JPH059954B2 - - Google Patents

Description

[Detailed description of the invention]

[Technical field of the invention] This invention relates to a method for manufacturing a thick film multilayer substrate,
In particular, the present invention relates to a device in which a conductor layer can be formed using a copper-based conductor paste. [Technical Background of the Invention and Problems Therewith] As is well known, hybrid integrated circuits have recently come into widespread use in order to reduce the size and weight of electronic devices and the like. This hybrid integrated circuit is
In general, it is constructed by soldering chip-type passive elements or active elements without lead wires to a thick film substrate made by printing a conductive material and a resistive material on an insulating substrate. In the conventional manufacturing method of such a thick film substrate, a pair of wiring conductor layers is first formed on an insulating substrate made of a ceramic material such as alumina. This wiring conductor layer is made of, for example, silver-palladium (Ag/palladium).
It is formed by printing and firing a conductive paste containing Pd) powder using a screen printing method. A resistor is then formed between the pair of wiring conductor layers by printing and firing a resistor paste containing, for example, ruthenium oxide (RuO ₂ ) powder and glass frit using a screen printing method. By the way, in the thick film substrate as mentioned above,
In order to achieve high-density packaging, wiring conductor layers are formed in multiple layers with insulating layers interposed therebetween. On the other hand, the above silver-palladium conductor paste has an impedance (conductor resistance) of 20 to 50 [m
It has various problems such as high ohm/b], is susceptible to insulation deterioration due to migration of silver due to moisture absorption, and is economically disadvantageous because it is a noble metal. Therefore, in recent years, it has been considered to use a copper-based conductive paste instead of the silver-palladium-based conductive paste. When this copper-based conductive paste is fired in a nitrogen gas atmosphere to the extent that the copper does not oxidize, it has a resistance of 2 to 5 [mΩ/ro].
It has the advantage of not only being able to form a conductor with low impedance, but also being economically advantageous. By the way, copper-based conductor paste needs to be fired in a nitrogen gas atmosphere to prevent oxidation.
Resistance paste used to form resistors must be fired in air to obtain properties within a practical range. For this reason, a procedure is followed in which the resistance paste is first fired in air, and then the copper-based conductor paste is fired in a nitrogen gas atmosphere. However, if you first fire the resistor paste in air and then repeat the firing of the copper-based conductor paste in a nitrogen gas atmosphere at a normal high temperature to form a multilayer conductor layer, the resistance of the resistor will increase. A problem arises in that the values vary widely. For this reason, conventionally, when manufacturing thick-film multilayer boards using copper-based conductor paste, ruthenium oxide-based resistance paste, which is baked in air and has less variation in resistance value, has been used as a conductor for multilayer wiring. As for the paste, it was necessary to use a mixture of a silver-palladium based conductive paste and a copper based conductive paste, as shown in FIG. In FIG. 4a, a silver-palladium based conductive paste is printed on an insulating substrate 11 made of a ceramic material such as alumina, and is fired in air at a high temperature of about 850 to 900 DEG C. to form a lower conductor 12. Next, the fourth
As shown in FIG. 4b, an insulating paste made of a high melting point crystallized glass dielectric is printed as an insulating layer 13 so as to cover a predetermined portion of the lower conductor 12, and as shown in FIG. 4c, a resistor 14 is printed. A ruthenium oxide-based resistance paste is printed, and the insulation paste and resistance paste are simultaneously fired in air at a high temperature of about 850 to 900°C. Thereafter, as shown in FIG. 4d, a copper-based conductor paste is printed on the insulating layer 13 so as to be approximately perpendicular to the lower conductor 12, and baked at a low temperature of about 600 to 650°C in a nitrogen gas atmosphere. Then, the upper layer conductor 15 is formed, and finally the resistor is laser trimmed to obtain the final resistance value. In other words, in the past, a silver-palladium conductor paste and a copper conductor paste were mixed, and the number of firings in a nitrogen gas atmosphere was reduced as much as possible.
This is intended to suppress large variations in the resistance value of the resistor 14. [Purpose of the Invention] This invention was made in consideration of the above circumstances, and it is an extremely good method that can suppress fluctuations in the resistance value of a resistor by forming a conductor layer using an entirely copper-based conductor paste. An object of the present invention is to provide a method for manufacturing a thick film multilayer substrate. [Summary of the Invention] That is, the method for manufacturing a thick film multilayer board according to the present invention includes a first step of printing a resistance paste on an insulating substrate and baking it at high temperature in air to form a resistor; After this first step, a copper-based conductive paste is printed on the insulating substrate, and a first step is performed in a non-oxidizing gas atmosphere.
a second step of forming a lower conductor layer by firing at a lower temperature than the firing temperature of the step; after this second step, an insulating paste made of a low melting point crystallized glass composition is applied on the lower conductor layer; print,
A third step is to form an insulating layer by firing in a non-oxidizing gas atmosphere at a temperature lower than the firing temperature in the first step, and after this third step, the resistor is connected to the insulating layer. The fourth step is to print a copper-based conductor paste and to form an upper body layer by firing it in a non-oxidizing gas atmosphere at a temperature lower than the firing temperature of the first step. , The conductor layer is formed entirely using copper-based conductor paste, and the fluctuation in the resistance value of the resistor is kept to a minimum. [Embodiment of the Invention] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. In FIG. 1A, reference numeral 16 denotes a ceramic substrate made of alumina or the like, on which a resistor 17 is formed by printing a ruthenium oxide-based resistance paste and firing it in air at a high temperature of about 850° C. for about 30 minutes. Next, as shown in FIG. 1b, a copper-based conductive paste is printed on the ceramic substrate 16,
Approximately 30 at a low temperature of approximately 600 to 650℃ in a nitrogen gas atmosphere
The lower layer conductor 18 is formed by firing for a minute. Then, as shown in FIG. 1c, an insulating paste made of a low melting point crystallized glass composition (details will be described later) is printed to cover the lower conductor 18,
Approximately 30 at a low temperature of approximately 600 to 650℃ in a nitrogen gas atmosphere
The insulating layer 19 is formed by baking for a minute. Thereafter, as shown in FIG. 1d, a copper-based conductive paste is printed on the insulating layer 19 so as to be connected to the resistor 17, and heated at approximately 600 to 650°C in a nitrogen gas atmosphere.
The upper layer conductor 20 is formed by firing at a low temperature for about 30 minutes. In the above manufacturing process, the conductor connected to the resistor 17 needs to be the upper layer conductor 20 that is printed and fired last. The reason for this is that if the conductor connected to the resistor is the lower layer conductor, as is generally done with conventional silver-palladium conductors, the upper layer, lower layer conductor, and insulating layer will be formed after the resistor is formed. Repeated firing at a low temperature of approximately 600 to 650℃ for the purpose of manufacturing can cause the resistance value to fluctuate greatly, as shown by the broken line in Figure 2, and the temperature coefficient (TCR) of the resistor to deteriorate significantly, making mass production difficult. This is because they lack sex. On the other hand, as mentioned above, by making the conductor connected to the resistor 17 the upper layer conductor 20 that is printed and fired last, even if repeated firing is performed, the conductor connected to the resistor 17 can be printed and fired as shown by the solid line in FIG. It is possible to suppress fluctuations in resistance value to a small extent, and there is little deterioration of TCR, making it practical. Here, an insulating paste made of the above-mentioned low melting point crystallized glass composition will be explained. That is, this insulating layer material contains 5 to 20 SiO ₂ by weight%.
ZnO 45-60, B ₂ O ₃ 15-30, R ₂ O (Li ₂ O +
Na ₂ O + K ₂ O) from 0.1 to 3, RO (MgO + CaO +
BaO + SrO) 0.5 to 10, Al ₂ O ₃ 0.5 to 5, Bi ₂ O ₃
0.5-5, F 0.5-2, SnO ₂ at a ratio of 0.5-2, and further CoO, P ₂ O ₅ , ZrO ₂ , CdO,
Contain one or more types of PbO in a ratio of 0.1 or more and the upper limit of each does not exceed 2, 2, 5, 5, 3, respectively, crystallize at a temperature of 650℃ or higher, and crystallize at a temperature of 650℃ or lower It is designed to be fired at a certain temperature. Here, the reasons for limiting each component to the above-mentioned mixing ratio are as follows. SiO ₂ : If it is less than 5%, the viscosity during melting will be low;
Hard to vitrify. Moreover, if the amount is more than 20%, the softening temperature will increase, making it impossible to fire at low temperatures (600°C). ZnO: If it is less than 45%, crystallization will not be possible,
If it exceeds 60%, the crystallization temperature will drop too much. _B2O3 : If it is less than 15% _, the softening temperature will be high,
If it exceeds 30%, sufficient crystallization will not be possible. R ₂ O: Li ₂ O, to promote glass melting;
One or more of Na ₂ O and K ₂ O can be added, but if the total amount exceeds 3%, the insulation resistance value will decrease. RO: MgO, to promote glass melting
If at least one of CaO, BaO, and SrO is added, and the amount is less than 0.5%, no promoting effect will occur;
%, the expansion coefficient becomes too large. Al ₂ O ₃ : If it is less than 0.5%, the crystallization temperature will be too low, and if it is more than 5%, the softening temperature of the glass will be too high. Bi ₂ O ₃ : If it is less than 0.5%, the wettability of the glass to the alumina substrate will be poor, and if it is more than 5%, the expansion coefficient will become too large. F: Added to promote melting of glass,
If it exceeds 2%, the expansion coefficient becomes large. SnO ₂ : Added to improve the water resistance of glass. If it is less than 0.5%, there is no effect, and if it is more than 2%, the effect does not improve. For CoO, _P2O5 , _ZrO2 , CdO, _PbO ,
If one or more of these are contained at 0.1% or more, the insulation resistance will not deteriorate and the stability of the glass will be maintained.
If it exceeds 5.3%, the glass will become non-uniform and no increase in effectiveness can be expected. Specifically, the raw materials are mixed to have the composition shown in Table 1. In Table 1, sample numbers (1) to (4) indicate low melting point crystallized glass, and sample number (5) indicates a conventional insulating layer material. Then, the mixture prepared as shown in Table 1,
It is melted and vitrified in a platinum crucible at a temperature of 1300-1400℃. Next, this glass is crushed and sieved, and then crushed by a wet method to obtain a powder having an average particle size of 5 μm. This powder is then kneaded with an appropriate amount of vehicle (for example, ethyl cellulose and terpineol) to form a glass paste. After that, a first layer of silver-palladium (Ag-Pd) based conductor and ruthenium oxide (RuO ₂ ) was formed by printing and firing on the alumina substrate in advance.
The glass paste was printed so as to cover the wiring layer made of the resistor system, and baked at 600° C. for 10 minutes to form an insulating layer with a thickness of about 40 μm. Then, on this insulating layer, Ag-
A Pd-based conductor is printed and formed using a conventional method. In this way, the crystallization temperature of the glass composition is set to 650℃.
By firing at a lower temperature (600°C) than that, the insulating layer can be formed without being completely crystallized, and pinholes do not occur as in the conventional method. Physical properties of the glass composition produced as described above, insulation resistance value of the insulating layer formed, solder wettability of the Ag-Pd conductor on the insulating layer, adhesion of the insulating layer to the alumina substrate surface, and printing resistance. Table 2 shows the rate of change in resistance value of the body. In this case, the insulation resistance was determined by applying 50 V DC between each conductor of the first wiring layer and the second wiring layer after leaving it in a constant temperature and humidity layer at 60°C and 95% for 1000 hours. This is the resistance value at room temperature. In addition, the solder wettability was determined by Pb− containing 2% Ag.
Using Sn eutectic solder, it was immersed at 230°C for 3 seconds and then pulled out, and was judged as good if 90% or more of the second layer conductor area was wet with the solder. Furthermore, the adhesion to the alumina substrate surface was determined by soldering a lead wire to the second layer conductor, pulling it vertically, and measuring the peel strength between the alumina substrate surface and the insulating layer. A rating of ² or higher was considered good. In addition, the rate of change in resistance value is the ratio of the resistance value (R ₀ ) of the printed resistor before forming the insulating layer to the resistance value (R ₁ ) after forming the insulating layer, that is, R ₁ −R ₀ / The value of R ₀ ×100 was shown.

【table】

【table】

〔Effect of the invention〕

Therefore, as detailed above, according to the present invention, it is possible to form a conductor layer using a conductive paste entirely made of copper, thereby suppressing the resistance value fluctuation of the resistor to a small extent, and improving mass production and economy. It is possible to provide an extremely good method for manufacturing a thick film multilayer substrate with excellent properties.

[Brief explanation of the drawing]

FIG. 1 is a side sectional view showing an embodiment of the method for manufacturing a thick film multilayer substrate according to the present invention, FIGS. 2 and 3 are characteristic diagrams for explaining the effects of the embodiment, and FIG. 4 1 is a side sectional view showing a conventional method for manufacturing a thick film multilayer substrate. 11... Insulating substrate, 12... Lower layer conductor, 13...
...Insulating layer, 14...Resistor, 15...Upper layer conductor,
16...Ceramic substrate, 17...Resistor, 18
... lower layer conductor, 19 ... insulating layer, 20 ... upper layer conductor.

Claims (1)

[Claims] 1. A first step of printing a resistor paste on an insulating substrate and baking it at high temperature in air to form a resistor; After this first step, printing a resistor paste on the insulating substrate. a second step of printing a copper-based conductor paste and firing it in a non-oxidizing gas atmosphere at a temperature lower than the firing temperature of the first step to form a lower conductor layer; After that, an insulating paste made of a low melting point crystallized glass composition is printed on the lower conductor layer, and is fired in a non-oxidizing gas atmosphere at a temperature lower than the firing temperature in the first step to form an insulating layer. After this third step, a copper-based conductor paste to be connected to the resistor is printed on the insulating layer, and then baked in the first step in a non-oxidizing gas atmosphere. A method for manufacturing a thick film multilayer substrate, comprising: a fourth step of forming an upper conductor layer by firing at a temperature lower than the above temperature.