JP7301732B2 - Ceramic circuit board with screw pad member and semiconductor device using the same - Google Patents

Description

Embodiments described later relate to a ceramic circuit board with a screw pad member and a semiconductor device using the same.

A ceramic circuit board has strength, heat dissipation and insulation. International Publication No. 2017/056360 (Patent Document 1) discloses a ceramic circuit board in which a ceramic substrate and a copper plate are bonded by an active metal bonding method. In Patent Document 1, the size of the protruding portion of the bonding layer and the side shape of the copper plate are controlled. This improves the TCT (thermal cycle) characteristics of the ceramic circuit board.
A semiconductor device in which a semiconductor element is mounted on a ceramic circuit board is fixed by various methods. One of them is a screw structure. In Japanese Patent Laying-Open No. 2003-197824 (Patent Document 2), a ceramic substrate is provided with a screw hole, and a reinforcing member is provided in the screw hole. In Patent Document 2, a reinforcing member is provided in a screw hole to suppress the occurrence of cracks during screwing. However, the formation of screw holes in the ceramic substrate itself causes a decrease in the strength of the ceramic substrate. For this reason, there has been a demand for a screwing structure that does not require a drilling process.
Japanese Patent Application Laid-Open No. 2005-45105 (Patent Document 3) discloses a structure in which a pressure contact member is provided on the creeping surface of a ceramic circuit board. In Patent Document 3, screwing is performed via a module case and a pressure contact member.

International Publication No. 2017/056360 JP 2003-197824 A JP-A-2005-45105

Patent document 3 has a structure in which screw holes are not provided in the ceramic substrate. With such a structure, it is possible to prevent deterioration of the strength of the ceramic substrate due to the provision of the screw holes. On the other hand, it cannot be said that the TCT characteristic of the semiconductor device after the screwed structure is always sufficient. Further, in Patent Document 3, a module case is interposed between the pressing member and the screw for screwing. In a screw-fixed structure via an intermediate member such as a module case, the alignment process becomes complicated.
SUMMARY OF THE INVENTION The present invention is intended to address such problems, and provides a ceramic circuit board with a screw pad member capable of improving the TCT of a semiconductor device after a screw structure. Another object of the present invention is to provide a ceramic circuit board with a screw-fastening pad member that can simplify the alignment process for the screw-fastening structure.

A ceramic circuit board with a screw pad member according to an embodiment has a screw pad member made of a metal plate on one surface of the ceramic substrate of the ceramic circuit board. It is characterized in that it is bonded to the substrate and has a structure in which the bonding layer protrudes from the end of the screw pad member.

1 is a top view showing an example of a ceramic circuit board with a screw pad member according to an embodiment; FIG. The figure which shows an example of the structure which the joining layer of the screw pad|pad member protruded. BRIEF DESCRIPTION OF THE DRAWINGS The side view which shows an example of the ceramics circuit board with a screw pad member concerning embodiment. 1 is a side view showing an example of a semiconductor device according to an embodiment; FIG.

A ceramic circuit board with a screw pad member according to an embodiment has a screw pad member made of a metal plate on one surface of the ceramic substrate of the ceramic circuit board. It is characterized in that it is bonded to the substrate and has a structure in which the bonding layer protrudes from the end of the screw pad member.
FIG. 1 shows an example of a ceramic circuit board with a screw pad member according to the embodiment. FIG. 2 shows an example of a structure in which the bonding layer of the screw pad member protrudes. In the figure, 1 is a ceramic circuit board with a screw pad member, 2 is a ceramic substrate, 3 is a metal circuit board, 4 is a screw pad member, and 5 is a joining layer. L is the length of the joint layer protrusion of the screw pad member, and H is the thickness of the joint layer protrusion of the screw pad member.

A ceramic circuit board 1 with a screw pad member has a metal circuit board 3 and a screw pad member 4 on a ceramic substrate 2 . A screw pad member 4 is provided on the creeping surface of the ceramics substrate 2 . The creeping surface of the ceramic substrate 2 means within 5 mm from the edge of the ceramic substrate 2 . Therefore, the screw pad member 4 is provided within 5 mm from the edge of the ceramics substrate 2 . Moreover, it is preferable that the screw pad member 4 is provided within a range of 0.1 to 5 mm from the edge of the ceramic substrate 2 . If it is within 0.1 mm from the end, the joint layer, which will be described later, has a small area for providing the protruding portion. On the other hand, if it exceeds 5 mm, the place where the metal circuit board 3 is provided becomes small. Therefore, it is preferable that the screwing pad member 4 is provided within a range of 0.1 to 5 mm, more preferably 0.3 to 3 mm from the edge of the ceramic substrate 2 .

Also, the screw pad member 4 is joined to the ceramic substrate 2 via the joining layer 5 . The screw pad member 4 is preferably made of the same material as the metal circuit board 3 . If the metal circuit board 3 is a copper plate, it is preferable that the screw pad member 4 is also a copper plate. Similarly, if the metal circuit board 3 is an aluminum plate, it is preferable that the screw pad member 4 is also an aluminum plate. By using the same material as the metal circuit board 3 for the screwing pad member 4, it becomes easy to form the bonding layer protruding portion in the etching process.
The ceramic circuit board 1 with a screw pad has a protruding portion in the bonding layer 5 that joins the screw pad member 4 . The length L of the protruding portion of the bonding layer 5 of the screw pad member 4 is preferably 2 μm or more and 200 μm or less. Moreover, the thickness H of the protruding portion of the bonding layer 5 of the screw pad member 4 is preferably 5 μm or more and 50 μm or less. Further, it is preferable that the length L of the protruding portion/the height H of the protruding portion be in the range of 0.5 or more and 3.0 or less.
By providing the joint layer protruding portion in the screw pad member 4, the joint strength of the screw pad member 4 can be improved. Therefore, it is possible to employ a screwing structure in which the screw head is in contact with the screwing pad member 4 . In addition, by providing the protruding portion in the bonding layer, it is possible to improve the TCT (thermal cycle) characteristics of the semiconductor device after screwing.

Also, the bonding layer 5 preferably contains an active metal. A bonding layer containing an active metal can form a strong bond with a metal plate. A bonding layer containing an active metal is called an active metal bonding layer.
The active metal for joining copper plates is one or more selected from Ti (titanium), Nb (niobium), Zr (zirconium), and Hf (hafnium). Moreover, Ag (silver) and Cu (copper) are mentioned as components other than an active metal. Also, one or more selected from In (indium), Sn (tin), and C (carbon) may be added. In addition, a copper alloy plate shall also be contained in a copper plate.
Also, the active metal for joining the aluminum plates is Si (silicon). Moreover, Al (aluminum) is mentioned as components other than an active metal. In addition, an aluminum alloy plate shall also be contained in an aluminum plate.

The bonding layer preferably has a Vickers hardness of 250 or less. As shown in Patent Document 1, when the thickness of the metal circuit board 3 is 0.6 mm or more, the Vickers hardness of the bonding layer is preferably 250 or less. When the thickness of the metal circuit board 3 is 0.6 mm or more, it is preferable that the thickness of the screw pad member 4 is also 0.6 mm or more. Moreover, it is preferable that the metal circuit board 3 and the screw pad member 4 have the same thickness. Since the metal circuit board 3 and the screw pad member 4 are made of the same material and have the same thickness, it is easy to manufacture by an etching process. Conventionally, metal circuit boards and screw pad members have been formed by an etching process as in Patent Document 2, but the screw pad members have not been provided with protruding portions of the joining layer. In the ceramic circuit board with the screw pad member according to the embodiment, the joint strength of the screw pad member can be improved by providing the screw pad member with the joint layer protruding portion.

Further, when a straight line is drawn on the side surface of the screw pad member 4 from a point half the thickness of the screw pad member 4 to the end of the screw pad member 4 on the ceramic substrate 1 side, this straight line and the ceramic substrate It is preferable that the angle θ formed by the plane direction of 1 is 80° or less. The fact that the angle θ is 80° or less means that the side surface of the screw pad member 4 has an inclined shape that widens toward the ceramic substrate 1 . Since the side surface of the screw pad member 4 has an inclined shape, the TCT characteristic can be improved.

Moreover, the length of the long side of the screw pad member 4 is preferably 1/5 or less of the length of the long side of the ceramics substrate 2 . The screw pad member 4 may be provided so as to encircle the creeping surface of the ceramics substrate 2 . On the other hand, if the screw pad member 4 is provided on the entire creepage surface, the space for providing the metal circuit board 3 is reduced. Since the screwing pad member 4 is provided with the joint layer protruding portion, the joint strength is improved. Therefore, reliability can be ensured even if the screw pad member 4 is small.
The long side of the screw pad member 4 is the longest side in the case of a polygonal shape. Polygonal shapes include squares, rectangles, triangles, pentagons, hexagons, trapezoids, and the like. In the case of a polygonal shape, the corners may be rounded. R-shape means a shape having a radius of curvature.
Further, when the screw pad member 4 is L-shaped, V-shaped, or the like, the longest side is the long side. When the screw pad member 4 has a circular shape, the longest diagonal line is taken as the long side. Circular shapes include perfect circles and ellipses. When the screw pad member 4 is star-shaped, S-shaped, or the like, the longest diagonal line is taken as the long side.

Moreover, it is preferable that a plurality of screwing pad members 4 be provided, and at least one pair thereof be arranged on a diagonal line. The screwing pad member 4 is used for screwing. By arranging them on the diagonal line, it is possible to suppress positional deviation during screwing. Arrangement on a diagonal line indicates an arrangement in which a diagonal line is drawn from one screwing pad member 4 and another screwing pad member 4 exists on the diagonal line. Taking FIG. 1 as an example, the lower left screw pad member and the upper right screw pad member are arranged diagonally. Therefore, there are two pairs of diagonal arrangements in FIG.
At least one pair should be arranged on the diagonal line, and there may be screw pad members 4 that are not arranged on the diagonal line. For example, the screw pad member 4 can be provided in the middle of the long side of the ceramics substrate 2 . Moreover, the number of the screwing pad members 4 is preferably an even number, but may be an odd number.
Also, the corners of the ceramic substrate 2 may be chamfered. By chamfering the corners of the ceramics substrate 2 , it is possible to facilitate alignment with the screw pad member 4 .

The screw pad member 4 and the metal circuit board 3 are provided on the same surface of the ceramic substrate 2, and the heat sink 6 is provided on the opposite surface. Preferably, there is an overlap with the screwed pad member 4 when pulled.
FIG. 3 shows an example of a ceramic circuit board with a screw pad member provided with a heat sink on the back surface of the ceramic board 2 . In the figure, 1 is a ceramic circuit board with a screw pad member, 2 is a ceramic substrate, 3 is a metal circuit board, 4 is a screw pad member, 5 is a bonding layer, 6 is a heat sink, and 7 is from the edge of the heat sink. A line drawn vertically.
The end portion of the heat sink 6 indicates the outermost part of the side surface of the heat sink 6 . In other words, it is the portion closest to the creeping surface of the side surface of the heat sink 6 . When the vertical line 7 is drawn from the edge of the heat sink 6, it is preferable that there is a portion that overlaps the screw pad member 4. As shown in FIG. The fact that there is an overlapping portion means that the heat sink 6 exists on the back side of the screw pad member 4 . The screwing pad member 4 is used for screwing. When screwing, stress is applied to the creeping surface of the ceramic substrate 2 . Since the radiator plate 6 exists on the back side of the screw pad member 4, the effect of alleviating the stress applied to the creeping surface of the ceramic substrate 2 can be obtained. As a result, damage to the ceramic substrate 2 during screwing can be suppressed. Also, the TCT characteristics of the semiconductor device 10 after screwing the ceramic circuit board 1 with the screw pad member can be improved.

Moreover, it is preferable that the ceramic substrate 2 is not formed with holes for screwing. If the ceramic substrate 2 is provided with holes for screwing, cracks may occur. Moreover, the presence of cracks may cause breakage when a screwing stress is applied. Moreover, the presence of cracks causes deterioration of the TCT characteristics when the thickness of the screw pad member 4 is set to 0.6 mm or more. For this reason, it is preferable that there are no screwing holes. In addition, the elimination of the step of providing the screwing hole also has the effect of reducing the manufacturing cost.

Moreover, the ceramic substrate 2 is preferably one selected from a silicon nitride substrate, an alumina substrate, an Algyl substrate, and an aluminum nitride substrate.
The silicon nitride substrate has a high three-point bending strength of 600 MPa or more. In addition, it preferably has a thermal conductivity of 50 W/m·K or more, more preferably 80 W/m·K or more.
The alumina substrate has a thermal conductivity of 20 to 30 W/m·K and a three-point bending strength of about 400 to 500 MPa, but is inexpensive. Also, the Algil substrate is made of a sintered body in which aluminum oxide and zirconium oxide are mixed. The Alsil substrate has a three-point bending strength of about 450 to 550 MPa, which is relatively high.
Also, the aluminum nitride substrate has a high thermal conductivity of 170 W/m·K or more, but its three-point bending strength is about 350 to 450 MPa.
A silicon nitride substrate is preferable among the ceramic substrates. As described above, the silicon nitride substrate has high three-point bending strength. If the ceramic substrate has high strength, breakage during screwing can be suppressed. Therefore, the ceramic substrate preferably has a three-point bending strength of 600 MPa or more, more preferably 700 MPa or more. A silicon nitride substrate is preferable because it has a three-point bending strength of 600 MPa or more, more preferably 700 MPa or more.

Also, the thickness of the ceramic substrate is preferably 0.70 mm or less, more preferably 0.40 mm or less. As for the ceramic circuit board, the thinner the ceramic board, the lower the thermal resistance. On the other hand, when the ceramic substrate becomes thin, it becomes more susceptible to breakage during screwing. If the substrate has a high strength such as a silicon nitride substrate, even if the thickness of the substrate is reduced to 0.40 mm or less, breakage during screwing can be suppressed. Furthermore, if a silicon nitride substrate is used, the thickness of the substrate can be reduced to 0.30 mm or less. Therefore, it is preferable that the ceramic substrate is a silicon nitride substrate having a three-point bending strength of 600 MPa or more. The silicon nitride substrate preferably has a three-point bending strength of 600 MPa or more and a thermal conductivity of 50 W/m·K or more. The thickness of the ceramic substrate is preferably 0.10 mm or more. If the thickness is less than 0.10 mm, the ceramic substrate may be damaged during screwing.

In addition, it is preferable that the area of the screw pad member 4 has an area where the contact area with the screw head is 15% or more. As described above, in the ceramic circuit board 1 with screw pad member according to the embodiment, the size of the screw pad member 4 can be reduced. On the other hand, if the screwing pad member 4 is too small, the stress relaxation effect during screwing is reduced. Therefore, it is preferable that the area of the screw pad member 4 is such that the contact area with the screw head is 15% or more.
The contact area with the screw head shall be obtained by the following method. First, the contactable area of the screw head is obtained. The contactable area of the screw head is the area obtained by subtracting the area of the grooved portion from the area of the screw head when viewed from above. For example, the screw head when viewed from above is circular with a diameter of 10 mm. In addition, the diameter of the portion provided with the screw groove is set to be circular with a diameter of 3 mm. The contactable area of the screw head is 5 mm×5 mm×3.14−1.5 mm×1.5 mm×3.14=71.435 mm 2 . When the screwing structure is adopted, the contact area between the screwing pad member 4 and the contactable area of the screw head is defined as the contact area with the screw head.
If the contact area between the screw pad member 4 and the screw head is small, it becomes like a point contact and the stress at the screwed portion increases. By increasing the contact area between the screw pad member 4 and the screw head, surface contact is obtained. Surface contact can disperse the stress at the screwed portion. If the contact area between the screw pad member 4 and the screw head is too large, the screw pad member 4 may become large. An increase in the size of the screw pad member 4 narrows the place where the metal circuit board 3 is arranged. Therefore, the contact area between the screw pad member 4 and the screw head is preferably 15% or more and 45% or less.

As for the protruding portion of the bonding layer 5 of the metal circuit board 3, the length L of the protruding portion of the bonding layer 5 is preferably 2 μm or more and 200 μm or less. Moreover, the thickness H of the protruding portion of the bonding layer 5 of the metal circuit board 3 is preferably 5 μm or more and 50 μm or less. Further, it is preferable that the length L of the protruding portion/the height H of the protruding portion be in the range of 0.5 or more and 3.0 or less.
Further, when a straight line is drawn on the side surface of the metal circuit board 3 from a point half the thickness of the metal circuit board 3 to the edge of the metal circuit board 3 on the ceramic substrate 1 side, this straight line and the plane of the ceramic substrate 1 It is preferable that the angle θ formed with the direction is 80° or less. The fact that the angle θ is 80° or less means that the side surface of the metal circuit board 3 has an inclined shape that widens toward the ceramic substrate 1 . Since the side surface of the metal circuit board 3 has an inclined shape, the TCT characteristics can be improved.

Moreover, it is preferable that the screw pad member 4 and the metal circuit board 3 have substantially the same side shape. As described above, the side shape is the thickness of the metal plate, the protrusion of the bonding layer, and the slanted shape of the metal plate. The metal plate indicates both the screw pad member 4 and the metal circuit board 3 .
The side shapes of the screw pad member 4 and the metal circuit board 3 shall be observed in an arbitrary cross section. Observation of the cross-sectional shape shall be made using a cross-sectional SEM photograph. Also, the section of the metal circuit board 3 closest to the screw pad member 4 shall be observed.
In the cross-sectional SEM photograph, when the difference in thickness between the screw pad member 4 and the metal circuit board 3 is 0 mm or more and 0.1 mm or less, it is determined that they are substantially the same. Also, in the cross-sectional SEM photograph, if the difference in the area of the protruding portion of the bonding layer between the screw pad member 4 and the metal circuit board 3 is 0% or more and 20% or less, it is judged that they are substantially the same. Also, in the cross-sectional SEM photograph, if the difference in angle θ between the screw pad member 4 and the metal circuit board 3 is 0° or more and 10° or less, it is determined that they are substantially the same. again,
When the thickness of the screwing pad member 4 and the metal circuit board 3, the difference in the area of the joint layer protruding portion, and the difference in the angle θ all satisfy the above ranges, the side surfaces of the screwing pad member 4 and the metal circuit board 3 The shapes are substantially the same.

The ceramic circuit board 1 with a screw pad member as described above can be used in a semiconductor device. Specifically, the semiconductor element 11 is mounted on the metal circuit board 3 of the ceramic circuit board 1 with a screw pad member. Besides the semiconductor element 11, a metal terminal such as a lead frame may be mounted. Also, wire bonding may be applied. Further, it is assumed that a plurality of semiconductor elements 11 may be provided.
Moreover, it is preferable that the semiconductor device has a screw structure. FIG. 4 shows an example of the semiconductor device according to the embodiment. In the figure, 10 is a semiconductor device, 11 is a semiconductor element, 12 is a screw, and 13 is a mounting board. FIG. 4 illustrates a structure in which a semiconductor element 11 is mounted on a ceramic circuit board 1 with a screw pad member and screwed to a mounting board 13 with screws 12 .
A ceramic circuit board 1 with a screw pad member is provided with a screw pad member 4 on its creeping surface. Therefore, a screw-fixed structure can be obtained without providing a screw hole in the ceramic substrate. Also, a structure in which the screw head of the screw 12 is directly in contact with the screw pad member 4 can be adopted. The mounting board 13 is used as a place for screwing. It may be a heat sink, a housing, or the like. Also, the semiconductor device 10 may be provided with mold resin.
In addition, it is preferable that the area of the screw pad member 4 has an area where the contact area with the screw head is 15% or more. By making surface contact between the screw head and the screw pad member, it is possible to relax the screwing stress. The semiconductor device according to the embodiment can improve the TCT characteristics even after the screw structure.
Moreover, cracking of the ceramic substrate can be suppressed even if the screwing torque is set to 0.05 N·m or more. Although the upper limit of the screwing torque is not particularly limited, it is preferably 0.50 N·m or less.

Next, a method for manufacturing a ceramic circuit board with a screw pad member according to the embodiment will be described. The method of manufacturing the ceramic circuit board with screw pad members according to the embodiment is not particularly limited as long as it has the above structure.
First, a bonded body of a ceramic substrate and a metal plate is produced.
The ceramic substrate 2 is preferably one selected from a silicon nitride substrate, an alumina substrate, an Alsil substrate, and an aluminum nitride substrate. The ceramic substrate is preferably a silicon nitride substrate having a three-point bending strength of 600 MPa or more and a thermal conductivity of 50 W/m·K or more. Also, the silicon nitride substrate preferably has a thickness of 0.40 mm or less, more preferably 0.30 mm or less.
Also, the metal plate is preferably a copper plate or an aluminum plate. In particular, the metal plate is preferably a copper plate. The thermal conductivity of copper is approximately 400 W/m·K, while that of aluminum is approximately 240 W/m·K. Since the copper plate has a higher thermal conductivity, the heat dissipation is higher. Also, the Vickers hardness of copper is about 370 MPa, while that of aluminum is about 170 MPa. Since copper plate is harder, it is suitable for screwing.
The active metal bonding method shall be used for bonding the ceramic substrate and the metal plate. The active metal joining method is a joining method using a joining brazing material containing an active metal.
The active metal for joining copper plates is one or more selected from Ti (titanium), Nb (niobium), Zr (zirconium), and Hf (hafnium). Moreover, Ag (silver) and Cu (copper) are mentioned as components other than an active metal. Also, one or more selected from In (indium), Sn (tin), and C (carbon) may be added. In addition, a copper alloy plate shall also be contained in a copper plate.
Also, the active metal for joining the aluminum plates is Si (silicon). Moreover, Al (aluminum) is mentioned as components other than an active metal. In addition, an aluminum alloy plate shall also be contained in an aluminum plate.

In the active metal bonding method, an active metal brazing material paste is applied onto a ceramic substrate, and a metal plate is placed thereon. The thickness of the metal plate is preferably 0.6 mm or more. Moreover, it is preferable that the metal plate arranged on the surface on which the screwing pad member 4 is provided has substantially the same length and width as the ceramic substrate. "Substantially the same" means that the length of the metal plate is within a range of ±2 mm with respect to the lengths of the long and short sides of the ceramic substrate. By making the vertical and horizontal sizes of the ceramic substrate and the metal plate approximately the same, the metal circuit board and the screw pad member can be formed in the same etching process. If the length of the metal plate exceeds 2 mm, the amount to be removed by etching increases, causing an increase in cost. Moreover, if the length of the metal plate exceeds 2 mm and is small, it may be difficult to provide the screw pad member on the creeping surface of the ceramic substrate in the same etching process. Further, by making the vertical and horizontal sizes of the ceramic substrate and the metal plate substantially the same, the difference in thickness between the screw pad member 4 and the metal circuit board 3 can be 0 mm or more and 0.1 mm or less.
Also, the metal plate used as the heat sink 6 preferably has substantially the same length and width as the ceramic substrate 2 . Also, the metal plate that will become the metal circuit board is called the front metal plate, and the metal plate that will become the heat sink is called the back metal plate. When producing a joined body, it is preferable that the front metal plate and the back metal plate have substantially the same length and width. Approximately the same means that the vertical and horizontal sizes of the front metal plate and the back metal plate are within a range of ±2 mm. It is also possible to dispose the screw pad member 4 and the metal circuit board 3 separately and join them together. However, if there is too much difference in size between the front and back metal plates, the joined body tends to warp. If warping occurs, the load of the warping process increases, which is not preferable.

Next, a heat bonding step is performed. The heating temperature is, for example, in the range of 700-900.degree. Further, the heat bonding step is preferably performed in a vacuum (1×10 ⁻³ Pa or less).
Next, an etching process is performed. The front metal plate forms the metal circuit board 3 and the screw pad member 4 . Moreover, it is preferable that the joint layer protruding portion and the side surface shape of the metal circuit board 3 and the screw pad member 4 are substantially the same.
In the cross-sectional SEM photograph, if the difference in the area of the protruding portion of the bonding layer between the screw pad member 4 and the metal circuit board 3 is 0% or more and 20% or less, it is determined that they are substantially the same. Also, in the cross-sectional SEM photograph, if the difference in angle θ between the screw pad member 4 and the metal circuit board 3 is 0° or more and 10° or less, it is determined that they are substantially the same.
Moreover, it is preferable to etch the heat sink so that the angle .theta. Moreover, the surface of the screw pad member 4 may be chemically polished as necessary.
Through the steps described above, a ceramic circuit board with a screw pad member can be manufactured.

(Example)
(Examples 1 to 6, Comparative Examples 1 to 3)
A bonded body was fabricated using an active metal bonding method using a silicon nitride substrate and a copper plate. In addition, the vertical and horizontal sizes of the silicon nitride substrate and the copper plate were made substantially the same. Also, the front copper plate is a copper plate that serves as a metal circuit board and a screw pad member. The back copper plate is a copper plate that serves as a heat sink. The conjugates produced are as shown in Table 1.

Next, each joined body was etched. Thus, a ceramic circuit board with a screwing member according to the example was produced. Also, as a comparative example, a ceramic circuit board was prepared without a screwing member. Examples and comparative examples are shown in Tables 2 and 3.

In the embodiment, one screw pad member is provided at each of the four corners of the ceramic circuit board (four in total). Further, in the embodiment, when a vertical line is drawn from the edge of the heat sink, there is a portion overlapping with the screw pad member.
Next, a semiconductor device was manufactured by mounting a semiconductor element on the metal circuit board. Each semiconductor device was screwed. At that time, the contact area between the screw pad member and the screw head was changed by changing the size of the screw head. Moreover, the screwing structure was performed by changing the screwing torque.
The presence or absence of breakage of the ceramic substrate during screwing was measured. Also, the TCT characteristics of the semiconductor device after screwing were measured.
Twenty screwing steps were performed to check for damage to the ceramic substrate during screwing. When even one piece was damaged, it was evaluated as "damaged", and when not even one was damaged, it was evaluated as "not damaged".
In the TCT test, one cycle was −40° C.×30 minutes→25° C.×10 minutes→175° C.×30 minutes→25° C.×10 minutes. In the TCT test, the test objects were those in which the ceramic substrate was not damaged in the screwing process.
Table 4 shows the results.

As can be seen from the table, in the example, the ceramic substrate was not damaged during the screwing process. Moreover, no breakage of the ceramic circuit board after TCT was confirmed.
On the other hand, the comparative example was damaged because it did not have a screw pad member. Therefore, it can be seen that the ceramic circuit boards with screw pad members according to the examples are highly reliable.

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

REFERENCE SIGNS LIST 1... Ceramic circuit board with screw pad member 2... Ceramic substrate 3... Metal circuit board 4... Screw pad member 5... Bonding layer 6... Radiator plate 7... Line drawn vertically from the edge of the radiator plate 10... Semiconductor device REFERENCE SIGNS LIST 11: Semiconductor element 12: Screw 13: Mounting boat L: Width of bonding layer protrusion H: Thickness of bonding layer protrusion

Claims (10)

A screw pad member and a metal circuit board are provided on the same surface of the ceramic substrate, and a heat sink is provided on the opposite surface. The screw pad member is joined to the ceramic substrate through the joint layer, and has a structure in which the joint layer protrudes from the end of the screw pad member. Ceramic circuit board with pad material. 2. A ceramic circuit board with a screw pad member according to claim 1, wherein the length of the long side of the screw pad member is 1/5 or less of the length of the long side of the ceramic substrate. 3. A ceramic circuit board with screw pad members according to claim 1, wherein a plurality of screw pad members are provided, and at least one pair thereof is arranged diagonally. 4. The ceramic circuit board with a screw pad member according to claim 1, wherein corners of the ceramic board are chamfered. 5. The ceramic circuit board with a screw pad member according to claim 1, wherein the ceramic board does not have holes for screwing. 6. The ceramic circuit board with a screw pad member according to claim 1, wherein the ceramic board has a thickness of 0.4 mm or less. 7. The ceramic circuit board with a screw pad member according to claim 1, wherein the ceramic substrate is a silicon nitride substrate having a three-point bending strength of 600 MPa or more. 8. The ceramic circuit with a screw pad member according to any one of claims 1 to 7, wherein the area of the screw pad member is such that the contact area with the screw head is 15% or more. substrate. 9. A semiconductor device comprising a ceramic circuit board with a screw pad member according to claim 1 and a semiconductor element mounted thereon. 10. The semiconductor device according to claim 9, wherein the semiconductor device is screwed so that the screw head is in contact with the screw pad member.

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