JP7503069B2 - Composite substrate and manufacturing method thereof, and circuit substrate and manufacturing method thereof - Google Patents

Description

The present disclosure relates to a composite substrate and a manufacturing method thereof, and a circuit substrate and a manufacturing method thereof.

Power modules that control large currents are used in fields such as automobiles, electric railways, industrial equipment, and power generation. The circuit board mounted on the power module has an insulating ceramic substrate. The following technology, as described in Patent Document 1, is known as a method for manufacturing a circuit board. That is, a composite substrate is formed by bonding metal layers to both sides of a ceramic substrate having scribe lines formed on its surface. Then, the metal layer on the surface of the composite substrate is processed into a circuit pattern by etching. The composite substrate is then divided along the scribe lines to manufacture multiple circuit substrates.

When multiple components, such as ceramic substrates, are joined with a joining material, such as a brazing material, ultrasonic inspection is known as an index for evaluating the condition of the joining material. Patent Document 2 proposes a method of emitting ultrasonic waves and using the height of the reflected echo as a method of determining the amount of the second component present between the first and third components.

JP 2007-324301 A JP 2014-209099 A

Circuit boards are required to ensure quality, such as insulation, depending on the application. For example, if there are defects such as scratches in the ceramic substrate that provides insulation in a circuit board, the insulation will be impaired. For this reason, it is necessary to eliminate defects as much as possible. However, ceramic substrates are more prone to defects than other materials, making it difficult to completely eliminate defects. For this reason, it is necessary to inspect for defects before forming the circuit board and to eliminate sections containing defects with a high degree of precision.

On the other hand, if a ceramic substrate with a defect in only one section is discarded as a defective product, the yield of the circuit substrate will decrease. For this reason, if there was technology that could identify defective sections with high accuracy even when using ceramic substrates with defects, it would be possible to make a significant contribution to improving the reliability of circuit substrates.

Therefore, the present disclosure provides a composite substrate capable of producing a highly reliable circuit board and a method for manufacturing the same. It also provides a highly reliable circuit board and a method for manufacturing the same.

A composite substrate according to one aspect of the present disclosure is a composite substrate comprising a ceramic substrate, a metal plate, and a brazing material layer joining them, wherein the ceramic substrate has a plurality of partitions defined by partition lines on at least one surface, at least one of the plurality of partitions is a defective partition having a defect, and has a poor bond between the defective partition and the metal plate above it.

Such a composite substrate has a poor joint between the defective section and the metal plate above it. Such a poor joint can be easily detected by ultrasonic testing. This allows defective sections having defects in the ceramic substrate to be identified with high accuracy. Therefore, even if a ceramic substrate having defects is used, a highly reliable circuit substrate can be obtained. Despite having defects, this ceramic substrate can be used to manufacture circuit substrates, and therefore the circuit substrates can be manufactured with a high yield. In other words, the above composite substrate makes it possible to manufacture highly reliable circuit substrates with a high yield.

At least one selected from the group consisting of a recess in the brazing material layer of the composite substrate and a recess in the metal plate may constitute a defective joint. This makes it easier to detect the defective joint, and allows the manufacture of a circuit board with higher reliability.

A recess in the brazing material layer may constitute a defective joint, and the surface of the ceramic substrate may be exposed to the defective joint at the recess. This makes it easier to detect the defective joint, and allows the production of a circuit board with higher reliability.

At least one selected from the group consisting of the brazing material layer and the metal plate in the composite substrate may have an altered portion on the defective partition portion, and the altered portion may constitute a defective joint portion. Such a defective joint portion can be easily formed. Therefore, the manufacturing process of the composite substrate can be simplified.

Above the defective section in the composite substrate, the metal plate may have an identification section on the surface opposite the ceramic substrate. This allows the defective section to be detected with even higher accuracy. This allows the manufacture of circuit boards with even higher reliability.

A circuit board according to one aspect of the present disclosure is a circuit board comprising a ceramic substrate, a plurality of conductor portions, and a brazing material layer joining them, wherein the ceramic substrate has a plurality of partition portions defined by partition lines on at least one surface, a plurality of conductor portions are provided so as to be independent in each of the plurality of partition portions, and at least one of the plurality of partition portions is a defective partition portion having a defect, and has a poor connection between the defective partition portion and the conductor portion provided thereon.

Such a circuit board has a poor joint between the defective partition and the conductor portion provided thereon. Such a poor joint can be easily detected by ultrasonic inspection. Therefore, defective partitions having defects in the ceramic substrate can be removed with high accuracy. Therefore, even if the ceramic substrate has a defective partition, the defective partition can be identified with high accuracy, and the circuit substrate has high reliability. Furthermore, despite the ceramic substrate having defects, the ceramic substrate can be used to manufacture circuit substrates, and therefore the circuit substrates can be manufactured with a high yield. In other words, the circuit substrate has high reliability and can be manufactured with a high yield.

The defective joint in the circuit board may be formed by at least one selected from the group consisting of a recess in the brazing material layer and a recess on the ceramic substrate side of the conductor. This makes it easier to detect the defective joint, and further increases the reliability of the circuit board.

The defective joint in the circuit board is formed by at least a recess in the brazing material layer, and the surface of the ceramic substrate may be exposed to the defective joint in the recess in the brazing material layer. This makes it easier to detect the defective joint, and further increases the reliability of the circuit board.

At least one selected from the group consisting of the brazing material layer and the conductor portion in the circuit board may have an altered portion on the defective partition portion, and the altered portion may constitute a defective joint portion. Such a defective joint portion can be easily formed. Therefore, the manufacturing process of the circuit board can be simplified.

The conductor portion above the defective section may have an identification portion on the surface opposite the ceramic substrate. This allows the defective section to be detected with even higher accuracy, thereby further improving the reliability of the circuit board.

A method for manufacturing a composite substrate according to one aspect of the present disclosure includes the steps of applying a brazing filler metal to a surface of a ceramic substrate having a plurality of partitions defined by partition lines on the surface, at least one of which is a defective partition having a defect; deforming or altering at least a portion of the brazing filler metal applied to the defective partition; and joining the ceramic substrate and a metal plate via the brazing filler metal to provide a poor joint between the defective partition and the metal plate above it.

In the manufacturing method of the composite substrate, a defective joint is provided between the defective section and the metal plate thereon. Such a defective joint can be easily detected by ultrasonic testing. Therefore, the defective section having a defect in the ceramic substrate can be identified with high accuracy. Therefore, even if a ceramic substrate having a defect is used, a circuit substrate having high reliability can be obtained. Although the ceramic substrate has a defect, it can be used to manufacture a circuit substrate, and therefore the circuit substrate can be manufactured with a high yield. In other words, the manufacturing method of the composite substrate makes it possible to manufacture a circuit substrate having high reliability with a high yield. In this disclosure, "deform or change" includes the case where either one of deformation and change occurs, and the case where both deformation and change occur.

In the manufacturing method of the composite substrate, in the step of deforming or altering a portion of the brazing material, the brazing material applied to the defective section may be irradiated with laser light to deform or remove the brazing material and form a recess. This makes it possible to easily form a joint defect that is easy to detect.

A method for manufacturing a composite substrate according to one aspect of the present disclosure includes the steps of: applying a brazing filler metal to a plurality of partitions on a surface of a ceramic substrate, the plurality of partitions being defined by partition lines on the surface, at least one of which is a defective partition having a defect; and joining the ceramic substrate and a metal plate via the brazing filler metal to provide a poor joint between the defective partition and the metal plate above it.

A method for manufacturing a composite substrate according to one aspect of the present disclosure includes the steps of: applying a brazing material to a surface of a ceramic substrate having a plurality of partitions defined by partition lines on the surface, at least one of which is a defective partition having a defect; deforming or altering a portion of the surface of a metal plate; and joining the ceramic substrate and the metal plate via the brazing material so that the deformed or altered portion on the surface faces the defective partition, thereby providing a poor joint above the defective partition.

In each of the above-mentioned manufacturing methods for composite substrates, a defective joint is provided between the defective section and the metal plate above it. Such a defective joint can be easily detected by ultrasonic testing. This makes it possible to identify defective sections having defects in the ceramic substrate with high accuracy. Therefore, even if a ceramic substrate having a defect is used, a highly reliable circuit substrate can be obtained. Despite having a defect, this ceramic substrate can be used to manufacture circuit substrates, and therefore the circuit substrates can be manufactured with a high yield. In other words, the above-mentioned manufacturing methods for composite substrates make it possible to manufacture highly reliable circuit substrates with a high yield.

Any of the above-mentioned methods for manufacturing a composite substrate may include a step of detecting a defective joint in a bonded substrate obtained by bonding a ceramic substrate and a metal plate using ultrasonic waves, and a step of providing an identification section on a portion of the metal plate above a defective section having a defective joint. This allows the defective section to be identified and removed with even higher accuracy.

A method for manufacturing a circuit board according to one aspect of the present disclosure includes removing a portion of the metal plate in a composite board obtained by any of the manufacturing methods described above, and forming a plurality of independent conductor portions in each of a plurality of partition portions.

The circuit board obtained by this manufacturing method has a poor joint between the defective partition and the conductor portion provided thereon. Such a poor joint can be easily detected by ultrasonic inspection. Therefore, defective partitions having defects in the ceramic substrate can be removed with high accuracy. Therefore, even if the ceramic substrate has a defective partition, the defective partition can be removed with high accuracy, and the circuit substrate has high reliability. Furthermore, despite the ceramic substrate having defects, the ceramic substrate can be used to manufacture circuit substrates, and therefore the circuit substrates can be manufactured with a high yield. In other words, it is possible to manufacture highly reliable circuit substrates with a high yield.

According to the present disclosure, it is possible to provide a composite substrate capable of producing a highly reliable circuit board and a method for producing the same. It is also possible to provide a highly reliable circuit board and a method for producing the same.

FIG. 1 is a perspective view of a composite substrate according to an embodiment. FIG. 2 is a perspective view showing an example of a ceramic substrate provided in the composite substrate of FIG. FIG. 3 is a cross-sectional view taken along line III-III in FIG. FIG. 4 is a diagram for explaining a method of ultrasonic flaw detection for detecting a joint defect. FIG. 5 is an enlarged cross-sectional view showing a modified example of the composite substrate according to the embodiment. FIG. 6 is an enlarged cross-sectional view showing another modified example of the composite substrate according to the embodiment. FIG. 7 is a perspective view of a circuit board according to an embodiment. FIG. 8 is a cross-sectional view taken along line VIII-VIII in FIG. FIG. 9 is a perspective view of a circuit board according to another embodiment. FIG. 10 is a perspective view showing a ceramic substrate having a brazing material applied to its surface. FIG. 11 is a diagram showing an example of a composite substrate having a resist pattern formed on its surface.

Below, one embodiment of the present disclosure will be described, with reference to the drawings where appropriate. However, the following embodiment is an example for explaining the present disclosure, and is not intended to limit the present disclosure to the following content. In the description, the same reference numerals will be used for the same elements or elements having the same functions, and duplicated descriptions will be omitted where appropriate. Furthermore, unless otherwise specified, positional relationships such as up, down, left, right, etc. will be based on the positional relationships shown in the drawings. Furthermore, the dimensional ratios of each element are not limited to those shown in the drawings.

Figure 1 is a perspective view of a composite substrate according to one embodiment. The composite substrate 200 comprises a pair of metal plates 110, 111 arranged to face each other, and a ceramic substrate 100 between the pair of metal plates 110, 111. The metal plates 110, 111 may be copper plates. The ceramic substrate 100, the metal plates 110, and the metal plates 111 may each be the same in shape and size, or may be different. The metal plates 110, 111 and the ceramic substrate 100 are joined by a brazing layer (not shown).

An example of the composite substrate 200 is one in which the ceramic substrate 100 is made of aluminum nitride and the metal plates 110, 111 are made of copper or aluminum. The metal plate 110 has an identification portion 112 on the surface 110a opposite to the ceramic substrate 100 side for identifying the position of a defective partition portion having a defect in the ceramic substrate 100.

The identification portion 112 may be configured as a recess, or may be configured as an attachment such as a sticker. Alternatively, it may be a mark in a color different from the surroundings of the identification portion 112. A plurality of identification portions 112 may be provided on one defective partition. When there are a plurality of defective partitions, the identification portions 112 are provided on the surface 110a above the plurality of defective partitions, respectively. The metal plate 111 may or may not have a similar identification portion on the surface opposite to the bonding surface with the ceramic substrate 100.

Figure 2 is a perspective view showing an example of a ceramic substrate provided in the composite substrate 200. The ceramic substrate 100 in Figure 2 has a flat plate shape. The ceramic substrate 100 is divided into a plurality of sections by division lines on the surface 100A. The surface 100A is provided with a plurality of division lines L1 extending along a first direction and arranged at equal intervals, and a plurality of division lines L2 extending along a second direction perpendicular to the first direction and arranged at equal intervals. The division lines L1 and L2 are perpendicular to each other.

The dividing lines L1 and L2 may be, for example, a plurality of depressions arranged in a straight line, or may be linear grooves. Specifically, they may be scribe lines formed by laser light. Examples of laser sources include carbon dioxide lasers and YAG lasers. Scribe lines can be formed by intermittently irradiating laser light from such laser sources. The dividing lines L1 and L2 do not have to be arranged at equal intervals, and are not limited to being perpendicular. Furthermore, the dividing lines may be curved or bent instead of straight. The ceramic substrate 100 has a plurality of dividing sections 10 defined by the dividing lines L1 and L2.

Of the multiple partitions 10, one partition 10 has a defect 11. A partition 10 having a defect 11 in this manner is referred to as a defective partition 10a. The defective partition 10a may have multiple defect parts 11. In addition, the ceramic substrate 100 may have multiple defective partitions 10a.

The defect 11 refers to a factor that affects the withstand voltage characteristics when made into a circuit board, and examples of the defect include cracks, as well as dents such as holes and scratches. In this embodiment, the defect 11 appears on the surface 100A. However, the shape is not limited to this, and may be, for example, a crack that reaches from the surface 100A to the opposite back surface 100B. In other words, the defect may be exposed on the surface 100A or the back surface 100B, or may not be exposed. A defect that is not exposed can be detected, for example, by non-destructive testing. From the viewpoint of ease of detection by visual inspection, etc., the defect may be exposed on the surface 100A and/or the back surface 100B of the ceramic substrate 100.

Figure 3 is a cross-sectional view taken along line III-III in Figure 1. As shown in Figures 2 and 3, partition 10 (defect partition 10a) is composed of a three-dimensional area surrounded by a partial area of front surface 100A surrounded by partition lines L1, L2, a partial area of back surface 100B corresponding to said partial area, and an imaginary line VL drawn parallel to the thickness direction of ceramic substrate 100 from partition lines L1, L2.

A brazing material layer 40 is provided between the pair of metal plates 110, 111 and the ceramic substrate 100. The brazing material layer 40 has the function of joining the pair of metal plates 110, 111 and the ceramic substrate 100, and is formed by firing the brazing material. The brazing material layer 40 provided on the defective partition 10a has a void portion 42, which constitutes the defective joint portion 50. Since the composite substrate 200 has the defective joint portion 50, it is easily detected by ultrasonic inspection or the like. Since the defective joint portion 50 is provided between the defective partition 10a and the metal plate 110, the defective joint portion 50 can be detected with high accuracy. Therefore, the position of the defective partition 10a can be identified with high accuracy.

In the present disclosure, the detection of the joint failure 50 can be performed using a commercially available ultrasonic inspection device based on the acoustic impedance specific to each material and the reflectance that depends on the combination of the materials. The joint failure 50 is detected by a pulse reflection method that evaluates the reflected waveform obtained by irradiating ultrasonic waves from the surface 110a of the metal plate 110 using, for example, an ultrasonic inspection device manufactured by Dia Electronics Co., Ltd. (probe: manufactured by Toray Engineering Co., Ltd., frequency: 25 MHz, aperture: 6 mm, focal length: 20 mm).

Specifically, as shown in FIG. 4, while the composite substrate 200 is immersed in water 64 contained in a container 62, ultrasonic waves are applied from the probe 60 to the surface 110a of the metal plate 110 in the composite substrate 200. If the thickness of at least one of the metal plates 110, 111 (conductor portion) is greater than 0.4 mm, the ultrasonic waves are focused on the brazing material layer 40 of the composite substrate 200. In this state, an interface flaw scan is performed while moving the composite substrate 200 horizontally (in the direction of the arrow P). A portion where the ratio of the interface echo intensity from the brazing material layer 40 to the surface echo intensity from the surface 110a is 0.5 or more may be determined to be a joint failure portion 50.

In the case of the circuit board described later, the poor connection portion 50 can be detected in the same manner as in the composite substrate 200. The ratio of the interface echo intensity to the surface echo intensity of the void portion that is normally detected in the composite substrate 200 and the circuit substrate described later is 0.4 or more. By making the poor connection portion 50 such that the ratio of the interface echo intensity to the surface echo is greater than the ratio in the void portion that is normally detected, the defective section 10a can be more easily identified.

When only metal plates 110, 111 (conductor parts) having a thickness of 0.4 mm or less are included, the focus is placed on the back surface 111b (bottom surface) opposite to the front surface 110a where the ultrasonic waves are incident, and the echo intensity from this bottom surface (bottom echo intensity) is measured. In this state, the composite substrate 200 is moved horizontally while performing an interface flaw scan. The ratio of the bottom echo intensity in the poor joint part 50 to the bottom echo intensity from the normal part, which is a part that does not have the poor joint part 50, may be 0.2 or less. The ratio of the void part that is usually detected in the composite substrate and the circuit substrate is greater than 0.2 and less than 0.5. By making the poor joint part 50 such that the ratio of the bottom echo intensity is smaller than the ratio of the bottom echo intensity in the void part that is usually detected, the defective section 10a can be more easily identified.

As described above, by changing the detection method for the poor connection portion 50 depending on the thickness of the metal plate or conductor portion, the poor connection portion 50 can be detected with sufficiently high accuracy.

The joint failure 50 does not need to be located directly above the defect 11 in the defect partition 10a, but may be located between the defect partition 10a and the metal plate 110. This is because it is sufficient to be able to distinguish between a portion (divided substrate) having the defect partition 10a and a portion (divided substrate) having a partition 10 without the defect 11. The identification portion 112 on the surface 110a of the metal plate 110 is located above the defect partition 10a so as to correspond to the defect partition 10a. Therefore, the presence or absence of the defect partition 10a and its position can be determined by the identification portion 112. In other words, when the virtual line VL is extended to the metal plate 110, the partition having the identification portion 112 determined by the virtual line VL is located directly above the defect partition 10a.

3, the poor joint portion 50 may be configured as a void portion 42 where the surface 100A of the ceramic substrate 100 is not covered with the brazing material layer 40 and the surface 100A is exposed, or may be configured as a recess formed in the brazing material layer 40. If the cavity portion that constitutes the poor joint portion 50 is large, the detection accuracy by ultrasonic inspection can be improved.

The poor joint portion 50 is a portion where the metal plate 110 and the ceramic substrate 100 are not joined by the brazing material layer 40. The outer periphery of each partition 10 has a non-jointed portion 52 where the brazing material layer 40 is not provided, but such a non-jointed portion 52 does not correspond to the poor joint portion 50. The poor joint portion 50 is a portion where the metal plate 110 and the ceramic substrate 100 are joined by the brazing material layer 40 in the partition 10 other than the defective partition 10a, but where the metal plate 110 and the ceramic substrate 100 are not joined by the brazing material layer 40 in the defective partition 10a. Therefore, by comparing the state of joining by the brazing material layer 40 in the partition 10 other than the defective partition 10a with the state of joining by the brazing material layer 40 in the defective partition 10a, it is possible to determine whether or not the poor joint portion 50 exists.

In this embodiment, the poor joint portion 50 is provided in the brazing material layer 40 on the metal plate 110 side, but is not limited thereto. For example, the poor joint portion 50 may be provided in the brazing material layer 40 on the metal plate 111 side, or may be provided in the brazing material layers 40 on both the metal plate 110 side and the metal plate 111 side. In addition, the brazing material layer 40 may be formed so as to cover the entire surfaces of the front surface 100A and the back surface 100B of the ceramic substrate 100.

Figure 5 is an enlarged cross-sectional view showing a modified example of the composite substrate of this embodiment. In Figure 5, the cross-sectional structure of the defective partition 10a and its neighboring parts in the composite substrate 202 is enlarged. The composite substrate 202 differs from the composite substrate 200 in that the altered portion 44 formed on the brazing material layer 40 side constitutes the poor joint portion 50. The other configuration of the composite substrate 202 may be the same as that of the composite substrate 200. The altered portion 44 has a different composition from the brazing material layer 40 around the altered portion 44 and is composed of a component that does not bond with the metal plate 110. The altered portion 44 is formed at the interface with the metal plate 110. The altered portion 44 may be, for example, in the form of a seal or tape. It is preferable that the altered portion 44 contains a component that does not react with the metal plate 110, such as ceramics or metal, even at high temperatures.

Figure 6 is an enlarged cross-sectional view showing another modified example of the composite substrate of this embodiment. Figure 6 shows an enlarged cross-sectional structure of the defective partition 10a and its surrounding area in the composite substrate 204. The composite substrate 204 differs from the composite substrates 200 and 202 in that the altered portion 113 on the metal plate 110 side constitutes the poor bonding portion 50. The other configurations of the composite substrate 204 may be the same as those of the composite substrates 200 and 202.

The altered portion 113 has a composition different from that of the metal plate 110 around the altered portion 113, and is composed of a component that is not joined by the brazing material layer 40. The altered portion 113 may be composed of, for example, an oxide. It is also preferable that the altered portion 113 contains a component that does not react with the brazing material layer 40 at high temperatures. In yet another modified example, a recess may be provided in the metal plate 110 instead of the altered portion 113. Such a recess can also constitute the poor joint portion 50. In yet another modified example, the altered portion 113 of the metal plate 110 and the altered portion 44 in the brazing material layer 40 shown in FIG. 5 may constitute the poor joint portion.

Since the composite substrates 200, 202, and 204 have a defective joint 50 on the defective partition 10a or between the defective partition 10a and the metal plate 110, the defective partition 10a having the defective portion 11 can be detected with high accuracy. Therefore, the defective partition 10a having the defective portion 11 can be identified with high accuracy. Therefore, even if the ceramic substrate 100 having the defective portion 11 is used to manufacture a circuit substrate, the occurrence of defective products can be suppressed, and a circuit substrate having high reliability can be obtained. In this way, even if the ceramic substrate 100 having the defective portion 11 is used to manufacture a circuit substrate, a circuit substrate having high reliability can be manufactured with a high yield. In other words, the composite substrates 200, 202, and 204 make it possible to manufacture a circuit substrate having high reliability with a high yield.

In this embodiment, the partition lines L1 and L2 are formed only on one side of the surface 100A of the ceramic substrate 100, but this is not limited to the above. That is, the partition lines L1 and L2 may also be formed on the back surface 100B opposite the front surface 100A of the ceramic substrate 100. In addition, the defect portion 11 and the partition lines L1 and L2 do not need to coexist on the front surface 100A. For example, the defect portion 11 may be exposed only on the back surface 100B, or may be present inside the ceramic substrate 100. The joint failure portion 50 may be provided on the metal plate 111 side, not on the metal plate 110 side.

In this embodiment, among the multiple partitions 10, only the defective partition 10a has a defect 11, but this is not limited to the above. In another modified example, the ceramic substrate may have two or more partitions having defects. In addition, it is not necessary to provide a poor joint 50 on all defective partitions 10a having defects. For example, a poor joint 50 may be provided only on defective partitions 10a having defects 11 that are visually detected on the front surface 100A and the back surface 100B.

7 is a perspective view of a circuit board according to one embodiment. The circuit board 300 includes a ceramic substrate 100 and a plurality of conductors 20 arranged to face each other across the ceramic substrate 100. The conductors 20 are bonded to the ceramic substrate 100 via a brazing material layer 40. The conductors 20 are provided on the front surface 100A and the back surface 100B independently for each partition 10. That is, a pair of conductors 20 is arranged to face each other in each of the plurality of partitions 10 including the defective partition 10a. The poorly bonded portion 50 of the ceramic substrate 100 is covered with the conductors 20. On the other hand, the defective portion 11 may or may not be covered with the conductors 20. Such a circuit board 300 can be formed using a composite substrate 200.

Figure 8 is a cross-sectional view taken along line VIII-VIII in Figure 7. As shown in Figures 7 and 8, partition 10 (defect partition 10a) is composed of a three-dimensional area surrounded by a partial area of front surface 100A surrounded by partition line L1 (L2), a partial area of back surface 100B corresponding to said partial area, and an imaginary line VL drawn parallel to the thickness direction of ceramic substrate 100 from partition lines L1 and L2.

The conductor portion 20 and the ceramic substrate 100 are joined by a brazing material layer 40. The brazing material layer 40 has the function of joining a pair of conductor portions 20 arranged opposite each other for each partition portion 10 to the ceramic substrate 100, and is formed by firing a brazing material. The brazing material layer 40 formed on the defective partition portion 10a has a void portion 42, which constitutes the poor joint portion 50.

Since a joint failure 50 is provided between the defective section 10a having the defect 11 and the conductor section 22 thereon, even if the defect 11 is minute, the defective section 10a can be detected with high accuracy by ultrasonic inspection. Detection of the joint failure 50 by ultrasonic inspection can be performed in the same way as for a composite substrate.

The conductor portion 22 has an identification portion 112 on its surface. Therefore, the portion having the defective partition portion 10a can be identified with high accuracy. After dividing the circuit board 300 into each partition portion 10 to form divided boards, divided boards not including the defective portion 11 can be obtained by eliminating the divided boards having the defective partition portion 10a including the defective portion 11. In this way, it is possible to use the ceramic substrate 100 having the defective portion 11 in the manufacture of circuit boards, and high reliability can be ensured. Therefore, highly reliable circuit boards can be obtained with a high yield.

In a modified example, the poor joint portion 50 may be provided in the brazing material layer 40 on the back surface 100B side, or may be provided in the brazing material layer 40 on both the front surface 100A side and the back surface 100B side. The poor joint portion 50 in the circuit board 300 may also be configured with a degenerated portion 44 formed on the brazing material layer 40 side, as in FIG. 5. An example of the degenerated portion 44 may be the same as that of the composite board 202. Such a circuit board can be formed using the composite board 202. The poor joint portion 50 may also be configured with a degenerated portion on the conductor portion 22 side, as in FIG. 6. An example of the degenerated portion may be the same as that of the composite board 204. Such a circuit board can be formed using the composite board 204.

An example of a circuit board 300 is one in which the ceramic substrate 100 is made of aluminum nitride and the conductor portion 20 is made of copper or aluminum.

9 is a perspective view of a circuit board according to another embodiment. The circuit board 310 in FIG. 9 includes a ceramic substrate 102 and conductor portions 24 arranged opposite each other with the ceramic substrate 102 in between. The conductor portions 24 are joined to the ceramic substrate 102 via a brazing material layer 40. The conductor portions 24 are provided independently for each partition 10 on the front surface 102A and the back surface 102B. That is, a pair of conductor portions 24 is arranged opposite each other in each of a plurality of partition portions 10 including the defective partition portion 10a. The shape of the conductor portion 24 is not particularly limited. The conductor portion 26 in the defective partition portion 10a may or may not cover the defect in the ceramic substrate 102.

The ceramic substrate 102 has a defective partition 10a having a defect similar to that of the ceramic substrate 100. A poor joint (not shown) is provided between the defective partition 10a and the conductor portion 26. The circuit substrate 310 differs from the circuit substrate 300 of FIGS. 7 and 8 in that it has a ceramic substrate 102 instead of the ceramic substrate 100, and in that it has a conductor portion 24 having a different shape from the conductor portion 20 instead of the conductor portion 20. The other configurations may be the same as those of the circuit substrate 300 of FIGS. 7 and 8.

The ceramic substrate 102 has an identification mark 12 at an end 14 of the surface 102A. The end 14 is an area surrounding a plurality of partitions 10 in which the conductor portions 24 are formed. The identification mark 12 may be configured with a plurality of recesses arranged according to a predetermined rule. Furthermore, the identification mark 12 is not limited to being configured with recesses, and may be configured, for example, with a two-dimensional pattern. The identification mark 12 may be, for example, a two-dimensional barcode such as a QR code (registered trademark), or a one-dimensional code such as a barcode. Furthermore, it may be a three-dimensional code, for example, by utilizing information regarding the depth of the recesses.

By having the identification mark 12, it is possible to improve the traceability of the ceramic substrate 102, as well as the composite substrate and the circuit substrate using the same. For example, the identification mark 12 may be a code associated with the position information of the defective partition 10a in the ceramic substrate 102. By having such an identification mark 12, it is possible to identify the ceramic substrate 102 having the defective partition 10a, and to perform subsequent process management with high accuracy. For example, a poor joint portion 50 may be provided based on the information associated with the identification mark 12, or an identification portion 112 may be provided in the conductor portion 26.

The circuit board 310 is cut along the dividing lines L1 and L2 and divided into a plurality of divided boards. At this time, based on the position information of the defective dividing portion 10a associated with the identification mark 12, the divided board having the defective dividing portion 10a can be separated from the other divided boards and discarded. The end portion 14 may be cut off from the circuit board 310 and discarded.

The divided substrates obtained from the circuit substrate 300 in FIG. 7 and the circuit substrate 310 in FIG. 9 can be manufactured or semi-manufactured as components for use in, for example, power modules. For example, electronic components are mounted on the conductor portions 20, 24 in the divided substrates. In each of the above embodiments, it is possible to prevent defective partitions having defects from being manufactured or semi-manufactured as divided substrates among the multiple partitions of the ceramic substrate. This improves the reliability of the circuit substrate.

Next, a first embodiment of a method for manufacturing a composite substrate will be described. The method for manufacturing a composite substrate of this embodiment includes a step A of applying a brazing material to the surface of a ceramic substrate having a plurality of partitions defined by partition lines on the surface, at least one of which is a defective partition having a defect, a step B of deforming or altering at least a portion of the brazing material applied to the defective partition, and a step C of joining the ceramic substrate and a metal plate via the brazing material to form a defective joint between the defective partition and the metal plate above it.

The ceramic substrate used in step A may be, for example, the ceramic substrate 100 shown in Figure 2. The ceramic substrate 100 can be obtained by irradiating the surface of a base material made of ceramic with laser light to form partition lines L1, L2 that partition the surface into multiple sections, and providing multiple partition sections 10 defined by the partition lines L1, L2. At least one of the multiple partition sections 10 is a defective partition section 10a having a defect section 11.

As the substrate made of ceramics, a flat ceramic substrate having an external shape as shown in Figure 2 is used. There are no particular limitations on the type of ceramic, and examples include carbides, oxides, and nitrides. Specific examples include silicon carbide, alumina, silicon nitride, aluminum nitride, and boron nitride.

Examples of the laser light irradiated onto the surface of the substrate include a carbon dioxide laser and a YAG laser. By intermittently irradiating the laser light from such a laser source, scribe lines that become the division lines L1 and L2 are formed. The division lines L1 and L2 may be used as cutting lines when dividing the circuit board 300 in a later process.

The defective portion 11 in the ceramic substrate 100 may be detected visually or by non-destructive testing such as ultrasonic testing and infrared testing. A paste-like brazing material 43 is applied to the front surface 100A and rear surface 100B of the ceramic substrate 100 having the defective partition portion 10a obtained in this manner, as shown in FIG. 10, by a method such as a roll coater method, a screen printing method, or a transfer method. The brazing material 43 contains, for example, metal components such as silver and titanium, an organic solvent, and a binder. The viscosity of the brazing material may be, for example, 5 to 20 Pa·s. The content of the organic solvent in the brazing material may be, for example, 5 to 25 mass%, and the content of the binder may be, for example, 2 to 15 mass%. The brazing material 43 may be applied to the entire front surface 100A and rear surface 100B, or may be applied in an island shape for each partition portion 10.

In step B, at least a portion of the surface of the brazing material 43 applied to the defect partition 10a is deformed or altered. When forming the void 42 (FIG. 3), for example, a portion of the brazing material applied to the defect partition 10a may be irradiated with laser light to remove or deform the portion. By removing or deforming a portion of the surface of the brazing material 43 in this manner, a ceramic substrate is obtained in which a recess 42a is formed in the brazing material 43 applied to the defect partition 10a, as shown in FIG. 10.

Although only the front surface 100A side is shown in FIG. 10, the brazing material 43 may be applied to the back surface 100B side as well. Examples of the laser light include a carbon dioxide laser and a YAG laser. The method of forming the recess 42a is not limited to the above-mentioned method, and the recess 42a may be formed, for example, by removing a part of the brazing material 43 using any jig or the like. The bottom surface of the recess 42a may be formed by the front surface 100A of the ceramic substrate 100.

In step C, metal plates 110, 111 are bonded to the front surface 100A and back surface 100B of the ceramic substrate 100 to which the brazing material 43 has been applied to obtain a bonded body. The metal plates 110, 111 may have a flat plate shape similar to that of the ceramic substrate 100. The bonded body is then heated in a heating furnace to form a brazing material layer 40 as shown in FIG. 3, thereby sufficiently bonding the ceramic substrate 100 and the metal plate 110.

The heating temperature may be, for example, 700 to 900°C. The atmosphere in the furnace may be an inert gas such as nitrogen. The bonded bodies may be heated under reduced pressure below atmospheric pressure, or under vacuum. The heating furnace may be of a continuous type in which multiple bonded bodies are continuously supplied and heated, or may be of a batch type in which one or multiple bonded bodies are heated. The bonded bodies may be heated while pressing them in the stacking direction.

By the above-mentioned heating, a poor joint 50 consisting of a void 42 as shown in Figure 3 is formed in the brazing material layer 40 on the defective partition 10a. By providing an identification portion 112 on the surface 110a of the metal plate 110 in the composite substrate thus obtained, a composite substrate 200 as shown in Figures 1 and 3 can be obtained.

Before providing the identification portion 112, a process of detecting the bonded portion 50 in the bonded substrate obtained by bonding the ceramic substrate 100 and the metal plates 110 and 111 using ultrasonic waves and a process of providing the identification portion 112 in a part of the metal plate 110 on the defect partition portion 10a having the bonded portion 50 may be performed. As described above, the detection of the bonded portion 50 using ultrasonic waves may be performed using a commercially available ultrasonic flaw detection device based on the acoustic impedance specific to each material and the reflectance that depends on the combination of the materials. In the process of providing the identification portion 112, for example, a stamping machine may be used to stamp the metal plate 110 on the bonded portion 50, or a sticker or the like may be attached.

The manufacturing method of the composite substrate according to the second embodiment includes a process D of applying a solder material to a plurality of partitions other than the defective partitions on the surface of a ceramic substrate having a plurality of partitions defined by partition lines on the surface, at least one of which is a defective partition having a defect, and a process C of joining the ceramic substrate and a metal plate via the solder material to form a poor joint between the defective partition and the metal plate above it.

As the ceramic substrate used in step D, the ceramic substrate 100 in FIG. 2 can be used, as in step A. In step D, the brazing material is applied to the multiple partitions 10 other than the defective partition 10a, whereas the brazing material is not applied to at least a portion of the defective partition 10a. As a result, when a composite substrate is obtained by performing step C, a poor joint 50 can be provided between the defective partition 10a and the metal plate 110. Step C may be performed in the same manner as in the first embodiment. Also, as in the first embodiment, a step of detecting the poor joint 50 using ultrasonic waves and a step of providing an identification part on the part of the metal plate above the defective partition 10a having the poor joint 50 may be performed.

The manufacturing method of the composite substrate according to the third embodiment includes a step A of applying a soldering material to the surface of a ceramic substrate having a plurality of partitions defined by partition lines on the surface, at least one of which is a defective partition having a defect; a step E of deforming or altering a portion of the surface of a metal plate; and a step F of joining the ceramic substrate and the metal plate via the soldering material so that the deformed or altered portion on the surface faces the defective partition, thereby providing a poor joint on the defective partition.

Step A of the third embodiment is performed in the same manner as step A of the first embodiment, for example, using the ceramic substrate shown in Figure 2. In step E, a portion of the surface of the metal plate is deformed or altered. For example, the portion may be made into a recess using a stamping machine or the like, or the portion may be heated and oxidized. When a portion of the surface of the metal plate is altered by oxidation or the like, an altered portion 113 as shown in Figure 6 is obtained. By providing the altered portion 113 on the surface of the metal plate 110, a poor bonding portion 50 can be provided on the defective partition portion 10a when a composite substrate is obtained by performing step F.

In step F, the ceramic substrate and the metal plate are laminated via the brazing material so that the altered portion 113 faces the defective partition 10a to obtain a laminate. The laminate is heated or the like in the same manner as in step C to form a brazing material layer 40, and the ceramic substrate 100 and the metal plate 110 are sufficiently bonded. In this manner, a composite substrate 204 having a defective joint 50 on the defective partition 10a can be obtained. Thereafter, in the same manner as in the first embodiment, a step of detecting the defective joint 50 using ultrasonic waves and a step of providing an identification portion 112 on a part of the metal plate 110 on the defective partition 10a having the defective joint 50 may be performed. The step of providing the identification portion 112 may be performed during step E, or before or after step E. In addition, since steps A and E are steps of processing the ceramic substrate and the metal plate, respectively, the order is not limited and they may be performed simultaneously.

In any of the manufacturing methods of the first to third embodiments described above, a composite substrate capable of identifying defective partitions with high accuracy can be manufactured. In these manufacturing methods, even if a ceramic substrate having defects is used, a circuit board having high reliability can be manufactured. The manufacturing method of the composite substrate of the present disclosure is not limited to the above-mentioned embodiment. For example, in the first embodiment, the recess 42a is formed in step B, but instead, the brazing material 43 may be altered. For example, a powder containing a component different from the constituent components of the brazing material 43 may be attached to the surface of the brazing material 43 to cause the brazing material 43 to be altered. In step C, when such a brazing material 43 is heated to form the brazing material layer 40, an altered portion 44 is generated and a poor joint portion 50 can be provided.

In one embodiment, the method for manufacturing a circuit board includes a process for removing a portion of the metal plate 110 in the composite board 200 (202, 204) to form an independent conductor portion 20 (24) for each partition portion 10, following any of the above-mentioned methods for manufacturing a composite board. This process may be performed, for example, by photolithography. Specifically, first, as shown in FIG. 11, a photosensitive resist is printed on the surface 110a of the metal plate 110 constituting the composite board 200. Then, an exposure device is used to form a resist pattern having a predetermined shape. The resist may be negative or positive. Uncured resist is removed, for example, by washing.

Figure 11 is a perspective view showing a composite substrate 200 with a resist pattern 30 formed on the surface 110a. Although only the surface 110a side is shown in Figure 11, a similar resist pattern is also formed on the surface 110b side of the metal plate 111. The resist pattern 30 is formed in areas on the surfaces 110a and 110b that correspond to each partition portion 10 of the ceramic substrate 100.

After forming the resist pattern 30, the portions of the metal plate 110 that are not covered by the resist pattern 30 are removed by etching. This exposes the front surface 100A and back surface 100B of the ceramic substrate 100 in those portions. The resist pattern 30 is then removed to form independent conductor portions 20 for each partition portion 10. These conductor portions 20 are formed in pairs for each partition portion 10, sandwiching the ceramic substrate 100 therebetween, as shown in FIG. 7.

Through the above steps, a circuit board 300 as shown in Figure 7 is obtained. By changing the resist pattern 30, a circuit board 310 as shown in Figure 9 can be obtained.

The circuit board 300 (310) is cut along the dividing lines L1, L2 and divided into a number of divided boards. If the divided boards having defects are eliminated and the divided boards having no defects are manufactured or semi-manufactured as components for use in, for example, a power module, the use of the divided boards having defects as components can be avoided, and the reliability of the components can be increased. For example, electronic components are mounted on the conductor portions 20 (24) of the divided boards.

Although several embodiments of the present disclosure have been described above, the present disclosure is not limited to the above embodiments. For example, the shapes of the conductor portions 20 provided in each partition portion 10 do not need to be the same, and each partition portion 10 may have a different shape. The conductor portions 20, 24 in the circuit boards 300, 310 may be subjected to any surface treatment. For example, a portion of the surface of the conductor portions 20, 24 may be covered with a protective layer such as solder resist, and the other portions of the surface of the conductor portions 20, 24 may be subjected to a plating treatment.

According to the present disclosure, a composite substrate is provided that can produce a highly reliable circuit board. Also provided is a highly reliable circuit board and a method for manufacturing the same.

10...partition, 10a...defective partition, 11...defective portion, 12...identification mark, 14...end, 20, 22, 24, 26...conductor portion, 30...resist pattern, 40...soldering material layer, 42...void portion, 42a...recess, 43...soldering material, 44...deteriorated portion, 50...poorly joined portion, 52...non-joined portion, 60...probe, 62...container, 64...water, 100, 102...ceramic substrate, 100A...surface, 100B...rear side, 110, 111...metal plate, 110a, 110b...surface, 112...identification portion, 113...deteriorated portion, 200, 202, 204...composite substrate, 300, 310...circuit substrate.

Claims (18)

A composite substrate including a ceramic substrate, a metal plate, and a brazing layer that bonds the ceramic substrate and the metal plate,
the ceramic substrate has a plurality of partitions defined by partition lines on at least one surface;
At least one of the plurality of compartments is a defective compartment having a defect, and has a poor joint between the defective compartment and the metal plate thereover;
The composite substrate has an identification mark, which is a code associated with position information of the defect partition, on a surface of the ceramic substrate . 2. The composite substrate according to claim 1, wherein the ceramic substrate has the plurality of partitions and an edge portion surrounding the partitions, and the identification mark is provided on the edge portion. 3. The composite substrate according to claim 1 , wherein the defective joint portion is at least one selected from the group consisting of a recess in the brazing material layer and a recess in the metal plate. the recess in the brazing material layer constitutes the defective joint portion,
4. The composite substrate according to claim 3 , wherein the surface of the ceramic substrate is exposed to the defective joint in the recess. At least one selected from the group consisting of the brazing material layer and the metal plate has an altered portion on the defect compartment,
The composite substrate according to claim 1 , wherein the deteriorated portion constitutes the defective bonding portion. 6. The composite substrate according to claim 1 , wherein the metal plate has an identification portion on a surface opposite to the ceramic substrate above the defect partition. A circuit board including a ceramic substrate, a plurality of conductor portions, and a brazing material layer that bonds the conductor portions together,
the ceramic substrate has a plurality of partitions defined by partition lines on at least one surface, and the plurality of conductor portions are provided independently in each of the plurality of partitions;
At least one of the plurality of partitions is a defective partition having a defect, and has a joint failure between the defective partition and the conductor provided thereon;
a circuit board having, on a surface of the ceramic substrate, an identification mark which is a code associated with position information of the defective partition; 8. The circuit board according to claim 7, wherein the ceramic substrate has the plurality of partitions and an edge portion surrounding the partitions, and the identification mark is provided on the edge portion. 9. The circuit board according to claim 7, wherein the defective joint portion is at least one selected from the group consisting of a recess in the brazing material layer and a recess on the ceramic substrate side of the conductor portion. the recess in the brazing material layer constitutes the defective joint portion,
The circuit board according to claim 9 , wherein the surface of the ceramic substrate is exposed to the defective joint in the recess. at least one selected from the group consisting of the brazing material layer and the conductor portion has an altered portion on the defect partition portion,
The circuit board according to claim 7 , wherein the deteriorated portion constitutes the defective joint portion. The circuit board according to claim 7 , wherein the conductor portion above the defect compartment has an identification portion on a surface opposite to the ceramic substrate. A step of applying a brazing material to a surface of a ceramic substrate having a plurality of partitions defined by partition lines on the surface, at least one of the plurality of partitions being a defective partition having a defect;
deforming or altering a portion of the brazing material applied to the defect compartment;
and joining the ceramic substrate and a metal plate via the brazing material to provide a defective joint between the defect compartment and the metal plate above the defect compartment. In the step of deforming or modifying a portion of the brazing material,
The method for manufacturing a composite substrate according to claim 13 , further comprising irradiating the brazing material applied to the defect partition with laser light to deform or remove the brazing material to form a recess. a step of applying a brazing material to a surface of a ceramic substrate having a plurality of partitions defined by partition lines on the surface, at least one of the plurality of partitions being a defective partition having a defect, the plurality of partitions being except for the defective partition;
and joining the ceramic substrate and a metal plate via the brazing material to provide a joint defect between the defect compartment and the metal plate thereover. A step of applying a brazing material to a surface of a ceramic substrate having a plurality of partitions defined by partition lines on the surface, at least one of the plurality of partitions being a defective partition having a defect;
A step of deforming or altering a portion of a surface of a metal plate;
a step of joining the ceramic substrate and the metal plate via the brazing material so that a deformed or altered portion on the surface faces the defective partition, thereby providing a poor joint above the defective partition. detecting the bonding failure portion using ultrasonic waves;
The method for producing a composite substrate according to claim 13 , further comprising the step of providing an identification portion on a portion of the metal plate above the defective partition having the poor bonding portion. A method for manufacturing a circuit board, comprising the steps of removing a portion of the metal plate in a composite board obtained by the manufacturing method according to any one of claims 13 to 17 , and forming a plurality of independent conductor portions in each of the plurality of partition portions.

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