Electrolysis: processes – compositions used therein – and methods – Electrolytic coating – Coating predominantly nonmetal substrate
Reexamination Certificate
2000-09-28
2002-03-19
Wong, Edna (Department: 1741)
Electrolysis: processes, compositions used therein, and methods
Electrolytic coating
Coating predominantly nonmetal substrate
Reexamination Certificate
active
06358390
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to methods for forming electrodes for electronic devices. In particular, the present invention relates to a method for forming electrodes for electronic devices formed of a ceramic material or a composite ceramic material composed of a ceramic and a resin.
2. Description of the Related Art
Hitherto, in order to form electrodes on surfaces of electronic devices which are formed of non-electroconductive materials (or poorly electroconductive materials), such as ceramics, composite ceramic materials composed of ceramics and resins, or the like (hereinafter collectively referred to as a “ceramic material”), various methods have been employed, for example, sputtering, deposition, printing of an electroconductive paste, electroless plating, or an electrolytic plating after an electroconductive treatment applied to surfaces of electronic devices by the methods mentioned above.
Formation of electrodes by sputtering and deposition is performed by the following methods. An electronic device is placed in a vacuum container, a metal lump to be used as an electrode material is melted by resistance heating, electron beam or the like so as to vaporize as metal atoms for deposition, or on the other hand, a metal target is bombarded with an inert gas such as argon so as to yield metal atoms for sputtering. Individual films are formed by deposition of associated metal atoms described above on surfaces of the electronic devices, so that electrodes are formed. However, the methods described above have problems in that expensive and large apparatuses are necessary, deposition is relatively slow, it is difficult to fill and form an electrode inside a through hole having a high aspect ratio, the manufacturing costs are high due to poor performance in mass production, and the like. Accordingly, the advantage of these methods as methods for forming electrodes of electronic devices that must be mass-produced has been relatively low.
Formation of electrodes by printing an electroconductive paste is performed by the following method. That is, a powdered metal in the form of a paste is coated on an electronic device by printing, and the device is baked in a baking furnace at several hundreds to one thousand and several hundreds degree Celsius, whereby an electrode is formed. However, since a baking process at a high temperature is necessary, the method cannot be applied to an electronic device formed of a material having a relatively low melting point, such as a composite ceramic material composed of a resin and a ceramic. In addition, since an electroconductive paste generally contains a glass frit, and the glass frit may react with a ceramic material during baking, there are fears in that electric characteristics of the device may vary and/or physical strength thereof may be degraded in some cases.
Formation of electrodes by electroless plating is performed by a method of, for example, immersion in a solution composed of a complex or a colloid containing palladium or tin, so that a catalytic metal is deposited on a surface of a ceramic material having no electric conductivity. In this state, when a ceramic material is immersed in an electroless plating bath composed of a metal ion, a complexing agent, a reducing agent, an additive, and the like, a reduction reaction occurs by catalytic action of the catalytic metal, and hence, an electrode composed of a metal plated film is formed on the surface of the ceramic material. However, troublesome procedures for controlling the plating bath are necessary for the method described above, since, for example, the composition of the plating bath is complicated, a reducing agent or the like must be constantly supplied, and performance of the plating bath is degraded by generation of by-product materials such as oxides. In addition, disposal of wastewater from the plating bath is difficult and expensive. Furthermore, there are problems in the practical use of the method, such as slow deposition rate during plating, gas pockets generated by hydrogen, and the like.
Formation of electrodes by electrolytic plating is performed by the following method. That is, a metal film, which is to be used as an underlying layer, is formed on a surface of a ceramic material beforehand by sputtering, deposition, printing, electroless plating, or the like. The ceramic material is then immersed in an electrolytic plating bath containing a metal ion, and the metal is deposited on the metal film by conducting electricity in the underlying metal film, whereby an electrode composed of a metal plated film is formed. However, in the method described above, when an electrode is formed on a non-conductive material, an underlying layer for depositing a metal ion must be formed beforehand, so that the number of steps is increased, and the cost thereof is increased. In addition, the process in the method described above is accompanied by problems previously described in the various methods for forming an underlying metal film.
As a method for forming electrodes, which solves the problems of the method for forming electrodes described above, a method called the “direct plating method” has recently attracted attention. This is a method in which a palladium-tin colloid, powdered carbon or powdered graphite is adsorbed inside through holes formed in printed circuit boards, or the like so that the through holes are electroconductive, a metal is then deposited inside the through holes by electrolytic plating, and as a result, electrodes are formed. According to this method, a process for forming an underlying metal film prior to electrolytic plating can be simplified, and hence, the cost for forming electrodes can be considerably reduced. However, the method cannot be applied to a formation method for electrodes for electronic devices formed of ceramic materials. That is, an electroconductive material, such as a palladium-tin colloid, used in this method has a characteristic in that it is easily bonded with chemical groups, such as hydroxide and carbonyl groups. By etching a resin material forming a printed circuit board or the like using an alkali or the like, these chemical groups mentioned above can be formed on a surface of the resin material. As a result, an electroconductive material can be deposited on the surface of the printed circuit board. On the other hand, chemical groups cannot be formed on the surface of a ceramic material by etching or the like, and hence, an electroconductive material cannot be deposited and an electrode cannot be formed.
SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to realize a method for depositing an electroconductive material on a surface of an electronic device, the lack of which has been the reason direct plating cannot be applied to an electronic device composed of a ceramic material, and is to provide a method for forming an electrode of an electronic device in which the process thereof is simple, the production cost thereof is reduced and characteristics of the electronic device cannot be degraded.
The method for forming an electrode on a surface of an electronic device formed of a ceramic material comprises the steps of: adjusting a polarity of a surface charge by contacting, e.g., by immersing, the electronic device in a solution containing a cationic or an anionic surfactant; depositing an electroconductive material on the surface of the electronic device by contacting the electronic device with an electroconductive solution containing the electroconductive material having a polarity opposite to the adjusted polarity of the surface charge; and performing electrolytic plating using the electroconductive material deposited on the surface of the electronic device as an underlying metal film.
Any cationic or anionic surfactant which can impart a surface charge to the electronic device can be used. Typical anionic surfactants which can be used are linear alkylbenzenesulfonic acid, polycarbonic acid, polyoxycarbonic acid, phenolsulfonic acid, alkylet
Kunishi Tatsuo
Yoshida Yasushi
Murata Manufacturing Co. Ltd.
Ostrolenk Faber Gerb & Soffen, LLP
Wong Edna
LandOfFree
Method for forming electrode does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method for forming electrode, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for forming electrode will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2824012