JPH0794866A - Ceramic multilayered board and its manufacture - Google Patents

Abstract

PURPOSE:To obtain a ceramic multilayered board which can evade imperfect conduction after baking, between an Au based conductor connection via and an Ag based inner conductor wiring. CONSTITUTION:In a ceramic multilayered board obtained by stacking in order necessary n-green sheets 20-1...20-n and thermocomprssion-bonding them, an Au based conductor connection via 26 which connects an Au based outer conductor wiring 22 on the first layer green sheet 20-1 with an Ag based inner conductor wiring 24 on the second layer green sheet 20-2 is connected with an Ag based inner conductor wiring 24 through an Ag based conductor pad 30. The size of the pad 30 is equivalent to the diameter of the connction via containing at least position deviation amount. Ag based conductor is applied to the connection via 28 which connects mutually the inner conductor wirings 24.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ceramic multi-layer substrate, and more particularly, to reduce conduction failure caused by diffusion of an Ag-based conductor into an Au-based connection via between an Au-based conductor connection via and an Ag-based internal conductor wiring. And a method for manufacturing the same.

[0002]

2. Description of the Related Art In recent years, a multilayer substrate has been used as a circuit substrate as electronic devices have become smaller and lighter and have a higher density. Furthermore, in order to meet the demand for high-speed signal propagation, that is, high frequency, the dielectric constant is lower than that of alumina and 10
A vitreous material that sinters at a low temperature of 00 ° C. or lower is used as an insulating material, and the wiring material has a high conductivity and a low melting point
Ceramic multilayer substrates using metals such as g-based, Au, and Cu have been developed.

For example, as a ceramic multilayer substrate of this type, in JP-A-62-279695, an Au-based conductor is used for the uppermost surface, and a low-cost and low-resistance Ag-based conductor is used for the internal conductor wiring. The Au-based conductor is used for the connection via that connects the Au-based conductor wiring pattern and the Ag-based conductor wiring pattern of the internal conductor wiring, and the Ag-based conductor is used for the connection via that connects each layer of the Ag-based conductor wiring pattern of the internal conductor wiring. A ceramic multi-layer substrate having a structure as shown in FIG.

In FIG. 3, reference numeral 10 indicates a ceramic multi-layer substrate, and this ceramic multi-layer substrate 10 includes n green sheets 10- each made of a glassy material as an insulating material.
1 to 10-n. For example, as the green sheets 10-1 to 10-n, a solvent such as toluene, an organic binder, and a plasticizer are added to a mixed powder for a ceramic insulator made of glass powder and alumina powder, and sufficiently kneaded to form a slurry, The one prepared by a normal doctor blade method and punched into a predetermined size is used. In this conventional example, the Au-based conductor wiring pattern 12 is printed on the first layer green sheet 10-1, and the second layer green sheet 10-2 to the nth layer green sheet 10-n are printed. An Ag-based conductor wiring pattern 14 is printed on. The green sheet 10-1 of the first layer is provided with connection vias 16 filled with Au-based conductors at required locations.
Green sheets 10-2 to 10-n from the second layer to the nth layer
A connecting via 18 filled with an Ag-based conductor is provided at a required position. Each of these green sheets 10-1 to 10
A desired ceramic multilayer substrate is manufactured by stacking -n, thermocompression-bonding and firing at 900 ° C.

As described above, since the uppermost wiring uses the Au-based conductor, it has excellent migration resistance and high reliability, and the Ag-based conductor wiring is completely contained in the inside of the substrate and isolated from the substrate surface. As a result, the resistance to migration under an electric field in wet water is improved, and a ceramic multilayer substrate in which a connection failure due to migration is unlikely to occur is obtained.

[0006]

However, in the ceramic multi-layer substrate having the above-mentioned structure for improving the migration resistance, the connection via 16 filled with the Au-based conductor and the Ag-based internal conductor wiring 14 are electrically connected. The problem that a defect occurs occurs. As a result of observing the cross-sections of these defective conduction parts, Ag of the Ag-based internal conductor wiring 14 diffuses into the connection via 16 during firing, and the Ag-based internal conductor wiring 14 around the connection portion between the via 16 and the Ag-based internal conductor wiring 14. It was found that the thickness of the conductor wiring 14 was reduced and that a disconnection or a conduction failure occurred at a portion around the connection portion. It was also considered to increase the thickness of the Ag-based internal conductor wiring so that a sufficient thickness remains even if Ag diffuses into the Au-based conductor via.
However, printing such a thick Ag conductor paste on a green sheet has a problem that not only the accuracy of the line is deteriorated due to sagging at the pattern edge portion, but also warping and cracking occur. The same problem also occurs when the Au-based conductor to be the wiring pattern is formed by post-baking.

Therefore, an object of the present invention is to provide a ceramic multilayer substrate and a method for manufacturing the same, which can avoid defective conduction between an Au-based connecting via and an internal conductor wiring using an Ag-based conductor, which occurs after firing. .

[0008]

A ceramic multilayer substrate according to the present invention is constructed by alternately laminating a plurality of conductor wiring layers and ceramic insulating layers, and various active elements and passive elements in each of the conductor wiring layers. Is used as the outer conductor wiring layer on the surface to be connected to the inner conductor wiring layer sandwiched by the ceramic insulating layers among the conductor wiring layers.
In a ceramic multilayer substrate configured by using a g-based conductor and a connection via filled with a metal conductor for connection between the conductor wiring layers, an outer conductor wiring layer of the Au-based conductor and an inner conductor of the Ag-based conductor. An Au-based conductor is used as the filling metal of the connection via connecting to the first layer of the wiring layer, and the connection via is connected to the first-layer internal conductor wiring layer of the Ag-based conductor via the Ag-based pad. It is characterized in that it is configured to be connected.

In the ceramic multilayer substrate, a green sheet is punched out to a predetermined size, a via hole is punched at a required position in each punched green sheet, and then a first layer is formed using a mask. A printing and filling step of filling the via hole of the green sheet to be filled with an Au-based conductor paste and filling the via hole of the second and subsequent layers of the green sheet with an Ag-based conductor paste, A desired wiring pattern is screen-printed on the first green sheet using an Au-based conductor paste, and a desired wiring pattern is printed on the second and subsequent green sheets using an Ag-based conductor paste. A of the second layer to be printed and to be connected to the via hole filled with the Au-based conductor paste of the first layer
After conducting the second conductor printing on the wiring of the g-based conductor using the paste of the Ag-based conductor to provide a pad, the green sheet of the first layer and the green sheets of the second and subsequent layers are formed. It can be obtained by laminating and pressing in a predetermined order and then simultaneously firing.

In the method for manufacturing the ceramic multilayer substrate, Au is formed on the first-layer green sheet.
Except for the step of screen printing using a system conductor paste, after firing the green sheet that has been laminated and pressed, a desired wiring pattern is screen printed using the Au system conductor paste on the first-layer green sheet. It can also be obtained by a method of firing thereafter.

[0011]

According to the ceramic multilayer substrate of the present invention, the outermost conductor wiring pattern using the uppermost Au-based conductor and Ag are used.
The connection via using the Au-based conductor for connecting to the internal conductor wiring pattern using the system conductor has a structure in which the connection via is connected to the internal conductor wiring pattern via the pad of the Ag-based conductor larger than the diameter of the connection via. Therefore, Ag of Ag diffusion to the connection via generated during firing is supplied from the pad.
For this reason, it is possible to prevent the reduction in the thickness of the internal conductor wiring layer using the Ag-based conductor caused by Ag diffusion, and avoid the conduction failure.

Further, according to the method for manufacturing a ceramic multilayer substrate according to the present invention, in both cases of the co-firing manufacturing method and the post-firing manufacturing method, A
By adding a second conductor printing step using Ag-based conductor paste to the green sheet on which the internal conductor wiring pattern of the Ag-based conductor to which the connection via using the u-based conductor is connected is printed, An Ag-based pad for preventing conduction failure can be provided at the internal conductor wiring turn portion to which the connection via of the Au-based conductor is to be connected.

[0013]

EXAMPLES Examples of ceramic multilayer substrates according to the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 is a diagram showing a cross-sectional structure of a ceramic multilayer substrate showing an embodiment of the present invention, and FIG. 2 is a main process diagram in a manufacturing method for manufacturing the ceramic multilayer substrate. Hereinafter, along the steps of the manufacturing method of FIG.
The cross-sectional structure will be described with reference to FIG. In FIG. 2, reference numeral A indicates a green sheet manufacturing step. In this step A, a solvent, an organic binder and a plasticizer are added to a raw material powder made of glass-alumina to form a slurry, and a green sheet is manufactured by a doctor blade method. Next, in the blank step B, this green sheet is punched into a predetermined size.

In step C, a required number of green sheets punched to a predetermined size are prepared, and numbers are provisionally assigned in order from the uppermost layer, and C1 represents the first layer of green sheet 20-1. C2 is the second layer of green sheets 20-2, C3 ...
The green sheet 20-3 serving as the layer ... The green sheet 20-n serving as the nth layer. The respective green sheets C1 ... Cn are sequentially processed through the steps D to F to the laminating step G, but the differences distinguished by the subscripts 1 to n of the respective steps are applied to the respective green sheets C1 to Cn. In addition to the different via punch patterns and conductor printing mask patterns, there are the following differences. That is, for the green sheet C1, the point of using an Au-based conductor as the via paste in the via filling step E1 and the conductor printing step F
1. The point that an Au-based conductor is used as the conductor paste, the point that an Ag-based conductor is used as the via paste in the via filling step E2 for the green sheet C2, and the conductor printing step F
Conduct F2 and F22 twice, and use Ag as a conductor paste.
For the green sheets C3 ... Cn, via filling steps E3 ... En and conductor printing steps F3 ... Fn are used.
The difference is that an Ag-based conductor is used for the via paste and the conductor paste used in the above.

Next, in the via punching steps D1 ... Dn, via holes for interlayer connection are formed at required locations on the respective green sheets C1 ... Cn.

In the via filling step E1 ... En, the required conductor paste is filled in the via holes of each green sheet.
Here, the Au-based conductor paste 26 is used in the via filling step E1 for the first layer green sheet C1, and the Ag-based conductor paste 28 is used in the via filling step E2 ... En for the second and subsequent green sheets C2 ... Cn. .

In the conductor printing process F1 ... Fn, a wiring pattern is printed using a required conductor paste. That is,
The upper circuit wiring pattern 22 is conductor-printed on the first-layer green sheet C1 using an Au-based conductor paste.
Conductors are printed on the green sheets C2 ... Cn on and after the second layer by using an Ag-based conductor paste for the internal circuit wiring pattern 24. The upper circuit wiring pattern 22 of the uppermost layer is an external conductor wiring layer to which active elements such as transistors and LSIs and passive elements such as resistors and capacitors are connected, and Au-based conductors are used to improve reliability. There is. Here, in the second layer green sheet C2, after conducting the conductor printing (1) step F2 of the internal wiring circuit pattern 24, in the conductor printing (2) step F22, the first layer Au-based conductor connecting via 2 is further formed.
6 on the internal wiring circuit pattern 24 connected to 6,
The pad 30 is printed with a conductor using an Ag-based conductor paste. The thickness of the pad 30 at this time is set to a thickness that does not cause disconnection or defective conduction in the underlying Ag-based conductor wiring pattern 24 even when Ag diffuses into the Au-based conductor connection via during firing to be described later.

The via paste and the conductor paste are prepared in advance in the paste preparation process P. In the paste preparation step P, the via paste and the conductor paste are prepared by kneading metal powders of Au-based and Ag-based conductors, a binder and a solvent, respectively.

In the next laminating step G, the required number of green sheets C after the conductor printing steps F1 ... Fn are finished.
1 ... Cn are piled up in a predetermined order, and a temperature of about 100 ° C. and 1
A pressure of 00 to 150 kg / cm ² is applied and thermocompression bonding is performed.

Further, in the burnout step H, 40
A binder removal treatment is performed at a temperature near 0 ° C. to remove the binder.

Finally, in the firing step I, firing is performed at 900 ° C. to obtain the ceramic multilayer substrate 20 having the structure shown in FIG.

A feature of the method for producing a ceramic multilayer substrate by co-firing according to the present invention is that a conductor printing step F22 is added to the second layer green sheet C2. The conductor printing step F22 is performed at least on the Au-based conductor via diameter on the Ag-based conductor wiring pattern position formed in the conductor printing step F2 to be connected to the Au-based conductor via of the first layer green sheet C1. This is a step of providing an Ag-based conductor pad having a diameter including a positional deviation.

The uppermost Au-based conductor wiring pattern 22
1. The green sheet C1 is laminated without performing the conductor printing step F1 and after firing, the conductor printing of the Au-based conductor wiring pattern 22 is performed, and the firing is performed. Then, the structure of the ceramic multilayer substrate of FIG. You can also get it.
This manufacturing method by post-baking is suitable for applications in which the Au-based conductor wiring pattern 22 is aligned with the ceramic multilayer substrate that has been shrunk by baking and does not require much accuracy.

[0025]

As is apparent from the above-described embodiments, in the conventional firing method, either the simultaneous firing method or the post-firing method, during the firing, the Ag between the connection via using the Au-based conductor and the Ag-based conductor wiring is changed. Diffuses into the Au-based conductor connection via,
Although the thickness of the g-based conductor wiring was reduced around the connection vias, causing disconnection or poor conduction, according to the ceramic multilayer substrate of the present invention, the Au-based connection via 26 and the Ag-based conductor wiring 24 are connected to the Ag-based conductor wiring 24. With the structure in which the connection is made via the pad 30, it is possible to suppress a reduction in the wiring thickness of the Ag-based conductor wiring around the Au-based conductor connection via that occurs during firing, and it is possible to avoid disconnection or defective conduction. .

In either the co-firing or post-firing manufacturing method, the second conductor printing is performed by printing a predetermined pad after conducting the conductor printing of the internal wiring circuit pattern on the second layer green sheet. Since it suffices to add the step of performing, the manufacturing method can be easily changed.

Although the preferred embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and various design changes can be made without departing from the spirit of the present invention. Is.

[Brief description of drawings]

FIG. 1 is a sectional structural view showing an embodiment of a ceramic multilayer substrate according to the present invention.

FIG. 2 is a process diagram showing the main steps of the method for manufacturing the ceramic multilayer substrate of FIG.

FIG. 3 is a sectional structural view showing a conventional ceramic multilayer substrate.

[Explanation of symbols]

 10 Ceramic Multilayer Substrate 10-1 First Layer Green Sheet 10-n nth Layer Green Sheet 12 Au-based Conductor Wiring 14 Ag-based Internal Conductor Wiring 16 Au-based Conductor Connection Via 18 Ag-based Conductor Connection Via 20 Ceramic Multilayer Substrate 20 -1 First layer green sheet 20-n nth layer green sheet 22 External circuit wiring pattern (Au-based external conductor wiring) 24 Internal circuit wiring pattern (Ag-based internal conductor wiring) 26 Au-based conductor connection via 28 Ag-based Conductor connection via 30 pad

Claims (3)

[Claims] 1. A conductor wiring layer and a ceramic insulating layer are alternately laminated in a plurality of layers, and Au is formed on the outer conductor wiring layer on the surface to which various active elements and passive elements are to be connected in each conductor wiring layer. In addition to using a system conductor, an Ag system conductor is used for an inner conductor wiring layer sandwiched by a ceramic insulating layer in each conductor wiring layer, and a connection via filled with a metal conductor is used for connection between the conductor wiring layers. In the ceramic multilayer substrate configured as above, an Au-based conductor is used as a filling metal of a connection via connecting the outer conductor wiring layer of the Au-based conductor and the first layer of the inner conductor wiring layer of the Ag-based conductor. At the same time, the connection via is configured to be connected to the first-layer internal conductor wiring layer of the Ag-based conductor via the Ag-based pad. 2. A green sheet as a first layer, which is punched into a predetermined size, punches a via hole at a required position in each punched green sheet, and then uses a mask. The printing and filling step of filling the via holes with Au-based conductor paste and filling the via holes of the green sheets of the second and subsequent layers with Ag-based conductor paste, and then performing the first filling
Au the required wiring pattern on the green sheet as the second layer
Screen printing using a system conductor paste, the conductor patterns required for the second and subsequent green sheets are printed using an Ag system conductor paste, and the first layer of the Au system conductor paste is used. After conducting a second conductor printing using a paste of Ag-based conductor for providing a pad on the wiring of the Ag-based conductor of the second layer to be connected to the filled via hole, the first layer A method for producing a ceramic multilayer substrate, comprising laminating a green sheet and a second and subsequent green sheets in a predetermined order, pressing the sheets, and then firing them simultaneously. 3. The method for manufacturing a ceramic multilayer substrate according to claim 2, wherein a green sheet that is laminated and pressed is formed on the green sheet that is the first layer except for the step of screen printing using an Au-based conductor paste. A method for manufacturing a ceramic multilayer substrate, comprising: after firing, screen-printing a required wiring pattern on the first-layer green sheet using an Au-based conductor paste, and then firing.