JPH02296314A - Manufacture of chip component - 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] Industrial Application Field The present invention relates to a method for manufacturing chip components such as multilayer ceramic capacitors, which are a type of electronic circuit component that contributes to the miniaturization, weight reduction, and thickness reduction of electronic devices. This is related to 2.-7.

BACKGROUND OF THE INVENTION In recent years, as electronic devices have become lighter, thinner, and smaller, demand for chip components such as multilayer ceramic capacitors has been increasing. Regarding such chip components, the present inventors previously reported in Japanese Unexamined Patent Application Publication No. 15401/1983 that the surface of the terminal electrode portion is made smooth to improve the reliability of soldering when mounting on a printed circuit board. We proposed a structure that allows

The manufacturing process of this chip component will be explained using a multilayer ceramic capacitor as an example, with reference to FIGS. 2(A) to 2(D). First, a metal glaze paste based on IT alloys such as Pd is coated as an internal electrode on the surface of a ceramic dielectric such as titanium or barium using a screen printing method, and this is sequentially manipulated to form a ceramic dielectric. A sheet in which internal electrodes were alternately laminated was produced), and this sheet was punched into individual pieces of the required dimensions to produce a capacitor element material in which internal electrodes were exposed alternately on the opposite end faces. This was fired at a high temperature of 1 aoo'c to produce laminated and fired ceramic capacitor elements in the form of individual pieces. FIG. 21(m) shows a ceramic capacitor element manufactured as described above, in which 1 is a ceramic dielectric and 2 is a Pb-based internal type electrode.

Next, as shown in FIG. 2(B), a conductive wire is attached to both ends of the individual piece-shaped ceramic capacitor element made as described above.
Ag paste, which is a raw metal, was applied and baked to form an Ag-based electrode film 3. Although Ag is used here, C
It is possible to use materials that have electrical conductivity, such as U, Ni, and alloys thereof.

Next, as shown in FIG. 2(G), conductive metal is deposited by barrel plating on the Ag-based electrode layers 3 at both ends of the ceramic capacitor element having the Ag-based electrode films 3 formed at both ends as described above. Using N1, the Ni film 4 has a thickness of 3
It was formed at ~5 μm.

Next, as shown in the second fl (D), a conductive metal such as Sn or an alloy of Sn and Pb is applied to the Ni film 4 at both ends of the ceramic capacitor element by the same barrel plating method. was formed with a thickness of 3 to 5 μm.

Thereafter, heating and melting treatment is performed at a temperature higher than the melting point of the solder film 5, which is the outermost layer metal film of the terminal electrode part, to form a solder 1 pattern 5a as the outermost layer and film, as shown in FIG. 2(E). By doing so, a multilayer ceramic capacitor was manufactured. Here, the above-mentioned heating and melting treatment is performed in the above-mentioned Japanese Patent Application Laid-open No. 63-1
As shown in Publication No. 5401, for example, FIG. 2(D)
After immersing the ceramic capacitor element manufactured in the state shown in , in a rosin-based flux, the outermost layer of the terminal electrode part is remelted by performing a heat treatment at a temperature higher than the melting temperature of the solder film 5. A solder film 5& made of a metal film can be formed.

Also, the base of Handa j 5 (6a) (here N1 4)
It is necessary that the metal material has a higher melting point than the solder film 5 (5a) and has good affinity with the solder film 5 (5a).

Problems to be Solved by the Invention However, in the method of manufacturing a chip component previously proposed by the present inventors, the solder film 6, which is the outermost electrode film of the terminal electrode part, is heated and melted (when the surface is A situation occurred in which the molten metal moved due to the tension, and the thickness of the molten metal at the corners was lost.
As shown in E), at the corner A of the outermost electrode film, the second metal film, that is, the N1 film 4, was deliberately exposed from the solder layer 5 (5a), which is the outermost electrode film. Due to the oxidation of this metal film (Ni+Picture 4), mounting solder on the printed circuit board is sometimes difficult, and soldering does not adhere to that part, which is a problem. It had

The present invention attempts to solve this problem,
The purpose of mounting soldering is to provide a method for manufacturing chip components that does not cause defects.

Means for Solving the Problems In order to solve the problem in section 9, the present invention provides two functional elements.
A conductive metal film made of gold other than Sn or an alloy of Sn and Pb is formed on at least one layer of the conductive metal film as a base for the electrode 1, and a conductive metal film is formed on the base conductive metal film. The outermost electrode film of the electrode film has a melting point S of the second layer counting from the outermost electrode film.
layer of an electrode film made of an alloy of Sn or Sn and Pb. After forming an alloy of Sn and Pb with a lower temperature than one point, a second layer counting from the melting point of the outermost electrode film and the outermost electrode film is formed. The electrode film is heated and melted at an intermediate temperature on the joint surface of the electrode film.

Effect: According to this manufacturing method, since the metal film of the outermost layer of the terminal electrode is heated and melted, the surface area becomes smaller than before heating and melting due to the surface tension that acts during melting, which smooths the surface and makes it easier to store. The adhesion of foreign matter and adsorption of gas inside the product are extremely reduced, ensuring reliable soldering even during long-term storage. In addition, since foreign substances and gases that have been adsorbed or occluded on the surface or inside the recesses are released during melting, the outermost layer itself becomes clean and free of impurities, and the solder film brittleness and solderability are reduced. This will lead to improved reliability. Since the heating and melting treatment is performed at a temperature between the melting point of the outermost electrode film and the melting point of the second electrode film counting from this outermost electrode film, only the outermost electrode film is melted. When molten metal moves due to surface tension, it is the second layer of electrode film counted from the outermost electrode film that is exposed at the corner.
Since the electrode film in the second layer is also made of Sn or an alloy of Sn and Pb, there is no possibility that soldering defects may occur when soldering to a printed circuit board, where the solder sometimes does not adhere to the corners. Therefore, the reliability of soldering can be improved.

EXAMPLE Hereinafter, an example of the present invention will be described with reference to the drawings.

FIGS. 1(M) to (I') are cross-sectional views showing the manufacturing process of a multilayer ceramic capacitor according to an embodiment of the present invention.
The process of forming the terminal electrode portion is mainly shown.

In Figs. 1 (M) to (F), 1 is a ceramic dielectric, 2 is a Pd-based internal electrode, 3 is an Ag-based electrode film, and 4 is a Ni film, which are the same as the conventional example in Fig. 2. belongs to.

Further, 6 is a Sn film, and 7 is a Sn film with a composition ratio of Sn and Pb of 60:
40 is the solder film, 71L is Sn that has been heat-melted.
The solder film has a composition ratio of Pb and Pb of 60:40.

Next, the manufacturing process of the multilayer ceramic capacitor according to this example will be explained. First, the steps from FIG. 1(M) to FIG. 1(G) are the same as the steps from FIG. 2(M) to (0) of the conventional example, and the explanation thereof will be omitted. Then, DI film 4 is placed on both ends.
As shown in FIG. 1(D), a Sn film 6 is deposited on the Ni film 4 on both ends of the ceramic capacitor element formed with Sn, which is a conductive metal, by barrel plating.
was formed with a thickness of 3 to 6 μm. Then, Fig. 1 IC)
As shown in FIG. 2, the soil of the Sn film 6 on both ends of the ceramic capacitor element having the Sn film 7 formed thereon was coated with the same barrel plating method, and the composition ratio of Sn and Pb, which are conductive metals, was 60: Use a solder with a thickness of 40, and a solder film with a thickness of 1
It was formed to have a thickness of ~2 μm.

Next, as mentioned above, the composition ratio of Sn and Pb is 60:
By subjecting a ceramic capacitor element having a solder film 7 of No. 40 formed on both ends thereof to heat-melting treatment, the heat-melted Sn and Pb as shown in FIG.
A solder film 7a having a composition ratio of 60:40 is formed. The above-mentioned heating and melting treatment in this example was carried out using coconut oil, which is a high-boiling liquid, in a glass cylindrical container, as disclosed in Japanese Patent Application Laid-Open No. 63-29905, which was previously proposed by the present inventors. The coconut oil in the container is made to have a temperature gradient that becomes lower as it goes downwards, and the coconut oil in the container is heated from the high temperature side to the low temperature side as shown in Figure 1 (IC). The ceramic capacitor element with the solder film 7 formed on the outermost layer at both ends is moved as shown in FIG. The solder film 7a was formed by cooling and solidifying the solder film 7a. Here, the temperature of the high-temperature part, which is the heat-melting processing part, is the melting point (1 sa 'c) and the melting point (232'C) of the Sn film 6 which is the second layer counting from the outer layer part of the top 10 page, which is 200 °C,
The melting time was 1.5 seconds.

Table 1 below shows samples with various terminal electrode structures prepared by the same method as explained above, and the heating melting treatment temperature and the breakage of the Sn film or Sn and Pb alloy film at the corners. Width, soldering after being placed in a humid bath at 86° C. and 85° C. for 240 hours shows reliability and solder wetting time. Sample 1 shown in Table 1 is based on the above example. Here, the cutting width of the Sn film or the alloy film of Sn and Pb at the corners was measured by polishing the cross section of the ceramic capacitor element and using a metallurgical microscope. In addition, regarding soldering reliability, those in which the area of the part to which no solder adhered accounted for 6% or more of the entire terminal electrode part were judged to be defective. Further, the solder wetting time was measured by the meniscograph method. Note that the terminal electrode structure in the table shows the number of layers counted from the outermost layer and the components of each layer.

As shown in Table 1 above, when the terminal electrode packaging is viewed from the outermost layer side, there is a single layer of Sn, a single layer of 3N and Pb alloy, and S
In the case of sample 4.5, in which the first and second layers are made of a metal other than n or an alloy of Sn and Pb, respectively, the Sn film at the corner part is not yet Sn. Breaks occurred in the Pb alloy film, and many soldering defects occurred. Furthermore, even in cases such as sample 6, where the heating and melting treatment was performed at a temperature higher than the melting point of the first and second layer electrode films, counting from the outermost layer, the soldering was also defective. It happened a lot.

Then, the outermost electrode film is formed of an alloy of Sn and Pb,
The second electrode film counting from the outermost 4 films is
The outermost electrode film was formed from an alloy of n or Sn and Pb, and the melting point of the outermost electrode film was lower than that of the second electrode film, and was subjected to heating 4 melting treatment at a temperature between the melting points of both. Samples 1 and 2.3 according to the present invention had good characteristic results as shown in Table 1, respectively. In addition, in sample 2, S was found in the third layer counting from the outermost layer.
This is an example in which an N film is provided, and the above-mentioned N1 film and Ag-based electrode film are formed below it. The second layer Sn/Pb = 90/10 solder film has a higher melting point than the second layer Sn/Pb-90/10 solder film, and the third layer Sn/Pb-90/10 solder film The melting point of the membrane is high A
Ru.

In the above embodiment, only a multilayer ceramic capacitor was described, but the present invention is not limited thereto, and similar effects can be obtained with a square plate-shaped chip resistor. In addition, the Sn formed on the terminal electrode part
The base of the at least two electrode films made of an alloy of Sn and Pb is not limited to the N1 film and the Ag-based electrode film in the main example.
A combination of B-alloy, 1-Pb alloy, etc. may be used, and the point is that at least one conductive metal film consisting of Sn and a-group other than the alloy of Sn and Pb is provided.

Effect of the Invention 14 /, -7 As described above, according to the present invention, the outermost electrode film of the terminal electrode portion has a melting point of 21st as counted from the outermost electrode film.
- After forming the electrode film with Sn or an alloy of Sn and Pb whose melting point is lower than the melting point of the electrode film made of an alloy of Sn and Pb, a second layer counting from the outermost electrode film and the outermost electrode film is formed. By heating and melting the electrode at a temperature intermediate to the melting point of the electrode, it is possible to improve the solder wettability and the reliability of soldering for long-term storage. In particular, since the heating and melting treatment was carried out at a temperature between the melting point of the first layer electrode film and the melting point of the second layer electrode film, counting from the outermost layer, the melting point was the lowest melting point. The outer layer weight + i is only the film, and if the molten metal moves due to surface tension, the electrode film of the second layer counting from the outermost layer is also Sn or Sn exposed at the corner. By being made of an alloy of Pb and Pb, soldering defects that sometimes occur when soldering to printed circuit boards does not adhere to the corners, and the reliability of soldering is improved. This has the effect of being able to do this.

[Brief explanation of drawings]

Figures 1 (M) to (F) are cross-sectional views showing the manufacturing process of a laminated ceramic wolf/answer according to the method of the present invention, and Figure 2 (M)
~(IC) is a sectional view showing an actual speed process of a multilayer ceramic capacitor in a conventional example. 1...Ceramic dielectric, 2...Pd-based internal electrode, 3...Ag-based electrode film, 4...Ni
Film, 6...8n film, 7+71L...solder film.

Claims (1)

[Claims] A conductive metal film made of a metal other than Sn or an alloy of Sn and Pb is formed on both ends of the functional element as a base for at least one electrode film, and further an electrode is provided on the conductive metal film as the base. The outermost electrode film of the film is Sn or S whose melting point is the second layer counting from the outermost electrode film.
Sn and P are lower than the melting point of the electrode film made of an alloy of n and Pb.
A chip component formed of the alloy of (b) and then heated and melted at a temperature between the melting point of the outermost electrode film and the melting point of the second electrode film counted from the outermost electrode film. manufacturing method.