JP2000260225A - Electroconductive paste - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electroconductive paste capable of forming a crack-free external electrode. SOLUTION: This electroconductive paste is composed of electroconductive powder chiefly including Ag, organic vehicle, and glass frit. When heating is made with the mean temp. rise rate between 200 and 500 deg.C over 100 deg.C/min and that from room temp. to 580 deg.C over 45 deg.C/min, the max. shrinking speed during heating to 580 deg.C should be below 7%/min and the tensile elongation at 500 deg.C be over 5%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductive paste, and more particularly to a conductive paste suitable for an external electrode of a chip-type electronic component.

[0002]

2. Description of the Related Art Conventionally, a conductive paste mainly comprises a metal powder, an organic vehicle, and a glass frit, and is obtained by dispersing the metal powder and the glass frit in the organic vehicle.

[0003] In addition, the external electrodes of the chip-type electronic component are formed by applying a conductive paste to a predetermined region on the chip-type body,
Baking after drying removes the binder component in the conductive paste and is formed.

[0004]

However, in the case where a conventional conductive paste is applied, dried and baked to form an external electrode such as a chip-type electronic component, the conductive paste shrinks during firing and the electrode during sintering is formed. Internal stress may occur in the film and cracks may occur.

An object of the present invention is to solve the above-mentioned problems and to provide a conductive paste capable of forming a crack-free external electrode.

[0006]

Means for Solving the Problems To achieve the above object, a conductive paste of the present invention comprises a conductive powder mainly composed of Ag, an organic vehicle, and a glass frit.
Average temperature rise rate between 200 and 500 ° C is 100 ° C / min
As described above, the average heating rate between room temperature and 580 ° C is 45 ° C / mi.
When heated at n or more, the maximum shrinkage rate during heating to 580 ° C. is 7% / min or less, and the tensile elongation at 500 ° C. is 5% or more.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A crack generated in an external electrode of a chip-type electronic component is caused by shrinkage stress generated due to sintering shrinkage when a coating film of a conductive paste is baked. It is caused by exceeding the strength. Therefore, there is a means of increasing the strength of the coating film or reducing the contraction stress.

However, when the conductive paste is baked to form the external electrodes of the chip-type electronic component, the binder component in the conductive paste burns and disappears. And the density decreases, and the film strength of the coating film decreases during the temperature rise.

Further, when the burning of the binder is completed in the firing process, the sintering of the Ag powder starts. As described above, since the density of the coating film is reduced by the burning of the binder, the sintering of the Ag powder rapidly progresses, and a large shrinkage stress is generated in the coating film.

[0010] Here, a coating film was formed using conductive pastes of various compositions and baked, and the presence or absence of cracks in the external electrodes was observed. Conventionally, generally, the average rate of temperature rise between 200 and 500 ° C. during baking of a conductive paste is about 60 ° C./min. Therefore, the average heating rate between 200 and 500 ° C. is 100 ° C./min or more, and between room temperature and 580 ° C. so that cracks occur in the external electrodes with a probability of approximately 100% when the conventional conductive paste is baked. A confirmation experiment was performed by heating to 580 ° C. at an average temperature rising rate of 45 ° C./min or more. As a result, it was found that a maximum contraction rate was exhibited at around 500 ° C. In addition, when a conductive paste was actually applied to the chip-type element body, dried and baked to form an external electrode, a crack occurred in the external electrode at around 500 ° C. as shown in FIG. Accordingly, it was concluded that the generation of cracks as shown in FIG. 1 can be prevented by satisfying that the coating film strength at 500 ° C. is sufficiently high and the shrinkage rate during this time is low.

The conductive paste of the present invention comprises a conductive powder mainly composed of Ag, an organic vehicle, and a glass frit. Although the particle size of the conductive powder is not particularly limited, for example, a granular powder of 1 μm or less, a spherical powder of 5 μ or more, a flat powder, or the like can be appropriately used. The organic vehicle is not particularly limited, and for example, a solution obtained by dissolving a binder such as ethyl cellulose resin in a solvent such as kerosene can be used as appropriate. Although the glass frit is not particularly limited, for example, B ₂ O ₃ —SiO ₂ —PbO system, B ₂ O ₃ —SiO ₂ —Zn
O-based glass frit or the like can be used as appropriate.

Further, the conductive paste of the present invention comprises 200
An average temperature rising rate between 100 ° C. and 500 ° C. or more,
The maximum shrinkage rate is 7% / m during heating up to 580 ° C at an average temperature rising rate of 45 ° C / min or more between room temperature and 580 ° C.
It is required to be not more than in. When the shrinkage rate is low, the shrinkage stress generated per unit time is small. When the maximum shrinkage rate exceeds 7% / min, the shrinkage stress at around 500 ° C. of the baking temperature exceeds the strength of the coating film. Cracks occur in the external electrode obtained after firing.

[0013] The conductive paste of the present invention comprises 200
An average temperature rising rate between 100 ° C. and 500 ° C. or more,
5% tensile elongation at 500 ° C. when heated at an average temperature rising rate of 45 ° C./min or more between room temperature and 580 ° C.
That is required. Those with high tensile elongation indicate that they have excellent adaptability to relieve shrinkage stress even if the coating film shrinks during baking, but this tensile elongation is 5%.
If it is less than, the shrinkage stress cannot be sufficiently reduced, and the external electrode obtained after firing will crack.

[0014]

EXAMPLES First, Ag powder, glass frit, and an organic vehicle in which ethyl cellulose resin was dissolved in a petroleum hydrocarbon solvent were mixed to obtain conductive pastes 1 to 8. The compositions of the conductive pastes 1 to 8 are summarized in Table 1.

[0015]

[Table 1]

Next, the conductive pastes 1 to 8 are applied to a predetermined thickness on a PET film by using a doctor blade to form coating films, respectively.
After drying at 50 ° C., this was cut and processed by a cutter to a width of 3 mm, a length of 15 mm and a dry coating thickness of 0.15 mm to obtain dried test pieces 1 to 8. Next, the dried test pieces 1 to 8 were heated from room temperature to 500 ° C. in the air at an average temperature rising rate of 200 ° C./500° C./100° C./min and an average temperature rising rate of room temperature to 580 ° C. at 45 ° C./min. After heating, when the temperature reached 500 ° C., a tensile test was performed at a load speed of 50 g / min.
The tensile elongation was measured. For the measurement of tensile elongation, a test piece was fixed to a chuck, and TMA / SS120 manufactured by Seiko Denshi was used.
Performed using

Next, conductive pastes 1 to 8 are prepared,
This was processed in the same manner as described above to obtain dried test pieces 1 to 8, and these were heated from room temperature to 580 ° C in the air at 200 to 500 ° C.
The average temperature rise rate during the period is 100 ° C./min, room temperature to 580 ° C.
The average heating rate during the heating was 45 ° C./min, and the amount of shrinkage during the heating was measured to determine the maximum shrinking rate. The measurement of the maximum contraction rate was performed by fixing the test piece to the chuck and using TMA / SS120 manufactured by Seiko Denshi. The maximum contraction rate is the average contraction rate obtained from the time required for 5% contraction and the amount of contraction in the region where the contraction is the steepest in the graph with the vertical axis representing the contraction rate (%) and the horizontal axis representing time (min). And

Next, a ceramic green sheet mainly composed of BaTiO ₃ as a dielectric main component and a predetermined number of internal electrodes made of Ag / Pd are laminated and fired.
A plurality of chip-type bodies having a size of 1.5 mm were prepared.

Next, conductive pastes 1 to 8 were applied to the exposed end portions of the chip-shaped element body to form coating films having a thickness of 80 μm. To 580 ° C, the average heating rate between 200 and 500 ° C is 100 ° C / min, the average heating rate between room temperature and 580 ° C is 45 ° C / min, and the external electrodes 1-8 are baked at 580 ° C. And external electrodes 1 to
No. 8 was inspected for cracks. Table 2 summarizes the tensile elongation at 500 ° C., the shrinkage rate, and the presence or absence of cracks in the external electrodes of the chip-type electronic component. For the samples 1 and 6, the relationship between the shrinkage ratio and the firing time is summarized in the graph of FIG.

[0020]

[Table 2]

As apparent from Table 2, the tensile elongation was 5%.
As described above, Samples 1 to 5 satisfying the shrinkage rate of 7% / min or less
In each case, no crack was generated in the external electrode as shown in FIG. On the other hand, Sample 6 having a tensile elongation of 3.3%, Sample 7 having a tensile elongation of 2.8%, and Sample 8 having a tensile elongation of 0.7% and a shrinkage rate of 3.7% / min were all as shown in FIG. The external electrode was cracked.

As is clear from the graph of FIG.
Sample 1 stops expanding around 400 ° C. and starts shrinking, whereas Sample 6 starts shrinking around 500 ° C. and 550 ° C.
Since the shrinkage ratios of the sample 1 and the sample 6 become substantially the same in the vicinity, it can be seen that the slope of the graph of the sample 6 is steeper than that of the sample 1 and the maximum shrinkage speed is larger.

In the embodiment of the present invention, Table 1
The composition of the conductive paste is not particularly limited as long as the maximum shrinkage rate and the tensile strength at the time of firing are within a predetermined range.

[0024]

As described above, according to the conductive paste of the present invention, it is composed of a conductive powder mainly composed of Ag, an organic vehicle, and a glass frit. When heated at an average temperature rising rate of 45 ° C./min or more between room temperature and 580 ° C.
Maximum shrinkage rate during heating to 580 ° C is 7% / min
Hereinafter, by being characterized in that the tensile elongation at 500 ° C. is 5% or more, the film strength of the coating film at the time of baking is sufficiently strong, and an external electrode without cracks after baking can be formed.

[Brief description of the drawings]

FIG. 1 is a photograph in which an external electrode made of a conductive paste according to the present invention is observed from an end surface direction of a chip-type electronic component.

FIG. 2 is a photograph in which an external electrode made of a conventional conductive paste is observed from an end surface direction of a chip-type electronic component.

FIG. 3 is a graph showing the relationship between the shrinkage ratio and the firing time of the conductive paste of Example 1 according to the present invention and the conductive paste of Comparative Example 6;

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4J038 EA011 HA066 HA476 KA20 NA20 PB09 5E319 AB05 5G301 DA03 DA34 DA42 DD01

Claims (1)

[Claims] 1. An electroconductive powder containing Ag as a main component, an organic vehicle, and a glass frit, wherein an average temperature rising rate between 200 and 500 ° C. is 100 ° C./min.
As described above, the average heating rate between room temperature and 580 ° C is 45 ° C / mi.
a conductive paste having a maximum shrinkage rate of 7% / min or less during heating to 580 ° C. and a tensile elongation at 500 ° C. of 5% or more when heated at n or more.