WO2023188670A1 - 回路基板及びその製造方法 - Google Patents

回路基板及びその製造方法 Download PDF

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Publication number
WO2023188670A1
WO2023188670A1 PCT/JP2023/000025 JP2023000025W WO2023188670A1 WO 2023188670 A1 WO2023188670 A1 WO 2023188670A1 JP 2023000025 W JP2023000025 W JP 2023000025W WO 2023188670 A1 WO2023188670 A1 WO 2023188670A1
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WIPO (PCT)
Prior art keywords
metal plate
bonding layer
ceramic plate
plate
circuit board
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Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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PCT/JP2023/000025
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English (en)
French (fr)
Japanese (ja)
Inventor
晃正 湯浅
貴裕 中村
善幸 江嶋
厚樹 五十嵐
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Denka Co Ltd
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Denka Co Ltd
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Priority to JP2023533899A priority Critical patent/JP7555493B2/ja
Publication of WO2023188670A1 publication Critical patent/WO2023188670A1/ja
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Ceased legal-status Critical Current

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    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
    • H05K1/00—Printed circuits
    • H05K1/02—Details
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
    • H05K3/00—Apparatus or processes for manufacturing printed circuits
    • H05K3/38—Improvement of the adhesion between the insulating substrate and the metal
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10W—GENERIC PACKAGES, INTERCONNECTIONS, CONNECTORS OR OTHER CONSTRUCTIONAL DETAILS OF DEVICES COVERED BY CLASS H10
    • H10W70/00—Package substrates; Interposers; Redistribution layers [RDL]
    • H10W70/60—Insulating or insulated package substrates; Interposers; Redistribution layers

Definitions

  • the present disclosure relates to a circuit board and a method for manufacturing the same.
  • a circuit board included in such a power module includes a ceramic substrate and a copper plate, which are joined via a brazing material containing an active metal. Such a circuit board is affected by heat generated from semiconductor elements mounted on a power module.
  • Patent Document 1 in order to improve TCT reliability evaluated by TCT (Temperature Cycle Test), it is proposed to form a protruding part in a part of the bonding layer that bonds the ceramic substrate and the copper circuit board. has been done.
  • a second brazing material layer (Ag-Cu-Ti brazing material layer) is formed on both sides of a ceramic substrate so as to surround a first brazing material layer (Ag-Ti brazing material layer).
  • a technique has been proposed in which a first brazing material layer is disposed between a ceramic substrate and a copper plate, and a second brazing material layer is disposed outside the copper plate. Such techniques are intended to prevent peeling of the solidified brazing material layer and improve the bonding reliability of insulated circuit boards.
  • circuit boards are used in the future. For this reason, it is thought that circuit boards with even higher levels of reliability will be required. Therefore, the present disclosure provides a circuit board with excellent bonding reliability between a ceramic plate and a metal plate, and a method for manufacturing the same.
  • a circuit board includes a ceramic plate, a metal plate, and a bonding layer for bonding the ceramic plate and the metal plate, and the bonding layer is perpendicular to the main surface of the ceramic plate on which the metal plate is provided.
  • the thickness DE of the bonding layer between the edge of the metal plate and the ceramic plate is greater than the thickness of the bonding layer between the center of the metal plate and the ceramic plate.
  • the thickness of the bonding layer between the metal plate and the ceramic plate is greater than the thickness D C , and the bonding layer is formed continuously from between the edge of the metal plate and the ceramic plate to between the center of the metal plate and the ceramic plate.
  • the bonding layer that bonds the edges has more peeling. and defects such as voids are likely to occur. When such defects occur, there is a concern that heat cycle characteristics and electrical characteristics may deteriorate. For example, the following may be considered as a factor why defects are more likely to occur in the bonding layer that bonds the ends of the metal plates.
  • the brazing metal layer When laminating a metal plate and a ceramic plate using, for example, a brazing metal layer, if pressure is applied to the metal plate and ceramic plate along the stacking direction, the brazing metal layer will not be sufficiently pressurized near the center of the metal plate. , densely packed. On the other hand, near the ends of the metal plate, the brazing material moves outward from between the metal plate and the ceramic plate, so that it is not pressurized as much as near the center. Therefore, it is difficult to fill the ends of the metal plate with the brazing material more densely than near the center. Therefore, defects such as peeling of the bonding layer and voids occur near the ends of the metal plate, and the bonding layer tends to be more likely to be separated.
  • the bonding layer of the circuit board of the present disclosure is formed continuously from between the edge of the metal plate and the ceramic plate to between the center of the metal plate and the ceramic plate. This allows the metal plate and the ceramic plate to be firmly joined.
  • the thickness DE of the bonding layer between the edge of the metal plate and the ceramic plate is larger than the thickness D C of the bonding layer between the center of the metal plate and the ceramic plate.
  • Such a circuit board can be manufactured by making the brazing material layer thicker between the edge of the metal plate and the ceramic plate than between the center of the metal plate and the ceramic plate. Therefore, the bonding layer between the end of the metal plate and the ceramic plate is also formed under sufficient pressure.
  • the circuit board of the present disclosure has excellent bonding reliability between the ceramic plate and the metal plate.
  • the circuit board of the present disclosure has excellent bonding reliability between the ceramic plate and the metal plate.
  • by suppressing the occurrence of defects in the bonding layer it is possible to reduce the discharge source where charges are concentrated when a voltage is applied, thereby improving electrical characteristics.
  • the ratio of the thickness D E to the thickness D C may be 5 or more. Thereby, defects such as peeling of the bonding layer and voids near the ends of the metal plate can be sufficiently reduced. Therefore, the reliability of bonding the ceramic plate and the metal plate can be further improved.
  • the maximum area of the gap in the bonding layer between the ceramic plate and the metal plate may be 1000 ⁇ m 2 or less when viewed in the above-mentioned cross section. Such a circuit board has better bonding reliability.
  • the bonding layer When viewed in the above cross section, the bonding layer has a protruding portion formed to protrude outward from the lower end of the side surface of the metal plate, and the ratio of the length L of the protruding portion to the thickness DE of the bonding layer is It may be 0.1 or more.
  • ceramic plates and metal plates have different coefficients of thermal expansion, so thermal stress is generated by heat cycles. Such thermal stress is concentrated in the bonding layer at the end of the metal plate. Since the protruding portion of the bonding layer has a sufficiently long length L, thermal stress can be sufficiently alleviated.
  • Such a circuit board has excellent durability against heat cycles.
  • the bonding layer When viewed in the cross section, the bonding layer may have a gradient portion in which the thickness increases from the center toward the ends.
  • This type of bonding layer is created by the fact that when a ceramic plate and a metal plate are bonded together using a brazing material, the brazing material that forms the bonding layer flows smoothly from the center of the metal plate toward the edges. It is formed by spreading it evenly. This makes it possible to sufficiently reduce defects in the bonding layer not only at the edges but also at the center. Thereby, the bonding reliability of the circuit board can be further improved.
  • the metal plate When viewed in the above cross section, the metal plate has a convex shape, and the convex surface of the metal plate may be bonded to the ceramic plate by a bonding layer.
  • the height of the convex portion on the convex surface may be 10 to 100 ⁇ m. This makes it possible to further improve the bonding at the circuit ends.
  • the appearance of the circuit board can be further improved by sufficiently suppressing the flow of the brazing material onto the main surface of the circuit board.
  • a method for manufacturing a circuit board includes a step of applying a brazing material to the main surface of a ceramic plate to provide a brazing material layer, and laminating a ceramic plate and a metal plate with the brazing material layer sandwiched therebetween.
  • the process includes a step of producing a laminate, and a step of heating the laminate to obtain a bonded body in which a ceramic plate and a metal plate are bonded by a bonding layer.
  • the thickness of the second portion of the brazing material layer that contacts the end portion of the metal plate is made larger than the thickness of the first portion of the brazing material layer that contacts the end portion of the metal plate.
  • the brazing metal When laminating a metal plate and a ceramic plate through a brazing metal layer, if pressure is applied to the metal plate and ceramic plate along the stacking direction, the brazing metal will be sufficiently pressurized near the center of the metal plate, making it dense. is filled with. On the other hand, near the ends of the metal plate, the brazing material moves outward from between the metal plate and the ceramic plate, and is not sufficiently pressurized. Therefore, it is difficult to fill the ends of the metal plate with the brazing material more densely than near the center. Therefore, defects such as peeling and voids in the bonding layer that joins the metal plate and the ceramic plate tend to occur more easily near the ends of the metal plate.
  • the thickness of the metal plate is greater than the thickness of the first portion of the brazing material layer that contacts the center of the metal plate.
  • the thickness of the second portion of the brazing material layer that contacts the end portion is increased. Therefore, when the metal plate and the ceramic plate are stacked with the brazing material layer sandwiched therebetween, the second portion that contacts the end of the metal plate is also sufficiently pressurized.
  • defects such as peeling of the bonding layer and voids at the ends of the metal plate can be suppressed. Therefore, it is possible to manufacture a circuit board with excellent bonding reliability between the ceramic plate and the metal plate. By suppressing the occurrence of defects in the bonding layer, such a circuit board can reduce the discharge source where charges are concentrated when a voltage is applied, and improve the electrical characteristics.
  • the second portion may be formed by applying the brazing material more times than the first portion. Thereby, the second portion, which is thicker than the first portion, can be smoothly formed.
  • the brazing material is applied so that n 2 - n 1 ⁇ 2 is satisfied, where the number of times the brazing material is applied in the first part is n 1 times, and the number of times the brazing material is applied in the second part is n 2 times.
  • a brazing filler metal layer may also be provided.
  • the circuit board obtained by the above manufacturing method has a gap between the edge of the metal plate and the ceramic plate when viewed in a cross section that is perpendicular to the main surface of the ceramic plate and passes through the center of the metal plate, the brazing material layer, and the ceramic plate.
  • the thickness DE of the bonding layer at the center of the metal plate may be larger than the thickness D C of the bonding layer between the center of the metal plate and the ceramic plate.
  • the bonding layer may be formed continuously from between the edge of the metal plate and the ceramic plate to between the center of the metal plate and the ceramic plate.
  • Such a circuit board has excellent bonding reliability between the ceramic plate and the metal plate.
  • the present disclosure can provide a circuit board with excellent bonding reliability between a ceramic plate and a metal plate, and a method for manufacturing the same.
  • FIG. 1 is a plan view of the circuit board.
  • FIG. 2 is a sectional view taken along line II-II of the circuit board in FIG.
  • FIG. 3 is an enlarged sectional view showing a part of the cross section of FIG. 2 in an enlarged manner.
  • FIG. 4 is a schematic cross-sectional view for explaining a method of manufacturing a circuit board.
  • FIG. 5 is a SEM photograph of a cross section of the circuit board of Example 1.
  • FIG. 6 is a SEM photograph of a cross section of the circuit board of Example 1.
  • FIG. 7 is a SEM photograph of a cross section of the circuit board of Example 2.
  • FIG. 8 is an SEM photograph of a cross section of the circuit board of Comparative Example 1.
  • FIG. 9(A) is an optical electron micrograph of the circuit board of Example 1.
  • FIG. 9(B) is an optical electron micrograph of the circuit board of Example 2.
  • FIG. 9(C) is an optical electron micrograph of the circuit board of Comparative Example 1.
  • FIG. 10(A) is an image of ultrasonic testing (SAT) of the circuit board of Example 1.
  • FIG. 10(B) is an image of ultrasonic testing (SAT) of the circuit board of Example 2.
  • FIG. 10C is an image of ultrasonic testing (SAT) of the circuit board of Comparative Example 1.
  • a circuit board includes a ceramic plate, a metal plate, and a bonding layer that bonds the ceramic plate and the metal plate.
  • the material of the ceramic plate is not particularly limited, and may be made of, for example, a nitride sintered body, a carbide sintered body, or an oxide sintered body. Specific examples include silicon nitride sintered bodies, aluminum nitride sintered bodies, aluminum oxide sintered bodies, and silicon carbide sintered bodies. There is no particular restriction as long as it is in the shape of a ceramic plate.
  • the thickness of the ceramic plate may be, for example, 0.2 to 2 mm, or 0.32 to 1.1 mm.
  • the metal plate may be a copper plate, for example.
  • the shape is not particularly limited as long as it is plate-like.
  • the thickness of the metal plate may be, for example, 0.1 to 1.2 mm, or 0.2 to 0.8 mm.
  • the metal plate may have a plating film on its surface.
  • the metal plate may have convex main surfaces on one side and the other side.
  • the metal plate may be warped so that one main surface is convex and the other main surface is concave.
  • at least one main surface of the metal plate may be a tapered surface such that the center portion protrudes more than the end portions.
  • the bonding layer may contain one or more metals selected from the group consisting of silver, copper, tin, and active metals. Two or more metals may be an alloy.
  • the active metal may include one or more selected from the group consisting of titanium, hafnium, zirconium, and niobium.
  • the bonding layer may contain at least one member selected from the group consisting of silver, copper, and alloys thereof.
  • Silver and copper contained in the bonding layer may be contained in the bonding layer as an alloy such as an Ag--Cu eutectic alloy.
  • the content of silver in the bonding layer may be 60 to 95% by mass in terms of Ag.
  • the content of silver and copper in the bonding layer may be 75 to 100% by mass, 85 to 99% by mass, or 90 to 98% by mass in terms of Ag and Cu, respectively. This makes it possible to sufficiently reduce the residual stress in the bonding layer and improve the denseness of the bonding layer.
  • the content of the active metal in the bonding layer may be 0.5 to 5 parts by mass based on 100 parts by mass of Ag and Cu in total. By setting the content of the active metal to 0.5 parts by mass or more, the bondability between the ceramic plate and the bonding layer can be improved. On the other hand, by setting the content of the active metal to 5 parts by mass or less, formation of a fragile alloy layer at the bonding interface can be suppressed.
  • the metal contained in the bonding layer may be contained as a nitride, oxide, carbide, or hydride.
  • the bonding layer may include titanium nitride and/or titanium hydride ( TiH2 ). This makes it possible to sufficiently increase the bonding strength between the ceramic plate and the metal plate.
  • TiH 2 titanium nitride and/or titanium hydride
  • the content of TiH 2 may be, for example, 1 to 8 parts by weight based on 100 parts by weight of Ag and Cu in total.
  • the titanium nitride phase contained in the bonding layer may be formed into a layer on the contact surface of the bonding layer with the ceramic plate.
  • the titanium nitride phase may be formed in a continuous layer throughout the bonding layer.
  • the bonding strength between the ceramic plate and the metal plate can be further increased.
  • the fact that the titanium nitride phase is continuous in a layered manner can be confirmed by examining the cross section using, for example, an electron beam microanalyzer (EPMA).
  • EPMA electron beam microanalyzer
  • the cross section in the present disclosure is a cross section that is perpendicular to the main surface of the ceramic plate on which the bonding layer is provided and passes through the center of the metal plate, the bonding layer, and the ceramic plate.
  • the thickness DE of the bonding layer between the edge of the metal plate and the ceramic plate is greater than the thickness D C of the bonding layer between the center of the metal plate and the ceramic plate.
  • Such a circuit board has excellent bonding reliability between the ceramic plate and the metal plate. A method for measuring the thickness DE and the thickness DC of the bonding layer in the present disclosure will be described later.
  • FIG. 1 is a plan view showing an example of the circuit board of this embodiment.
  • the circuit board 100 includes a ceramic plate 10 and a metal plate 21 bonded to the main surface 10A of the ceramic plate 10 via a bonding layer 31.
  • two metal plates 21 are provided on the main surface 10A of the ceramic plate 10, but the invention is not limited to this.
  • the number of metal plates may be one, or three or more.
  • the shapes of the plurality of metal plates may be the same or different.
  • the bonding layer 31 has a protruding portion 31A that is formed along the outer edge of the metal plate 21 so as to surround the metal plate 21.
  • FIG. 2 is a sectional view taken along the line II-II of the circuit board in FIG. 1. That is, FIG. 2 is perpendicular to the main surface 10A (main surface 10B) of the ceramic plate 10 on which the bonding layer 31 is provided, and the center portion 21C (center portion 22C) of the metal plate 21 (metal plate 22), the bonding layer 31 ( A cross section through the bonding layer 32) and the ceramic plate 10 is shown.
  • the bonding layer 31 is formed continuously from between the end portion 21E of the metal plate 21 and the ceramic plate 10 to between the center portion 21C of the metal plate 21 and the ceramic plate 10. That is, the bonding layer 31 is connected from the center portion 31C to the end portion 31E without being separated.
  • a metal plate 22 is also provided on the main surface (main surface 10B) opposite to the main surface 10A of the ceramic board 10. Like the metal plate 21, the metal plate 22 is also bonded to the main surface 10B of the ceramic plate 10 via the bonding layer 32. In this example, the metal plate 22 is also provided on the main surface 10B, but the present invention is not limited thereto. That is, the metal plate may be provided only on one main surface of the ceramic plate.
  • the shape, size, and number of metal plates joined to main surface 10A and main surface 10B may be the same or different.
  • FIG. 3 is an enlarged sectional view showing the vicinity of the end 21E of the metal plate 21 and the end 31E of the bonding layer 31 in the cross section shown in FIG.
  • the thickness DE may be, for example, 20 ⁇ m or more, 30 ⁇ m or more, or 40 ⁇ m or more, from the viewpoint of sufficiently increasing the bonding strength between the metal plate 21 and the ceramic plate 10.
  • the thickness DE may be 100 ⁇ m or less, 80 ⁇ m or less, or 60 ⁇ m or less.
  • An example of the range of the thickness DE is 20 to 100 ⁇ m.
  • the thickness DE may be different for each cross section. In any cross section, the thickness DE may be within the above range.
  • the thickness DC of the bonding layer 31 between the center portion 21C of the metal plate 21 and the ceramic plate 10 is measured as follows. As shown in FIG. 2, a virtual straight line VL2 is drawn from the center of the main surface 21A of the metal plate 21 so as to be perpendicular to the main surface 10A of the ceramic plate 10. The virtual straight line VL2 in FIG. 2 and the virtual straight line VL1 in FIG. 3 may be parallel to each other. The thickness of the bonding layer 31 along the virtual straight line VL2 drawn in this way is "thickness D.sub.C. "
  • the thickness DC may be, for example, 1 ⁇ m or more, 2 ⁇ m or more, or 3 ⁇ m or more, from the viewpoint of sufficiently increasing the bonding strength between the metal plate 21 and the ceramic plate 10.
  • the thickness D C may be 15 ⁇ m or less, 10 ⁇ m or less, or 8 ⁇ m or less from the viewpoint of shortening the melting time of the brazing material containing powder.
  • An example of the range of the thickness D C is 1 to 15 ⁇ m. When a plurality of cross sections as shown in FIG. 2 (FIG. 3) are viewed, the thickness D C may be different for each cross section. In any cross section, the thickness D C may be within the above range.
  • the thickness DE of the end portion 31E of the bonding layer 31 is larger than the thickness D C of the center portion 31C of the bonding layer 31. That is, the relationship D E > D C holds true.
  • Such a bonding layer 31 is formed in a sufficiently pressurized state even near the end portion 31E. Therefore, it is possible to suppress the metal plate 21 from peeling off at the end portion 31E and the formation of voids in the bonding layer 31.
  • the ratio of the thickness D E to the thickness D C may be 5 or more, or may be 6 or more.
  • the ratio of the thickness D E to the thickness D C may be 20 or less, or may be 15 or less.
  • An example of the range of the ratio of the thickness D E to the thickness D C (D E /D C ) is 5 to 20.
  • the bonding layer 31 may have a gradient portion 35 in which the thickness of the bonding layer 31 increases from the center portion 31C toward the end portions 31E.
  • the bonding layer 31 having such a gradient portion 35 when the ceramic plate 10 and the metal plate 21 are bonded using a brazing material, the brazing material that becomes the bonding layer 31 moves from the center portion 31C to the end portion 31E. It flows and forms sufficiently smoothly.
  • Such a bonding layer 31 is formed by sufficiently evenly spreading the brazing material. Therefore, defects in the bonding layer 31 can be sufficiently reduced not only near the end portion 31E of the bonding layer 31 but also near the center portion 31C.
  • the bonding layer 31 may have a slope portion 35 closer to the end portion 31E than the center portion 31C. Thereby, the occurrence of defects at the end portion 31E can be further suppressed.
  • the bonding layer 31 of the circuit board 100 has a protruding portion 31A that is formed to protrude outward from the lower end 70 of the metal plate 21.
  • the protruding portion 31A may expand like a skirt toward the main surface 10A of the ceramic plate 10.
  • concentration of thermal stress occurring at the end portion of the bonding layer 31 due to the difference in thermal expansion coefficient between the ceramic plate 10 and the metal plate 21 can be alleviated.
  • the length L of the protruding portion 31A may be 5 ⁇ m or more, 10 ⁇ m or more, 30 ⁇ m or more, or 50 ⁇ m or more.
  • the length L of the protruding portion 31A may be, for example, 500 ⁇ m or less, or 300 ⁇ m or less, in consideration of the size of the ceramic plate 10.
  • An example of the range of the length L of the protruding portion 31A is 5 to 500 ⁇ m.
  • the length L of the protruding portion 31A is measured as follows. As shown in FIG. 3, a virtual straight line VL3 passing through the end point E1 of the protruding portion 31A on the main surface 10A of the ceramic plate 10 and perpendicular to the main surface 10A is drawn. Virtual straight line VL3 is parallel to virtual straight line VL1. The shortest distance between the lower end 70 of the side surface 21S of the metal plate 21 (the boundary between the metal plate 21 and the bonding layer 31) and the virtual straight line VL3 is the "length L.” When looking at a plurality of cross sections as shown in FIG. 2 (FIG. 3), the length L of the protruding portion 31A may be different for each cross section. In any cross section, the length L may be within the above range.
  • the ratio (L/D E ) of the length L of the protruding portion 31A to the thickness D E of the bonding layer 31 may be 0.1 or more, 0.5 or more, or 1 or more. good. Since such a bonding layer 31 has a protruding portion 31A having a sufficiently long length L, thermal stress can be sufficiently alleviated. Such a circuit board 100 has excellent durability against heat cycles.
  • the ratio of the length L to the thickness D E (L/D E ) may be 10 or less, 5 or less, or 3 or less, in consideration of the size of the ceramic plate 10.
  • An example of the range of the ratio of length L to thickness D E (L/D E ) is 0.1 to 10.
  • the voids in the bonding layer 31 be small, and it is preferable that the bonding layer 31 has no voids.
  • the void portion becomes a portion where the ceramic plate 10 and the metal plate 21 are not joined. For this reason, when the gap becomes large, separation between the ceramic plate 10 and the metal plate 21 is likely to occur, resulting in a decrease in bonding reliability.
  • the maximum area of the void portion may be 1000 ⁇ m 2 or less, 500 ⁇ m 2 or less, or 300 ⁇ m 2 or less. As shown in FIGS.
  • the area of the void is measured in a cross section that is perpendicular to the main surface 10A of the ceramic plate 10 and passes through the center 21C of the metal plate 21, the bonding layer 31, and the ceramic plate 10. Specifically, it may be determined by observing this cross section with an SEM (scanning electron microscope) and performing image processing on the region including the void.
  • SEM scanning electron microscope
  • the metal plates 21 and 22 When viewed in cross section in FIG. 2, the metal plates 21 and 22 have a convex shape.
  • One main surface of the metal plates 21 and 22 is a convex surface, and the convex surface is in contact with the bonding layers 31 and 32. That is, the convex surfaces of the metal plates 21 and 22 are bonded to the ceramic plate 10 by the bonding layers 31 and 32.
  • the height of the convex portion on the convex surface may be 10 to 100 ⁇ m. By setting the height of the convex portion to 10 ⁇ m or more, it is possible to prevent the brazing material from becoming excessive when the brazing material is applied multiple times to the portions that contact the ends of the metal plates 21 and 22.
  • the height of the convex portion can be determined as the difference between the thickness D E and the thickness D C (D E ⁇ D C ). That is, the height of the convex portion is measured based on the height at the outer edge of the metal plates 21 and 22.
  • the structures and shapes of the bonding layer 32 and metal plate 22 provided on the main surface 10B side of the ceramic plate 10 are the same as those of the bonding layer 31 and metal plate 21 provided on the main surface 10A side.
  • the metal plate 21 and the metal plate 22 may function as a circuit board having a function of transmitting an electric signal or a heat sink having a function of transmitting heat.
  • the metal plates 21 and 22 may have both the function of transmitting heat and the function of transmitting electric signals.
  • the structures and shapes of the bonding layer and the metal plate provided on each of the pair of main surfaces may be different from each other.
  • a method for manufacturing a circuit board includes a step of applying a brazing material to the main surface of a ceramic plate to provide a brazing material layer, and a step of laminating a ceramic plate and a metal plate with the brazing material layer sandwiched therebetween to form a laminate. and a step of heating the laminate to obtain a bonded body in which a ceramic plate and a metal plate are bonded by a bonding layer.
  • a green sheet is produced by molding a slurry containing an inorganic compound powder, a binder resin, a sintering aid, a plasticizer, a dispersant, a solvent, and the like.
  • inorganic compounds include aluminum nitride (AlN), silicon nitride (Si 3 N 4 ), silicon carbide, and aluminum oxide.
  • Sintering aids include rare earth metals, alkaline earth metals, metal oxides, fluorides, chlorides, nitrates, sulfates, and the like. These may be used alone or in combination of two or more. By using a sintering aid, sintering of the inorganic compound powder can be promoted.
  • binder resins include methyl cellulose, ethyl cellulose, polyvinyl alcohol, polyvinyl butyral, and (meth)acrylic resins.
  • plasticizers include purified glycerin, glycerin triolate, diethylene glycol, phthalic acid plasticizers such as di-n-butyl phthalate, and dibasic acid plasticizers such as di-2-ethylhexyl sebacate.
  • dispersants include poly(meth)acrylates and (meth)acrylic acid-maleate copolymers.
  • solvent include organic solvents such as ethanol and toluene.
  • Examples of methods for forming the slurry include the doctor blade method and the extrusion method.
  • the green sheet obtained by molding is degreased and sintered.
  • Degreasing may be performed, for example, by heating at 400 to 800°C for 0.5 to 20 hours. Thereby, the amount of residual organic matter (carbon) can be reduced while suppressing oxidation and deterioration of inorganic compounds.
  • Sintering may be performed by heating to 1700 to 1900° C. in a non-oxidizing gas atmosphere such as nitrogen, argon, ammonia or hydrogen. In this way, for example, a ceramic plate 10 can be obtained. If necessary, the ceramic plate may be laser-processed to cut the ends or provide a scribe line on the main surface of the ceramic plate.
  • the above degreasing and sintering may be performed with a plurality of stacked green sheets.
  • a release layer made of a release agent may be provided between the green sheets in order to facilitate separation of the base materials after firing.
  • the mold release agent for example, boron nitride (BN) can be used.
  • the release layer may be formed, for example, by applying a slurry of boron nitride powder by spraying, brushing, roll coating, screen printing, or the like.
  • the number of green sheets to be laminated may be, for example, 8 to 100, or 30 to 70, from the viewpoint of efficient mass production of ceramic plates and sufficient degreasing.
  • a brazing filler metal is applied to the main surface of the ceramic plate thus obtained.
  • the brazing filler metal contains, for example, Ag, Cu, Sn, an active metal, a metal compound containing these as constituent elements, an organic solvent, a binder, and the like.
  • the viscosity (20° C.) of the brazing filler metal may be, for example, 5 to 20 Pa ⁇ s.
  • the content of the organic solvent in the brazing filler metal may be, for example, 5 to 25% by mass, and the content of the binder may be, for example, 2 to 15% by mass.
  • a brazing material layer is provided on the main surface of the ceramic plate by applying a brazing material using a method such as a roll coater method, screen printing method, or transfer method.
  • a brazing material layer When providing the brazing material layer, the thickness of the second portion of the brazing material layer that contacts the end portion of the metal plate is made larger than the thickness of the first portion of the brazing material layer that contacts the center portion of the metal plate.
  • the thickness of the brazing material layer may be changed by changing the coating conditions to provide a first portion and a second portion having mutually different thicknesses.
  • the first portion and the second portion may have different thicknesses by changing the number of times the brazing material is applied. That is, the second portion may be formed by applying the brazing material more times than the first portion. Thereby, the first portion and the second portion having mutually different thicknesses can be easily provided on the main surface of the ceramic plate.
  • FIG. 4 is a schematic cross-sectional view for explaining an example of a method for manufacturing a circuit board.
  • the first portion 81 and the second portion 82 are formed by applying a brazing material to the main surfaces 10A and 10B of the ceramic plate 10.
  • the first brazing material layer 41 is formed by applying the brazing material only once.
  • the brazing material is applied three times, and the second brazing material layer 42 and the third brazing material layer 43 are provided in this order on the first brazing material layer 41.
  • the number of laminated brazing material layers in the first portion 81 and the second portion 82 is not particularly limited.
  • the first portion 81 may have a two-layer structure
  • the second portion 82 may have a four-layer structure.
  • a metal plate 21 and a metal plate 22 are bonded and laminated to the main surface 10A and the main surface 10B of the ceramic plate 10 provided with the brazing material layer in this way, respectively.
  • the main surfaces 21B and 22B of the metal plates 21 and 22 are tapered surfaces (convex surfaces) that are respectively convex with respect to the main surfaces 10A and 10B of the ceramic plate 10. Therefore, in the metal plates 21 and 22, the thickness of the end portions 21E and 22E is smaller than the thickness of the center portions 21C and 22C, respectively.
  • the use of such metal plates 21 and 22 is not limited, and for example, a metal plate whose main surfaces 21B and 22B facing the ceramic plate 10 are curved so as to have a convex shape may be used.
  • a laminate is obtained by pressing the metal plates 21 and 22 in the direction toward the ceramic plate 10 (in the direction of the arrow in FIG. 4). With the pressing, the brazing material layer spreads smoothly, and a laminate in which the ceramic plate and the metal plates 21 and 22 are well bonded by the brazing material layer is obtained.
  • the obtained laminate is heated in a heating furnace to join the ceramic plate 10 and the metal plates 21 and 22 to obtain a joined body.
  • the heating temperature may be, for example, 700 to 900°C.
  • the atmosphere in the furnace may be an inert gas such as nitrogen, and the reaction may be performed under reduced pressure below atmospheric pressure or under vacuum.
  • the heating furnace may be of a continuous type that continuously manufactures a plurality of joined bodies, or may be one that manufactures one or more joined bodies in a batch manner. Heating may be performed while pressing the joined body in the stacking direction of the laminate.
  • each brazing filler metal layer flows and reacts with the metal plate, forming a bonding layer.
  • the thickness D E at the end is greater than the thickness D C at the center.
  • a large bonding layer is also formed.
  • surface treatment such as forming a plating film on the metal plate may be performed.
  • cutting or the like may be performed to adjust the shape of the bonding layer. In this way, for example, the circuit board 100 can be manufactured.
  • the number of applications of the brazing material in the first part is n 1 times
  • the number of applications of the brazing material in the second part is n 2 times, so that n 2 - n 1 ⁇ 2 is satisfied.
  • a brazing material layer may be provided by applying a material.
  • the present disclosure is not limited to the above embodiments.
  • the thickness D at the end portion is greater than the thickness at the center portion. It is sufficient if the thickness is larger than the thickness DC .
  • Numerical ranges that are arbitrary combinations of the upper and lower limits specifically described in each of the above embodiments are also included in the present disclosure.
  • the present disclosure also includes numerical ranges in which the upper limit and/or lower limit are replaced with values of Examples described below.
  • the present disclosure includes the following contents [1] to [11].
  • [1] Comprising a ceramic plate, a metal plate, and a bonding layer for bonding the ceramic plate and the metal plate, When viewed in a cross section that is perpendicular to the main surface of the ceramic plate on which the bonding layer is provided and passes through the center of the metal plate, the bonding layer, and the ceramic plate, the edge of the metal plate and the ceramic plate are The thickness DE of the bonding layer between the metal plate and the ceramic plate is larger than the thickness D C of the bonding layer between the center portion of the metal plate and the ceramic plate, In the circuit board, the bonding layer is formed continuously from between the end portion of the metal plate and the ceramic plate to between the center portion of the metal plate and the ceramic plate.
  • the bonding layer has a protruding portion formed to protrude outward from the lower end of the side surface of the metal plate, and the protrusion is larger than the thickness DE of the bonding layer.
  • the thickness DE of the bonding layer is larger than the thickness D C of the bonding layer between the center portion of the metal plate and the ceramic plate, [8] to [10], wherein the bonding layer is formed continuously from between the end portion of the metal plate and the ceramic plate to between the center portion of the metal plate and the ceramic plate.
  • the metal plate was obtained by punching and was warped so that one principal surface was convex and the other principal surface was concave.
  • the braze metal contained Ag, Cu, Sn, and TiH2 .
  • the mass ratio of Ag and Cu was 9:1.
  • the brazing filler metal contained 3 parts by mass of Sn and 3.5 parts by mass of TiH 2 based on 100 parts by mass of Ag and Cu in total.
  • a brazing filler metal was applied to predetermined locations on both main surfaces of the ceramic plate by screen printing. At this time, as shown in FIG. 4, the brazing material was applied three times to the portion where the end of the metal plate comes into contact, forming a second portion with a three-layer structure. On the other hand, the portion where the center of the metal plate came into contact formed a first portion having a one-layer structure. After forming the brazing material layer, a metal plate was bonded to the main surface of the ceramic plate via the brazing material layer. At this time, the convex main surface of the metal plate and the main surface of the ceramic plate were bonded together so that they faced each other.
  • a laminate was obtained by pressing the metal plate on the main surface of the ceramic plate toward the ceramic plate at 0.015 MPa. A total of 24 metal plates were bonded to the main surface of the ceramic plate. Thereafter, the laminate was heated at 790° C. for 1 hour in vacuum. In this way, a bonded body was obtained in which the metal plate was bonded to the main surface of the ceramic plate via the bonding layer. Thereafter, electroless plating was performed using a Ni--P plating solution (phosphorous concentration: 8 to 12% by mass) to form a circuit board having a plating film on the metal plate.
  • Ni--P plating solution phosphorous concentration: 8 to 12% by mass
  • FIG. 5 and 6 are SEM photographs taken at different positions.
  • FIG. 6 shows a cross-sectional image at a higher magnification than FIG. 5.
  • the thickness DE of the bonding layer 31 between the end of the metal plate 21 and the ceramic plate 10 is the thickness of the bonding layer 31 between the center of the metal plate 21 and the ceramic plate 10. It was bigger than DC .
  • the specific measurement procedure was as follows.
  • a virtual straight line VL0 was drawn passing through the lower end of the side surface of the metal plate 21 and perpendicular to the main surface of the ceramic plate 10. Then, a virtual straight line VL1 was drawn so as to be parallel to the virtual straight line VL0 and to have an interval of 100 ⁇ m between the virtual straight line VL0 and the virtual straight line VL0. The thickness DE of the bonding layer 31 was measured on this virtual straight line VL1.
  • the protruding portion of the bonding layer 31 had a shape that expanded into a skirt shape toward the main surface of the ceramic plate 10.
  • the length L of this protruding portion was determined as the distance between a virtual straight line VL3 passing through the end point E1 of the protruding portion 31A on the main surface of the ceramic plate 10 and perpendicular to the main surface 10A, and a virtual straight line VL0 parallel to this.
  • the height of the convex portion on the convex surface (contact surface with the bonding layer) of the metal plate 21 was calculated using the formula (D E ⁇ D C ).
  • Example 2 A circuit was constructed in the same manner as in Example 1, except that when applying the brazing material to the ceramic plate, the second part of the two-layer structure was formed by applying the brazing material twice to the part where the end of the metal plate contacts. A substrate was formed and evaluated. The results were as shown in Table 1.
  • FIG. 7 is a SEM photograph of a cross section of the circuit board of Example 2.
  • the thickness DE of the bonding layer 31 between the end of the metal plate 21 and the ceramic plate 10 is the thickness of the bonding layer 31 between the center of the metal plate 21 and the ceramic plate 10. It was bigger than DC .
  • the cross section shown in FIG. 7 had no voids, but the other cross sections had voids.
  • the area S of the void portion having the largest area was as shown in Table 1. The area S of the void portion was determined by image processing the SEM image.
  • FIG. 8 is an SEM photograph of a cross section of the circuit board of Comparative Example 1. Bonding layer 131 was not formed between the end of metal plate 121 and ceramic plate 110. The bonding layer 131 did not continue from between the end of the metal plate 121 and the ceramic plate 110 to between the center of the metal plate 121 and the ceramic plate 110, and was separated.
  • FIG. 9 is an optical electron micrograph taken from the side of the circuit boards of Example 1, Example 2, and Comparative Example 1.
  • the photograph (A) in FIG. 9 shows the circuit board of Example 1.
  • the photograph (B) in FIG. 9 shows the circuit board of Example 2.
  • the photograph (C) in FIG. 9 shows the circuit board of Comparative Example 1.
  • Photographs (A), (B), and (C) all show a part of the metal plate on the upper side, a part of the ceramic plate on the lower side, and a bonding layer between them.
  • FIG. 10 is an image of ultrasonic testing (SAT) of the circuit boards of Example 1, Example 2, and Comparative Example 1.
  • Image (A) in FIG. 10 is the circuit board of Example 1.
  • Image (B) in FIG. 10 is the circuit board of Example 2.
  • Image (C) in FIG. 10 is the circuit board of Comparative Example 1.
  • the edges of some of the metal plates were white (indicated by circles in the figure). This white portion indicates that there are voids in the bonding layer.
  • the image (B) of FIG. 10 it was also confirmed that there were voids in the bonding layer that bonded several metal plates. In contrast, no voids were observed in the image (A) of FIG. 10.
  • a circuit board with excellent bonding reliability and a method for manufacturing the same are provided.

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  • Engineering & Computer Science (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Manufacturing & Machinery (AREA)
  • Structure Of Printed Boards (AREA)
  • Manufacturing Of Printed Wiring (AREA)
  • Ceramic Products (AREA)
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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH10190176A (ja) * 1996-12-26 1998-07-21 Denki Kagaku Kogyo Kk 回路基板
JP2007095955A (ja) * 2005-09-28 2007-04-12 Kyocera Corp 回路基板およびその製造方法
JP2007311527A (ja) * 2006-05-18 2007-11-29 Mitsubishi Materials Corp パワーモジュール用基板およびパワーモジュール用基板の製造方法並びにパワーモジュール
JP2008311294A (ja) * 2007-06-12 2008-12-25 Mitsubishi Materials Corp パワーモジュール用基板の製造方法
JP2022000871A (ja) * 2018-07-31 2022-01-04 京セラ株式会社 電気回路基板及びパワーモジュール

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2019003725A1 (ja) 2017-06-28 2019-01-03 京セラ株式会社 パワーモジュール用基板およびパワーモジュール

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH10190176A (ja) * 1996-12-26 1998-07-21 Denki Kagaku Kogyo Kk 回路基板
JP2007095955A (ja) * 2005-09-28 2007-04-12 Kyocera Corp 回路基板およびその製造方法
JP2007311527A (ja) * 2006-05-18 2007-11-29 Mitsubishi Materials Corp パワーモジュール用基板およびパワーモジュール用基板の製造方法並びにパワーモジュール
JP2008311294A (ja) * 2007-06-12 2008-12-25 Mitsubishi Materials Corp パワーモジュール用基板の製造方法
JP2022000871A (ja) * 2018-07-31 2022-01-04 京セラ株式会社 電気回路基板及びパワーモジュール

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