JP7034121B2 - Circuit boards and electronic devices - Google Patents

Description

The present invention relates to circuit boards and electronic devices.

Conventionally, as a circuit board used in an electronic device equipped with an electronic component such as an IGBT (Insulated Gate Bipolar Transistor) such as a power module or a switching module, for example, a metal plate is formed on the upper surface of an insulating substrate made of a ceramic sintered body or the like. The one that is joined is used.

The metal plate of the circuit board forms a circuit for electrically connecting electronic components to an external electric circuit. The electronic components mounted on the circuit board are electrically connected to the metal plate, and the electronic components and the external electric circuit are electrically connected to each other via the metal plate.

Japanese Patent Application Laid-Open No. 2002-100848

In recent years, in order to facilitate electrical connection of a circuit board to an external electric circuit, a circuit board having lead terminals bonded to an exposed surface such as the upper surface of a metal plate has been used.

However, when the lead terminal is joined to the upper surface of the metal plate or the like, the thickness of the metal part (total of the metal plate and the lead terminal) at the joint portion between the lead terminal and the metal plate is only the conventional metal plate. It is larger than the thickness of the metal part. Therefore, at the joint between the lead terminal and the metal plate, the thermal stress caused by the difference in the thermal expansion rate between the metal part and the insulating substrate becomes larger than before, and the insulating substrate is mechanically damaged such as cracks at this joint. There was a problem that the possibility of occurrence increased.

The circuit board of one aspect of the present invention includes an insulating substrate, a metal plate, and a rod-shaped lead terminal. The insulating substrate has a first surface, and the metal plate has a second surface located opposite to the surface facing the first surface and an opening located on the second surface. It is joined to the first surface, and the lead terminal is joined to the bottom of the opening by a joining material. The bottom portion includes the first surface, and the lead terminal has a first portion located on the bottom side and a second portion located following the first portion, and the first portion is provided. The portion has a larger cross-sectional area than the second portion in a cross-sectional view of the central axis along the extending direction of the lead terminal, and the second portion is the first portion in a plan view from the second surface. It is located near the center of the portion, and the boundary between the first portion and the second portion is located farther from the first surface than the second surface.

The circuit board of one aspect of the present invention includes an insulating substrate, a metal plate, and a rod-shaped lead terminal. The insulating substrate has a first surface, and the metal plate has a second surface located opposite to the surface facing the first surface and an opening located on the second surface. It is joined to the first surface, and the lead terminal is joined to the bottom of the opening by a joining material. The bottom comprises the first surface, the opening has a first opening and a second opening, and the lead terminal is the bottom of the first opening and the bottom of the second opening, respectively. The first opening is deeper than the second opening and is located at the bottom of the first opening in a plan view from the second surface. The outer circumference of the lead terminal is larger than the outer circumference of the lead terminal located at the bottom of the second opening.

According to the circuit board of one aspect of the present invention, since it has the above configuration, the metal portion at the joint portion between the lead terminal and the metal plate is divided by the depth of the recess (distance from the opening of the recess to the bottom surface). The thickness can be kept small. Therefore, it is possible to effectively reduce the thermal stress caused by the difference in the thermal expansion rate between the metal portion and the insulating substrate at the joint portion between the lead terminal and the metal plate. Therefore, it is possible to provide a circuit board in which the occurrence of cracks in the insulating substrate due to thermal stress is effectively suppressed.

Further, according to the electronic device of one aspect of the present invention, since the electronic component is mounted on the circuit board having the above configuration, cracks and the like of the insulating substrate are suppressed, and long-term reliability is improved. On the other hand, an effective electronic device can be provided.

It is a perspective view which shows the circuit board and the electronic device of embodiment of this invention. (A) is a cross-sectional view showing an example of a cross section taken along the line AA of FIG. 1, and (b) is a cross-sectional view showing another example. (A) is an enlarged cross-sectional view showing a main part of the circuit board and the electronic device shown in FIG. 2 (a), and (b) is a cross-sectional view showing a modified example of (a). (A) is an enlarged cross-sectional view showing a main part of the circuit board and the electronic device shown in FIG. 2 (b), and (b) is a cross-sectional view showing a modified example of (a). It is a perspective view which shows the other example of the circuit board and the electronic device of embodiment of this invention. It is a perspective view which shows the other example of the circuit board and the electronic device of embodiment of this invention.

Hereinafter, the circuit board and the electronic device of the present invention will be described with reference to the drawings. The distinction between top and bottom in the following description is for convenience and does not specify the top and bottom when the circuit board and electronic device are actually used.

The circuit board 10 and the electronic device 20 according to the embodiment of the present invention will be described with reference to FIGS. 1 and 2. FIG. 1 is a perspective view showing a circuit board 10 and an electronic device 20 according to an embodiment of the present invention. 2A is a cross-sectional view showing an example of a cross section taken along the line AA of FIG. 1, and FIG. 2B is a cross-sectional view showing another example of the cross section taken along the line AA of FIG.

In the example shown in FIG. 1, the circuit board 10 has an insulating substrate 1 and a metal plate (first metal plate) 2 arranged on a main surface (upper surface in the example of FIG. 1) 1a of the insulating substrate 1. There is. The substrate main body 9 is formed by the insulating substrate 1 and the first metal plate 2. The substrate main body 9 has a recess 2a in a portion where the first metal plate 2 is joined to the insulating substrate 1. Further, a lead terminal 4 is arranged on the main surface 1a of the insulating substrate 1, and the lead terminal 4 is joined to the bottom of the recess 2a by a bonding material 3. Further, in the example of this embodiment, another metal plate (second metal plate) is placed on the main surface (hereinafter, also referred to as a lower surface) (unsigned) on the side opposite to the main surface 1a on which the first metal plate 2 is arranged. 6 is arranged. Further, the electronic component 7 is mounted on the circuit board 10, and the electronic device 20 is basically formed.

The second metal plate 6 is for heat dissipation, for example, and has a function of dissipating heat generated in the electronic component 7 and conducted through the insulating substrate 1 to the outside. Further, the second metal plate 6 may form a part of a conductive path described later together with the first metal plate 2. Further, the second metal plate 6 may have both the above-mentioned heat dissipation and the functions of the conductive path.

The insulating substrate 1 is made of an electrically insulating material, and is made of, for example, ceramics such as aluminum oxide ceramics, mulite ceramics, silicon carbide ceramics, aluminum nitride ceramics, and silicon nitride ceramics. Among these ceramic materials, silicon carbide ceramics, aluminum nitride ceramics, or silicon nitride ceramics have higher thermal conductivity, which affects heat dissipation. Further, in terms of mechanical strength, silicon nitride ceramics or silicon carbide ceramics are higher.

When the insulating substrate 1 is made of a relatively high-strength ceramic material such as silicon nitride ceramics, the insulating substrate 1 is cracked due to thermal stress caused by the difference in thermal expansion rate between the first metal plate 2 and the insulating substrate 1. Since the possibility is reduced, it is possible to realize a circuit board 10 capable of passing a larger current while reducing the size.

The thinner the thickness of the insulating substrate 1, the better in terms of thermal conductivity, for example, about 0.1 mm to 1 mm, which may be selected according to the size of the circuit board 10 or the thermal conductivity or strength of the material to be used.

If the insulating substrate 1 is made of silicon nitride ceramics, for example, a suitable organic binder, a plasticizer and a solvent are added and mixed with raw material powders such as silicon nitride, aluminum oxide, magnesium oxide and yttrium oxide to form a slurry. Then, a ceramic green sheet (ceramic raw sheet) is formed by adopting the conventionally known doctor blade method or calendar roll method, and then the ceramic green sheet is appropriately punched to form a predetermined shape. If necessary, a plurality of sheets are laminated to form a molded body, and then this is manufactured by firing at a temperature of 1600 to 2000 ° C. in a non-oxidizing atmosphere such as a nitrogen atmosphere.

The first metal plate 2 arranged on the upper surface 1a of the insulating substrate 1 functions as a part of a conductive path for electrically connecting the electronic component 7 mounted on the circuit board 10 to an external electric circuit (not shown). .. In the example shown in FIG. 1, a plurality of first metal plates 2 are bonded to the upper surface 1a of the insulating substrate 1. Each of the first metal plates 2 forms, for example, an electrically independent circuit from each other, and is electrically connected to different electrodes (not shown) of the electronic component 7 via a bonding wire 8 or the like. The different electrodes of the electronic component 7 are, for example, the respective electrodes for a large current and a control signal.

The bonding wire 8 is, for example, a so-called gold wire or an aluminum wire, one end of which is connected to the electrode as described above, and the other end of which is connected to a predetermined portion of the first metal plate 2. Further, if necessary, a plurality of first metal plates 2 may be connected to each other.

The first metal plate 2 can be manufactured, for example, by subjecting a copper plate material to metal processing such as cutting, rolling, or etching, and processing it into a predetermined shape and size as the first metal plate 2. The second metal plate 6 can also be manufactured by the same method using the same material as the first metal plate 2.

The plurality of first metal plates 2 are bonded to the upper surface 1a of the insulating substrate 1 via, for example, an Ag—Cu based brazing material 5. The brazing filler metal 5 contains, for example, at least one of titanium, hafnium, and zirconium, which is an active metal material, so that the brazing filler metal 5 is firmly bonded to the insulating substrate 1 by getting wet. Further, the brazing filler metal 5 may have at least one of In and Sn, for example. The thickness of the brazing filler metal 5 may be, for example, about 5 to 100 μm.

The lead terminal 4 has a function of facilitating external electrical connection of the circuit board 10 and the electronic device 20. The lead terminal 4 in the examples shown in FIGS. 1 and 2 is a columnar lead pin, the bottom of which is inserted into the recess 2a and joined to the substrate body 9. The lead terminal 4 in this example has a portion having a diameter larger than that of other portions (so-called nail head portion) at the bottom portion inserted into the recess 2a, and the nail head portion is inside the recess 2a and the substrate main body 9 is formed. It is joined to.

In the circuit board 10 and the electronic device 20 of this embodiment, lead terminals 4 having different diameters are arranged. Each lead terminal 4 has a different diameter depending on the magnitude of the energized current, and the one for a large current through which a larger current flows has a larger diameter than the one for a control signal. Further, in the example of FIG. 1, even for a large current having a large diameter, by providing a plurality of lead terminals (not shown) in parallel, the individual lead terminals can be connected as compared with the case of connecting with one lead terminal 4. The diameter can be reduced.

In the case of the lead terminal 4 of this embodiment, for example, the end portion of the lead terminal 4 opposite to the nail head portion is electrically and mechanically connected to a predetermined portion of the external electric circuit via solder or the like. Ru. As a result, the electronic component 7 and the external electric circuit are electrically connected to each other. The electronic device 20 may be mounted on an external electric circuit via a heat radiating member (not shown) such as a heat sink.

The recess 2a of the substrate body 9 is provided in a portion where the first metal plate 2 is joined to the insulating substrate 1. Therefore, the recess 2a is actually provided from the upper surface of the first metal plate 2 toward the inside of the first metal plate 2. In the example shown in FIG. 2A, the recess 2a is provided in a part of the first metal plate 2 in the thickness direction. That is, in the example shown in FIG. 2A, the hole provided in the upper surface of the first metal plate 2 is the recess 2a, and the bottom portion of the recess 2a is located in the first metal plate 2. Further, in the example shown in FIG. 2B, the recess 2a is provided so as to penetrate the first metal plate 2 in the thickness direction. That is, the through hole provided from the upper surface to the lower surface of the first metal plate 2 is the recess 2a, and the bottom portion of the recess 2a is the upper surface 1a of the insulating substrate 1. The recess 2a may be provided at a depth from the upper surface 1a of the insulating substrate 1 to the inside of the insulating substrate 1 (not shown). That is, the recess 2a may be a non-penetrating type or a penetrating type with respect to the first metal plate 2.

In both the examples of FIGS. 2A and 2B, the metal at the joint portion between the lead terminal 4 and the first metal plate 2 is equal to the depth of the recess 2a (the distance from the opening of the recess 2a to the bottom). The thickness of the portion can be kept small. Therefore, in the joint portion between the lead terminal 4 and the first metal plate 2, the thermal stress caused by the difference in the thermal expansion rate between the metal portion (the portion where the first metal plate 2 and the lead terminal 4 are combined) and the insulating substrate 1 Can be effectively reduced. Therefore, it is possible to provide the circuit board 10 in which the generation of cracks and the like in the insulating substrate 1 due to thermal stress is effectively suppressed.

The circuit board 10 is provided with nickel plating on the surface of the conductor portion (first metal plate 2, second metal plate 6, etc.) and, if necessary, gold plating to prevent corrosion and facilitate mounting of the electronic component 7. You may do it.

Further, according to the electronic device 20 of the embodiment, since the electronic component 7 is mounted on the circuit board 10 having the above configuration, cracks and the like of the insulating substrate 1 are suppressed, and long-term reliability is improved. On the other hand, an effective electronic device 20 can be provided.

The connection between the lead terminal 4 and the substrate main body 9 is performed via the bonding material 3 as described above. The bonding material 3 is, for example, a brazing material such as Ag—Cu type, P—Cu type, P—Cu—Sn type or P—Cu—Sn—Ni type brazing material. Further, the bonding material 3 also functions as a conductive path for electrically connecting the lead terminal 4 and the first metal plate 2 of the substrate main body 9.

In the circuit board 10 and the electronic device 20 of the embodiment, since the lead terminal 4 is bonded to the substrate body 9 of the lead terminal 4 via the bonding material 3 in the recess 2a, the bonding material 3 is easily fastened in the recess 2a. Can be kept. Therefore, for example, the possibility that the bonding material 3 spreads to an unnecessary portion such as the upper surface of the first metal plate 2 is effectively reduced. Therefore, for example, the possibility that the bonding material 3 extends to the portion of the first metal plate 2 to which the bonding wire 8 is connected is reduced. Therefore, it is possible to prevent the bonding wire 8 from being hindered from being connected to the first metal plate 2 due to the spread of the bonding material 3, and to provide the electronic device 20 having high electrical connection reliability of the electronic component 7. can. Further, it is possible to provide a circuit board 10 in which such an electronic device 20 can be easily manufactured.

Further, since the unnecessary spread of the bonding material 3 is suppressed, it becomes easy to wet and spread the bonding material 3 on the side surface of the nail head of the lead terminal 4, and the area of the substrate body 9 (first metal plate 2, etc.) is wider. Can be joined with. This makes it possible to obtain the effect of improving the bonding strength between the lead terminal 4 and the substrate main body 9.

Further, since the lead terminal 4 is inserted into the recess 2a and joined, the lead terminal 4 can be easily positioned with respect to the first metal plate 2.

The recess 2a is formed by, for example, when the first metal plate 2 is manufactured by metal processing such as etching as described above, the portion corresponding to the recess 2a is also removed by etching. Can be done.

Further, for the depth of the recess 2a (including selection of penetration type or non-penetration type), the etching depth should be partially adjusted appropriately by using a masking method or the like at the time of etching processing. Can be adjusted by.

In the example shown in FIG. 2A, the bottom portion of the recess 2a is located in the first metal plate 2. In other words, the inner surface (side surface and bottom surface) of the recess 2a is a part of the first metal plate 2. Therefore, the bonding material 3 is interposed between the bottom surface of the recess 2a and the nail head portion of the lead terminal 4. In this case, since the bonding material 3 is directly bonded to the first metal plate 2, it is advantageous for reducing the electric resistance between the lead terminal 4 and the first metal plate 2.

In the example shown in FIG. 2B, the recess 2a penetrates the first metal plate 2 in the thickness direction. At the bottom of the recess 2a, a part of the brazing material 5 that joins the insulating substrate and the first metal plate 2 is exposed. Therefore, the bonding material 3 is interposed between the brazing material 5 exposed at the bottom of the recess 2a and the nail head portion of the lead terminal 4. In this case, since the bonding material 3 is bonded to the brazing material 5 which is a metal material of the same type, it is advantageous in improving the bonding strength between the lead terminal 4 and the substrate main body 9.

In the examples of FIGS. 2A and 2B, the joining material 3 may extend to the side surface of the recess 2a (exposed surface of the first metal plate 2) and are joined. In this case, the bonding strength of the lead terminal 4 to the first metal plate 2 via the bonding material 3 can be further improved. Moreover, the electrical resistance of each other can be further reduced.

3A is an enlarged cross-sectional view showing a main part of the circuit board 10 and the electronic device 20 shown in FIG. 2A, and FIG. 3B is a cross-sectional view showing a modified example of FIG. 3A. It is a figure. Further, FIG. 4A is an enlarged cross-sectional view showing a main part of the circuit board 10 and the electronic device 20 shown in FIG. 2B, and FIG. 4B is a modification of FIG. 4A. It is sectional drawing which shows. In FIGS. 3 and 4, the same parts as those in FIGS. 1 and 2 are designated by the same reference numerals.

In the examples shown in FIGS. 3 and 4, the lead terminal 4 is located in the recess 2a in a biased manner in the first direction. The first direction is a direction in which the central portion of the recess 2a approaches any part of the outer peripheral portion. In other words, in each of the examples shown in FIGS. 3 and 4, the lead terminal 4 is located not in the central portion of the recess 2a but in a part of the outer peripheral portion.

In the case of each of the examples shown in FIGS. 3 and 4, the distance between the lead terminal 4 (side surface of the nail head portion) and the first metal plate 2 (inner side surface of the recess 2a) is short in the first direction, and both are used. The thickness of the bonding material 3 interposed between the two is relatively thin. Since the bonding material 3 is an alloy such as silver wax, the electric resistance tends to be higher than that of the first metal plate 2 using pure copper or the like. Therefore, the bonding material 3 between the lead terminal 4 and the metal plate 2 tends to have higher electric resistance. The thinner the thickness, the smaller the electrical resistance tends to be. Therefore, the electric resistance between the lead terminal 4 and the first metal plate 2 can be reduced more effectively. In each of the examples shown in FIGS. 3 and 4, the distance between the lead terminal 4 and the first metal plate 2 is relatively long in the second direction opposite to the first direction. The effect of reducing the electric resistance is greater than the increase of the electric resistance between the lead terminal 4 and the first metal plate 2 due to the above. Therefore, the electric resistance between the lead terminal 4 and the first metal plate 2 can be reduced more effectively.

When the first direction is the direction of the shortest energization path of electricity (the direction of linearly connecting the electrode of the electronic component 7 and the external electric circuit, etc.), the electric resistance is further effectively reduced. Further, if the bonding material 3 rises high on the side surface portion of the nail head portion of the lead terminal 4, the conductive path becomes wide. At this time, if the climbing in the first direction is higher than the climbing in the second direction, the electric resistance can be further reduced.

Further, in the case of each example shown in FIGS. 3 and 4, since it is easy to reduce the thickness of the bonding material 3 interposed between the lead terminal 4 and the first metal plate 2 in the first direction, the lead terminal 4 It is also easy to have a configuration (not shown) in which the metal plate 2 is in direct contact with the first metal plate 2 in the recess 2a. When the lead terminal 4 is in direct contact with the first metal plate 2, the electrical resistance between the two can be further effectively reduced. Therefore, in this case, it is possible to provide the circuit board 10 and the electronic device 20 having higher electrical characteristics such as conduction resistance.

In addition, FIG. 3A is an example in which the recess 2a is a non-penetrating type and the upper surface (exposed surface) of the bonding material 3 is relatively flat, and in FIG. 3B, the recess 2a is a non-penetrating type. This is an example in which the upper surface (exposed surface) of the bonding material 3 is concavely curved in the second direction.

When the upper surface (exposed surface) of the bonding material 3 is relatively flat, more bonding material 3 can be fastened in the recess 2a so as not to protrude from the recess 2a. Therefore, the amount (volume) of the bonding material 3 can be increased to facilitate the reduction of electrical resistance and the like. Further, when the upper surface (exposed surface) of the bonding material 3 is concavely curved in the second direction, the thermal stress acting on the bonding material 3 can be dispersed and relaxed along the curved upper surface. Therefore, it is advantageous in improving the long-term reliability of the bonding between the lead terminal 4 and the substrate main body 9 against thermal stress. In each of the examples shown in FIGS. 3A and 3B, since the recess 2a is a non-penetrating type, the electricity between the first metal plate 2 and the lead terminal 4 on the bottom surface of the recess 2a is as described above. The effect of reducing resistance can also be obtained.

The upper surface of the nail head portion of the lead terminal 4 may be higher or lower than the upper surface of the first metal plate 2. However, if the upper surface of the nail head of the lead terminal 4 is lower than the upper surface of the first metal plate 2 by d1 as in the example shown in FIG. 3A, even if the lead terminal 4 is formed, the insulating substrate 1 is formed. It has the effect of making it difficult for the location of the maximum stress applied to the surface to change. Therefore, in the case of this example, the reliability design becomes easier.

FIG. 4A is an example in which the recess 2a is a penetration type and the upper surface (exposed surface) of the bonding material 3 is relatively flat, and FIG. 4B is a non-penetration type recess 2a. This is an example in which the upper surface (exposed surface) of the bonding material 3 is concavely curved in the second direction. In the example shown in FIG. 4 (a), the same effect as the example shown in FIG. 3 (a) can be obtained. In the example shown in FIG. 4 (b), the same effect as the example shown in FIG. 3 (b) can be obtained. In each of the examples shown in FIGS. 4A and 4B, since the recess 2a is a penetration type, the first metal plate 2 does not exist in the lead terminal 4. As a result, even if the lead terminal 4 is joined, the difference (d2) between the upper surface of the nail head portion in FIG. 4A and the upper surface of the metal plate 2 is the difference between the upper surface of the nail head portion and the metal plate 2 in FIG. 3A. In the difference (d1) on the upper surface of the above, it becomes easy to make d2> d1. Therefore, since the stress due to the difference in thermal expansion becomes small, the stress applied to the insulating substrate 1 can be further relaxed. Therefore, the circuit board 10 is more effectively suppressed from the generation of cracks and the like in the insulating substrate 1 due to thermal stress. Further, as described above, by joining the bonding material 3 and the brazing material 5 at the bottom of the recess 2a, it is possible to obtain the effect of improving the bonding strength between the lead terminal 4 and the substrate main body 9.

The shape of the upper surface of the joint material 3 (whether it has a flat shape or a curved shape, etc.) is a condition such as the temperature at which the joint material 3 is melted, the temperature at which the joint material 3 is melted, the temperature rise and temperature decrease, and the like. Can be controlled by appropriately adjusting. For example, when the melting temperature is near the melting point of the bonding material 3, the upper surface of the bonding material 3 tends to have a flat shape, and when the melting temperature is 20 to 100 ° C. higher than the melting point, the upper surface tends to have a curved shape. Further, when a composition having a relatively poor wettability is used as the bonding material 3, the upper surface tends to have a flat shape, and when a composition having an excellent wettability is used, the upper surface tends to have a curved shape.

FIG. 5 is a perspective view showing another example of the circuit board 10 and the electronic device 20 according to the embodiment of the present invention. In FIG. 5, the same parts as those in FIGS. 1 to 4 are designated by the same reference numerals. In the example shown in FIG. 5, the recess 2a is located on the outer peripheral portion of the first metal plate 2 in a plan view. The recess 2a located on the outer peripheral portion of the first metal plate 2 has an opening on the side surface of the first metal plate 2 in a part of the outer peripheral portion thereof. In this form, it can be said that a part (virtual part) of the outer peripheral portion (virtual portion) of the circular recess 2a is located outside the outer peripheral portion of the insulating substrate 1 in a plan view.

In this case, since a part of the recess 2a has an opening on the side surface of the first metal plate 2, the thermal stress applied to the insulating substrate 1 immediately below the side surface of the first metal plate 2 is further reduced. Therefore, the circuit board 10 and the electronic device 20 are more effectively suppressed from the generation of cracks and the like in the insulating substrate 1 due to thermal stress.

In the example shown in FIG. 5, the recess 2a located on the outer peripheral portion of the first metal plate 2 is joined to the lead terminal 4 for a large current. In this way, when the recess 2a to which the lead terminal 4 for large current is joined is located on the outer peripheral portion of the first metal plate 2, a large current flows and even if the connection portion generates heat. The thermal stress applied to the insulating substrate 1 immediately below the side surface of the first metal plate 2 is unlikely to increase. Therefore, the circuit board 10 is more effectively suppressed from the generation of cracks and the like in the insulating substrate 1 due to thermal stress.

When the recess 2a is located on the outer peripheral portion of the first metal plate 2, for example, an opening is provided on the side surface of the first metal plate 2 within a range of about 25 to 50% of the outer circumference of the circular recess 2a. You just have to do it. Within this range, the angle between the side surface (line segment shape) of the first metal plate 2 and the side surface (arc shape) of the recess 2a is 45 degrees or more in a plan view, and the angle (first metal plate 2) is 45 degrees or more. Of these, the portion adjacent to the opening of the recess 2a) is suppressed from excessive concentration of stress.

Further, in the example shown in FIG. 5, when the lead terminal 4 is positioned so as to be biased toward the first direction in the recess 2a, the first direction is set in the direction opposite to the opening. If the lead terminal 4 is located near the opening in the recess 2a, the effect of shortening the distance between the lead terminal 4 (the side surface of the nail head portion) and the inner surface of the recess 2a is effective. Will be inadequate. Therefore, the effect of reducing the electric resistance between the lead terminal 4 and the first metal plate 2 may be insufficient.

FIG. 6 is a perspective view showing another example of the circuit board 10 and the electronic device 20 according to the embodiment of the present invention. In FIG. 6, the same parts as those in FIGS. 1 to 4 are designated by the same reference numerals. Also in the example shown in FIG. 6, the recess 2a is located on the outer peripheral portion of the first metal plate 2 in a plan view. That is, the recess 2a located on the outer peripheral portion of the first metal plate 2 has an opening on the side surface of the first metal plate 2 in a part of the outer peripheral portion thereof. Further, in the example shown in FIG. 6, the lead terminal 4 is a flat lead formed of a strip-shaped metal material. One end of the flat lead is inserted into the recess 2a through the opening of the recess 2a on the side surface of the first metal plate 2. In the recess 2a, one end of the main surface or the like of the strip-shaped lead terminal 4 is joined to the bottom surface or the side surface of the recess 2a via the bonding material 3.

In the case of the flat lead type lead terminal 4, for example, the other end of the main surface on the same side of the lead terminal 4 that is joined to the substrate main body 9 in the recess 2a is a predetermined position of the external electric circuit. It is electrically and mechanically connected to the part via solder or the like. As a result, the electronic component 7 and the external substrate are electrically connected to each other.

With such a flat lead lead terminal 4, the lead terminal 4 is easily bent (flexible), so that the degree of freedom in mounting the electronic device 20 (circuit board 10) is improved. Specifically, in order to connect to the heat dissipation member described above so as to have the highest heat dissipation, it is easy to increase the degree of freedom in orientation when mounting the electronic device 20. For example, the degree of freedom such as changing the direction with other circuit members (not shown) mounted on an external electric circuit is improved.

Even in the case of the lead terminal 4 of the flat lead, if the thickness of the lead terminal 4 is thinner than that of the first metal plate 2, cracks and the like of the insulating substrate 1 due to thermal stress are more effective in the portion where the lead terminal 4 is formed. The circuit board 10 is suppressed.

Further, in the example shown in FIG. 6 of the above embodiments, the bottom portion of the recess 2a may be a part of the main surface 1a of the insulating substrate 1. There may be a portion where the brazing material 5 does not exist at the bottom of the recess 2a, and the main surface 1a of the insulating substrate 1 may be exposed at this portion. The exposed main surface 1a of the insulating substrate 1 is in contact with the lead terminal 4 or the bonding material 3. In this case, the bonding material 3 may be the same material as the brazing material 5, or may be formed collectively. When they are collectively formed, the portion joined to the first metal plate 2 is the brazing material 5, and the portion joined to the lead terminal 4 is the joining material 3.

In this case, only the bonding material 3 is interposed between the lead terminal 4 and the insulating substrate 1. Since the brazing material 5 uses an alloy such as Ag—Cu alloy, it is harder than the lead terminal 4 using pure copper or the like. Therefore, since the alloy layer becomes thinner due to the elimination of the brazing filler metal 5, the stress applied to the insulating substrate 1 at the portion where the lead terminal 4 is joined can be further relaxed. Therefore, the circuit board 10 is more effectively suppressed from the generation of cracks and the like in the insulating substrate 1 due to thermal stress.

At this time, if the first metal plate 2 and the lead terminal 4 are assembled at the same time, the man-hours required for manufacturing the circuit board 10 and the electronic device 20 can be reduced. It should be noted that this effect can be similarly obtained even with the lead terminal 4 of the columnar lead pin as in the above-described embodiment.

The present invention is not limited to the examples of the above embodiments, and various modifications can be made within the scope of the gist of the present invention. For example, the insulating substrate 1, the first metal plate 2, the second metal plate 6, and the like are not limited to a rectangular parallelepiped shape, but also a rectangular plate shape or an elliptical plate shape in which corners are chamfered in an arc shape. It may be in the shape of. Further, all or part of the side surface may be inclined, or a shape having a step on the side surface or the like may be used.

1 ... Insulation substrate 1a ... Main surface (upper surface)
2 ... 1st metal plate (metal plate)
2a ... Recess 3 ... Joint material 4 ... Lead terminal 5 ... Wax material 6 ... Second metal plate (other metal plate)
7 ... Electronic components 8 ... Bonding wire 9 ... Board body
10 ・ ・ ・ Circuit board
20 ... Electronic device

Claims (7)

An insulating substrate with a first surface and
A metal plate having a second surface located opposite to the surface facing the first surface and an opening located on the second surface and joined to the first surface.
A rod-shaped lead terminal, which is joined by a joining material, is provided at the bottom of the opening.
The bottom includes the first surface.
The lead terminal has a first portion located on the bottom side and a second portion located following the first portion.
The first part has a larger cross-sectional area than the second part in a cross-sectional view of the central axis along the extending direction of the lead terminal.
The second part is located near the center of the first part in a plan view from the second surface.
A circuit board characterized in that the boundary between the first part and the second part is located farther from the first surface than the second surface. An insulating substrate with a first surface and
A metal plate having a second surface located opposite to the surface facing the first surface and an opening located on the second surface and joined to the first surface.
The bottom of the opening is provided with a rod-shaped lead terminal joined by a joining material.
The bottom includes the first surface.
The opening has a first opening and a second opening.
The lead terminal is joined to the bottom of the first opening and the bottom of the second opening by a bonding material, respectively.
The first opening is deeper than the second opening,
A circuit board characterized in that the outer circumference of the lead terminal located at the bottom of the first opening is larger than the outer circumference of the lead terminal located at the bottom of the second opening in a plan view from the second surface. .. The circuit board according to claim 1 or 2, wherein the lead terminal is located unevenly in the first direction in the opening. The circuit board according to any one of claims 1 to 3, wherein the lead terminal is in direct contact with the metal plate in the opening. The bonding material located in the second direction opposite to the first direction in the opening is dependent on claim 3 or claim 3, characterized in that the bonding material is concavely curved toward the first surface. The circuit board according to claim 4. The circuit board according to any one of claims 1 to 5, wherein the opening is located on the outer peripheral portion of the metal plate in the plan view. The circuit board according to any one of claims 1 to 6.
An electronic device including electronic components mounted on the circuit board.

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