JP2021068850A - Ceramic metal circuit board and semiconductor device arranged by use thereof - Google Patents

Abstract

To provide a ceramic metal circuit board which enables the increase in the adhesion with a mold resin.SOLUTION: A ceramic metal circuit board comprises a metal part provided on at least one face of a ceramic substrate. In at least one portion of the face with the metal part provided thereon, a concave portion having a depth of from 5% up to 70% of a thickness of the ceramic substrate is provided at a place where the metal part is not provided. It is preferred that the total area of the concave portion provided at the place in the portion of the face with the metal part provided thereon, where the metal part is not provided is 0.1% to 50% of that of a portion of the face with the metal part provided thereon, where the metal part is not provided.SELECTED DRAWING: Figure 1

Description

The embodiment generally relates to a ceramic metal circuit board and a resin-molded semiconductor device using the same.

As a semiconductor element, there is a power element typified by an IGBT or the like. Power elements are becoming more sophisticated year by year. In addition, the operation compensation temperature (junction temperature) is becoming higher as the performance of semiconductor elements is improved. Further, as for the ceramic metal circuit board on which the semiconductor element is mounted, a ceramic metal circuit board having excellent heat resistance cycle characteristics (TCT characteristics) has been developed in order to cope with an increase in the operation compensation temperature. For example, in International Publication WO2013 / 09423 (Patent Document 1), the TCT characteristics are improved by optimizing the side shape of the copper circuit board. In Patent Document 1, reliability is improved even if a semiconductor element having an operating temperature of 170 ° C. or higher is mounted.
Further, a semiconductor device in which a semiconductor element is mounted on a ceramic metal circuit board is often resin-molded. By resin molding, productivity can be improved, conduction failure can be prevented, and deterioration can be prevented. For example, in International Publication WO2018 / 173921 (Patent Document 2), a recess is provided in a metal circuit board. By providing a recess in the metal circuit board, the adhesion with the mold resin is improved.

International Publication WO2013 / 09423 International Publication WO2018 / 173921 International Publication WO2017 / 056360

In Patent Document 2, the adhesion with the mold resin is improved by providing a recess in the metal circuit plate. However, semiconductor elements, lead frames, and the like cannot be mounted in places where recesses are provided. For this reason, there are restrictions on mounting locations such as semiconductor elements.
The present invention is for solving such a problem, and for providing a ceramic metal circuit board capable of suppressing restrictions on mounting locations such as semiconductor elements and improving adhesion to a mold resin. It is a thing.

The ceramic metal circuit board according to the embodiment is a ceramic metal circuit board having a metal circuit portion provided on at least one surface of the ceramics substrate, and the ceramic substrate is provided at a position where the metal circuit portion is not provided on the surface provided with the metal circuit portion. It is characterized in that a recess having a depth of 5% or more and 70% or less of the thickness of the ceramic is provided.

Since the ceramic metal circuit board according to the embodiment is provided with a recess in the ceramic substrate, the adhesion to the mold resin is improved. Therefore, the reliability of the resin-molded semiconductor device can be improved.

The figure which shows an example of the ceramic metal circuit board which concerns on embodiment. The figure which shows another example of the ceramic metal circuit board which concerns on embodiment. The figure which shows still another example of the ceramic metal circuit board which concerns on embodiment. FIG. 5 is a cross-sectional view showing an example of a ceramic metal circuit board according to an embodiment. The figure which shows an example of the semiconductor device which concerns on embodiment.

The ceramic metal circuit board according to the embodiment is a ceramic metal circuit board in which a metal portion is provided on at least one surface of the ceramics substrate, and ceramics are provided at a position where no metal portion is provided on at least one of the surfaces provided with the metal portion. It is characterized in that a recess having a depth of 5% or more and 70% or less of the thickness of the substrate is provided.
1 and 2 show an example of a ceramic metal circuit board according to an embodiment. In the figure, 1 is a ceramic metal circuit board, 2 is a ceramic substrate, 3 is a metal part (front metal part), 4 is a recess (4-1 is a dot-shaped recess), and 5 is a metal part (back metal part). .. FIG. 1 is a top view of the ceramic metal circuit board 1 as viewed from the surface provided with the surface metal portion. Further, FIG. 2 is a top view of the ceramic metal circuit board as viewed from the surface provided with the back metal plate. The metal portion 3 is used in a place where a semiconductor element, a terminal, or the like is mounted. The metal part 3 is called a surface metal part. Further, the metal portion 5 is used for a heat sink. The metal portion 5 is called a back metal portion. The ceramic metal circuit board 1 according to the embodiment is not limited to such an embodiment. For example, the metal portion may be provided on only one side of the ceramic substrate. Further, three or more metal parts may be provided. Further, the metal portions on both sides may be used as a surface metal portion on which a semiconductor element or the like is mounted.
Further, FIG. 3 shows an example in which the groove-shaped recess 4-2 is provided. Further, FIG. 4 shows a cross-sectional view of a ceramic metal circuit board. In the figure, T is the thickness of the ceramic substrate, and U is the depth of the recess.
The ceramic metal circuit board according to the embodiment is provided with a metal portion on at least one surface of the ceramics substrate. The metal part on which the semiconductor element is mounted is called the front metal part 3, and the metal part used as the heat sink is called the back metal part 5.

Examples of the metal part include various things such as a metal plate, a thin film, and a metallized layer. Examples of the metal plate include a copper plate (including a copper alloy plate) and an aluminum plate (including an aluminum alloy plate). Examples of the thin film include a sputtering film and a plating film. Further, various materials such as Ni (nickel), Pt (platinum), Ti (titanium), Cu (copper), and Ag (silver) can be applied as the material of the thin film. The metallized layer is obtained by firing a metal paste to harden it. Examples of the metallized layer include W (tungsten), Mo (molybdenum), Ag (silver), Cu (copper), Ti (titanium) and the like.
Further, the metal portion is preferably a metal plate having a thickness of 0.3 mm or more. Further, it is preferably a metal plate having a thickness of 0.5 mm or more. Further, it is preferable that the copper plate has a thickness of 0.5 mm or more. In recent years, as the performance of semiconductor elements has improved, the surface metal portion 3 is required to have an energizing capacity. If the copper plate has a thickness of 0.3 mm or more and further 0.5 mm or more, the energizing capacity can be increased. Further, the back metal portion 5 is also preferably a copper plate having a thickness of 0.3 mm or more in order to improve heat dissipation.

Examples of the ceramic substrate 2 include a silicon nitride substrate, an aluminum nitride substrate, an aluminum oxide substrate, and an argyl substrate.
The silicon nitride substrate can have a high strength of three-point bending strength of 500 MPa or more, and further 600 MPa or more. Further, there are those having a thermal conductivity of 50 W / m · K or more, and further 80 W / m · K or more. In particular, in recent years, there is also a silicon nitride substrate having both high strength and high thermal conductivity. If the silicon nitride substrate has a three-point bending strength of 600 MPa or more and a thermal conductivity of 80 W / m · K or more, the substrate thickness can be reduced to 0.4 mm or less, and further to 0.3 mm or less.
Further, the aluminum nitride substrate and the alumina substrate have a three-point bending strength of about 300 to 450 MPa. The argyl substrate is a sintered body in which aluminum oxide and zirconium oxide are mixed. The strength of the Argyle substrate is also around 550 MPa. If the strength is less than 500 MPa and the substrate thickness is as thin as 0.4 mm or less, the possibility of the substrate cracking during molding increases. In other words, when a ceramic substrate having a three-point bending strength of less than 500 MPa is used, it is preferable to increase the substrate thickness to 0.5 to 0.7 mm.
The three-point bending strength shall be measured by JIS-R-1601, and the thermal conductivity shall be measured by the laser flash method according to JIS-R-1611.
Further, the ceramic substrate preferably has a three-point bending strength of 500 MPa or more. By increasing the strength of the ceramic substrate, it is possible to make it hard to be damaged even if a recess is provided.

Further, the ceramic metal circuit board according to the embodiment has a recess having a depth of 5% or more and 70% or less of the thickness of the ceramic substrate in a portion where the metal portion is not provided on at least one of the surfaces provided with the metal portion. It is characterized by the provision of.
The depth U of the recess is in the range of 5% or more and 70% or less with respect to the thickness T of the ceramic substrate 2. This indicates that 5% ≦ (depth U of the recess / thickness T of the ceramic substrate) × 100 (%) ≦ 70%. The depth U of the recess may be such that the depth of at least one recess is within this range. Further, it is preferable that the depth U of all the recesses is within the range of 5 to 70% of the thickness T of the ceramic substrate.

By providing the recess, the adhesion with the mold resin can be improved. That is, the adhesion can be improved by improving the anchor effect by allowing the mold resin to enter the recess.
When the depth U of the recess is less than 5% of the thickness T of the substrate, the effect of improving the adhesion is small. Further, if the depth U of the recess exceeds 70% of the substrate thickness T, the strength of the ceramic substrate 2 may decrease. Therefore, it is preferable that the depth U of the recess is within the range of 5 to 70% of the thickness T of the ceramic substrate, and further within the range of 10 to 40%. For example, when the recess depth U on the front side is 40% of the substrate thickness T and the recess depth U on the back side is 40% of the substrate thickness T, the sum of the recess depths U on the front and back sides is 80 of the substrate thickness T. It may be%. This indicates that when the recesses are provided on both sides of the ceramic substrate, the depth U of one recess may be 70% or less of the substrate thickness T.

Further, the concave portion has various shapes such as a dot type and a groove type.
The dot-shaped recess has various shapes such as a circular shape, a polygonal shape, and a star shape when viewed from the upper surface. Further, the circular shape may be a perfect circle or an ellipse. In addition, various polygons such as triangles, quadrangles, pentagons, and hexagons can be mentioned. Examples of the quadrangle include a square, a rectangle, a rhombus, and a trapezoid.
Further, the dot-shaped recess preferably has a maximum diameter of 0.1 mm or more. The maximum diameter of the dot-shaped recess is the longest diagonal line when the surface of the ceramic substrate 2 is viewed from the upper surface. If the maximum diameter is less than 0.1 mm, it is difficult for the mold resin to enter the recess. The upper limit of the maximum diameter of the dot-shaped recess is not particularly limited, but it is preferably 2/3 or less of the creepage distance. The creepage distance is the shortest distance from the end portion of the ceramic substrate 2 to the metal portion (metal portion 3 or metal portion 4). If it is larger than 2/3 of the creepage distance, the strength of the end portion of the ceramic substrate 2 may be lowered. Therefore, the maximum diameter of the dot-shaped recess is preferably 2/3 or less, more preferably 1/2 or less of the creepage distance.
Further, the dot-shaped concave portion preferably has a circular shape. If it is circular, the mold resin easily enters the recess. If a gap is created in the recess, it may cause partial discharge.

Further, the groove-shaped recess has various shapes such as a straight line, a square shape, and a wavy shape.
FIG. 4 shows an example in which a square groove-shaped recess is formed. In FIG. 4, a groove-shaped recess 4-2 is provided along the creeping surface of the ceramic substrate 2 and the metal portion 3. When the groove-shaped recess is linear or corrugated, it may be provided at an arbitrary location along the surface of the ceramic substrate 2 and the metal portion 3. For example, the groove-shaped recesses may be provided only at one location along the surface of the ceramic substrate 2 and the metal portion 3, or may be provided at all four locations.
Further, the groove-shaped recess preferably has a minimum width of 0.1 mm or more. The minimum width of the groove-shaped recess is the smallest width when the surface of the ceramic substrate 2 is viewed from the upper surface. If the minimum width is less than 0.1 mm, there may be a portion where the mold resin does not enter the groove-shaped recess. The upper limit of the minimum width of the groove-shaped recess is not particularly limited, but it is preferably 2/3 or less of the creepage distance. If it is larger than 2/3 of the creepage distance, the strength of the end portion of the ceramic substrate 2 may be lowered. Therefore, the minimum width of the groove-shaped recess is preferably 2/3 or less, more preferably 1/2 or less of the creepage distance.

Further, when a plurality of metal portions 3 are provided, recesses may be provided between the metal portions 3. Regarding the recesses provided between the metal portions 3, the maximum diameter of the dot-shaped recesses or the minimum width of the groove-shaped recesses is preferably 0.1 mm or more. Further, it is preferably 2/3 or less, more preferably 1/2 or less between the metal portions 3.
Further, the recess 4 may have a structure in which both the dot-shaped recess 4-1 and the groove-shaped recess 4-2 are combined. In the case of an elliptical concave portion, a dot type is used when the maximum diameter / minimum width ratio is 3 or less, and a groove type is used when the ratio exceeds 3.

Further, the total area of the recesses provided in the portion of the surface provided with the metal portion where the metal portion is not provided is 0.1% or more and 50% or less of the portion of the surface provided with the metal portion in which the metal portion is not provided. Is preferable.
When the ceramic metal circuit board 1 is viewed from the upper surface, the area of the portion where the metal portion 3 is not provided is defined as the area A. The total area of the locations where the recesses are provided is defined as the area B. (Area B / Area A) × 100 (%) is preferably 0.1% or more and 50% or less. If the area B is less than 0.1%, the effect of providing the recess is small. Further, if the area B is larger than 50%, the strength along the surface of the ceramic substrate 2 may decrease. Therefore, the ratio of the area B is preferably in the range of 0.1 to 50%, more preferably 0.8 to 10%.

Further, when a plurality of recesses 4 are provided, the distance between adjacent recesses 4 is preferably 5 mm or less. If the distance between the adjacent recesses 4 exceeds 5 mm, the area without the recesses increases. As the area without recesses increases, the possibility of peeling of the mold resin increases. Therefore, the distance between the adjacent recesses 4 is preferably 5 mm or less, more preferably 3 mm or less.
Further, when the metal portions 3 are provided on both surfaces of the ceramic substrate 2, it is preferable to provide recesses 4 on both surfaces of the ceramic substrate 2. By providing recesses on both sides, peeling of the mold resin on both sides can be suppressed. In other words, when the back side of the ceramic metal circuit board is also resin-molded, it is preferable to provide recesses on both sides. Further, the size of the recess when the recess is provided on the back surface is as described above.

Further, when the recesses 4 are provided on both sides of the ceramic substrate 2, the positions may be the same on the front and back sides, or may be offset positions. FIG. 4 shows an example in which the recesses 4 are provided on the front and back surfaces of the ceramic substrate 2. The left side of FIG. 4 is an example in which recesses are provided at the same positions on the front and back sides. Further, the right side of FIG. 4 is an example in which recesses are provided by shifting the positions on the front and back sides. It is preferable that the recess 4 is not a through hole. This is because if it is a through hole, the mold resin is not filled and a gap is formed, so that the pressure resistance function is lowered. Therefore, when recesses are provided on the front and back sides, they shall not be through holes.
Further, it is preferable that the cross-sectional shape of the recess is one selected from U-shaped, V-shaped, rectangular, and circular. Of these, a U-shape or a V-shape is preferable. The U-shape and the V-shape have a shape that becomes thinner toward the depth of the recess. That is, the entrance side is wide and the depth direction is narrow. With such a structure, the mold resin easily enters the recess.

The ceramic metal circuit board as described above is suitable for a semiconductor device on which a semiconductor element is mounted. Further, it is suitable for a semiconductor device including a mold resin. FIG. 5 shows an example of a semiconductor device. In the figure, 1 is a ceramic metal circuit board, 6 is a semiconductor element, 7 is a terminal, 8 is a base plate, 9 is a mold resin, and 10 is a semiconductor device. Although FIG. 5 shows an example in which two semiconductor elements 6 and one terminal 7 are provided, the semiconductor device according to the embodiment is not limited to such a structure.
For example, three or more metal parts 3 may be provided, or the number of semiconductor elements and terminals may be increased. Further, wire bonding may be used instead of the terminals. Further, in FIG. 5, the back surface side of the ceramic metal circuit board 1 is also resin-molded, but only the front surface side may be resin-molded.
A device in which a semiconductor element 6 is mounted on a ceramic metal circuit board 1 is called a semiconductor device 10. Further, the terminal 7 shall be provided as needed. The terminal 7 also includes a lead frame. The semiconductor device 10 is arranged on the base plate 8. The base plate 8 is for mounting the semiconductor device 10, but may have a structure without a base plate. Examples of the base plate 8 include a heat sink base, a case (package type container), and a housing.

The semiconductor device 10 arranged on the base plate 8 is resin-molded. The resin is filled so as to fill the gap of the semiconductor device 10. At this time, the resin enters the recess 4. By solidifying the filled resin, the mold resin 9 is obtained.
Since the semiconductor device 10 according to the embodiment is provided with the recess 4, the adhesion to the mold resin 9 can be improved. Further, by filling a part or all of the concave portion 4 with the mold resin 9, the share strength of the mold resin can be set to 3 MPa or more. Further, by filling all the recesses 4 with the mold resin without gaps, the shear strength can be set to 6 MPa or more.

Further, by improving the adhesion of the mold resin, the TCT characteristics of the semiconductor device provided with the mold resin can be improved. Peeling of the mold resin can be suppressed when the TCT test (heat resistance cycle test) is performed. For example, -40 ° C x 30 minutes-> room temperature (25 ° C) x 10 minutes-> 175 ° C x 30 minutes-> room temperature (25 ° C) x 10 minutes is set as one cycle, and resin peeling is suppressed even after 300 cycles. Can be done.

The resin peeling causes damage to the ceramic metal circuit board 1 and deterioration of the insulating function due to the generation of voids in the molded resin. Both of them impair the reliability of the semiconductor device. Since the semiconductor device according to the embodiment suppresses the peeling of the mold resin, the reliability can be improved. In other words, it is possible to provide a ceramic metal circuit board suitable for a semiconductor device including a mold resin.
Further, it is possible to suppress the amount of partial discharge charge of the semiconductor device after the TCT test and improve the dielectric strength. The amount of partial discharge charge (pc: picocuron) when 5 kV is applied can be reduced to 10 pc or less. Further, the withstand voltage can be 5 kV or more.
Further, as described above, the reliability can be further improved by using a ceramic substrate having a three-point bending strength of 500 MPa or more. In particular, some silicon nitride substrates have a high three-point bending strength of 500 MPa or more, and further 600 MPa or more. For example, the silicon nitride metal circuit board of International Publication WO2017 / 056360 (Patent Document 3) shows excellent reliability even in a TCT test at 250 ° C. on the high temperature side. On the other hand, when the TCT characteristics were measured with the mold resin provided, the resin sometimes peeled off.

The coefficient of linear expansion of the silicon nitride substrate is ^{around 2.6 × 10-6} / K. The aluminum nitride substrate is ^{around 4.5 × 10-6} / K, the aluminum oxide substrate is around 8 × ^10-6 / K, and the argyl substrate is around 8 × ^10-6 / K. On the other hand, the coefficient of linear expansion of the epoxy resin is ^{around 50 × 10-6} / K, and the coefficient of linear expansion of the silicone resin is around 20 × ^10-6 / K. Where K is Kelvin.
Although the silicon nitride substrate has high strength, the difference from the coefficient of linear expansion with the resin is large. If the difference in the coefficient of linear expansion is large, it causes the resin to peel off when a thermal load is applied. By providing the concave portion in the ceramic metal circuit board according to the embodiment, the resin peeling can be suppressed. Epoxy resin and silicone resin are resins used as mold resins. Therefore, it is effective for a silicon nitride metal circuit board in which the difference in linear expansion coefficient from that of the molded resin is large.

Next, a method for manufacturing the ceramic metal circuit board according to the embodiment will be described. As long as the ceramic metal circuit board according to the embodiment has the above configuration, the manufacturing method thereof is not particularly limited, but the following can be mentioned as a manufacturing method for obtaining a good yield.

First, a ceramic metal circuit board is prepared.
Examples of the metal part include various things such as a metal plate, a thin film, and a metallized layer. Examples of the metal plate include a copper plate (including a copper alloy plate) and an aluminum plate (including an aluminum alloy plate). Examples of the thin film include a sputtering film and a plating film. Further, various materials such as Ni (nickel), Pt (platinum), Ti (titanium), Cu (copper), and Ag (silver) can be applied as the material of the thin film. The metallized layer is obtained by firing a metal paste to harden it. Examples of the metallized layer include W (tungsten), Mo (molybdenum), Ag (silver), Cu (copper), Ti (titanium) and the like.
When a copper plate or an aluminum plate is used as the metal plate, it is preferable to join by the active metal method or the direct joining method. Further, when the silicon nitride metal circuit board is produced by the active metal bonding method, those of Patent Documents 1 to 3 can be referred to.
Further, if necessary, the metal plate shall be etched and patterned. Further, as in Patent Document 1 or Patent Document 3, it is assumed that the brazing material protrudes and the side shape of the metal plate is prepared. In addition, the metal part shall be plated as necessary.

Next, a process for providing a recess shall be performed. Examples of the processing for providing the recess include laser processing, blasting, drilling, and cutting.
Laser processing is a method of irradiating a ceramic substrate with a laser to form recesses. By adjusting the spot diameter of the laser, the maximum diameter of the dot type and the minimum width of the groove type can be controlled. Further, by scanning the laser, a groove-shaped recess can also be formed. Further, the depth U of the recess can be controlled by adjusting the output of the laser. Further, examples of the laser include a CO ₂ laser and a green laser.

Further, the blasting process is a method of forming a recess by hitting particles called a projection material. The size of the recess can be adjusted by controlling the size of the projecting material and the stress of impact. It is preferable to apply a mask to a portion where the recess is not desired and perform blasting.

Further, drilling is a method of providing a recess with a drill. Further, cutting is a method of providing a recess using a cutting tool.

Among these processing methods, laser processing is preferable. Blasting, drilling and cutting are methods of applying stress to a ceramic substrate. Therefore, cracks may occur in the ceramic substrate when the recess is formed. In the case of laser machining, no stress is generated, so that the occurrence of cracks can be suppressed. In the case of laser machining, it is easy to control the cross-sectional shape of the recess into a U-shape or a V-shape.
The ceramic metal circuit board according to the embodiment can be manufactured by performing a process of providing a recess. Further, the process of providing the recess may be performed before the step of providing the metal portion on the ceramic substrate. By providing the concave portion before providing the metal portion, the concave portion can have a function as a positioning mark at the time of printing the brazing material.

Next, a method of manufacturing the semiconductor device according to the embodiment will be described.
First, a step of mounting the semiconductor element on the ceramic metal circuit board according to the embodiment is performed. In addition, terminals shall be mounted and wire bonding shall be performed as necessary.
Next, the semiconductor device is arranged on the base plate. Examples of the base plate 8 include a heat sink base, a case (package type container), and a housing.

Next, the resin molding process shall be performed. Examples of the resin used in the molding process include epoxy resin and silicone resin.
Further, various methods such as a transfer method and a compression method are applied to the molding process. There is also a molding method using a potting gel. In recent years, the transfer method has been used because of its good mass productivity. The transfer mold is a method in which the resin is softened by heating in a plunger, and the softened resin is poured into a mold to be cured. Since the softened resin is used, it is easy to fill the resin into the gaps of the semiconductor device having a complicated shape. In particular, it is easy to fill the inside of the recess of the ceramic metal circuit board with the resin. In addition, since the mold resin is solidified at once, it is excellent in mass productivity and productivity. In the potting process, the case of the package may be used as it is.

(Example)
(Examples 1 to 7, Comparative Examples 1 to 4)
The ceramic metal circuit boards shown in Table 1 were prepared. The metal part is a metal plate joined by an active metal joining method. Those using a copper plate as the metal part were joined using an Ag-Cu-Sn-Ti active metal brazing material. Further, those using an Al plate (aluminum plate) as the metal portion were joined using an Al—Si-based active metal brazing material. In addition, the ceramic substrate was unified to have a size of 60 mm × 50 mm.

Next, the metal portion was etched and patterned. Further, the front side metal plate was provided with four pattern shapes. In addition, we prepared the ones with different creepage distances.
The step of forming the recess was performed before joining the metal plates. The processing for forming the concave portion was performed by laser processing. The dot-shaped recess was _{formed by a CO 2} laser, and the groove-shaped recess was formed by a green laser. The size of the recess is as shown in Tables 2 and 3. The dot-shaped recess showed the maximum diameter. The groove-shaped recess showed the minimum width. The creepage distances are shown in Tables 2 and 3. The creepage distance ratio is shown as the ratio of the maximum diameter (or minimum width) of the recess / creepage distance. The area A is the total area of the ceramic metal circuit board where no metal portion is provided. Further, the area B is the total area provided with the recesses. Further, in Example 9 and Comparative Example 2, no recess was provided on the back surface side. Further, in Comparative Examples 3 to 5, no recess was formed.

Next, the semiconductor element and the metal terminal were mounted on the ceramic metal circuit board according to the examples and the comparative examples. In addition, wire bonding was performed. As a result, a semiconductor device was manufactured. The semiconductor device was placed on the base plate, and the mold resin was provided by transfer molding. Epoxy resin was used as the mold resin. By this step, a semiconductor device provided with a mold resin was prepared.
For each semiconductor device, the filling rate of the resin in the recess, the share strength of the mold resin, the presence or absence of resin peeling after the TCT test, the amount of partial discharge charge, and the dielectric strength were measured.
For the filling rate of the resin in the recess, an arbitrary cross section was measured and an average value was obtained. Further, in the measurement of the shear strength of the mold resin, the bonding strength of the mold resin was measured by the shear test. In the TCT test, one cycle is -40 ° C x 30 minutes → room temperature (25 ° C) x 10 minutes → 175 ° C x 30 minutes → room temperature (25 ° C) x 10 minutes, and the mold resin peels off after 300 cycles. The presence or absence was measured. For the peeling of the mold resin, the ratio of the area where the resin peeling was confirmed in the area A was determined by the ultrasonic flaw detection method (SAT). In addition, the presence or absence of damage to the ceramic substrate after the TCT test was measured.
Further, for the measurement of the partial discharge charge amount, the partial discharge charge amount (pc: picocuron) when 5 kV was applied was determined using a partial discharge measuring device after the TCT test. Specifically, the applied voltage is increased to 5 kV at about 1 kV / sec. Hold for 60 seconds at an applied voltage of 5 kV. The average value of the partial discharge charge amount (pc) in the last 5 seconds of the holding time shall be measured.
On the other hand, the withstand voltage is first held at 1 kV for 60 seconds using a withstand voltage tester after the TCT test, and the presence or absence of dielectric breakdown is confirmed. When dielectric breakdown did not occur, the voltage was increased in step 0.5 kV and the voltage was applied for 60 seconds, and thereafter, the applied voltage was increased until dielectric breakdown occurred, and the same confirmation was performed.
If the maximum applied voltage that does not cause dielectric breakdown is less than 5 kV, it is displayed as "defective (x)", if it is 5 kV or more and 7 kV or less, it is displayed as "good (○)", and if it exceeds 7 kV, it is displayed as "best (◎)". did.
The results are shown in Table 4.

As can be seen from the table, in the semiconductor device according to the embodiment, the adhesion strength of the mold resin was improved. Along with this, the resin peeling can be suppressed. Further, by controlling the recess size and the area ratio, damage to the ceramic substrate after the TCT test can be suppressed. In Example 9, since the recess was not provided on the back surface side, the resin peeled off on the back surface side. Therefore, it can be seen that it is preferable to provide recesses on both sides. The cross-sectional shape of the recess was U-shaped.
Further, the discharge charge of the example was 10 pc or less in the amount of discharge charge. The withstand voltage of the examples was 5 kV or more. Even after the TCT test, the resin peeling and damage to the ceramic substrate can be suppressed, so that the insulating property can be maintained.

On the other hand, in Comparative Example 1, since the recess depth U was small, the effect of providing the recess was insufficient. Further, in Comparative Example 2, since the recess depth U was large, the ceramic substrate was damaged. Since Comparative Example 3 and Comparative Example 4 did not have a recess, the rate of resin peeling was large. Further, in Comparative Example 3 and Comparative Example 4, the three-point bending strength of the ceramic substrate was as small as less than 500 MPa, so that the ceramic substrate was damaged. Therefore, it can be seen that it is preferable to provide a recess in a ceramic substrate having a three-point bending strength of 500 MPa or more. In addition, since the resin is less likely to peel off and the ceramic substrate is less likely to be damaged, the deterioration of the insulating property is significantly suppressed.

Although some embodiments of the present invention have been illustrated above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other embodiments, and various omissions, replacements, changes, etc. can be made without departing from the gist of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are also included in the scope of the invention described in the claims and the equivalent scope thereof. Moreover, each of the above-described embodiments can be implemented in combination with each other.

1 ... Ceramic metal circuit board 2 ... Ceramic substrate 3 ... Metal part (surface metal part)
4 ... Recessed 4-1 ... Dot-shaped recess 4-2 ... Groove-shaped recess 5 ... Metal part (back metal part)
6 ... Semiconductor element 7 ... Terminal 8 ... Base plate 9 ... Mold resin 10 ... Semiconductor device T ... Ceramic substrate thickness U ... Depth of recess

Claims (12)

In a ceramic metal circuit board in which a metal portion is provided on at least one surface of a ceramics substrate, 5% or more and 70% of the thickness of the ceramic substrate is provided in a place where no metal portion is provided on at least one of the surfaces provided with the metal portion. A ceramic metal circuit board characterized in that a recess having the following depth is provided. The total area of the recesses provided on the surface provided with the metal portion without the metal portion is 0.1% or more and 50% or less of the portion provided with the metal portion on the surface without the metal portion. The ceramic metal circuit board according to claim 1. The ceramic metal circuit board according to any one of claims 1 to 2, which has metal portions and recesses on both sides of the ceramic substrate. The ceramic metal circuit board according to any one of claims 1 to 3, wherein the thickness of the ceramic substrate is 0.1 mm or more and 0.4 mm or less. The ceramics according to any one of claims 1 to 4, wherein the ceramic substrate is a silicon nitride substrate having a three-point bending strength of 500 MPa or more, and the metal circuit portion is a metal plate having a thickness of 0.3 mm or more. Metal circuit board. The ceramic metal circuit board according to any one of claims 1 to 5, wherein a metal plate is provided on a surface opposite to the surface on which the metal circuit portion is provided. The ceramic metal circuit board according to any one of claims 1 to 6, wherein the cross-sectional shape of the recess is one selected from U-shaped, V-shaped, rectangular, and circular. The ceramic metal circuit board according to any one of claims 1 to 7, wherein the recess is one or two selected from a dot shape or a groove shape. A semiconductor device characterized in that a semiconductor element is mounted on the ceramic metal circuit board according to any one of claims 1 to 8. The semiconductor device according to claim 9, further comprising a mold resin. The semiconductor device according to claim 10, wherein the mold resin is filled in a part or all of the recesses. The semiconductor device according to any one of claims 10 to 11, wherein the share strength of the mold resin is 3 MPa or more.

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