JP2012049310A - Wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wiring board in which a through conductor, connecting multiple wiring conductors on the upper and lower surfaces of an insulation layer electrically, can be prevented from peeling off from the inside surface of a through hole.SOLUTION: The wiring board comprises an insulating plate 1 made of a sintered ceramic body and having a through hole 3 penetrating in the thickness direction, and a through conductor 2 filling the through hole 3. A buffer layer 4 made of a sintered body containing air gaps 4a internally is interposed between the inside surface of the through hole 3 and the side surface of the through conductor 2. Since thermal expansion of the through conductor 2 can be absorbed by deformation of the buffer layer 4 containing the air gaps 4a, projection of the through conductor 2 from the insulating plate 1 can be prevented by preventing expansion of the through conductor 2 in the length direction.

Description

  The present invention includes an insulating plate having a through hole penetrating in the thickness direction, and a through conductor filled in the through hole penetrating the insulating plate in the thickness direction, and the upper and lower surfaces of the insulating plate are interposed through the through conductor. The present invention relates to a wiring board in which conductors such as wiring conductors are electrically connected to each other.

  Conventionally, as a wiring board used for mounting electronic components, etc., an insulating plate made of a ceramic sintered body and having a wiring conductor formed on the main surface (upper surface and lower surface), and a through-penetrating through the insulating plate in the thickness direction A device provided with a hole and a through conductor (via conductor) attached to the inner surface of the through hole is used. The wiring conductors on the upper and lower surfaces of the insulating plate have portions that are vertically overlapped at the positions where the through holes are formed, and these portions are electrically connected vertically via the through conductors.

  In such a wiring board, for example, an electrode of an electronic component or a probe for performing an electrical inspection of the electronic component is connected to the wiring conductor on the upper surface of the insulating plate, and the lower wiring conductor is connected to an external electric circuit board such as a circuit board. Is done. Then, the electronic component is electrically connected to an external electric circuit via the wiring conductor on the upper surface of the insulating plate, the through conductor, and the wiring conductor on the lower surface of the insulating plate, and transmission and reception of signals and electrical connection to the electronic component are performed. Inspects are performed.

  The through conductor is formed by forming a through hole with a circular opening in a predetermined position of an insulating layer made of a ceramic sintered body by laser processing, and after filling the metal paste such as silver-palladium into the through hole, the metal paste Is heated and bonded to the inner side surface of the through hole as a metal material.

JP-A-3-62992

  However, in such a wiring board, there is a difference in the coefficient of thermal expansion between the insulating plate and the through conductor (the through conductor is larger), so that a resin insulating layer is further added to the main surface of the insulating plate when mounting electronic parts. There is a problem that the through conductor may protrude outward from the main surface of the insulating plate due to heat generated when the other insulating layers are laminated. When the through conductor protrudes, for example, mechanical damage such as a crack occurs in the wiring conductor or the resin insulating layer laminated on the main surface of the insulating plate, and the reliability as the wiring board is lowered.

  The present invention has been completed in view of the above-mentioned problems of the prior art, and its purpose is to have a through conductor disposed on an insulating plate made of a ceramic sintered body protruding outward from the main surface of the insulating plate. An object of the present invention is to provide a wiring board capable of suppressing this.

  The wiring board of the present invention is a wiring board comprising a ceramic sintered body and having an insulating plate having a through hole penetrating in the thickness direction, and a through conductor filled in the through hole. A buffer layer made of a sintered body containing voids is interposed between the through conductors.

In the wiring board of the present invention, in the above configuration, the buffer layer is formed by melting the ceramic sintered body partially melted on the inner surface of the through-hole and solidifying after containing the void. It is characterized by being formed of a quality layer.

  In the wiring board of the present invention, in the above configuration, a resin insulating layer in contact with the buffer layer is laminated on the main surface of the insulating plate, and a part of the resin material forming the resin insulating layer is It has entered into the space of the buffer layer located on the main surface side of the insulating plate.

  According to the wiring board of the present invention, an insulating plate made of a ceramic sintered body and having a through hole penetrating in the thickness direction, and a through conductor filled in the through hole, the gap between the through hole and the through conductor is provided. In addition, since a buffer layer made of a sintered body including voids is interposed inside, when the through conductor thermally expands, the voids are included and compared to a ceramic sintered body that forms an insulating plate. The buffer layer that is easily deformed can be deformed according to the expansion of the through conductor. Therefore, expansion of the penetrating conductor in the length direction can be suppressed, and the penetrating conductor can be effectively suppressed from projecting outside the main surface of the insulating plate.

  Further, the wiring board of the present invention has the above-described configuration, wherein the buffer layer is solidified after the ceramic sintered body is partially melted on the inner side surface of the through hole, and is formed by a melt-modified layer including voids inside. When formed, the buffer layer may be formed by a melt-modified layer that is formed on the inner surface of the through hole when the through hole is formed by laser processing. Therefore, in this case, since the buffer layer can be formed simultaneously with the formation of the through hole, the productivity of the wiring board capable of suppressing the protrusion of the through conductor can be increased.

  In addition, since the melt-modified layer contains a glass component generated when the ceramic sintered body once melted, the buffer layer is deformed as compared with the case where the buffer layer is formed of a ceramic sintered body similar to an insulating plate, for example. It is effective in making the buffer layer easy to do.

  In the wiring board of the present invention, in the above configuration, the resin insulating layer in contact with the buffer layer is laminated on the main surface of the insulating plate, and a part of the resin material forming the resin insulating layer is the main plate of the insulating plate. In the case of entering the gap of the buffer layer located on the surface side, in addition to suppressing the protrusion of the through conductor, a configuration suitable for improving the migration resistance can be obtained.

  That is, in this case, since the buffer layer and the resin insulating layer are in close contact with the resin material that has entered the gap, the movement of the conductor component (ion) of the through conductor in the gap can be suppressed. Therefore, migration in which ions move from the end surface of the through conductor to the outside (for example, another adjacent through conductor) through the end surface of the buffer layer can be effectively suppressed. In this case, even if the resin material does not enter the gap, it is considered that the path of ions moving from the end face of the through conductor to the outside can be lengthened by the gap, but the resin material enters the gap. Since the movement of ions is suppressed, the effect of suppressing migration can be further increased.

  In addition, since the resin material is, for example, a polyimide resin and has a lower elastic modulus than the melt-modified layer and easily deforms, even if the resin material enters the gap, the buffer layer is difficult to deform. There is no such thing.

(A) is a top view which shows the principal part in an example of embodiment of the wiring board of this invention, (b) is sectional drawing in the AA of (a). It is principal part sectional drawing which expands and shows the principal part B of the wiring board shown in FIG. It is a top view which shows typically an example of the whole wiring board shown in FIG. It is principal part sectional drawing which expands and shows the principal part in the other example of embodiment of the wiring board of this invention.

  The wiring board of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1A is a top view showing a main part in an example of an embodiment of a wiring board of the present invention, and FIG. 1B is a cross-sectional view taken along line AA in FIG. FIG. 2 is an enlarged cross-sectional view showing a main part B of the wiring board shown in FIG. FIG. 3 is a plan view schematically showing an example of the entire wiring board whose main part is shown in FIG. 1 to 3, 1 is an insulating plate, 2 is a through conductor, 3 is a through hole, and 4 is a buffer layer. The through-conductor 2 is filled in the through-hole 3 formed in the insulating plate 1 so that the buffer layer 4 is interposed between the inner surface of the through-hole 3 and the through-conductor 2 to basically form a wiring board. ing. FIG. 1 shows a part of the wiring board, and such a part is arranged in a plurality of vertical and horizontal arrangements, and the entire wiring board as schematically shown in FIG. 3 is configured. .

  The insulating plate 1 is composed of an aluminum oxide sintered body, an aluminum nitride sintered body, a mullite sintered body, a glass ceramic sintered body, crystallized glass in which crystal components are precipitated in a glass base material, mica, or titanic acid. It is formed of a ceramic sintered body such as a ceramic material (so-called machinable ceramics), which is made of a microcrystalline sintered body of aluminum or the like and can be machined substantially as accurately as a metal material.

  If the insulating plate 1 is made of, for example, an aluminum oxide sintered body, it can be manufactured as follows. That is, a ceramic green sheet is formed by forming a slurry prepared by adding and mixing an appropriate organic binder and organic solvent to raw material powders such as aluminum oxide and silicon oxide into a sheet shape by a sheet forming technique such as a doctor blade method or a lip coater method. After that, the ceramic green sheet can be made into an appropriate shape and size by cutting or punching and fired at a temperature of about 1300 to 1500 ° C.

  The insulating plate 1 has, for example, a square plate shape, a disk shape, etc., for example, an upper surface is mounted with an electronic component (not shown) for mounting and electrical checking (electrical and mechanical connection of the electronic component to the wiring board) Then, it is used as a part for mounting to make an electronic device, or for temporarily placing an electronic component for electrical check). Electronic components include semiconductor integrated circuit elements such as ICs and LSIs, semiconductor elements including optical semiconductor elements such as LEDs (light emitting diodes), PDs (photodiodes), and CCDs (charge coupled devices), surface acoustic wave elements, and crystal vibrations. Various electronic components such as a piezoelectric element such as a child, a capacitive element, a resistor, and a micromachine (so-called MEMS element) in which a minute electromechanical mechanism is formed on the surface of a semiconductor substrate can be given.

  In the example shown in FIGS. 1 to 3, wiring conductors 5 are respectively formed on the upper surface and the lower surface of the insulating plate 1. The wiring conductor 5 is electrically connected to an electronic component, for example, and functions as a terminal for connecting a probe for transmitting / receiving a signal to the electronic component and performing an electrical check on the electronic component. The wiring conductors 5 on the upper and lower surfaces of the insulating plate 1 are electrically connected to each other via a through conductor 2 that penetrates the insulating plate 1 in the thickness direction.

  The electrical connection between the wiring conductor 5 and the electronic component is performed, for example, by joining an electrode (not shown) of the electronic component to a predetermined portion of the wiring conductor 5 via a conductive connecting material such as solder. In this case, the wiring conductor 5 is formed in a comparatively large pattern (as a so-called connection pad) such as a circular shape covering the end face of the through conductor 2 as shown in FIGS. The area may be increased to improve the reliability of the electrical connection to the electronic component.

  The wiring conductor 5 is made of, for example, a metal material such as copper, silver, palladium, gold, platinum, nickel, cobalt, tungsten, molybdenum, manganese, or an alloy material of these metal materials. If the wiring conductor 5 is made of tungsten, for example, a paste of tungsten prepared by kneading tungsten powder together with an organic solvent and a binder is applied to the main surface of the ceramic green sheet to be the insulating plate 1 by a screen printing method or the like. It can form by apply | coating to a predetermined pattern by a method, and baking simultaneously with a ceramic green sheet after that.

  The through hole 3 is formed, for example, by subjecting the insulating plate 1 made of a ceramic sintered body to drilling processing (laser processing) by laser beam irradiation. When the through hole 3 is formed by drilling the insulating plate 1 made of a ceramic sintered body (not in the state of the unfired ceramic green sheet), the dimensional accuracy due to shrinkage during firing is reduced. Unaffected by decline. Therefore, this case is advantageous in increasing the positional accuracy of the through hole 3 in the insulating plate 1.

  The through hole 3 has, for example, a circular shape with a diameter of about 200 μm to 700 μm, and the through conductor 4 is filled inside the through hole 3.

  The through conductor 2 is made of, for example, a metal material such as copper, silver, palladium, gold, platinum, nickel, cobalt, tungsten, molybdenum, manganese, or an alloy material of these metal materials. Since the through conductor 2 is for electrically connecting the conductors disposed above and below the insulating plate 1 such as the upper and lower wiring conductors 5, for example, the electrical resistance of the through conductor 2 is kept low. In consideration of the above, copper or silver is particularly suitable as the metal material for forming the through conductor 2.

  The through conductor 2 is formed by, for example, embedding a conductive paste prepared by kneading silver or copper powder together with an organic solvent and a binder by a method such as screen printing using vacuum suction in the through hole 3. By heating together with the insulating plate 1, the through holes 3 can be filled. In this case, a glass component may be added to the metal material forming the through conductor 2 in order to improve the adhesion to the insulating plate 1 (the inner surface of the through hole 3).

  In such a wiring board, for example, an electrode of an electronic component (not shown) and a probe (not shown) for performing an electrical inspection of the electronic component are connected to the wiring conductor 5 on the upper surface of the insulating plate 1. The wiring conductor 5 is connected to an external electric circuit board (not shown) such as a circuit board. The electronic component is electrically connected to an external electric circuit via the wiring conductor 5 on the upper surface of the insulating plate 1, the through conductor 2, and the wiring conductor 5 on the lower surface of the insulating plate 1. An electrical check for electronic components is performed. The electrical check for the electronic component is, for example, an inspection of whether or not the integrated circuit of the semiconductor integrated circuit element operates normally. In this case, in order to collectively inspect a plurality of semiconductor integrated circuit elements (not shown) formed on a semiconductor substrate (silicon wafer or the like) before cutting into individual pieces, for example, FIG. A wiring board as shown in FIG. 5 is used in which a wiring board is arranged on a mother board having the same size as a semiconductor substrate. In this case, the wiring board (wiring board arranged in large numbers) can be used as a so-called probe card.

  In the wiring board of the present invention, a buffer layer 4 made of a sintered body having a gap 4a inside is interposed between the side surface of the through conductor 2 and the inner side surface of the through hole 3. The buffer layer 4 is solidified after the ceramic sintered body is melted once, for example, a ceramic sintered body or crystallized glass similar to the insulating plate 1, a sintered body of glass material and ceramic filler particles (glass ceramic sintered body). Formed by a sintered body such as a melt-modified body. The buffer layer 4 is for absorbing thermal expansion of the through conductor 2 having a larger thermal expansion coefficient than the insulating plate 1 made of a ceramic sintered body.

  In this case, since the buffer layer 4 has a gap 4a inside, the deformation due to stress is easier than the ceramic sintered body forming the insulating plate 1 by the amount of the gap 4a. Therefore, the buffer layer 4, which is more easily deformed than the ceramic sintered body forming the insulating plate 1, can be deformed according to the expansion of the through conductor 2. Therefore, expansion of the through conductor 2 in the length direction can be suppressed, and the through conductor 2 can be effectively suppressed from projecting outside the main surface of the insulating plate 1.

  In the wiring board of the present invention, since the protrusion of the through conductor 2 from the insulating plate 1 (main surface) is suppressed as described above, the wiring conductor 5 and the resin insulating layer 6 are not peeled off by the protrusion of the through conductor 2. Deformation and the like can be effectively suppressed. Therefore, the probe can be easily and surely connected to the wiring conductor 5, and a wiring substrate with high bonding reliability of the resin insulating layer 6 to the insulating plate 1 can be obtained. Further, since peeling of the through conductor 2 from the insulating plate 1 (specifically, the inner surface of the through hole 3) is suppressed, electrical connection between the upper and lower surfaces of the insulating plate 1 via the through conductor 2 is prevented. It is possible to provide an effective wiring board for increasing reliability.

  The sintered body having the voids 4a can be formed, for example, by heating and sintering a ceramic material or glass material containing a resin material (not shown) that decomposes when heated. For example, before filling the through hole 3 of the insulating plate 1 with the conductive paste to be the through conductor 2, a ceramic material containing the above resin material is deposited on the inner surface of the through hole 3, and the conductive paste By heating together, the buffer layer 4 having the gap 4 a can be interposed between the side surface of the through conductor 2 and the inner side surface of the through hole 3.

  The gap 4a is preferably as large as the total volume is large in order to absorb the thermal expansion of the buffer layer through conductor 2, but if it is too large, the mechanical strength of the buffer layer 4 is reduced, and the through conductor 2 and the through hole 3 are reduced. There is a possibility that the bonding strength between the two will be low. Therefore, it is preferable that the total volume of the gap 4a is as large as possible within a range in which the bonding strength between the through conductor 2 and the through hole 3 can be ensured.

  In consideration of such conditions, the gap 4a is set to a volume of about 3 to 20% in total with respect to the total volume of the buffer layer 4 in order to effectively absorb the thermal expansion of the through conductor 2. That's fine.

For example, the insulating plate 1 is made of an aluminum oxide sintered body (thermal expansion coefficient is about 7 × 10 ⁻⁶ / ° C.), and the conductive material forming the through conductor 2 has a thermal expansion coefficient of about 8 to 20 × 10 ⁻ If the metal material (copper, silver, titanium, etc.) at about ⁶ / ° C. is used, the gap 4 a may be set to a volume of about 3 to 15% in total with respect to the buffer layer 4.

  The thickness of the buffer layer 4 (for example, the difference between the inner diameter and the outer diameter of the cylindrical buffer layer 4) is the material of the insulating plate 1 and the through conductor 2 and the dimensions of the through conductor 2 (thickness and length such as diameter). What is necessary is just to set suitably according to the calorie | heat amount etc. which act on a wiring board.

  The buffer layer 4 preferably has a large thickness in order to absorb the thermal expansion of the through conductor 2. However, if the buffer layer 4 is too thick, miniaturization and high density of the wiring board are hindered or difficult to form. There is a possibility that the productivity of the substrate is lowered. Therefore, the thickness of the buffer layer 4 is preferably set in the range of about 5 to 50 μm.

  In the example shown in FIG. 1, the gap 4a has an indefinite cross-sectional shape, but the cross-sectional shape may be circular or elliptical. Since the deformation of the buffer layer 4 for absorbing the thermal expansion of the through conductor 2 mainly occurs in the thickness direction, the gap 4a preferably has a large dimension in the thickness direction of the buffer layer 4.

  When a plurality of voids 4a are dispersed in the length direction of the buffer layer 4, these voids 4a may have the same or different sizes and shapes. In any case, the effect of absorbing the thermal expansion of the through conductor 2 can be obtained over the entire length of the buffer layer 4.

  Considering that the thermal expansion of the through conductor 2 is effectively absorbed by deformation of the buffer layer 4, it is preferable that the gaps 4 a are arranged evenly distributed throughout the buffer layer 4. In this case, even if the gap 4a is exposed on the inner surface of the buffer layer 4 (the surface in contact with the through conductor 2), if the glass component is added to the through conductor 2 as described above, It is mainly the glass component in the through conductor 2 that enters the glass, and the glass component has a smaller thermal expansion in the glass than the conductor metal such as copper in the through conductor 2. Therefore, the glass that has entered the gap 4 does not expand more than the through conductor 2, and this glass can be deformed when the through conductor 2 is thermally expanded to buffer the expansion of the through conductor 2. Therefore, even in such a case, the buffer property of the buffer layer 4 is not impaired.

  Moreover, the space | gap 4a shall consist of the melt-modification layer (no code | symbol) formed by the melt-modified body which solidifies after the part corresponded to the inner surface of the through-hole 3 among the insulating plates 1 once fuse | melted. Also good. In the melt-modified layer, since the ceramic sintered body forming the insulating plate 1 is once melted and turned into a liquid state as described above, air is entrained when rapidly cooled and solidified, so that a void 4a is formed inside. The Therefore, in this case, a sintered body having voids 4 a can be easily formed, and this sintered body can be formed as a buffer layer 4 on the inner surface of the through hole 3 in a layered manner. In this case, since the buffer layer 4 has already been formed on the inner side surface of the formed through hole 3, the side surface of the through conductor 2 is penetrated by filling the through hole 3 with a conductive paste and heating. A wiring board in which the buffer layer 4 is interposed between the inner surface of the hole 3 can be easily manufactured.

  Further, in order to melt the ceramic sintered body that forms the insulating plate 1 along the inner surface of the through hole 3, the through hole 3 may be formed by laser processing the insulating plate 1. When the insulating plate 1 is melted and removed by the laser beam in the thickness direction and the through hole 3 is formed, the ceramic sintered body is partially melted by heat also on the inner surface of the through hole 3. When the laser beam irradiation is stopped, the inner surface of the through hole 3 is cooled and solidified, and a melt-modified layer that becomes the buffer layer 4 is formed.

  That is, in the wiring board of the present invention, the buffer layer 4 is formed by a melt-modified layer containing voids inside, which is solidified after the ceramic sintered body is partially melted on the inner surface of the through-hole 3. When the through hole 3 is formed by laser processing, the buffer layer 4 can be formed by a melt-modified layer generated on the inner surface of the through hole 3. Therefore, in this case, since the buffer layer 4 can be formed simultaneously with the formation of the through hole 3, the productivity of the wiring board capable of suppressing the protrusion of the through conductor 2 can be increased.

  In addition, since the melt-modified layer includes a glass component generated when the once sintered ceramic sintered body is solidified, the buffer layer 4 is, for example, compared with a case where the ceramic sintered body similar to the insulating plate 1 is formed. It is effective in forming a buffer layer that is easily deformed. When the ceramic sintered body is, for example, an aluminum oxide sintered body, the elastic modulus is about 330 to 360 GPa, and the elastic modulus of the glass component is about 10 to 80 GPa (all at 1 atm). is there.

  When the buffer layer 4 is formed of a melt-modified layer, the number, size, and shape of the voids 4a inside the buffer layer 4 can be adjusted by the wavelength, pulse width, laser output, etc. of the laser beam.

Further, in the wiring board of the present invention, in the above configuration, as shown in FIG. 4, the resin insulating layer 6 in contact with the buffer layer 4 is laminated on the main surface of the insulating plate 1, and the resin insulating layer 6 is formed. When a part 6a of the resin material enters the gap 4a of the buffer layer 4 located on the main surface side of the insulating plate 1, in addition to suppressing the protrusion of the through conductor 2, the migration resistance is improved. A wiring board suitable for the above can also be obtained. That is, in this case, since the buffer layer 4 and the resin insulating layer 6 are in close contact with a part 6a of the resin material that has entered the gap 4a, the conductor component (ion) of the through conductor 2 in the gap 4a moves. Can be suppressed. Therefore, the migration of ions from the end face of the through conductor 2 through the end face of the buffer layer 4 to the outside (for example, another adjacent through conductor 4) can be effectively suppressed. In this case, even if the resin material 6a does not enter the gap 4a, it is possible to lengthen the ion movement path from the end face of the through conductor 2 to the outside by the gap 4a, but the resin material 6a has the gap 4a. Since the movement of ions is more effectively suppressed by entering, the effect of suppressing migration can be further increased.

  The resin material that forms the resin insulating layer 6 is, for example, a polyimide resin, and is a material that has a lower elastic modulus than the melt-modified layer and is easily deformed. Therefore, even if the resin material enters the gap 4a. The buffer layer 4 is not likely to be deformed. The polyimide resin has an elastic modulus of about 1 to 15 GPa, and the elastic modulus of the melt-modified layer 4 (sintered body) is about 10 to 60 GPa or about 330 to 360 GPa (both as described above). 1 atm).

  The resin insulating layer 6 is for arranging, for example, another wiring conductor (not shown) electrically connected to the wiring conductor 5 on the upper surface. A multilayer wiring board can be manufactured by laminating the resin insulating layer 6 and another wiring conductor on the insulating plate 1 of the wiring board.

  Such a resin insulation layer 6 can be laminated | stacked on the insulating board 1 of a wiring board by laminating | stacking the paste or sheet | seat of a non-hardened polyimide resin on the upper surface of the wiring board 1, for example, and making it harden | cure after that.

  Other wiring conductors that are electrically connected to the wiring conductor 5 are, for example, metal materials such as copper, silver, palladium, gold, platinum, aluminum, chromium, nickel, cobalt, titanium, tungsten, molybdenum, manganese, or these metals. It is made of an alloy material, and can be disposed on the upper surface of the resin insulating layer 6 by a thin film forming method such as sputtering, vapor deposition or plating.

  The electrical connection between the wiring conductor 5 and another wiring conductor is performed by forming a through conductor (via conductor) (not shown) in the resin insulating layer 6 by using a metal material such as copper and plating. However, this can be done via this via conductor.

A ceramic substrate made of an aluminum oxide sintered body has a diameter of about 680μm and a length of about 2500
A through-hole of μm is formed by laser processing, a silver paste is filled as a conductor paste inside the through-hole, heated at about 300 ° C. to form a through-conductor, and the wiring of Examples 1 and 2 described below 100 substrates were prepared for each. After 100 temperature wiring tests (-20 ° C to + 80 ° C, 1000 cycles) as an acceleration test for 100 wiring boards of Examples 1 and 2 and Comparative Example produced, the presence or absence of protrusion of the through conductor from the metal The appearance was confirmed using a microscope. Moreover, about the wiring board in which the protrusion generate | occur | produced in the penetration conductor, cross-sectional observation was performed using the scanning electron microscope, and the protrusion amount was measured.

Example 1
A buffer layer having a thickness of about 30 μm is formed between the side surface of the through conductor and the inner side surface of the through hole by a melt-modified layer, and the maximum of each of the gaps is about 50 to 60 μm and the minimum is about 10 to 20 μm. A standard-shaped (generally elongated elliptical spherical) void was formed in the buffer layer. The total volume of the voids was about 10% with respect to the volume of the buffer layer.

(Example 2)
A buffer layer having a thickness of about 30 μm is formed by a melt-modified layer between the side surface of the through conductor and the inner side surface of the through hole, and has a spherical shape with a diameter of about 3 to 10 μm or a long axis of about 10 to 20 μm. An oval spherical void having a short axis of about 5 μm was formed in the buffer layer. The total volume of the voids was about 5% with respect to the volume of the buffer layer.

(Comparative example)
A through hole was formed in the ceramic green sheet by punching, and after firing, the same conductive paste as in Examples 1 and 2 was filled into the through hole and heated under the same conditions to form a through conductor. As for the wiring board of the comparative example, 100 pieces were produced, and the presence or absence of protrusion of the through conductor was confirmed in the same manner as in Examples 1 and 2.

(Test results)
As a result, in the wiring boards of Examples 1 and 2, the through conductors did not protrude or peel from the insulating plate, whereas in the comparative wiring board, the two through conductors in one wiring board In each of the wiring boards, protrusions of about 5 μm occurred on one through conductor.

  From the above results, the effect of suppressing the protrusion of the through conductor in the wiring board of the present invention could be confirmed.

DESCRIPTION OF SYMBOLS 1 ... Insulation board 2 ... Through-conductor 3 ... Through-hole 4 ... Buffer layer 4a .... Air gap 5 ... Wiring conductor 6 ... Resin insulation layer 6a ...... A part of resin material

Claims (3)

A wiring board made of a ceramic sintered body, comprising an insulating plate having a through hole penetrating in the thickness direction, and a through conductor filled in the through hole, the inner surface of the through hole and the through conductor A wiring board characterized in that a buffer layer made of a sintered body including voids is interposed between a side surface and a side surface. The buffer layer is formed of a melt-modified layer including the voids inside thereof, which is solidified after the ceramic sintered body is partially melted on the inner surface of the through hole. The wiring board according to claim 1. The buffer layer in which a resin insulating layer in contact with the buffer layer is laminated on the main surface of the insulating plate, and a part of the resin material forming the resin insulating layer is located on the main surface side of the insulating plate The wiring board according to claim 1, wherein the wiring board enters the gap.

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