JP4151578B2 - Conductor paste - Google Patents

Description

  The present invention relates to a conductor paste used for screen printing used for forming a wiring pattern on a ceramic circuit board.

  The formation of a wiring pattern by a printing method on a ceramic circuit board is generally performed by printing a conductor paste on the ceramic circuit board by a screen printing method, and then drying and firing. This conductor paste is obtained by mixing and kneading an organic vehicle, conductor particles, glass particles and a dispersant. As the conductor particles, metal particles such as silver, palladium, platinum and tungsten are mainly used. Glass particles are a binding material that melts during firing to form metal films that are brought into contact with each other to form a conductor film. The conductor film also has a function of fixing the conductor film to a ceramic substrate. Glass particles having a proper composition are used. Further, the dispersant functions to prevent the conductor particles and glass particles from being uniformly dispersed in the organic vehicle and separated or aggregated over time.

  The organic vehicle is obtained by dissolving a resin component in an organic solvent, and has a function of interposing between conductive particles and glass particles and connecting them together to form a paste. Note that the organic vehicle and the dispersion material are removed by combustion or decomposition during firing, and do not remain in the conductor film. When the conductor paste is printed by a screen printing method, one of the most important characteristics is the viscosity characteristic of the conductor paste. The viscosity of the conductor paste varies depending on its temperature, shear rate (share rate), elapsed time after manufacture, and the like, but it is the viscosity characteristic of the organic vehicle that most affects such a viscosity characteristic.

  For example, in order to reduce the change of the viscosity of the conductor paste with the elapsed time after manufacture, that is, the change of the viscosity of the conductor paste with time, an organic vehicle is prepared by dissolving two or more types of resin components having different viscosity values in a solvent. However, attempts have been made to produce a conductor paste using this (Patent Document 1). In Patent Document 1, an organic vehicle prepared by mixing two types of ethyl cellulose having different viscosity values or a conductor paste manufactured using the same is prepared using an organic vehicle prepared using single molecular weight ethyl cellulose or the same. It is shown that the change in viscosity with time is smaller than that of the manufactured conductor paste.

In Patent Document 1, although not described the shear rate during the viscosity measurement, the evaluation index of the viscosity characteristic of the conductor paste, at a shear rate of 1 point of the range of shear rate 1 sec ^-1 of 10 sec ^-1 The measured viscosity or the ratio of viscosities measured at two shear rates is often used. However, the conductor paste managed by these evaluation indices may suddenly have poor printability due to differences in production lots, causing troubles such as blurring, clogging, and deterioration of plate separation. In addition, the printability, which was good in the initial stage of printing, may cause the same trouble by repeated times.

JP 2000-273367 A (page 2-3, Table 1)

Factors such Drabble, shear rate applied to the conductive paste during the actual screen printing is in the range of a speed higher than 10 sec ^-1 from 1 sec ^-1, ranging from shear rate 1 sec ^-1 of 10 sec ^-1 Even if the viscosity characteristics in the range are within a certain control range, during actual screen printing, it will be out of the range of viscosity characteristics where good printability can be obtained due to differences in production lots of conductor paste and changes over time. In addition, the viscosity characteristics of the conductive paste may change due to repeated printing. However, the conventional methods for evaluating the viscosity characteristics of conductive pastes cannot select conductive pastes with high stability and thus have difficulty in obtaining conductive pastes with high stability. .

  The present invention has been made to solve the above-described problems, and an object of the present invention is to obtain a conductive paste having a highly stable printability.

  In the conductor paste according to the present invention, the ethyl cellulose is 0.8 wt% to 1.3 wt% and the polypropylene glycol is 0.5 wt% to 1.0 wt% based on the total weight of the conductor particles, glass particles, dispersant and conductor paste. % By weight, di-n-butyl phthalate from 0.15% to 0.25% by weight and the balance comprising terpineol.

The present inventors have made studying the relationship viscosity characteristics and printability of the conductive paste, the actual scope of 100sec ^-1 ~850sec ^-1 close to a range of shear rate applied to the conductive paste during the screen printing When the viscosity characteristic of the conductor paste is η and the shear rate is D, the viscosity formula η = μD ^n-1 (μ: non-Newton coefficient, n: non-Newton index, 0 <n <1) The conditions that can be approximately approximated are the conditions for obtaining a conductive paste having high printing stability, and the conductive paste using the organic vehicle containing the above components has the content of each component of the organic vehicle, particularly the content of polypropylene glycol. It has been found that by adjusting, a viscosity characteristic that can be approximated by the viscosity formula η = μD ⁿ⁻¹ within a wide range of shear rate can be obtained. The present invention has been made based on these.

According to the present invention, in a conductor paste used for screen printing comprising conductor particles, glass particles, a dispersant, and an organic vehicle, the organic vehicle is 0.8% to 1.3% by weight of ethyl cellulose with respect to the total weight of the conductor paste. Since the polypropylene glycol contains 0.5 wt% to 1.0 wt%, di-n-butyl phthalate contains 0.15 wt% to 0.25 wt%, and the remainder includes terpineol, the shear rate is 100 sec ^{− In} the range of ^{1 to} 850 sec ⁻¹ , it is possible to obtain a conductive paste having a viscosity characteristic that can be approximately approximated by the viscosity formula η = μD ⁿ⁻¹ and having high printability.

Embodiment 1 FIG.
FIG. 1 is a process diagram showing a process for producing a conductor paste according to Embodiment 1 of the present invention. In FIG. 1, the conductor particles 10, the glass particles 12, the organic vehicle 14, and the dispersant 16 are weighed in predetermined amounts, and mixed and kneaded in a mixing / kneading step 18 with three rolls (not shown). By kneading for a long time at room temperature, the conductor particles 10 and the glass particles 12 are almost uniformly dispersed in the organic vehicle 14, and a conductor paste 20 having a predetermined viscosity characteristic is obtained.

  Hereinafter, the present invention will be described in detail with reference to examples and comparative examples. Table 1 shows the content of each component of Examples A to C (shown as A to C in Table 1) and Comparative Examples D and E (shown as D and E in Table 1) in% by weight. It is.

  The solid substance represents the conductor particles 10 and the glass particles 12, and the resin solution represents the organic vehicle 14 and the dispersant 16, respectively, and the content of each of the solid substance and the resin solution is 100%. The conductor particles 10 are composed of silver particles having an average particle diameter of 1 to 3 μm and palladium particles having an average particle diameter of 1 μm, and the average particle diameter of the glass particles 12 is 1.6 μm. As the dispersant 16, homogenol L-18 (registered trademark, manufactured by Kao Corporation), which is a polymer surfactant, was used.

  The organic vehicle 14 is a mixture of ethyl cellulose, polypropylene glycol, di-n-butyl phthalate and terpineol. Ethyl cellulose and polypropylene glycol are resin components that increase the viscosity of the mixture, and di-n-butyl phthalate and terpineol are solvent components that dissolve the resin component. When these components are mixed and dissolved, no heat treatment is performed, and the mixture is stirred and mixed for a long time at room temperature. Since the heat treatment is not performed, thermal damage to the resin component can be prevented, and the effect of the resin component on the viscosity characteristics of the organic vehicle 14 and the conductive paste 20 using the organic vehicle 14 can be stably and reproducible. Can get high.

Example A~C well, a viscosity of the conductive paste 20 of Comparative Examples D and E, the result of shear rate was measured in the range of ^{100sec -1 ~850sec} -1 in FIG. The viscosity was measured at 25 ° C. using a cone / plate type rotational viscometer.

FIG. 2 shows a logarithmic graph with shear rate on the horizontal axis and viscosity on the vertical axis. The measurement results of the viscosity of the conductor pastes 20 of Examples A to C and Comparative Examples D and E are plotted and connected by the broken lines indicated by A to E, respectively. In the range of shear rate ^{100sec -1 ~850sec} -1, the viscosity of the conductive paste 20 in the embodiment A~C is plotted on the downward-sloping straight line log-log graph in Figure 2, viscosity equation eta = [mu] d ^It has a viscosity characteristic that can be approximated by ^n-1 .

On the other hand, the viscosity of Comparative Examples D and E of the conductive paste 20 is about 300 sec ^-1 shear rate, respectively, and from the region of about 500 sec ^-1 greater difference from the straight line downward to the right, viscosity equation eta = [mu] d ^The viscosity characteristics cannot be approximated with ^n-1 .

  Such a significant difference between the viscosity characteristics of Examples A to C and the viscosity characteristics of Comparative Examples D and E is a significant difference in printability in screen printing. The conductive paste 20 having the same viscosity characteristics as in Examples A to C can suppress occurrence of troubles in screen printing such as fading, clogging, deterioration of plate separation, and the like, and can realize highly stable printability. .

The significant difference between the viscosity characteristics of Examples A to C and the viscosity characteristics of Comparative Examples D and E is mainly caused by the difference in the content of polypropylene glycol. As shown in Table 1, the content of polypropylene glycol in the conductor paste 20 of Examples A to C is in the range of 0.5 wt% to 1.0 wt%. On the other hand, the content of polypropylene glycol in the conductive paste 20 of Comparative Examples D and E is not in the range of 0.5 wt% to 1.0 wt%, and is 1.2 wt% and 0.4 wt%, respectively. . By setting the content of polypropylene glycol in the range of 0.5 wt% to 1.0 wt%, the range of shear rate at which the viscosity characteristics of the conductor paste 20 can be approximately approximated by the viscosity formula η = μD ⁿ⁻¹ is expanded. There is an effect that can.

In FIG. 2, although the shear rate indicates the results of the viscosity was measured at different shear rates of 14 in the range of ^{100sec -1 ~850sec} -1, conductor paste 20 of the present invention, a temperature of 25 ° C If the viscosity satisfies the conditions of 50 Pa · sec or less at a shear rate of 100 sec ⁻¹ and 2 Pa · sec or more at a shear rate of 850 sec ⁻¹ , the viscosity characteristic can be approximately approximated by the viscosity equation η = μD ⁿ⁻¹ , The conductor paste 20 has a sufficiently stable printability. Therefore, during manufacture or use of the conductive paste 20 of this invention, shear rate 100 sec ^-1 and need only measure the viscosity at shear rate 850sec ^-1, conveniently grasp the quality, it can be managed There is an effect.

Next, Example F (shown as F in Table 2) shown in Table 2 will be described. The content of each component of the conductor paste 20 of Example F is as shown in Table 2, the content of polypropylene glycol is 0.7% by weight, and the viscosity characteristic of the conductor paste 20 is the viscosity formula η = μD ^{n−. 1} is within the range of 0.5% by weight to 1.0% by weight, which is the range of the content of polypropylene glycol that can broaden the range of the shear rate that can be approximately approximated.

  FIG. 3 shows the measurement of the viscosity of the conductor paste 20 remaining on the screen mask for printing after screen printing was performed several hundred times using the conductor paste 20 of Example F shown in FIG. The result measured under the same conditions as the result is shown. The viscosity characteristic of the conductor paste 20 of Example F after being used for screen printing shown in FIG. 3 is equivalent to the viscosity characteristic of the conductor paste 20 of Examples A to C shown in FIG. The viscosity characteristics of the paste 20 hardly change even when a high shear rate is repeatedly applied by performing screen printing several hundred times. That is, it can be said that the conductor paste 20 of Example F has durability against screen printing. This durability is a characteristic common to the conductor paste 20 of the present invention including Examples A to C, and is a remarkable effect of the present invention.

It is process drawing which shows the manufacturing process of the conductor paste by Embodiment 1 of this invention. It is a graph which shows the viscosity characteristic of the conductor paste by Embodiment 1 of this invention. It is a graph which shows the viscosity characteristic of the conductor paste by Embodiment 1 of this invention.

Explanation of symbols

10 conductor particles, 12 glass particles, 14 organic vehicle, 16 dispersant.

Claims (2)

In the conductive paste used for screen printing comprising conductive particles, glass particles, a dispersant and an organic vehicle, the organic vehicle is composed of 0.8% to 1.3% by weight of ethyl cellulose and polypropylene glycol based on the total weight of the conductive paste. A conductor paste comprising 0.5% to 1.0% by weight, di-n-butyl phthalate from 0.15% to 0.25% by weight and the balance comprising terpineol. 2. The conductor paste according to claim 1, wherein the viscosity at a temperature of 25 ° C. is 50 Pa · sec or less at a shear rate of 100 sec ⁻¹ and 2 Pa · sec or more at a shear rate of 850 sec ⁻¹ .

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