Semiconductor device manufacturing: process – Packaging or treatment of packaged semiconductor – Including adhesive bonding step
Reexamination Certificate
1998-06-23
2001-07-03
Smith, Matthew (Department: 2825)
Semiconductor device manufacturing: process
Packaging or treatment of packaged semiconductor
Including adhesive bonding step
C438S106000, C438S118000, C438S120000, C438S121000, C438S124000
Reexamination Certificate
active
06255138
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a microencapsulated electroconductive filler. More particularly, the invention relates to a process for producing a microencapsulated electroconductive filler by coating the surfaces of electroconductive filler particles with an insulating polymer. The electroconductive filler can be used, for example, in an anisotropic conductive adhesive by being incorporated in an insulating adhesive.
BACKGROUND OF INVENTION
As recent models of electrical and electronic parts are becoming smaller in size and thickness, the electrical circuits used in those models are required to have a higher packing density and a finer definition. Interconnections of such miniature circuits are conventionally established by using anisotropic electroconductive adhesives. Among such anisotropic conductive adhesives, those which are shaped in sheet are commonly used in connecting terminals of a circuit board to a flexible circuit. A recent attempt made in the art is to apply an anisotropic conductive adhesive when a semiconductor chip is to be directly mounted on a circuit board (see, for example, JP-A-5-320413 (The term “JP-A” used herein means an unexamined published Japanese patent application)).
In order to establish electrical connections using an anisotropic conductive adhesive, terminals having a plurality of electrodes arranged at spacings of several tens of micrometers to several thousand micrometers and other terminals to be connected that also have similarly spaced electrodes are press bonded to each other, with the anisotropic conductive adhesive being interposed, such that electrical path is formed only between opposed electrodes. However, if the addition of the conductive filler is excessive or not uniform, or if the resin becomes fluid when the opposed terminals are pressed, two adjacent electrodes may occasionally be shorted as shown in FIG.
5
.
In order to prevent the shorting of adjacent electrodes, JP-A-62-76215, JP-A-62-176139 and JP-A-63-237372 have proposed the use of a particulate conductive filler having the surfaces of filler particles coated with a thermoplastic resin, and JP-B-8-2995 (The term “JP-B” used herein means an examined Japanese patent publication) has proposed the use of a particulate conductive filler having the surfaces of filler particles coated with a thermosetting resin.
As described above, JP-B-8-2995 discloses a process for producing the particulate conductive filler having the surfaces of filler particles coated with a thermosetting resin. Specifically, a solvent and conductive fine particles (oil phase) that have been already treated with a coupling agent so that reactant A is present on the surface, are dispersed in water (aqueous phase) that has dissolved therein a reactant B which is capable of reacting with reactant A, to thereby form a suspension. By applying heat or by adding a catalyst to the suspension, the two reactants are allowed to react with each other on the surfaces of the conductive filler particles to form an insulating resin.
A problem with this technique is that due to the presence of oil- and water-soluble ingredients, a complicated procedure has been required to isolate and recover the coated microcapsules of conductive filler. As a result, the overall manufacturing process is complicated, involving many steps while lacking the operating efficiency and the adaptability for mass production. If the microencapsulated filler is to be used in fixing IC chips and the like, the entrance of impurity ions such as chloride ions should be avoided by all means since they corrode electrodes and other components to lower the device reliability. To meet this requirement, additional steps of purification may have been necessitated.
SUMMARY OF INVENTION
An object of the invention is to solve the above described problems of the conventional techniques.
Other objects and effects of the present invention will become apparent from the following description.
The above described objectives of the present invention have been achieved by proving the following constitutions.
(1) A process for producing a microencapsulated electroconductive filler comprising conductive filler particles each having an insulating resin coated on the surface thereof, which comprises:
a first step of treating the surface of conductive filler particles with a coupling agent having reactive functional group A at a terminal end or in a side chain of its molecule; and
a second step of allowing said coupling agent having functional group A present on the surface of said conductive filler particles to undergo nonaqueous polymerization reaction with a reactant B which is polymerizable with said functional group A, to thereby form an insulating resin layer on the surface of said conductive filler particles.
(2) The process according to the above (1), wherein said coupling agent having functional group A used in said first step is at least one compound selected from the group consisting of an aluminum-base coupling agent, a titanate-base coupling agent, a silane-base coupling agent and a zircoaluminate-base coupling agent.
(3) The process according to the above (1), wherein the addition amount of said coupling agent having functional group A in said first step is from 0.1 to 15 wt % based on the weight of said conductive filler particles to be treated.
(4) The process according to the above (1), wherein said surface treatment of said first step comprises the steps of:
dissolving said coupling agent having functional group A in a solvent to form a solution of said coupling agent; and then
dispersing said conductive filler particles into the solution.
(5) The process according to the above (4), wherein said dispersing step to disperse said conductive filler particles into the solution is conducted by mixing with agitation.
(6) The process according to the above (4), wherein said dispersing step to disperse said conductive filler particles into the solution is conducted by applying ultrasonic waves with agitation.
(7) The process according to the above (1), wherein said coupling agent is an amine compound having an amino or imino group as said functional group A, and said reactant B is a compound having an epoxy group at a terminal end or in a side chain of its molecule.
(8) The process according to the above (1), wherein said coupling agent is an epoxy compound having an epoxy group as said functional group A, and the reactant B is an amine compound having an amino or imino group at a terminal end or in a side chain of its molecule.
(9) The process according to the above (1), wherein said second step comprises a step of dispersing said coupler-treated conductive filler particles uniformly in the reactant B.
(10) The process according to the above (9), wherein said second step further comprises a step of performing polymerization reaction between the reactant B and the coupling agent having functional group A under agitation.
(11) The process according to the above (9), wherein said dispersing step to disperse said coupler-treated conductive filler particles uniformly in said reactant B is conducted using an agitator running at an agitation rate of 2,000 to 10,000 rpm.
(12) The process according to the above (11), wherein the reactant B is of a liquid nature.
(13) The process according to the above (12), wherein said reactant B has a viscosity of 20 to 20,000 mPa·s (25° C.).
(14) The process according to the above (1), wherein said second step is conducted while heating the reaction system to from 40 to 60° C.
(15) The process according to the above (1), wherein said second step further comprises adding a polymerization catalyst to the reaction system.
The present invention also relates to an anisotropic conductive adhesive comprising an insulating adhesive and a microencapsulated electroconductive filler prepared by the process as claimed in claim
1
.
The present invention also relates to an electronic component comprising two or more terminals each having a plurality of electrodes, said terminals being interconnected with one another using an aniso
Smith Matthew
Sughrue Mion Zinn Macpeak & Seas, PLLC
Three Bond Co. Ltd.
Yevsikov V.
LandOfFree
Process for producing microencapsulated electroconductive... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Process for producing microencapsulated electroconductive..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Process for producing microencapsulated electroconductive... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2474361