Ceramic wiring member and method for manufacturing ceramic wiring member

Abstract

Provided is a ceramic wiring member that allows a wire to be stably bonded to a surface electrode. The ceramic wiring member comprises a body part and a surface electrode. The body part includes: a mounting part on which an electronic component is mounted; and an electrode formation part that is positioned outside the mounting part and in which the surface electrode is formed in such a manner that the surface electrode is embedded inward from a flat surface of the body part. The surface electrode has a rectangular shape in a plan view. In at least one of a cross section orthogonal to a first direction perpendicular to a pair of sides facing each other in a direction from the mounting part toward the surface electrode in the surface electrode having a rectangular shape in a plan view and a cross section orthogonal to a second direction perpendicular to the first direction in a plan view, at least a portion of an upper surface of the surface electrode that is adjacent to a flat surface of the electrode formation part is flat and is located at the same height as the flat surface of the electrode formation part, or at least a portion of the upper surface of the surface electrode that is adjacent to the flat surface of the electrode formation part is located lower than the flat surface of the electrode formation part in the thickness direction of the electrode formation part.

Description

Ceramic wiring member and method for manufacturing a ceramic wiring member

[0001] This disclosure relates to a ceramic wiring member and a method for manufacturing a ceramic wiring member. This application claims priority under Japanese Patent Application No. 2024-169334, filed on 27 September 2024, incorporating all the provisions contained herein.

[0002] Wire bonding is a technique that uses wires made of materials such as gold, aluminum, and copper to connect electrodes of electronic components such as semiconductor devices, integrated circuits, and solid-state image sensors to electrodes of ceramic wiring materials such as ceramic packages and ceramic circuit boards.

[0003] Referring to Figure 8, the ceramic package 100 is a ceramic wiring member capable of mounting electronic components 110 and protecting the electronic components 110 from the external environment. The ceramic package 100 has a cavity 101, and the electronic components 110 are mounted inside the cavity 101. The cavity 101 is hermetically sealed using a lid 102, thereby protecting the electronic components 110 from the external environment.

[0004] Furthermore, the ceramic package 100 plays a role in electrically connecting the electronic component 110 to the external circuit board 111. Surface electrodes 103, which serve as connection terminals to the electronic component 110, are formed on the flat surface of the ceramic package 100 by, for example, applying a conductive paste by screen printing. The tip of a wire 112, for example, made of gold wire, is joined to the electrode of the electronic component 110, and the wire 112 is joined to the surface electrode 103 while forming a loop. This electrically connects the electronic component 110 and the ceramic package 100. The ceramic package 100 also has a back electrode 105, which serves as a connection terminal for external connection, and is electrically connected to the circuit board 111 by, for example, solder 113. Although not shown in Figure 8, vias, wiring, and inner layer electrodes are formed inside the ceramic package 100.

[0005] In recent years, electronic devices have become smaller and more highly integrated, which has led to an increase in the number of electrodes in electronic components 110 and a reduction in the size of the wires 112. Therefore, it is necessary to increase the number of surface electrodes 103 for wire bonding while narrowing their width and forming them at narrow intervals on the ceramic package 100. Here, the surface electrodes 103 for wire bonding are formed by screen printing, but when the width of the surface electrode 103 is narrowed, the shape of the cross-section of the electrode top surface 104 becomes a curved shape that is convex upward, such as a semicircle or semiellipse, as shown in Figure 9(C). When the shape of the cross-section of the electrode top surface 104 becomes a curved shape that is convex upward, the bonding area between the surface electrode 103 and the wire 112 decreases. As a result, the surface electrode 103 and the wire 112 are bonded unstablely, which can lead to connection failures.

[0006] Patent Document 1 discloses the following technique for flattening the upper surface of a surface electrode for wire bonding: A conductive paste, which is the material for the surface electrode, is applied to the surface of a green sheet, which is the base material for the ceramic substrate, and then a portion of the conductive paste is embedded in the green sheet. As a result, the upper surface of the surface electrode formed on the ceramic substrate is flattened by etching the portion that protrudes from the surface of the ceramic substrate.

[0007] Japanese Patent Application Publication No. 10-125719

[0008] However, in Patent Document 1, the cross-sectional shape of the upper surface of the surface electrode is gently curved upwards, but it is not flat. Therefore, there is a problem in that the bonding stability is poor when a wire is joined to the upper surface of the surface electrode.

[0009] One of the objectives of this disclosure is to provide a ceramic wiring member that can stably bond wires to surface electrodes, and a method for manufacturing the ceramic wiring member.

[0010] A ceramic wiring member according to this disclosure comprises a main body and a surface electrode. In the ceramic wiring member according to this disclosure, the main body includes a mounting portion on which an electronic component is mounted, and an electrode forming portion located outside the mounting portion and on which the surface electrode is formed so as to be embedded inward from the flat surface of the main body. The surface electrode has a rectangular shape in plan view. At least a portion of the upper surface of the surface electrode adjacent to the flat surface of the electrode forming portion is flat in at least one of a cross section perpendicular to a first direction perpendicular to a pair of opposing sides in the direction from the mounting portion toward the surface electrode in a rectangular surface electrode in plan view, and a cross section perpendicular to a second direction perpendicular to the first direction in plan view, and is located at the same height as the flat surface of the electrode forming portion, or is located lower than the flat surface of the electrode forming portion in the thickness direction of the electrode forming portion.

[0011] A method for manufacturing a ceramic wiring member according to this disclosure includes the steps of: forming a laminate of a ceramic green sheet and an absorbent layer; forming a surface electrode on the absorbent layer; embedding the surface electrode in the absorbent layer by pressurization; and firing the green sheet laminate containing the laminate in which the surface electrode is embedded.

[0012] According to this disclosure, a ceramic wiring member can be provided that can stably bond wires for wire bonding to surface electrodes.

[0013] Figure 1 is a cross-sectional view showing the schematic shape of a ceramic wiring member according to this disclosure. Figures 2(A) to 2(C) are plan views of a surface electrode. Figures 3(A) and 3(B) are cross-sectional views when the surface electrode is cut along a vertical plane including the line A-A in Figure 2. Figures 4(A) and 4(B) are cross-sectional views when the surface electrode is cut along a vertical plane including the line A-A in Figure 2. Figure 5 is a schematic diagram showing the manufacturing process of a ceramic wiring member according to this disclosure. Figure 6 is a schematic diagram showing the manufacturing process of a ceramic wiring member according to this disclosure. Figures 7(A) and 7(B) are schematic cross-sectional views showing a part of the process for forming a surface electrode in the manufacturing process of a ceramic wiring member according to this disclosure. Figure 8 is a schematic cross-sectional view showing the configuration of a conventional ceramic package. Figures 9(A) to 9(C) are schematic cross-sectional views showing a part of the process for forming a surface electrode provided in a conventional ceramic package. Figure 9(A) is a cross-sectional view showing the state after conductive paste has been printed on the surface of the green sheet and dried. Figure 9(B) is a cross-sectional view showing the state after the green sheet has been pressed and the conductive paste has been embedded within the green sheet. Figure 9(C) is a cross-sectional view showing the state after the green sheet laminate has been fired and surface electrodes have been formed on the ceramic substrate.

[0014] [Summary of Embodiments] First, embodiments of ceramic wiring members according to this disclosure will be listed and described.

[0015] A ceramic wiring member according to a first aspect of the present disclosure comprises a main body and a surface electrode. In the ceramic wiring member according to a first aspect of the present disclosure, the main body includes a mounting portion on which an electronic component is mounted, and an electrode forming portion located outside the mounting portion and on which the surface electrode is formed so as to be embedded inward from the flat surface of the main body. The surface electrode has a rectangular shape in plan view. In a rectangular surface electrode in plan view, in at least one of a cross section perpendicular to a first direction perpendicular to a pair of opposing sides in the direction from the mounting portion toward the surface electrode and a cross section perpendicular to a second direction perpendicular to the first direction in plan view, at least a portion of the upper surface of the surface electrode adjacent to the flat surface of the electrode forming portion is flat and at the same height as the flat surface of the electrode forming portion, or at least a portion of the upper surface of the surface electrode adjacent to the flat surface of the electrode forming portion is located lower than the flat surface of the electrode forming portion in the thickness direction of the electrode forming portion.

[0016] Furthermore, "same height" does not necessarily mean that the flat surface of the electrode formation area and the top surface of the surface electrode are at exactly the same height. For example, if the height difference between the flat surface of the electrode formation area and the top surface of the surface electrode is within 3 μm, they are considered to be at the same height. Also, "flat" does not necessarily mean perfectly flat; minute irregularities are acceptable. For example, if the difference in irregularities (the difference in height between the highest peak and the lowest valley) is within 5 μm, the top surface of the surface electrode is considered flat.

[0017] In the ceramic wiring member according to the first aspect of this disclosure, at least a portion of the upper surface of the surface electrode is flat and located at the same height as the flat surface of the electrode forming portion, or at a lower position than the flat surface of the electrode forming portion. Therefore, by joining the wire for wire bonding to the flat portion of the upper surface of the surface electrode that is at the same height as the flat surface of the electrode forming portion, or to the portion that is at a lower position than the flat surface of the electrode forming portion, the bonding area between the surface electrode and the wire is increased. As a result, the ceramic wiring member according to the first aspect of this disclosure allows the wire to be strongly bonded to the surface electrode. Consequently, the reliability and durability of the wire bonding can be improved.

[0018] As a ceramic wiring member according to a second aspect of the present disclosure, the ceramic wiring member according to the first aspect described above can be configured such that, in at least one cross-section, the upper surface of a surface electrode located lower than the flat surface of the electrode forming portion is flat, or the upper surface of a surface electrode located lower than the flat surface of the electrode forming portion is curved convexly toward the inside of the electrode forming portion.

[0019] As a ceramic wiring member according to a third aspect of this disclosure, the ceramic wiring member according to the first or second aspect described above can be configured such that at least a portion of the lower surface of the surface electrode is curved convexly toward the inside of the electrode forming portion opposite to the upper surface in at least one cross-section. According to the ceramic wiring member according to the third aspect, since at least a portion of the lower surface of the surface electrode is a convex curved surface that curves convexly toward the inside of the electrode forming portion, the stress when a wire is joined to the surface electrode can be relieved. As a result, the reliability of wire bonding can be improved.

[0020] As a ceramic wiring member according to the fourth aspect of this disclosure, a ceramic wiring member according to any one of the first to third aspects described above can be configured such that the width of the surface electrode is 30 μm or more and 300 μm or less. According to the ceramic wiring section of the fourth aspect, a large number of surface electrodes can be provided on the ceramic wiring member at narrow intervals. As a result, a ceramic wiring member with high wiring density can be provided. In addition, stable surface electrodes can be formed.

[0021] As a ceramic wiring member according to the fifth aspect of this disclosure, a ceramic wiring member according to any one of the first to fourth aspects described above can be configured such that the thickness of the surface electrode is 3 μm or more and 50 μm or less. According to the ceramic wiring portion of the fifth aspect, the adhesion strength of the surface electrode to the electrode formation portion can be improved. Furthermore, a stable surface electrode can be formed.

[0022] As a ceramic wiring member according to the sixth aspect of this disclosure, a ceramic wiring member according to any one of the first to fifth aspects described above has a surface electrode whose upper surface includes, in a plan view, a first side on the side closer to the mounting part and a second side on the side further from the mounting part along the first direction, and between at least 20% and 40% of the total length of the surface electrode in the first direction from the first side, the upper surface of the surface electrode in a cross-section perpendicular to the first direction is flat and at the same height as the flat surface of the electrode forming part, or the upper surface of the surface electrode in a cross-section perpendicular to the first direction is lower than the flat surface of the electrode forming part. In wire bonding, it is common for the wire to be joined to the vicinity of that portion along the total length of the surface electrode in the first direction. Therefore, the reliability of wire bonding can be improved according to the ceramic wiring member according to the sixth aspect.

[0023] As a ceramic wiring member according to the seventh aspect of this disclosure, a ceramic wiring member according to any one of the first to seventh aspects described above can be configured such that, between at least 10% and 90% of the total length of the surface electrode in the second direction, the upper surface of the surface electrode in a cross-section perpendicular to the second direction is flat and at the same height as the flat surface of the electrode forming portion, or the upper surface of the surface electrode in a cross-section perpendicular to the second direction is lower than the flat surface of the electrode forming portion. In wire bonding, it is common for the wire to be joined to the vicinity of that portion along the total length of the surface electrode in the second direction. Therefore, the reliability of wire bonding can be improved according to the ceramic wiring member according to the seventh aspect.

[0024] As a ceramic wiring member according to the eighth aspect of this disclosure, a ceramic wiring member according to any one of the first to eighth aspects described above can be configured such that the upper surface of the surface electrode is flat over its entire surface and at the same height as the flat surface of the electrode forming portion, or is lower than the flat surface of the electrode forming portion over its entire surface. According to the ceramic wiring portion of the eighth aspect, the upper surface of the surface electrode does not protrude above the surface of the electrode forming portion. Therefore, the bonding area between the surface electrode and the wire is increased, allowing the wire to be strongly bonded to the surface electrode. As a result, the reliability and durability of the wire bonding can be improved.

[0025] A method for manufacturing a ceramic wiring member according to a first aspect of the present disclosure includes the steps of forming a laminate of a ceramic green sheet and an absorbent layer, forming a surface electrode on the absorbent layer, embedding the surface electrode in the absorbent layer by pressurization, and firing a green sheet laminate including the laminate in which the surface electrode is embedded.

[0026] According to the method for manufacturing a ceramic wiring member according to the first aspect of this disclosure, a ceramic wiring member in accordance with this disclosure can be manufactured without polishing the upper surface of the surface electrodes or the like after sintering.

[0027] [Specific Examples of Embodiments] Next, specific embodiments of the ceramic wiring member of the present disclosure will be described with reference to the drawings. In the following drawings, the same or corresponding parts are denoted by the same reference numerals, and their descriptions will not be repeated.

[0028] [Description of the Structure of the Ceramic Wiring Member] Figure 1 is a schematic cross-sectional view showing the configuration of a ceramic wiring member 1 according to an embodiment of the present disclosure. The ceramic wiring member 1 of this embodiment is a ceramic package that can mount an electronic component 10 and protects the electronic component 10 from the external environment. The ceramic wiring member 1 comprises a main body portion 2 and a conductive portion formed of a conductive material.

[0029] The conductive portion includes a surface electrode 3 for wire bonding, which serves as a connection terminal to the electronic component 10; a back electrode 4, which serves as a connection terminal for external connections; and an inner layer electrode 5 provided inside the main body 2. Although not shown in Figure 1, the conductive portion also includes vias and wiring provided inside the main body 2, etc. The conductive portion is formed from a conductive material containing, for example, at least one of tungsten (W), molybdenum (Mo), and copper (Cu).

[0030] The main body 2 is made of ceramic. The ceramic material used to make up the main body 2 is, for example, alumina (Al ２ O ３ ), Zirconia (ZrO ２ Examples include silicon dioxide (SiO₂), silicon carbide (SiC). The ceramic constituting the main body 2 may have silicon dioxide (SiO₂) as a sintering aid. ２ ), calcium oxide (CaO), magnesium oxide (MgO), manganese oxide (MnO, Mn ２ O ３ ), and calcium carbonate (CaCO3) ３ It may include at least one selected from the group consisting of ). The ceramic constituting the main body 2 may contain other components.

[0031] The main body 2 includes a plate-like portion 20 and a frame portion 23. The plate-like portion 20 is flat and has a pair of parallel main surfaces, a first main surface 21 and a second main surface 22, which are spaced apart in the thickness direction. The first main surface 21 includes a mounting portion 21A on which electronic components 10 such as semiconductor elements, integrated circuits, and solid-state image sensors are mounted. The second main surface 22 constitutes the surface on which the back electrode 4 is formed. The planar shape of the plate-like portion 20 (shape viewed in a direction perpendicular to the main surfaces) is not particularly limited, but in this embodiment it is a square shape, for example, a rectangle.

[0032] The frame portion 23 is cylindrical and rises from the first main surface 21 of the plate-shaped portion 20. The frame portion 23 defines the cavity 29, which is the space on the first main surface 21 of the plate-shaped portion 20. In other words, the ceramic wiring member 1 has a cavity 29 surrounded by the frame portion 23 on the first main surface 21 of the plate-shaped portion 20. The electronic component 10 is mounted on the mounting portion 21A inside the cavity 29. The planar shape of the frame portion 23 is not particularly limited, but in this embodiment, both the outer and inner circumferences are square, for example, rectangular, and the outer circumference of the frame portion 23 is the same size as the outer circumference of the plate-shaped portion 20 and follows the outer circumference of the plate-shaped portion 20.

[0033] In this embodiment, the frame portion 23 is composed of two parts with different inner circumferences. The frame portion 23 includes an electrode forming portion 24 with a small inner circumference formed on the plate-shaped portion 20, and a lid mounting portion 26 with a large outer circumference formed on the electrode forming portion 24. The electrode forming portion 24 is located inside the lid mounting portion 26 and outside the mounting portion 21A, and has a flat, annular surface 25 surrounded by the lid mounting portion 26. The lid 6 is attached to the flat, annular upper end surface of the lid mounting portion 26, for example, via an adhesive layer 8. When the lid 6 is attached to the main body portion 2, the cavity 29 is hermetically sealed. As a result, the electronic component 10 is protected from the external environment by preventing atmospheric gases such as water vapor from entering with high airtightness. The lid 6 can be made of, for example, metal, ceramic, or resin. If the electronic component 10 is a solid-state image sensor, a transparent plate such as a glass plate is used for the lid 6.

[0034] Referring to FIGS. 1 and 2, a plurality of surface electrodes 3 serving as connection terminals with the electronic component 10 are formed at intervals on the flat surface 25 of the electrode forming portion 24. The ceramic package serves to electrically connect the electronic component 10 to an external circuit board 11. Each surface electrode 3 is connected to a corresponding electrode among the plurality of electrodes provided on the electronic component 10 by wire bonding, whereby the electronic component 10 and the ceramic package are electrically connected. In FIG. 2, the position of the A-A line of the surface electrode 3 indicates the position where the wire 12 is joined to the surface electrode 3. The wire 12 connecting the surface electrode 3 and the electrode of the electronic component 10 is an elongated wire formed of gold, aluminum, copper, or the like. The wire 12 has a tip end joined to the electrode of the electronic component 10, extends toward the surface electrode 3 while forming a loop, and has an end opposite to the tip end joined to the surface electrode 3.

[0035] Referring to Figures 1 and 2, the planar shape of the surface electrode 3 in this embodiment is a longitudinal shape (a shape in which the length is greater than the width) extending along the direction from the inner circumference to the outer circumference of the frame portion 23, for example, a vertically elongated rectangle. The longitudinal direction of the surface electrode 3 coincides with the axial direction in which the wire 12 connecting the surface electrode 3 and the electrode of the electronic component 10 extends. Also, the longitudinal direction of the surface electrode 3 coincides with a first direction perpendicular to a pair of opposing sides 32, 33 in the direction from the mounting portion 21A toward the surface electrode 3 in a rectangular surface electrode 3 when viewed from above. Referring to Figure 2(B), the planar shape of the surface electrode 3 may be a horizontally elongated rectangle in which the width is greater than the length. Alternatively, referring to Figure 2(C), the planar shape of the surface electrode 3 may be a type of rectangle, a square shape in which the lengths of the four sides are equal. Furthermore, the rectangular shape includes, for example, a shape in which at least one corner is beveled at a certain angle to form a straight line in plan view, i.e., a chamfered shape, as well as a shape in which at least one corner is a smooth curve, i.e., a chamfered shape, and a shape in which at least one corner is recessed. In addition, the rectangular shape includes parallelograms and trapezoids in which a pair of opposing sides 34, 35 in a second direction perpendicular to the first direction are not at a right angle to the other pair of sides 32, 33 but are only slightly (for example, within 5°) of a right angle. The rectangular planar shape of the surface electrode 3 allows for the formation of more surface electrodes 3 within the limited width of the electrode forming section 24. The number of wires 12 connected to the surface electrode 3 may be one or two or more.

[0036] Referring to Figures 1 and 3, the surface electrode 3 is formed on the electrode forming portion 24 such that it is embedded inside the electrode forming portion 24 from the flat surface 25 of the electrode forming portion 24. In other words, on the flat surface 25 of the electrode forming portion 24, a recess 27 is formed that is indented from the flat surface 25 in the direction of the plate-like portion 20, and the surface electrode 3 is embedded in the recess 27.

[0037] The upper surface 30 of the surface electrode 3 to which the wire 12 is joined is exposed. The upper surface 30 of the surface electrode 3 includes portions that do not protrude upward from the flat surface 25 of the adjacent electrode forming portion 24. In other words, at least a portion of the upper surface 30 of the surface electrode 3 is flat throughout its entire length from one end to the other in a cross-section perpendicular to the axial direction of the wire 12 (a cross-section perpendicular to the longitudinal direction of the surface electrode 3, a cross-section perpendicular to the first direction), and is located at the same height as the flat surface 25 of the electrode forming portion 24 in the thickness direction of the electrode forming portion 24. Alternatively, at least a portion of the upper surface 30 of the surface electrode 3 is located lower than the flat surface 25 of the electrode forming portion 24 in its entire length from one end to the other in a cross-section perpendicular to the first direction, that is, it is located below the flat surface 25 of the electrode forming portion 24. In other words, the upper surface 30 of the surface electrode 3 should be flat in at least a portion of the entire area from one end to the other in a cross-section perpendicular to the first direction, and should be at the same height as the flat surface 25 of the electrode forming portion 24, or at a lower position than the flat surface 25 of the electrode forming portion 24.

[0038] Specifically, as shown in FIG. 3(A), the upper surface 30 of the surface electrode 3 may include a portion that is flat over the entire area from one end to the other end of the upper surface 30 in a cross-section orthogonal to the first direction. Here, "flat" is not limited to being completely flat, and minute irregularities are allowed. For example, when the difference in irregularities (the difference in height between the highest peak and the lowest valley) on the upper surface 30 of the surface electrode 3 is within a range of 5 μm, the upper surface 30 of the surface electrode 3 is regarded as flat. When the upper surface 30 of the surface electrode 3 is a flat surface, the upper surface 30 is located at the same height as the flat surface 25 of the electrode formation portion 24 and is flush and connected to the flat surface 25. Here, "the same height" is not limited to the case where the flat surface 25 of the electrode formation portion 24 and the upper surface 30 of the surface electrode 3 are exactly at the same height. For example, when the difference in height between the flat surface 25 of the electrode formation portion 24 and the upper surface 30 of the surface electrode 3 is within a range of 3 μm, both are regarded as being located at the same height. In addition, at least a part of the upper surface 30 of the surface electrode 3 may be flat over the entire area from one end to the other end of the upper surface 30 in a cross-section orthogonal to the second direction perpendicular to the first direction in a plan view and may be located at the same height as the flat surface 25 of the electrode formation portion 24.

[0039] Furthermore, as shown in Figure 3(B), the upper surface 30 of the surface electrode 3 may include a portion that curves downward inward toward the inside of the electrode forming portion 24 in a cross-section perpendicular to the first direction, from one end to the other. In other words, at least a portion of the upper surface 30 of the surface electrode 3 may be a concave curved surface that gradually approaches the flat surface 25 of the electrode forming portion 24 as it moves away from the most concave position. If the upper surface 30 of the surface electrode 3 is uneven, the upper surface 30 is considered to be curved downward inward if the approximate curve of the upper surface 30 is downward convex. If the upper surface 30 of the surface electrode 3 is a concave curved surface, the upper surface 30 is located lower than the flat surface 25 of the electrode forming portion 24. Both ends of the upper surface 30 in the width direction are connected to the flat surface 25 of the electrode forming portion 24 by being at the same height as the flat surface 25. Here, "same height" is not limited to the flat surface 25 of the electrode forming portion 24 and both ends in the width direction of the upper surface 30 of the surface electrode 3 being at exactly the same height. For example, if the height difference between the flat surface 25 of the electrode forming portion 24 and both ends in the width direction of the upper surface 30 of the surface electrode 3 is within 3 μm, they are considered to be at the same height. If the upper surface 30 of the surface electrode 3 is a concave curved surface, the cross-sectional shape of the upper surface 30 is, for example, a circular arc shape or an elliptical arc shape. At least a portion of the upper surface 30 of the surface electrode 3 may be curved in a convex shape toward the inside of the electrode forming portion 24 in a cross-section perpendicular to the second direction, from one end to the other of the upper surface 30.

[0040] Furthermore, in the case where at least a portion of the upper surface 30 of the surface electrode 3 is flat, as shown in Figure 3(A), both ends of the upper surface 30 of the surface electrode 3 in the width direction do not need to be connected to the flat surface 25 of the electrode forming portion 24, as shown in Figure 4(A). In other words, at least a portion of the upper surface 30 of the surface electrode 3 may be lower than the flat surface 25 of the electrode forming portion 24 over its entire length from one end to the other. Note that in the example of Figure 4(A), the upper surface 30 of the surface electrode 3 may be uneven.

[0041] Furthermore, in the case where at least a portion of the upper surface 30 of the surface electrode 3 is a concave curved surface, as shown in Figure 3(B), both ends of the upper surface 30 of the surface electrode 3 in the width direction do not need to be connected to the flat surface 25 of the electrode forming section 24, as shown in Figure 4(B). In other words, both ends of the upper surface 30 of the surface electrode 3 in the width direction may be located lower than the flat surface 25 of the electrode forming section 24.

[0042] As described above, at least a portion of the upper surface 30 of the surface electrode 3 adjacent to the flat surface 25 of the electrode forming portion 24 should be flat throughout its entire length from one end to the other in at least one of the cross-sections perpendicular to the first direction and the cross-section perpendicular to the second direction, and should be at the same height as the flat surface 25 of the electrode forming portion 24, or should be lower than the flat surface 25 of the electrode forming portion 24 throughout its entire length from one end to the other. Furthermore, the upper surface 30 that is lower than the flat surface 25 of the electrode forming portion 24 in at least one of the cross-sections perpendicular to the first direction and the cross-section perpendicular to the second direction is preferably flat throughout its entire length from one end to the other, or preferably curved convexly toward the inside of the electrode forming portion 24 throughout its entire length from one end to the other. The state of the upper surface 30 of the surface electrode 3 can be confirmed by cross-sectional observation of the surface electrode 3 using a SEM.

[0043] On the upper surface 30 of the surface electrode 3, the portion located at the same height as the flat surface 25 of the electrode forming portion 24, or the portion located lower than the flat surface 25 of the electrode forming portion 24, is preferably provided within the following range. Specifically, referring to Figure 2(A), in the surface electrode 3, along the first direction, the end closer to the mounting portion 21A is defined as the first side 32 (one of the pair of short sides in the illustrated example), the end further from the mounting portion 21A is defined as the second side 33 (the other of the pair of short sides in the illustrated example), and the total length of the surface electrode 3 in the first direction is defined as length L. On the upper surface 30 of the surface electrode 3, the portion located at the same height as the flat surface 25 of the electrode forming portion 24, or located lower than the flat surface 25 of the electrode forming portion 24, preferably occupies the portion between at least 20% (2L / 10 in Figure 2(A)) and 40% (4L / 10 in Figure 2(A)) of the length L of the surface electrode 3 from the first side 32, more preferably occupying the portion between at least 10% and 70% of the length L of the surface electrode 3, even more preferably occupying the portion between at least 5% and 80% of the length L of the surface electrode 3, and most preferably occupying the portion between the first side 32 and the second side 33 of the surface electrode 3.

[0044] Furthermore, on the upper surface 30 of the surface electrode 3, the portion located at the same height as the flat surface 25 of the electrode forming portion 24, or the portion located lower than the flat surface 25 of the electrode forming portion 24, is preferably provided within the following range. Specifically, referring to Figure 2(A), in the surface electrode 3, one end in the second direction is defined as the third side 34 (one of the pair of long sides in the illustrated example), the other end in the second direction is defined as the fourth side 35 (the other of the pair of long sides in the illustrated example), and the total length of the surface electrode 3 in the second direction is defined as the width W. On the upper surface 30 of the surface electrode 3, the portion located at the same height as the flat surface 25 of the electrode forming portion 24, or the portion located lower than the flat surface 25 of the electrode forming portion 24, preferably occupies the portion between at least 10% of the width W of the surface electrode 3 from the third side 34 (the W / 10 position in Figure 2(A)) and 90% (the 9W / 10 position in Figure 2(A)), and most preferably occupies the portion between the third side 34 and the fourth side 35 of the surface electrode 3.

[0045] As described above, it is most preferable that the upper surface 30 of the surface electrode 3 is at the same height as the flat surface 25 of the electrode forming section 24, or lower than the flat surface 25 of the electrode forming section 24, throughout its entire surface. This prevents the upper surface 30 of the surface electrode 3 from protruding above the flat surface 25 of the electrode forming section 24. As a result, the bonding area between the surface electrode 3 and the wire 12 is increased. Therefore, the wire 12 can be strongly bonded to the surface electrode 3, improving the reliability and durability of the wire bonding.

[0046] The surface electrode 3 may be covered with a plating layer to improve the reliability of the connection with the wire 12. When the surface electrode 3 is covered with a plating layer, the surface electrode 3 is connected to the wire 12 via the plating layer. The plating layer is composed of, for example, a nickel plating film, or a laminated film in which a gold plating film is formed on top of the nickel plating film. The plating layer is formed on the surface electrode 3 to have a predetermined thickness, for example by electroplating. Regarding the thickness of the plating layer, the thickness of the nickel plating film is, for example, 1 μm to 10 μm, and the thickness of the gold plating film is, for example, 0.1 μm to 2 μm. When the surface electrode 3 is covered with a plating layer, the plating layer covering the surface electrode 3 may protrude upward from the flat surface 25 of the electrode forming portion 24. Alternatively, the plating layer may be composed of, for example, a nickel plating film, a laminated film in which a palladium plating film is formed on top of the nickel plating film, and a gold plating film is formed on top of the palladium plating film. In this case, the thickness of the plating layer is, for example, 1 μm to 10 μm for the nickel plating film, 0.05 to 2.0 μm for the palladium plating film, and 0.05 μm to 2 μm for the gold plating film.

[0047] Referring to Figure 3, at least a portion of the lower surface 31 of the surface electrode 3 that contacts the recess 27 of the electrode forming portion 24 may be curved such that, for example, in a cross section perpendicular to the first direction, it protrudes downward inward toward the electrode forming portion 24 over its entire length from one end to the other. In other words, at least a portion of the lower surface 31 of the surface electrode 3 may be a convex curved surface that gradually approaches the flat surface 25 of the electrode forming portion 24 as it moves away from the most protruding position. When the lower surface 31 of the surface electrode 3 is a convex curved surface that curves downward, the cross-sectional shape of the lower surface 31 may be, for example, a circular arc shape or an elliptical arc shape. The lower surface 31 of the surface electrode 3 may include, for example, a portion that curves downward inward toward the electrode forming portion 24 in a cross section perpendicular to the second direction.

[0048] During wire bonding, the wire 12 is joined to the surface electrode 3 using a jig called a capillary while applying pressure and heating. If the lower surface 31 of the surface electrode 3 is a convex curved surface, the stress when the wire 12 is joined to the surface electrode 3 can be reduced, thus enabling stable bonding by wire bonding.

[0049] Referring to Figure 3, the width (total length in the second direction) W of the surface electrode 3 is not particularly limited, but is preferably 30 μm or more and 300 μm or less, and preferably 50 μm or more and 250 μm or less. A width W of 300 μm or less of the surface electrode 3 allows numerous surface electrodes to be provided on the ceramic wiring member at narrow intervals, thus providing a ceramic wiring member with high wiring density. A width W of 30 μm or more of the surface electrode 3 allows the surface electrode 3 to be easily formed by printing, thus enabling the formation of a stable surface electrode 3. On the other hand, the length L of the surface electrode 3 is not particularly limited, but is, for example, 200 μm or more and 750 μm or less.

[0050] Referring to FIG. 3, the thickness T of the surface electrode 3 (the distance between the highest part and the lowest part of the surface electrode 3) is not particularly limited, but is preferably 3 μm or more, more preferably 5 μm or more, and even more preferably 16 μm or more. When the thickness T of the surface electrode 3 is 3 μm or more, the adhesion strength of the surface electrode 3 to the electrode formation portion 24 can be increased. On the other hand, the thickness T of the surface electrode 3 is preferably 50 μm or less, more preferably 40 μm or less, and even more preferably 30 μm or less. When the thickness T of the surface electrode 3 is 50 μm or less, the surface electrode 3 can be easily formed by printing, so that a stable surface electrode 3 can be formed.

[0051] Referring to FIG. 1, a plurality of back surface electrodes 4 serving as connection terminals with the circuit board 11 are formed on the second main surface 22 of the plate-like portion 20 at intervals. The back surface electrode 4 is formed on the second main surface 22 of the plate-like portion 20 so as to protrude from the second main surface 22.

[0052] The back surface electrode 4 may be covered with a plating layer 7 for the purpose of enhancing the reliability of bonding with the solder 13. When the back surface electrode 4 is covered with the plating layer 7, the back surface electrode 4 is bonded to the solder 13 via the plating layer 7. When the back surface electrode 4 is covered with the plating layer 7, the plating layer 7 covering the back surface electrode 4 may protrude downward from the second main surface 22 of the plate-like portion 20.

[0053] [Explanation of the manufacturing method of the ceramic wiring member] FIGS. 5 and 6 schematically show the manufacturing method of the ceramic wiring member 1. First, referring to FIG. 5(a), a ceramic green sheet 9 is prepared. The ceramic wiring member 1 is composed of a green sheet laminate in which a plurality of ceramic green sheets 9 are laminated. The ceramic green sheet 9 is, for example, a sheet in which a layer containing a ceramic material is formed on a support film of polyethylene terephthalate (PET).

[0054] As the ceramic material, for example, alumina (Al ２ O ３ ), zirconia (ZrO ２Examples include silicon dioxide (SiO₂) and silicon carbide (SiC). Ceramic materials may also include silicon dioxide (SiO₂) as a sintering aid. ２ ), calcium oxide (CaO), magnesium oxide (MgO), manganese oxide (MnO, Mn ２ O ３ ), and calcium carbonate (CaCO3) ３ The ceramic material may contain at least one selected from the group consisting of ). The ceramic material may contain glass components such as lithium silicate glass and ZnO glass. The ceramic material may contain inorganic components such as aluminum (Al), silicon (Si), calcium (Ca), manganese (Mn), and magnesium (Mg).

[0055] The ceramic green sheet 9 is manufactured, for example, by the following method: Pre-dried ceramic material powder is weighed in a predetermined ratio, and resin, plasticizer, solvent, dispersant, etc. are added and mixed using a mixer to obtain a slurry containing the ceramic material powder. Grinding may be performed simultaneously with mixing. After degassing the slurry by reduced pressure, the slurry is coated onto a support film using a casting method such as the doctor blade method or the lip coater method and dried. This produces the ceramic green sheet 9.

[0056] The thickness of the ceramic green sheet 9 is adjusted to a desired thickness after sintering. For example, the thickness of the ceramic green sheet 9 is between 10 μm and 500 μm. The planar dimensions of the ceramic green sheet 9 are between 10 mm × 10 mm and 300 mm × 300 mm.

[0057] Next, a green sheet laminate that will become the main body 2 is formed using multiple ceramic green sheets 9. For example, referring to Figure 5(b), the portion that will become the electrode formation portion 24 is formed using the ceramic green sheets 9. Specifically, an absorption layer 90 is formed on one main surface of the ceramic green sheet 9. In Figure 5(b), the portion that will become the electrode formation portion 24 is formed using one ceramic green sheet 9, but the portion that will become the electrode formation portion 24 may be formed using multiple ceramic green sheets 9.

[0058] The absorbent layer 90 is a layer formed from a predetermined composition. The composition forming the absorbent layer 90 (absorbent layer composition) includes inorganic and organic components. The inorganic component is the same as the ceramic material contained in the ceramic green sheet 9. The organic component includes a resin and a plasticizer. The inclusion of a resin and a plasticizer in the absorbent layer composition allows the absorbent layer 90 to bond the ceramic green sheets 9 together well, and also allows the absorbent layer 90 to deform appropriately to conform to the shape of the ceramic green sheet 9 and the conductive paste 91 that forms the surface electrode 3. The resin content in the absorbent layer composition is, for example, 65 vol% to 90 vol% relative to 100 vol% of the inorganic component material powder in the absorbent layer composition. The plasticizer content in the absorbent layer composition is, for example, 16 vol% to 40 vol% relative to 100 vol% of the inorganic component material powder in the absorbent layer composition.

[0059] The absorbent layer 90 can be formed, for example, by screen printing a slurry containing an inorganic component, an organic component, and a dispersant added as needed, as the absorbent layer composition, and then drying it.

[0060] By forming the absorption layer 90 using the above-described absorption layer composition, the storage modulus of the absorption layer 90 in the temperature range (lamination temperature range) during the lamination of the ceramic green sheets 9 described later becomes lower than the storage modulus of the absorption layer 90 in the room temperature range, making the absorption layer 90 more susceptible to plastic deformation during the lamination of the ceramic green sheets 9. The storage modulus of the absorption layer composition in the above-described lamination temperature range is, for example, 1.60 × 10⁻⁶. ７ Pa or more 2.00×10 ８ It is less than Pa. The storage modulus of the ceramic green sheet 9 is, for example, 2.00 × 10⁻⁶. ８ The above 4.00 x 10 ８ It is less than or equal to Pa.

[0061] Next, referring to Figure 5(c), a conductive paste 91 for forming the surface electrode 3 is applied to the laminate of the ceramic green sheet 9 and the absorption layer 90, for example, by screen printing onto the absorption layer 90 formed on one main surface of the ceramic green sheet 9, and then dried. The conductive paste 91 contains conductive material powder, resin, and solvent, and is applied to the absorption layer 90 according to a predetermined shape of the surface electrode 3. The width of the conductive paste 91 to be applied is not particularly limited, but is for example 36 μm to 360 μm. As a result, the width of the formed surface electrode 3 is for example 30 μm to 300 μm. The thickness of the conductive paste 91 to be applied is not particularly limited, but is for example 3.6 μm to 100 μm. As a result, the thickness of the formed surface electrode 3 is for example 3 μm to 50 μm. As a result, when the conductive paste 91 is embedded inside the green sheet 9 by heat pressing during the formation of the green sheet laminate described later, as shown in Figure 7(B), the lower surface of the conductive paste 91 tends to become a convex curved surface that curves downward. Although not shown in Figure 5(c), vias and the like can be formed in the laminate of the ceramic green sheet 9 and the absorption layer 90 by, for example, forming through holes that penetrate in the thickness direction and then filling the through holes with conductive paste, if necessary.

[0062] Next, referring to Figure 5(d), a cavity 29 is formed in the laminate of the ceramic green sheet 9 and the absorption layer 90. This results in a laminate of the ceramic green sheet 9 and the absorption layer 90 that constitutes the electrode forming portion 24 of the main body 2.

[0063] Similarly, the ceramic green sheet 9 is used to form the plate-like portion 20 and, if necessary, the lid mounting portion 26. Specifically, referring to Figure 6(a), a conductive paste 92 for forming the back electrode 4 is applied to one main surface of the ceramic green sheet 9, and then it is dried. Furthermore, if necessary, a conductive paste for forming the inner layer electrode is applied to the other main surface of the ceramic green sheet 9, or vias are formed on the ceramic green sheet 9. This gives the ceramic green sheet 9 that constitutes the plate-like portion 20. A cavity 29 is also formed in the ceramic green sheet 9. This gives the ceramic green sheet 9 that constitutes the lid mounting portion 26. In Figure 6(a), the plate-like portion 20 and the lid mounting portion 26 are formed using one ceramic green sheet 9, but multiple ceramic green sheets 9 may be used to form the plate-like portion 20 and the lid mounting portion 26.

[0064] Next, referring to Figure 6(b), the laminate of the ceramic green sheet 9 and the absorption layer 90 that constitute the electrode forming portion 24 and the ceramic green sheet 9 that constitutes the plate-like portion 20 are laminated together, and then the two are heated and pressed together using a press or the like to form a laminate. The temperature and pressure used when forming this laminate are, for example, a temperature of 60°C to 120°C and a pressure of 10 kgf / cm². ２ More than 70kgf / cm ２ The process is as follows: During this step, the conductive paste 91, which will become the surface electrode 3, is embedded in the absorption layer 90. Specifically, the absorption layer 90 undergoes appropriate plastic deformation during heat bonding, so that the conductive paste 91, which will become the surface electrode 3, is completely embedded in the absorption layer 90.

[0065] In other words, as shown in Figure 9(A), in the conventional example, the conductive paste 91 that will become the surface electrode 103 is directly applied onto the ceramic green sheet 9. Therefore, as shown in Figure 9(B), even if an attempt is made to embed the conductive paste 91 into the ceramic green sheet 9 by pressing, the conductive paste 91 cannot be completely embedded into the ceramic green sheet 9, and as a result, as shown in Figure 9(C), the upper surface 104 of the surface electrode 103 after firing does not reach the same height as the surface 25 of the electrode forming part 24. Furthermore, when forming a surface electrode 103 with a thickness of 3 μm to 50 μm and a width of 30 μm to 300 μm after firing, the upper surface 104 of the surface electrode 103 tended to take on an upwardly curved shape as shown in Figure 9(C). In contrast, in this disclosure, as shown in Figure 7(A), an absorption layer 90 is provided on the ceramic green sheet 9, and the conductive paste 91 is applied on the absorption layer 90 to form the surface electrode 3. As a result, the conductive paste 91 can be completely embedded in the absorption layer 90, as shown in Figure 7(B). Then, by subsequent firing, the surface electrode 3 can be formed into the shape shown in Figures 3(A)(B) and 4(A)(B).

[0066] Next, referring to Figure 6(c), the ceramic green sheet 9 that will form the lid mounting portion 26 is laminated onto the laminate obtained in Figure 6(b), and then the two are heat-pressed together to form a single laminate. This gives rise to the green sheet laminate that will form the main body portion 2.

[0067] Next, the ceramic wiring member 1 is obtained by firing the green sheet laminate obtained in Figure 6(c). Finally, a plating layer is formed on the upper surface 30 of the exposed surface electrode 3 and the lower surface 40 of the back electrode 4 by electroplating.

[0068] In the ceramic wiring member 1 manufactured by the manufacturing method shown in Figures 5 and 6, the conductive paste 91 that forms the surface electrode 3 is completely embedded in the absorption layer 90 by the heat compression during the formation of the green sheet laminate described above. Therefore, as shown in Figures 3(A)(B) and 4(A)(B), the upper surface 30 of the surface electrode 3 is either a flat surface or a concave surface due to the volume reduction during firing, and is located at the same height as or lower than the flat surface 25 of the electrode forming section 24. At this time, it is desirable that the ratio of the conductive paste 91 that forms the surface electrode 3 (the value obtained by dividing the dimensions before firing by the dimensions after firing) is greater than or equal to the ratio of the absorption layer 90. Also, the lower surface 31 of the surface electrode 3 is curved so as to protrude downward toward the inside of the electrode forming section 24. Note that in the ceramic wiring member 1, the boundary between the ceramic green sheet 9 and the absorption layer 90 is not necessarily distinguishable.

[0069] According to the above-described method for manufacturing ceramic wiring members, for example, even without polishing the upper surface 30 of the surface electrode 3 after sintering, the upper surface 30 of the surface electrode 3 can be made to the same height as the surface 25 of the electrode forming section 24, or lower than the surface 25 of the electrode forming section 24. Therefore, manufacturing costs can be reduced. Naturally, in this case, the upper surface 30 of the surface electrode 3 has an unpolished surface, i.e., a fired surface.

[0070] According to the above-described method for manufacturing ceramic wiring members, when the conductive paste 91 for forming the surface electrode 3 is embedded in the absorption layer 90 formed on the ceramic green sheet 9, even if the ceramic green sheet 9 deforms to the point of being slightly concave, the deformation of the ceramic green sheet 9 is absorbed by the absorption layer 90 formed on the opposite side of the absorption layer 90 in which the conductive paste 91 is embedded. This suppresses the formation of gaps between the upper and lower stacked ceramic green sheets 9 and suppresses unevenness in the thickness of the stack. Therefore, it is possible to form a green sheet stack with little or no gaps between the upper and lower stacked ceramic green sheets 9 and with little or no unevenness in thickness.

[0071] [Modified Example] In the ceramic wiring member 1 according to the above embodiment, the cover 6 is not necessarily required.

[0072] In the ceramic wiring member 1 according to the above-described embodiment, the surface electrode 3 does not necessarily have to have a rectangular shape in plan view. For example, the effects of the present invention can be obtained if the shape is symmetrical with respect to the center line of the surface electrode 3 in the first and second directions. Specifically, possible plan view shapes of the surface electrode 3 include elliptical and circular shapes.

[0073] In the method for manufacturing a ceramic wiring member according to the above-described embodiment, an absorption layer 90 may be formed on the other main surface of the ceramic green sheet 9 that constitutes the plate-shaped portion 20, and a back surface electrode 4 may be formed on this absorption layer 90.

[0074] In the manufacturing method of the ceramic wiring member according to the above embodiment, an absorption layer 90 is formed on the ceramic green sheet 9, and the surface electrode 3 is embedded in the absorption layer. In contrast, in a modified example, the storage modulus of the ceramic green sheet 9 may be adjusted, and the surface electrode 3 may be embedded in the ceramic green sheet 9 to manufacture the ceramic wiring member.

[0075] In the embodiments described above, the ceramic wiring member 1 was a ceramic package, but the ceramic wiring member according to this disclosure may be a ceramic circuit board. The frame portion 23 is not necessarily required.

[0076] The embodiments disclosed herein should be understood to be illustrative in all respects and not restrictive in any way. The scope of the invention is defined by the claims and not by the foregoing description, and all modifications within the meaning and scope of the claims are intended to be included.

[0077] 1: Ceramic wiring member, 2: Main body, 3: Surface electrode, 4: Back electrode, 5: Inner layer electrode, 6: Lid, 7: Plating layer, 8: Adhesive layer, 9: Ceramic green sheet, 10: Electronic component, 11: Circuit board, 12: Wire, 13: Solder, 20: Plate-shaped part, 21: First main surface, 21A: Mounting part, 22: Second main surface, 23: Frame part, 24: Electrode forming part, 25: Surface of electrode forming part, 26: Lid installation part, 27: Recess, 29: Cavity, 30: Top surface of surface electrode, 31: Bottom surface of surface electrode, 32: First side of surface electrode, 33: Second side of surface electrode, 34: Third side of surface electrode, 35: Fourth side of surface electrode, 40: Bottom surface of back electrode, 41: Top surface of back electrode, 70: Top surface of plating layer, 90: Absorption layer

Claims

1. A ceramic wiring member comprising a main body and a surface electrode, wherein the main body includes a mounting portion on which an electronic component is mounted, and an electrode forming portion located outside the mounting portion and formed so as to be embedded in the main body from a flat surface, the surface electrode having a rectangular shape in plan view, and in at least one of the cross-sections of the rectangular surface electrode, which is perpendicular to a first direction perpendicular to a pair of opposing sides in the direction from the mounting portion toward the surface electrode and perpendicular to a second direction perpendicular to the first direction in plan view, at least a portion of the upper surface adjacent to the flat surface of the surface electrode is flat and at the same height as the flat surface, or at least a portion of the upper surface adjacent to the flat surface of the surface electrode is lower than the flat surface in the thickness direction of the electrode forming portion.

2. The ceramic wiring member according to claim 1, wherein in at least one cross-section, the upper surface located lower than the flat surface is flat, or the upper surface located lower than the flat surface is curved convexly toward the inward side of the electrode forming portion.

3. The ceramic wiring member according to claim 1 or claim 2, wherein at least a portion of the lower surface of the surface electrode is curved convexly toward the inward side of the electrode forming portion opposite to the upper surface of the surface electrode in at least one cross-section.

4. The ceramic wiring member according to claim 1 or claim 2, wherein the width of the surface electrode is 30 μm or more and 300 μm or less.

5. The ceramic wiring member according to claim 1 or claim 2, wherein the thickness of the surface electrode is 3 μm or more and 50 μm or less.

6. The ceramic wiring member according to claim 1 or 2, wherein the upper surface of the surface electrode includes, in a plan view, a first side on the side closer to the mounting portion and a second side on the side further from the mounting portion along the first direction, and between the first side and at least 20% and 40% of the total length of the surface electrode in the first direction, the upper surface of the surface electrode in a cross section perpendicular to the first direction is flat and at the same height as the flat surface, or the upper surface of the surface electrode in a cross section perpendicular to the first direction is lower than the flat surface.

7. The ceramic wiring member according to claim 1 or 2, wherein, between a position at least 10% and 90% of the total length of the surface electrode in the second direction, the upper surface of the surface electrode in a cross section perpendicular to the second direction is flat and at the same height as the flat surface, or the upper surface of the surface electrode in a cross section perpendicular to the second direction is lower than the flat surface.

8. The ceramic wiring member according to claim 1 or 2, wherein the upper surface of the surface electrode is flat throughout its entire surface and is located at the same height as the flat surface, or is located lower than the flat surface throughout its entire surface.

9. A method for manufacturing a ceramic wiring member, comprising the steps of: forming a laminate of a ceramic green sheet and an absorbent layer; forming a surface electrode on the absorbent layer; embedding the surface electrode in the absorbent layer by pressurization; and firing the green sheet laminate containing the laminate in which the surface electrode is embedded.

Images