JP2021185611A - Silicon nitride based ceramic assembled board - Google Patents

Abstract

To provide a silicon nitride based ceramic assembled board which suppresses cracks, fractures, chipping or burrs at corners.SOLUTION: A silicon nitride based ceramic assembled board 12 includes a silicon nitride based ceramic board part 20 having a plurality of circuit formation parts 19, and an edge 21, and also has a chamfering part 22 at four corners of the outer circumference of the edge 21. The silicon nitride based ceramic assembled board has a board thickness of 0.2-1.0 mm. The wall surface of the chamfering part comprises a laser machined surface, and a board side excluding the chamfered part comprises a laser machined surface and a fracture surface from a board surface in order in the thickness direction. The fracture surface of the board side connects directly to the wall surface of the chamfered part, and a ridge angle part where the fracture surface and the wall surface are connected has a sharp shape.SELECTED DRAWING: Figure 5(a)

Description

The present invention relates to a silicon nitride-based ceramic assembly substrate for taking a large number of circuit boards.

For circuit boards used for semiconductor modules, power modules, etc., ceramic substrates are used in terms of thermal conductivity, insulation, strength, etc., and metal circuit boards such as Cu and Al and metal heat dissipation plates are used in these ceramic substrates. It is joined to form a circuit board. Alumina and aluminum nitride have been widely used as ceramic substrates for such circuits, but recently, silicon nitride with high strength and improved thermal conductivity has been used so that it can be used even in harsher environments. It has come to be.

The circuit board is a metal circuit made by joining a metal plate such as a Cu plate to a single ceramic assembly board that is large enough to cut out a large number of circuit ceramic substrates by an active metal brazing method or a direct bonding method. After forming the plate and the metal heat dissipation plate, the ceramic assembly substrate is mass-produced by a method of dividing the ceramic assembly substrate into a predetermined size.

As a method of dividing the ceramic assembly board into individual circuit boards, a recess or a groove is formed in the ceramic assembly substrate by laser processing before joining the Cu plate or the like, and the ceramic assembly board with the circuit board is bent after joining. A method of dividing by a recess or a groove is adopted.

WO 2009/154295 (Patent Document 1) can be easily and surely divided by bending it to take a large number of circuit boards, but it is continuous on one or both sides of the ceramic sintered substrate so as not to be inadvertently divided during handling. Disclosed is a rectangular ceramic assembly substrate in which a groove is provided by laser processing and the difference Δd between the maximum depth portion and the minimum depth portion in the length direction of the continuous groove is within the range of 10 to 50 μm. .. However, it was found that when the ceramic substrate is divided along the continuous grooves formed by laser processing near the four sides of the ceramic substrate, cracks and chips are likely to occur at the corners of the obtained rectangular ceramic assembly substrate.

Japanese Patent Laid-Open No. 2008-198905 (Patent Document 2) is an assembly substrate 300 for taking a large number of ceramic substrates 301, as shown in FIG. 13, from a plurality of non-penetrating holes formed by laser scribing. Disclosed is an assembly substrate 300 having a lattice-shaped dividing groove 303 and a diamond-shaped chamfered through hole 304 formed by laser cutting at the intersection of the dividing grooves 303. In addition, 302 is a surplus portion to be discarded. However, when a large number of diamond-shaped chamfered through holes 304 are formed in the assembly substrate 300, a large amount of thermal stress due to laser cutting is concentrated in the vicinity of the diamond-shaped chamfered through holes 304, which not only makes it easy for cracks to occur from the chamfered portion. Since the volume to be chamfered is large, the entire assembly substrate 300 may be warped and the alignment of the assembly substrate 300 may be inaccurate. In addition, it takes time to form the diamond-shaped chamfered through hole 304 by laser cutting, and there is a problem that the productivity is not good. Further, the technique of Patent Document 2 is a technique for manufacturing an individual circuit board from a ceramic assembly substrate, not a technique for manufacturing a ceramic assembly substrate from a ceramic sintered substrate.

In Japanese Patent Application Laid-Open No. 2011-233687 (Patent Document 3), as shown in FIG. 14, a plurality of rectangular wiring board regions 403 (regions in which wiring conductors 404 are provided) provided on the mother substrate 401 and each wiring are provided. The dummy region 402 formed around the substrate region 403, the dividing groove 412 formed along the boundary between the wiring board region 403 and the dummy region 402, and the wiring board region 403 and the dummy region 402 are formed. A multi-layer wiring board having a triangular through hole 413 and a notch 414 penetrating the mother substrate 401 from the through hole 413 to the dividing groove 412 (412x, 412y) is disclosed. However, it takes too much time to form the triangular through hole 413 and the notch 414, and the productivity is not good. Further, as in Patent Document 2, when the triangular through hole 413 is formed by laser processing, not only a large thermal stress is concentrated but also the volume to be lightened is large, so that the entire mother substrate 401 is warped. .. Further, the technique of Patent Document 3 is also a technique for manufacturing an individual wiring board from an assembly substrate, not a technique for manufacturing an assembly substrate from a sintered substrate.

WO 2009/154295 Gazette Japanese Unexamined Patent Publication No. 2008-198905 Japanese Unexamined Patent Publication No. 2011-233687

Therefore, an object of the present invention is a method for easily and surely manufacturing a silicon nitride-based ceramic assembly substrate in which cracks and chips are suppressed at corners from a silicon nitride-based ceramics sintered substrate, and a silicon nitride-based substrate obtained by such a method. It is to provide a ceramic assembly substrate.

In view of the above purpose, as a result of diligent research, the inventors have formed a continuous groove-shaped side break line consisting of scrib holes and a slit-shaped square break line on the silicon nitride-based ceramics sintered substrate, and sintered the silicon nitride-based ceramics. We discovered that the silicon nitride-based ceramic assembly substrate can be separated without cracks or chips by dividing the substrate along the side break line, and came up with the present invention.

That is, the silicon nitride-based ceramic assembly substrate of the present invention is a rectangular silicon nitride-based ceramic assembly substrate having a silicon nitride-based ceramic substrate portion having a large number of circuit forming portions and an edge portion and having chamfered portions at four corners. There,
The thickness of the silicon nitride-based ceramic assembly substrate is 0.2 to 1.0 mm, and the thickness is 0.2 to 1.0 mm.
The wall surface of the chamfered portion is composed of a laser machined surface.
The side surface of the substrate excluding the chamfered portion is composed of a laser machined surface and a fracture surface in order from the surface of the substrate in the thickness direction.
The fracture surface of the side surface of the substrate is directly connected to the wall surface of the chamfered portion.
The ridge angle portion connecting the fracture surface of the side surface of the substrate and the wall surface of the chamfered portion has a sharpened shape.

The wall surface of the chamfered portion has an arithmetic average surface roughness Ra of 0.1 μm or more and less than 0.3 μm, and the arithmetic average surface roughness Ram at the central portion of the wall surface of the chamfered portion in the substrate thickness direction and the substrate thickness direction. Arithmetic mean surface roughness Rao on the opening side,
Rao ＞ Ram
It is preferable to satisfy.

It is preferable that the silicon nitride-based ceramic assembly substrate is formed with break lines for dividing into the individual circuit forming portions.

The silicon nitride-based ceramic assembly substrate of the present invention is
Multiple first copper plates forming a circuit are joined to one surface,
It is preferable that a plurality of second copper plates serving as heat dissipation plates are bonded to positions on the other surface that match the first copper plate.

The silicon nitride-based ceramic assembly substrate of the present invention is
It is preferable that a plurality of second break lines for dividing into individual circuit forming portions are formed on the surface (one surface) to which the first copper plate is joined.

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide a silicon nitride-based ceramic assembly substrate in which cracks and chips are suppressed from occurring at the corners of the silicon nitride-based ceramic assembly substrate, and thus the manufacturing yield is improved.

It is a top view which shows an example of the method of this invention which manufactures the silicon nitride based ceramics assembly substrate. It is a partially enlarged plan view which shows the corner break line. It is a partially enlarged plan view which shows how the corner break line is formed. FIG. 3 is a cross-sectional view taken along the line AA of FIG. It is a partially enlarged sectional view which shows the chamfered surface of the silicon nitride based ceramics assembly substrate. It is a top view which shows the silicon nitride-based ceramics assembly board which bonded the plurality of first copper plates which become circuit boards to one surface. It is a bottom view which shows the silicon nitride based ceramics assembly substrate which bonded the plurality of second copper plates which become a heat dissipation plate to the other surface. It is a top view which shows the circuit board. It is a partially enlarged plan view which shows another example of a corner break line. It is a partially enlarged plan view which shows the silicon nitride based ceramics assembly substrate which has a burr in the side surface region near a chamfered surface. It is a top view which shows the manufacturing method of the comparative example 1. FIG. It is a top view which shows the silicon nitride based ceramics assembly substrate which formed the crack. It is a top view which shows the manufacturing method of the comparative example 2. It is a top view which shows the silicon nitride based ceramics assembly substrate which cracked. It is a top view which shows the ceramic assembly substrate disclosed in JP-A-2008-198905. It is a top view which shows the wiring board disclosed in Japanese Patent Application Laid-Open No. 2011-233687.

Embodiments of the present invention will be described in detail below, but the present invention is not limited thereto. Further, the description of each embodiment can be applied to other embodiments unless otherwise specified.

[1] Method for manufacturing a silicon nitride-based ceramic assembly substrate The method of the present invention for manufacturing a silicon nitride-based ceramic assembly substrate will be described with reference to FIGS. 1 and 2.

(1) Formation of side break lines As shown in FIG. 1, side break lines 13 are formed on each outer edge portion 10 of the rectangular silicon nitride-based ceramics sintered substrate 1. In order to facilitate the division of the silicon nitride-based ceramics sintered substrate 1, it is preferable that each side break line 13 extends to the opposite side 11 (extends over the entire length of each side of the substrate 1). The adjacent side break lines 13 along the four sides 11 of the rectangular silicon nitride based ceramics sintered substrate 1 intersect at the intersection 15. The portion 16 between each side break line 13 and each side 11 of the silicon nitride based ceramics sintered substrate 1 is a portion to be removed by division along each side break line 13, and is called a “side margin portion”. Further, the triangular region 17 surrounded by the adjacent edge break lines 13 and one corner break line 14 (described later) intersecting both of them is referred to as a “corner margin portion”. The rectangular region having the chamfered portion surrounded by the four side break lines 13 and the four corner break lines 14 corresponds to the silicon nitride based ceramic assembly substrate 12.

The break lines 13 on each side are preferably formed by continuously irradiating the inside of each outer edge portion 10 of the silicon nitride-based ceramics sintered substrate 1 while moving the beam spot of the fiber laser minutely. The edge break line 13 is microscopically a continuous groove in which a large number of scribe holes formed by the beam spot of the fiber laser are overlapped. Fiber lasers _{can focus on smaller beam spots than CO 2} lasers and YAG lasers, have a large depth of focus, have high conversion efficiency, and have high output. The continuous groove by the fiber laser _{has less thermal influence than the intermittent hole by the YAG laser and the CO 2} laser, and can reduce the melting and scattered matter in the surface oxidation region and around the groove.

On the other hand, irradiation with a YAG laser and a CO ₂ laser forms relatively deep intermittent holes, so that the periphery of the groove is greatly affected by heat. Therefore, the surface of the silicon nitride-based ceramics sintered substrate 1 is widely oxidized _{, and oxides such as Si and SiO 2} and melts such as sintering aids are often scattered around due to the thermal energy of the laser. .. As a result, microcracks may occur on the surface of the substrate, which may reduce the joining reliability and cause joining defects due to void formation.

The width of the side break line 13 is preferably 300 μm or less, more preferably 10 to 100 μm, and most preferably 20 to 80 μm. The width of each side break line 13 is measured at the same height as the substrate surface. The depth of the side break line 13 is less than half the thickness of the silicon nitride-based ceramics sintered substrate 1, preferably 1/8 to 1/2, and more preferably 1/4 to 1/2. be. When the thickness of the silicon nitride-based ceramics sintered substrate 1 is, for example, 0.32 mm, the depth of the side break line 13 is preferably 40 to 160 μm, more preferably 80 to 160 μm.

Since the side break line 13 having the above size is long, it is preferable to form the edge break line 13 by one scanning of the fiber laser beam spot in consideration of productivity, but of course, the scanning of the fiber laser beam spot may be repeated a plurality of times.

In the illustrated example, the side break line 13 has the same length as the corresponding side 11 (extending to the opposite sides 11 and 11 of the substrate 1), but the adjacent vertical and horizontal side break lines 13 and 13 intersect. As long as it is, it may be shorter than the corresponding side 11. In this case, when trying to break one side margin portion 16, the side break line 13 does not extend to the portion beyond the intersection 15, so a part of the side side of the board 1 is folded without the side break line 13. become. However, since the portion is sufficiently separated from the angular break line 14, it does not affect the surface roughness of the chamfered surface 140 formed by the angular break line 14. When the side break line 13 is shorter than the corresponding side 11, the width of the side margin portion 16 is preferably about 5% or less of the length of the substrate.

(2) Formation of square break lines When the silicon nitride-based ceramics sintered substrate 1 is divided into the silicon nitride-based ceramics assembly substrate 12 and the side margin portion 16, cracks and chips are found at the four corners of the silicon nitride-based ceramics assembly substrate 12. In order to prevent this from occurring, an angle break line 14 that intersects both of the edge break lines 13 is formed in the vicinity of each intersection 15 of the adjacent edge break lines 13. Each corner break line 14 is a slit penetrating the silicon nitride based ceramics sintered substrate 1. By forming the slit-shaped square break line 14 on the substrate, the stress concentration at the four corners of the silicon nitride based ceramic assembly substrate 12 is relaxed.

When the thickness of the silicon nitride-based ceramics sintered substrate 1 is, for example, 0.32 mm, the width of the angular break line 14 is preferably 10 to 200 μm, more preferably 20 to 150 μm, and most preferably 30 to 100 μm.
The length of the angular break line 14 is preferably 2.8 to 8.4 mm, more preferably 3.0 to 8.0 mm, and most preferably 3.5 to 7.5 mm. The crossing angle, which is the inclination of the angle break line 14 with respect to the side break line 13, is preferably 30 to 60 °. If the crossing angle is too small, the edges of the side margins may remain unbroken and become burrs when splitting. Further, since the angle break line 14 intersects with two orthogonal side break lines 13, it is preferable to set the upper limit of the intersection angle to 60 ° in relation to the margin angle. In particular, when the crossing angle is set to 45 °, the silicon nitride-based ceramics sintered substrate 1 can be used without waste.

Although the step of forming the side break line 13 may be performed after the step of forming the corner break line 14, it is preferable to perform the step of forming the corner break line 14 after the step of forming the side break line 13. In the latter case, since the intersection 15 of the side break lines 13 can be used as a reference point when forming the corner break line 14, the machining accuracy of the corner break line 14 is improved.

As shown in FIG. 2, it is preferable that the angular break line 14 extends (advances) from the adjacent side break line 13 into the side margin portion 16 by the length L1 respectively. The advance length L1 of the angular breakline 14 is preferably larger than the diameter of the fiber laser beam spot used to form the angular breakline 14 and less than 3.5 mm. When the advance length L1 is larger than the diameter of the fiber laser beam spot, not only the formation of burrs in the vicinity of the corner break line 14 can be suppressed, but also the corner margin portion 17 can be prevented from remaining in the chamfer portion 22 (corner margin). It is more preferable from the viewpoint of productivity because there is no need to manually fold the part and there is no rework). As shown in FIG. 8, if the burr 27 is present on the edge portion 21 of the silicon nitride based ceramic assembly substrate 12, it is not possible to accurately align the edge portion 21 in the circuit board forming step. On the other hand, if the advance length L1 is set to 3.5 mm or more, the side margin portion 16 is likely to be divided into a plurality of pieces between the corner break lines 14, and the man-hours for removing the scattered pieces may increase.

The slit-shaped angle break lines 14 penetrating the silicon nitride-based ceramics sintered substrate 1 are preferably formed by repeating the scanning of the fiber laser beam spot a plurality of times (for example, 10 times). By repeating the scanning of the fiber laser beam spot a plurality of times, scribe holes are formed while gradually overlapping until the silicon nitride-based ceramics sintered substrate 1 is penetrated. Therefore, when the silicon nitride-based ceramics sintered substrate 1 is divided into the silicon nitride-based ceramic assembly substrate 12, the side margin portion 16 and the corner margin portion 17 by suppressing the formation of cracks and particulate protrusions on the inner surface due to thermal shock. In addition, it is possible to suppress the growth of cracks and the occurrence of chips. The particulate protrusions are reattached to silicon nitride-based ceramics removed by irradiation with a fiber laser beam, and are likely to occur when the irradiation energy in one scan of the fiber laser beam spot is high. Since the particulate protrusions may fall off from the silicon nitride based ceramic assembly substrate 12 in the process of forming the circuit board and cause a defect in the circuit board, it is preferable to suppress the generation of the particulate protrusions as much as possible.

The inner surface (wall surface of the chamfered portion) of the angular breakline 14 with few cracks and particulate protrusions has a low to relatively high energy incident on the machined portion when the angular breakline 14 is formed by multiple scans. Since the fiber laser beam spot of No. 1 can be used and the scanning speed can be increased when the incident energy is high, the arithmetic average surface roughness Ra is as small as 0.1 μm or more and less than 0.3 μm, and the processing time can be shortened. On the other hand, under the condition that the angular break line 14 is formed in one scan, the arithmetic average surface roughness Ra of 0.5 μm or more and less than 1.0 μm is obtained by irradiating the machined part with a fiber laser beam spot with suppressed incident energy density. be able to. However, since the angular break line must penetrate the substrate, the scanning speed of the beam spot cannot be increased, so that many cracks and particulate protrusions due to thermal shock are likely to be formed. The arithmetic mean surface roughness Ra is specified in JIS B0601: 2001.

As shown in FIG. 3, the diameter of the beam spot 14a of the fiber laser forming the angular break line 14 is preferably 10 to 100 μm. When forming the angular breakline 14 by scanning multiple times in order to finish the inner wall surface of the angular breakline 14 smoothly, the moving speed (also referred to as scanning speed) of the beam spot 14a should be 150 mm / sec or more. It is preferably 150 to 550 mm / sec, and more preferably 150 to 550 mm / sec. The irradiation pitch of the beam spot 14a is, for example, 3 μm.

Since the intensity distribution of the laser is close to the Gaussian distribution (high intensity in the central part) and grooving proceeds from the central part with high intensity, the slit-shaped angular break line 14 is on the opening side (as shown in Fig. 4 (a)). The part (which is easy to process in the part where the irradiation energy of the fiber laser is small) is wider than the central part (the part where the irradiation energy of the fiber laser is large). As shown in FIG. 4 (b), the wall surface (chamfered surface) 140 of the chamfered portion formed by the slit-shaped corner break line 14 is opened in the thickness direction of the substrate 1. When divided into three equal parts, the wall surface portion 140m and the penetrating side wall surface portion 140e (opposite the opening side wall surface portion 140o), the arithmetic average surface roughness Rao of the opening side wall surface portion 140o is relative to the arithmetic average surface roughness Ram of the central wall surface portion 140m. It is preferable to satisfy the relationship of Rao> Ram. The arithmetic mean surface roughness Rao is measured along the longitudinal direction of the angular break line 14 at a depth of 20 to 30 μm from the surface of the silicon nitride based ceramics sintered substrate 1. Further, the arithmetic mean surface roughness Ram is measured along the longitudinal direction of the angular break line 14 at the position of the center in the thickness direction of the silicon nitride based ceramics sintered substrate 1.

The ceramic melt is discharged as the processing of the slit-shaped square break line 14 progresses, but at the initial stage of processing, the ceramic melt is discharged from the opening side which is the laser incident surface side, and the square break line 14 is made of silicon nitride. When the ceramic sintered substrate 1 is penetrated, the ceramic melt is also discharged from the penetrating side. Since the melting point of the ceramic melt is high, solidification starts before it is completely discharged, and it reattaches to the opening side wall surface portion 140o and the through side wall surface portion 140e to roughen the surface. Further, in the open side wall surface portion 140o, as the width of the angular break line 14 widens, it becomes easier to process in the portion where the energy density of the fiber laser beam is low, but as a result of repeating the scanning of the fiber laser beam spot multiple times, the central wall surface In the part 140m, the ratio of processing in the part where the energy density of the laser beam is high increases. As a result, it is presumed that the degree of melting and flattening of the silicon nitride-based ceramics sintered substrate 1 is greater in the central wall surface portion 140 m than in the opening side wall surface portion 140o, and the relationship of Rao> Ram is established.

When the slit is formed by repeating the scanning of the beam spot of the fiber laser multiple times, the heat input per hour into the silicon nitride based ceramics sintered substrate 1 is larger than that of the case where the slit is formed by one scanning of the beam spot. Since there are few small cracks, the occurrence of fine cracks due to thermal shock at the central wall surface 140 m is small, and the surface roughness is also small. Therefore, the dimensional accuracy and reliability of the angle break line 14 are improved.

(3) Dividing the silicon nitride-based ceramics sintered substrate When the silicon nitride-based ceramics sintered substrate 1 having the side break lines 13 and the square break lines 14 formed is folded along the side break lines 13, the silicon nitride-based ceramics sintered substrate is sintered. The substrate 1 is divided into a silicon nitride based ceramic assembly substrate 12, a side margin portion 16, and a corner margin portion 17. Since the corner margin portion 17 formed by the adjacent side break line 13 and the corner break line 14 is connected to the side margin portion 16 via each side break line 13, the silicon nitride based ceramics set together with the side margin portion 16. Separated from substrate 12. Therefore, it is not necessary to separately provide a step for separating the corner margin portion 17.

[2] Silicon nitride-based ceramic assembly substrate The silicon nitride-based ceramic assembly substrate 12 of the present invention has a silicon nitride-based ceramic substrate portion 20 and an edge portion 21 having a large number of circuit forming portions 19 as shown in FIG. 5 (a). It is preferable that the chamfered portions 22 are provided at the four corners, and the wall surface (chamfered surface) of the chamfered portion 22 obtained by the corner break line 14 also has an arithmetic average surface roughness Ra of 0.1 μm or more and less than 0.3 μm. .. The thickness of the silicon nitride-based ceramic assembly substrate 12 is preferably 0.2 to 1.0 mm, more preferably 0.25 to 0.65 mm. The fracture toughness value of the silicon nitride based ceramic assembly substrate 12 ^{is preferably 5.0 MPa · m 1/2} or more, and more preferably ^{5.0 to 7.5 MPa · m 1/2} .

Further, since the square break line 14 has a slit shape, the silicon nitride-based ceramics sintered substrate 1 is deformed such as warp as compared with the diamond-shaped or triangular through hole as described in Patent Documents 2 and 3. It is suppressed, and the alignment by the outer edge or the mark of the silicon nitride-based ceramics sintered substrate 1 can be accurately performed. Further, by simply forming a continuous groove-shaped side break line 13 composed of scrib holes and a slit-shaped square break line 14, the silicon nitride-based ceramics sintered substrate 1 is accurately divided along the side break line 13. Since the silicon nitride-based ceramic assembly substrate 12 can be separated, the cost is low and the productivity is high.

[3] Circuit board formation method As shown in FIGS. 5 (a) and 5 (b), a plurality of first copper plates 23a for forming a circuit are joined to one surface of a silicon nitride based ceramic assembly board 12. , A plurality of second copper plates 23b serving as heat dissipation plates are joined at positions aligned with the first copper plate 23a on the other surface. A plurality of second break lines 24 for dividing into individual circuit forming portions (parts where the circuit plates are provided) 19 are formed on the surface of the silicon nitride ceramic assembly substrate 12 to which the first copper plate 23a is joined. Similar to the side break line 13, the second break line 24 is composed of scribe holes formed by continuously irradiating the beam spot of the fiber laser while moving it minutely, and has the same width and depth as the side break line 13. It suffices to have.

By folding the silicon nitride-based ceramic assembly substrate 12 along the second break line 24, the silicon nitride-based ceramic assembly substrate 12 is divided into a silicon nitride-based ceramic substrate portion 20 and an edge portion 21. The edge portion 21 is removed as a margin portion, and the circuit board 28 shown in FIG. 6 is obtained. However, in FIG. 6, reference numeral 23a'indicates a circuit board made of the first copper plate, and reference numeral 25'indicates a ceramics substrate obtained by dividing the ceramics substrate portion according to the circuit plate 23a'.

Hereinafter, the present invention will be specifically described based on examples. The present invention is not necessarily limited to the following examples.

Example 1
Sheet molding containing 20% by mass of the binder resin component with respect to 100 parts by mass of the ceramic component consisting of 95% by mass of silicon nitride powder, 2% by mass of MgO powder, and 3% by mass of Y ₂ O _{3 powder.} The body was sintered at a maximum temperature of 1850 ° C. for 5 hours to prepare a rectangular silicon nitride-based ceramics sintered substrate 1 having a thickness of 0.32 mm and a length of 150 mm and a width of 200 mm. Using a fiber laser (wavelength: 1.06 μm, output 100 W, oscillation frequency: 50 kHz), four side break lines 13 with a width of 35 μm and a depth of 120 μm inside the outer edge 10 of the silicon nitride based ceramics sintered substrate 1. Formed. The width of the side margin portion 16 was set to 5 mm in the longitudinal direction of the silicon nitride-based ceramics sintered substrate and 6 mm in the lateral direction of the silicon nitride-based ceramics sintered substrate. Further, using the same fiber laser, a slit-shaped angular break line 14 was formed under the following conditions.
Fiber laser beam spot diameter: 35 μm
Beam spot scanning speed: 200 mm / s
Beam spot irradiation pitch: 4 μm
Number of beam spot scans: 10 times Angle break line width: 35 μm
Overall length of corner break line: 4.2 mm
Advance length of corner break line L1: 0.7 mm
Crossing angle of corner breakline with respect to side breakline: 45 °

The silicon nitride-based ceramics sintered substrate 1 was folded along each side break line 13 and divided into a silicon nitride-based ceramics assembly substrate 12 having a chamfered portion 22 and a side margin portion 16 and a corner margin portion 17. The corner margin portion 17 was separated in a state of being attached to the side margin portion 16 and did not become separate scraps. After the above separation work, the front surface and the back surface of the silicon nitride based ceramic assembly substrate 12 were cleaned and the surface roughness was adjusted by a wet blast treatment using alumina abrasive grains.

The chamfered surface 140 of the silicon nitride-based ceramic assembly substrate 12 obtained by dividing the five silicon nitride-based ceramics sintered substrates 1 was observed with a laser microscope. As a result, it was confirmed that there were no cracks, particulate protrusions, burrs or cracks on the chamfered surface 140 and the adjacent side surfaces (laser machined surface and fracture surface). On the chamfered surface 140, the arithmetic average surface roughness Rao of the opening side wall surface portion was 0.2 μm, and the arithmetic average surface roughness Ram of the central wall surface portion was 0.16 μm. In the region 22a adjacent to the chamfered portion 22, the arithmetic mean surface roughness Ra on the side surface of the substrate (composed of the laser machined surface and the fracture surface) formed by folding the side break line 13 is 0.4 μm on the laser machined surface. Ra was 0.7 μm in the fracture surface.

A brazing material paste was applied to both sides of the silicon nitride based ceramic assembly substrate 12 by a screen printing method. _{For the brazing filler metal, add 0.3 parts by mass of TiH 2} to an alloy powder consisting of 70% by mass Ag, 3% by mass In, and 27% by mass Cu (100 parts by mass in total), and further add an organic solvent. It was a paste to which a binder component was added. After the brazing material is dried, the first and second copper plates having a thickness of 0.3 mm are placed on both sides of the silicon nitride based ceramic assembly substrate 12 and heated at 800 ° C. for 20 minutes while pressurizing in a vacuum. The first and second copper plates were bonded to the ceramic assembly substrate 12. The thickness of the brazing filler metal layer after joining was about 30 μm.

After applying ultraviolet curable alkaline peeling type etching resist ink to the first and second copper plates of the obtained bonded body, the etching resist ink is cured into a pattern for a circuit plate and a heat dissipation plate by irradiating with ultraviolet rays. I let you. Etching is performed with a copper chloride-based etching solution (a mixed solution containing copper chloride, hydrochloric acid and hydrogen peroxide) kept at 30 ° C, and the unnecessary copper plate parts other than the circuit plate and heat dissipation plate patterns (that is, the resist is coated). No copper plate part) was removed.

In order to remove unnecessary brazing filler metal parts protruding from the copper plate, a first brazing filler metal etching treatment (etching treatment with an acidic solution containing a carboxylic acid and / or a carboxylate and hydrogen peroxide), and a second brazing filler metal. Etching treatment (etching treatment with a solution containing ammonium hydrogenfluoride and hydrogen peroxide) was performed in order.

The conjugate was immersed in a sodium hydroxide aqueous solution having a concentration of 3% by mass to remove residual resist, and then subjected to gloss treatment (chemical polishing) using a sulfuric acid-based general commercial solution. After washing with ion-exchanged water, the surfaces of the first copper plate 23a and the second copper plate 23b (circuit plate and heat dissipation plate) were Ni-plated. In this way, an aggregate of circuit boards having a circuit board 23a'plated on both sides and a heat dissipation plate was obtained.

As shown in FIGS. 5 (a) and 5 (b), a second break line 24 is formed in an aggregate of circuit boards, and the second break line 24 is divided along the second break line 24 to correspond to a margin portion. As shown in FIG. 6, a plurality of circuit boards 28 having circuit boards 23a'and heat dissipation plates (not shown) on both sides of the ceramic substrate 25'were obtained by separating the edge portions 21.

Example 2
The scanning speed of the beam spot of the fiber laser is 33 mm / s, the irradiation energy density is higher than that of Example 1, and the same as that of Example 1 except that the angular break line 14 that penetrates the front and back in one scan is formed. A silicon nitride-based ceramics sintered substrate 1 having a side break line 13 and a square break line 14 was obtained.

The silicon nitride-based ceramics sintered substrate 1 was folded along the side break line 13 and divided into a silicon nitride-based ceramics assembly substrate 12 having a chamfered portion 22 and a side margin portion 16 and a corner margin portion 17. No cracks, burrs or cracks were formed on the chamfered portion 22 (chamfered surface 140) and the side surface (laser machined surface and fracture surface) of the silicon nitride based ceramic assembly substrate 12. However, minute particulate protrusions were formed on the chamfered surface 140. Since the particulate protrusions may fall off as foreign matter (dust) in the process of forming the circuit board, they were removed by cleaning. The arithmetic mean surface roughness Ra is Rao = 0.8 μm and Ram = 0.5 μm on the chamfered surface 140, Ra2 = 0.5 μm on the laser-machined surface of the side break line 13, and Ra3 = 0.7 μm on the fracture surface, respectively. there were. A second break line 24 was formed after joining the first and second copper plates 23a and 23b for the circuit board and the heat dissipation plate to both sides of the silicon nitride based ceramic assembly substrate 12 with a brazing material. By dividing the silicon nitride-based ceramic assembly substrate 12 along the second break line 24, the same circuit board as in Example 1 was obtained.

Example 3
The angular break line 14 of Example 1 was changed to the slit-shaped angular break line 34 (L1 = 0 mm) shown in FIG. The corner break line 34 was terminated at the intersection with the side break line 13. The silicon nitride based ceramics sintered substrate 1 having the side break line 13 and the corner break line 34 was folded along the side break line 13 and divided into the silicon nitride based ceramic assembly substrate 12, the side margin portion 16 and the corner margin portion 17. .. No cracks or cracks were generated on the chamfered surface 140 of the silicon nitride-based ceramic assembly substrate 12 and the side surfaces (laser-machined surface and fracture surface) adjacent to the chamfered surface 140. As shown in FIG. 8, burrs 27 exceeding the tolerance were formed in the side surface region near the chamfered surface 140 of the silicon nitride based ceramic assembly substrate 12, but the ratio of burrs 27 exceeding the tolerance was 1%. The first and second copper plates for the circuit board and the heat dissipation plate are joined to both sides of the silicon nitride ceramic assembly board 12 on which the burrs 27 are not formed with a brazing material, and the layers are divided after etching treatment, as in Example 1. Circuit board was obtained. In Example 3, the rate at which burrs 27 were formed was 1% (yield 99%), but this is not a problem.

Comparative example 1
As shown in FIG. 9, both the side break line 113 and the square break line 114 formed on the silicon nitride based ceramic sintered substrate 101 are continuous grooves having a width of 35 μm and a depth of 120 μm (not penetrating the substrate). .. The angle break line 114 was tilted 45 ° with respect to the side break line 113 formed along the side 111. Other conditions were the same as in Example 1. In this comparative example, the number of steps for separating the corner margin portion 117 is increased as compared with the above embodiment.

The silicon nitride-based ceramics sintered substrate 101 is folded along the side break line 113, divided into the silicon nitride-based ceramic assembly substrate 112 and the side margin portion 116, and then folded along the square break line 114 to form a triangular shape. The corner margin portion 117 was separated. No burrs or cracks occurred on the chamfered surface and the adjacent side surface (laser machined surface and fracture surface) of the silicon nitride based ceramic assembly substrate 112, but as shown in FIG. 10, the ratio of cracks 134 formed was 6%. It was (yield 94%). This was lower than the target yield (95% or more).

Comparative example 2
As shown in FIG. 11, the silicon nitride-based ceramics sintered substrate 201 formed only on the side break line 213 formed along the side 211 is folded along the side break line 213 to form the silicon nitride-based ceramic assembly substrate 212 and the sides. It was divided into a margin part 216. No burrs were generated on the side surfaces (laser machined surface and fracture surface) of the silicon nitride based ceramic assembly substrate 212, but the rate of cracks was 6%, and the silicon nitride ceramic assembly substrate 212 cracked as shown in FIG. The rate of occurrence of (the cracked corner 217 was separated) was 2%. Therefore, the yield of Comparative Example 2 was lower than the target yield.

1,101,201: Silicon nitride based ceramics sintered substrate
10: Outer edge of silicon nitride based ceramics sintered substrate
11,111,211: Edge
12, 112, 212: Silicon nitride based ceramic assembly substrate
13, 113, 213: Edge break line
14, 34, 114: Corner break line
14a: Beam spot
140: Wall surface of chamfered part (chamfered surface)
140o: Opening side wall surface
140m: Central wall surface
140e: Penetrating side wall surface
15, 115: Intersection of edge break lines
16,116: Edge margin
17: Corner margin
19: Circuit forming part
20: Silicon nitride based ceramic substrate
21: Edge
22: Chamfering part
22a: Area adjacent to the chamfer
23a: First copper plate
23a': Circuit board
23b: Second copper plate
24: Second break line
25: Each ceramic substrate
25': Ceramic substrate
27: Bali
28: Circuit board
117: Corner margin
134: Crack
216: Edge margin
217: Broken corner
L1: Length of advance of corner break line

Claims (2)

A rectangular silicon nitride-based ceramic assembly substrate having a silicon nitride-based ceramic substrate portion having a large number of circuit forming portions and an edge portion, and having chamfered portions at the four corners of the outer peripheral portion of the edge portion.
The thickness of the silicon nitride-based ceramic assembly substrate is 0.2 to 1.0 mm, and the thickness is 0.2 to 1.0 mm.
The wall surface of the chamfered portion is composed of a laser machined surface.
The side surface of the substrate excluding the chamfered portion is composed of a laser machined surface and a fracture surface in order from the surface of the substrate in the thickness direction.
The fracture surface of the side surface of the substrate is directly connected to the wall surface of the chamfered portion.
A silicon nitride-based ceramic assembly substrate characterized in that a ridge angle portion connecting the fracture surface of the side surface of the substrate and the wall surface of the chamfered portion has a sharpened shape. The silicon nitride-based ceramic assembly substrate according to claim 1.
Multiple first copper plates forming a circuit are joined to one surface,
A silicon nitride-based ceramic assembly substrate, characterized in that a plurality of second copper plates serving as heat dissipation plates are bonded to positions on the other surface that match the first copper plate.

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