device 103 is smaller than that of the heat sink 105 made of a metal material, so the mounting surface of the semiconductor device 103 bends along the mounting surface of the heat sink 105. In order to facilitate understanding, FIG. 1 shows the heat sink 105 and the semiconductor device 103 in a slightly exaggerated convex warped state.

[0007] 1B, although the semiconductor device 103 and the heat sink 105 can be brought into close contact, the semiconductor device 103 bends to become convex upwards to match the surface of the heat sink 105. At this time, since the hardness of the resin package 102 is not large, a large stress is generated in the center portion indicated by L of the semiconductor device 103. Specifically, a bending moment force of F×A is generated in the center portion indicated by L of the semiconductor device 103. This moment force generates an excessive stress in the center portion of the substrate 100, which may cause a crack 106 in the substrate 100.

[0008] SUMMARY OF THE PRESENT EMBODIMENT An object of the present invention is to provide a semiconductor device that can prevent damage caused by stress due to bending when fastened with screws. [Means for solving the problem]

[0009] According to one aspect of the present invention Semiconductor device and heat sink assembly teeth, a semiconductor device; and a heat sink having an upper surface formed to be slightly convex upward, the semiconductor device comprising: a rectangular substrate having an element and a pattern on its upper surface; first and second plate-like lead frames electrically connected to the substrate and fixed on the substrate; and a sealing member, the first lead frame having a first reinforcing portion extending from one side to the other side in the longitudinal direction of the substrate along the upper surface of the substrate, a first terminal connected to the first reinforcing portion, and a first fixing portion having an upper end connected to the first reinforcing portion and a lower end fixed to the substrate, the second lead frame having a second reinforcing portion extending from the other side to the one side in the longitudinal direction of the substrate along the upper surface of the substrate, a second terminal connected to the second reinforcing portion, and a first fixing portion having an upper end connected to the second reinforcing portion. a second fixing portion connected to the first lead frame and having a lower end fixed to the substrate, the first reinforcing portion and the second reinforcing portion being spaced apart from each other such that a part of the first reinforcing portion and a part of the second reinforcing portion overlap each other when viewed from the short-side direction of the substrate, the sealing member covers the outer peripheral surface and the upper surface of the integrated body of the first lead frame, the second lead frame and the substrate except for the first terminals and the second terminals, and has a plate-like rectangular parallelepiped shape as a whole, screw holes are formed at both ends of the sealing member in the longitudinal direction for screwing the sealing member to the upper surface of the heat sink, and the sealing member is screwed to the heat sink by screws inserted into the screw holes such that the lower surface of the sealing member abuts against the upper surface of the heat sink. .

[0010] According to another aspect of the present invention, Semiconductor device and method for assembling heat sink teeth, The method includes the steps of preparing a heat sink having an upper surface that is slightly convex upward, preparing a semiconductor device, and attaching the semiconductor device to the heat sink, the semiconductor device comprising: a rectangular substrate having an element and a pattern on an upper surface thereof; first and second plate-like lead frames that are electrically connected to the substrate and fixed on the substrate; and a sealing member, the first lead frame having a first reinforcing portion extending from one side to the other side in the longitudinal direction of the substrate along the upper surface of the substrate, a first terminal connected to the first reinforcing portion, and a first fixing portion having an upper end connected to the first reinforcing portion and a lower end fixed to the substrate, the second lead frame having a second reinforcing portion extending from the other side to the one side in the longitudinal direction of the substrate along the upper surface of the substrate, a second terminal connected to the second reinforcing portion, and a first fixing portion having an upper end connected to the second reinforcing portion. and a second fixing portion whose lower end is fixed to the substrate, the first reinforcing portion and the second reinforcing portion are spaced apart from each other so that a portion of the first reinforcing portion and a portion of the second reinforcing portion overlap each other when viewed from the short side direction of the substrate, the sealing member covers the outer peripheral surface and upper surface of the integrated body of the first lead frame, the second lead frame and the substrate, excluding the first terminal and the second terminal, and has an overall plate-like rectangular shape with a lower surface slightly warped downwardly and convexly, screw holes are formed at both longitudinal ends of the sealing member for screwing the sealing member to the upper surface of the heat sink, and the process of attaching the semiconductor device to the heat sink is a process of screwing the sealing member to the heat sink with screws inserted into the screw holes, with the lower surface of the sealing member abutting the upper surface of the heat sink. Effect of the Invention

[0011] According to the semiconductor device of the present invention, damage to the semiconductor device caused by the bending force applied when the semiconductor device is fastened with screws can be suppressed. [Brief description of the drawings]

[0012] [Figure 1] 1A and 1B are cross-sectional views for explaining a problem that occurs after a conventional semiconductor device is fastened with screws. [Diagram 2] 1A and 1B are a top view and a left view of a semiconductor device according to an embodiment of the present invention. [Diagram 3] 1 is a top view showing a structure of a lead frame of a semiconductor device according to an embodiment; [Figure 4] 13 is a perspective view of a first reinforcing portion 13d and a second reinforcing portion 13e. FIG. [Diagram 5] 5A and 5B are cross-sectional views for explaining the effect of the semiconductor device according to the embodiment after it is screwed. [Figure 6] 13 is a top view showing a structure of a lead frame of a semiconductor device according to a modified example. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] (Embodiment) A semiconductor device 10 according to an embodiment of the present invention will be described below with reference to Fig. 2 and Fig. 3. Fig. 2(A) and (B) are a top view and a left view of the semiconductor device according to the embodiment of the present invention. Fig. 3 is a top view showing the structure of a lead frame of the semiconductor device according to the embodiment.

[0014] In these drawings, the longitudinal direction of the semiconductor device 10 may be referred to as the left-right direction, and the lateral direction as the up-down direction.

[0015] The semiconductor device 10 has an external appearance in the form of a rectangular parallelepiped sealing member 15 having long and short sides, with a plurality of input / output terminals 14 protruding from the sealing member 15. In this example, the plurality of input / output terminals 14 are bent downward. Note that the input / output terminals 14 do not necessarily have to be bent.

[0016] The semiconductor device 10 includes, for example, a power semiconductor that controls and supplies power. The semiconductor device 10 includes a substrate 12 on which elements such as power semiconductors are mounted and patterns are formed. The semiconductor device 10 is wired with an input side lead frame 11a, a first output side lead frame 11d, and a second output side lead frame 11e. The input side lead frame 11a is formed by punching and bending a single metal plate. Similarly, the first and second output side lead frames 11d and 11e are also formed by punching and bending a single metal plate. The first output side lead frame 11d corresponds to the first lead frame of the present invention. The second output side lead frame 11e corresponds to the second lead frame of the present invention.

[0017] The manufacturing process of the semiconductor device 10 includes a first step of forming a metal plate for a lead frame into a predetermined shape by cutting and bending a single metal plate, a second step of fixing the metal plate for the lead frame to the substrate 12, a third step of sealing with a sealing member 15, and a fourth step of cutting the connecting portions of the metal plate for the lead frame to form terminals.

[0018] In the first step, the metal plate for the input side lead frame including the input side lead frame 11a and the metal plate for the output side lead frame including the first output side lead frame 11d and the second output side lead frame 11e are formed into a predetermined shape. All the input terminals 14a of the input side lead frame 11a are connected to the metal plate for the input side lead frame. The first output terminal 14d of the first output side lead frame 11d and the second output terminal 14e of the second output side lead frame 11e are connected to the metal plate for the output side lead frame. The first output side lead frame 11d further includes three first fixing parts 20d. The second output side lead frame 11e further includes three second fixing parts 20e.

[0019] The first output terminal 14d corresponds to the first terminal of the present invention, and the second output terminal 14e corresponds to the second terminal of the present invention.

[0020] In the second step, the fixing portion 20a of the metal plate for the input side lead frame is fixed to a predetermined position on the substrate 12. Also, the first fixing portion 20d and the second fixing portion 20e of the metal plate for the output side lead frame are fixed to predetermined positions on the substrate 12.

[0021] In the third step, each lead frame metal plate is sealed with a sealing member 15. At this time, the input terminal 14a of the input side lead frame metal plate and the first output terminal 14d and the second output terminal 14e of the output side lead frame metal plate are exposed.

[0022] In the fourth step, three input side lead frames 11a are formed by cutting the connecting portions of the metal plate for the input side lead frame. That is, three separate input terminals 14a are formed. Similarly, a first output side lead frame 11d and a second output side lead frame 11e are formed by cutting the connecting portions of the metal plate for the output side lead frame. That is, two separate first output terminals 14d and second output terminals 14e are formed.

[0023] Through the above steps, three input lead frames 11a, a first output lead frame 11d, and a second output lead frame 11e are formed. Then, the input / output terminals 14 are bent as necessary, thereby completing the semiconductor device 10.

[0024] The structure of the completed semiconductor device 10 will now be described with reference to FIG.

[0025] The input side lead frame 11a has three input terminals 14a exposed from the sealing member 15. The first output side lead frame 11d has a first output terminal 14d exposed from the sealing member 15. The second output side lead frame 11e has a second output terminal 14e exposed from the sealing member 15.

[0026] The input lead frame 11a has a fixed portion 20a bent from above the substrate 12 downward toward the substrate 12. Similarly, the first output lead frame 11d has a first fixed portion 20d bent from above the substrate 12 downward toward the substrate 12. The second output lead frame 11e has a second fixed portion 20e bent from above the substrate 12 downward toward the substrate 12.

[0027] The fixed portion 20a of the input lead frame 11a is fixed to the pattern of the substrate 12. The first fixed portion 20d of the first output lead frame 11d is bonded to the upper surface of the element. The second fixed portion 20e of the second output lead frame 11e is bonded to the upper surface of the element.

[0028] The input terminal 14a, the first output terminal 14d, and the second output terminal 14e are exposed from the sealing member 15, and the input side lead frame 11a, the first output side lead frame 11d, and the second output side lead frame 11e are sealed by the sealing member 15 together with their fixed portions.

[0029] The sealing member 15 has screw holes 16a, 16b formed at both left and right ends.

[0030] Next, the shapes of the first output side lead frame 11d and the second output side lead frame 11e will be described in detail with reference to Fig. 3. In Fig. 3, a line connecting the midpoints of the upper and lower long sides of the sealing member 15 is taken as a center line L.

[0031] The first output-side lead frame 11d has a first reinforcing portion 13d extending rightward from the left end beyond the center line L along the long side of the upper side of the sealing member 15 in Fig. 2. The first output terminal 14d and the first fixed portion 20d are connected by this first reinforcing portion 13d.

[0032] The second output lead frame 11e has a second reinforcing portion 13e that extends from the right end of the upper side of the sealing member 15 to near the center of the substrate 12 and further extends from this portion toward the first output terminal 14d. In other words, the second output lead frame 11e has a second reinforcing portion 13e that extends downward in the figure from the right end of the upper side of the sealing member 15 and further extends leftward beyond the center line L along the long side of the upper side of the sealing member 15. The second reinforcing portion 13e has an inverted L shape as a whole. The second output terminal 14e and the second fixed portion 20e are connected by this second reinforcing portion 13e.

[0033] Due to the above-mentioned shape, the first reinforcing portion 13d and the second reinforcing portion 13e overlap with each other over a width W that extends to the left and right from the center line L of the sealing member.

[0034] FIG. 4 shows a perspective view of the first reinforcing portion 13d and the second reinforcing portion 13e.

[0035] As shown in the figure, the first reinforcing portion 13d and the second reinforcing portion 13e overlap with each other by a predetermined width W that extends to the left and right from the center line L. Therefore, the first reinforcing portion 13d and the second reinforcing portion 13e are embedded in the sealing member 15 in a state where they overlap beyond the center line L of the sealing member 15. The first reinforcing portion 13d and the second reinforcing portion 13e are composed of parts of the first output side lead frame 11d and the second output side lead frame 11e, and are formed without adding a separate member or a separate process.

[0036] 5(A) and (B) are cross-sectional views for explaining the states before and after screwing of the semiconductor device 10. These cross-sectional views show a cross section taken along the line AA in FIG.

[0037] As shown in FIG. 5(A), before the semiconductor device 10 is screwed, the mounting surface of the semiconductor device 10 is formed to be slightly convex downward, and the mounting surface of the heat sink 20 is formed to be slightly convex upward. Note that FIG. 5 shows the heat sink 105 and the semiconductor device 103 in a slightly exaggerated state in order to make it easier to understand. In this state, the screw j30 is inserted into the screw hole of the sealing member 15 and screwed to bring the semiconductor device 10 and the heat sink 20 into close contact. FIG. 5(B) shows the state in which the semiconductor device 10 and the heat sink 20 are in close contact after screwing. In FIG. 5(B), the hardness of the semiconductor device 10 is smaller than that of the heat sink 20, so the mounting surface of the semiconductor device 10 bends along the mounting surface of the heat sink 20. At this time, a force F is applied by tightening the screw 30, so a bending moment force is generated in the range from the screw 30 to the center line L, and this moment force generates stress in the board 12. Note that similar stresses are generated on both sides of the center line L.

[0038] However, as shown in Fig. 4, the first reinforcing portion 13d and the second reinforcing portion 13e overlap with a width W that extends from the center line L to the left and right, so the strength of the substrate 12 is reinforced and the stress does not concentrate in the center of the center line L. The stress is dispersed to the first reinforcing portion 13d and the second reinforcing portion 13e. As a result, as shown in Fig. 5(B), it is possible to prevent excessive stress from concentrating near the center line L of the substrate 12 and causing cracks.

[0039] Here, what is important is that the first reinforcement portion 13d and the second reinforcement portion 13e overlap with a width W that spreads from the center line L to the left and right. If the substrate 12 were reinforced only with the first reinforcement portion 13d or the second reinforcement portion 13e, a space would be generated in the left and right direction of the first output side lead frame 11 and the second output side lead frame 11e where the reinforcement portion is missing. Then, when the semiconductor device 10 is screwed, excessive stress would be applied to a portion of the substrate 12 corresponding to this space. In the embodiment, since the first reinforcement portion 13d and the second reinforcement portion 13e overlap with a width W that spreads from the center line L to the left and right, there is no space in the left and right direction of the first output side lead frame 11 and the second output side lead frame 11e where the reinforcement portion is missing. Therefore, when the semiconductor device 10 is screwed, no portion is generated in the substrate 12 that becomes weak due to stress.

[0040] Moreover, since the first reinforcing portion 13d and the second reinforcing portion 13e overlap with a width W that spreads out laterally from the center line L, excessive stress near the center line L of the substrate 12 can be further prevented.

[0041] The width W is experimentally designed to be an optimum value based on the size of the semiconductor device 10 including its left and right length, the degree of bending when the semiconductor device 10 is screwed, etc. Also, it is desirable for the width W to be a value that expands by the same dimension on both sides about the center line L, but some deviation in the left and right dimensions is permissible.

[0042] With the above-mentioned structure, the semiconductor device 10 can be fixed to the heat sink 20 by the screw 30 through the screw holes 16a and 16b (not shown) formed on the short side of the semiconductor device 10. In the semiconductor device 10, the strength of the substrate 12 is increased by the first reinforcing portion 13d and the second reinforcing portion 13e, and the stress generated in the substrate 12 is dispersed to the first reinforcing portion 13d and the second reinforcing portion 13e. Therefore, damage to the substrate 12 due to the above-mentioned stress, particularly the occurrence of cracks near the center line L of the substrate 12, can be suppressed. In this way, the substrate 12 of the semiconductor device 10 is reinforced by the first reinforcing portion 13d and the second reinforcing portion 13e, and as a result, cracks near the center line L of the semiconductor device 10 where the maximum stress is likely to occur can be prevented.

[0043] (Modification) A semiconductor device 10a according to a modified example will be described below with reference to the drawings. Fig. 6 is a top view showing the structure of a lead frame of the semiconductor device according to the modified example.

[0044] The semiconductor device 10a has the same external shape as the semiconductor device 10. The wiring inside the semiconductor device 10a, that is, the shapes of the first output side lead frame 11d and the second output side lead frame 11e, are different from those of the semiconductor device 10. Specifically, compared to the semiconductor device 10, the semiconductor device 10a has a smaller number of elements and a smaller number of first fixing portions 20d of the first output side lead frame 11d and second fixing portions 20e of the second output side lead frame 11e.

[0045] A semiconductor device 10a shown in FIG. 6 differs from the semiconductor device 10 in FIG. 2 in that the first reinforcing portions 13d and the second reinforcing portions 13e are aligned in a row in the left-right direction, whereas they are aligned in two rows.

[0046] The first output-side lead frame 11d has a first reinforcing portion 13d extending rightward from the upper left end of the sealing member 15 along its upper side. The first reinforcing portion 13d connects the first output terminals 14d. The first reinforcing portion 13d has a first narrow width portion 13d-1 extending from slightly to the left of the center line L, beyond the center line L, toward the second reinforcing portion 13e on the right side.

[0047] The second output-side lead frame 11e has a second reinforcing portion 13e extending leftward along the upper side from the upper right end of the sealing member 15. The second reinforcing portion 13e connects the second output terminals 14e. The second reinforcing portion 13e has a second narrow width portion 13e-1 extending from a position slightly to the right of the center line L, beyond the center line L, toward the first reinforcing portion 13d on the left side.

[0048] The first narrow width portion 13d-1 is located above the second narrow width portion 13e-1. The first narrow width portion 13d-1 and the second narrow width portion 13e-1 overlap with each other at a width W extending from the center line L to the left and right, with a predetermined insulation clearance in the vertical direction between them. The predetermined insulation clearance is set to a length at which insulation is maintained between the first narrow width portion 13d-1 and the second narrow width portion 13e-1. This width is determined by the magnitude of the current flowing through the first narrow width portion 13d-1 and the second narrow width portion 13e-1.

[0049] In the above configuration, the first reinforcing portion 13d and the second reinforcing portion 13e overlap with a width W' that spreads left and right from the center line L, so the strength of the substrate 12 is reinforced and the stress does not concentrate in the center of the center line L. The stress is dispersed to the first reinforcing portion 13d and the second reinforcing portion 13e. As a result, as in the embodiment shown in FIG. 5(B), it is possible to prevent excessive stress from concentrating near the center line L of the substrate 12 and causing cracks.

[0050] The semiconductor device according to the present invention is not limited to the semiconductor device 10, 10a, and can be modified within the scope of the present invention. In addition, the configurations of the semiconductor device 10, 10a may be arbitrarily combined. As long as the fixing parts for mounting the lead frame to the element or the substrate are connected by the reinforcing parts overlapping near the center line L of the long side of the semiconductor device 10, 10a, the input side and output side of the present example are not limited. [Explanation of symbols]

[0051] 10, 10a: semiconductor device 11d: First output lead frame 11e: Second output lead frame 12: Substrate

Claims

1. A heat sink having an upper surface formed so as to be slightly convex upward; A semiconductor device, The semiconductor device includes a rectangular substrate having an element and a pattern on an upper surface thereof, first and second plate-like lead frames electrically connected to the substrate and fixed onto the substrate, and a sealing member; the first lead frame has a first reinforcing portion extending from one side to the other side in a longitudinal direction of the substrate along an upper surface of the substrate, a first terminal connected to the first reinforcing portion, and a first fixed portion having an upper end connected to the first reinforcing portion and a lower end fixed to the substrate; the second lead frame has a second reinforcing portion extending from the other side to the one side in the longitudinal direction of the substrate along an upper surface of the substrate, a second terminal connected to the second reinforcing portion, and a second fixed portion having an upper end connected to the second reinforcing portion and a lower end fixed to the substrate, the first reinforcing portion and the second reinforcing portion are spaced apart from each other such that a portion of the first reinforcing portion and a portion of the second reinforcing portion overlap each other when viewed from a short-side direction of the substrate, the sealing member covers an outer peripheral surface and an upper surface of an integrated body of the first lead frame, the second lead frame, and the substrate, except for the first terminals and the second terminals, and has a plate-like rectangular parallelepiped shape as a whole; a screw hole for screwing the sealing member to the upper surface of the heat sink at both ends in a longitudinal direction of the sealing member; the sealing member is screwed to the heat sink by screws inserted through the screw holes so that a lower surface of the sealing member abuts an upper surface of the heat sink, in the semiconductor device and heat sink assembly.

2. A step of preparing a heat sink having an upper surface formed to be slightly convex upward; providing a semiconductor device; and attaching the semiconductor device to the heat sink; The semiconductor device includes a rectangular substrate having an element and a pattern on an upper surface thereof, first and second plate-like lead frames electrically connected to the substrate and fixed onto the substrate, and a sealing member; the first lead frame has a first reinforcing portion extending from one side to the other side in a longitudinal direction of the substrate along an upper surface of the substrate, a first terminal connected to the first reinforcing portion, and a first fixed portion having an upper end connected to the first reinforcing portion and a lower end fixed to the substrate; the second lead frame has a second reinforcing portion extending from the other side to the one side in the longitudinal direction of the substrate along an upper surface of the substrate, a second terminal connected to the second reinforcing portion, and a second fixed portion having an upper end connected to the second reinforcing portion and a lower end fixed to the substrate, the first reinforcing portion and the second reinforcing portion are spaced apart from each other such that a portion of the first reinforcing portion and a portion of the second reinforcing portion overlap each other when viewed from a short-side direction of the substrate, the sealing member covers an outer peripheral surface and an upper surface of an integrated body of the first lead frame, the second lead frame, and the substrate, except for the first terminals and the second terminals, and has a plate-like rectangular parallelepiped shape as a whole, the lower surface of which is slightly warped downwardly in a convex manner, a screw hole for screwing the sealing member to the upper surface of the heat sink at both ends in a longitudinal direction of the sealing member; A method for assembling a semiconductor device and a heat sink, wherein the step of attaching the semiconductor device to the heat sink is a step of screwing the sealing member to the heat sink with a screw inserted into the screw hole so that the lower surface of the sealing member abuts the upper surface of the heat sink.

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