JP2013165149A - Multilayer ceramic substrate and manufacturing method of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve a problem of a conductor pad for connection of a multilayer ceramic substrate used for electrical connection with an external device such that a film is separated because film adhesion of a conductor pad for connection deteriorates due to thermal and mechanical stress during an assembly process or after assembly.SOLUTION: In a multilayer ceramic substrate, deterioration in film adhesion of a connection conductor pad 20 is prevented by burying of a part of a conductor part on a periphery of a connection conductor pad 20 in a ceramic substrate 2 to reinforce the connection conductor pad 20. In addition, the connection conductor pad is reinforced by extension of the conductor part which becomes a starting point of separation of the connection conductor pad 20 and coating of the extension part with a ceramic layer.

Description

  The present invention relates to a multilayer ceramic substrate and a manufacturing method thereof.

  Today, multilayer ceramic substrates are widely used as package substrates for high-frequency circuits. In recent years, the substrate size has been reduced due to the downsizing and cost reduction of devices, and the connecting conductor pads for signal connection with mounted components and external devices are smaller and higher in density.

  The wiring between the multilayer ceramic substrate and the external device is often joined by soldering, wire bonding, ribbon bonding or the like. This joining is performed by thermocompression bonding, ultrasonic joining, or the like, and the connecting conductor pad formed on the substrate has a minimum size necessary for joining. For this reason, a connecting conductor pad is formed in a portion close to the end face of the substrate, and the area of the connecting conductor pad is substantially equal to the required area for joining. In particular, in the ribbon bond joining, the joining portion often extends to the vicinity of the end of the connecting conductor pad from the necessity of shortening the distance to the connection partner. For this reason, stress due to the difference in linear expansion coefficient is generated at the joint between the external device and the ceramic substrate, and the stress is concentrated particularly on the end portion of the connecting conductor pad. As a result, there is a problem that the connecting conductor pad is easily peeled off from the end.

  Further, the connection conductor pad is often subjected to gold plating with nickel as a base in order to prevent oxidation of the conductor. It has been confirmed that due to the corrosive action of nickel caused by gold plating, the pad end is damaged and the adhesion strength is further reduced.

  Patent Document 1 describes a method for increasing the adhesion by covering a part of an electrode pad with a dielectric layer by a screen printing method using a dielectric paste as a method for solving the above problems. Further, according to Patent Document 2, as a method for improving the metallization strength of the connecting conductor pad, a method for increasing the metal particle diameter and the film thickness in the conductor paste is described.

Japanese Patent Application Laid-Open No. 07-176864 Japanese Patent Laid-Open No. 09-199851

  However, in the conventional manufacturing method shown in Patent Document 1, a part of the surface of the connecting conductor pad is covered with a dielectric, and the pad size is reduced, making connection difficult. Further, the reinforcing dielectric paste swells around the connecting conductor pad, which causes a problem in joining.

  Further, in the conventional manufacturing method shown in Patent Document 2, increasing the metal particle diameter and the film thickness in the conductor paste does not particularly improve the adhesion of the end portion of the connecting conductor pad. There was a problem that caused the entire substrate to warp.

  The present invention has been made in view of the above, and an object of the present invention is to provide a multilayer ceramic substrate that secures adhesion strength at the end of the connecting conductor pad of the multilayer ceramic substrate and suppresses peeling, and a method for manufacturing the same. And

  A multilayer ceramic substrate according to the present invention includes a multilayered ceramic layer, a conductor part formed on a surface of the ceramic layer, and a conductor pad including an extension extending from an end of the conductor part. The extension is formed in the ceramic layer. The extension may extend obliquely downward or directly below the ceramic layer. The extension may be bent in a U shape inside the ceramic layer.

  The method for manufacturing a multilayer ceramic substrate according to the present invention includes a printing step of printing a ceramic paste so as to face an upper surface or a peripheral edge of the conductive paste after printing the conductive paste on the laminated green sheets; A pressing step for pressing the conductor paste and the ceramic paste after the printing step, and a firing step for firing the green sheet after the pressing step, and extending from the end of the conductor portion formed on the surface of the ceramic layer. The existing extension may be formed inside the ceramic layer.

  According to the present invention, a multi-layer ceramic substrate having sufficient bonding strength can be easily manufactured in the connecting conductor pad at the end of the substrate, contributing to quality improvement.

It is a figure which shows the structure of the multilayer ceramic substrate which concerns on Embodiment 1, (a) is a schematic diagram which shows a cross section, (b) is a cross-sectional schematic diagram which expanded the conductor pad end part for connection. It is a figure which shows the shape of the conductor pad end part for a connection which concerns on Embodiment 1, (a) is a top view of a 1st aspect, (b) is a top view of a 2nd aspect. It is a figure which shows the shape of the conductor pad end part for connection which concerns on Embodiment 1, (a) is a top view of a 3rd aspect, (b) is a top view of a 4th aspect, (c) is 5th. The top view of a mode of (d) is a top view of a 6th mode. It is a figure which shows the shape of the conductor pad end part for a connection which concerns on Embodiment 1, (a) is a top view of a 7th aspect, (b) is a top view of an 8th aspect. 3 is a flowchart showing a method for manufacturing a multilayer ceramic substrate according to the first embodiment. 5 is a schematic cross-sectional view showing the method for manufacturing the multilayer ceramic substrate according to Embodiment 1. FIG. 6 is an enlarged schematic cross-sectional view of a connection conductor pad end portion of a multilayer ceramic substrate according to Embodiment 2. FIG. 6 is a schematic cross-sectional view showing a method for manufacturing a multilayer ceramic substrate according to Embodiment 2. FIG. 6 is an enlarged schematic cross-sectional view of a connecting conductor pad end of a multilayer ceramic substrate according to Embodiment 3. FIG. 6 is a schematic cross-sectional view showing a method for manufacturing a multilayer ceramic substrate according to Embodiment 3. FIG. 6 is an enlarged schematic cross-sectional view of a connecting conductor pad end portion of a multilayer ceramic substrate according to Embodiment 4. FIG. 6 is a schematic cross-sectional view showing a method for manufacturing a multilayer ceramic substrate according to Embodiment 4. FIG. FIG. 9 is an enlarged schematic cross-sectional view of a connecting conductor pad end portion of a multilayer ceramic substrate according to a fifth embodiment.

  Hereinafter, embodiments of a method for producing a multilayer ceramic substrate according to the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiments, and it goes without saying that the embodiments include those that can be easily conceived by those skilled in the art and those that are substantially the same.

Embodiment 1 FIG.
1A and 1B are diagrams showing a configuration of a multilayer ceramic substrate according to a first embodiment of the present invention. FIG. 1A is a schematic cross-sectional view, and FIG. . 2 is an enlarged schematic cross-sectional view of a portion 1 of FIG. 1 (a) provided with connection conductor pads for a multilayer ceramic substrate according to Embodiment 1, and FIG. 2 (a) is a plan view of the first embodiment; (B) is a top view of a 2nd aspect. 1 and 2, the multilayer ceramic substrate 10 according to the first embodiment is composed of a ceramic pad 2 laminated in multiple layers and a conductive pad including a connecting conductive pad 20 formed on the ceramic layer 2. . The connecting conductor pad 20 includes a conductor portion 3 formed on the ceramic layer 2 and a plating layer 4 formed on the conductor portion 3. The conductor portion 3 is connected to a conductor extension portion 3 a extended from the end portion, and the conductor extension portion 3 a is buried in the ceramic layer 2.

  FIG. 2 is an enlarged schematic view of the end shape of the connecting conductor pad of the multilayer ceramic substrate according to the first embodiment, where (a) is a plan view of the end shape of the first mode, and (b) is a second view. It is a top view of the edge part shape of an aspect. FIG. 3 is an enlarged schematic view of the end shape of the connecting conductor pad of the multilayer ceramic substrate according to the first embodiment. FIG. 3A is a plan view of the end shape of the third mode, and FIG. The top view of the end shape of an aspect, (c) is a top view of the end shape of a 5th aspect, (d) is a top view of the end shape of a 6th aspect. In addition, although the plating layer 4 is formed on the conductor part 3, illustration of the plating layer 4 is abbreviate | omitted here and it has illustrated in the state which the conductor part 3 exposed to the board | substrate surface. The conductor extension 3a buried in the substrate is indicated by a broken line.

  As shown in the first embodiment of FIG. 2 (a), the end portion of the connecting conductor pad 20 of the multilayer ceramic substrate 10 has a conductor portion 3 exposed on the substrate surface and a conductor extension portion 3a buried inside the substrate. In either case, the corner may be a right angle. Further, as shown in the second mode of FIG. 2B, the conductor extension 3b embedded in the substrate is narrower than the width of the conductor 3 exposed on the substrate surface, and the corners are chamfered. Yes.

  3A, the conductor extension 3c embedded in the substrate is narrower than the width of the conductor 3 exposed on the substrate surface, and the end has a triangular shape. It has become. 3B, the conductor extension 3d embedded in the substrate is narrower than the width of the conductor 3 exposed on the substrate surface, and the end is semicircular. It has become.

  Further, as shown in the fifth mode of FIG. 3 (c), the conductor extension 3e buried in the substrate has a width that is slightly wider in a trapezoidal shape than the width of the conductor 3 exposed on the substrate surface, The corner is a right angle. Further, as shown in the sixth mode of FIG. 3 (d), the conductor extension 3f buried in the substrate has a width slightly larger than the width of the conductor 3 exposed on the substrate surface, and has a right angle. It has a rectangular shape. As described above, the conductor extension parts 3e and 3f are slightly disadvantageous for reducing the wiring pitch of the connection conductor pad 20 by being wider than the width of the conductor part 3 exposed on the substrate surface. The peel resistance of 20 is further improved.

  Furthermore, FIG. 4 is a figure which shows the shape of the connection conductor pad edge part which concerns on Embodiment 1, (a) is a top view of a 7th aspect, (b) is a plane of an 8th aspect. The conductor extension 3g embedded in the substrate is a conductor extension 3g, 3h in FIGS. 4A and 4B, which is a conductor extended from the end of the conductor 3 of the connecting conductor pad. All or part of it may be divided into several narrow conductors. 4A shows an example in which the conductor extension 3g is divided into three conductors, and FIG. 4B shows an example in which the conductor extension 3h is divided into two conductors.

  Each of the embodiments of the conductor extension portions 3a to 3h in FIGS. 2 to 4 described so far may be formed independently or may be a composite shape.

Next, a method for manufacturing the multilayer ceramic substrate 10 will be described. FIG. 5 is a flowchart showing a method for manufacturing the multilayer ceramic substrate 10 according to the first embodiment.
First, in order to form a VIA (via) conductor, a drilling (drilling process) for forming a VIA hole is executed (step S1).
This drilling step is a step of forming holes in a plurality of ceramic green sheets (hereinafter referred to as “green sheets”) by a method such as punching. The green sheet to be used has a thickness of, for example, 100 μm, and the hole to be formed has, for example, 150 μm.

After the drilling process is completed, a process of filling the VIA hole formed in the drilling process with the conductive paste (VIA filling process) is performed (step S2).
In this VIA filling step, the conductor paste is filled using, for example, a screen printing method.

After the VIA filling process is completed, a process (pattern printing process) of printing a conductor pattern such as wiring on a green sheet is performed (step S3).
For printing the conductor pattern, for example, a screen printing method is used. In this manner, necessary types and numbers are prepared in the same manner.

After the pattern printing process is completed, a stacking / pressing process is performed (step S4).
This lamination / pressing step is a step of laminating and pressing the green sheet on which the VIA conductor and the conductor pattern are formed. When the green sheets are stacked, for example, the green sheets are stacked after matching the relative positions of the green sheets by matching holes processed at the same place on the plane.

  Further, as a pressing method, for example, an isotropic hydraulic pressing method using a liquid as a medium can be used. The pressing method is not limited to this, and any pressing method can be applied as long as the green sheets can be brought into close contact with each other.

When the lamination / pressing process is completed, the laminated body is fired (firing process) (step S5).
After firing, the conductor exposed on the surface is plated (plating step) (step S6).
Thereafter, the laminate is cut and separated into individual multilayer ceramic substrates. A multilayer ceramic substrate can be manufactured by such a process.

Next, a method for manufacturing the multilayer ceramic substrate 10 shown in FIG. 1 according to the first embodiment will be described.
6A, 6B, and 6C are schematic cross-sectional views illustrating a method for manufacturing a multilayer ceramic substrate according to Embodiment 1, and are a pattern printing step (step) that is a part of the flowchart of FIG. An example of S3) and a lamination press process (step S4) is shown. In FIG. 6, only the conductor extension 3a that is an extension of the conductor 3 will be described, but the conductor extensions 3b to 3h can be manufactured in the same manner.

  After the unillustrated drilling step (step S1) and VIA filling step (step S2) are completed, the conductor paste 6 is applied on the green sheet 5 filled with VIA in the step of FIG. 6A corresponding to step S3. Printed. At the time of this printing, the conductor part 3 of the connecting conductor pad and the conductor extension part 3a serving as the extension part are simultaneously printed.

  Subsequently, in the step shown in FIG. 6B of step S3, the conductor paste 6 faces the upper surface or the peripheral end so as to cover only the conductor extension 3a of the conductor part 3 of the connecting conductor pad. The ceramic paste 7 is printed. The ceramic paste 7 is a paste obtained by adding a solvent to a green sheet.

  After that, in the stacking process of step S4 shown in FIG. 6C, the flat plate 8 is placed on the upper surface of the printed and stacked green sheet 5 and pressed.

  Thereafter, the ceramic paste 7 and the green sheet 5 are integrated in the firing step to form the ceramic layer 2. However, the conductor extension 3a is embedded in the ceramic layer 2 as shown in FIG.

  Thereby, a part of the periphery of the connecting conductor pad 20 is buried in the ceramic substrate 10 and reinforced, thereby preventing deterioration of the film adhesion. Further, the conductor portion 3 that becomes the starting point of the peeling of the connecting conductor pad 20 is extended, and the conductor extension portions 3a to 3h are covered with a ceramic dielectric (ceramic layer 2) to be reinforced. As a result, a multi-layer ceramic substrate having sufficient bonding strength can be easily manufactured in the connecting conductor pad at the end of the substrate, contributing to quality improvement.

  As described above, the multilayer ceramic substrate 10 according to the first embodiment extends from the ceramic layers 2 stacked in multiple layers, the conductor portion 3 formed on the surface of the ceramic layer 2, and the end of the conductor portion 3. And a conductor pad 10 (conductor pad) for connection comprising the conductor extension 3a (extension), and the conductor extension 3a is formed and buried inside the ceramic layer 2. .

  Further, in the method of manufacturing the multilayer ceramic substrate 10 according to the first embodiment, after the conductor paste 6 is printed on the laminated green sheets 5, the ceramic paste 7 is applied to the upper surface or the peripheral edge of the conductor paste 6. A printing step for printing, a pressing step for pressing the conductor paste 6 and the ceramic paste 7 after the printing step, and a firing step for firing the green sheet 5 after the pressing step. A conductor extension 3a (extension) extending from the end of the conductor 3 formed on the surface may be formed inside the ceramic layer.

  As described above, the multilayer ceramic substrate 10 and the method for manufacturing the same according to the first embodiment improve the adhesion of the connecting conductor pad 20 and the conductor pad formed by the conductor part 3 does not peel off. Thereby, the quality of the high frequency circuit board using the multilayer ceramic substrate 10 becomes more stable.

  Hereinafter, in the connection conductor pad 20 described in the first embodiment, various embodiments relating to the buried portion of the conductor portion 3 will be described.

Embodiment 2. FIG.
FIG. 7 is a schematic cross-sectional view of a portion 1 in which the end of the connecting conductor pad 20 is enlarged in the multilayer ceramic substrate 10 according to the second embodiment. FIG. 8 is a schematic cross-sectional view illustrating a method for manufacturing the multilayer ceramic substrate 10 according to the second embodiment. In FIG. 7, the conductor extension portion 3 i extends from the end portion of the conductor portion 3, and the end portion is buried in the ceramic layer 2 in a diagonally downward direction inside the ceramic layer 2. In addition, the end part shape of the conductor extension part 3i seen from the upper surface may be shape | molded in various shapes like the conductor extension parts 3b thru | or 3h.

  Next, a method for manufacturing the multilayer ceramic substrate 10 shown in FIG. 8 will be described. After the pattern printing process (step S3) which is a part of the flowchart of FIG. 5 is performed as described in FIG. 5, the lamination press process (step S4) of the second embodiment shown in FIG. 8 is performed.

In FIG. 8A, the connecting conductor pad conductor portion 3 and the conductor extension portion 3 i before being buried, which is an extension portion thereof, are printed on the green sheet 5. Further, a ceramic paste 7 is printed on the green sheet 5 so as to cover the conductor extension 3i before being buried.
Here, another green sheet 5 b is laminated on the ceramic paste 7.

  Further, in FIG. 8B, the plate 8 having a flat surface is placed on the upper surface of the green sheet 5b, and the green sheet 5b is pressed. As a result, the green sheet 5b and the ceramic paste 7 are crushed together with the conductor extension 3i and buried in the ceramic layer.

  Thereafter, the ceramic paste 7 and the green sheet 5b are integrated in the firing step to form the ceramic layer 2. Thus, as shown in FIG. 7, the conductor extension 3 i is bent obliquely downward and embedded in the ceramic layer 2.

  As described above, in the multilayer ceramic substrate 10 and the manufacturing method thereof according to the second embodiment, the conductor extension 3 i may extend obliquely downward inside the ceramic layer 2. Thereby, the adhesion of the connecting conductor pad 20 is improved, and the conductor pad formed by the conductor part 3 does not peel off. Thereby, the quality of the high frequency circuit board using the multilayer ceramic substrate 10 becomes more stable.

Embodiment 3 FIG.
FIG. 9 is a schematic cross-sectional view of a portion 1 in which the end portion of the connecting conductor pad 20 is enlarged in the multilayer ceramic substrate 10 according to the third embodiment. FIG. 10 is a schematic cross-sectional view illustrating the method for manufacturing the multilayer ceramic substrate 10 according to the third embodiment. In FIG. 9, the end portion of the conductor extension portion 3 j extending from the end portion of the conductor portion 3 is buried in the ceramic layer 2 in the direction directly below the inside of the ceramic layer 2.

  Next, a method for manufacturing the multilayer ceramic substrate 10 shown in FIG. 10 will be described. In the pattern printing process (step S3) and the laminating press process (step S4) which are a part of the flowchart of FIG. 5, the process of Embodiment 3 shown in FIG. 10 is performed.

  In FIG. 10A, ceramic paste 7 is first printed on green sheet 5 which is not shown and filled with VIA. Here, the ceramic paste 7 is printed on the green sheet 5 so as to surround a region where the conductor extension 3j is formed. At this stage, the surface of the green sheet 5 is exposed in the region where the conductor extension 3j is formed.

  Next, in FIG. 10B, the conductor paste 6 is printed on the green sheet 5 in the region where the ceramic paste 7 and the conductor extension 3j are formed. Thus, the conductor extension 3j is formed, and the conductor paste 6 is simultaneously printed on the connecting conductor pad conductor 3 and the conductor extension 3j.

  Thereafter, in the stacking step of FIG. 10C, the conductor extension 3j is buried in the green sheet 5 by placing the flat plate 8 on the upper surface and pressing it.

  Subsequently, the ceramic paste 7 and the green sheet 5 are integrated into a ceramic layer 2 in a firing process. Thus, as shown in FIG. 9, the conductor extension 3j has a shape that is curved downward and buried in the ceramic layer.

  As described above, in the multilayer ceramic substrate 10 and the method for manufacturing the same according to the third embodiment, the conductor extension 3j may extend directly below the inside of the ceramic layer 2. Thereby, the adhesiveness of the conductor pad 20 for connection is improved, and peeling does not arise about the conductor pad which the conductor part 3 forms. Thereby, the quality of the high frequency circuit board using the multilayer ceramic substrate 10 becomes more stable.

Embodiment 4 FIG.
FIG. 11 is a schematic cross-sectional view of a portion 1 in which the end portion of the connecting conductor pad 20 is enlarged in the multilayer ceramic substrate 10 according to the fourth embodiment. FIG. 12 is a schematic cross-sectional view illustrating the method for manufacturing the multilayer ceramic substrate 10 according to the fourth embodiment. In FIG. 11, the conductor extension 3 k extended from the end of the conductor 3 is folded back into a U shape inside the ceramic layer 2 and is buried immediately below the connecting conductor pad conductor 3.

  Next, a method for manufacturing the multilayer ceramic substrate 10 shown in FIG. 12 will be described. In the pattern printing process (step S3) and the laminating press process (step S4) which are a part of the flowchart of FIG. 5, the process of Embodiment 4 shown in FIG. 12 is performed.

In FIG. 12A, the conductor 3k-1 before the formation of the conductor extension 3k is first printed with the conductor paste 6 on the green sheet 5 filled with a hole and VIA (not shown).
Next, in FIG.12 (b), the ceramic paste 7 is printed on the green sheet 5 so that the conductor 3k-1 may be enclosed.

  Next, in FIG. 12B, the conductor paste 6 is printed on the ceramic paste 7. At this time, the conductor 3k-1 is printed simultaneously. Thereafter, in the laminating process, the plate 8 having a flat surface is placed on the upper surface and pressed.

  Subsequently, in FIG. 12 (c), the ceramic paste 7 and the green sheet 5 are integrated in the firing step to form the ceramic layer 2. Thus, as shown in FIG. 11, the conductor extension 3k is curved in a U shape and buried in the ceramic layer.

  Thus, in the multilayer ceramic substrate 10 and the manufacturing method thereof according to Embodiment 4, the conductor extension 3k may be bent into a U shape inside the ceramic layer 2. Thereby, the adhesiveness of the conductor pad 20 for connection is improved, and peeling does not arise about the conductor pad which the conductor part 3 forms. Thereby, the quality of the high frequency circuit board using the multilayer ceramic substrate 10 becomes more stable.

Embodiment 5 FIG.
FIG. 13 is a schematic cross-sectional view of a portion 1 in which the end portion of the connecting conductor pad 20 is enlarged in the multilayer ceramic substrate 10 according to the fifth embodiment. In FIG. 13, the conductor extension portion 31 is extended from the end portion of the conductor portion 3 of the connecting conductor pad 20 and buried in the ceramic layer 2 downward. That is, the conductor extension part 31 extends vertically downward from the conductor part 3.

  Next, a method for manufacturing the multilayer ceramic substrate 10 shown in FIG. 6 will be described. In the fifth embodiment, a VIA hole serving as an extension is formed in the drilling step (step S1) in the flowchart of FIG. Next, a conductor is formed in the VIA hole serving as an extension in the VIA filling step (step S2).

  Then, in a pattern printing process (step S3), a conductor pattern is printed and the conductor part 3 is formed. At that time, the connecting conductor pad 20 and the conductor extension 3l which is an extension thereof are connected. Furthermore, in the laminating step (step S4), after the plate 8 having a flat surface is placed on the upper surface and pressed, the conductor extension 3l is buried in the ceramic substrate after firing.

  As described above, in the fifth embodiment, the desired connecting conductor pad 20 having the conductor extension 3l buried as the VIA conductor is formed inside the ceramic substrate through the manufacturing process described above. The effect improves adhesion.

  2 ceramic layer, 3 conductor part, 3a-3l conductor extension part, 4 plating layer, 5, 5b green sheet, 6 conductor paste, 7 ceramic paste, 8 metal plate, 10 multilayer ceramic substrate, 20 conductor pad for connection.

Claims (4)

Ceramic layers stacked in multiple layers;
A conductor pad formed of a conductor portion formed on the surface of the ceramic layer, and an extension portion extending from an end portion of the conductor portion;
With
A multilayer ceramic substrate in which the extension is formed inside the ceramic layer.   The multilayer ceramic substrate according to claim 1, wherein the extension portion extends obliquely downward or directly below the ceramic layer.   The multilayer ceramic substrate according to claim 1, wherein the extension is bent in a U shape inside the ceramic layer. After printing the conductive paste on the laminated green sheets, a printing step of printing the ceramic paste facing the upper surface or peripheral edge of the conductive paste;
After the printing step, a pressing step for pressing the conductor paste and the ceramic paste,
A firing step of firing the green sheet after the pressing step;
With
The manufacturing method of the multilayer ceramic substrate which forms the extension part extended from the edge part of the conductor part formed in the ceramic layer surface inside the said ceramic layer.

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