JP2003110239A - Multilayer ceramic board and manufacturing method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve junction strength on the interface between a dielectric layer and an electrode layer in a multilayer ceramic board. SOLUTION: On the interface between the dielectric and electrode layers of a multilayer ceramic board, a plurality of lattice stripes are formed continuously. Burning is made under specific oxygen concentration conditions, thus continuously forming the lattice stripes of a crystal lattice in the electrode layer in the dielectric layer at a relatively low burning temperature, and hence improving the junction strength between the electrode layer and dielectric layer of the multilayer ceramic board.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multilayer ceramic substrate in which a dielectric layer and an electrode layer are laminated and integrally fired at a relatively low temperature, and a method for manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, as a ceramic electronic component,
A multilayer ceramic substrate in which ceramic green sheets are laminated is known. The multilayer ceramic substrate has a structure in which a ceramic green sheet as a dielectric layer and an electrode layer made of a conductive paste provided on the surface of the green sheet are laminated on each other.

In such a laminated structure, in a ceramic molded body in which a conductive paste forming an electrode layer and a ceramic green sheet forming a dielectric layer are laminated on each other, the electrode layer and the dielectric layer are simultaneously fired. , Or
It is manufactured by applying a conductive paste to a ceramic substrate that has been fired in advance, and then firing the conductive paste.

During such firing, shrinkage generally occurs in the article to be fired. Since the conductive paste forming the electrode layer and the ceramic green sheet or the ceramic fired body forming the dielectric layer have different shrinkage properties, deformation or warpage occurs due to the difference, and further, the electrode layer and the dielectric body The layers are separated.

[0005]

DISCLOSURE OF INVENTION Problems to be Solved by the Invention The inventor has made the shrinkage behavior inconsistent by matching the shrinkage behavior of the conductive paste functioning as an electrode layer during firing with the shrinkage behavior of the ceramic green sheet or the ceramic fired body. We have been developing technology to prevent warping and peeling based on

[0006] In such research, the present inventor has proposed a method of combining the contraction behaviors of the two layers in order to integrate the contraction behaviors at the interface between the electrode layer and the dielectric layer and prevent warpage and peeling of both layers. In addition to the solution in 1), I thought that it could be solved by further strengthening the bonding strength at the bonding interface of both layers.

Further, in the case of a multilayer ceramic substrate, conventionally, regarding the bonding strength at the interface between both layers, the peeling strength in the forced peeling test is adopted as the criterion for judgment, and it is judged that it should be a predetermined size or more. Came. By the way,
It has been generally said that a multilayer ceramic substrate has no practical problem as long as it has a strength of 5 N / mm ² or more.

However, the inventor of the present invention has found that the peeling situation may be greatly different even when the peeling strength is the same even though the peeling strength test is performed on a large number of multilayer ceramic substrates. Therefore, it is considered that it is necessary to consider not only the peel strength but also the qualitative viewpoint of the peeling situation.

Peeling includes interfacial peeling, in which both layers are peeled at the interface, and element peeling, in which the layers are not peeled at the interface but are torn in one of the layers. Interfacial peeling is
The peel strength is smaller than that of the element peeling. In addition, the interfacial peeling is easier than the peeling of the element body at once when the peeling is started, and the peeling of the element body is preferable as a product because it has toughness against peeling.

An object of the present invention is to integrate shrinkage behavior at the interface between a dielectric layer and an electrode layer in a multilayer ceramic substrate to improve the bonding strength between the dielectric layer and the electrode layer of the multilayer ceramic substrate, The purpose is to provide a multilayer ceramic substrate that does not separate at the interface between the body layer and the electrode layer.

[0011]

In order to achieve the above-mentioned object, the inventor of the present invention produced various multilayer ceramic substrates in which electrode layers and dielectric layers were laminated, and of these layers, both layers were formed. For the structure observation of the multilayer ceramic substrate with sufficient bonding strength,
It was performed from a microscopic viewpoint from the atomic level using an EM photograph.

[0012] According to the TEM photograph, in the multilayer ceramic substrate having a sufficient bonding strength of both layers, lattice fringes are formed at the interface between the electrode layer and the dielectric layer such that a plurality of parallel lines cross each other. I found out that

From the above results, by producing the multilayer ceramic substrate so that the lattice fringes are continuously formed at the interface between the electrode layer and the dielectric layer, the interfacial peeling is well suppressed and the sufficient bonding strength is obtained at the interface. It has been found that a multilayer ceramic substrate can be obtained. It was also found that in the multilayer ceramic substrate where such continuous lattice fringes were observed, an oxidized electrode layer was found. Further, in such a multilayer ceramic substrate, in the peeling mode during the forced peeling test, it was found that the interfacial peeling, which peels into both layers at the bonding interface, is less than 80% of the area of the bonding interface. The present invention has been made based on such novel findings.

By the way, Japanese Patent Laid-Open No. 2001-144447 describes a multi-layer substrate having a structure in which a refractory metal such as W, Mo or W-Mo is used as an electrode layer and aluminum nitride is used as a dielectric layer. It is stated that diffusion between layers and dielectric layers was found within a range of 10 μm from the bonding interface. It is described that the aluminum nitride particles are epitaxially grown toward the bonding interface. However, there is no description of data, photographs, etc. demonstrating and supporting such epitaxial growth, and the fact cannot be objectively confirmed only by the above publication.

Further, in the above publication, the epitaxial growth toward the bonding interface is manifested by high temperature firing at which diffusion is extremely remarkable, for example, firing at 1800 ° C., and mutual diffusion is promoted by high temperature firing. , Said such growth will appear.

However, as described above, all the multilayer ceramic substrates in which continuous lattice fringes are confirmed at the interface between both layers are manufactured by low temperature firing below 1400 ° C. The present inventor is conducting research on suppression of warpage and peeling after firing in a multilayer ceramic substrate using a low-temperature sintered oxide-based dielectric layer, and lattice fringes are continuously formed at the interface between the electrode layer and the dielectric layer. That TEM is formed
I confirmed it for the first time in the photograph.

In the present invention, an experiment was conducted using an electrode material containing Ag, Cu, or Ni as a main component and an oxide-based dielectric layer, and continuous experiments observed at the interface between both layers were conducted. It is presumed that such lattice fringes are related to the firing temperature and firing conditions for integrating the oxide-based dielectric layer and the electrode layer.

Further, in the multilayer ceramic substrate of the present invention in which lattice fringes are continuously observed at the interface between both layers, element peeling in which the electrode layer and the dielectric layer are peeled from other than the interface is always observed in the forced peel test. Was done. There is also a case where interfacial peeling, in which the electrode layer and the dielectric layer are peeled from each other at the bonding interface, is also observed, but it has been confirmed that at least a part of the element peeling is always present. Especially, peel strength is 5N / m
In the case of m ² or more, it was confirmed that the area percentage of interfacial peeling to the bonded interface was less than 80%.

On the other hand, when such a lattice pattern is not confirmed, the bonding strength between the electrode layer and the dielectric layer is weak, and in the forced peeling test, only the interface peeling phenomenon in which the electrode layer and the dielectric layer peel from the bonding interface. It was confirmed that the interfacial peeling was greater than 80% in terms of the area percentage of the bonded interface even when the peeling of the element body was found. At this time, the bonding strength between the electrode layer and the dielectric layer is smaller than 5 N / mm ² .

That is, as described above, when the area percentage of element peeling is 20% or more, the rapid progress of peeling can be suppressed and the toughness against peeling can be imparted.

Further, in the production of the multilayer ceramic substrate of the present invention, the continuous formation of lattice fringes is confirmed at the interface between the electrode layer and the dielectric layer, and the area percentage of element peeling is 20% or more in the forced peeling test. As described below, it became clear that manufacturing conditions different from those of the conventional method for manufacturing a multilayer ceramic substrate are required.

That is, it became clear that the presence of at least a certain amount of oxygen, though a trace amount, is essential during firing. A multilayer ceramic substrate having the constitution of the present invention could be manufactured by using an oxide-based ceramic material and further keeping the inside of the firing furnace at a constant oxygen concentration.

The minimum amount of oxygen in the firing atmosphere is extremely small. For example, even if the initial atmosphere in the furnace is made of a non-oxidizing gas, the oxide-based ceramics can be used as the dielectric layer. In some cases, the above-mentioned minimum amount may be satisfied by oxygen released from the oxide-based ceramics during firing.

The presence of a trace amount of oxygen realizes appropriate oxidation of the electrode layer, which promotes the formation of lattice fringes continuously crossing the interface between both layers and contributes to the construction of the multilayer ceramic substrate of the present invention. It is supposed that there is. As described above, it is clear that the production of the multilayer ceramic substrate of the present invention requires conditions different from those of the above-mentioned conventional technique in conditions such as the dielectric layer, the electrode layer, the firing temperature, and the firing atmosphere.

That is, the multi-layer ceramic substrate of the present invention is a multi-layer ceramic substrate obtained by firing laminated dielectric layers and electrode layers, wherein the interface between the dielectric layers and the electrode layers is the interface. It is characterized in that the lattice fringes crossing each other are continuously formed.

In the present invention, whether or not the lattice fringes are formed depends on whether or not it can be observed by a TEM (transmission electron microscope) photograph or the like. Here, since it is difficult in terms of observation technology to observe continuous lattice fringes at all of the interfaces, it is sufficient if at least a plurality of lattice fringes crossing the interface can be observed.

The dielectric layer is made of a low temperature sintered oxide-based ceramic material, preferably Pb as an oxide.
It is preferable that a low melting point oxide such as O, Bi ₂ O ₃ or V ₂ O ₅ is included, and the electrode layer is formed of at least one metal selected from materials containing Ag, Cu and Ni as main components. .

If Ag is selected here, 900
~ 950 ° C, 1000 to 1050 when Cu is selected
When ° C or Ni is selected, it is desirable to select the material composition of the dielectric layer with a temperature of 1400 ° C or lower as a guide and integrally fire the dielectric layer. In the present invention, sintering at 1400 ° C. or lower is called low temperature sintering, and at the interface between the dielectric layer and the electrode layer, a plurality of lattice fringes crossing the interface are continuously formed at a sintering temperature of 1400 ° C. or lower. A multilayer ceramic substrate can be obtained.

Furthermore, in this multilayer ceramic substrate, it is desirable that at least a part of the main component of the electrode layer is oxidized.

Further, in the multilayer ceramic substrate of the present invention,
When forcibly peeling off the electrode layer and the dielectric layer,
It is characterized in that the rate of interfacial peeling from the interface between the electrode layer and the dielectric layer is less than 80% in terms of the percentage of the bonded interface.

Further, the present invention is a method for manufacturing a multilayer ceramic substrate in which laminated dielectric layers and electrode layers are integrally fired, and the firing of the dielectric layers and the electrode layers is performed in one step.
Manufacture of a multi-layer ceramic substrate, characterized in that the dielectric layer is fired at a temperature of 400 ° C. or lower using an oxide and / or fired in an atmosphere in which oxygen exists in the furnace body. Is the way.

Here, it is desirable that the oxygen concentration in the furnace body is 1 ppm or more.

[0033]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the drawings.

First, a method for manufacturing a multilayer ceramic substrate according to the present invention will be described with reference to the process chart of the method for manufacturing a multilayer ceramic substrate shown in FIG. As shown in FIG. 1, a sheet molding process 100 is performed by using a slurry containing a ceramic composition of a predetermined composition such as a main component Al ₂ O ₃ —SiO ₂ system to function as a dielectric layer, a resin binder, a plasticizer, and an organic solvent. Then, the doctor blade 111 is passed through to form a green sheet (ceramic green sheet) G having a predetermined layer thickness.

In the multilayer ceramic substrate of the present invention, the above-mentioned cell is used.
As a Lamix composition, SrO-Al ₂O₃-SiO₂System, BaO-Al
₂O₃-SiO₂System, SrO-Al₂O₃System, CaO-ZrO₂System, PbO-TiO₂System,
PbO-ZrO₂-TiO₂System, Fe₂O₃-Y₂O₃System, Bi₂O₃-Nb₃O₃System, BaO-
Nd₂O₃System, Li₂O-Nb₂O₃-ReO type, BaO-TiO2 type, etc.
An oxide-based ceramic material that can be bonded is used. Well
In addition, as a resistor component of the multilayer ceramic substrate, RuO₂System
The components may be used together.

The green sheet G formed as described above is then dried, and after the drying, the cutting / frame attaching step 1
As shown in 02, it is cut into a predetermined size and attached to the frame 112.

While being attached to the frame 112, a through hole 113 is formed by forming a hole at a predetermined position of the green sheet G as shown in the through hole forming step 103. In the through hole 113, the through hole filling step 1
As shown in 04, a conductive paste that functions as an electrode layer is filled by screen printing. Thereafter, as shown in the internal conductor printing step 105, an internal conductor 114 having a predetermined use and arrangement for communicating with the conductive paste in the through hole 113 is printed.

A material containing a metal such as Ag, Cu, or Ni as a main component is used as an electrode component in the conductive paste. For example, when an Ag paste is produced, it is sufficient to use a paste prepared with a composition of Ag powder of 85% by weight and organic content of 15% by weight. Also, depending on the characteristics required for the electrode layer, Pt or R
There is no problem even if u or a glass component containing B ₂ O ₃ or SiO ₂ is added. Cu paste, N
In the case of the i paste as well, similar to the Ag paste, Cu powder and organic components having a desired composition, and Ni powder and organic components may be prepared in a paste form.

In this way, a plurality of green sheets G having internal electrodes formed on the sheets are prepared by screen printing using the conductive paste prepared as described above, and as shown in the laminating / pressure bonding step 106. Then, the green sheets are laminated and pressure-bonded.

In the pressed state, as shown in the cutting step 107, the green sheet laminate 1 is cut into a predetermined size.
Form 15. As shown in the degreasing / firing step 108, the green sheet laminated body 115 is degreased and then placed in a firing furnace and heated to a predetermined temperature to be fired to produce a multilayer ceramic substrate. Alternatively, the conductive paste may be formed on the baked substrate by printing, and the conductive paste may be formed again by baking.

When firing, the firing temperature depends on the material of the green sheet, but in the case of Ag, 900 to 950 ° C., C
1000 to 1050 ° C. for u, 140 for Ni
The material is selected with 0 ° C. or less as a guide, and the firing atmosphere in the furnace body is set to have an oxygen concentration of 1 ppm or more.
This can be done by using a mixed gas with the desired oxygen concentration, or by introducing a non-oxidizing gas such as nitrogen or argon during heating in the atmosphere and replacing the atmosphere with the non-oxidizing gas in the furnace. I'll do it.

In the multilayer ceramic substrate 116 thus formed, as shown in the external terminal baking step 109, external terminals for achieving electrical connection with the inside are baked to form electrodes. Then, the plating step 110
As shown in (3), the surface can be plated to obtain a final product as a multilayer ceramic substrate. It is possible to obtain a multilayer ceramic substrate having extremely high conductivity and high reliability.

Such a multilayer ceramic substrate is often used as an electronic component in products such as mobile phones. For example, in a mobile phone, it can be used as various circuit electronic components such as a coupler in a transmission circuit, a high power amplifier, a bandpass filter, a lowpass filter, an antenna switch, and a module component that combines these.

With respect to the multilayer ceramic substrate manufactured according to the above procedure, as shown in FIG. 2, the state of the structure near the interface 10 between the dielectric layer A and the electrode layer B was observed. The observation sample was prepared as follows. First, the multilayer ceramic substrate,
With a diamond cutter, approximately 0.
Cut to a thickness of 2 mm. Then, both surfaces of the cut out piece are polished with a diamond paste to a thickness of 20 μm or less. Finally, argon ion etching was performed, and the holes were partially polished, and the 20
A portion thinner than μm was used as an observation visual field.

An FE-TEM (HF-2100 manufactured by Hitachi, Ltd.) was used for the observation, and the acceleration voltage was 200 kv.
The state of the interface between the electrode layer and the dielectric layer was observed with.

FIG. 2 shows a TEM photograph at the interface between the electrode layer and the dielectric layer in the multilayer ceramic substrate of the present invention manufactured by applying the manufacturing method of the present invention, and FIG. 3 shows the interface portion of FIG. FIG.

As a result of the observation, as shown in FIG. 3, at the interface 10 where the dielectric layer A and the electrode layer B are joined, a plurality of lines running in parallel, that is, a plurality of lattice stripes 20 are formed at the interface 10.
It is formed continuously so as to traverse.

Incidentally, in the case shown in FIG. 2, observation is performed at a magnification of 500,000 times. For more detailed observation, the accelerating voltage of the electron beam may be increased to 200 kv or more, but the irradiation of the electron beam accelerated to 200 kv or more causes the sample to melt and sufficient observation cannot be performed.

Further, the white background portion 30 in FIG. 3 is a portion in which the lattice fringes 20 are not observed, but this is where the influence of focus shift is large. Also, the dotted line corresponds to the interface 40 between Ag particles and Ag particles.
It is considered that the grid pattern is broken at 0.

Next, the bonding strength of both layers of the multilayer ceramic substrate in which the lattice fringes are continuously formed over the interface 10 in this manner was examined. The bonding strength is the dielectric layer A
It was specifically verified by a forced peeling test between the electrode layer B and the electrode layer B. In the verification, a multilayer ceramic substrate in which a continuous pattern of lattice fringes continuously observed through the interface 10 is not seen was used for comparison as a test.

The forced peeling test was conducted in the following manner.
That is, a 1 × 1 mm square adhesion test piece is simultaneously formed on a 5 × 5 mm square substrate surface of the multilayer ceramic substrate according to the present invention, which is formed by the above-described manufacturing method and has continuous lattice fringes 20 on the interface 10. After forming by firing, φ0.5mm × 2
A 0 mm nickel-plated Kovar pin was soldered into a test piece.

For the test, Shimadzu Corporation Autograph (A
(G-G type) using a fixed Kovar pin of 1 mm /
The bond strength is the value obtained by dividing the maximum stress when the Kovar pin is disengaged from the substrate by the bonding area between the electrode layer and the dielectric layer at a speed of a minute.

In this forced peeling test, two types of peeling modes, interface peeling and element peeling, are observed. 4 and 5,
The situation of both peeling modes of element body peeling and interface peeling is shown.

FIG. 4A shows a state before the forced peeling as seen from above on the Kovar pin side. Figure 4
(B), (C), and (D) show the state of the element peeling mode when a forced peeling test is performed using the sample shown in (A). The sample of FIG. 4A is a dielectric layer A composed of Al ₂ O ₃ —SiO ₂ ceramics and 100% Ag.
And an electrode layer B having a composition of, and continuous lattice fringes 20 are observed at the interface 10 between the two layers.

FIG. 4B shows the state on the Kovar pin side after the forced peel test, and FIG. 4C shows the peeled state on the element body side after the forced peel test. FIG. 4D shows the state of element peeling in cross-sectional states before and after the forced peeling test.

As is clear from FIGS. 4 (B), (C) and (D), no peeling occurs at the interface between the dielectric layer A and the electrode layer B in the peeling of the element body, and either of both layers is peeled off. It is a situation where the layer is destroyed by being forcibly pulled in the layer. In the case shown in FIGS. 4 (B) and 4 (D), the part torn in one of the dielectric layers A is attached to the kovar pin side, and FIGS. 4 (C) and 4 (D) are attached to the element body side. As shown in (), a concave portion corresponding to the portion brought to the Kovar pin side is observed.

FIG. 5A shows a state before the forced peeling as seen from above on the Kovar pin side. Figure 5
(B), (C), and (D) show the state of the interface peeling mode. The sample before the forced peeling test shown in FIG. 5A has a dielectric layer A and an electrode layer B having the same composition as that in which the element peeling was observed, and the lattice fringes 20 continuous on the interface 10 of both layers. It is composed of a multi-layered ceramic substrate in which is not observed. FIG. 5B shows the state on the Kovar pin side after the forced peel test, and FIG. 5C shows the peeled state on the element body side after the forced peel test. In the figure, the range where the electrode layer is peeled off is indicated by a broken line. FIG. 5D shows the state of interfacial peeling in the cross-sectional state of the test piece before and after the forced peeling test.

As shown in FIGS. 5B to 5D, in the interface peeling, the two layers are separated from each other at the bonding interface between the dielectric layer A and the electrode layer B, and FIGS. The state in which one layer is pulled and attached to the other layer, which is seen in the peeling of the element body, is not observed.

As described above, as the peeling mode in the forced peeling test, interfacial peeling and element body peeling are observed, but normal peeling is observed in a state in which both interface peeling and element body peeling modes are mixed. The Rukoto. Therefore, as an index showing the mixed state of both peeling modes, in the following description, one of the peeling modes of interface peeling and element peeling is focused and the area percentage of the peeling mode is used.

Here, the area percentage of the peeling mode is the sum of the areas where one peeling mode is observed after the forced peeling test with respect to the bonding area at the interface between the dielectric layer and the electrode layer before the forced peeling test. Is defined as the percentage of the above-mentioned bonded area.

As shown in Tables 1 and 2, the inventor of the present invention, in a multilayer ceramic substrate having various combinations of a dielectric layer of oxide-based ceramics and an electrode layer, the presence or absence of lattice fringes at the interface between both layers and the bonding. The strength was verified.

Table 1 below shows Examples 1 to 8 in which lattice fringes continuously formed at the interface of both layers are observed.
Up to. Comparative Examples 1 to 3 are exemplified as the case where the lattice fringes on the interface are not observed.

Each of the samples of Examples 1 to 8 and Comparative Examples 1 to 3 has the composition of the dielectric layer and the electrode layer shown in Table 1, and the samples of the above-mentioned multilayer ceramic substrate shown in FIG. It was manufactured according to the manufacturing method. However, in the production, the firing temperature and the oxygen concentration are set under the conditions shown in Table 1, respectively.

In addition, Table 2 corresponds to Examples 1 to 8 and Comparative Examples 1 to 3 of Table 1, and the presence or absence of lattice fringes at the interface between the dielectric layer and the electrode layer and the presence or absence of detection of oxidation of the electrode component. Shows the area percentage (%) of interfacial peeling in the peeled area in the forced peeling test, and the bonding strength (N / mm ² ).

In Tables 1 and 2, since Comparative Example 1 had a low firing temperature and a low oxygen concentration, continuous lattice fringes were not obtained, and the area percentage of interfacial delamination was 100%, and almost no bonding strength was obtained. Comparative Example 2 is a nitride-based ceramic and has a low oxygen concentration, so that continuous lattice fringes cannot be obtained.
Almost no bonding strength can be obtained with 100% interfacial peeling.

[0066]

[Table 1]

[0067]

[Table 2]

From Examples 1, 5, 7, 8 of Tables 1 and 2 and Comparative Example 3, even if a multilayer ceramic substrate having an electrode layer and a dielectric layer of the same composition was used, It can be seen that the peeling condition in the forced peeling test and the bonding strength of both layers are different between the case where continuous lattice fringes are confirmed at the interface with the body layer and the case where such lattice fringes are not confirmed.

Regarding the peeling situation, the present inventor produced a number of multilayer ceramic substrates having electrode layers and dielectric layers having the same composition, in addition to those shown in the above table, and at the interface between both layers. A forced peeling test was conducted for the case where continuous lattice fringes were observed and the case where they were not observed, and the results were observed.

The results are similar to the comparison results of the above-mentioned Example and Comparative Example 3 when lattice fringes are observed at the interface between both layers.
It was confirmed that the element peeling mode was always confirmed, and that the area percentage of interfacial peeling did not reach 100%. on the other hand,
It was found that when the lattice fringes are not observed, the area percentage of interfacial peeling may be 100%, and the area percentage of the element body peeling is smaller than when the lattice fringes are observed.

Further, as the bonding strength increases, the interface peels off.
It is also confirmed that the area percentage of is smaller. Example 7
Then, the minimum required 5N /
mm ²Although the joint strength of the
The area percentage of surface peeling is 70%. 5 N / mm²Than
If the joint strength is also high, it is clear from the table.
As a result, the area percentage of interfacial peeling is less than 70%.
I see.

Further, in the multilayer ceramic substrate,
It is generally said that if the bonding strength is 20 N / mm ² , bonding between the dielectric layer and the electrode layer is sufficient.
From, the joining strength was obtained in Examples 2 and 8. Both examples have different compositions of the dielectric layer and the electrode layer, but the bonding strength is 20 N /
a mm ^2, and the area percentage of the interfacial peeling is 20%. From these results, it is presumed that the area percentage of interfacial peeling is preferably less than 20% in order to obtain a sufficient bonding strength of 20 N / mm ² required for the multilayer ceramic substrate.

It is also confirmed from Tables 1 and 2 that the oxygen concentration during firing has an influence on the bonding strength having a significant correlation with the area percentage of such interfacial peeling.
That is, the higher the oxygen concentration, the higher the bonding strength. When the oxygen concentration is 1 ppm or less, for example, as shown in Comparative Example 3, the peeling strength (5 N / mm ² ) generally required for a multilayer ceramic substrate cannot be obtained, but when the oxygen concentration is 1 ppm or more, such a bonding strength is obtained. It is understood that the criteria of are met. As shown in Example 7, if the oxygen concentration during firing is 1 ppm, the minimum required bonding strength is 5 N /
It can be seen that mm ² is secured.

From the above results, the following is confirmed. That is, when a lattice fringe is observed across the interface between the dielectric layer and the electrode layer, the area percentage of interfacial delamination in the forced delamination test is higher than when the lattice fringe is not formed. Is small and the bonding strength is correspondingly large.

In order to secure the minimum bonding strength of 5 N / mm ² required for the multilayer ceramic substrate, at least the area percentage of interfacial peeling must be less than 80%. In addition, 20N / which is considered to have sufficient bonding strength
In order to secure the bonding strength of mm ² or more, at least the area percentage of interfacial peeling must be less than 20%.

Further, the formation of lattice fringes at the interface, which is related to the area percentage of the interfacial peeling and the bonding strength, is greatly affected by the oxygen concentration during firing of the multilayer ceramic substrate. Minimum bonding strength required for multilayer ceramic substrates 5
In order to secure N / mm ² , it is preferable to set the oxygen concentration during firing to at least 1 ppm.

In this way, if the lattice fringes at the interface between the electrode layer and the dielectric layer are continuously formed,
Even at a low firing temperature of 00 ° C. or less, the bonding strength of both layers can be improved.

Further, based on this fact, the continuous lattice fringes at the interface between the dielectric layer and the electrode layer contribute to the formation of a multilayer ceramic substrate that does not peel off by integrating the contraction behavior at the interface. It can also be inferred.

Further, in the multilayer ceramic substrate according to the present invention in which continuous lattice fringes are observed at the interface between both layers, at least a part of the main component of the electrode layer is oxidized at the interface between the dielectric layer and the electrode layer. Was first confirmed by the present inventor. When such lattice fringes were not observed, as shown in Comparative Examples 1 to 3 in Tables 1 and 2, it was not possible to detect the oxidized electrode layer at the interface.

Regarding the oxidation of the electrode metal at such an interface, the interface between the electrode layer and the dielectric layer is exposed by polishing,
It can be verified by measuring the binding energy of the metal by XPS (X-ray photoelectron spectroscopy) analysis of the sample. For example, in the case of Ag, the binding energy standard values of Ag, Ag ₂ O, and AgO are 368.2 ev and 36, respectively.
7.8 ev and 367.4 ev. Therefore, in the case of partially oxidized Ag, the peak of the binding energy is 36
It shifts to a lower energy side than 8.2 ev. By measuring the energy peak value in this way, it is possible to confirm the oxidation of the electrode metal at the interface.

Next, in the comparison of Examples 2 and 6 in which the main component of the electrode layer is Cu and the main component of the dielectric layer is CaO--ZrO ₂ system, the dielectric layer and the electrode layer are integrally fired. In the case of Example 2 of the multilayer ceramic substrate formed by the above method, the electrode layer is provided on the previously sintered dielectric layer even though the multilayer ceramic substrate is fired at the same firing temperature in the firing atmosphere of the same oxygen concentration. It can be seen that the peel strength is higher than that in the case where only the electrode layer is separately fired.

From the above results, even when lattice fringes are formed at the interface between both layers, the simultaneous firing of the dielectric layer and the electrode layer makes the firing of the dielectric layer and the electrode layer separate. It is confirmed that it is more preferable than the case.

In Tables 1 and 2, in Comparative Example 1, the main component of the electrode layer was W, and the main component of the dielectric layer was Examples 1, 5 and
This is a case where the same Al ₂ O ₃ —SiO ₂ system as in 7 and 8 is used. In such Comparative Example 1, continuous lattice fringes were not observed at the interface between the electrode layer and the dielectric layer. It is considered that continuous lattice fringes cannot be obtained because the oxygen concentration is low and the firing temperature is low. The area percentage of interfacial peeling was 100%, indicating no bonding.

On the other hand, in Comparative Example 2, since the nitride-based ceramics had a low oxygen concentration, continuous lattice fringes were not obtained, and 100% interfacial delamination was not observed at all.

In the above description, the case where an oxide-based ceramic material is used as the main component of the dielectric layer has been described, but the main component of the dielectric layer is a non-oxide-based ceramic material as shown in Table 3. Ceramic materials can be used.

With such a structure, when the oxygen concentration was 1 ppm or more in the firing atmosphere, continuous lattice fringes were observed at the interface between the electrode layer and the dielectric layer, as shown in Example 9 of Table 4. On the other hand, as shown in Comparative Example 4, when the oxygen concentration during firing was less than 1 ppm, for example, at 0.1 ppm, no lattice fringe that continuously crossed the interface was observed.

In Comparative Example 4 in which no continuous lattice fringes were observed at the interface, unlike in Comparative Examples 1 to 3, a small bonding strength was obtained, but the area percentage of interfacial delamination was as high as 90%. Further, from Comparative Example 4, it can be seen that the area percentage of interfacial peeling may not be 100% even if lattice fringes are not confirmed at the interface.
That is, it is presumed that exfoliation of the body is slightly present.

However, if no lattice fringes are observed,
For example, even if a certain degree of bonding strength is obtained, the area percentage of interfacial peeling is 70% or more, and it can be seen that the bonding strength is small and the practical bonding strength is not achieved even if element peeling is mixed.

[0089]

[Table 3]

[0090]

[Table 4]

The present invention does not have to be limited to the configurations shown in the above embodiments, and various modifications may be made without departing from the spirit of the present invention.

[0092]

According to the present invention, by forming continuous lattice fringes whose structure is observed in a TEM photograph at the interface between the electrode layer and the dielectric layer of the multilayer ceramic substrate, as compared with the case where such lattice fringes are not found, The bonding strength of both layers can be improved.

By thus improving the bonding strength between the electrode layer and the dielectric layer, the contraction behavior of the interface between the electrode layer and the dielectric layer is further integrated, and even if peeling should occur, The toughness against peeling can be imparted to the multilayer ceramic substrate so that the interfacial peeling does not become the dominant peeling mode.

According to the present invention, the bonding strength between the electrode layer and the dielectric layer of the multilayer ceramic substrate is determined from the viewpoint that the lattice fringes of the electrode layer are continuously formed on the dielectric layer by observing the structure of a TEM (transmission electron microscope). , Can be confirmed.

According to the present invention, the bonding strength between the electrode layer and the dielectric layer of the multilayer ceramic substrate can be determined from the viewpoint of the peeling mode which is different from the peeling strength. Therefore, the peeling time and the toughness against peeling, which were not considered in the conventional peeling strength, can be added to the judgment factors of the bonding strength.

According to the present invention, the electrode layer material and the dielectric layer material are appropriately selected and laminated, an oxidizing atmosphere is appropriately formed in the furnace body, and the electrodes are sintered together at a relatively low temperature. It is possible to surely continuously form the lattice fringes of the layer on the dielectric layer.

[Brief description of drawings]

FIG. 1 is a process chart showing an embodiment of a method for manufacturing a multilayer ceramic substrate of the present invention.

FIG. 2 is a TEM drawing-substituting photograph (observation magnification: 500,000 times) showing a continuous state of lattice fringes of an electrode layer of a multilayer ceramic substrate according to an embodiment of the present invention in a dielectric layer.

FIG. 3 is an explanatory view showing the state of the interface shown in FIG. 2 in an easy-to-understand manner.

FIG. 4A is a plan view of the sample before the forced peeling test as seen from above on the Kovar pin side, and FIGS. 4B and 4C show the continuous state of the lattice stripes of the electrode layer on the dielectric layer. FIG. 3A is an explanatory diagram showing the peeling state of the multilayer ceramic substrate on the Kovar pin side and the element body side after the forced peeling test, and FIG. 6D is a sectional view showing the state of the element body peeling before and after the forced peeling test.

FIG. 5A is a plan view of the sample before the forced peeling test as seen from above on the Kovar pin side, and FIGS. 5B and 5C show the continuous state of the lattice fringes of the electrode layer on the dielectric layer. FIG. 3A is an explanatory diagram showing the peeling state of the multilayer ceramic substrate on the Kovar pin side and the element body side after the forced peeling test, and FIG. 6D is a sectional view showing the state of interfacial peeling before and after the forced peeling test.

[Explanation of symbols]

10 interfaces 20 plaid 30 white background 40 interfaces 101 sheet forming process 102 Cutting / frame attaching process 103 Through hole forming process 104 Through hole filling process 105 Inner conductor printing process 106 Laminating / pressing process 107 cutting process 108 Degreasing and firing process 109 External terminal baking process 110 plating process A dielectric layer B electrode layer G green sheet

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 5E343 AA02 AA23 BB24 BB25 BB44                       BB72 DD03 ER36 GG02                 5E346 AA33 CC18 CC32 CC37 CC39                       DD34 DD45 EE27 EE28 FF18                       GG04 GG05 GG06 GG08 GG09                       GG10 GG17 HH11

Claims (7)

[Claims] 1. A multilayer ceramic substrate obtained by firing a laminated dielectric layer and an electrode layer, wherein lattice fringes crossing the interface are continuously formed at an interface between the dielectric layer and the electrode layer. A multilayer ceramic substrate characterized by being formed. 2. The multilayer ceramic substrate according to claim 1, wherein the dielectric layer is made of a low temperature sintered oxide-based ceramic. 3. The multilayer ceramic substrate according to claim 1, wherein the electrode layer is made of at least one metal selected from materials containing Ag, Cu, and Ni as main components. . 4. The multilayer ceramic substrate according to claim 1, wherein at least a part of a main component of the electrode layer is oxidized. 5. The multilayer ceramic substrate according to claim 1, wherein the electrode layer and the dielectric layer are forcibly separated from each other,
A multilayer ceramic substrate, characterized in that the rate of interfacial peeling from the interface between the electrode layer and the dielectric layer is less than 80% in terms of area percentage of the bonded interface. 6. A method for manufacturing a multilayer ceramic substrate, comprising integrally firing a laminated dielectric layer and an electrode layer, wherein the firing of the dielectric layer and the electrode layer is performed at a temperature of 1400 ° C. or lower. Firing using an oxide for the dielectric layer,
And / or a method of manufacturing a multilayer ceramic substrate, characterized in that the furnace body is fired in an atmosphere in which oxygen is present. 7. The method of manufacturing a multilayer ceramic substrate according to claim 6, wherein the oxygen concentration in the furnace body is 1 ppm or more.