CA2343632A1 - Die attach adhesives for use in microelectronic devices - Google Patents

Abstract

A thermoplastic or thermosetting adhesive for bonding an electronic component to a substrate in which the adhesive is cured in situ from a curable composition comprises one or more poly- or mono-functional maleimide compounds, or one or more poly- or mono-functional vinyl compounds other than maleimide compounds, or a combination of maleimide and vinyl compounds, a curing initiator and optionally, one or more fillers.

Description

i Patent # 1734A
DIE ATTACH ADHESIVES
FOR USE iN MSCROELECTRONIC C7EV1CES
This application is a continuation-in-part of application serial number 091336,245, filed 18 June 1999.
FIELD OF THE INVENTION
This invention relates to compositions that are suitable for use as adhesives in microelectronic devices or semiconductor packages.
BACKGROUND OF THE INVENTION
Adhesive compositions, particularly conductive adhesives, are used for a variety of purposes in the fabrication and assembly of semiconductor packages and microelectronic devices. The mare prominent uses are the bonding of integrated circuit chips to lead frames or other substrates, and the bonding of circuit packages or assemblies to printed vvire boards.
The requirements far conductive adhesives in electronic packaging are that they have good mechanical strength, curing properties that do not affect the component or the carrier, and thixotropic properties compatible with existing application equipment currently used in the industry.
Another important aspect of an adhesive bonding or interconnection technology is the ability to rework the bond. For single chip packaging involving high volume commodity products, a failed chip can be discarded without significant lass. However, it becomes expensive to discard multi-chip packages with only one failed chip; consequently, the ability to rework the failed chip would be a manufacturing advantage. Today, one of the primary thrusts within the semiconductor industry is to develop adhesives that will meet al! the requirements for adhesive strength and flexibility, but that will also be reworkable, that is, will be capable of being removed without destroying the substrate.
SUMMARY OF THE INVENTION
This invention is an adhesive composition for use in electronic devices that comprises one ar mare mono- or polyfunc;tianai maleimide compounds, or one ar more mono- or poiyfunctionai vinyl compounds other than maieimide compounds, or a combination of maleimide and vinyl compounds, a curing initiator, and optionally, one ar more fillers. The composition can be designed to be r eworkable.
in another embodiment, this invention is the cured adhesive that results from the just described curable adhesive composition.
!n another embodiment, this invention is a microelectronic assembly comprising an electronic component bonded to a substrate with a cured adhesive composition prepared from a composition co~t~prising one or more mono- or poiyfunctional maleimide compounds, or one or more mono- or poiyfunctional vinyl compounds, or a combination of maleimide and vinyl compounds, a curing initiator, and optionally one or more fiNers.
DETAILEt~ OESCRIPTION OF THE INVENTION
The maleimide and vinyl compounds used in the adhesive compositions of this invention are curable compounds, meaning that they are r capable of polymerization, with or without crossiinking. As used in this specification, to cure will mean to polymerize, with or ~nrithout crossiinking.
Cross-linking, as is understood in the art, is the attachrnent of two poiymer chains by bridges of an element, a molecular group, or a compound, and in generaN will take place upon heating. As cross-linking density is increased, the properties of a material can be changed from thermoplastic to thermosetting.
it is possible to prepare polymers of a wide range of cross-link density by the judicious choice and amount of mono- or pofyfunctional compounds.
~ Q The greater proportion of polyfunctionai compounds reacted, the greater the cross-link density. If thermoplastic properties are desired, the adhesive compositions can be prepared from mono-functional compounds to limit the cross-link density. A minor amcunt of poly-functional compounds can be added to provide some cross-linking and strength as the composition, ~S provided the amount of poly-functional compounds is limited to an amount that does not diminish the desired thermoplastic properties. Within these parameters, the strength and elasticity of individual adhesives can ~e tailored to a particular end-use application.
In those cases where it is necessary to rework~the assembly and 20 thermoplastic materials are used, the electronic component can be pried off the substrate, and any residue adhesive can be heated until it softens and is easily removed.
The cross-link density can also be controlled to give a wide range of glass transition temperatures in the cured adhesive to ~nrithstand subsequent 25 processing and operation temperatures.

in the inventive adhesive compositions, the maleimide compounds and the vinyl compounds may be used independently, or in combination. The maleimide or vinyl compounds, or both, will be present in the curable package adhesive compositions in an amount from 2 to 98 weight percent based on the organic components present (excfuding any fillers), The adhesive compositions wi(I further comprise at least one free-radical initiator, which is defined to be a chemical species that decomposes to a molecular fragment having one or more unpaired electrons, highly reactive and usually short-Nved, which is capable of initiating a chemical reaction by means of a chain mechanism. The free-radical initiator will be present in an amount of 0.1 to 10 percent, preferably 0.1 to 3.0 percent, by weight of the organic compounds (excluding any filler). The free radical curing mechanism gives a fast cure and provides the composition with a lone shelf fife before cure. Frefe;-r ed free-radical initiators include peroxides, such as butyl peroctoates and dicumyl peroxide, and azo compounds, such as 2,2'-azobis(2-methyl-propanenitrile) and 2,2'-azobis(2-methyl-butanenitriie).
Alternatively, the adhesive compositions may contain a photoinitiator in lieu of the free-radical initiator, and the curing process may then be initiated by UV radiation. The photoinitiator wil! be present in art amount of 0.1 to 10 percent, preferably 1 to 5.0 percent, by weight of the organic compounds (excluding any filler). In some cases, both photoinitiation and thermal initiation may be desirable. For example, the curing profess can be started by UV irradiation, and in a later processing step, curing can be completed by the application of heat to accomplish a free-radical cure.
in general, these compositions wil( cure within a temperature range of 80-200°C, and curing wii( be effected within a length of time of less than 1 minute to 60 minutes. As will be understood, the time and temperature curing profile for each adhesive composition will vary, and different compositions can be designed to provide the curing profile that will be suited to the particular industrial manufacturing process.
Suitable conductive fillers for the adhesives are silver, copper, gold, palladium, platinum. In some circumstances, nonconductive fillers may be needed, for example to adjust theology, such as, alurnina, silica, and tetlon.
As used throughout this specifccation, the notation C(O) refers to a carbonyl group.
Maleimide Compounds The maleimide compounds suitable for use in the adhesive compositions of this invention have a structure represented by the formula:
[M-X ,"j"- Q , or by the forrnuia: [iVl-Z mJ"- K. lror these specific formulae, when lower case "n" is the integer 1, the compound will be a mono-functional compound; and when lower case "n" is an integer 2 to 6, the compound will be a poly.functional compound.
[M-X m]"- Q , or by the formula: [M-Z m]~- K.
Formula [M-X ",J~- Q represents those compcjunds in which:
z0 M is a maieimide moiety having the structure R
I N-in which R' is H or C, to CS alkyl;
each X independently is an aromatic group selected from the aromatic groups having the structures (i) through (1V):

a 0 ~ II
O-G- ~~NHiC~NH-\ ~\ ., {1V) O -C-NH-\
Q is a linear or branched chain alkyl, alkyloxy, alkylene, alkyleneoxy, aryl, or aryloxy alkyl amine, alkyl sulfide, aikylene amine, alkylene sulfide, aryl sulfide species, which may contain saturated or unsatlarated cyclic or .0 heterocyciic substituents pendant from the chain or as part or" the backbone in the chain, and in which any heteroatom present may or may not be directly attached to X;
or Q is a urethane having the structure:

p II il II
-Rz-X-C-NH-R3-NH_C-t0_Rs-O_C_Na-f-Rs-NH-C-}V .X-R2-in which each RZ independently is an alkyl, aryl, or arylalkyl group having 1 to 18 carbon atoms; R3 is an alkyl or alkyloxy chain having up to 100 atoms in the chain, which chain may contain aryl substituents; X is O, S, N, or P; and v is 0 to 50;
or Q is an ester having the structure:
O O
a n -R3-C-O.-Rs-p~C- Rs-in which R' is an alkyl or alkyloxy chain having up to 100 atoms in the chain, which chain may contain aryl substituents;
or Q is a siioxane having the structure:
-(CR'z)e {SiR'-oIf-SiR42 (CR'z) 9 in which the R' substituent independently for each position is N or an alkyl group having 1 to 5 carbon atoms and the R° substituent independently for each position is H, an alkyl group having 1 to 5 carbon atoms or an aryl group, and a and g are independentty 1 to 10 and f is 1 to SO; and mis0ori,andnisl to6.
Preferred compositions are aliphatic bismaieimides in which the maieimide funtionaiity is (inked to the backbone through urethane or urea linkages, such as in the following preferred compounds:
~ Q
N _ I O HN-o--~ o HN
zo and O O O O
iu~~~o~r~r~ rv Formula (M-Z m]"- K represents those compounds in which _. . ._.._..___ _. _ _.-._ M is a maleimide moiety having the structure N-O in which R' is H or C~ to CS alkyl;
Z is a linear or branched chain alkyl, aikyioxy, alkyl amine, alkyl sulfide, alkylene, alkyieneoxy, alkylene amine, alkyiene sulfide, aryl, aryloxy, or aryl sulfide species, which may contain saturated or unsaturated cyclic or heterocyciic substituents pendant from the chain or as. part of the backbone in the chain, and in which any heteroatom present may or may not be directly attached to K;
or Z is a urethane having the structure:
O O O O
i~ n n -~-X-c-NH-R3-N~-c_(Q_Rs-o-c_NH_~-Nrl-c-),~ x-Rz_ Io in which each RZ independently is an alkyl, aryl, or arylalkyi group having 1 to 18 carbon atoms, and R~ is an alkyl or alkyloxy chain having up to 100 atoms in the chain, which chain may contain aryl substituents~, and v is 0 to 50;
or Z is a siioxane having the structure:
-{CR'2)e [SiR'z-OIr-SiR'2-~CR'z)g- in which the R' substituent independently for each position is H or an alkyl group having 1 to 5 carbon atoms and the R4 substituent independently for each position is H, an alkyl group having 1 to 5 carbon atoms or an aryl group, and°e and g are independently 1 to 10 and f is 1 to 50;
K is an aromatic group selected from the aromatic groups having the structures (VI) through (X111) (although only one bond may be shown to i~, a , represent connection to the aromatic group K, this will t:fe deemed to represent any number ofi additional bonds as described and defined by n):
(V) (VI) / O
\ ; p in which p is 1 to 100;
(V11) -.,, p in which p is 1 to 100;
(Vlil) \~
(IX) Rs Rb \ ~
R in which R5, Rfi, and R' are a linear or Branched chain alkyl, alkyloxy, alkyl amine, alkyl sulfide, aikyiene, a(kyleneox;y, alkyiene amine, alkylene sulfide, aryl, aryloxy, or aryl sulfide species, which may contain 5 saturated or unsaturated cyclic or heterocyclic substituents pendant from the chain or as part of the backbone in the chain, and in which any heteroatom present may or may not be directly attached to the aromatic ring; or R', R°, and Rare a sifoxane having the structure -(CR'Z)e {SiR'Z-O]f-SiR'2-(CH3)9 - in which the R' substituent is N or an alkyl group having 1 to S carbon s atoms and the R' substituent independently for each position is an alkyl group having 1 to 5 carbon atoms or an aryl group, and a is 1 to 10 and f is 1 to 50;
(xj ct~~
i c -p CH3 (xl) H
-C
II ~0~ 1 -c_~ s c o~ 1 .
and (:CII) II
c ~o-c c-ol-i n andmis0orl,andnislto6.
Preferred maleimide compounds, particularly for reworkable compositions, are N-butyiphenyl maleimide and N-ethyiphenyl maleimide.
Vinyl Compounds The vinyl compounds (other than the maleimides herein) suitable for use in the adhesive compositions of this invention will have the structure:

r R~ R2 R ~ R2 B-~ Q ~ 8-Z m K
' tn n or n For these specific structures, when louver case "n" is the integer 1, the compound will be a mono-functional compound; and when Power case "n" is an integer 2 to 6, the compound will be a poly-functional S compound.
In these structures, R' and RZ are H or an alkyl having 1 to 5 carbon atoms, or together form a 5 to 9 membered ring with the carbons farming the vinyl group; B is C, S, N, O, C(O), O-C(O), C(O)-O, C(O)NH or C(O)N(Re), in which RB is C; to C5 alkyl; m is 0 or 1; n is 1-6; and X, Q, Z, and K are as described above.
Preferably, 8 is O, C(O), C(O)-O, C(O)NH or t:(O)N(R~); more preferably B is O, C(O), O-C(C), C(O)-O, or C(0)l~l(R~).
The preferred vinyl compounds for use as adhesives are vinyl ethers or aikenyl sufides. Examples of suitable vinyl compounds are the following:

t CH3(CH2)lo~S ~~O~CHZ) ~~0~/.~g ~(CH2)laCH3 and ~O (CHZ)~-O
Other Composition Components.
Depending on the nature of the substrate to which the adhesive is to be bonded, the adhesive may also contain a coupling agent. A coupling agent as used herein is a chemical species containing a polymerizabie functional group for reaction with the maieimide and other vinyl compound, li and a functional group capable of condensing with metal hydroxides present on the surface of the substrate. Such coupling agents and the preferred amounts for use in compositions for particular substrates are known in the art.
Suitable coupling agents are silanes, silicate esters, metal acrylates or methacrylates, titanates, and compounds containing a chelating ligand, such as phosphine, mercaptan, and acetoacetate. When present, coupling agents typically will be in amounts up to 10 percent by weight, and preferably in amounts of fl.1-3.0 percent by weight, of the maleimide and other monofunctionai vinyl compound.
1fl 1n addition, the adhesive compositions may contain compounds that lend additional flexibility and toughness to the resultant cured adhesive.
Such compounds may be any thermoset or thermoplastic rn;aterial having a Tg of SO°C or less, and typically will be a polymeric material characterized by free rotaiion about the chemical bonds, the presence or' ether groups, and the absence of ring structures. Suitable such modifiers include polyacryiates, poly(butadiene), poiyTHF ( polymerized tetrahydrofuran), CTI3N (carboxy-terminated butadiene-acryionitrile) rubber, and polypropylene g(ycal. When present, toughening compounds may be in an amount up to about 15 percent by weight of the maieimide and other monofunctional vtnyl compound.
24 If siloxane moieties are not part of the maleimide or vinyl compound structure, siioxanes can be added to the package formulations to impart elastomeric properties. Suitable siloxanes are the metf~acry(oxypropyi-terminated poiydimethyl siloxanes, and the aminopropyl-terminated polydimethylsiloxanes, available from United Chemical Technologies and others.
i2 Other additives, such as adhesion promoters, in types and amounts known in the art, may also be added.
Performance Properties These compositions will perform within the commercially acceptable range for die attach adhesives. Commerically acceptable values for die shear for the adhesives on a 80 X 80 milt silicon die are in the range of greater than or equal to 1 kg at room temperature, and greater than or equal to 0.5 kg at 240°C, and for warpage for a 500 X 500 mile die are in the range of less than or equal to 70 pm at room temperature.
The coefficient of thermal expansion (CTE) is the change in dimension per unit change in temperature for a given rnateriai. Different materials will have different rates of expansion. if the CTE is very different for elements attached together, thermal cycling can cause the attached elements to bend, crack, or deiaminate. In a typical semiconductor assembly, the CTE
of the chip is in the range of 2 or 3 ppml°C; for organic circuit board substrate.
the CTE is greater than 30 ppml°C; therefore, the CTE of the adhesive is best between that of the substrate and die.
When a polymer is subjected to the application of heat, it will move through a transition region between a hard, glassy state to a soft, rubbery state. This region is known as the glass transition region or Tg. If a graph of expansion of the polymer versus temperature is piottecf,,the glass transition region is the intersection between the lower temperaturelglassy region coefficient of thermal expansion and the higher temperaturelrubbery region coefficient of thermal expansion. Above this region, thf: rate of expansion increases significantly. Consequently, it is preferred that the glass transition of the polymer be higher than normal operating temperatures experienced during the application, and if reworkabiiity is needed, that the glass transition be lower than any rework temperature.
Another embodiment of this invention include; the maleimides having the formulae (fbi-X ",]"- Q and [fit-Z ",]~- K as described herein in which Q
and Z can be an ester having the structure O O O O
R3 O C-R3 C O R3-~p C-R3-C O R3 P
or the structure O O O O
_Rs_C_O-R3 O_C-R3-~-C_0_R3,O-C-R3 p in which p is 1 to 100, each R' can independently be an alkyl or alkyloxy chain having up to 100 atoms in the chain, which chain may contain aryl substituents, or a siloxane having the structure -(CR'z)e {5iR4z-0]f-SiR'Z--{CR'Z) g in which the R' substituent independently for each position is H or an alkyl group having 1 to 5 carbon atoms, the R4 substituent independently for each position is an alkyl group having 1 to 5 carbon atoms or an aryl group, a and g are independently 1 to 10 and f is 1 to 50.
Another embodiment of this invention includes the vinyl compounds having the structures R~ Rz FR R2 ~B- Q ~B-Zm K
~n n and n as described herein.in which B is C, S, N, O, C(O), C(O}NH or C(O)N(Re), in which Re is C, to C5 alkyl.
Another embodiment of this invention include; the vinyl compounds having the structures R ~R2 R ~Rz s-Xm Q B_Z m~K
n and n as described herein in which Q and Z can be an ester having the structure -R3-G-C-~3-C-(~-R3~"-C-R3 ~-O R3~
or the structure O O O O
II fi ii 11 ~R~_C,_O_,RJ_G-C-R~! C~C-RJ-.p-C_.R~._;a in which p is 1 to 100, each R3 can independently be an alkyl or aikylaxy chain having up to 100 atoms in the chain, which chain may contain aryl substituents, or a siioxane having the structure -{CR'2)e (SiR'Z-Ojf-SiR'Z {CR'Z)9 in which the R' substituent independently for each position is H or an alkyl group having 1 to 5 carbon atoms, the R' substituent independently for each position is an alkyl group having 1 to 5 carbon atoms or an aryl group, a and g care independently 1 to 10, and f is 1 to 50.
Another embodiment of this invention includes the curable adhesive composition as described herein containing pan anionic or cationic curing initiator. The types and useful amounts of such initiators are well known in the art.
EXAMPLES
Various maieimide and vinyl compounds were prepared and formulated into adhesive compositions. The compositions were investigated for viscosity and thixotropic index for the uncured composition, and for curing pro~ie, glass transition temperature, coeffccient of then~nal expansion, thermal mechanical analysis, and in some cases reworkabiiity for the cured composition.
E,~A~f~LL 1.
Preparation of Butadiene-Acryionitriie Bismafeimide HZ NH C-N
CH3 \ ~ CH3 lm n Hn ~ NHz 1. malefic anhydride acetone 2. Ac20, NaOAc, Et3N
O

~~ NH CN
CH3 i ~ i ~O O
O O ~ ~ CH3 \
-iN N
O

Amino-terminated butadiene-acrylonitrile (sold as Hycar resin 1300 X42 ATBiV by SF Goodrich, in which the m and n depicted in the structure are integers to provide a number average molecular weigi~t of 3600) (450 g, 500 mmol based on amine equivalent weight AEW = 450g) was dissolved in CHC13 (1000 m~) in a 3 L four-necked flask equipped with addition funnel, mechanical stirrer, internal temperature probe and niirogen inlet/outiet. The stirred solution was placed under nitrogen and cooled on an ice bath. The addition funnel was charged with maieic anhydride (98.1 g, 1 mol) in CNCI3 (50 mt_) and this solution was added to the reaction over 30 minutes, maintaining the internal reaction temperature below 10°C. This mixture was stirred for 30 minutes on ice, then allowed to warm to room temperature and stirred for an additional 4hours. To the resulting slurry was added acetic anhydride (AczO) (653.4 g, 6 mol), triethylamine (E:3i~l) (64.8 g, 0.64 mai) and sodium acetate (NaOAc) {62.3 g, 0.76 mol). The reaction was heated to mild 15 refiux for 5 hours, allowed to cool to room temperature, and subsequently extracted with H20 (1 L), satd. iVaHC03 {1 L) and HZO (2x1 i_). Solvent was removed in vacuo to yield the maleimide terminated butadiene acrylonitrile.

EXANIPt.E 2 Preparation of Tris(maleimide) Derived From Tris(epoxypropyl)isocyanurate '~0 0 ~~O 0 cat. NR3 O
H \ /

O
OH OH _ ~. °~ °~ o- \

\ i ~ o~ o i r rn --~: '~~ ~/'~
O
Tris(epoxypropyl)isocyanurate (99.0 g, 0.33 moi) is dissolved in THF
(500mL) in a 21_ three-necked flask equipped with mechanical stirrer, internal temperature probe and nitrogen inletloutlet. To this solution is added hyroxyphenylmaieimide (189.2 g, 1 mof} and benzyidimethylamine (1.4 g, 0.05 wt. %). The solution is heated to 80°C for 7 hours The reaction then is allowed to cool to roam temperature, is filtered, and the filtrant washed with HClaq (500mL) and distilled H20 (1 L). The resulting solid, triazinetris(maleimide), is vacuum dried at room temperature.

Preparation of Maleimidoethyipalmitate \ \
O HO~~ 0 O
~.-w 0 ~
H3c(HZc)1 ~ci ~. ~3c(HZC)14~o'~N~

5 Palmitoyf chloride (274.9 g, 1 mo!) is dissolved in EtzO (500 mL) in a 2 L three-necked flask equipped with mechanical stirrer, internal temperature probe, addition funnel and nitrogen inletloutiet. NaHC03 (84.0 g, 1 mat) in distilled H20 (500 mL) is added with vigorous stirring and the solution cooled on an ice bath under nitrogen. The addition funned is charged with hydroxyethylmaleimide (141 g, 1 mol) in Et,O (100 mL) and this solution added to the reaciion over a period of 30 minutes, maintaining an internal T<10°C during the addition. The reaction is stirred for another 80 minutes on ice, then allowed to warm to room temperature and stirred for 4 hours. The reaction is transferred to a separatory funnel and the isolated organic layer 15 washed with distilled HZO (500 mL), 5% HClag (500 mt_) and distilled H20 (2x500 mL). The organics are isolated, dried over MgS04 anhyd., filtered and solvent removed in vacuo to yield the aliphatic maleimide.

EXAMPt-E 4 Preparation of Bismaieimide Derived from 5-lsocyanato-1-{isocyanatomethyl ) 1, 3, 3-trimethylcyclohexane NCO
O
NCO HO~ N
cat. Sn~f O
~\
l~
O
HN ~~O

~.~ ~, J~ J~ ~ , 5-fsocyanato-1-{isocyanatomethyl)-1, 3, 3-trimethylcyciohexane 111.1S g, 0.5 moi) is solvated in THF (500 mi_) in a 1 L. three-necked flask equipped with mechanical stirrer, addition funnel and nitrogen inlet/outiet.
The reaction is placed under nitrogen, and dibutyltin dilaurate (cat. Sn") (6.31 g, 10 mmol) and hydroxyethylmaleimide (141 g, 1 moi) are added with stirring, and the resulting mixture heated for four hours at 70°C. The addition funnel is charged with hydroxyethylmaieimide (141 g, 1-moi) dissolved in THF (100 ml_). This solution is added to the isocyanate: solution over 30 minutes, and the resulting mixture heated for an additional 4 hours at ?0°C.
The reaction is allowed to cool to roam temperature and soiuent removed in vacuo. The remaining oil is dissolved in CHzCl2 ( 1 L) and washed with 10%

HClaq (1 L) and distilled HZO (2x1 L). The isolated organics are dried fiver MgSOQ, filtered and the solvent removed ir7 vacuo to yield the maleimide.

5 Preparation of Dimer Divinyl Ether Derived From Pripof 2033 ,.~o~
"Dimer Divinyl Ether" (and cyclic isomers) 8is(1, 10-phenanthroline)Pd(UAc)z (0.21 g, 0.54 mmol) was dissolved in a mixture of butyl vinyl ether (8.18 g, 81.i' mmois), heptane (100 mL) and "dimer diol" (sold as Pripol 2033 by Unichema, 15.4 g, 27.2 mmol) in 2 L three-necked flask equipped with a mechanical .stirrer under nitrogen.
This solution was heated to fight reflux for 6 h. The solution was allowed to cool to room temperature and subsequently poured onta activated carbon (20 g) and stirred for 1 hour.. The resulting slurry was filtered, and excess butyl vinyl ether and heptane were removed n vacuo to yield the divinyl ether as a yellow oil. The product exhibited accepiable'H NMR, FT-IR and'3C NMR
spectral characteristics. Typical viscosity -100 cPs.

Preparation of Dimer Diacrylate Derived From Dimer Dioi (Pripoi 2033) O
CI
1-i0 O H 0 O
~C 36 Et 3N, acetone 36 A dimer dial (sold as Pripoi 2033 by Unichema, 284.4 g, 500 mmoi}
is dissolved in dry acetone (500 mL) in a 1 L three-necked flask equipped with mechanical stirrer, addition funnel and internal temperature probe under nitrogen. Triethyiamine (101.2 g, 1 mol) is added to this solution and the solution cooled to 4°C on an ice bath. Acryioyl chloride: (90.5 g, 1 mol) solvated in dry acetone (100 m~) is charged into the addition funnel and added to the stirred reaction solution over the course of 80 minutes, maintaining an internal temperature =10°C. This solution is stirred on ice for an additional 2 hours, khen allowed to warm to room temperature and stirred for 4 hours. Sulk solvent is removed via a rotary evaporator, and the remaining residue solvated in CHzCIZ (1 L). This solution is washed with 5%
HClaq (800 mL), and Hz0 (2x800mi_). The isolated org;snics are dried over MgSO, anhyd. and filtered, and the solvent removed in vacuo to yield the diacrylate as an oil.

~i Preparation of N-ethyiphenyl Maleirnide 4-Ethyl aniline (12.12g) was dissolved in 50 ml of anhydrous ethyl ether and slowly added to a stirred solution of 9.81 g o:. maieic anhydride in 100 ml of anhydrous ethyl ether chii(ed in an ice bath. After completion of the addition, the reaction mixture was stirred for 30 minutes. The light yellow crystals were filtered and dried. Acetic anhydride (200 m1) was used to dissolve the mafeamic acid and 20 g of sodium acetate;. The reaction mixture was heated in an oil bath at 160°C. After 3 hours of reflux, the solution was cooled to room temperature, placed in a 1 L beaker in ice water and stirred vigorously for 1 hour. The product was suction-filtered and recrystailized in hexane. The collected crystalline material was dried at 50°C in a vacuum oven overnight. F T I~R and ~MR analysis showed the characteristics cf ethyl maieimide.

Preparation of Sis(alkenylsulfide~) O 0 HO~ O O
O~C~OH , ~O~C ~O
cat. H
Vazo 52 2 eg. HST ~CH2)loCH3 O O
3C(HzC)~o S~O~C~O~~S~'(CHZ)~oC~i~
0imer acid (sold under the trademark Empol 1024 by Unichema) (574.6 g, 1 moi) and propargyl alcohol (112.1 g, 2 moi) are sofvated in toluene (1 L) in a 3 L three-necked flask equipped with mechanical stirring and a Oean-Stark distillation apparatus. Concentrated HzSO4 (6 mL) is added and the solution refluxed for 6 hours until 36 mL of H20 is azeotropically distilled.
The solution is allowed to cool to room temperature, is washed with H20 {2X1 L), dried over ~lgSO4 anhyd. and the solvent rernoved in vacuo to yield the propargyi ester intermediate as an oil.
This ester intermediate (650.7 g, 1 mof) is solvated in THF (200 mL) in a 1 L three-necked rlask equipped with rer'lux condenser, mechanical stirrer and internal temperature probe under nitrogen. Lauryl mercaptan (404.8 g, 2 moi) and 2,2'-azobis(2,4-dimethylpentanenitrile) (sold under the trademark Vazo 52 by OuPont) (11 g) are added and the resulting mixture heated to 70°C an an oil bath with stirring for 7 hours. The reaction is allowed to cool to room temperature and solvent removed in vacuo to yield the alkenyi sulfide as an oil.
EXAMPLE A.
Preparation of 6-mafeimidocaproic acid 6-maieimidocaproic acid O O
OH
N
O

The acid functional maleimide, 6-maleimidocaproic acid, was synthesized using known methodology.' Aminocaproic; acid (100 g, 7.6x10'' mols) was dissolved in glacial acetic acid (50 mL) in a 500 mL four-necked flask equipped with mechanical stirring, an internal temperature probe and an addition funnel. The addition funnel was charged with a solution of malefic anhydride (7~.8 g, 7.6x10'' mois) dissolved in acetonii:riie (75 mL). This solution was added to the aminocaproic acid at room i:emperature dropwise over 1 hour, maintaining an internal reaction temperature less than 35°C. The reaction was stirred for three hours after the addition was complete. The reaction slurry was filtered, and the isolated filtrate was dried in a vacuum oven {P-25 T) overnight at 70°C to yield 166 g of off ~r~hite solid (95°/°). The product amic acid exhibited F T -iR and 'H i~fvlP. spectral characteristics consistent with literature data.
The amic acid described above {166 g, 7.2x10'' mois) was solvated in a solution of toluene (200 mL}, benzene {200 mL} and triethylamine (211 mL, 1.51 mol} in a 1 L three-necked flask equipped with mechanical stirring and a Dean-Stark trap under nitrogen. This solution was heated to reflux for 4 h and the water produced collected in the Dean-Stark Trap. Distilled water {400 mL) was added to the reaction flask to dissolve tire triethylamrnonium salt of the product which largely separated from the bulk solution during the reaction. This aqueous layer was isolated, acidified tapes-1 with 50% HC1, and extracted with ethyl acetate {600 mL). This organic foyer was washed with distilled water (400 mL). The isolated organic layer was dried over MgSOa, followed by solvent removal in vacuo to yield an off white solid (76.2 g, 50%). The product 6-maleimidocaproic acid was spectrographically identical to literature material by FT-IR and 'H NMR.
EXAMPLE 8.
Preparation of "Diner Diester Bismaleimide"
O
O N
C) O

N

"Diner Diester Sismaleimide" (and cyclic; isomers) Pripol 2033 ("diner diol", Uniqema, 92.4 g, i.~i9x10'' mols), 6-maieimidocaproic acid (75.0 g, 3.55x10'' mots) and H~S04 (0.50 mL, -8.5x10v mots) were slurried in toluene (300 mL) in a 1 L four-necked flask equipped with mechanical stirrer, a Dean-Stark trap and an internal temperature probe under nitrogen. The reaction was treated to light refiux far two hours and the water evolved collected in the Dean-Stark trap. The trap was drained and -50 mL of toluene solvent was distilled off of the reaction to remove trace moisture and drive the esteritication equilibrium to completion.
The reaction was allowed to cool to room temperature, additional toluene (100 mL) was added (on the laboratory scale it is preferable to add diethyl ether in place of toluene at this point), and the solution was washed with saturated NaHCO, aq. (300 mL) and distilled water (300 mL). The organic Payer was isolated and dried aver anhydrous MgS04, and the soiwent removed in vacuo to yield an orange oil (107.2 g, 68%). The material can be further purifred by eluting a toluene solution of the resin through a short plug of silica or alumina.
This liquid bismaleimide resin exhibited acceptable FT-1R,'~1 NMR, and "C
NMR data. Typical rl-2500 cf's.
EXAMPLE C.
Preparation of "Oecane Diof Oiester Bisrnaleimde"
O
O O
N ~'O~. wC 1\1 \
O O
O
"Decane Diof Oiester Bismafeimide"
The general procedure described in Exarnpie 8. was applied substituting decane dial (29.5 g, 1.69x70'' mots) for Pripol 2033. This process yielded a solid, moderately soluble bismaleimide (5~..i3 g, 58%). The product exhibited satisfactory FT-IR and'H NA~R data.

EXAMPLE D
Preparation of "Glycerol Triester Tris(maieimide)"
O
N
\\0 N

O
O O
N
O
O
The protocol outlined in example 8. was utilized substituting glycerol (10.4 g, 1.13x10'' mal) for Pripol 2033. Tire product was a viscous liquid which exhibited acceptable FT-iR and'I~ ~IMR data.
EXAMPLE E.
Preparation of "Bis(m-nitrobenzyl carbamate) of iPDI"

NOz N ~O w O H
:, "8is(m-nitrobenzy( carbamate) of IPDI"

lsophorone diisocyanate ("1PJ1", 100.0 g, 4.Sxi0'' cools), m-nitrobenzyl alcohoE (137.8 g, 9.0x10'' mots) and dibutyl tin dilaurate (2.8 g, 4.5x10'' mots) were solvated in dry toluene (1500 mL) in a 2L three-necked flask equipped with mechanical stirrer, reflux condenser and internal temperature probe under nitrogen. The resulting solution was heated to 90°C
for 4 h. No isocyanate band was observed in the IR of the solids portion of the sample. The solution was allowed to cool to room temperature and washed with distilled Hz0 (100 mL). Tfi~e organic layer was isolated and solvent removed in vacuo to yield a yellow liquid which exhibited acceptable FT-iR and'H NMR characteristics.
EXAMPLE F.
Preparation of "8is(m-aminobenzyi carbamate) of IPDI"

O~ N
p ~ C~ ~ NHZ
"Sis(m-aminobenzyl carbamate) of iPDI"
The dinitro compound from Example E. (8.28 q;, 1.57x10'2 mots) was dissolved in ethanol (100 mL) in a 500 mL three-necked round bottom flask equipped with magnetic stirring under nitrogen. Cyclohexene (28.6 mL, 2.82x10'' cools) was added, followed by 5% PdIC (4.14. g). The resulting slurry was reftuxed lightly for 6.5 h. The FT-lR of a filtered aliquot of this 3556s 2g solution exhibited no nitro stretching bands at 1528 crn'' and 1352 cm''. The bulk solution was allowed to cool to room temperaturE: and filtered. Solvent was removed in vacuo to yield a yellow semisolid (6.6 g, 90%) which exhibited acceptable FT-iR and'H PVMR spectral characteristics.
EXAMPLE G.
Preparation of "Bis(m-rnaleimidobenzyl carbamate) of iPDi"
0~~0 H O O
w ~ O ~ \
O
O
"8is(m-mafeimidobenzyi carbamate) of i°t71"
The diamine from Example F (6.6 g, 1.41x1'2 mo(s) was solvated in acetone (60 mL) in a 250 mL four-necked flask equipped with magnetic stirrer and addition funnel under nitrogen and cooled to 4°C. Malefic anhydride {2.76 g, 2.82x10'2 moss) dissloved in acetone (20 mL) was ;added over the course of 30 minutes. The resulting solution was stirred at 4°C for for 1 h, and subsequently was allowed to warm to room temperature and stirred overnight.
FT-iR analysis indicated no malefic anhydride remained as judged by the absence of the anhydride stretching band at -1810 crn~' To the above amic acid solution was added acetic anhydride {8.5 mL, 9.0x10'2 mois), triethylamine {1.26 mL, 9.0x10'3 mols) and sodium acetate (0.88 g, 1.1 x10'2 mois). The resulting sciution was rei7uxed lightly for 4 h s under nitrogen. The reaction was allowed to~cool to room temperature and bulk solvent was removed in vacuo. The resulting viscous liquid was resoivated in methyiene chloride {200 mL) and extracted with distilled water {3x200 mL). The organics were then dried over MgSO, anhyd., filtered and solvent removed in vacuo to yield a ligh# brown solid {6.75 g, 76%). This material exhibited acceptable FT-IR and'H NMR spectral features.
EXAMPLE H.
Preparation of "Bis(m-nitrobenzyl carbamate) of DDi 1410"
r~ ~ N(~Z
\H
H
.~-N ~~O ~~. NU2 C) "Bis(m-nitrobenzyl carbamate) of DDi 1410" (and cyclic isomers) DDI 1410 (Henkei, "Dimer Diisocyanate", 99.77 g, 1.65x10'' moss based on 13.96 % NCO), m-nitrobenzyl alcohol (50.8 ci, 3.32x10'' mots) and dibutyltin dilaurate {0.5 mL, 8.3x10"' mo(s) were solvated in toluene (150 mL) in a 1 L four-necked flask equipped with mechanical stirrer, reflux condenser and internal temperature probe under nitrogen. The reaction was heated to 85°C for 2.5 h. FT-IR analysis of an aliquot of the reaction indicated complete comsumption of isocyanate functionality as judged by the lack of a band at 2272 cm~. Solvent was removed from the reaction in vacuo to yield a yellow oil which solidified upon standing at room temperature (152.4 g, 102% {trace toluene)). This solid exhibited satisfactory FT-iR and 'H NMR spectral features.
EXAMPLE 1.
Preparation of "Bis(m-aminobenzyi carbamatc~) of DDI 1410"
O
I MHz ~~~p i H
~I~O
~ ~1H2 "Sis(m-aminobenzyl carbamate) of DDI 1410" {and cyclic isomers) The diamine product of Example H (39.6 g, 4.32x10'2 orals) and stannous chloride dihydrate (97.55 g, 4.32x10'' mots) were slurried in ethyl acetate (300 mt_) in a 1 L three-necked flask equipped with mechanical stirrer and a rerlux condensor under nitrogen. The reaction vvas heated to light reflux and stirred vigorously for 3 h. The solution was allowed to cool to room temperature and brought to pH 7-8 with a solution of saturated sodium bicarbonate. The mixture was pushed through a 25 micron filter to yield a mixture which separated into a cloudy aqueous layer c~nd a moderately clear organic Payer. The aqueous layer was isolated and washed with ethyl acetate (100 mt-). The organic layers were combined, washed with distilled water {300 ml.) and dried aver anhydrous MgS04. The siurr~wvas Fltered and solvent removed from the filtrate in vacuo to yield yellow, sticky solid {33.8 g, 92°!°).

EXAMPLE J.
Preparation of "l3is(m-maleimidobenzyl carbamate) of DDI 1410"

.~ w I'V
O~ O
E-( O
N O
~ N I
O
O
"8is(m-maleimidobenzyi carbamate) of DDI 1410"' (and cyclic isomers) 5 Maieic anhydride {15.4 g, 1.57X10'z mois) was dissolved in acetone (300 mL) in a 2 L four-necked flask equipped with mechanical stirrer, internal temperature probe and addition funnel under nitrogen. This soiutionn was cooled to -4°C on an ice bath. A solution of the diamine prepared in Example ! {63.4 g, 7.48x10'2 moil) in acetone (70 mL) was charged to the addition 10 funnel and added to the mafeic anhydride solution over a period of 30 minutes maintaining an internal temperature of <10°C. The resulting solution was stirred for 1 h and subsequently allowed to warm to room temperature and stir for 2 h.
To this solution of amic acid was added acetic anhydride (24.7 mL, 15 2.62x10" cools), triethylamine {6.25 mL, 4.48x10'2 roofs) and manganese acetate tetrahydrate (0.37 g, 1.50x10'' cools). This solution was heated to light reflux far 6.5 h, then allowed to cool to room temperature. Bulk solvent was removed in vacuo, and the resulting dark liquid was dissolved in diethyl ether (500 mL). This solution was washed with dist. E~ZO (500 mL). The 20 isolated organic layer was then washed with saturated NaHG03 aq. (500 mL) i i'~

w r and again with disc. H20 (500 mL). The organics were isolated, dried over anhyd. MgSOd, and solvent removed in vacuo to yield ,3 viscous orange oil.
This material exhibited FT-IR; 'H NMR and "C NMR spectral features consistent with the expected bismaieimide product.
EXAMPLE AA.
Law Stress Die Attach Adhesive Formulation and Die Shear Strengths on Various Leadframes A silver filled die attach adhesive formulation having a viscosity of 9011 cPs {5 rpm, cone and plate) and thixotropic index: of 5.36 was produced by combining the following at room temperature using a mechanical mixer:
Liquid bismaleimide of Example 8: 2.644 g Dimer divinyl ether of Example 5: 2.844 g Ricon 131MA20 (Ricon Resins, lnc.): 0.661 g Siiquest A-174 (Witco Carp.): 0.040 g USP-90MD (Witco Corp.): 0.099 XD0026 (NSCC trade secret): 0.119 SF-96 silver flake 23.794 The resulting paste was dispensed onto various metal leadframes as detailed below, and 120 x120 mif silicon die were placed onto the adhesive bead to produce an approximately 1 mil bondline. Samples were "snap cured" a# 200°C for 60 seconds; and die shear strengths at room temperature and 240°C were measured. These samples were then subjected to elevated temperature and humidity (85°CI85% RH) for 48 hours. Die shear strengths were then again measured at room temperature and 240°C. Results are tabulated in Table 1.
Table 1. Die Shear Strengths {DSS) of MaleimideNinyi Ether Die Attach Adhesive ~lo Moisture Exposure After Moisture Exposure {48 h/85C185 RH) Cure Profile 60 s1200C 60 sJ200C

Test 25C 240C ~ 25C 240C

Temperature Cu leadframe 4.88+J-1.46+!-0.356.54+l-0.821.84+/-0.76 DSS (kg) 0.25 Ag-Cu feadframe 5.29+/-2.17+I-0.439.50+l-1.881.56+f-0.72 DSS {kg) 0.34 Pd-Cu 5.52+I- 1.99+I-0.4411.9+!-1.33.53+I-0.66 DSS (kg) 0.39 Typical moisture uptake for these devices after saturation at 85°CI85°J° RN was 0.18 weight percent. Weight loss during cure was 0.16+I-0.05 weight percent.
;=.'CAiV(P~E E8.
HAST Testing of MaleimidelVinyl Ether Die Attach Adhesive Similarly to Example AA, 120x120 mil die were. attached to leadframes of various compositions utilizing the adhesive composition given in Example AA. The bonded die were then cured using "snap cure" (60 sl200°C} and "fast oven cure" conditions (15 min.1173''!;.}. The resulting cured devices were subjected to simulated HAST testing conditions (130°C, 85°J°
RH) for 130 hours. The devices exhibited good adhesion as measured by die shear strength (DSS} at both room temperature and elevaied temperature as shown in Tabte 2.

i i, r Table 2. Die Shear Strengths after simulated HAST Testing Cure Profile60 s1 200_C 15 minut esll75C

Test 25C 240C 25C 240C

Temperature Cu leadframe15.3+I-1.81.12+l-0.3517.2+l-0.81.25+l-0.39 DSS (kg) Ag-Cu ieadframe16.3+I-1.92.81 +/-0.5514.8+l-1.82.6+l-1.6 DSS (kg) Pd-Cu 15.7+/1.73.04+l-0.4614.4+I-0.72.96+l-0.90 DSS (kg) Example CC. Warpage of Large Die Bonded with ~IaieimideNinyi Ether Die Attach Adhesive The die attach composition described in Example AA. was used to bond 500x500 mil die to Pd-Cu feadframes. The assembled pieces were "snap cured" and measured for die warpage at several temperatures and times. T ypical results are given in T able 3. T i1e performance exhlbtted by this adhesive qualifies it as a "low stress" material.
Table 3. Warpage of MaleimideNinyi Ether Die Attach Adhesive on 500x500 mil Die (-Thermal History 1 min1200°C ~ +1 min/240°C_~ +4 h1175''C
Warpaqe (um) ~ 10.4+I-1.3 T 11.9+/-1.4 14.1+l-1.6~
EXAMPLE DD. Therrnai Analysis of MaleimideNinyl Ether Die Attach Adhesive The composition of Example AA. was used to produce -1 mil films using a drawdown bar. The films were "snap cured" (6.0 s, 200°C) on a hot plate or oven cured (4 h1175°C) and characterized by dynamic mechanical analysis (DMA). Results are summarized in Table 4.
3ssss 36 i ~', Table 4. Thermal Analysis of MaieimideNinyi Ether Die Attach i=iims Cure Profile 60 s1200C 4 h1175C

T9 (C) -1 35 Modulus (E'} at 421,300 513,900 -65C (psi) Moduius (E') at 5,864 23,980 100C {psi) The materials exhibited moduii below T9 typical of a low stress adhesive. The materials' moduii at temperatures above T~ are sufficient to withstand typical wirebonding conditions without failure.
EXAMPLE EE
Preparation of a siloxane bismaleimide O O
1 ~i \
\ ~~'.~°'~o~ sy°~si-° Is~0.r~d~,~

Carbinoi-terminal siioxane {DMS-C15,Gelest inc.; 27.26 g, 27.2 mmol) and N, N-dimethylaminopyridine (DMAP; 0.07 g, 0.55 mmol) were solvated in CHZCiZ (200 mL) in a 500 mL four-necked flask equipped with mechanical stirring, addition funnel and internal temperature probe under nitrogen. This solution was cooled to -5°C on an ice bath. A solution of dicyciohexyicarbadiimide {DCC; 14.08 g, 68.1 mmoi) in CHZCIz (50 mL) was charged into the addition Funnel. This DCC solution Nras added to the siioxane/DMAP solution over the course of 45 minutes while maintaining an i i' r internal temperature of <10°C. This solution was stirr~:d on the ice batch for two hours, at which point FT-lR analysis of an aliquot of the solution indicated the presence of ester (1740 cm'') and residual DCC {:2120 cm''). The solution was allowed to warm to room temperature and stirred for an additional three hours. FT-lR analysis stilt indicated the presence of 1:)CC. Acetic acid {20 mL) was added to the reaction and the solution was stirred for an additional one hour, at which point FT-iR indicated no residual L)CC. The solution was filtered to remove precipitated dicyciahexylurea {DCU), and solvent was removed from the filtrate in uacuo. The remaining oil was re-solvated in heptane (200 mL) and cooled to -5°C for one week. The resulting solution was filtered from a precipitated reddish solid to yield a fight brown solution.
This solution was scurried with silica gel {10 g) for one hour at room temperature, i=altered and solvent removed ire nacuo to yield a light brown liquid which exhibited acceptable'H NN1R, z9Si iVMR and F-f-iR spectral features.

Claims (4)

1. A curable adhesive composition for use in bonding an electronic component to a substrate comprising a maleimide compound and a curing initiator selected from the group consisting of a free-radical initiator, a photoinitiator, and a combination of those, the maleimide compound having the formula (M-X m)n - Q in which n is 1 to 6, and (a) M is a maleimide moiety having the structure:
in which R1 is H or an alkyl group having 1 to 5 carbon atoms;
(b) X is an aromatic group selected from the group of aromatic groups having the structures:
and (IV) and (c) Q is an ester having the structure:
in which R3 is a siloxane having the structure -(CR1 2)g - (O)1,0 -(CR1 2)e-(Si-R4 2-O)f-Si-R4 2-(CR1 2)g-(O)1,0 -(CR1 2)g -in which the R1 substituent independently for each position is H or an alkyl group having 1 to 5 carbon atoms, R8 is a linear or branched chain alkyl or alkylene oxy having 1 to 20 carbon atoms, R4 substituent independently for each position is an alkyl group having 1 to 5 carbon atoms or an aryl group, e and g are independently 1 to 10, and f is 1 to 50.

2. A curable adhesive composition for use in bonding an electronic component to a substrate comprising a maleimide compound and a curing initiator selected from the group consisting of a free-radical initiator, a photoinitiator, and a combination of those, the maleimide compound having the formula M n - Q in which n is 1 to 6, and (a) M is a maleimide moiety having the structure:
in which R1 is H or an alkyl group having 1 to 5 carbon atoms;
(b) Q is an ester having the structure:
in which R3 is a siloxane having the structure -(CR1 2)g -(O)1.0 -(CR1 2)e-(Si-R4 2-O)f-Si-R4 2-(CR1 2)g - in which the R1 substituent independently for each position is H or an alkyl group having 1 to 5 carbon atoms, R8 is a linear or branched chain alkyl or alkylene oxy having 1 to 20 carbon atoms, R4 substituent independently for each position is an alkyl group having 1 to 5 carbon atoms or an aryl group, e and g are independently 1 to 10, and f is 1 to 50.

3. A curable adhesive composition according to claim 2 in which the maleimide compound has the formula

4. An electronic assembly comprising an electronic component bonded to a substrate with a cured adhesive composition prepared from a composition according to any one of the preceding claims.