JP2009218287A - Through-hole filled substrate, and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a through-hole filled substrate whose through-hole has a high allowable current value, and to provide a method of manufacturing the same. <P>SOLUTION: A through conductor 24 is composed of an intermediate layer 26 and an inner peripheral conductor 28 using two kinds of conductor pastes differing in baking shrinkage rate, so the intermediate layer 26 is firmly fixed to an inner peripheral surface of the through-hole 22 and the inner peripheral conductor 28 and then the through conductor 24 composed of them is firmly fixed in the through-hole 22. Further, the paste for the inner peripheral conductor has a small baking shrinkage rate and then size variation of the through conductor 24 during baking and in a temperature cycle is suppressed, so peeling of the through conductor 24 from the inner peripheral surface of the through-hole 22 and breaking of wiring between wiring layers 16 and 20 on upper and lower end surfaces thereof are suitably suppressed in combination with firm fixation of the intermediate layer 26 to the inner peripheral surface of the through-hole 22. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a through-hole-filled board in which a through-hole filled in a through-hole formed in the board and a manufacturing method thereof.

  For example, in a thick film circuit board using a ceramic substrate made of alumina or the like, a through hole (that is, a through hole) is provided in the substrate, a conductor layer is formed on the inner wall surface of the through hole, and wiring provided on both sides of the substrate is provided. They are connected to each other (see, for example, Patent Documents 1 and 2). Although such a through hole has high conductivity, the conductor cross-sectional area in the substrate thickness direction is small, so it is used for small current applications, for example, about 1 (A). A structure is desired. For example, a current of about 50 to 60 (A) is desired for a board for an electric power steering (EPS) of a large vehicle.

In order to allow a large current to flow, it is necessary to increase the cross-sectional area of the conductor in the through hole. For example, it is conceivable to fill the entire through hole with a conductive material. However, since the conductive paste for through holes has a large shrinkage due to firing, there is a problem of peeling from the inner wall surface when the through holes are filled and fired. In addition, since the end surface is remarkably recessed from the substrate surface due to firing shrinkage, there is a problem that it is difficult to ensure connection with wiring on both surfaces of the substrate.
Japanese Patent Laid-Open No. 03-050781 Japanese Patent Laid-Open No. 09-307207 JP 2006-287019 A JP 2000-058995 A JP 2001-094223 A JP 2004-343056 A JP 2007-027684 A

  On the other hand, conventionally, various structures in which a conductor is filled in a through hole have been proposed. For example, a metal film made of Ni and Cr is formed on the wall surface of the through hole by sputtering or the like, and an electrode material made of Cu and Sn is filled (see, for example, Patent Document 3). Also, there is a type in which a metallized layer of W or Mo is provided on the inner wall surface of the through hole and a plated layer of Cu or Ag is filled (see, for example, Patent Document 4). In addition, there is a type in which a Cu-W metal column containing 20 to 35 (% by weight) of Cu is disposed in the through hole and the metal circuit boards on both sides of the substrate are connected to this (for example, see Patent Document 5). Also, there is a type in which a Cu-based conductor layer baked at 750 (° C.) or less is provided on both surfaces of the substrate, and the conductor layers on both sides are connected by an Ag-based conductor filled in the through hole (see, for example, Patent Document 6). .).

  However, the structures described in Patent Documents 3 and 4 require film formation by sputtering, metallization, and the like, and thus there is a problem that the manufacturing process becomes complicated and the manufacturing cost increases. Moreover, in the structure described in the said patent document 5, since the said metal pillar is brazed to the metallizing layer provided in the inner wall surface of the through-hole, the metallization is necessary, the process becomes complicated and the cost increases. There's a problem. Moreover, since the metal pillar and the metal circuit board are simply brought into contact with each other, it is necessary to extremely smooth the contact surfaces in order to ensure sufficient conductivity. Increase costs further. In addition, the structure described in Patent Document 6 is difficult to realize when it is easily peeled off from the inner wall surface of the through-hole when using a general thick film silver paste for a conductor film that has large firing shrinkage as described above.

  Incidentally, filling a through hole provided in a ceramic substrate with a metal material has been conventionally performed for the purpose of improving heat dissipation of the substrate, and is referred to as a thermal via (see, for example, Patent Document 7). ). A heat sink made of metal such as aluminum that has excellent heat conduction is placed on the back side of the board. Is increased. Since the temperature rise on the substrate surface is suppressed by such improvement in heat dissipation, for example, the mounting density of components on the substrate surface can be increased. As a result, it is easy to reduce the size and increase the functionality of the substrate.

  The thermal via needs to have both end surfaces in close contact with the component and the heat sink so that the above-described heat transfer is performed satisfactorily. Therefore, for example, by using a material having a large particle size and suppressed sinterability, firing shrinkage is reduced, and the end surface is suitably suppressed from being recessed from the substrate surface. However, when the thermal via paste was used as it is for the through holes, through-holes where electrical connection with the wiring layers on both sides of the substrate could not be obtained were generated at a rate of about 40 (%). Moreover, even in the through holes in which electrical connection was initially obtained, the resistance value in the direction of the substrate thickness was as high as, for example, about 12.6 (mΩ) on average, and further, when the thermal cycle test was performed, electrical connection was made in all the through holes. It was lost and turned out to be unusable for wiring connections. The above paste for thermal vias has a small contact area between particles as a result of suppression of sinterability and low adhesion strength to the ceramic substrate, resulting in low conductivity and shrinkage during firing or cooling cycle. It is considered that the connection with the wiring layer was broken due to peeling from the inner wall surface of the through hole.

  The present invention has been made in the background of the above circumstances, and an object thereof is to provide a through-hole-filled substrate having a high permissible through-hole current value and a method for manufacturing the same.

  In order to achieve such an object, the gist of the first invention is that a wiring layer formed in a predetermined planar shape on both surfaces of a ceramic substrate is filled and formed in a through-hole penetrating the substrate in the thickness direction. A through-hole-filled substrate connected to each other by through conductors, wherein (a) the through conductor is a cylindrical intermediate layer made of a first conductor material fixed to an inner peripheral surface of the through hole, and the intermediate An inner conductor made of a second conductor material fixed to the inner circumference of the layer, and the first conductor material has a larger firing shrinkage ratio than the second conductor material and has an adhesive strength to the ceramic substrate. Is that it is expensive.

  In addition, the gist of the second invention for achieving the above object is that a wiring layer formed in a predetermined planar shape on both sides of a ceramic substrate is filled and formed in a through-hole penetrating the substrate in the thickness direction. A method of manufacturing through-hole-filled substrates connected to each other by through conductors, wherein: (a) a predetermined first conductor paste is applied to the inner peripheral surface of the through-holes and subjected to a firing treatment; An intermediate layer forming step of forming an intermediate layer of a predetermined thickness that constitutes the outer peripheral portion of the conductor; and (b) a predetermined second conductor paste filled in the through-hole in which the intermediate layer is formed and fired. Forming an inner peripheral conductor that forms an inner peripheral portion of the through conductor, and the first conductor paste has a larger firing shrinkage ratio than the second conductor paste and Contact with the ceramic substrate High wear strength.

  According to the first aspect of the invention, the through conductor is composed of an intermediate layer and an inner peripheral conductor on the inner peripheral side thereof, but the first conductor material constituting the intermediate layer is the second conductor constituting the inner peripheral conductor. Since the adhesive strength with the ceramic substrate is higher than that of the material, the inner peripheral conductor is firmly fixed in the through hole through the intermediate layer, and the through-hole having the intermediate layer and the inner peripheral conductor is extended. The conductor is firmly fixed to the ceramic substrate. At this time, since the second conductor material has a smaller firing shrinkage ratio than the first conductor material, the dimensional change of the through conductor during firing or cooling / cooling cycle is suppressed, so that the intermediate layer is formed on the inner wall surface of the through hole. Combined with being firmly fixed, the through conductor is preferably prevented from peeling from the inner wall surface of the through hole and from being disconnected between the wiring layers on both sides of the ceramic substrate. The through hole is filled with the through conductor, but the intermediate layer made of the first conductor material having a relatively high firing shrinkage rate has high conductivity and the second conductor has a relatively low firing shrinkage rate. Since the inner conductor made of material is also inferior to the intermediate layer, the conductivity of the entire through conductor is limited to the case where only a thin intermediate layer is provided in the through hole, that is, the through hole does not fill the conductor. Compared to the case of a hole or a case where the entire through conductor is made of the second conductor material, the improvement is remarkably improved. Therefore, a through-hole-filled substrate having a high through-hole allowable current value can be obtained.

  According to the second invention, in the intermediate layer forming step, the intermediate layer is formed by applying and baking the first conductor paste on the inner peripheral surface of the through hole, and in the inner peripheral conductor forming step, the intermediate layer is formed. The inner conductor is formed by filling and firing the second conductor paste in the through hole in which the layer is formed. That is, a through conductor having an intermediate layer and an inner peripheral conductor is formed. At this time, since the first conductor paste has higher adhesive strength with the ceramic substrate than the second conductor paste, the inner peripheral conductor is firmly fixed in the through-hole through the intermediate layer, and The through conductor provided with the intermediate layer and the inner peripheral conductor is firmly fixed to the ceramic substrate. At this time, since the second conductor paste has a smaller shrinkage in firing than the first conductor paste, the dimensional change of the through conductor during firing or cooling cycle is suppressed, so that the intermediate layer is formed on the inner wall surface of the through hole. Combined with being firmly fixed, the through conductor is preferably prevented from peeling from the inner wall surface of the through hole and from being disconnected between the wiring layers on both sides of the ceramic substrate. Further, the through-hole is filled in the through-hole, but the intermediate layer produced from the first conductor paste having a relatively high firing shrinkage rate has high conductivity and has a relatively low firing shrinkage rate. Since the inner conductor formed from the two-conductor paste is also inferior to the intermediate layer, the conductivity of the entire through conductor is that when only a thin intermediate layer is provided in the through hole, that is, the conductor in the through hole. Compared to the case of a through hole not filled with, and the case where the entire through conductor is formed of the second conductor paste, the improvement is markedly improved. Therefore, it is possible to manufacture a through-hole-filled substrate having a high allowable current value of the through-hole.

In the present application, firing shrinkage, the film thickness after drying T _d, when the film thickness after firing was T _f, a value obtained by _{[(T d -T f) /} T d] × 100 is there.

  Moreover, in the said manufacturing method, it is better to perform each baking process separately and it is not preferable to perform the said intermediate | middle layer formation process and the said inner periphery conductor formation process separately. That is, the “intermediate layer” in the “filling the through hole in which the intermediate layer is formed with the second conductive paste” preferably means an intermediate layer that has been subjected to a firing treatment.

  In addition, the first conductor material, the second conductor material, the first conductor paste, and the second conductor paste have desired adhesive strength and conductivity within a range satisfying the relationship between the firing shrinkage ratio and the adhesive strength with the ceramic substrate. Appropriate ones can be used so as to obtain the properties. As the first conductor material or the first conductor paste for forming the intermediate layer, those conventionally used for through-holes or those having sinterability equivalent thereto can be suitably used. Further, as the second conductor material or the second conductor paste for forming the inner peripheral conductor, a metal paste conventionally used for thermal vias or a material having sinterability equivalent thereto can be suitably used. .

  Incidentally, the conventionally used through-hole conductor has a relatively high bonding strength with the ceramic substrate, but has a relatively high firing shrinkage rate. Conventional thermal via conductors have a relatively small firing shrinkage ratio, but have a relatively low adhesive strength with a ceramic substrate. Therefore, even when using any of these two types of conductors, if the through hole is filled alone, the force in the peeling direction generated by the shrinkage during firing and cooling cycle easily exceeds the adhesive strength. As a result, disconnection occurs between the inner peripheral surface and the wiring layer formed on the surface.

  Here, preferably, the first conductive material or the first conductive paste contains bismuth oxide and copper oxide. In this way, bismuth oxide has the advantage of promoting the sintering of the conductor powder and improving the wettability between the conductor paste and the ceramic, and copper oxide has the advantage of improving the adhesion between the produced conductor film and the ceramic. Therefore, when these are contained, a filled conductor having higher conductivity and less occurrence of disconnection can be obtained.

  Preferably, the intermediate layer has a portion extending around the through hole on at least one surface of the ceramic substrate. This further suppresses the intermediate layer from peeling from the inner peripheral surface of the through hole. Such a hook-shaped portion can enjoy a sufficient effect even if it is provided on only one surface of the ceramic substrate, but it is more preferable in terms of prevention of peeling and securing conduction if it is provided on both surfaces.

Preferably, the first conductive paste is made of conductive silver powder having a spherical shape having an average particle size in the range of 0.4 to 0.6 (μm) and a specific surface area of 1.5 to 1.8 (m ² / g). The second conductor paste includes a silver powder having a maximum particle size of 10 (μm) or more and an average particle size larger than that contained in the first conductor paste as a conductor component. In this way, since the first conductor paste contains silver powder having a sufficiently small particle size and high sinterability as a conductor component, an intermediate layer having high adhesion to the ceramic substrate and high conductivity can be generated. Further, since the second conductor paste contains silver powder having a sufficiently large particle size and low sinterability as a conductor component, an inner peripheral conductor having a sufficiently small firing shrinkage ratio can be obtained. The silver powder contained in the first conductor paste is preferable in terms of sinterability as the average particle size is smaller. However, if it is less than 0.4 (μm), handling becomes extremely difficult and dispersibility also deteriorates. The conductor component contained in the first conductor paste is not particularly limited and may be a copper-based or gold-based material, but a silver-based material is most preferable. The particle diameter is measured by a laser diffraction / scattering method, and the average particle diameter is a 50% average particle diameter measured by a particle size distribution meter.

  Preferably, the first conductive paste is a paste in which the silver powder is coated with zirconium oxide. In this way, since the sintering of the silver powder is suppressed by the zirconium oxide film, oversintering, abnormal grain growth, etc. are unlikely to occur, and a first conductor paste having appropriate sinterability can be obtained.

  Preferably, the silver powder contained in the second conductor material or the second conductor paste is manufactured by an atomizing method. In this way, since the silver powder produced by the atomizing method has a spherical shape and low sinterability, the second conductor material having a smaller firing shrinkage ratio than the first conductor material and the first conductor paste and It is suitable as a conductor component of the second conductor paste.

  Preferably, both of the intermediate layer and the inner peripheral conductor are made of a silver-based thick film material, and the wiring layer is made of a copper-based thick film material. Since the through conductor composed of the intermediate layer and the inner peripheral conductor has a sufficiently high adhesive strength with the ceramic substrate, it has a characteristic that it is difficult to peel off from the inner peripheral surface of the through hole. Even in a combination such as a copper-based thick film material in which it is difficult to ensure the adhesive strength between conductors, disconnection between the wiring and the through conductor can be suitably suppressed to ensure conduction. Therefore, a through-hole-filled substrate in which wiring is provided with a copper-based material that is cheaper than silver-based or gold-based material can be obtained.

  Preferably, the first conductor material and the first conductor paste have a firing shrinkage rate of 50 (%) or more. The first conductor material and the first conductor paste for forming the intermediate layer are desired to have high adhesive strength with the ceramic substrate and high conductivity, but have a firing shrinkage of 50% or more. If it is the material which has, adhesive strength and electroconductivity will become high enough.

  Preferably, the second conductor material and the second conductor paste contain particles having a shrinkage-inhibiting action (hereinafter referred to as a shrinkage-inhibiting agent). The first invention and the second invention are not limited to the above-described one that reduces the sintering shrinkage rate of the second conductor material and the second conductor paste by including silver powder having low sinterability as a conductor component as described above. Moreover, the thing which made the baking shrinkage rate of these 2nd conductor material and 2nd conductor paste small by adding the particle | grains which have a baking inhibitory effect is contained. Examples of the firing shrinkage agent include silicon nitride and palladium. Moreover, it is also preferable to use together the silver powder with low sinterability as described above and the shrinkage inhibitor.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. In the following embodiments, the drawings are appropriately simplified or modified, and the dimensional ratios, shapes, and the like of the respective parts are not necessarily drawn accurately.

  FIG. 1 is a view schematically showing a cross-section of the main part of a through-hole-filled substrate 10 according to an embodiment of the present invention. In FIG. 1, the through-hole-filled substrate 10 includes a substrate 12, a front surface side wiring layer 16 provided on the front surface 14 of the substrate 12, and a back surface side wiring layer 20 provided on the back surface 18 (hereinafter, these are particularly distinguished). When not, it is referred to as wiring layers 16 and 20) and a through conductor 24 provided in a through hole 22 provided through the substrate 12 in the thickness direction.

  The substrate 12 is made of alumina, which is often used for thick film circuit boards, for example, and has a thickness dimension of about 0.8 (mm), for example. The through hole 22 provided in the substrate 12 has a diameter of about 0.2 (mm), for example, and the entire inside thereof is filled with the through conductor 24. That is, the through hole 22 is filled with the conductor in close contact with the inner wall surface.

  The upper and lower end surfaces of the through conductors 24 are located on substantially the same plane as the front surface 14 and the back surface 18 of the substrate 12, respectively. That is, the upper and lower end surfaces of the through conductor 24 are located on the same plane as the front surface 14 and the rear surface 18, or are slightly recessed or slightly protruded. FIG. 1 depicts a slightly protruding state. The through conductor 24 is located on the outer peripheral side, and has a cylindrical intermediate layer 26 fixed to the inner peripheral surface of the through hole 22, and a columnar inner peripheral conductor 28 fixed to the inner peripheral surface of the intermediate layer 26. It consists of and.

  The intermediate layer 26 and the inner peripheral conductor 28 are both made of a thick film conductor material, for example, thick film silver. The intermediate layer 26 can be suitably used for, for example, a through-hole conductor, and is firmly fixed to the inner peripheral surface of the through-hole 22 with a thin thickness of about 2 to 3 (μm), for example. Further, the intermediate layer 26 has a relatively high conductivity such that a resistance value between the front surface 14 and the back surface 18 of the substrate 12 (hereinafter referred to as an end surface resistance value) is about 3 to 4 (mΩ), for example. The intermediate layer 26 has its upper and lower ends slightly protruding from the front surface 14 and the back surface 18, and the protruding end portion spreads around the through hole 22 in a bowl shape to the front surface 14 and the back surface 18. Each is fixed.

  On the other hand, the inner peripheral conductor 28 is conventionally used for thermal vias, for example, and has a diameter of, for example, about 194 to 196 (μm), and a resistance value between end faces of, for example, 3 to 4 (mΩ). ) Having a certain degree of conductivity. The inner peripheral conductor 28 has a larger cross-sectional area than the intermediate layer 26, but the conductivity between the inner peripheral conductors 28 is inferior, so that the resistance value between the end faces is approximately the same. The upper and lower ends of the inner peripheral conductor 28 are located on substantially the same plane as both ends of the intermediate layer 26. Since the through conductor 24 is composed of the intermediate layer 26 and the inner peripheral conductor 28 as described above, the overall resistance value between end faces is, for example, about 2.5 (mΩ) and has a relatively high conductivity.

  The intermediate layer 26 is made of a material having a relatively high sinterability, for example, containing about 98.9 (wt%) silver and about 1.1 (wt%) inorganic oxide as conductor components. The inorganic oxide is, for example, bismuth oxide and copper oxide, and is contained in a ratio of about 2: 1, for example.

  The inner conductor 28 includes, for example, about 94.1 (wt%) and about 5.1 (wt%) of silver and tin as conductor components and about 0.8 (wt%) of metal oxide, respectively. It consists of material which has low sinterability compared with material. Examples of the metal oxide include aluminum oxide, silicon oxide, iron oxide, zinc oxide, and rubidium. Zinc oxide is included in the range of about 0.5 (wt%), and other oxides are included in the range of 0.1 (wt%) or less. ing.

  The wiring layers 16 and 20 are made of, for example, a thick film conductor material containing copper as a conductor component, and are provided on the surface 14 with a thickness of about 5 to 150 (μm), for example. FIG. 2 shows an enlarged view of the main part of the surface side wiring layer 16. The front-side wiring layer 16 is provided with conductor wiring in a predetermined planar shape. For example, a connection portion 30 having a sufficiently larger area is provided on the through hole 22. . Although illustration of the planar shape is omitted, the back surface side wiring layer 20 is similarly provided with a conductor wiring having a connection portion on the through hole 22 in a planar shape different from that of the front surface side wiring layer 16.

  As described above, since both the wiring layers 16 and 20 are provided on the through hole 22, they are respectively fixed to the upper and lower end surfaces of the through conductor 24 provided therein. As a result, the wiring layers 16 and 20 are electrically connected through the through conductor 24. As described above, since the through conductor 24 has a relatively high conductivity of, for example, a resistance value of about 2.5 (mΩ), the wiring layers 16 and 20 on the front surface 14 and the back surface 18 are connected with a low resistance. . Moreover, since the through conductor 24 has a large cross-sectional area by filling the through hole 22 with a conductor, it has a connection structure in which a thin conductor layer is provided on the inner peripheral surface of the through hole 22. In comparison, for example, there is an advantage that a large current of about 50 to 60 (A) can be applied.

  Although not shown, the through hole 22 and the through conductor 24 as described above are provided in large numbers on the substrate 12, and the wiring layers 16 and 20 are provided at a plurality of locations via the plurality of through conductors 24. Are connected to each other. Further, electronic components such as ICs and resistors are mounted on the substrate 12, and a heat sink is fixed to the back surface 18 of the substrate 12 with an adhesive or the like as necessary. When the heat sink is provided in this way, the through conductor 24 filled in the through hole 22 can also function as a thermal via for releasing heat from the front surface 14 side to the back surface 18 side. However, since these are unnecessary for understanding the present embodiment, illustration and detailed description are omitted.

  FIG. 3 is a process flowchart for explaining the main part of the manufacturing process of the through-hole-filled substrate 10 described above. First, in the intermediate layer paste applying / drying step P1, the separately prepared intermediate layer paste is applied from the back side to the through hole 22 of the substrate 12 manufactured separately, and dried. Thereby, a coating film for forming the intermediate layer 26 is formed.

The substrate 12 is formed, for example, by forming the through-hole 22 in a ceramic unfired sheet formed by using a well-known appropriate sheet forming method, cutting it into a predetermined size, and subjecting it to a firing process. It is manufactured by. Moreover, said intermediate | middle layer paste is prepared by the following composition, for example. In the following composition, the conductor has an average particle diameter (D ₅₀ ) of 0.4 to 0.6 (μm), a specific surface area of 1.5 to 1.8 (m ² / g), has a spherical shape, and is coated with ZrO _{2 on} the surface. Using. The inorganic oxides are bismuth oxide and copper oxide. The intermediate layer paste thus constituted has high sinterability because it contains fine silver powder, and for example, shrinkage of about 50 (%) occurs during firing. It can be suitably used for forming a hole conductor. The average particle diameter is a 50% average particle diameter measured by a laser diffraction / scattering method using a particle size distribution meter.

  Next, in the firing step P2, the applied intermediate layer paste is fired. This firing process is performed at a firing temperature of about 850 (° C.) in an oxidizing atmosphere, for example. As a result, the intermediate layer 26 is generated from the intermediate layer paste. At this time, since the intermediate layer paste has high sinterability as described above, the generated intermediate layer 26 is firmly fixed to the inner peripheral surface of the through hole 22. In this embodiment, the intermediate layer paste application / drying step P1 and the firing step P2 correspond to the intermediate layer forming step.

  Next, in the inner conductor paste applying / drying step P3, a separately prepared inner conductor paste is applied and filled in the through hole 22 in which the coating film for the intermediate layer 26 is formed, and then subjected to a drying process. . The filling of the paste is performed, for example, by applying the paste to the through hole 22 from the front surface 14 side while sucking from the back surface 18 side. Thereby, a filling for forming the inner peripheral conductor 28 is generated.

The above-mentioned inner conductor paste is, for example, commercially available for thermal vias (for example, TR6906 manufactured by Tanaka Kikinzoku Kogyo Co., Ltd.) and prepared, for example, in the following composition. In the following composition, silver is produced by, for example, the atomizing method, and is a relatively coarse particle having a maximum particle size measured by a grind gauge (also referred to as a particle size gauge) of about 40 to 45 (μm). The glass is made of boron, silicon, calcium, aluminum, etc., the binder is, for example, ethyl cellulose, and the solvent is, for example, terpineol, butyl diglycol acetate, or aromatic hydrocarbon. Since the inner conductor paste contains a relatively coarse silver powder, it has low sinterability, and the firing shrinkage is, for example, about -2.1 (%).

  The maximum particle diameter by the above-mentioned grind gauge is a value obtained by a linear method evaluation that reads a scale at a position where three or more continuous lines of 10 (mm) or more appear side by side. When observed with an electron microscope (SEM), most of the particles were 10 to 15 (μm), that is, the average particle size was about 10 to 15 (μm), and particles of 40 (μm) or more were not recognized. Therefore, the maximum particle size is considered to be a measurement value of agglomerates in which several particles of about 10 (μm) are aggregated, and in this example, the silver powder constituting the inner conductor paste has a maximum particle size. Those having an average particle diameter of 10 (μm) or more and larger than the silver powder contained in the intermediate layer paste are used.

  Next, in the firing step P4, the coated / filled inner conductor paste is fired. This firing process is performed at a firing temperature of about 850 (° C.) in an oxidizing atmosphere, for example. As a result, the inner peripheral conductor 28 is generated from the inner peripheral conductor paste and is integrated with the intermediate layer 26 to generate the through conductor 24. At this time, since the inner peripheral conductor paste has a low firing shrinkage ratio as described above, the dimensional change during firing is small, so that the produced inner peripheral conductor 28 is solid while being firmly fixed to the intermediate layer 26. While being kept in a state, the amount of dents from the front surface 14 and the back surface 18 of the upper and lower end surfaces is kept small. In this embodiment, the inner conductor paste applying / drying step P3 and the firing step P4 correspond to the inner conductor forming step.

  Next, in the wiring formation step P5, a separately prepared thick film conductor paste is applied to the front surface 14 and the back surface 18 of the substrate 12 in a predetermined planar shape, and predetermined according to the composition of the thick film conductor paste. The front surface side wiring layer 16 and the back surface side wiring layer 20 are formed by performing a baking treatment at a temperature. Thereby, the through-hole-filled substrate 10 is obtained. The thick film conductor paste is prepared by dispersing a conductor material such as copper and an inorganic binder in a vehicle, for example. If necessary, prior to the formation of the wiring, a separately prepared thick film resistor paste is applied to predetermined locations on the front surface 14 and the back surface 18 of the substrate 12, for example, in a rectangular pattern. A thick film resistor is formed by performing a baking process at a predetermined temperature according to the composition.

  Next, in the protective layer forming step P6, a separately prepared glass paste is applied to the back surface 18 of the substrate 12 so as to cover the wiring layer 20, and is subjected to a baking treatment at a temperature corresponding to the type of the glass, which is not shown. A protective layer is formed. The protective layer may be made of a synthetic resin. In that case, the resin paste may be used instead of the glass paste, and the firing temperature may be changed according to the material.

  According to the present embodiment, the through conductor 24 includes the intermediate layer 26 and the inner peripheral conductor 28 using the two kinds of conductor pastes having different firing shrinkage rates as described above. Since it is firmly fixed to the inner peripheral surface of the through hole 22 and the inner peripheral conductor 28, the inner peripheral conductor 28 is firmly fixed to the through hole 22 through the intermediate layer 26, and as a result, constituted by them. The through conductor 24 is firmly fixed in the through hole 22. In addition, since the inner conductor paste has a small firing shrinkage ratio, the dimensional change of the through conductor 24 during firing and cooling / cooling cycles is suppressed, so that the intermediate layer 26 is firmly fixed to the inner peripheral surface of the through hole 22. Combined with this, the through conductor 24 is peeled off from the inner peripheral surface of the through hole 22 and the disconnection between the upper and lower end surfaces of the wiring layers 16 and 20 is suitably suppressed.

  Next, the results of evaluating the characteristics of the through conductor 24 of the through hole filling substrate 10 of the example in which the through conductor 24 is formed as described above, together with comparative examples having different configurations will be described. The through-hole-filled substrate 32 shown in FIG. 4 comprises the entire through conductor 34 using the same conductor paste as the inner peripheral conductor 28. This is referred to as Comparative Example 1. Further, in the through hole filling substrate 36 shown in FIG. 5, intermediate layers 38 and 40 are provided so as to cover the upper and lower end surfaces of the through conductor 34 similar to the through hole filling substrate 32, and the wiring layers 16 and 20 are provided thereon. Is. The intermediate layers 38 and 40 are formed using the same conductive paste as the intermediate layer 26. This is referred to as Comparative Example 2. About these Examples and Comparative Examples 1 and 2, the filling property in the through hole, the bonding state with the wiring layers 16 and 20, the adhesiveness to the inner wall, and the resistance value reliability were evaluated.

  The above filling property and adhesiveness were determined by observing the cross-section of the through-hole 22 with an SEM and the appearance. The filling property was determined to be acceptable when there was no cavity in the through conductor. Further, the adhesiveness was determined to be acceptable if there was no gap between the inner peripheral surface of the through hole 22. In addition, the resistance value reliability was measured by measuring the resistance value between the upper and lower end surfaces of the through-hole 22 after manufacturing, after leaving at high temperature, and after cooling cycle, and evaluated the initial value and the degree of change. A resistance value of 5 (mΩ) or less was accepted.

  6 to 9 show SEM photographs of the cross section near the through hole 22 of Comparative Example 1, FIGS. 10 to 13 show SEM photographs of the cross section near the through hole 22 of Comparative Example 2, and FIGS. The SEM photograph of the cross section of the through-hole 22 vicinity of each is shown. 6, 10, and 14 show the entire image of the through hole 22, FIGS. 7, 11, and 15 show the vicinity of the opening of the through hole 22, and FIGS. 8, 12, and 16 show the inner peripheral surface of the through hole 22. The vicinity of the boundary with the through conductors 24 and 34, FIGS. 9, 13, and 17 are further enlarged views of the vicinity of the boundary.

  The fillability was determined based on FIGS. 6, 10, 14 and the like. However, no cavities were observed in any of the examples and comparative examples 1 and 2, and all were satisfactory. Moreover, the joining state with the wiring layers 16 and 20 was determined based on FIG. 7, FIG. 11, FIG. In each photograph, the boundary between the wiring layer 16 and the through conductors 24 and 34 appears at a position slightly less than half from above, the portion extending in the horizontal direction is the wiring layer 16, and the portion extending in the vertical direction is the through conductors 24 and 34. . In Comparative Examples 1 and 2, there are large gaps at these boundaries, but in the Examples, no gaps are observed, and it can be seen that the bonded state is good. Moreover, the adhesiveness with the inner wall was judged based on FIG. 8, FIG. 9, FIG. 12, FIG. 13, FIG. The left part in each photograph is the substrate 12, and the right part is the through conductors 24 and 34. In Comparative Examples 1 and 2, there is clearly a gap between the substrate 12 and the through conductor 34, but in the example, there is no gap and a good adhesion state is obtained.

  As described above, in Comparative Examples 1 and 2, there are gaps between the wiring layers 16 and 20 and the substrate 12 and the through conductor 34. As described above, the through conductor 34 is suppressed in sintering due to the use of coarse silver powder, and thus has a characteristic that the shrinkage during firing is small and the dimensional change is small. However, as a result of the reduced sinterability, the adhesive strength between the substrate 12 and the wiring layers 16 and 20 is also reduced, which is caused by shrinkage during firing and subsequent cooling and heating cycles. The through conductor 34 is peeled off from the substrate 12 or is easily broken with the wiring layers 16 and 20.

  FIG. 18 shows the results of measuring the initial resistance values of Comparative Examples 1 and 2 and the Example. In each comparative example and example, st1 to st6 are sample numbers. Each sample was manufactured with 12 pieces per side, and for each of the 12 pieces, the resistance value of the through hole 22 at a predetermined position was measured, and the measurement data was shown for each sample number. However, in Comparative Examples 1 and 2, there were some that were disconnected from the beginning and could not be measured (that is, the resistance value was infinite), so only those that could be measured, ie, st1 of Comparative Example 1 was 7 points, and st2 and st3 were Only one point of data is shown for each. Since all st4 was not measurable, there is no data. In Comparative Example 2, only data of 7 points and 11 points of st1 is shown. In Comparative Example 2, all 12 points of st3 to st6 could be measured.

  As shown in FIG. 18 above, in Comparative Example 1, there were many disconnections from the beginning of about 40 (%), and even those that were not disconnected showed an average high resistance value of 12 (mΩ) or more. Therefore, it is not suitable for wiring connection between the front surface 14 and the back surface 18. On the other hand, in Comparative Example 2, there was a case where disconnection occurred at st1 and st2, and the resistance value was about 6 (mΩ) in some through holes 22 where the connection was obtained. 22 is 5 (mΩ) or less, and the average is about 4.5 (mΩ), which is lower than the standard value of 5 (mΩ). Also, in the examples, it was confirmed that all the samples were securely connected and all had extremely high conductivity of 3 (mΩ) or less and an average value of about 2.4 (mΩ). Moreover, as shown in FIG. 18, the variation in the embodiment is extremely small.

  FIG. 19 summarizes the results of confirming the resistance value change by leaving the samples of Comparative Examples 1 and 2 and the example at high temperature or exposing them to a cooling cycle. In the high temperature standing test, the sample was held at 150 ± 3 (° C.) for 200 hours, 500 hours, and 1000 hours, and the resistance value after holding was measured. In the thermal cycle test, the sample is cooled to -40 ± 5 (° C), held for 30 minutes, heated to 150 (° C), and cooled and heated for 30 minutes for 200 cycles, 500 cycles, and 1000 cycles. The resistance value after each specified number of times was measured. Switching between the cooling temperature and the heating temperature was performed within 15 minutes. In addition, about the comparative example 1, only the thermal cycle test was done.

  As shown in FIG. 19, in the cooling / heating cycle test of Comparative Example 1, the resistance value increased remarkably at 200 cycles, and all the wires were disconnected at 500 cycles, making measurement impossible. On the other hand, in the high temperature standing test of Comparative Example 2, a tendency for the resistance value to increase as the standing time increased was clearly observed, and the resistance value increased by an average of about 2.7 (%) after standing for 500 hours. Therefore, it cannot be said that Comparative Example 2 has sufficient reliability although the change is smaller than that of Comparative Example 1. Further, in the cooling cycle test, a rapid increase in resistance value is observed in a relatively small number of cooling cycles, and the resistance value increases by about 76.6 (%) in 500 hours. Therefore, it cannot be said that Comparative Example 2 has sufficient resistance to the cooling and heating cycle.

  On the other hand, in the high temperature storage test of the example, almost no change in the resistance value was observed, and the increase in the resistance value remained at about 0.15 (%) even after being left for 500 hours. In the thermal cycle test, although a slight increasing tendency was observed, the increase was only about 4.8 (%) at 500 cycles, and the average was maintained at about 2.5 (mΩ) after 1000 cycles.

  According to the above results, the intermediate layer 26 having a high firing shrinkage ratio and a high adhesive strength to the substrate 12 and the inner peripheral conductor 28 having a low fired shrinkage rate and a low adhesive strength to the substrate 12 as in the present embodiment. By adopting a structure including the through conductor 24, the through-hole-filled substrate 10 having a low resistance value and high reliability can be obtained.

  In Comparative Example 1, the reason why the resistance value was initially high and the resistance value was remarkably increased in the cooling / heating cycle test and became unmeasurable was as shown in FIG. It is considered that a crack was generated between the through conductor 34 and the through conductor 34, and these were disconnected. In Comparative Example 1, since the through conductor 34 having low adhesion strength with the substrate 12 is merely filled in the through hole 22, the through conductor 34 and the substrate 12 are shown in FIGS. Are in a state where a gap is formed between them, that is, in a state where they are not bonded. Therefore, it is considered that conduction between the through conductor 34 and the wiring layers 16 and 20 is broken due to slight expansion and contraction of the through conductor 34 during the cooling / heating cycle test, and electrical conduction cannot be obtained.

  In Comparative Example 2, intermediate layers 38 and 40 having high adhesion strength between the substrate 12 and the through conductor 34 are provided between the wiring layers 16 and 20 and the through conductor 34. And the wiring layers 16 and 20 are improved, and disconnection is less likely to occur. However, it is the same as that of Comparative Example 1 that there is no provision for suppressing the expansion and contraction of the through conductor 34. As a result, partial tearing easily occurs in the cooling and heating cycle, and the resistance value increases remarkably. It is considered a thing.

  Compared to these comparative examples 1 and 2, in the structure of the example, the intermediate layer 26 is provided between the inner peripheral conductor 28 made of the same material as the through conductor 34 and the inner peripheral surface of the through hole 22. Since the through conductor 24 is firmly fixed to the inner peripheral surface of the through hole 22, shrinkage and expansion of the through conductor 24 are suppressed, and tearing at the interface with the wiring layers 16 and 20 is preferably suppressed. Conceivable.

  As mentioned above, although this invention was demonstrated in detail with reference to drawings, this invention can be implemented also in another aspect, A various change can be added in the range which does not deviate from the main point.

It is a figure which shows typically the principal part cross section of the through-hole filling board | substrate of one Example of this invention. It is a top view which expands and shows the principal part of the wiring layer provided on the through hole of the through hole filling board | substrate of FIG. It is process drawing for demonstrating the principal part of the manufacturing process of the thick film circuit board of FIG. It is a figure which shows typically the structure of the through-hole filling board | substrate of the comparative example 1. FIG. It is a figure which shows typically the structure of the through-hole filling board | substrate of the comparative example 2. FIG. 2 is a through-hole cross-sectional SEM image of Comparative Example 1. It is a figure which expands and shows the through-hole opening part vicinity of FIG. It is a figure which expands and shows the through-hole intermediate part of FIG. It is a figure which expands further and shows the through-hole intermediate part of FIG. 6 is a cross-sectional SEM image of a through hole of Comparative Example 2. It is a figure which expands and shows the through-hole opening part vicinity of FIG. It is a figure which expands and shows the through-hole intermediate part of FIG. It is a figure which further expands and shows the through-hole intermediate part of FIG. It is a through-hole cross-sectional SEM image of an Example. It is a figure which expands and shows the through-hole opening part vicinity of FIG. It is a figure which expands and shows the through-hole intermediate part of FIG. It is a figure which expands further and shows the through-hole intermediate part of FIG. It is a figure which shows the initial stage resistance value of an Example and a comparative example. It is a figure which shows the result of having evaluated the resistance value change of the Example and the comparative example.

Explanation of symbols

10: Through hole filled substrate, 12: Substrate, 14: Front surface, 16: Front side wiring layer, 18: Back side, 20: Back side wiring layer, 22: Through hole, 24: Through conductor, 26: Intermediate layer, 28: Inner conductor, 30: connection

Claims (7)

A through-hole-filled substrate in which wiring layers formed in a predetermined planar shape on both surfaces of a ceramic substrate are connected to each other by through conductors filled in through-holes that penetrate the substrate in the thickness direction,
The through conductor includes a cylindrical intermediate layer made of a first conductor material fixed to the inner peripheral surface of the through hole, and an inner peripheral conductor made of a second conductor material fixed to the inner peripheral surface of the intermediate layer. The through-hole-filled substrate is characterized in that the first conductor material has a larger firing shrinkage ratio and a higher adhesive strength with the ceramic substrate than the second conductor material.   The through-hole-filled substrate according to claim 1, wherein the first conductor material contains bismuth oxide and copper oxide.   3. The through-hole-filled substrate according to claim 1, wherein the intermediate layer has a portion extending around the through hole on at least one surface of the ceramic substrate. This is a method of manufacturing a through-hole-filled substrate in which wiring layers formed in a predetermined planar shape on both surfaces of a ceramic substrate are connected to each other by through conductors filled in through-holes that penetrate the substrate in the thickness direction. And
An intermediate layer forming step of forming an intermediate layer of a predetermined thickness dimension constituting the outer peripheral portion of the through conductor by applying a predetermined first conductor paste to the inner peripheral surface of the through hole and performing a firing process;
An inner circumference conductor forming step of forming an inner circumference conductor constituting an inner circumference portion of the through conductor by filling a predetermined second conductor paste into the through hole in which the intermediate layer is formed and performing a firing treatment; The method of manufacturing a through-hole-filled substrate, wherein the first conductor paste has a larger firing shrinkage ratio and a higher adhesive strength with the ceramic substrate than the second conductor paste.   The method for manufacturing a through-hole-filled substrate according to claim 4, wherein the first conductor paste contains bismuth oxide and copper oxide. The first conductor paste contains, as a conductor component, silver powder having a spherical shape with an average particle diameter in the range of 0.4 to 0.6 (μm) and a specific surface area in the range of 1.5 to 1.8 (m ² / g). The said 2nd conductor paste contains silver powder whose maximum particle diameter is 10 (micrometer) or more and whose average particle diameter is larger than what is contained in the said 1st conductor paste as a conductor component. Manufacturing method of through-hole filled substrate.   The method for manufacturing a through-hole-filled substrate according to claim 6, wherein the first conductor paste is obtained by coating the silver powder with zirconium oxide.