KR20050020756A - Improved interface adhesive - Google Patents

Abstract

The present invention relates to a one-component 96-100% solid thermoset based on thermal interface die assemblies and epoxy resins useful in integrated circuit packages that enable the conduction of heat generated by the die assemblies. The adhesive is located between the die and the lid, the lid and the heat sink and / or between the die and the heat sink. The interfacial adhesive composition consists of an inorganic component and an organic component. The inorganic component consisting of the thermally conductive filler is present in 70-85% by weight, the organic component is 60-70% by weight of glycidal ether of the bisphenol compound, acyclic aliphatic or cycloaliphatic or mononuclear aromatic diglycidal ether 4-30 Weight percent, 3-30 weight percent single function epoxy compound and 20-30 weight percent polyamine anhydride adduct.

Description

Improved interface adhesive

The present invention relates to one component 96-100% solids, thermoset, silver filled thermal interface adhesives based on epoxy resins and useful in integrated circuit packages that allow conduction of heat generated by a die. The adhesive may be placed between the die and the lid, between the lid and the heat sink (integrated heat spreader), and / or between the die and the heat sink. When the parts are properly positioned, the package is heated to allow the resin to flow and make contact. Further heating causes the resin to cure, forming a permanent thermal bridge between each component.

Surface mounting of electronic devices is well developed in automated package assembly systems. Interfacial adhesives have been used in several approaches for mechanical shock and vibration encountered during shipping and use, as well as to provide lid attachment, sink attachment and primarily thermal transfer from flip chip devices. Since semiconductor devices operate at high speeds and small line thicknesses, the thermal transfer properties of the adhesive are important for device operation. Thermal interface adhesives are dies because the adhesives themselves due to interfacial resistance (θint) and bulk resistance (θadh) are typically the most thermally resistant materials in a die-adhesive-lid-adhesive-sink or die-adhesive-sink configuration. Or a valid thermal passage must be formed between the lid and the heat sink. Thermal interface adhesives must also maintain effective thermal transfer characteristics through reliability tests that simulate actual conditions of use over the life of the device. Reliability testing includes exposure to a temperature of 130 ° C, 85% relative humidity for a specified time, exposure to 85 ° C, 85% relative humidity, and high temperature storage at 125-160 ° C. The adhesive should not be peeled off from the substrate, otherwise the bulk thermal resistance of the adhesive will degrade after exposure to the reliability test, resulting in breakage of the package. Interfacial adhesives may be applied after reflow of the metal or polymer interconnects and after the under-fill. The measured amount of interfacial adhesive is typically dispensed on the die surface and around the carrier substrate in the flipped flip chip assembly θjc. The adhesive may also be dispensed on top of the heat sink and die surface that is placed in the die-sink application [theta] ja. In addition, the adhesive may be dispensed on the lid surface and the heat sink placed on the sink-lid application θca. After the adhesive has been dispensed, it is attached at a predetermined pressure and time. The assembly is then heated to cure the adhesive.

Curable adhesives have been prepared using polyamide resins and epoxy resins, as described in US Pat. No. 2,52,523 (Lenfru and colleagues). However, the compositions described in this patent have inferior properties when applied as adhesives. For example, the compositions described in this patent do not have good adhesive strength upon curing and provide limited working time after mixing of the components. In addition, such compositions exhibit poor flexibility when applied to substrates at ambient temperatures and poor adhesion resistance to heat, water and organic solvents.

U.S. Pat. No. 3,488,665 (McGrandle and colleagues) discloses a method of mixing polyamide with epoxy to provide a product that is cured after application to a substrate. However, the product is used to provide a rigid, rigid coating on the flexible sheet material.

U.S. Patent No. 4042708 (meta) provides an adhesive system consisting of an epoxy resin and a polyamide, in which the polyamide is substantially derived from primary and tertiary amines, in particular the polyamide of the patent Having 1,4-bis-primary amino lower alkyl piperazine. Although it has been suggested that secondary amines can be used to prepare polyamides as chain extenders and flexible agents, secondary amines are less preferred reactants and are suggested to be embedded in the polyamide structure.

U.S. Patent No. 3,325,734 (Kong) discloses a thermosetting epoxy resin composition consisting of polyglycidyl ether, (a) amino terminal polyamides of polymeric fatty acids and aliphatic dicarboxylic acids, and (b) polyoxy alkylene diamines. have. Especially preferred are dimer fatty acids or mixed dimers and trimer acids.

U.S. Pat.No. 40,70225 (V. H. Barttrop) describes a latent or slowly cured adhesive system made from epoxy resins and primary amine terminated polyamides. Polyamides are prepared from polymerized tall oil fatty acids, polyoxypropyleneamines, 1,4-bis-amino propyl piperazine and ethylene diamine.

U.S. Patent No. 4042708 (Meta) discloses polyamide curatives of 1,4-bis (3-amino propyl) piperazine, dimerized tall oil fatty acids, polyoxy propylene diamines, and epoxy resins made from ethylene diamine or piperazine. Described. Polyamide is EPON as metal-metal adhesive Used with the 828.

U.S. Patent No. 5,518,80 discloses an encapsulation resin for electronic components consisting of cycloaliphatic epoxy resins, curing agents, accelerators, fillers and optionally pigments. The curing agent may be methylnadine anhydride and the filler may be amorphous silica.

U.S. Patent No. 5248710 discloses a flip chip encapsulation composition consisting of a dual function epoxy resin, a silicone modified epoxy resin, an imidazole curing agent soluble in epoxy resin, and a fused silica filler.

U.S. Patent No. 5416138 mainly contains (A) epoxy resins containing 50-100% by weight of diglycidyl ethers of substituted bisphenols, and (B) phenolic resin curing agents containing 30-100% by weight of flexible phenolic resin curing agents. The epoxy resin composition for semiconductor device seal | stickers comprised from (C) an inorganic filler, and (D) hardening accelerator is disclosed.

U.S. Pat.No. 5,3,377,77 contains essentially (1) epoxy resins having two or more epoxy groups per molecule, (2) acid anhydrides, (3) (a) liquid latent curing accelerators, and (b) latent curing which is soluble in epoxy resins. An acid anhydride containing one package epoxy resin composition consisting of at least one of an accelerator and (c) a latent cure accelerator soluble in acid anhydride, and (4) a latent cure accelerator that is dispersible is disclosed.

There are a number of latent amine curing agents derived from compounds of different functions for epoxy resin systems. Among these are blocking or hindering imidazoles, polyamidoamines, polyamide condensates of dimer acids and diethylenetriamine, triethylenetetramine, and aromatic polyamines.

U.S. Pat.No. 6046282 discloses 5-95% by weight consisting of amide and / or imidazoline reaction products of polyalkylene polyamines and C ₂ -C ₇ aliphatic monocarboxylic acids or C ₇ -C ₁₂ aromatic monocarboxylic acids. A reduced viscosity reactive diluent, which is a mixture of a lower reactive diluent and a highly viscous polyamidoamine epoxy curative, is disclosed.

U.S. Pat.No. 6614460 discloses amine adducts with at least one alkyl acrylate, at least one reinforcing comonomer, polyepoxide resin, and epoxy resin, alkylene epoxide, acrylonitrile, or fatty acid or manny base ( Screen printable adhesive compositions are disclosed that can be applied to substrates at room temperature, consisting of condensation products with Mannich, base).

U.S. Pat. A rheologically stable and thermosetting flexible electrically conductive epoxy based adhesive composition is disclosed which consists of a polymer mixture comprising a latent epoxy resin curing agent and (b) an electrically conductive filler consisting of a metal.

In view of the foregoing, the design of integrated circuit package heat dissipation is limited by thermal interface materials. Long-term qualitative defects can result from many forms of breakdown in the adhesive. Nickel Clad Copper Tungsten Caps and Aluminum Deposition Corrosion of nickel clad copper tungsten caps is also a recurring problem. Improvements in the thermal interfacial material in the form of 100% solid thermoset epoxy adhesives, in particular the improvement of bond lines in the 75-125 micron range, are of industrial importance in enabling high output loads.

Suitable adhesives must have certain fluid handling characteristics and exhibit specific adhesion, controlled shrinkage and low corrosiveness to provide long term defect free service beyond the thermal coverage of the electronic circuit package. Desirable properties for thermal interface materials such as sharp and well-defined stability and reproducibility Tg, initial high and stable electrical conductivity, and the ability to withstand high temperatures and voltages over repeated "switching" cycles without loss of these properties, While known, adhesives that realize all these requirements are not readily found. While it is known to introduce latent thermal curatives in order to avoid voids after curing while leaving the heating of the resin under vacuum for a long period of time without causing premature gelation, the crosslinked polymer network is achieved in achieving an improvement in thermal conductivity. The effect of is not well understood.

A drawback to the highly charged thermoset epoxy resin compositions currently used in microelectronics applications such as for underfill is their extended curing schedule at distribution temperatures and the useful practical time and the ability to remain stable viscosity until curing is initiated. . In modern continuous dispensing processes via mechanical pumping devices in which the beads of the interfacial adhesive must be placed accurately, the breakdown of the pump is due to the adhesive.

It has become industrially important to provide a partial, high solid, thermoset adhesive that is intended to exhibit controlled shrinkage after curing and improved thermal conductivity after curing of 10 W / mK or more.

A variety of thermally conductive fillers have been commonly used with solvent-containing epoxy resins and approach or exceed this level of bulk thermal conductivity, but relatively high solvent levels worsen shrinkage, pore formation, and exfoliation. Contribute to Common syringe dispensing techniques include time-pressure, positive displacement, and auger valve techniques.

In systems containing up to 4% of volatile components at high filler levels (more than 70% by weight) in liquid epoxy adhesives, the dispensing device will not function properly and will result from the loss of fluidity of a portion of the highly filled epoxy adhesive in the dispensing device. I knew that.

If a stable adhesive can maintain free flow during continuous dispensing, a balance of properties is required in the cured solid phase thermal interface adhesive and is affected by the polymer composition. In addition to maintaining filler levels above 70% by weight in the free flowing fluid, the organic component also contributes significantly to the resulting cured thermal conductivity, shrinkage, and coefficient of thermal expansion (CTE), so that after circulating from -55 ° C to 125 ° C It is essential for long term defect free service in assembled units.

The technical problem associated with providing a partially curable epoxy adhesive that can be dispensed to obtain a thin bond line between a die and a lid of about 20μ-150μ or between a lid and a heat sink is overcome by the present invention. To date, bulk thermal conductivity of 10 W / m ° K or higher can be achieved in highly filled thermoset epoxy formulations by the addition of non-reactive solvents, plasticizers or other liquid viscosity reducing diluents, but is accepted in the incorporation of such non-reactive diluents. An unacceptable rate of contraction occurs. It is of industrial importance to provide a low viscosity, 100% solids, solvent free, thus exhibiting a bulk thermal conductivity of at least 4 W / m ° K but preferably at least 10 W / m ° K while shrinking is small. It exhibits a volume resistivity of 200 mΩ-cm or less, preferably up to 100 mΩ-cm.

Critical fluid properties for high speed dispensing of the thermal interface embodiment were Haake at 25 ° C. at 2.0 sec-¹ using a 1 °: 35 mm cone. Viscosity of less than about 10,000 poise measured using RS1 conn and plate controlled stress flow meters. Preferred viscosities according to the invention were observed in the range of 1200-6000 poise at 2.0 sec-1. The thixotropic index as a ratio of viscosity at 0.2 sec-¹ to viscosity at 2.0 sec-¹ is in the range of 3-about 7. After 24 hours at 25 [deg.] C., the present invention shows the viscosity stability of viscosity change of more than 24 hours and less than 30%. The present invention provides sufficient flow and wetting of the adhesive material dispensed from the syringe or to the part to be joined when printed using a screen printer, as practiced in conventional automated assembly lines.

As a feature of the invention, there is provided a 96-100% solid, one-component thermosetting interfacial material consisting of 75-90% by weight of a thermally conductive filler and 10-25% by weight of an organic component, wherein the organic component is a bis 60-70% by weight of diglycidyl ethers of phenolic compounds, 4-30% by weight of acyclic aliphatic or cycloaliphatic or mononuclear aromatic diglycidyl ethers having an epoxy equivalent of 200 or less, single functional epoxy compounds having an equivalent of 250 or less 3 -30% by weight, polyamine anhydride 20-30% by weight (in a stoichiometric ratio of 0.9-1.3 to the total epoxy equivalent weight), and optionally 0.5-1.3% by weight of disability imidazole, all percentages being 100% in total .

The proportion of each component contributes to achieving a specific range of unique balances for viscosity, thixotropic index, CTE, shrinkage, and thermal conductivity, as shown by the examples below.

In one method of use, the thermal interface material is Asymtec (Asymtek ) Or Cam Alot (Camalot It is dispensed through the nozzle by an auger screw dispenser available from and attached to the underside of the lid before contacting the lid to the substrate. By properly placing the lid on the die, heat is applied to the lid to form a stable thermal bridge, thereby allowing the resin to flow to bridge the gap between the die and the opposing face of the lid, and then curing the resin to form a solid do.

Cured adhesives provide utility as an alternative to soldering for the heat transfer required to dissipate heat, for example, from high power electronic devices. The adhesive provides long term reliability, high thermal conductivity, low thermal resistance, low shrinkage, and low degassing for high performance flip chip devices as a thermal passage between die and lid, die and sink, or lid and sink. The expression 96-100% total solids is defined by measuring the cumulative weight loss of 4% -0% by weight of the adhesive after curing and after exposure to 300 ° C.

All percentages described below are expressed in weight percent and are a total of 100% of all components or all of all components. The adhesive is thermoset, which means that it is insoluble with a cure storage modulus of 1-5 gigapascals, preferably 2-4 gigapascals, as measured by DMTA.

The interfacial adhesive composition is composed of an inorganic component and an organic component up to 100% of the adhesive composition. The inorganic component is present in 70-85% by weight of the mixture of inorganic and organic components and the organic component represents 15-25% by weight of the total. Generally, with respect to the organic component, it is 60-70% by weight of diglycidyl ether of bisphenol compound, 4-30% by weight of acyclic aliphatic or cycloaliphatic or mononuclear aromatic diglycidyl ether, 3-30% by weight of monofunctional epoxy compound, It consists of 20-30% by weight of polyamine anhydride adduct.

Diglycidyl ethers of bisphenol compounds

Bisphenol epoxies include, for example, isomeric mixtures of 2,2-bis- (4-hydroxyphenyl) -propane (bisphenol A), dihydroxyphenyl methane (bisphenol F), bisphenol G, tetrabromobisphenol A, 4,4 ' -Dihydroxydiphenyl cyclohexane, 4,4'-dihydroxy-3,3'-dimethyldiphenyl propane, 4,4'-dihydroxydiphenyl, 4-4'-dihydroxybenzophenol, Bis- (4-hydroxyphenyl) -1,1-ethane, bis- (4-hydroxyphenyl) -1,1-isobutane, bis- (4-hydroxyphenyl) -methane, bis- (4- Diglycidal ethers of compounds such as hydroxyphenyl) -ether and bis- (4-hydroxyphenyl) -sulfone. Bisphenol diglycidyl ethers are widely available. Araldite GY and PY Bisphenol F Bisphenol A epoxy liquid resin under Epoxy liquid, DER-332 diglycidyl ether of bisphenol A, epoxy equivalent 175, EP-828 diglycidyl ether of bisphenol A, epoxy equivalent 185, EP of bisphenol F -807 diglycidyl ether, epoxy equivalent 170, PY-302-2 diglycidyl ether of bisphenol AF, epoxy equivalent 175, diglycidyl ether of bisphenol AD, epoxy equivalent 173, and the like. More preferable is EPICLON 830S is an electronic grade diglycidyl ether of bisphenol. Based on the total weight of the organic components, the amount of bisphenol epoxy compound is present at 60-70% by weight, preferably 62-65% by weight.

Dual function epoxy material

In addition to bisphenol epoxy bifunctional resins include acyclic aliphatic diglycidyl ethers, cycloaliphatic diglycidyl ethers and mononuclear aromatic diglycidyl ethers having an epoxy equivalent of 200 or less.

These are widely available commercially. Some non-limiting examples include (1) Hepoxy having an epoxy equivalent of about 130 Diglycidyl ether of 1,4-butanediol, available from Cell Chemical Company of Houston under the name 67: (2) Hepoxy, having an epoxy equivalent of about 135 Diglycidyl ether of nemopentyl glycol, available from Cell Chemical Company under the name 68: (3) Hepoxy having an epoxy equivalent of about 160 Diglycidyl ether of cyclohexane dimethanol, available from Cell Chemical Company under the name 107: (4) Epoxy equivalent of about 190 and DER 736 and DER Aliphatic diglycidyl ethers such as diglycidyl ether of polyoxy propylene glycol commercially available from Dow Chemical under the name 336 (which has an epoxy equivalent of 182-192 and a viscosity of 4000-8000 cps at 25 ° C.). Typical mono mononuclear polyglycidal ethers are resorcinol (1,3-benzenediol) diglycidyl ether, 1,2-benzenediol (pyrocatechol) diglycidyl ether, and 1,4-benzenediol (hydroquinone Diglycidyl ether. The amount of diepoxy compound in excess of 30% often leads to breakage of the dispensing pump. Too little diepoxy compound leads to unacceptable increase in viscosity, making it difficult to achieve the bond line thickness formation described above.

The concentration of the bifunctional epoxy resin having an epoxy equivalent of 200 or less can be varied within a certain range depending on the specially selected other components of the adhesive. However, the amount of bifunctional acyclic aliphatic, cycloaliphatic or mononuclear aromatic epoxy having up to 200 equivalents present in the organic composition is preferably 4-10% by weight of the organic component.

Monofunctional epoxy materials

3-30% by weight of the monofunctional epoxy organic component, preferably 5-10% by weight, 1,2-hexene oxide, 1,2-heptene oxide, isoheptene oxide, 1,2-octene oxide And C ₆ -C ₂₀ alkylene oxides such as 1,2-dodecane monooxide, 1,2-pentadecene oxide, butadiene monooxide, isoprene monooxide, styrene oxide, methyl glycidyl ether, ethyl glycy Dyl ether, C ₁₂ , C ₁₄ alkyl monoglycidyl ether, phenyl glycidyl ether, n-butyl glycidyl ether, cresyl glycidyl ether, isopropyl glycidyl ether, tolyl glycidyl ether, glycid Such as oxypropyl trimethoxysilane, octyl glycidyl ether, nonyl glycidyl ether, decyl glycidyl ether, dodecyl glycidyl ether, pt-butyl phenyl glycidyl ether, o-cresyl glycidyl ether Aliphatic, cyclofatty Represented by monoglycidyl ethers of the group and aromatic alcohols. Versatinic acid (Cadura from Cell Chemical Company) Commercially available under the name E), or also monoepoxy esters, such as glycidyl esters of other acids such as t-nonanoic acid, t-decanoic acid, t-undecanoic acid do. Likewise, unsaturated monoepoxy esters such as glycidyl acrylate, glycidyl methacrylate, or glycidyl laurate may be used as desired. In addition, mono epoxidized oils may also be used. Excess monofunctional epoxy compounds above a specified level cause the distributor pump to break and overretract to lead to exfoliation. Too few single functional epoxy compounds lead to unacceptable increase in viscosity, making it difficult to achieve the bond line thickness formation described above.

There are various known amine adducts, namely "modified amines", "polyamides", curing agents, which are called synonymous. Amide adducts are known and are available in a variety of derivatives. However, it has been observed that the cured physical properties are significantly affected by the form of the adducts. Clearly, conventional polyamine adducts are prepared from active hydrogen containing components such as primary and secondary amines. Examples in the literature include adducts of amines and epoxy resins, adducts of amines and alkylene epoxides or acrylonitrile and condensation reaction products of amines with fatty acids or manny bases. By using polyamine anhydride adducts, a surprising balance of properties is achieved in the present invention. The polyamine adduct must optionally have an elevated melting point from 60 ° C. to 200 ° C. and is suitable for activation for curing in the molten state. It is believed that the reaction via amine groups is superior to anhydrides under the same conditions as in the practice according to the invention. The preparation utilizes condensation reactions and is advantageous for salt formation by the continuous removal of water or other byproducts of condensation in accordance with conventional practice well known in the art.

The polyamines used to prepare the polyamides are preferably diamines or consist of diamines. Typically two or more different diamines can be used in the reaction with anhydrides to form polyamine adducts. Useful polyamines include saturated aliphatic polyamines. Some of the many known forms of typical diamines are dialkylenetriamines, in particular diethylenetriamine (DETA), trialkylenetetramine and tetraalkylenepentaamine, with the alkylene moiety being an ethylene or alkoxyethylene moiety such as ethylene Diamine, diethylene triamine, and triethylene tetraamine are preferred, and also 1,6-diamino hexane, 1,3-diamino propane, imino-bis (propyl amine), methyl amino-bis (propyl amine) Etc. are suitable. Many of the available polyoxyalkylenediamines are characterized by the following formula.

Wherein X may vary from 2 to typically 20 wide. If X is about 5.6, the commercial substance is Jeffamine If D-400 or X is 2.6, the commercial substance is Jeffamine -230 (eg Huntsman). Other diamines include 1,2-propylene diamine, 1,3-propylene diamine, 1,4-butane diamine, 1,5-pentane diamine, 1,3-pentane diamine, 1,6-hexane diamine, 3,3,5 -Trimethyl-1,6-hexane diamine, 3,5,5-trimethyl-1,6-hexane diamine, 3,5,5-trimethyl-1,6-hexanediamine, 2-methyl-1,5-pentane diamine , Bis- (3-aminopropyl) -amine, N, N'-bis- (3-amino propyl) -1,2-ethane diamine, N- (3-aminopropyl) -1,2-ethane diamine, 1 , 2-diaminocyclohexane, 1,3-diaminocyclohexane, 1,4-diaminocyclohexane, aminoethyl piperazine, poly (alkylene oxide) diamine and triamine (e.g., Jeffamine D-2000, Such as Jeffamine D-4000, Jeffamine T-403, Jeffamine EDR-148, Jeffamine EDR-192, Jeffamine C-346, Jeffamine ED-600, Jeffamine ED-900, Jeffamine ED-2001), Meta-xylene diamine, phenylene diamine, 4,4′-diamino diphenyl methane, toluene diamine, isophorone diamine, 3,3′-dimethyl-4,4′-di Diamino-dicyclohexyl methane, 4,4'-diamino-dicyclohexyl methane, 2,4'-diamino-dicyclohexyl methane is Dia. Likewise branched aliphatic diamines can be used, for example trimethyl hexamethylenediamine. Each full amines are C ₁ - ₁₂ alkyl group may be substituted in the carbon skeleton by a - ₁₄ alkyl group, preferably C _1.

Examples of polyoxyalkylene diamines include polyoxyethylene diamine, polyoxypropylene diamine, polyoxybutylene diamine, polyoxypropylene / polyoxyethylene blocks and random copolymer diamines, polyoxypropylene / polyoxyethylene / polyoxypropylene block air. Copolymer diamine, polyoxybutylene / polyoxypropylene / polyoxybutylene block copolymer diamine, polyoxypropylene / polyoxybutylene / polyoxypropylene block copolymer diamine, polyoxyethylene / polyoxybutylene block or random air Coalescing diamines, and polyoxypropylene / polyoxybutylene blocks or random copolymer diamines. The polyoxybutylene may contain 1,2-oxybutylene, 2,3-oxybutylene or 1,4-oxybutylene units. The length of the polyoxyalkylene block, ie the number of oxyalkylene groups in the block, may vary greatly, typically from 2-20, preferably 2-6.

Anhydrides may be saturated aliphatic or cycloaliphatic or aromatic and may contain 3-12 carbon atoms such as phthalic anhydride (PA), hexa hydrophthalic anhydride, tetrahydrophthalic anhydride, methyl-tetrahydrophthalic anhydride, trimellitic acid Substituted alkenyl anhydrides, oxalic anhydrides, malonic anhydrides, succinic anhydrides, glutaric anhydrides, adipic anhydrides, such as anhydrides, succinic anhydrides, chloric anhydrides, alkenyl succinic anhydrides, and octenyl succinic anhydrides Pimelic anhydride, suveric anhydride, azelaic anhydride, sebacic anhydride, and mixtures thereof.

It is more preferable that the polyamide adduct has a molecular weight of 1000 or less, and most preferably a molecular weight of 500 or less. Most preferred polyamine anhydride adducts have the following structure.

The material is available from Ciba Specialty Chemicals and the recommended stoichiometric ratio of polyamine adducts to total epoxy equivalent is 0.9-1.3. The amount of polyamine adduct is preferably present at 23-25% by weight relative to the total weight of the organic components of the adhesive.

Most embodiments of the present invention contain one or more fillers, the choice of which will depend on the particular end use intended as described herein. Examples suitable as thermal interfacial adhesives contain 75-90% by weight relative to the total interfacial material weight (organic and inorganic) of the thermally conductive particulate filler. Thermally conductive particulate fillers available include silver, alumina, aluminum nitride, silicon nitride, boron nitride, silicon carbide, and mixtures thereof. Thermally conductive particulate materials include materials having particles in the range of about 5-20 microns in diameter. Preferred are mixtures of silver flakes and powdered silver which selectively cooperate with a filler selected from the group consisting of graphite, metal oxides, metal carbides, metal nitrides, carbon black, nickel fibers, nickel flakes, nickel beads and copper flakes. Most preferred fillers are silver flakes, silver spheres, and mixtures of graphite. Graphite is optionally used at 0.1-5% by weight of the inorganic component. In a more preferred embodiment the organic component is mixed with a thermally conductive filler which is a mixture of metal silver flakes and silver powder, in which case the weight ratio of flakes to powder is 5: 1-20: 1. In another preferred embodiment, the silver flakes, silver powder and graphite constitute a thermally conductive filler.

In addition to silver filled thermal interfacial adhesives, in adhesive embodiments such as encapsulants, inorganic oxide powders such as fused silica powder, alumina and titanium oxides, and nitrates of aluminum, titanium, silicon and tungsten are present except silver. The low viscosity resulting from the use of these fillers results in a different rheology compared to the filling thermal interface adhesive, but the organic component provides moisture absorption resistance. These fillers may be provided commercially since they have been pretreated with a silane adhesion / wetting promoter.

Other additives that are not essential are to be included in commercial practice, as some are illustrated below. Carbon black or additives such as colorants, adhesion promoters, wetting agents may be included. One or more types of functionalized organosilane adhesion promoters are preferably used directly or included as the aforementioned pretreatment for the filler as a tie-coating between the atomizing filler and the curable component. Typically the silane additive is used directly at 1-3% by weight of the organic component to provide adhesion promotion and wetting enhancement between the fluid adhesive and the substrate to be bonded. Representative organic functional silane compounds useful in the present invention include (A) tetraalkoxysilanes, organopolysiloxanes containing at least one alkenyl group or silicon-bonded hydrogen atoms and acryloxy substituted alkoxy silanes, as described in US Pat. Hydrolysis reaction product:

(B) Alloy silanes with addition of acrylate or methacrylate: (C) Mixtures of epoxy- and vinyl-functional organosilicon compounds as described in US Pat. No. 408,7585: (D) Partial allyls of epoxyfunctionalsilanes and polyhydric alcohols Ethers may be included.

Ethylenically unsaturated organopolysiloxanes and organohydrogen polysiloxanes are described in US Pat. No. 3,315,652: US Pat. No. 3220972: and US Pat. No. 3410886. Preferred ethylenically unsaturated organic polysiloxanes are those containing higher alkenyl groups, such as those described by Kerik and his colleagues, US Pat. The ethylenically unsaturated organic polysiloxanes, organic hydrogen polysiloxanes, and crosslinking agents described herein are described by reference.

Also suitable are epoxy substituted organosilanes or organic polysiloxanes, containing at least one epoxy group and hydrolyzable groups, each bonded to a silicon atom. Epoxy groups are bonded by alkylene groups containing at least one carbon atom. Alternatively, the epoxide group may be part of carbocycling which is bonded to the silicon atom via an alkylene group. Preferred epoxy functional silanes are represented by the formula R ¹ -Si-R ² mR ^3-m . Wherein R ¹ represents an epoxy alkyl group or an epoxy substituted cycloalkyl group, R ² represents an alkyl group, R ³ represents a hydrolyzable group, and m is 0 or 1. Examples of suitable hydrolyzable groups represented by R ³ include, but are not limited to, alkoxy, carboxy, ie R ¹ C (O) 0-and methoxymo. In a preferred embodiment the hydrolyzable group is an alkoxy group containing 1-4 carbon atoms. Many epoxy functional silanes are described in US Pat. The epoxy functional silane is preferably a mono (epoxyhydrocarbyl) trialkoxysilane in which the carbon atom of the epoxy group is separated from the silicon atom by an alkylene group. One example is 3-glycidoxyoxytrialkoxy silane wherein the alkoxy group is methoxy or ethoxy.

Representative other organofunctional silanes suitable as materials to cure together include, but are not limited to, silanes containing groups having extractable hydrogen such as amino-, mercapto-, and hydroxy groups.

Representative hydroxyl group-containing silanes have the following general formula (A).

Wherein R is a divalent aliphatic, cycloaliphatic or aromatic saturated or unsaturated group having 1-20 carbon atoms, preferably an alkylene group having 1-9 carbon atoms, and most preferably an alkylene group having 2-4 carbon atoms desirable. R ¹ is a monovalent aliphatic, cycloaliphatic or aromatic group having 1-20 carbon atoms, an alkyl group having 1-4 carbon atoms, a cycloalkyl group having 4-7 ring carbon atoms, having 6,10 or 14 nuclear carbon atoms It is preferably selected from the group consisting of such aryl groups containing an aryl group and at least one substituted alkyl group having 1-4 carbon atoms. R ² is a monovalent aliphatic, cycloaliphatic or aromatic organic group having 1-8 carbon atoms, preferably selected from the group consisting of an alkyl group having 1-4 carbon atoms and R ³ -OR ⁴ , wherein R ³ is 1 An alkylene group having 4 carbon atoms (methyl, ethyl, propyl, butyl), and R ⁴ is an alkyl group having 1-4 carbon atoms. And a is 0 or 1, with 0 being preferred.

Amido functional silanes are preferred and include those having the following general formula (B).

Wherein R, R ¹ , R ² and a are as described above for Formula (A): R ⁵ has hydrogen, a monovalent aliphatic group having 1-8 carbon atoms, 4-7 carbon atoms A monovalent cycloaliphatic group containing one or more substituted alkyl groups having 6 nuclear carbon atoms and one or more substituted alkyl groups having 1-4 carbon atoms, and R ⁶ NHR ⁷ , wherein R ⁶ is 1 -Is selected from the group consisting of divalent aliphatic, cycloaliphatic, and aromatic groups having 20 carbon atoms, preferably there are at least two carbon atoms separating the nitrogen atom pairs, and alkylene groups of 2-9 carbon atoms are preferred: R ⁷ is the same as R ^5, and hydrogen is preferable. Amino Functional Silanes SILQUEST Available under the trade name.

Sulfur containing organic silanes such as mercaptofunctional silanes are commercially available and can be used commercially. Many methods for the preparation of sulfur containing organosilicon compounds have been described in the art. For example, US Pat. No. 5,397,739 discloses the reaction of alkali metal alcoholates with hydrogen sulfide to form alkali metal hydrosulfides which are then reacted with alkali metals to give alkali metal sulfides. The resulting alkali metal sulfide is then reacted with sulfur to give an alkali metal polysulfide and then finally with a hydrogen functional silane. US Pat. Nos. 5466846, 5596116, and 55489701 describe methods for preparing silane polysulfides.

Representative specific organic silanes are hydroxypropyltrimethoxysilane, hydroxypropyltriethoxysilane, hydroxybutyltrimethoxysilane, g-aminopropyltrimethoxysilane, g-aminopropyltripropoxysilane, g-amino Isobutyltriethoxysilane, g-aminopropylmethyldiethoxysilane, g-aminopropylethyldiethoxysilane, g-aminopropylphenyldiethoxysilane, d-aminobutyltriethoxysilane, d-aminobutylmethyldiethoxysilane , d-aminobutylethyl diethoxysilane, g-aminoisobutylmethyl diethoxysilane, N-methyl-g-aminopropyltriethoxysilane, N-phenyl-g-aminopropyl-g-aminopropyltriethoxysilane , N-beta-aminoethyl-g-aminoisobutyltriethoxysilane, Ng-aminopropyl-d-aminobutyltriethoxysilane, N-aminohexyl-g-aminoisobutylmethyldiethoxysilane, methylaminopropyltri Ethoxysilane, g- The unexposed profile methoxydiethylene the like silane, g- glycidoxypropyl trimethoxysilane.

The cured glass transition temperature (Tg) is not critical but is within 20-125 ° C. Preferred embodiments exhibit Tg in the range of electronic actuators using thermal interface adhesives, which are generally 20-90 ° C., while alpha ¹ CTE (below Tg) is about 30-70 ppm, while alpha ² CTE (Tg). Above) was only 100 ppm, which is within the acceptable thermal expansion range expected to provide long term service as a thermal interface in Level 1 or Level 2 applications.

Typical use (lid-die interface adhesive)

A thermally conductive adhesive that forms a thermal bridge between the die and the metal lid can be pre-applied to the lid on the lower side facing the die. Generally existing lids vary in length, width and depth, but are generally rectangular and have a perimeter rim or flange that provides a surface along which the lid can be bonded to the substrate. The central portion of the lid is concave with respect to the flange to provide a concave shape and is generally flat.

Die attach adhesive

Die attach adhesive is used to attach the semiconductor chip, ie lead the frame. Such adhesives must be able to be dispensed in small quantities at high speed with sufficient capacity control to allow deposition on the substrate in a continuous process for the production of the bonded semiconductor assembly. Rapid curing of the adhesive is very desirable. It is also important that the cured adhesive must exhibit high adhesion, high thermal conductivity, high moisture resistance, high temperature stability and good reliability. The conductive die attach adhesive prepared according to the present invention consists of the resin composition of the present invention and at least one conductive filler. Typically the electrically conductive adhesive comprises at least one type of silver flake. Other suitable electrically conductive fillers include silver powder, gold powder, carbon black, and the like. For thermally conductive adhesives (non-electrically conductive), fillers such as silica, boron nitride, diamond, carbon fibers and the like may be used. The amount of electrically and / or thermally conductive filler, preferably in an amount of about 20-90% by weight, more preferably in an amount of about 40-80% by weight, is sufficient to impart conductivity to the cured adhesive. In addition to electrically and / or thermally conductive fillers, other components may also be present, such as adhesion promoters, anti bleed agents, rheology modifiers, flexible agents, and the like.

Glove Top Encapsulant

Encapsulating agents are resin compositions used to completely enclose or encapsulate a wire bonded die. The encapsulating agent prepared according to the present invention consists of the organic component composition of the present invention and a nonconductive filler such as silica, boron nitride, carbon fiber and the like. Such encapsulating agents preferably provide good temperature stability that can withstand thermal cycling from -55 ° C to 125 ° C, for example for 1000 cycles, such as good temperature storage of 1000 hours at 150 ° C, without breaking 200-500 It can pass the pressure cooker test at 120 ° C. at 14.7 psi for hours, and pass the HAST test at 140 ° C., 85% humidity at 44.5 psi for 25 hours without breaking.

Heat sink adhesive

As noted above, the thermosetting interfacial adhesive embodiments of the present invention provide for direct thermal interface between a heat sink or integrated heat spreader and a semiconductor die (level 1) and between a lid and a heat sink (level 2) in semiconductor packaging. Is easily adapted.

Example

The following prescription is Housechild It was prepared using a centrifugal mixer.

Epoxy Additives of Aliphatic Polyamines with Primary-Class Amino Groups

Epoxy Additives of Aliphatic Polyamines Having 2-second Anino Group

3-modified imidazole

4-hinder 2,4-imidazole (optional)

Viscosity is from 1 °, 25 ℃ and 0.2sec 2.0sec ^{-1 -1} and using a 35mm koun hake Measurements were made using RS1 conn and plate controlled stress flow meters. The viscosity of the silver filled examples according to the invention was observed in the range of 2.0 sec ⁻¹ to 1200-6000 poises. The preferred viscosity in the preferred embodiment shown in 2.0sec ^-1 was 2200-3200 poise. Thixotropic dimension is the ratio of viscosity at 0.2 sec ^{−1 /} vis at 2.0 sec ⁻¹ .

Bulk Thermal Conductivity Matisse Measurement was made using a hot disk analyzer. The sample was gelled in an aluminum mold at 150 ° C. for 40 minutes and then post-cured at 150 ° C. for 20 minutes. The resulting casting was 0.75 inches (18 mm) in diameter and 0.5 mm inches (12.7 mm) in depth. The lower sides of the two castings were then polished and polished to a smooth and parallel finish. The casting was placed in a device with a sensor installed between two polished surfaces. The sample was properly fixed and then a voltage was applied through the sensor to measure the temperature rise on the surface. The amount of heat not absorbed by the sample and the applied voltage was used to measure the bulk conductivity of the material through the software provided by the device. The thermal conductivity of the examples according to the invention, provided at 5-25 W / mK, typically 10-20 W / mK, was a surprising improvement. Thermal conductivity of 20-27 W / mK is easily achieved by incorporation of 0.5-5% graphite with silver flakes and silver powder.

Post-curing contraction is Perkin Elmer It was measured using TMA7. Castings of the adhesive were made by gelling the formulation in an aluminum mold at 150 ° C. for 40 minutes. The sample was removed from the mold and then post-cured at 150 ° C. for an additional 60 minutes. The casting was about 0.75 inches (18 mm) in diameter and 0.5 inches (12.5 mm) deep. A band saw was used to remove a portion of the casting about 5 mm x 5 mm x 12.5 mm deep. The upper and lower sides of the sample were polished to obtain a final sample having a depth of 5 mm x 5 mm x 10.5 mm. Shrinkage was measured for each sample for at least 24 hours up to 125 ° C. at a temperature ramp of 25-125 ° C. at a rate of 10 ° C. per minute and then at isothermal at 125 ° C. for 24 hours. An instrument with a probe diameter of 3 mm was set in a penetration manner. The force used was 50 mN. Shrinkage was calculated using the maximum (probe position) obtained at the start of isothermal and the value at 1420 minutes. The post cure shrinkage observed in the examples was 0.1-1.3%. The following equation yields the shrinkage rate. (Maximum value-1420 minutes value) / maximum value ^* 100 = percent shrinkage.

In other examples not described, the proportion of essential ingredients was adjusted over one or more specific organic component ranges, with a significantly lower thermal conductivity (3-5 W / mK). For example, the proportion of aliphatic diglycidyl ether is increased to about 35%, the bisphenol F diglycidyl ether is reduced to about 30%, all else being the same, and the cured bulk thermal conductivity is reduced to 4 W / mK. It became. As can be seen by the test of the control example, the other modified polyamine adducts have thermal conductivity of 2.87 and 2.0 W / mK, respectively, compared to Example 1, which is 16.8 W / mK.

The interfacial composition is readily adapted to flip chip packages formed by connecting a semiconductor chip to a carrier substrate such as a circuit board and then appropriately sealing the intervening space with a material according to the present invention. Semiconductor devices installed on a carrier substrate at predetermined locations provide wire electrodes that are electrically connected by suitable electrical connection means, such as solder. In order to improve the reliability, the space between the semiconductor chip 2 and the carrier substrate 1 is sealed with the thermosetting resin composition 3 and then cured. The cured product of the thermosetting resin composition must completely fill the space.

Claims (19)

96- consisting of a substrate with a semiconductor die, an integrated heat spreader, an optional lid and a cured bulk thermal conductivity of 5-27 W / mK, consisting of 74-90 wt% of thermally conductive particulate filler, and 10-25 wt% of organic components. Consisting of a thermally interfacial material consisting of a 100% solid adhesive, the organic component being 60-70% by weight of a diglycidyl ether of a bisphenol compound, an acyclic aliphatic, cycloaliphatic or mononuclear aromatic diglycidyl ether having an epoxy equivalent of 200 or less A die assembly comprising 4-30% by weight, 3-30% by weight of a single functional epoxy compound having an equivalent of 250 or less and 20-30% by weight of a polyamine anhydride adduct having a melting point of 60-200 ° C. The bisphenol compound according to claim 1, wherein the bisphenol compound is 2,2-bis- (4-hydroxyphenyl) -propane, an isomer mixture of dihydroxydiphenyl methane, bisphenol G, tetrabromo bisphenol A, 4,4'- Dihydroxydiphenyl cyclohexane, 4,4'-dihydroxy-3,3-dimethyldiphenyl propane, 4,4'-dihydroxydiphenyl, 4,4'-dihydroxybenzophenol, bis- (4-hydroxyphenyl) 1,1-ethane, bis- (4-hydroxyphenyl) -1,1-isobutane, bis- (4-hydroxyphenyl) -methane Die assembly. The method of claim 1, wherein the polyamine is diethylenetriamine, triethylenetetramine, tetraethylenepentamine, diethoxyethylenetriamine, triethoxyethylenetetramine, tetraethoxyethylenepentamine, ethylenediamine, diethylenetri Is selected from the group consisting of amines, triethylenetetramine, 1,6-diaminohexane, 1,3-diamino propane, imino-bis (propyl amine), and methylimino-bis (propylamine) Die assembly. The method of claim 1, wherein the acyclic aliphatic, cycloaliphatic or mononuclear aromatic diglycidyl ether is selected from the group consisting of diglycidyl ether of 1,4-butanediol, diglycidyl ether of neopentyl glycol, and diglyc of cyclohexane dimethanol. From groups consisting of cydyl ether, diglycidyl ether of polyoxypropylene glycol, resorcinol diglycidyl ether, 1,2-benzenediol diglycidyl ether, and 1,4-benzenediol diglycidyl ether Die assembly, characterized in that selected. The method of claim 1, wherein the single function epoxy compound is 1,2-hexene oxide, 1,2-heptene oxide, isoheptene oxide, 1,2-octene oxide, 1,2-dodecane monooxide, 1,2- Pentadecene oxide, butadiene monooxide, isoprene monooxide, styrene oxide, methyl glycidyl ether, ethyl glycidyl ether, phenyl glycidyl ether, n-butyl glycidyl ether, cresyl glycidyl ether, isopropyl Glycidyl ether, tolyl glycidyl ether, glycid oxy propyl trimethoxy silane, octyl glycidyl ether, nonyl glycidyl ether, decyl glycidyl ether, dodecyl glycidyl ether, C ₁₂ , C ₁₄ Alkyl monoglycidyl ether, pt-butylphenyl glycidyl ether, o-cresyl glycidyl ether, glycidyl ester versatinic acid, glycidyl ester of t-nonanoic acid, glycidyl of t-decanoic acid Esters, and t- Die assembly to that selected features from the group consisting of a glycidyl ester of decanoic acid. The die assembly of claim 1, wherein the thermally conductive particulate filler is selected from the group consisting of silver, alumina, aluminum nitride, silicon nitride, boron nitride, silicon carbide, and mixtures thereof. 7. The die assembly of claim 6, wherein the thermally conductive particulate filler is silver. 8. The die assembly of claim 7, wherein the thermally conductive particulate filler is a mixture of silver flakes and silver powder. It can exhibit a cured bulk thermal conductivity of 5-27 W / mK and consists of an adhesive consisting of 75-90% by weight of thermally conductive particulate filler and 10-25% by weight of an organic component, wherein the organic component is diglycidyl of a bisphenol compound 60-70 wt% ether, 4-30 wt% acyclic aliphatic, cycloaliphatic or mononuclear aromatic diglycidyl ether having an epoxy equivalent of 200 or less, 3-30 wt% of a monofunctional epoxy compound having an equivalent of 250 or less and 60 A thermally curable thermal interface material comprising 20-30% by weight of a polyamine anhydride adduct having a melting point of -200 ° C. 10. The composition of claim 9, wherein the bisphenol compound is 2,2-bis- (4-hydroxy phenyl) -propane, an isomeric mixture of dihydroxy phenyl methane, bisphenol G, tetrabromo bisphenol A, 4,4'-di Hydroxydiphenyl cyclohexane, 4,4'-dihydroxy-3,3-dimethyldiphenyl propane, 4,4'-dihydroxydiphenyl, 4,4'-dihydroxy benzo phenol, bis- ( Characterized in that it is selected from the group consisting of 4-hydroxyphenyl) -1,1-ethane, bis- (4-hydroxy phenyl) -1,1-isobutane and bis- (4-hydroxy phenyl) -methane Thermal curing thermal interface material. The method according to claim 9, wherein the polyamine of the adduct is diethylene triamine, triethylenetetramine, tetraethylenepentamine, diethoxyethylenetriamine, triethoxyethylenetetramine, tetraethoxyethylenepentamine, ethylene diamine, Selected from the group consisting of diethylene triamine, triethylene tetramine, 1,6-diamino hexane, 1,3-diamino propane, imino-bis (propyl amine) and methylimino-bis (propyl amine) A thermally curable thermal interface material, characterized in that it is a residue of a polyamine. The method of claim 9, wherein the acyclic aliphatic, cycloaliphatic or mononuclear aromatic diglycidyl ether is selected from the group consisting of diglycidyl ether of 1,4-butanediol, diglycidyl ether of neopentyl glycol, and diglycile of cyclohexane dimethanol. With cydyl ether, diglycidyl ether of polyoxypropylene glycol, resorcinol diglycidyl ether, 1,2-benzenediol diglycidyl ether, and 1,4-benzenediol (hydroquinone) diglycidyl ether Heat curable thermal interface material, characterized in that it is selected from the group consisting. The method of claim 9, wherein the monofunctional epoxy compound is 1,2-hexene oxide, 1,2-heptene oxide, isoheptene oxide, 1,2-octene oxide, 1,2-dodecane monooxide, 1,2- Pentadecene oxide, butadiene monooxide, isoprene monooxide, styrene oxide, methyl glycidyl ether, ethyl glycidyl ether, phenyl glycidyl ether, n-butyl glycidyl ether, cresyl glycidyl ether, isopropyl Glycidyl ether, tolyl glycidyl ether, glycidoxy propyltrimethoxysilane, octyl glycidyl ether, nonyl glycidyl ether, decyl glycidyl ether, dodecyl glycidyl ether, C ₁₂ , C ₁₄ Alkyl monoglycidyl ether, pt-butyl phenyl glycidyl ether, o-cresyl glycidyl ether, glycidyl ester versatinic acid, glycidyl ester of t-nonanoic acid, glycidyl of t-decanoic acid Esters, and t-luck Thermosetting thermal interface material to that selected features from the group consisting of a car with the glycidyl ester of the acid. 10. The thermally curable thermal interface material of claim 9, wherein the thermally conductive particulate filler is selected from the group consisting of silver, alumina, aluminum nitride, silicon nitride, boron nitride, silicon carbide, and mixtures thereof. 15. The thermosetting thermal interface material of claim 14, wherein said thermally conductive particulate filler is silver. 16. The thermal curing thermal interface material of claim 15, wherein the thermally conductive particulate filler is a mixture of silver flakes and silver powder. 10. The method of claim 9, wherein the viscosity is about 10,000 poise at 25 ° C. (1 °, hack at 25 ° C. and 2.0 sec ⁻¹ using a 35 mm cone). Thermally curable thermal interface material, as measured using an RS1 conn and plate controlled stress flow meter. 10. The thermal curing thermal interface material of claim 9, wherein the polyamine anhydride adduct has the following structure. 10. The method of claim 9, wherein the diglycidyl ether of bisphenol is a diglycidyl ether of bisphenol F, and the acyclic aliphatic, cycloaliphatic or mononuclear aromatic diglycidyl ether is 1,4-butane diol diglycidyl ether, Selected from the group consisting of cyclohexane dimethanol diglycidyl ether, and resorcinol diglycital ether, wherein the monofunctional epoxy compound is 1,2-hexene oxide, 1,2-heptene oxide, isoheptene oxide, 1 , 2-octene oxide, 1,2-dodecane monooxide, 1,2-pentadecene oxide, butadiene monooxide, isoprene monooxide, styrene oxide, methyl glycidyl ether, ethyl glycidyl ether, phenyl glycidyl Ether, n-butyl glycidyl ether, cresyl glycidyl ether, isopropyl glycidyl ether, tolyl glycidyl ether, glycid oxy propyltrimethoxysil Ran, octyl glycidyl ether, nonyl glycidyl ether, decyl glycidyl ether, domesyl glycidyl ether, C ₁₂ , C ₁₄ alkyl monoglycidyl ether, pt-butylphenyl glycidyl ether, o-cre Group consisting of sil glycidyl ether, glycidyl ester versatinic acid, glycidyl ester of t-nonanoic acid, glycidyl ester of t-decanoic acid, and glycidyl ester of t-undecanoic acid Heat curable thermal interface material.