JP2007113012A - Adhesive for connecting circuit part - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an adhesive enabling the manufacture of a circuit board having remarkably improved connection reliability while preventing the increase of the connection resistance and the peeling of adhesive at the connected part. <P>SOLUTION: A phenoxy resin and an acrylic rubber are dissolved in ethyl acetate. A liquid epoxy compound containing a microencapsulated latent curing agent is added to the solution and stirred. Fused silica and nickel particles are dispersed in the solution to obtain a solution for film coating use, and an adhesive film is produced from the solution. The adhesive film is pasted on an Ni/Au-plated Cu circuit printed board, the bump of a chip is positioned opposite to the Ni/Au-plated Cu circuit printed board and the assembly is heated and pressed to complete the connection work. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an adhesive for connecting a circuit member, which is used for bonding and fixing a semiconductor chip to a substrate with an adhesive by, for example, a flip chip mounting method and electrically connecting both electrodes.

  In the semiconductor mounting field, flip chip mounting, in which an IC chip is directly mounted on a printed circuit board or a flexible wiring board, has attracted attention as a new mounting form corresponding to cost reduction and high precision. As the flip chip mounting method, there are known a method in which solder bumps are provided on the terminals of the chip to perform solder connection, and a method in which electrical connection is made through a conductive adhesive. In these methods, there is a problem that when the stress based on the difference in thermal expansion coefficient between the chip to be connected and the substrate is exposed to various environments, it is generated at the connection interface and connection reliability is lowered. For this reason, a method of injecting an epoxy resin-based underfill material into the gap between the chip and the substrate is generally studied for the purpose of alleviating the stress at the connection interface. However, the underfill injection process complicates the process and is disadvantageous in terms of productivity and cost. Recently, flip-chip mounting using an anisotropic conductive adhesive having anisotropic conductivity and a sealing function has attracted attention from the viewpoint of process simplicity in order to solve such problems.

  However, when the chip is directly mounted on the substrate via the anisotropic conductive adhesive, stress based on the difference in thermal expansion coefficient between the chip and the substrate is generated in the connection part under the temperature cycle test, and the thermal shock test, PCT test, solder When a reliability test such as a bath immersion test is performed, there is a problem in that the connection resistance increases and the adhesive peels off. In addition, when a protruding electrode is formed on the connection terminal of the chip, stress based on the difference in thermal expansion coefficient between the chip and the substrate is concentrated in the reliability test, and the protruding electrode is peeled off from the chip electrode interface. However, there is a problem that poor conduction occurs. The present invention provides a circuit board that does not increase connection resistance at the connection portion and does not peel off the adhesive, and greatly improves connection reliability.

  The adhesive for connecting a circuit member of the present invention is an adhesive for connecting a circuit member that is interposed between opposing circuit electrodes, pressurizes the opposing circuit electrodes, and electrically connects the electrodes in the pressurizing direction. In addition, 10 to 200 parts by weight of an inorganic filler having an average particle diameter of 3 microns or less is contained with respect to 100 parts by weight of the adhesive resin composition.

  The adhesive may contain 0.1 to 30% by volume, preferably 0.2 to 20% by volume of conductive particles having a larger average particle size than the average particle size of the inorganic filler. The adhesive resin composition preferably has an elastic modulus at 40 ° C. of 30 to 1500 MPa after curing, and the adhesive resin composition contains at least an epoxy resin, an acrylic rubber, and a latent curing agent, and is in the form of a film. A circuit member connecting adhesive is preferred. Acrylic rubber having a glycidyl ether group in its molecule is used.

  According to the adhesive of the present invention, since the coefficient of thermal expansion is not as large as that of the conventional adhesive, the stress at the interface between the chip and the ACF can be relieved, and the elastic modulus at 40 ° C. is 30 as an adhesive resin composition. In the case of ˜1500 MPa, the adhesive resin composition can absorb stress generated in reliability tests such as thermal shock, PCT and solder bath immersion tests, and thus increase the connection resistance at the connection even after the reliability test And there is no peeling of adhesive, and connection reliability is greatly improved. Further, since the adhesive of the present invention has a small thermal expansion coefficient and can relieve stress at the interface between the chip and the ACF, a protruding electrode is provided on the electrode pad of the chip when connecting the chip and the substrate via the adhesive. In this case, peeling of the protruding electrode from the electrode pad under the temperature cycle test can be greatly reduced. Therefore, the adhesive of the present invention is suitable for electrically connecting the LCD panel and TAB, TAB and flexible circuit board, LCD panel and IC chip, and IC chip and printed board only in the pressurizing direction at the time of connection. Used.

  Examples of the circuit member used in the present invention include a semiconductor chip, a printed circuit board, and a flexible wiring board based on polyimide or polyester. On the electrode pad of the semiconductor chip or substrate, the bump formed by plating or the tip of the gold wire is melted with a torch or the like to form a gold ball, and after the ball is pressed onto the electrode pad, the wire is cut. Protruding electrodes such as wire bumps obtained in this manner can be provided and used as connection terminals.

  As the adhesive resin composition used in the present invention, a mixture of an epoxy resin and a latent curing agent such as imidazole, hydrazide, boron trifluoride-amine complex, sulfonium salt, amine imide, polyamine salt, dicyandiamide or the like is used. In order to relieve stress based on the difference in thermal expansion coefficient of the circuit member, an adhesive resin composition having an elastic modulus at 40 ° C. of 30 to 1500 MPa after bonding is preferable. For example, as an adhesive resin composition that can obtain good fluidity at connection and high connection reliability, epoxy resin and imidazole, hydrazide, boron trifluoride-amine complex, sulfonium salt, amine imide, polyamine salt, Examples of the adhesive include a mixture of latent curing agents such as dicyandiamide and an acrylic rubber blended so that the elastic modulus at 40 ° C. after bonding is 30 to 1500 MPa. The elastic modulus of the cured adhesive film can be measured by using, for example, Rheospectra DVE-4 manufactured by Rheology Co., Ltd. (pull mode, temperature rising at 10 Hz, 5 ° C./min).

  Examples of the acrylic rubber used in the present invention include a polymer or copolymer having at least one of acrylic acid, acrylic acid ester, methacrylic acid ester or acrylonitrile as a monomer component. Among them, glycidyl acrylate containing a glycidyl ether group, A copolymer acrylic rubber containing glycidyl methacrylate is preferably used. The molecular weight of these acrylic rubbers is preferably 200,000 or more from the viewpoint of increasing the cohesive strength of the adhesive. If the blending amount of acrylic rubber in the adhesive is 15 wt% or less, the elastic modulus at 40 ° C. after bonding exceeds 1500 MPa, and if it exceeds 40 wt%, the elastic modulus can be reduced, but melting at the time of connection Since the viscosity increases and the exclusion of the molten adhesive between the connection electrode boundaries or at the interface between the connection electrode and the conductive particles is reduced, it becomes impossible to ensure electrical continuity between the connection electrodes or between the connection electrodes and the conductive particles. For this reason, as an acrylic compounding quantity, 15-40 wt% is preferable. Since these acrylic rubbers blended in the adhesive have a peak temperature of dielectric loss tangent due to the rubber component in the vicinity of 40 to 60 ° C., the elastic modulus of the adhesive can be reduced. In addition, a thermoplastic resin such as a phenoxy resin can be blended in the adhesive to facilitate film formation. In particular, the phenoxy resin is preferable because it has a similar structure to the epoxy resin and has characteristics such as excellent compatibility with the epoxy resin and excellent adhesion. Film formation is liquefied by dissolving or dispersing the adhesive resin composition composed of at least epoxy resin, acrylic rubber, phenoxy resin, and latent curing agent and conductive particles in an organic solvent, and applied to a peelable substrate. It is carried out by removing the solvent below the activation temperature of the curing agent. The solvent used at this time is preferably an aromatic hydrocarbon-based and oxygen-containing mixed solvent because the solubility of the material is improved.

  The inorganic filler used in the present invention is not particularly limited, and examples thereof include powders such as fused silica, crystalline silica, calcium silicate, alumina, and calcium carbonate. The blending amount of the inorganic filler is 10 to 200 parts by weight with respect to 100 parts by weight of the adhesive resin composition, and the larger the blending amount, the more effective it is to reduce the thermal expansion coefficient. The conduction failure based on the adhesiveness and the elimination of the adhesive at the connecting portion occurs, and if the blending amount is small, the thermal expansion coefficient cannot be lowered sufficiently, so 20 to 90 parts by weight is preferable. The average particle size is preferably 3 microns or less for the purpose of preventing poor conduction at the connection. Further, it is desirable to use a spherical filler for the purpose of preventing a decrease in resin fluidity at the time of connection and damage to the passivation film of the chip.

  In the adhesive of the present invention, conductive particles can be dispersed for the purpose of positively imparting anisotropic conductivity in order to absorb the height variation of the bumps of the chip and the circuit electrodes. In the present invention, the conductive particles are, for example, metal particles such as Au, Ni, Ag, Cu, W and solder or metal particles formed by plating or vapor deposition of a thin film such as gold or palladium on the surface of these metal particles, such as polystyrene. Conductive particles in which a conductive layer of Ni, Cu, Au, solder, or the like is provided on a spherical core material of the above polymer can be used. The particle size needs to be smaller than the minimum distance between the electrodes on the substrate, and when there is a variation in the height of the electrodes, it is preferably larger than the variation in height, and preferably larger than the average particle size of the inorganic filler. 1 μm to 10 μm is preferable. The amount of conductive particles dispersed in the adhesive is 0.1 to 30% by volume, preferably 0.2 to 15% by volume. When the adhesive for connecting a circuit member of the present invention is a film adhesive, the film thickness is not particularly limited, but it is preferably thicker than the gap between the first and second circuit members, and generally in the gap. On the other hand, a film thickness of 5 μm or more is desirable.

Example 1
50 g of phenoxy resin and 125 g of acrylic rubber (molecular weight: 850,000) copolymerized with butyl acrylate (40 parts), ethyl acrylate (30 parts), acrylonitrile (30 parts) and glycidyl methacrylate (3 parts) are dissolved in 400 g of ethyl acetate. To obtain a 30% solution. Next, 325 g of a liquid epoxy (epoxy equivalent 185) containing a microcapsule type latent curing agent is added to this solution and stirred, and fused silica (average particle size: 0.5 μm) is added to 100 parts by weight of the adhesive resin composition. On the other hand, 40 parts by weight and further 2 vol% of nickel particles (diameter: 3 μm) were dispersed to obtain a film coating solution. This solution was applied to a separator (silicone-treated polyethylene terephthalate film, thickness 40 μm) with a roll coater, and dried at 100 ° C. for 10 minutes to produce an adhesive film 1 having a thickness of 45 μm. In addition, the 40 degreeC elastic modulus measured with the dynamic viscoelasticity measuring device only of the adhesive resin composition except the fused silica and nickel particle of this adhesive film 1 was 800 MPa. Next, using the produced adhesive film 1, a chip (10 mm × 10 mm, thickness: 0.5 mm) with gold bumps (area: 80 μm × 80 μm, space 30 μm, height: 15 μm, number of bumps 288) and Ni / Au plated Cu The circuit printed circuit board was connected as shown below. An adhesive film (12 mm × 12 mm) was attached to a Ni / Au plated Cu circuit printed board (electrode height: 20 μm, thickness: 0.8 mm) at 80 ° C. and 10 kgf / cm ² , and then the separator was peeled off. The bumps and Ni / Au plated Cu circuit printed circuit board (thickness: 0.8 mm) were aligned. Next, the main connection was performed by heating and pressing from above the chip under the conditions of 180 ° C., 30 g / bump, and 20 seconds. The connection resistance after this connection is a maximum of 6 mΩ per bump, an average of 2 mΩ, and an insulation resistance of 10 ⁸ Ω or more. These values are from the thermal shock test at −55 to 125 ° C., 1000 cycle treatment, PCT test (121 No change even after 10 seconds of immersion in a solder bath at 260 ° C. for 200 hours at 2 ° C., and good connection reliability was exhibited.

Example 2
50 g of phenoxy resin and 175 g of acrylic rubber (molecular weight: 850,000) copolymerized with butyl acrylate (40 parts), ethyl acrylate (30 parts), acrylonitrile (30 parts) and glycidyl methacrylate (3 parts) are dissolved in 525 g of ethyl acetate. To obtain a 30% solution. Next, 275 g of a liquid epoxy (epoxy equivalent 185) containing a microcapsule type latent curing agent is added to this solution and stirred, and fused silica (average particle size: 0.5 μm) is added to 100 parts by weight of the adhesive resin composition. 60 parts by weight, and further 2 vol% of nickel particles (diameter: 3 μm) were dispersed to obtain a film coating solution. This solution was applied to a separator (silicone-treated polyethylene terephthalate film, thickness 40 μm) with a roll coater, and dried at 100 ° C. for 10 minutes to produce an adhesive film 2 having a thickness of 45 μm. The elastic modulus at 40 ° C. measured by a dynamic viscoelasticity measuring instrument using only the adhesive resin composition excluding fused silica and nickel particles of the adhesive film 2 was 400 MPa. Next, using the produced adhesive film 2, a chip (10 mm × 10 mm) with gold bumps (area: 80 μm × 80 μm, space 30 μm, height: 15 μm, number of bumps 288) and Ni / Au plated Cu circuit printed circuit board (electrode height) Connection: 20 μm, thickness: 0.8 mm) was performed as shown below. Adhesive film (12mm x 12mm) was attached to Ni / Au plated Cu circuit printed circuit board at 80 ° C, 10kgf / cm ² , separator was peeled off, and chip bump and Ni / Au plated Cu circuit printed circuit board were aligned Went. Next, the main connection was made by heating and pressing from above the chip under the conditions of 170 ° C., 30 g / bump, and 20 seconds. The connection resistance after this connection is 18 mΩ at the maximum per bump, the average is ⁸ mΩ, and the insulation resistance is 10 ⁸ Ω or more. These values are the thermal shock test at −55 to 125 ° C., 1000 cycle treatment, PCT test (121 No change even after 10 seconds of immersion in a solder bath at 260 ° C. for 200 hours at 2 ° C., and good connection reliability was exhibited.

Example 3
50 g of phenoxy resin, 100 g of acrylic rubber (molecular weight: 850,000) copolymerized with butyl acrylate (40 parts), ethyl acrylate (30 parts), acrylonitrile (30 parts) and glycidyl methacrylate (3 parts) were dissolved in 350 g of ethyl acetate. A 30% solution was obtained. Next, 350 g of a liquid epoxy (epoxy equivalent 185) containing a microcapsule type latent curing agent is added to this solution and stirred, and fused silica (average particle size: 0.5 μm) is added to 100 parts by weight of the adhesive resin composition. On the other hand, 60 vol parts, and further 5 vol% of conductive particles having an Au layer formed on the surface of a polystyrene core (diameter: 5 μm) were dispersed to obtain a film coating solution. This solution was applied to a separator (silicone-treated polyethylene terephthalate film, thickness 40 μm) with a roll coater and dried at 100 ° C. for 10 minutes to produce an adhesive film 3 having a thickness of 45 μm. The elastic modulus at 40 ° C. measured by a dynamic viscoelasticity measuring device using only the adhesive resin composition excluding fused silica and nickel particles of the adhesive film 3 was 1000 MPa. Next, using the produced adhesive film 3, a chip (10 mm × 10 mm, thickness: 0.5 mm) with gold bumps (area: 80 μm × 80 μm, space 30 μm, height: 15 μm, number of bumps 288) and Ni / Au plated Cu A circuit printed board (electrode height: 20 μm, thickness: 0.8 mm) was connected as shown below. Adhesive film 3 (12 mm × 12 mm) was attached to a Ni / Au plated Cu circuit printed board at 80 ° C. and 10 kgf / cm ² , then the separator was peeled off, and the chip bumps and the positions of the Ni / Au plated Cu circuit printed board Together. Next, the main connection was made by heating and pressing from above the chip under the conditions of 170 ° C., 30 g / bump, and 20 seconds. The connection resistance is 5 mΩ at the maximum per bump, 1.5 mΩ on average, and the insulation resistance is 10 ⁸ Ω or more. These values are 1000 cycles of thermal shock test at −55 to 125 ° C., PCT test (121 ° C., 2 atmospheres) No change even after 200 seconds of immersion in a solder bath at 260 ° C. for 200 hours, showing good connection reliability.

Example 4
50 g of phenoxy resin and 100 g of acrylic rubber (molecular weight: 850,000) copolymerized with butyl acrylate (40 parts), ethyl acrylate (30 parts), acrylonitrile (30 parts) and glycidyl methacrylate (3 parts) are dissolved in 350 g of ethyl acetate. To obtain a 30% solution. Next, 350 g of a liquid epoxy (epoxy equivalent 185) containing a microcapsule type latent curing agent is added to this solution and stirred, and fused silica (average particle size: 0.5 μm) is added to 100 parts by weight of the adhesive resin composition. On the other hand, conductive particles having an Au layer formed on the surface of 40 parts by weight and a polystyrene core (diameter: 5 μm) were dispersed by 5 vol% to obtain a film coating solution. This solution was applied to a separator (silicone-treated polyethylene terephthalate film, thickness 40 μm) with a roll coater and dried at 100 ° C. for 10 minutes to produce an adhesive film 4 having a thickness of 45 μm. The elastic modulus at 40 ° C. measured by a dynamic viscoelasticity measuring instrument using only the adhesive resin composition excluding fused silica and nickel particles of the adhesive film 4 was 1000 MPa. Moreover, the average thermal expansion coefficient of 110-130 degreeC measured by TMA method of the adhesive film 4 was 111 ppm. Next, using the produced adhesive film 4, a chip (1.7 mm × 17 mm, thickness: 0.5 mm) with an gold bump (area: 50 μm × 50 μm, 362 bump, space: 20 μm, height: 15 μm) and an ITO circuit A glass substrate (thickness: 1.1 mm) was connected as shown below. The adhesive film 4 (12 mm × 12 mm) was attached to a glass substrate with an ITO circuit at 80 ° C. and 10 kgf / cm ² , the separator was peeled off, and the chip bumps and the glass substrate with an ITO circuit were aligned. Next, the main connection was made by heating and pressing from above the chip under the conditions of 180 ° C., 40 g / bump, and 20 seconds. The connection resistance is a maximum of 150 mΩ per bump, an average of 80 mΩ, and an insulation resistance of 10 ⁸ Ω or more. These values are the thermal shock test 1000 cycle treatment at −40 to 100 ° C., the PCT test (105 ° C., 1.. Even at 100 atm (2 atm), there was no change and good connection reliability was shown.

Example 5
50 g of phenoxy resin and 125 g of acrylic rubber (molecular weight: 850,000) copolymerized with butyl acrylate (40 parts), ethyl acrylate (30 parts), acrylonitrile (30 parts) and glycidyl methacrylate (3 parts) are dissolved in 400 g of ethyl acetate. To obtain a 30% solution. Next, 325 g of a liquid epoxy (epoxy equivalent 185) containing a microcapsule type latent curing agent is added to this solution and stirred, and fused silica (average particle size: 0.5 μm) is added to 100 parts by weight of the adhesive resin composition. On the other hand, 60 parts by weight and 2 vol% of nickel particles (diameter: 3 μm) were dispersed to obtain a film coating solution. This solution was applied to a separator (silicone-treated polyethylene terephthalate film, thickness 40 μm) with a roll coater and dried at 100 ° C. for 10 minutes to produce an adhesive film 5 having a thickness of 45 μm. The elastic modulus at 40 ° C. measured by a dynamic viscoelasticity measuring device using only the adhesive resin composition excluding fused silica and nickel particles of the adhesive film 5 was 800 MPa. Next, a bumpless chip (10 mm × 10 mm, thickness: 0.5 mm, pad electrode: Al, pad diameter: 120 μm) and Ni / Au plated Cu bumps (diameter: 100 μm, The connection of the Ni / Au plated Cu circuit printed circuit board on which a space of 50 μm, a height of 15 μm, and a number of bumps of 200) was formed was performed as shown below. The adhesive film 5 (12 mm × 12 mm) was attached to a Ni / Au plated Cu circuit printed circuit board (electrode height: 20 μm, thickness: 0.8 mm) at 80 ° C. and 10 kgf / cm ² , and then the separator was peeled off to form a chip. The Ni pad and the Ni / Au plated Cu circuit printed board (thickness: 0.8 mm) with Ni / Au plated Cu bumps were aligned. Next, the main connection was performed by heating and pressing from above the chip under the conditions of 180 ° C., 30 g / bump, and 20 seconds. The connection resistance after this connection is a maximum of 8 mΩ per bump, an average of 4 mΩ, and an insulation resistance of 10 ⁸ Ω or more, and these values are the thermal shock test at −55 to 125 ° C., 1000 cycle treatment, PCT test (121 No change even after 10 seconds of immersion in a solder bath at 260 ° C. for 200 hours at 2 ° C., and good connection reliability was exhibited.

Claims (6)

  A circuit member connecting adhesive that is interposed between opposing circuit electrodes and pressurizes the opposing circuit electrodes to electrically connect the electrodes in the pressurizing direction, with respect to 100 parts by weight of the adhesive resin composition, An adhesive for connecting circuit members, comprising 10 to 200 parts by weight of an inorganic filler having an average particle size of 3 microns or less.   The adhesive for connecting circuit members according to claim 1, wherein the conductive particles having an average particle diameter larger than the average particle diameter of the inorganic filler are contained in an amount of 0.1 to 30% by volume.   The adhesive for circuit member connection according to claim 1 or 2, wherein an elastic modulus at 40 ° C after curing of the adhesive resin composition is 30 to 1500 MPa.   4. The adhesive for connecting circuit members according to claim 1, wherein the adhesive resin composition contains at least an epoxy resin, an acrylic rubber, and a latent curing agent. 5.   5. The adhesive for connecting circuit members according to claim 4, wherein the acrylic rubber contains a glycidyl ether group in its molecule.   The adhesive for a circuit member connection according to any one of claims 1 to 5, wherein the shape is a film shape.