JPH10226769A - Film adhesive and method for connection - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a film adhesive which can give a circuit board not problematic in increased resistance at the connected part and peeling and having markedly improved reliability of connection by selecting a film adhesive having a multilayer structure comprising an adhesive layer prepared by adding a specified amount of an inorganic filler to an adhesive resin composition and an adhesive layer comprising based on an adhesive resin composition. SOLUTION: A film adhesive interposed between opposite circuit electrodes and electrically connecting the electrodes to each other in the direction of pressing when the electrodes are pressed against each other is prepared so that it may have a multilayer structure comprising an adhesive layer comprising 100 pts.wt. adhesive resin composition and 10-200 pts.wt. inorganic filler and an adhesive layer based on an adhesive resin composition. It is desirable that the adhesive resin composition develops a modulus of 30-1,5000Mpa at 40 deg.C after being cured. The adhesive resin composition used is one containing an epoxy resin, an acrylic rubber and a latent curing agent. The mean particle diameter of the inorganic filler is desirably 3μm or below.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a film-like adhesive and a circuit used for fixing a semiconductor chip to a substrate with an adhesive and electrically connecting both electrodes by, for example, a flip chip mounting method. The present invention relates to a method for connecting members.

[0002]

2. Description of the Related 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 mode corresponding to cost reduction and high precision. As a flip-chip mounting method, a method of providing a solder bump on a terminal of a chip and performing solder connection or a method of performing electrical connection via a conductive adhesive is known. In these methods, there is a problem in that when exposed to various environments, stress based on the difference in thermal expansion coefficient between the chip to be connected and the substrate is generated at the connection interface and connection reliability is reduced. For this reason, a method of injecting an epoxy resin-based underfill material into a gap between a chip and a substrate is generally studied for the purpose of reducing stress at a connection interface. However, there is a problem that the underfill injection step complicates the process and is disadvantageous in terms of productivity and cost. In order to solve such a problem, flip-chip mounting using an anisotropic conductive adhesive having anisotropic conductivity and a sealing function has recently attracted attention from the viewpoint of process simplicity.

[0003]

However, when a chip is directly mounted on a substrate via an anisotropic conductive adhesive, a stress based on a difference in thermal expansion coefficient between the chip and the substrate occurs in a connection portion under a temperature cycle test. Thermal shock test, PC
When a reliability test such as a T test or a solder bath immersion test is performed, there is a problem that the connection resistance increases and the adhesive is peeled off. In the case where 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 on the interface between the protruding electrode and the chip in the reliability test, and the protruding electrode is separated from the interface of the chip electrode. However, there is a problem that conduction failure occurs. An object of the present invention is to provide a circuit board which does not increase the connection resistance at the connection portion or peels off the adhesive, and greatly improves connection reliability.

[0004]

The film adhesive of the present invention is interposed between opposing circuit electrodes, presses the opposing circuit electrodes, and electrically connects the electrodes in the pressing direction. Adhesive 1 comprising an adhesive resin composition containing 10 to 200 parts by weight of an inorganic filler per 100 parts by weight of an adhesive resin composition, and an adhesive layer 2 containing an adhesive resin composition as a main component And a multi-layer structure having the following.

According to the bonding method of the present invention, a first circuit member having a first connection terminal and a second circuit member having a second connection terminal having a larger thermal expansion coefficient than the first circuit member are provided.
The adhesive layer 1 according to claim 1, wherein the first connection terminal and the second connection terminal are arranged to face each other, and the adhesive according to claim 1 is interposed between the first connection terminal and the second connection terminal arranged opposite to each other. On one circuit member side, the adhesive layer 2 is interposed so as to face the second circuit member, and is heated and pressurized to electrically connect the first connection terminal and the second connection terminal arranged opposite to each other. It is characterized by the following.

The elastic modulus at 40 ° C. after curing of the adhesive resin composition of the adhesive layer 1 and / or the adhesive layer 2 is 30 to 150.
The pressure is preferably 0 MPa, and the adhesive resin composition of the adhesive layer 1 and / or the adhesive layer 2 contains an epoxy resin, an acrylic rubber, and a latent curing agent.
The acrylic rubber preferably has a glycidyl ether group in its molecule. The average particle diameter of the inorganic filler is preferably 3 μm or less, and the adhesive resin composition of the adhesive layer 2 may contain 0.2 to 20% by volume of conductive particles. It is preferable that the average particle size of the conductive particles contained in the material is larger than the average particle size of the inorganic filler.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Circuit members 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 pads of the semiconductor chip and the substrate, the bumps formed by plating and the tips of the gold wires are melted with a torch or the like to form gold balls, and the balls are pressed on the electrode pads, and then the wires are cut. A protruding electrode such as a wire bump obtained by the above method can be provided and used as a connection terminal.

The adhesive resin composition used in the present invention includes epoxy resin and imidazole, hydrazide, boron trifluoride-amine complex, sulfonium salt,
A mixture of a latent curing agent such as an amine imide, a polyamine salt, and dicyandiamide is used.
An adhesive resin composition having an elastic modulus at 0 ° C. of 30 to 1500 MPa is preferred. 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, salt of polyamine, A mixture of a latent curing agent such as dicyandiamide has an elastic modulus at 40 ° C. after bonding of 30 to 1500 MPa.
An adhesive containing an acrylic rubber so that The elastic modulus of the adhesive film cured product is, for example, Rheology Co., Ltd. Rheospectra DVE-4 (pulling mode,
It can be measured using a frequency of 10 Hz and a temperature rise at 5 ° C./min).

The acrylic rubber used in the present invention is a polymer or copolymer containing at least one of acrylic acid, acrylic acid ester, methacrylic acid ester and acrylonitrile as a monomer component. Among them, it contains a glycidyl ether group. A copolymer acrylic rubber containing glycidyl acrylate or 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. The amount of acrylic rubber in the adhesive is 15 wt.
% Or less, the elastic modulus at 40 ° C. after bonding is 1500M.
If it exceeds Pa, and if it exceeds 40 wt%, the modulus of elasticity can be reduced, but the melt viscosity at the time of connection increases, and the removability of the molten adhesive between the connection electrode boundaries or at the interface between the connection electrode and the conductive particles decreases. As a result, it becomes impossible to secure electrical continuity between the connection electrodes or between the connection electrodes and the conductive particles. Therefore, the acrylic compounding amount is preferably 15 to 40% by weight. These acrylic rubbers compounded in the adhesive have a peak temperature of dielectric loss tangent due to the rubber component in the vicinity of 40 to 60 ° C., so that the elastic modulus of the adhesive can be reduced. In addition, a thermoplastic resin such as a phenoxy resin can be blended with the adhesive in order to make the film formability easier. 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 adhesiveness. Film formation, at least these epoxy resin, acrylic rubber, phenoxy resin, an adhesive composition comprising a latent curing agent and conductive particles are liquefied by dissolution or dispersion in an organic solvent,
It is performed by applying the composition on a peelable substrate and removing the solvent at a temperature lower than the activation temperature of the curing agent. As the solvent used at this time, a mixed solvent of an aromatic hydrocarbon type and an oxygen-containing type is preferable because the solubility of the material is improved.

[0010] The inorganic filler used in the present invention is not particularly limited. For example, fused silica,
Powders such as crystalline silica, calcium silicate, alumina, calcium carbonate and the like can be mentioned. The compounding amount of the inorganic filler is
It is 10 to 200 parts by weight with respect to 100 parts by weight of the adhesive resin composition. The larger the amount is, the more effective the lowering of the coefficient of thermal expansion is. Conduction failure based on the decrease in the exclusion of the agent
If the compounding amount is small, the thermal expansion coefficient cannot be sufficiently reduced,
20 to 90 parts by weight are preferred. The average particle size is
It is preferable that the thickness be 3 μm or less for the purpose of preventing conduction failure at the connection portion. In addition, it is desirable to use a spherical filler for the purpose of preventing a decrease in the fluidity of the resin 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 variations in the height of chip bumps and circuit electrodes. In the present invention, the conductive particles are, for example, Au, Ni, A
g, Cu, W or metal particles such as solder or metal particles formed by plating or depositing a thin film of gold or palladium on the surface of these metal particles. Conductive particles provided with a conductive layer of Au, solder, or the like can be used. It is necessary that the particle size is smaller than the minimum distance between the electrodes of the substrate, and if there is a height variation of the electrodes, it is preferably larger than the height variation, and preferably larger than the average particle size of the inorganic filler. And 1 μm to 10 μm are preferred. Also,
The amount of conductive particles dispersed in the adhesive is 0.1 to 30% by volume.
And preferably 0.2 to 15% by volume. Although the film thickness of the film adhesive of the present invention is not particularly limited, it is preferable that the film adhesive is thicker than the gap between the first and second circuit members. desirable.

[0012]

【Example】

Example 1 50 g of a phenoxy resin and butyl acrylate (40
Parts), 125 g of an acrylic rubber (molecular weight: 850,000) obtained by copolymerizing ethyl acrylate (30 parts), acrylonitrile (30 parts) and glycidyl methacrylate (3 parts) was 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 was added to the solution, and the mixture was stirred, and fused silica (average particle diameter: 0.5 μm) was added to 100 parts by weight of the resin adhesive composition. Was dispersed in an amount of 40 parts by weight to obtain a film coating solution. This solution was applied to a separator (silicone-treated polyethylene terephthalate film, thickness 40 μm) using a roll coater.
It was dried at 00 ° C. for 10 minutes to produce an adhesive film 1 having a thickness of 25 μm. The elastic modulus of this adhesive film 1 at 40 ° C. measured with a dynamic viscoelasticity measuring device of only the adhesive resin composition excluding the fused silica was 800 MPa. An adhesive film 2 having a thickness of 25 μm was produced in the same manner as in the production of the adhesive film 1 except that nickel particles (diameter: 3 μm) were dispersed at 2 vol% instead of dispersing the fused silica. Next, the produced adhesive film 1 and adhesive film 2 were laminated to obtain a film adhesive. Using this film adhesive, a gold bump (area: 80 μm × 80 μm)
m, space 30 μm, height: 15 μm, number of bumps 28
8) With tip (10mm x 10mm, thickness: 0.5m)
m) and the connection of the Ni / Au-plated Cu circuit printed circuit board were performed as follows. An adhesive film 2 (12 mm × 12 mm) of this film adhesive is coated on a Ni / Au-plated Cu circuit printed board (electrode height: 20 μm, thickness:
0.8 mm) at 80 ° C. and 10 kgf / cm ² , the separator was peeled off, the chip was opposed to the adhesive film 1 side, and the bumps of the chip and the Ni / Au plated Cu circuit printed circuit board (thickness: 0. 8 mm). Then, heating and pressurization were performed from above the chip under the conditions of 180 ° C., 50 g / bump, and 20 seconds, and the actual connection was performed.
The connection resistance after this connection is up to 6 mΩ per bump,
The average is 2 mΩ 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 atm) for 200 hours,
There was no change even after 10 seconds of immersion in the solder bath at 60 ° C., indicating good connection reliability.

EXAMPLE 2 50 g of a phenoxy resin and butyl acrylate (40
Parts), ethyl acrylate (30 parts), 175 g of an acrylic rubber (molecular weight: 850,000) copolymerized with acrylonitrile (30 parts) and glycidyl methacrylate (3 parts) was 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 was added to this solution, and the mixture was stirred, and fused silica (average particle diameter: 1 μm) was added to 100 parts by weight of the adhesive resin composition. 60 parts by weight were dispersed to obtain a film coating solution. This solution was applied to a separator (silicone-treated polyethylene terephthalate film, thickness 40 μm) using a roll coater.
The resultant was dried at a temperature of 10 ° C. for 10 minutes to prepare an adhesive film 1 having a thickness of 20 μm. The modulus of elasticity at 40 ° C. of this adhesive fill 1 measured at 40 ° C. by a dynamic viscoelasticity measuring instrument using only the adhesive resin composition excluding the fused silica was 400 MPa. An adhesive film 2 having a thickness of 20 μm was produced in the same manner as in the production of the adhesive film 1 except that nickel particles (diameter: 5 μm) were dispersed at 2 vol% instead of dispersing the fused silica. Next, the produced adhesive film 1 and adhesive film 2 were laminated to obtain a film adhesive. Using this film adhesive, 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 /
The connection of the Au plating Cu circuit printed circuit board was performed as shown below. Adhesive film 2 of this film adhesive
(12 mm x 12 mm) Ni / Au plated Cu circuit printed circuit board (electrode height: 20 μm, thickness: 0.8 mm)
After adhering at 80 ° C. and 10 kgf / cm ² , the separator was peeled off, the chip was opposed to the adhesive film 1 side, and the bump of the chip and the position of the Ni / Au plated Cu circuit printed circuit board (thickness: 0.8 mm) I made a match. Then
The main connection was performed by heating and pressing from above the chip under the conditions of 180 ° C., 50 g / bump, and 20 seconds. The connection resistance after this connection is up to 18mΩ per bump and 8m on average
Ω, insulation resistance is 10 ⁸ Ω or more, and these values are −5
1000 cycles of thermal shock test at 5-125 ° C, PC
There was no change even after a T test (121 ° C., 2 atm) for 200 hours and a solder bath immersion at 260 ° C. for 10 seconds, showing good connection reliability.

Example 3 50 g of a phenoxy resin, butyl acrylate (40
Parts), ethyl acrylate (30 parts), acrylonitrile (30 parts), and 100 g of an acrylic rubber (molecular weight: 850,000) copolymerized with glycidyl methacrylate (3 parts) were 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 was added to this solution, and the mixture was stirred and fused silica (average particle diameter: 0.5 μm)
Was dispersed in 60 parts by weight based on 100 parts by weight of the adhesive resin composition to obtain a film coating solution. This solution was applied to a separator (silicone-treated polyethylene terephthalate film, thickness 40 μm) using a roll coater.
After drying at 0 ° C. for 10 minutes, an adhesive film 1 having a thickness of 25 μm was prepared. The modulus of elasticity at 40 ° C. of this adhesive film 1 measured by a dynamic viscoelasticity measuring instrument using only the adhesive resin composition excluding the fused silica was 1000 MPa. An adhesive film 2 having a thickness of 25 μm was prepared in the same manner except that 5 vol% of conductive particles having an Au layer formed on the surface of a polystyrene core (diameter: 5 μm) was dispersed instead of dispersing fused silica in the preparation of the adhesive film 1. Was prepared. Next, the produced adhesive film 1 and adhesive film 2 were laminated to obtain a film adhesive. Using this film adhesive, a gold bump (area: 80 μm × 80 μm, space 30 μm,
Height: 15 μm, chip with bump number 288) (10 m
mx 10 mm, thickness: 0.5 mm) and a Ni / Au plated Cu circuit printed circuit board were connected as shown below. The adhesive film 2 of this film adhesive (12 mm
x12 mm) on a Ni / Au plated Cu circuit printed circuit board (electrode height: 20 μm, thickness: 0.8 mm) at 80 ° C.
After sticking at 10 kgf / cm ² , the separator was peeled off, the chip was opposed to the adhesive film 1 side, and the bump of the chip and a Ni / Au plated Cu circuit printed board (thickness:
0.8 mm). Then, 180
The main connection was performed by heating and pressing from above the chip under the conditions of 50 ° C., 50 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
200 ° C, 260 ° C solder bath immersion 1
There was no change even after 0 seconds, indicating good connection reliability.

EXAMPLE 4 50 g of a phenoxy resin and butyl acrylate (40
Parts), 125 g of an acrylic rubber (molecular weight: 850,000) obtained by copolymerizing ethyl acrylate (30 parts), acrylonitrile (30 parts) and glycidyl methacrylate (3 parts) was 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 was added to this solution, and the mixture was stirred and fused silica (average particle diameter: 0.5 μm)
Was dispersed in 100 parts by weight of the adhesive resin composition to obtain a film coating solution. This solution was applied to a separator (silicone-treated polyethylene terephthalate film, thickness 25 μm) using a roll coater.
After drying at 10 ° C. for 10 minutes, an adhesive film 5 having a thickness of 25 μm was prepared. The modulus of elasticity at 40 ° C. of this adhesive film 4 measured by a dynamic viscoelasticity measuring instrument using only the adhesive resin composition excluding the fused silica was 800 MPa. An adhesive film 2 having a thickness of 25 μm was produced in the same manner as in the production of the adhesive film 1 except that nickel particles (diameter: 3 μm) were dispersed at 2 vol% instead of dispersing the fused silica. Next, the produced adhesive film 1 and adhesive film 2 were laminated to obtain a film adhesive. Using this film adhesive, a bumpless chip (10 mm × 10 mm, thickness:
0.5mm, pad electrode: Al, pad diameter: 120μ
m) and Ni / Au plated Cu bumps on the circuit (diameter: 1)
The connection of the Ni / Au-plated Cu circuit printed circuit board having 00 μm, the space 50 μm, the height: 15 μm, and the number of bumps 200) was performed as shown below. The adhesive film 2 (12 mm × 12 mm) of this film adhesive is
80 ° C. on Ni / Au plated Cu circuit printed circuit board (electrode height: 20 μm, thickness: 0.8 mm) formed with i / Au plated Cu bumps (diameter: 100 μm, space: 50 μm, height: 15 μm, number of bumps: 200) , 10kg
After adhering at f / cm ² , the separator was peeled off, the chip was opposed to the adhesive film 1 side, and the bump of the chip was
/ Au plating Cu circuit printed circuit board (Thickness: 0.8m
m) was performed. Then, 180 ℃, 50g
Heating and pressurization were performed from above the chip under the conditions of / bump and 20 seconds to make the actual connection. The connection resistance after this connection is up to 8 mΩ per bump, 4 mΩ on average, and the insulation resistance is 10 mΩ.
⁸ Ω or more, and these values are 1000 cycles of thermal shock test at −55 to 125 ° C., PCT test (121 ° C.,
There was no change even after immersion in a solder bath at 260 ° C. for 2 hours for 200 hours and good connection reliability was exhibited.

[0016]

According to the circuit board using the film-like adhesive of the present invention, like the conventional circuit board, an inorganic filler having a small coefficient of thermal expansion of the adhesive is provided on the connecting member side having a small coefficient of thermal expansion such as a chip. Since the material-containing adhesive layer 1 has the adhesive layer 2 mainly composed of an adhesive composition disposed on the side of a circuit member such as a printed circuit board having a large thermal expansion coefficient, the temperature cycle, P
Since it is possible to absorb the stress based on the difference in thermal expansion coefficient between circuit members that occurs in reliability tests such as CT and IR reflow tests, there is no increase in connection resistance at the connection part or peeling of the adhesive even after the reliability test. Connection reliability is greatly improved.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kazuhiro Isaka 48 Wadai, Tsukuba, Ibaraki Prefecture, Hitachi Chemical Co., Ltd.Tsukuba R & D Co., Ltd. Within the Research Laboratory (72) Inventor Kazuyoshi Kojima 48 Wadai, Tsukuba, Ibaraki Prefecture Within Tsukuba Development Laboratory, Hitachi Chemical Co., Ltd.

Claims (8)

[Claims] 1. A film-like adhesive for circuit connection which is interposed between opposed circuit electrodes and presses the opposed circuit electrodes to electrically connect the electrodes in the pressure direction, comprising an adhesive resin composition. A film having a multilayer structure comprising an adhesive layer 1 containing 10 to 200 parts by weight of an inorganic filler per 100 parts by weight of a substance and an adhesive layer 2 mainly containing an adhesive resin composition. Glue. 2. The elastic modulus at 40 ° C. after curing of the adhesive resin composition of the adhesive layer 1 and / or the adhesive layer 2 is 30 to 15.
The film adhesive according to claim 1, which has a pressure of 00 MPa. 3. The film adhesive according to claim 2, wherein the adhesive resin composition of the adhesive layer 1 and / or the adhesive layer 2 contains an epoxy resin, an acrylic rubber, and a latent curing agent. 4. The film adhesive according to claim 3, wherein the acrylic rubber contains a glycidyl ether group in its molecule. 5. The film adhesive according to claim 1, wherein the average particle size of the inorganic filler is 3 μm or less. 6. The film adhesive according to claim 1, wherein the adhesive resin composition of the adhesive layer 2 contains 0.1 to 30% by volume of conductive particles. 7. The film adhesive according to claim 6, wherein the average particle size of the conductive particles contained in the adhesive composition of the adhesive layer 2 is larger than the average particle size of the inorganic filler. 8. A first connection member comprising: a first circuit member having a first connection terminal; and a second circuit member having a second connection terminal having a larger thermal expansion coefficient than the first circuit member. And the second connection terminal are opposed to each other, and the adhesive according to claim 1 is disposed between the first connection terminal and the second connection terminal which are opposed to each other. The adhesive layer 2 is interposed so as to be opposed to the second circuit member, and the first connection terminal and the second connection terminal arranged opposite to each other are electrically connected by applying heat and pressure. Connection method.