KR20070000399A - Dual-stage wafer applied underfills - Google Patents

Abstract

A 100% non-volatile, one-part liquid underfill encapsulant is disclosed for application to the active side of a large wafer or integrated circuit chip. Upon coating, the encapsulant is converted to a liquefiable, tack-free solid by exposure to radiation, particularly in the UV, visible and infrared spectrum. The underfill-coated wafer exhibits outstanding shelf aging of months without advancement of cure. The large wafer can be singulated into smaller wafer sections and stored for months after which during solder reflow assembly, the wafer connects are fixed and the underfill liquefies, flows out to a fillet and transitions to a thermoset state on heat activated crosslinking. ® KIPO & WIPO 2007

Description

Dual-Stage Wafer Applied Underfills

TECHNICAL FIELD The present invention relates to microelectronic chip assemblies, and more particularly to methods and materials for applying underfill to integrated circuit wafers.

Surface mounting of electronic components is well developed in automated package assembly systems. Integrated circuits consist of devices such as transistors and diodes and devices such as resistors and capacitors connected together by conductive connections to form one or more functional circuits. The device has a wafer having a surface which undergoes a series of assembly steps to form a pattern of identical integrated circuits separated from each other by a scribe line or a repeating rectangular pattern of the Soe Street on the surface of the wafer serving as the boundary between the dice, chips or dies. Or assembled to a sheet of silicon. In later stages of the assembly process, singulated dice from the wafer are bonded to the substrate to form an integrated circuit package (IC package).

In general, flip chip technology relates to an assembly in which the active side of an integrated circuit die is attached to a package substrate or a printed circuit board (collectively referred to as a PCB). Flip chip assemblies can be designed with or without underfill packaging. In connection with the use of flip chips, chips are formed with small bumps or bowls of solder (hereinafter referred to as "bumps" or "solder bumps") placed in the position of the active surface designed to correspond to the recesses in the surface of the circuit board. . The chip is mounted by matching the bump with the substrate such that the solder bump is sandwiched between the pad of the circuit board and the corresponding pad of the chip. After the flux is applied, the assembly is heated until the solder is reflowed. Upon cooling, the solder cures and thus flip chips are mounted on the surface of the substrate. Conventional underfills are used in a number of separate approaches and applied to mounted chips to protect the chip from chemical erosion, moisture, airborne contaminants, and mechanical shock, vibration, and temperature cycling encountered during transportation and use. Conventional capillary flip chip underfill processes involve the steps of chip and circuit board alignment, flux distribution, solder reflow, underfill application, underfill flow and curing.

Underfills used in chip packages serve to protect solder joints that interconnect chips and packages or circuit boards from environmental factors such as moisture and contaminants, and to redistribute mechanical stress, thereby increasing device life. Protection of the chip from contaminants such as moisture and the resulting corrosion of the metal interconnects is achieved. Improper selection of adhesives, however, can cause flip chip packages to fail in various ways, such as shrinkage, delamination, hydrolysis, instability, corrosion, and contamination by underfill.

The chip underfill is designed to avoid stressing between the adhesive surfaces as a result of the different coefficients of thermal expansion between the chip, the connection, the underfill and the substrate. The failure mode due to stress is more prevalent as the substrate is organic and the device size increases. Chip underfills include ceramic or organic PCBs (eg FR4 epoxy) that may or may not be coated with a solder mask; Metal alloy or organic connections; And adhesives to substrates such as integrated circuit dies (chips), which typically consist of silicon or other inorganic compounds and which may or may not be coated with a thin surface stabilization layer.

In one of two fundamental ways of packaging electronic components, the components are soldered to the same side of the substrate on which they are mounted. These devices are referred to as "surface mounted". Two types of conventional underfill are intended for use with devices that are actually surface mounted in a capillary flow and "nonflow" manner. Detailed descriptions of these technologies can be found in the literature (see, eg, McGrawhill 2000, Low Cost Flip Chip Technologies for John E. C. Lau's DCA, WLCSP and PBGA assemblies). In these technologies, heat is typically used to cure the liquid thermoset formulation or to laminate a solid film into the assembly. Vacuum is sometimes used to remove air voids from the system. Underfill is typically applied to surface mount (SMT) assembly lines for chip in packages or chip on boards. The use of conventional flow and nonflow underfills requires several steps in the SMT line, which is typically a barrier to these microelectronics assembly lines.

Representative conventional non-flow underfills are described in US Pat. No. 6180696. The underfill material is first dispensed onto the substrate or semiconductor chip and then simultaneously to the reflowing solder bumps and the curing underfill encapsulant. The underfill described in U. S. Patent No. 6180696 consists of a mixture of an epoxy resin and / or an epoxy resin, an organic carboxylic anhydride curing agent, a curing accelerator, a solvent, a viscosity modifier, a binder, and a surfactant. Underfill formulations exhibit a cure peak temperature in the range of 180-240 ° C. These underfills should be stored at temperatures below zero (° C.) to prevent hardening acceleration.

Underfill is distinguished from photoresist materials imaginable as pattern formations coated on PC substrates, but there are some similarities to the use of ubiquitous epoxy resins. Coatings for photoresist applications are known to utilize photoinitiators for curing in a zone exposed to activating radiation through a mask, and a second thermally active free radical cure component for carrying out polymerization in non-radioactive or shadow zones. . One commonly used second curing mechanism relies on the addition of thermally activated peroxides to the formulation, but its use is ruled out since temperatures above 100 ° C. are usually required to initiate peroxide induced polymerization. .

U.S. Patent No. 5077376 discloses an epoxy adhesive containing a latent heat cure component. U.S. Pat.No.507,7376 discloses a liquid epoxy that leads to the widespread use of epoxy resin compositions containing latent curing agents such as dicyandiamide, dibasic dihydrazide, boron trifluoride-amine adducts, guanamine, melamine and the like. The storage stability problem of is described. However, the U.S. patent describes defects in that dicyandiamide, dibasic dihydrazide and guanamine require high temperatures of 150 ° C. or higher to cure.

U. S. Patent No. 5523443 describes a dual cure conformal coating comprising an ultraviolet curable polymerizable system and a moisture cure mechanism. The polymerizable coating system is a one component system comprising at least one alkoxy silyl-urethane-acrylate or methacrylate, acrylate or methacrylate or vinyl ether diluent, polymerization initiator in the form of a cationic or free radical photoinitiator, and a metal catalyst. .

U.S. Patent No. 5249101 (IBM, 1993) describes the brittleness of a protective epoxy coating for a circuit in the circuitry of a chip carrier having an elastic modulus of at least about 10,000 psi (69 MPa) leads to cracking and delamination. U. S. Patent No. 5249101 proposes a coating consisting of an acrylate urethane oligomer, an acrylate monomer and a photoinitiator to provide a coating having an elastic modulus of about 10,000 psi or less and a chloride ion concentration of 10 ppm or less. The underfill application of acrylate urethane wafers lacks sufficient thermal resistance, making solder reflowing difficult.

U.S. Patent No. 5494981 describes curable compositions of cycloaliphatic epoxy resins, cyanate ester resins, optionally polyols, and Bronsted acid as initiators. Upon curing, the composition provides a permeable polymer network (IPN). IPNs are useful as high temperature stable vibration damping materials, adhesives, binders for abrasives and protective coatings.

U. S. Patent No. 5672393 describes acrylics that react at high speed upon exposure to radiation, including ultraviolet and visible wavelengths, to initially form relatively thick surfaces and eventually cure to relatively low stress coatings with good physical confinement and surface properties. Rate encapsulation formulations are described. The method involves exposing the formulation to radiation to initiate photopolymerization and thermal polymerization, and the apparatus includes closely spaced actinic radiation and thermal energy sources. The catalyst system includes a photoinitiator component and a thermal initiator component that reacts to temperatures up to 120 ° C.

U. S. Patent No. 5706579 describes a method for assembling an integrated circuit package that is assembled from a die, a printed circuit board, and a metal lid using a beta executable resin that is pre-applied to the metal lid and contains a thermally conductive filler material. The lid is properly positioned on the die and the substrate and the package is heated to allow the resin to flow and make contact with the die. Further heating cures the resin to form a permanent thermal bridge between the die and the lid.

U. S. Patent No. 6194788 describes an integrated thermoplastic two-part underfill for flip chips. The underfill consists of an acetate diluent with an epoxy resin and a molten acidic epoxy curative.

U.S. Patent 6,306,306 (alpha metal, filed Sep. 14, 1999) describes a method of applying a solvent based underfill to a flip chip. The method attaches the bump wafer to the expandable carrier substrate, first sawing the wafer to form individual chips, extending the carrier substrate in a bidirectional manner to form channels between each of the individual chips, and then underfilling Applying the material around the bump surface of the chip and around the edge of the chip. Although the underfill material is not described, it is described that the underfill material is left to dry after coating and then cuts the underfill material in the channels between the chips to remove the individual chips coated with the underfill from the carrier.

U.S. Pat. No. 6,638,359 describes a b-stage film of low Tg epoxy based underfill containing a thermoplastic polymer having a molecular weight of 5,000-200,000. In addition, U. S. Patent No. 6383659 describes that epoxy resin compositions in self-polymerizing form, typically containing imidazole or phenol cured forms, exhibit limited storage stability, moisture resistance, and high temperature performance of the cured composition, and the B-step It is described as difficult to control the progress of the reaction.

The known technique illustrates a dual cure approach to forming a coating, but has nothing to do with the storage of a b-stage coating containing a second cure component in a fragile substrate, such as a silicon wafer. Wafer warpage, breakage, and long term ambient storage at temperatures reaching about 50 ° C. can occur during transport and storage except in controlled environments.

Problems encountered in wafer application underfill are encountered when the underfill is applied and cured and then there is a delay of several months until the solder reflow phase for the dual stage cure underfill. Ie initial wetting and adhesion of the liquid coating; Thin layer separation from the wafer Solidification of the coating at ambient temperature; Long-term ambient temperature storage of coated wafers without loss of reflow capability from curing or promoting gel content; Avoiding thin layer separation from the wafer during singulation or dicing; Ability to be stenciled within the wafer saw street; Slow onset of thickening during initial heating from solder reflow; The ability of the underfill to spill around the chip forming the fillet when the surrounding collar is not used; Absence of voids in the underfill after the solder reflow step; And long term reliability (no defects) in the device for a useful useful life.

All of these technical problems associated with wafer action underfilling for long term storage prior to assembly are not addressed by known underfill materials. The object is therefore to directly apply a liquid underfill to the active surface of a large wafer, for example a wafer having a surface area of 100-500 mm 2 or more by conventional coating methods, and then to solidify the coated wafer or diced portion for a prolonged period (eg several months). And materials and methods for separating underfill applications and flip chip assembly for storage. In this case, the subsequent wafer deposition process must avoid problems with the properties of the cured underfill.

FIG. 1 shows the DSC curve for Example 6 showing melting point, thermosetting initiation, and peak temperature of reaction, and FIG. 2 shows DSC curve for Example 7, showing melting point, thermosetting initiation, and peak temperature of reaction. It is shown.

The present invention relates to a wafer-underfill assembly and method for the direct application of one-part, solvent-free, nonmagnetic underfill, typically to the active side of the wafer, with a coating thickness of about 0.003-0.070 inches (0.076-1.77 mm). Initially the underfill is a liquid coating that partially or completely covers the wafer solder bumps. Underfill is a filled 100% solid (essentially nonvolatile) liquid coating. The underfill solidifies on the wafer in a state of being solid and thermally liquefied by exposure to actinic radiation of about 50-2400 mj / cm 2. The underfill may be applied in a lattice pattern outside the wafer so street, or a continuous coating may be formed that may undergo dicing of the wafer into singulated portions or dies. The coated wafer or coated singulated portion may be stored for approximately several months prior to assembly and solder interconnection. In an assembled chip utilizing the application of a peripheral encapsulant applied around a wafer application underfill, the thermal curing initiation of the solid and heat liquefiable underfill may be at least 150 ° C. For underfills that liquefy by heat and flow up to the edges of the wafer and flow upward to form fillets to some extent, the thermosetting active temperature of the underfill must be at least 170 ° C. The heat applied to reflow the solder is sufficient to activate the melt flow of the underfill before activating the thermosetting system, which causes the underfill to gel into the solid thermoset state. In the thermoset cure state, the underfill exhibits a coefficient of curvature of 10 Gpa or less.

One-component liquid underfills consist of a mixture of one or more ethylenically unsaturated monomers, one or more epoxy curable materials, one or more photoinitiators, latent heat curables, thermally conductive materials, and electrically insulating fillers as photocurable components, with 5-30 of the total underfill weight. It is characterized by the photocurable component which represents% and the epoxy resin component which represents 10-45% of the total underfill weight. Preferred photocurable components consist of 100% single functional ethylenically unsaturated acrylate or methacrylate monomers. Preferred photopolymerizable components are single functional cycle ethers and / or cycle acetals of acrylic acid.

In the method feature, the underfill according to the invention is suitable for conventional coating techniques on the active surface of the wafer, for example by spin casting, stenciling, printing or the like. The rheology of the liquid underfill material can be easily adapted to the chosen coating application method. The liquid underfill is applied to a large wafer bump or active surface supported on a substrate to easily form a solid freestanding layer that is subjected to photoinduced radical polymerization and remains attached to the wafer. Photocuring solidification creates a viscous, solid underfill surface without warping the wafer. The ambient solid state underfill coating remains heat liquefied during long periods of ambient storage and also withstands exposure at 50 ° C. for several months without stressing the wafer.

The delay period during which the photocured and thermally liquefiable solid underfill coated wafer or singulated portion is stored before the solder joint is formed is indefinite, for weeks, months, and years. Storage conditions during the delay period may include exposure of the underfill to ambient temperature without refrigeration. Wafer application underfills are distinguished from conventional thermoplastic or thermoset materials cast from solvents, melts processed using heat, and / or vacuum. On the other hand, according to the present invention, the underfill is a 100% solid material which undergoes photoinduction solidification via addition polymerization at the wafer active surface and promotes hardening at ambient temperature over a significant delay time until a second thermal curing occurs. Thermoplastic underfill is maintained in a thermoplastic state, and thermoplastic underfill is of constant importance, including non-thin layer separation, absence of void formation, sufficient reflow under solder reflow conditions, and long term adhesion under repeated thermal cycle conditions in a thermoset state without failure or breakdown of the device. Has characteristics. The thermoset cure underfill exhibits a coefficient of curvature at 25 ° C. of 1000-5000 MPa and a coefficient of thermal expansion below the glass transition temperature in the range of 15-60 ppm / ° C., more typically about 25 (+/− 10) ppm / ° C.

Wafer-level underfill consists of a 100% solid mixture. There are no volatile components such as solvents that contribute to weight loss during prolonged ambient storage. The absence of volatile components avoids solvent removal steps and promotes shrinkage control and thin layer separation of the photoinduced solidified coating from the surface of the active surface of the wafer. Removal of volatile organic components prevents unacceptable shrinkage and stress, and degassing during the solder reflow step, and prevents the formation of voids between the wafer or portion and the PCB. Underfill is for visa purposes. In other words, the components used do not provide a fluxing function and are non-acidic.

In general method features, the present invention provides the application of a liquid underfill adhesive to an integrated circuit wafer, the application of a controlled dosage of photon energy (ultraviolet, visible, infrared, etc.), the application of underfill in a state capable of liquefying by heat or melt flowable. Application, in some cases singulating the wafer by dicing or sawing, and storage of the coated wafer or dice during the delay period. After the delay period, an electrical connection is made and the applied photocured solid underfill is liquefied by heat and flows to the edge of the device during solder reflow to undergo a curing transition from the heated liquid to a thermoset solid state. During the delay of storage the coating of the invention remains in a liquefiable solid state and does not increase the gel content. Thus, as a feature, by weight, a photocurable one-component composition consisting of a photocurable acrylate component, a multifunctional epoxy resin, at least one photoinitiator, a nonelectroconductive filler, and a non-fluxing thermally active epoxy curative An ambient temperature stable integrated circuit wafer is provided having an active surface attached to an underfill composition that is constructed, wherein in the thermoset state the underfill has a curvature factor of 1000-5000 MPa at 25 ° C., and the underfill of 15-50 ppm / ° C. The thermal expansion coefficient below the glass transition temperature of a composition is shown.

In another aspect, the present invention relates to a two-step method for curing a wafer applied underfill composition. The method includes applying the underfill composition to the active side of the semiconductor wafer in liquid form. Application methods include spin casting, printing or stenciling a liquid nonvolatile (100% solid) coating directly onto the active side of the chip. The coated wafer is solidified via ultraviolet radiation at a dose selected to form a solid coating. The solid coated wafer can be diced into portions in any case. The wafer or portion may be subjected to ambient temperature storage, followed by a second step of forming electrical connections of the solder bumps to the PCB in the solder reflow step, followed by thermal curing of the solid underfill in a thermoset state.

The 100% solid underfill composition comprises a photocurable acrylate component consisting essentially of single functional ethylenically unsaturated monomers and / or oligomers, multifunctional epoxy resins, photoinitiators, potential epoxy thermal initiators, and inorganic CTE-reducing fillers. The underfill is not alkali soluble in the solid state and does not contain acidic groups such as free carboxyl, phosphate, or sulfonate groups in liquid photocurable unsaturated monomers, oligomers and / or polymers. The components (% by weight) used in the wafer composition are mixed at 100% by weight in total and are as follows.

ingredient weight%

Photocurable acrylate component -------------------- 5-30%

Liquid Multifunctional Epoxy Resin ----------------------- 10-45%

Photo Initiator -------------------------------------- 0.3-3%

Low CTE Filler ------------------------------- 40-70%

Potential Cure Accelerator ---------------------------- 1-3%

Underfill compositions are self-supporting and storage stable, solid and heat liquefied prior to transition to a thermoset state, and retain adhesion to the active surface of the wafer or portion for long delays at ambient temperature, providing underfill application and solder reflow chip installation. Enable separation of steps. The present invention enables the storage of wafers at ambient conditions for later installation on a PCB.

The photocurable component of the underfill composition comprises an ethylenically unsaturated monomer or a mixture of monomers having at least six carbon atoms in the chemical structure. Mixing monomers having up to 6 carbon atoms can cause problems when photocuring from unacceptable volatile to solid state, and converts into photocurable, heat liquefied solid state that tends to stress the attached chip Contraction may occur. Underfills containing at least 10% by weight of liquid multifunctional ethylenically unsaturated comonomers relative to the total weight of the photocurable component lead to insufficient melt flow of heat liquefiable underfill during the solder reflow step during chip installation. It is therefore a preferred feature that no polyunsaturated monomer is present in the underfill or is limited to at most 10% by weight of the underfill curable component.

The term photocurable component relates to ethylenically unsaturated monomers and / or oligomers used collectively. More preferred are ethylenically unsaturated substances comprising vinyl esters, vinyl ethers, and / or α, β-unsaturated acrylate esters. Preferred photocurable components are ethylenically unsaturated acrylates, unsaturated oligomers, or pendant unsaturated oligomers, and mixtures thereof as monomers. The term oligomer means an unsaturated compound that is liquid at 25 ° C. or can be dissolved in a photocurable liquid carrier. Non-functional or saturated thermoplastic polymer diluents such as polyacrylates, polyvinylethers, polyvinyl esters, polyesters, polyamides, polyolefins, and functionalized derivatives and the like can be used, and the softening temperature of the diluents can be reduced from heat to solder reflow temperature. Thereby not significantly delaying the melt flow of the liquefiable underfill. Such diluents can be used for precise control or for various features such as increased melt flow properties and / or cohesive strength.

When the wafer application underfill containing the photocurable acrylate component is polymerized under the influence of ultraviolet radiation, the underfill is converted from the liquid state to the solid state at ambient temperature. The solid remains thermoplastic, meaning that it remains heat liquefiable until it is cured by heat. The amount of photocurable component is 5-30% by weight of the total underfill weight. The amount of multifunctional epoxy material is important relative to the weight of the photocurable component to provide adequate solidification upon photocuring and to maintain melt flow during the solder reflow step. Above the 10-45 weight percent multifunctional epoxy material range, there is also an increased tendency of underfill to damage the wafer after photocuring. Below this range, the cohesive strength is insufficient in heat liquefiable solids and creep increases during ambient temperature storage prior to solder reflow. The cross-sectional thickness of the underfill coating on the active surface is preferably most of the dimensions to which a portion of the solder bumps are exposed. By exposure it is meant that the metal may be exposed to air or may be a thin residue of an underfill of less than about 0.01 μm over the outermost protruding area of the solder bumps. In a preferred embodiment, the thickness of the underfill coating after photocuring is 50-90% of the profile of the solder bumps. The profile is the depth of the solder bump portion extending beyond the surface plane of the wafer active surface.

Photocurable oligomers optionally used herein are solids that can be liquid at ambient temperature or dissolved in liquid ethylenically unsaturated acrylate monomers. The oligomers contain one or more pendant or terminal ethylenically unsaturated groups. Typical oligomers contain two terminal unsaturated groups. The average number of unsaturated groups in the oligomeric photocurable acrylate component having a molecular weight of 500-3000 may be 1-2. The photocurable acrylate component exclusively excludes di-, or tri- or tetra- and higher ethylenically unsaturated monomers, dimers (dimers) or trimers (trimers).

The underfill embodiment of the present invention exhibits melt flow under solder reflow conditions sufficient to flow outward toward the chip edge to completely fill the gap between the chip bottom and the PCB. In some cases, the outflow may include flowing up along the die edge to form a fillet. Photocured solid underfill adheres well to the wafer and has sufficient cohesive strength for long term storage and dicing has not yet wrapped or destroyed the wafer. After the storage delay period, the thermally liquefiable solid has a weight ratio of the photocurable acrylate component to the epoxy functional component in the range of 1:10 to 1: 2, wherein the photocurable component is a single functional and multifunctional monomer and / or oligomer If it contains a certain ratio of, it will flow sufficiently under the influence of heat encountered in the solder reflow step. At ratios of photocurable components to epoxy functional components of 1:10 or less, underfills typically lack sufficient cohesive strength or exhibit unacceptable surface viscosity. At a ratio of 1: 2 or greater, the wafers show lapping and breakage, and the underfill tends to delaminate or undergo insufficient flow for fillet formation.

Typical mono-ethylenically unsaturated monomers usable herein are those having at least six carbon atoms, acrylic acid or C ₁ -C ₄ Alkyl C ₃ -C ₁₂ alkyl esters of alkylsubstituted acrylic acids, collectively include (alk) acrylates. Specific examples of suitable single functional monomers include butyl acrylate, ethyl methacrylate, butyl methacrylate, t-butyl methacrylate, cyclohexyl methacrylate, trimethylcyclohexyl methacrylate, cycle ether acrylate, and monocycle acetal Acrylates. Monocycle acetal acrylates are known and are described in US Pat. Acetal acrylates are trimethylol propane, trimethylol ethane, glycerin, 1,2,4-butanetriol, 1 And polyols such as 2,5-pentanetriol, and 1,2,6-hexane triol. Typical photocurable components are mixtures of cyclic ether containing acrylates such as tetrahydrofurfuryl acrylate (THFA), and cyclic alkylol formal acrylates. Preferred monofunctional acrylates are tetrahydrofurfuryl acrylate, tetrahydrofurfuryl methacrylate, pentaerythritol monomethacrylate, pentaerythritol monoacrylate, trimethylolpropane monomethacrylate, trimethylolpropane monoacrylate And cyclic alkylol formal acrylates, and ketal acrylates. Acetal and ketal acrylates may also include isomeric mixtures. Cyclic alkylol formals and ketal acrylates are readily prepared by esterifying acrylate or methacrylate monomers with monohydroxy acetals derived from triols such as trimethylol propane and triethylolpropane. Structures of suitable triol starting materials that can react with aldehydes or ketones and can be acylated using acrylates of methacrylate include the following.

Preferred cyclic alkylol formal acrylates have the following structural formulas (A-C).

Wherein R ₁ Is for example -CH _2- , -CH ₂ CH ₂ -as C ₁ -C ₄ Alkylene group, R ₂ , R ₃ and R ₄ are H or such as -CH ₃ , -CH ₂ C ₁ as CH ₃ etc. -C ₄ It is an alkyl group.

 The most preferred cyclic alkylol formal acrylate is trimethylol propane formal acrylate (formula B).

Other photocurable monomers used alone or in a mixture with any of the above monomers include acetoacetoxyethyl methacrylate, 2-acetoacetoxyethyl acrylate, 2-acetoacetoxypropyl methacrylate, 2-aceto Acetoxypropyl acrylate, 2-acetoacetamidoethyl methacrylate, 2-acetoacetamidoethyl acrylate, 2-cyanoacetoxyethyl methacrylate, 2-cyanoacetoxyethyl acrylate, N- (2-cyanoacetoxyethyl) acrylamide, 2-propionylacetoxyethyl acrylate, N- (2-propionylacetoxyethyl) methacrylamide, N-4- (acetoacetoxybenzyl) phenyl acrylamide , Ethylacryloyl acetate, acryloylmethyl acetate, N-ethacryloyloxymethylacetoacetamide, ethyl methacryloyl acetoacetate, N-allylcyanoa Tamide, methylacryloyl acetoacetate, N- (2-methacryloyloxymethyl) cyano acetamide, ethyl-α-acetoacetoxy methacrylate, N-butyl-N-acryloyloxyethylaceto Reaction products of hydroxyl groups containing acrylates and anhydrides such as acetamide, monoacrylatepolyols, and monomethacryloyloxyethyl phthalate. Copolymerizable with the (alk) acrylate monomer, the monomer does not fall to a remarkable degree compared to the acrylate monomer.

Rapid photocuring of acrylic monomers is a desirable feature. Photocurable ethylenically unsaturated monomers other than acrylates and alkacrylates are limited to about 6 or more carbon atoms, such as butyl vinyl ether, isobutyl vinyl ether, cyclohexyl vinyl ether p- (2-aceto acetyl) ethyl styrene, And 4-aceto acetyl-1-methacryloylpiperazine, but are not limited thereto. Ethylenically unsaturated monomers containing epoxy reactive groups such as active hydrogen containing groups are not used in the photocurable component.

Examples of known multifunctional ethylenically unsaturated compounds are ethylene di-unsaturated monomers such as ethylene glycol diacrylate, polyethylene glycol diacrylate, ethylene glycol dimethacrylate, hexanediol diacrylate and triethylene glycol diacrylate. Typical tri-unsaturated monomers include trimethylol propane triacrylate (TMPTA), trimethylol propane, trimethacrylate, glycerol, triacrylate, pentaerythritol triacrylate, and pentaerythritol trimethacrylate. Typical acrylic unsaturated photocurable materials include SR 205, SR 306, CD 401, SR 508, SR 603, SR 9036 (Sartomer, Exton, PA).

Other suitable photopolymerizable oligomeric materials may be included in the photocurable component, in particular for example bisphenol based polyether acrylates, vinyl ether capped oligomers, hydroxy functional acrylates and reaction products of methacrylates and epoxides, acrylate polys Ethers, ethylenically unsaturated polyalkylethers, the aforementioned cycle ether acrylates and cycle ether acetal acrylates.

The photopolymerizable component may be a mixture of an ethylenically unsaturated oligomer and a monounsaturated acrylate monomer having a number average molecular weight of 500-5,000, preferably 1,000-4,000. The photocurable liquid oligomer may be composed of urethane acrylate oligomers having no active isocyanate groups. Urethane acrylate oligomers may also be mixed with ethylenically unsaturated acrylate monomers. Acrylate urethanes can be aliphatic or aromatic. Examples of commercially available acrylate urethanes include PHOTOMER (eg PHOTOMER 6010) (Henkel Corp. Hoboken, N.J); EBECRYL 220 (hexafunctional aromatic urethane acrylate of molecular weight 1000); EBECRYL 284 (aliphatic urethane diacrylate with molecular weight 1200 diluted with 1,6-hexanediol diacrylate); EBECRYL 4827 (aromatic urethane diacrylate of molecular weight 1600); ENECRYL 4830 (aliphatic urethane diacrylate with molecular weight 1200 diluted with tetra ethylene glycol diacrylate); EBECRYL 6602 (trifunctional aromatic urethane acrylate of molecular weight 1300 diluted with trimethylol propane ethoxy triacrylate); EBECRYL 840 (aliphatic urethane diacrylate of molecular weight 1000 (UCB Radcure Inc. Smyma, Ga); SARTOMER (e.g. SARTOMER 9635, 9645, 9655, 963-B80, 966-A80) (Sartomer Co. Exton, Pa), and There are those known as UVITHANE (eg, UVITHANE 782) (Morton International, Chicago, Ill).

Included with the photocurable acrylate component is an acrylate modified epoxy material having at least one photocurable unsaturated acrylate group, such as a diacrylate ester of bisphenol A epoxy resin, but such mixtures are not preferred. Typical acrylate modified epoxies are obtained by the reaction of the hydroxyl and oxirane groups of the acrylate. Unreacted epoxy curable function does not remain at all. Examples of commercially available acrylate epoxy are those under the name of Radcure Specialties (CMD). Other suitable acrylic unsaturated epoxy oligomers or pupane acrylate oligomers such as CN 929, CN 136, CN 970, CN 104, CN 120 C 60 are commercially available from Sartomer. Proprietary acrylate modified epoxy liquids may be formulated with additional single function or multifunctional acrylates. The amount of additional monofunctional or multifunctional acrylate onomers is included in the total composition range in the photocuring component.

Typical diacrylate functional photocurable materials include SR 205, SR 306, SR 508, CD 401, SR 603, SR 9036, typical tree functional materials include SR 350, SR 444, CD 501, SR 9021, Tetra functional acrylates include SR 295, SR 355, SR 399, SR 9041.

The thermosetting multifunctional epoxy resin component of the underfill contains at least two epoxy groups, has a viscosity of about 10,000 poise or less at 25 ° C., an average weight (WPE) for epoxides in the range of about 100-1000, and an average molecular weight of about 500 It contains at least one liquid resin in the range of -3500. Easily available epoxies are known and include diglycidyl ethers of bisphenol A, 2,2-bis-4- (2,3-epoxypropoxy) -phenyl) propane. Suitable epoxide compounds commercially available are sold under the names EPON 828, EPON 1004 and EPON 1001 F available from Shell Chemicals, and DER-331, DER-332 and DER-334 available from Dow Chemical. Other suitable epoxy resins include cycloaliphatic epoxides, glycidyl ethers of phenol formaldehyde novolacs (eg, DEN-431 and DEN-428 available from Dow Chemical). Mixtures of free radical curable resins and epoxy resins are also described in US Pat. No. 471138 and US Pat. No. 5,256,170. In a preferred embodiment, a biphenyl epoxy resin having a WPE of about 192 g / eq, a diglycidyl ether of bisphenol F having a WPE of about 172 g / eq, and a triglycidyl of p-aminophenol having a WPE of about 101 g / eq A mixture of three epoxy resins, which is a mixture of ethers, is used. These three epoxy resins are available under the names RSS, EPICLON, and ARALDITE.

The liquid wafer coating contains about 1-3% by weight of at least one photoinitiator that is effective to solidify the liquid underfill to a non-viscous surface when exposed to conventional levels of actinic radiation. The type of photoinitiator chosen depends on the desired depth of cure, the type of contrast agent used, and preferably the wavelength of radiation used. Commercially available free radical-generating photoinitiators suitable for use herein include acylphosphine oxide type photoinitiators such as those sold under the names IRGACURE® and DAROCUR®, available from benzophenone, benzoin ether and Swiss Vassel Ciba Specialty Chemicals. However, it is not limited thereto.

Preferred photoinitiator systems are a mixture of 25-50% ketone functional photoinitiator and 50-75% monoacylphosphine, bisacylphosphine oxide, or phosphinate containing photoinitiator. Examples of ketone photoinitiators include 1-hydroxy cyclohexyl phenylketone, hydroxy methylpropanone, dimethoxyphenylacetophenone, 2-methyl-1- [4- (methylthio) -phenyl] -2-morpholinopropanone -1, 1- (4-isopropylphenyl) -2-hydroxy-2-methylpropan-1-one, 1- (4-dodecyl-phenyl) -2-hydroxy-2-methylpropane-1- On, 4- (2-hydroxyethoxy) phenyl-2 (2-hydroxy-2-propyl) -ketone, diethoxyphenyl acetophenone, 2,4,6-trimethylbenzoyl diphenylphosphone, 2-hydroxy Hydroxy-2-methyl-1-phenyl propane-1-one, 1- [4- (2-hydroxyethoxy) phenyl] -2-hydroxy-2-methyl propane-1-one, and 2-hydroxy There is City Oak Santen-9-On. Typical acyl phosphine oxide photoinitiators include ethyl 2,4,6-trimethylbenzoyldiphenyl phosphine oxide, 2,4,6-trimethylbenzoyldiphenyl phosphine oxide, 2,4,6-triethylbenzoyldiphenyl phosphine oxide And 2,4,6-triphenylbenzoyldiphenylphosphine oxide. Specific examples of photoinitiator components for deep curing of liquid underfill applied to a wafer include 0.2-0.5 wt.% Of 1-hydroxy cyclohexyl phenyl ketone relative to the total weight of the underfill, and 0.5-0.7 wt.% Relative to the total weight of the underfill. Phenylbis (2,4,6-trimethyl benzoyl) phosphine oxide.

A actinic radiation source that does not raise the coating temperature above 120 ° C. may be used to perform photocuring solidification of the underfill in a solid liquefiable gel state. Ultraviolet light is most easily used as well as forms such as RS type solar lamps, carbon arc lamps, xenon arc lamps, mercury vapor lamps and tungsten halogen compounds. Radiant energy is emitted from point sources or in the form of parallel rays. However, divergent beams can also be used as actinic light sources. Ultraviolet radiation doses in the range of 100-2400 mJ / cm 2 provide a depth of underfill cure of about 1.2-1.8 mm and are effective at completing radical polymerization at underfill temperatures of 100 ° C. or less. The underfill composition is photocured to a viscous surface. The curing period may be adjusted according to the ultraviolet source, the underfill photocuring component concentration, and the appropriate choice of contrast agent.

When assembling a package, automatic visual inspection of the product requires the use of pigments to provide contrast between the substrate, underfill and chips. Contrast agents such as carbon black and pigments available under the name Sandorin® of Clariant AG are suitable. In one embodiment, 15 weight percent dispersion of carbon black in epoxy resin is used to mix 0.1-0.2 weight percent carbon black in the underfill to provide an effective control for automatic visual inspection.

Thermosetting  system

The epoxy curing system used in the present invention is in a non-fluxing form consisting of a latent heat accelerator having a curing initiation temperature of at least 150 ° C, preferably at least 160 ° C ± 5 ° C, more preferably at least 175 ° C ± 5 ° C. The solidified and cured underfill is modified by using a latent heat curing agent for the epoxy resin to initiate curing in a thermoset state at the temperature encountered immediately after solder reflow occurs. Dicyandiamide cannot be used alone as a thermosetting agent but may be used in small amounts with a latent heat accelerator, which is preferably absent. Preferred latent curing agents include amines and amine adducts, which are imidazole and urea derivatives such as 2,4,6-trimethyl-1,3-bis (3,3-dimethyl ureido) benzene and 1,5- Bis (3,3-dimethyl ureido) naphthalene. Thermosets should not be treated with halogens. As an example, the curing agent may be obtained by a known method of mixing an epoxy compound or an isocyanate compound and an amine compound, or by mixing an epoxy compound or an isocyanate compound, an amine compound, and an active hydrogen compound as described in US Pat. No. 5543486. . Various blocked amines are suitable. Preferred thermosetting agents are amines blocked with tertiary amines and urea moieties. Typical imidazoles suitable for the thermosetting component include 2-methylimidazole; 2-ethylimidazole; 2-ethyl-4-methylimidazole; 2-phenylimidazole; 2-phenyl-4-methylimidazole; 2-undecenyl imidazole; 1-vinyl-2-methylimidazole; 2-n-heptadecylimidazole; 2-undecylimidazole; 2-heptadecylimidazole; 2-ethyl-4-methylimidazole; 1-benzyl-2-methylimidazole; 1-propyl-2-methylimidazole; 1-cyanoethyl-2-methylimidazole; 1-cyanoethyl-2-ethyl-4-methylimidazole; 1-cyanoethyl-2-undecyl imidazole; 1-cyanoethyl-2-phenylimidazole; 1-guanaminoethyl-2-methylimidazole; 2- (p-dimethylaminophenyl) -4,5-diphenylamidazole; 2- (2-hydroxyphenyl) -4,5-diphenylimidazole; 2-phenyl-4-hydroxymethylimidazole; 2-phenyl-4,5-di (hydroxymethyl) -imidazole; Di (4,5-diphenyl-2-imidazole) -benzene-1,4,2-naphthyl-4,5-diphenylimidazole; Addition products of imidazole and trimellitic acid; Addition products of imidazole and 2-n-heptadecyl-4-methylimidazole; Phenylimidazole Benzylimidazole; 1- (dodecyl benzyl) -2-methylimidazole; 2- (2-hydroxyl-4-t-butylphenyl) -4,5-diphenylimidazole; 2-methyl-4,5-diphenylimidazole; 2,3,5-triphenylimidazole; 2-styrylimidazole; 2- (3-hydroxy phenyl) -4,5-diphenylimidazole; 1-benzyl-2-methylimidazole; And 2-p-methoxystyrylimidazole. Preferred thermosetting agents are available from Air Products & Chemicals under the name Curezol? 2-PHZ-S.

Other thermosets may be composed of blocked Lewis acids, for example latent metal acetoacetate functional curatives such as aluminum chelates, ethyl acetoacetate metal diisopropylate, metal tris (ethyl acetoacetate), alkyl acetoacetate metal Diisopropylate, aluminum monocetyl acetonate bis (ethyl acetoacetate), aluminum tris (acetyl acetonate), and an example of a cycle aluminum oligomer is cyclic aluminum oxide isopropylate.

In order to provide adequate reflow of photocurable liquefiable solids, thermal curing and photo-acceleration of the photocurable solids on the wafer or die do not occur at all during the storage delay period. The minimum thermosetting onset temperature is predetermined by the choice of thermosetting agent used and occurs after initiation of solder reflow at temperatures of 150 ° C. or higher. Preferably the minimum underfill thermoset initiation is in the range of 150 ° C-225 ° C. The onset temperature and peak cure rate of thermosetting are readily measured by automated scanning calorimetry and are known in the art. The onset temperature of thermosetting depends on the choice and amount of accelerator and should not be above 280 ° C. The onset of thermosetting should not be too close to peak temperatures that are typically 250 ° C. or near for eutectic solder and 300 ° C. or near for lead-free solder. Typical solder reflow times take 3-4 minutes and typically underfill is exposed to peak temperatures for up to 30 seconds. Thermosetting initiated at temperatures below 150 ° C. leads to inadequate underfill liquefaction and flow.

Nonconductive fillers are used to limit the CTE in the underfill. These fillers are known and various forms are suitable. There are available microelectronics grades of fused silica, crystalline silica, boron, nitrides of aluminum and silicon, magnesia, magnesium silicates, and silica coated aluminum that can be selected based on the desired properties and cost. Viscosity buildup in liquid underfill is a selection criterion. Due to the absence of solvents or unreacted diluents, the underfill embodiments according to the invention can be easily adapted to methods using relatively low viscosity coatings, such as known spin coating methods. Spin castable underfill embodiments according to the present invention exhibit typical viscosities that are relatively lower than typical viscosities used in underfills applied by stenciling or printing.

In a preferred embodiment, the underfill is applied by stencil printing in a pattern covering at least 70% of each wafer area between the soot streets. Under thermoset conditions, the CTE of the underfill is in the range of 15-50 ppm / ° C., and spherical fused silica is used in amounts of nonconductive filler levels, preferably in the range of 40-70% by weight (preferably 45-60% by weight). It requires particles. More preferably, inorganic low CTE fillers are used in amounts of 45-55% by weight. Preferred low CTE inorganic fillers have an average particle size of at least 10 μm and an average size no greater than about 75 μm. The upper limit of filler diameter used must be less than or equal to the thickness of the underfill coating mentioned above.

In any case, the underfill may contain an adhesion promoter. Typically useful amounts are 3-8% by weight. Adhesion promoters are known and include organic silanes, organic polysiloxanes, organic hydropolysiloxanes, prehydrolyzed organic silanes, siloxanes, and silsequioxanes. Typical organic silanes are mono (epoxyhydrocarbyl) such as, for example, r-glycidoxy propyltrimethoxy silan, r-glycidoxy propyl methyldiethoxy silane and β- (3,4-epoxycyclohexyl) ethyl trimethoxy silane. ) Containing epoxy functional groups such as trialkoxy silanes, with ethylenically unsaturated groups being preferred. Ethylenically unsaturated organosilicon compounds include 3- (meth) acrylopropyl trimethoxy silane, vinyl triethoxy silane, allyltrimethoxy silane and multi-alkenyl functional siloxanes such as 1,1,3,3-tetramethyldi Mono- or multi-alkenyl functional free silanes such as siloxane and hydrocyclization of 1,2,4-trivinylcyclohexane and / or 1,3,5-trivinylcyclohexane.

One method of applying underfill to a wafer involves known screen printing techniques. The wafer underfill according to the present invention can be advantageously dipped into the wafer in a pattern that is precisely tailored to cover the area outside the wafer surface of Soo Street. The underfill applied by the printing method preferably contains any rheological modifier. Suitable known forms are amorphous pure silica or silylate amorphous pure silica available from Cabot Corporation.

In any case, known flow regulators can be used. Thermoplastic flow regulators increase the tendency of liquefiable underfill to leak out during heat during solder reflow. Typical flow enhancers include about 0.2-0.6 I.V polymethacrylate high polymers available under the name Elvacite®. Elvacite® 2013, for example, is believed to be 64% butyl methacrylate / 36% methylmethacrylate copolymer with an I.V of 0.2 as ICI acrylic. Other flow regulators known in the art include Lanco® Flow P10 (Wicklip Lubrizol, Ohio) and MODAFLOW® Powder (St. Louis Solutia, Missouri). Flow enhancers may be based on SAN, or α-olefin polymers and the like. Preferred flow enhancers are Elvacite? Thermoplastic PMMA copolymer with a molecular weight of 60,000 such as 4026 (INEOS acrylics). The suggested amount of any thermoplastic flow enhancer as weight percent of the photocurable component is 1.0-10.0 weight percent. Within a range of controlling the fluidity of the underfill in the state of photocuring, heat liquefying, small amounts of plasticizers such as carboxy esters of up to 10% by weight, or lubricants such as ethylene-bis stearamide may be used.

Test Methods

1. Glass transition temperature (Tg)

Using a sample of b-stage or thermoset material, the glass transition temperature is measured using a thermomechanical analyzer at a heating rate of 5 ° C./min, a dynamic mechanical analyzer at a heating rate of 5 / ° C., and / or a heating rate of 5 ° C. Differential scanning calorimetry at

2. thermal expansion coefficient

Measurement of the coefficient of thermal expansion above and below Tg is measured by the use of conventional thermomechanical analyzers.

3. Viscosity

The Brookfield VDIII + corner and plate flowmeters are suitable, but Haake® HeoStress I was used.

4. Die shear adhesion is tested according to ASTM D 1002.

5. The thermal and oxidative stability is measured by thermogravimetric analysis. Underfill shows a weight loss of less than 5% at 300 ° C. in air.

Photopolymerization  Condition

The following conditions using an AETEK UV treatment allow the liquid underfill to adequately solidify through the depth of the coating.

Lamp 1 (W) Lamp 2 (W) Belt Speed (fpm) Curing Energy (mj / ㎠)

400 400 34 1170

200 200 30 761

200 200 45 515

200 200 60 384

200 200 65 349

200 200 70 327

125 125 30 712

125 125 70 297

200 0 45 274

200 0 60 205

200 0 70 176

125 0 70 149

125 0 90 116

Work example

Underfill Examples 1-4 were prepared by adding the ingredients to a housechild cup and then mixing for 30 seconds at 3000 rpm. The formulations were spin coated onto Umicore® semiconductor wafers with a 4 inch (10.1 cm) diameter x 400 ± μm thickness.

The coated wafers were photocured with an Aetec UV oven at 30 fpm, N ₂ atmosphere, and a setting of 200 W / 200 W in a single pass. The film was viscous in a liquefiable gel state. The storage of the underfill in the photocured state for 8 months was confirmed by DSC and no additional curing action occurred. The thermosetting onset temperature was 150 ° C ± 2 ° C, and there was a peak exotherm at 166 ° C.

Example  One

ingredient Parts by weight

Bisphenol A-Epichlorohydrin Epoxy 19.03

   Resin (residue epichlorohydrin 〈1 ppm)

  RSL-1462 (Shell Resins, Inc)

   (CAS # 25068-38-6)]

2. Poly (acrylic) unsaturated urethane acrylate

   Oligomer [CN 120 C 60 (Sartomer)]

3. Epoxy acrylate oligomer 18.50

  CN 136 (Sartomer)

4. Epoxy Curing Agent 1 1.14

  Ancamine 2441 (Air Products and Chem)

5. Epoxy Curing Agent 2 1.33

  [Dyhard? 100s (SKWCHEM)]

6. Trifunctional acrylate 7.00

  [SR 351 (Sartomer)]

7. Photoinitiator

  Irgacure 184 2.00

  Irgacure 819 1.00

8. Fused Silica 50.00

[F5 BLDX (Denka)]

                                                   Total 100.00

Example  2

ingredient Parts by weight

1.Bisphenol A-Epichlorohydrin Epoxy 36.28

   Resin (residue epichlorohydrin 〈1 ppm)

  RSL-1462 (Shell Resins, Inc)

   (CAS # 25068-38-6)]

2. Epoxy Curing Agent 1 2.18

  Ancamine 2441 (Air Products and Chem)

3. Epoxy Curing Agent 2 2.54

  [Dyhard? 100s (SKWCHEM)]

4. Trifunctional acrylate 6.00

  [SR 351 (Sartomer)]

5. Photoinitiators

  Irgacure 184 1.50

  Irgacure 819 1.50

6. Fused Silica 50.00

[F5 BLDX (Denka)]

                                                   Total 100.00

Example  3

ingredient Parts by weight

1.Bisphenol A-Epichlorohydrin Epoxy 36.29

   Resin (residue epichlorohydrin 〈1 ppm)

  RSL-1462 (Shell Resins, Inc)

   (CAS # 25068-38-6)]

2. Latent Amine Accelerators 2.18

  Ancamine 2441 (Air Products and Chem)

3. Dicyane diamide 2.54

  [Dyhard? 100s (SKWCHEM)]

4. Trifunctional acrylate 6.00

  [SR 351 (Sartomer)]

5. Photoinitiators

  Irgacure 184 2.00

  Irgacure 819 1.00

6. Fused Silica 50.00

[F5 BLDX (Denka)]

                                                   Total 100.00

Example  4

ingredient Parts by weight

Bisphenol A-Epichlorohydrin Epoxy 18.15

   Resin (residue epichlorohydrin 〈1 ppm)

  RSL-1462 (Shell Resins, Inc)

   (CAS # 25068-38-6)]

2. Acrylate modified epoxy oligomer 19.50

  CN 136 (Sartomer)

3. Latent Amine Accelerators 2.18

  Ancamine 2441 (Air Products and Chem)

4. Dicyane diamide 2.54

  [Dyhard? 100s (SKWCHEM)]

5. Trifunctional acrylate 6.00

  [SR 351 (Sartomer)]

6. Photoinitiator

  Irgacure 184 1.50

  Irgacure 819 1.50

7. Fused Silica 50.00

[F5 BLDX (Denka)]

                                                   Total 101.37

Examples 5-7 were prepared and then Umicore® having a 4 inch (10.1 cm) diameter by 400 μm thickness. Spin-coated the semiconductor wafer. The coated wafers were photocured with an AETEC UV curing oven at a setting of 200 f / 200 W in 30 fpm, N ₂ atmosphere, and single pass. The photocured film of Example 5-7 was not viscous in a state capable of solid thermal liquefaction.

Example  5

In the preparation of Example 5, ingredients 1-4 were mixed together in a 40 g house child cup and then heated to 60 ° C. until the photoinitiator was completely dissolved. The samples were then mixed in a house child mixer for 30 seconds at 3000 rpm. The remaining ingredients were added individually with mixing between each addition. Silica was added with increasing amounts while mixing.

ingredient Parts by weight

CN 136 (amine modified acrylate epoxy) 6.70

2.SR 203 (THFMA) 12.40

Irgacure 184 (photoinitiator) 0.30

4.Ingacure® 819 (photoinitiator) 0.50

5.RSL-1462 (diglycidyl ether of bis A epoxy) 14.35

6.RSS-1407 (biphenyl epoxy resin) 14.35

7.Curezol? 2 PHZ-S (Imidazole Potential Curative) 1.43

8. Filler (fused silica) 49.99

                                                   Total 100.02

The thermosetting start temperature of Example 5 was 167 degreeC.

Example 5 Tg-UV-B stage 23.56 ℃ Tg-Thermoset 106.25 ℃ CTE-below Tg 40.37 ppm / ℃ CTE-above Tg 107.7 ppm / ℃ Storage coefficient (＠ 25 ℃) 2.761 Mpa Storage coefficient (＠ 175 ℃) 0.025 Gpa

Example  6

Except 50% of the fused silica, the ingredients were added to a 40 g house child cup and then mixed at 300 rpm for 30 seconds to prepare Example 6. The remainder of the fused silica was then added with mixing at 3000 rpm for 30 seconds. The mixture was heated in an oven at 45 ° C. for 30 minutes to dissolve the photo initiator. The solution mixture was mixed again at 3000 rpm for 30 seconds.

Raw material Parts by weight

SR 203 (THFMA) 19.10

Irgacure? 184 (photoinitiator) 0.30

Ingacure® 819 (Photoinitiator) 0.50

RSS-1407 (biphenyl epoxy resin) 28.66

Curezol? 2 PHZ-S (imidazole latent curative) 1.43

Filler (fused silica) 50.01

                                                    Total 100.00

1 shows the DSC scan curve for Example 6. FIG. The conditions for the differential scanning calorimeter are as follows. That is, DSC (Perkin-Elmer Model DSC 7) was used, and heating conditions were 20 ° C.-300 ° C. at 5 ° C./min.

All samples were tested in the photocured state. The scanning results show the melting temperature of the solid epoxy resin at 95.23 ° C., the curing start temperature of 191.65 ° C., and the peak reaction temperature for thermal curing at 193.71 ° C.

Example  7

Example 7 was prepared by adding the ingredients, except 50% fused silica, to a 40 g housechild cup and mixing at 3000 rpm for 30 seconds. The remainder of the fused silica was then added with mixing at 3000 rpm for 30 seconds. The mixture was heated in an oven at 45 ° C. for 30 minutes to dissolve the photoinitiator. The solution mixture was mixed again at 3000 rpm for 30 seconds.

Raw material Parts by weight

SR 285 (THFA) 19.05

Irgacure? 184 (photoinitiator) 0.30

Ingacure® 819 (Photoinitiator) 0.50

RSS-1407 (biphenyl epoxy resin) 28.71

Curezol (imidazole) 1.44

Filler (fused silica) 50.01

                                                    Total 100.00

2 shows the DSC scan curve for Example 7. FIG.

The conditions for the differential scanning calorimeter are as follows. That is, DSC (Perkin-Elmer model DSC 7) was used, and heating conditions were 20 ° C.-300 ° C. at 5 ° C./min.

All samples were tested in the photocured state. The scanning results show the melting temperature of the solid epoxy resin at 99.5 ° C., the curing initiation temperature of 189.62 ° C., and the peak reaction temperature for thermal curing at 192.6 ° C.

Example  8

Example 8 was prepared by adding the ingredients, except 50% fused silica, to a 40 g housechild cup and mixing for 30 seconds at 3000 rpm. The remainder of the fused silica was then added with mixing at 3000 rpm for 30 seconds. The mixture was heated in an oven at 45 ° C. for 30 minutes to dissolve the photoinitiator. The solution mixture was mixed again at 3000 rpm for 30 seconds.

Raw material Parts by weight

CN 136 (amine modified acrylate epoxy) 6.70

SR 203 (THFMA) 12.40

Irgacure? 184 (photoinitiator) 0.30

Ingacure® 819 (Photoinitiator) 0.50

RSL-1462 (diglycidyl ether of bis A epoxy) 8.61

RSS-1407 (biphenyl epoxy resin) 20.09

Curezol? (Imidazole) 1.43

Filler [F5 BLDX (fused silica)] 49.99

                                                   Total 100.02

Example 8 Tg-Light B-Step WAU 31.47 ℃ Tg-Thermoset 116.44 ℃ CTE-below Tg 40.56 ppm / ℃ CTE-above Tg 120.5 ppm / ℃ Storage coefficient (25 ℃) 3.313 Mpa Storage coefficient (175 ℃) 0.0268 Gpa

Comparative Example A (77-5)

ingredient Parts by weight

1. 43.00 with tri (acrylic) function

   Acrylate modified epoxy

   Oligomer Mixture [CN 120 C 60 (Sartomer)]

2. Tri (acrylic) monomer 4.00

  [SR 351 (Sartomer)]

3. Dicyane diamide

  [Dyhard? 100 s (SKWChem)] 1.33

4. Photoinitiator

   Irgacure? 184 2.00

   Irgacure? 819 1.00

5. Fused Silica 50.00

[F5 BLDX (fused silica)]

                                                     Total 100.00

Comparative Example A was thinly separated from the wafer after storage for 24 hours after photocuring, which was thought to be due to excessive shrinkage caused by photocuring.

compare Example  B

ingredient Parts by weight

Bisphenol A-Epichlorohydrin Epoxy 18.15

   Resin (residue epichlorohydrin 〈1 ppm)

  RSL-1462 (Shell Resins, Inc)

   (CAS # 25068-38-6)]

2. Tri (acrylic) monomers and acrylates 20.5

   Modified Epoxy Oligomer Mixture [CN 120 C 60 (Sartomer)]

3. Potential Amine Accelerators 1.09

  [Ancamine? 2441 (Air Products and Chem)]

4. Dicyane diamide 1.27

  [Dyhard? 100 s (SKWCHem)]

5. Photoinitiators

  Irgacure 184 1.50

  Irgacure 819 1.00

6. Fused Silica 50.00

[F5 BLDX (Denka)]

                                                   Total 100.00

Comparative Example B also thinned after 24 hours of storage.

The present invention has particular industrial utility as wafer application underfills and methods of making them, and the compositions of the present invention can also be used in microelectronics applications such as glove tops, direct chip attachment and other applications to thermoset compositions in addition to underfills. It may be.

Although described above with respect to some preferred embodiments, various modifications are possible without departing from the scope and spirit of the invention.

Claims (6)

In an ambient temperature stable integrated circuit wafer having an active surface attached to an underfill composition, the underfill composition comprises a liquid photocurable acrylate component, a multifunctional epoxy resin, at least one photoinitiator, a non-electrically conductive filler, and a non-fluxing heat activated epoxy. Composed of a photocurable one-component composition consisting of a curable one-component mixture, the underfill in a solid state at 25 ° C. at 1000-5000 MPa, and below the glass transition temperature of the underfill composition at 15-50 ppm / ° C. Ambient temperature stability integrated circuit wafer. 5-30% monofunctional unsaturated photocurable component, 10-45% multifunctional epoxy resin, 0.3-3% at least one photoinitiator, in a liquid, 100% solid, non-magnetic, one-component underfill composition, 40-70 Consisting of% non-electrically conductive filler, the underfill exhibits a coefficient of curvature of 1000-5000 MPa at 20 ° C. and a coefficient of thermal expansion below its glass transition temperature of 15-50 ppm / ° C. in the heat curable state. An underfill composition. The photocurable component of claim 2 wherein the photocurable component is a C ₃ -C ₁₂ alkyl ester of acrylic acid and a C ₁ -C ₄ alkyl substituted C ₃ -C _{12 of} acrylic acid. An underfill composition comprising at least one compound selected from the group consisting of esters. The method of claim 2, wherein the photocurable component is tetrahydrofurfuryl acrylate, tetrahydrofurfuryl methacrylate, pentaerythritol monomethacrylate, pentaerythritol monoacrylate, trimethylolpropane monomethacrylate, trimethyl An underfill composition, characterized in that it is selected from at least one of a group consisting of all propane monoacrylate, acyclic alkylol formal acrylate, and ketal acrylate. 3. The photocurable component of claim 2 wherein the photocurable component is bisphenol polyether acrylate, vinyl ether capped oligomer acrylated epoxy resin, ethylenically unsaturated polyalkylether, poly (cycle) ether acrylate and polycycle (ether) acetal acrylate An underfill composition characterized in that the unsaturated oligomer selected from the group consisting of. The underfill composition of claim 4, further comprising a mono unsaturated acrylate monomer, wherein the oligomer has a number average molecular weight of 500-5000.