FLUX-COMPATIBLE EPOXY-PHENOLIC ADHESIVE COMPOSITIONS FOR LOW GAP UNDERFILL APPLICATIONS

Abstract

Provided are flux-compatible epoxy-phenol adhesive compositions useful as a low gap underfill and novel phenols useful therein. The flux-compatible epoxy-phenol adhesive compositions include an epoxy component including an epoxy compound having a cycloaliphatic, alicyclic or mixed cycloaliphatic-aromatic backbone, a multifunctional phenolic component, and a catalyst. The flux-compatible compositions are useful as an underfilling sealant which (1) rapidly fills the underfill space in a semiconductor device, such as a flip chip assembly, (2) enables the device to be securely connected to a circuit board by short-time heat curing and with good productivity, and (3) demonstrates excellent solder reflow resistance.

Claims

1. A flux-compatible epoxy-phenol adhesive for low-gap underfill applications comprising: an epoxy component comprising an epoxy compound having a cycloaliphatic, alicyclic or mixed cycloaliphatic-aromatic, alicyclic-aromatic backbone; a multifunctional phenolic component; and a catalyst.

2. The flux-compatible epoxy-phenol adhesive of claim 1, wherein the epoxy compound is selected from EP4088S, Eponex1510, HP7200L, Hyloxy modifier 107, mono and multifunctional decahydronaphthalene glycidyl ether, mono and multifunctional DCPD glycidyl ethers, diglycidyl ether of hydrogenated bisphenol A, mono and multifunctional adamantyl glycidyl ethers, cycloaliphatic glycidyl esters, glycidyl compounds derived from cycloaliphatic monoamines and diamines, mono and multifunctional epoxides of cyclic monoene and polyenes and mixtures thereof.

3. The flux-compatible epoxy-phenol adhesive of claim 1, wherein the catalyst is selected from imidazoles, substituted imidazoles, latent imidazoles, encapsulated imidazoles, phenol functionalized imidazoles, and naphthol functionalized imidazoles.

4. The flux-compatible epoxy-phenol adhesive of claim 3, wherein the catalyst is selected from Technicure EMI 24-CNI, Curezol 2-PHZ-S, Curezol 2-PZ, Curezol 2PZ-azine, ikardar 3123, Ajicure series, Technicure series, Resicure series, Technirez series, and amine and polyamine functional imidazoles.

5. The flux-compatible epoxy-phenol adhesive of claim 1, wherein the phenol is selected from structures I, II, III and/or IV: ##STR00012## wherein X is a monocyclic, bicyclic or polycyclic ring structure that is cycloaliphatic or alicyclic optionally with aliphatic side chains; the oxygen of the ester group is connected directly to the ring or to the aliphatic side chain; X.sub.1 is alkylene or branched alkylene optionally comprising hetero atoms O or S; R.sub.3 is H, alkyl or cycloalkyl; L.sub.1 and L.sub.2 are independently selected from a covalent bond, alkylene, branched alkylene, and cycloalkylene optionally comprising heteroatoms O or S; R.sub.1 and R.sub.2 are independently H, methyl or OH with the proviso that at least one of R.sub.1 or R.sub.2 in each ring is OH; and the ester group present in structures I, II, III and IV can be primary or secondary ester group.

6. The flux-compatible epoxy-phenol adhesive of claim 1, wherein the multi-functional phenolic component is selected from the following phenolic compounds: ##STR00013## DCPD novolak, cresol novolak, bisphenol A novolak, phenol novolak, triazine novolak, diallylbisphenol A, dihydroxynaphthalene (all isomers), 2-allylphenylnovolak, dihydroxybenzophenone (all isomers), trihydroxybenzophenone (all isomers), Rezicure 3000, bis(4-hydroxyphenyl)sulfide, and bis(4-hydroxyphenyl)sulfone.

7. The flux-compatible epoxy-phenol adhesive of claim 1, wherein the phenolic component is selected from structures V, VI and/or VIII: ##STR00014## wherein R is an aliphatic, cycloaliphatic, alicyclic, mixed aromatic-cycloaliphatic or polymer backbone; in addition, R can be a fused ring in Structures V and VII; R.sub.1 and R.sub.2 are H, alkyl or OH with the proviso that at least one of R.sub.1 or R.sub.2 is OH; n=1-10; and the fused ring attached to the phenol ring in Structure V is optional and when present may be aromatic, cycloaliphatic, alicyclic or heterocyclic.

8. The flux-compatible epoxy-phenol adhesive of claim 1 further comprising a maleimide resin.

9. The flux-compatible epoxy-phenol adhesive of claim 8 wherein the maleimide resin is a bismaleimide, a polyfunctional maleimide of structures VIII and IX: ##STR00015## wherein L is selected from a covalent bond, alkylene, cycloalkylene, and branched alkylene optionally with hetero atoms O or S; L can also contain an ester or carbonate linkages; and the fused ring in structure VIII is optional and when present it is aromatic, cycloaliphatic, alicyclic or heterocyclic.

10. The flux-compatible epoxy-phenol adhesive of claim 9 wherein the bismaleimide or polyfunctional maleimide is obtained by imidization of mono or multifunctional primary amines with maleic anhydride or obtained by Fisher esterification of mono or multifunctional aliphatic, cycloaliphatic, alicyclic or aralkyl alcohols with 6-maleimidocaproic acid.

11. The flux-compatible epoxy-phenol adhesive of claim 1, wherein the ratio of the epoxy resin to the phenol is from 1:1 to 1:0.05.

12. The flux-compatible epoxy-phenol adhesive of claim 1 which further comprises curing agents, accelerators, catalysts, flow modifiers, fillers, adhesion promoters and thixotropic agents.

13. A phenol selected from: ##STR00016##

14. A phenol selected from one or more of structures I, II, III and IV: ##STR00017## wherein X is a monocyclic, bicyclic or polycyclic ring structure that is cycloaliphatic or alicyclic optionally with aliphatic side chains; and the oxygen of the ester group is connected directly to the ring or to the aliphatic side chain; X.sub.1 is alkylene or branched alkylene optionally with hetero atoms O or S; R.sub.3 is H, alkyl or cycloalkyl; L.sub.1 and L.sub.2 are independently selected from a covalent bond, alkylene, branched alkylene, and cycloalkylene optionally comprising heteroatoms O or S; R.sub.1 and R.sub.2 are independently H, methyl or OH with the proviso that at least one of R.sub.1 or R.sub.2 in each ring is OH; and the ester group present in structures I, II, III and IV can be a primary or secondary ester group.

15. A phenol selected from one of more of structures V, VI and VII: ##STR00018## wherein R is an aliphatic, cycloaliphatic, alicyclic, mixed aromatic-cycloaliphatic or polymer backbone; in addition, R can be a fused ring in structures V and VII; R.sub.1 and R.sub.2 are H, alkyl or OH with the proviso that at least one of R.sub.1 or R.sub.2 is OH; n=1-10; and the fused ring attached to the phenol ring in structure V is optional and when present may be aromatic, cycloaliphatic, alicyclic or heterocyclic.

16. A phenol selected from one or more of structures VIII and IX: ##STR00019## wherein L is selected from a covalent bond, alkylene, cycloalkylene, and branched alkylene optionally with hetero atoms O or S; L can also contain an ester or carbonate linkages; and the fused ring in structure VIII is optional and when present it is aromatic, cycloaliphatic, alicyclic or heterocyclic.

17. The flux-compatible epoxy-phenol adhesive of claim 1 wherein: the epoxy compound is selected from EP4088S, Eponex1510, HP7200L, Hylox modifier 107 and mixtures thereof; the multifunctional phenol is selected from: ##STR00020## and the catalyst is selected from Technicure EMI 24-CN, Curezol 2-PHZ-S, Curezol 2-PZ, Curezol 2PZ-azine, and Aardur 3123.

Description

DETAILED DESCRIPTION

[0032] As noted, the disclosure provides a flux-compatible epoxy-phenol adhesive composition usual for low gap underfill applications. The composition broadly comprises an epoxy component, a phenolic component, and a catalyst.

[0033] The epoxy component may be selected from epoxy compounds having a cycloaliphatic, alicyclic, mixed cycloaliphatic-aromatic, or mixed alicyclic-aromatic backbone. Particularly useful epoxy resins are EP4088S, Eponex1510, HP7200, Hyloxy modifier 107 and mixtures thereof, shown in the formulas below, although other resins having a cycloaliphatic, mixed cycloaliphatic-aromatic backbone and/or aromatic backbone may be used. Examples include monofunctional and difunctional decahydronaphthalene glycidyl ethers supplied by Sugai Chemical Industry, mono and multifunctional glycidyl ethers based on cycloaliphatic backbones such as adamantane ring structure, including mono and multifunctional decahydronaphthalene glycidyl ether, mono and multifunctional DCPD glycidyl ethers, diglycidyl ether of hydrogenated bisphenol A, mono and multifunctional adamantyl glycidyl ethers, cycloaliphatic glycidyl esters, mono and multifunctional epoxides of cyclic monoene and polyenes and mixtures thereof.

##STR00003##

[0034] The phenolic component may be a multifunctional phenol and may be selected from those whose formulas are given below:

##STR00004##

[0035] These multifunctional phenolsPhenols 1-4are novel and form another aspect of the present disclosure.

[0036] In addition to the above novel phenols, certain known alicyclic phenols may be used as the phenolic component of the composition. Suitable phenols are sold by DIC International Chemicals under the trade name Phenolite phenol novolak resins. Particularly suitable known phenols are DCPD novolac and cresol novolac. Also useful are bisphenol A novolak, phenol novolak, triazine novolak, diallylbisphenol A, dihydroxynaphthalene (all isomers), 2-allylphenylnovolak, dihydroxybenzophenone (all isomers), trihydroxybenzophenone (all isomers), Rezicure 3000, bis(4-hydroxyphenyl)sulfide, and bis(4-hydroxyphenyl)sulfone.

[0037] The phenolic component may also be a multifunctional phenol represented by the general structures I, II, III and/or IV:

##STR00005##

wherein R is an aliphatic, cycloaliphatic, alicyclic, mixed aromatic-cycloaliphatic or polymer backbone; in addition, R can be a fused ring in Structures V and VII; [0038] R.sub.1 and R.sub.2 are H, alkyl or OH with the proviso that at least one of R.sub.1 or R.sub.2 is OH; [0039] n=1-10; and [0040] the fused ring attached to the phenol ring in Structure V is optional and when present may be aromatic, cycloaliphatic, alicyclic or heterocyclic.

[0041] The above imide or phthaleimide functional phenols can be obtained by imidization of aliphatic, alicyclic, aromatic, aralkyl amines with mono or multifunctional anhydrides. The anhydrides can be selected from methylhexahydrophthalic anhydride, nadic anhydride (methyl-5-norbornene-2,3-dicarboxylic anhydride; MNA) or 5-norbornene-2,3-dicarboxylic anhydride, hexahydro-4-methylphthalic anhydride (MHHPA), methyltetrahydrophthalic anhydride (MTHPA), methylcyclohexene-1,2-dicarboxylic anhydride, methylbicyclo[2.2.1] heptane-2,3-dicarboxylic anhydride, bicyclo[2.2.1] heptane-2,3-dicarboxylic anhydride, (2-dodecen-1-yl)succinic anhydride, glutaric anhydride, citraconic anhydride, methylsuccinic anhydride, 2,2-dimethylsuccinic anhydride, 2,2-dimethylgiutaric anhydride, 3-methylglutaric anhydride, 3,3-tetramethyleneglutaric anhydride, 3,3-dimethylglutaric anhydride, several isomers of hydroxyphthaleic anhydride or mixtures thereof.

[0042] The polyfunctional anhydrides that can be used for the imidization reaction include polypropylene-graft-maleic anhydride, polyethylene-graft-maleic anhydride, butadiene-

##STR00006##

wherein X is a monocyclic, bicyclic or polycyclic ring structure that is cycloaliphatic or alicyclic optionally with aliphatic side chains; and the oxygen of the ester group is connected directly to the ring or to the side chain; [0043] X.sub.1 is alkylene or branched alkylene optionally comprising heteroatoms O or S; [0044] R.sub.3 is H, alkyl or cycloalkyl; [0045] L.sub.1 and L.sub.2 are independently selected from a covalent bond, alkylene, branched alkylene, and cycloalkylene optionally comprising heteroatoms O or S; [0046] R.sub.1 and R.sub.2 are independently H, methyl or OH with the proviso that at least one of R.sub.1 or R.sub.2 in each ring is OH; and [0047] the ester functionality present in structures I, II, III and IV can be primary or secondary ester group.

[0048] The phenol used in the flux compatible epoxy-phenol adhesive compounds may be selected from compounds of structures V, VI and/or VII:

maleic anhydride copolymers, styrene-maleic anhydride copolymers and other copolymers and terpolymers of maleic anhydride, itaconic anhydride and citraconic anhydride.

[0049] Amines and amine functional phenols that can be used for the imidization reaction include but not limited to several isomers of aminophenol, catechol amines, aminonaphthols, dimer diamine, TCD-diamine (3(4),8(9)-bis(aminomethyl)-tricyclodecane), cyclohexylamines, aliphatic, cycloaliphatic and alicyclic primary diamines.

[0050] The epoxy-phenol adhesive compositions may further comprise a maleimide resin, which can be a bismaleimide, a polyfunctional maleimide or phenol functional maleimide of structures VIII and IX represented below.

##STR00007##

wherein L is selected from a covalent bond, alkylene, cycloalkylene, and branched alkylene optionally with hetero atoms O or S; L can also contain an ester or carbonate linkages; and

[0051] the fused ring in structure VIII is optional and when present it is aromatic, cycloaliphatic, alicyclic or heterocyclic.

[0052] The maleimide resin may be obtained by the imidization reaction of mono or multifunctional primary amines with maleic anhydride or may be obtained by Fisher esterification of mono or multifunctional aliphatic, cycloaliphatic, alicyclic or aralkyl alcohols with 6-maleimidocaproic acid. The phenol functional maleimides also may be obtained by the imidization reaction of several isomers of amino phenols, aminonaphthols, catechol amines or side chain amine functional phenols with maleic anhydride.

[0053] A variety of catalysts may be used, included among which are imidazoles, substituted imidazoles, latent imidazoles, encapsulated imidazoles, phenol functionalized imidazoles, and naphthol functionalized imidazoles. The imidazole catalyst Technicure EMI-24CN was found to be a particularly desirable curing agent. For instance, at a 4% concentration, an epoxy-phenol adhesive composition having this catalyst showed an excellent balance of Tg and other performance properties. Latent imidazoles sold under the trade name Curezol that are available from Evonik Corporation, encapsulated imidazoles from A&C catalysts and phenol or naphthol functionalized imidazoles such as Aradur 3123 can be used. Preferred catalysts include Technicure EMI 24-CN, Curezol 2-PHZ-S, Curezol 2-PZ, Curezol 2PZ-azine, Aardur 3123, and amine and polyamine functional imidazoles.

[0054] The ratio of the epoxy component to the phenolic component may be from 1:1 to 1:0.05. The ratio is preferably 1:0.2, and more preferably 1:0.1. The combination of the epoxy component and the phenolic component typically makes up about 50% of the adhesive composition, the balance being selected from curing agents, accelerators, catalysts, flow modifiers, fillers, adhesion promoters, and thixotropic agents.

[0055] In certain embodiments, the adhesive compositions may further comprise one or more flow additives, adhesion promoters, conductivity additives, rheology modifiers, or the like, as well as mixtures of any two or more thereof. Various additives may be contained in the composition as desired, for example, organic or inorganic fillers, thixotropic agents, silane coupling agents, diluents, modifiers, coloring agents such as pigments and dyes, surfactants, preservatives, stabilizers, plasticizers, lubricants, defoamers, leveling agents and the like; however it is not limited to these. In particular, the composition preferably comprises an additive selected from the group consisting of organic or inorganic filler, a thixotropic agent, and a silane coupling agent. These additives may be present in amounts of about 0.1% to about 50% by weight of the total composition, more preferably from about 2% to about 10% by weight of the total composition.

[0056] The thixotropic agent may include, but is not limited to, talc, fume silica, superfine surface-treated calcium carbonate, fine particle alumina, plate-like alumina; layered compounds such as montmorillonite, spicular compounds such as aluminum borate whisker, and the like. Among them, talc, fume silica and fine alumina are particularly desired. These agents may be present in amounts of about 1% to about 50%, more preferably from about 1% to about 30% by weight of the total composition.

[0057] The silane coupling agent may include, but is not limited to, -aminopropyltriethoxysilane, -mercaptopropyltrimethoxysilane, -methacryloxypropyltrimethoxysilane, -glycidoxypropyltrimethoxylsilane, and the like.

[0058] As used herein, flow additives refers to silicon polymers, ethyl acrylate/2-ethylhexyl acrylate copolymers, alkylol ammonium salt of phosphoric acid esters of ketoxime, and the like, as well as combination. Several of these additives are available from commercial sources such as BYK and Evonik Corporation.

[0059] The present disclosure provides the following non-limiting and non-exhaustive examples.

EXAMPLES

[0060] Several imidazole catalysts were screened in phenol-epoxy formulations as shown in Table 1. Some of the formulations tested showed higher Tg when suitable imidazole accelerators are used. A liquid imidazole catalyst (Technicure EMI-24CN) appeared to perform best in terms lowering cure temperature. Low viscosity of this catalyst was an added advantage.

TABLE-US-00001 TABLE 1 Initial formulation screening of phenol cured epoxy system DSC Formu- peak lation Components temp Tg F1 BPF DGE, 1,1,1(trishydroxyphenyl)ethane, 125 C. 132 C. curezol 2PZ (6%) F2 BPF DGE, 1,1,1(trishydroxyphenyl)ethane, 125 C. 115 C. 1-(2-cyanoethyl)-2-phenylimidazole (Technicure EMI-24CN) (5%) F3 830CRP, GY 9820, 160 C. 138 C. 1,1,1(trishydroxyphenyl)ethane, curezol 2PHZ-S (5%) F4 830CRP, GY 9820, 130 C. 126 C. 1,1,1(trishydroxyphenyl)ethane, curezol 2PZ (5%) F5 830CRP, GY 9820, 130 C. 143 C. 1,1,1(trishydroxyphenyl)ethane, curezol 2PZ azine (5%)

[0061] It was found that epoxy resins possessing a cycloaliphatic backbone showed good flux compatibility. Some of the epoxy resins that were screened for flux compatibility in neat form include EP4088S, Eponex1510, HP7200L, Hyloxy modifier 107 and a mixture of the above. All of these epoxy resins have cycloaliphatic or mixed cycloaliphatic-aromatic backbones. The flux compatibility study was performed using epoxy resins containing about 5% of flux and heating the mixture to about 80 C. for about 30 minutes and speed mixing the mixture. Upon cooling to room temperature and storing they resulted in clear mixtures without any haze.

[0062] For the phenolic component, several multifunctional phenols were made that contained cycloaliphatic or aliphatic backbones, as described in the examples below.

Example 1: Synthesis of tetrafunctional Phenol 1

[0063] ##STR00008##

[0064] In a 1 L 3 necked flask equipped with a thermocouple, mechanical stirrer and a condenser were placed 4,8-Bis(hydroxymethyl)tricyclo[5.2.1.0.sup.2,6]decane (49.2 g, 250 mmol), diphenolic acid (143.5 g, 500 mmol), PTSA (3 g, 1.5%) in toluene 600 mL. The mixture was stirred with azeotropic distillation of water for 12h. After cooling to ambient temperature, the toluene was decanted and the remaining solid was dissolved in 1 L of ethyl acetate. The solution was washed once with water, twice with aqueous sodium bicarbonate solution and once with water. After the solution was dried over anhydrous Na.sub.2SO.sub.4, the solvent was evaporated using a rotary evaporator under reduced pressure. The last traces of solvent were removed under high vacuum at 80 C. for several hours to give Phenol 1 as a violet solid (152 g, 83%).

Example 2: Synthesis of Tetrafunctional Phenol 2

[0065] ##STR00009##

[0066] In a 1 L 3 necked flask equipped with a thermocouple, mechanical stirrer, and a condenser were placed 3-methyl-1,5-pentanediol (8.94 g, 75 mmol), diphenolic acid (43.11 g, 150 mmol), PTSA (1.1 g, 2.2%) in toluene 400 mL. The mixture was stirred with azeotropic distillation of water for 12h. After cooling to ambient temperature, the toluene was decanted and the resulting solid was dissolved in 600 mL of ethyl acetate. The solution was washed once with water, twice with aqueous sodium bicarbonate solution and once with water. After drying the solution over anhydrous Na.sub.2SO.sub.4, the solvent was evaporated using rotary evaporator under reduced pressure. The last traces of solvent were removed under high vacuum at 80 C. for several hours to give Phenol 2 as a violet solid (38 g, 88%).

Example 3: Synthesis of Difunctional Phenol 3

[0067] ##STR00010##

[0068] In a 1 L 3 necked flask equipped with a thermocouple, mechanical stirrer and a condenser were placed 4,8-Bis(hydroxymethyl)tricyclo[5.2.1.0.sup.2,6]decane (54.4 g, 277 mmol), 4-hydroxybenzoic acid (76.55 g, 554 mmol), PTSA (2.6 g, 2%) in toluene 600 mL. The mixture was stirred with azeotropic distillation of water for 12h. After cooling to ambient temperature, the toluene was decanted and the resulting solid was dissolved in 1 L of ethyl acetate. The solution was washed once with water, twice with aq. sodium bicarbonate solution and once with water. After drying the solution over anhydrous Na.sub.2SO.sub.4, the solvent was evaporated using rotary evaporator under reduced pressure. The last traces of solvent were removed under high vacuum at 80 C. for several hours to give phenol 3 as a violet solid (95 g, 77%).

Example 4: Synthesis of Tetrafunctional Phenol 4

[0069] ##STR00011##

[0070] In a 1 L 3 necked flask equipped with a thermocouple, mechanical stirrer and a condenser were placed 4,8-Bis(hydroxymethyl)tricyclo[5.2.1.0.sup.2,6]decane (35 g, 177 mmol), 3,4-dihydroxyphenylacetic acid (59.96 g, 356 mmol), PTSA (1.9 g, 2%) in toluene 600 mL. The mixture was stirred with azeotropic distillation of water for 48h. After cooling to ambient temperature, the toluene was decanted and the remaining solid was dissolved in 1 L of ethyl acetate. The solution was washed once with water, twice with aqueous sodium bicarbonate solution and once with water. After drying the solution over anhydrous Na.sub.2SO.sub.4, the solvent was evaporated using rotary evaporator under reduced pressure. The last traces of solvent were removed under high vacuum at 80 C. for several hours to give phenol 4 as a brown solid (79 g, 82%).

[0071] Several unfilled epoxy-phenol formulations were made and screened as shown in Table 2 below.

TABLE-US-00002 TABLE 2 Unfilled epoxy-phenolic formulations Formulations 1 2 3 4 5 6 183C 180C 180D 178B 178F 178D (g) (g) (g) (g) (g) (g) EPN 9820 5.73 5.44 3.28 2.66 1.68 EP4088S 3.73 1.99 1.89 3.28 3.04 1.93 BPA DGE 3.14 2.98 HP7200L 2.32 MY 0510 5.13 3.24 7.56 5.48 3.46 Hyloxy modifier 107 1.47 o,o-Diallyl bisphenol A 1.414 0.56 0.707 TD2131 1.13 2.0 1.9 Phenol 1 of example 1 0.56 Technicure EMI-24CN 0.492 0.57 0.62 0.62 0.49 0.311 DSC peak temp( C.) 140 C. 138 C. NA 136 C. 137 C. 140 C. Tg ( C.) 154 C. 115 C. 155 C. 150 C. 144 C. 134 C.

[0072] Table 2 above shows several epoxy-phenolic unfilled formulations and their cure and Tg profile. The amount of imidazole catalyst was kept constant at 4 wt % in all of these the formulations. Use of Hyloxy modifier 107 was found to be beneficial for lower viscosity. However, this cycloaliphatic epoxy negatively affected the Tg. Use of tetrafunctional phenol 1 appeared to increase the Tg significantly as compared to the formulation that used diallylbisphenol A (Formulation 5 vs 6 in Table 2).

[0073] Since cycloaliphatic epoxy resins showed good flux compatibility in neat form, several filled formulations were made blending them with other epoxy resins to get a balance of Tg, viscosity and flux compatibility. Several epoxy-phenolic formulations were developed that at least partially contained epoxy resins possessing cycloaliphatic backbone to improve flux compatibility. In contrast to unfilled formulations, filled formulations showed significant decrease in Tg when silica was used as filler as compared to the equivalent unfilled formulations. To obtain a Tg in the range of 120-140 C., the formulations were modified by adding multifunctional phenols possessing cycloaliphatic-aliphatic backbones to make the formulations shown in Table 3.

TABLE-US-00003 TABLE 3 Epoxy-phenolic filled formulations using flux compatible epoxy resins Formulations 1 2 3 4 5 6 (g) (g) (g) (g) (g) (g) 178D 178F 180D 180E 183C 183D EPN 9820 10.06 10.04 16.21 12.95 EP4088S 11.313 11.30 5.63 4.49 13.97 11.98 BPA DGE 8.89 7.1 HP7200L 8.68 7.45 MY0510 20.531 20.51 9.662 17.0 19.24 23.065 Tetrafunctional phenol 1 2.13 Phenol-novolac TD2131 5.72 4.57 4.24 3.62 O,O-diallylbisphenol A 4.23 2.13 Technicure EMI-24CN 1.86 1.87 1.85 1.85 1.85 1.85 SE2050 silica 50.0 50.0 49.975 49.975 49.975 49.975 KD1 1.0 1.0 1.0 1.0 1.0 1.0 W9010 0.5 0.5 0.5 0.5 0.5 0.50 Z6040 0.5 0.5 0.5 0.5 0.5 0.50 PC1344 0.05 0.05 0.05 0.05 0.05 0.05 Total 100.0 100.0 100.0 100.0 100.0 100.0

[0074] The Tg and viscosity profiles of several of the filled formulations of Table 3 are shown in Table 4. One distinct feature of the epoxy-phenolic chemistry was an increase in Tg observed after the 2.sup.nd DSC Tg ramp even though the DSC peak temperature was lower. This result may be coming from additional crosslinking during the 2.sup.nd heating. The increased Tg might benefit in the reliability of the device when it is subjected to multiple solder reflow conditions.

TABLE-US-00004 TABLE 4 Cure profile, viscosity and Tg of prototype formulations DSC Peak Cure Viscosity 1.sup.st Tg 2.sup.nd Tg Temperature @ 20 s.sup.1 after after Formu- ( C.) (cP) 25-260 C. 2.sup.nd ramp of lation w/o flux 0 hr DSC ramp 25-260 C. 1 160 3169 99 119 2 150 7377 113 128 3 139 48902 123 127 4 137 23291 141 143 5 138 16441 120 132 6 138 10972 126 143