JPH111673A - Polyglycidylpihenyl ether of alkylene or alkyleneoxy chain for use in microelectronics adhesive - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an epoxy compd. which gives the major component of an adhesive which cures rapidly and exhibits high strengths and flexibility by selecting an epoxy compd. which contains a medium-length main oligomer chain comprising repeating alkylene or alkyleneoxy units and has arom. parts at only the molecular terminals and two or less hydroxyl groups. SOLUTION: The objective compd. is a flexible epoxy compd. having a total chlorine content of lower than 0.1 wt.% and a structure represented by the formula (R<1> is H, 1-18C alkyl, 1-5C alkoxy, aryl, alkaryl, 1-5C perfluoroalkyl, or 1-5C acyl; n is 1-3; and when q is 1-6, then the flexible chain is CH2 CH2 CH2 CH2 O and when q is 3-10, the flexible chain is CH2 CH2 O). To prevent the ionic contamination of the compd., it is prepd. by a synthetic method which does not use epichlorohydrin. The compd. is liq. at room temp., has a neat resin viscosity of 25,000 cP or lower at 25 deg.C, and, when cured, exhibits a glass transition point of 150 deg.C or lower and an elastic modulus of 2.0 MPa or lower.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001] The present invention relates to flexible epoxy compounds for use in microelectronic adhesives that can be rapidly cured and have low or no ionic contamination, and a method of synthesizing the same.

One step in the manufacture of semiconductor integrated circuits is to bond a silicon chip or die with an adhesive to a copper frame over which metal conductors extend. The bonded die and wire frame assembly are encapsulated with a polymer sealant and connected to external circuitry by means of metal wires extending from the encapsulation.

[0003] Epoxy formulations are preferred as die bonding or encapsulating adhesives due to their excellent adhesive strength. Conventionally used epoxies are aromatic epoxies due to their strength, but are inherently hard and brittle. During manufacture, the adhesive and the substrate undergo repeated thermal cycling. If the adhesive and the substrate have significantly different coefficients of thermal expansion, the thermal cycling stress can result in adhesive failure, substrate bending, or die failure. Thus, an important criterion for adhesives used in microelectronics is that the adhesive be strong and flexible to absorb thermal cycling.

A second important criterion is that the adhesive can cure rapidly at a speed commensurate with the speed of the assembly line. The required rapid cure time is typically 2
At 00 ° C. for 30-60 seconds, which is known as snap cure (rapid cure). This combination of adhesive strength, flexibility and fast setting criteria is difficult to achieve with a single adhesive.

It is also important that the epoxy formulation be free of ionic contamination, especially sodium and chloride ion contamination, and that it be free of bound chlorine. These contaminants can cause corrosion of the metal wires in the semiconductor device, which can ultimately result in destruction of the device.

[0006] To impart flexibility, the epoxy can co-react with the aliphatic softener, however, this reduces adhesive strength due to the reduced level of aromatic moieties. The addition of a softener also reduces the rapid curability because the softener has a high molecular weight per epoxy. Furthermore, when the aliphatic and aromatic epoxies cure, they cannot co-react due to differences in reaction rates,
Prior to curing, low molecular weight compounds volatilize and high molecular weight compounds cannot be completely cured. Sometimes this combination of factors is fatal in fast cure formulations, even with slow cure formulations.

[0007] One possible means to solve some of these problems is to combine aromatic and aliphatic moieties in the same polymer backbone, but currently available polymers of this type are It has a high aromatic / aliphatic ratio, which makes it less flexible. Furthermore,
The method of preparation of these materials results in high chlorine contamination,
It is harmful in microelectronics applications. This polymer also has a high viscosity, which requires the addition of a solvent as a diluent. During rapid cure, cure is sometimes faster than complete evaporation of the solvent, which results in voids in the cured adhesive and can damage microelectronic chips or devices. For this reason, low viscosity materials that do not require solvents are preferred.

[0008] The problems associated with imparting strength and rapidly curing flexible compounds are amplified as the microelectronics industry moves to larger die sizes. This has strength and purity, and
There is a continuing need for improved flexible epoxies that are formulated into rapidly cured die attach adhesives.

[0009] The present invention is directed to a flexible epoxy resin that can be used to formulate a fast setting die attach adhesive, encapsulant and coating. Epoxy is
Prepared by a synthetic route that avoids the use of epichlorohydrin, which includes ionic contaminants (eg, including sodium ions, chloride ions and organically bound chlorine)
At a lower level of about 0.1% compared to prior art compositions.
Not more than 1% by weight. Prior art compositions contain higher levels of contaminants, especially when not subjected to rigorous purification methods, which significantly reduce yields. Furthermore, this synthetic route allows the preparation of well defined chemical structures, rather than mixtures of various resins.

The epoxy resin is liquid at room temperature,
Has a Tg value after curing of 150 ° C. or less, and at 25 ° C.
It has a pure resin viscosity of 25,000 cps or less. Thus, no solvent is required to incorporate these epoxies into adhesives containing high levels of fillers (e.g., heat or conductive fillers).

The elastic modulus,% strain and glass transition temperature (Tg) values of these epoxies show high flexibility. The elastic modulus is usually 2.0 MPa or less. % Distortion is usually
5% or more. The Tg values after curing of these epoxies are below 150 ° C, and in some cases will be below 100 ° C.

In another aspect, the invention relates to adhesives made with these epoxies for use in microelectronic applications. The flexibility of these compounds is compounded with conductive materials, such as silver flakes, and is retained when used to bond silicon chips to metal leadframe substrates. The cured epoxy shows a high radius of curvature of 350 mm or more (the larger the radius of curvature, the less the chip bends, thereby indicating a flexible adhesive).

[0013] The cured epoxy also exhibits good adhesive strength, measured as die shear strength. Die shear is a measure of the force required to remove the bonded chips from the metal substrate and is 13 MPa or more for these compounds.

Furthermore, the adhesive does not show any loss of flexibility or strength. Preferably, the formulation comprises 20 to 80 parts by weight of a flexible epoxy and 80 to 20 parts by weight of an aromatic O-glycidyl ether (based on a total of 100 parts by weight), a curing agent, a conductive filler and the desired By the epoxy resin 1
Contains 20 to 50 parts by weight of phenolic hardener (pphr) per 00 parts.

The composition of the epoxy resin includes a medium length alkylene or oligomer backbone oligomer backbone to provide flexibility, but sufficient crosslink density to produce useful adhesive properties. Must be maintained. The flexible backbone is terminated at one or both ends containing an aromatic moiety having one or more epoxy functional groups. Thus, the compound has no more than two aromatic moieties, which are only present at the termini. Limiting the number and location of the aromatic moieties in the polymer backbone maintains the strength imparted to the cured material by the aromatic moieties and the flexibility imparted to the cured material by the aliphatic moieties To maximize.

This compound has no more than two hydroxyl groups in the molecule; limiting the number of hydroxyl groups to no more than two results in low viscosity.

Epoxy has one of the following general formulas:

Embedded image (Wherein R ′ is H, C _1-18 alkyl, C _1-5 alkoxy or aryl or alkylaryl or C
_1-5 acyl, n is an integer from 1 to 3, and the flexible chain is as described for each structure above, and p, q and r are as described for each structure. ).

As used herein, alkyl refers to a hydrocarbon group derived from an alkane and has the general formula C _n
Has a H _{2n + 1;} alkoxy refers to an alkyl group containing also oxygen; aryl group refers to a group having a ring structure characteristic of benzene; alkylaryl group refers to a group having both an alkyl and aryl structures; perfluoro Alkyl is 1
An acyl group refers to an organic acid group in which one or more hydrogens have been replaced by fluorine; and an acyl group refers to an organic acid group in which the OH group of the carboxyl group has been replaced by some other substituent;
It is attached to the phenyl ring.

[0019] The flexible epoxy resin can be prepared by any suitable synthetic method that results in a product that is not ion-contaminated. A preferred synthetic route avoids the use of epichlorohydrin, and (a) preparing an olefin precursor by attaching an alkylene or alkyleneoxy chain to a phenoxy compound having an olefin group; and (b) To oxidize to the corresponding epoxide.

In step (a), the flexible alkylene or alkyleneoxy chain terminates in a functional group that is activated for nucleophilic substitution. Preferably, this functional group is an epoxy, chloro, sulfonate or toluene sulfonate. The flexible chain is derived by nucleophilic addition of a phenolate compound to drive out chloride, sulfonate or alkoxy (by opening the epoxy ring) functionality. The phenolates are prepared from the reaction of sodium hydroxide or other alkali metal hydroxide with a phenolic compound having only one hydroxyl group. Phenolic compounds having only one hydroxyl group ensure that nucleophilic substitution occurs only once and results in a well-defined chemical structure (ie, the product is not a mixture). The phenolic compound is also substituted with an olefin moiety, preferably an allyl group, which is inert to nucleophilic substitution and acts as a site for the final epoxide product. In step (b), the olefin on the phenol group is converted to an oxirane (epoxide).

Preparation of Olefin Precursor The olefin precursor to the epoxy compound can preferably be prepared by any of the general methods described below. A more detailed description of each method is provided in the examples.

I. Diglycidyl compounds of alkylene or alkyleneoxy chains of appropriate length corresponding to any of the above general structures in the final product can be obtained in the presence of a catalyst effective to catalyze the condensation reaction between the phenolic compound and oxirane. To react with a phenol compound having one or more olefin groups.

Preferred diglycidyl compounds are 1,4-butanediol glycidyl ether; 1,12-dodecanediol glycidyl ether; polyethylene glycol diglycidyl ether, poly (tetramethylene glycol) diglycidyl ether and polypropylene glycol diglycidyl ether. Wherein the polyglycol portion of the molecule has a molecular weight of less than 2000 daltons; 1,2,9,10-diepoxydecane, 1,2,13,14-diepoxytetradecane and similar compounds; and poly (caprolactone) diol Diglycidyl ether.

Preferred olefin-functionalized phenolic compounds are 2-allylphenol; 2,6-diallylphenol;
4-diallylphenol; 4-allyl-2-methoxyphenol; and other similar phenolic compounds. The phenolic compound can be used in excess to effect a high degree of reaction with the diglycidyl compound, and the excess can be removed from the product by distillation. The phenolic compounds also provide the necessary 2 in the product formation.
It may be substituted with a group that does not inhibit any of the two steps.

Preferred catalysts are chloride, bromide, hydrogen sulfate, quaternary ammonium or phosphonium salts of acetic acid, and other known catalysts, for example, triphenylphosphine. A more preferred catalyst is a quaternary ammonium salt containing a lower alkyl component, especially tetramethylammonium chloride.

II. An alkylene or alkyleneoxy chain of suitable length corresponding to any of the above general structures in the final product and having a leaving group at the end of the chain such as chloride, bromide, iodide or tosylate Can react with alkali metal or alkaline earth metal salts of phenoxides containing olefin groups.

The alkylene or alkyleneoxy compound having a leaving group is generally derived from the corresponding alcohol by converting the hydroxyl group to a leaving group using known reactions. For example, alkylene or alkyleneoxy chloride can be derived from an alcohol by reaction with SOCl ₂ . Tosylate can be derived from an alcohol by reaction with tosyl chloride in the presence of a base. Examples of suitable alcohol-terminated alkylene or alkyleneoxy chains are 1,4-butanediol; 1,12-dodecanediol; poly (caprolactone)
Diols; polyethylene glycols; and 1,10-decanediol.

The olefin-functionalized phenoxide compound is
Derived from the corresponding phenolic compound by the action of an alkali metal or alkaline earth metal hydroxide in the presence of an azeotropic solvent. These reactions are well known in the art. Suitable azeotropic solvents are toluene, xylene, p-
Contains cymene and similar solvents.

After forming the epoxidation precursor of the olefin end group , the olefin is oxidized by any method effective to provide the corresponding epoxy. Various methods of effectively performing the oxidation process have been described in the literature and, as oxidizing agents, organic peracids such as peracetic acid or trifluoroacetic acid; peroxyimidic acids; dioxirane compounds such as dimethyldioxirane; Including the use of inorganic acids such as peroxytungstic acid systems; metal catalyst systems such as methyltrioxorhenium and hydrogen peroxide, titanium catalyzed t-butyl hydroperoxide and manganese-salen catalyzed oxidants.

The preferred epoxidation method uses inorganic peracids, peracetic acid and peroxyimidic acid as primary oxidizing agents. Further details of each method are provided in the examples.

Preferred inorganic peracids are based on tungstic acid, phosphotungstic acid and similar compounds, using hydrogen peroxide as secondary oxidizing agent. The oxidation process is improved by using a two-phase system and using a quaternary ammonium or phosphonium salt as a phase transfer catalyst.

[0032] Peracetic acid in acetic acid can also be successfully used as an oxidizing agent. Many solvents are suitable for this oxidation, but the rate is faster in chlorinated solvents such as dichloroethane. In this way, the accumulated acetic acid begins to attack oxirane as the reaction proceeds to complete conversion. The result is a product with a low oxirane content (high WPE) and a higher viscosity than when the oxidizing agent is an inorganic peracid in the presence of a quaternary onium salt.

Peroxyimidic acid as oxidizing agent offers the advantage that the by-product is acetamide, which is non-toxic to oxirane. Preferred peroxyimidic acids are derived from acetonitrile and hydrogen peroxide. The optimal conditions for peroxyimidic acid oxidation are the use of KHCO ₃ , a reaction temperature close to 40 ° C., and
Optionally, includes the use of an aqueous sponge, for example, 2,2-dimethoxypropane.

Although the flexible epoxy compositions of the present invention are useful as oven cured adhesives, their use can be extended if they have rapid cure properties. The epoxy can be formulated into an adhesive that exhibits good adhesive strength, flexibility, and rapid curing capability. Preferred formulations are 20-80 parts by weight of a flexible epoxy and 80-2
It will contain 0 parts by weight of the aromatic O-glycidyl ether resin (100 parts by weight in total), the curing catalyst and optionally one or more fillers. Generally, the curing catalyst is an imidazole catalyst present in an amount of about 5 to 10 parts by weight per 100 parts by weight of resin, and the filler is a thermally or electrically conductive filler, such as silver flake, Conductive or thermally conductive fillers or silica can be used. The filled diglycidyl ether is preferably present in an amount of 25% by volume of the adhesive formulation.

The aromatic O-glycidyl ether (aromatic epoxy) will be substituted with one or more aromatic rings and, if desired, one or more C ₁ -C ₃ groups. The aromatic epoxy has an epoxy equivalent weight (WPE, weight per epoxy) of 200 or less and can be obtained with the corresponding phenolic curing agent. Exemplary aromatic epoxies are bisphenol F diglycidyl ether, bisphenol A diglycidyl ether, resorcinol diglycidyl ether and epoxyphenol novolak.

The adhesive formulation comprises a phenolic curing agent having one or more hydroxyl groups per aromatic ring (derived from the aromatic epoxy described above) at 20-50 parts per 100 parts resin. It may further include. Exemplary phenolic curing agents include commercially available phenol novolak resins,
Bisphenol F, bisphenol A and resorcinol. The addition of the phenolic resin improves the adhesive strength of the formulation after exposure to moisture and thermal shock at 250 ° C., and acts to inhibit bleeding of the flexible epoxy from the formulation.

In general, any effective curing catalyst can be used in an effective catalytic amount. The preferred curing catalyst is an imidazole catalyst and is usually present in an amount of about 5 parts per 100 parts resin. Preferred imidazole catalysts are imidazole, 2-ethylimidazole,
2-ethyl-4-methylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole and 2-undecylimidazole.

[0038] The filler may be any thermally or electrically conductive material known to be suitable in microelectronics applications and may be used in any effective amount. For many applications, the preferred filler is silver flake, but other conductive or thermally conductive materials may be used, and preferably are present in an amount of about 25% of the volume of the adhesive formulation.

The following examples illustrate the preparation of representative olefin precursors (adducts) by two synthetic routes and the epoxidation of olefins by three epoxidation methods to provide epoxy compounds (epoxies). An evaluation test method is provided and the performance is shown in the table.

[0040] Also disclosed are fast-curing die bond adhesive formulations comprising a flexible epoxy and an O-glycidyl ether aromatic epoxy and formulations comprising a phenolic curing agent. Test Method The following test method is used to evaluate the sample epoxy resin. Epoxy equivalent for each epoxy product (WPE,
(Weight per epoxy equivalent) was determined by dissolving the compound in glacial acetic acid and then titrating with standardized HBr / acetic acid (about 0.1N) to the violet / green transition of the crystal violet indicator. The viscosity of each sample was determined at 25 ° C. at various spindle speeds using a Brookfield cone and plate viscometer.

The amount of hydrolyzable chlorine was determined by the following method: 1-5 g (approximately 0.1 mg) of resin was placed in a clean 125 ml Erlenmeyer flask having a Teflon-coated magnetic stir bar. Accurately weighed. 40 ml of 0.1 N KOH dissolved in methanol was added. The flask equipped with a reflux condenser was placed in a water bath heated by a magnetic stirrer / hot plate unit. Reflux the stirred solution for exactly 15 minutes, then remove the flask,
It was allowed to cool to room temperature. The liquid was transferred to a clean 250ml beaker. The sample flask was rinsed three times with 50 ml of methanol and the liquid was transferred to a beaker. 10 ml of glacial acetic acid was added and chloride ions were titrated potentiometrically to the final point with a 0.005 N AgNO ₃ solution. The hydrolyzable chloride content was calculated in ppm as follows: Chloride (ppm) = (ml _{titrant) (N AgNO 3) (3.55x10} 4) / amount of weight g total chloride samples were determined by the following method: to a clean Erlenmeyer flask with a magnetic stir bar 1-5 g (approximately 0.1 mg) of the resin was accurately weighed in. 30 ml of dioxane and 15 ml of 3N KOH solution were added in ethanol. The flask equipped with a reflux condenser was placed in a water bath heated to 100 ° C. by a magnetic stirrer / hot plate unit. The sample solution was refluxed for 30 minutes. The flask was removed and it was allowed to cool to room temperature. 400ml clean liquid
Transferred to beaker. Sample flask with 50 ml of methanol
Rinse once and the liquid was transferred to a beaker. 100 ml of glacial acetic acid was added. Using a silver electrode with a KNO ₃ salt bridge, 0.00
Potentiometric titration with a 5N AgNO ₃ solution to the final point. Chloride ion was calculated in ppm as above. Example I. Olefin precursor synthetic adduct A :

Embedded image

The reactor was a 500 ml round bottom flask equipped with a mechanical stirrer, thermometer and condenser. The reagents 2-allylphenol (159 g, 1.19 mol), 1,
4-butanediol diglycidyl ether (120g, 0.59mol) and 1% tetramethylammonium chloride catalyst
(2.5 g) was added to the reactor and stirred at 50 ° C. for about 1 hour. Raise the temperature to 70 ° C and at that temperature add one more reagent
Stirred for hours; thereafter, the temperature was raised to 120 ° C. and the reagents were maintained at that temperature, while the progress of the reaction was monitored by gas chromatography (GC). It was determined to be complete after 4 hours, at which time the reaction was cooled and work-up was started.

The reaction mixture was transferred to a one-necked flask and placed on a kugelrohr apparatus (120 ° C./0.1 mmHg) to remove any residual starting material, especially 2-allylphenol.

Transfer the adduct to a 1000 ml separatory funnel and
Dissolved in 300 ml of toluene. This organic phase is 5% sodium carbonate (3x200mL), 10% sodium sulfate (3x200mL)
And rinsed with toluene through a neutral alumina pad (about 200 mL).

Toluene was converted to 60 with a rotary evaporator.
℃ / 25mmHg Removed by vacuum, then kuge at 70 ℃ / 0.1mmHg
All residual solvents were removed on an lrohr apparatus.

The adduct was obtained in 90% yield and was characterized by IR and ¹ H NMR spectroscopy. It is 65 at 25 ° C
It had a viscosity ranging from 0 to 870 cps.

Adduct B

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Adduct B was prepared in the same manner as used for Adduct A, except that 2,6-diallylphenol (310 g,
1.78 mol) in the presence of 4.5 g of tetramethylammonium chloride in 1,4-butanediol diglycidyl ether
(180 g, 0.89 mol). The temperature of the reaction mixture was gradually raised to 180 ° C. and held there for 1 hour until the reaction was complete as indicated by GC. The product was isolated in 81% yield as described for Adduct A and IR and ¹ H NMR
The characteristics were examined with a spectrometer. It had a viscosity of 983 cps at 25 ° C.

Adduct C :

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Adduct C was prepared in a similar manner to that used for Adduct A, except that 2-allylphenol (8.44 g, 0.1%) was used.
063 mol) in 1,2,13,14-diepoxytetradecane (6.48
g, 0.0286 mol; prepared by oxidation of 1,13-tetradecadiene) in the presence of 0.1 g of tetramethylammonium chloride. The temperature of the reaction mixture was raised to 185 ° C,
It was held there for 3.3 hours until the reaction was complete as indicated by GC. The product was obtained in a yield of 81 as described in Adduct A.
% And characterized by IR and ¹ H NMR spectroscopy.

Adduct D :

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The reactor was a 1 liter multi-neck flask equipped with a mechanical stirrer, thermometer, Dean-Stark trap and condenser. Solid sodium hydroxide pellets (19.95 g, 0.5 mol) and 83 mL of xylene were added to the apparatus under a gentle nitrogen purge and heated to 70 ° C. with a heating mantle. At that temperature, 20
2-Allylphenol (66.9) dissolved in 0 mL xylene
g, 0.5 mol) was introduced through a slow dropping funnel while the system was refluxed. Dean water generated as a by-product
-Removed by azeotropic distillation in a Stark trap and then De
Additional xylene (225 mL) was evaporated with an-Stark trap to remove any trapped water.

Thereafter, 125 ml of p-cymene, 25 ml of dimethylformamide and 0.1 g of KI were added, and the whole content was cooled to 100.degree. Poly dissolved in 50 mL of p-cymene
Dichloride of (tetrahydrofuran) -250 (45 g, 0.17 mol; prepared by reacting poly (tetrahydrofuran) -250 with thionyl chloride, available from BASF Corp.) was introduced into the flask through a slow dropping funnel. Reaction temperature 150 ℃
And held for 24 hours. Upon cooling, the by-product salt (sodium chloride) is removed by filtration and the pH is neutral (
The filtrate was washed with 5% sodium hydroxide (2 × 150 mL) and then with 10% sodium sulfate (150 mL each) until pH = 7) on the test strip. The solvent was first rotary evaporated and then Kugelrohr equipment (130 ° C / 0.2mm
Hg). The product was recovered in 95% yield and the IR
And ¹ H NMR spectroscopy.

Adduct E :

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The reactor was a 5 liter multi-neck flask equipped with a mechanical stirrer, thermometer, Dean-Stark trap and condenser. Solid sodium hydroxide pellets (79.2 g, 1.98 mol) and 1 L of xylene were added to the reactor under a gentle nitrogen purge, and 13
Heated to 5 ° C (reflux). At that temperature, 2-allylphenol (267 g, 1.98 mol) was introduced through a slow dropping funnel while continuing to reflux the system. The water produced as a by-product is removed by azeotropic distillation in a Dean-Stark trap,
An additional 100 ml of xylene was then evaporated by a Dean-Stark trap to remove any trapped water.

The internal temperature was reduced to 90 ° C. and 100 mL of dimethylformamide and tetraethylene glycol ditosylate (400 g, 0.79 mL) dissolved in 300 mL of xylene.
5 mol; prepared by reacting p-toluenesulfonyl chloride with tetraethylene glycol in the presence of pyridine) was introduced into the flask through a slow dropping funnel. Reaction temperature 12
Raised to 0 ° C. and held there for 2 hours. The reaction was cooled and the by-product salt (sodium tosylate) was removed by filtration. Neutral pH (pH = 7 on test strip)
The filtrate was washed with 5% sodium hydroxide (2 × 600 mL) until then, and then with 10% sodium sulfate (3 × 300 mL).

The solvent was first removed on a rotary evaporator and then on a kugelrohr apparatus (80 ° C./0.2 mmHg). The product was recovered in 95% yield and IR and ¹ H
Analyzed by NMR spectroscopy.

Example II: Synthesis of epoxy compound Epoxy A:

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Adduct A was oxidized in two ways to provide Epoxy A; using peracetic acid and peroxyimidic acid.

1. The oxidation reactor with peracetic acid was a 500 mL flask equipped with a mechanical stirrer, thermometer and slow dropping funnel. Adduct A (75 g, 0.16 mol, 0.32 mol olefin functionality),
1,2-dichloroethane (150 mL) and sodium acetate (4.7
g) was added to the reactor and brought to 23 ° C. using a water bath. The introduction of peracetic acid (94.7 g) (35% in acetic acid) was started and the reaction exothermed to 29 ° C. After completing the addition, remove the water bath for 30 minutes.
Heated to ° C. The internal temperature rose to 38 ° C. After 10 minutes,
The temperature was reduced to 35 ° C and kept at a temperature of 35 ° C for 5 hours. Reaction completion was monitored by disappearance or minimization of the 1635 cm ^-1 absorption of the IR spectrometer. Upon completion, 300 mL of distilled water was added to the reaction mixture. The phases were separated and the organic phase was washed with 300 mL of 5% sodium bicarbonate solution, after which
Washed with 200 mL of 5% sodium sulfite solution. The emulsion was broken by adding toluene (300 mL). Thereafter, the organic phase is washed with 200 mL of 10% sodium sulfate and
Washed with 0 mL of distilled water.

The organic phase was separated off, dried over magnesium sulfate and filtered off with suction. First, the solvent was removed with a rotary evaporator (50 ° C / 20 mmHg).
r Removed with equipment (60 ° C / 0.1mmHg). The final product is isolated as an oil, and 7280 cps at 25 ° C., epoxy equivalent
= 269 (calculated = 251) and was characterized by IR and ¹ H NMR spectroscopy. Total chlorine = 717 ppm. In a second preparation of this material, EEW = 274, viscosity 6550 cps, hydrolyzable chlorine = 519 ppm and total chlorine = 719 ppm.

[0062] 2. Acetonitrile / hydrogen peroxide (Peru
Oxidation with xyimidic acid): 250 ml reactor equipped with mechanical stirrer, thermometer and slow dropping funnel
It was a round bottom flask. Adduct A (30.0 g, 0.0638 mol, 0.128 mol olefin functionality), methanol (74 m
L), acetonitrile (11.54 g, 0.2815 mol) and KHCO
₃ (7.12 g, 0.7111 mol) was added to the apparatus and heated to 40 ° C. At that temperature, 30% H ₂ O ₂ (10.0 g, 0.0882 mol) was added dropwise. The reaction mixture was kept at 40 ° C. for 7 hours, at which point a further 30% H ₂ O ₂ (13.8 g, 0.1218 mol) was added dropwise. The reaction was kept at 40 ° C. for another 20 hours.

Thereafter, 2,2-dimethoxypropane (48 g, 0.
462 moles, i.e., 0.5 with H ₂ O reference from 30% hydrogen peroxide
(Equivalent) was added dropwise. The reaction was heated at 40 ° C. for an additional 24.5 hours, which resulted in a minimum IR trace of the reaction sample at 1637 cm ^−1.
Corresponds to the point showing absorption. The peroxide was neutralized by the addition of 10% Na ₂ SO ₃ , which was determined on KI-starch indicator test strips. Methanol and acetonitrile were removed on a rotary evaporator (40 ° C./25 mmHg) in vacuo. The residue was taken up in 150 mL of toluene and washed with distilled water (150 mL). Emulsification was moderated by the addition of 10% Na ₂ SO ₄ . The organic phase is separated off and the solvent is first removed on a rotary evaporator (80 ° C./25 mmHg), followed by kugelr
It was removed with an ohr device (80 ° C / 0.1mmHg).

The product was isolated in 74% yield (23.7 g), epoxy equivalent = 315 (calculated = 251), viscosity = 6270 cps at 25 ° C., and characterized by IR and ¹ H NMR spectroscopy. Was. Hydrolyzable chlorine was 455 ppm and total chlorine was 564 ppm.

Epoxy B :

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Adduct B was oxidized by two methods to provide epoxy B: peracetic acid and peroxyimidic acid

1. Oxidation with peracetic acid Adduct B was oxidized as described for the synthesis of Epoxy A using 35% peracetic acid. Adduct B (110g, 0.
Was treated with peracetic acid (210 mL of a 35% solution, 1.09 mol) in 220 mL of 1,2-dichloroethane at 35 ° C.
The product was recovered in 85% yield and 176 (calc = 154).
The viscosity was 25,300 cps at 25 ° C. and was characterized by IR and ¹ H NMR spectroscopy. Hydrolyzable chlorine was 467 ppm and total chlorine was 620 ppm.

2. Acetonitrile / hydrogen peroxide (Peru
Oxidation with xyimidic acid): Adduct B was oxidized using acetonitrile and hydrogen peroxide as described for the synthesis of epoxy A. Acetonitrile and hydrogen peroxide generated peroxyimidic acid in situ. Adduct B (150 g, 0.27 mol) was treated with acetonitrile (97 g), potassium bicarbonate (60.5 g), 30% hydrogen peroxide (200 g), 2,2-dimethoxypropane (812.5 g) and methanol (375 mL). Until the IR absorption at 163 cm ^-1 no longer changes significantly
The reaction was performed at 40 ° C. The product was isolated in 74% yield (23.7 g), epoxy equivalent = 229 (calculated = 154), viscosity = 2 at 25 ° C.
0,900 cps and characterized by IR and ¹ H NMR spectroscopy. Hydrolysable chlorine = 624 ppm and total chlorine = 8
It was 39 ppm.

Epoxy C:

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Oxidation using a peroxytungstic acid catalyst provided Epoxy C. Peroxytungsten
Oxidation with acid : 60 mL of adduct C (17 g, 0.035 mol)
Of dichloroethane, to which 3.8 g of tetrabutylammonium hydrogen sulfate were added and this was stirred vigorously at room temperature. 10 ml into this vigorously stirred solution
Sodium tungstate dihydrate in distilled water (6.3g)
And an aqueous mixture containing a sufficient amount of 85% phosphoric acid to adjust the pH to 6.5. Then 30% hydrogen peroxide (15.
(7 g, 0.138 mol) were added at room temperature and the combined contents were stirred for 96 hours. At that point, the absorption of 1637 cm ^-1
The IR spectrum was minimized.

The phases were separated, and the organic layer was washed with 5% sodium sulfite (2 × 100) until the peroxide was completely quenched.
The product was isolated by washing with (mL). The solvent was removed on a rotary evaporator at a temperature below 40 ° C. and the residue was dissolved in 100 ml of toluene. The toluene layer was washed with 150 mL of 5% sodium carbonate, water (2 × 150 mL), and then with 10% sodium sulfate (2 × 150 mL). The toluene was removed from the organic layer first on a rotary evaporator and then on a kugelrohr apparatus under high vacuum (80 ° C / 0.1 mmHg). The product is an isolated oil in 93% yield and has an epoxy equivalent = 289 (calculated = 263), viscosity = 91 at 25 ° C.
00 cps and characterized by IR and ¹ H NMR spectroscopy. Hydrolysable chlorine = 883 ppm and total chlorine = 959 pp
m.

Epoxy D :

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Adduct D was oxidized by two methods to provide epoxy D: using peracetic acid and peroxytungstic acid. 1. Oxidation with peracetic acid Using 35% peracetic acid in 1,2-dichloroethane at 35 ° C,
As described in the synthesis of epoxy A, adduct D
(50 g, 0.107 mol) was oxidized. The product was isolated as an oil in 60% yield, which had an epoxy equivalent = 274 (calculated = 249), viscosity at 25 ° C. = 417 cps, IR and ¹ HN
The characteristics were examined by MR spectroscopy. Hydrolyzable chlorine: 35 ppm and total chlorine: 103 ppm.

2. With peroxytungstic acid catalyst
Using sodium tungstate dihydrate and hydrogen peroxide, as described in the synthesis of Epoxy C,
Adduct D (67.8 g, 0.14 mol) was oxidized. The product
Isolated as an oil in 83% yield, it had an epoxy equivalent = 252 (calculated = 249), viscosity at 25 ° C. = 410 cps, and was characterized by IR and ¹ H NMR spectroscopy. Hydrolyzable chlorine = 53 ppm and total chlorine = 100 ppm
Met.

Epoxy E :

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Adduct E was oxidized by two methods:
Uses peracetic acid and peroxytungstic acid catalysts.

1. Oxidation with peracetic acid Using 35% peracetic acid in 1,2-dichloroethane at 35 ° C,
As described in the synthesis of epoxy A, adduct E
(30 g, 0.07 mol) was oxidized. The product was isolated as a 91% yield oil, which had an epoxy equivalent = 258 (calculated
= 229), viscosity at 25 ° C. = 397 cps, IR and ¹ H NMR
The characteristics were examined with a spectrometer. In a second preparation of this material, EEW = 259, viscosity = 354 cps, hydrolyzable chlorine = below the detection limit, and total chlorine = 785 ppm.

2. For peroxytungstic acid catalysis
Using sodium tungstate dihydrate and hydrogen peroxide as described in the synthesis of Epoxy C:
Adduct E (24 g, 0.056 mol) was oxidized. The product
Isolated as an oil in 94% yield and epoxy equivalent =
241 (calculated value = 229), viscosity at 25 ° C. = 347 cps, and characterized by IR and ¹ H NMR spectroscopy. Hydrolyzable chlorine was 58 ppm and total chlorine was 578 ppm.

Epoxy F, Comparative Example:

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As a comparison with the embodiment of the present invention,
Epoxy F was prepared by the method described in U.S. Pat. No. 3,522,210 to ers, Examples 1A and 15.

Preparation of Bisphenol Compound (Example 1):
A 1 liter flask equipped with a mechanical stirrer, thermometer, slow dropping funnel, condenser and nitrogen blanket was charged with bisphenol A (228.29 g, 1.0 mol), 150 g of dimethyl sulfoxide (DMSO) and 150 g of toluene. After the solid was dissolved, a 50% aqueous NaOH solution (80 g, 1.0 g
Mol) was added over 20 minutes. The temperature rose to about 50 ° C and heat was applied to raise the temperature to 100-110 ° C. Reflux was reached at 101 ° C., at which point 2-chloroethyl ether (71.5 g, 58.6 mL, 0.5 mol) was added via a slow dropping funnel over 18 minutes. The reaction temperature was held at reflux for 36.75 hours, at which point the pH had not reached 7-8, but GC analysis indicated that the reaction had ceased with bisphenol A consumption. Toluene (150mL)
Was added and an azeotropic distillation was started to remove about 60 mL of H ₂ O and another 40 mL of toluene was further removed to ensure drying. The organic solution was filtered, neutralized with concentrated HCl to pH = 6 and re-filtered. One solution was placed in a round bottom flask and stripped on a rotary evaporator at 60 ° C./11 mmHg to collect 300 mL of distillate. Further distillation was performed at ambient pressure (about 760 mmHg) and 170 ° C. pot temperature, after which a vacuum of about 30 mmHg was established and the pot temperature was raised to 219 ° C. (steam temperature 122 ° C.). The flask was cooled to room temperature.

Preparation of Diglycidyl Ether with Flexible Linking Chain (Example 15): 400 g of ethanol and 240 ml
Dissolved material in epichlorohydrin and transferred to a 2 liter multi-neck flask for a second reaction. The solution was heated to 60 ° C., at which point about 70 mL of 50% NaOH was added (about 7 mL for 25 min, about 10 mL for 5 min, about 46 mL for 35 min and about 7 mL for 15 min). The reaction mixture was transferred to a 2 liter single neck flask and the ethanol, water and epichlorohydrin were removed on a rotary evaporator at 96 ° C./11 mm Hg. The residue was dissolved in 600 mL of methyl isobutyl ketone and 800 mL of water, transferred to a separatory funnel, and the phases were separated. Wash the organic layer with 200 mL of water, which becomes an emulsion,
Mitigation was achieved by adding 0 mL of saturated sodium sulfate. The pH of the water wash was about 7 (neutral). The organic solution was placed on a rotary evaporator and the solvent was removed at 95 ° C./11 mmHg. This material was further stripped in a kugelrohr apparatus at 133 ° C./1.5 mmHg. The product, a dark amber toffee-like consistency, was isolated in 89% yield and had an epoxy equivalent WPE = 357.5, hydrolyzable chlorine = 435 ppm, bound chlorine = 2103 ppm and total chlorine = 2538 ppm .

[0083]

[Table 1]

A comparison of the epoxy compounds of the present invention with the prior art compound F shows that the hydrolyzable chlorine content is similar, and a method for the treatment of epoxide-containing molecules to reduce this value. It can further be seen in the literature (see, for example, US Pat. No. 4,785,06).
See issue 1. It is in column 2, hydrolyzable chlorine,
We are discussing the combined chlorine, and the total chlorine. ). Nevertheless, when considering the prevention of corrosion of sensitive microelectronic circuit conductors, the total chlorine value is important, and the reported methods reduce this chlorine contamination from epichlorohydrin-based synthetic routes. However, it cannot be effectively eliminated.

Example III. Epoxy Flexibility and Strength Epoxy is measured as modulus of elasticity,% strain,
Die shear was tested as a measure of the radius of curvature and its adhesive strength.

The elastic modulus is an elastic coefficient indicating a stress / strain ratio when a material is deformed under a dynamic load. These epoxies exhibit a low modulus of elasticity, preferably below 2.0 MPa. % Strain is a measure of resistance to deformation, and these compounds have an elongation% strain of 5% or more;
And in certain cases, the test sample yielded significantly.

When compounded into silver flakes and the silicon chips are bonded to a metal leadframe substrate, the cured epoxy has a high radius of curvature of over 350 mm,
Good die bonding strength of not less than MPa was shown.

The cured Tg value of these epoxies was 15
0 ° C. or lower, and in some cases 100 ° C.
It will be below.

Modulus of elasticity The following equipment was used to prepare epoxy plaques for modulus and% strain bending tests: 2 Pyrex plates, 10 × 10 3/16 ", FJ
Gray Co .; Copper wire (23 "/ test); Silicone tube
ID = 3/32 ", outer diameter (OD) = 5/32", wall = 1/32 "(about 23" / test); aluminum spacer (2 "x3 / 4" x1 / 8 "); binder chip size Medium (5/8 "); Airtech International, In
c. Release ALL # 50.

To prepare plaque moldings, two glass (Pyrex) plates were washed with toluene and then with acetone. Apply a thin coat of Release ALL # 50 on one side of each plate with clean lugs and allow to cool at room temperature.
Dried for 10 minutes. The plate was dried in the oven at 125 ° C. for 30 minutes. Insert a 23 "long copper wire into a 23" long silicone tubing, and insert the wire / tube
It was bent into a U-shape and fitted between the two glasses as a reservoir for the liquid epoxy formulation before curing. An aluminum spacer was placed along the edge of the coated side of the glass plate. The wire / tube mold was then placed on the covered side of the gas plate, inside the spacer. The second glass plate, wire / tube mold and spacer were placed on the first glass plate so that the wire / tube mold and spacer were sandwiched between the two plates. The two glass plates were clamped using a binder clip.

A sample of 90.25 g of epoxy resin was added to 250 mL of 1
Poured into a one-necked flask. The sample was degassed on a Kugelrohr apparatus at 70-75 ° C and 0.2 mm Hg for about 20 minutes and cooled to 50 ° C. (4.75 g) based on 100 parts by weight of epoxy
Parts by weight of 2-ethyl-4-methylimidazole were added to the sample with mixing. The sample is 2mmHg at 50 ℃ with Kugelrohr instrument
The sample was degassed for about 20 minutes.

The epoxy sample was poured into the cavity formed by the U-shaped wire / tube and glass plate mold, taking care not to form air pockets. The poured epoxy sample was cured in an upright position in a programmable furnace according to the following program: 50 ° C
30 minutes at 50 ° C to 125 ° C at 1 ° C / min; 1 hour at 125 ° C; 10 ° C / min from 125 ° C to 175 ° C; 1 hour at 175 ° C; cooling to 60 ° C at 90 minutes.

The epoxy plaque obtained after peeling from the mold was 3 "x0.5" with a water-cooled diamond blade saw.
Cut into pieces. The 0.5 "cut was cut slightly larger and then the plaque was ground to exactly 0.5".

The plaques were subjected to bending tests using an Instron 4507 at room temperature in a three-point bending mode according to ASTM method D790-84a. The data from these experiments are shown in the following table, Young's modulus,% strain and Tg (tan
δ peak).

Die shear Each epoxy (100 parts by weight of epoxy plus 5 parts of 2-ethyl-4-methylimidazole as curing catalyst) was added to 25% by volume of silver flakes and silver was completely wetted. Until mixed. The mixture was degassed under vacuum at room temperature for 15-20 minutes, then left at room temperature for 60 minutes with frequent stirring.

A silicon chip (80 × 80 mil ² ) was coated on one side with the adhesive formulation and placed on a copper lead frame (D / L) and cured at 175 ° C. for 1 hour. The samples were tested for die shear strength at room temperature (RT) after curing. Die shear strength was measured using a Hybrid mmachine Products Corp. Die Shear Tester (Model 1750) / Chatillon DFI 50 digital force gauge. Read the force required to remove the bonded die in kg, and
Ten samples were averaged and converted to die shear strength in MPa. Preferred die shear strength values are at least 13 MPa.

Each epoxy to be tested was prepared, degassed, and degassed, as described above, in the radius of curvature die shear test method.
Aged for hours. The silicon chip (200X600 mil ²⁾ was coated on one side with adhesive and placed on a lead frame,
Then, it was cured in an oven at 175 ° C. for 1 hour. The radius of curvature of the cured sample was measured using a Tokyo Seimitsu SURFCOM texturometer and the average of three samples was millimeter (m
m) reported in units. The preferred radius of curvature was 350 mm or more.

Control Epoxy The control epoxy resin was as follows: A bisphenol F diglycidyl ether sold under the trade name of Dai Nippon's product Deal EPICLON 830S, having the following formula:

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EPON 828, a product of Shell Corporation
Bisphenol A diglycidyl ether sold under the trade name of

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EPON 871 which is a product of Shell Corporation
Diglycidyl dimer acid sold under the trade name of

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A polyglycol diepoxide sold under the trade name DER 732, a product of Dow Corporation, having the following formula:

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Performance Results Epoxy AE was tested according to the test method described above and compared to control aromatic epoxy resins and epoxy resins containing softeners. The results of the flexibility and strength performance tests and comparison with the control epoxy showed low modulus and high% strain compared to the control.
Notably, a small number of flexible epoxies yielded during the strain test compared to the control, all of which cured rapidly.

All of the epoxies of the present invention and the aromatic control epoxies exhibited high bond strengths and, in some cases, very high radii of curvature. The control samples of EPON 871 epoxy resin and DER 732 epoxy resin were based on reactive softeners, which exhibited high radius of curvature values but suffered from low die shear strength.

The control blend of EPON 871 epoxy resin (reactive softener) and aromatic bisphenol F epoxide exhibits good die shear strength, but at the expense of loss of flexibility as indicated by the radius of curvature. Achieved by paying.

[0105]

[Table 2] Curing catalyst: a = 2-ethyl-4-methylimidazole, 4-
6 pphr (parts per 100 parts resin); curing catalyst b = phenol novolak (HRJ-1167 from Schenectady Chemical), 10 pp
hr and 2-ethyl-4-methylimidazole, 4 pphr.

Example IV: A rapidly cured adhesive formulation , a patented flexible epoxy designated Epoxy C, D and E of the present invention and Epoxy X is compounded into a die bond adhesive. , 80 parts by weight of flexible epoxy and
Contains 20 parts by weight of aromatic O-glycidyl ether, and
20 or 40 parts (pphr) of epoxy resin phenolic hardener was included per 100 parts of epoxy resin. 5pph hardener
r was 2-ethyl-4-methylimidazole.

Epoxy X is a patented flexible diepoxy synthesized from dimer acid and has 36 carbon chains between the two epoxy end groups. The aromatic epoxy was as follows. Shell Corporation product
It is a bisphenol F epoxy resin sold under the trade name of EPON 862 and has the following structure.

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An epoxy resin with a patent right, designated by epoxy Y and having the following structure.

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The phenol curing agent is Schenectady Chemic
al phenol novolak resin sold under the trade name HRJ-1167 and has the following structure:

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The preparation of the formulation was as follows: the phenolic hardener resin was dissolved in the flexible epoxy at 130 ° C .; the imidazole catalyst was dissolved in the aromatic epoxy;
The two mixtures were blended and the blend was mixed with 25% by volume silver flake.

Similar controls to these formulations and commercial products
80x80 mil using die binder ^TwoAnd 200x600mi
Le^TwoThe silicon die was bonded to a copper lead frame. This
Rapidly cure these assemblies at 225 ° C for 1 minute,
It was completely cured as measured by DSC analysis.

The adhesive formulation was tested for die shear strength and radius of curvature as described in Example III. Die shear tests were performed at (i) room temperature (RT), (ii) 250 ° C. for 1 minute (250 ° C./1 minute) followed by 250 ° C. (simulating wire bonding during production), (iii) ) boiled for 2 hours in water, and after heating for 1 minute at 250 ° C. at _{250 ℃ (100 ℃ H 2 O} ; resistance to 250 ° C. / 1 min) (moisture, and solder reflow processes, 220 ° C. ~ It is intended to test the resistance to a phenomenon known as "popcorn", which is the mechanical failure of a fully encapsulated package after exposure to moisture between 260 ° C)
Made on a x80 mill ² die.

The results are shown in the following table and show that the rapidly cured formulations containing the flexible epoxies of the present invention maintain flexibility and good die shear strength at room temperature and after thermal shock. Die shear strength after moisture exposure and after thermal shock is in an acceptable range for use as a die bonding adhesive.

[0114]

[Table 3]

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Stephen P. Fenelli United States, New Jersey 08876, Hillsborough, Haverford Court 79

Claims (11)

[Claims] 1. A flexible epoxy compound, comprising: 0.1
Has a total chlorine content of less than 10% by weight, and Wherein R ′ is H, C _1-18 alkyl, C _1-5 alkoxy or aryl or alkylaryl, C _1-5 perfluoroalkyl or C _1-5 acyl;
When n is an integer of 1 to 3 and q is an integer of 1 to 6, the flexible chain is CH ₂ CH ₂ CH ₂ CH ₂ O, or q is an integer of 3 to 10. When the flexible chain is CH ₂ CH ₂ O. A compound having the general structure of (1). 2. It has a total chlorine content of less than 0.1% by weight, and Wherein R ′ is H, C _1-18 alkyl, C _1-5 alkoxy or aryl or alkylaryl, C _1-5 perfluoroalkyl or C _1-5 acyl;
n is an integer of 1 to 3, and p is an integer of 6 to 16. A flexible epoxy compound having the structural formula (1). 3. It has a total chlorine content of less than 0.1% by weight, and Wherein R ′ is H, C _1-18 alkyl, C _1-5 alkoxy or aryl or alkylaryl, C _1-5 perfluoroalkyl or C _1-5 acyl;
When n is an integer of 1 to 3 and r is an integer of 1 to 10, the flexible chain is CH ₂ CH ₂ CH ₂ CH ₂ O, or r is an integer of 3 to 10. in some case, a flexible chain is CH ₂ CH ₂ O, or, when r is an integer of 10 to 20, the flexible chain is CH _2. A flexible epoxy compound having the structural formula (1). (4) The flexible epoxy compound according to claim 1, which has a structure of the following. (5) The flexible epoxy compound according to claim 1, which has a structure of the following. (6) 3. The flexible epoxy compound according to claim 2, having the structure: (7) 4. The flexible epoxy compound according to claim 3, having the structure: (8) 4. The flexible epoxy compound according to claim 3, having the structure: 9. A flexible epoxy comprising the flexible epoxy of claim 1.
Adhesive for use in microelectronics applications. 10. An adhesive for use in microelectronics applications, comprising the flexible epoxy of claim 2. 11. An adhesive for use in microelectronics applications, comprising the flexible epoxy of claim 3.