JPH0513100B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to an inorganic dielectric composition that can be crystallized by heat treatment, and mainly relates to a dielectric composition used as a substrate material for multilayer electronic circuits. BACKGROUND OF THE INVENTION In recent years, electronic circuits using ceramic substrates with excellent heat dissipation properties and which can be easily formed by thick film printing have been used. and,
Multilayer electronic circuit boards are beginning to be used to achieve smaller size and higher performance. There are generally three methods for manufacturing multilayer circuit boards: (a), (b), and (c) described below. (a) Printing multilayer method on ceramic sintered body (b) Printing multilayer method on green sheet (c) Green sheet lamination multilayer method Multilayer substrate by printing multilayer method on ceramic sintered body in (a) To explain the manufacturing method, as shown in Figure 1, first a first conductor layer is printed, dried, and fired on a ceramic sintered body that will become a substrate (steps 1 to 3), and then a first insulating layer is printed, dried, and fired (steps 1 to 3). printing, drying, and firing the layer (steps 4 to 6), printing and drying the second insulating layer on top of it (steps 7 and 8), printing and drying the second conductive layer (steps 9 and 10), The second insulating layer is fired all at once (step 11). On this occasion,
The first and second insulating layers are printed so that micro holes called via holes are formed, and the second conductor layer is printed so that the material used for the second conductor layer is filled into the micro holes. The first conductor layer and the second conductor layer
The conductor layer is connected. Next, a third layer is placed on the second conductor layer.
The insulating layer is printed, dried, and fired, and the layers are stacked using the same procedure as for the second insulating layer and subsequent layers (steps 1 to 11). As shown in Figure 2, the manufacturing method of a multilayer board using the printing multilayer method on a green sheet (b) is as follows: First, the first conductor layer is printed on a ceramic green sheet that will become the substrate after firing. Dry (steps 12 and 13), then print and dry the first insulating layer thereon (steps 14-15), and then print and dry the second conductive layer and second insulating layer (steps 16-15). 19) After that, the same procedure is repeated for the number of layers (steps 12 to 19), and the green sheet, conductor layer, and insulating layer are fired all at once (step 20). In the method for manufacturing a multilayer board using the green sheet lamination multilayer method (c), as shown in FIG. 24) Print and dry conductor layers with different patterns (steps 25 to 30). Next, a desired number of green sheets with different conductor patterns are laminated (step 31), crimped under moderate pressure and temperature (step 32), cut to desired external dimensions, and fired (step 31). 33, 34). Electrical conduction between each conductor layer is achieved by conductors filled in micropores in the green sheet. In both manufacturing methods (b) and (c), the thick film of the top layer is formed after baking the substrate (steps 21 and 35). Comparing the three manufacturing methods (a), (b), and (c), (a)
Although multi-layering is possible with a relatively simple technique, the practical limit on the number of layers is 4 to 6 layers, and a larger number of layers would result in severe surface irregularities and would not be practical. In (b), the process can be streamlined by firing the green sheet, printed insulating layer, and conductive layer at the same time. However, in (b) as well as (a), as the number of layers increases, the surface unevenness increases, so the limit number of layers is still 4.
~6 layers. The number of layers in (c) is theoretically possible to be infinite, and in reality, multilayer substrates with about 30 to 40 layers have been reported. However, their production requires extremely advanced technology and there are many process issues. Among the above three manufacturing methods (a), (b), and (c), the present invention relates to the green sheet lamination multilayer method (c). The prior art will be described in more detail with reference to FIG. First, micropores that will become via holes are formed in different patterns on multiple green sheets made of a mixture of alumina powder and organic matter molded to a predetermined thickness (steps 22 to 24), and conductor layers with different patterns are formed on each green sheet. Print and dry (steps 25-30). W and Mo are mainly used as conductor materials. Filling the via holes with conductor material is done at the same time as the conductor printing process (steps 25 to 27).
Alternatively, the via holes alone are filled with conductive material before the printing process. After the conductors are dried, a predetermined number of green sheets each having a different conductor pattern are laminated (step 31), and the sheets are pressed together at an appropriate temperature (step 32). Next, it is cut into desired external dimensions (step 33) and fired in a reducing atmosphere at about 1600° C. (step 34) to obtain a multilayer substrate.
The fired substrate is thoroughly cleaned and then proceeds to the step of forming a thick film for the uppermost layer (step 35). Problems to be Solved by the Invention However, in the conventional techniques as described above, the firing temperature is high and a reducing atmosphere is used, resulting in high equipment costs and inconvenience in handling. In addition, since alumina is used as the green sheet material and the firing temperature is high, only high melting point metals such as W and Mo can be used as the conductor material, resulting in a problem of high conductor resistance. was. In view of the above problems, the present invention uses Au as a conductor material.
By using low melting point metals with low resistance values such as Ag, Ag/Pd, etc., the firing temperature is low and firing in air is possible, reducing equipment costs and making handling easier. The present invention provides a dielectric composition for a multilayer substrate. Means for Solving the Problems In order to solve the above problems, the dielectric composition of the present invention contains 20 to 60% SiO ₂ in terms of oxide,
A basic composition consisting of 5 to 20% ZnO, 10 to 40% BaO, and 2 to 15% of at least one of B ₂ O ₃ and Sb ₂ O ₃ (weight%), also calculated in terms of oxide. ,
1 to 6% of at least one of SnO ₂ , CaO, MgO, SrO, and PbO, 0.2 to 3% of at least one of K ₂ O, Na ₂ O, and Li ₂ O, and 0.2 to 3% of at least one of Al ₂ O ₃ and ZrO ₂ It contains at least one additive with a composition of 3 to 40% (wt%). Effect The dielectric composition for multilayer substrates of the present invention has a dielectric composition of about 870
It is a material that can be sintered at a low temperature of 980°C to 980°C, and also exhibits sufficient characteristics as a ceramic substrate for forming electronic circuits. By using the material of the present invention, low melting point metal Au,
It becomes possible to use Ag, Ag/Pd, and Cu. Au,
Since Ag and Ag/Pd do not oxidize even in air, a reducing atmosphere is unnecessary, and Au, Ag, and Cu have lower resistance values than W and Mo. Therefore, low-temperature firing in air reduces equipment costs and facilitates handling. The reasons for the limitations in the composition of the present invention are as follows. SiO ₂ is the basic composition constituting the substrate and the main material for forming glass. If SiO ₂ is less than 20%, the sintering temperature will be high, making it impossible to use low melting point metals such as Ag, Au, Ag/Pd, and Cu as internal conductors.
Moreover, if the SiO ₂ content exceeds 60%, the bending strength becomes too small to be practical as a substrate. BaO is a component of glass formation and crystallization.
When BaO is less than 10%, devitrification occurs mainly during glass melting, and the dielectric loss tangent deteriorates. When BaO exceeds 40%, the softening temperature and crystallization temperature become high, and as a result, the sintering temperature becomes too high. ZnO is also a component of glass formation and is the basic composition as a substrate. ZnO is less than 5% and
If ZnO exceeds 20%, it will not be sintered sufficiently densely and will become water absorbent. B ₂ O ₃ and Sb ₂ O ₃ are also basic compositions of the substrate structure, and if at least one of B ₂ O ₃ and Sb ₂ O ₃ is less than 2%, it becomes water absorbent and has low bending strength. B ₂ O ₃ ,
If at least one of Sb ₂ O ₃ exceeds 15%, the ceramic will be significantly deformed during sintering. At least one type of SnO ₂ , CaO, MgO, SrO, and PbO is used, usually two or more, for the purpose of improving the sinterability of the substrate, controlling the coefficient of thermal expansion, and improving the dielectric loss tangent.
It is added in a combination of three types. SrO ₂ , CaO,
1% of at least one of MgO, SrO, and PdO
If it is less than this, sintering will be insufficient, water absorption will increase, and dielectric loss tangent will increase, which is not preferable.
If at least one of SrO ₂ , CaO, MgO, SrO, and PbO exceeds 6%, the dielectric loss tangent becomes large, which is not preferable. The coefficient of thermal expansion is controlled in various ways depending on the use of the substrate, but when used as a normal thick film hybrid integrated circuit, especially when forming a circuit using thick film conductor paste and thick film resistor paste, the coefficient of thermal expansion of alumina is 6.0 to 6.5 × 10. ^-6 /°C, and when mounting an IC silicon chip directly on a board, the thermal expansion coefficient of silicon is 4 x
Preferably, it corresponds to 10 ^-6 /°C. It is difficult to judge the quality of a substrate based on the coefficient of thermal expansion alone, but a substrate with a value that is significantly different from both values cannot be put to practical use. K ₂ O, Na ₂ O, and Li ₂ O are added for the purpose of improving the sinterability of the substrate, preventing water absorption, and further suppressing deformation of the substrate. If at least one of K ₂ O, Na ₂ O, and Li ₂ O is less than 0.2%, the substrate deforms significantly.
The board warps significantly. If at least one of K ₂ O, Na ₂ O, and Li ₂ O exceeds 3%, sintering will be insufficient and water absorption will occur. Al ₂ O ₃ , ZrO ₂ are used as fillers for substrates,
It is mainly added to improve bending strength. Al ₂ O ₃ ,
If at least one of ZrO ₂ is less than 3%, the bending strength is too low to be of practical use. Also, Al ₂ O ₃ C,
If the content of at least one of ZrO ₂ exceeds 40%, the sintering temperature will be high and the sintering will be insufficient, resulting in water absorption, and the bending strength will also decrease. Examples Examples of the dielectric composition for multilayer substrates of the present invention will be described below. First, to prepare the glass, weigh each raw material of the basic composition to prepare a batch so that it has the composition shown in Table 1 below.
The mixture is melted by heating at 1500° C. for 1 to 3 hours, and a glass plate is formed by, for example, a roll-out method. Next, the average particle size of this glass plate is measured using an alumina ball, etc.
The dielectric composition of the present invention is produced by preparing a powder of 0.5 to 5 μm and adding additives of approximately the same particle size. Note that the raw material powder used in this case is expressed in terms of oxide for clarity, but it goes without saying that minerals, oxides, carbonates, hydroxides, and other forms can also be used in the usual manner. Next, an example of a method for manufacturing a ceramic multilayer substrate by a green sheet lamination multilayer method using the dielectric composition thus obtained will be described. First, 10 parts by weight of polyvinyl butyral and 6 parts by weight of dibutyl phthalate were added to 100 parts by weight of the above composition.
parts by weight, 0.4 parts by weight of glyceryl monooleate,
20 parts by weight of 1-1-1 trichloroethane and 39 parts by weight of isopropyl alcohol were added and mixed in a ball mill for 24 hours to prepare a slurry. Using this slurry, a green sheet with a thickness of 0.1 mm was produced on a polyester film by the doctor blade method, and after sufficient aging, micropores to serve as via holes were formed by mechanical processing. Next, this via hole was filled with a conductive material by a printing method using a metal mask. The conductor material used was Au, and its melting point was 1062°C. Next, a conductive layer was printed on a green sheet using the same conductive material and dried. via hole pattern,
Multiple green sheets, each with a different printed conductor pattern, were brought together under pressure of 200 kg/cm ² at a temperature of 80°C. Next, after cutting the outer shape, it was fired at a maximum temperature of 870 to 1340°C for a maximum temperature holding time of 60 minutes. After the fired multilayer substrate was ultrasonically cleaned with pure water, a thick film was formed on the top layer on the front and back sides, and the board was completed to function as an electronic circuit. Table 1 shows the characteristics of the substrates produced by the above manufacturing method according to the composition of the dielectric composition. As for the characteristics, the bending strength, water absorption rate, and dielectric loss tangent were measured for the substrate that functions as an electronic circuit, and the results are shown in Table 1. In addition, the sintering temperature in the same table is determined by estimating the approximate sintering temperature for each composition in advance from differential thermal analysis, and the sintering temperature at which the water absorption rate is 0.0% and the bending strength is maximum. selected. Regarding the presence or absence of warpage deformation, the external shape was visually observed after the substrate was sintered, and those with irregularities and warp undulations on the surface of the substrate, as well as large deformations, were determined to be unsuitable for practical use.

【table】

[Table] * Comparative example For reference, Table 2 shows 96% of conventional materials.
Shows the properties of Al ₂ O ₃ .

[Table] As shown in Table 1 and Table 2, and as described above, the composition according to the present invention can be fired at a low temperature of 870 to 980°C,
Moreover, it fully exhibits the characteristics as a ceramic substrate for forming electronic circuits, and its characteristics are superior to that of the conventional material, 96% Al ₂ O ₃ . Effects of the invention As is clear from the above explanation, by using the material of the present invention, low melting point metals Au, Ag,
Ag/Pd, Cu can be used, Au, Ag,
Since Ag/Pd does not oxidize even in air, a reducing atmosphere is unnecessary, and Au, Ag, and Cu have smaller resistance values than W and Mo. Therefore, low-temperature firing in air reduces equipment costs and makes handling easier.

[Brief explanation of the drawing]

Figure 1 is a flowchart showing the manufacturing process of a multilayer board by printing multilayer on a ceramic sintered body, Figure 2 is a flowchart showing the manufacturing process of a multilayer board by printing multilayer on a green sheet, and Figure 3 is a flowchart showing the manufacturing process of a multilayer board by printing multilayer on a green sheet. The figure is a flowchart showing the manufacturing process of a multilayer board using the green sheet lamination multilayer method.

Claims (1)

[Claims] 1. At least one of SiO ₂ 20-60%, ZnO 5-20%, BaO 10-40%, B ₂ O ₃ , Sb ₂ O ₃ 2-15 in terms of oxides % At least one of SnO ₂ , CaO, MgO, SrO, PbO 1 (M) to 6%, At least one of K ₂ O, Na ₂ O, Li ₂ O 0.2 to 3
%, Al ₂ O ₃ and ZrO ₂ at a composition of 3 to 40% (weight %).