JP2009188218A - Multilayer board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a multilayer board for improving connection reliability between the via hole conductor of a resin layer and the surface conductor of a ceramic substrate. <P>SOLUTION: The multilayer board S includes: a ceramic multilayer board 10 made of a plurality of laminated ceramic layers 11A and provided with a first surface electrode 12A made of a sintered metal baked integrally with the plurality of ceramic layers 11A on a lower surface; and a resin layer 20 laminated on the lower surface of the ceramic multilayer board 10 and provided with a via hole conductor 22 electrically connected to a first surface electrode 12A. In the multilayer board S, a recess 12E is formed in the first surface electrode 12A and the via hole conductor 22 is fitted to the recess 12A. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a multilayer substrate in which a ceramic substrate and a resin layer are laminated, and more specifically, to improve the connection reliability between a via-hole conductor formed in the resin layer and a surface electrode formed on the surface of the ceramic substrate. The present invention relates to a multilayer substrate that can be produced.

  For example, as shown in FIG. 4, the multilayer substrate includes a ceramic multilayer substrate 1 and a resin layer 2 laminated on the ceramic multilayer substrate 1. The ceramic multilayer substrate 1 includes a surface conductor 1A formed on both upper and lower surfaces, an in-plane conductor 1B formed inside the ceramic multilayer substrate 1, and an interlayer electrically connecting the upper and lower surface conductors 1A and the in-plane conductor 1B. Connecting conductor 1C. The resin layer 2 includes a surface electrode 2A formed on the lower surface, and a via-hole conductor 2B that electrically connects the surface electrode 2A and the surface electrode 1A of the ceramic multilayer substrate 1.

  As a technique related to such a multilayer substrate, for example, there is a technique described in Patent Document 1. In the technique of Patent Document 1, the following two methods are adopted when the surface electrode of the ceramic multilayer substrate and the via-hole conductor of the resin layer are electrically connected.

  In the first method, as shown in FIG. 5 of Cited Document 1, an uncured resin layer having a surface conductor formed on one main surface is prepared, and a laser is applied to the resin layer with the surface conductor as a bottom surface. To form a via hole. The via hole is filled with a conductive paste to form a via hole conductor. After this uncured resin layer is pressure-bonded to a ceramic multilayer substrate on which circuit components are mounted, the resin layer is cured. In the second method, as shown in FIG. 7 of Cited Document 1, after circuit components are mounted on the ceramic multilayer substrate, an uncured resin layer is formed on the ceramic multilayer substrate. Subsequently, a via hole is formed in the uncured resin layer by using the surface conductor of the ceramic multilayer substrate as a bottom surface by a laser, and then a via paste is filled in the via hole to form a via hole conductor. Thereafter, the uncured resin layer is cured together with the via-hole conductor. In either method, since a via hole is formed in the resin layer using a laser, the via hole has a tapered shape as shown in FIG.

JP 2003-188538 A

  However, in the first method of Patent Document 1, when laminating an uncured resin layer on a ceramic multilayer substrate, the large-diameter side of the via-hole conductor is aligned with the surface conductor of the ceramic multilayer substrate. Although the connection area of the conductor with the surface conductor can be increased, the uncured resin layer is pressure-bonded to the ceramic multilayer substrate, so that the via-hole conductor is deformed and displaced from the surface conductor with the deformation of the resin layer, There is a risk of poor connection. On the other hand, in the second method of Patent Document 1, since the via hole is formed after pressure bonding to the ceramic multilayer substrate, there is no problem as in the first method, but the via hole tapers toward the surface conductor of the ceramic multilayer substrate. Therefore, even if this via hole is filled with a conductive paste and cured, the connection area with the surface conductor is small, and there is a risk of causing a problem in connection reliability.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a multilayer substrate that can improve the connection reliability between the via-hole conductor of the resin layer and the surface conductor of the ceramic substrate.

  The multilayer substrate according to claim 1 of the present invention comprises a ceramic substrate comprising a ceramic layer, and a surface conductor made of a sintered metal fired integrally with the ceramic layer on at least one main surface, and the ceramic A multilayer substrate including a resin layer formed on the main surface of the substrate and formed with a via-hole conductor electrically connected to the surface conductor, wherein the surface conductor has a recess. At the same time, the via-hole conductor is fitted into the recess.

  The multilayer substrate according to claim 2 of the present invention is the multilayer substrate according to claim 1, wherein an interlayer connection conductor is formed on the surface layer of the ceramic layer so as to overlap the via-hole conductor in plan view. The concave portion penetrates the surface conductor, and the via-hole conductor is in contact with the interlayer connection conductor.

  The multilayer substrate according to claim 3 of the present invention is characterized in that, in the invention according to claim 1 or 2, the surface conductor has high laser absorptivity.

  The multilayer substrate according to claim 4 of the present invention is characterized in that, in the invention according to claim 3, the surface conductor is formed by sintering a paste containing glass and alumina as fillers. is there.

  According to a fifth aspect of the present invention, in the multilayer substrate according to the third or fourth aspect, the surface conductor has a surface roughness adjusted.

  The multilayer substrate according to claim 6 of the present invention is the multilayer conductor according to any one of claims 3 to 5, wherein the surface conductor has a surface of the sintered metal having high laser absorption. It is characterized by being formed of metal.

  In the multilayer substrate according to claim 7 of the present invention, in the invention according to claim 6, the metal having high laser absorption is selected from Ni, Sn, Al, Zn, Pb and Bi. It is characterized by being at least one metal.

  The multilayer substrate according to claim 8 of the present invention is the multilayer substrate according to any one of claims 1 to 7, wherein the main surface of the ceramic substrate on which the surface conductor is formed is A conductor different from the surface conductor is formed, and the surface conductor is thicker than the conductor.

  The multilayer substrate according to claim 9 of the present invention is characterized in that, in the invention according to any one of claims 1 to 8, a circuit component is embedded in the resin layer. It is.

  ADVANTAGE OF THE INVENTION According to this invention, the multilayer substrate which can improve the connection reliability of the via-hole conductor of a resin layer and the surface conductor of a ceramic substrate can be provided.

  Hereinafter, the present invention will be described based on the embodiment shown in FIGS. 1A and 1B are diagrams showing an embodiment of the multilayer substrate of the present invention, FIG. 1A is a sectional view showing the whole of the multilayer substrate, and FIG. 2 is an enlarged cross-sectional view showing a portion surrounded by a circle, FIG. 2 is a cross-sectional view corresponding to FIG. 1B showing another embodiment of the multilayer substrate of the present invention, and FIGS. FIG. 2 is a process diagram showing a main manufacturing process of the multilayer substrate shown in FIG.

First Embodiment A multilayer substrate S of the present embodiment includes, for example, a ceramic multilayer substrate 10 and a first multilayer laminated on one main surface (lower surface) of the ceramic multilayer substrate 10 as shown in FIG. Resin layer 20, second resin layer 30 laminated on the other main surface (upper surface) of ceramic multilayer substrate 10, first electronic component 40 mounted on the lower surface of ceramic multilayer substrate 10, and ceramic multilayer And a second electronic component 50 mounted on the upper surface of the substrate 10.

  The first electronic component 40 is composed of, for example, passive electronic components such as a capacitor, an inductor, and a resistor, and is sealed from the external environment by the first resin layer 20. The second electronic component 50 is composed of an active electronic component such as a gallium arsenide semiconductor element or a silicon semiconductor element, and is sealed from the external environment by the second resin layer 30.

  As shown in FIGS. 1A and 1B, the ceramic multilayer substrate 10 includes a ceramic laminate 11 in which a plurality of ceramic layers 11A are laminated, and a patterned conductor formed on the ceramic laminate 11 in a predetermined pattern. 12. The pattern conductor 12 includes first and second surface conductors (hereinafter referred to as “surface electrodes”) 12A, 12A ′, and 12B formed in a predetermined pattern on both upper and lower surfaces of the ceramic laminate 11, and ceramic laminates. An in-plane conductor 12C formed in a predetermined pattern at the interface between the upper and lower ceramic layers 11A in the body 11, and the first and second surface electrodes 12A, 12A ′, 12B and the surface penetrating the ceramic layer 11A vertically And an interlayer connection conductor 12D that electrically connects the inner conductor 12C in a predetermined pattern. Two types of first surface electrodes 12 </ b> A and 12 </ b> A ′ are formed on the lower surface of the ceramic multilayer substrate 10. One first surface electrode 12A is preferably formed thicker than the other first surface electrode 12A '. Here, for convenience, the thin first surface electrode 12A 'is referred to as a third surface electrode 12A'. Each conductor constituting the pattern conductor 12 is fired integrally with the ceramic laminate 11 and formed as a sintered metal. The first electronic component 40 is connected to the third surface electrode 12A ′ on the lower surface of the ceramic laminate 11 via solder or the like, and the second electronic component 50 is soldered to the second surface electrode 12B on the upper surface or the like. Connected by.

  Also, as shown in FIGS. 1A and 1B, the first resin layer 20 includes a surface electrode 21 formed in a predetermined pattern on the lower surface, and a surface electrode 21 formed on both left and right ends. And a via-hole conductor 22 that electrically connects the first surface electrode 12A of the ceramic multilayer substrate 10. The via hole conductor 22 is formed by filling the via hole 22A with a conductive paste. In the present embodiment, the via hole 22 </ b> A is formed by laser after the first resin layer 20 is laminated on the ceramic multilayer substrate 10. Therefore, the diameter of the via-hole conductor 22 gradually decreases from the surface electrode 21 side toward the first surface electrode 12A side of the ceramic multilayer substrate 10, and the connection area between the via-hole conductor 22 and the first surface electrode 12A Is getting smaller. Reference numeral 23 denotes a solder mask.

  Thus, a recess 12E is formed on the surface of the first surface electrode 12A of the ceramic multilayer substrate 10 as shown in FIG. 1B, and the tip of the via-hole conductor 22 is fitted into the recess 12E. Match. Since the recess 12E is formed in the first surface electrode 12A, the connection area between the first surface electrode 12A and the via-hole conductor 22 increases, and the two are electrically connected reliably, and the connection reliability between the two is improved. It has improved. Particularly in the present invention, the first surface electrode 12A is formed of a sintered metal. Since the sintered metal is porous, the recesses 12E are easily formed by laser irradiation. Conventionally, the reflectance of the surface electrode is increased to prevent the surface electrode from being damaged. However, in the present invention, the laser beam is intentionally absorbed by the first surface electrode 12A to actively form the recess 12E.

  Further, the first surface electrode 12A is formed thicker than the third surface electrode 12A 'on which the first electronic component 40 is mounted and the wiring pattern as described above. By making the first surface electrode 12A thicker than the third surface electrode 12A ′ and the wiring pattern, a deeper recess 12E can be formed, and the connection area between the via-hole conductor 22 and the first surface electrode 12A is increased. Can be made. Further, the multilayer substrate S can be thinned by thinning the third surface electrode 12A '.

  The first surface electrode 12A has high laser absorptivity. By increasing the laser absorptivity of the first surface electrode 12A, when the via hole 22A is formed by irradiating the laser to the first resin layer 20, the absorption of the laser that has reached the first surface electrode 12A And the recess 12E is more easily formed. As a technique for increasing the laser absorptivity of the first surface electrode 12A, for example, a method of adding a filler having a high laser absorptivity to metal powder, a method of adjusting the surface roughness of the first surface electrode 12A, and laser absorption There is a method of using a highly metallic material as an electrode material.

In the method of adding a filler, for example, the first surface electrode 12A is formed using a conductive paste in which a metal powder such as Cu powder as an electrode material is added with a filler having high laser absorptivity such as Al ₂ O ₃ or glass. To do. The conductor paste preferably has 0.1 to 15% by weight filler added to the metal powder, and more preferably has 0.2 to 5% by weight filler added thereto. Cu powder is preferable as the metal powder. In the method based on the surface roughness, the surface roughness of the first surface electrode 12A can be appropriately adjusted by adding an inorganic filler to the conductor paste. The surface roughness of the first surface electrode 12A is preferably adjusted to a range of 0.1 to 20 μm by Ra, and more preferably a range of 2 to 10 μm. In the method using a metal material having high laser absorption, it is preferable to use at least one metal selected from, for example, Ni, Sn, Al, Zn, Pb, and Bi as the electrode material.

  A shield metal film 31 is formed on the upper surface of the second resin layer 30, and the second electronic component 50 sealed with the second resin layer 30 is protected from external electromagnetic waves by the shield metal film 31. be able to. When a via hole conductor is formed in the second resin layer 30, the via hole conductor can be formed in the same manner as the first resin layer 20.

Thus, the material of the ceramic layer 11A is not particularly limited as long as it is a ceramic material. For example, a low temperature co-fired ceramic (LTCC) material is preferable. The low-temperature sintered ceramic material is a ceramic material that can be sintered at a temperature of 1050 ° C. or less and can be simultaneously fired with Ag, Cu, or the like having a small specific resistance. Specifically, as the low-temperature sintered ceramic, a glass composite LTCC material obtained by mixing borosilicate glass with ceramic powder such as alumina or forsterite, ZnO-MgO-Al ₂ O ₃ -SiO ₂ crystal Non-glass using crystallized glass-based LTCC material using a crystallized glass, BaO—Al ₂ O ₃ —SiO ₂ ceramic powder, Al ₂ O ₃ —CaO—SiO ₂ —MgO—B ₂ O ₃ ceramic powder, etc. System LTCC materials and the like.

  By using a low-temperature sintered ceramic material as the material of the ceramic laminate 11A, a low melting point metal having a low resistance and a low melting point such as Cu can be used as the pattern conductor 12. As a result, a sintered metal can be formed by simultaneously firing the ceramic laminate 11 and the pattern conductor 12 at a low temperature of 1050 ° C. or lower.

  In addition, a high temperature co-fired ceramic (HTCC) material can be used as the ceramic material. Examples of the high-temperature sintered ceramic material include alumina, aluminum nitride, mullite, and other materials added with a sintering aid such as glass and sintered at 1100 ° C. or higher. At this time, as the pattern conductor 12, a metal selected from Mo, Pt, Pd, W, Ni, and alloys thereof is used.

  As described above, according to the present embodiment, the first surface electrode 12A is formed of a plurality of laminated ceramic layers 11A, and the lower surface is formed of a sintered metal integrally fired with the plurality of ceramic layers 11A. In the multilayer substrate S provided with the ceramic multilayer substrate 10 and the resin layer 20 formed on the lower surface of the ceramic multilayer substrate 10 and formed with the via-hole conductor 22 electrically connected to the first surface electrode 12A, Since the first surface electrode 12A has a recess 12E and the via-hole conductor 22 is fitted in the recess 12E, the first surface electrode 12A and the via-hole conductor 22 are connected by the recess 12E. The connection area is increased as compared with the conventional case where the surface electrode 12A is connected on the flat surface, and the connection reliability between the first surface electrode 12A and the via-hole conductor 22 is improved. Further, since the first surface electrode 12A is formed of a porous sintered metal, the recess 12E can be easily formed by irradiating a laser.

  Further, according to the present embodiment, since the first surface electrode 12A has high laser absorptivity, the laser for forming the via hole 22A in the first resin layer 20 is not reflected by the first surface electrode 12A. By being absorbed, the recess 12E can be formed more easily. Further, since the first surface electrode 12A is formed by sintering a conductive paste containing glass and alumina as fillers in metal powder, the first surface electrode 12A absorbs the laser by the filler and is It becomes easy to form the recess 12E in one surface electrode 12A.

  Further, in the present embodiment, when the laser absorptivity of the first surface electrode 12A is increased by adjusting the surface roughness, it becomes easy to form the recess 12E in the first surface electrode 12A. When the surface of the first surface electrode 12A made of sintered metal is formed by coating with a metal having high laser absorption such as Ni, Sn, Al, Zn, Pb and Bi, the first surface electrode The recess 12E can be easily formed by absorbing the laser on the surface of the electrode 12A.

  Further, a third surface electrode 12A ′ and a wiring pattern different from the first surface electrode 12A are formed on the lower surface of the ceramic multilayer substrate 10 on which the first surface electrode 12A is formed. The electrode 12A is thicker than the third surface electrode 12A ′. Accordingly, the recess 12E of the first surface electrode 12A can be deepened, the connection reliability with the via-hole conductor 22 can be increased, and the third surface electrode 12A ′ is mounted by being thinned. Thus, the height of the electronic component 40 can be reduced, and the multilayer substrate S can be made thinner. In addition, since the first and second electronic components 40 and 50 are embedded in the first and second resin layers 20 and 30, the multilayer substrate S can be configured as an electronic component module with high functionality. .

Second Embodiment The multilayer substrate of the present embodiment is configured according to the first embodiment except that a concave portion penetrating the surface conductor is formed in the surface conductor of the ceramic multilayer substrate. Therefore, the following description will be made with reference to FIG. 2 with the same reference numerals assigned to the same or corresponding parts as those in the first embodiment, focusing on the differences from the first embodiment.

  As in the first embodiment, the multilayer substrate S ′ according to the present embodiment includes the ceramic multilayer substrate 10, the first resin layer 20 laminated on the lower surface of the ceramic multilayer substrate 10, and the upper surface of the ceramic multilayer substrate 10. And a laminated second resin layer (not shown). The first surface electrode 12A of the ceramic multilayer substrate 10 is formed with a recess 12E 'that reaches the interlayer connection conductor 12D through the first surface electrode 12A. The recess 12E 'has a structure in which a through-hole formed in the first surface electrode 12A and a recess formed in the interlayer connection conductor 12D are connected. In the present embodiment, since the recess 12E ′ is formed deeper than that of the first embodiment, the tip end portion of the via-hole conductor 22 of the first resin layer 20 is fitted deeply into the recess 12E ′ and the connection area. The connection reliability between the via-hole conductor 22 and the first surface electrode 12A is improved as compared with the case of the first embodiment.

  According to the present embodiment, the interlayer connection conductor 12D is formed on the uppermost layer of the plurality of ceramic layers 11A of the ceramic multilayer substrate 10 so as to overlap the via hole conductor 22 of the first resin layer 20 in plan view. Since the via-hole conductor 22 is also in contact with the interlayer connection conductor 12D that passes through and is connected to the first surface electrode 12A, the connection reliability between the via-hole conductor 22 and the first surface electrode 12A, and further the interlayer connection conductor 12D. The characteristics are improved as compared with the case of the first embodiment.

  Hereinafter, specific examples will be described with reference to FIGS.

Example 1
In this example, a multilayer substrate was produced, and the connection reliability between the surface electrode of the ceramic multilayer substrate of the multilayer substrate and the via-hole conductor of the resin layer was verified as follows.
1. Preparation of Ceramic Multilayer Substrate First, BaO, SiO ₂ , Al ₂ O ₃ , B ₂ O ₃ , and CaO are prepared as starting materials, and a predetermined amount of each starting material is weighed and mixed. The obtained mixture was calcined at 1300 ° C. for 2 hours, and the obtained calcined product was pulverized to obtain a calcined powder. An appropriate amount of a binder, a plasticizer and a solvent were added to the calcined powder and kneaded to obtain a ceramic slurry. This ceramic slurry was formed into a sheet having a thickness of 100 μm using a doctor blade method to produce a ceramic green sheet. Furthermore, this ceramic green sheet was cut into a rectangular shape having a length of 100 mm and a width of 100 mm.

Next, a via hole having a diameter of 200 μm was formed at a predetermined position of the ceramic green sheet. Moreover, the conductor paste which consists of Cu powder, a suitable quantity binder, a filler, a dispersing agent, etc. was prepared. This conductor paste was printed on a rectangular ceramic green sheet by screen printing, and the via hole of the ceramic green sheet was filled with the conductor paste to form a via hole conductor. Similarly, an in-plane conductor was formed by screen printing using a conductor paste made of Cu powder, an appropriate amount of binder, filler, dispersant and the like. In particular, as the conductive paste for forming the surface electrode on the surface of the ceramic multilayer substrate on which the resin layer is provided, a paste obtained by adding an appropriate amount of glass, Al ₂ O ₃ or the like as a filler to Cu powder was used.

  Next, a plurality of rectangular ceramic green sheets were laminated and pressed to obtain a laminate having a thickness of 1 mm. This laminate was fired at a temperature of 800 to 1000 ° C. for 5 hours. A ceramic multilayer substrate 10 shown in a) was obtained. The ceramic multilayer substrate 10 includes a ceramic laminate 11 and a pattern conductor 12. The pattern conductor 12 includes first and second surface electrodes 12A, 12A ', 12B, an in-plane conductor 12C, and an interlayer connection conductor 12D as shown in FIG.

2. Preparation of Resin Layer Prepare silica as inorganic filler and liquid epoxy resin as thermosetting resin, weigh so that silica is 90% by weight and liquid epoxy resin is 10% by weight, and add a dispersant to this and mix. A paste-like mixture was prepared. The obtained paste-like mixture is made of polyethylene terephthalate and dropped onto a release film having a release treatment with silicon on the surface, and a pressure-press is performed to obtain a plate-like resin prepreg sheet having a thickness of 100 μm. Obtained.

3. Production of Multilayer Substrate A resin prepreg sheet was cut into a rectangular shape with a length of 100 mm and a width of 100 mm. A resin in which a cured resin layer 120 is laminated as shown in FIG. 3B by stacking the cut resin prepreg sheet on the ceramic multilayer substrate 10 and press-bonding it at a temperature of 160 ° C. for 60 minutes by a vacuum press. A multilayer ceramic substrate 200 with layers was obtained.

  Then, a carbon dioxide laser is irradiated from the resin layer 120 side toward the desired surface electrode 12A for connection on the ceramic multilayer substrate 10, and a via hole having a diameter of 150 μm is formed in the resin layer 120 as shown in FIG. 122A was formed. At this time, a recess (not shown) was formed on the surface of the connecting surface electrode 12A in a range not penetrating the surface electrode 12A. As a result of measuring the amount of depressions in the recess, the average diameter was 125 μm and the maximum depth was 8 μm.

  Next, via hole conductor paste made of Cu, Sn, Ag, and an appropriate amount of resin binder is filled into the via hole 122A of the ceramic multilayer substrate 200 with a resin layer by screen printing, and as shown in FIG. A conductor 122 was formed.

  On the other hand, a copper foil having a thickness of 18 μm was stacked on the resin prepreg sheet to prepare a resin prepreg sheet 120 ′ with a copper foil. The copper foil formed on the resin prepreg sheet 120 'was etched by photolithography to produce a surface electrode 21' on the surface. Also for the resin prepreg sheet 120 ′ with a surface electrode, a via hole 122 ′ A having a diameter of 150 μm was formed at a desired position using a carbon dioxide laser. Then, a via hole conductor paste was filled into the via hole 122'A of the resin prepreg sheet 120 'with a surface electrode to form a via hole conductor 122'.

  Next, as shown in FIG. 3E, the ceramic multilayer substrate 200 with a resin layer and the resin prepreg sheet 120 ′ with a surface electrode are aligned, and the resin prepreg sheet 120 ′ with a surface electrode is laminated on the resin layer 120. Then, pressure bonding was performed at 160 ° C. for 60 minutes by a vacuum press to obtain a multilayer substrate.

  As shown in Table 1, samples of multilayer substrates having different via hole diameters and depths of recesses on the surface electrode were prepared by the above procedure.

4). Multilayer substrate connection reliability test The sample obtained as described above was subjected to an HST test in which the temperature raising and lowering operation was repeated in the range of -55 ° C to + 125 ° C, the connection reliability was verified, and the results are shown in Table 1. It was. In Table 1, ◎, ○, and Δ indicate the number of temperature cycles in the above temperature range and the presence / absence of connection failure at each number of cycles.
◎: No connection failure occurred up to 5000 cycles ○: No connection failure occurred up to 2000 cycles △: No connection failure occurred up to 1000 cycles

  According to the results shown in Table 1, it was proved that the connection defect does not occur as the concave portion of the surface electrode is deeper and the via hole diameter is larger.

  Note that the present invention is not limited to the above embodiments. The present invention includes all the structures as long as a concave portion is formed on the surface of the surface conductor on the ceramic substrate side of the multilayer substrate, and the via hole conductor on the resin layer side is fitted and connected to the concave portion. . For example, in each of the above embodiments, a ceramic multilayer substrate formed by laminating a plurality of ceramic layers is used, but a ceramic substrate composed of a single ceramic layer can also be used.

  INDUSTRIAL APPLICABILITY The present invention can be suitably used for multilayer substrates used for electronic devices and the like and methods for manufacturing the same.

(A), (b) is a figure which shows one Embodiment of the multilayer board | substrate of this invention, respectively, (a) is sectional drawing which shows the whole, (b) expands the part enclosed by (circle) of (a). FIG. It is sectional drawing equivalent to FIG.1, (b) which shows other embodiment of the multilayer substrate of this invention. FIGS. 3A to 3E are process diagrams showing main manufacturing steps of the multilayer substrate shown in FIG. It is sectional drawing equivalent to (b) of FIG. 1 which shows an example of the conventional multilayer substrate.

Explanation of symbols

S, S 'multilayer substrate 10 ceramic multilayer substrate 11 ceramic layer 12A surface electrode (surface conductor)
12D Interlayer connection conductor 12E Recess 20, 30 Resin layer 22 Via hole conductor

Claims (9)

A ceramic substrate comprising a ceramic layer and having a surface conductor formed of a sintered metal fired integrally with the ceramic layer on at least one main surface; and the surface conductor laminated on the main surface of the ceramic substrate And a resin layer formed with a via-hole conductor electrically connected to the multilayer substrate,
A multilayer substrate, wherein a concave portion is formed in the surface conductor, and the via-hole conductor is fitted in the concave portion.   An interlayer connection conductor is formed on the surface layer of the ceramic layer so as to overlap the via hole conductor in plan view, the recess penetrates the surface conductor, and the via hole conductor is in contact with the interlayer connection conductor. The multilayer substrate according to claim 1, wherein:   The multilayer substrate according to claim 1, wherein the surface conductor has high laser absorbability.   The multilayer substrate according to claim 3, wherein the surface conductor is formed by sintering a paste containing glass and alumina as a filler. The surface conductors, multi-layer substrate according to claim 3 or claim 4, characterized in that the surface roughness is adjusted.   The multilayer substrate according to any one of claims 3 to 5, wherein the surface conductor has a surface of the sintered metal formed of a metal having high laser absorptivity.   The multilayer substrate according to claim 6, wherein the metal having high laser absorption is at least one metal selected from Ni, Sn, Al, Zn, Pb, and Bi.   The main surface of the ceramic substrate on which the surface conductor is formed is formed with a conductor different from the surface conductor, and the surface conductor is thicker than the conductor. The multilayer substrate according to any one of the above.   The multilayer substrate according to any one of claims 1 to 8, wherein a circuit component is embedded in the resin layer.

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