JP7299121B2 - Circuit boards, electronic components and electronic modules - Google Patents

Description

TECHNICAL FIELD The present disclosure relates to a circuit board including terminal electrodes arranged along the outer periphery of an insulating substrate, an electronic component, and an electronic module.

2. Description of the Related Art As a circuit board on which electronic elements such as semiconductor elements, sensor elements, or capacitive elements are mounted, one including a plurality of terminal electrodes provided on the lower surface of an insulating substrate made of an insulating material such as ceramics is used. An electronic component having an electronic element mounted on the upper surface of such a circuit is mounted on an external wiring board, and the terminal electrodes of the circuit board and the wiring of the external wiring board are connected with a conductive connecting material such as solder to form an electronic component. be a module.

As such a circuit board, there is a circuit board in which a plurality of terminal electrodes are arranged in the outer edge area of the lower surface, and a large ground electrode or heat radiation conductor is arranged in the central area inside (see, for example, Patent Document 1). When a conductor with a large central area and a terminal electrode with a small outer edge area are connected to an external wiring board by soldering using a conductive bonding material, the thickness of the solder that is joined to the large conductor in the central area tends to be thick. The distance between the terminal electrode and the circuit board becomes large, and the solder that is joined to the terminal electrode becomes thin, which may cause poor connection or reduced connection reliability.

On the other hand, the large conductor in the central region is divided into multiple conductors to reduce the area of each of the plurality of conductors in the central region, thereby reducing the volume and thickness of the solder that is joined to the conductor in the central region. (For example, see Patent Document 2 and Patent Document 3.).

JP 2004-014645 A JP-A-59-082790 JP-A-2000-223622

However, due to heat during solder mounting of electronic components and thermal stress due to heat during operation of electronic elements, conductive connecting materials such as solder may be cut, or terminal electrodes may be peeled off from the insulating substrate. This is because the terminal electrodes arranged in the outer edge region where the thermal stress is large are small. A conductor with a large central region functions as a reinforcement against such thermal stress and also as a reinforcement against reduction in bonding area due to miniaturization. If a conductor with a large central region that functions as a reinforcement is divided into multiple conductors, the joint area of the conductor in the central region becomes smaller, which may reduce the joint strength and connection reliability of the circuit board to the external wiring board. was there.

A circuit board according to one aspect of the present disclosure includes an insulating substrate having a first surface and a second surface opposite to the first surface, the first surface having a square shape in plan view; a circuit conductor including a plurality of terminal electrodes located in an outer edge region on the first surface of an insulating substrate; and one center conductor located in a central region inside the outer edge region of the first surface; The surface of the central conductor has a lattice shape with a plurality of irregularities, the central conductor has concave portions and convex portions, and the concave portions or the convex portions are located at the outer edge of the central conductor. The ones located in the central part of the central conductor are larger, or the recesses or protrusions are smaller in the central part of the central conductor than those located in the outer edge of the central conductor.

An electronic component according to one aspect of the present disclosure includes the circuit board configured as described above and an electronic element.

An electronic module according to one aspect of the present disclosure includes the electronic component configured as described above and a module wiring board on which the electronic component is mounted.

According to the circuit board of one aspect of the present disclosure, since the central conductor has a grid-like surface formed by unevenness, the surface of the central conductor is divided into a plurality of regions with small widths and small areas, so that it is flat. Compared to a large surface, the likelihood that a conductive bonding material such as solder that is bonded to it will collect in the center and make the center too thick is reduced. Also, only the surface of the central conductor is divided and the area of the entire central conductor is not reduced. Therefore, it becomes a small-sized circuit board excellent in bonding strength and connection reliability with an external wiring board or the like.

According to an electronic component of one aspect of the present disclosure, since it includes the circuit board having the configuration described above, it is possible to provide an electronic component that is advantageous in terms of connection reliability to an external wiring board and miniaturization.

According to the electronic module of one aspect of the present disclosure, since it includes the electronic component including the circuit board having the configuration described above and the wiring board for the module, the connection reliability between the electronic component and the wiring board is effectively improved. An improved and compact electronic module can be provided.

1 shows the appearance of an example of a circuit board, (a) is a perspective view from the second surface (upper surface) side, and (b) is a perspective view from the first surface (lower surface) side. (a) is a plan view from the second surface (upper surface) side of the circuit board shown in FIG. 1, (b) is a cross-sectional view along line BB of (a), and (c) is the first surface. It is a top view from the (lower surface) side. Fig. 3 shows the appearance of another example of a circuit board, where (a) is a perspective view from the second surface (upper surface) side, and (b) is a perspective view from the first surface (lower surface) side. (a) is a plan view from the second surface (upper surface) side of the circuit board shown in FIG. 3, (b) is a cross-sectional view along line BB of (a), and (c) is the first surface. It is a top view from the (lower surface) side. Fig. 3 shows the appearance of another example of a circuit board, where (a) is a perspective view from the second surface (upper surface) side, and (b) is a perspective view from the first surface (lower surface) side. (a) is a plan view from the second surface (upper surface) side of the circuit board shown in FIG. 5, (b) is a cross-sectional view along line BB of (a), and (c) is the first surface. It is a top view from the (lower surface) side. (a) and (b) are both plan views from the first surface (lower surface) side, showing an example of another circuit board. (a) and (b) are both plan views from the first surface (lower surface) side, showing an example of another circuit board. (a) and (b) are both plan views from the first surface (lower surface) side, showing an example of another circuit board. (a) is a fragmentary sectional view showing an enlarged portion A of FIG. 4(b), and (b) and (c) are fragmentary sectional views of other circuit boards. (a) to (c) are all cross-sectional views of other circuit boards. (a) is a perspective view showing an example of a circuit board, an electronic component, and an electronic module, and (b) is a sectional view taken along line BB of (a).

A circuit board, an electronic component, and an electronic module according to embodiments of the present disclosure will be described with reference to the accompanying drawings. FIG. 1 shows the appearance of an example of a circuit board, FIG. 1(a) is a perspective view from the second surface (upper surface) side, and FIG. 1(b) is a perspective view from the first surface (lower surface) side. be. 2(a) is a plan view from the second surface (upper surface) side of the circuit board shown in FIG. 1, and FIG. 2(b) is a cross-sectional view taken along line BB of FIG. 2(c) is a plan view from the first surface (lower surface) side. 3 shows the appearance of another example of the circuit board, FIG. 3(a) is a perspective view from the second surface (upper surface) side, and FIG. 3(b) is a perspective view from the first surface (lower surface) side. It is a diagram. 4(a) is a plan view from the second surface (upper surface) side of the circuit board shown in FIG. 3, and FIG. 4(b) is a sectional view taken along line BB of FIG. 4(c) is a plan view from the first surface (lower surface) side. 5 shows the appearance of another example of the circuit board, FIG. 5(a) is a perspective view from the second surface (upper surface) side, and FIG. 5(b) is a perspective view from the first surface (lower surface) side. It is a diagram. 6A is a plan view from the second surface (upper surface) side of the circuit board shown in FIG. 5, and FIG. 6(c) is a plan view from the first surface (lower surface) side. 7A and 7B are plan views from the first surface (lower surface) side showing an example of another circuit board. 8(a) and 8(b) are plan views from the first surface (lower surface) side showing an example of another circuit board. 9(a) and 9(b) are both plan views from the first surface (lower surface) side, showing an example of another circuit board. FIG. 10(a) is a fragmentary cross-sectional view showing an enlarged portion A of FIG. 4(b), and FIGS. 10(b) and 10(c) are fragmentary sectional views of other circuit boards. FIGS. 11(a), 11(b) and 11(c) are cross-sectional views of essential parts of other circuit boards. FIG. 12(a) is a perspective view showing an example of a circuit board, an electronic component, and an electronic module, and FIG. 12(b) is a sectional view taken along line BB of FIG. 12(a). In addition, FIG. 12 cuts out and shows a part of the electronic module (the part where electronic parts are mounted). In the plan views and perspective views of FIGS. 1 to 9, circuit conductors such as central conductors and terminal electrodes are hatched in dots so that they can be easily distinguished from others. In addition, in FIG. 8A, concave portions and convex portions are shaded differently so that the unevenness can be easily distinguished. Note that the distinction between upper and lower sides in the following description is for the sake of convenience, and does not limit the upper and lower sides when the circuit board, the electronic component, etc. are actually used.

As in the examples shown in FIGS. 1 to 9, the circuit board 100 has a first surface 11 and a second surface 12 opposite to the first surface 11, and the shape of the first surface 11 in plan view is symmetrical. a circuit conductor 2 including a plurality of terminal electrodes 21 positioned in an outer edge region 11o of the first surface 11 of the insulating substrate 1; , and the surface of the central conductor 3 has a lattice shape with a plurality of irregularities.

According to the circuit board 100 of the present disclosure, the surface of the central conductor 3 has a lattice shape with a plurality of unevennesses (the convex portions 31 and the concave portions 32). is divided into areas of Accordingly, compared to the case where the surface of the central conductor 3 is flat and large, the conductive bonding material 310 such as solder to be bonded to the central conductor 3 gathers at the center, thereby providing a conductive connection between the central conductor 3 and the external wiring board 400 . This reduces the possibility that the volume (thickness) of the adhesive material 310 becomes too large. Therefore, the possibility that the conductive bonding material 310 to be bonded to the terminal electrode 21 is thinned to cause poor connection or deterioration in connection reliability is reduced. Moreover, since the area of the entire central conductor 3 does not decrease, the bonding strength with the external wiring board 400 or the like does not decrease. Therefore, the compact circuit board 100 is excellent in bonding strength and connection reliability with the external wiring board 400 and the like.

The insulating substrate 1 is a basic part of the circuit board 100 and functions as an electrical insulator for arranging the circuit conductors 2 such as the terminal electrodes 21 electrically insulated from each other. Also, the insulating substrate 1 is a portion that functions as a base for mounting and fixing the electronic element 200, for example. The square shape does not have to be a strict square, but a square with notches in the sides and corners as in the examples shown in FIGS. 1 to 9, or a square with rounded corners. etc. Further, although the examples shown in FIGS. 1 to 9 are square, they may be rectangular. The insulating substrate 1 may be formed by laminating a plurality of insulating layers 1a, as in the examples shown in FIGS. 2, 4, 6 and 10 to 12, for example.

The outer edge region 11o on the first surface 11 of the insulating substrate 1 is a region outside the chain double-dashed line shown in FIGS. 1(b) and 2(c), for example. A central region 11c is located in the center of the first surface 11 inside the outer edge region 11o. The outer edge region 11o of the first surface 11 is a region along the outer edge of the first surface 11, and is 8% to 15% of the length of one side of the first surface 11 inward from the outer edge of the first surface 11. It is a part of the width of about. Therefore, the central region 11c is a rectangular portion located in the center of the first surface 11 and having a side length of about 85% to 92% of the length of one side of the first surface 11. FIG. For example, if the insulating substrate 1 has a square shape in plan view, the central region 11c also has a square shape, and if the insulating substrate 1 has a rectangular plan view shape, the central region 11c also has a rectangular shape. be.

A plurality of terminal electrodes 21 are provided on the lower surface 11 of the insulating substrate 1 , that is, the first surface 11 as the circuit board 100 . The plurality of terminal electrodes 21 are arranged along the outer edge of the first surface 11 of the insulating substrate 1 in the outer edge region 11o of the first surface 11, as in the examples shown in FIGS. 1 to 9, for example. In the examples shown in FIGS. 1 to 9, the shape of the terminal electrode 21 is a rectangular shape extending inward from the outer edge. In each plan view from the first surface (lower surface) side, the boundary between the central region 11c and the outer edge region 11o and the two-dot chain line indicating the outer edge of the central region 11c connect the inner ends of the terminal electrodes 21, and the central region The shape of 11c is square.

One central conductor 3 is provided in the central region 11c. The outer shape of the central conductor 3 follows the shape of the central region 11c and is slightly smaller than the central region 11c so as not to short-circuit with the terminal electrode 21 in the outer edge region 11o. Therefore, the shape of the central conductor 3 is also rectangular.

The central conductor 3 may function as part of the circuit conductor 2 or may not function as the circuit conductor 2 . For example, center conductor 3 may be a ground conductor that functions as part of circuit conductor 2 . A circuit board 100 in which the central conductor 3 is a ground conductor and the central conductor 3 and the circuit conductor 2 (inner conductor 23) are electrically connected as in the examples shown in FIGS. 4 and 6 can be used. . Even if the center conductor 3 is provided with protrusions 31 and recesses 32 in order to reduce the thickness of the conductive bonding material 310 to be joined (even if the surface is in a grid pattern due to unevenness), the center conductor 3 is not divided, so the ground conductor is not divided. can be made large. As a result, a stable ground potential can be obtained, and the circuit board 100 can process stable high-frequency signals.

When the central conductor 3 does not function as the circuit conductor 2, it is not electrically connected to the circuit conductor 2 and the circuit of the external wiring board 400, for example, for reinforcing the above-described bonding strength and connection reliability. Alternatively, it functions as a heat radiating device for radiating heat generated by the electronic element 200 to the outside. Even when the central conductor 3 functions as part of the circuit conductor 2, it also functions for reinforcement and heat dissipation. When the central conductor 3 is used for reinforcement, the joint area with the conductive joint material 310 becomes large due to the irregularities on the surface. Further, when the central conductor 3 is used for heat dissipation, even if the surface is in a grid pattern due to unevenness, the overall area of the central conductor 3 in plan view does not decrease. Heat transfer paths are not reduced. Therefore, the compact circuit board 100 is excellent in bonding strength, connection reliability, and heat dissipation to the external wiring board 400 and the like. Also, in this case, if the number of internal conductors 23 (penetrating conductors) connected to the central conductor 3 is large, the heat transfer to the central conductor 3 and the bonding strength between the central conductor 3 and the insulating substrate 1 are further improved.

The fact that the surface of the central conductor 3 has a lattice shape with a plurality of irregularities means that the surface of the central conductor 3 is not flat but has irregularities, and the irregularities form a lattice pattern in plan view. be. For example, in the example shown in FIGS. 1 and 2, concave portions 32 having a square shape in plan view are arranged in a matrix of 3×3, convex portions 31 between the concave portions 32 are lattice-shaped, and concave portions 32 are window portions. It has a grid pattern. In the example shown in FIGS. 3 and 4, convex portions 31 having a square shape in plan view are arranged in a matrix of 2×2, concave portions 32 between the convex portions 31 are lattice-shaped, and the convex portions 31 are window portions. It has a grid pattern. The protrusions 31 and recesses 32 in the examples shown in FIGS. 1 and 2 and the examples shown in FIGS. 3 and 4 may be reversed. For example, the convex portions 31 having a square shape in plan view may be arranged in a 3×3 matrix, or the convex portions 31 having a square shape in plan view may be arranged in a 2×2 matrix. good too. Therefore, in the examples shown in FIGS. 7 to 9, the same portion of the central conductor 3 is labeled 31 (32) or 32 (31) to indicate that it is either the convex portion 31 or the concave portion 32. there is

It can also be said that the surface of the central conductor 3 has a lattice shape with a plurality of irregularities, and that the convex portions 31 or the concave portions 32 are arranged at lattice points in a mathematical planar lattice. In the examples shown in FIGS. 1 and 2 or the examples shown in FIGS. 3 and 4, concave portions 32 or convex portions 31 are arranged at lattice points of a square lattice. On the other hand, in the example shown in FIGS. 5 and 6 and in the example shown in FIG. 7A, the concave portions 32 are arranged at the lattice points of the orthorhombic lattice, and in the example shown in FIG. A convex portion 31 or a concave portion 32 is arranged at the point. It can also be said that the convex portions 31 or the concave portions 32 are arranged in an island shape in plan view.

In the central conductor 3 of the example shown in FIG. 8( a ), both the convex portion 31 and the concave portion 32 are squares having the same size in plan view, and are not the lattice pattern having the above-described lattice and window portions, but the overall shape. The lattice pattern as is a checkered lattice. In the central conductor 3 of the example shown in FIG. 8(b), of the small square protrusions 31 (or recesses 32) arranged in a 4×4 matrix, the central four are integrated into a large one. It is a square convex portion 31 (or concave portion 32). In this way, an array of convex portions 31 (or concave portions 32) of different sizes is also a lattice pattern.

1 and 2, the example shown in FIGS. 3 and 4, and the example shown in FIG. 8, the central conductor 3 has a lattice pattern in which square protrusions 31 or recesses 32 are arranged. The central conductor 3 of the example shown in FIGS. 5 and 6 has a lattice pattern in which square (square-shaped) concave portions 32 with rounded corners are arranged. The central conductor 3 in the example shown in FIG. 7A has a lattice pattern in which circular protrusions 31 (or recesses 32) are arranged. The center conductor 3 in the example shown in FIG. 7(b) has regular hexagonal convex portions 31 (or concave portions 32) arranged mainly, and half trapezoids and isosceles triangles of regular hexagons are arranged on the outer edge to form a hexagonal lattice. It has a grid pattern. The center conductor 3 in the example shown in FIG. 9A has a lattice pattern in which rectangular protrusions 31 (or recesses 32) are arranged. The central conductor 3 of the example shown in FIG. 9(b) has four square protrusions 31 (or recesses 32) arranged in the center and rectangular protrusions 31 (or recesses 32) arranged in the outer periphery. It has a grid pattern. In this way, the shape of the windows of the lattice pattern (the convex portions 31 or the concave portions 32 arranged at the lattice points) is not particularly limited, and a plurality of windows (the convex portions 31 or the concave portions arranged at the lattice points) are not particularly limited. 32) may not be identical in shape and size.

Up to this point, it has been explained that the protrusions 31 are arranged and the rest is the recesses 32, or that the recesses 32 are arranged and the rest is the protrusions 31, but the projections 31 and the recesses 32 It may have both. For example, in the central conductor 3 of FIG. 8B, the small square portion of the outer edge may be the convex portion 31 and the large square portion of the central portion may be the concave portion 32 .

The height of the protrusions 31 or the depth of the recesses 32 for making the surface of the central conductor 3 have a lattice shape can be set to about 1/3 to 1/2 of the overall thickness of the central conductor 3 . Further, the thickness of the entire central conductor 3, ie, the thickness up to the tip of the projection 31, is about the same as the thickness of the other circuit conductors 2 and at most about 1 to 3 times the thickness. This is because if the central conductor 3 is made too thick to form a lattice, it is disadvantageous from the standpoint of reducing the height of the circuit board 100 and cost.

In this manner, the surface of the central conductor 3 is in a grid pattern with a plurality of unevennesses (projections 31 and recesses 32). For example, if there is one small concave portion 32 in the central portion of the central conductor 3, the depth of the concave portion 32 is small and the frame-like peripheral portion is large. The difference from when is flat is small. When there is one large concave portion 32 in the central portion of the central conductor 3, the bottom surface of the concave portion 32 is large, so the conductive bonding material 310 is concentrated in the center of the bottom surface, and the overall flatness is different from the case where the bottom surface is flat. small. Also, when there is one protrusion 31 in the central portion of the central conductor 3, the conductive bonding material 310 concentrates in the central portion of the convex portion 31, that is, in the central portion of the central conductor 3. is. When the surface of the central conductor 3 is in a lattice shape with unevenness, the end face of one protrusion 31 is small, and there are recesses 32 between the protrusions 31, 31, and the thickness of the conductive bonding material 310 is small at that portion. Therefore, it is difficult for the conductive bonding material 310 to be concentrated in the central portion of the central conductor 3 as a whole and to become thick.

Since the surface of the central conductor 3 is grid-like, two or more protrusions 31 or recesses 32 are arranged in different directions, such as 2×2 in the examples shown in FIGS. 3 and 4 . This is because if there is one in one direction, the length of the surface of the central conductor 3 in that direction does not become smaller than the overall length, and the above effects may not be obtained sufficiently. Also, if the convex portion 31 (or the concave portion 32) is too small, the portion (the concave portion 32) other than the convex portion 31 becomes too large, and thus the above effect may not be obtained sufficiently. Therefore, the convex portions 31 (or concave portions 32) arranged at the lattice points are, for example, rectangular having a side length of 20% to 40% of the length of one side of the central conductor 3, or It may be circular with a diameter of 20% to 40% of the length of one side of the .

The central conductor 3 can be a circuit board 100 having a central recess 32, for example as shown in FIGS. If there is a recess 32 in the center where the conductive bonding material 310 tends to be thick, even if the conductive bonding material 310 gathers in the center of the central conductor 3, the conductive bonding material 310 will enter the recess 32. An increase in the distance between 100 and wiring board 400 to which circuit board 100 is bonded is more effectively suppressed. The central portion in this case is the central portion of the central conductor 3 in plan view, and is the area located in the center when the central conductor 3 is equally divided into nine areas of 3×3 in the direction along the outer edge. is. In the example shown in FIG. 8(b), one recess 32 is located in the central portion, the recess 32 is large, and the entire central portion is located within the recess 32. In the example shown in FIG. On the other hand, in the example shown in FIG. 8A, there is one recessed portion 32 at the center of the central portion, and a part of the recessed portion 32 is positioned at each of the four corners of the central portion. Also, as in the example shown in FIG. 9B, recesses 32 can be arranged at the four corners of the central portion. In this manner, the recess 32 preferably occupies 50% or more of the central portion of the central conductor 3, and it is more effective to have the recess 32 at the center of the central portion.

As described above, the surface of the central conductor 3 has a lattice shape in which the protrusions 31 or the recesses 32 are arranged like islands in plan view. When the convex portions 31 are arranged in an island shape, the conductive bonding material 310 is more effective when joining the circuit board 100 to the wiring board 400 than in the case where the concave portions 32 are arranged in an island shape. Therefore, the bonding strength between the circuit board 100 and the wiring board 400 and the thermal conductivity from the circuit board 100 to the wiring board 400 are improved. When the circuit board 100 and the wiring board 400 are joined together, for example, when solder paste is used and the protrusions 31 are arranged like islands, the organic component in the solder paste becomes gaseous by heating. This is because it is easy to escape to the outside. This is because when the conductive bonding material 310 is a conductive adhesive, it is difficult for air to be involved in the application, and the air is easily released.

In the example shown in FIG. 10( a ), the thickness Tt of the terminal electrode 21 is smaller than the thickness Tc of the central conductor 3 . Even in this case, the possibility that the conductive bonding material 310 that is bonded to the terminal electrode 21 will become thin and cause a connection failure or a decrease in connection reliability will be reduced. On the other hand, in the examples shown in FIGS. 10(b), 10(c) and 11(a), the thickness Tt of the terminal electrode 21 is the same as the thickness Tc of the central conductor 3 . 11(b) and 11(c), the thickness Tt of the terminal electrode 21 is greater than the thickness Tc of the central conductor 3. As shown in FIG. Thus, the circuit board 100 in which the thickness Tt of the terminal electrode 21 is equal to or greater than the thickness Tc of the central conductor 3 can be obtained. Here, the thickness Tc of the central conductor 3 is the thickness at the thickest portion and the thickness at the convex portion 31, and being equal to or greater than the thickness Tc of the central conductor 3 is strictly the same as the thickness Tc of the central conductor 3. However, the thickness Tc of the central conductor 3 may be 90% or more of the thickness Tc. When the thickness Tt of the terminal electrode 21 is approximately the same as the thickness Tc of the central conductor 3 , the thickness of the conductive bonding material 310 that is bonded to the central conductor 3 is reduced by the amount that enters the recess 32 of the central conductor 3 . . Furthermore, when the thickness Tt of the terminal electrode 21 is larger than the thickness Tc of the central conductor 3, the distance between the terminal electrode 21 and the wiring substrate 400 becomes smaller than the distance between the central conductor 3 and the wiring substrate 400, and the terminal electrode 21 The conductive bonding material 310 to be bonded becomes more difficult to thin.

The surface of the terminal electrode 21 in the example shown in FIG. 10 is flat, whereas the terminal electrode 21 has a convex portion 21a on the surface as in the example shown in FIG. be able to. In such a case, since the bonding area between the terminal electrode 21 and the conductive bonding material 310 is increased, the bonding strength and bonding reliability between the terminal electrode 21 and the wiring board 400 are improved. Even if the surface of the terminal electrode 21 has a recess, the bonding area increases, but since the terminal electrode 21 is small and the recess formed therein is even smaller, it is difficult for the conductive bonding material 310 to enter the recess. Voids are more likely to occur in the bonding material 310, and the bonding strength may decrease. The convex portion 21a has a convex portion (convex portion 21a) in the central portion of the surface of the terminal electrode 21, as in the examples shown in FIGS. 8(c) and 11(a). can be a shape in which the is protruded. While this example has one convex portion 21a, a plurality of convex portions 21a may be provided as in the examples shown in FIGS. 9(a) and 11(b). Alternatively, as in the examples shown in FIGS. 9B and 11C, the entire surface of the terminal electrode 21 may be a convex portion 21a tapered to form a convex curved surface. As described above, it is preferable that the surface of the terminal electrode 21 does not have any concave portions, so it is preferable that the end faces of the convex portions 21a also have no concave portions.

The circuit board 100 of the example shown in FIGS. 5 and 6 has one corner pad 4 at each of the four corners of the outer edge region 11o. Thermal stress is generated between the circuit board 100 and the external wiring board 400, and the thermal stress applied to the terminal electrodes 21 near the corners increases. A corner pad 4 is provided at a position close to the terminal electrode 21 to which a large thermal stress is applied, and the corner pad 4 and the external wiring board 400 are joined together, thereby reinforcing the joint at the corner of the circuit board 100, thereby The compact circuit board 100 is excellent in bonding strength and connection reliability with the wiring board 400 and the like. Such a corner pad 4 can also be applied to the circuit board 100 of the examples shown in FIGS. 1-4 and 7-9.

In addition, in order to further increase the bonding strength of the terminal electrode 21 , the central conductor 3 and the corner pad 4 to the insulating substrate 1 , an insulating film covering the outer edge portions of these and the first surface 11 of the insulating substrate 1 is provided. It can be a circuit board 100 . Since the outer edge portion, which tends to be the starting point of peeling, is pressed by the insulating film, it becomes more difficult to peel off even when stress is applied. Therefore, the compact circuit board 100 with superior bonding strength and connection reliability is obtained.

As in the example shown in FIG. 12, the electronic component 300 includes the circuit board 100 and the electronic element 200 as described above. Since the electronic component 300 includes the circuit board 100 configured as described above, the electronic component 300 is advantageous in improving connection reliability to the wiring 401 (terminal) of the external wiring board 400, and provides a small electronic component 300. can do.

The upper surface opposite to the first surface (lower surface) 11 of the circuit board 100 is the second surface 12 on which the electronic element 200 is mounted. 1 and 2 and the circuit board 100 of the example shown in FIG. 12, the insulating substrate 1 has the cavity 1b on the second surface 12, but the circuit board of the example shown in FIGS. It may be a flat insulating substrate 1 without a cavity 1b, like the circuit substrate 100 in the example shown in 100 and FIGS. The circuit board 100 has connection electrodes 22 as circuit conductors 2 electrically connected to the electronic element 200 on the second surface 12 . When the cavity 1b is provided, the connection electrode 22 is provided inside the cavity 1b. In the examples shown in FIGS. 1, 2 and 12, the cavity 1b has a stepped portion between the opening and the bottom surface, and the connection electrode 22 is provided on the stepped portion. The cavity 1b may not have a stepped portion, in which case the connection electrode 22 is provided on the bottom surface of the cavity 1b.

In the electronic component 300 of the example shown in FIG. 12, the electronic element 200 is mounted on the bottom surface of the cavity 1b. are electrically connected by bonding wires. Therefore, in the circuit board 100 of the example shown in FIGS. 1, 2 and 12, the plurality of connection electrodes 22 are arranged inside the cavity 1b along the outer circumference of the cavity 1b. As in the examples shown in FIGS. 3 and 4 , when (the insulating substrate 1 of) the circuit board 100 is flat, the connection electrodes 22 are formed along the outer circumference of the second surface 12 (upper surface) of the insulating substrate 1 . arrayed. On the other hand, when the electronic element 200 is flip-chip connected, the plurality of connection electrodes 22 are arranged in the central portion of the second surface 12 as in the examples shown in FIGS. 5 and 6, for example. When flip-chip connecting the electronic element 200 to the circuit board 100 having the cavity 1b, the connection electrodes 22 are arranged in the center of the bottom surface of the cavity 1b.

In addition, the circuit board 100 in the example shown in FIG. 12 has a mounting conductor 5 for fixing the electronic element 200 and for grounding as necessary at the center of the second surface 12 (bottom surface of the cavity 1b). ing. Thus, the number and arrangement of the circuit conductors 2 on the second surface 12 can be set so as to correspond to the electronic device 200 to be mounted. In addition, in the example shown in FIG. 12 , the mounting conductor 5 is connected to the central conductor 3 . When the central conductor 3 is the above-described ground conductor, the electronic element can be 200 can be connected to ground potential at a relatively large lower surface. Further, when the central conductor 3 is for heat radiation as described above, the heat generated by the electronic element 200 is dissipated by a bonding material such as a brazing material, the mounting conductor 5, and the inside connecting the mounting conductor 5 and the central conductor 3. Heat is efficiently transferred to the central conductor 3 via the conductor 23 .

As in the example shown in FIG. 12B, the connection electrodes 22 on the second surface 12 and the terminal electrodes 21 on the first surface 11 are connected by an internal conductor 23 inside the insulating substrate 1 . Thereby, the electronic element 200 mounted on the second surface 12 is electrically connected to the external wiring board 400 via the connection member 210 and the circuit conductor 2 (the connection electrode 22, the internal conductor 23 and the terminal electrode 21). It is a circuit board 100 that can

In electronic component 300 of the example shown in FIG. 12, electronic element 200 and connecting member 210 are accommodated in cavity 1b, and lid 221 is bonded with bonding material 222 so as to close the opening of cavity 1b. The lid 221 and the bonding material 222 function as a sealing member 220 that hermetically seals the electronic element 200 . When solder is used as the bonding material 222, a seal conductor can be provided on the second surface 12 so as to surround the cavity 1b. Also, when the circuit board 100 is flat like the examples shown in FIGS. 3 to 6, it can be sealed with a cap-like lid. Alternatively, a sealing resin can be used as the sealing member 220, and sealing can be performed by covering the second surface 12 of the circuit board 100, the electronic element 200, the connection member 210, and the like with the sealing resin.

Further, as in the example shown in FIG. 12, the electronic module 500 includes the electronic component 300 configured as described above and a module wiring board 400 on which the electronic component 300 is mounted. According to such an electronic module 500, since it is provided with the electronic component 300 including the circuit board 100 configured as described above and the wiring board 400 for the module, the connection reliability between the electronic component 300 and the wiring board 400 is effective. This results in a compact electronic module 500 that is substantially improved.

In the example shown in FIG. 12, the terminal electrodes 21 of the circuit board 100 and the wirings 401 on the upper surface of the wiring board 400 are electrically and mechanically connected by a conductive bonding material 310 such as solder. When the terminal electrode 21 is electrically connected to the wiring 401 of the wiring board 400 via the conductive bonding material 310, the electronic component 300 and the wiring 401 of the wiring board 400 are electrically connected to each other. As a result, it is possible to exchange electrical signals, potentials, or the like between electronic component 300 and wiring board 400 . Further, since the electronic component 300 has the electronic element 200 electrically connected to the circuit conductor 2 of the circuit board 100, the electronic element 200 and the wiring 401 of the wiring board 400 are electrically connected to each other.

As described above, the insulating substrate 1 is a rectangular flat plate in plan view (top view). The insulating substrate 1 is, for example, a plate having a rectangular shape of 5 mm to 20 mm×5 mm to 20 mm and a thickness of 0.5 mm to 2 mm. The insulating substrate 1 is formed by stacking a plurality of insulating layers 1a. Although the insulating substrate 1 shown in FIGS. 2, 4 and 6 is composed of five insulating layers 1a, the number of insulating layers 1a is not limited to these. When the insulating substrate 1 has the cavity 1b on the second surface 12, the cavity 1b has a wall thickness of 0.5 mm or more between the inner surface of the cavity 1b and the outer surface of the insulating substrate 1, and is flat. The visual shape may be a square of 4 mm to 19 mm×4 mm to 19 mm, and the depth from the second surface 12 may be 0.4 mm to 1.5 mm.

The insulating substrate 1 is made of a ceramic sintered body such as an aluminum oxide sintered body, a glass ceramic sintered body, an aluminum nitride sintered body, or a mullite sintered body. If the insulating substrate 1 is made of a sintered glass ceramic, for example, it can be manufactured as follows. First, raw material powders containing powders of silicon oxide and boron oxide as glass components and powders of aluminum oxide as filler components as main components are kneaded with an appropriate organic binder and organic solvent to form a slurry. This slurry is formed into a sheet by a forming method such as a doctor blade method or a lip coater method to produce a ceramic green sheet that will serve as the insulating layer 1a. Thereafter, this ceramic green sheet is cut into a suitable size, and a plurality of shaped ceramic green sheets are stacked to produce a laminate. After that, the insulating substrate 1 can be manufactured by firing this laminate at a temperature of about 900 to 1000.degree. When the insulating substrate 1 has the cavity 1b on the second surface 12, the cavity 1b and the notches on the side surfaces of the insulating substrate 1 may be formed by forming through holes or the like corresponding to these shapes in the ceramic green sheet.

The planar view shape of the cavity 1b on the second surface 12 of the insulating substrate 1 is a square with rounded corners along the outer edge of the second surface 12 of the insulating substrate 1 in the example shown in FIGS. If the cavity 1b has such a shape without corners, the possibility of cracks starting from the corners occurring when stress is applied to the insulating substrate 1 is reduced.

A circuit conductor 2 is provided on an insulating substrate 1 . As described above, the terminal electrode 21 is provided on the outer edge region 11o of the first surface 11 (lower surface) of the insulating substrate 1, and the connection electrode 2 is provided on the second surface 12 (upper surface).
2, an internal conductor 23 is provided inside the insulating substrate 1 . The connection electrode 22 on the upper surface 12 and the terminal electrode 21 on the lower surface 11 are electrically connected by an internal conductor 23 . The internal conductor 23 has internal conductor layers provided between the insulating layers 1a and through conductors penetrating the insulating layers 1a.

The shape of the terminal electrode 21 is, for example, a rectangular shape extending inward from the outer edge of the first surface 11 of the insulating substrate 1 as shown in FIGS. ×The length from the outer edge is 0.5 mm to 2 mm. The term "rectangular shape" means that it is not strictly rectangular, but also includes rounded corners. A shape with cut corners is also included. The shape of the terminal electrode 21 is not particularly limited. The arrangement of the connection electrodes 22 varies depending on the method of connecting the electronic element 200 as described above, and the shape and dimensions of the connection electrodes 22 can be adjusted according to the arrangement.

In the example circuit board 100 shown in FIGS. 1 to 9, the insulating substrate 1 has a notch extending from the first surface 11 to the second surface 12 on the side surface. A conductor is also formed on the inner surface of the notch and is connected to the terminal electrode 21 on the first surface 11 . It can also be said that the terminal electrode 21 extends from the first surface 11 to the inner surface of the notch. In the example shown in FIGS. 1 and 2, the conductor is provided on a portion of the inner surface of the notch on the first surface 11 side. In the examples shown in FIGS. 3 and 4 and the examples shown in FIGS. 8 and 9, the conductor is provided on the entire inner surface of the notch. In the examples shown in FIGS. 5 and 6, the notches are filled with conductors. The terminal electrode 21 can be provided from the first surface 11 to the side surface of the insulating substrate 1 without providing the notch on the side surface. In either case, as in the example shown in FIG. It is positioned between the terminal electrode 21 on the first surface 11 and the terminal electrode 21 on the side surface including the inner surface of the notch. The bonding area of the conductive bonding material 310 is increased, and the conductive bonding material 310 between the side surface and the wiring 401 of the wiring board 400 is formed with a meniscus-shaped fillet portion, and the stress can be reduced by the fillet portion. , mounting reliability is further enhanced.

The circuit conductors 2 such as the terminal electrodes 21, the connection electrodes 22 and the internal conductors 23 are made of, for example, metal materials such as tungsten, molybdenum, manganese, copper, silver, palladium, gold, platinum, nickel or cobalt, or these metal materials. It is made of an alloy material or the like containing. Such a metal material or the like is provided at a predetermined position of the insulating substrate 1 as a metallized layer, for example, when the insulating substrate 1 is made of the ceramic sintered body as described above.

The terminal electrodes 21, the connection electrodes 22, and the internal conductor layers of the internal conductors 23 of the circuit conductors 2 are formed, for example, of copper metallized layers when the insulating substrate 1 is made of a glass-ceramic sintered body as described above. can do. In the case of a copper metallized layer, a metal paste prepared by mixing copper powder with an organic solvent and an organic binder is printed on the surface of the ceramic green sheet serving as the insulating layer 1a by a method such as screen printing. , and then co-fired with the ceramic green sheet. As for the portion of the through conductor of the internal conductor 23, a through hole is previously formed in the ceramic green sheet serving as the insulating layer 1a, and the metal paste is applied in the through hole of the ceramic green sheet by a method such as screen printing. can be formed by filling with and co-firing. If the side surface of the insulating substrate 1 has a notch and the terminal electrode 21 extends into the notch, the metal paste is applied to the inner surface of the through-hole of the ceramic green sheet by a method such as screen printing. It can be formed by printing, coating, and co-firing. Through-holes in the ceramic green sheet can be formed by a method such as mechanical drilling or laser processing.

Conductors other than the circuit conductors 2, such as the central conductor 3, the corner pads 4, and the mounting conductors 5, can also be formed in the same manner as the circuit conductors 2. FIG.

The shape of the corner pad 4 is not limited to a circular shape as in the examples shown in FIGS. 5 and 6, and may be an elliptical shape, a polygonal shape such as a square, or the like. For reinforcement, it is preferable to use corner pads 4 having as large an area as possible. If the shape of the corner pad 4 does not have corners where thermal stress or the like tends to concentrate, peeling due to thermal stress or the like is less likely to occur. The thermal stress acts on the corner pads 4 arranged at the corners of the circuit board 100 toward the center of the circuit board 100 in plan view. Therefore, it is better to make the length in this direction as large as possible. Therefore, the corner pad 4 can have a shape extending from the corner of the circuit board 100 (the corner of the outer edge region 11o) to the corner of the central region 11c. The corner pads 4 can be further extended to the central conductor 3 and connected.

The corner pad 4 is provided at a corner of the outer edge region 11o where the terminal electrode 21 is not arranged. It can be circular from 0.3 mm to 1.8 mm.

In the case where an insulating film covering the outer edge of the terminal electrode 21 and the first surface 11 of the insulating substrate 1 is provided, the insulating film may have a thickness of 0.03 mm or more from the outer circumference, although it depends on the size of the terminal electrode 21 and the like. It covers a 0.3 mm portion. Note that the dimensions of the terminal electrodes 21 and the like described above are the actual dimensions of the terminal electrodes 21 and the like, which are the portions exposed from the openings of the insulating film when the insulating film is provided.

The insulating film is bonded to and integrated with the first surface 11 of the insulating substrate 1 . More specifically, when the insulating substrate 1 is made of a ceramic sintered body, the insulating film is made of the same material as the ceramics of the insulating substrate 1, and is integrated by simultaneous firing. Therefore, the insulating film and the insulating substrate 1 are firmly bonded.

Such an insulating film can be formed, for example, as follows. First, a metal paste is printed on the ceramic green sheets in patterns corresponding to the terminal electrodes 21 , the central conductors 3 and the corner pads 4 . Next, a ceramic paste to be an insulating film is applied so as to overlap a predetermined portion of the printed metal paste and a predetermined portion of the ceramic green sheet. The ceramic paste can be produced by adding an appropriate organic binder and an organic solvent to raw material powders similar to the slurry for producing the ceramic green sheets and kneading the mixture. By firing the metal paste, the ceramic paste, and the ceramic green sheets at the same time, the insulating film is bonded to the first surface 11 of the insulating substrate 1 and integrated.

The conductors exposed on the outer surface of the insulating substrate 1, such as the terminal electrodes 21 and connection electrodes 22 of the circuit conductors 2, the central conductors 3, and the corner pads 4, are applied to the metallized layer by electroplating, electroless plating, or the like. A plating layer such as nickel and gold may be further deposited by a method.

The electronic elements 200 mounted on the circuit board 100 include semiconductor integrated circuit elements such as ICs (Integrated Circuits) and LSIs (Large-Scale Integrated Circuits), and LEDs (Light Emitting Diodes). diode), PD (Photo Diode), CCD (Charged-Coupled Device), CMOS
Optical semiconductor elements such as (Complementary Metal-Oxide Semiconductor), sensor elements such as current sensor elements or magnetic sensor elements, micromachines in which minute electromechanical mechanisms are formed on the surface of a semiconductor substrate, so-called Various electronic elements such as MEMS (Micro electromechanical systems) elements are included. Also, the electronic element 200 may be a passive component such as a piezoelectric element, a capacitive element, or a resistor. Also, a plurality of electronic elements 200 may be mounted, and a plurality of types of elements may be included.

Mechanical connection of the electronic element 200 to the circuit board 100 is performed, for example, by a low-melting-point brazing material such as solder, an adhesive, or, if necessary, a bonding material (not shown) having electrical conductivity such as a conductive adhesive. . The electrical connection between the electrodes (no reference numerals) of the electronic element 200 and the circuit conductors 2 of the circuit board 100 is, for example, in addition to the connection by the connection members 210 such as bonding wires as shown in FIG. Electrical and mechanical connections can also be made by so-called flip-chip connections using metal bumps and conductive adhesives as connecting members 210 . In the case of flip-chip bonding, the mechanical connection can be reinforced with an underfill material.

When the sealing member 220 is composed of a lid 221 and a bonding material 222 as in the example shown in FIG. As the bonding material, metal bonding materials such as solder and brazing material, resin bonding materials such as resin adhesives and conductive adhesives, glass bonding materials, and the like can be used. When the sealing member 220 is a sealing resin, for example, an epoxy resin or an epoxy resin containing a filler can be used.

If the electronic element 200 is a semiconductor element such as a semiconductor integrated circuit element, various electrical signals are exchanged between the electronic element 200 and the electronic circuits (not shown) of the circuit board 100 and the external wiring board 400. Then, various processing such as calculation or storage is performed in the semiconductor device (electronic device 200). If the electronic element 200 is a sensor element such as an acceleration sensor element, physical quantities such as acceleration detected by the sensor element (electronic element 200) are transmitted to the circuit board 100 and the external wiring board 400 as electric signals. This electrical signal is transmitted to the electronic circuit of the circuit board 100 and the external wiring board 400 or other electronic elements (not shown) mounted on the circuit board 100, and the electronic equipment on which the circuit board 100 is mounted. It is used for processing such as control.

The manufactured electronic component 300 is electrically and mechanically connected to the wiring board 400 via the conductive bonding material 310 . That is, the example shown in FIG. An electronic module 500 such as is fabricated. The wiring board 400 may be a ceramic wiring board, or may be a printed wiring board in which resin such as epoxy is used as an insulating layer and metal such as copper foil is used as wiring 401 . The conductive bonding material 310 may be made of metal such as solder or brazing material, or may be a conductive adhesive.

In the above description, the circuit board 100 is a ceramic wiring board in which the insulating substrate 1 is made of a ceramic sintered body. can.

Reference Signs List 1 Insulating substrate 1a Insulating layer 1b Cavity 11 First surface (lower surface)
11o... Outer edge area 11c... Central area 12... Second surface (upper surface)
2 circuit conductor 21 terminal electrode 21a convex portion 22 connection electrode 23 inner conductor 3 central conductor 31 convex portion 32 concave portion 4 Corner pad 5 Mounting conductor 100 Circuit board 200 Electronic element 210 Connecting member 220 Sealing member 221 Lid 222 Joining material 300 Electronic component 310 Conductive bonding material 400 Wiring board 401 Wiring 500 Electronic module

Claims (6)

an insulating substrate having a first surface and a second surface located opposite to the first surface, wherein the first surface has a square shape in plan view;
a circuit conductor including a plurality of terminal electrodes positioned in an outer edge region of the first surface of the insulating substrate; and one central conductor positioned in a central region inside the outer edge region of the first surface. ,
the surface of the central conductor has a lattice shape with a plurality of irregularities,
the central conductor has a concave portion and a convex portion;
the recesses or protrusions located at the central portion of the central conductor are larger than those located at the outer edge of the central conductor;
or,
The circuit board , wherein the recesses or protrusions are smaller at a central portion of the central conductor than at an outer edge of the central conductor. 2. The circuit board according to claim 1, wherein said recess is located in the central portion of said central conductor. 3. The circuit board according to claim 1, wherein the thickness of the terminal electrode is equal to or greater than the thickness of the central conductor. 4. The circuit board according to any one of claims 1 to 3, wherein the terminal electrode has a convex portion on its surface. An electronic component comprising the circuit board according to any one of claims 1 to 4 and an electronic element. An electronic module comprising: the electronic component according to claim 5; and a module wiring board on which the electronic component is mounted.

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