JP2001312920A - Conductive paste - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a conductive paste which does not generated recesses or edge-shaped projections on an external electrode and exhibiting superior property in application forms, when it is used for forming an external electrode of an electronic component. SOLUTION: This conductive paste is comprised of at least a conductive powder, glass frits, resin and rosin-based resin and contains the rosin-type resin of 1-10 weight percent.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductive paste applied and baked to form a conductor such as an external electrode of an electronic component, and more particularly to an improvement in a resin contained in the conductive paste. It is about.

[0002]

2. Description of the Related Art Conventional firing type conductive pastes are:
Usually, it contains at least a conductive powder, a glass frit, other additives, and a solvent. Such a conductive paste is used for forming external electrodes of an electronic component such as a multilayer ceramic capacitor.

When external terminal electrodes are formed from such a conductive paste, the electrode forming surface of the electronic component is immersed in a paste bath containing a conductive paste in a predetermined area on the surface of the electronic component by dipping. Is applied, and the conductive paste is baked, and the conductive paste is applied to both ends of the multilayer ceramic capacitor.

[0004] Inside such a multilayer ceramic capacitor, internal electrodes are formed in a plurality of layers, and the ends of these internal electrodes are exposed at any end face of the ceramic laminate. Therefore, the conductive paste applied to both end surfaces of the ceramic laminate evaporates the solvent in the drying step, and comes into contact with the end of the internal electrode,
The external electrode formed by baking the conductive paste also maintains a state of being in contact with the end of the internal electrode, and is in a state of being electrically connected to the internal electrode.

Conventionally, regarding the shape of the external electrode formed by applying and baking a conductive paste to an electronic component, the shape, the particle size, the amount of the metal powder, the shape, the particle size, the amount of the glass powder, It is known that it depends on the type and amount of the resin, the added amount and boiling point of the solvent, and the drying conditions for drying the conductive paste.

[0006]

In the above-mentioned conventional conductive paste drying step, the solvent of the conductive paste is evaporated at a drying temperature of 150 to 200 ° C. in order to improve the production speed. Here, the conductive paste applied on the electronic component is near the center of the end face side where the thickness is the largest,
As shown in FIG. 2A, a corner-shaped projection 4 is formed. This is because a thread pulled between the ceramic laminate and the paste tank during dipping remains. Thereafter, when the paste is subjected to gravity during drying, the conductive paste moves from the center of the end of the electronic component toward the periphery, and as shown in FIG. A conductive paste is obtained.

[0007] However, if the flow of the conductive paste at the drying temperature is too large, a depression 3 is formed after drying as shown in FIG. Alternatively, if the flow is insufficient, after drying, the corner-shaped projections 4 are formed as shown in FIG. These dents 3 or corners
The projections 4 remain even after baking, resulting in a problem of poor appearance.

The dents 3 and the horn-like projections 4 generated on the surface of the external electrode 2 not only impair the appearance of the product, but also make it difficult to mount the product in a predetermined posture during mounting. . In addition, there is a problem that the horn-shaped projections 4 are broken in a later process and become foreign matters, and the process must be stopped. Furthermore, in order to solve these problems, all the products must be inspected, which causes an increase in manufacturing cost. Therefore, a conductive paste capable of forming the external electrode 2 without the depression 3 and the horn-shaped projection 4 is desired.

The present invention solves the above problems, and when used to form external electrodes of electronic components,
It is an object of the present invention to provide a conductive paste having excellent shape and capable of forming an external electrode having no dents or square projections in a coating and drying step.

[0010]

In order to achieve the above object, the conductive paste of the present invention comprises at least a conductive powder, a glass frit, a resin and a rosin-based resin,
Provided is a conductive paste, wherein the content of the rosin-based resin is 1 to 10% by weight.

According to the conductive paste of the present invention, since the rosin-based resin contains 1 to 10% by weight, the rosin-based resin is convected by a convection of metal powder, glass powder, resin and the like when the solvent is evaporated in the drying step. Thus, the shape at the time of application of the paste can be maintained at a predetermined shape. As a result, dents and angular projections can be suppressed.

This is because, in order to uniformly form a paste on the end of an electronic component, the drying temperature needs to be higher than the softening point of the rosin-based resin, but the difference between the drying temperature and the softening point is low. If it is too large, the fluidity of the paste at the drying temperature is too large.

In this way, the shape of the external electrode is improved, the flatness and flatness of the surface are ensured, and it is possible to perform printing without generating dents or angular projections.

The softening point refers to a temperature at which the resin starts to be easily deformed. As an example, the ring and ball method will be described. That is, a ring made of brass filled with a sample (resin) is horizontally held in a water bath, and a steel ball having a constant weight is placed on the center of the sample (resin).
The bath temperature is raised at a constant temperature, the sample (resin) gradually softens, the steel ball descends, and the temperature at the time when the steel plate finally reaches the low plate at the position of 25 mm in thickness is defined as the softening point.

Therefore, by using the conductive paste of the present invention, it is possible to form a good external electrode having no dents or square projections on an electronic component such as a multilayer ceramic capacitor. Further, in the conductive paste of the present invention, any metal powder, glass powder, resin, and solvent can be used.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the conductive paste of the present invention will be described in detail. FIG. 1 is a plan view showing an electronic component (multilayer ceramic capacitor) 1 in which external electrodes are formed using the conductive paste of the present invention.

The electronic component (multilayer ceramic capacitor) 1 shown in FIG. 1 includes a rectangular parallelepiped ceramic body and external electrodes 2 formed on end faces of the ceramic body. To form these external electrodes 2, a conductive paste is prepared, the conductive paste is applied to the end face of the ceramic body by dipping, dried, and baked.

A rosin-based resin is used for the above-mentioned conductive paste. The softening point of the rosin-based resin is not particularly limited, and rosin-based resins having all softening points are used. However, in order to effectively use the conductive paste of the present invention, the softening point of the rosin-based resin is set to be lower than the drying temperature of the conductive paste by one.
It is preferable to use a resin whose temperature is lower by ５０50 ° C., and more preferably, a rosin resin specified at a temperature lower by 10１０〜20 ° C. may be used. If the softening point of the rosin-based resin exceeds a temperature 1 ° C. lower than the paste drying temperature, the flow of the rosin-based resin during drying may be insufficient, and after drying, as shown in FIG. The protrusion 4 may be formed. On the other hand, when the drying temperature is lower than 50 ° C., the fluidity of the paste at the drying temperature tends to increase, and the dents 3 may be formed after drying as shown in FIG.
However, the drying temperature of the conductive paste varies depending on the solvent and the like, but is preferably from 150 to 200 ° C, more preferably from 160 to 180 ° C. 150 ° C
If it is lower, the type of solvent that evaporates during the drying process is limited,
If the temperature exceeds 200 ° C., a jig for fixing the ceramic body may deteriorate. However, it is not limited to this.

The rosin-based resin is added to the conductive paste by one.
-10 wt%, preferably 3-4 wt%. 1%
When it is less than the above, the effect of controlling the fluidity during drying by the rosin-based resin is reduced. Conversely, if it exceeds 10%, there is a problem that the rosin-based resin does not burn sufficiently at the time of baking and remains in the external electrode 2 of the electronic component (multilayer ceramic capacitor) 1 as a final product.

In this embodiment, the case where silver powder is used as the conductive component will be described. However, when other noble metal powders and base metal powders are used, spherical and flat powders may be mixed at an arbitrary ratio. The same effect can be obtained even when blended.

The type of the rosin resin is not particularly limited. For example, a cellulose resin, an acrylic resin, an alkyd resin, an epoxy resin and the like are used.

In this embodiment, the case where the external electrode 2 of the multilayer ceramic capacitor 1 is formed will be described as an example. However, the conductive paste of the present invention is not limited to the multilayer ceramic capacitor, but may be a piezoelectric resonance component or a chip resistor. It can be suitably used when forming external electrodes of various electronic components such as.

[0023]

EXAMPLES Examples of the present invention will be described below in more detail with reference to comparative examples and comparative examples.

A silver powder, a glass powder (alkali borosilicate), a resin component and a solvent were mixed in the proportions shown in the table. Here, as the resin component, a cellulose resin and a rosin-based resin were blended, and a rosin-based resin was selected as the rosin-based resin. As the solvent, benzyl alcohol and α-terpineol were used to prepare a conductive paste.

After this conductive paste is applied to the ceramic body, dried at 170 ° C. and baked at 700 to 800 ° C., the state of occurrence of dents, angular projections, etc. is examined to evaluate its shape. did. Table 1 shows the results.

In Table 1, the shape is judged to be good or bad when one of the dents 3 and the horn-shaped projections 4 is determined as x. , The dents 3 and the horn-shaped projections 4 were evaluated as ○.

[0027]

[Table 1]

As shown in FIG. 1, the external electrode formed by the conductive paste using the rosin-based resin blended in the ratio within the range of the present invention has the dents 3 and the square projections 4 as shown in FIG. No outbreaks were noted. However, when the amount of the rosin-based resin added was 0 wt% as in sample No. 1, the effect was not obtained, and the fluidity of the paste was increased. Also, as in sample No. 6,
When the addition amount of the rosin-based resin was 15 wt%, the fluidity at the time of drying was remarkably reduced, and the occurrence of square projections 4 was observed.

In the case of the rosin resin having a softening point of 140 ° C. or higher, as shown in FIG. In the case of the present invention at 75 and 115 ° C., the fluidity during drying was increased, and even when an appropriate amount of the rosin-based resin was added, generation of dents was slightly observed. However, the present invention has no problem.

It should be noted that the present invention is not limited to the above embodiment, and various changes and improvements may be made without departing from the scope of the present invention.

[0031]

As described above, the conductive paste of the present invention contains 1 to 10% by weight of a rosin-based resin as a resin component.
Suppress dents and horns on the surface during drying,
Can be prevented.

Therefore, by using the conductive paste of the present invention, it is possible to form good external electrodes without dents or protrusions on electronic components such as multilayer ceramic capacitors.

As a result, it is possible to prevent dents and projections at the central portion of the external electrode, so that it is possible to eliminate the 100% inspection of products which was conventionally required and to reduce the manufacturing cost. Will be possible.

[Brief description of the drawings]

FIG. 1 is a plan view showing an electronic component (multilayer ceramic capacitor) in which external electrodes are formed using a conductive paste of the present invention.

FIG. 2 is a partially enlarged view showing a state when a conductive paste applied to an electronic component (multilayer ceramic capacitor) is dried.

FIG. 3 is a plan view showing a state in which dents have occurred on the surface of an external electrode in a drying step after applying a conventional conductive paste.

FIG. 4 is a plan view showing a state in which angular projections are generated on the surface of an external electrode in a drying step after applying a conventional conductive paste.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Electronic component (multilayer ceramic capacitor) 2 External electrode 3 Depression 4 Square projection

Claims (1)

[Claims] 1. A conductive paste comprising at least a conductive powder, a glass frit, a resin and a rosin-based resin, wherein the content of the rosin-based resin is 1 to 10% by weight.