JPH0369197B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a ceramic multilayer substrate, particularly a ceramic multilayer substrate that can be fired at a low temperature. 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 types of 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 and 15), and then print and dry the second conductor layer and second insulating layer (steps 16 to 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 it is possible to form multiple layers using 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, manufacturing them 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 example of conventional technology) 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). , print and dry conductor layers with different patterns (steps 25 to 30). W and Mo are mainly used as conductor materials. Filling the via holes with conductive material may be performed simultaneously with the conductor printing process (steps 25 to 27), or the via holes may be filled with the conductive material alone prior to 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, cut to the desired external dimensions (step 33), and approximately
Calcinate in a reducing atmosphere at 1600℃ (step 34),
It becomes a multilayer board. The fired substrate is thoroughly cleaned and then proceeds to the step of forming a thick film for the uppermost layer (step 35). (Second example of prior art) As described in the "Multilayer Ceramic Substrate" disclosed in Japanese Patent Publication No. 59-22399, first, a composite composition of glass material and alumina material and a mixture of organic matter are made to a predetermined thickness. Different patterns of microholes are formed in each of the formed green sheets (steps 22 to 24), and conductor layers with different patterns are printed and dried (steps 25 to 30). Single elements such as Ag, Au, Pd, and Pt, or alloys thereof, are used as conductor materials. Filling the via holes with conductive material may be performed simultaneously with the conductor printing process (steps 25 to 27), or the via holes may be filled with the conductive material alone prior to 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,
Cut to desired external dimensions (step 33) and heat to 700℃~
It is fired in air at 1400°C (step 34) to become 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 first example of the prior art as described above, the firing temperature was high and a reducing atmosphere was used, resulting in high equipment costs and inconvenience in handling. Also,
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. . In addition, in the second example of the prior art, although the problems of the first example can be solved, it has the disadvantage that controlling the firing shrinkage rate is more difficult than with alumina alone due to the number of composite compositions made of glass material and alumina material, and the yield rate is lower. There was a problem that the value was low. Incidentally, the variation in the firing shrinkage rate of the multilayer substrate according to the first example was ±0.5% to ±1.0%, and the firing shrinkage rate of the multilayer substrate according to the second example was ±1.0% to ±2.5%. In view of the above problems, the present invention uses Ag as a conductor material.
We use low melting point metals with low resistance such as Au, Pd, Pt, etc. or their alloys, and the firing temperature is low, allowing firing in air to reduce equipment costs.
The object of the present invention is to provide a ceramic multilayer substrate which is easy to handle and can be fired at a low temperature in air and has a variation in firing shrinkage of less than ±1.0%. Means for Solving the Problems In order to solve the above problems, the ceramic multilayer substrate of the present invention contains SiO ₂ 5-55% by weight, B ₂ O ₃ 1-30% by weight, Li ₂ in terms of oxides. At least one of O, Na ₂ O, K ₂ O
0.01-10% by weight, at least one of MgO, CaO, ZnO, BaO
The basic composition has a composition of 0.05 to 25% by weight, and also contains at least one of Al ₂ O ₃ , ZrO ₂ , and TiO ₂ in terms of oxides.
The insulating layer is formed from a dielectric composition containing 15 to 65% by weight of additives. Function The ceramic multilayer substrate of the present invention has a temperature of approximately 870°C to 980°C.
The insulating layer is formed of a dielectric composition that can be sintered at a low temperature of .degree. C., and exhibits sufficient characteristics as a ceramic substrate for forming electronic circuits. In the present invention, low melting point metals such as Ag, Au, Pd,
It is possible to use a single element such as Pt or an alloy thereof, and since these metals are difficult to oxidize even in the air, a reducing firing atmosphere is unnecessary, and Au and Ag have lower resistance values than W and Mo. Therefore, low-temperature firing in air reduces equipment costs and facilitates handling. Furthermore, since the ceramic multilayer substrate of the present invention has a variation in firing shrinkage rate of less than ±1.0, the yield is high and mass production is good. 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 the SiO ₂ content is less than 5%, the firing temperature will be high, making it impossible to use low melting point metals such as Ag, Au, Pt, and Pd as internal conductors, and the variation in firing shrinkage rate will increase. Also, SiO ₂ is 55
If it exceeds %, the bending strength becomes too small, and the firing shrinkage rate also varies greatly, making it impractical as a substrate. B ₂ O ₃ is also the basic composition of the substrate configuration,
If B ₂ O ₃ is less than 1%, it becomes water-absorbent and has low bending strength. Moreover, if B ₂ O ₃ exceeds 30%, the ceramic will be significantly deformed during sintering. MgO, CaO, ZnO, and BaO are added to improve the sinterability of the substrate, control the coefficient of thermal expansion, and improve the dielectric loss tangent. MgO, CaO, ZnO,
If at least one type of BaO is less than 0.05%, the sinterability is insufficient, and if it exceeds 25%, 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 the silicon chip of the IC is directly mounted on the substrate, it is preferable to match the coefficient of thermal expansion of silicon, 4×10 ^-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 to improve the sinterability of the substrate, prevent water absorption, and suppress deformation of the substrate. If at least one of K ₂ O, Na ₂ O, and Li ₂ O is less than 0.01%, the substrate deforms significantly.
The board warps significantly. If at least one of K ₂ O, Na ₂ O, and Li ₂ O exceeds 10%, sintering will be insufficient and water absorption will occur. Al ₂ O ₃ , ZrO ₂ , and TiO ₂ are used as fillers for substrates, and are added mainly to improve bending strength and suppress variations in firing shrinkage rate. At least one of Al ₂ O ₃ , ZrO ₂ , TiO ₂
If it is less than 15%, the bending strength is too small and the firing shrinkage rate varies too much to be of practical use. Also, Al ₂ O ₃ ,
If at least one of ZrO ₂ and TiO ₂ exceeds 65%, 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, when preparing the glass, weigh each raw material of the basic composition and adjust the batch so that it has the composition shown in Table 1 below.
It is melted by heating for 1 to 3 hours at a temperature of 0.degree. C., and a glass plate is formed by, for example, a roll-out method. Next, this glass plate is crushed with an alumina ball etc. to an average particle size of 0.5~
The dielectric composition of the present invention is produced by forming the powder into a powder of 5 μm and adding additives having approximately the same particle size. Note that the raw material powder used in this case is expressed in terms of oxides for clarity, but minerals, oxides, carbonates,
Of course, it can also be used in the form of hydroxide or the like by conventional methods. 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 glycerin 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 that would become 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 to complete the substrate, which can 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 96% Al ₂ O ₃ , which is a conventional material. Effects of the invention As is clear from the above explanation, by using the material of the present invention, low melting point Ag, Au, Pd, Pt
These metals do not oxidize even in the air, so there is no need for a reducing atmosphere, and the resistance values of Au and Ag are smaller than those of W and Mo. Therefore, low-temperature firing in air reduces equipment costs and makes handling easier. Furthermore, since the ceramic multilayer substrate of the present invention has a variation in firing shrinkage rate of less than ±1.0%, it has a high yield and is suitable for mass production.

[Brief explanation of drawings]

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. In terms of oxide, 5 to 55% by weight of SiO ₂ , 1 to 30% by weight of B ₂ O ₃ , and at least one of Li ₂ O, Na ₂ O, and K ₂ O
0.01-10% by weight, at least one of MgO, CaO, ZnO, BaO
Species 0.05-25% by weight, at least one of Al ₂ O ₃ , ZrO ₂ , TiO ₂
A ceramic multilayer substrate in which an insulating layer is formed from a dielectric composition having a composition of 15 to 65% by weight.