Ceramic scribe circuit board, ceramic circuit board, method for manufacturing a ceramic scribe circuit board, method for manufacturing a ceramic circuit board, and method for manufacturing a semiconductor device.

Abstract

To enable the efficient manufacturing of small ceramic circuit boards from large, high-strength, thin ceramic scribe circuit boards that combine heat dissipation and electrical insulation properties. [Solution] The ceramic scribe substrate according to the embodiment has a continuous groove formed by irradiation with a fiber laser on the surface side of the scribe line that forms the ceramic substrate of the ceramic circuit substrate to which the metal circuit is bonded, wherein the depth of the continuous groove is greater than 40 [μm] and within the range of 0.15 times or more and 0.5 times or less the thickness of the ceramic substrate.

Description

[Technical Field]

[0001] Embodiments generally relate to a ceramic scribed circuit board, a ceramic circuit board, a method for manufacturing a ceramic scribed circuit board, a method for manufacturing a ceramic circuit board, and a method for manufacturing a semiconductor device. [Background Art]

[0002] In recent years, along with the development of semiconductor elements requiring large currents such as those used in power electronics and next-generation power semiconductors, demand for ceramic circuit boards having both heat dissipation and electrical insulation properties has been increasing year by year. In particular, as heat generation from elements increases with the trend toward miniaturization and higher performance, the thickness of ceramic substrates tends to be reduced to achieve efficient heat dissipation. Furthermore, metal circuits tend to be thickened to allow large currents to flow.

[0003] On the other hand, in order to reduce the manufacturing cost of ceramic substrates, it is common practice to manufacture them in larger sizes and then divide them into product-sized pieces. Among ceramic substrates, silicon nitride substrates have high strength, high toughness and excellent heat dissipation properties, and a method of obtaining multiple individual pieces by using scribe lines formed by laser processing is disclosed as one method of dividing a large substrate into product-sized pieces (Patent Document 1). According to Patent Document 1, when dividing the substrate into multiple pieces after laser processing, excessive microcracks do not occur in the silicon nitride substrate, and scribe line processing for obtaining multiple pieces can also be performed easily and at low cost.

[0004] In contrast, a method has been disclosed in which scribe lines are made on a ceramic substrate using a laser, then it is bonded to a metal plate using the activated metal method, and a circuit is formed by etching (Patent Document 2). According to Patent Document 2, the laser processing is performed before bonding the copper plate; if it is performed after etching, metal is deposited and the insulation resistance decreases. As a laser processing method after bonding the copper plate to the ceramic substrate, a processing method in which the laser output and laser speed are controlled has been disclosed (Patent Document 3). According to Patent Document 3, the metal (copper) on the ceramic substrate (Al2O3) is ablated (removed), a good appearance can be obtained, and a substrate with almost no residue and no copper oxidation can be obtained. However, this method requires limiting the laser output and laser speed, and even when a very good appearance is obtained by limiting them, a small amount of residue and copper oxidation still occurs.

[0005] On the other hand, the increased thickness of the ceramic substrate before splitting and the increased thickness of the metal circuit result in greater residual stress after bonding due to the difference in thermal expansion coefficients between the two materials, highlighting the challenges that arise from laser processing of ceramic circuit boards. For example, because silicon nitride substrates have high strength, a large force is required to break them along the scribe line, necessitating deep laser penetration in the thickness direction of the silicon nitride substrate. However, if the silicon nitride substrate is thin, there is a high possibility of splitting due to forces applied during processing or transport after laser scribe line formation. Conversely, if the laser is penetrated shallowly in the thickness direction of the silicon nitride substrate, the possibility of splitting during intermediate processes is reduced, but a large force is required during breaking, creating a workload and potentially causing chipping or cracking on the outer edge.

[0006] In other words, while it is possible to form scribe lines on a ceramic substrate before division using laser processing, it was found that controlling the processing method of the scribe lines is necessary to improve work efficiency after scribe line formation and to prevent chipping and cracking. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2002-176119 [Patent Document 2] Japanese Patent Publication No. 2007-324301 [Patent Document 3] Japanese Patent Publication No. 2020-524607 [Overview of the project] [Problems that the invention aims to solve]

[0008] In recent years, the rising junction temperatures of power semiconductor chips have led to a demand for higher reliability in circuit boards. Therefore, there is a need for high-strength, thin ceramic circuit boards that combine heat dissipation and electrical insulation without compromising reliability.

[0009] The embodiment solves these problems and relates to a cost-effective ceramic scribe circuit board that enables the efficient manufacture of small ceramic circuit boards from large, high-strength, thin ceramic scribe circuit boards that combine heat dissipation and electrical insulation properties. [Means for solving the problem]

[0010] The ceramic scribed circuit board according to the embodiment has a series of connected grooves formed by irradiation with a fiber laser on the surface side of the scribe lines that form the ceramic substrate of the ceramic circuit board to which metal circuits are bonded, and the depth of the series of grooves is greater than 40 [μm] and within the range of 0.15 times or more and 0.5 times or less the thickness of the ceramic substrate. [Brief explanation of the drawing]

[0011] [Figure 1] A top view showing an example of the laser-scribed surface of a ceramic scribed circuit board according to an embodiment. [Figure 2]A bottom view showing the back surface of a ceramic scribe circuit board according to an embodiment. [Figure 3] Figure 1 shows a side view of the ceramic scribe circuit board. [Figure 4] A top view showing an example of a brazing material printing surface when creating a ceramic scribe circuit board according to the embodiment. [Figure 5] Figure 4 shows a side view of the ceramic scribe circuit board. [Figure 6] A diagram showing a side view of a ceramic scribe circuit board according to an embodiment, after the metal plate has been installed. [Figure 7] A cross-sectional view showing an example of a ceramic scribe circuit board according to the embodiment. [Figure 8] A magnified section cross-sectional view of part A in Figure 7. [Figure 9] A side view showing an example of a ceramic circuit board according to the embodiment. [Figure 10] A side view showing an example of a semiconductor module integrated with a resin mold according to an embodiment. [Modes for carrying out the invention]

[0012] Hereinafter, embodiments of ceramic scribe circuit boards, ceramic circuit boards, methods for manufacturing ceramic scribe circuit boards, methods for manufacturing ceramic circuit boards, and methods for manufacturing semiconductor devices will be described in detail with reference to the drawings.

[0013] The scribe lines provided on the ceramic scribed circuit board according to the embodiment are for forming the ceramic circuit board, and refer to the scribe lines before division into ceramic circuit boards and the scribe line marks after division (hereinafter referred to as "scribe lines"). In the ceramic scribed circuit board having scribe lines, the scribe lines are provided with continuous grooves formed by connecting a plurality of grooves through irradiation of a laser, for example, a fiber laser, and the depth of the continuous grooves is greater than 40 [μm] from the laser irradiation surface side, and is in a range of 0.15 times or more and 0.5 times or less of the substrate thickness.

[0014] Fig. 1 is a top view showing an example of a laser scribed surface (front surface) of the ceramic scribed circuit board according to the embodiment. Fig. 2 is a back view of Fig. 1, and Fig. 3 is a side view where the upper side is the front surface. Reference numeral 2 denotes a multi-cavity ceramic substrate, reference numeral 3 denotes a metal circuit, reference numeral 3A denotes a metal heat sink, reference numeral 4 denotes ceramic substrates (four ceramic substrates), reference numeral 5 denotes a peripheral portion not used as a product, reference numeral 6 denotes a scribe line, reference numeral 7 denotes a bonding layer (for example, a brazing material portion), and reference numeral 13 denotes ceramic circuit boards to be products (four ceramic circuit boards). As shown in Fig. 3, the ceramic circuit board 13 may include the ceramic substrate 4, the metal circuit 3 and the metal heat sink 3A bonded together via the brazing material portion 7.

[0015] Note that the ceramic scribed circuit board 1 includes a multiple ceramic substrate 2 from which a plurality of ceramic circuit boards can be obtained by division, and a single ceramic substrate (not shown) from which one ceramic circuit board can be obtained by division. FIG. 1 shows an example of the multiple ceramic substrate 2 from which a total of four ceramic circuit boards 13, two in each of the vertical and horizontal directions, can be obtained by multiple processing via laser scribing along a total of six scribe lines 6, three in each of the vertical and horizontal directions. The ceramic scribed circuit board 1 is not limited to such multiple ceramic substrates 2, and may be a single ceramic substrate having scribe lines that allow processing a ceramic circuit board into a product shape, or may be a multiple ceramic substrate having scribe lines that allow obtaining more than two ceramic circuit boards in the vertical and horizontal directions. Further, it is not necessary to form scribe lines 6 on the entire periphery of the ceramic substrate 4, and it is sufficient that the scribe lines 6 are provided on at least one side. In addition, although the ceramic scribed circuit board 1 has a rectangular shape in the top view of FIG. 1, it may have a substantially polygonal shape.

[0016] When the multiple ceramic substrate 2 is a silicon nitride substrate, it can have a high three-point bending strength of 600 [MPa] or more, further 700 [MPa] or more. Also, some of such substrates have a thermal conductivity of 50 [W / m·K] or more, further 80 [W / m·K] or more. When the multiple ceramic substrate 2 is an aluminum nitride substrate, it can have a high thermal conductivity of 170 [W / m·K] or more, further 230 [W / m·K] or more. Also, some of such substrates have a three-point bending strength of 350 [MPa] or more, further 450 [MPa] or more. In particular, in recent years, there are also silicon nitride substrates and aluminum nitride substrates that have both high strength and high thermal conductivity. These multiple ceramic substrates 2 may be single plates, or may have a three-dimensional structure such as a multilayer structure.

[0017] Scribe line 6 is a laser scribe line processed with a laser. A fiber laser is preferred. Because fiber lasers have a small spot diameter, they enable thin, deep, and high-speed processing. The fiber laser in question conforms to the definition in JIS-Z 3001-5 (2013).

[0018] The metal plate used in the metal circuit 3 can be copper (Cu), copper alloys, or aluminum (Al). It is preferable that the ceramic substrate 4 and the metal circuit 3 are joined via a bonding layer 7. It is also preferable that the metal heat sink 3A is joined via the bonding layer 7. Furthermore, it is preferable to provide a bonding layer 7 between the ceramic substrate 4 and the metal circuit 3 using an activated metal brazing material containing an activated metal such as Ti (titanium). In addition to Ti, Zr (zirconium) can also be used as an activated metal. Examples of activated metal brazing materials include mixtures mainly composed of Ti, Ag (silver), or Cu. An example of an activated metal brazing material containing Ti, Ag, and Cu is one in which Ti is 0.1 [wt%] to 10 [wt%], Cu is 10 [wt%] to 60 [wt%], and Ag is the remainder. Furthermore, if necessary, one or more elements selected from In (indium), Sn (tin), Al, Si (silicon), C (carbon), and Mg (magnesium) may be added in an amount of 1 wt% to 15 wt%.

[0019] In the active metal bonding method using metal brazing material, it is preferable to form the active metal brazing material into a paste. The paste is a mixture of brazing material components and organic matter, but the brazing material components must be uniformly mixed. This is because if the brazing material components are unevenly distributed, the brazing will not be stable and it will cause bonding failure. The active metal brazing material paste is printed on the surface of the ceramic substrate, and the metal circuit 3 is placed on top of it. Figure 4 shows an example of the brazing material printed surface when manufacturing the ceramic scribe circuit board 1 according to the embodiment. Figure 4 is both the front and back surface of the ceramic scribe circuit board 1 during manufacturing. Figure 5 shows a side view of Figure 4. This is heated at 600°C to 900°C to bond with the metal circuit 3. According to the active metal bonding method, the bonding strength between the ceramic substrate 4 and the metal circuit 3 can be 16 kN / m or more.

[0020] Returning to the explanation of Figures 1 to 3, the metal plate to be joined as the metal circuit 3 can be either a plate pre-processed into a pattern shape for circuit formation, or a single plate without pattern processing. Figure 6 shows a side view of the ceramic circuit board according to the embodiment after brazing using a single metal plate. Reference numerals 8 and 8A indicate a single metal plate (for example, a copper plate). When a single plate is used, etching is performed after joining the metal plate to process it into a pattern shape. It is also possible to print the brazing material onto the entire surface of the ceramic substrate and perform the joining, and then form the circuit by etching the brazing material at the same time as the metal plate. Furthermore, the thickness of the metal plate is not particularly limited, but it is preferable to be 0.3 [mm] or more, and more preferably 0.6 [mm] or more. A thicker metal plate can increase the current capacity. It can also improve heat dissipation.

[0021] Returning to the explanation of Figures 1 to 3, a thin metal film mainly composed of one of the following metals may be applied to the surface of the metal circuit 3: Ni (nickel), Ag (silver), and Au (gold). Examples of these thin metal films include plating films and sputtered films. By applying a thin metal film, corrosion resistance and solder wettability can be improved.

[0022] Figure 7 shows an example of a cross-section of the ceramic scribe circuit board 1 according to the embodiment. Figure 7 is a cross-sectional view of GG in Figure 1. Reference numeral 9 denotes the laser irradiation surface (front surface), which is the side on which the laser is irradiated; reference numeral 12 denotes a continuous groove in which multiple grooves are connected on the surface side due to laser irradiation; reference numeral 10 denotes a group of discontinuous grooves (multiple recesses) in which multiple grooves are not connected on the deeper side due to laser irradiation; and 11 denotes the non-laser irradiated surface (back surface), which is the side on which the laser is not irradiated and is the side opposite to the laser irradiation surface 9. In addition, the ceramic scribe circuit board 1 should be provided with continuous grooves 12 such that the continuous grooves 12 are provided on the surface side of at least one of the scribe lines 6 on the four sides of the ceramic substrate 4 of the ceramic circuit board 13 formed by the ceramic scribe circuit board 1.

[0023] Figure 8 is an enlarged view of section A in Figure 7. The symbol T represents the thickness of each ceramic substrate in the multi-cavity ceramic substrate 2, the symbol D1 represents the distance from the surface of the ceramic substrate to the deepest part of the continuous groove 12 (depth of the continuous groove 12), and the symbol D2 represents the distance from the deepest part of the continuous groove 12 to the deepest part of the discontinuous groove group 10 (depth of the discontinuous groove group 10). Note that since the multi-cavity ceramic substrate 2 is a type of ceramic substrate, the thickness of the multi-cavity ceramic substrate 2 is synonymous with the thickness of the ceramic substrate 4.

[0024] The depth D1 of the continuous groove 12 and the depth D2 of the discontinuous groove group 10 can be determined from the cross-section of the ceramic substrate. The cross-section of the ceramic substrate 4 after division along the scribe line 6 is photographed using a microscope or scanning electron microscope (SEM). In the magnified photograph, a line is drawn parallel to the surface of the ceramic substrate 4 at the deepest point of the continuous groove 12 (the peak between adjacent grooves of the discontinuous groove group 10), and the distance from the surface of the ceramic substrate 4 to this deepest point is measured as depth D1. Similarly, in the magnified photograph, a line is drawn parallel to the surface of the image showing the ceramic substrate 4 at the deepest point of the discontinuous groove group 10, and the distance from the deepest point of the continuous groove 12 to the deepest point of the discontinuous groove group 10 is measured as depth D2. This allows for the simple acquisition of depths D1 and D2. The depth D1 of the continuous groove 12 may be measured based on the position of one peak in the discontinuous groove group 10, or it may be measured based on the positions of multiple equally spaced peaks in the discontinuous groove group 10, for example, 10 peaks, and the arithmetic mean may be taken. In the case of the depth D2 of the discontinuous groove group 10, the depth of one groove in the discontinuous groove group 10 may be measured, or the depths of multiple equally spaced grooves in the discontinuous groove group 10, for example, 10 grooves, may be measured and the arithmetic mean may be taken.

[0025] The depth D1 of the continuous groove 12 from the laser irradiation surface 9 is greater than 40 [μm]. The continuous groove 12 is formed to smoothly divide the high-strength ceramic substrate. By making the depth of the continuous groove 12 greater than 40 [μm], it becomes unnecessary to apply a large force when dividing the substrate. Furthermore, it is preferable that the depth of the continuous groove 12 be greater than 70 [μm], and more preferably greater than 90 [μm].

[0026] On the other hand, the depth D1 of the continuous groove 12 is in the range of 0.15 times or more and 0.5 times or less the thickness T of the ceramic substrate 4. If the depth D1 is less than 0.15 times the thickness T of the ceramic substrate 4, a large force is applied during division, making it easy for defects such as cracks and fissures to occur at the division points of the ceramic substrate 4 after division. Also, if the depth D1 exceeds 0.5 times the thickness T of the ceramic substrate 4, it will be divided by even a small force applied during the processing or transportation, making stable manufacturing impossible. Furthermore, the depth D1 of the continuous groove 12 is preferably 0.2 times or more and 0.45 times or less the thickness T of the ceramic substrate 4, and more preferably 0.25 times or more and 0.4 times or less.

[0027] The depth D2 of the discontinuous groove group 10 formed deeper than the continuous groove 12 is greater than 0 and less than or equal to 0.45 times the thickness of the ceramic substrate 4. If the depth D2 exceeds 0.45 times the thickness T of the ceramic substrate 4, it will break apart with even a small force applied during the processing or transport, making stable manufacturing impossible. Furthermore, the depth D2 of the discontinuous groove group 10 is preferably between 0.05 and 0.4 times the thickness T of the ceramic substrate 4, and more preferably between 0.1 and 0.35 times.

[0028] In Figure 8, W represents the width of the opening of the discontinuous groove group 10 (hereinafter referred to as the "groove opening width"), and P represents the distance between adjacent grooves in the discontinuous groove group 10 (hereinafter referred to as the "groove distance"). In Figure 8, the groove distance P of the discontinuous groove group 10 is measured from the distance between the deepest parts of adjacent grooves, but it is also possible to measure the distance between the shallowest parts of adjacent grooves. The groove opening width W and the groove spacing P are determined, for example, by measuring the groove spacing P and groove opening width W between adjacent grooves at 10 points where the aforementioned depth D2 was measured, and then taking the arithmetic mean.

[0029] The groove distance P of the discontinuous groove group 10 is preferably between 10 [μm] and 100 [μm]. If the groove distance P is greater than 100 [μm], a large force is applied during splitting, making it easy for defects such as chipping and cracking to occur at the splitting points of the ceramic substrate 4. Also, if the groove distance P is less than 10 [μm], the substrate will split with even a small force during the processing or transport, making stable manufacturing impossible. Furthermore, the groove distance P of the discontinuous groove group 10 is preferably between 20 [μm] and 90 [μm], and more preferably between 30 [μm] and 80 [μm].

[0030] The groove opening width W of the discontinuous groove group 10 is preferably 5 [μm] or more and 50 [μm] or less. If the groove opening width W is greater than 50 [μm], a large force is applied during division, making it easy for defects such as chipping and cracking to occur at the division points of the ceramic substrate after division. Also, if the groove opening width W is less than 5 [μm], it will be divided by even a small force applied during the processing or transport, making stable manufacturing impossible. Furthermore, the groove opening width of the discontinuous groove group 10 is preferably 10 [μm] or more and 45 [μm] or less, and more preferably 15 [μm] or more and 40 [μm] or less.

[0031] Furthermore, it is preferable that the difference in brightness between the laser irradiation marks of the continuous grooves 12 and the brightness of the surface of the ceramic substrate 4 (difference in groove brightness) be 4 or less. If assist gas is not used during laser processing, the surface of the continuous grooves 12 will turn black due to laser processing residue. Although the laser residue may be removed in a later process, if it remains on the surface, it may peel off. Furthermore, if the residue is conductive, it may reduce the insulating properties of the surface of the ceramic substrate 4. In addition, increasing the laser output without using assist gas can increase the processing speed, but it will increase the damage to the surface of the continuous grooves 12. For this reason, a smaller difference in brightness between the laser irradiation marks of the continuous grooves 12 and the brightness of the surface of the ceramic substrate will reduce the damage to the ceramic substrate 4. Furthermore, it is preferable that the difference in brightness between the laser irradiation marks of the continuous grooves 12 and the brightness of the surface of the ceramic substrate 4 be 3 or less, and more preferably 2 or less. The brightness is based on the definition in JIS Z8721 (1993).

[0032] The ceramic circuit board 13, after being divided by laser processing, can form a semiconductor. Figure 9 shows an example of a ceramic circuit board 13 according to this embodiment. Reference numeral 3 denotes a metal circuit, and reference numeral 3A denotes a metal heat sink. Three metal circuits are bonded to the surface of the ceramic substrate 4, and one metal heat sink 3A is bonded to the back surface. In Figure 1, one metal circuit 3 is formed on the surface of the ceramic substrate 4, but in Figure 9, three metal circuits 3 are formed on the surface of the ceramic substrate 4, and there is no limit to the number. In the ceramic substrate 4 shown in Figure 9, it is possible to form metal circuits 3 on the laser irradiation surface 9 on the ceramic substrate 4 where the scribe lines are formed. This is because laser scribing of the ceramic substrate 4 results in less damage during laser scribing and allows for stress relief.

[0033] Such a ceramic circuit board 13 is suitable for a semiconductor module characterized by mounting a semiconductor element on a metal circuit 3 via a bonding layer. Figure 10 shows an example of a semiconductor module (semiconductor device) according to the embodiment. In Figure 10, reference numeral 13 denotes a ceramic circuit board, reference numeral 14 denotes a semiconductor module, reference numeral 15 denotes wire bonding, reference numeral 16 denotes a semiconductor element, reference numeral 17 denotes a resin mold, and reference numeral 18 denotes a lead frame. In Figure 10, a semiconductor element 16 is bonded to the metal circuit 3 of the ceramic circuit board 13 via a bonding layer (not shown). Similarly, a lead frame 18 is bonded via a bonding layer (not shown). Furthermore, the metal circuit 3 adjacent to the semiconductor element 16 is electrically connected by wire bonding 15. The ceramic circuit board 13 to which the wire bonding 15 is connected is integrated with a resin mold 17 to form a semiconductor module 14. The semiconductor module 14 is not limited to this structure. For example, either the wire bonding 15 or the lead frame 18 may be present. Furthermore, multiple semiconductor elements 16, wire bonding 15, and lead frames 18 may be provided on the metal circuit 3.

[0034] Furthermore, the bonding layer that joins the semiconductor element 16 and the lead frame 18 can be made of solder, brazing material, etc. Lead-free solder is preferred. Solder refers to materials with a melting point of 450°C or lower. Brazing material refers to materials with a melting point exceeding 450°C. Materials with a melting point of 500°C or higher are called high-temperature brazing materials. High-temperature brazing materials mainly composed of silver are an example.

[0035] When the entire ceramic circuit board 13 is sealed with resin mold 17, it is desirable that the laser-scribed surface be the outer surface (metal circuit 3 side), as shown in Figure 9 of the ceramic circuit board 13. This is because resin has difficulty filling the discontinuous grooves 10 created by laser scribing, which may result in voids. Since voids hinder heat dissipation, scribe lines 6 are formed on the outer surface (metal circuit 3 side) to suppress the formation of voids on the metal heat sink 3A side. This is because, when heat generated from the semiconductor element 16 is transmitted vertically downwards and at a 45° angle from vertically downwards across the ceramic substrate 4, it is possible to prevent a decrease in heat dissipation on the metal heat sink 3A side due to voids.

[0036] While semiconductor elements 16 bonded to metal circuits 3 are becoming smaller, the amount of heat generated from the chips is steadily increasing. Therefore, improving heat dissipation is crucial for the ceramic circuit board 13 on which the semiconductor elements 16 are mounted. Furthermore, to improve the performance of semiconductor modules 14, multiple semiconductor elements 16 are now mounted on the ceramic circuit board 13. If even a single semiconductor element 16 exceeds its intrinsic temperature, its resistance changes to a negative temperature coefficient. This can lead to thermal runaway, where power flows in a concentrated manner, causing instantaneous destruction. Therefore, improving heat dissipation is effective. Semiconductor modules 14 can also be used in PCUs (Power Control Units), IGBTs (Insulated-Gate Bipolar Transistors), and IPMs (Intelligent Power Modules) used in automobiles (including electric vehicles), railway vehicles, industrial machinery, and inverters for air conditioners, etc. Automobiles are increasingly becoming electric vehicles. Improving the reliability of semiconductor modules 14 directly contributes to the safety of automobiles. The same applies to railway vehicles and industrial equipment.

[0037] Next, a laser scribing method for a silicon nitride-copper circuit substrate, one of the ceramic scribe circuit substrates 1 according to the embodiment, will be described. As long as the laser scribe line of the silicon nitride substrate has the above-described configuration, the manufacturing method is not particularly limited, but the following are examples of methods for obtaining a good yield. Below, an example is given in which a ceramic scribe circuit substrate 1 is used in which a silicon nitride substrate is used as the ceramic substrate 4 and a copper plate is used as the metal circuit 3.

[0038] First, a silicon nitride substrate is prepared. In particular, considering the overall heat dissipation of the ceramic circuit board 13 produced from the silicon nitride substrate, it is preferable that the thermal conductivity be 50 [W / m·K] or higher and the three-point bending strength be 600 [MPa] or higher. Also, when electrical conductivity is to be established between the metal circuit 3 on the surface and the metal heat sink 3A on the back surface by through holes, a silicon nitride substrate with through holes is prepared. When providing through holes in the silicon nitride substrate, the through holes may be provided in advance at the molding stage. Alternatively, the process of providing through holes may be carried out in the silicon nitride sintered body. The process of providing through holes can include laser processing similar to laser scribing, cutting, etc. Cutting can include drilling holes with a drill or the like.

[0039] Next, a copper plate to be used in the metal circuit is prepared. Preferably, the silicon nitride substrate and the copper plate are joined via a bonding layer. Preferably, the bonding layer is an activated metal brazing material containing an activated metal such as Ti. The activated metal brazing material mainly consists of either Ag (silver) or Cu in addition to Ti, with Ti in an amount of 0.1 [wt%] to 10 [wt%], Cu in an amount of 10 [wt%] to 60 [wt%], and Ag as the remainder. If necessary, one or more elements selected from In (indium), Sn (tin), Al, Si (silicon), C (carbon), and Mg (magnesium) may be added in an amount of 1 [wt%] to 15 [wt%].

[0040] Next, an activated metal brazing paste containing activated metals such as Ti is printed onto a silicon nitride substrate. A copper plate is placed on the silicon nitride substrate with the printed brazing paste. This is then heated at a temperature between 600°C and 900°C to bond the plates. The heating process may be carried out in a vacuum or a non-oxidizing atmosphere as needed. If carried out in a vacuum, 1 × 10 -2 The pressure is preferably [Pa] or less. Non-oxidizing atmospheres include nitrogen and argon atmospheres. By using a vacuum or non-oxidizing atmosphere, oxidation of the bonding layer can be suppressed. This improves the bonding strength.

[0041] The copper plate to be joined can be either one that has been pre-processed into a pattern shape for circuit formation, or a single plate that covers the entire surface of the silicon nitride substrate without any pattern processing. If a single plate is used, etching is performed after joining to create the pattern shape. It is also possible to form the circuit by printing a brazing material onto the entire surface of the silicon nitride substrate and joining them, and then etching the brazing material at the same time as the metal plate.

[0042] A silicon nitride substrate with a circuit formed on it is placed on the precision processing table of a fiber laser processing machine. A fiber laser is irradiated onto the silicon nitride substrate to form a scribe line consisting of continuous grooves 12 and discontinuous groove groups 10. At this time, the continuous grooves 12 and discontinuous groove groups 10 of a predetermined size are formed according to the conditions of the fiber laser processing machine. The shape and size of the continuous grooves 12 and other grooves irradiated with the fiber laser are as described above.

[0043] The completed ceramic scribed circuit board 1 is divided to manufacture a silicon nitride copper circuit board as a ceramic circuit board 13. When applying force to the ceramic scribed circuit board 1 for division, it is preferable to do so from the non-laser side. Next, a process of bonding semiconductor elements 16 and the like to the silicon nitride copper circuit board is performed. A bonding layer is provided at the location where the semiconductor elements are to be bonded. Solder or brazing material is preferred for the bonding layer. After providing the bonding layer, the semiconductor elements 16 are placed on top of it. If necessary, a lead frame 18 is also bonded via the bonding layer. Wire bonding 15 may also be provided if necessary. The required number of semiconductor elements 16, lead frames 18, and wire bonding 15 are provided. The silicon nitride copper circuit board with the semiconductor elements 16, lead frames 18, and wire bonding 15 is sealed inside by molding it with resin. Some of these processes can be performed before scribing (dividing). For example, division may be performed after providing the bonding layer.

[0044] A laser scribe method for an aluminum nitride metal circuit board, one of the ceramic circuit boards 13 according to the embodiment, will now be described. First, an aluminum nitride substrate is prepared. In particular, considering the heat dissipation of the entire circuit board, it is preferable that the thermal conductivity is 170 [W / m·K] or higher and the three-point bending strength is 350 [MPa] or higher. The manufacturing method for laser scribe of an aluminum nitride substrate is not particularly limited as long as it has the above-described configuration, but in order to obtain a good yield, the same manufacturing process as for the silicon nitride copper circuit board described above should be taken. For example, the specific gravity of a silicon nitride substrate or an aluminum nitride substrate is about 3.1 to 3.4. The specific gravity of an aluminum oxide substrate is about 3.0 to 4.0.

[0045] The specific gravity of copper plates is approximately 8.5 to 9.0. Since metal plates are heavier than ceramic substrates, the weight of the ceramic circuit board with the metal plate attached increases. In addition, etching processes are necessary to impart circuit shapes to the metal plate. This increases the number of times the ceramic circuit board 13 needs to be transported. By applying fiber laser scribe processing to the ceramic circuit board 13, damage to the ceramic circuit board 13 during transport can be suppressed. Furthermore, in recent years, attempts have been made to increase the thickness of the copper plate. In other words, it is suitable for producing multiple ceramic circuit boards 13 using copper plates, and even more so, copper plates with a thickness of 0.6 [mm] or more.

[0046] (Examples 1-42, Comparative Examples 1-27) For the ceramic scribe circuit boards used in Examples 1-42 and Comparative Examples 1-27, silicon nitride substrates with dimensions of 40 mm (length) x 50 mm (width) and thicknesses of 0.32 mm, 0.25 mm, and 0.50 mm, and aluminum nitride substrates with dimensions of 40 mm (length) x 50 mm (width) and thicknesses of 0.64 mm and 0.80 mm were prepared. The silicon nitride substrates had a thermal conductivity of 90 W / m·K and a three-point bending strength of 650 MPa. The aluminum nitride substrates had a thermal conductivity of 170 W / m·K and a three-point bending strength of 400 MPa.

[0047] Next, copper plates were bonded to the ceramic substrate on both sides using the activated metal bonding method. The copper plates used were oxygen-free copper measuring 40 mm (length) x 50 mm (width) x 0.5 mm (thickness). The activated metal brazing material used in the activated metal bonding method was an activated metal paste made by mixing 2 wt% Ti, 10 wt% Sn, 30 wt% Cu, and the remainder Ag with organic components to form a paste. The activated metal paste was printed onto the surface of the ceramic substrate using a screen printing machine with a 320 x 320 mm, 250 mesh, stainless steel V screen mesh and dried, and then the activated metal paste was printed onto the reverse side and dried.

[0048] Copper plates were placed on both the front and back surfaces of a ceramic substrate onto which paste had been printed and dried. The substrate was then sandwiched between plate-shaped jigs, and a weight was placed on top to perform heat bonding. The heat bonding was performed at a bonding temperature of 810°C for 10 minutes in a vacuum (1 × 10⁻⁶). -2 [Pa] or below) was used. After heat bonding, the copper plates were etched to create circuit shapes. The front copper plate was given three circuit shapes with pullbacks, and the back copper plate was also etched to create pullbacks around its perimeter.

[0049] Next, as shown in Figure 1, a fiber laser was used to process 101 ceramic substrates on the surface side before splitting, using an assist gas. Six laser lines were applied to each substrate under the conditions of Examples 1-42 and Comparative Examples 1-6, 8-13, 15-22, and 24-26. In Comparative Examples 7, 14, 23, and 27, processing was performed without the use of an assist gas. One of the ceramic scribed circuit boards after laser processing under each condition was split, and the area near the center of the cross-section of the split ceramic circuit board (approximately 10 mm from the edge) was observed with a SEM at 100x magnification and a photograph was taken. Lines were drawn on the substrate surface, at the deepest point of the continuous grooves, and at the deepest point of the discontinuous groove groups. The distances to each line were measured to determine the depth D1 of the continuous grooves and the depth D2 of the discontinuous groove groups.

[0050] Furthermore, the inter-groove distance P and groove opening width W of the discontinuous groove groups were determined by measuring the inter-groove distance and opening width W between adjacent discontinuous groove groups at 10 consecutive points in the photograph and taking the arithmetic mean. The measurement results for the examples and comparative examples are shown in Table 1. In Table 1, silicon nitride substrates are denoted as Si3N4 and aluminum nitride substrates as AlN.

[0051] Furthermore, the brightness of the surface and continuous grooves of the ceramic scribe circuit boards, which were observed using SEM images after being divided under each condition, was measured using a micro-surface spectrophotometer, and the difference was determined. The measurement results for the examples and comparative examples are shown in Table 2.

[0052] [Table 1] TIFF2026139819000003.tif150128

[0053] Next, the laser-processed ceramic scribed circuit boards were separated using an automatic board splitting machine to obtain ceramic circuit boards. The appearance of the ceramic circuit boards was inspected, and any remaining cracks, chips, or cracks around the edges of the board were counted as scribe defects.

[0054] A voltage withstand test was performed on scribed ceramic circuit boards, with the voltage applied between the front and back surfaces of the board. The voltage withstand test was conducted using a high-voltage testing device from Kikusui Electronics Co., Ltd. A voltage of 5 kV for 1 minute was applied between the metal circuit on the front surface (3 locations) and the metal heat sink on the back surface, for a ceramic board thickness of 0.5 mm. The failure rate [%] at which continuity occurred was evaluated.

[0055] A semiconductor element was mounted in the central circuit area of ​​the ceramic circuit board according to the examples and comparative examples. Next, wire bonding was performed. Subsequently, resin molding was performed using the transfer molding method. Next, the porosity between the resin and the ceramic circuit board was evaluated by ultrasonic testing (SAT) around the substrate on the side of the metal heat sink where the semiconductor element was not bonded to the ceramic circuit board according to the examples and comparative examples. The porosity [%] was calculated as (total length of the area where voids existed and the resin did not adhere to the ceramic substrate / perimeter length of the ceramic substrate) × 100, and a porosity of less than 95 [%] was considered a resin delamination defect.

[0056] The results obtained for the examples and comparative examples are shown in Table 2. For the scribed surface, the side on which metal circuits were etched in three locations and semiconductor elements were bonded was designated as the circuit side, and the opposite side was designated as the non-circuit side.

[0057] [Table 2] TIFF2026139819000005.tif145128

[0058] As can be seen from Tables 1 and 2, in the ceramic scribed circuit boards of Examples 1 to 42, the depth D1 of the continuous grooves in the ceramic substrate was greater than 40 [μm], the continuous groove depth / substrate thickness (D1 / T) was 0.15 or more and 0.5 or less, and the continuous groove group depth / substrate thickness (D2 / T) was greater than 0 and 0.45 or less. The difference in groove brightness and the orientation of the scribed surface were within a preferred range. In contrast, the ceramic scribed circuit boards of Comparative Examples 1 to 27 were outside the preferred range.

[0059] Ceramic circuit boards manufactured from ceramic scribed circuit boards according to Examples 1 to 42 had no scribe defects or a low defect rate. This is because laser scribes capable of dividing the ceramic scribed circuit board were formed under a constant scribe load. In contrast, comparative examples 1 to 6, 8 to 13, 15 to 22, 26, and 27 had many scribe defects. This is because the laser scribes were not sufficiently formed, making it impossible to divide along the lines under a constant scribe load, resulting in chipping defects and cracking defects.

[0060] Ceramic circuit boards manufactured from ceramic scribed circuit boards according to Examples 1 to 42 either did not exhibit voltage withstand failure or had a low failure rate. This was because the generation of residue that causes voltage withstand failure during laser processing was reduced. In contrast, comparative examples 7, 14, 23, and 27 exhibited many voltage withstand failures. This was because the residue generated during laser scribing became the starting point for current flow.

[0061] Furthermore, ceramic circuit boards manufactured from ceramic scribed circuit boards according to Examples 1 to 42 either did not experience resin peeling defects or had a low defect rate. This was because there were no residues from laser processing by laser scribing, nor traces of continuous and discontinuous groove groups, in the resin-molded areas, thus preventing unbonded areas due to laser residue and voids caused by traces of continuous and discontinuous groove groups. In contrast, Comparative Examples 24, 25, and 27 experienced many resin peeling defects. This was because unbonded areas due to laser residue and voids caused by continuous and discontinuous groove groups were the cause of the peeling defects.

[0062] Although several embodiments of the present invention have been illustrated above, these embodiments are presented as examples only and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims of the invention and its equivalents. Furthermore, the embodiments described above can be implemented in combination with each other. [Explanation of Symbols]

[0063] 1...Ceramic scribe circuit board 2... Entire multi-cavity ceramic metal substrate 3...metal circuit 3A...metal heat sink 4...Ceramic substrate 5... Peripheral area 6...Scribe lines 7...Joining layer 13...Ceramic circuit boards

Claims

1. On the surface side of the scribe lines that form the ceramic substrate of the ceramic circuit board to which metal circuits are joined, a series of connected grooves are provided by irradiation with a fiber laser. The depth of the continuous groove is greater than 40 [μm] and within the range of 0.15 times or more and 0.5 times or less the thickness of the ceramic substrate. The deeper side of the scribe line is provided with a group of discontinuous grooves that are not connected by irradiation with a fiber laser, The depth of the discontinuous groove group is greater than 0 and less than or equal to 0.45 times the thickness of the ceramic substrate. The distance between adjacent grooves in the discontinuous groove group is 10 [μm] or more and 100 [μm] or less. The width of each groove in the aforementioned discontinuous groove group is 5 [μm] or more and 50 [μm] or less. The ceramic substrate is either a silicon nitride substrate or an aluminum nitride substrate. When the ceramic substrate is the silicon nitride substrate, the three-point bending strength is 600 [MPa] or more. A ceramic scribe circuit board characterized in that, when the ceramic substrate is the aluminum nitride substrate, the three-point bending strength is 350 [MPa] or more.

2. When the ceramic substrate is the silicon nitride substrate, the thickness is 0.25 [mm] or more and 0.50 [mm] or less. The ceramic scribe circuit board according to claim 1, characterized in that, when the ceramic substrate is the aluminum nitride substrate, the thickness is 0.64 mm or more and 0.80 mm or less.

3. The ceramic scribe circuit board according to claim 1, characterized in that the thickness of the metal plate forming the metal circuit is 0.3 mm or more.

4. The ceramic scribe circuit board according to any one of claims 1 to 3, characterized in that the scribe lines are formed on the surface on which the metal circuit is formed.

5. The ceramic scribe circuit board according to any one of claims 1 to 3, characterized in that the ceramic substrate is a silicon nitride substrate with a thermal conductivity of 50 [W / m·K] or more, or an aluminum nitride substrate with a thermal conductivity of 170 [W / m·K] or more.

6. The ceramic scribe circuit board according to any one of claims 1 to 3, characterized in that the difference between the brightness of the laser irradiation marks of the continuous grooves and the brightness of the surface of the ceramic substrate is 4 or less.

7. On the surface side of at least one of the four scribe lines, a continuous groove is provided, formed by irradiating with a fiber laser, where multiple grooves are connected. The depth of the continuous groove is greater than 40 [μm] and within the range of 0.15 times or more and 0.5 times or less the thickness of the ceramic substrate. The deeper side of the scribe line is provided with a group of discontinuous grooves that are not connected by irradiation with a fiber laser, The depth of the discontinuous groove group is greater than 0 and less than or equal to 0.45 times the thickness of the ceramic substrate. The distance between adjacent grooves in the discontinuous groove group is 10 [μm] or more and 100 [μm] or less. The width of each groove in the aforementioned discontinuous groove group is 5 [μm] or more and 50 [μm] or less. The ceramic substrate is either a silicon nitride substrate or an aluminum nitride substrate. When the ceramic substrate is the silicon nitride substrate, the three-point bending strength is 600 [MPa] or more. A ceramic circuit board characterized in that, when the ceramic substrate is the aluminum nitride substrate, the three-point bending strength is 350 [MPa] or more.

8. A method for manufacturing a ceramic scribe circuit board, characterized in that, after forming continuous grooves on the surface side of the ceramic scribe circuit board according to any one of claims 1 to 3 using a fiber laser, a group of discontinuous grooves in which the grooves are not connected is formed on the deeper side using a fiber laser.

9. A method for manufacturing a ceramic circuit board, characterized by manufacturing a ceramic circuit board by applying stress to the ceramic scribed circuit board described in any one of claims 1 to 3 and dividing it along the scribe line.

10. The method for manufacturing the ceramic circuit board described in claim 9, A method for manufacturing a semiconductor device, characterized by manufacturing a semiconductor device by mounting semiconductor elements on the aforementioned ceramic circuit board.

11. The method for manufacturing a semiconductor device according to claim 10, characterized in that the ceramic circuit board and the semiconductor element are integrated by resin molding.

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