JPH09205002A - Method for manufacturing chip electronic component - Google Patents

Abstract

PROBLEM TO BE SOLVED: To remove a metal film adhered to an element portion of a chip and form a metal layer excellent in wetness for solder on a terminal electrode by a method wherein, after a metal film excellent in wetness for solder is formed on the entire face of a chip, the metal film is heated and melted at a melting point or higher in vapor or liquid. SOLUTION: A terminal electrode 4 is formed in a dip type on both end faces of an element 1, and on the faces by plating, a metal film (solder film) 3 excellent in solder wetness is formed on the entire face of the element 1 and the terminal electrode 4. Next, the metal film 3 is heated and melted and alloyed with an underlayer metal on a face of the terminal electrode 4 to form a metal layer 5 excellent in solder wetness, and it gathers to the side of the terminal electrode 4 by a surface stress of the molten metal on the face of the element 1. Alternatively, it becomes metal balls and drops by its weight while cooled and solidified. After cooled, the metal balls formed on the face of the element 1 are removed by ultrasonic cleaning. Thereby, it is possible to form the metal layer 5 excellent in solder wetness on the face of the element 1 only in the terminal electrode 4 without peculiar coating.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a chip type electronic component (hereinafter referred to as a chip).

[0002]

2. Description of the Related Art Conventionally, as a method of manufacturing a chip, a method described in Japanese Patent Application Laid-Open No. 3-250603 is known. Generally, a chip has a metal layer with good wettability to solder formed on the surface of the terminal electrode by a method such as plating.However, if the element body with a low specific resistance such as a thermistor is plated, the surface of the element body Since a metal layer is formed on the metal layer, a method of coating the surface of the element body with plating-resistant glass or resin is used to prevent this.

A conventional method for manufacturing a chip will be described below with reference to FIG. 4 by taking a thermistor as an example. FIG. 4 is a perspective view of a conventional chip. In FIG. 4, 1 is an element body, 2 is a glass layer, 4 is a terminal electrode, and 5 is a metal layer.

After the glass is applied and baked on the upper and lower flat surfaces of the element body 1 fired on a flat plate, it is cut into strips, and the exposed side surface of the element body 1 is again applied with glass and fired into chips. Disconnect. Electrode paste is applied and baked on both end portions of the cut chip-shaped element that are not covered with glass to form the terminal electrodes 4. After that, a metal layer 5 having good solder wettability is formed on the terminal electrode 4 by plating.

[0005]

However, according to the conventional method, the metal layer 5 having good wettability to solder is formed only on the surface of the terminal electrode 4, so that the surface of the element body 1 is made of a glass layer having resistance to plating. 2 had to be provided, which was troublesome. Therefore, the present invention aims to eliminate conventional insulators such as glass layers.

[0006]

In order to achieve this object, the present invention is to form a metal film having good solder wettability on the entire surface of a chip and then heat and melt it to form a metal ball shape on the surface of the chip body. Then, a metal layer having good solder wettability is formed only on the surface of the terminal electrode, and the metal ball is removed.
When the metal film is heated and melted, it is not compatible with the element body on the surface of the element body, becomes spherical due to the surface tension, and is alloyed with the base metal on the surface of the terminal electrode to form a metal layer having good solder wettability. Therefore, the metal balls on the surface of the element body can be easily removed.

[0007]

The method for manufacturing a chip according to claim 1 of the present invention is a method of forming a metal layer having good solder wettability only on the surface of a terminal electrode of the chip, and by a surface coating method such as plating. , A metal film having good solder wettability is formed on the entire surface of the chip, and then the metal film is heated and melted in a gas or a liquid at a temperature equal to or higher than its melting point, and the metal film adhered to the surface of the element body of the chip is It is formed into a metal ball shape and is removed in a later step to form a metal layer having good solder wettability only on the terminal electrode of the chip.

According to a second aspect of the present invention, a chip provided with a metal film having a good solder wettability is moved from a high temperature to a low temperature side in a high boiling point liquid having a temperature gradient so that the chip is kept at the high temperature side. The metal film is melted to form a metal ball on the surface of the chip body, and a metal layer alloyed with the base metal is formed on the surface of the terminal electrode. After cooling and solidification on the low temperature side, the metal ball on the surface of the body is ultrasonically cleaned. The surface of the element body is poorly compatible with the element body and becomes a metal ball shape due to its surface tension, so that it can be easily removed by ultrasonic cleaning.

The invention according to claim 3 of the present invention is a thermistor material in which the resistivity of the element body is 500 Ω · cm or less, and even if the resistivity of the element body is low, a special coating having solder plating resistance is provided. A metal layer having good solder wettability can be formed only on the chip terminal electrodes without processing.

An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a partially cutaway perspective view of a chip according to the present invention, FIG. 2 is a sectional view in which a metal film having good solder wettability is formed on the entire chip, and FIG. 3 is a view showing an example of a metal film melting device. The components of the chip shown in FIG. 1 are basically the same as those of the conventional product shown in FIG. 4, but the glass layer 2 is not provided on the surface of the element body 1. In FIG. 3, 7 is a chip thermistor, 8 is a glass cylinder, 9 is a high boiling point heating solvent, 10 is a mantle heater, and 11 is a parts feeder. The first embodiment will be described by taking a chip thermistor using a thermistor material as an example.

First, a kneaded material obtained by kneading a thermistor material having a specific resistance of 20 Ω · cm and a binder is extruded into a sheet having a thickness of 0.5 mm, cut into a predetermined size, and fired at a temperature of 1300 ° C. The thermistor. The plate thermistor was cut into a size of 2.0 mm × 1.25 mm to obtain a chip thermistor element body 1. Ag paste is applied to both end faces of the element body 1 by a dip method and baked at 800 ° C. to form the terminal electrodes 4. A metal film (solder film) having good solder wettability was formed on the surface by electrolytic barrel plating. In this case, since the specific resistance of the element body 1 of the chip thermistor is as low as 20 Ω · cm, the metal film 3 is formed on the entire surface of the element body 1 and the terminal electrode 4 as shown in FIG. Next, the metal film 3 was heated and melted using the melting device shown in FIG. The structure of the melting apparatus is such that a glass cylindrical container 8 having a length of 150 cm and an inner diameter of 5 cm is installed vertically, and a product outlet is provided at the bottom. A heating solvent 9 (hereinafter referred to as glycerin) is put in the cylindrical container 8, and the cylindrical container 8 is heated by a mantle heater 10 provided on the outer periphery of the upper part, and a chip thermistor is opened from the upper opening of the cylindrical container 8. 7 is put into the parts feeder 11 to melt the metal film 3 on the surface of the element body 1 of the chip thermistor 7. In the method, only the upper portion of the glass cylindrical container 8 is heated to 200 to 280 ° C. by the mantle heater 10. Therefore, the glycerin 9 in the cylindrical container 8 repeats convection only in the upper part of the cylindrical container 8, and the lower part is kept at a temperature close to room temperature.
In this state, the chip thermistor 7 charged from the upper part of the cylindrical container 8 is heated to a temperature of 200 ° C. or higher, the metal film 3 on the surface thereof is melted, and the surface of the terminal electrode 4 is alloyed with the base metal to prevent solder wettability. A good metal layer 5 is formed, and the surface of the element body 1 gathers on the terminal electrode 4 side due to the surface tension of the molten metal, or becomes a metal ball on the surface of the element body 1. Then, it is cooled and solidified while gradually falling in the glycerin 9 by its own weight. Therefore, the chip thermistors 7 can be taken out from the lower portion of the cylindrical container 8 without sticking to each other. After cooling, the metal balls formed on the surface of the element body 1 of the chip thermistor 7 can be easily removed by ultrasonic cleaning. As a result, the metal film 3 is removed from the surface of the element body 1 of the chip thermistor 7, and the metal layer 5 having good solder wettability can be formed on the surface of the terminal electrode 4.

Although Ag is used for the terminal electrode 4 in this embodiment, Cu, an alloy of Ag and Pd, Pd, Au, Zn and N are used.
Even if an electrode material containing i or the like is used, and solder is used for the metal film 3 having good solder wettability, this is also a metal other than solder having good solder wettability, such as Sn or In, which melts at a relatively low temperature. If so, similar results are obtained. The method for forming the metal film 3 is not limited to plating, and methods such as vacuum deposition, sputtering and painting can be used. Further, as the heating solvent for the metal film 3, similarly, other than glycerin 9 can be used as long as it has a high boiling point. Further, when the treatment is performed in a gas instead of the liquid, it is necessary to use a horizontal heating device in which the chip thermistors 7 do not overlap each other.

[0013]

As described above, according to the present invention, good solder wettability can be achieved only on the surface of the terminal electrode without forming a special plating-resistant coating layer on the surface of the chip body as in the prior art. It becomes possible to manufacture a chip-type electronic component having a metal layer.

[Brief description of drawings]

FIG. 1 is a partially cutaway perspective view of a chip-type electronic component according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of a metal film formed on the chip type electronic component.

FIG. 3 is a sectional view showing a schematic configuration of a heating and melting apparatus for the metal coating.

FIG. 4 is a partially cutaway perspective view of a conventional chip-type electronic component.

[Explanation of symbols]

 1 Element body 3 Metal film 4 Terminal electrode 5 Metal layer 7 Chip thermistor 8 Cylindrical container 9 Heating solvent 10 Mantle heater 11 Parts feeder

Claims (3)

[Claims] 1. A method of forming a metal layer having good wettability with respect to solder on the surfaces of terminal electrodes formed on both end surfaces of the chip type electronic component, the method comprising: To form a metal film having good wettability by a surface coating method such as plating, coating, vacuum deposition or sputtering, and then heating the metal film in a gas or liquid to a temperature above its melting point to melt the chip. A method for manufacturing a chip-type electronic component, comprising: removing the metal coating adhered to a body portion of the mold electronic component and forming a metal layer having good wettability with respect to solder on the terminal electrode. 2. A chip-type electronic component provided with a metal film having good solder wettability on the entire surface is moved from a high temperature to a low temperature in a high boiling point liquid having a temperature gradient, and the metal film is melted on the high temperature side. A metal ball is formed on the surface of the base body of the chip-type electronic component, and an alloyed metal layer is formed on the surface of the terminal electrode. After cooling and solidification on the low temperature side, the metal ball on the surface of the base body is removed by ultrasonic cleaning. 1. A method for manufacturing a chip-type electronic component according to 1. 3. The element body of the chip-type electronic component is made of a thermistor material having an element body specific resistance of 500 Ω · cm or less.
Alternatively, the method for manufacturing the chip-type electronic component according to the item 2.