Patent Publication Number: US-2023134940-A1

Title: Metal component and ceramic substrate

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based on and claims the benefit of priority from prior Japanese patent application No. 2021-180087 filed on Nov. 4, 2021, the entire contents of which are incorporated herein by reference. 
     TECHNICAL FIELD 
     The present disclosure relates to a metal component and a ceramic substrate. 
     BACKGROUND ART 
     A ceramic substrate including a conductive layer is suggested. In some cases, a metal component is bonded to the conductive layer by using a solder material, through an opening portion formed in the ceramic substrate. 
     CITATION LIST 
     Patent Literature 
     Patent Literature 1: JP2019-212668A 
     Patent Literature 2: JP2009-188389A 
     SUMMARY OF INVENTION 
     When the metal component is bonded to a conductive part located in the opening portion of the substrate by using the solder material, the flux contained in the solder is in a state in which it is difficult to volatilize, resulting in a bonding layer containing many voids in the solder, which lowers bonding reliability. In particular, in long-term use under high-temperature environment of 200° C. or higher, the bonding reliability is deteriorated due to fatigue of the solder. 
     An object of the present disclosure is to provide a metal component and a ceramic substrate capable of improving bonding reliability under high-temperature environment. 
     According to one aspect of the present disclosure, a columnar metal component comprises: 
     a first main surface; and 
     a second main surface on an opposite side to the first main surface, 
     wherein the first main surface includes a first groove, and wherein the metal component includes a through-hole penetrating the metal component from the first main surface to the second main surface. 
     According to the present disclosure, it is possible to improve bonding reliability under high-temperature environment. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG.  1    is a cross-sectional view showing an outline of a ceramic substrate according to a first embodiment. 
         FIG.  2    is a top view showing a metal component in the first embodiment. 
         FIG.  3    is a bottom view showing the metal component in the first embodiment. 
         FIG.  4    is a front view showing the metal component in the first embodiment. 
         FIG.  5    is a bottom view showing a first wiring layer. 
         FIG.  6    is a cross-sectional view showing a bonding structure between the first wiring layer and the metal component in the first embodiment. 
         FIG.  7    is a cross-sectional view showing the bonding structure between the first wiring layer and the metal component in the first embodiment. 
         FIG.  8    is a cross-sectional view showing the bonding structure between the first wiring layer and the metal component in the first embodiment. 
         FIG.  9    is a top view showing a metal component in a second embodiment. 
         FIG.  10    is a cross-sectional view showing a bonding structure between the first wiring layer and the metal component in the second embodiment. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinafter, embodiments of the present disclosure will be specifically described with reference to the accompanying drawings. Note that, in the specification and drawings, the constitutional elements having substantially the same functional configurations are denoted with the same reference signs, and the overlapping descriptions may be omitted. In addition, in the present disclosure, the X1-X2 direction, the Y1-Y2 direction, and the Z1-Z2 direction are defined as directions orthogonal to each other. The plane including the X1-X2 direction and the Y1-Y2 direction is described as the XY plane, the plane including the Y1-Y2 direction and the Z1-Z2 direction is described as the YZ plane, and the plane including the Z1-Z2 direction and the X1-X2 direction is described as the ZX plane. Note that, for convenience, the Z1-Z2 direction is defined as the upper and lower direction, the Z1 side is defined as the upper side, and the Z2 side is defined as the lower side. In addition, ‘in atop view’ means seeing a target object from the Z1 side, and ‘planar shape’ means a shape of a target object as seen from the Z1 side. However, the metal component and the ceramic substrate can be used in inverted states, or can be arranged at an arbitrary angle. 
     First Embodiment 
     First of all, a first embodiment will be described. The first embodiment relates to a ceramic substrate. 
     [Outline of Configuration of Ceramic Substrate] 
     First, an outline of a ceramic substrate according to the first embodiment will be described.  FIG.  1    is a cross-sectional view showing an outline of a ceramic substrate according to the first embodiment. As shown in  FIG.  1   , a ceramic substrate  1  includes a first wiring layer  11 , a first ceramic layer  12 , a second wiring layer  13 , a second ceramic layer  14 , a third wiring layer  15 , a third ceramic layer  16 , an electrode  17  and a fourth ceramic layer  18 . The first ceramic layer  12 , the second ceramic layer  14 , the third ceramic layer  16 , and the fourth ceramic layer  18  constitute a ceramic insulating base material. 
     The first wiring layer  11  is formed on one surface (surface on the Z2 side) of the second ceramic layer  14 . As a material of the first wiring layer  11 , tungsten (W) may be used, for example. As the material of the first wiring layer  11 , molybdenum (Mo) or the like may also be used. A thickness of the first wiring layer  11  may be set to about 5 μm, for example. The first wiring layer  11  is an example of the conductive layer. 
     As a material of the second ceramic layer  14 , for example, sodium oxide (Na 2 O), aluminum oxide (Al 2 O 3 ), boron oxide (B 2 O 3 ), silicon dioxide (SiO 2 ) or the like can be used. A thickness of the second wiring layer  14  may be set to about 10 μm, for example. 
     The second ceramic layer  14  is formed with a first via hole  14   x  for exposing an upper surface (surface on the Z1 side) of the first wiring layer  11 . The first via hole  14   x  is formed to penetrate through the second ceramic layer  14 . 
     The second wiring layer  13  is formed on the other surface (surface on the Z1 side) of the second ceramic layer  14 . The second wiring layer  13  includes a via fill filled in the first via hole  14   x  and a wiring pattern formed on the second ceramic layer  14 . The second wiring layer  13  is electrically connected to the first wiring layer  11  exposed into the first via hole  14   x . A thickness of the wiring pattern constituting the second wiring layer  13  may be set to about 5 μm, for example. 
     The third ceramic layer  16  is formed on the second ceramic layer  14  so as to cover the second wiring layer  13 . As a material of the third ceramic layer  16 , for example, sodium oxide (Na 2 O), aluminum oxide (Al 2 O 3 ), boron oxide (B 2 O 3 ), silicon dioxide (SiO 2 ) or the like can be used. A thickness of the third wiring layer  16  may be set to about 10 μm, for example. The third ceramic layer  16  is formed with a second via hole  16   x  for exposing an upper surface (surface on the Z1 side) of the second wiring layer  13 . The second via hole  16   x  is formed to penetrate through the third ceramic layer  16 . 
     The third wiring layer  15  is formed on the third ceramic layer  16 . The third wiring layer  15  includes a via fill filled in the second via hole  16   x  and a wiring pattern formed on the third ceramic layer  16 . The third wiring layer  15  is electrically connected to the second wiring layer  13  exposed into the second via hole  16   x . A thickness of the wiring pattern constituting the third wiring layer  15  may be set to about 5 μm, for example. 
     The fourth ceramic layer  18  is formed on the third ceramic layer  16  so as to cover the third wiring layer  15 . As a material of the fourth ceramic layer  18 , for example, sodium oxide (Na 2 O), aluminum oxide (Al 2 O 3 ), boron oxide (B 2 O 3 ), silicon dioxide (SiO 2 ) or the like can be used. A thickness of the fourth wiring layer  18  may be set to about 10 μm, for example. The fourth ceramic layer  18  is formed with a third via hole  18   x  for exposing an upper surface (surface on the Z1 side) of the third wiring layer  15 . The third via hole  18   x  is formed to penetrate through the fourth ceramic layer  18 . 
     The electrode  17  includes a via fill filled in the third via hole  18   x . A surface  17   a  of the electrode  17  on the Z1 side is substantially flush with a surface  16   a  of the fourth ceramic layer  18  on the Z1 side. That is, the surface  17   a  of the electrode  17  is exposed from the surface  16   a  of the fourth ceramic layer  18 . The electrode  17  is electrically connected to the third wiring layer  15  exposed into the third via hole  18   x . A thickness of the electrode  17  may be set to about 5 μm, for example. 
     The first ceramic layer  12  is formed on one surface (surface on the Z2 side) of the second ceramic layer  14  so as to cover the first wiring layer  11 . The first ceramic layer  12  is formed with an opening portion  12   x , and a part of the first wiring layer  11  is exposed into the opening portion  12   x  of the first ceramic layer  12 . As a material of the first ceramic layer  12 , for example, sodium oxide (Na 2 O), aluminum oxide (Al 2 O 3 ), boron oxide (B 2 O 3 ), silicon dioxide (SiO 2 ) or the like can be used. A thickness of the first wiring layer  12  may be set to about 15 μm, for example. The first ceramic layer  12  is an example of the insulating layer. 
     A metal component  120  is provided on an inner side of the opening portion  12   x . The metal component  120  is bonded to the first wiring layer  11  by a solder bonding layer  30 . The solder bonding layer  30  preferably has a melting point of 250° C. or higher and a low coefficient of thermal expansion. A composition of the solder bonding layer  30  is preferably Au—Sn, Sn—Sb, Sn—Cu, Sn—Bi, or those obtained by adding Ag, Ge, Sb, Ni or the like to the same. 
     [Composition of Metal Component] 
     Next, a configuration of the metal component  120  will be described.  FIG.  2    is a top view showing a metal component in the first embodiment.  FIG.  3    is a bottom view showing the metal component in the first embodiment.  FIG.  4    is a front view showing the metal component in the first embodiment. 
     As shown in  FIGS.  2  to  4   , the metal component  120  in the first embodiment has a cylindrical shape. The metal component  120  has a first main surface  121 , a second main surface  122  on an opposite side to the first main surface  121 , and a side surface  123 . 
     The first main surface  121  is formed with a plurality of first grooves  126  each extending radially from a center to an outer edge. In  FIG.  2   , eight first grooves  126  are formed at intervals of 45 degrees in a circumferential direction, for example. However, the number of the first grooves  126  formed on the first main surface  121  is not limited to eight. The number of the first grooves  126  may be less than eight, or more than eight, but at least four first grooves  126  are formed at intervals of 90 degrees in the circumferential direction. For example, a depth of the first groove  126  is 50 μm to 100 μm, and a width thereof is 100 μm to 300 μm. 
     The metal component  120  is formed with a plurality of through-holes  127  penetrating the metal component  120  from the first main surface  121  to the second main surface  122 . In the first main surface  121 , the positions of the first grooves  126  and the through-holes  127  are misaligned to each other. In other words, the positions of the first grooves  126  and the through-holes  127  do not overlap each other. A total of four through-holes  127  are formed at intervals of 90 degrees in the circumferential direction, for example. For example, a diameter of the through-hole  127  is 100 μm to 300 μm. 
     The side surface  123  is formed with a plurality of second grooves  128 . The plurality of second grooves  128  connects to the first main surface  121  and the second main surface  122 . In other words, the side surface  123  connects the first main surface  121  and the second main surface  122 , and the plurality of second grooves  128  extend from the first main surface  121  to the second main surface  122 . A total of eight second grooves  128  are formed at intervals of 45 degrees in the circumferential direction, for example. Each of the second grooves  128  connects to the first groove  126  in the first main surface  121 . For example, a depth of the second groove  128  is 50 μm to 100 μm, and a width thereof is 100 μm to 300 μm. 
     A diameter of the metal component  120  is smaller than a diameter of the opening portion  12   x . There is a gap  143  between the metal component  120  and an inner wall surface of the opening portion  12   x  (refer to  FIGS.  6  and  7   ). 
     [Configuration of First Wiring Layer] 
     Next, a configuration of the first wiring layer  11  will be described.  FIG.  5    is a bottom view showing the first wiring layer. 
     As shown in  FIG.  5   , the first wiring layer  11  has a convex portion  130  protruding into the opening portion  12   x . The convex portion  130  has a cylindrical shape. For example, a height of the convex portion  130  is 50 μm to 100 μm. A diameter of the convex portion  130  is smaller than the diameter of the opening portion  12   x , and a gap  142  exists between the convex portion  130  and the inner wall surface of the opening portion  12   x  (refer to  FIGS.  7  and  8   ). For example, a size of the gap  142  is 50 μm to 100 μm. The gap  142  is an example of the second gap. On the convex portion  130 , for example, nickel plating or gold plating on nickel plating is preferably performed. 
     A surface  131  of the convex portion  130  on the Z2 side is formed with a plurality of third grooves  136  extending radially from a center to an outer edge. A total of eight third grooves  136  are formed at intervals of 45 degrees in the circumferential direction, for example. For example, a depth of the third groove  136  is 50 μm to 100 μm, and a width thereof is 100 μm to 300 μm. 
     [Bonding Structure Between First Wiring Layer and Metal Component] 
     Next, a bonding structure between the first wiring layer  11  and the metal component  120  will be described.  FIGS.  6  to  8    are cross-sectional views showing a bonding structure between the first wiring layer  11  and the metal component  120 .  FIG.  6    corresponds to a cross-sectional view taken along a line VI-VI in  FIGS.  2 ,  3  and  5   .  FIG.  7    corresponds to a cross-sectional view taken along a line VII-VII in  FIGS.  2 ,  3  and  5   .  FIG.  8    corresponds to a cross-sectional view taken along a line VIII-VIII in  FIGS.  2 ,  3  and  5   . 
     As shown in  FIGS.  6  to  8   , the metal component  120  is inserted in the opening portion  12   x  so that the first main surface  121  faces the surface  131  of the convex portion  130 . For example, in the top view, the through-hole  127  of the metal component  120  and the third groove  136  of the convex portion  130  may overlap each other. The solder bonding layer  30  is provided between the first main surface  121  and the surface  131 . 
     As shown in  FIGS.  6  and  7   , the gap  143  exists between the metal component  120  and the inner wall surface of the opening portion  12   x . In addition, as shown in  FIG.  8   , in the portion in which the second groove  128  is formed, a gap  141  larger than the gap  143  exists between the metal component  120  and the inner wall surface of the opening portion  12   x . The gap  141  is an example of the first gap. 
     When bonding the metal component  120  to the first wiring layer  11 , a solder material serving as the solder bonding layer  30  is disposed between the first wiring layer  11  and the metal component  120 , the solder material is melted by heating, and thereafter, the solder bonding layer  30  is formed by cooling. The solder material contains flux, and when melted, the flux volatilizes. In the present embodiment, the volatilized flux is discharged to an outside of the opening portion  12   x  through, for example, the third groove  136  and the through-hole  127 , and is also discharged to the outside of the opening portion  12   x  through the first groove  126  or third groove  136  and the second groove  128 . For this reason, it is difficult for a void to exist in the solder bonding layer  30 . That is, according to the present embodiment, it is possible to reduce voids in the solder bonding layer. 
     In addition, the molten solder material gathers between the first main surface  121  and the surface  131 , and also flows into the gap  141 , the gap  142 , and the through-hole  127 . For this reason, while a large contact area can be obtained between the solder bonding layer and the first wiring layer  11 , a large contact area can also be obtained between the solder bonding layer  30  and the metal component  120 . Therefore, it is possible to obtain an excellent anchor effect. 
     Further, a thickness (dimension in the Z1-Z2 direction) of the solder bonding layer is not uniform within a plane parallel to the XY plane. For example, thicknesses are different from each other among a portion positioned between the first main surface  121  and the surface  131 , a portion slotted into the third groove  136 , and a portion slotted into the first groove  126 . In general, when used at a high temperature of 200° C. or higher, an intermetallic compound may grow with aging change and the like in the solder bonding layer, and a fatigue failure may occur in the solder bonding layer with the growth of the intermetallic compound. On the other hand, in the present embodiment, since the thickness of the solder bonding layer is not uniform, the fatigue failure of the solder bonding layer  30  with growth of the intermetallic compound can be suppressed. 
     In this way, according to the first embodiment, it is possible to improve bonding reliability. 
     For example, power may be supplied to the first wiring layer  11  via the metal component  120 . 
     Second Embodiment 
     Next, a second embodiment will be described. The second embodiment is different from the first embodiment, in terms of the configuration of the metal component.  FIG.  9    is a top view showing a metal component in the second embodiment. 
     In the second embodiment, a metal component  220  is provided on an inner side of the opening portion  12   x , instead of the metal component  120 . The metal component  220  is bonded to the first wiring layer  11  by the solder bonding layer  30 . 
     The metal component  220  is formed with a plurality of through-holes  227  penetrating from the first main surface  121  to the second main surface  122 , instead of the through-holes  127 . In the first main surface  121 , positions of the first groove  126  and the through-hole  227  overlap each other. A total of four through-holes  227  are formed at intervals of 90 degrees in the circumferential direction, for example. For example, a diameter of the through-hole  227  is 100 μm to 300 μm. 
     The other configurations of the metal component  220  are similar to those of the metal component  120 . 
     Next, a bonding structure between the first wiring layer  11  and the metal component  220  will be described.  FIG.  10    is a cross-sectional view showing a bonding structure between the first wiring layer  11  and the metal component  220 .  FIG.  10    corresponds to a cross-sectional view taken along a line X-X in  FIG.  9   . 
     As shown in  FIG.  10   , the metal component  220  is inserted in the opening portion part  12   x  so that the first main surface  121  faces the surface  131  of the convex portion  130 . For example, in the top view, the through-hole  227  of the metal component  220  and the third groove  136  of the convex portion  130  may deviate from each other in the circumferential direction. 
     The other configurations are similar to those of the first embodiment. 
     When bonding the metal component  220  to the first wiring layer  11 , a solder material serving as the solder bonding layer  30  is disposed between the first wiring layer  11  and the metal component  220 , the solder material is melted by heating, and thereafter, the solder bonding layer  30  is formed by cooling. The solder material contains flux, and when melted, the flux volatilizes. In the present embodiment, the volatilized flux is discharged to the outside of the opening portion  12   x  through, for example, the first groove  126  and the through-hole  227 , and is also discharged to the outside of the opening portion  12   x  through the first groove  126  or third groove  136  and the second groove  128 . 
     Therefore, also in the second embodiment, it is possible to improve the bonding reliability, similar to the first embodiment. 
     Note that, in the present disclosure, the planar shape of the ceramic substrate is not particularly limited. For example, the planar shape of the ceramic substrate may be a rectangular shape or a circular shape. 
     The material of the metal component is not particularly limited, and, for example, a material in which nickel plating has been implemented on a base material of a tungsten-copper alloy may be used. 
     In addition, the shape of the metal component is not limited to the cylindrical shape, and may be a polygonal column shape or the like. 
     Although the preferred embodiments and the like have been described in detail, the present disclosure is not limited to the above-described embodiments and the like, and a variety of changes and replacements can be made for the above-described embodiments and the like without departing from the scope defined in the claims.