JPH0447476B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a ceramic multilayer wiring board used in electronic devices and the like. Conventional technology Conventionally, ceramic multilayer wiring boards produced using the green sheet lamination method use alumina for the insulating layer and tungsten or molybdenum for the conductive wiring material, and are fired at a temperature of approximately 1500 to 1600°C in a reducing atmosphere. It was on. Recently, as materials for low-temperature firing, glass materials and titanium tin barium borate materials (commonly known as BSB) are used as insulating materials, and gold, silver palladium, copper, and nickel are used as conductive wiring materials. Report on ceramic multilayer wiring board that can be fired (Electronic Ceramics March 1985)
Monthly issue) has been published. Problems to be Solved by the Invention However, in alumina-based multilayer substrates, the temperature of alumina and tungsten or molybdenum -
Because the shrinkage curves are similar, it is possible to obtain a multilayer substrate without deformation or warping of the substrate, but the disadvantage is that the firing process costs are high because the firing temperature is high and firing is performed in a reducing atmosphere. There is. In addition, in order to obtain higher-density, multi-functional ceramic multilayer substrates, it is necessary to form resistors, capacitors, etc., which are passive elements in the circuit, in each layer. Since the temperature is as high as 1,500 to 1,600°C, there is a problem in that it is technically and economically difficult to simultaneously form practical passive elements within the layer. In order to solve the above problems, low temperature fired ceramic multilayer wiring boards are being developed. However, in proceeding with this development,
It has been discovered that there are unexpected problems with conventional alumina multilayer substrates. The first problem is that the temperature-contraction curves of the board material and conductive wiring material are different, causing warping of the multilayer board.
This results in deformation. Although many reports and patent applications have been made regarding substrate materials for low-temperature firing, there are almost no detailed reports on this most important issue. If we try to put it into practical use, fixing the ceramic composition will limit the range of conductive wiring materials that can be used, and conversely, fixing the conductive wiring material will limit the range of ceramic compositions that can be used. . The second problem is the solder wettability of the conductive wiring material of the outermost layer. When used as a wiring board for electric circuits, this problem is also very important, as not only the type of conductive wiring material but also the composition of the ceramic board has a great influence on solderability.
The details of this will be described later, but certain components of the ceramic substrate diffuse into the conductive wiring material of the outermost layer, impeding solder wettability. Therefore, the solder wettability of the conductive wiring material of the outermost layer is also limited by the ceramic composition and the conductive wiring material. In addition, in order to improve solder wettability, Ni and Cu
Even if plated, the next step is to print a RuO ₂ -based resistance paste and bake it in air at 850°C, so the plated area will erode. Furthermore, if Au plating is applied, the cost will be high and process costs will be required. A third problem is that expensive conductive wiring materials must be used. Table 1 shows the market prices of various metals.

[Table] When cheap base metal materials such as Cu and Ni are used as conductive wiring materials that can be fired at 850℃ to 1000℃,
These base metal materials require a reducing atmosphere, which increases the running cost of the process.Also, as mentioned earlier with the disadvantages of alumina-based multilayer substrates, when trying to form passive elements such as resistors and capacitors in the layers, RuO ₂ -type resistors are reduced and lose their function as resistors, and most of the currently reported capacitors are oxide-based, so they lose their function as capacitors when fired in a reducing atmosphere. Most conductive wiring materials that can be fired in air are precious metals, such as gold, silver, and silver-palladium alloys, but the cost of gold is extremely high, so ceramic multilayer wiring boards are used in general electrical equipment other than computer-related equipment. However, in many cases, it is not practical due to cost. Furthermore, there are many reports that Ag, which is inexpensive among noble metals, has poor reliability because it diffuses into ceramic substrates. However, it goes without saying that the reliability at this time is affected by the ceramic composition and the thickness of the ceramic insulating layer. In the case of silver-palladium alloys, the Ag content is 70% by weight, as is usually used in hybrid ICs.
% or more, practical use is possible in terms of both cost and impedance. As described above, if the present invention is to be put to practical use, it is necessary to solve all of the above-mentioned problems, and the ceramic multilayer wiring board of the present invention solves all of the conventional problems. Means for Solving the Problems The ceramic multilayer wiring board of the present invention has a ceramic insulating layer containing 45 to 60% by weight of Al ₂ O ₃ , 24 to 33% by weight of SiO ₂ , 2.4 to 3.3% by weight of B ₂ O ₃ . _Na2O1.2 ~1.65wt%, _K2O0.8 ~1.1wt%, CaO3.2~4.4wt%,
The composition is selected so that the total amount is 100% by weight in the composition range of 1.2 to 1.65% by weight of MgO and 7.2 to 9.9% by weight of PbO, and the conductive wiring material of the internal layer is 70 to 100% by weight of Ag, 7.2 to 9.9% by weight of Pd The composition was selected so that the total amount was 100% by weight within a composition range of 30% by weight, and the conductive wiring material in the outermost layer was 70 to 95% by weight of Ag and 5 to 30% by weight of Pd.
It is composed of a composition selected so that the total amount is 100% by weight within the composition range. Function Since the ceramic multilayer wiring board of the present invention can be fired in air at a low temperature of, for example, 900°C, the firing process is simpler and energy saving can be achieved compared to conventional alumina multilayer boards. Also,
The compatibility between the ceramic composition forming the ceramic insulating layer and the conductive wiring material in the present invention is good;
A ceramic multilayer wiring board without warping or deformation can be obtained, and the conductive wiring material of the uppermost layer has excellent solder wettability. In addition, both the cost and impedance of the conductive wiring material are sufficient for practical use. Embodiment FIG. 1 is a partially cutaway perspective view showing an embodiment of the ceramic multilayer wiring board of the present invention.
b, 1c, and 1d are ceramic insulating layers, 2 is an internal conductive layer, and 3 is an external conductive layer, and there is no particular feature in their arrangement. Table 2 shows the compositions of the three types of glass powders A, B, and C used in this experiment. (Unit is weight%)

[Table] Table 3 lists the ceramic composition of the board and the evaluation results as a multilayer wiring board (composition units are weight %).

【table】

[Table] The ceramic composition shown in Table 2 is
Glass powder A with an average particle size of about 2 μm shown in the table,
B and C are mixed with alumina having an average particle size of approximately 1.8 μm.The compositions of sample numbers 1 to 5 in Table 3 are a mixture of glass powder A and alumina. The composition is a mixture of glass powder A and alumina in a weight ratio of 60:40.
Similarly, sample numbers 6 to 10 are a mixture of glass powder B and alumina, and sample numbers 11 to 15 are a mixture of glass powder C and alumina. Among the evaluation items shown in Table 3, regarding compatibility with the internal conductor, as shown in Figure 3, the internal conductor layer 2 with a width of 8 mm is
A test sample was prepared by laminating five green sheets 4 of 35 mm x 0.25 mm in size, and fired in air according to the firing profile shown in FIG. 2 to evaluate warping and deformation of the ceramic multilayer substrate. The internal conductor layer 2 used at this time had metal components in weight ratios of Ag/Pd=100/0, 95/5, 90/10, 80/20,
There are five types of 70/30, and the ceramic composition that satisfies the compatibility with all five types of internal conductors is ○.
Ceramic compositions that were not compatible with even one type of internal conductor were given a rating of x. Figure 4 A, B, and C show the compatibility of ceramic samples 3, 8, and 11 in Table 3 with 100% Ag.
If the combination is incompatible, the substrate will be deformed as shown in FIG. 4C. Among the evaluation items shown in Table 3, regarding solder wettability, green sheets of each ceramic composition had metal components in weight ratios of Ag/Pd=95/5,
Printing 90/10, 80/20, 70/30 conductive paste,
After drying and laminating and crimping these green sheets,
Firing was performed using the firing profile shown in Figure 2.
The obtained board was immersed in a solder bath at 260° C. for about 2 seconds to test the solder wettability of the outermost layer conductor. Ceramic compositions with solder all over the surfaces of the four types of conductors mentioned above were given a rating of ○, and even if one type of conductor had no solder all over the surfaces, a rating of × was given. From the experimental results, ceramic composition sample number 1~
Only No. 4 had extremely poor solderability. In order to investigate the cause of this, surface elemental analysis of the outermost layer conductor was conducted using the Auger analysis method for sample numbers 3 and 8 when the metal component was used as the outermost layer conductor at a weight ratio of Ag/Pd = 80/20. Ivy. The results are shown in FIGS. 5 and 6. Figure 5 shows sample number 3 of ceramic composition.
FIG. 2 is a chart showing the results of surface analysis of Ag/Pd with a combination of Ag/Pd=80/20. Figure 6 shows ceramic composition sample number 8 and Ag/Pd=
FIG. 2 is a chart showing the results of surface analysis of Ag/Pd using a combination of 80/20. In all cases, the sputtering speed was 150〓/MiN, so
Sputtering time on the X axis for both Figures 5 and 6
The 10 minute point indicates a depth of 1500 Å from the Ag/Pd surface. If you compare Figures 5 and 6, you will notice a big difference. In Figure 5, Ag/Pd
It can be seen that there is a large amount of SiO ₂ on the surface and a large amount of O ₂ . In Figure 6, Si exists on the surface of Ag/Pd, but at a depth of 1500 Å from the surface
It was found that SiO ₂ did not exist. In addition, electron micrographs of these Ag/Pd surfaces (4000x magnification)
are shown in FIGS. 7 and 8. Figure 7 shows sample number 3 of ceramic composition.
With the combination of Ag/Pd=80/20 (weight ratio), Ag/Pd
This is an electron micrograph (4000x magnification) of the surface of
Figure 8 shows ceramic composition sample number 8 and Ag/Pd.
This is an electron micrograph (4000x magnification) of the surface of Ag/Pd with a combination of =80/20 (weight ratio). Comparing Figures 7 and 8, it can be seen that there is a significant difference.
In Fig. 7, it appears that the Ag/Pd surface is covered with a glass-like substance, but in Fig. 8, only Ag/Pd particles can be seen. This is because in ceramic composition sample number 3, that is, glass A-based composition, the amorphous glass in the ceramic substrate is
It is thought that it diffuses into Ag/Pd and inhibits solder wettability. As described above, the composition of the ceramic substrate has a large effect on the solderability of the outermost layer conductor. Among the evaluation items shown in Table 2, the test sample used for the evaluation of interlayer reliability was approximately 200 μm after firing.
Approximately 2cm x 2cm on both sides of the ceramic insulation layer with a thickness of
It was created so that the counter electrode was formed with an area of .
The material of the counter electrode used at this time has a metal component in weight ratio of Ag/Pd=100/0, 95/5, 90/10, 80/
A total of five types of electrode materials, 20 and 70/30, were tested for one ceramic composition using the above five types of electrode materials. The test method is to apply a voltage of 100V to the counter electrode, leave the test sample in an environment of 85℃ and 85% RH for 1000 hours, then return the sample to the room, apply 50V to the counter electrode, and measure the insulation resistance. At this time,
Ceramic compositions in which insulation resistance values are all 10 ¹⁰ Ω or more when combining the above five types of electrode materials for one ceramic composition are given a rating of ○, and even if the insulation resistance of one electrode material is less than 10 ¹⁰ Ω. and,
The ceramic composition was given a rating of x. Summarizing the above experimental results, the ceramic compositions that can be practically used as ceramic multilayer wiring boards are within the range of ceramic composition samples Nos. 6 to 9. Effects of the Invention As described above, the ceramic multilayer wiring board of the present invention can be fired in the air at a low temperature of, for example, 900°C, so it can save energy and has the possibility of incorporating passive elements such as resistors and capacitors. There is no warpage or deformation of the board after firing, and the solder wettability of the outermost layer conductor is also good. In addition, the inner layer conductor
Even when 100% Ag is used, there is no migration of Ag between layers, and the electrical resistance of the conductor is low, making it extremely useful in practice as it can provide a highly reliable and low-cost ceramic multilayer wiring board.

[Brief explanation of the drawing]

FIG. 1 is a partially cutaway perspective view of an embodiment of the ceramic multilayer wiring board of the present invention, FIG. 2 is a diagram showing the firing profile of the ceramic multilayer wiring board, and FIG. 3 is a diagram showing the ceramic composition and internal conductor. Fig. 4 is a plan view showing an example of the results of evaluating the compatibility between the ceramic composition and the internal conductor, and Fig. 5 is a perspective view of an evaluation sample for evaluating the compatibility of the ceramic composition with the internal conductor. FIG. 6 is a diagram showing the results of Auger analysis of the Ag/Pd surface, which shows the results of Auger analysis of the Ag/Pd surface with good solder wettability. 1a, 1b, 1c, 1d...ceramic insulating layer, 2...inner conductor, 3...outermost layer conductor, 4...
green sheet.

Claims (1)

[Claims] 1. The ceramic insulating layer contains 45 to 60% by weight of Al ₂ O ₃ ;
_SiO2 24-33% by weight, _{B2O3 2.4-3.3} % by weight,
_Na2O1.2 ~1.65wt%, _K2O0.8 ~11wt%,
CaO3.2-4.4% by weight, MgO1.2-1.65% by weight,
The composition was selected so that the total amount was 100% by weight in the composition range of 7.2 to 9.9% by weight of PbO, and the metal component of the conductive wiring material in the internal layer was in a weight ratio of Ag/Pd =
100/0 to 70/30, and be composed of a composition selected so that the metal component of the outermost conductive wiring material has a weight ratio of Ag/Pd = 95/5 to 70/30. A ceramic multilayer wiring board featuring: 2. The ceramic multilayer wiring board according to claim 1, wherein the conductive wiring material of the internal layer is 100% by weight Ag.