Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
  • H01B1/00—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors
  • H01B1/20—Conductive material dispersed in non-conductive organic material
  • H01B1/22—Conductive material dispersed in non-conductive organic material the conductive material comprising metals or alloys
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G73/00—Macromolecular compounds obtained by reactions forming a linkage containing nitrogen with or without oxygen or carbon in the main chain of the macromolecule, not provided for in groups C08G12/00 - C08G71/00
  • C08G73/06—Polycondensates having nitrogen-containing heterocyclic rings in the main chain of the macromolecule
  • C08G73/0622—Polycondensates containing six-membered rings, not condensed with other rings, with nitrogen atoms as the only ring hetero atoms
  • C08G73/0638—Polycondensates containing six-membered rings, not condensed with other rings, with nitrogen atoms as the only ring hetero atoms with at least three nitrogen atoms in the ring
  • C08G73/065—Preparatory processes
  • C08G73/0655—Preparatory processes from polycyanurates
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K3/00—Use of inorganic substances as compounding ingredients
  • C08K3/02—Elements
  • C08K3/08—Metals

Definitions

• the present invention relates generally to the field of adhesives, and more particularly to die attach compositions for attaching semiconductor devices to carrier substrates.
• Cyanate ester resins developed during the 1980s, join epoxy resins and bismaleimide resins as the third major class of thermosetting resins.
• Polycyanurates or cross-linked cyanate resins are prepared by the cyclopolymerization of aromatic cyanate esters. These cyanate esters are bisphenol derivatives containing a plurality of cyanate functional groups. When heated, the cyanate functionality undergoes exothermic trimerization to form substituted triazine rings. Subsequent curing produces the thermosetting resin.
• Cyanate esters are currently employed in rapidly curing adhesive compositions used to bond semiconductor devices or chips, also known as dice, to carrier substrates.
• adhesive compositions include, in addition to the cyanate ester, thermally and/or electrically conductive filler, alkylphenol (as a proton donor participating in the cyclotrimerization cure of the cyanate ester monomer) , and a curing catalyst dissolved in the alkylphenol.
• Cyanate ester adhesive compositions have eliminated many of the deficiencies inherent in epoxy adhesives and polyimide adhesives, such as low glass transition temperature, high degree of ionic contamination, retention of solvent and lengthy cure.
• cyanate ester containing attach paste compositions exhibit some deficiency with respect to homogeneity, i.e., such pastes have a tendency to become non-homogeneous at ambient temperatures.
• die attach pastes containing electrically conductive filler and polycyanate ester monomer in a variety of ways, e.g., in assuring the stability of paste homogeneity, in extending the pot life of such die attach pastes, in reducing the cost of preparation, as well as the ease of preparation, by avoiding the use of potentially detrimental components (e.g., alkylphenols are acidic species, which are potentially corrosive) , by avoiding the use of volatile components (which upon cure may bleed out and/or which may lead to the creation of voids in the cured resin) , and the like.
• potentially detrimental components e.g., alkylphenols are acidic species, which are potentially corrosive
• compositions for attaching a semiconductor device to a substrate comprise liquid polycyanate ester-containing monomer vehicle, electrically conductive filler and a curing catalyst, preferably in the substantial absence of alkylphenol.
• Optional treatment of the filler to render it free of catalytically active metal ions has the potential to significantly extend the pot life of the composition.
• a paste composition for attaching a semiconductor device to a substrate comprising a liquid monomer vehicle comprising at least one polycyanate ester monomer, electrically conductive filler, and a metal catalyst, preferably in the substantial absence of alkylphenol.
• the die attach paste compositions of the invention employ liquid monomer vehicle comprising at least one polycyanate ester monomer, preferably in the substantial absence of alkylphenol. It has been found that polycyanate ester monomer performs a vital role in die attach paste compositions, particularly when a paste is used in hermetic packages. It is well known that the cyanate function reacts readily with moisture. This reaction is used to provide a powerful gettering action on residual moisture left in a hermetic package after it has been sealed.
• Monomer vehicle contemplated for use in the practice of the present invention is generally liquid under ambient conditions.
• the term "ambient” as used herein refers to temperatures of about 25 ⁇ 2°C.
• a liquid monomer vehicle ensures that paste compositions will not be compromised by monomer crystallization during use, but will maintain a homogeneous consistency, and also avoids the need for extraneous solvent/diluent (e.g., alkylphenol) as an aid to vehicle preparation. While it is possible to heat a sample of paste until all of the monomer is melted, this puts an unreasonable burden on the user. Furthermore, the user may not be able to ascertain when all of the monomer is melted. Use of a non-homogenous paste could result in failures in die attach.
• liquid monomer vehicles contemplated herein include vehicles selected from the group consisting only of liquid monomers; vehicles selected from the group consisting of solid monomer(s) miscible and/or soluble in liquid monomer(s) ; and vehicles selected from the group consisting of solid monomers which, when combined, provide a liquid monomer mixture.
• Monomer(s) which may be combined with polycyanate ester monomer is/are selected based on the following criteria: the monomer(s) should be soluble in or miscible with polycyanate ester monomer and should be non-reactive with polycyanate ester monomer at ambient temperatures, unless such reaction(s) is reversible at temperatures above ambient temperature.
• Cyanate ester monomers that can be employed in the practice of the present invention contain two or more ring forming cyanate (-O-O ⁇ N) groups which cyclotrimerize to form substituted triazine rings upon heating. Because no leaving groups or volatile byproducts are formed during curing of the cyanate ester monomer, the curing reaction is referred to as addition polymerization.
• Suitable polycyanate ester monomers that may be used in the practice of the present invention include, for example, l,l-bis(4- cyanatophenyl) methane, 1,1-bis(4-cyanatopheny1)ethane, 2 , 2-bis (4-cyanatophenyl) propane, l,3-bis[2-(4- cyanatophenyl) propyl]benzene, and the like.
• Polycyanate ester monomers utilized in accordance with the present invention may be readily prepared by reacting appropriate dihydric phenols with a cyanogen halide in the presence of an acid acceptor.
• Monomers that may be combined with polycyanate ester monomer(s) in accordance with the present invention are selected from those monomers which undergo addition polymerization.
• Such monomers include vinyl ethers, divinyl ethers, diallyl ethers, di ethacrylates, dipropargyl ethers, mixed propargyl allyl ethers, monomaleimides, bismaleimides, and the like.
• Examples of such monomers include cyclohexanedimethanol monovinyl ether, trisallylcyanurate, 1,l-bis(4-allyloxyphenyl)ethane, 1, 1-bis (4-propargyloxyphenyl) ethane, l,l-bis(4- allyloxyphenyl-4 '-propargyloxyphenyl)ethane, 3-(2,2- dimethyltrimethylene acetal)-1-maleimidobenzene, 2,2,4- trimethylhexamethylene-l,6-bismaleimide, 2,2-bis[4-(4- maleimidophenoxy)phenyl]propane, and the like.
• Various monomers may be combined to obtain a liquid monomer vehicle, without the need for any added solvent/diluent, such as alkylphenol.
• solvent/diluent such as alkylphenol.
• 1,1-bis(4-cyanatophenyl)ethane, having a melting point of 29"C, and 2,2,4-trimethylhexamethylene-l,6-bismaleimide, having a melting point range of 75 to 125°C were combined (in the absence of alkylphenol) , mixtures containing up to 12 wt. percent bismaleimide were found to remain liquid indefinitely. The lowest melting mixture contained 8 wt.
• the thermal stability of polymer derived from this mixture was lower than that of the polycyanate ester homopolymer.
• the decomposition onset temperature for the polymer derived from the mixture was 355°C. It is believed that the polymerized mixture consists of an interpenetrating network of cyanate and propargyl resins since differential scanning calorimetric studies indicate the presence of two separate cure events. Despite the lower decomposition onset temperature, this mixture is suitable for use for die attach in solder seal hermetic packages since such assemblies are usually processed at 330°C or lower.
• the thermal stability of the polymer derived from this mixture was somewhat lower than that of the polycyanate ester homopolymer.
• the decomposition onset temperature for the polymer derived from the mixture was 395°C, or about 24 degrees lower than the decomposition onset temperature of the polycyanate ester homopolymer.
• the mixture is suitable for use in solder seal hermetic, microelectronic packages because the highest temperature required to seal these packages is far lower than the decomposition temperature for the polymer derived from the mixture.
• the melting point of l,l-bis(4- propargyloxyphenyl)ethane can be significantly depressed by the partial reduction of the propargyl function to allyl.
• Approximately 20% of the propargyl groups had to be reduced to allyl in order for the product to be a room temperature- stable liquid. It is also necessary to keep the total fraction of allyl groups below 30% since the allyl moiety does not produce an independent cure.
• the 20/80 allyl/propargyl monomer was combined with 1,1-bis(4- cyanatophenyl)ethane, it was found that from 5 to 100 wt. percent allyl/propargyl monomer provided stable liquids at room temperature.
• Cyclohexanedimethanol monovinyl ether a liquid, is miscible in all proportions with 1,1-bis(4- cyanatophenyl)ethane, even in the absence of added solvent/diluent, such as alkylphenol.
• the vinyl ether monomer significantly depresses the viscosity of the dicyanate ester monomer when present at a concentration of at least 5 wt. percent.
• the presence of just 5 wt. percent monovinyl ether monomer also enhances the supercooling behavior of the dicyanate ester monomer. Mixtures containing at least 25 wt. percent monovinyl ether monomer did not freeze at 5 ⁇ C, even when seeded with crystals of the dicyanate ester monomer.
• the decomposition onset temperature in air is 363"C for polymer derived from a mixture consisting of 20 wt. percent monovinyl ether monomer and 80 wt. percent dicyanate ester monomer. This polymer is also suitable for use for die attach in solder seal packages.
• the decomposition onset temperature for a mixture containing 15 wt. percent bismaleimide monomer and 85 wt. percent dicyanate ester monomer was 431°C, which is approximately the same as the decomposition onset temperature for the polycyanate ester homopolymer.
• percent dimethacrylate monomer were approximately the same as the viscosity of pure dicyanate ester monomer.
• the onset for thermal decomposition in air for a mixture containing 20 wt. percent dimethacrylate monomer was 409°C, which is only slightly lower than the decomposition onset temperature of the polycyanate ester homopolymer.
• Examples of electrically conductive fillers contemplated for use in the practice of the present invention include, for example, silver, nickel, cobalt, copper and aluminum fillers, as well as alloys of such metals. Both powder and flake forms of filler may be used in the attach paste compositions of the present invention.
• the preferred thickness of flake is under 2 microns with a dimension of about 20 to about 25 microns.
• Flake employed herein preferably has a surface area of 2 about 0.15 to 5.0 m /g and a tap density of 0.4 to 5.5 g/cc.
• Powder employed herein preferably has a diameter of about
• Electrically conductive fillers are optionally rendered free of catalytically active metal ions according to the present invention by treatment with chelating agents, reducing agents, non-ionic lubricating agents, or mixtures of such agents.
• Treating solutions are prepared by adding the agent(s) to a suitable solvent such as a lower alkyl ketone (e.g., acetone), a lower alcohol (e.g., isopropyl alcohol) , and the like.
• Filler is then added to the treating solution to obtain a slurry containing approximately 50 wt. percent filler in a treating solution containing from about 0.5 to 10 wt. percent treating agent, based on total weight of filler.
• the resulting slurry is agitated at room temperature for a minimum of five minutes up to 48 hours. The amount of time will vary depending on the quantity of metal soap on the filler being treated.
• lubricants Virtually all commercially available filler is coated with one or more lubricants.
• the lubricants used most often are stearic and oleic acids.
• the function of lubricants is to prevent agglomeration of the particles (especially powder particles) and to prevent the welding or "coining" of these particles during the mechanical milling process used to produce silver flake products.
• These fatty acid lubricants become chemically bound to the surface of the metal filler by the formation of metal carboxylate salts (i.e. metal soaps) at the metal filler/lubricant interface.
• carboxylate salts occurs spontaneously according to the following reaction sequence upon exposure of a fatty acid coated silver powder or flake to oxygen:
• chelating agent based on the weight of silver powder
• an appropriate solvent such as ketones (e.g., acetone, methyl ethyl ketone (MEK) , pentanone, and the like), aqueous ketones (e.g., aqueous acetone, aqueous MEK, and the like), lower alcohols (e.g., methanol, ethanol, isopropyl alcohol, butanol, and the like); aqueous alcohols (e.g., aqueous methanol, aqueous ethanol, aqueous isopropanol, and the like) ; cyclic ethers (e.g., tetrahydrofuran (THF) , dioxane, and the like); aqueous cyclic ethers (e.g., aqueous THF, aqueous dioxane, and the like) ; and so forth.
• ketones e.g., ace
• Di-amide are reaction products of diethylenetria inepentaacetic (DTPA) dianhydride or ethylenediaminetetraacetic (EDTA) dianhydride, respectively, and Jeffamine M600, a poly (isopropyleneoxide) marketed by Texaco Chemical Company, Houston, Texas. This poly(propyleneoxide) product is capped at one end with a methoxy group and at the other end with a primary amine group.
• DTPA diethylenetria inepentaacetic
• EDTA ethylenediaminetetraacetic
• DTPA-MPEG-350 diester is the reaction product of DTPA dianhydride and methoxy polyethoxyethanol.
• DTPA-Oleyl diamide is the reaction product of DTPA dianhydride and oleyl amine.
• Additional chelating agents that are suitable for use in the present invention include hydroxycarboxylic acids (e.g., malic acid, lactic acid, glycolic acid and gluconic acid), aminocarboxylic acids (e.g., 1,6- diaminohexane-N,N,N' ,N'-tetraacetic acid, l,3-diamino-2- hydroxypropane-N,N,N' ,H'-tetraacetic acid, 1,2- diaminocyclohexane-N,N,N * ,N ' -tetraacetic acid, diethylenetriaminepentaacetic acid, N-hydroxy- ethylenediaminetriacetic acid, nitriloacetic acid and ethylenediaminetetraacetic acid) , as well as amides and esters derived from such acids or their anhydrides.
• hydroxycarboxylic acids e.g., malic acid, lactic acid, glycolic acid and
• Thiocarboxylic acids suitable for use as chelating agents in the present invention include, in addition to those already mentioned, thioglycolic acid and thiosalicylic acid. Chelating agents are believed to retard unwanted catalysis by displacing fatty acids from metal carboxylates present on the surface of the filler. A simple test confirmed this theory. Approximately 0.50g of silver octoate was weighed into each of two vials. An identical quantity of acetone was added to each vial. One half gram of tartaric acid was then added to the first vial while the second vial had no further additions (the second vial was used as a control for the first vial) . Both vials were sealed and heated at 40°C for 70 hours.
• the chelating agents shown in Table 2 are ionic chelating agents.
• Non-ionic chelating agents such as N,N,N' ,N'tetrakis(2-hydroxypropyl)-ethylenediamine or tris[2-(2-methoxyethoxy)ethylamine]amine are ineffective at quenching the catalysis. Presumably, the ineffectiveness of these non-ionic chelating agents resides in the absence of any sufficiently acidic protons to participate in the above reaction.
• the significance of the reaction shown above is that it represents a mechanism by which metal carboxylates
• metal soaps i.e. metal soaps
• DTPA- and EDTA-Jeffamine M600-Di-Amides are DTPA- and EDTA-Jeffamine M600-Di-Amides. These agents, as discussed earlier, are reaction products of DTPA or EDTA dianhydride with a poly(propyleneoxide)monoamine.
• Use of such chelating lubricants in the attach paste compositions of the invention permits chelation of metal ion while at the same time providing lubrication of filler particles (especially powder particles) .
• Lubrication of filler particles is especially important to prevent agglomeration of the particles and to prevent welding or "coining" of the particles during mechanical milling processes used to produce the filler.
• Poly(alkyleneoxide)-derived chelating lubricants are infinitely miscible with the monomer vehicle employed herein. The significance of this becomes apparent when filler treated with a fatty acid lubricant is added to the same monomer vehicle. Pastes containing filler treated with the chelating lubricants described herein can be loaded to higher solids content (while maintaining acceptable viscosity) than pastes containing filler treated with fatty acid lubricants. This is a significant advantage because both the electrical and thermal conductivity of the final fired paste will be enhanced by loading at higher solids.
• Additional agents having both chelating and lubricating properties can be prepared by reaction of the dianhydride of either diethylenetria ineEentaacetic acid (DTPA) or ethylenediaminetetraacetic acid (EDTA) with two equivalents of a homo- or co-oligomeric poly(alkylene oxide) capped at one end with an alkoxy or aryloxy group and at the other end with either an a ino group or an hydroxy group. Opening of the anhydride ring with an amino function yields an amide. Opening of the anhydride ring with an hydroxy function yields an ester. In both cases, a carboxylic acid function is obtained as well.
• DTPA diethylenetria ineEentaacetic acid
• EDTA ethylenediaminetetraacetic acid
• Oligomeric poly(alkylene oxides) suitable for reaction with DTPA or EDTA include, for example, methoxy polypropoxyisopropylamine , butyloxy polyisopropoxyisopropylamine, methoxy polyethoxyethanol, nonylphenoxy polyethoxyethanol, and the like.
• the present invention also relates to the use of other agents to inhibit this unwanted catalysis.
• a second group of substances found to be useful in retarding unwanted catalysis are mild reducing agents including covalent hydrides such as, for example, silicon hydrides, boron hydrides, aluminum hydrides, and the like.
• Covalent hydrides contemplated for use in the practice of the present invention include silicon hydrides, boron hydrides or aluminum hydrides of the formula:
• R H-S Ii-R or wherein each R is independently hydrogen or a hydrocarbyl radical of 1 up to 20 carbon atoms.
• silicon hydrides contemplated for use in the practice of the present invention include triphenylsilane, dimethyl octadecylsilane, diethylmethylsilane, diphenylmethylsilane, phenylsilane, ethyldimethylsilane, n-hexylsilane, methylphenylsilane, octadecylsilane, octylsilane, pentamethy ldisiloxane , pheny ldimethy lsilane , phenylmethylvinylsilane, tetramethyldisiloxane , triethylsilane, trihexylsilane, triisopropylsilane, trimethyldisilane, trimethylsilane
• boron hydrides contemplated for use in the practice of the present invention incl ⁇ de 9- borabicyclo[3.3.1]nonane, thexylborane, disiamylborane, and the like, as well as Lewis base complexes of borane such as borane-tetrahydrofuran, borane-methylsulfide, borane- pyridine, borane-trimethylamine, borane-triethylamine, and the like.
• aluminum hydrides contemplated herein include aluminum hydride (preferably as its Lewis acid-base complex with tetrahydrofuran) , diisobutylaluminum hydride, and the like.
• a control paste comprising 80% silver powder in 1,1-bis(4-cyanatophenyl) ethane exhibited an exotherm maxima of 155"C and an onset temperature of 105°C.
• a test paste was prepared with the addition of 5% by weight diphenylmethyl silane in 1,1- bis(4-cyanatophenyl)ethane.
• the test paste had an exotherm maxima of 201°C immediately after it was prepared. Five hours later the paste had an exotherm maxima of 218°C. However, after 24 hours it had dropped to 195°C.
• the shift in the exotherm of the test paste suggested some degree of change was occurring in the paste over time, i.e., storage of the test paste in the presence of air permitted some regeneration of catalytic species.
• a third group of agents useful in retarding unwanted catalysis are non-ionic lubricants.
• non-ionic lubricants include, for example, fatty acid monoesters of glycerol such as glycerol monooleate.
• Use of non-ionic lubricants is particularly advantageous because of the superior pot life of pastes containing filler treated with such agents. For example, the pot life of pastes made with fatty acid coated flake is only about 6 hours at room temperature. When flake of approximately the same surface area is treated with a non-ionic lubricant and incorporated into a paste, the pot life of the paste is increased to a minimum of 18 hours and a maximum of 48 hours.
• the pot life extension associated with filler treated with non- ionic lubricant is especially apparent for filler particles having a low surface area. It may be that particles having a higher surface area, even when treated with non-ionic lubricant, still have some carboxylate salt contamination.
• Metal catalysts employed in the practice of the present invention are metal acetylacetonates which are metal chelates wherein the preferred metal is a transition metal.
• suitable metals employed herein are cobalt, manganese, tin, zinc, copper and nickel, all in the divalent state; manganese, iron, cobalt and aluminum, all in the trivalent state; and tetravalent titanium.
• the presently most preferred metal catalyst is cobalt(III) acetylacetonate.
• the phrase "substantial absence of alkylphenol” refers to alkylphenol levels below that which can be readily determined using available analytical techniques. It is understood by those of skill in the art that “substantial absence” does not exclude the presence of trace quantities of alkyphenols, which may be introduced into the die-attach composition of the invention from a variety of sources. Typically, substantial absence refers to levels of alkylphenol below about 1 part per hundred composition.
• the attach paste compositions of the invention can be prepared by mixing liquid monomer vehicle, optionally treated filler and catalyst (preferably in the absence of alkylphenol) , in a planetary mixer under vacuum or an in inert atmosphere for about 30 minutes to 1 hour. Thereafter, the homogeneous paste which is obtained is subjected to additional mixing on a three-roll mill for a minimum of fifteen minutes at room temperature.
• the paste is preferably stored at low temperatures, e.g. -40"C, until needed.
• liquid monomer vehicle preferably substantially free of alkylphenol
• the optionally treated filler is present in the range of about 80 to about 92 wt. percent
• the metal catalyst is present in the range of 50 to about 1500 pp .
• additives include, for example, fumed silica and certain antioxidants.
• Incorporation of a small amount of fumed silica may be beneficial in that it reduces the amount of liquid bleed that can occur during the curing process. Specifically, introduction of fumed silica reduces the amount of uncured monomer that wicks out onto the substrate. Minimizing liquid bleed is desirable since excessive spread of monomer can result in contamination of the die being attached to the substrate.
• the addition of a small amount of fumed silica can also be used to increase the thixotropic index of a paste. This effect is particularly important when low surface area metal fillers are employed in the preparation of an attach paste.
• such a paste composition may give a "taily dispense", a term referring to a paste that does not break off cleanly from an automatic dispensing head. This results in a tail of paste dragging across a component during the assembly process, which may make the component unusable.
• fumed silica is incorporated in the paste compositions of the invention, the amount will vary from about 0.2 wt. percent to about 2 wt. percent.
• thermo-oxidative stability of a high temperature polymer can be improved by the incorporation of an antioxidant.
• Use of an antioxidant in paste compositions containing high temperature polymers and finely divided silver can be very beneficial.
• Silver metal can act as an oxidation catalyst and contribute to early thermal degradation. This effect is especially evident when the filler employed is a high surface area silver powder.
• the severity of the problem increases as the solids loading of silver powder increases. For example, thermal degradation onset for a paste loaded with 85 wt. percent silver powder is about 390°C. A paste made with identical ingredients loaded by only 80 wt. percent silver powder had a decomposition onset around 400°C.
• Antioxidants that are suitable for use in the attach paste compositions of the invention include, for example, 4,4'- dioctyldiphenylamine, 3,3'diethyl-5,5•-dinonyldiphenyl amine, tris (2 , 4-di-tert-butylphenyl) phosphite, tetrakis(2,4-di-tert-butylphenyl)-4,4'-biphenylene diphosphonite, phosphited polyalkyl polyphenols such as Geltrol brand phosphited polyalkyl polyphenol sold by Goodyear (Akron, OH) , and the like.
• DTPA dianhydride Diethylenetriaminepentaacetic dianhydride (0.26g) was added with stirring to a solution of 0.84g of Texaco Jeffamine M600 in 2g of anhydrous N- methylpyrrolidone. The reaction mixture was allowed to stand for two hours at 60°C and then diluted with 20 ml of cyclohexane. Two liquid phases formed (Jeffamine M600 is fully miscible with cyclohexane) . The larger supernatant phase was decanted and the remaining phase stirred with 20 ml of fresh cyclohexane which was also subsequently decanted. This procedure was repeated with two more 20 ml portions of cyclohexane and the final residual liquid dried under vacuum at 50°C overnight. A yield of l.OOg of DTPA- Jeffamine M600 diamide was obtained as a viscous liquid.
• 1,1-Bis(4-hydroxypeny1)ethane 50.Og
• 150 ml of dimethylsulfoxide 150 ml were added to a double-necked 500 ml flask, fitted with a mechanical stirrer and cooled in an ice/water bath. Stirring was continued until all solid material had dissolved. Thereafter, an equivalent of powdered potassium hydroxide was added portionwise to the reaction mixture over a period of one hour with stirring. After the addition of base, 37.25g of propargyl chloride was added drop wise through a liquid addition funnel over a one hour period. After addition of propargyl chloride was complete, the ice bath was removed and the solution was stirred for an additional two hours.
• the crude bispropargyl ether was recovered by first diluting the reaction mixture with an equal volume of water and then washing the aqueous phase 3X with methylene chloride. The organic washes were combined and washed once with dilute aqueous base followed by 2X washings with water. The organic phase was dried over magnesium sulfate. Using a rotary evaporator, the solvent was removed by first evaporating under atmospheric pressure and then stripping at reduced pressure and elevated temperature ( ⁇ 80 ⁇ C).
• the crude ether was distilled using a falling film molecular distillation apparatus using chlorobenzene as a refluxing solvent.
• reaction product was isolated using suction filtration and air dried overnight. A light yellow solid was obtained (120.7g, 91.0% yield).
• Acetic anhydride 150.Og, 1.47 moles
• 26.9g (0.328 moles) sodium acetate
• 3.30g 0.33 moles
• triethylamine 100.Og (0.328 moles) of the reaction product described in the preceding paragraph
• the reaction mixture was stirred in an inert atmosphere at 70°C for a period of 2 hours.
• a small quantity of paste was made from the treated silver by dispersing 0.85 grams of the treated silver in 0.15 grams pure 1,1-bis(4-cyanatophenyl)ethane (employing no alkylphenol as solvent/diluent or as co-catalyst for polymerization of cyanate ester monomer) .
• An analogous paste was also made using the untreated silver flake as a control.
• the paste with the treated silver gave a fluid, low viscosity product at 85% solids.
• the cure profile for both pastes was determined by Differential Scanning Calorimetry (DSC) .
• the control paste had an exotherm maximum at 162"C and an exotherm onset at 104°C.
• the paste containing treated silver had an exotherm maximum at 209°C, with onset at 157°C.
• the paste containing treated silver had a pot life of approximately seven days at room temperature. The pot life of the control paste was less than one day at room temperature.
• a blend of silver powder of varying particle size was obtained by blending three different powders in the percentages shown below:
• the blended silver powder was treated as described in EXAMPLE I. Pastes were then made with treated and untreated material by dispersing 88% by weight solids in a mixture of polycyanate ester monomer comprising 85 wt. percent 1,1-bis(4-cyanatophenyl)ethane and 15 wt. percent 2,2-bis(4-cyanatophenyl)propane (employing no alkylphenol as solvent/diluent or as co-catalyst for polymerization of cyanate ester monomer) .
• the paste with the treated silver was a very fluid, low viscosity paste. DSC was performed on both pastes.
• the control pastes had an exotherm maximum at 165°C with an onset at 107°C.
• the corresponding ,values for the paste containing the treated material by contrast, were 204"C and 159°C, respectively.
• the pot-life of the control paste was less than one day whereas the pot life of the paste containing treated silver was greater than one week.
• the paste containing treated silver retained 98% of its original cure exotherm after 255 hours at room temperature. Moreover, the viscosity of this sample did not change during this period.
• the control paste retained only 87% of its original cure exotherm after 21.5 hours and was transformed into an unusable paste with a putty-like consistency.
• the silver powder blend used in this example was prepared as described in EXAMPLE II.
• a paste was then made with treated material by dispersing 88% by weight solids in a mixture of polycyanate ester monomer comprising 85% 1,1-bis(4-cyanatophenyl)ethane and 15 wt. percent 2,2-bis(4-cyanatophenyl)propane (employing no alkylphenol as solvent/diluent or as co- catalyst for polymerization of cyanate ester monomer) .
• a blend of silver flake of varying particle size was obtained by blending four different flakes in the percentages shown below:
• the blended flake was treated as described in EXAMPLE I. Pastes were then made with treated and untreated material by dispersing the flake in polycyanate ester monomer comprising 85 wt. percent l,l-bis(4- cyanatophenyl)ethane and 15 wt. percent 2,2-bis(4- cyanatophenyl)propane (employing no alkylphenol as solvent/diluent or as co-catalyst for polymerization of cyanate ester monomer) . Both pastes contained 83 wt. percent solids.
• the treated silver paste was a fluid, low viscosity dispersion. DSC was run on both pastes.
• the control paste had an exotherm maximum at 152°C with an onset temperature of 127°C.
• the paste containing the treated silver flake had an exotherm maximum at 206°C and an onset temperature of 148°C.
• the pot life for the control paste was approximately 48 hours while the pot life of the paste containing treated silver retained useful dispense characteristics for about six days.
• a blend of silver flake of varying particle size was obtained by blending four different flakes in the percentages shown below:
• the blended flake was treated as described in EXAMPLE I.
• Pastes were then made with treated and untreated material by dispersing flake in monomer comprising 92 wt. percent 1,1-bis(4-cyanatophenyl) ethane and 8 wt. percent 2,2,4-trimethylhexamethylene-l,6- bismaleimide (employing no alkylphenol as solvent/diluent or as co-catalyst for polymerization of cyanate ester monomer) . Both pastes contained 84 wt. percent solids.
• the paste containing the treated material was a fluid, low viscosity dispersion. DSC analysis was performed on both pastes.
• the control paste had an exotherm maximum of 155°C and an onset of 123°C.
• the paste containing the treated material had an exotherm maximum at 218"C with an onset temperature of 180°C.
• the pot life of the control paste was approximately 40 hours, while the paste containing treated material retained useful dispense characteristics for about 10 days.
• the high surface area fumed silica is available as Aerosil 805 from Degussa Corporation, 65 Challenger Road, Ridgefield Park, New Jersey.
• the silver flake comprised 17 wt. percent flake having a surface are of 0.25 m /g and 63.13 wt. percent flake having a surface area of
• the silver flake and fumed silica were mixed with liquid cyanate ester (employing no alkylphenol as solvent/diluent or as co-catalyst for polymerization of cyanate ester monomer) in a ceramic vessel at room temperature until the solids were thoroughly wetted.
• the resulting paste was then processed on a three-roll mill until the dispersion became homogeneous. During processing, the mill was cooled with recirculating water maintained at 23 ⁇ 2°C. Using a Brookfield viscometer, the viscosity of the paste at 10 rpm was 170 x 10 3 centipoise.
• the thixotropic index defined as the 1 rpm viscosity value divided by the 20 rpm value, was 11.00. This paste cured in two minutes at 200°C to yield a tough adhesive bond with minimal voiding. The tensile strength of the paste was equal to or greater than 2600 psi immediately after curing. The tensile strength was unchanged after 100 temperature cycles between -65 and 150°C. The radius of curvature (a measure of residual stress left after cure) was 7.5 ⁇ 1.5 meters.
• This paste composition had a pot life at room temperature of approximately eighteen hours.
• the product can be kept for more than six months with full retention of excellent dispense characteristics as long as the storage temperature is equal to or less than -40°C.
• the silver flake comprised 6.80 wt. percent flake having a surface area of 1.91 m/g, 17.01 wt. percent flake having a surface area of 0.65 m 2 /g and 40,81 wt. percent flake having a surface area of 0.25 m 2 /g.
• the flake had been treated with 0.5 percent tartaric acid and 5.0 percent DTPA-Jeffamine M600 (based on weight of flake) in acetone followed by 3X rinses in acetone.
• cyanate ester monomers (employing no alkylphenol as solvent/diluent or as co-catalyst for polymerization of cyanate ester monomer) were heated and stirred until a homogeneous liquid was obtained. The remaining ingredients were mixed with this liquid in a ceramic vessel until the solids appeared to be thoroughly wetted by the co onomer vehicle. The mixture was then processed on a three roll mill until a smooth, homogeneous paste was obtained.
• the paste had a 10 rpm viscosity of 61 x 10 centipoise and a thixotropic index of 10.81. This paste could be cured in 5 minutes at 240°C to yield a tough adhesive substantially free of voids.
• the post cure adhesion was at least 2600 psi and did not degrade even after 100 temperature cycles between -65 and 150°C.
• the radius of curvature for this paste was found to be 4.5 ⁇ 0.3 meters. Any radius of curvature greater than 1.0 meters is generally recognized in the art as characteristic of a functional attach paste.
• This paste had a room temperature pot life of approximately 80 hours. The pot life of this product exceeds six months if stored at -40°C.
• the cyanate ester monomers (employing no alkylphenol as solvent/diluent or as co-catalyst for polymerization of cyanate ester monomer) were heated and stirred together to yield a homogeneous liquid.
• the solid ingredients were then added to this liquid and the mixture was thoroughly stirred until the solids were completely wetted by the liquid phase.
• the paste was then made homogeneous by means of three roll milling.
• the viscosity of the paste after milling was 175 x 10 centipoise at 10 rpm, and the thixotropic index was 9.81.
• the paste was used to attach 500 mi .l2 si.licon dice to alumina substrates.
• the paste cured in 5 minutes at 240°C to yield a tough nearly void-free bond.
• the tensile strength of this bond exceeded 2600 psi and was found to be unchanged even after 100 temperature cycles between -65 and 150°C.
• the radius of curvature measured for this paste was 8.3 ⁇ 1.8 meters.
• This paste had acceptable dispensibility when stored at room temperature for approximately 100 hours and had a shelf life of at least six months when stored at -40°C.

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• Organic Chemistry (AREA)
• Physics & Mathematics (AREA)
• Dispersion Chemistry (AREA)
• Spectroscopy & Molecular Physics (AREA)
• Adhesives Or Adhesive Processes (AREA)
• Die Bonding (AREA)

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• 1994
  • 1994-02-23 EP EP94912153A patent/EP0686170A4/en not_active Withdrawn
  • 1994-02-23 AU AU64417/94A patent/AU6441794A/en not_active Abandoned
  • 1994-02-23 WO PCT/US1994/001776 patent/WO1994019402A2/en not_active Application Discontinuation
  • 1994-02-23 JP JP6519172A patent/JPH08510482A/ja active Pending
  • 1994-02-23 SG SG1995001686A patent/SG42790A1/en unknown

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