JP2017118050A - Semiconductor unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor unit capable of stably performing cooling without causing a leak path even in fluid.SOLUTION: The conductor unit is used for an electrical apparatus, has a semiconductor S supported on a substrate 1 and is formed with an uneven surface R having liquid-repellent on a surface of the substrate 1 at a position along a direction in which an electric current runs through a conductor 1b connected with the semiconductor S.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a semiconductor unit that is cooled by being immersed in a fluid.

  As a semiconductor unit to be cooled as described above, Patent Document 1 discloses a technique in which a heat generating component of a vehicle inverter is immersed in lubricating oil of a transmission.

  In Patent Document 1, a vehicle inverter is configured by mounting a large-capacity capacitor and a power module on an electronic board, and uses the property that the lubricating oil is an electrical insulator. A configuration is adopted in which the lubricant is brought into direct contact with the inverter without ensuring.

  Patent Document 2 discloses a technology that uses a resin that does not contain a halogen-based flame retardant as a material for sealing a substrate on which a semiconductor chip is mounted, and includes a gettering portion that captures impurity ions around the semiconductor chip. It is shown. Although this document does not describe cooling by contacting with a fluid, it describes the effectiveness that a substance causing ion migration does not reach a semiconductor.

  In Patent Document 3, the bonding portion between the substrate and the heating element is cooled with a first coolant liquid having insulation, and the aqueous second cooling liquid is brought into contact with a portion different from the bonding portion on the heating element for cooling. Techniques for performing are shown.

  In this Patent Document 3, a semiconductor element is electrically connected to a substrate and is sealed as a semiconductor package. The insulating refrigerant liquid and the aqueous refrigerant liquid are separated into two layers in the casing, the insulating coolant is used for cooling the surface including the joint portion of the semiconductor package, and the aqueous refrigerant liquid is used for cooling the other parts. It is comprised so that it may be used.

JP 2013-256983 A JP 2010-114287 A Japanese Patent No. 5590128

  The transmission lubricant shown in Patent Document 1 contains metal particles and metal ions that cannot be removed by an oil filter. In the configuration in which the substrate is brought into contact with the lubricant, the metal particles grow on the substrate. It is also conceivable that metal ions are deposited on the substrate as metal. In such a case, an electrical leakage path is caused between the semiconductor terminals and the circuit of the substrate.

  The phenomenon in which metal ions are deposited on the substrate as a metal and the insulating portion conducts is called ion migration. This phenomenon occurs when the oil temperature is high and a high voltage is applied to the semiconductor element. Cheap. That is, when the oil temperature is high, the metal of the lead frame and the metal constituting the printed wiring of the substrate are likely to elute as metal ions in the lubricating oil. In addition, metal deposition is likely to occur in an environment where a high voltage electric field acts. These factors led to ion migration, leading to an electrical leak path.

  In particular, the environment in which the oil temperature is high and a high voltage is applied to the semiconductor element is severe, and as described in Patent Document 1, the lead frame of the semiconductor element and the printed wiring of the substrate are in direct contact with the lubricating oil. It is conceivable to cause ion migration. Moreover, it is thought that it is difficult to endure an environment if it is not the structure which contacts a fluid like patent document 2. FIG. Further, as in Patent Document 3, the structure using two types of refrigerant liquid becomes complicated, and in the case of using a fluorine-based inert liquid as an insulating refrigerant, a fluid such as vehicle mission oil is used. It will be unsuitable for cooling using.

  Thus, a semiconductor unit that can be stably cooled without causing a leak path even when immersed in a fluid is required.

The present invention is used in electrical equipment,
The semiconductor is supported by the substrate, and an uneven surface having liquid repellency is formed on the surface of the substrate at a position along a direction in which a current flows through a conductor connected to the semiconductor.

In such an electric device, various fluids may adhere to the surface of the substrate depending on the installation position. Therefore, as in this configuration, an uneven surface is formed on the surface of the substrate at a position along the direction of current flow through the conductor connected to the semiconductor, so that the uneven surface repels fluid (becomes wet). Because of its difficult nature, fluid contact with the uneven surface is suppressed. By suppressing the contact of the fluid in this manner, even if the metal contains fine metal particles, the fine metal particles do not adhere to the substrate or the semiconductor, and even if the fluid contains metal ions. , The phenomenon of precipitation of the metal ions can be suppressed.
As a result, a semiconductor unit that can be stably cooled without causing a leak path even when immersed in a fluid was constructed.

  In the present invention, a current flows in the thickness direction of the substrate inside the semiconductor, and an uneven surface having liquid repellency may be formed on a side surface of the semiconductor.

  According to this, since the current flows in the thickness direction of the substrate inside the semiconductor, the uneven surface is formed on the side surface of the semiconductor in addition to the uneven surface formed on the substrate, so that the uneven surface repels fluid. Due to its high properties (properties that are difficult to become wet), fluid contact with the uneven surface is suppressed. This also prevents the metal fine particles from adhering to the substrate or the semiconductor even if the fluid contains metal fine particles, and the metal ions to precipitate even if the fluid contains metal ions. Can be suppressed.

  In the present invention, the concave portion of the concave-convex surface may be formed by laser beam irradiation.

  According to this, since the concave portion can be formed by laser beam irradiation, for example, it is not necessary to use a liquid-repellent substance, and it is possible to form fine irregularities.

  In the present invention, the contact angle of the fluid may be 120 degrees or more on the uneven surface.

  According to this, since the contact angle is large, the fluid in contact with the uneven surface is favorably repelled, and the performance of the uneven surface is further improved.

  In the present invention, the uneven surface and the surface of the semiconductor may be covered with an electrical insulating film.

  According to this, by forming the insulating film, leakage and discharge can be suppressed even when a high voltage is applied to the semiconductor. In addition, the formation of the insulating film prevents the metal fine particles and metal ions contained in the fluid from coming into direct contact with the water repellent surface or the semiconductor surface. In particular, in the form in which the insulating film covers the uneven surface, these boundaries are formed in a form bent along the unevenness.For example, even if the fluid enters the boundary, the time until the fluid reaches the semiconductor is lengthened. This can prevent the occurrence of leak paths.

  In the present invention, a region of the substrate adjacent to the semiconductor and the surface of the semiconductor may be covered with a sealing member.

  According to this, the surface of the substrate and the surface of the semiconductor can be protected by covering with the sealing member.

It is sectional drawing of the electric power control part which supported the semiconductor on the board | substrate. It is sectional drawing of the electric power control part which formed the uneven surface in the pattern of a board | substrate. It is sectional drawing of the electric power control part in which the insulating film was formed ranging from the board | substrate to the semiconductor. It is sectional drawing of the electric power control part sealed with the sealing member. It is an expanded sectional view of an uneven surface and an insulating film. It is sectional drawing of the electric power control part of another embodiment (a). It is sectional drawing of the electric power control part of another embodiment (b).

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
As shown in FIG. 1, a power control unit (an example of a semiconductor unit) is configured by supporting a semiconductor S on a substrate 1. This power control unit controls the power supply to the driving motor in the hybrid type vehicle, and is configured to control a power of several hundred to several kilovolts and several tens to several hundred amps of current. ing.

  In the drawing, a power control unit composed of a power MOSFET is shown, and a substrate 1 has a pattern 1b formed as a conductor of copper or the like on the upper surface of a ceramic plate 1a. A conductive bonding material 2 is bonded to the upper surface of the pattern 1b, and a chip-like semiconductor S is supported on the upper surface of the bonding material 2.

  The board | substrate 1 may be formed from resin, a flexible substrate, and glass epoxy. The pattern 1b may be formed of a metal such as aluminum or another alloy, or may be a bus bar. Further, a heat radiating plate may be used as the substrate 1.

  Although not shown in the drawing, a pair of leads made of a conductor are connected to a predetermined portion on the upper surface of the power semiconductor S so as to be electrically connected by a bonding technique. In this semiconductor S, one of the pair of leads serves as a gate terminal, the other serves as a source terminal, and the pattern 1b serves as a drain terminal. Further, as the semiconductor S, a semiconductor made of IGBT or SiC can be used. The power control unit is not limited to the traveling motor, and may be configured to control power supply to other electric actuators.

  The power control unit is configured to be cooled in contact with the ATF by being immersed in ATF (ATF is an abbreviation for Automatic Transmission Fluid) used for shift control of the automatic transmission of the vehicle. The ATF is an insulating oil and is an example of a fluid.

  The power control unit is disposed in a return path from the ATF cooler or in a tank that stores the ATF. In addition, you may use mission oil or engine oil as a fluid which cools an electric power control part.

  ATF contains metal fine particles and metal ions that cannot be removed by a filter. Therefore, when the power control unit is in contact with the ATF for a long period of time, the metal fine particles adhere to the substrate 1 or the semiconductor S and grow to create a conductive portion between the pattern 1b and the lead, or the pattern 1b. In some cases, a conduction path is created between the semiconductor S and the semiconductor S, resulting in a leak path.

  As a specific example of the phenomenon, when the high-temperature ATF is in contact with the substrate 1 for a long period of time, the lead metal and the pattern 1b metal are dissolved into the ATF as metal ions. When the metal ions are dissolved in the ATF in this way, ion migration is caused by the action of a high-voltage electric field, and a conduction portion is created between the pattern and the lead, and the deposited metal is formed between the pattern 1b and the semiconductor S. A conduction part is created between them and a leak path is caused.

  In order to deal with such inconvenience, the power control unit has liquid repellency (water repellency, oil repellency) due to fine unevenness on the surface of the pattern 1b surrounding the semiconductor S in the substrate 1 as shown in FIG. The uneven surface R is formed. Further, as shown in FIG. 3, an insulating resin coating is applied from the uneven surface R formed in the pattern 1 b to the surface of the semiconductor S to cover them with the insulating film 4. Further, a sealing member 5 made of resin is formed so as to cover the surface of the insulating film 4 as shown in FIG. The cross-sectional views shown in FIGS. 1 to 4 coincide with the steps for manufacturing the power control unit.

  As shown in FIG. 4, the sealing member 5 is made of an epoxy resin or the like, and a large number of dimples 5 a are formed on the surface of the sealing member 5. The dimple 5 a forms a turbulent flow on the surface of the sealing member 5 when the ATF flows, and suppresses the generation of an ATF vortex on the surface of the sealing member 5. The thermal expansion coefficient of the sealing member 5 is desirably equal to that of the semiconductor S or the substrate 1.

  The direction of the current flowing through the lead is usually along the surface of the pattern 1b. Therefore, an uneven surface R having liquid repellency is formed on the surface of the pattern 1b along the direction in which the current flows. Thereby, adhesion of metal fine particles and ion migration are suppressed, and inconvenience that a conductive portion is created between the pattern 1b and the lead is suppressed. In addition, by forming the uneven surface R in this way, the inconvenience of forming a conductive portion between the front and back surfaces of the semiconductor S is also suppressed.

  The concavo-convex surface R is formed by forming a large number of fine line-shaped grooves by irradiating the surface of the pattern 1b with a laser beam from a beam generator 8 of a femtosecond fiber laser. . A plurality of grooves formed in this way become concave portions, and a region sandwiched between adjacent grooves becomes convex portions. When the uneven surface R is formed, it is not always necessary to form a line-shaped groove, and the unevenness may be formed by forming a large number of recesses. The uneven surface R may be formed by plasma processing or the like instead of laser processing.

  In order to improve the liquid repellency on the uneven surface R, it is necessary to reduce the surface energy by bringing many points on the uneven surface R into contact with the ATF. However, when the concavo-convex pitch is larger than a predetermined limit, or when the concavo-convex height is low (the groove is shallow), the ATF comes into contact with the recess (bottom of the groove), and the surface energy is not reduced. On the other hand, when the concavo-convex pitch is extremely narrow, a plurality of adjacent convex portions are in contact with the ATF, so that a wide surface is similar to that in contact with the ATF, and the surface energy is not reduced.

  As shown in FIG. 5, the insulating film 4 is formed by coating a material such as parelin (trade name), polyamideimide, or methylsilane with a film pressure of less than 10 μm. Although the insulating film 4 is formed with a fixed thickness, it may be formed so as to increase the film thickness of the insulating film 4 in the groove portion, as indicated by a two-dot chain line in FIG. The uneven surface of the present embodiment formed in this way has a contact angle of 120 degrees or more when, for example, the fluid is oil.

[Operation / Effect of Embodiment]
In this manner, the uneven surface R is formed, the uneven surface R and the semiconductor S are covered with the insulating film 4, and these are covered with the sealing member 5, so that the ATF directly contacts the substrate 1 and the semiconductor S. Reduce inconvenience. As a result, even in a situation where the ATF oil temperature is high, the voltage applied to the semiconductor S is high, and a large current flows through the semiconductor S, a leak path is not caused and stable use is possible over a long period of time.

  In addition, since the boundary between the concavo-convex surface R and the insulating film 4 is formed in a bent shape along the concavo-convex portion, even when ATF enters the boundary portion, the distance until the ATF reaches the semiconductor S is increased. The occurrence of a leak path can be made extremely low.

  A pair of leads are connected to the surface of the semiconductor S, and the direction of current flowing through these leads is along the surface of the pattern 1b. Accordingly, a concavo-convex surface R having liquid repellency is formed on the surface of the pattern 1b so as to follow the direction in which this current flows. Thereby, the uneven surface R suppresses adhesion of metal fine particles and ion migration, and suppresses inconvenience that a conductive portion is created so as to connect the pattern 1b and the lead. As a result, as in another embodiment (a) described later, even if the power control unit in which only the uneven surface R is formed on the surface of the pattern 1b is immersed in the ATF and cooling is performed, the leakage path is suppressed.

[Another embodiment]
In addition to the above-described embodiments, the present invention may be configured as follows (the components having the same functions as those of the embodiments are given the same numbers and symbols as those of the embodiments).

(A) As shown in FIG. 6, the uneven surface R may be formed by forming fine unevenness on the side surface of the semiconductor S and the side surface of the bonding material 2. By forming the concave / convex surface R in this manner, it is possible to improve the property that the ATF repels in the region extending from the pattern 1b to the surface of the semiconductor S (the property that does not easily become wet).

  In this configuration, since a current flows in the thickness direction of the substrate 1 (vertical direction in the figure) inside the semiconductor S, a fine uneven surface R is formed on the side surface of the semiconductor S and the side surface of the bonding material 2. Has been. Thereby, the uneven surface R suppresses the adhesion of metal fine particles and ion migration, suppresses the inconvenience of creating a conductive portion so as to connect the front surface and the back surface of the semiconductor S, and suppresses the occurrence of a leak path.

  In this configuration, the uneven surface R is formed in advance on the side surface of the semiconductor S and the side surface of the bonding material 2, and these are supported on the substrate 1. Thus, the configuration in which the uneven surface R is formed on the side surface of the semiconductor S and the side surface of the bonding material 2 can be combined with the configuration in which the uneven surface R is formed on the pattern 1b. Further, by forming the insulating film 4 and the sealing member 5 in the combined configuration as described above, it is possible to further suppress the occurrence of a leak path.

(B) As shown in FIG. 7, the sealing member 5 that covers the surface of the insulating film 4 is formed of a resin so that the center portion has a shape that protrudes smoothly. The dimple 5a is formed. By smoothing the shape of the sealing member 5 in this way, the flow of the ATF is made smooth, and the dimple 5a creates a turbulent flow when the ATF flows, and the vortex flows to the ATF on the surface of the sealing member 5. Is further suppressed.

  In FIG. 7, when the shape of the sealing member 5 is, for example, a rectangular non-smooth shape, the ATF flows from the left side to the right side in FIG. A vortex flow is generated in the vicinity, and this vortex flow acts so as to peel off the sealing member 5 from the substrate 1 at the joint between the right side portion of the sealing member 5 and the substrate 1. If the force due to this vortex is stronger than the bonding force between the sealing member and the substrate 1, the sealing member 5 may be peeled off from the substrate 1. When the sealing member 5 is peeled off from the substrate 1, it is conceivable that ATF enters from the peeled portion and causes ion migration, leading to an electrical leak path.

The sealing member 5 shown in FIG. 7 has a shape in which the central portion protrudes smoothly, and a large number of dimples 5a are formed on the surface of the sealing member 5, so that the surface of the sealing member 5 is shown in FIG. When the ATF flows from the left side to the right side, the flowing ATF acts to press down the sealing member 5 at the joint between the right side portion of the sealing member 5 and the substrate 1, and the sealing member Since the separation of the ATF flow with respect to 5 and the substrate 1 is delayed, the flow of the vortex can be suppressed at the joint between the right portion of the sealing member 5 and the substrate 1.
Therefore, ATF can suppress the force that acts to peel off the sealing member 5 from the substrate 1 at the joint portion between the sealing member 5 and the substrate 1, and thus can suppress the occurrence of ion migration and leak path. .

(C) A power control unit that does not include the insulating film 4 and the sealing member 5 is used so as to be immersed in the ATF and contact the ATF. That is, as shown in FIG. 2, the surface having the uneven surface R formed only on the surface of the ceramic plate 1a, the surface of the ceramic plate 1a, the side surface of the semiconductor S, as in the other embodiment (a) described above, A structure in which the uneven surface R is formed on the side surfaces of the bonding material 2 is brought into contact with a fluid such as ATF to perform cooling.

  In such a configuration, the fluid is repelled by the liquid repellent performance on the concavo-convex surface R (because it does not become wet), so that it is possible to suppress the adhesion of metal fine particles and ion migration.

(D) Without providing the sealing member 5, as shown in FIG. 3, a power control unit in which only the insulating film 4 is formed on the surface of the concavo-convex surface R is used so as to be immersed in ATF and contact with ATF or the like.

  Even in such a configuration, since the insulating film 4 is formed as thin as less than 10 μm, it is possible to obtain a good insulating effect while exhibiting liquid repellency.

(E) As the substrate 1, for example, a surface of a glass epoxy plate material in which a metal foil is formed by a printed wiring technique may be used, and the uneven surface R may be formed on the surface of the plate material and the surface of the metal foil. . Alternatively, a semiconductor element may be encapsulated in a package of resin or the like as the semiconductor S, and a terminal exposed on the outer surface of the package, and the uneven surface R may be formed on the outer surface of the package and the surface of the terminal.

  In the present embodiment, the power control unit is configured to be immersed in the ATF, but is not particularly limited to this configuration, and may be configured to be immersed in a liquid (water, oil).

  The present invention can be widely used for semiconductor units that may come into contact with a fluid, such as a semiconductor unit that is cooled by being immersed in a fluid.

1 Substrate 4 Insulating film 5 Sealing member R Uneven surface S Semiconductor

Claims (6)

Used in electrical equipment,
A semiconductor unit in which a semiconductor is supported by a substrate, and a concavo-convex surface having liquid repellency is formed on a surface of the substrate at a position along a direction in which a current flows through a conductor connected to the semiconductor.   2. The semiconductor unit according to claim 1, wherein a current flows in a thickness direction of the substrate inside the semiconductor, and an uneven surface having liquid repellency is formed on a side surface of the semiconductor.   The semiconductor unit according to claim 1, wherein the concave portion of the concave-convex surface is formed by laser beam irradiation.   The semiconductor unit according to any one of claims 1 to 3, wherein a contact angle of the fluid is 120 degrees or more on the uneven surface.   The semiconductor unit according to claim 1, wherein the uneven surface and the surface of the semiconductor are covered with an electrical insulating film. The semiconductor unit according to claim 1, wherein a region of the substrate adjacent to the semiconductor and a surface of the semiconductor are covered with a sealing member.

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