JPS6325493B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of forming electrodes by electroless plating on the surface of an element body made of a ceramic substrate or the like.

As a method for forming electrodes on various electronic components such as oxide ceramic semiconductors such as ceramic capacitors, positive temperature coefficient thermistors, or varistors, or wiring patterns of IC boards, electroless methods mainly composed of base metals such as nickel and copper have been used. The Metsuki method is known.
This electroless plating method is used to reduce costs by substituting for expensive silver, or to effectively bring out the electrical properties of the element, but it also improves the adhesion of the electroless plating layer. Therefore, it is necessary to activate the electrode forming region of the element body in advance. Conventionally, when activating this elemental body,
The element body was immersed in a solution of palladium chloride PdCl ₂ , tin chloride SnCl _{2 ,} etc., so that the palladium Pd or tin Sn attached to the surface of the element body acted as a catalyst for the plating reaction. FIGS. 1a to 1e are diagrams for explaining this conventional electrode forming method.

First, the element body 1 (Fig. 1 a), which has been subjected to pre-treatments such as surface roughening, cleaning, degreasing, drying, and sensitization, is
The entire surface of the element body 1 is activated by immersing it in a solution 2 such as PdCl ₂ or SnCl ₂ (FIG. 1b). Said
_PdCl2 or _SnCl2 solution 2 has a concentration of 0.01-0.05%
It is a dilute aqueous solution of about
Immerse in the liquid for 1 to 2 minutes at a temperature of 25°C. After this, when element body 1 is pulled up from solution 2, element body 1
A catalytic agent 3 such as PdCl ₂ or SnCl ₂ that serves as an initiator for the plating reaction is deposited on the entire surface (Fig. 1c).
When the element body 1 thus obtained is immersed in an electroless plating bath 4 containing nickel or copper as the main component (Fig. 1d), the elements adhere to the entire surface of the element body 1.
PdCl ₂ or SnCl ₂ serves as a catalyst for the plating reaction,
An electroless plating layer 5 is deposited on the entire surface of the element body 1 (FIG. 1e).

Next, after passing through a cleaning and drying process, unnecessary portions of the plating layer 5 are removed by chemical etching or centerless polishing (FIG. 1f) to form a predetermined electrode pattern, and then cleaning is performed. Through necessary processes such as heat treatment, a tin and solder plating layer is applied on top of the plating layer 5 to improve solderability, and further cleaning,
Completed after a drying process.

As mentioned above, conventionally, when activating the element body, the element body is immersed in a PdCl ₂ or SnCl ₂ solution,
Because the method used was to form an electroless plating layer on the entire surface of the element, selective plating limited only to the electrode formation area was impossible. It had to be removed by etching or centerless polishing. Therefore, the conventional electrode forming method has the following drawbacks.

(1) The manufacturing cost is high due to the large number of steps, such as the process of removing unnecessary plating layers and the pretreatment process before entering the activation process.

(2) When unnecessary plating layer 5 is removed by centerless polishing or sandblasting, etc., the plating layer 5, which is a metal layer, is directly removed mechanically, so interfacial peeling of the plating layer 5, decrease in adhesive strength, This tends to cause deterioration over time, breakage or cracking of the element body 1, generation of microracks, etc., and it has been extremely difficult to manufacture highly reliable products at a high yield. Particularly in cases where the element body is thin, commercialization has sometimes had to be abandoned due to a lack of mechanical strength.

(3) For centerless polishing, as shown in Figure 1f, approximately 10 to 15 elements 1 are connected in a series using an adhesive 6 such as paraffin, and centerless polishing is performed in this state. It is customary to do
Even if such measures are taken, the plating layer 5 will still be removed directly, so the above-mentioned drawbacks will not be removed, and instead the process will be complicated, damage to the plating layer 5, and the plating layer 5 will be removed. This tends to cause difficulty in separating the element body 1 due to the spread and entanglement of the particles.

(4) When unnecessary parts of the plating layer 5 are removed using a chemical etching method, there are many etching steps, which increases manufacturing costs. This tends to lead to deterioration of various properties.

(5) Since this method simply performs electroless plating on the element body 1, the adhesive strength of the plating layer 5 is weak, and residual ions of the plating solution are present at the interface between the plating layer 5 and the element body 1. This tends to cause peeling of the plating layer 5, resulting in deterioration of various electrical characteristics or deterioration over time. In addition, in the positive temperature coefficient thermistor, in order to obtain ohmic contact, a frit-containing silver baked electrode is formed on the plating layer 5.
Methods have been proposed to improve the adhesive strength of silver, prevent deterioration over time, and improve solderability, but silver is a finite resource and has recently increased in price, so This results in increased costs.

The present invention eliminates the above-mentioned conventional drawbacks, and makes it possible to form an electroless plating layer in a predetermined pattern directly on the electrode formation area of the element body without requiring a plating layer removal process. It is an object of the present invention to provide an electrode forming method that is economical with a small number of electrodes and can form highly reliable electrodes.

In order to achieve the above object, the method for forming an electrode of an electronic component according to the present invention includes, when forming an electrode made of an electroless plating layer on the surface of an element body, a glass frit is applied to the electrode formation region of the element body. The present invention is characterized in that a catalyst paste containing the catalytic material and serving as a catalyst for the electroless plating reaction is applied, and then electroless plating treatment is performed.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The content of the present invention will be specifically described below with reference to the accompanying drawings, which are examples. FIGS. 2a to 2d are diagrams showing the steps of the method for forming electrodes of electronic components according to the present invention.

Catalyst paste 7, which serves as a catalyst for the glass frit electroless plating reaction, is applied in a predetermined pattern to the electrode forming regions on both sides of the element body 1 (FIG. 2a), which has been formed to have a predetermined shape. For example, it is applied by means such as screen printing. The catalyst paste 7 is preferably a paste containing the same amount of Pd or Sn as a conventional catalyst solution consisting of PdCl ₂ and SnCl ₂ . Specifically, for example 99
A paste containing 1% of Pd chelate (palladium ethylenediaminetetraacetate), Pd fatty acid salt, or tin chloride is suitable.

Next, the element body 1 coated with the catalyst paste 7 is passed through a furnace and heated at a temperature of around 300°C for about 10 to 60 minutes, thereby decomposing and liberating the organic matter in the catalyst paste 7, as well as Pd, Sn, etc. A metal component of is baked onto the surface of the element body 1. In this case, since a small amount of vitreous frit such as lead borosilicate glass powder is added to the catalyst paste 7 in advance, the frit adheres to the interface of the element body, as in the case of baking a well-known frit-containing silver paste. Metal components such as Pd and Sn can be firmly adhered to the element body 1 by the melted frit.

Next, element body 1 is added to a 1% hydrochloric acid aqueous solution for 10
After being immersed for about a minute to activate, and further washed with water, it is immersed in an electroless plating bath 8 (FIG. 2c). The electroless plating bath 8 may basically be a nickel-based or copper-based bath having a composition well known in the art. Nickel-based electroless plating baths include nickel chloride-sodium hypophosphite-sodium hydroxyl acetate bath, nickel chloride-sodium hypophosphite-sodium citrate bath, nickel sulfate-sodium hypophosphite-sodium acetate bath, and nickel chloride-sodium hypophosphite-sodium acetate bath. A nickel-sodium hypophosphite-sodium succinate bath is suitable; copper-based electroless plating baths include a copper sulfate-sodium tartrate bath and a copper sulfate-sodium plating bath.
A sodium EDTA bath is suitable.

Place element 1 in these electroless plating baths at a bath temperature of 80~
Soak at a temperature of about 90°C for about 5 to 30 minutes.
In this case, metal components such as Pd and Sn baked on the surface of the element 1 act as catalysts for the electroless plating reaction, so the catalyst paste applied area provided on the electrode formation area of the element 1 is Although the electroless plating layer is deposited in the area where the catalyst paste is not applied, the electroless plating layer cannot be deposited on other parts where the catalyst paste is not applied. 9 will be formed (FIG. 1d).

In this way, the plating layer 9 was selectively formed only in the electrode forming area, and after further washing with water and drying, the plating layer 9 was formed in an N ₂ atmosphere for the purpose of improving adhesion.
Heat treatment is performed at a temperature of around 400℃ for about 1 hour. As a result, the frit that had adhered to the surface of the element 1 is dissolved again, and the melted frit allows the plating layer 9 to firmly adhere to the surface of the element 1 without residual ions of the plating solution remaining on the interface. This effectively prevents interfacial peeling of the electrodes, deterioration of electrical characteristics, and deterioration over time.

Through the above steps, the electronic component according to the present invention is
Now you can solder the lead wire to the electrode.
Furthermore, tin and solder plating may be applied to the plating layer 9 according to the soldering conditions to improve solderability, followed by washing and drying. In this way, the structure in which tin/solder plating is applied on the plating layer 9 can provide an electrode structure that is much cheaper than silver baking and has excellent solderability.

As described above, in the method for forming an electrode of an electronic component according to the present invention, when forming an electrode made of an electroless plating layer on the surface of an element body, the electrode formation region of the element body contains glass frit. Since the method is characterized in that a catalyst paste serving as a catalyst for the electroless plating reaction is applied and then an electroless plating treatment is performed, the following effects can be obtained.

(1) Electroless plating can be applied selectively only to the electrode formation area. As a result, (a) the step of removing unnecessary portions of the electroless plating layer becomes unnecessary, the number of steps is reduced, mass productivity is improved, and manufacturing costs are reduced.

(b) There is no room for various problems such as interfacial peeling of the plating layer, decrease in adhesive strength, deterioration over time, damage or cracking of the element body, and generation of micro-cracks, as seen in centerless polishing, etc. Highly reliable products can be manufactured with good yield.

(c) Even if the thickness of the element body becomes thinner, electrodes can be formed using electroless plating layers without any problems.

(d) There is no possibility of damage to the element as seen in chemical etching processes.

(2) By including glassy frit in the catalyst paste, the adhesion strength of the plating layer to the element body can be improved, and interfacial peeling, deterioration over time, etc. can be effectively prevented. Moreover, it is much cheaper than the case of improving adhesion strength using the conventional silver baking method.

(3) As shown in the example, by applying tin/solder plating on the plating layer, it is possible to form electrodes with excellent solderability at a much lower cost than the conventional silver baking method. can.

(4) Since no silver is used, there is no possibility of silver migration or solder eating phenomena, improving reliability.

[Brief explanation of the drawing]

1A to 1F are diagrams showing a conventional method of forming electrodes of electronic components, and FIG. 2 is a diagram showing a method of forming electrodes of electronic components according to the present invention. 1...Element body, 7...Catalyst paste, 9...Electroless plating layer.

Claims (1)

[Scope of Claims] 1. When an electrode consisting of an electroless plating layer is formed on the surface of an element body, a catalyst containing glassy frit and serving as a catalyst for the electroless plating reaction is provided in the electrode formation region of the element body. A method for forming electrodes for electronic components, which is characterized by applying a paste and then performing electroless plating. 2. The method of forming an electrode for an electronic component according to claim 1, wherein the catalyst paste contains a palladium chelate or a fatty acid salt. 3. The method for forming an electrode for an electronic component according to claim 1, wherein the catalyst paste contains tin chloride. 4. An electrode for an electronic component according to claim 1, 2 or 3, characterized in that after electroless plating treatment, tin/solder plating is performed on the electroless plating layer. Formation method.