JPH0426799B2 - - 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 2, first a first conductor layer is printed, dried, and fired on a ceramic sintered body that will serve as a substrate.
Next, the first insulating layer is printed, dried, and fired, the second insulating layer is printed and dried on top of that, and the second conductive layer is printed and dried.
It is dried, and the second insulating layer is fired all at once. 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 are connected. Next, a third insulating layer is printed, dried, and fired on the second conductor layer, and the layers are stacked in the same manner as the second and subsequent insulating layers. In the manufacturing method of a multilayer board using the multilayer printing method on a green sheet (b), as shown in Figure 3, the first conductor layer is first printed on a ceramic green sheet that will become the substrate after firing. dry, then print and dry a first insulating layer thereon, then print and dry a second conductive layer and a second insulating layer,
Thereafter, the same procedure is repeated for each number of layers to collectively fire the green sheet, conductor layer, and insulating layer. In the method for manufacturing a multilayer board using the green sheet lamination multilayer method (c), as shown in Figure 1, micropores with different patterns are first formed in each of a plurality of ceramic green sheets (steps 1 to 3). ), and print and dry conductor layers with different patterns (steps 4 to 9). Next, the desired number of green sheets with different conductor patterns are stacked together (Step 10), crimped together under moderate pressure and temperature (Step 11), cut into desired external dimensions, and then fired (Step 10). 12・13). 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 (in c, the step
14). Comparing the three manufacturing methods (a), (b), and (c),
(a) can be multilayered with relatively simple technology, but
The practical limit on the number of layers is 4 to 6 layers, and if the number of layers is more than that, the surface becomes extremely uneven and is not suitable for practical use.
In (b), the process can be streamlined by firing the green sheet, printed insulating layer, and conductive layer at the same time. However, in case of (b), similarly to (a), as the number of layers increases, the surface unevenness increases, so the limit number of layers is 4 to 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). With reference to FIG. 3, the conventional technique of this green sheet lamination multilayer method will be described in more detail. First example of conventional technology The first example is a high-temperature firing multilayer board manufacturing method, in which microscopic holes, which will become via holes, are formed in multiple green sheets made of a mixture of alumina powder and organic matter molded to a predetermined thickness. Each conductor layer is formed with a different pattern, and a conductor layer with a different pattern is printed and dried. Conductor materials mainly include W,
Mo is used. The via holes are filled with the conductive material at the same time as the conductor printing process, or the via holes are filled with the conductive material alone before the printing process. After the conductor has dried, a predetermined number of green sheets each with a different conductor pattern are laminated,
Integrate under pressure at moderate temperature. Next, it is cut into desired external dimensions and fired in a reducing atmosphere at approximately 1600°C to form a multilayer substrate. The fired substrate is thoroughly cleaned and then undergoes the thick film formation process (step) for the top layer.
Proceed to step 14). (Second example of prior art) The second example is a method for manufacturing a low-temperature firing multilayer board, and as disclosed in Japanese Patent Publication No. 59-22399,
A _B2O3 - _SiO2 - _PbO - _{Al2O3 -} based material is used for the ceramic layer. First, B ₂ O ₃ −SiO ₂ −PbO−Al ₂ O ₃
A mixture of green materials and organic matter is formed into multiple green sheets to a predetermined thickness, and micropores that become via holes are formed in different patterns on each green sheet.
Print and dry conductor layers with different patterns. Single elements such as Ag, Au, Pd, and Pt, or alloys thereof, are used as the conductor material. The via holes are filled with conductive material at the same time as the conductor printing process, or the via holes are filled with the conductive material alone before the printing process. After the conductors are dried, a predetermined number of green sheets each having a different conductor pattern are laminated and integrated under pressure at an appropriate temperature.
Next, cut to desired external dimensions and heat at 700℃ to 1400℃.
It is fired in air to form a multilayer substrate. The fired substrate is thoroughly cleaned and then proceeds to the step of forming the thick film of the uppermost layer. (Third Example of Prior Art) The third example is a method for manufacturing a multilayer board of low temperature firing type, similar to the second example, and is disclosed in Japanese Patent Application Laid-Open No. 60-235744 or Japanese Patent Application No. 186919-1982. A _{B2O3 - SiO2-} ( _{Al2O3 , ZrO2} , _TiO2 ) based material is used for the substrate composition. The manufacturing process is the same as the second example of the prior art, so the explanation will be omitted. 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,
Alumina is used as the green sheet material.
Due to the high firing temperature, only high-melting point metals such as W and Mo can be used as conductor materials, resulting in a high resistance value of the conductor (7 to 15 mΩ/□ for W and Mo). Ta. In addition, although the second and third examples of the conventional technology can solve the problems of the first example, they do not have heat resistance and cause large warping when the surface thick film material is fired at about 850 degrees Celsius after printing and drying. Another problem was that when the substrate was fired together with the internal conductor, the internal conductor components were diffused into the substrate material, reducing the insulation resistance value between and within the layers. 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. alone 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 that is easy to handle, has improved heat resistance, and suppresses diffusion of internal conductor components into the substrate material. Means for Solving the Problems In order to solve the above problems, the ceramic multilayer substrate of the present invention contains at least one of Al ₂ O ₃ , ZrO ₂ , and TiO ₂ in terms of oxides.
32 to 65% by weight (hereinafter simply expressed as %) SiO ₂ 8 to 27% B ₂ O ₃ 5 to 18% At least one of BaO, SrO, CaO, and MgO
6-22% ZnO 0.5-8% At least one of Na ₂ O, K ₂ O, Li ₂ O
An insulating layer that insulates a plurality of conductor layers is formed using an inorganic composition having a composition of 0.01 to 7%. Further, the ceramic multilayer substrate of the present invention preferably contains at least one of Al ₂ O ₃ , ZrO ₂ , and TiO ₂ in terms of oxides.
45-65% SiO ₂ 9-16% B ₂ O ₃ 6-12% At least one of BaO, SrO, CaO, MgO
7-18% ZnO 1-4% At least one of Na ₂ O, K ₂ O, Li ₂ O
It is even more preferable to form the insulating layer with an inorganic composition having a composition of 0.01 to 3%. Function The ceramic multilayer substrate of the present invention has a temperature of approximately 870°C to 950°C.
The insulating layer is formed of an inorganic composition that can be sintered at low temperatures of 0.degree. C., and exhibits sufficient characteristics as a ceramic substrate for forming electronic circuits. In the present invention, the conductor material is a low melting point metal.
Ag, Au, Pd, Pt, etc. alone or their alloys can be used, and since these metals are difficult to oxidize even in the air, a reducing firing atmosphere is unnecessary. 3 mΩ/□) is lower than that of W and Mo (7 to 15 mΩ/□).
Therefore, low-temperature firing in air reduces equipment costs and facilitates handling. Furthermore, since the ceramic multilayer board of the present invention has excellent heat resistance, no warping occurs even when the surface thick film material is fired at a temperature of about 850°C, and when the board and internal conductor are fired together, the internal Since the conductor component does not diffuse into the substrate material, the insulation resistance between and within layers is excellent. 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 sintering 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. In addition, if SiO ₂ is less than 8% or more than 27%, the crystallization balance with other compositional elements will be disrupted, and although properties such as sintering temperature, sintering shrinkage rate, and bending strength may be almost satisfied, heat resistance will be poor. Problems arise with diffusion of internal conductor components. That is, _SiO2
If there is too much or not enough, the crystallization balance will be disrupted and the amorphous portion in the substrate will increase, resulting in softening and movement of composition components during re-firing. In other words,
When a surface thick film material is fired at around 850°C (substrate is re-fired), the substrate softens and undergoes significant deformation such as warping. This effect is even more noticeable when the substrate is fired with both ends supported instead of the entire surface supported. In addition, when the movement of the composition components increases, the internal conductor components diffuse toward the substrate side, and the composition components of the substrate diffuse toward the internal conductor side, resulting in
The insulation resistance value between layers deteriorates. The content of SiO ₂ is more preferably 9 to 16%. B ₂ O ₃ is also the basic composition of the substrate composition,
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. Furthermore, if B ₂ O ₃ is less than 5% or more than 18%, the crystallization balance will be disrupted in the same way as SiO ₂ and similar phenomena and problems will occur. More desirably, _B2O3 is _6-12 %. MgO, CaO, ZnO, BaO, and SrO are added to improve the sinterability of the substrate, control the coefficient of thermal expansion, and improve the dielectric loss tangent. MgO, CaO,
At least one of ZnO, BaO, SrO is 0.05%
If it is less than 25%, 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 (6.0 to 6.5) is used.
It is preferable to match the coefficient of thermal expansion to 4×10 ^-6 /°C, and when a silicon chip of an IC is directly mounted on a substrate, it is preferable to match the coefficient of thermal expansion of silicon to 4×10 ^-6 /°C. It is difficult to judge the quality of a board based on the coefficient of thermal expansion alone, but a board with a value that is significantly different from both values cannot be put to practical use. Furthermore, if at least one of BaO, SrO, CaO, and MgO is less than 6% or more than 22%, the crystallization balance will be disrupted, and if ZnO is less than 0.5% or more than 8%, the crystallization balance will be disrupted. However, the same problem occurs when the crystallization balance is disrupted by SiO ₂ . More preferably, the content of at least one of BaO, SrO, CaO, and MgO is 7 to 18%. 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 0.01%, 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. In addition, at least one of Na ₂ O, K ₂ O, and Li ₂ O
If the amount of seeds is less than 0.01% or more than 7%, the crystallization balance will be disrupted. More preferably, _N2O ,
At least one of K ₂ O and Li ₂ O is present in an amount of 0.01 to 3% by weight. Al ₂ O ₃ , ZrO ₂ , and TiO ₂ are used as fillers for the substrate, 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 , and TiO ₂
If it is less than 32%, the bending strength is too high and the firing shrinkage rate varies too much to be of practical use. Also Al ₂ O ₃ , ZrO ₂ ,
If at least one of TiO ₂ exceeds 69%, the sintering temperature will be high and the sintering will be insufficient, resulting in water absorbency and the bending strength will also decrease. Also, at least one of Al ₂ O ₃ , ZrO ₂ , and TiO ₂
If the amount of seeds is less than 32% or more than 69%, the crystallization balance will be disrupted. More preferably Al ₂ O ₃ ,
At least one of ZrO ₂ and TiO ₂ accounts for 45 to 65%. 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 at a temperature of 1 to 3 hours at a temperature of 1 to 3 hours, and a glass plate is formed by, for example, a roll-out method. The next glass plate is sized with an alumina ball etc. to an average particle size of 0.5 to 5μ.
The dielectric composition of the present invention is produced by preparing a powder of m 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, to 100 parts by weight of the above composition, 10 parts by weight of polyvinyl butyral, 6 parts by weight of dibutyl phthalate, 0.4 parts by weight of glyceryl monooleate, 1,
20 parts by weight of 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 is 95%
It was an alloy consisting of Ag and 5% Pd. 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 and a maximum temperature holding time of 60 minutes. After the fired multilayer board was ultrasonically cleaned with pure water, thick film circuits were formed on both sides of the board, completing the board that can function as an electronic circuit. The characteristics of the substrate obtained by the above manufacturing method are
Shown in the table. As for the characteristics, bending strength, water absorption rate, and dielectric loss tangent were measured for the substrate that functions as an electronic circuit. In addition, the sintering temperature in the same table is determined by estimating the approximate sintering temperature in advance from differential thermal analysis for each composition, and the water absorption is 0.0.
%, and the sintering temperature at which the bending strength was maximized was 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. Regarding heat resistance, the sintered substrate is supported at both ends with a support span of 100 mm, and the peak temperature retention time is
The temperature at which the board warped by 0.3 mm/100 mm or more in 15 minutes was defined as the heat-resistant limit temperature of the board.
If it has a heat resistance limit temperature of 820°C or higher, there is no practical problem, but it is more desirable to have properties of 850°C or higher.
A temperature below 820°C is a failure. In addition, regarding the diffusion of the internal conductor component (in this experiment, we used Ag-Pd as the internal conductor, we focused on the diffusion of the Ag component), we observed and measured the diffusion depth from the characteristic X-ray image of the cross section of the substrate. In practice, there is no problem if the diffusion depth is less than 10 μm, and more preferably the diffusion depth is less than about 3 μm. Diffusion exceeding 10 μm was rejected.

【table】

[Table] * Comparative example

【table】

[Table] For reference, Table 3 shows the characteristics of 96% Al ₂ O ₃ , which is the insulator used in the first example of the prior art.

[Table] As stated above, the ceramic multilayer substrate formed from the composition of the present invention can be fired at a low temperature of 870 to 980°C, and moreover, it fully exhibits the characteristics as a ceramic substrate for forming electronic circuits. , its properties are traditional materials. ₉₆ % _Al2O3 , _{B2O3 - SiO2}
−PbO−Al ₂ O ₃ based material, B ₂ O ₃ −SiO ₂ (Al ₂ O ₃ ,
It is superior to ceramic multilayer substrates made of ZrO ₂ , TiO ₂ )-based materials. Effects of the Invention According to the present invention, the firing temperature for forming a ceramic multilayer substrate is low, a low melting point metal material with a low resistance value can be used as the conductor material, and firing can be performed in air. , equipment costs can be reduced, and the resistance value of the conductor of the resulting multilayer board can be lowered. In addition, since the diffusion of internal conductor components into the insulating layer can be suppressed, the insulation resistance of the insulating layer does not decrease, and since it has excellent heat resistance, it is possible to create an excellent ceramic multilayer board without problems such as warping of the board. can get.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an example of the manufacturing process of a ceramic multilayer substrate to which the present invention is applied, and FIGS. 2 and 3 are diagrams showing other examples of the conventional manufacturing process of a ceramic multilayer substrate.

Claims (1)

[Claims] 1. The insulating layer that insulates the plurality of conductor layers is made of at least one of Al ₂ O ₃ , ZrO ₂ , and TiO ₂ in terms of oxides.
32-69% by weight SiO ₂ 8-27% by weight B ₂ O ₃ 5-18% by weight At least one of BaO, SrO, CaO, MgO
6-22% by weight ZnO 0.5-8% by weight At least one of Na ₂ O, K ₂ O, Li ₂ O
A ceramic multilayer substrate comprising an inorganic composition having a composition of 0.01 to 7% by weight.