JPS5815205A - Method of treating nickel electrode of ceramic electronic part - 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 The present invention relates to a processing method characterized by mechanical processing for improving the soldering properties of nickel electrodes of ceramic electronic components.

An example of a so-called Vh ceramic electronic component constructed using ceramic is a positive temperature coefficient thermistor. This positive temperature coefficient thermistor uses a barium titanate semiconductor ceramic as the substrate, and a general haze is added to the nickel electrode by electroless plating. However, electroless plated nickel electrodes do not have ohmic properties, and therefore, in order to satisfy this ohmic property, it is necessary to perform heat treatment at a temperature of 1 to 300 Cv.However, nickel has no ohmic properties. The change in free energy for oxide formation is greater than that of silver or copper.

In addition, the -tan produced oxide St is extremely dense and hard V.

Therefore, it is known that when the nickel electrode hard wire is attached after heat treatment, the No. 11 solder is extremely difficult to corrode as it is. To solve this problem, the following methods have traditionally been used: ◎ The first is to apply nickel, coat it with silver,
This is the method of burning it. In this case, the baking of the steel also serves as the process power and the ohmic heat treatment of the nickel.The second method is to use a strong chlorine-based flux.

However, all of the above-mentioned methodologies have their own problems. The first method described above uses expensive silver, which increases the cost, and also has problems such as the scissors being eaten away by the solder. On the other hand, the second method uses a strong flux, which affects the ceramic body and causes
This leads to deterioration of properties, and there is also the problem of corrosion due to residual chlorine.

Therefore, it is desired to realize a method that can perform good soldering on heat-treated nickel electrodes without using expensive silver or strong chlorine-based flux that causes deterioration of characteristics.

Therefore, the main object of the present invention is to provide a method for treating nickel electrodes of ceramic electronic components that can meet the above-mentioned needs.

Simply put, this invention is a processing method characterized by mechanically polishing the surface of a heat-treated nickel film to remove oxides.

The above-mentioned polishing includes, for example, mechanically polishing the nickel film using an abrasive and an elastic cloth in a reciprocating direction, a one-way direction, a rotational direction, or a combination of two or three thereof. will be carried out.

Typically a 1<7 polish is used. When this mechanical polishing is performed, oxides on the surface of the nickel film are removed, and a nickel electrode with excellent solderability is obtained.

Hereinafter, specific embodiments of the present invention will be described.

First, a disk-shaped titanium barium-based semiconductor ceramic was used as a substrate, and the surface thereof was electrolessly plated with nickel. Next, a heat treatment was carried out in which the substrate was held for 1 hour at various temperature conditions ranging from 350"C to 500"C.The ceramic substrate having the nickel film thus heat-treated is shown in FIG. It is shown as.

FIG. 1 is a perspective view of a polishing apparatus illustrating the polishing process.

Referring to FIG. 1, a polishing machine 5 is prepared in which a wool felt 4 having a thickness of 5 mm is attached to the outer peripheral surface of a reel 3 having a shaft 2 and having an outer diameter of 20 cm. A dropper 7 containing an abrasive 6 is arranged above the polisher 5. In the dropper 7, alumina powder 30F, which is used as the abrasive 6 to break down the particle size of 0.5 μm or less, is mixed with 100 cc of water and stored therein. Inside the dropper 7, a stirrer 8 rotates to prevent precipitation of the alumina powder. The abrasive 6 dropped from such a dropper 7 is supplied onto the felt 4. The ceramic substrate l having the nickel film to be polished is brought into contact with the felt 4 with a pressing force of about 100 to 2009. This polishing time is 30 seconds ~
A sample is prepared by being changed for 10 minutes. Such polished samples are designated by the reference numeral 9 in Figures 2 and 3.

FIGS. 2 and 3 are a front view and a side view, respectively, showing the appearance of a sample prepared for testing solderability. Referring to FIGS. 2 and 3, a 0.6-glue diameter wire was attached to sample 9, and then each of zinc chloride-based, halogen-containing rosin-based, and non-halogen weakly activated rosin-based 7 lux for a few seconds, 230”C ± 5°
It was immersed in tin-lead solder No. C for a few seconds. For each condition,
We made 10 samples each, and the average soldering results are shown in Table 9i1. 0 11th! In V), the solder adhesion area ratio was measured by visually observing the ratio of the spread of solder to the portion of sample 9 that was stuck to the electrode surface. Here, xx-I wonder if there is any solder attached at all.

Product X: 4 drops of solder adhesion area wheel 3011I.

(Solder adhesion area ratio 30% - 90chi is none) ○ ...Solder adhesion area ratio 90% or more.

◎　・・・Solder adhesion area car 1oon.

It shows.

The tensile strength of the lead wire is as shown in Figure 4.
The figure shows the tensile strength of the lead wire when the lead wire 0 is pulled in the direction of the arrow 11 with respect to the sample 9.

Also, in flux vh, l...Zinc chloride flux.

2...Halogen-containing C-gin-based flux.

3... Rosin-based flux containing stearic acid.

It shows.

Table 'l As is clear from Table 1, for those without polishing, that is, for the polishing time of 0 minutes, Norano (sample 7fL1 to 3):
When a weak flux was used, no solder adhered at all (sample thickness), and when a chlorine-based 7-lamp flux was used, solder began to adhere (sample mass 2°3), giving a satisfactory result. This was obtained only when a strong chlorine-based flux was used (sample layer 3).

However, when using such a chlorine-based 7RAX, the laminate substrate deteriorates and cannot be put to practical use.

On the other hand, those that were polished (samples A4 to 13)
has a satisfactory solder adhesion area ratio and lead wire tensile strength even when using a non-halogen weak flux. Note that samples at heat treatment temperature [35Q@C (samples A4 to 9)
], when comparing the polishing time of 1 minute (Samples 4 to 6) and 3 minutes (Samples 7 to 9), almost the same results are obtained. In addition, satisfactory results were also obtained for the samples (samples JK10 to JK12) in which the heat treatment temperature was raised to 500°C. In this case, by increasing the polishing time, the oxide film can be removed and the solderability can be improved (sample height 12). In other words, the polishing time can be selected depending on the heat treatment temperature.

υmentioned above? The samples shown in Table 1 were polished using felt and abrasive separately, and water was applied during polishing. Alternatively, it is also possible to polish using a cloth containing an abrasive in advance. In this case
9 below.

A non-woven fabric (commercially available) to which about 400 mesh of abrasive was attached was used in place of the felt 40 in step B for 7 hours, and the polishing was carried out without adding any new abrasive or water.The results are as follows: The results are shown in Table 2. In Table 2, the numbers representing the flux, the symbols for evaluating the solder adhesion area ratio, and the method for testing the lead wire tensile strength are the same as in Table 1.

No. 251! ! As is clear from Table 11!2, it can be seen that almost the same results as V in Table 1, so-called neuf polishing, can be obtained even when a nonwoven fabric containing an abrasive in advance is used. However, in this case, since the polishing ability is higher than that of puff polishing, care must be taken because if the polishing time is prolonged, not only the oxide film on the surface of the nickel film but also the nickel film itself may be removed. Therefore, in this case, the polishing time was chosen to be 30 seconds to 1 minute.

Next, we will compare the life characteristics of the electrode obtained according to the present invention and a conventional electrode made of nickel with chains baked into it. This life characteristic was determined by determining the rate of change in resistance value. FIG. 5 is a graph showing life characteristics. As shown in Figure 5, the sample was a finished product that had been subjected to exterior dipping, and the test conditions were a voltage of 200V to each electrode. It was applied continuously in a normal humidity atmosphere.

In FIG. 5, those plotted with circles and connected with solid lines indicate conventional nickel electrodes on which chains are baked. Those plotted with Δ marks and connected with dotted lines indicate Sample &5 in Table 1. The horizontal axis shows the voltage application time (minutes), and the vertical axis shows the resistance value quality and resistance rate (chi). % As shown in Fig. 5, sample A5 is made of rosin-based slacks containing a small amount of carbon dioxide, and the conventional chain burn-in shows almost the same life characteristics as the nickel electrode. I understand.

As described above, according to the present invention, oxides on the surface of the heat-treated nickel J film are removed by mechanical polishing, so soldering is possible with excellent soldering properties. A nickel electrode can be obtained. Therefore, since a weak flux can be used during this soldering, there is less deterioration of the ceramic board, and therefore the characteristic deterioration force f
less, and reliability is improved. In addition, since there is no need to use expensive silver, a very inexpensive electrode can be obtained. Not using this chime reduces the number of steps, leading to further cost reductions.

Thus, it can be said that this invention is extremely effective in practice. The nickel electrode to which this invention is applied is
In addition to the above-described positive temperature coefficient thermistor, it may also be an electrode of an electronic component such as a ceramic capacitor. Furthermore, the present invention is equally applicable to electronic components that are directly soldered to a printed circuit board as a chip or to electronic components that have lead wires attached in advance by soldering.

The nickel film to which this invention is directed is not only formed by electroless plating, but may also be formed by vacuum evaporation, sputtering, etc.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of a polishing apparatus illustrating the polishing process. FIGS. 2 and 3 are a front view and a side view, respectively, showing the appearance of a sample prepared for testing solderability. FIG. 4 is a front view of a sample illustrating the state of measurement of lead wire tensile strength. FIG. 5 is a graph showing life characteristics. In the figure, l is a ceramic substrate, 41 is felt, 5 is
is a polishing machine, 6 is an abrasive, and 94 is a sample. Figure 1 Attached figure Figure 5 added/li 'Sword 21-

Claims (1)

[Claims] (1) Including the steps of forming a nickel film to serve as an electrode on the surface of a ceramic substrate, further heat-treating the nickel film, and mechanically polishing the surface of the heat-treated nickel film to remove oxides. Nickel electrode treatment method for ceramic electronic components. Q1 The polishing is puff polishing, Claim No. tl
) A method for treating nickel electrodes of ceramic electronic components as described in section 2.