JP7439485B2 - semiconductor module - Google Patents

Description

The present invention relates to semiconductor modules, particularly power semiconductor modules.

Power semiconductor modules are widely used in fields that require efficient power conversion. Examples include renewable energy fields such as solar power generation and wind power generation, which have been attracting attention in recent years, in-vehicle fields such as hybrid cars and electric vehicles, and railway fields such as rolling stock.

These power semiconductor modules have built-in switching elements and diodes, and conventionally, Si (silicon) semiconductors have been used for the elements. Recently, wide bandgap semiconductors such as SiC (silicon carbide) semiconductors have begun to be used.

Wide bandgap semiconductors such as SiC have characteristics such as higher voltage resistance, higher heat resistance, and lower loss than Si semiconductors, and by using them in power semiconductor modules, devices can be made smaller and have lower losses. At that time, the power semiconductor element is sealed with a sealing material containing an epoxy resin that has excellent moisture resistance, heat resistance, and mechanical properties.

Conventional power semiconductor modules have a structure sealed with a sealing material (for example, Patent Document 1), but terminal pins for external connection from a circuit board sealed with a sealing material are sealed with a sealing material. It has a structure that comes directly from the

WO 2015/025447 A1

The present invention has been made in view of the above-mentioned problems, and its purpose is to easily attach external connection electrodes (external busbars) to takeout terminals or busbars in a module, and to provide highly reliable Our goal is to provide semiconductor modules. Another object of the present invention is to provide a power semiconductor module in which the joint portion of the bus bar in which the takeout terminal pin and the female screw are integrated is reinforced, and which has even higher reliability.

The semiconductor module of the present invention includes:
A laminated substrate with semiconductor elements mounted on it,
Multiple external terminal pins installed on the mounting surface of the laminated board,
a conductive bus bar held by the plurality of external terminal pins and electrically connected to the plurality of external terminal pins;
a conductive external connection female screw integrated into the bus bar;
The device includes at least a sealing portion made of resin in which the multilayer substrate, the semiconductor element, and the bus bar are embedded.

According to the semiconductor module according to the present invention, the bus bar connected to the external terminal pin of the semiconductor module has a structure of a bus bar with an integrated female screw, so that the external bus bar can be attached by simple screw tightening, and the reliability is high. A semiconductor module can be provided. Furthermore, by covering the joint between the take-out terminal pin and the integrated female screw bus bar with a sealing material, deformation such as warping of the semiconductor module can be suppressed, and a highly reliable semiconductor module can be provided.

1 is a conceptual diagram schematically showing a cross-sectional structure of a power semiconductor module according to Example 1 of the present invention. FIG. 2 is a conceptual diagram schematically showing a cross-sectional structure of a power semiconductor module according to Example 2 of the present invention. It is a conceptual diagram which shows typically the cross-sectional structure of the power semiconductor module of Example 3 of this invention. It is a conceptual diagram which shows typically the cross-sectional structure of the power semiconductor module of Example 4 of this invention. It is a conceptual diagram which shows typically the cross-sectional structure of the power semiconductor module of Example 5 of this invention. FIG. 7 is a perspective view schematically showing the internal structure of a power semiconductor module according to Example 6 of the present invention. FIG. 6 is a perspective view schematically showing the appearance of a power semiconductor module according to Example 6 of the present invention.

Embodiments of the present invention will be described below with reference to the drawings. These can be modified as appropriate and applied in combination. Further, in the following description and the accompanying drawings, substantially the same or equivalent parts are designated by the same reference numerals. Note that the present invention is not limited to the embodiments described below.

In addition, although a case will be described below in which the semiconductor module 10 is a power semiconductor module in which a power semiconductor element is mounted as a semiconductor element, the present invention can be applied to a semiconductor module in which various semiconductor elements are mounted.

FIG. 1 is a cross-sectional view schematically showing the structure of a power semiconductor module 10 that is Example 1 of the present invention.

As shown in FIG. 1, the power semiconductor element 11 is mounted on a laminated substrate 20 via a bonding layer 12 such as solder.

A plurality of external terminal pins 25 are provided upright on the mounting surface of the laminated board 20. A conductive bus bar 15 is provided which is held by the plurality of external terminal pins 25 and electrically connected to the plurality of external terminal pins 25 . The bus bar 15 is a bus bar of an electric wiring member for supplying current to each electronic component and wiring, and is a conductive plate-shaped connecting member, and is held substantially parallel to the laminated substrate 20. Copper, which has low electrical resistance, is mainly used.

An implant pin 13 is provided on the upper surface of the power semiconductor element 11 , which is erected by a bonding layer (not shown) such as solder and connected to an electrode of the power semiconductor element 11 . An implant-type printed circuit board 14 held by external terminal pins 25 is attached between the bus bar 15 and the power semiconductor element 11 . Implant pin 13 is electrically connected to printed circuit board 14 .

External terminal pin 25 is joined to bus bar 15. Further, a conductive female screw (female screw) 30 is provided on the bus bar 15, and the bus bar 15 and the female screw 30 are integrated (hereinafter also referred to as a bus bar with an integrated female screw).

The female thread 30 has a columnar shape such as a cylinder, and a threaded portion (thread groove) 31 is provided on the inner surface of the threaded hole to receive a male thread. More specifically, the central axis of the columnar shape is perpendicular to the bus bar 15. Further, the female thread 30 may have a prismatic shape such as a square prism, but when covered with resin, stress is concentrated at the corners, so a cylindrical shape is preferable. Alternatively, it may have an elliptical columnar shape. An external wiring terminal (for example, an external bus bar) from an external circuit or the like can be fixed to the female screw 30 with a screw to establish an electrical connection between the bus bar 15 and the external wiring terminal.

Note that in this specification, the upper surface or the lower surface is a relative term that refers to the upper and lower sides in the attached drawings for the purpose of explanation, and does not limit the upper and lower sides in relation to the usage mode of the power semiconductor module 10. do not have.

In this embodiment, the semiconductor element 11, the laminated substrate 20, the implant pin 13, the printed circuit board 14, and the bus bar 15 are embedded in a sealing part 17 made of an insulating sealing resin, and are insulated and sealed. Further, a portion of the external terminal pin 25 is exposed from the sealing portion 17, and the entire female thread 30 is exposed from the sealing portion 17. Note that it is preferable that the joint portion between the external terminal pin 25 and the bus bar 15 is covered with the sealing portion 17. This is because the joint portion is fixed by the sealing portion 17, and the reliability (strength) of the joint portion is increased against stress and thermal stress during screw fastening.

Note that in this specification, a member that is embedded in the sealing portion 17 and is insulated and sealed is referred to as a sealed member.

The power semiconductor element 11 is, for example, a power chip such as an IGBT (Insulated Gate Bipolar Transistor) or a diode chip, but various Si devices, or wide gap semiconductor elements such as a SiC device or a GaN device can be used. Further, these devices may be used in combination. For example, a hybrid module using a Si-IGBT and a SiC-SBD (Schottky Barrier Diode) can be used. The number of power semiconductor elements 11 to be mounted is not limited to the illustrated form, and a plurality of power semiconductor elements 11 may be mounted on the laminated substrate 12.

The laminated substrate 20 is composed of an insulating substrate 22, a second conductive plate 21 formed on one surface (back surface), and a first conductive plate 23 formed on the other surface (top surface). ing. As the insulating substrate 22, a material with excellent electrical insulation and thermal conductivity can be used.

Examples of the material of the insulating substrate 22 include Al ₂ O ₃ , AlN, and SiN. Particularly in high-voltage applications, a material having both electrical insulation and thermal conductivity is preferable, and AlN and SiN can be used, but the material is not limited to these.

As the first conductive plate 23 and the second conductive plate 21, metal materials such as Cu and Al, which have excellent workability, can be used. Further, Cu or Al that has been treated with Ni plating for the purpose of rust prevention or the like may also be used. Examples of the method for disposing the conductive plates 21 and 23 on the insulating substrate 22 include a direct bonding method (Direct Copper Bonding method) and a brazing metal bonding method (Active Metal Brazing method).

The bonding layer 12 that bonds the power semiconductor elements 11 can be formed using lead-free solder. For example, Sn-Ag-Cu system, Sn-Sb system, Sn-Sb-Ag system, Sn-Cu system, Sn-Sb-Ag-Cu system, Sn-Cu-Ni system, Sn-Ag system, etc. can be used. However, it is not limited to these.

As the printed circuit board 14, a polyimide film board or an epoxy film board on which a conductive layer of Cu, Al, or the like is formed can be used. As the implant pin 13, a copper pin made of copper can be used. The printed circuit board 14 can be used for wiring upper surface electrodes (for example, source and gate electrodes) of the power semiconductor element 11.

Both the conductive layer of the printed circuit board 14 and the implant pins 13 may be made of Cu or Al treated with Ni plating or the like for the purpose of preventing rust. Alternatively, it may be subjected to a treatment such as Sn plating for the purpose of bonding.

The printed circuit board 14 and the implant pins 13 electrically connect the power semiconductor elements 11 to each other or the power semiconductor elements 11 and the laminated substrate 20. The implant pin 13 and the laminated substrate 20 or the implant pin 13 and the power semiconductor element 11 can be bonded by a bonding layer similar to the solder bonding layer 12 described above.

By pulling out the external terminal pins 25 bonded by the above-mentioned solder bonding layer 12 to the outside of the sealing part 17 from above the laminated board 20, they can be used as external connection terminals with external wiring terminals from an external circuit, etc. .

Note that the upper surface electrode of the power semiconductor element 11 is electrically connected to the wiring of the printed circuit board 14, and the external terminal pin 25 is insulated from the wiring of the printed circuit board 14.

As the bus bar 15, a metal material such as Cu or Al, which has excellent conductivity, can be used. Further, for purposes such as rust prevention, it is preferable to perform a treatment such as Ni plating. There are no particular limitations on the shape, thickness, etc., but in order to integrate with the female thread 30, a plate shape with a thickness of about 0.8 mm to 1.5 mm is preferable. If it is thicker than this, it will be heavy, and if it is thinner than this, it will be difficult to hold the female thread 30.

The bus bar 15 and the external terminal pin 25 can be joined by laser welding, solder joining, or the like.

The female thread 30 is provided so that its entirety is the upper part of the bus bar 15. If a portion of the female thread 30 extends to the lower part of the bus bar 15, the height of the sealing portion 17 that can be covered with the sealing resin increases accordingly. Further, the connection portion between the external terminal pin 25 and the bus bar 15 becomes high, the length of the external terminal pin 25 becomes long, and the external terminal pin 25 becomes easily bent during manufacturing, resulting in a defect.

Similar to the bus bar 15, the female thread 30 can be made of a metal material such as Cu or Al that has excellent conductivity. Further, for purposes such as rust prevention, it is preferable to perform a treatment such as Ni plating. The female thread 30 preferably has a cylindrical shape. This is because if there are corners, electric fields and the like will concentrate, resulting in discharge and noise.

Moreover, it is preferable that the outer diameter of the female thread 30 is 6 mm or more. If it is less than this, the rigidity will be weak against the force when tightening the screws, and a load will be applied to the joint between the bus bar 15 and the external terminal pin 25 described above. It is preferable that the threaded portion 31 is M4 or larger. If the screw is smaller than this, the screw itself becomes difficult to handle, and connection with an external bus bar (not shown) becomes difficult. As a method for integrating the bus bar 15 and the female thread 30, caulking, solder joint, screw type, laser welding, etc. are used, but connection by caulking is simple and preferable. Note that caulking is a method of fixing a screw and a bus bar by providing irregularities that allow them to fit into each other.

Further, the height (length) of the female screw 30 depends on the screw used, but is preferably at least twice the screw diameter. By making the screws a certain length and adding weight, the overall rigidity of the module increases, making it less likely to deform. Further, if the height of the female screw 30 is low, when the female screw 30 and the external bus bar 15 are fastened together using another male screw, the strength of the connection between the male screw and the female screw 30 will be weakened.

The member to be sealed is sealed with the following resin composition (sealing material) to form a power semiconductor module 10 having the sealed portion 17 as an outer shape. As shown in FIG. 1, the sealing part 17 preferably covers the back surface of the bus bar 15, covers the side surfaces of the bus bar, and even covers the member to be sealed under the bus bar from the viewpoint of strength. Note that the side surface of the bus bar is a surface formed between two main surfaces of a plate-shaped bus bar. Alternatively, as shown in FIG. 2, which will be described later, it may be formed to cover the upper part of the bus bar 15 and partially cover the female thread 30.

The sealing portion 17 can be formed from an epoxy resin composition that includes an epoxy resin as a main ingredient, a curing agent, and optionally an inorganic filler and other additives. As the main component of the epoxy resin, aliphatic epoxy or alicyclic epoxy can be used. Alternatively, maleimide resins and cyanate resins can be used, and two or more of them, including epoxy resins, may be used as a mixture.

Aliphatic epoxy refers to an epoxy compound in which the carbon to which an epoxy group is directly bonded is a carbon that constitutes an aliphatic hydrocarbon. Therefore, even if the main skeleton contains an aromatic ring, compounds that satisfy the above conditions are classified as aliphatic epoxies. Examples of aliphatic epoxy resins include, but are not limited to, bisphenol A epoxy, bisphenol F epoxy, bisphenol AD epoxy, biphenyl epoxy, cresol novolak epoxy, trifunctional or higher polyfunctional epoxy, and the like. . These can be used alone or in combination of two or more.

The alicyclic epoxy resin refers to an epoxy compound in which two carbon atoms forming an epoxy group form an alicyclic compound. Examples of the alicyclic epoxy resin include, but are not limited to, monofunctional epoxy, bifunctional epoxy, trifunctional or more polyfunctional epoxy, and the like. The alicyclic epoxy resin can also be used alone or in a mixture of two or more different alicyclic epoxy resins.

The curing agent is not particularly limited as long as it reacts with the epoxy resin base material and can be cured, but it is preferable to use an acid anhydride curing agent. Examples of acid anhydride curing agents include aromatic acid anhydrides, specifically phthalic anhydride, pyromellitic anhydride, trimellitic anhydride, and the like. Alternatively, cyclic aliphatic acid anhydrides, specifically tetrahydrophthalic anhydride, methyltetrahydrophthalic anhydride, hexahydrophthalic anhydride, methylhexahydrophthalic anhydride, methylnadic anhydride, etc., or aliphatic acid anhydrides, specifically Specific examples include succinic anhydride, polyadipic anhydride, polysebacic anhydride, and polyazelaic anhydride. The blending amount of the curing agent is preferably 50 to 170 parts by weight, more preferably 80 to 150 parts by weight, based on 100 parts by weight of the epoxy resin base resin. If the amount of the curing agent is less than 50 parts by mass, the glass transition temperature may decrease due to insufficient crosslinking, and if it exceeds 170 parts by mass, it may be accompanied by a decrease in moisture resistance, high heat distortion temperature, and heat resistance stability.

The epoxy resin composition can further include a curing accelerator as an optional component. As the curing accelerator, imidazole or its derivatives, tertiary amines, boric acid esters, Lewis acids, organometallic compounds, organic acid metal salts, etc. can be appropriately blended. The amount of the curing accelerator added is preferably 0.01 to 50 parts by weight, more preferably 0.1 to 20 parts by weight, based on 100 parts by weight of the epoxy resin base resin.

Inorganic fillers that the epoxy resin composition may contain as optional components include, for example, fused silica, silica, alumina, aluminum hydroxide, titania, zirconia, aluminum nitride, talc, clay, mica, and glass fiber. etc., but are not limited to these. These inorganic fillers can increase the thermal conductivity of the cured product and reduce the coefficient of thermal expansion. These inorganic fillers may be used alone or in combination of two or more. Further, these inorganic fillers may be microfillers or nanofillers, and two or more types of inorganic fillers having different particle sizes and/or types may be used in combination. In particular, it is preferable to use an inorganic filler having an average particle size of about 0.2 to 20 μm. The amount of the inorganic filler added is preferably 100 to 600 parts by mass, more preferably 200 to 400 parts by mass, when the total mass of the epoxy resin base agent and curing agent is 100 parts by mass. If the amount of the inorganic filler is less than 100 parts by mass, the sealing material may have a high coefficient of thermal expansion, making it easy to peel or crack. If the amount is more than 600 parts by mass, the viscosity of the composition may increase and extrusion moldability may deteriorate.

The epoxy resin composition may also contain optional additives to the extent that their properties are not impaired. Examples of additives include, but are not limited to, flame retardants, pigments for coloring resins, plasticizers and silicone elastomers for improving crack resistance. These optional components and their additive amounts can be determined as appropriate by those skilled in the art, depending on the specifications required for the semiconductor device and/or the sealing material.

Note that, as described above, a power semiconductor module is shown in which the outer shape is the sealing material, but a case may also be used. Specifically, a member to be sealed may be mounted on a case made of resin such as PPS (polyphenylene sulfide), and the member to be sealed may be embedded with the resin composition.

Example 1 of the present invention will be specifically described below. However, the present invention is not limited to the scope of the following examples.

A power semiconductor module 10 was manufactured and evaluated as described below. As the laminated substrate 20, a Denka SIN plate (manufactured by Denki Kagaku Kogyo, frame length 1.0 mm) having a conductive plate thickness of 0.3 mm and an insulating substrate thickness of 0.32 mm was used.

On the laminated substrate 20, solder and power semiconductor elements 11, solder and implant pins 13, external terminal pins 25, and printed circuit board 14 were soldered and disposed in an N ₂ reflow oven.

Furthermore, the external terminal pin 25 (Φ1 mm) is laser welded to a bus bar with an integrated female thread (female thread part: outer diameter M12, thread part M4, height 10 mm, bus bar part: thickness 1 mm) in which the female thread 30 and the bus bar 15 are integrated. Then, the member to be sealed was set in a mold.

Aliphatic epoxy resin main agent: jER630 (manufactured by Mitsubishi Chemical), curing agent: jER Cure 113 (manufactured by Mitsubishi Chemical), inorganic filler: Excelica, average particle size of several μm to several tens of μm (Tokuyama), mass ratio 10:5: After mixing in Step 3, vacuum defoaming was performed and the mixture was poured into a mold. This was first cured at 100° C. for 1 hour and then secondary cured at 150° C. for 3 hours to obtain a power semiconductor module 10 in which the bus bar 15 was sealed.

According to this embodiment, by embedding the bus bar 15 in the sealing part 17, it is possible to ensure the adhesion between the bus bar 15 and the sealing part 17, thereby providing a highly reliable power semiconductor module. I can do it.

FIG. 2 is a schematic cross-sectional view of a power semiconductor module 10 according to Example 2 of the present invention.

As shown in FIG. 2, in this embodiment, the sealing portion 17 may be provided such that at least a portion of the female thread 30 is embedded in the sealing portion 17. More specifically, the power semiconductor element 11, the laminated substrate 20, the implant pin 13, the printed circuit board 14, the external terminal pin 25, the entirety of the bus bar 15, and at least a portion of the female thread 30 are embedded in the sealing part 17. A sealing portion 17 is provided as shown in FIG.

In this way, when the lower part of the female thread 30 is covered so as to be buried in the sealing part 17, the joint part between the bus bar 15 and the external terminal pin 25 is fixed and protected by the sealing material, so that heat can be avoided. This is preferable because reliability is improved without cracking or cracking even when bending stress is applied.

Thus, the power semiconductor module 10 was obtained in the same manner as in Example 1 except that the sealing part 17 was provided. Note that, as described above, the female screw 30 fixes an external wiring terminal (for example, a plate-shaped external bus bar) and makes an electrical connection, so the upper surface of the female screw 30 is not buried but is sealed so as to be exposed. A section 17 is provided.

More specifically, the upper surface of the sealing portion 17 was sealed to a position 8 mm above the bus bar 15. That is, the sealing portion 17 was formed so that the lower 8 mm portion of the female thread 30 having a height of 10 mm was embedded.

According to this embodiment, by providing the sealing part 17 so that at least a part of the female thread 30 is embedded in the sealing part 17, the female thread integrated bus bar (that is, the bus bar 15 and the female thread 30) and the sealing part 17 can be improved, and a highly reliable power semiconductor module can be provided.

FIG. 3 is a schematic cross-sectional view of a power semiconductor module 10 according to Example 3 of the present invention.

As shown in FIG. 3, in this embodiment, the outer periphery of the female thread 30 is knurled. Note that, hereinafter, the knurled portion will be referred to as knurling 30A. Note that the knurling process is a process that creates fine irregularities on the surface.

The sealing portion 17 is provided such that at least a portion of the knurl 30A is embedded in the sealing portion 17. Further, the knurling process is preferably formed on all the parts embedded in the resin. Providing the knurling 30A on the outer periphery of the female thread 30 can improve the adhesion between the female thread 30 and the sealing portion 17. Note that it is preferable that the entire knurling 30A is configured to be embedded in the sealing portion 17 in order to improve adhesion.

Moreover, it is preferable that the knurling 30A has a vertical groove structure (flat). That is, it is preferable to have a plurality of grooves formed along the height direction of the female thread 30 (the depth direction of the sealing part 17). This is because the female screw 30 is fastened to the external wiring terminal by the male screw. At this time, torque is applied to the female thread 30 in the rotational direction with respect to the central axis of the screw hole. With the longitudinal grooves, good fastening can be achieved without peeling or gaps occurring between the resin composition of the sealing portion and the surface of the female thread 30.

According to this embodiment, it is possible to further improve the adhesion between the female screw integrated bus bar (that is, the bus bar 15 and the female screw 30) and the sealing portion 17, and it is possible to provide a highly reliable power semiconductor module.
[Evaluation of Example 1-3]
A thermal cycle test was conducted on the power semiconductor modules of Examples 1 to 3 and Comparative Example 1. As Comparative Example 1, a power semiconductor module was used that was the same as in Example 1 except that the female screw integrated bus bar was not used.

In Examples 1 to 3, the female screw 30 and the plate-shaped external bus bar were fastened using male screws. Further, the comparative example has a structure in which the external terminal pin 25 is exposed outside the sealing resin, and the external terminal pin and the external bus bar are soldered.

In the thermal cycle test, the environmental temperature was raised and lowered within a predetermined temperature range, and for 10 power semiconductor modules under each condition, the temperature cycle was repeated to raise and lower the temperature between -40°C and 125°C, and the test was carried out every 100 cycles. I took it out and checked to see if there was any damage to the attachment part of the external bus bar. Confirmed up to 300 cycles. When the joint between the external terminal pin 25 and the external bus bar was broken, and when the joint between the female screw 30 and the external bus bar was broken, respectively, it was defined as failure.

Further, a screw tightening test was conducted on the power semiconductor modules of Examples 1 to 3. The tightening torque was 6Nm and 8Nm. Failure was defined as a case where the joint between the female thread integrated bus bar 15 and the external terminal pin 25 was broken, or a case where the female thread 30 and the sealing material were separated.

In thermal cycle evaluation, the power semiconductor modules of Examples 1 to 3 in which the external bus bar was attached with screws were not destroyed, but in the case of comparative example 1 in which the external bus bar was attached by soldering, the bonding strength was insufficient and some of them were destroyed. This is thought to be because sufficient strength was maintained by tightening the screws.

Depending on how the module is used, the entire module may repeatedly deform due to the heat generated by the module or the environmental temperature of the power electronics equipment itself, and large bending stress is also generated at the joints between the bus bars and external connection terminals. However, as mentioned above, no damage occurred in this structure.

In the screw tightening test, there was no problem with the power semiconductor modules of Examples 1 to 3 with normal tightening torque (3 Nm), but with stronger tightening torque (6, 8 Nm), the female screw integrated bus bar 15 and the external terminal pin 25 Embodiments 2 and 3 in which the joints were covered with a sealing material had higher reliability, and Embodiment 3 in which the female thread 30 was knurled to have a longitudinal groove structure had higher reliability. In the structure of Example 1, the joint between the female screw integrated bus bar 15 and the external terminal pin 25 was subjected to a load and broke due to the tightening torque, but by covering this part with a sealing material, the strength was stronger than the tightening torque. It is thought that it has become.

FIG. 4 is a cross-sectional view schematically showing the configuration of a power semiconductor module 10 according to Example 4 of the present invention.

The power semiconductor module 10 of Example 4 has the same configuration as the power semiconductor module 10 of Example 3, but in particular, the embedding thickness of the sealing part 17 is set to H ₀ (module height). The embedding thickness of the sealing part 17 is determined so as to satisfy 0.33≦H ₁ /H ₀ ≦0.67, where H ₁ is the embedding thickness of the female thread 30 by the sealing part 17 . ing.

As described above, semiconductor modules undergo deformation such as warping and twisting due to thermal stress caused by their own heat generation and environmental thermal changes. This deformation adds bending stress, causing problems such as cracks in the sealing material, peeling of the interface between the sealing material and the laminated substrate, and cracking in the solder joints. Therefore, it is desirable to suppress deformation. It has been found that the structure including the integrated busbar and female thread of the present invention suppresses its deformation.

The following table shows a comparison of the warpage reduction rate (%) of Examples in which H ₁ /H ₀ was changed and the results of a ΔTc power cycle test (hereinafter also simply referred to as a power cycle test). Note that the power cycle test is a test in which a semiconductor module and a cooling fin are attached via a thermal compound, and the module is actually operated to apply a thermal stress stress and measure the thermal resistance. As shown in Figure 1, sample 0 is the case where the side and bottom of the bus bar are sealed with the sealing part and the bus bar is not buried in the sealing part. The reduction rate when used as a standard was evaluated as the warpage reduction rate. Note that a warpage reduction rate of 15% was defined as an effectiveness standard (effective).

The power cycle test was conducted in the following manner. The back surfaces of the power semiconductor modules of this example and sample 0 were attached to cooling fins using a thermal compound, and the case temperature Tc (temperature of the back surface of the laminated substrate 20) and the surface temperature of the cooling fins Tf (the surface of the cooling fins facing the semiconductor module) were measured. The thermal resistance Rth (K/W) was measured between The temperature conditions were ΔTc = 75°C (25°C to 100°C). Judgment conditions are: × (high thermal resistance) if the thermal resistance increases by 20% from the initial stage after 20,000 cycles, △ (slightly good) if it increases by 10% or more, and ○ (good) if it increases by less than 20%. I judged it.

As shown in the table below, it was found that by setting H ₁ /H ₀ within the above range, it was possible to realize a highly reliable semiconductor module with smaller module warpage than when it was outside the range. In other words, by increasing the embedding thickness H ₁ of the female thread 30 by a certain degree, the rigidity of the entire module can be improved and reliability can be improved, but if H ₁ is too large, stress will increase and the embedding effect will be reduced. It is thought that then.

According to this embodiment, it is possible to further improve the adhesion between the female screw integrated bus bar (that is, the bus bar 15 and the female screw 30) and the sealing portion 17, and it is possible to provide a highly reliable power semiconductor module.

FIG. 5 is a cross-sectional view schematically showing the configuration of a power semiconductor module 10 according to Example 5 of the present invention.

The power semiconductor module 10 of Example 5 has the same configuration as the power semiconductor module 10 of Example 3, but in particular, the area of the upper surface of the sealing part 17 is S ₀ and the area of the upper surface of the female screw 30 is The area of the upper surface of the sealing portion 17 and the area of the upper surface of the female thread 30 are determined so as to satisfy 0.1≦S ₁ /S ₀ ≦0.2, where S 1 is S ₁ . Note that the evaluation was performed with the area S ₀ of the upper surface of the sealing portion 17 of each sample being constant (6170 mm ² ).

The warpage reduction rate (%) and power cycle results of Examples in which S ₁ /S ₀ were changed are shown in the table below in comparison with Sample L, Sample U, and Sample 0. Note that sample L and sample U have values slightly outside the range of the lower and upper limits of S ₁ /S ₀ , respectively. In addition, sample 0 is the case in which the bottom of the bus bar is sealed with the sealing part and the bus bar is not buried in the sealing part, and the reduction rate is based on the warpage between the mounting rings on the back side of the module in sample 0. was evaluated as the warpage reduction rate. Note that a warpage reduction rate of 15% was defined as an effectiveness standard (effective).

As shown in Table 3 below, it was found that by setting S ₁ /S ₀ within the above range, it was possible to realize a highly reliable semiconductor module with smaller module warpage than when it was outside the range. . In addition, "Sample L" in the table has a small warpage reduction effect, and "Sample U" in the table has a warpage reduction effect, but is out of range because the insulation distance between the terminals (female thread 30) is insufficient. did.

6A and 6B are perspective views schematically showing the configuration of a power semiconductor module 10 according to Example 6 of the present invention. More specifically, FIG. 6A is a perspective view schematically showing the power semiconductor module 10 before being embedded with the sealing part 17, and FIG. 6B is a perspective view schematically showing the power semiconductor module 10 after being embedded with the sealing part 17.

As shown in FIG. 6A, in the power semiconductor module 10 of Example 6, the laminated substrate 20 is composed of a plurality of laminated substrate pieces arranged side by side with gaps on the same plane. In this embodiment, the laminated board 20 consists of three laminated board pieces 20A, 20B, and 20C.

Further, the bus bar 15 is composed of a plurality of bus bar pieces arranged side by side with gaps on the same plane. In this embodiment, the bus bar 15 consists of three bus bar pieces 15A, 15B, and 15C.

These laminated board pieces 20A, 20B, 20C and bus bar pieces 15A, 15B, 15C are connected with gaps by external terminal pins 25, and are connected in directions that intersect with each other (in this embodiment, directions that intersect perpendicularly with each other). ).

In the case shown in FIGS. 6A and 6B, each of the busbar pieces 15A and 15B has three female threads 30, and the busbar piece 15C has two female threads 30 (smaller than the female threads of the busbar pieces 15A and 15B). Integrated and installed.

As shown in FIG. 6B, the laminated board pieces 20A, 20B, 20C, the busbar pieces 15A, 15B, 15C, a plurality of semiconductor elements (not visible in the figure because they are hidden behind the busbar pieces), and the female screw 30 are sealed. It is buried in section 17.

According to this embodiment, in a semiconductor module in which a plurality of semiconductor elements are mounted, a multilayer substrate, a semiconductor element, and a female screw integrated bus bar are buried in the sealing part 17, and a semiconductor module with high adhesion and high reliability is provided. can do. Furthermore, it is possible to provide a semiconductor module that has high rigidity not only in the direction parallel to the laminated substrate but also in the orthogonal direction, and can reduce warpage and twisting.

As described above in detail, according to this embodiment, external connection electrodes (external busbars) can be attached by simple screw tightening, and a highly reliable semiconductor module can be provided. Moreover, the connection and fixation of the takeout terminal pin (female thread for external connection) and the bus bar are reliable and strong, and a highly reliable semiconductor module can be provided.

11 Semiconductor element 12 Bonding layer 13 Implant pin 14 Printed circuit board 15 Bus bar 17 Sealing part 20 Laminated substrate 21 Second conductive plate 22 Insulating substrate 23 First conductive plate 25 External terminal pin 30 Female thread 30A Knurl 31 Screw groove

Claims (8)

A laminated substrate with semiconductor elements mounted on it,
a plurality of external terminal pins erected on the mounting surface of the laminated board;
a conductive bus bar held by the plurality of external terminal pins and electrically connected to the plurality of external terminal pins;
a conductive female screw for external connection provided integrally with the bus bar on the upper surface side of the bus bar ;
a sealing portion made of resin that embeds the entirety of the laminated substrate, the semiconductor element , and the bus bar, and at least a portion of the female thread ;
Equipped with
A semiconductor module, wherein the embedding thickness (H ₀ ) of the sealing portion and the embedding thickness (H ₁ ) of the female thread by the sealing portion satisfy 0.33≦H ₁ /H ₀ ≦0.67. . The semiconductor module according to claim 1 , wherein an area (S ₀ ) of the upper surface of the sealing portion and an area (S ₁ ) of the upper surface of the female thread satisfy 0.1≦S ₁ /S ₀ ≦0.2. 3. The semiconductor module according to claim 1, wherein an outer peripheral portion of at least a portion of the female thread embedded in the sealing portion is knurled. 3. The semiconductor module according to claim 1, wherein an outer peripheral portion of at least a portion of the female thread embedded in the sealing portion has a vertical groove structure. 5. The semiconductor module according to claim 1, wherein the bus bar and the female thread are integrated into the bus bar by caulking or bonding. The laminated board consists of a plurality of laminated board pieces juxtaposed with gaps on a plane, the bus bar consists of a plurality of bus bar pieces juxtaposed with a gap on a plane, and the plurality of laminated board pieces 6. The semiconductor module according to claim 1, wherein the plurality of busbar pieces are arranged in directions that intersect with each other. A laminated substrate with semiconductor elements mounted on it,
a plurality of external terminal pins erected on the mounting surface of the laminated board;
a conductive bus bar held by the plurality of external terminal pins and electrically connected to the plurality of external terminal pins;
a conductive external connection female screw integrated into the bus bar;
a sealing part made of resin in which the laminated substrate, the semiconductor element, and the bus bar are embedded;
Equipped with
The semiconductor module , wherein the female thread is entirely exposed from the sealing portion . 8. The semiconductor module according to claim 1, wherein the female thread has a cylindrical shape.

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