JP2015216228A - Resin sealed electric power semiconductor device and manufacturing method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a resin sealed electric power semiconductor device and a manufacturing method thereof capable of reducing the size while ensuring a proper insulation distance and preventing short-circuiting due to crossing wires.SOLUTION: A resin sealed electric power semiconductor device 20 includes: plural semiconductor elements 3; plural lead frames 2 for supplying the power to the semiconductor elements 3; and plural wires 7 connecting the semiconductor elements 3 and the lead frames 2 therebetween. The semiconductor element 3, the lead frame 2 and the plural wires 7 are sealed with a mold resin. The plural wires 7 are disposed in parallel extending in a direction crossing a flow direction of the mold resin 15. The wiring length of the wire 7 at the downstream side of the flow direction is equal to or larger than the wiring length of the wire 7 at the upstream side in the flow direction.

Description

  The present invention relates to a resin-encapsulated power semiconductor device and a method for manufacturing the same, and to a reliability securing method for an inherent loop wire.

  As a conventional semiconductor device, a device in which a built-in substrate and a lead frame are connected by a thick aluminum wire is known (see, for example, Patent Document 1).

JP 2013-175609 A

  The power semiconductor devices for factory automation (FA) devices such as inverters, servo amplifiers, and programmable logic controllers have the following problems. A plurality of FA devices are arranged in the control panel in the horizontal direction. However, if the width is 10 mm wide, for example, if 10 devices are arranged, the width of the control panel is increased by 100 mm. As a form of FA equipment, there is a so-called bookshelf type in which the thickness is reduced, and this type meets the customer's needs for miniaturization. Large is a particularly big issue.

  For this reason, there is a demand for reducing the width of the power semiconductor device itself used for the FA equipment as much as possible.

  When manufacturing a resin-encapsulated power semiconductor device, the electrodes provided at various locations of the lead frame are connected to the substrate with wires, and the mold resin is applied from the horizontal direction to the lead frame and substrate disposed in the mold. When injected, the mold resin flows horizontally in the mold. At this time, the mold resin is liquefied, but when the liquefied resin collides with the wire from the direction perpendicular to the extending direction of the wire, a phenomenon of wire flow in which the wire deforms occurs.

  If wires with different voltages come into contact with each other due to the wire flow, or if the insulation distance required for withstand voltage is not secured, a short circuit failure or leak failure may occur, requiring a complicated inspection process or reliability. There arises a problem such as a restriction on the period in which the data can be secured.

  For this reason, in the resin-encapsulated power semiconductor device, in order to prevent the wires from being short-circuited and to ensure an appropriate insulation distance, it is necessary to ensure a certain distance between the wires. However, this has hindered miniaturization of the resin-encapsulated power semiconductor device.

  The present invention has been made in view of the above, and obtains a resin-encapsulated power semiconductor device and a method for manufacturing the same, which are miniaturized while preventing a short circuit between wires and ensuring an appropriate insulation distance. For the purpose.

  In order to solve the above-described problems and achieve the object, the present invention has a plurality of wires arranged in parallel, and the plurality of wires are sealed together with a semiconductor element by a mold resin. In the semiconductor device, the plurality of wires are arranged along the flow direction of the mold resin, and the wire length of the downstream wire in the flow direction is equal to or longer than the wire length of the upstream wire in the flow direction. It is characterized by.

  According to the present invention, even if the wire is deformed, there is an effect that it is possible to prevent a short circuit and ensure an appropriate insulation distance without contacting the downstream wire.

FIG. 1 is a cross-sectional view of a resin-encapsulated power semiconductor device according to the first embodiment of the present invention. FIG. 2 is a top view of the resin-encapsulated power semiconductor device according to the first embodiment. FIG. 3 is a top view of the resin-encapsulated power semiconductor device according to the first embodiment. FIG. 4 is an enlarged view of the wire. FIG. 5 is a diagram showing the process of the wire falling from the direction of viewing the wire loop linearly. FIG. 6 is a diagram showing the wires of the power semiconductor device according to the second embodiment of the present invention. FIG. 7 is a diagram illustrating a state in which the primary connection and the secondary connection are alternately switched and wired. FIG. 8 is a cross-sectional view of a mold for manufacturing the power semiconductor device according to the fourth embodiment. FIG. 9 is a diagram showing a state in which the injection of the mold resin is completed. FIG. 10 is a diagram illustrating a state in which the space in which the movable pin is located is filled with resin. FIG. 11 is a diagram showing the shape of the wire before and after filling with the mold resin. FIG. 12 is a cross-sectional view of a wire.

  Embodiments of a power semiconductor device according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

Embodiment 1 FIG.
FIG. 1 is a cross-sectional view of a resin-encapsulated power semiconductor device according to the first embodiment of the present invention. FIG. 2 is a top view of the resin-encapsulated power semiconductor device according to the first embodiment. In the resin-encapsulated power semiconductor device 20, the lead frame 2 for supporting and fixing the semiconductor element 3 and connecting to the external wiring is arranged so as not to three-dimensionally interfere with the substrate 1. A semiconductor element 3 is disposed on the lead frame 2. An insulating sheet 16 and a metal base 17 are disposed on the opposite surface of the lead frame 2 where the semiconductor element 3 is disposed, and heat generated by the semiconductor element 3 is radiated through the metal base 17. A plurality of wires 7 are connected between the electrode 4 provided on the semiconductor element 3, the electrode 5 on the substrate 1, and the electrode 6 provided on the lead frame 2. As a material for the wire 7, aluminum that can be bonded at normal temperature is excellent in workability. However, copper, a composite material of copper and aluminum can be used as the material for the wire 7, and other metals. Or a combination of metals may be used as the material of the wire 7.

  The substrate 1, the lead frame 2, the semiconductor element 3, and the wire 7 are sealed with a mold resin 15. In FIG. 2, an arrow A indicates the flow direction when resin sealing is performed with the mold resin 15.

  FIG. 3 is a top view of the resin-encapsulated power semiconductor device according to the first embodiment and shows a state before 15 is injected. The wires 7 before molding are arranged approximately in parallel. The short wires 7 are arranged on the upstream side in the flow direction of the mold resin 15 and the long wires 7 are arranged on the downstream side. Therefore, when attention is paid to two adjacent wires 7, the wiring length of the downstream wire 7 is equal to or longer than the wiring length of the upstream wire 7.

  When molding with the mold resin 15, the wire 7 is affected by the flow of the mold resin 15 and is deformed so as to draw a convex arc on the downstream side as shown in FIG. 2. When each wire 7 is deformed by the mold resin 15, the movement amount becomes shorter as the short wire 7 becomes larger and as the long wire 7 becomes larger, the distance between the wires 7 increases after the molding resin 15 is injected. .

  In the first embodiment, by arranging the wires 7 in this way, a short circuit and an unnecessary decrease in the distance between the wires 7 are prevented. As a result, the yield of the resin-encapsulated power semiconductor device 20 can be improved.

  FIG. 4 is an enlarged view of the wire. A wire 7 connects between the electrodes 4 a and 4 b of the semiconductor element 3 and the electrode 5 of the substrate 1. The right side of the figure is the upstream in the injection of the mold resin 15, and the left is the downstream. The semiconductor elements 3 are arranged so that the wires 7 become shorter in order from the upstream to the downstream. The wire 7 is deformed according to the flow of the mold resin 15, but the upstream side of the flow of the mold resin 15 is short and the downstream side is long, so that the distance between the wires 7 is prevented from becoming too short. Yes. Contrary to this example, when the long wire 7 is arranged upstream and the short wire 7 is arranged downstream, the moving distance of the long wire 7 is larger than the moving distance of the short wire 7, so the distance between the wires 7. Is unnecessarily reduced, and the resin-encapsulated power semiconductor device 20 cannot be downsized.

  Experiment verification was performed about the magnitude | size of the movement distance of the wire 7. FIG. First, regarding the force required for the deformation of the wire 7, the force necessary for the wire 7 to become a bow shape due to the flow in the horizontal direction is very small, 0.4 mN to 1 mN in the case of an aluminum wire of 300 μm. It was. The wire 7 is initially elastically deformed when a force starts to be applied, but plastic deformation starts when a force is further applied. Once compositional deformation of the wire 7 began, the deformation did not stop until the wire 7 became a uniform bow shape. The shape of the arc formed at this time was such that the arc having the same radius as the entire length of the wire 7 was tilted.

  FIG. 5 is a diagram showing the process of the wire falling from the direction of viewing the wire loop linearly. The right side of the figure is the upstream in the injection of the mold resin 15, and the left is the downstream. Viscous resistance is generated according to the flow of the mold resin 15, and a force F in a direction parallel to the flow is applied to the wire 7. The base of the wire 7 undergoes plastic deformation, and the wire 7 gradually goes to sleep. At this time, a component force Fa in the direction in which the wire 7 is stretched and a component force Fb in the direction in which the wire 7 is tilted are generated with respect to the direction of the viscous resistance by the mold resin 15.

  As the wire 7 falls, the component force Fb in the direction in which the wire 7 is intended to fall becomes smaller, and saturates when the component force Fb becomes smaller until the base of the connecting portion reaches the elastic range. At this time, as the wire 7 has a larger overall length, even when the wire loop height is the same, the distance at which the wire 7 collapses tends to be larger when viewed from the vertical direction. This is because the base of the connecting portion of the wire 7 is plastically deformed so that the wire 7 is tilted. However, the shorter the wire length, the more the elastic deformation range becomes. This is probably because the greater the height, the greater the width of the fall.

  That is, the arrangement of the wires 7 is arranged so that the wire length increases from the upstream side to the downstream side of the mold resin 15 as shown in FIG. Since it is sufficient to prepare a space, the resin-encapsulated power semiconductor device can be further downsized.

  The total length of the wire 7 is determined by the horizontal length of the wire 7 and the wire loop height. When the wire length is 20 mm or more, the movement of the wire 7 is particularly large, but the wire loop height is basically limited to the same height, specifically about 2 mm to 4 mm, because it is restricted by the thickness of the mold. It will be. That is, when the wire 7 comes into contact with the upper surface of the mold, a phenomenon occurs in which the wire 7 does not flow due to friction, and the amount of movement of the wire 7 greatly changes depending on whether or not it comes into contact with the upper surface of the mold. On the other hand, when it comes into contact with the mold, the aluminum wire as the wiring member is exposed on the upper surface of the power semiconductor device, so that the product becomes defective. For this reason, the wire 7 needs a certain amount of clearance with respect to the upper surface of the mold.

  The loop height of the wire 7 is rich in mechanical reproducibility, and can be realized at the time when the experiment verification is performed so that the accuracy is usually within about ± 0.2 mm. However, there are resin parts used in the wire feed system, specifically members called holes that guide the wire at the tip of the tool, called wire guides, and resin tubes that pass through the wire. The frictional resistance changes due to wear. That is, the wire loop height usually varies in the range of ± 0.2 mm, but in the long term, it varies by about ± 0.5 mm.

  Therefore, the wire loop height needs to ensure a distance of at least 0.5 mm + the resin thickness necessary for insulation with respect to the upper surface of the mold. In the case of an epoxy resin, for example, by ensuring a resin thickness of about 0.2 mm, if there is no conductive contact on the upper surface, insulation can be ensured, and preferably a total clearance of 0.7 mm or more is preferably secured. It is necessary. That is, there is a restriction on the height of the wire loop, and a free height cannot be realized. Therefore, it is necessary to set the height in consideration of the above restriction.

  Regarding the set of adjacent wires 7 having different lengths, even if the wire 7 is deformed due to the flow of the mold resin 15, if the distance between the adjacent wires 7 is ensured to be equal to or higher than the wire loop height, the adjacent wires 7 Can be avoided. That is, the same effect can be exhibited even if a plurality of sets are arranged by opening a minimum clearance of the distance through which the wires 7 do not interfere with each other.

Embodiment 2. FIG.
FIG. 6 is a diagram showing the wires of the power semiconductor device according to the second embodiment of the present invention. In the present embodiment, with respect to the adjacent wires 7, the arrangement of the primary connection side 7a and the secondary connection side 7b, that is, the direction of drawing the wire loop is aligned. That is, the direction from the primary connection side 7 a to the secondary connection side 7 b is aligned by the plurality of wires 7.

  The shape of the arc is determined by the influence of the wire loop height and the wire length. By the way, the height of the wire loop is actually processed by NC (Number Control) control of the trajectory of the head of the wire bonding apparatus. As a normal trajectory, after bonding the primary connection side 7a, the tool is moved vertically, moved to the horizontal while feeding the wire after reaching a predetermined height, and then lowered to the height of the secondary connection. . In the process of moving the tool horizontally, the primary connection portion of the wire 7 is fixed, and a line connecting with the wire guide attached to the wire bond tool extends slightly on the curve and is drawn out.

  After the primary connection is made first, the tool and wire guide are raised vertically. At this time, the wire is also pulled out vertically. The angle then falls as the tool and wire guide move horizontally. The deformation at this time becomes an end portion of the region where the shape of the tool in which the wire 7 is deformed by the primary connection called a neck portion between the region where the wire loop is connected to the region where the wire loop is connected is transferred. As the tool and wire guide move, this part plastically deforms. When the tool and wire guide are lowered toward the secondary connection, the distance from the wire guide to the root of the primary connection is shortened, but the wire drawn from the wire guide has a tension that does not return. The wire is loosened because it is only applied. Therefore, an arc is formed when the tool and wire guide are lowered to the height of the secondary connection. The length by which the wire is drawn most is determined by the square root of the sum of the raised height from the primary connection and the square of the horizontal distance (three square theorem).

  Since the length by which the wire 7 is drawn out becomes large with respect to the distance between the primary connection and the secondary connection after the secondary connection, the arc shape is determined by this difference. As a result of the deformation of the base of the primary connection side 7a due to plastic deformation, an insufficient return of elastic deformation called so-called spring back occurs, whereas the formation of such a root shape is secondary on the secondary connection side 7b. Springback does not occur because it occurs for the first time after connection and the wire 7 is not deformed thereafter. As a result, when the root of the primary connection side 7a is compared with the root of the secondary connection side 7b, the primary connection side is unequal. Arcs are formed. That is, the highest top portion 7c of the arc is formed at a position slightly shifted to the primary connection side 7a from the center of the arc.

  Thus, since the primary connection side 7a is more inclined at the primary connection side 7a and the secondary connection side 7b, the wire 7 has the same length by aligning the direction of drawing the wire loop. Even when the wires 7 are wired in parallel, the position of the top portion 7c of the loop can be made uniform, and the clearance between the wires 7 can be secured. That is, as shown in FIG. 6, when the wires 7 are bonded in the same direction in which the wire loops are drawn, the parallel spacing can be maintained, so that the distance between the adjacent wires 7 can be made closer. Thereby, the resin-encapsulated power semiconductor device can be reduced in size.

  FIG. 7 is a diagram illustrating a state in which the primary connection and the secondary connection are alternately switched and wired. When the primary connection side 7a and the secondary connection side 7b are alternately switched and wired, the position of the top portion 7c of the loop is alternately changed, and when the adjacent wires 7 are arranged with a close interval, the wires 7 The distance gets closer. Therefore, in order to prevent a short circuit between the wires 7 and to secure an insulation distance, the interval between the wires 7 must be widened, which hinders the miniaturization of the power semiconductor device.

Embodiment 3 FIG.
In Embodiment 3, with respect to adjacent wires, the wire loop height is set higher for the wire on the downstream side of the mold resin flow. Changing the wire loop height for each wire can be easily realized by setting the rising height after the primary connection by NC control. Since the downstream wire falls more greatly, even if the wire falls, the downstream wire moves away from the upstream wire. Therefore, even if the arrangement between adjacent wires is narrowed, the contact between the wires is less likely to occur, so that the resin-encapsulated power semiconductor device can be reduced in size.

Embodiment 4 FIG.
FIG. 8 is a cross-sectional view of a mold for manufacturing the power semiconductor device according to the fourth embodiment. The mold 10 has a structure in which a cavity 13 is formed between an upper mold 11 and a lower mold 12, and includes a movable pin driving mechanism 14 that causes the movable pin 8 to protrude from the upper mold 11 into the cavity 13.

  The movable pin 8 is lowered by the movable pin driving mechanism 14 so as to protrude into the cavity 13 before the molding resin 15 is injected.

  The movable pin 8 is disposed between the adjacent wires 7. The mold resin 15 is injected with the movable pin 8 lowered into the cavity 13, but the wire 7 on the upstream side of the movable pin 8 comes into contact with the movable pin 8. It will not flow further downstream. That is, the wire 7 has a shape in which an arc defined by the primary connection portion and the movable pin 8 and an arc defined by the movable pin 8 and the secondary connection portion are combined. Since the downstream wire 7 does not come into contact with the movable pin 8, it flows more downstream. As a result, the distance between the wires 7 does not become narrow, so that the wires 7 can be arranged with higher density. FIG. 9 is a view showing a state where the injection of the mold resin 15 is completed.

  The resin is raised by the movable pin drive mechanism 14 before and after the injection is completed and is extracted from the cavity 13.

  When the resin injection is completed and the resin is cured and then extracted from the cavity 13, the mold resin 15 does not exist in the space where the movable pin 8 was present, but before the mold resin 15 is cured, the movable pin By removing 8 from the cavity 13, the resin has fluidity even in a very small amount, so that the space in which the movable pin 8 was present is filled with the resin.

  For example, when the movable pin 8 is pulled out from the cavity when the injection of the mold resin 15 is completed, the molding pressure is continuously applied, so that the space where the movable pin 8 was filled is filled with resin. FIG. 10 is a diagram illustrating a state in which the space in which the movable pin is located is filled with resin.

  FIG. 11 is a diagram showing the shape of the wire before and after filling with the mold resin. As a result, as shown in FIG. 11, the wire 7 has a shape in which the arc becomes a lid at the position where the wire 7 is in contact with the movable pin 8, and the clearance between the wires 7 can be made closer.

  In the power semiconductor according to the present embodiment, the trace of the movable pin remains on the surface in contact with the upper surface of the mold. If the movable pin is bent, it will be broken when the movable pin is pulled out, so that some strength is required. Specifically, the required strength can be exhibited, for example, made of steel having a diameter of 2 mm. When there is no part directly under the movable pin, the pin can be lowered to a region that does not contact the surface of the lead frame or the insulating substrate on which the power element of the power semiconductor device is arranged. However, for example, in the case of a power semiconductor device using a process in which a resin insulating sheet is disposed under a lead frame and the lead frame and the insulating sheet are simultaneously bonded and cured when the lead frame and the insulating sheet are molded with the mold resin 15, If the pin is pulled out when the injection into the mold is almost completed, the pressure of the mold resin 15 drops rapidly, the pressure applied to the insulating sheet is lowered, and the insulation of the insulating sheet cannot be sufficiently exhibited. Arise. That is, in order to sufficiently exhibit the insulating properties and adhesiveness of the insulating sheet, it is necessary to apply the molding pressure of the mold resin 15 while the insulating sheet is heated and softened in the mold and to compress the insulating sheet. .

  According to this process, the insulating sheet is compressed in the thickness direction, so that a trace of such a process remains. Since there is a relationship in which the pressure is lost as the movable volume of the movable pin is larger, there is a situation where it is not desired to increase the moving height of the movable pin. There is also a circumstance that the diameter of the movable pin does not want to be increased. That is, it can be said that increasing the strength of the movable pin is not a good measure in a resin-encapsulated power semiconductor device using an insulating sheet. As the diameter of the movable pin, a diameter of 1.5 mm to 3 mm was appropriate from the above two reasons, that is, from the viewpoint of pin strength and volume change.

  If the movable pin 8 is not pulled out from the cavity 13, the wire 7 is exposed at the place where it is in contact with the movable pin 8. As a result, the wire 7 comes into contact with the pin marks on the surface of the power semiconductor device. Is exposed, and it is necessary to increase the creeping discharge distance from the viewpoint of insulation. By pulling out the movable pin 8 to a position where it does not come into contact with the wire 7, it is possible to achieve a state in which the wire 7 is not exposed in the area of the trace of the movable pin 8, thereby preventing the wire 7 from being exposed. As described above, the step of lowering the movable pin, the step of injecting the mold resin 15, and the step of extracting the movable pin before the mold resin 15 is cured are provided, so that the wire 7 is brought into contact with the movable pin 8 when the mold resin 15 is injected. The power semiconductor device can be miniaturized because it can be supported and the distance between the wires can be secured.

Embodiment 5 FIG.
The wire 7 applied to the power semiconductor device according to the fifth embodiment of the present invention includes an insulating coating 9. FIG. 12 is a cross-sectional view of a wire. Further, the wire bonding apparatus is provided with a mechanism for removing the insulating coating 9. In order to peel off the insulating coating 9, the insulating coating 9 is made of an insulating material having a melting point and a boiling point higher than the molding temperature of the mold resin 15 and a high laser light absorption rate. A laser beam is irradiated to the wire connection part of the tool of the wire bonder, and the coating resin is removed by ablation processing. By using the wire 7 having the insulating coating 9 and the wire bonder with the insulating coating removing mechanism, wiring using the wire 7 having the insulating coating 9 becomes possible. As a result, even if the wires 7 come into contact with each other, since the insulating coating 9 remains in the middle of the wire loop, a short circuit between the wires 7 cannot occur. Therefore, even if the arrangement between adjacent wires is reduced, the contact between the wires 7 hardly occurs, and the resin-encapsulated power semiconductor device can be downsized.

  As described above, the resin-encapsulated power semiconductor device according to the present invention is useful in that it can be miniaturized while ensuring the interval between adjacent wires.

  DESCRIPTION OF SYMBOLS 1 Board | substrate, 2 Lead frame, 3 Semiconductor element, 4, 5, 6 Electrode, 7 Wire, 7a Primary connection side, 7b Secondary connection side, 7c Top part, 8 Movable pin, 9 Insulation coating, 10 Mold, 11 Upper mold , 12 Lower mold, 13 cavity, 14 movable pin driving mechanism, 15 mold resin, 16 insulating sheet, 17 metal base, 20 resin-encapsulated power semiconductor device.

Claims (5)

A semiconductor element, a lead frame for energizing the semiconductor element, and a plurality of wires connecting the semiconductor element and the lead frame, wherein the semiconductor element, the lead frame, and the plurality of wires are molded resin The plurality of wires are resin-encapsulated power semiconductor devices arranged in parallel so as to extend in a direction intersecting the flow direction of the mold resin,
The resin-encapsulated power semiconductor device according to claim 1, wherein a wire length of the downstream wire in the flow direction is equal to or longer than a wire length of the upstream wire in the flow direction.   The resin-encapsulated power semiconductor device according to claim 1, wherein the plurality of wires are aligned in a direction from a primary connection position to a secondary connection position.   The resin-encapsulated power semiconductor device according to claim 1, wherein the plurality of wires include an insulating coating.   4. The resin-encapsulated power semiconductor device according to claim 1, wherein a wire loop height is higher in a downstream wire in the flow direction. 5. Connected to the substrate with a plurality of wires arranged in parallel using an upper mold with a movable pin and a lower mold in which a cavity is formed between the upper mold and the upper mold when engaged with the upper mold A method of manufacturing a resin-encapsulated power semiconductor device in which a semiconductor element is sealed with a mold resin,
Projecting the movable pin from the upper mold into the cavity in which the semiconductor element has been disposed so that the tip of the movable pin is positioned between the plurality of wires;
Injecting the mold resin into the cavity so that the mold resin flows along the parallel direction of the plurality of wires, and allowing the movable pin to support the downstream wire in the flow direction of the mold resin. When,
A method of manufacturing a resin-encapsulated power semiconductor device, comprising: a step of accommodating the movable pin in the upper mold and extracting the mold from the cavity before the curing of the mold resin is completed.

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