JPS5969908A - Method of forming external electrode of chip type electronicpart - 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 Field of Industrial Application The present invention relates to a method for forming external electrodes of chip-shaped electronic components used in printed wiring boards and the like of electronic components.

Conventional configurations and their problems In recent years, electronic components have become more and more chip-based, with capacitors, resistors, etc. being representative examples. Improving soldering properties and soldering heat resistance are becoming important.

FIG. 1 shows the specific structure of a chip component 1 made of ceramic as a substrate, and Aq with a Pct content of 20 to 30.
The external electrode 2 may also be formed using a -Pd alloy.

It is well known that the external electrodes of the chip-type electronic components configured as described above contain a large amount of PB gold to prevent silver corrosion, which increases the cost. The Aq-Pd external electrode has the disadvantage that soldering heat resistance cannot be sufficiently guaranteed because the conditions for attaching it are becoming stricter and the number of immersions in a soldering bath is generally increased.

On the other hand, from the viewpoint of improving the heat resistance of semi-finishing and soldering,
A method has been proposed in which a Ni and Sn or Sn-Pb electrode layer is formed on Pd by electrolytic plating, but N
Since the Sn and Sn plating solutions use strong acids with pH 4 and PH 1 to 2, highly acid-resistant glass frits (hereinafter referred to as G and F) must be used for Ag-Pd. Currently, the acid-resistant G and F considered are Δ1203.
G and F, which contain a large amount of SiO2 and the like and have relatively light specific gravity, are used. However, the electric current (G and F on the electrode surface when baking the pot)
, which had the disadvantages of floating and cracking, poor plating coverage during Ni plating, and failure of soldering in the finished product after Sn4 plating with PB.

Purpose of the Invention In view of the above-mentioned drawbacks, the present invention has been developed by forming two types of Aq electrode layers with different glass contents, on which a N1 layer is formed by electroless or electroplating, and furthermore, a Sn layer is formed by electrolytic plating on top of the N1 layer. Or form a Sn-Pb electrode layer and
This provides a method for forming external electrodes with excellent heat resistance and soldering properties without using solder.

Structure of the Invention In order to achieve this object, the method for forming external electrodes of chip components of the present invention is based on the premise of a plating process with excellent solder heat resistance, and a method for forming external electrodes of chip components using a method of forming external electrodes of a chip component containing 7 to 20% of G and F, which have excellent acid resistance. 1A
The q electrode layer is formed, and the second layer is G, F, which has a relatively large specific gravity and little glass lifting, and the second layer has a force of 2 to 4%.
The third electrode layer and the fourth electrode layer thereon are made of Ni and Sni, respectively.
It is composed of n-Pb. According to this configuration,
Chip components having external electrodes with excellent soldering properties and soldering heat resistance can be obtained.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 2 shows a cross-sectional state of an external electrode of a chip component in an embodiment of the present invention.

In FIG. 2, 1 is a chip component having a ceramic substrate as in FIG. 1, and 3 is a first A containing 7 to 20% of G, F, and i as main components (Si02+Al203).
g electrode layer. 4 is a second Ag electrode layer containing G and F whose main components are P bo T S 102 in a total amount of 2 to 4%. 5 is a Ni layer as a third electrode layer formed by electrolytic plating or electroless plating, and 6 is a Sn layer as a fourth electrode layer formed by electrolytic plating.
-P b layer. FIG. 3 shows the relationship between the electrode adhesion strength after six layers of plating and the G, F, and content rates in the first electrode layer 3. In FIG. 4, the Nf plating yield is obtained by surface elemental analysis of the relationship between the G, F, content and S i /A g ratio in the second electrode layer 4 using an X-ray microanalyzer. Si/Ag ratio is 6
By forming the third electrode layer and the fourth electrode layer by plating when the temperature is less than 98%, the solderability is good, and the solderability is 98% or more.

When the content of G and F in the first Aq electrode layer 3 is less than 7 parts, the electrode adhesion strength is 1Kg /
cnf or less, and the strength of the finished product as an external electrode terminal is poor, resulting in a decrease in quality. In addition, the content of G, , F is 20. %, glass components will precipitate on the surface,
Adhesion with the second 8th q electrode layer 4 decreases. And the second
When the G and F content of the 8q electrode layer 4 exceeds 4 parts, the glass component floats to the surface and the coverage of the plating becomes poor.
G again.

If the content of F is less than 2%, the adhesive effect due to the glass component is reduced, resulting in poor adhesion to the first Ag electrode layer 3.

In this way, G and F have excellent acid resistance in the first electrode layer.

An Aq electrode layer containing 7 to 20% is formed, a second electrode layer is entirely formed with an Ag electrode layer containing G, F, and 2 to 4%, and then a third electrode layer and a fourth electrode layer are plated. is the electrode adhesion strength 1. It has OK9/rtU or more and can ensure solderability of 98% or more. As described above, the first electrode layer is formed of silver containing 7 to 20% of G and F, the second electrode layer is formed of silver containing 2 to 4% of G and F, and the third electrode layer is formed of silver containing 2 to 4% of G and F.
According to the method of forming the electrode layer and the fourth electrode layer by plating, it has become possible to obtain an external electrode that has excellent adhesive strength with the ceramic substrate, and has excellent solder heat resistance and solderability.

Effects of the Invention As described above, according to the present invention, it is possible to provide a chip 70 component having an external electrode that is inexpensive, has excellent solderability and soldering heat resistance, and its industrial value is extremely high. .

[Brief explanation of the drawing]

Fig. 1 is a sectional view of a conventional 6-chip component, Fig. 2 is a sectional view of a 0-tick part in an embodiment of the method of the present invention, and Fig. 3 is an adhesion after being immersed in a plating solution for 60 minutes to explain the present invention. Figure 4 shows the relationship between strength and content of G, F, and content. FIG. 3 is a surface elemental analysis diagram showing the relationship between content and S i /A g ratio. 1...Chip parts using ceramic as a substrate, 3
. . . 1st Ag electrode layer, 4 . . . 2nd AC
! Electrode layer, 5...Ni layer, 6...Sn
4 or 5n-Pb layer. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
figure! =27- Fig. 3 - Riparasufu 1 not toi 1 ari (φ)

Claims (1)

[Claims] When forming external connection electrodes for chip components using ceramic as a substrate, an electrode layer consisting of 80 to 93% silver and 20 to 7% glass is formed as the first electrode layer, and silver is used as the second electrode layer. An electrode layer consisting of 96 to 98% glass and 4 to 2 pieces of glass is formed by electrolytic plating or electroless plating to form a third electrode layer of Ni, and on top of that a Ni layer is formed by electrolytic plating as a fourth electrode layer. A method for forming an external electrode of a chip-shaped electronic component, comprising forming an electrode layer made of Sn or Sn-Pb.