Method for manufacturing ceramic circuit board and ceramic joined body

Abstract

This method for manufacturing a ceramic circuit board according to an embodiment comprises a joined body manufacturing step, a positioning step, and a circuit forming step. The joined body manufacturing step includes manufacturing a ceramic joined body in which a metal plate is joined to at least one surface of a ceramic substrate, and an outer peripheral portion including a portion of the outer periphery of the ceramic substrate is exposed from the metal plate in a plan view from the metal plate side. The positioning step includes positioning the ceramic joined body using the outer peripheral portion of the ceramic substrate of the ceramic joined body. The circuit forming step includes forming a metal circuit by removing an unnecessary portion of the metal plate from the positioned ceramic joined body.

Description

Method for manufacturing a ceramic circuit board and a ceramic bonded body

[0001] The invention according to the embodiment generally relates to a method for manufacturing a ceramic circuit board and a ceramic bonded body.

[0002] A ceramic circuit board is an essential component for power modules that require high reliability, and is widely used in inverters of automobiles (especially electric vehicles), railway vehicles, solar power generation facilities, and various industrial machines. With the recent demands for energy conservation and higher output, these power modules are required to be smaller and more densely mounted. Along with this, higher dimensional accuracy is required for the metal circuit patterns that make up the substrate.

[0003] In addition, heat dissipation characteristics are also required with the increase in output of industrial equipment. In order to ensure high heat dissipation, it is common to use a metal plate with a certain thickness as the metal circuit. The method for forming the metal circuit in such a ceramic circuit board is mainly divided into two types. One is a method of bonding a metal plate processed in advance into the shape of a circuit pattern to a ceramic substrate. The other is a method of removing unnecessary portions of the metal plate from a ceramic bonded body in which a metal plate is bonded to a ceramic substrate to form a metal circuit. In the former method, it is difficult to handle complex circuit shapes and fine pitch (where the interval between adjacent circuits is narrow) patterns. Also, when bonding the ceramic substrate and the metal circuit, misalignment defects are likely to occur. Therefore, in order to manufacture individual ceramic circuit boards with good dimensional accuracy, it is effective to use the latter method.

[0004] Japanese Patent Application Laid-Open No. 2011-54893

[0005] To manufacture ceramic circuit boards that maximize the area of ​​the ceramic substrate and enable high-density mounting, it is effective to bond a metal plate of roughly the same size as the ceramic substrate to the ceramic bond. However, in such ceramic bond, the outer perimeter is defined by the metal plate. Therefore, it is difficult to position guide pins against the side surface of the ceramic substrate in the bonded ceramic bond, and misalignment during subsequent processes such as etching can lead to defects in the formation of the metal circuit.

[0006] Furthermore, in ceramic circuit boards, metal plates are sometimes bonded to both sides of the ceramic substrate. In particular, with this type of ceramic circuit board configuration, the ceramic substrate is covered by the metal plates in the ceramic bonded body before processing, making it even more difficult to determine the precise position of the ceramic substrate.

[0007] Furthermore, in recent years, to increase productivity, a method has been employed in which scribe lines for division are made in large ceramic substrates using lasers, and then the substrates are individually separated after metal circuit formation. However, when using such large ceramic substrates, the impact of misalignment during bonding between the metal plate and the ceramic substrate is significant, leading to a greater occurrence of defects in the positional alignment of the metal circuit formation.

[0008] The problem that this invention aims to solve is to provide a method for manufacturing a ceramic circuit board and a ceramic bond that enables the formation of metal circuits with high dimensional accuracy.

[0009] The method for manufacturing a ceramic circuit board according to this embodiment comprises a bonded body manufacturing step, a positioning step, and a circuit formation step. The bonded body manufacturing step manufactures a ceramic bonded body in which a metal plate is bonded to at least one surface of a ceramic substrate, and when viewed from the metal plate side in a plan view, the outer peripheral portion including a part of the outer periphery of the ceramic substrate is exposed from the metal plate. The positioning step positions the ceramic bonded body using the outer peripheral portion of the ceramic substrate of the ceramic bonded body. The circuit formation step removes unnecessary portions of the metal plate from the positioned ceramic bonded body and forms a metal circuit.

[0010] A plan view showing a first example of a ceramic joint according to the embodiment. A plan view showing a second example of a ceramic joint according to the embodiment. A plan view showing a third example of a ceramic joint according to the embodiment. A plan view showing a fourth example of a ceramic joint according to the embodiment. A plan view showing a fifth example of a ceramic joint according to the embodiment. A plan view showing a sixth example of a ceramic joint according to the embodiment. A plan view showing a seventh example of a ceramic joint according to the embodiment. An enlarged plan view of the area around a recess in the ceramic joint according to the embodiment. A plan view showing an example of the shape of a recess in the ceramic joint according to the embodiment. A plan view showing an example of a positioning device for the ceramic joint according to the embodiment. A plan view showing an example of a method for positioning the ceramic joint according to the embodiment by bringing it into contact with a guide pin. Embodiment

[0011] The manufacturing method for ceramic circuit boards and the ceramic bonded body will be described in detail below with reference to the drawings.

[0012] The method for manufacturing a ceramic circuit board according to this embodiment comprises a bonded body manufacturing step, a positioning step, and a circuit formation step. The bonded body manufacturing step manufactures a ceramic bonded body in which a metal plate is bonded to at least one surface of a ceramic substrate, and when viewed from the metal plate side in a plan view, the outer peripheral portion including a part of the outer periphery of the ceramic substrate is exposed from the metal plate. The positioning step positions the ceramic bonded body using the outer peripheral portion of the ceramic substrate of the ceramic bonded body. The circuit formation step removes unnecessary portions of the metal plate from the positioned ceramic bonded body to form a metal circuit.

[0013] First, we will explain the manufacturing process for a ceramic bond in which a metal plate is attached to a ceramic substrate. Figures 1 to 7 show examples of ceramic bonded bodies as plan views. Figure 8 shows an enlarged view of an example of the area around a recess in a ceramic bonded body. In Figures 1 to 7, reference numeral 1 denotes the ceramic bonded body, reference numeral 2 denotes the ceramic substrate, reference numeral 2A denotes the outer peripheral portion including a part of the outer periphery of the ceramic substrate 2, reference numeral 3 denotes the metal plate, and reference numeral 4 denotes the recess formed in the metal plate 3. As shown in Figures 1 to 7, when viewed from the metal plate 3 side in a plan view, the metal plate 3 occupies most of the ceramic bonded body 1, but the outer peripheral portion 2A of the outer periphery of the ceramic substrate 2 is exposed (bare).

[0014] Examples of materials for the ceramic substrate 2 used in the ceramic bond 1 include silicon nitride, aluminum nitride, aluminum oxide, and Algil (a composite material of aluminum oxide and zirconium oxide). Among these, silicon nitride, which has high strength and high thermal conductivity, is preferred. The three-point bending strength of aluminum nitride and aluminum oxide is about 300 to 450 MPa, but silicon nitride can have a strength of 500 MPa or more, and even 650 MPa or more. Algil has a strength of about 550 MPa, but its thermal conductivity is relatively low at 30 to 50 W / m·K. With silicon nitride, there are materials with a strength of 60 W / m·K or more, and even 80 W / m·K or more. By using a material with high strength and high thermal conductivity, a thinner ceramic substrate can be used. If a thinner ceramic substrate can be used, the semiconductor device can be made smaller.

[0015] Preferably, the thickness of the ceramic substrate 2 is 0.1 mm or more and 2.0 mm or less. Since strength decreases as the thickness decreases, if a ceramic substrate 2 thinner than 0.1 mm is used, the strength of the ceramic circuit board and semiconductor device, which are created by removing a portion of the metal plate 3 of the ceramic bond 1, will decrease and become more prone to breakage. If it exceeds 2.0 mm, the thermal resistance of the ceramic substrate will increase, and the heat dissipation performance of the ceramic circuit board may decrease. More preferably, the thickness of the ceramic substrate 2 is 0.1 mm or more and 1.0 mm or less.

[0016] Examples of materials for the metal plate 3 of the ceramic joint 1 include copper plates, copper alloy plates, aluminum plates, aluminum alloy plates, and iron alloy plates. A material with high electrical conductivity is preferred. The thermal conductivity of copper is approximately 400 W / m·K, and the thermal conductivity of aluminum is approximately 240 W / m·K. To improve the heat dissipation of the metal plate, oxygen-free copper with high heat dissipation is preferred, and oxygen-free copper with a copper purity of 99.96% by mass or higher as specified in JIS-H-3100 is more preferred. If aluminum is used, pure aluminum as specified in JIS-H-4000 is preferred. Note that JIS-H-4000 corresponds to ISO 6361, and JIS-H-3100 corresponds to ISO 197, etc.

[0017] Furthermore, the metal plate 3 is preferably 0.2 mm or thicker, and more preferably 0.5 mm or thicker. Using a thicker metal plate 3 improves both the heat dissipation and current conductivity properties of the ceramic circuit board. There is no upper limit to the thickness of the metal plate 3, but if it exceeds 2.0 mm, it will take time to remove unnecessary parts in the circuit formation process, which may reduce production efficiency. Moreover, in order to perform the circuit formation process efficiently, the thickness of the metal plate 3 is preferably 0.2 mm or more and 1.5 mm or less, and most preferably 0.5 mm or more and 1.0 mm or less.

[0018] The outer dimensions of the planar surfaces of the ceramic substrate 2 and metal plate 3 used in the ceramic bonded body 1 are preferably 10 mm x 10 mm or larger. While the outer dimensions shown are for rectangular planar surfaces, the planar surfaces may also be circular, semicircular, or chamfered. If the planar surface is circular, the diameter is preferably 10 mm or larger. Furthermore, the ceramic substrate 2 may have pre-defined scribe lines for division using a laser or the like.

[0019] The outer dimensions of the metal plate 3 are preferably the same as, slightly smaller than, or slightly larger than the ceramic substrate 2. Specifically, the ratio of the difference between the outer dimensions of the metal plate 3 and the outer dimensions of the ceramic substrate 2 (the ratio of the difference to the outer dimensions of the ceramic substrate (or metal plate)) is preferably less than 5%. More preferably, the ratio of the difference between the outer dimensions of the metal plate 3 and the outer dimensions of the ceramic substrate 2 is 3% or less. When the outer dimensions of the metal plate 3 are larger than those of the ceramic substrate 2, and both planes are circular, the difference in diameter is used. On the other hand, when both planes are polygonal (including rectangles), the distance between at least one side is used.

[0020] To manufacture a ceramic circuit board that maximizes the planar area of ​​the ceramic substrate 2 and enables high-density mounting, it is effective to bond a metal plate 3 with a similar planar size to the ceramic substrate 2. Since the metal plate 3 is stretched in a later bonding process, it is possible to use one that is smaller than the ceramic substrate 2. However, if a metal plate 3 that is 5% or more smaller in external dimensions than the ceramic substrate 2 is used, the stretching of the metal plate 3 may be insufficient, and the metal plate 3 may not be formed over a sufficient area on the ceramic substrate 2. If the area on the ceramic substrate 2 where the metal plate 3 is not bonded is large, the area on the ceramic substrate 2 where circuits can be formed will be reduced. In addition, there is a risk that the metal plate 3 will not be bonded to the position where circuits should be formed. On the other hand, if the metal plate 3 is larger than the ceramic substrate 2, it is possible to bond the metal plate 3 to the entire area of ​​the ceramic substrate, but the portion of the metal plate 3 that is not bonded to the ceramic substrate 2 will be removed in a later circuit formation process. For this reason, when using a metal plate 3 that is larger than the ceramic substrate 2, it is preferable that the difference in external dimensions is less than 2.5%.

[0021] The ceramic bonded body 1 is manufactured by joining the ceramic substrate 2 and the metal plate 3 described above. In order to expose a part of the ceramic substrate 2 in the ceramic bonded body 1, (1) the ceramic substrate 2 and the metal plate 3 are arranged offset along the planar direction of the front and back surfaces, or (2) the metal plate 3 is pre-processed with chamfering or recesses. In order to make the most effective use of the area of ​​the ceramic substrate 2 as a circuit forming surface, it is preferable that the metal plate 3 is joined to 95% or more, more preferably 97% or more, of the area of ​​the circuit forming surface of the ceramic substrate 2 in the ceramic bonded body 1.

[0022] The arrangement described in (1) above is shown in Figures 2 and 3. In this case, it is preferable that the ratio of the length of the outer peripheral portion 2A to the total outer peripheral length of the ceramic substrate 2 is 80% or less, more preferably 70% or less. In the method of arranging the ceramic substrate 2 and the metal plate 3 offset in the planar direction, as shown in Figure 2, the ceramic substrate 2 is joined with an offset in the planar direction such that one or more sides of the ceramic substrate 2, for example, one side, are exposed from the metal plate 3 in a planar view of the ceramic joint 1. Alternatively, as shown in Figure 3, the ceramic substrate 2 may be joined with an offset in the planar direction such that one or more sides of the ceramic substrate 2, for example, two sides, are exposed from the metal plate 3 in a planar view of the ceramic joint 1. When joining the ceramic substrate 2 and the metal plate 3 with an offset in the planar direction as shown in Figures 2 and 3, the ceramic substrate 2 and the metal plate 3 are arranged in advance by predicting the stretching of the metal plate 3 during joining.

[0023] In the ceramic bonded body 1, the outer peripheral portion 2A of the ceramic substrate 2 that is exposed from the metal plate 3 is not bonded to the metal plate 3, and therefore a metal circuit cannot be formed. For this reason, it is preferable to treat the outer peripheral portion 2A of the ceramic substrate 2 that is exposed as an edge outside the circuit formation, or to remove it as an ear portion in a later process. Alternatively, a metal plate smaller than the ceramic substrate 2 can be used, and the metal plate can be positioned so that it does not overlap any side of the ceramic substrate 2 (so that the entire surface area of ​​the metal plate fits on the ceramic substrate) after predicting the stretching of the metal plate. However, this method is prone to misalignment during placement and misalignment of the bonding position due to stretching of the metal plate when bonding the metal plate and the ceramic substrate 2.

[0024] When joining the ceramic substrate 2 and the metal plate 3 by offsetting them in the planar direction in order to expose the outer periphery of the ceramic substrate 2, it is preferable that the exposed width d (shown in Figures 2 and 3) of the ceramic substrate 2 from the metal plate 3 in the ceramic joint 1 is less than 5% of the outer dimensions of the ceramic substrate 2. More preferably, the exposed width d is 2.5% or less as a percentage of the outer dimensions of the ceramic substrate 2. This is because if the exposed width d of the ceramic substrate 2 is 5% or more of the outer dimensions of the ceramic substrate 2, there will be areas on the ceramic substrate 2 where the metal plate 3 is not joined, which may reduce the area where circuits can be formed. Also, there is a risk that the metal plate 3 will not be joined to the position where circuits should be formed.

[0025] The arrangement described in (2) above is shown in Figures 1, 4, 5 to 7. In this case, the entire length of one or two sides of the ceramic substrate 2 may be exposed (not shown), partially exposed of one or two sides (Figures 1, 4, 6), or one or two corners may be exposed (Figures 5 to 7). In the former case, the entire length of one or two sides of the ceramic substrate may be exposed, and at least one of the other sides of the metal plate 3 may have a recess.

[0026] Methods for processing the metal plate 3 so that the ceramic substrate 2 is exposed include chamfering the corners of the metal plate 3 or creating recesses in the corners and edges of the metal plate. On the other hand, when recesses 4 are provided in the metal plate 3 to expose a part of the ceramic substrate 2, the recesses 4 should be provided so that the external position of the ceramic substrate 2 can be seen from the plane. For example, if the plane of the ceramic substrate 2 is rectangular, as shown in Figure 1, the recesses 4 are provided so that at least two non-parallel sides of the plane of the ceramic substrate 2 can be seen, exposing the outer periphery 2A. The metal plate 3 has at least one corner (four corners in the case of a rectangle), and each of the two sides connected to the corner has one or more recesses 4. If the positions of the two non-parallel sides can be seen, the position of the corner can be calculated based on those two sides. If the position of one corner is known, the positions of the remaining sides and corners can be determined from the size of the ceramic substrate 2.

[0027] Furthermore, as shown in Figure 4, if recesses 4 are provided that span two sides and one corner, the position of the ceramic substrate 2 can be determined using just one recess 4. Moreover, if recesses are provided so that three or more sides can be identified, positioning can be performed even more easily. For example, a design with recesses 4 at two corners as shown in Figure 5, or a design with recesses at one corner and one side as shown in Figure 6, is also effective. In addition, as long as there are recesses that allow the position of the ceramic substrate to be determined, it is acceptable to have recesses where the ceramic substrate is not exposed. Furthermore, if at least one recess 4 is provided on all four sides, the ceramic bonded body 1 can be set regardless of front, back, left, or right orientation during positioning, and the orientation adjustment of the ceramic bonded body 1 can be omitted.

[0028] Furthermore, if a chamfered shape is applied to the corners of the metal plate 3, the outer peripheral portion 2A of the ceramic substrate 2 will be exposed at the corners, as shown in Figure 7. In this case, the chamfer may be provided on only one corner of the metal plate 3, or on two or more corners.

[0029] Furthermore, when metal plates 3 are bonded to both sides of a ceramic substrate 2, it is preferable that the outer peripheral portion 2A of the ceramic substrate 2 is in the same position when viewed from either side of the ceramic substrate 2 after bonding. In locations where the outer peripheral portion 2 exists only when viewed from one side, the outer peripheral of the ceramic substrate 1 is defined by the outer peripheral of the metal plate 3, making it difficult to position the ceramic substrate 1 using its outer peripheral.

[0030] Figure 8 shows a plan view of the area around the recess 4 of the ceramic joint 1. Reference numeral 5 denotes the depth of the recess 4, reference numeral 6 denotes the width of the outer peripheral portion 2A, and reference numeral 7 denotes the depth of the outer peripheral portion 2A. The depth 5 of the recess 4 is the distance from the outer dimensions of the metal plate 3 excluding the recess 4 to the deepest part of the recess 4. The width 6 of the outer peripheral portion 2A is the length of the outer peripheral portion 2A. The depth 7 of the outer peripheral portion 2A is the distance from the bottom of the recess 4 to the outer peripheral of the ceramic substrate.

[0031] Since the bonding of the ceramic substrate 2 and the metal plate 3 is carried out at high temperatures, the metal plate 3 stretches during the bonding process. Therefore, in order to prevent the recess 4 from collapsing due to the stretching of the metal, it is necessary to appropriately set the size of the recess 4 considering the thermal expansion coefficient of the material used for the metal plate 3. An example of a preferred recess 4 is shown below.

[0032] The depth 5 of the recess 4 in the ceramic joint 1 is preferably 0.5 mm or more. If the depth 5 of the recess 4 is too small, there is a risk that the ceramic substrate 2 will not be exposed from the recess 4. Furthermore, the width 6 of the recess 4 is preferably 2.0 mm or more. If the width 6 of the recess 4 is less than 2.0 mm, it becomes difficult to position the ceramic joint 1 using the outer peripheral portion 2A. For example, in a method of positioning and fixing the ceramic joint 1 using a pin as a positioning guide, there is a risk that the pin will not be able to enter the recess 4. Note that if the width 6 of the recess 4 changes as it gets deeper, the width 6 of the recess 4 should be the width of the outer peripheral portion 2A.

[0033] The maximum width 6 of the recess 4 is not limited, but it should be adjusted so that the ratio of the length of the outer periphery to the total length of the outer periphery of the ceramic substrate 2 is 40% or less. More preferably, this ratio is 30% or less, and most preferably 20% or less. The larger this ratio, the smaller the area on which a metal circuit can be formed. Also, if a metal plate 3 for heat dissipation is bonded to the ceramic substrate 2, the heat dissipation performance will decrease due to the reduction in area.

[0034] Furthermore, the depth 7 of the outer peripheral portion 2A is 10 μm or more, preferably 100 μm or more. If the width of the outer peripheral portion 2A is small, there is a risk that the ceramic substrate 2 may not be properly detected when a camera or the like is used to position the ceramic bonded body 1.

[0035] The shape of the recess 4 is not limited, and various shapes can be applied as long as they are not shapes that are disadvantageous to the positioning of the ceramic joint 1. An example of the shape of the recess 4 is shown in Figure 9. As shown in Figure 9, the recess 4 may be a semicircular recess 8a, a rectangular recess 8b, a V-shaped recess 8c, a trapezoidal recess 8d, or a constricted recess 8e, etc. Also, when multiple recesses 4 are provided in a single ceramic joint 1, the multiple recesses 4 may be made the same shape, or different shapes may be combined.

[0036] Furthermore, various methods can be used to process the metal plate 3 for creating the recesses 4, such as laser processing, press processing, and cutting. Among these, press processing using a die is preferable because it offers high production efficiency, dimensional accuracy, and is less prone to generating burrs. When the number, width, and depth of the recesses 4 are small, wire cutting or laser processing is also preferable. These processing methods make it easy to process the recesses 4 into various shapes.

[0037] The ceramic substrate 2 and metal plate 3 described above are joined to obtain a ceramic bonded body 1. As a joining method, for example, the active metal brazing method (AMB method) can be used. The AMB method uses a brazing material containing an active metal, so high bonding strength can be obtained even when a thick metal plate 3 is used. Also, if the metal plate 3 is a copper plate, it is preferable to use the direct bonding method (DBC method) as the joining method to the ceramic substrate 2. The DBC method is a method of joining the ceramic substrate 2 and the metal circuit board by utilizing the reaction in which copper and oxygen in the copper plate form a eutectic compound (Cu-O eutectic). The joining temperature is high and warping is likely to occur, but it is simpler than the AMB method. In addition to the AMB method and DBC method, metallization methods using high melting point metal pastes such as tungsten and molybdenum may also be used as the joining method for the metal plate 3 and the ceramic substrate 2.

[0038] A ceramic bonded body 1 is obtained by joining a ceramic substrate 2 and a metal plate 3 at a high temperature. During this process, the metal plate 3 stretches. Therefore, even when ceramic substrates 2 and metal plates 3 of the same dimensions are used as components of the ceramic bonded body 1, a ceramic bonded body 1 is obtained in which the metal plate 3 occupies most of the outer periphery of the plane.

[0039] Next, we will describe the positioning process for positioning the ceramic bonded body 1 using the exposed outer peripheral portion 2A of the ceramic substrate 2. Positioning of the ceramic bonded body 1 can be done using a camera or by fixing it with a guide from a printing press. In the camera method, positioning is performed by recognizing the position of the entire ceramic substrate 2 using the outer peripheral portion 2A exposed from the recess. In the method using a guide from a printing press, the ceramic bonded body 1 is positioned by bringing a guide, such as a pin, into contact with the side surface corresponding to the outer peripheral portion 2A exposed by the recess 4.

[0040] For example, FIG. 10 shows a positioning device in which a guide pin 9 is arranged on a stage 10. If the ceramic joined body 1 of FIG. 1 is placed on the stage 10 and the side surface corresponding to the outer peripheral portion 2A of the ceramic joined body 1 is brought into contact with the guide pin 9 of the positioning device as shown in FIG. 11, the positioning of the ceramic joined body 1 conforming to the ceramic substrate 1 can be easily achieved. Further, by recognizing the position of the ceramic substrate 1 using a camera after the contact, more accurate positioning of the ceramic joined body 1 is possible.

[0041] Next, a circuit forming step of removing an unnecessary portion of the metal plate 3 from the ceramic joined body 1 and forming a metal circuit in the positioned state will be described. In general, an etching process is performed to form the metal circuit. In the etching process, first, an etching resist is printed in a circuit pattern shape on the metal plate 3 of the ceramic joined body 1 by screen printing or the like. Then, the printed ceramic joined body 1 is subjected to an etching process to dissolve and remove portions other than the resist-coated portions. Thereby, a ceramic circuit board having a metal circuit on the ceramic substrate 2 is obtained. A cleaning process using an acid or an alkali and an anti-rust treatment or the like may be provided after the etching process as necessary.

[0042] Further, a metal thin film mainly composed of one kind selected from Ni (nickel), Ag (silver), and Au (gold) may be provided on the surface of the metal circuit after etching. Examples of the metal thin film include a plating film and a sputtering film. By providing the metal thin film, the corrosion resistance and solder wetting property of the ceramic circuit board can be improved.

[0043] A semiconductor device can be obtained by mounting one or two or more semiconductor elements on the metal circuit of the ceramic circuit board obtained through the above steps. A plurality of the same elements or different elements may be provided as the semiconductor elements. The semiconductor device may include wire bonding or a lead frame for conduction.

[0044] By using the ceramic circuit board manufactured from the ceramic joined body 1 according to the present embodiment, a semiconductor device with good dimensional accuracy at the circuit forming position and capable of arranging electronic elements and the like at high density can be obtained.

[0045] (Example) A rectangular copper plate with a side length of 150.0 mm and a thickness of 0.8 mm was prepared as the metal plate 3. Also, a rectangular silicon nitride substrate with a side length of 150.0 mm and a thickness of 0.8 mm was prepared as the ceramic substrate 2.

[0046] (Test 1) In the example, rectangular recesses 4 with a width of 30.0 mm and a depth of 1.5 mm were formed one by one by laser at the centers of two opposite sides of the copper plate as the metal plate 3. On the other hand, in the comparative example, an unprocessed copper plate was used as it was.

[0047] An active metal brazing material composed of titanium, silver, copper, and tin was screen-printed on both sides of the silicon nitride substrate as the ceramic substrate 2 and dried. This silicon nitride substrate was placed on the copper plate, and another copper plate was further stacked on it to form a three-layer structure. The silicon nitride substrate and the copper plate were stacked so that their centers were visually aligned. Also, at this time, in the example, the positions of the recesses 4 of the metal plate 3 were arranged so that they were the same vertically. This was heated at 800 °C for 50 minutes and joined to obtain a silicon nitride joint as the ceramic joint 1. At this time, the copper plate was stretched by the heat joining, and the outer dimensions of the copper plate after joining exceeded the outer dimensions of the silicon nitride joint on both sides. In the example, the outer peripheral portion of the silicon nitride substrate could be confirmed from both recesses 4. In the comparative example, since there were no recesses 4, the entire silicon nitride substrate was hidden by the copper plate, and the position of the ceramic substrate could not be grasped at all from the appearance.

[0048] Next, etching resist was printed onto the silicon nitride bond. In the example, the side corresponding to the outer peripheral portion 2A exposed by the recess 4 was placed in contact with the guide pin 9, and the printing area was set based on the outer peripheral of the silicon nitride substrate. On the other hand, in the comparative example, the side corresponding to the outer peripheral of the metal plate was placed in contact with the guide pin 9. In the comparative example, the entire outer peripheral was a copper plate, and the position of the silicon nitride substrate could not be determined, so the printing area was set by inferring the approximate position of the ceramic substrate. Then, in both the example and the comparative example, etching resist was printed onto the positioned silicon nitride bond. The silicon nitride bond with the etching resist printed on it was subjected to an etching process, and by removing the copper plate other than the surface coated with etching resist, a silicon nitride circuit board as a ceramic circuit board having copper circuits was obtained.

[0049] Next, the misalignment of the metal circuit formation position on the silicon nitride circuit board was measured. A misalignment defect was defined as a misalignment of 50 μm or more from the target metal circuit formation position on the silicon nitride substrate. The occurrence rates of misalignment defects between 50 μm and 100 μm, and those between 100 μm and 100 μm were calculated. The results showed that in the comparative example, 30% of the defects were between 100 μm and 100 μm. Furthermore, 55% were between 50 μm and 100 μm. On the other hand, no misalignment defects occurred in the example.

[0050] (Test 2) An unprocessed metal plate 3 and a ceramic substrate 2 were placed using a jig so that two sides of the ceramic substrate 2 were visible by a width of 1.5 mm each. The metal plate 3 was then joined to the ceramic substrate 2 using the same procedure as in Test 1 to obtain a ceramic bonded body 1. The entire length of both sides of the ceramic substrate was visible in the ceramic bonded body 1. The ceramic bonded body 1 was positioned, printed, and etched in the same manner as in Test 1 to obtain a ceramic circuit board with a copper circuit. No misalignment defects occurred in this ceramic circuit board either.

[0051] According to at least one embodiment described above, the positioning of the ceramic bond 1 is performed using the outer peripheral portion of the ceramic substrate, thereby enabling the formation of the metal circuit with high dimensional accuracy.

[0052] 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.

Claims

1. A method for manufacturing a ceramic circuit board, comprising: a joint manufacturing step for manufacturing a ceramic joint in which a metal plate is bonded to at least one surface of a ceramic substrate, and when viewed from the metal plate side, an outer peripheral portion including a part of the outer periphery of the ceramic substrate is exposed from the metal plate; a positioning step for positioning the ceramic joint using the outer peripheral portion of the ceramic substrate of the ceramic joint; and a circuit forming step for removing unnecessary portions of the metal plate from the positioned ceramic joint to form a metal circuit.

2. The method for manufacturing a ceramic circuit board according to claim 1, wherein the metal plate is bonded to 95% or more of the surface of the ceramic substrate on which the metal circuit is formed.

3. The method for manufacturing a ceramic circuit board according to claim 1 or 2, wherein the outer dimensions of the metal plate are the same as those of the ceramic substrate, or the difference in outer dimensions between the metal plate and the ceramic substrate is less than 5%.

4. The method for manufacturing a ceramic circuit board according to claim 1 or 2, wherein the metal plate and the ceramic substrate are joined together with a planar offset such that one or more sides of the ceramic substrate are exposed as the outer peripheral portion.

5. The method for manufacturing a ceramic circuit board according to claim 1 or 2, wherein the manufacturing step of the bonded body involves processing the metal plate so that the entire length of one or two sides of the ceramic substrate is exposed as the outer peripheral portion to manufacture the ceramic bonded body.

6. The method for manufacturing a ceramic circuit board according to claim 1 or 2, wherein the process for manufacturing the bonded body involves processing the metal plate so that the outer peripheral portion is exposed from the metal plate in order to manufacture the ceramic bonded body.

7. The method for manufacturing a ceramic circuit board according to claim 6, wherein the manufacturing step of the bonded body involves chamfering the metal plate so that at least one corner of the ceramic substrate is exposed from the metal plate as the outer peripheral portion to manufacture the ceramic bonded body.

8. The method for manufacturing a ceramic circuit board according to claim 6, wherein the joint manufacturing step involves processing the metal plate into a recess to manufacture the ceramic joint.

9. The method for manufacturing a ceramic circuit board according to claim 6 or 7, wherein the ratio of the length of the outer peripheral portion exposed by recess processing or chamfering processing of the metal plate is 40% or less of the total length of the outer peripheral portion of the ceramic substrate.

10. The method for manufacturing a ceramic circuit board according to claim 7 or 8, wherein the metal plate has at least one corner and has one or more recesses on each of the two sides connected to the corner.

11. The method for manufacturing a ceramic circuit board according to claim 7 or 8, wherein the metal plate has a rectangular shape and has a recess at at least one corner to expose the outer peripheral portion of the ceramic substrate.

12. The method for manufacturing a ceramic circuit board according to claim 1 or 2, wherein the entire length of one or two sides of the ceramic substrate is exposed, and at least one side of the other side of the metal plate has a recess.

13. The method for manufacturing a ceramic circuit board according to claim 12, wherein the ratio of the length of the outer peripheral portion to the total outer peripheral length of the ceramic substrate is 80% or less.

14. The method for manufacturing a ceramic circuit board according to claim 1 or 2, wherein the positioning step involves fixing the ceramic bond by bringing the side surface of the ceramic bond corresponding to the outer peripheral portion exposed from the metal plate into contact with a positioning guide.

15. The method for manufacturing a ceramic circuit board according to claim 1 or 2, wherein the circuit formation step involves removing unwanted portions of the metal plate using an etching process.

16. A ceramic bond in which a metal plate is bonded to at least one surface of a ceramic substrate, wherein, when viewed from the metal plate side in a plan view, the outer peripheral portion of the ceramic substrate, including a part of its outer periphery, is exposed from the metal plate.

17. The ceramic bond according to claim 16, wherein the metal plate has a recess that exposes the outer peripheral portion of the ceramic substrate, and the depth of the recess in the metal plate is 0.5 mm or more and the width is 2.0 mm or more.

18. The ceramic bond according to claim 16 or 17, wherein the metal plate has a recess that exposes the outer peripheral portion of the ceramic substrate, and the outer peripheral portion of the ceramic substrate is exposed in the recess for a length of 10 μm or more.

Images