JP6040803B2 - 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.

As a conventional power module, a metal plate forming a conductor pattern layer is laminated on one surface of a ceramic substrate, and an electronic component such as a semiconductor chip is soldered on the conductor pattern layer, and the other side of the ceramic substrate is A metal plate serving as a heat dissipation layer is formed on the surface, and a heat sink is joined to the heat dissipation layer.
In a power module substrate used in such a power module, a circuit layer or the like is joined to the surface of the ceramic substrate by brazing, but there is a problem that warpage occurs due to thermal expansion and contraction at that time.

  Therefore, in Patent Document 1, in order to alleviate the amount of warpage of the power module substrate, a heat dissipation layer is formed by laminating a thick heat diffusion plate having ceramic plates on both sides between the circuit layer and the heat dissipation layer. It has been proposed to reduce the amount of warpage by providing the same buffering function as when forming a thick film.

  In addition, the power module may be sealed with a thermosetting resin such as an epoxy resin for the purpose of fixing or insulating the mounted electronic component.

JP 2003-86747 A Japanese Patent No. 4565249 Japanese Patent No. 4646417

By the way, various thermal stresses are generated in the power module substrate due to heat generation of electronic components to be mounted, temperature change in the surrounding environment, and the like. Therefore, it is not sufficient to alleviate the warpage caused by brazing between the metal plate and the ceramic substrate. In order to quickly dissipate the heat generated by the electronic components that occur intermittently during use, higher power cycle performance is achieved. Further, there is a demand for reliably preventing the occurrence of peeling of the metal layer, cracking of the ceramic substrate, and the like by heat cycles accompanying changes in the external environmental temperature.
Furthermore, when the power module is resin-sealed with a thermosetting resin such as an epoxy resin, the adhesive between the mold resin to be sealed and the aluminum is poor, so that the interface between the resin mold and the aluminum is broken, and the electronic component There was a problem that it was difficult to ensure the bondability.

  This invention is made | formed in view of such a situation, Comprising: Warpage generation | occurrence | production can be suppressed, Power cycle property, heat cycle property can be improved, and the joining property of an electronic component is ensured favorably. An object is to provide a power module that can be used.

  In order to quickly absorb the heat generated by the electronic component, it is effective to form the circuit layer thick. In this case, when aluminum is used for the circuit layer, the thermal stress is relieved and good bondability with the ceramic substrate can be secured, but there is a problem that it becomes difficult to form the circuit layer by etching.

In order to solve this, for example, as disclosed in Patent Document 2 and Patent Document 3, a multilayer structure in which a circuit layer is separated by a ceramic substrate is used, so that a lower layer portion is separated from an upper layer on which electronic components are mounted. It is thought that heat capacity can be secured.
However, if the thickness of the metal layer bonded to both sides of the ceramic substrate is different, warpage occurs due to the thermal expansion / contraction difference of each layer.
Furthermore, if the power module is warped before resin sealing, the thickness of the resin on the side of the circuit layer on which the electronic component is mounted becomes uneven, and when the power cycle is applied, There is a problem that the bonding reliability of the solder layer that joins the component and the circuit layer is lowered.

Therefore, the power module of the present invention includes a single intermediate layer made of aluminum or an aluminum alloy bonded in a laminated state between the first ceramic substrate and the second ceramic substrate, and the intermediate layer of the first ceramic substrate. Comprises a circuit layer made of aluminum or aluminum alloy bonded to the opposite surface, and a heat dissipation layer made of aluminum or aluminum alloy bonded to the surface opposite to the intermediate layer of the second ceramic substrate, The power module substrate has a ratio a / b of the thickness a of the circuit layer to the thickness b of the heat dissipation layer set to 0.5 or more and 1.5 or less, and a hole opened at an end of the intermediate layer The electronic component provided and bonded to the circuit layer and the power module substrate are sealed with a resin mold except for the surface of the heat dissipation layer. Together with the, and the structure in which the resin mold is provided in a state that has entered into the hole.

By having the intermediate layer laminated via the first ceramic substrate, the heat capacity of the entire power module substrate can be increased without increasing the thickness of the circuit layer to which the electronic component is bonded. . In addition, the heat spreader effect of the intermediate layer can quickly transmit and dissipate the heat generated by the electronic component to the heat dissipation layer, so that the solder layer does not cause distortion or cracks in the solder layer that fixes the electronic component. It can be kept healthy in the long term.
In addition, by forming the circuit layer, intermediate layer, and metal layer with aluminum or aluminum alloy with low tensile strength and proof stress, the generation of cracks and cracks in the ceramic substrate can be mitigated by reducing the stress caused by the difference in thermal expansion with the ceramic substrate. Can be prevented.
Moreover, the power module substrate, the ratio a / b of the thickness a of the circuit layer is set to 0.5 to 1.5 to the thickness b of the heat dissipation layer is formed substantially symmetrical shape via a further intermediate layer Therefore, the curvature which arises in the board | substrate for power modules can be suppressed.

  Further, by sealing the electronic component and the power module substrate with a resin mold, the resin is poured into and around the plurality of substrates and metal plates and electronic components stacked between the electronic component and the heat dissipation layer. At the same time, the resin enters the hole opened at the end of the intermediate layer, and the resin mold can be firmly held on the power module substrate. On the other hand, since the whole power module can be firmly held by the resin mold, it is possible to ensure good bondability of the electronic component. Also, by sealing the electronic component and the power module substrate with reduced warpage with a resin mold, the thickness of the resin on the circuit layer side on which the electronic component is mounted becomes uniform, and when the power cycle is loaded , The bonding reliability of the solder layer can be maintained.

In the power module of the present invention, it is preferable that a thickness a + c, which is a sum of the thickness c of the intermediate layer and the thickness a of the circuit layer, is set to 0.3 mm or more and 2.5 mm or less.
In this case, a good heat spreader effect can be obtained by setting the thickness a + c, which is the sum of the thickness c of the intermediate layer and the thickness a of the circuit layer, to 0.3 mm or more and 2.5 mm or less.
In addition, if thickness a + c is less than 0.3 mm, heat transfer performance will fall and sufficient heat spreader effect will not be acquired. On the other hand, when the thickness a + c exceeds 2.5 mm, the thermal resistance of the entire power module is increased and a sufficient heat spreader effect cannot be obtained.

  According to the present invention, it is possible to improve the power cycle performance and heat cycle performance by structurally suppressing the occurrence of warpage, and to ensure good bondability of electronic components, and to provide long-term reliability. A multi-layer power module having a high level can be obtained.

It is a longitudinal cross-sectional view which shows embodiment of the power module of this invention, and is equivalent to the arrow view along the AA line of FIG. It is a top view of the power module of FIG. It is an arrow line view which follows the BB line of FIG. FIG. 2 is an enlarged cross-sectional view showing the vicinity of a joint portion in FIG. 1. It is an exploded sectional view showing the state before joining. It is an expanded sectional view similar to FIG. 4 which shows the dimensional relationship between the through-hole of the ceramic substrate before joining, and the convex part of the metal plate for circuit layers. It is a front view which shows the example of the pressurization apparatus used with the manufacturing method of this invention. It is a top view explaining the structure of the intermediate | middle layer which is other embodiment of the power module of this invention. It is an expanded sectional view similar to FIG. 4 which shows the other example of a junction part vicinity. It is an expanded sectional view similar to FIG. 4 which shows the other example of a junction part.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
1 to 5 show the power module of the first embodiment. As shown in FIGS. 1 and 2, the power module 1 includes a power module substrate 10, an electronic component 7 such as a semiconductor chip mounted on the surface of the power module substrate 10, and a back surface of the power module substrate 10. The power module substrate 10 and the electronic component 7 are resin-sealed by a resin mold 9.

  The power module substrate 10 includes intermediate layers 5A and 5B bonded in a laminated state between the first ceramic substrate 2 and the second ceramic substrate 3, and the opposite side of the intermediate layers 5A and 5B of the first ceramic substrate 2. Circuit layers 4A to 4E bonded to the surfaces of the second ceramic substrate 3 and a heat dissipation layer 6 bonded to the surface of the second ceramic substrate 3 opposite to the intermediate layers 5A and 5B. 4A to 4E, the intermediate layers 5A and 5B, and the heat dissipation layer 6 are joined to each other by brazing or the like. The electronic component 7 is mounted on a part of the circuit layers 4A to 4E (4D and 4E in the illustrated example) arranged at the uppermost stage, and the heat sink 8 is joined to the heat dissipation layer 6 arranged at the lowermost stage.

The ceramic substrates 2 and 3 are made of AlN, Al ₂ O ₃ , SiC, Si ₃ N ₄ or the like, for example, to a thickness of 0.32 mm to 1.0 mm. The circuit layers 4A to 4B, the intermediate layers 5A and 5B, and the heat dissipation layer 6 are made of pure aluminum or aluminum alloy having a purity of 99.90% or more. The thickness of the circuit layer, the intermediate layer, and the heat dissipation layer is, for example, 0.25 mm to 2.5 mm.
For bonding the ceramic substrates 2 and 3 to the circuit layers 4A to 4E, the intermediate layers 5A and 5B, and the heat dissipation layer 6, for example, an Al—Si or Al—Ge brazing material is used.

Further, as shown in FIGS. 2 and 3, five circuit layers 4A to 4E are arranged at the uppermost stage, and two intermediate layers are arranged at the middle stage between the two ceramic substrates. One layer 6 is provided. The uppermost five circuit layers 4A to 4E are arranged one at the middle position (4C) and two on each side (4A, 4B and 4D, 4E). The intermediate layers 5A and 5B between the ceramic substrates 2 and 3 are formed in the shape of an elongated strip having a length capable of connecting the circuit layers 4A and 4D and 4B and 4E arranged on both sides of the uppermost stage, respectively. The two are arranged in parallel in the plane direction with a mutual interval therebetween, and as shown in FIG. 3, holes 51 are formed at the ends of these intermediate layers 5A and 5B. Reference numeral 51 a indicates the opening of the hole 51.
Then, the circuit layers 4A, 4D and 4B, 4E on both sides in the uppermost stage are paired and are electrically connected to each other via the intermediate layers 5A, 5B so as to be connected below the circuit layer 4C at the intermediate position. It is said that.

As its connection form, four through-holes 11 are formed in the first ceramic substrate 2, and four circuit layers 4A excluding the circuit layer 4C in the middle position among the five uppermost circuit layers 4A to 4E described above. , 4B, 4D, and 4E are each formed with a convex portion (corresponding to a metal member of the present invention) 12 in a columnar shape, and these convex portions 12 are inserted into the through holes 11, respectively, 3 is bonded to the intermediate layers 5A and 5B. In this case, as shown in FIG. 4, the convex portion 12 is joined to the intermediate layers 5A and 5B, and the vicinity of the middle between the joint P to the intermediate layers 5A and 5B and the lower surfaces of the circuit layers 4A, 4B, 4D and 4E. Is plastically deformed and slightly expanded in diameter, but a gap G is formed between the inner peripheral surface of the through hole 11.
The sizes of the through holes 11 and the protrusions 12 are the ratio of the bonding area A1 between the first ceramic substrate 2 and the intermediate layers 5A and 5B to the bonding area A2 between the second ceramic substrate 3 and the intermediate layers 5A and 5B. A1 / A2 is set to be 0.75 or more.

  Further, as shown in FIG. 1, the circuit layers 4 </ b> A to 4 </ b> E, the intermediate layers 5 </ b> A and 5 </ b> B, and the heat dissipation layer 6 have a ratio a / b of the thickness a of the circuit layers 4 </ b> A to 4 </ b> E to the thickness b of the heat dissipation layer 6. The thickness a + c, which is the sum of the thickness c of the intermediate layers 5A and 5B and the thickness a of the circuit layers 4A to 4E, is set to 0.3 mm or more and 2.5 mm or less. It is configured.

  In the power module 1, except for the surface of the heat dissipation layer 6, the power module substrate 10 and the electronic component 7 are sealed with a resin mold 9 such as an epoxy resin. And the resin mold 9 is provided in the state which entered also into the hole 51 opened to the edge part of intermediate | middle layer 5A, 5B. In addition, the resin sealing with the resin mold 9 is performed on the power module 1 for the purpose of fixing, insulating, and the like of the electronic component 7.

Next, a method for manufacturing the power module 1 configured as described above will be described.
Of the ceramic substrates 2 and 3, the first ceramic substrate 2 having the through holes 11 can be obtained by forming the through holes in the green sheet before firing of the ceramics by press working and firing. Its outer shape is processed after firing. The second ceramic substrate 3 having no through hole is subjected to external processing after firing the green sheet.

As shown in FIG. 5, the circuit layer metal plate 44C, the intermediate layer metal plates 45A and 45B, and the heat dissipation layer metal plate 46 are formed by temporarily bonding the brazing materials 13 and 14 to the surface with a volatile organic medium such as octanediol. It is fixed and punched together by pressing to form a metal plate with a brazing filler metal paste. In this case, for example, an Al—Si or Al—Ge brazing material 13 is attached to one surface of the uppermost circuit layer metal plate 44C and both surfaces of the middle intermediate layer metal plates 45A and 45B, and the lowermost The heat radiation layer metal plate 46 is attached with an Al—Si or Al—Ge brazing material 14 on one surface thereof.
Of the circuit layer metal plates 44A to 44E, the metal plates 44A, 44B, 44D, and 44E having the convex portions 12 are formed by previously forming the convex portions 12 on one side by press working, and the convex portions 12 are excluded. Thus, it forms by sticking the brazing material foil which pierced the hole to the plane around the convex part 12.

  The convex portion 12 is larger than the thickness of the ceramic substrate 2 having the through hole 11 and is set to a length that slightly protrudes from the ceramic substrate 2 when inserted into the through hole 11 as shown in FIG. In consideration of the dimensional variation of the thickness of the ceramic substrate 2, the length is set to be 0.02 mm to 0.2 mm larger than the maximum tolerance, for example, 0.05 mm larger. Further, the outer diameter D1 of the convex portion 12 and the inner diameter D2 of the through hole 11 of the ceramic substrate 2 are such that the convex portion 12 expands during pressurization, which will be described later, so that a gap G is formed even in the expanded diameter state. The outer diameter D1 of the convex portion 12 is 1.0 mm to 20 mm, and the inner diameter D2 of the through hole 11 of the ceramic substrate 2 is 1.1 mm to 28 mm. For example, the outer diameter D1 of the convex portion 12 is 10 mm, and the inner diameter D2 of the through hole 11 is 13 mm.

The two ceramic substrates 2 and 3 and the metal plates 44A to 44E, 45A, 45B, and 46 thus formed are joined as follows. First, the ceramic substrates 2 and 3, the circuit layer metal plates 44 </ b> A to 44 </ b> E, the intermediate layer metal plates 45 </ b> A and 45 </ b> B, and the heat dissipation layer metal plate 46 are alternately overlapped, and the circuit layer metal plates 44 </ b> A, 44 </ b> B, 44 </ b> D, The convex part 12 of 44E is made into the state inserted in the through-hole 11 of the corresponding 1st ceramic substrate 2, and the laminated body S is installed in the pressurization apparatus shown in FIG.
The pressure device 110 includes a base plate 111, guide posts 112 vertically attached to the four corners of the upper surface of the base plate 111, a fixed plate 113 fixed to the upper ends of the guide posts 112, and the base plates 111. A pressing plate 114 supported by a guide post 112 so as to freely move up and down between the fixing plate 113 and a spring provided between the fixing plate 113 and the pressing plate 114 to urge the pressing plate 114 downward. And urging means 115.
The fixed plate 113 and the pressing plate 114 are arranged in parallel to the base plate 111, and the above-described laminate S is arranged between the base plate 111 and the pressing plate 114. Carbon sheets 116 are disposed on both sides of the laminate S to make the pressure uniform.

In a state where the pressure is applied by the pressure device 110, the pressure device 110 and the pressure device 110 are installed in a heating furnace (not shown), and are brazed by heating to a brazing temperature of 630 ° C., for example. The applied pressure in this case is 0.5 MPa (5 kgf / cm ² ), for example.

By pressurizing in this manner, the convex portion 12 is plastically deformed and crushed during brazing, and is joined to the intermediate layer metal plates 45A and 45B, and the circuit layer metal plates 44A to 44B around the convex portion 12 are joined. The plane of 44E is in close contact with the surface of the first ceramic substrate 2, and a uniform bonding state can be obtained in the plane direction.
Even in the state after joining, the convex portion 12 partially enlarges the diameter, but as described above, a gap G is formed between the convex portion 12 and the inner peripheral surface of the through hole 11 in a state where the diameter is enlarged. Therefore, the convex portion 12 is not pressed against the inner peripheral surface of the through hole 11.

  Further, by bonding the ceramic substrates 2 and 3 and the intermediate layer metal plates 45A and 45B, the holes 51 opened at the end portions of the intermediate layers 5A and 5B are formed.

The power module substrate 10 manufactured in this way is mounted with the electronic component 7 on a part of the uppermost circuit layers 4A to 4E, as shown in FIGS. The power module substrate 10 and the electronic component 7 are resin-sealed to constitute the power module 1.
For example, a soft epoxy resin material before curing is poured from above the power module substrate 10 and the electronic component 7 into the gaps between the individual circuit layers 4A to 4E and the intermediate layers 5A and 5B. The epoxy resin material is heated to the curing temperature of the epoxy resin material until the epoxy resin material is filled. As a result, the power module substrate 10 and the periphery of the electronic component 7 and the gap can be resin-sealed by the resin mold 9. At this time, the epoxy resin material is poured into and around the ceramic substrates 2 and 3, the circuit layers 4 </ b> A to 4 </ b> E, the intermediate layers 5 </ b> A and 5 </ b> B, and the electronic component 7 constituting the power module substrate 10. The resin mold 9 can be firmly held on the power module substrate 10 by entering into the holes 51 opened at the ends of the 5A and 5B, and the electrons bonded to the power module substrate 10 can be retained. The joining state of the component 7 can be ensured satisfactorily. Further, by sealing the electronic component 7 and the power module substrate 10 in which warpage is suppressed by the resin mold 9, the thickness of the resin on the circuit layers 4A to 4E side on which the electronic component is mounted becomes uniform, and the power cycle When the load is applied, the bonding reliability of the solder layer can be maintained.
In addition, when connecting the heat sink 8 to the power module 1, the resin mold 9 is formed at a position escaped from the connection surface between the heat dissipation layer 6 and the heat sink 8 so that the resin mold 9 does not hinder attachment of the heat sink 8. Is done.

Finally, the heat sink 8 is attached via heat transfer grease or the like so that the heat sink 8 contacts the lowermost heat radiation layer 6.
The heat sink 8 is formed, for example, by extrusion molding of A6063 aluminum alloy. In the example of illustration, it extrudes in the direction orthogonal to a paper surface, and the straight fin 21 is formed in strip | belt-plate shape along the extrusion direction. Although not limited in size, for example, a plurality of straight fins 21 having a thickness of 4 mm and a height of 15 mm along the extrusion direction are formed on one surface of a plate-like portion 22 having a 50 mm square and a thickness of 5 mm. . The power module 1 is fixed by screwing or the like using a mounting bracket (not shown) with a leaf spring or the like sandwiched between the heat sink 8.

  This power module 1 has a multilayer circuit layer in which a part of the circuit layers 4A to 4E and the intermediate layers 5A and 5B, which are stacked via the first ceramic substrate 2, are connected to each other by a metal member. The heat capacity of the entire circuit layer can be increased without increasing the thickness of the circuit layers 4A to 4E. Further, the heat generated in the electronic component 7 is transferred from the circuit layers 4D and 4E to the intermediate layers 5A and 5B via the convex portions 12, and the heat is spread by the heat spreader effect of the intermediate layers 5A and 5B. 6 can be quickly transmitted and dissipated. Accordingly, the solder layer to which the electronic component 7 is fixed is not distorted or cracked, and the solder layer can be maintained soundly for a long time.

The power module 1, the ratio a / b of the thickness a of the circuit layer 4A~4E to the thickness b of the heat dissipation layer 6 is set to 0.5 to 1.5, further intermediate layer 5A, and 5B Therefore, the warp generated in the power module 1 can be suppressed.

Furthermore, the power module 1 is provided with a convex portion (metal member) 12 formed on one side of the circuit layers 4A, 4B, 4D, and 4E larger than the thickness of the first ceramic substrate 2 having the through holes 11, The convex portion 12 is plastically deformed and joined to adjust the thickness variation of the first ceramic substrate 2 according to the amount of plastic deformation of the convex portion 12. Therefore, stable bonding of the circuit layers 4A, 4B, 4D, 4E and the intermediate layers 5A, 5B arranged on both sides of the first ceramic substrate 2 can be obtained, the generation of thermal stress is reduced, and peeling and cracking are achieved. Etc. can be prevented.
Furthermore, since the gap G is formed between the convex portion 12 and the inner peripheral surface of the through-hole 11, even if thermal expansion and contraction is repeated due to a temperature cycle during use, the thermal stress in the through-hole 11 portion is reduced. It is alleviated, peeling of the joints and cracking of the ceramic substrates 2 and 3 are prevented, and high reliability as a power module can be maintained.

Moreover, a favorable heat spreader effect can be obtained by setting the thickness a + c, which is the sum of the thickness c of the intermediate layer and the thickness of the circuit layer a, to 0.3 mm or more and 2.5 mm or less.
In addition, if thickness a + c is less than 0.3 mm, heat transfer performance will fall and sufficient heat spreader effect will not be acquired. On the other hand, when the thickness a + c exceeds 2.5 mm, the thermal resistance of the entire power module is increased and a sufficient heat spreader effect cannot be obtained.

The sizes of the through holes 11 and the protrusions 12 are the ratio of the bonding area A1 between the first ceramic substrate 2 and the intermediate layers 5A and 5B to the bonding area A2 between the second ceramic substrate 3 and the intermediate layers 5A and 5B. It is preferable that A1 / A2 is set to be 0.75 or more. This is because if the ratio A1 / A2 is less than 0.75, stress concentrates on the second ceramic substrate 3 and cracking is likely to occur.
In order to improve heat dissipation, it is preferable that the outer diameter D1 of the convex portion 12 is large. For example, when the cross sectional area is larger than the projected area of the electronic component 7, the electronic component 7 is mounted on the extension of the convex portion 12. If you do, you will have excellent heat dissipation. Moreover, since a large current flows as a power module, the convex portion 12 having a large cross-sectional area is preferable because the current density is reduced.

In the present embodiment, the circuit layers 4A to 4E and the intermediate layers 5A and 5B are formed of aluminum or aluminum alloy having a small tensile strength and proof stress, and stress is generated due to a difference in thermal expansion from the ceramic substrates 2 and 3. By relaxing, it is possible to prevent the ceramic substrates 2 and 3 from cracking and cracking.
Further, in the present embodiment, the intermediate layers 5A and 5B are formed in an elongated strip shape as shown in FIG. 3, but can be bent and formed into an L shape in plan view as shown in FIG. The bent holes 51 can also be formed by arranging the bent portions so as to face each other. Moreover, the hole 51 opened to the end portion of the intermediate layer is not limited to the structure penetrating from one end portion of the intermediate layer to the other end portion, and as shown in FIG. A hole 51 dug in the end can also be formed. Also in this case, the resin mold 9 can be firmly held on the power module substrate 10 by the resin material entering the holes 51 and being cured.

An experiment was conducted to confirm the effect of the power module according to the present invention described above.
The power modules of Samples 1 to 5 in which the metal plates constituting the power module were set to the conditions shown in Table 1 were produced, and their “heat cycle performance”, “power cycle performance”, and “warping amount” were evaluated.
The metal plate for circuit layers and the metal plate for intermediate layers of each sample 1 to 5 were each formed to be 26 mm × 26 mm (26 mm square) with a pure aluminum plate (4N—Al) having a purity of 99.99% or more. The metal plate for the heat dissipation layer was formed of a plate material of 28 mm × 28 mm (28 mm square) with a pure aluminum plate having a purity of 99.99% or more. The thickness a of the circuit layer and the thickness b of the heat dissipation layer were as shown in Table 1. The thickness c of the intermediate layer was 1.2 mm. The first ceramic substrate and the second ceramic substrate disposed between the metal plates are brazed between the ceramic substrate and the metal plate by using AlN having a thickness of 0.635 mm and 30 mm × 30 mm (30 mm square). Thus, a power module substrate was manufactured. For samples 1 to 4, a hole opened at the end was provided, and for sample 5, a hole opened at the end was not provided in the intermediate layer.
And solder the IGBT semiconductor chip (electronic component) using Sn-Ag-Cu solder on the surface of each power module substrate, bond the connection wiring made of aluminum alloy, and resin seal with epoxy resin material Thus, modularized samples 1 to 5 were manufactured.

  In addition, the circuit layer and the intermediate layer are configured to be connected through a through hole formed in the first ceramic substrate by a convex portion protruding from the circuit layer, and the size and the like of the through hole and the convex portion are as follows. The ratio A1 / A2 of the bonding area A1 between the first ceramic substrate and the intermediate layer to the bonding area A2 between the second ceramic substrate and the intermediate layer was set to be 0.75 or more.

(Evaluation of heat cycle properties)
Each sample 1-5 is raised from −40 ° C. to 105 ° C. over 10 minutes, held at 105 ° C. for 15 minutes, then lowered from 105 ° C. to −40 ° C. over 10 minutes, and held at −40 ° C. for 15 minutes. 3000 heat cycles with a temperature history of 1 cycle were applied. Then, the peeling rate of the solder layer before applying the heat cycle and after applying the 3000 cycles was calculated from the following formula (1) by an ultrasonic inspection apparatus. In the ultrasonic flaw detection image, peeling is indicated by a white portion in the joint, and thus the area of the white portion was taken as the peeling area.
Peeling rate = (Peeling area / Solder layer area) × 100 (%) (1)
In the evaluation, the case where the difference in the peeling rate before and after applying the heat cycle is 5% or less is “◯”, and the case where it exceeds 5% is “x”.

(Evaluation of power cycle characteristics)
Each sample 1 to 5 is screwed to a heat sink, the heat sink is fixed to a water-cooled container, and the semiconductor chip is energized at 140 ° C. and de-energized (ON) with the cooling water temperature and flow rate kept constant. One cycle of 60 ° C. at OFF) was adjusted so as to be repeated every 10 seconds, and a power cycle test was performed by repeating this cycle 100,000 times. Then, before and after the power cycle test, the thermal resistance between the semiconductor chip surface and the heat sink inner surface (heat sink bottom surface) was measured from the semiconductor chip surface temperature, and the rate of increase in thermal resistance due to the power cycle test was determined. The case where the rate of increase in thermal resistance was 10% or less was evaluated as “◯”, and the case where it exceeded 10% was evaluated as “X”.

(Measurement of warpage)
The amount of warpage was measured with a non-contact three-dimensional measuring machine. In addition, the measurement was performed before resin sealing and the curvature amount of the circuit layer surface was measured.

  As can be seen from Table 1, Samples 2 and 3 in which the ratio a / b is set to 0.5 or more and 1.5 or less are excellent in heat cycle durability (heat cycle property), and after power cycle. The rate of increase in thermal resistance was also low. Further, the amount of warpage could be made smaller than that of the sample 1 of the comparative example. On the other hand, the sample 1 of the comparative example in which the ratio a / b was set to less than 0.5 resulted in a decrease in heat cycle performance and an increase in thermal resistance after power cycle. The sample 4 of the comparative example in which the ratio a / b was set to exceed 1.5 resulted in an increase in thermal resistance after the power cycle. Furthermore, the sample 5 of the comparative example which did not provide the hole of an intermediate | middle layer resulted in the heat cycle property falling.

In addition, this invention is not limited to the said embodiment, A various change can be added in the range which does not deviate from the meaning of this invention.
For example, when joining a metal plate made of aluminum or aluminum alloy, a copper layer having a thickness of about 0.4 μm is formed on one side of the metal plate by vapor deposition or the like, and a ceramic substrate is laminated on the copper layer. You may join by the liquid phase joining method (Transient Liquid Phase Diffusion Bonding).
In this transient liquid phase bonding method, a copper layer deposited on the surface of the metal plate is interposed at the interface between the metal plate and the ceramic substrate, and by heating, the copper first diffuses into the aluminum of the metal plate, The copper concentration in the vicinity of the copper layer of the metal plate increases and the melting point decreases, thereby forming a metal liquid phase at the bonding interface in the eutectic region of aluminum and copper. If the temperature is kept constant in a state where this metal liquid phase is formed, the metal liquid phase contacts and reacts with the ceramic substrate for a certain time at a certain temperature, and copper further diffuses into the aluminum, The copper concentration in the metal liquid phase gradually decreases and the melting point increases, and solidification proceeds while the temperature is kept constant. As a result, a strong bond between the metal plate and the ceramic substrate is obtained, and after solidification has progressed, it is cooled to room temperature. The applied pressure at that time is 98 kPa (1 kg / cm ² ) to 3.4 MPa (35 kg / cm ² ) and is heated at 600 ° C. for 0.5 hours in a vacuum of 10 ⁻³ to 10 ⁻⁶ Pa. .

Further, the embodiment has been described in which the convex portions are integrally formed on the metal plate. However, as shown in FIG. 9, the columnar metal member 31 is formed separately from the metal plates 4 and 5, and penetrates the ceramic substrate 2. It is good also as what arrange | positions the metal member 31 in the hole 11, and joins the both end surfaces to both the metal plates 4 and 5. FIG. In this case, joints P are formed on both end surfaces of the metal member 31.
Further, as shown in FIG. 10, convex portions (metal members) 12 </ b> A and 12 </ b> B are formed on both metal plates 4 and 5, respectively, and joined at a midpoint of the length of the through hole 11 of the ceramic substrate 2. It is good. In this case, the joint portion P is formed in the middle position of the through hole 11.
In addition, this metal member is not formed in a columnar shape, but is formed in a columnar shape having a polygonal cross section, and the through hole is also formed in the same polygon, so that the metal member can be prevented from rotating in the through hole. The metal plate can be easily positioned in the structure.
Furthermore, in addition to the shape with straight fins by extrusion as in the embodiment, the heat sink may have a pin-like fin formed by forging or the like, or a plate-like shape called a heat sink. These types are combined and defined as a heat sink.
In this embodiment, the heat module is attached after the power module is resin-sealed. However, the electronic component can be mounted and resin-sealed after the heat sink and the power module substrate are joined.

DESCRIPTION OF SYMBOLS 1 Power module 2 1st ceramic substrate 3 2nd ceramic substrate 4A-4E Circuit layer 5, 5A, 5B Intermediate layer 6 Heat radiation layer 7 Electronic component 8 Heat sink 10 Power module substrate 11 Through-hole 12, 12A, 12B Convex part (metal) Element)
13, 14 Brazing material 21 Fin 22 Plate-like portion 31 Metal member 110 Pressurizing device 111 Base plate 112 Guide post 113 Fixing plate 114 Pressing plate 115 Biasing means 116 Carbon sheet

Claims (2)

And further intermediate layer comprising a bonded aluminum or aluminum alloy laminated state between the first ceramic substrate and the second ceramic substrate, is bonded to the surface opposite to the intermediate layer of the first ceramic substrate A circuit layer made of aluminum or an aluminum alloy, and a heat dissipation layer made of aluminum or an aluminum alloy bonded to a surface of the second ceramic substrate opposite to the intermediate layer, the circuit corresponding to the thickness b of the heat dissipation layer A power module substrate having a ratio a / b of layer thickness a set to 0.5 or more and 1.5 or less is provided, and an opening is provided at an end of the intermediate layer, which is joined to the circuit layer. The electronic component and the power module substrate are sealed with a resin mold except for the surface of the heat dissipation layer. Power module, characterized in that it is provided in a state that has entered the section.   2. The power module according to claim 1, wherein a thickness a + c obtained by combining the thickness c of the intermediate layer and the thickness a of the circuit layer is set to 0.3 mm or more and 2.5 mm or less.

Images