Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Reexamination Certificate
1998-05-08
2001-07-24
Ball, Michael W. (Department: 1733)
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
C156S275700, C156S330000, C029S832000, C257S781000, C257S783000
Reexamination Certificate
active
06264785
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field of the Invention
The present invention relates to a mounting structure of an electronic part comprising an electronic part element in association with a terminal electrode and mounted on a substrate via an adhesive. The present invention further relates to a method of mounting the electronic part.
2. Art Related to the Invention
Soldering has been widely used to mount an electronic part on a substrate. To improve the soldering properties of an external electrode of the electronic part, soft solder, tin plating, gold plating, etc., is applied. Recently, there has been a tendency not to use soft solders containing lead.
An electrically conductive adhesive is often used to mount the electronic part on the substrate. However, because the conventional surface treatment, i.e., soft solder, tin plating, gold plating, etc., has been performed on the external electrodes of the electronic part, the bonding strength between the substrate and the electronic part constitutes a relatively weak mechanical bond.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an electronic part mounting structure wherein the bonding strength of the electronic part and a substrate can be improved by not only mechanical bonding but also chemical bonding, and to a mounting method thereof.
The present invention provides an electronic part mounting structure of the above mentioned kind, which is characterized in that a functional group having a nucleophilic substituting property is on a surface of said terminal electrode; and said terminal electrode is bonded to said adhesive by interatomic bonding.
As a result of interatomic bonding between the functional group having a nucleophilic substituting property in the terminal electrode and the functional group of a resin in the adhesive, not only is there an anchor effect by mechanical bonding as in the conventional case but also there is chemical bonding. Thus, the bond strength of the electronic part and the substrate is far more improved.
In the above described mounting structure of an electronic part, said functional group having the nucleophilic substituting property is preferably a hydroxy radical. By interatomic bonding (hydrogen bonding) between the hydroxy radical and a functional group of a resin in the adhesive, the effect as described above is obtained.
In the above described mounting structure of an electronic part, said adhesive may include an epoxy resin. By interatomic bonding between the functional group (e.g., hydroxy radical) having the nucleophilic property in the terminal electrode and the epoxy group in the adhesive, the above-described effect is obtained.
In the above described mounting structure of an electronic part, said adhesive may also be an electrically conductive adhesive including an electrically conductive powder.
Another aspect of the present invention provides a method of mounting an electronic part comprising the steps of: 1) preparing an electrically conductive paste comprising an electrically conductive powder, a photocatalyst and an organic vehicle; 2) coating said electrically conductive paste on an electronic part element and firing said electrically conductive paste to form a terminal electrode; 3) irradiating said terminal electrode; 4) coating an adhesive on said terminal electrode; and 5) mounting said electronic part on a substrate via said adhesive.
By irradiating the terminal electrode including the photocatalyst, a functional group enriched with nucleophilic substituting properties is formed on the surface of the terminal electrode and by interatomic bonding between the functional group and a functional group of a resin in the adhesive, the above-described effect is obtained.
In the above described method, said photocatalyst may be anatase-type TiO
2
. The use of anatase-type TiO
2
is effective in that the method can be safely and easily realized.
In the above described method, said radiation may be an ultraviolet ray. The use of ultraviolet rays is effective in efficiently and safely irradiating.
REFERENCES:
patent: 5310830 (1994-05-01), Okitsu et al.
patent: 5844320 (1998-12-01), Ono et al.
Ball Michael W.
Murata Manufacturing Co. Ltd.
Ostrolenk Faber Gerb & Soffen, LLP
Tolin Michael A.
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