JPH0878279A - Formation of outer electrode on electronic chip device - Google Patents

Abstract

PURPOSE: To form an outer electrode excellent in solder heat resistance and solderability. CONSTITUTION: A paste containing a metal. powder, a glass and/or an inorganic oxide is baked on the side face of a bare chip 3 comprising a sintered ceramic to form an underlying electrode 4. The underlying electrode is then subjected to abrasion and the surface layer is removed partially before plating films 5, 6 are formed. When the surface layer of the underlying electrode is removed partially by abrasion, glass and inorganic oxide projecting from the surface are removed and thereby continuous plating layers 5, 6 can be formed easily on the surface of the underlying electrode. Consequently, an outer electrode excellent in solderability and solder heat resistance can be formed without decreasing the content of glass and/or inorganic oxide in the conductive paste for forming the underlying electrode and thereby ensuring the plating liquid permeation resistance and the bonding strength to a bare chip of the underlying electrode.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming an external electrode of a chip type electronic component such as a multilayer ceramic capacitor, a chip resistor, a chip thermistor, a chip inductor, etc. And an external electrode having excellent solder heat resistance and solderability.

[0002]

2. Description of the Related Art Chip-type electronic components such as multilayer ceramic capacitors, chip resistors, chip thermistors, and chip inductors are bare chips made of a ceramic sintered body, internal electrodes provided therein, and conduction to the internal electrodes. As described above, it is mainly configured with the terminal electrode provided on the side surface of the ceramic body, and is mounted by soldering this terminal electrode to the substrate.

Conventionally, the terminal electrodes of chip type electronic parts are formed as follows. That is, first, a mixture of a noble metal powder and a glass frit is kneaded in an organic vehicle, the obtained conductive paste is applied to the side surface of the bare chip, and then baked at a temperature of about 600 to 800 ° C. to form a plating base electrode. Form. After that, a Ni (nickel) plating film is formed on the base electrode to prevent cracking (corrosion) during soldering, and further, in order to prevent deterioration of solderability due to oxidation of the Ni plating film. , Ni
An external electrode is formed by coating the surface of the plating film with a Sn (tin) plating film or a solder plating film.

[0004]

The above-mentioned conventional method of forming external electrodes of chip-type electronic parts has the following problems. That is, the adhesion strength of the base electrode to the bare chip is increased,
In addition, in order to prevent the penetration of the plating solution during plating and to obtain high reliability, the paste for forming the base electrode contains a glass frit that has a strong adhesive force and high resistance to the plating solution. The glass frit softens and flows during the firing process of the base electrode, and often floats on the surface of the base electrode as the precious metal powder is sintered, forming a glass layer on the surface. However, if glass is present on the surface of the base electrode, the formation of the plating film on the base electrode is hindered, the surface of the plating film becomes discontinuous, and a continuous plating film without defects cannot be formed. In this case, the solder heat resistance and solderability of the terminal electrode are impaired.

In order to easily form a continuous plating film and secure solder heat resistance and solderability, it is necessary to suppress the amount of glass frit compounded in the paste for forming the base electrode. In this case, the adhesive strength of the base electrode is insufficient, and it is impossible to prevent the plating solution from entering.

The present invention solves the above-mentioned conventional problems and prevents the formation of a plating film on the surface of a base electrode when forming an external electrode of a chip-type electronic component, thus ensuring high reliability and solder heat resistance. Another object of the present invention is to provide a method for forming an external electrode having excellent solderability.

[0007]

According to a first aspect of the present invention, there is provided an external electrode forming method for a chip type electronic component, wherein a paste containing metal powder and glass and / or an inorganic oxide is applied to a side surface of a bare chip made of a ceramic sintered body. In the method of forming an external electrode by forming a plated film on the underlying electrode after baking to form the underlying electrode, a surface of the underlying electrode is polished to form a surface layer of the underlying electrode before the plating film is formed. It is characterized by removing a part.

According to a second aspect of the present invention, there is provided an external electrode forming method for a chip-type electronic component, wherein the Ni plating film is formed on a base electrode containing Ag or Ag and Pd as a metal. A Sn or Sn / Pb plated film is formed on the Ni plated film.

According to a third aspect of the present invention, there is provided a method of forming an external electrode for a chip-type electronic component, which is characterized in that the polishing treatment is performed by using polishing powder.

According to a fourth aspect of the present invention, there is provided an external electrode forming method for a chip-type electronic component, wherein the polishing powder is SiC polishing powder.

According to a fifth aspect of the present invention, there is provided an external electrode forming method for a chip-type electronic component, which is characterized in that in the third or fourth aspect, the polishing process is performed by using polishing powder and a surfactant.

According to a sixth aspect of the present invention, there is provided a method of forming external electrodes for a chip-type electronic component, wherein the chip-type electronic component is a laminated ceramic capacitor in the method according to any one of the first to fifth aspects.

The present invention will be described in detail below with reference to the drawings.

FIG. 1 is a sectional view showing a monolithic ceramic capacitor according to an embodiment of a chip type electronic component manufactured by the method of the present invention.

The illustrated monolithic ceramic capacitor 10 is
A surface mounting type chip capacitor, a bare chip 3 obtained by firing a green chip obtained by laminating a plurality of ceramic dielectrics 2 having an internal electrode 1 a plurality of times, a plating base electrode 4, a Ni plating film 5 and a solder plating. The film 6 is formed.

Here, as the ceramic dielectric 2, a lead-based or barium titanate-based dielectric is used.
As the internal electrode 1, a noble metal such as Pd, Pt, Ag / Pd or a base metal such as Ni, Cu, Fe or Co is used.

The plating base electrode 4 is made of Ag, Pd, Pt,
A conductive paste obtained by kneading one or more metals such as Cu and glass frit or inorganic oxide powder with an inert organic vehicle is applied to both end surfaces of the bare chip 3 made of the ceramic dielectric 2. It is formed by coating and baking.

Specifically, the bare chip 3 is coated with a conductive paste, dried at 150 to 200 ° C., and then 600
The plating base electrode 4 is baked by baking at ℃ to 800 ℃. At that time, the glass frit softens and flows, and often floats to the surface of the base electrode due to the sintering of the metal to form a glass and / or an inorganic oxide layer on the surface. For this reason, the glass and / or the inorganic oxide are present on the surface of the plating base electrode after firing.

In the present invention, after the base electrode 4 is formed on the bare chip 3, the surface of the base electrode 4 is polished to remove a part of the surface layer of the base electrode 4 to burn the base electrode 4. Then, the glass and / or the inorganic oxide that are raised on the surface of the base electrode 4 are removed.

As a polishing treatment method, for example, polishing powder such as SiC, a surfactant, water and a bare chip after baking of the plating base electrode are put in a pot and rotated for a predetermined time, and then the bare chip is sieved to remove the polishing powder. Separated from
The method of drying after washing | cleaning at 100 degreeC-150 degreeC is mentioned.

In this case, the type of the polishing powder used is not particularly limited, and polishing powder of SiC or other various inorganic substances can be preferably used. The particle size of the polishing powder is preferably appropriately coarse, and in the normal case, the particle size of about 300 to 500 μm is suitable.

If the amount of the polishing powder used is too small, the effect of polishing and removing the glass and / or the inorganic oxide on the surface of the plating base electrode according to the present invention cannot be sufficiently obtained, and if it is too large, the handling property and the cost of the polishing powder are reduced. Will be at a disadvantage. Therefore, the polishing powder is a volume ratio of the chip to the chip: polishing powder =
It is preferable to use it so as to be 1: 3 to 10. Also,
Water is preferably used in a volume ratio of 1: 5 to 20 with respect to chips.

When the surfactant is mixed with the polishing powder and water, the dispersibility of the polishing powder is poor only with the polishing powder and water, and the effect of polishing and removing the glass and / or the inorganic oxide according to the present invention is sufficient. This is because the surfactant cannot be obtained, but it is preferable to use the surfactant by adding it in a proportion of 0.5 to 1% by weight based on the total amount of the polishing powder and water.

As the surfactant, a nonionic surfactant or the like can be used.

The amount of the surface layer portion of the base electrode removed by the polishing treatment can be appropriately adjusted by controlling the rotation time of the pot. Normally, the rotation time is 60
Approximately 240 minutes, approximately 10 to 50 μm of the surface layer of the base electrode
It is preferable to remove the m thick portion.

The component polished and removed by this polishing treatment is not limited to glass, but may be glass containing a crystalline inorganic oxide, or may be all crystallized.

After such a polishing treatment, according to a conventional method,
The Ni plating film 5 and the solder plating film 6 are sequentially laminated.

In the method of the present invention as described above, the target chip type electronic component is not particularly limited, and the present invention is applicable to various chip type electronic components such as a monolithic ceramic capacitor, a chip resistor, a chip thermistor and a chip inductor. Is applicable to.

[0029]

[Function] The bare chip is coated with a conductive paste for forming an external electrode and baked, and then a part of the surface layer of the base electrode is removed by a polishing treatment to remove the glass and / or the inorganic oxide that is raised on the surface of the base electrode. After the removal, the continuous plating layer can be easily formed on the surface of the base electrode. Thereby, without reducing the glass and / or the inorganic oxide compounding amount of the conductive paste for forming the base electrode, and thus ensuring the resistance to penetration of the plating liquid of the base electrode and the adhesive strength to the bare chip, It is possible to form an external electrode having excellent attachability and solder heat resistance.

[0030]

EXAMPLES The present invention will be described more specifically with reference to Examples and Comparative Examples below.

The laminated ceramic capacitor chip used in the following is 4.5 mm × 3.2 mm × 1.25 mm made of lead perovskite ceramic dielectric.
The thickness of the conductive paste for forming the base electrode includes 75% by weight of Ag as a metal and 10% by weight of PbO—ZnO—B ₂ O ₃ —SiO ₂ -based glass frit as a frit with respect to Ag. % Contained Ag paste was used.

Example 1, Comparative Example 1 After coating Ag paste on a capacitor chip, 200
The substrate was dried at 0 ° C for 10 minutes, and then kept at 750 ° C for 5 minutes to burn the base electrode. Next, the surface of the base electrode was polished.

In the polishing treatment, a capacitor chip having a base electrode formed at the following ratio in a pot, SiC polishing powder (average particle size 200 μm), a surfactant (nonionic surfactant) and water were put, and the mixture was rotated for 120 minutes. It was done by doing.

SiC polishing powder: 10 times the volume of the capacitor chip Water: 20 times the volume of the capacitor chip Surfactant: 0.5% by weight based on the total weight of the polishing powder and water This polishing treatment As a result, the glass layer having a thickness of about 10 μm that was raised on the surface of the base electrode was removed.

After that, Ni was formed on the base electrode by a conventional method.
A plating film and a Sn / Pb film were sequentially formed (Example 1).

For comparison, an external electrode was formed on the capacitor chip in the same manner except that the polishing process was not performed (Comparative Example 1).

With respect to the obtained multilayer ceramic capacitor, solderability, solder heat resistance and Ni plating film coverage were examined by the following methods, and the results are shown in Table 1.

Solderability The prepared sample was immersed in an ethanol solution containing 25% by weight of rosin.
After the second dipping, the eutectic solder Sn / Pb (= 63 /
37 (weight ratio)) for 2 seconds. Then, it was examined by a stereoscopic microscope (× 15 times) whether or not the surface of the external electrode was covered with 90% or more of solder, and the case where the area covered with solder was 90% or less was determined to be defective.

Solder heat resistance The prepared sample was immersed in an ethanol solution containing 25% by weight of rosin.
After the second dipping, the eutectic solder Sn / Pb (= 63 /
37 (weight ratio)) for 30 seconds. After that, a portion without solder was examined by a stereoscopic microscope (× 15) and an optical microscope observation of a cross section, and a portion having no Ni plating film of 10% or more was determined to be defective.

Ni plating film coverage After the Ni plating film was formed, the surface of the terminal electrode was observed with an optical microscope to examine the coverage of the Ni plating film on the base electrode.

[0041]

[Table 1]

As is clear from Table 1, according to the present invention, a product having excellent solderability and solder heat resistance can be produced by forming a good plating film on the base electrode.

In the above-mentioned embodiment, the monolithic ceramic capacitor is exemplified, but the present invention is not limited to the monolithic ceramic capacitor, and all chip type electronic parts having external electrodes such as chip resistors, chip thermistors, chip inductors and the like. It goes without saying that it can be applied to.

[0044]

As described in detail above, according to the external electrode forming method for a chip-type electronic component of the present invention, a very reliable chip-type electronic component excellent in solderability and solder heat resistance is provided. It

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a monolithic ceramic capacitor according to an embodiment of a chip-type electronic component manufactured by the method of the present invention.

[Explanation of symbols]

 1 Internal Electrode 2 Ceramic Dielectric 3 Bare Chip 4 Base Electrode 5 Ni Plating Film 6 Solder Plating Film 10 Multilayer Ceramic Capacitor

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location H01G 4/252 4/30 311 E 7924-5E 9174-5E H01G 1/14 V

Claims (6)

[Claims] 1. A base electrode is formed by baking a paste containing metal powder and glass and / or an inorganic oxide on a side surface of a bare chip made of a ceramic sintered body, and then a plating film is formed on the base electrode. A method of forming an external electrode by a method of forming an external electrode of a chip-type electronic component, the method comprising: polishing a surface of a base electrode to remove a part of a surface layer of the base electrode before forming a plating film. . 2. The method according to claim 1, wherein N is formed on the base electrode containing Ag or Ag and Pd as a metal.
An i-plated film is formed, and Sn is deposited on the Ni-plated film
Alternatively, a method of forming an external electrode of a chip-type electronic component, which comprises forming a Sn / Pb plating film. 3. The method according to claim 1 or 2, wherein
A method of forming an external electrode for a chip-type electronic component, wherein the polishing process is performed using polishing powder. 4. The method according to claim 3, wherein the polishing powder is Si.
A method for forming an external electrode for a chip-type electronic component, which is C polishing powder. 5. The method for forming an external electrode for a chip-type electronic component according to claim 3, wherein the polishing treatment is performed using polishing powder and a surfactant. 6. The method according to claim 1, wherein the chip-type electronic component is a laminated ceramic capacitor.