JPS5868803A - Conductive paste composition - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates primarily to a conductive paste composition used to form a conductive film on an electronic component made of porcelain.

Conventionally, silver oxide Ag
It is generally constructed by applying a silver paste containing fine powder of porcelain as a conductive component and containing low-melting frit glass 1 onto a porcelain body using a method such as screen printing, and then baking it. Ta. This silver paste fired electrode has advantages such as excellent electrical properties, good high frequency characteristics, high reliability, and easy and simple electrode film formation.
However, there were also the following drawbacks.

(a) Silver is a finite resource and expensive, so there was a limit to how much it could be reduced. Firstly, in ordinary ceramic capacitors, the ratio of electrode cost to the total cost is about 2/3, which is a very large weight.
I'm looking forward to it.

(b) When an electrode is exposed to a printed circuit, j, (conductor pattern on a board or an external electrode such as a lead wire), the "half-11 eating phenomenon" occurs in which silver diffuses and migrates within half a day. This tends to cause functional problems such as poor electrode adhesion or insufficient withstand capacity.

(c) Silver migration occurs, which tends to impair reliability, such as a drop in insulation withstand voltage. In particular, since it is impossible to completely prevent micro-cranks from entering the porcelain body due to thermal shocks and other factors during soldering, silver diffuses into these micro-cracks and causes silver migration. This has the disadvantage of accelerating the progression of the process and reducing reliability.

As a means of removing the defects of the electrode, the silver firing material mentioned above is a method of forming an electrode made of lJ+' metal such as nickel or copper by electroless plating or a combination of this and electroplating. Although attempts have been made, the plating film is easily oxidized, requires a special activated flux to connect with external conductors such as wires, and requires chemical treatment to adhere to the element body. Residual ions or residual ions in the penetrant may deteriorate the life characteristics. Moreover, when using electroless nickel plated electrodes, nickel itself has inferior electrical conductivity and physical properties such as soldering properties, poor high frequency properties, and lacks reliability compared to silver. resulting in disadvantages. Furthermore, compared to the simple process of printing, conventional silver paste firing requires a process in which the surface of the porcelain body is roughened, electroless polishing is applied, and then the outer periphery is polished to make the electrodes unique. There is also the disadvantage that the manufacturing process is extremely complicated.

Furthermore, when polishing the outer periphery, if the thickness of the porcelain body is thin, the polishing force will easily damage and crack the body, so it must be applied only to bodies with a certain thickness or more. There was a restriction that it had to be done.

In addition, metals can be produced using vapor phase methods such as vacuum evaporation and sputtering. ′! A method of forming a ji film has also been attempted. The typical metal used in this vapor phase method is thi, which has electrical properties similar to silver, but the adhesion of the metal thin film to the element body is weak, and the electrode easily peels off. There are many disadvantages in that it is difficult to continuously produce products with a thick film thickness, and furthermore, because the equipment cost is high, R1 has the disadvantage that the cost I/I is high as a result.

As described above, the conventional method of reducing the cost of electrode coatings, that is, using base metals, has many drawbacks.

The present invention solves the problem of the conventional spotting point described in 1-1, eliminates the half-eating phenomenon and silver migration t9- that are inevitable when using silver paste I, and has high frequency characteristics. A conductive paste composition that can form an electrode with very good reliability, half-life characteristics, etc., and that can be manufactured continuously and in large quantities when forming this electrode. The purpose is to provide

In order to achieve this object, the conductive paste composition according to the present invention contains fine copper powder and a glass frit whose main component is at least one of lead borosilicate, bismuth borosilicate, and zinc borosilicate. Named Toji Cho.

In order to form electrodes on a porcelain body using a conductive paste composition having such a composition, it is dispersed in an organic vehicle to form a paste, and then applied to the porcelain body by a method such as screen printing. This is applied in a neutral atmosphere (N
2) Baking is done by heat treatment inside. The reason for heat treatment in a neutral atmosphere is to prevent oxidation of the fine copper powder.

In this case, since the conductive paste composition according to the present invention contains fine copper powder, a copper electrode film is formed. Therefore, it is possible to form an electrode having the following excellent features.

(a) Fine copper powder has fewer resource constraints than fine silver powder and other precious metals, and is much cheaper.

Therefore, the electrode cost and ultimately the product cost are significantly reduced.

(b) Copper fine powder has the same electrical and physical properties as silver fine powder. Therefore, an electrode with good high frequency characteristics and high reliability can be formed.

(c) Silver migration and solder eating phenomena that cannot be avoided in the case of SR electrodes are completely eliminated. For this reason, reliability and life characteristics are significantly reduced.

(d) Even if micro-cracks occur in the porcelain body due to thermal shock during soldering, there is no silver migration or 1' rice eating phenomenon, so reliability and lifespan 'I'+ properties are improved. Never deteriorates.

(e) Since the firing material can be used to form electrodes, it is possible to form electrodes with strong adhesion and high tensile strength that are less susceptible to electrode peeling.

(f) Since a base-like silk composition is obtained in which each component is dispersed in an organic vehicle, electrodes can be formed using conventional processes such as roll transfer or screen printing. Therefore, it becomes possible to make the electrode manufacturing process continuous and to produce products prematurely.

(1.) Unlike electrode formation methods using electroless plating or electroplating, there is no deterioration in life characteristics due to oxidation of the plating film or residual ions, and there is no restriction due to the thickness of the porcelain body.

The glass frit is mainly composed of at least one of lead borosilicate, bismuth borosilicate, and zinc borosilicate, and corresponds to glass classification-I-1 low melting point solder glass, and is heated in a neutral atmosphere. When processed, it melts and has the function of bonding the fine copper powder, which is a conductive component, to the porcelain body. The amount of glass flint added also has a large effect on the characteristics when formed into an electrode. In a general ceramic capacitor, it is desirable that the volume ratio of the glass frit to the fine copper powder is 2 to 40%. If the amount of glass frit added is less than 2%, the tensile strength of the electrode will decrease significantly, while if the amount added is more than 40%, the tensile strength of the electrode will increase, but the solder quality will be reduced. rate decreases,
This is because the capacitance becomes smaller and the dielectric loss becomes larger.

The content of the present invention will be explained in more detail below with reference to Examples.

Example 1 A paste was prepared by dispersing fine copper powder and a lead borosilicate glass frit in a cellulose organic vehicle while changing the volume ratio of the lead borosilicate glass frit to the fine copper powder. After being coated on a barium titanate-based high dielectric constant porcelain body by screen printing, the firing material was heat-treated in a neutral atmosphere (N2). In this case, '11' is the ultimate tensile strength, the soldering property (half Ill is the good product rate) and the capacitance are shown in Table 1, and the electrode tensile strength and half 2, and the capacitance and dielectric loss are shown in FIG. In Table 1 and Figure 1, the electrode tensile strength is determined by applying a 6 mm diameter plate to an electrode formed by baking the disc-shaped porcelain body with a diameter of 8 mm and a thickness of 0.15 mm as described above. and directly on top of this 0.5mm
The lead wire was soldered, and the strength of the lead was 1 and the acid was 1. In addition, solderability is determined by immersing the porcelain body after the electrode firing material in solder using rosin flux and visually judging its semi-111 resistance, and soldering is expressed as a non-defective product rate. Ta. A eutectic solder having a melting point of 240° C. was used as the solder, and it was immersed for 2 to 3 seconds.

As shown in Table 1 and Figure 1, as the amount of glass frit added increases, the tensile strength increases, but on the contrary, V
IT] The sex will get worse. Furthermore, when the amount of glass flint added decreases, the solder properties improve, but the tensile strength decreases. In particular, when the amount of glass frit added exceeds 40%H by volume, the number of non-defective products decreases rapidly for half 111 fl. - The amount of glass frit added is 2 by volume.
%, the tensile strength is I K g/cm
It becomes below. In other words, in order to satisfy the tensile strength of the electrode and the semi-LSI at the same time, the amount of the glass frit added should be 2 to 40% by volume of the fine copper powder. This is desirable. If the amount added is within this range, the tensile strength of the electrode of conventional silver paste I/fired material will be 0.
．． The tensile strength IW is about 1 to 3 kg, whereas the tensile strength IW is about 1 to 3 kg.
The weight is about 6 kg, which is a significant improvement, and the soldering method is also able to maintain a high quality product rate of 80% or more, which is the same as before.

Furthermore, as shown in Figure 2, when the amount of glass frit added is in the range of 2 to 40% by volume, the capacitance increases from 1 to 35μ.
F, the dielectric loss is in the range of 1.5 to 4%, and excellent characteristics can be achieved.

Next, in the above example, half of [H solubility was measured for a ceramic capacitor using electrode paste I according to the present invention in which the amount of glass frit added was 10% by volume, and a commercially available silver electrode ceramic capacitor. The result will be as shown in Figure 3. For the measurement, both participants were immersed in a 300°C eutectic solder bath, and the change in capacitance at that time was measured according to the immersion time. As shown in Figure 3, the capacitance of conventional silver electrode porcelain capacitors decreases by 170% after 20 seconds of immersion.
It can be seen that the capacitance of the ceramic capacitor prepared using the electrode paste of the present invention decreased by only about 15% over the same period of time, and the deterioration of the characteristics was extremely small.

Next, FIG. 4 shows test data for silver migration. For the test, as shown in Figure 5,
A sample is used in which two electrodes 2.3 are provided on the surface of the alumina substrate 1 with a cap gl of 1.5 mm apart, and as shown in FIG. During this period, a DC voltage was applied by the variable DC power supply 4. There were two types of samples: a conventional product in which the electrode 2.3 was made of silver-fired metal, and a fired product made of the conductive paste l-S11 product according to the present invention.

As is clear from Fig. 4, in the case of conventional silver firing (q) electrodes, the current value increases rapidly after 2 to 3 minutes of voltage application, and migration progresses rapidly. When the conductive paste composition according to the present invention is used to form a copper paste fired electrode, almost no current flows even after 2 to 3 minutes of voltage application, and migration progresses. Hardly observed.Voltage application time is 7~
Only a small amount of current flows after 8 minutes.

In the above example, the additive glass frit) was explained using lead borosilicate as the main component, but in addition to lead borosilicate, similar effects could be obtained with bismuth borosilicate and zinc borosilicate. . Additionally, it has been found that when metal oxides such as bismuth oxide, lead oxide, and especially red lead are added as a third component in addition to fine copper powder and glass flint, dielectric loss is improved and capacitance is increased. Ta.

As described above, the conductive paste composition according to the present invention contains fine copper powder, lead borosilicate, bismuth borosilicate,
Since it is characterized by containing a glass frit whose main component is at least one type of zinc borosilicate, it does not cause the solder eating phenomenon or silver migration that is inevitable when using silver paste. It is possible to form electrodes or conductor patterns with very good high frequency characteristics, reliability, solder resistance, and life characteristics, and in forming these electrodes or conductor patterns, continuous manufacturing and mass processing are required. A possible conductive paste composition can be provided.

[Brief explanation of the drawing]

Figure 1 is a characteristic diagram showing the relationship between the volume ratio of lead borosilicate glass frit added to fine copper powder, electrode tensile strength and solder yield rate, and Figure 2 is a graph showing the relationship between capacitance and dielectric Figure 3 is a characteristic diagram showing the relationship between body loss and Figure 3 is a characteristic diagram showing the relationship between solder solubility.
Figure 5 is a plan view of the sample that was also tested, and Figure 6 is a diagram showing the test rack 1, which is a patent patent. Applicant: Tokyo Denki Kagaku Kogyo Co., Ltd. Kuda ↓; Takuchi Kuni l″+ Moromi 9 8 ♀ 8 L Summoning 2 smoked combustion E: 1 Shibu welcoming Bo Fig. 4 122- Fig. 5 Fig. 6

Claims (5)

[Claims] (1) A conductive paste composition characterized by containing fine copper powder and a glass frit whose main component is at least one of lead borosilicate, bismuth borosilicate, and zinc borosilicate. (2) The conductive paste composition according to claim 1, which contains a metal oxide. (3) The conductivity according to claim 1 or 2, wherein the total volume ratio of the glass frit and the metal molten to the copper fine powder is 2 to 40%. Paste composition. (4) The conductive paste composition according to claim 3, wherein the metal oxide is made of bismuth oxide. (5) The conductive paste composition according to claim 3, wherein the metal oxide is made of lead oxide.