JP6907546B2 - Power module - Google Patents

Description

The present invention relates to a power module used in a semiconductor device that controls a large current and a high voltage.

A power module used in a semiconductor device that controls a large current and a high voltage is connected to a semiconductor element, for example, as shown in Patent Document 1 in order to support a large current capacity and reduce wiring resistance. The wiring is formed by a lead frame made of copper, and a structure is adopted in which the joint portion between the semiconductor element and the lead frame is resin-sealed with an epoxy resin or the like.

Further, in this type of power module, for example, as shown in Patent Document 2, a circuit layer made of an aluminum plate or the like is bonded to one surface of a ceramic substrate such as aluminum nitride, and the other surface is formed. A power module substrate to which a heat radiating layer made of an aluminum plate or the like is bonded is used. Further, a power module substrate with a heat sink is manufactured by joining a heat sink made of copper or the like to the heat radiating layer of the power module substrate.

When a semiconductor element and a lead frame are bonded to the power module substrate to form a power module, for example, the semiconductor element is placed on the circuit layer of the power module substrate in which the circuit layer and the heat dissipation layer are bonded to both sides of the ceramics substrate. After joining by a method such as silver sintering joining or soldering, a lead frame made of copper is joined on the semiconductor element by soldering or the like.

Japanese Unexamined Patent Publication No. 2001-291823 Japanese Unexamined Patent Publication No. 2005-328087

In the above-mentioned power module, the aluminum or aluminum alloy, copper or copper alloy used for the circuit layer or the lead frame has a larger linear expansion coefficient than the semiconductor element. Therefore, the semiconductor element or the lead frame is joined by soldering. In this case, cracks may occur in the solder joint layer when repeatedly subjected to thermal stress due to changes in the usage environment or resistance heat generation of the element. When silver-sintered bonding is used instead of this soldering, the silver-sintered bonding layer has higher bonding reliability in a high temperature environment and excellent thermal conductivity as compared with the solder bonding layer, but compared to the solder bonding layer. Since it is thin and hard, a large thermal stress acts on the semiconductor element itself, which may cause damage to the semiconductor element.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide a power module capable of preventing damage to a semiconductor element while improving bonding reliability by using a silver sintered bonding layer.

In the power module of the present invention, one surface of the semiconductor element mounted on the substrate for the power module is bonded to the first copper-based low-line expansion material via a silver sintered bonding layer, and the other surface is copper or It is bonded to a lead frame made of a second copper-based low-wire expansion material containing a copper alloy and a low-wire expansion material via a silver sintered bonding layer, and these first copper-based low-wire expansion material and second copper are bonded. system and a low linear expansion material, the difference in linear expansion coefficient Ri der 5 ppm / ° C. or less, and a circuit layer made of the power module substrate is bonded in a stacked state to the front surface of the ceramic substrate of aluminum or aluminum alloy, said It is bonded to the surface of the circuit layer in a laminated state and has a spacer containing copper or a copper alloy and a low wire expansion coefficient material. The spacer is the first copper-based low wire expansion material, and the spacer and the spacer The ratio of the thickness to the lead frame is 0.2 or more and 5.0 or less, a base metal layer is formed on the surface of the circuit layer, and the spacer is formed on the base metal layer via a silver sintered bonding layer. joined becomes in the underlying metal layer, a glass layer formed on the circuit layer surface, that has a two-layer structure of the silver layer formed on the glass layer.

In this power module, both sides of the semiconductor element are bonded to the lead frame or the like by a silver sintered bonding layer, so that the bonding reliability is high even in a high temperature environment, and the silver sintered bonding layer is excellent in thermal conductivity, so that the semiconductor element The heat generated in the above can be dissipated quickly. Moreover, by joining copper-based low-wire expansion materials to both sides of the semiconductor element to reduce the difference in linear expansion from that of the semiconductor element, the thermal stress acting on the semiconductor element is reduced and its damage is prevented. Can be done.
In this case, if the difference in the coefficient of linear expansion of the two copper-based low linear expansion materials exceeds 5 ppm / ° C., the thermal stress acting on the semiconductor element increases due to the difference in linear expansion, which is not preferable.
Further, the height position (position in the stacking direction) of the lead frame can be adjusted by the spacer, and the lead frame can be pulled out at an appropriate position. Also in this case, the thickness ratio of the spacer and the lead frame is set to 0.2 or more and 5.0 or less so as not to cause damage to the semiconductor.

In the power module of the present invention, the power module substrate has a circuit layer made of copper or a copper alloy bonded in a laminated state on the surface of the ceramics substrate, and the power module substrate has the first copper-based low-line expansion. It may be a material, and the ratio of the thickness of the circuit layer to the lead frame may be 0.2 or more and 5.0 or less.

In this power module, the substrate for the power module on which the circuit layer made of copper or a copper alloy is laminated is a copper-based low wire expansion material. Copper or copper alloy itself has a larger coefficient of linear expansion than that of a semiconductor element, but since the circuit layer is bonded to the ceramic substrate in a laminated state, the linear expansion is dominated by the linear expansion of the ceramic substrate. It is a low-line expansion material as a substrate for a power module. In this case, if the ratio of the thickness of the circuit layer to the lead frame is less than 0.2 or more than 5.0, the effect of arranging and balancing the low wire expansion material on both sides is impaired, and the thicker wire is used. Expansion becomes dominant and may cause damage to the semiconductor element.

According to the power module of the present invention, the copper-based low-wire expansion material is bonded to both sides of the semiconductor element by the silver sintered bonding layer, so that the bonding reliability and thermal conductivity are excellent, and the copper-based low-wire expansion material is excellent. By reducing the difference in linear expansion of the above, it is possible to reduce the thermal stress acting on the semiconductor element and prevent its damage.

It is sectional drawing of the power module of 1st Embodiment of this invention. It is a flowchart which shows the manufacturing method of the power module of FIG. It is sectional drawing which shows the process of manufacturing by the manufacturing method of FIG. 2 in the order of a process. It is an enlarged cross-sectional view explaining the base metal layer. It is sectional drawing of the power module of the 2nd Embodiment of this invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

1. 1. 1st Embodiment <Overall structure>
As shown in FIG. 1, the power module 100 of the first embodiment is a power module substrate including a ceramic substrate 11, a circuit layer 12 formed on one surface of the ceramic substrate 11, and a heat dissipation layer 13 formed on the other surface. 10. The semiconductor element 30 mounted on the surface of the circuit layer 12 of the power module substrate 10 via a spacer 20, the lead frame 40 joined to the semiconductor element 30, the semiconductor element 30, and the power module substrate 10. It is composed of a mold resin 50 made of an epoxy resin or the like that seals the lead frame 40.

Ceramic substrate 11 that constitutes the power module substrate 10, for example AlN (aluminum nitride), _Si 3 _{N 4} (silicon nitride) nitride ceramics such as, or _Al 2 _{O 3} a (alumina) oxide ceramics such as It can be used and the thickness is set in the range of 0.2 mm to 1.5 mm.

The circuit layer 12 and the heat radiating layer 13 are formed of pure aluminum ((so-called 2N aluminum)) having a purity of 99.00% by mass or more, pure aluminum (so-called 4N aluminum) having a purity of 99.99% by mass or more, or an aluminum alloy, for example. It has a thickness of 0.1 mm to 5.0 mm, and is usually formed in a flat rectangular shape smaller than that of the ceramic substrate 11. The circuit layer 12 and the heat radiating layer 13 are joined to the ceramic substrate 11 with an alloy brazing material such as Al—Si, Al—Ge, Al—Cu, Al—Mg, or Al—Mn. ing. The circuit layer 12 and the heat radiating layer 13 are punched to a desired outer shape by press working and then bonded to the ceramic substrate 11, or a flat plate-shaped one is bonded to the ceramic substrate 11 and then etched. It is formed in an outer shape or is formed in a desired shape by either method.

The spacer 20 is a clad in which pure copper plates are bonded to both sides of a composite material in which copper (Cu) having high thermal conductivity is combined with a low linear expansion coefficient material such as tungsten (W), molybdenum (Mo), and chromium (Cr). It is a copper-based low wire expansion material made of a plate (the first copper-based low wire expansion material of the present invention). The thickness of the spacer 20 is preferably in the range of 0.5 mm to 6.0 mm. As the spacer 20, for example, a clad plate in which a pure copper plate having a thickness of 0.1 mm to 2.0 mm is bonded to both sides of a composite material having a thickness of 0.3 mm to 5.0 mm can be used. A Cu-Mo composite material is preferably used as the composite material, and in this case, Mo is preferably contained in the range of 55% by mass to 75% by mass.
The coefficient of linear expansion and thermal conductivity of the copper-based low-wire expansion material can be adjusted by changing the content ratio of the low-line expansion material and the ratio of the thickness of the clad pure copper plate. The coefficient of linear expansion will be described later. The thermal conductivity is, for example, 180 to 200 W / m · K.
In the illustrated example, two spacers 20 are joined to the circuit layer 12 side by side in the plane direction.

The semiconductor element 30 is an electronic component provided with a semiconductor, and is an IGBT (Insulated Gate Bipolar Transistor), a MOSFET (Metal Oxide Semiconductor Field Effect Transistor), a FWD (Free), or the like, depending on the required function. The semiconductor element is selected.
Such a semiconductor element 30 is provided with electrodes on the upper surface and the lower surface, and is in an electrically connected state between the circuit layer 12 and the lead frame 40. In this case, the semiconductor element 30 is bonded to each of the two spacers 20, and the lead frame 40 is provided in a state where the semiconductor elements 30 are connected to each other.

The lead frame 40 is formed in a strip shape by a copper-based low wire expansion material (second copper-based low wire expansion material of the present invention) similar to the spacer 20. In this case, as described above, in the copper-based low linear expansion material, the linear expansion coefficient and the like can be adjusted by the content ratio of copper and the low linear expansion coefficient material in the composite material and the thickness ratio of the clad pure copper plate. However, the coefficient of linear expansion is set so that the difference between the spacer 20 and the lead frame 40 is within 5 ppm / ° C. The coefficient of linear expansion of the semiconductor element 30 is, for example, 20 ppm / ° C. to 30 ppm / ° C. The thickness of the lead frame 40 is preferably in the range of 0.05 mm or more and 3.0 mm or less. Further, the thickness ratio of the spacer 20 and the lead frame 40 is set to 0.2 or more and 5.0 or less in order to effectively exert the effect of reducing the difference between these linear expansion coefficients.

Then, the spacer 20, the semiconductor element 30, and the lead frame 40 are bonded to the circuit layer 12 of the power module substrate 10 via the silver sintered bonding layer 71, respectively. In order to bond with the silver sintered bonding layer 71, a base metal layer 60 made of gold, silver, nickel or the like is formed on the bonding surface of the circuit layer 12. A base metal layer made of gold, silver, nickel, or the like may be formed on the joint surfaces of the spacer 20, the semiconductor element 30, and the lead frame 40 by plating, sputtering, or the like. The mold resin 50 is made of an epoxy resin or the like, except for the back surface of the heat dissipation layer 13 of the power module substrate 10, the side surfaces thereof, the ceramic substrate 11, the circuit layer 12, the spacer 20, the semiconductor element 30, and the semiconductor element of the lead frame 40. The periphery of the connection portion to 30 is integrally sealed. The end portion of the lead frame 40 is pulled out from the mold resin 50 to the outside.

<Manufacturing method of the first embodiment>
Next, a method of manufacturing the power module 100 configured in this way will be described. In this power module manufacturing method, as shown in FIG. 2, a power module substrate 10 is formed [power module substrate forming step], and a base metal layer 60 is formed on the planned joining surface of the circuit layer 12 of the power module substrate 10. After forming the base metal layer [base metal layer forming step], the spacer 20, the semiconductor element 30, and the lead frame 40 are laminated in this order on the circuit layer 12, and these are collectively joined [batch joining step], and then the resin is formed by the mold resin 50. It is formed by sealing [resin sealing step]. Hereinafter, the steps will be described in order.

[Substrate forming process for power module]
As shown in FIG. 3A, an aluminum plate 12'which becomes a circuit layer 12 and an aluminum plate 13' which becomes a heat dissipation layer 13 are laminated on each surface of the ceramic substrate 11 via a brazing material 15, and these are laminated. The structure is heated in a state of being pressurized in the stacking direction, and the brazing material 15 is melted to join the respective aluminum plates 12'and 13'to the ceramic substrate 11, and has a circuit layer 12 and a heat dissipation layer 13. The power module substrate 10 is formed (see FIG. 3B). Specifically, the laminated structure is placed in a furnace under pressure and heated at a temperature of 610 ° C. or higher and 650 ° C. or lower for 1 to 60 minutes in a vacuum atmosphere.

[Underground metal layer forming process]
Prior to batch joining, a base metal layer 60 made of gold, silver, nickel or the like is formed on the planned joining surface of the circuit layer 12.
The base metal layer 15 can be obtained by forming gold, silver, nickel or the like into a thin film by plating or sputtering. The base metal layer 60 on the surface of the circuit layer 12 can also be formed by applying a glass-containing silver paste and firing it.

(Method of forming a base metal layer with a glass-containing silver paste)
The method of forming the base metal layer 60 on the surface of the circuit layer 12 with the glass-containing silver paste will be described. The glass-containing silver paste includes silver powder, glass (lead-free glass) powder, resin, solvent, and the like. It contains a dispersant, and the content of the powder component composed of silver powder and glass powder is 60% by mass or more and 90% by mass or less of the entire glass-containing silver paste, and the balance is resin, solvent, and dispersant. Has been done. The silver powder has a particle size of 0.05 μm or more and 1.0 μm or less, and for example, an silver powder having an average particle size of 0.8 μm is preferable. The main component of the glass powder is bismuth oxide (Bi ₂ O ₃ ), zinc oxide (Zn _{O), boron oxide (B 2} O ₃ ), lead oxide (PbO ₂ ), or phosphorus oxide (P ₂ O ₅ ). It is supposed to contain seeds or two or more kinds, and the glass transition temperature thereof is 300 ° C. or higher and 450 ° C. or lower, the softening temperature is 600 ° C. or lower, and the crystallization temperature is 450 ° C. or higher. For example, a glass powder containing lead oxide, zinc oxide and boron oxide and having an average particle size of 0.5 μm is suitable.
Further, the weight ratio A / G of the weight A of the silver powder and the weight G of the glass powder is adjusted within the range of 80/20 to 99/1, for example, A / G = 80/5.
The solvent preferably has a boiling point of 200 ° C. or higher, and for example, diethylene glycol dibutyl ether is used.
The resin adjusts the viscosity of the glass-containing silver paste, and a resin that is decomposed at 350 ° C. or higher is suitable. For example, ethyl cellulose is used.
In addition, a dicarboxylic acid-based dispersant is appropriately added. The glass-containing silver paste may be formed without adding a dispersant.

In this glass-containing silver paste, a mixed powder in which silver powder and glass powder are mixed and an organic mixture in which a solvent and a resin are mixed are premixed with a dispersant by a mixer, and the obtained premix is premixed by a roll mill. After mixing while kneading, the obtained kneaded product is produced by filtering it with a paste filter. The viscosity of this glass-containing silver paste is adjusted to 10 Pa · s or more and 500 Pa · s or less, more preferably 50 Pa · s or more and 300 Pa · s or less.

This glass-containing silver paste is applied to the planned bonding surface of the circuit layer 12 by a screen printing method or the like, and after drying, it is fired at a temperature of 350 ° C. or higher and 645 ° C. or lower for a time of 1 minute or more and 60 minutes or less. As shown, a base metal layer 60 having a two-layer structure is formed, which is a glass layer 61 formed on the planned joining surface side and a silver layer 62 formed on the glass layer 61. At this time, when the glass layer 61 is formed, the aluminum oxide film 12a naturally generated on the surface of the circuit layer 12 is melted and removed, and the glass layer 61 is directly formed on the circuit layer 12. A silver layer 62 is formed on the glass layer 61. By firmly fixing the glass layer 61 to the circuit layer 12, the silver layer 62 is securely held and fixed on the circuit layer 12.
Conductive particles (crystalline particles) 63 containing at least one of silver and aluminum are dispersed in the glass layer 61, and it is presumed that they are precipitated inside the glass layer 61 during firing. Further, fine glass particles 64 are also dispersed inside the silver layer 62. It is presumed that the remaining glass components of the glass particles 64 are aggregated in the process of firing the silver particles.

The average crystal grain size of the silver layer 62 in the base metal layer 60 formed in this manner is adjusted within the range of 0.5 μm or more and 3.0 μm or less.
Here, if the heating temperature is less than 350 ° C. and the holding time at the heating temperature is less than 1 minute, the firing may be insufficient and the base metal layer 60 may not be sufficiently formed. On the other hand, when the heating temperature exceeds 645 ° C. or when the holding time at the heating temperature exceeds 60 minutes, the firing proceeds too much, and the average crystal grains of the silver layer 62 in the base metal layer 60 formed after the heat treatment. The diameter may not be within the range of 0.5 μm or more and 3.0 μm or less.
In order to reliably form the base metal layer 60, the lower limit of the heating temperature during the heat treatment is preferably 400 ° C. or higher, more preferably 450 ° C. or higher. Further, the holding time at the heating temperature is preferably 5 minutes or more, and more preferably 10 minutes or more.
On the other hand, in order to reliably suppress the progress of firing, the heating temperature during the heat treatment is preferably 600 ° C. or lower, and more preferably 575 ° C. or lower. Further, the holding time at the heating temperature is preferably 45 minutes or less, and more preferably 30 minutes or less.

(Silver paste layer)
These are laminated with the silver paste layer 70 interposed between the circuit layer 12, the spacer 20, the semiconductor element 30, and the lead frame 40 on which the base metal layer 60 is formed.
The silver paste layer 70 is a layer formed by applying a paste containing silver powder having a particle size of 0.05 μm to 100 μm, a resin, and a solvent.
As the resin used for the silver paste, ethyl cellulose or the like can be used. As the solvent used for the silver paste, α-terpineol or the like can be used.
The composition of the silver paste is such that the content of the silver powder is 60% by mass or more and 92% by mass or less of the whole silver paste, the content of the resin is 1% by mass or more and 10% by mass or less of the whole silver paste, and the balance is the solvent. It is good to do.
Further, the silver paste contains 0% by mass or more and 10% by mass or less of organic metal compound powder such as a carboxylic acid-based metal salt such as silver formate, silver acetate, silver propionate, silver benzoate, and silver oxalate. You can also let it. Further, if necessary, a reducing agent such as alcohol or an organic acid can be contained in the entire silver paste in an amount of 0% by mass or more and 10% by mass or less.
The viscosity of this silver paste is adjusted to 10 Pa · s or more and 100 Pa · s or less, more preferably 30 Pa · s or more and 80 Pa · s or less.
The silver paste is applied onto the base metal layer 60 of the circuit layer 12, the surface of the spacer 20 and the surface of the lead frame 40 by, for example, a screen printing method, and dried to obtain the silver paste layer 70. The silver paste layer 70 may be formed on any surface of the planned joining surfaces facing each other at the time of joining. In the example shown in FIG. 3C, the silver paste layer 70 is formed on the surface of the circuit layer 12, the surface of the spacer 20 facing the semiconductor element 30, and the surface of the lead frame 40 facing the semiconductor element 30. Has been done.

As the silver paste layer 70, a silver oxide paste in which the silver powder is replaced with the silver oxide powder can also be used. The silver oxide paste contains a silver oxide powder, a reducing agent, a resin, and a solvent, and in addition to these, an organometallic compound powder is contained. The content of the silver oxide powder is 60% by mass or more and 92% by mass or less of the whole silver oxide paste, and the content of the reducing agent is 5% by mass or more and 15% by mass or less of the whole silver oxide paste. The content is 0% by mass or more and 10% by mass or less of the whole silver oxide paste, and the balance is a solvent.

[Batch joining process]
As shown in FIG. 3C, the spacer 20 is superposed on the silver paste layer 70 of the circuit layer 12, the semiconductor element 30 is superposed on the silver paste layer 70 of the spacer 20, and the semiconductor element 30 is overlaid. The silver paste layers 70 of the lead frame 40 are overlapped with each other so as to be in a laminated state.
Then, it is heated to a temperature of 180 ° C. or higher and 350 ° C. or lower with a pressing force of 1 MPa or more and 20 MPa or less applied in the stacking direction. The holding time of the temperature may be in the range of 1 minute or more and 60 minutes or less. By this heat treatment, the silver paste layer 70 is sintered to form a silver sintered joint layer 71 between the circuit layer 12, the spacer 20, the semiconductor element 30, and the lead frame 40, and the silver sintered joint layer 71 forms a silver sintered joint layer 71. The circuit layer 12, the spacer 20, the semiconductor element 30, and the lead frame 40 are integrally joined.

When the silver paste layer 70 made of silver oxide paste containing silver oxide and a reducing agent is used, the reduced silver particles precipitated by the reduction of silver oxide at the time of joining (firing), for example, have a particle size of 10 nm to 1 μm. Since it is very fine, it is possible to form a dense silver sintered bonding layer 71 and bond it more firmly.

[Resin sealing process]
After joining the spacer 20, the semiconductor element 30, and the lead frame 40 to the power module substrate 10 as described above, the power module substrate 10, the spacer 20, and the semiconductor are removed except for the lower surface of the heat dissipation layer 13 of the power module substrate 10. The vicinity of the connection portion between the element 30 and the lead frame 40 is integrally sealed with the mold resin 50.
Specifically, the mold resin 50 is formed and sealed by a transfer molding method using, for example, a sealing material made of an epoxy resin or the like. The outer end of the lead frame 40 is exposed from the mold resin 50.

The power module 100 manufactured in this way is warped because the semiconductor element 30 is joined and pressurized while being sandwiched between the highly rigid power module substrate 10 and the lead frame 40. Is suppressed, and therefore, a good bonding state can be obtained without damaging the semiconductor element 30 and the like. Further, the spacer 20, the semiconductor element 30, and the lead frame 40 can be bonded to the power module substrate 10 at the same time, which facilitates manufacturing.

In this power module 100, since both sides of the semiconductor element 30 are bonded to the spacer 20 and the lead frame 40 by the silver sintered bonding layer 71, the semiconductor element 30 has high bonding reliability even in a high temperature environment and the silver sintered bonding layer. Since 71 has excellent thermal conductivity, the heat generated by the semiconductor element 30 can be quickly dissipated. Moreover, the spacer 20 and the lead frame 40 arranged on both sides of the semiconductor element 30 are made of a copper-based low wire expansion material, and the linear expansion difference between the spacer 20 and the lead frame 40 and the semiconductor element 30 is reduced to reduce the semiconductor. The thermal stress acting on the element 30 can be reduced to prevent its damage.

2. 2nd Embodiment FIG. 5 shows the power module 101 of the 2nd embodiment. In this 2nd embodiment, there is no spacer 20 provided in the 1st embodiment, and the circuit layer 17 of the power module substrate 16 is not provided. A semiconductor element 30 is bonded to the semiconductor element 30, and a lead frame 40 is bonded to the semiconductor element 30.
In this case, the ceramic substrate 1 of the power module substrate 16 is joined as a circuit layer 17 in a laminated state in which two small circuit portions 17a and 17b are arranged in the plane direction in the illustrated example, and each small circuit portion 17a is joined. , 17b, respectively, the semiconductor element 30 is bonded.

The circuit layer 17 and the heat radiating layer 18 of the power module substrate 16 are made of copper or a copper alloy. Although this copper or copper alloy itself has a relatively large coefficient of linear expansion, it is less likely to be deformed than the aluminum or its alloy of the first embodiment, so that the linear expansion of the surface of the circuit layer 17 causes the linear expansion of the ceramic substrate 11. Is dominated by. Therefore, the power module substrate 16 as a whole becomes a low wire expansion material (the first copper-based low wire expansion material of the present invention). In this embodiment, oxygen-free copper is used as the circuit layer 17 and the heat radiating layer 18.
As in the first embodiment, the lead frame 40 is a copper-based low linear expansion material (Cu) in which a low linear expansion material such as tungsten (W), molybdenum (Mo), or chromium (Cr) is combined. It is made of a second copper-based low wire expansion material).
The coefficient of linear expansion difference between the power module substrate 16 and the lead frame 40 is set to 5 ppm / ° C. or less, and the thickness ratio between the circuit layer 16 of the power module substrate 15 and the lead frame 40 is 0.2. It is set to 5.0 or more and 5.0 or less.

In this power module 101, the circuit layer 17 and the heat radiating layer 18 are formed on both sides of the ceramic substrate 11 as an active metal brazing material such as silver titanium (Ag-Ti) -based brazing material or silver-copper titanium (Ag-Cu-Ti) -based brazing material. A substrate 16 for a power module in which these are joined is produced by laminating through and heating to 800 ° C. or higher and 930 ° C. or lower in a state where a pressing force of 0.05 MPa or more and 1.0 MPa or less is applied in the laminating direction. Will be done. After that, the circuit layer 17, the semiconductor element 30, and the lead frame 40 are laminated with a silver paste layer interposed therebetween, and pressured and heated all at once in the same manner as in the first embodiment to obtain silver. After joining with the sintered bonding layer 71, it is finally sealed with the mold resin 50. Since the circuit layer 17 of the power module substrate 16 of this embodiment is made of copper or a copper alloy, it is not necessary to provide the base metal layer 60 formed on the circuit layer 12 made of aluminum or an alloy thereof of the first embodiment. A similar base metal layer may be formed. Further, a base metal layer such as gold, silver, or nickel may be formed on each of the planned bonding surfaces of the semiconductor element 30 and the lead frame 40 by plating, sputtering, or the like.
In the power module 101 manufactured in this manner, the lead frame 40 and the power module substrate 15 arranged on both sides of the semiconductor element 30 are made of a copper-based low-wire expansion material, and the heat acting on the semiconductor element 30 is generated. The stress can be reduced and the damage can be effectively prevented.

In addition, the present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention.

The circuit layers, spacers, and lead frames of the power module board were prepared with the materials and thicknesses shown in Table 1, and silver paste was applied to any of these facing surfaces to be joined, and then laminated and collectively joined. .. In this case, in Invention Examples 1 to 4 and Comparative Examples 1 and 2, a base metal layer was formed on the surface of the circuit layer made of aluminum by using the above-mentioned glass-containing silver paste. In Invention Examples 5 and 6 and Comparative Example 2, a semiconductor element was bonded to the circuit layer without using a spacer. In each case, the temperature at the time of joining was 300 ° C., and the load was 10 MPa. The power module to which this semiconductor element is bonded is subjected to a thermal shock test of -40 ° C on the low temperature side, 150 ° C on the high temperature side, and 1000 cycles in a liquid tank type thermal shock test device manufactured by ESPEC, and the presence or absence of damage to the semiconductor element is evaluated. did.
The presence or absence of damage to the semiconductor element is determined by using an ultrasonic image measuring device manufactured by Insight Co., Ltd., when the probability of cracks being found in the semiconductor element is 10% or less, and when the probability of cracks being found in the semiconductor element is 10%. The case where it exceeds is marked as x.
These results are shown in Table 1. In Table 1, "4N-Al" is aluminum with a purity of 99.99% by mass or more, "C1020" is oxygen-free copper, "Cu-Mo" is pure copper / copper molybdenum composite material / pure copper clad material, and "Cu-W". "Indicates a pure copper / copper tungsten composite material / pure copper clad material.

As can be seen from Table 1, damage to the semiconductor element could not be confirmed for a power module having a difference in coefficient of linear expansion of the materials on both sides of the semiconductor element within 5 ppm / ° C and a thickness ratio of 0.2 or more and 5.0 or less. rice field.

10 Power module board 11 Ceramic board 12 Circuit layer 13 Heat dissipation layer 15 Brazing material 16 Power module board (first copper-based low-wire expansion material)
17 Circuit layers 17a, 17b Small circuit part 18 Heat dissipation layer 20 Spacer (first copper-based low wire expansion material)
30 Semiconductor element 40 Lead frame (second copper-based low wire expansion material)
50 Mold resin 60 Base metal layer 61 Glass layer 62 Silver layer 70 Silver paste layer 71 Silver sintered joint layer 100,101 Power module

Claims (1)

One surface of the semiconductor element mounted on the power module substrate is bonded to the first copper-based low-wire expansion material via a silver sintered bonding layer, and the other surface is bonded to copper or a copper alloy with a low coefficient of linear expansion. It is bonded to a lead frame made of a second copper-based low wire expansion material including a material via a silver sintered bonding layer, and these first copper-based low wire expansion material and the second copper-based low wire expansion material are , Ri difference 5 ppm / ° C. der less linear expansion coefficient,
The power module substrate has a circuit layer made of aluminum or an aluminum alloy laminated on the surface of a ceramics substrate, and copper or a copper alloy and a low coefficient of linear expansion material bonded to the surface of the circuit layer in a laminated state. The spacer is the first copper-based low wire expansion material, and the thickness ratio of the spacer to the lead frame is 0.2 or more and 5.0 or less.
A base metal layer is formed on the surface of the circuit layer, and the spacer is bonded to the base metal layer via a silver sintered bonding layer.
The base metal layer is a power module, wherein the glass layer formed on the circuit layer surface, that you have a two-layer structure of a silver layer formed on the glass layer.

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