JP4426481B2 - Semiconductor device - Google Patents

Description

  The present invention relates to a semiconductor device, and more particularly, to a semiconductor device to which a radiation fin is attached.

2. Description of the Related Art Conventionally, a semiconductor device that generates a large amount of heat, for example, a semiconductor device in which a power semiconductor element is packaged with a resin, is attached with a radiation fin for releasing generated heat to the outside of the package. As schematically shown in FIG. 8, the semiconductor device 510 includes a heat sink 514 that is thermally connected to a semiconductor element and exposed from the package 512 in order to release heat to the outside of the package 512. The radiation fins 516 are contacted and fixed. The heat radiation fins 516 are fixed to the semiconductor device 510 with screws 518. The semiconductor device 510 has a U-shaped notch 520 on the outer edge, and a female screw that is screwed with the head 524 of the screw 518 and the screw 518 in a state where the shaft 522 of the screw 518 is accommodated in the notch 520. It fixes with respect to the radiation fin 516 so that it may be pinched | interposed into the radiation fin 516 in which 526 was formed. As shown in the figure, a washer 528 is disposed between the head 524 of the screw 518 and the semiconductor device 510. As a semiconductor device having a U-shaped cutout, for example, there is one disclosed in Patent Document 1.
JP 2002-208649 A

  However, when the screws are tightened to fix the radiating fins to the semiconductor device described above, the resin package is cracked, and in some cases, the package may be chipped. For example, as shown in FIG. 9A, when the screw 518 is tightened by rotating in the clockwise direction 530, the package 512 of the semiconductor device 510 is sandwiched between the head 524 of the screw 518 and the heat radiation fin 516. Receiving compression force. At the same time, the washer 528 rotates in response to the rotation of the screw 518 while being pressed against the package 512 by the head 524 of the screw 518. At this time, as shown in FIG. 9B, a portion (hatched portion in the drawing) 534 of the surface 532 of the package 512 that contacts the washer 528 receives a shearing force. As a result, a crack 542 is generated in the corner portion 540 sandwiched between the notch portion 520 and the side surface 538 that receives the outward shearing force 536 while receiving the compressive force. When the generated crack 542 develops, it may be chipped from the crack 542. Of course, if a crack or chip occurs, the reliability of the semiconductor device decreases.

  In view of the above, an object of the present invention is to provide a semiconductor device having a configuration capable of suppressing the occurrence of cracks due to screw tightening when attaching a radiation fin.

In order to achieve the above object, a semiconductor device according to the present invention has a notch, and a female screw that engages with the screw head and the screw in a state where a shaft portion of the screw is accommodated in the notch. A semiconductor device in which a semiconductor element mounted on a lead frame is sealed with a resin package and is fixed to the other member so as to be sandwiched between other members having a portion,
Formed by chamfering the apex formed by the side surface on which the notch is formed , the surface of the notch , and the surface in contact with the head of the screw, or the surface of the notch and the screw formed by chamfering the edges between the head and the contact surface, a chamfer for avoiding contact with the head of the screw when it is fixed by the screw to the other member,
When it secured by the screw to the other member, the compression force and entailment to the portion of the package located between the head and the other member of the screw, received from the said other member and the screw And a package reinforcing member that increases the rigidity of the portion so as to resist the above .

According to the present invention, by having the chamfered portion and the package reinforcing member, the occurrence of cracks during tightening screws as compared with the case where there is no the chamfered portion and the package reinforcing member is suppressed.

  FIG. 1 is a schematic view of a semiconductor device according to an embodiment of the present invention to which heat radiating fins are attached. The semiconductor device 10 has a substantially rectangular plate-shaped resin package 12, and a plurality of outer leads for electrical connection with components other than the semiconductor device 10 (only a part is shown for simplification of the drawing). For example, it is a DIP (Dual In-line Package) type semiconductor device in which 14 protrudes from two opposing side surfaces 16. Although not shown, a lead frame (inner lead) integrated with the outer lead 14 and a semiconductor element electrically connected to the lead frame are sealed inside the resin package 12.

  Further, the semiconductor device 10 has a heat dissipation thermally connected to a semiconductor element sealed inside the resin package 12 exposed at a heat dissipation fin contact surface 18 for contact with a heat dissipation fin (not shown). It has a plate 20.

Furthermore, the semiconductor device 10 has a notch 24 formed on the two side surfaces 22 facing each other from the side surface 22 toward the central portion of the semiconductor device 10. The notch 24 has a U-shape when viewed from a direction perpendicular to the heat radiation fin contact surface 18. Further, a surface facing the heat radiating fin contact surface 18 (hereinafter referred to as a “washer contact surface” because it is a surface that contacts the washer as will be described later) 28, a notch surface 26 of the notch 24, And a triangular flank ( so-called chamfering, hereinafter referred to as “ flank ” ) 30 that forms a side with the three surfaces, such as a cut surface formed by cutting off the apex formed by the three surfaces of the side surface 22. Have. Hereinafter, the configuration of the semiconductor device 10 around the notch 24, which is a feature of the present invention, will be described.

  The notch 24 functions when the heat radiation fin is fixed to the semiconductor device 10 with the heat radiation fin in contact with the heat radiation fin contact surface 18 (heat radiation plate 20). Specifically, the heat radiating fins are fixed to the semiconductor device 10 with screws.

  FIG. 2A is a diagram (a diagram viewed from a direction perpendicular to the surface 28) showing the periphery of the notch when the radiating fin is fixed to the semiconductor device with a screw, and FIG. It is sectional drawing seen from the A direction in Fig.2 (a). FIG. 3 is a diagram for showing details of the configuration around the notch.

  As shown in FIGS. 2A and 2B, fixing between the semiconductor device 10 and the heat radiating fin 40 is performed by heat dissipation in which the package 12 of the semiconductor device 10 is screwed with the head portion 44 of the screw 42 and the screw 42. It is carried out so as to be held between the fins 40 via washers 46. As shown in FIG. 3, the notch portion 24 has a width w and a depth d (distance from the side surface 22) that the shaft portion 48 of the screw 42 can accommodate. In other words, the shape (dimension) of the notch 24 is determined by the screw used.

  The depth d of the notch is designed to be a size that can accommodate the shaft portion of the screw at a minimum. Therefore, when viewed from a direction perpendicular to the washer contact surface, the screw head and the washer protrude from the side surface where the notch is formed. This is because if the notch portion is formed so that the screw head and the washer are completely disposed on the washer contact surface, the semiconductor device body becomes unnecessarily large (cannot be reduced in size). Further, if the screw head and the washer are completely disposed on the washer contact surface, a through hole is formed instead of a notch.

  The escape portion 30 functions as a non-contact portion that avoids contact with the washer 46 at the corner portion 50 sandwiched between the notch portion 24 and the side surface 22. As shown in FIG. 3, the non-contact portion is a right angle whose length of two sides is c with the apex 54 of the cut-out surface 26 and the side surface 22 as viewed from the direction perpendicular to the washer contact surface 28. This is an isosceles triangular region. By providing the relief portion 30 in the corner portion 50, the contact area with the washer 46 is reduced as compared with the case where the relief portion 30 is not provided, and the shearing force received from the washer 46 during screw tightening is also reduced. Since the shearing force acting on the corner portion 50 is reduced, the generation of cracks is suppressed as compared with the case where the escape portion 30 is not provided.

  In addition, the occurrence of cracks in the corner 50 is caused not only by the shearing force received from the washer 46 during screw tightening but also by the compressive force received by being sandwiched between the head 44 of the screw 42 and the radiation fin 40. In order to suppress the occurrence of cracks due to this compressive force, the reinforcing member 52 made of a part of the inner lead is disposed in the package 12 so as to exist between the washer 46 and the heat radiating fin 40 when the heat radiating fin is attached. Yes. As a result, the rigidity of the portion of the package 12 between the washer 46 and the radiating fin 40 is increased to resist the compressive force received during screw tightening, and as a result, cracks are generated compared to the case where the reinforcing member 52 is not provided. It is suppressed.

  The inventor has demonstrated the effect of suppressing crack generation according to the present embodiment through experiments. The inventor first uses semiconductor devices having different dimensions of the depth d of the notch (see FIG. 3; in other words, the distance L from the side surface 22 where the notch is provided) to the screw, and the reinforcing member dissipates heat. We confirmed the effect of existing between the fin and washer. Moreover, the influence by the magnitude | size of an escape part was investigated using the semiconductor device from which the magnitude | size of an escape part (size of a non-contact part) differs. The screws used were M3 screws (shaft diameter 3 mm, head diameter 5.5 mm), and washer for M3 screws with an inner diameter of 3.3 mm and an outer diameter of 8 mm. The width w of the notch is 3.2 mm corresponding to the M3 screw.

  The effect of the presence of the reinforcing member and the influence of the size of the relief part are measured by measuring the screw tightening torque (N · m), and the torque when a crack occurs in the package of the semiconductor device (the package withstands without generating a crack). It was evaluated by the torque limit. The higher this limit torque, the harder it is to crack, in other words, the cracking is suppressed.

  FIG. 4 shows a table of experimental results showing the effect of the reinforcing member on five types of semiconductor devices 1 to 5 having different notches. In the illustrated table, “1.8 or more” indicates that no crack occurred even when the screw was tightened with a torque of 1.8 N · m. From the experimental results shown in FIG. 4, it can be seen that the limit torque increases as the depth d of the notch increases (the screw moves away from the side surface) regardless of the presence or absence of the reinforcing member (in other words, crack cracks). It can be seen that the occurrence is suppressed.) In all the semiconductor devices, the limit torque is larger when the reinforcing member is present than when the reinforcing member is not present. Thereby, it turns out that the reinforcement member has suppressed generation | occurrence | production of the crack.

  FIG. 5 shows a table showing limit torques for six types of semiconductor devices 1 to 6 (the semiconductor device 1 does not have a relief portion) with different sizes of relief portions (non-contact portions). Yes. In the figure, “1.8 or more” indicates that no crack occurred even if the screw was tightened with a torque of 1.8 N · m. From the experimental results shown in FIG. 5, the limit torque is generally larger when the escape portion is present (when the non-contact portion is present) than when the clearance portion is not present (as compared with the semiconductor device 1). Further, the larger the non-contact portion (in other words, the smaller the contact area with the washer at the corner portion), the greater the limit torque (the occurrence of cracks is suppressed). Thereby, it turns out that the escape part (non-contact part) has suppressed generation | occurrence | production of the crack.

  The semiconductor device according to the present invention has been described with reference to one embodiment. However, the present invention is not limited to this embodiment, and other embodiments are possible. As above-mentioned, the relief part which forms a non-contact part in the corner which contacts a washer at the time of screw tightening cuts off the vertex formed from the washer contact surface, the notch surface, and the side surface in which the notch part was formed. It does not have to be a triangular surface that forms sides with three surfaces, such as a cut surface that is formed in this manner.

For example, as shown in FIG. 6A, the notch surface 126 and the washer formed by cutting off the side formed between the notch surface 126 of the notch portion 124 and the washer contact surface 128. The surface 130 may be disposed between the contact surface 128. It is obvious that the semiconductor device 10 of the present embodiment can be variously changed by those skilled in the art. For example , as shown in FIG. 6 (b), the side surface 224 and the washer contact, which are formed by cutting off the side formed between the side surface 222 where the notch 224 is formed and the washer contact surface 228, are formed. The surface 230 may be disposed between the contact surface 228 and the contact surface 228. In this way, there are various relief portions that form non-contact portions for reducing the contact area with the washer at the side surface where the notch portion is formed and the corner portion sandwiched between the notch portions, and are described in this specification. It is clear that the occurrence of cracks is suppressed even in escape portions other than the above-described form. Semiconductor devices having relief portions other than those described in this specification are also included in the present invention.

  Further, the reinforcing member is not formed from a part of the inner lead as described above, but may be formed by a member different from the inner lead. Moreover, you may form in another shape different from the above-mentioned shape. As shown in FIGS. 7A and 7B (a cross-sectional view seen from the direction B in FIG. 7A), for example, the reinforcing member 352 in the package 312 is a notch surface 326 of the notch 324. The plate member may be a U-shaped curved plate member as viewed from a direction perpendicular to the washer contact surface 328. Alternatively, as shown in FIG. 7, a part of the inner lead may be curved in a U shape along the notch surface 326 of the notch 324 to constitute the reinforcing member. As described above, there are various reinforcing members arranged in the package so as to exist between the washer and the radiating fin when the radiating fin is attached, and the occurrence of cracks is suppressed even in the reinforced member other than the embodiment described in the present specification. It is clear. Semiconductor devices having reinforcing members other than those described in this specification are also included in the present invention.

  For confirmation, the semiconductor device according to the present invention is fixed to the radiating fin so as to be sandwiched between the washer and the radiating fin, but is sandwiched between the screw head and the radiating fin without the washer. It is clear that this is a possible form. In this case, the relief portion forms a non-contact portion for reducing a contact area with the head portion of the screw at a corner portion sandwiched between the side surface where the notch portion is formed and the notch portion, and the reinforcing member is It arrange | positions in a package so that it may exist between the head of a screw and a radiation fin at the time of a radiation fin attachment.

  Finally, it is obvious that the semiconductor device according to the present invention is not limited to being attached to the heat radiating fins, and can be attached to members other than the heat radiating fins. Further, the cutout portion may have a shape other than the U shape when viewed from a direction perpendicular to the washer contact surface, and may be, for example, a U shape.

1 is a schematic external view of a semiconductor device according to the present invention. It is the figure which showed the notch part of the semiconductor device at the time of a radiation fin attachment. It is a figure for showing the detail of the notch part of a semiconductor device. It is a figure which shows the table | surface of the experimental result which demonstrates the effect of a reinforcement member. It is a figure which shows the table | surface of the experimental result which demonstrates the effect of an escape part. It is a figure which shows the notch part of the semiconductor device which concerns on other embodiment. It is a figure which shows the reinforcement member of the semiconductor device which concerns on other embodiment. It is a figure which shows the conventional semiconductor device and the attachment method of a radiation fin. It is a figure for demonstrating generation | occurrence | production of a crack in the package of the conventional semiconductor device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Semiconductor device, 12 Package, 14 Outer lead, 16 Side surface, 18 Radiation fin contact surface, 20 Heat sink, 22 Side surface, 24 Notch part, 26 Notch surface, 28 Washer contact surface, 30 Escape surface, 40 Heat dissipation Fin, 42 Screw, 44 Head, 46 Washer, 48 Shaft, 50 Corner, 52 Reinforcement, 54 Vertex,
122 side surface, 124 notch, 126 notch surface, 128 washer contact surface, 130 surface,
222 side surface, 224 notch, 226 notch surface, 228 washer contact surface, 230 surface,
312 package, 324 notch, 326 notch surface, 328 washer contact surface, 352 reinforcing member,
510 Semiconductor Device, 512 Package, 514 Radiation Plate, 516 Radiation Fin, 518 Screw, 520 Notch, 522 Shaft, 524 Head, 526 Female Screw, 528 Washer, 530 Rotation Direction, 532 Surface, 534 Contact Portion, 536 Shear force, 538 sides, 540 corners, 542 crack

Claims (4)

It has a notch on the outer edge, and is sandwiched between the head of the screw and another member having a female screw that is screwed with the screw in a state where the shaft portion of the screw is accommodated in the notch. A semiconductor device formed by sealing a semiconductor element mounted on a lead frame with a resin package, which is fixed to the other member as described above,
Formed by chamfering the apex formed by the side surface on which the notch is formed , the surface of the notch , and the surface in contact with the head of the screw, or the surface of the notch and the screw formed by chamfering the edges between the head and the contact surface, a chamfer for avoiding contact with the head of the screw when it is fixed by the screw to the other member,
And entailment to the package portion located between the head and the other member of the screw when it is fixed by the screw to the other member, the compressive force received from the said other member and the screw A semiconductor device comprising: a package reinforcing member that increases the rigidity of the portion so as to resist . Be one that is fixed to the other member so as to be sandwiched between the washer and the other member disposed between the head of the screw,
The chamfered portion avoids contact with the washer;
The semiconductor device according to claim 1, wherein the package reinforcing member is included in the package so as to be between the washer and another member. 3. The semiconductor device according to claim 1, wherein the package reinforcing member is a part of an inner lead of a lead frame. The semiconductor device according to claim 1, wherein the other member is a heat radiating fin.

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