JP4178565B2 - Adhesive for connecting circuit members - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
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.
[0002]
[Prior art]
In the field of semiconductor mounting, 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 and solder connection is made, 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.
[0003]
[Problems to be solved by the invention]
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 portion under the temperature cycle test, and thermal shock test, PCT test, solder bath When a reliability test such as an immersion test is performed, there is a problem that an increase in connection resistance or peeling of the adhesive occurs. 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.
[0004]
[Means for Solving the Problems]
The adhesive film for connecting a circuit member of the present invention is an adhesive film 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. The adhesive for circuit member connection containing 5 to 200 parts by weight of the inorganic filler in 100 parts by weight of the adhesive resin composition is applied to the separator and dried, at 40 ° C. after curing of the adhesive resin composition modulus of 400 ~ 1000 MPa der of is, is characterized in that the average particle size of the inorganic filler is 3 microns or less. The adhesive film for connecting a circuit member of the present invention is an adhesive film for connecting a circuit member that is interposed between opposing circuit electrodes, pressurizes the opposing circuit electrodes, and electrically connects the electrodes in the pressing direction. Then, an adhesive for connecting a circuit member, containing an adhesive resin composition, an inorganic filler and conductive particles, and containing 5 to 200 parts by weight of the inorganic filler in 100 parts by weight of the adhesive resin composition is applied to the separator. , dried becomes, the is characterized in that the modulus of elasticity at 40 ° C. after curing of the adhesive resin composition Ri 400 ~ 1000 MPa der, average particle size of the inorganic filler is 3 microns or less .
[0005]
Large conductive particles having an average particle diameter than the average particle size of the inorganic filler in adhesives may be contained 0.1 to 30 vol%. The adhesive resin composition preferably contains at least an epoxy resin, an acrylic rubber, and a latent curing agent. Acrylic rubber having a glycidyl ether group in its molecule is used.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
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 way can be provided and used as connection terminals.
[0007]
As the adhesive resin composition used in the present invention, a mixture of an epoxy resin and an imidazole-based, hydrazide-based, 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 circuit members, an adhesive resin composition having an elastic modulus at 40 ° C. of 30 to 2000 MPa after bonding is preferable. For example, as an adhesive resin composition that can obtain good fluidity and high connection reliability at the time of connection, 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 2000 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).
[0008]
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 2000 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. Further, 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. This is done by removing the solvent below the curing agent activation temperature. 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.
[0009]
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 5 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. Conductivity failure occurs due to a decrease in adhesiveness and the elimination of the adhesive at the connecting portion, and if the blending amount is small, the thermal expansion coefficient cannot be sufficiently reduced, so 7 to 90 parts by weight is preferable, and 7 to 40 parts by weight is the most. preferable. The inorganic filler can be used in an amount of 5 to less than 10 parts by weight with respect to 100 parts by weight of the adhesive resin composition. 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.
[0010]
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 polymer spherical core material is provided with a conductive layer such as Ni, Cu, Au, or solder 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.
[0011]
【Example】
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, 20 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 circuit printed circuit board The connection was made as shown below. An adhesive film (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 bump. The Ni / Au plated Cu circuit printed circuit board (thickness: 0.8 mm) was 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. for 1000 cycles, the 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.
[0012]
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. 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 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 a gold bump (area: 80 μm × 80 μm, space 30 μm, height: 15 μm, number of bumps 288) and a Ni / Au plated Cu circuit printed board (electrode height: 20 μm, The connection of (thickness: 0.8 mm) was performed as shown below. An adhesive film (12 mm x 12 mm) was attached to a Ni / Au plated Cu circuit printed circuit board at 80 ° C. and 10 kgf / cm ² , and then the separator was peeled off to align the chip bumps with the Ni / Au plated Cu circuit printed circuit board. It was. 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.
[0013]
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, 10 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 a gold bump (area: 80 μm × 80 μm, space 30 μm, height: 15 μm, number of bumps 288) and a Ni / Au plated Cu circuit printed circuit board ( The connection of electrode height: 20 μm and thickness: 0.8 mm was performed as shown below. Adhesive film 3 (12 mm x 12 mm) was attached to a Ni / Au plated Cu circuit printed board at 80 ° C. and 10 kgf / cm ² , and then the separator was peeled off to align the chip bumps with the Ni / Au plated Cu circuit printed board. 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 is 5 mΩ at 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.
[0014]
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 weight of the adhesive resin composition. 20 parts by weight with respect to parts, and 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 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.
Next, using the produced adhesive film 4, a chip (1.7 mm × 17 mm, thickness: 0.5 mm) with gold bumps (area: 50 μm × 50 μm, 362 bumps, space: 20 μm, height: 15 μm) and a glass substrate with ITO circuit (thickness) : 1.1 mm) was performed as shown below. The adhesive film 4 (12 mm × 12 mm) was attached to a glass substrate with ITO circuit at 80 ° C. and 10 kgf / cm ² , and then the separator was peeled off to align the chip bumps with the glass substrate with ITO circuit. 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 150 mΩ maximum per bump, the average is 80 mΩ, and the insulation resistance is 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.
[0015]
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 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 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 bump (diameter: 100 μm, space 50 μm) on the circuit using the produced adhesive film 5 The Ni / Au plated Cu circuit printed circuit board on which the height: 15 μm and the number of bumps 200) were formed was connected as shown below. 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 , then the separator was peeled off, and the chip Al The 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. These values are the thermal shock test 1000 cycle treatment at −55 to 125 ° C., the 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.
[0016]
【The invention's effect】
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 reduced. In the case of ˜2000 MPa, the adhesive resin composition can further absorb the stress generated in reliability tests such as thermal shock, PCT and solder bath immersion test, so that the connection resistance at the connection portion can be increased even after the reliability test. There is no peeling of the adhesive, and connection reliability is greatly improved. In addition, since the adhesive of the present invention has a small coefficient of thermal expansion and can relieve stress at the interface between the chip and the ACF, when a protruding electrode is provided on the electrode pad of the chip when connecting the chip and the substrate via the adhesive The 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.

Claims (3)

A circuit member connecting adhesive film interposed between opposing circuit electrodes, pressurizing the opposing circuit electrodes and electrically connecting the electrodes in the pressurizing direction,
The adhesive for circuit member connection containing 5 to 200 parts by weight of the inorganic filler in 100 parts by weight of the adhesive resin composition is applied to the separator and dried.
Modulus of 400 ~ 1000 MPa der at 40 ° C. after curing of the adhesive resin composition is,
The average particle size of the inorganic filler is 3 microns or less,
An adhesive film for connecting circuit members. A circuit member connecting adhesive film interposed between opposing circuit electrodes, pressurizing the opposing circuit electrodes and electrically connecting the electrodes in the pressurizing direction,
An adhesive for connecting a circuit member, containing an adhesive resin composition, an inorganic filler and conductive particles, and containing 5 to 200 parts by weight of the inorganic filler in 100 parts by weight of the adhesive resin composition is applied to the separator and dried. And
Modulus of 400 ~ 1000 MPa der at 40 ° C. after curing of the adhesive resin composition is,
The average particle size of the inorganic filler is 3 microns or less,
An adhesive film for connecting circuit members.   The adhesive film for connecting a circuit member according to claim 2, wherein the adhesive for connecting a circuit member contains 0.1 to 30% by volume of conductive particles having an average particle size larger than that of the inorganic filler.