CA2189801C - Method for production of microcapsule type conductive filler - Google Patents

Abstract

A method for the production of the microcapsule (MC) type conductive filler of this invention comprises (a) a step involving immersing minute conductive particles in an affinity agent thereby treating the surface of the minute conductive particles, (b) a step involving immersing and dispersing the surface-treated minute conductive particles in an epoxy monomer thereby forming a suspension, and (c) a step involving polymerizing the monomer in the suspension thereby forming a thermosetting insulating polymer on the surface of the minute conductive particles. There is also disclosed an MC type conductive adhesive agent having dispersed in an adhesive agent an MC type conductive filler coated with a thermosetting resin, the thermosetting resin coating having a thickness of not more than 3 µm and having no pinholes.

Description

METHQD FOR PRODUCTION
OF MTcR0rAPsur~ T~lPE CONDIrCTIVE FTrrrR
BA~KuuNL~ OF THE INVENTION
This application is a divisional application of CAnA-liAn Patent Application Serial No. 2,081,222 filed October 23, 1992.
1. Field of the Invention This invention relates to a method for the production of a microcapsule (MC) type conductive filler and more particularly to a method for coating the surface of minute con~ t; ve particles with an insulating polymer and to an MC
type adhesive agent having dispersed in an adhesive agent the coated MC type conductive f iller.
2. Description of the Related Art In the conventional method of adhesion, the adhesion effected by soft soldering or welding where the interface produced by this adhesion requires conductivity. The conventional method is effectively applicable only to a limited number of materials because of the heat factor. In contrast, the organic-inorganic composite conductive adhesive agent that is composed of a binder using a synthetic resin as a main -nPnt thereof and a conductive filler using a metal powder as a main component thereof finds utility in a wide variety of applications that involving different kinds of materials subject to adhesion. This adhesive agent, therefore, is an indispensable medium for conductive adhesion of plastic substances tsuch as epoxy and phenol resins) that do not adhere by soft soldering, for adhesion of NESA glass used in liquid crystal display devices, for adhesion of phosphor bronze with a carbon brush used in micrometers, and ~or adhesion of lead wires as in quartz oscillators and sdc meters, for exam~le.
Particularly, in the sPmi rnn~l~ctor industry, whic~i h ls been enjoying significant growth recently, IC's and LSI's of increasingly high quality have been developed and mass produced. For the A-~heC; nn o~ these semiconductor chips (silicon wafers) to lead - 2 - 2l8980l frames, though the method involving to an Au-Sn eutectic once prevailed, conductive a&esive agents formed by kn~r~ng an epoxy resin with silver powder now have multiple applications utility owing to their ability to lower cost and enhance productivity.
As a resin binder for conductive adhesive agents, while epoxy resin is generally used, polyimide type, phenol type, and polyester type resins are also used, though only partially. As a conductive filler, minute particles of such metals as gold, silver, and copper and amorphous carbon and graphite powder are generally used as well as metal oxides, though only partially. Silver powder is preferably used over the conductive f illers cited above because it is inl~7rrPn~ive, reliable and effective.
~he conductive adhesive agent is advantageous in various respects compared with conventional applications such as soft soldering and welding though it is not perfectly free from fault.
When this conductive adhesive agent is used between an LSI chip and patterns for mounting component parts, for example, an increase in the amount of minute . conductive particles that are incorporated in the conductive adhesive agent lowers insulation resistance as illustrated in Fig. 1 and increases the possibility of ad~acent patterns forming electric continuity. A
reduction in the amount of minute conductive particles reduces the electric continuity between the LSI and the patterns. Data indicate the necessity for rigidly 3 0 controlling the amount of minute conductive particles to be used in the conductive adhesive agent. And at the same time, reveal the fact that the minute conductive particles cannot be used in large amounts.
It is believed possible that this problem can be solved by a procedure that comprises preparing an ~C type conductive adhesive agent having dispersed in an adhesive agent, an MC type conductive filler f ormed by coating the surf ace of minute conductive particles with an insulating polymer, applying the MC
.

. ... .... .... .... . _ _ _ _ _ _ _ _ _ . .

_ 3 _ 2 l 898o t type conductive adhesive agent to the entire surface of the substrate of an IC or LSI chip, exerting pressure to bear on the interface between the chip and patterns deposited thereon, thereby rupturing the coating layer of the capsules and establishing electric continuity between the chip and the patterns, and meanwhile allowing the encapsulated minute conductive particles Lnterposed between the adjacent patterns to remain intact and continue to insulate these patterns from one another.
The insulating resins that are usable for coating the surface of minute conductive particles include thermoplastic resins and thermosetting resins as classified by kind. In terms of resistance to moisture absorption and electric insulating properties, thermosetting resins definitely excel thermoplastic resins. Since thermocompression bonding of a chip to a substrate is generally carried out at an elevated temperature of at least 170C, the insulating resin to be used is required to be stable enough to resist this elevated temperature though few thermoplastic resins can endure this temperature. In - contrast, most thermosetting resins can tolerate temperatures in the neighborhood of 200C.
For use as an insulating resin in the MC
type conductive filler, thermosetting resins that are advantageous in varlous respects over thermoplastic resins are suitable.
~or the application of an insulating resin coating to the surface of minute conductive particles, however, the procedure that involves dissolving the resin in a solvent, spraying the solution on the surface of the minute conductive particles, and drying the applied coating of the solution is predominant though since thermosetting resins are insoluble in solvents, this procedure applied conventionally is dif f icult and the application of a thermosetting resin coating to the surf ace of minute conductive particles, therefore, necessitates development of a novel coating ~ 4 ~ 21 898G l procedure .
~he prior techniques pert~ining to the MC
type conductive a&esive agent have been disclosed by Japanese IJnp~mined Patent Publications No. 176,139/1987, No. 76,215/1987, No. 47,943/1988, No. 54,796/1988, No. 103,874/lg90, and No. 103,875/1990, for example.
~irst, the disclosures of Japanese JJnP~minP~ Patent Publications No. 176,139/1987, No. 76,215/1987, No. 47,943/1988, and No. 54,796/1988 will be described. These patent publications disclose, as conductive adhesive agents, those produced by forming an int~ te conductive layer on s~hPri~l cores of resin and coating the int~ -rliAte layer ~ith a surface layer of an insulating thermoplastic resin and those prQduced by coating the surf ace of minute spherical conductive particles with an insulating thermoplastic resin.
Actual mounting of a chip on a substrate for a printed circuit by using such a conductive adhesive agent is attained by a procedure that comprises applying the conductive adhesive agent to the substrate and :- thermocompression bonding the chip to the substrate so ~rat the int~ i ate layer or the minute conductive particles will discharge a conductive function and the insulating thermoplastic resin an adhesive function and an insulating f unction . The techniques disclosed by these patent publications differ from the method using the MC type conductive adhesive agent of the present invention and these patent publications do not mention using a the~mosetting resin as an insulating resin f or coating the surf ace of the minute conductive particles .
Now, the disclosure of Japanese T7nP~mined Patent Publication No. 103,874~1990 will be described below. The invention of this patent publication pertains to an MC type conductive adhesive agent produced by dispersing in a film of an insulating adhesive agent serving as a binder an MC type _ _ _ _ _ _ _ _ _ . _ _ _ . . . . .. . . . . .. . . . _ . . .

conductive filler havlng minute conductive Qarticles coated with an insulating thermoplastic resin or thermosetting resin. Conductive union of two given members using this MC type conductive adhesive agent is accomplished by depositing this adhesive agent on the two members and pressing the two members against each other while being heated state. Thus, in the part expected to form electric continuity, the impact of the pressure exerted as described above ruptures the insulating resin layer of the MC filler and establishes the desired electric continuity, whereas in the part requiring insulation, the MC type conductive filler is allowed to remain intact and, therefore, retain stable insulation. Incidentally, this NC type conductive filler is manufactured by plasma polymerization or plasma CVD polymerization and there are times when the insulating f ilm of the NC
type filler may be formed of a thermosetting resin.
The number of kinds of thermosetting resins that can be manufactured by the plasma polymerization and the plasma CVD polymerization is very small because the number of kinds of gases usable for in~ection during . the polymerization is not large. Further in accordance with this method of plasma polymerization or plasma CVD polymerization, the cost is sufficiently high to render the manufacturing thereof impracticable and productivity is inferior because the amount of MC
type filler to be manufactured is small.
The disclosure of Japanese T~n~ Ami ned Patent Publication No. 103,875/1990 will be described below.
The inventLon of ~his patent publication pertains to the use of an MC type conductive adhesive agent produced by coating minute conductive particles with an insulating thermoplastic resin or thermosetting resLn. Actual mounting of a chip on a substrate for a printed circuit using this MC type conductive adhesive agent is attained by applying the conductive adhesive agent to the substrate and thermocompression bonding the chip to the substrate, with the in~ i Ate layer _ _ _ _ _ . . ..... .. . . .... . .. _ .... ....... . .. _ _ _ or the minute conductive particles discharging a conductive function and the insulating resin on the surface of the minute conductive particles an adhesive function and an insulating function. Incidentally, this MC type conductive filler is manufactured by either plasma polymerization or plasma CVD
polymerization. Thus, these prior techrliques are described as allowing what is formed by coating the surface of minute conductive particles with a thermosetting resin. In spite of these disclosures, thermosetting resins should be unusable for the purpose of coating because they do not melt with heat and, therefore, are incapable of functioning as an adhesive. Even if a th~ ~etting resin is used, the method of manufacturing the MC type conductive filler entails a serious drawback as pointed out in Japanese rTn~Y~min~tl Patent Publication No.
103, 874/1990.
Practically all the prior techniques pertaining to the manufacture of an MC type conductive filler or the conductive adhesive agent using this filler invariably use a thermoplastic resin. Even when the patent publications mention usability of a th~ ~setting resin, methods of manufacturing using such a 1-hr ~ ~ ~ctting resin are not disclosed with suf f icient specificity or are devoid of practicability and thus, these method cannot be actually used.
SUMMARY OF THE INVENTION
In accordance with an embodiment of the present invention there is provided a method for production of an MC type conductive filler comprising (a) a step of immersing minute conductive particles in an affinity agent thereby treating the surface of the minute conductive particles, (b) a step of ersing and dispersing the surface treated minute conductive -2~898~1 particles in an epoxy monomer thereby forming a suspension, and (c) a step of polymerizing the monomer in the suspension thereby forming a th~ -ctting insulating polymer on the surface of the minute conductive particles.
In accordance with another embodiment of the present invention there is provided an MC type conductive adhesive agent having dispersed in an adhesive agent an MC type conductive filler coated with a ~h,~ tting resin, the th. - setting resin coating having a thickness of not more than 3 ,~lm and having no pinholes.
The term "reactive substance" as used in this specification refers to a substance that is capable of forming an insulating polymer on the surface of a filler either by itself or through reaction with another reactive substance.
The substances that answer this description include monomer _ ~nf~nts, oligomer s~)mrrmf~nts, and polymer components that form an insulating polymer, for example.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will be better understood and objects and advantages other than those set forth above will become ~pparent when consideration is given to the following detailed description thereof. The description makes reference to the annexed drawings wherein:
Fig. 1 is a graph showing the relation between insulation resistance and conductivity with the amount of minute conductive particles as a parameter, Fig. 2 is a flow sheet of the production of a microcapsule type conductive filler, Fig.
3 is a type diagram of the microcapsule type conductive filler, Fig. 4 is a type diagram illustrating one example of a substrate, Fig. 5 is a typ-- diagram illust~-~ting one example of a glass chip, Fig. 6 is a type diagram illustrating sites for determination of electric continuity resistance and insulation resistance, Fig. 7 is a partially magnified diagram of Fig. 6, Fig. 8 is a photomicrograph of the microcapsule type conductive filler (15,000 magnifications), Fig. 9 is a photomicrograph of a part of union between a bump and a pad (504 magnifications), Fig. 10 is a type diagram illustrating the state of u~ ion between a chip and a 9 21~980t substrate, Fig. 11 is a fl:ow sheet of the production of a microcapsule type conductive filler as the second aspect of this invention, Fig. 12 is a type diagram illustrating a growth model of a triazine thiol film 5 on the surface of metal, and Fig. 13 is a type diagram illustrating the reaction ^ll;~ni~m of an epoxy monomer with triazine thiol.
D~Tr.~n DESCRIPTION OF TEIE PREFER~ED EMBODI~ENTS
The principle for the production of an MC
conductive filler will be described below.
~Production using one kind of monomer~
~ suspension is produced by dispersing minute conductive particles having the surface thereof treated with a coupling agent in a solution of a 15 monomer and a reaction initiator (oil phase) and adding the resultant dispersion dropwise to water having an emulsifier and a viscosity t~n~ncf~r dissolved therein (aqueous phase). By applying heat to this suspension, for example, the monomer is 20 polymerized in situ on the surface of the minute conductive particles and allowed to f orm a coating thereon. Examples of the monomer that is usable singly herein are divinyl benzene and acryl. A
~hermosetting polymer is obtained from divinyl benzene 25 monomer and a thermoplastic polymer from acryl monomer .
(Production using two or more kinds of r~
A suspension is produced by dispersing minute conductive particles having the surface thereof 30 treated with a coupling agent in the solution of a monomer in a solvent (oil phase) and adding the resultant dispersion dropwise to water having another monomer, an emulsifier, and a viscosity enhancer dissolved therein (a~ueous phase). sy applying heat 35 or adding a catalyst to this suspension, the are interfacially polymerized on the surface of the minute conductive particles and allowed to coat the minute conductive particles. The coating can be alternatively effected by preparing a suspension having at least two kinds of ~ , dissolved in the oil phase and subjecting the - I to in situ polymerization. Examples of the r-~ ~ that are usable in the form of a combination of two t -herein are epoxy/amine and bismaleimide/amine (both producing a thermosetting polymer).
In the production of the MC conductive filler, the following points must be taken into consideration.
( l ) The minute conductive particles should be treated in advance with a coupling agent. ~2) The sp value of the coupling agent to be used f or this treatment should be within +10 (cal/cm~)3S of that of the monomer to be used. (3) The viscosity of the aqueous phase should be in the range between 20 and 10,000 cps. (4) The suspension should be stirred at a rate in the range between 50 and 250 rpm to effect the reaction of the monomer. The reason for (l) is that since the monomolecular f ilm of the coupling agent on the surface of the minute conductive particles and the monomer molecules are intertwined, the monomer is retained on the surface of the minute conductive particles and the coating is ef f ected unif ormly . The . reason for (2) is that if the sp value deviates from t~re range of +lO (cal/cm~)~, the monomer is not thoroughly intertwined with the coupling agent and it is retained on the surf ace of minute conductive particles with difficulty. The reason for (3) is that the minute conductive particles settle and agglomerate if the viscosity is less than 20 cps and the separation of the MC type conductive filler after completion of the coating is not obtained if the viscosity exceeds 10,000 cps. The reason for (4) is that the minute conductive particles settle and agglomerate during the reaction of the monomer if agitation is omitted.
The minute conductive particles to be used for this method of production of the filler are only required to be made of a conductive metallic material.
The kind of metallic material is irrespective. For =
2 t ~q8~ t example, minute Cu particles having the surface thereof coated with Ag or minute Ag particles are preferably used.
The minute conductive particles are preferably spheres or psF~ srh Dres in shape . These minute conductive particles preferably have a diameter of not more than 50 ~m.
The insulating layer of a thermosetting resin for the MC
type conductive filler is preferably made of a cured epoxy/amine or bismaleimide/amine type resin. The insulating layer of ~h- --etting resin of the Mc type conductive filler preferably has a thickness of not more than 3 ,um.
This invention pertains in one aspect of an MC type conductive adhesive agent having dispersed in an adhesive agent the filler obtained as described above. The adhesive agent that can be effectively used in the MC type conductive adhesive agent is the same as mentioned above. For example, an epoxy type one-component polyimide or polyester adhesive agent is preferably used.
The viscosity of the adhesive agent mentioned above is preferably not more than 150,000 cps. The content of the MC
type conductive filler in the MC type conductive adhesive agent is preferably not more than 50% by volume.
One preferred method comprises forming a suspension by uniformly dispersing minute conductive particles allowing the presence of a solvent and a monomer (monomer A) on the surface thereof in water having another monomer (monomer B) dissolved therein and applying heat to the suspension thereby inducing the two monomers to react on the surface of the minute conductive particles and form an insulating polymer and conse~luently producing a microcapsule type filler. In this method, the monomer A and the monomer B are monomer c, ~ ~ents that are intended to form an insulating polymer. When a polyamide is intended to form the insulating polymer, for example, adipic acid dichloride serves as the monomer A and hexamethyIene diamine as the monomer B. Where polyurethane is intended to form the insulating polymer, for example, ..

tetramethylene diisocyanate serves as the monomer A and methamethylene glycol as the monomer B.
The solvents that are effectively usable for dissolving the monomer A include dichloroethane, chloroform, carbon tetrachloride, xylene, toluene, benzene, dichloromethane, alcohol and ethyl acetate, for example. The suspension is heated for the purpose of promoting the reaction of the monomers therein. The temperature of this heating is in the range between normal room temperature and boiling point of the solvent. It is selected in accordance with the particular quality of the suspension to be heated.
In the method described above, the minute conductive particles must be treated with a coupling agent before using.
This treatment serves the purpose of f ixing the monomer A on the minute conductive particles.
Further, in the method described above, the viscosity of the aqueous phase having the monomer B dissolved therein is preferably adjusted so as to fall in the range between 20 and 10,000 cps by the addition of a viscosity PnhAn~ r. During the application of heat to the suspension mentioned above, the suspension must be stirred at a rate in the range between 50 and 250 rpm for reacting the two monomers.
The monomers are preferably used in an amount that is at least sufficient for the monomers to form a film of not less than 0 . 05 ~Lm in thickness on the surface of the minute conductive particles.
Now, the present invention will be described in detail below with reference to working examples. Of course, this invention is not limited to the working examples.
The affinity enhancer such as a triazine thiol, which is used at the step (a) in the method, allows effective polymerization of the monomers because it is capable of inducing uniform adhesion of the epoxy resin monomer to the surface of the minute metallic particles and opening the heterocycles in the resin. As a re~ult, the heretofore 2 1 8980 ~

difficult coating of the surface of the minute conductive particles with the thermosetting resin can be easily attained by the method of this invention. Further, since the coating film of the thermosetting resin is superior to the coating film of a thermoplastic resin in strength, the MC type conductive filler can be incorporated in a large amount in the adhesive agent and the MC type conductive adhesive agent consequently produced can effect an adhesive union o~ two given members with higher reliability than the conventional technique.
Now, this invention will be described more specifically below with reference to working examples, which are illustrative of and not limitative in any sense of this invention .
Examples 1 to 13 and Comparative Examples 1 to 3 cited hereinbelow pertain to the first and second aspects of this invention .
~~ le 1 A microcapsule type conductive adhesive agent was produced with the following materials.
Minute conductive particles: Minute pq~ nqrheres of Cu having the surface thereof plated with Ag tAg/Cu, average ~ r ~ ~r 5 ,~lm) .
Dispersant: Titanate type coupling agent.
Mnnl `:.: Bisphenol A type epoxy (BPA) and tetraethylene pentamine (TEPA).
Adhesive agent: Epoxy type one-component adhesive agent.
(l) Production of microcapsule type conductive filler (using a monomer and a solvent respectively in oil phase and 3 0 aqueous phase) .
Coating of silver powder with cured BPA and - 14 - 2 1 ~9 80 1 TEPA
An aqueous phase was prepared by dissolving 25 g of polyvinyl alcohol, 2 g of an emulsifier, and 10 g of TEPA in 400 ml of water. An oil phase was prepared by dissolving 7 g of BPA in 15 ml of dichloroethane and adding to the resultant solution 15 g of silver powder treated with a titanate type coupling agent in Acc~)r~An~e with the flow chart illustrated in ~ig. 2. By exposing the oil phase to an ultrasonic wave for 20 minutes, the silver powder agglomerated therein was dispersed. Then, the a~ueous phase was stirred with a homogenizer at a rate of 3,000 rpm and, at the same time, the oil phase was ~rAC~llA 1 1 y added dropwise to the stirred aqueous phase to produce a suspension allowing the presence of the oil phase on the surface of the silver powder. This suspension was kept at 60C and stirred with a three-one motor at a ra~e of 180 rpm for four hours.
Thereafter, a microcapsule type conductive filler A
having the surface of minute conductive particles (silver powder~ coated with a polymer as illustrated in Fig. 3 was separated and dried at 60C for :- 30 minutes, to afford an NC type conductive filler.
Since the production of this NC type conductive filler forms the subject matter of this invention, the production of the MC type filler set forth in Example 1 above will be described more specifically below (in the following description, the amounts of part o~ the raw materials are different from those of the preceding paragraph).
1.1 Treatment of f ine metallic particles with a coupling agent To ensure retention of the monomer on the surace of f ine metallic particles, the f ollowing treatment with a coupling agent was carried out. In 50 ml of ethanol, 0 . 3 g of a titanate type coupling agent and 6 g of minute Ag/Cu particles were retained at 60C and sub~ected to ultrasonic dispersion for 10 minutes. Then, by keeping the solution at 60C and .
11 in~ ethanol by dist~llation, the treatment of the suriace of minute metallic particles with the coupling agent was effected. Incidentally, the amount of coupling agent to be used must be in the range between 0.1 and 1096 by weight and is preferably 5~ by weight, based on the amount of the minute metallic particles. The reason for the particular range is that the surface of the minute metallic particles cannot be uniormly coated with the coupling agent if the amount is less than O.196 by weight and the minute metallic particles cohere if the amount exceeds 10~6 by weight. Further, the solubility parameter of the coupling agent is desired to be within ilO ~cal/cm3)llz of that of the monomer to be used in the oil phase.
This range is important f or the purpose of improving the molecular intertwining of the coupling agent and the monomer.
1. 2 Preparation of aqueous phase An aqueous phase was prepared by dissolving 1.5 g of an ~ml~lR;fier, 14.5 g of PVA (viscosity of the aqueous phase 20 cps), and 10 g of TEPA in 200 ml.
Here, the amount of PVA to be added must be controlled :- 60 as to adjust the viscosity of the aqueous phase in -the range between 1 and 1,000 cps and preclude the otherwise possible sedimentation of the minute metallic particles.
1. 3 Preparation of oil phase An oil phase was prepared by dissolving 10 g of BPA in 30 ml of ethyl acetate and adding 7 g of minute Ag~Cu particles to the resultant solution. The solvent to be used for the oil phase must exhibit solubility of not less than O.1~ in water. If a solvent not satisfying this condition is used, the solvent in the produced NC filler intervenes between 35 the polymer and the minute metallic particles and, when this MC filler is used in the conductive adhesive agent, the entrapped solvent causes corrosion of the product oE union. The solubility of the solvent to be used is preferably about 396 in water.
. , ....... . . . .... . .. .. .... . . . _ _ _ _ _ _ _ _ 2~8~80~
1. 4 Dispersion of minute Ag/Cu part~cles The oil phase was exposed to an ultrasonic wave for 10 minutes to effect thorough dispersion of the minute Ag/Cu particles therein. Though the minute 5 Ag/Cu particles used in this example were spheres in shape, the coating is equally effected when these particles are pseudospheres or fish scales in shape.
When the ~C filler is intended for use in the ~qC type conductive adhesive agent, the particles in the shape of fish scales are not used advantageously because they do not serve as spacers between the bump and the pad as shown in Table 8.
1. 5 Preparation of suspension A suspension was prepared by stirring the agueous phase with a homogenizer at a rate of 4,000 rpm and, at the same time, adding the oil phase gradually to the stirred aqueous phase dropwise. The operating speed of the homogenizer must be in the range between 500 and 10,000 rpm. The reason for the particular range is that no homogeneous suspension is obtained if the speed is less than 500 rpm and the minute Ag/Cu particles are damaged if the speed . exceeds 10,000 rpm.
l . 6 Interfacial polymerization reaction The suspension prepared in 1. 5 above was stirred with a three-one motor at 150 rpm and heated at 60C to Lnduce a reaction for four hours. The stLrring must be carrLed out with an operatLonal speed kept in the range between 50 and 250 rpm., whLch prevents sedLmentatLon of the mLnute metallLc partLcles ( to whLch occurs Lf the speed Ls less than 50 rpm), cohesion (whLch occurs Lf the speed Ls larger than 250 rpm) durLng the LntPr~a~ polymerization reaction .
(2) Observation of cross section of microcapsule type conductor filler The microcapsule type conductive filler produced as described above was buried Ln an epoxy resLn, allowed to set thereLn, and cut wLth a _ _ _ _ _ _ . . . . .... ..

microtome to expose the cross section of the filler for visual observation.
(3) C~nfinr~tion of insulation of microcapsule type conductive f iller The filler was dispersed between two opposed glass substrates having the surface thereof coated with ITO and tested for insulation between the glass substrates .
( 4 ) Preparation of conductive adhesive agent The microcapsule type conductive filler prepared in ( 1 ) above was mixed in a voluminal proportion of 2096 with an epoxy type one-~ nt adhesive agent. The resultant mixture was thoroughly stirred to effect dispersion of the filler therein to afford a microcapsule type conductive adhesive agent.
( 5 ) Bonding of chip to substrate A 40 ,um conductive adhesive agent prepared in (2) above was uniformly applied to a substrate (number of pads 128, interval between pads 100 llm, and size pad 200 ,~Lm Cl) illustrated in Fig. 4. The substrate and a glass chip ( 128 pins ) illustrated in Fig. 5 to which the substrate was tacked by bumping were sub~ected to thermocompression bonding at a temperature of 170C, 30 sec, and 35 g/bump. In the diagram of Fig. 4, 2 represents an electrode and 4 represents an electrode to be used for such evaluations as a test f or electric continuity .
( 6 ) Test for electric continuity and test for insulation 3 0 The product of union obtained by bonding in ( 3 ) above was tested f or electric - continuity by the four-t-~nm;n~l method using the sites of measurement illustrated in Fig . 6 and Fig . 7 and was tested f or insulation by using a high-resistance meter (insulation resistance meter).
Incidentally, the measurement of electric continuity was made at circuit 1, circuit 2, circuit 3, and circuit 4 and that of insulation resistance at insulation part 1, insulation part 2, and insulation _ _ _ _ _ _ _ _ _ _ _ . . .. . .. ..... . _ . _ . .. . _ .

- 18 ~ ~ ~ 8 98 0 ~
part 3 as illustrated in Eig. 7.
( 7 ) Observation of state of adhesion of chip to substrate The product of union obtained by bonding in ( 3 ) above was sectioned and the cross section consequently exposed was visually ~ m~n~d to determine the state of adhesion of the filler to the chip and the substrate.
(Results ) ~1) Observation of cross section of microcapsule type conductive f iller Fig. 8 is a photograph o a cross section of the microcapsule type conductive filler. It is clearly noted f rom the photograph that an insulating polymer was present on the surface of a minute conductive particle, indicating that the particle was completely coated.
( 2 ) Conf irmation of insulation with microcapsule type conductive f iller The two opposed glass substrates were found to be insulated from each other, indicating that the microcapsule type conductive f iller served to ef f ect . insulation.
( 3 ) Measurement of electric continuity The results of the test f or electric continuity are shown in Table 1. All the circuits used for the test invariably showed highly satisf actory results of electric continuity not exceeding 1.5 n (not more than 0.2 Q per ~oint).
To be specific, the chip and the substrate were joined as illustrated in Fig. 10 and the electric continuity resistance was not more than 0 . 2 Q per ~oint and, in spite of the high filler content of 2096 by volume, the adjacent patterns showed highly satisfactory insulation in th~ order of 1 x 10ll Q.

;
~ - 19 2 1 89 80 1 Table 1 Electric continuity resistance Side of measurement Circuit 1 Circuit 2 Circuit 3 Circuit 4 A 1.1034 1.1298 1. 0865 1. 2051 5 s 1.1298 l . 2114 1.1695 1.1326 C 1.2365 1.1511 1.1233 1.1519 D 1.2562 1.1145 1.2314 1.1413 In: Q
(4) Measurement of insulation resistance Table 2 shows the results of the test for insulation resistance. Even though the amount of filler incorporated was as large as 20~ by volume (substantially equal to the amount of silver paste for a die bond ), the ad~acent patterns displayed highly satisfactory insulation of not less than 101l Q.
Table 2 Insulation resistance Side of measurement Insulation l Insulation 2 Insulation 3 A 3.6 2.5 2.8 B 2.1 2.6 3.0 C 1.5 2.7 3.0 - . D 1.8 2.0 3.0 In: 101l n ( 5 ) Observation of state of union between chip and substrate (bump and pad) Fig. 9 is a photograph showing a cross section of the joint between the bump and the pad. It is clearly noted f rom this photograph that the microcapsule type conductive f iller was amply present between the bump and the pad.
Example 2 A microcapsule type conductive filler was produced by faithfully following the procedure of Example 1, excep~ that minute Ag particles ( average diameter 0.1 ~Lm) were used instead as minute conductive particles. It was evaluated in the same 4 0 manner as in Example 1.
(Results ) _ 20 --( 1 ) Observation of cross section of microcapsule type conductive f iller Similarly to the filler illustrated in Fig. 8, an insulating polymer was found to have uniformly coated the surface of agglomerated minute conductive particles.
(2) Cnnfir~-tion of insulation with microcapsule type conductive flller The filler showed the same degree of insulation as found in Example l.
( 3 ~ ~easurement of electric continuity resistance The electric continuity resistance was substantially the same as in Example 1.
( 4 ) Neasurement of insulation resistance The insulatLon resistance was substantially the same as in Example 1.
( 5 ) Observation of state of union between chip and substrate (bump and pad) Similarly to the product of union illustrated in Fig. 9, the microcapsule type conductive filler was amply p~esent between the pad and the bump.
~ Exam~le 3 ~icrocapsule type conductive f iller and a&esive agent were produced by faithfully following the procedure- of Example l, except that 10 g of h~q~ l~ (BDqI) and 0.1 g of rl;;~ohicyclo~ln~iPc~
were used in place of the monomer sP~. They were evaluated in the same manner as in Example 1.
(Results ) (1) Observation of cross section of microcapsule type conductive filler Similarly to the product of union illustrated in Fig. 8, an insulating polymer was found to have coated minute conductive particles completely.
(2) Cnnfirr~tion of insulation with microcapsule type conductive filler The filler showed the same degree of - 21 - 2t89801 insulation as in Example ~.
( 3 ) ~eas~rement o~ electric continuity resistance The f iller showed the same degree of electric continuity resistance as in Example l.
( 4 ) Measurement of insulation resistance The f iller showed the same degree of insulation resistance as in Example l.
( 5 ) Observation of state of union between chip and substrate (bump and pad) The state of union was the same as that found in Example 1.
Com~arative Exam~le l ~ l ) Preparation of microcapsule type conductive filler A microcapsule type conductive f iller was produced by the coating method described below using the following materials.
Minute conductive particles: 30 g of minute Ag/Cu particles (same as those of Example 1) Polymer: PMNA ( average particle aiameter 0 .15 ,um) (m.p. 135C) A microcapsule type conductive filler coated wi-th PM~A was produced by dissolving 5 g of P~MA in 100 ml of xylene, spraying the resultant solution into minute conductive particles, and drying the particles (for expulsion of xylene).
( 2 ) Observation of cross section of microcapsule type conductive filler 3 0 ~ 3 ) ~on f ~ tion of insulation with microcapsule type conductive filler t 4 ) Preparation of conductive adhesive agent ( 5 ) Bonding of chip to substrate (6) Test for electric continuity and test for insulation ( 7 ) Observation of state of union between bump and pad The operations of ( 2 ) to ( 7 ) indicated above were carried out in the same manner under the same _ _ , . . . .. . . .. _ . . .. . _ - 22 ~ 218980;
conditions as those of ( 2 r to ( 7 ) of Example 1.
(Results ~
( 1 ) Observation of cross section of microcapsule type conductive filler Similarly to the minute conductive particles of ( 7 ), Example 1 illustrated in Fig . 8, the filler particles were found to be completely coated with PMN~. '' ( 2 ) Conf irmation of insulation with microcapsule type conductive filler 5jm~lArly to the filler of Example 1, the microcapsule type conductive f iller retained insulation .
( 3 ) l~easurement of electric continuity resistance All the circuits, ~;m~ li3rly to those of Example 1, showed highly satisfactory electric continuity resistance of not more than 1. 5 Q .
( 4 ) ~easurement of insulation resistance Table 3 shows the results of the mea~uL. L. Of the total of 12 insulation parts, two insulation parts showed electric continuity, probably because the bonding was made at a temperature of 200C
an-d the PlD!SA was conseguently ~ sed or fused to establish contact between the minute conductive particles .
Table 3 Insulation resistance Side of mea:,uL~ L Insulation 1 Insulation 2 Insulation 3 A 1.5 2.5 x 10 510 B 2.1 x 101l 8 150 C 20 2. 7 x 101l 26 D 35 10 3 . 0 x 10 In: Q

( 5 ) State of union between bump and pad Similarly to the results of ( 5 ) in Example 1, the microcapsule type conductive filler was amply present between the bump and the pad.
_ . _ , . . .,, : . ,, _ _ _ _ _ _ . , ~omParative Example 2 Preparation of microcapsule type conductive f iller A mi~luu~ ule type conductive filler was produced by faithfully following the procedure of Example, except that Cu particles 60 llm in diameter were used as minute cûnductive particles.
The produced microcapsule type conductive f iller was evaluated in the same manner under the same conditions as described in (2) to (7) of Example l.
(Results ) The produced f iller having the surf ace thereof completely coated with a polymer showed insulation.
The electric continuity resistance and the state of union between the bump and the pad were equal tû those obtained in Example l. No insulation was retained between the ad~acent pads.
ComParative Example 3 A microcapsule type conductive filler produced by following the procedure of Example l was mixed with an epoxy type adhesive agent having a viscosity of 210 ,-'~. 000 cps.
(Results ) The filler could not be dispersed in the adhesive agent because the viscosity of the adhesive agent was unduly high.
Example 4 The use of two kinds of ~ - , a thermosetting resin, and a solvent was omitted and a monomer were used in both the oil phase and the a~[ueous phase.
A microcapsule type conductive filler and a microcapsule type conductive adhesive agent were produced by faithfully following the Procedure of Example l, except that an oil phase obtained by dispersing 7 g of conductive particles treated with a coupling agent in lO g of sPA in accordance with the flow sheet shown in Fig. 2 was used dichloroethane instead of ethyl acetate solvent in the oil phase.
They were evaluated in the same manner as in .. .. _ _ . _ ........ .. . . .

- 24 - 2 ~ 8 ~ 8 0 1 Example 1.
( Results ~
In all the items of evaluation, the results were equal to those obtained in Example ~.
Exam~le 5 One kind of monomer was used and a thermosetting resin and a solvent were used, and one kind of monomer was used in the oil phase.
A microcapsule type conductive filler and a microcapsule type conductive adhesive agent were produced by following the procedure of Example 1, except that an aqueous phase was prepared by dissolving 12 g of polyvinyl alcohol and 1. 5 g of an emulsifier in 200 ml of water and a solution of 10 g of divinyl benzene and 0.1 g of benzoyl peroxide in 15 ml of ethyl acetate was used as an oil phase.
~Results ) In all the items of evaluation, the results were almost the same as those obtained in Example 1.
ExamPle 6 Two kinds of - r.~ were used, including a thermosetting resin and a solvent, and two kinds of : r ~ ~ were used in the oil phase.
- A microcapsule type conductive filler and a microcapsule type conductive adhesive agent were produced by f ollowing the procedure of Example 1, except that an aqueous phase was prepared by dissolving 12 g of polyvinyl alcohol and 1. 5 g of an emulsifier in 200 ml of water and an oil phase was prepared with 15 ml of ethyl acetate and 5 g of imidazole. They were evaluated in the same manner as in Example 1.
(Results ) In all the items of evaluation, the results were nearly the same as those obtained in Example 1.
Example 7 Two kinds of monomers and a thermosetting resin were used only in the oil phase and no solvent was us ed .
. . . _ _ _ _ . .

-- 25 - 21898~1 .
An MC f iller and an ~C conductive adhesive agent were produced by faithfully following the procedure of Example 6, except that the use of ethyl acetate was omitted. They were evaluated in the same manner as in Example 6.
(Results ) In all the items of evaluation, the results were nearly the same as those obtained in Example 1.
ExamPle 8 One kind of monomer and a thermosetting resin were used and no solvent was used. The monomer was used in the oii phase.
A microcapsule type conductive filler and a microcapsule type conductive adhesive agent were produced by following the procedure of Example 2, except that an aqueous phase was prepared by dis801ving 12 g of polyvinyl alcohol and an emulsifier in 200 ml of water and an oil phase was prepared by dispersing in 10 g of divinyl benzene 0.1 g of benzoyl peroxide and 7 g of minute conductive particles treated with a coupling agent in accordance with the flow sheet illustrated in Fig. 2 without using ethyl -- acetate ( solvent ) . They were evaluated in the same manner as in Example 2.
(Results ) In all the items of evaluation, the results were nearly the same as those obtained in Example 1.
Example 9 A blend of a thermoplastic resin and a thf ,seLLing resin and a solvent were used. ~he monomer was used in the oil phase.
A microcapsule type conductive filler and a microcapsule type conductive adhesive agent were produced by following the procedure of Example 1, except that 5 g of methyl methacrylate, 5 g of f ~r--olf~;mide, and 0.1 g of azoisobutyronitrile were used as nl ~ in place of BPA and TEPA. They were evaluated in the same manner as in Example 1.
(Results ) ,, , ,, . _ .. . . . . .

- 26 - 218q8(}1 In all the items of evaluation, the results were nearly the same as those obtained in Example 1.
ExamPle 10 A blend of a thermoplastic resin and a ~h~ LLing resin and a solven~ were used. The monomer was used in the oil phase and the aqueous phase .
A microcapsule type conductive filler and a microcapsule type conductive adhesive agent were produced by following the procedure of Example 1, except that an agueous solution was prepared by dissolving 12 g of polyvinyl alcohol, 1. 5 g of an emulsifier, and 15 g of hexamethylene diamine in 200 ml of water and a solution of 7 g of adipic acid and 7 g of BPA in 15 ml of ethyl acetate was used as an oil phase. They were evaluated in the same manner as in Example 1.
( Results ) In all the items of evaluation, the results were nearly the same as those obtained in Example l.
Example 11 A blend of - I - was used in the oil phase and . no solvent was used.
An MC filler and an MC type conductive adhesive agent were produced by following the procedure of Example lO, except that ethyl acetate was omitted.
They were evaluated in the same manner as Example 10.
(Results ) In all the items of evaluation, the results were nearly the same as those obtained in Example 1.
Example 1 2 A blend of , rs was used in the oil phase and the aqueous phase and no solvent was used.
An MC type filler and an MC type conductive adhesive agent were produced by following the procedure of Example 11, except that ethyl acetate was omitted. They were evaluated in the same manner as in Example 11.
(Results ) . _ ........ . .

_ 27 - 2 1 a980 1 In all the items of evaluation, the results were nearly the same as those obtained in Example l.
Example 13 An NC type filler produced by the procedure of Example 1 was tested for the following items.
(l) Effect of sp (solubility parameter) value of coupling agent on production of MC type f iller Table 4 shows the results of the test performed on MC fillers prepared using coupling agents of different sp values with respect to electric continuity .
Table 4 Results of test of MC type f iller for insulation Difference of sp values of Results of test for coupling agent and monomer insulation o Insulatlon 5 Insulation 10 Insulation 11 Electric continuity The results indicate that the dif f erence ~ between the sp value of the monomer (epoxy resin) 25 . and the sp value of the coupling agent must be within 10 (cal/cm~) 112. The possible reason for this limit is that the monomer molecules and the coupling agent molecules are intertwined with dif f iculty and retention of the monomer on the surface of the minute conductive particles is not attained. Incidentally, the sp value o the epoxy resin is 10.9 (cal/cm3)l/2.
(2) Effect of viscosity of agueous phase on stability of suspension Table 5 shows the results of the test performed involving the effect of changes in the viscosity of the aqueous phase on the stability Of the suspension-- 28 - 2 t 8 98 0 7 Table 5 Relatian between viscosity of aqueous phase and suspension viscosity 5 Of aqueous lo 20 loo looo loOOO 11, ooo phase ~cps) Stability Sediment- Suspension not of ation of producible and suspension minute i Stable stable Stable stab1e~c filler after par~icles reaction not observed effectible The results indicate that the viscosity of the a~ueous solution is proper in the range between 20 and 10,000 cps.
( 3 ) Ef f ect of stirring speed on stability of suspension Table 6 shows the ~esults of the test performed involving the effect of the stirring speed (30, 50, 250, and 300 rpm~ on the stability of the 20 suspension.
Table 6 Relation of speed of stirring and stability of suspension ~ stirring 30 50 250 300 Stability Sedimentation Adhesion of minute of of minute conductive particles to suspension conductive Stable Stable beaker wall observed particles obs erved The results indicate that the stirring must be carried out at a rate in a range between 5 0 and 250 rpm.
( 4 ) Relation of particle diameter and insulation resistance of minute conductive particles Table 7 shows the results of the test performed on minute conductive particles of diameters 10, 30, 50, and 70 ~m for insulation.

- 29 _ 2 1 8 9~ t Table 7 RelatiOn between particle diameter and insulating property of coated minute conductlve particles Particle diameter (um) of Results of test for 5minute conductive particles insulation Insulation 3 o Insulation Insulation 7 0 l~lectric continuity The results indicate that the minute conductive particles to be used should have a diameter of not more than 5 0 ,um .
( 5 ) Relation between shape and electric continuity resistance of minute conductive particles .
Table 8 shows the results o the test performed on minute conductive particles having different shapes of spheres, pseudospheres, and fish scales with respect to electric continuity.
Table 8 Relation between shape and conductivity of minute conductive particles Shape of minute Conductivity (l~umber of deective conductive particles portions/number of sites of measurement) Spheres 0 /10 0 Pseudospheres 0 /10 0 l~i sh s ca l es 2 3 /10 0 In the case of a filler using minute particles of the shape of fish scales, the surface completely coated with a polymer, the insulation was satisfactory, and the ad~acent pads were insulated from each other. Absolutely no electric continuity was es~h~ . Thouyh the filler was present between the bump and the pad, it failed to serve as a medium for union 4 0 thereo . The results indicate that the minute conductive particles should be in the shape of . . . .

_ 30 _ 2 1 898 ~ 1 either spheres or pseudospheres.
6 ) Relation between thickness and electric continuity resistance of an insulating resin layer Table 9 shows the results of the test performed on insulating resin layers formed of the MC type conductive filler with different thicknesses with respect to electric continuity.
Table 9 Relation between thickness and conductivity of insulating resin Thickness (,um) of Resistance per site of measureInent insulating resin ( Q ) 0.1 0.1 2.0 0.4 3.0 0.5 4.0 1.5 It is noted from Table 9 that the resistance to electric continuity was high and points of poor electric continuity were detected when the thickness of the insulating resin layer (coating layer) was 4.0 ,um. The results indicate that the thickness of the insulating resin layer is desired to be not more than 3 ~
( 7 ) Content of MC type ~iller Table lO shows the relation between the MC
type ~iller and the state of curing of the adhesive 3 0 agent .

.
Table 10 Content of ~IC type conductLve filler and state of adhesive agent Content ( % ) 1 10 30 50 55 65 70 State of Good Good Good Good Good Poor Poor curing adhesion adhesion Poor A~lhPfiir n: Complete wetting of filler with adhesive agent not obtained because of excess amount of filler.
The results indLcate that the content of the ~C type conductive filler must not be more than 609; by volume. ~ow, the third and fourth aspects of this invention will be described specifically below with reference to Examples 14 to 16.
Exam~le 1 4 An l~C ty~e conductive adhesive agent was produced with the following materials.
~inute conductive particles: ~inute Cu pseudospheres having the surface plated with Ag (Ag~Cu, average particle diameter 5 ,um~.
Adhesive agent: A composition consisting of an ~ epoxy resin as the main component and an acid ~ anhydride as the curing agent ) .
Affinity agent: ~ri~zinR thiol (RTD).
~onomer: Bisphenol A type epoxy resin (BPA) (produced by Shell and marketed under ~ri~lcl ~rk designation of "Epikote 828 " ) .
(1) ~Iethod for production of ~C type conductive filler The minute metallic particles were subjected to a surface treatment. ~irst, the minute metallic particles were washed with an acid and then with an alkali, and pretreated with Triclene to defat and clean the surface thereof. The cleaned minute metallic particles were immersed in a triazine thiol solution to be coated with a film of t.ri~7inr~, thiol.
This solution was prepared by dissolving tr~7~nP
thiol in acetone in a concentration of 10-4 mol/lit.
~o uniform film is obtained if the concentration is - 32 - 2 ~ ~ ~8 0 1 .
lower than this level and the speed of treatment is too high to be controlled as re~uired if the concentration exceeds 10 ~ mol/l. The temperature of this treatment is not lower than 17C. It is desired to be in the range of 20 + 3C because the speed of the treatment is too high to be controlled as desired if the temperature is unduly high. The time of treatment is desired to be in the range of 30 +
5 minutes in due consideration of the relation between the concentration mentioned above and the temperature.
It goes without saying ~hat for such conditions as concentration, temperature, and time of the treatment, the magnitudes thereo to be selected should be optimum for obtaining a film having a suitable thickness and a suitable constitution depending on the purpose or use thereof. Then, the minute metallic particles were washed with the solvent used and methanol and the wet minute metallic particles were dried to complete the surf ace treatment . In a solution of 10 g of epoxy monomer (BPA) in 15 ml of ethyl acetate, 10 g of the surface-treated minute metallic particles were stirred with a homogeni~er at - 150 rpm as illustrated in Fig. 11 to form a suspension a~d induce a reaction to ef fect the coating of the surface of Ag/Cu particles with an insulating resin layer .
Here, the principle of the production of the MC type conductive filler will be described below.
When a suspension is formed by disperslng minute metallic particles in a solution of tr;A7;
thiol in an organic solvent, this tr;~7;nl~ thiol reacts with the OH group on the surface of the metallic particles to form a relevant salt. As a result, the surf ace of the minute metallic particles is coated with a tr;A7in~ thiol film. When a suspension is formed by dispersing the minute metallic particles treated will tr~7;ne thiol in a solution of the monomer, the surface of the minute metallic particles undergoes a reaction. Conseguently an l!~C
_ 21 89~û 1 type conductive filler having the surface of minute metallic particles coated with the poLymer is obtained .
Now, the reaction ~h;~n i ~m lnvolved herein 5 will be described below.
The ~r;~7lnP thiol is a compound having a structural formula I shown below.
R

N N-H
s,l~ ~is N

H
(wherein R stands for a group represented by -SH, -N(CH~)2, -NHC6H5, -N(C4Hg~z, -N(C8H~7)2, ~N(CI2H2s)2~
N ( CH2CH=CH2 ) 2, -NHC8H~6CH=CHC8HI7, -NCH2C6H4CH=CH2 ( C8HI7 ), or 2 0 -NHC6H4 ) .
~7hen the minute metallic particles are sub~ected to a surface treatment with this ~ri~7in~
thiol, there ensues a reaction path in which a monomolecular film of triazine thiol is formed on the - surface of the minute metallic particles in the first s~ep and the monomolecular film develops into a polymolecular film in the second step as illustrated in Fig. 12, with the result that the surface of the minute metallic particles will be coated with the triazine thiol film. ~.7hen the minute metallic particles that have undergone the surf ace treatment are mixed with an epoxy monomer, the triazine thiol acts as a cross-linking agent for the epoxy monomer to undergo a reaction illustrated in Fig. 13 and gives rise to a cured product of epoxy. Consequently, an MC
type conductive filler having a surface of the minute metallic particles coated with the epoxy resin i5 obtained .
Here, it is necessary tb pay attention to the following points.
( 1 ) The production of the triazine thiol f ilm mu5t be carried out in an atmosphere of nitrogen . ( 2 ) .. _ .. .. ... .. , . _ _ _ 2 t 8q80t The fr;~in~ thiol concen~ration must be not more than lO ~ mol/liter. (3) The reaction of the monomer must be carried out with the suspension stirred at a rate in the range between 50 and 250 rpm. The reason for ( 1 ) is that the minute metallic particles readily undergo corrosion in the presence of air because they have a large surface area. The reason for (2) is that the concentration of RTD (~r;;~;nr thiol) must be kept below 10 3 mol/liter because the amount of film i8 calculated from the amount of unreacted RTD. The reason for ( 3 ) is that the minute metallic particles settle and agglomerate during the reaction of the monomer when stirring is omitted.
( 2 ) Observation of cross section of capsule type minute metallic particles The produced f iller was embedded in the epoxy resin, allowed to cure, and cut with a microtome to expose a cross section of the capsule type minute metallic particle to visual observation.
( 3 ) Conf irmation of insulation with capsule type minute metallic particles . The produced MC type conductive f iller was ' agglomerated into a crh~r;n~ mass and tested for insulation resistance with an insulation resistance meter used at freely selected points of measurement.
( 4 ) Production of conductive adhesive agent An MC type conductive adhesive agent was produced by mixing an MC type conductive adhesive agent with 20% by volume of the MC type conductive filler prepared in ( l ) above . The results of the test indicate the viscosity of the produced adhesive agent was so high as to jeopardize the workability if the voluminal proportion ~re~r~d 20 %, the produced adhesive agent was barely usable if the voluminal proportion was up to 6096 of the MC type conductive filler, and the adhesive agent included parts allowing no electric continuity if the voluminal proportion was unduly small. Thus, the optimum content of the MC
type filler is fixed at 20% by volume. Here, the .. .. , . , . . .. _ _ = .

2t'~q8~1 adhesive agent used herein was a one-component type for facilitating the process of production.
(5) Union of chip and substrate A substrate illustrated in Fig. 4 to which the conductive adhesive aqent produced in ( 4 ) above was applied and a glass chip ( 12~ pins, 300 um pitch, and electrode interval 100 um) illustrated in Fig. 6 on which stud bumps were formed were subjected to ~he c~ ~ ~ssion bonding at 175C, 30 s, and 20 g/bump.
(6) Test for electric continuity and test for insulation Samples of the product of union indicated in (5) above.were tested for electric continuity resistance by the four-~ n~l method using the points of measurement illustrated in Fig. 6 and Fig. 7 and tested for resistance with a resistance meter.
(Results ) ( 1 ) Observation of cross section of microcapsule type conductive filler The condition of the surface of minute - conductive particles coated uniformly with an i~sulating resin as illustrated by a type diagram of Fig. 3 was cnn f~
( 2 ) Insulation resistance of microcapsule type conductive f iller The magnitudes of insulation measured at all the points invariably exceeded a high level of 1 x 101l Q.
(3) ~easurement of electric continuity resistance and insulation resistance between bonded chip and substrate The union between the chip and the substrate was obtained as illustrated by a type diagram in Fig. 10. The magnitudes of electric continuity resistance were satisfactory, invariably falling ~elow 0 . 2 Q per point of contact . Though the f iller was incorporated in such a large proportion as 20% by volume, highly satisfactory insulation of 1 x 101l Q
.. , , ., _, ,, .. .. _ _ _ _ _ _ _ _ , . ~ ~ . , -36- 2~8~
was found between the ad~acent patterns.
~his example represents one case of using tiazine thiol as an affinity agent. This invention is not limited to this particular affinity agent.
5 Naturally, any compound possessing a reactive group that exhibits affinity for both the metal and the monomer i nt~ntlf~ to coat the metal can be used as an af f inity agent .
ExamPle 15 In the production of capsule type minute metallic particles by the procedure of Example 14, the stirring of the suspension was carried out at varying rates of 30, 50, 250, and 300 rpm to determine the effect of the stirring speed on the stability of the suspension.
~Results ) Table 11 shows the effect of the stLrring speed (30, 50, 250, and 300 rpm) on the stability of the suspension. The results indicate that the stirring speed must be in the range between 5 0 and 25 0 rpm f or 20 the sake of suspension stability.
Table 11 Relation between stirring speed and suspension stability Speed of st rring 30 50 250 300 ( rpm) suSpension Sedimentation of Adheslon of ~inute stability minute conductive Stable Stable conductive particles particles observed to beaker wall observed ExamPle 1 6 An ~C type conductive filler and a capsule type conductive adhesive agent were produced by following the procedure of Example 14, except that alcohol was used in the place of acetone. They were evaluated in the same manner as in Example 14.
(Results ) In all the items of evaluation, the results we~e nearly the same as those obtained in Example 14.
This invention is constructed as described above, .... .. _ . . .. , _ , ,, - 37 - 2 1 ~ 9 ~ O ~
it enables an MC type conductive filler coated with a thermosetting resin possessed of better characteristic properties than a thermoplastic resin to be produced easily at a low cost. Thus, this invention realizes a practica~ MC type conductive adhesive agent excellent liAhl~;ty ~ p~ fon~n~.

Claims (16)

1. A method for the production of a microcapsule (MC) type conductive filler comprising (a) a step involving immersing minute conductive metallic particles in an affinity agent thereby treating the surface of said minute conductive metallic particles, (b) a step involving immersing and dispersing said surface-treated minute conductive metallic particles in an epoxy monomer thereby forming a suspension, and (c) a step involving polymerizing the monomer in said suspension thereby forming a thermosetting insulating polymer on the surface of said minute conductive metallic particles.

2. A method according to claim 1, wherein said step (a) is preceded by a step involving cleaning the surface of minute conductive metallic particles.

3. A method according to claim 1, wherein the minute conductive metallic particles are extracted after said step (a) and are subjected to a step involving washing and drying prior to said step (b).

4. A method according to claim 1, wherein said affinity agent is triazine thiol.

5. A method according to claim 1, wherein said affinity agent is dissolved in a solvent during said step (a).

6. A method according to claim 5, wherein said solvent is acetone or an alcohol.

7. A method according to claim 4, wherein the concentration of triazine thiol is not more than 10 -3 mol/liter.

8. A method according to claim 1, wherein said immersion of said step (a) is conducted at a temperature of not lower than 17°C.

9. A method according to claim 1, wherein said immersion of said step (a) is conducted for a time period of 30 ~ 5 minutes.

10. A method according to claim 1, wherein the immersion treatment is carried out in an atmosphere of nitrogen.

11. A method according to claim 1, wherein said affinity agent reacts on the surface of minute metallic particles to form a relevant salt and deposit a coating film on the surface of said minute metallic (conductive) particles.

12. A method according to claim 1, wherein the stirring of said suspension thereby causing the reaction during said step (c) is carried out at a rate in the range between 50 and 250 rpm.

13. An MC type conductive adhesive agent having dispersed in an adhesive agent an MC type conductive filler coated with a thermosetting resin, obtained by means of a method in accordance with any one of claims 1 to 12, the thermosetting resin coating having a thickness of not more than 3µm.

14. An MC type conductive adhesive agent according to claim 13, wherein said adhesive agent is an epoxy type one-component adhesive agent.

15. An MC type conductive adhesive agent according to claim 13, wherein said adhesive agent incorporates therein capsule type minute metallic (conductive) particles in a proportion of not more than 60% by volume.

16. An MC type conductive adhesive agent according to claim 13, wherein said thermosetting resin coating has no pinholes.