WO2009136920A1

WO2009136920A1 - Multifunctional nitrones in non-radical systems

Info

Publication number: WO2009136920A1
Application number: PCT/US2008/062904
Authority: WO
Inventors: Osama M. Musa; Laxmisha M. Sridhar
Original assignee: Henkel Corporation
Priority date: 2008-05-07
Filing date: 2008-05-07
Publication date: 2009-11-12
Also published as: TW200946560A

Abstract

This invention is a curable composition comprising a multifunctional nitrone and another compound, such as, acrylate, maleimide, cyanate ester, or epoxy. The nitrone undergoes crosslinking with the other compound through cycioaddition or by nitrone dipole mediated ring opening, without the sensitivity to oxygen suffered by free radical curing. Formula (I) and formula (II).

Description

MULTIFUNCTIONAL NITRONES IN NON-RADICAL SYSTEMS

BACKGROUND OF THE INVENTION

[0001] This invention relates to the use of nitroπes in the cure of non-raclica! mediated organic chemistry systems, and in particular in the cure of formulations for adhesives, coatings, and encapsulants. In one embodiment, the adhesives, coatings, and encapsulants are used in electronic applications.

[0002] Much of the curing chemistry used in current adhesives, coatings, and encapsulants involves initiation by radicals. Radical cure has the disadvantages of oxygen sensitivity before and during cure, and significant shrinkage after cure, creating a need for a chemistry that avoids these problems.

SUMMARY OF THE INVENTION

[0003] This invention is a curable composition comprising a multifunctional nitrone and another compound. For purposes of this specification and the claims, compound is deemed to include monomers, oligomers, and polymers. Such compounds include acrylates, maleimides, cyanate esters, and epoxies The nitrone undergoes crosslinking with the other compound through cycloaddition or ring opening initiated by the nitrone dipole without the sensitivity to oxygen experienced by free radical curing or crosslinking.

[0004] Nitrone chemistry can provide a wide range of curing temperatures in curable compositions comprising a nitrone and one or more other compounds. The curing temperature will depend on the particular compound Within the electronics packaging industry, lower cure temperatures would be useful, for example, in die attach operations (silicone dies attached to substrates), underfill operations (encapsulation of solder electrical connections within an electronic package}, and dual cure operations (B-staging one chemistry at a lower temperature than the curing temperature); higher cure temperatures would be useful, for example, in those applications where the curable composition is used in place of a metallic solder.

BRIEF DESCRIPTION OF THE DRAWINGS

[0005] Figure 1 depicts a semiconductor die on an array and metal leadframe showing the placement of a die attach adhesive. Figure 2 depicts a flip-chip semiconductor electrically joined to a substrate with solder and underfilled with an encapsulant composition. DETAILED DESCRIPTION OF THE INVENTION

[0006] Nitrones are 1 ,3-dipolar species prepared through an easy one step, room temperature condensation reaction between an aldehyde and an alkylhydroxylamine as depicted here:

[0007] Nitrones are known to participate in 1 ,3-dιpolar cycloaddition reactions with dipoiarophiles (2π-partners) to give cycloadducts. The cycloaddition reaction is insensitive to oxygen and moisture and generates a five-membered ring called an isoxazohdine:

1,3 Dipole Isoxazolidine

[0008] Nitrones also can initiate polymerization of heterocyclic monomers, such as epoxies, by ring opening: I_÷ Polymer

[0009] Complex compounds are prepared by the reaction of multifunctional nitrones with multifunctional 2π-partners. An example of such reaction is shown here in which a bismaleimide is reacted with a difunctiona! nitrone. The reaction was conducted in dimethylformamide (DMF) at 75^QC:

[0010] Exemplary compounds that are suitable for cure with nitrones include, but are not limited to, those compounds that contain functionality reactive with nitrone groups, such as, epoxy, acrylate (which includes methacrylate), maleimide (which includes multifunctional compounds, such as bis- and tris-maleimides), cyanate ester, and vinyl (such as in vinyl ethers and styrenes) Those functionalities can be appended to a wide variety of compounds, such as polyesters, poly(butadienes), siliconized olefins, silicone resins, siloxanes, and other such materials. In one embodiment, the compounds are selected from the group consisting of epoxies, acryiates, maleimides, and cyanate esters.

[0011] Exemplary solid aromatic bismaleimide (BMI) powders for use in compositions

O O

with the nitrones are those having the structure { O O j_n which X is an aromatic group. Bismaleimide resins having these X bridging groups are commercially available, and can be obtained, for example, from Sartomer (USA) or HOS-Technic GmbH (Austria).

[0012] Additional exemplary maleimides for use in compositions with the nitrones include

those having the generic structure ^N

' ⁿ in which n is 1 to 3 and X¹ is an aliphatic or aromatic group Exemplary X¹ entities include, poly(butadienes), poly(carbonates), poly(urethanes), poly(ethers), poly(esters), simple hydrocarbons, and simple hydrocarbons containing functionalities such as carbonyl, carboxyl, amide, carbamate, urea, or ether. These types of compounds are commercially available and can be obtained, for example, from National Starch and Chemical Company and Dainippon Ink and Chemical, Inc. [0013] Specific preferred maleimides

include

in which C₃₆ represents a linear or branched chain (with or without cyclic moieties) of 36 carbon atoms;

[0014] Suitable acrylates for use in formulation with the inventive compounds include

those having the generic structure

which n is 1 to 6, R¹ is -H or -CH₃. and X² is an aromatic or aliphatic group Exemplary X² groups include poly(butadienes), poiy(carbonates), poly(urethanes), poly{ethers), poly(esters), simple hydrocarbons, and simple hydrocarbons containing functionalities such as carbonyl, carboxyi, amide, carbamate, urea, or ether Commercially available materials include butyl (meth)acrylate, isobutyl (meth)acrylate, 2-ethyl hexyl (meth)acrylate, isodecyl (meth)acrylate, n-lauryl (meth)acrylate, alkyl (meth)acrylate, tridecyl (meth)acrylate, n-stearyl (meth)acrylate, cyclohexyl(meth)acrylate, tetrahydro-furfuryl(meth)acryiate, 2-phenoxy ethyi(meth)acrylate, isobornyl(meth)acrylate, 1,4-butanediol dι(meth)acrylate, 1.6 hexanediol dι(meth)acrylate, 1 ,9-nonandιol dι(meth)acrylate, perfluorooctylethyl (meth)acrylate, 1 ,10 decandiol di(meth)acrylate, nonylphenol polypropoxylate (meth)acrylate, and poiypentoxylate tetrahydrofurfuryl acrylate, available from Kyoeisha Chemical Co., LTD; poiybutadiene urethane dimethacrylate (CN302, NTX6513) and poiybutadiene dimethacrylate (CN301 , NTX6039, PRO6270) available from Sartomer Company, Inc, polycarbonate urethane diacrylate (ArtResin UN9200A) available from Negami Chemical Industries Co., LTD; acrylated aliphatic urethane oligomers (Ebecryl 230, 264, 265, 270,284, 4830, 4833, 4834 4835, 4866, 4881 , 4883, 8402, 8800-20R, 8803, 8804) available from Radcure Specialities, Inc, polyester acrylate oligomers (Ebecryl 657, 770, 810, 830, 1657, 1810, 1830) available from Radcure Specialities, Inc , and epoxy acrylate resins (CN104, 111 , 112, 115, 116, 117, 118, 119, 120, 124, 136) available from Sartomer Company, Inc In one embodiment the acrylate resins are selected from the group consisting of isobornyl acrylate, isobornyl methacrylate, lauryl acrylate, lauryl methacrylate, poiy(butadιene) with acrylate functionality and poly(butadιene) with methacrylate functionality

[0015] Suitable epoxies for use in compositions with the nitrones include bisphenol, naphthalene, and aliphatic type epoxies Commercially available materials include bisphenol type epoxy resins (Epiclon 830LVP, 830CRP, 835LV, 850CRP) available from Dainippon Ink & Chemicals, Inc , naphthalene type epoxy (Epiclon HP4032) available from Dainippon Ink & Chemicals, Inc ; aliphatic epoxy resins (AraJdite CY179, 184, 192, 175, 179) available from Ciba Specialty Chemicals, (Epoxy 1234, 249, 206) available from Union Carbide Corporation, and (EHPE-3150) available from Daicel Chemical Industries, Ltd Other suitable epoxy resins include cycloaliphatic epoxy resins, bisphenol-A type epoxy resins, bisphenol-F type epoxy resins (e g RSL 1739 from Hexion Specialty Chemicals), epoxy novolac resins, biphenyl type epoxy resins, naphthalene type epoxy resins, dicyclopentadiene-phenol type epoxy resins, reactive epoxy diluents, and mixtures thereof

[0016] Suitable cyanate esters for use m compositions with the nitrones include those

N E=CC-O-1 — ) having the generic structure \ 'n _tn which n is 1 or larger, and X⁷ is a hydrocarbon group Exemplary X⁷ entities include bisphenol, phenol or cresol novolac, dicyclopentadiene, polybutadiene, polycarbonate, polyurethane, pofyether, or polyester Commercially available materials include, AroCy L-10, AroCy XU366, AroCy XU371 , AroCy XU378, XU71787 02L, and XU 71787 07L, available from Huntsman LLC, Pπmaset PT30, Pπmaset PT30 S75, Pπmaset PT60, Pπmaset PT60S, Pπmaset BADCY, Pπmaset DA230S, Pπmaset MethylCy, and Pπmaset LECY, available from Lonza Group Limited, 2-allyphenoi cyanate ester, 4-methoxyphenol cyanate ester 2,2-bιs(4-cyanatophenol)-1 ,1 ,1 ,3,3,3- hexafluoropropane, bisphenol A cyanate ester, diallylbispheno! A cyanate ester, 4- phenylphenol cyanate ester, 1 ,1 ,1-trιs(4-cyanatophenyl)ethane, 4-cumylphenol cyanate ester, 1 ,1-bιs(4-cyanateophenyl)ethane, 2,2,3,4,4, 5, 5,6, 6,7, 7-dodecafluorooctanedιol dicyanate ester, and 4,4^!-bιsphenol cyanate ester, available from Oakwood Products, Inc

[0017] Suitable vinyl ethers for use in compositions with the nitrones include those having

the generic structure

m which n is 1 to 6 and X³ is an aromatic or aliphatic group. Exemplary X entities include poly(butadienes), poly(carbonates), poly(urethanes), poly(ethers), poly(esters), simple hydrocarbons, and simple hydrocarbons containing functionalities such as carbonyl, carboxyl, amide, carbamate, urea, or ether. Commercially available resins include cyclohenanedimethanol divinylether, dodecylviπylether, cyclohexyl vinylether, 2-ethylhexyl vinylether, dipropyleneglycol divinylether, hexanediol divinylether, octadecylviπylether, and butandiol divinylether available from International Speciality Products (ISP); Vectomer 4010, 4020, 4030, 4040, 4051 , 4210, 4220, 4230, 4060, 5015 available from Sigma-Aldrich, lnc

[0018] Suitable poly(butadienes) for use in compositions with the nitrones include poly{butadιenes), epoxidized poly(butadιenes), maleic poly(butadienes), acryiated poly(butadienes), butadiene-styreπe copolymers, and butadiene-acrylomtrile copolymers. Commercially available materials include homopolymer butadiene (Ricon130, 131, 134, 142, 150, 152, 153, 154, 156, 157, P30D} available from Sartomer Company, lnc, random copolymer of butadiene and styrene (Ricon 100, 181 , 184) available from Sartomer Company Inc.; maleinized poly(butadιene) (Ricon 130MA8, 130MA13, 130MA20, 131 MA5, 131MA10, 131 MA17, 131 MA20, 156MA17) available from Sartomer Company, Inc.; acryiated poiy(butadienes) (CN302, NTX6513, CN301 , NTX6039, PRO6270, Ricacryl 3100, Ricacryl 3500) available from Sartomer Inc., epoxydized poly(butadienes) (Polybd 600, 605) available from Sartomer Company. Inc. and Epolead PB3600 available from Daicel Chemical Industries, Ltd, and acrylonitrile and butadiene copolymers (Hycar CTBN series, ATBN series, VTBN series and ETBN series) available from Hanse Chemical.

[0019] Suitable siliconized olefins for use in the compositions with the nitrones are obtained by the selective hydrosilation reaction of silicone and divinyl materials, having the generic structure,

in which n-i is 2 or more, n₂ is 1 or more and n_!>n₂. These materials are commercially available and can be obtained, for example, from National Starch and Chemical Company

[0020] Suitable silicones for use in compositions with the nitrones include reactive silicone resins having the generic structure

in which π is 0 or any integer, X⁴ and X⁵ are hydrogen, methyl, amine, epoxy, carboxyl, hydroxy acrylate methacrylate, mercapto, phenol, or vinyl functional groups R² and R³ can be -H, -CH₃, vinyl phenyl, or any hydrocarbon structure with more than two carbons Commercially available materials include KF8012, KF8002, KF8003, KF-1001 , X-22-3710, KF6001 X-22-164C, KF2001 , X- 22-170DX, X-22-173DX, X-22-174DX X-22-176DX KF-857 KF862, KF8001 , X-22-3367, and X-22-3939A available from Shin-Etsu Silicone International Trading (Shanghai) Co , Ltd

[0021] Suitable styrenic compounds for use in compositions with the nitrones include

those resins having the generic structure

in which n is 1 or greater, R⁴ is -

H Or -CH₃, and X⁶ is an aliphatic group Exemplary X³ entities include poly(butadιenes) polycarbonates), poly(urethanes), poly(ethers) poly(esters), simple hydrocarbons and simple hydrocarbons containing functionalities such as carbonyl, carboxyl, amide, carbamate urea, or ether These resins are commercially available and can be obtained, for example, from National Starch and Chemical Company or Sigma-Aldπch Co

[0022] For some applications, one or more fillers or spacers, or both, may be added to the curable composition and usually are added for improved Theological properties, stress reduction, and bondline control Examples of suitable πonconductive fillers include alumina, aluminum hydroxide, silica, vermicuiite, mica, wollastonite, calcium carbonate titania, sand, glass, barium sulfate, zirconium, carbon black, organic fillers, and organic polymers including but not limited to halogenated ethylene polymers, such as, tetrafluoroethylene, trifluoroethylene, vinylidene fluoride vinyl fluoride, vinylidene chloride, and vinyl chloride Examples of suitable conductive fillers include carbon black graphite, gold, silver, copper, platinum, palladium, nickel, aluminum, silicon carbide, boron nitride, diamond, and alumina The particles may be of any appropriate size ranging from nano size to several mm, depending on whether they are used as fillers or spacers (spacers typically being the larger size particles with more uniformity of size) The choice of such size for any particular end use is within the expertise of one skilled in the art Filler may be present in any amount determined by the practitioner to be suitable for the chosen end use SYNTHETIC EXAMPLES

[0023] Melting points, curing temperatures, and heat of polymerization for the neat nitrones and for the curable compositions containing the nitrones and other compounds were determined by differential scanning calorimeter (DSC). Thermogravametric Analysis (TGA) was performed on a TGA (TA 2950) thermogravimetric analyzer instrument.

[0024] EXAMPLE 1 SYNTHESIS OF NITRONE A

A solution of potassium hydroxide (23.71 g, 0.3593 mol) in 108 ml_ of ethanol was added slowly to a solution of N-methylhydroxylamine hydrochloride (30 00 g, 0 3557 mol) in 18 mL of water The resulting precipitate was filtered by vacuum filtration and discarded A 50OmL 4-neck round-bottom flask was equipped with condenser and mechanical stirrer and charged with a suspension of 1 ,4-benzenedialdehyde (19.29 g, 0.1437mol) in 54 mL of ethanol. To this suspension was added N-methylhydroxylamine solution dropwise (filtrate). The mixture was stirred overnight, and the precipitate was then vacuum filtered and washed with water. The solid product was dried overnight under vacuum at room temperature. The yield was approximately 41 0%. ¹H-NMR was recorded in DMSO (solvent) and evidenced the desired product. The melting point was 252⁰C. The heat of polymerization was determined to be 435 J/g when a sample was heated from 40⁰C to 300⁰C at 10⁰C per minute. TGA showed weight loss at 200°C to be 0.26%, at 240°C to be 0.44%, at 26O⁰C to be 77.1 %, and at 300⁰C to be 77 8%.

[0025] EXAMPLE 2. SYNTHESIS OF NITRONE B

Nitrone B may be prepared according to the same procedure for the synthesis of Nitrone A except that 1 ,3-beπzenedialdehyde will be used instead of 1 ,4-benzenedιaldehyde. [0026] EXAMPLE 3. SYNTHESIS OF NITRONE C

The starting dialdehyde was first prepared according to the following reaction scheme:

A 500 mL, 4-neck round-bottom flask equipped with condenser, bubbler, and mechanical stirrer and was charged with 4-hydroxybenzaldehyde (11.12 g, 0.0911 mol), triethylamine (17.05 g, 0.1689 mol), DMAP (0.9476 g, 0.0078 mol), and 100 mL of CH₂CI₂. The contents were cooled to below 10⁰C in an ice bath. Azelaoyl chloride (10.25 g, 0.0455 mol) was charged to an addition funnel and added dropwise to the reaction flask. The mixture was stirred under 1O⁰C, the condenser and ice bath were removed and the solution warmed to room temperature and stirred overnight. The mixture was then filtered and the filtrate was washed with water, brine and washed twice with sodium bicarbonate. To purify the product from the baseline spot on TLC, silica gel (10.0 g) was added and the solution stirred for one hour. Once the baseline was removed and checked by TLC the solvent was removed and ¹H-NMR was performed in CDCI₃ evidencing the presence of the dialdehyde.

[0027] Nitrone C was prepared from the diaidehyde according to the following reaction scheme:

A solution of potassium hydroxide (2.84 g, 0.0506 mol) in 11 mL of ethanol was added slowly to a solution of N-methylhydroxylamine hydrochloride (4.2Og, 0.0506mo!) in 2mL of water. The resulting solid precipitate was stirred for 15 minutes and then removed and discarded. A 10OmL 3-neck round-bottom flask was equipped with condenser and stir bar and charged with a suspension of the difunctional aldehyde (10.0Og, 0.0253mol) (shown above in the reaction scheme) in 6mL of ethanoi Into the suspension was added the rest of the matter from the rwnethylhydroxylamine hydrochloride solution. A new product precipitated The new mixture with precipitate was stirred overnight, and then vacuum filtered and washed with water. The solid product was dried overnight under vacuum at room temperature. The yield was approximately 45.0%. ¹H-NMR was performed in DMSO and evidenced the desired product. The melting point was 152°C.

[0028] EXAMPLE 4 SYNTHESIS OF NITRONE D

Nitrone D was prepared according to the following reaction scheme starting from 4- hydroxybenzaldehyde:

A solution of potassium hydroxide (20.14 g, 0 359 mol) in 108 mL of ethanoi was added slowly to a solution of n-methylhydroxySamine hydrochloride (30.00 g, 0.359 mol) in 18 mL of water. The resulting solid precipitate was stirred for 15 minutes and removed by vacuum filtration and discarded. A 500 mL 4-neck round-bottom flask was equipped with condenser and mechanical stirrer and charged with a suspension of 4-hydroxybenzaidehyde (36 55 g, 0 299 mol) in 71 mL of ethanoi. Into the suspension was added the rest of the matter from the n-methylhydroxyl-amine hydrochloride solution. A new product precipitated. The new mixture with precipitate was stirred overnight, and then vacuum filtered and washed with water The solid product was dried overnight under vacuum at room temperature. The yield was approximately 67.0% ¹H-NMR was performed in DMSO and evidenced the desired product The melting point was 232°C. [0029] EXAMPLE 5 SYNTHESIS OF NITRONE E

Nitroπe E was prepared according to the following reaction scheme starting from 3- hydroxybenzaldehyde:

A solution of potassium hydroxide (20. Ug, 0.359mol) in 108mL of ethanoi was added slowly to a solution of n-methylhydroxylamiπe hydrochloride (30.0Og, 0.359mol) in 18m L of water The resulting solid precipitate was stirred for 15 minutes and then removed by vacuum filtration and discarded A 50OmL 4-neck round-bottom flask was equipped with condenser and mechanical stirrer and charged with a suspension of 3-hydroxybenzaldehyde (36.55g, 0.299mol) in 71 mL of ethanoi. Into the suspension was added the rest of the matter from the n-methylhydroxyiamine hydrochloride solution. A new product precipitated The new mixture with precipitate was stirred overnight, and then vacuum filtered and washed with water. The solid product was dried overnight under vacuum at room temperature to give the Nitrone in good yield. ¹H-NMR was performed in DMSO and evidenced the product. The melting point was 205⁰C.

[0030] EXAMPLE 6 SYNTHESIS OF NITRONE F

The starting 4-propynyloxy benzaldehyde was first prepared according to the following reaction scheme:

To a solution of 4-hydroxy benzaidehyde (24.5 g, 0.2 mol) in DMF was added K₂CO₃ (33.31 g, 0.2 mol) The mixture was stirred for 15 minutes. Propargyl bromide (15 12 ml) was added and the resulting solution was stirred at room temperature overnight. The mixture was diluted with ethyl acetate and filtered off to remove K₂CO₃. The filter cake was washed with ethyl acetate The filtrate was taken in a separatory funnel and washed with water (4 x 200 mL), brine, and dried over anhydrous MgSO₄. Solvent evaporation followed by drying in a vacuum oven overnight provided the benzaidehyde, whose ¹H NMR spectrum was clean (29.5 g, 92 %).

[0031] The benzaidehyde was then used to prepare the nitroπe, according to the following reaction scheme:

To a suspension of N-methylhydroxyJamine hydrochloride (15.66 g, 0.187 mol} in CH₂CI₂ (75 mL) was added triethylamine (26.14 mL, 0.187 mol). The resulting mixture was stirred for 15 minutes at room temperature. The precipitate was filtered off and washed with CH₂CI₂ (25 mL). The filtrate was added dropwise to a stirred solution of the aldehyde (20 g, 0.125 mol) in CH₂CI₂ (150 mL). The resulting mixture was stirred at room temperature overnight. CH₂Cl₂ was evaporated off; ice-cold water (50 mL) was added to the residue and the precipitate filtered off The solid was washed successively with cold water (20 mL), cold acetone (40 mL) and dried in a vacuum oven This afforded the nitrone product, whose ¹H NMR spectrum was clean (DMSO) (14.2 g, 77%) The melting point was 132°C.

[0032] EXAMPLE 7 SYNTHESIS OF NITRONE G

The starting 4-benzyioxybenzaldehyde was first prepared according to the following reaction scheme:

To a solution of 4-hydroxybeπzaldehyde (1Og, 81.9 mmol) in DMF (75 mL) was added potassium carbonate (13.57g, 98.2 mmol). The mixture was stirred for 15 minutes at room temperature. Benzyl bromide (9 73mL, 81.9 mmol) was added and the mixture stirred at room temperature overnight. Ethyl acetate (500 mL) was added and the precipitate filtered off and washed with ethyl acetate (50 mL). The filtrate was washed with water (4χ200mL) and brine (10OmL). The organic layer was dried over anhydrous MgSO₄ and the solvent evaporated. The product was dried in vacuum and submitted for ¹H NMR The NMR indicated that the compound was pure (15.2g, 87%)

[0033] The 4-benzyloxybenzaldehyde was used to prepare the nitrone according to the following reaction scheme:

To a suspension of N-methylhydroxylamine hydrochloride (7 8g, 93.3 mmol) in dichloro- methane (5OmL) was added triethyiamine (13,02mL, 93.3mmol). The mixture was stirred for 20 minutes The precipitate was filtered and washed with dichloromethane (2OmL) The filtrate was added dropwise to a solution of aldehyde (13.2g, 62.2mL) in dichloromethane (8OmL) and stirred overnight at room temperature. Dichloromethane was evaporated and cold water was added to the residue (10OmL) and stirred for 15 minutes The precipitate was filtered and washed with water, 1 :1 CH₂Ci₂ : heptane (75mL) and dried under vacuum to give the solid nitrone (12.32g, 82%). Nitrone G has a meiting point of 117°C and is miscible with other resins

[0034] EXAMPLE 8. SYNTHESIS OF NITRONE H

The starting dimesylate was prepared according to the following reaction scheme:

99% R = long chain alkyl group

To a solution of dimerdiol (Uniqema) (9.07g, 16.2 mmol) in CH₂CI₂ (10OmL) at 0⁰C was added triethylamine (6 8mL) followed by MeSO₂CI (2.77mL, 35.7mmoi) dropwise over a period of 10 minutes After stirring for two hours at the same temperature, after the T.L.C indicated the disappearance of starting materia! (as visualized by UV chamber), water (10OmL) was added and the mixture was diluted with EtOAc (30OmL) The organic layer was washed with water (3χ10OmL)₁ brine and dried over anhydrous MgSO₄ for 30 minutes. The solvent was evaporated and the product was dried under vacuum for two hours to afford the mesylate (11.6g, 99%).

[0035] The diaidehyde was prepared from the dimesyiate according to the following reaction scheme:

89%

R = long chain alkyl group

A suspension of K₂CO₃ (21.63g, 156 mmol) and 4-hydroxybenzaldehyde (15.66g, 128mmol) in DMF (50OmL) was stirred with a mechanical stirrer at room temperature for 30 minutes. A solution of the dimesyiate in DMF (5OmL) was added dropwise and the resulting mixture was heated at 8O⁰C for six hours. After T.L.C (thin layer chromatography) indicated the disappearance of starting material, the reaction mixture was cooled to room temperature and diluted with a 1 :1 mixture of ethyl acetate and heptane (50OmL) The precipitate was filtered off and washed with heptane:ethyl acetate(1 :1 , 20OmL) The filtrate was taken in a separatory funnel and washed with water several times (4χ400mL), followed by a wash with brine (30OmL). The organic layer was dried over anhydrous MgSO₄ (30 minutes) and the solvent was evaporated at 50⁰C for three hours. The resultant viscous liquid was dried under vacuum for two hours to give the diaidehyde (39 4g, 89%)

[0036] The nitrone was synthesized from the diaidehyde according to the following reaction scheme:

R = long chain alkyl group

To a suspension of N-methylhydroxylamine hydrochloride (3.75g, 44.9 mmol) in CH₂CI₂ (2OmL) was added triethylamine (6.26mL, 44.9 mmol). The mixture was stirred for 15 minutes. The precipitate was filtered and washed with CH₂CI₂ (15ml_) The filtrate was added dropwise to a solution of the aldehyde (4.3g, 5.6mmol) in CH₂CI₂ and stirred overnight at room temperature The mixture was diluted with EtOAc (25OmL) and the organic layer was washed with water (4χ50mL), brine, and dried over anhydrous MgSO₄. Solvent evaporation furnished a viscous liquid, which was dried using a Kugelrohr at 6O⁰C for three hours to give the nitrone as a very viscous liquid (4 24g, 93%). The viscosity was 7000 mPa.s at 50⁰C. This reaction was highly reproducible.

PERFORMANCE EXAMPLES AND DISCUSSION

[0037] The above nitrones were formulated into curable compositions comprising one or more of the following resins in various molar ratios. The compositions contained no solvent The neat resins and compositions were cured by Differential Scanning Calorimetry (DSC) and the cure temperatures (Cure T1 and Cure T2) and heats of polymerization (ΔH) recorded in the table for each example. (Melting points noted above were also determined by DSC.) Th ermo-grava metric Analysis (TGA) was used to determine weight loss and was performed on TGA (TA 2950) instrument.

[0038] TrisMaleimide (TMI)

[0039] Cyanate Ester (CE)

[0040] Bis F Epoxy (Epoxy)

[0041] Acrylate

[0042] Bismaleimide (BMI)

in which C₃₆ represents a linear or branched chain (with or without cyclic moieties) of 36 carbon atoms

[0043] EXAMPLE 9. DSC FOR COMPOSITIONS CONTAINING NITRONE A AND CYANATE ESTER Nitrone A was blended with cyanate ester (CE) in various molar ratios. The DSC scans indicated a two stage curing process and an increase in curing temperature as the amount of nitrone decreased. The results are reported in Table 1

[0044] TABLE 1 : DSC DATA FOR NITRONE A AND CYANATE ESTER

[0045] EXAMPLE 10 DSC FOR COMPOSITIONS CONTAINING NITRONE A₁ CYANATE ESTER,

AND EPOXY

Nitrone A was blended with the cyanate ester (CE) and BisF epoxy shown above into compositions in various molar ratios The compositions were cured by DSC The results are reported in Table 2

[0046] TABLE 2: DSC DATA FOR NITRONE A, CYANATE ESTER AND EPOXY

[0047] The DSC peak for the second entry is very broad merging T1 and T2. For the third and fourth entries, most of the curing took place during the first exotherm, therefore, ΔH 2 is low for these cures

[0048] EXAMPLE 11 TGA OF COMPOSITIONS CONTAINING NITRONE A AND EPOXY

Nitrone A in combination with epoxy was tested by TGA for weight loss at 200⁰C and compared to control samples of cyanate ester, epoxy, and a composition of a 1 : 1 molar ratio of cyanate ester and epoxy The results are reported in Table 3

[0049] TABLE 3: TGA DATA FOR NITRONE A AND EPOXY

[0050] EXAMPLE 12 DSC FOR COMPOSITIONS CONTAINING NITRONE C, CYANATE ESTER, EPOXY, MALEIMIDE, AND ACRYLATE

Nitrone C was blended with cyanate ester, cyanate ester and epoxy, maleimide, and acrylate, and cured by DSC The results are reported in Table 4 and indicate that the introduction of an aliphatic backbone into the nitrone will decrease the heat of polymerization, for example, compared to Nitrone A [0051] TABLE 4: DSC DATA FOR NITRONE C, CYANATE ESTER, EPOXY, MALEIMIDE, AND

AC RYLATE

[0052] EXAMPLE 13 DSC FOR COMPOSITIONS CONTAINING NITRONE D, CYANATE ESTER, EPOXY, ACRYLATE, AND MALEIMIDE

Nitrone D has one nitrone functionality and one phenolic functionality Nitrone D was blended with cyanate ester, cyanate ester and epoxy, maleimide, and acrylate, and cured by DSC The results are reported in Table 5 and indicate a two stage curing process Those formulations that did not show a second cure peak reacted completely in the first exotherm

[0053] TABLE 5: DSC DATA FOR NITRONE D₁ CYANATE ESTER, EPOXY, ACRYLATE AND MALEIMIDE

[0054] The presence of the phenolic functionality on Nitrones D and E presents an opportunity to add additional functionality and/or molecular weight and/or aromaticity to these nitrones The phenolic group can be reacted with a compound or resin having a functionality reactive with the phenolic hydroxyl group That compound may contain an additional functionality not reactive with the phenolic hydroxyl, therebv adding that additional functionality to the nitrone Further, the compound may be composed of aliphatic chains of various lengths and branching, or aliphatic groups in combination with aromatic groups to add molecular weight and/or aromaticity to the nitrone Such nitroπes are included in this invention

[0055] EXAMPLE 14 DSC FOR COMPOSITIONS CONTAINING NITRONE E₁ CYANATE ESTER, EPOXY, ACRYLATE AND MALEIMIDE

Nitrone E was blended with cyanate ester, cyanate ester and epoxy, maleimide, and acrylate, and cured by DSC The results are reported in Table 6 and indicate that Nitrone E cures some compounds slower than Nitrone D

[0056] TABLE 6: DSC DATA FOR NITRONE E, CYANATE ESTER, EPOXY, ACRYLATE AND

MALEIMIDE

[0057] EXAMPLE 15 DSC FOR COMPOSITIONS CONTAINING NITRONE AND EPOXY

Nitrones are also capable of ring opening, and thus, for example, epoxy or oxetane rings will open initiated by the nitrone dipoie Several nitrones were used in combination with epoxy and cured by DSC The results are reported in Table 9

[0058] Table 9: DSC Data for Nitrone and Epoxy

[0059] EXAMPLE 16 PROPERTIES FOR COMPOSITIONS CONTAINING NITRONE F, ACRYLATE, EPOXY, MALEIMIDE, AND CYANATE ESTER

Nitrone F exhibited a melting point of 132°C with a heat of polymerization of 1531 J/g in neat form, as measured by DSC. It was compatible with other resins. TLC analysis indicated Nitrone F to be appreciably non-polar DSC data is reported in Table 10.

[0060] Table 10: DSC DATA FOR NITRONE F

[0061] The TGA performance of Nitrone F with epoxy in different mole ratios was investigated and the results are shown in Table 11

[0062] TABLE 11 : TGA DATA FOR NITRONE F, EPOXY, ACRYLATE, AND CYANATE ESTER

[0063] The mechanical properties of Nitrone F in combination with epoxy and cyanate ester (cobalt acetoacetonate as catalyst, 1 wt.%) were evaluated, the results are reported in Table 12. Increasing the amount of Nitrone F from 0.2 mol to 0.4 mol in the composition resulted in increased ΔH, although the cure temperature was lowered by 10⁰C. Nitrone F also improved the T₉ (glass transition temperature) of the cured material by 20⁰C on increased loading. [0064] TABLE 12: MECHANICAL PROPERTIES OF NITRONE F AND EPOXY AND CYANATE ESTER

[0065] EXAMPLE 17. DSC AND TGA OF NITRONE G AND MALEIMIDE, ACRYLATE, AND CYANATE ESTER

The curing behavior and the TGA performance of Nitrone G with different resins were evaluated and the results are shown in Table 13. Nitrone G exhibited considerably less heat of polymerization than any of the Nitrones A to F indicating that the ΔH can be reduced by increasing the molecular weight of the nitrone All of the Nitrone G compositions exhibited good thermal stability showing less than 10% weight loss at 200⁰C.

[0066] TABLE 13: DSC AND TGA OF NITRONE G AND MALEIMIDE, ACRYLATE, AND CYANATE ESTER

[0067] The mechanical properties of Nitrone G also were investigated and the results are reported in the following table. Cobalt acetoacetonate was used as the curing initiator at 1 wt%. [0068] TABLE 14: MECHANICAL PROPERTIES OF NITRONE G EPOXY, AND CYANATE ESTER

[0070] EXAMPLE 18 TGA AND DSC FOR COMPOSITIONS CONTAINING NITRONE H ACRYLATE, CYANATE ESTER, AND BISMALEIMIDE

Nitrone H was evaluated by DSC (differential scanning caloπmetry) and TGA (thermal gravimetric analysis) performance in various resin formulations TGA results indicated that Nitrone H exhibited good thermal stability and the blend with cyanate ester exhibited minimum weight loss at 0 37% at 200⁰C The results are disclosed in the Table 15

[0071] Table 15: TGA AND DSC DATA FOR NITRONE H, ACRYLATE CYANATE ESTER, AND BISMALEIMIDE

[0072] UTILITY

These compositions are useful as adhesives and encapsulants particularly within the semiconductor packaging industry They can be used as attach adhesives for adhering a semiconductor die (which includes a semiconductor die package) to a substrate as shown in Figure 1 , and as encapsulants for underfilling the gap caused by solder joints connecting semiconductors to substrates or as an encapsulant for covering and protecting a semiconductor package as shown in Figure 2 Thus in further embodiments this invention is a semiconductor adhered to a substrate with a composition as herein described, and a semiconductor electrically connected to a substrate by solder joints in which a gap formed between the semiconductor and substrate by the solder joints is filled with a composition as herein described

Claims

WHAT IS CLAIMED:

1. A curable composition comprising a πitrone and at least one other curable compound selected from the group consisting of epoxy, cyanate ester, acrylate, maleimide, and combinations of these.

2 The curable composition according to ciaim 1 in which the at least one other curable compound is selected from the group consisting of epoxy and cyanate ester.

3. The curable composition according to claim 1 in which the at least one other curable compound is selected from the group consisting of acrylate and maleimide.

4. The curable composition according to claim 1 in which the at least one other curable compound is selected from the group consisting of

o-°

and combinations of these

5 The curable composition according to any one of claims 1 to 4 in which the nitrone is selected from the group consisting of

(Nitrone A)

(NITRONE B)

(NITRONE C)

(NITRONE D)

(NlTRONE E)

(NlTRONE F)

(NlTRONE G)

and

(NlTRONE H)

6 A semiconductor package comprising a semiconductor adhered to a substrate with the composition comprising a nitrone and at least one other curable compound

7 The semiconductor package according to claim 6 in which the one other curable compound is selected from the group consisting of epoxy, cyanate ester, acrylate, maleimide, and combinations of these, and the nitrone is selected from the group consisting of

(Nitrone A)

(NlTRONE B)

(NlTRONE C)

(NlTRONE D)

(NlTRONE E)

(NlTRONE F)

(NlTRONE G) and

(NiTRONE H). 8 A semiconductor package electrically connected to a substrate by solder joints, in which a gap formed between the semiconductor and substrate by the solder joints is filled with a composition comprising a nitrone and at least one other curable compound.

9 The semiconductor package according to claim 8 in which the one other curable compound is selected from the group consisting of epoxy, cyanate ester, acrylate, maieimtde, and combinations of these, and the nitrone is selected from the group consisting of

(Nitrone A)

(NITRONE B)

(NITRONE C)

(NITRONE D)

(NlTRONE F)

(NlTRONE G) and

(NlTRONE H).