JP2002151549A - Anisotropic conductive film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an anisotropic conductive film which can bond at least a semiconductor element and an electrode and/or a circuit board and an electrode easily and rigidly with high reliability while suppressing damage on the semiconductor element and the circuit board as much as possible. SOLUTION: The anisotropic conductive film 1 comprises a film basic material 2 of insulating material, and a plurality of conduction paths 3 insulated from each other in the film basic material 2 and arranged substantially in parallel with the thickness direction Z thereof to penetrate the film basic material 2 wherein the conduction path 3 has a part 4 projecting from the film basic material plane 2a on at least one side in the axial direction and the projecting part 4 has a solder later 6 like a thin film at the forward end thereof.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an anisotropic conductive film, and more particularly, to an anisotropic conductive film used for bonding a semiconductor element to a circuit board.

[0002]

2. Description of the Related Art An anisotropic conductive film is a film exhibiting anisotropy in conductivity. The film exhibits conductivity in a direction penetrating the front and back of the film, but exhibits insulation in a direction in which the film surface spreads. Things. Therefore, an anisotropic conductive film is inserted between a bare semiconductor element (chip) cut out from a wafer state and an external circuit board (hereinafter, simply referred to as a circuit board), and these three elements are joined to form a semiconductor element. And the electrodes of the circuit board are electrically connected to each other through the conductive path of the anisotropic conductive film. With the recent large-scale integration of semiconductor integrated circuits and fine pitch of connection terminals (electrode pads, etc.),
The use of anisotropic conductive films in mounting semiconductor devices is increasing.

[0003] Conventionally, as an anisotropic conductive film, a film formed by dispersing conductive fine particles serving as a conductive path in a film made of an adhesive insulating material is known. However, this conventional anisotropic conductive film has a problem that it is difficult to connect to an object having a fine pitch due to its structure, and a problem that the electrode shape of a semiconductor element must be convex (bump shape). . In view of this, as an anisotropic conductive film capable of coping with fine pitch, the present applicant has disclosed in International Publication WO98 / 07216 an anisotropic conductive film in which a plurality of conductive paths are insulated from each other and penetrate in the thickness direction of the film. Conductive film (that is, a film having a structure in which a number of conductive paths are insulated from each other, each penetrates a film base made of an insulating resin, and both ends of each conductive path are exposed on the front and back surfaces of the film base). Has been proposed.

[0004]

SUMMARY OF THE INVENTION In a semiconductor device in which a semiconductor element and a circuit board are electrically connected via an anisotropic conductive film having a structure in which a conductive path penetrates in the thickness direction of the film, an anisotropic conductive film is provided. The bonding between the film and the semiconductor element and between the anisotropic conductive film and the circuit board is usually performed by bonding a film substrate having adhesiveness to the electrode surface of the semiconductor element (electrode surface of the circuit board) to form a conductive path and an electrode. Are kept in contact with each other. However, in such an embodiment, depending on the type of insulating resin used for the film substrate, there may be cases where sufficient bonding strength cannot be obtained or sufficient electrical conductivity cannot be obtained.

In the above-described embodiment, the bonding is performed by applying heat and pressure. However, in order to obtain a sufficiently reliable contact state between the conductive path and the electrode, the bonding temperature is 280 ° C.
It is necessary to perform the above-mentioned processing at a temperature of about 350 ° C. and a pressure of about 1.4 MPa to 3.0 MPa for about 0.3 to 1 minute. Great damage.

SUMMARY OF THE INVENTION The object of the present invention has been made in view of the above circumstances, and it is possible to easily and firmly join at least the electrodes between the semiconductor element and the electrodes between the electrodes with the circuit board with high reliability. An object of the present invention is to provide an anisotropic conductive film capable of minimizing damage to a semiconductor element and a circuit board during bonding.

[0007]

Means for Solving the Problems The present inventors have made intensive studies to solve the above-mentioned problems, and as a result, have completed the present invention. The present invention is as follows. (1) A film substrate made of an insulating material and a plurality of conductive members which are insulated from each other in the film substrate, and are arranged so that their axial directions are substantially parallel to the thickness direction of the film substrate and penetrate therethrough. A passage, wherein the conduction path has a protrusion protruding from the film substrate surface on at least one side in the axial direction, and the protrusion has a thin-film solder layer at the tip thereof. Conductive film. (2) The anisotropic conductive film according to the above (1), wherein the average protrusion height of the protrusion is 0.1 μm to 7 μm. (3) The anisotropic conductive film according to the above (1) or (2), wherein the thickness of the solder layer is 0.1 μm to 5 μm. (4) The method according to any one of (1) to (3), wherein the conductive path includes a projecting portion projecting from both surfaces of the film substrate, and the projecting portion has a thin-film solder layer at a tip thereof. One side conductive film.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
FIG. 1 shows a preferred example of an anisotropic conductive film 1 of the present invention.
FIG. As shown in FIG. 1, the anisotropic conductive film 1 of the present invention basically includes a film substrate 2 made of an insulating material and a plurality of conductive paths 3 made of a conductive material. The conduction path 3 has a length in the axial direction larger than the length (thickness) of the film substrate 2 in the thickness direction Z and penetrates through the film substrate 2. On both sides as in the embodiment shown in
It has a projection 4 projecting from the film surface 2a. The conduction path 3 is formed at least in a portion within the film substrate 2 (hereinafter, referred to as a portion).
The “substrate 5 in the substrate” may be referred to as being substantially parallel to the thickness direction Z of the film substrate 2 (parallel in FIG. 1).

In the present invention, the protruding portion 4 has a thin-film solder layer 6 at its tip, that is, at the end farthest from the film surface 2a. Materials for forming the solder layer 6 include Sn, Sn / Ag, Sn / Pb, and Sn / Z.
n, Sn / Ag / Cu, Sn / Bi and the like.
Examples of a method for forming the solder layer 6 include screen printing, electrolytic plating, and electroless plating.

FIG. 2 is a simplified diagram showing an example of joining a semiconductor element 11 and a circuit board 12 using the anisotropic conductive film 1 of the present invention shown in FIG. First, as shown in FIG. 2A, the circuit board 12 is placed on a stage (not shown) heated to, for example, about 50 ° C. to 150 ° C., and the anisotropic material of the present invention is placed on the circuit board 12. The conductive film 1 is placed. At this time, the conductive path 3 of the anisotropic conductive film 1 is aligned with the electrode 13 of the circuit board 12.

Next, as shown in FIG. 2B, the semiconductor element 11 is aligned while its electrodes 14 are opposed to the conductive paths 3 located on the electrodes 13 of the circuit board 12.
It is placed on the anisotropic conductive film 1. That is, the semiconductor element 11 is arranged in such a manner that the electrode 14 of the semiconductor element 11 and the electrode 13 of the circuit board 12 face each other with the conduction path 3 interposed therebetween.
And the circuit board 12 sandwich the anisotropic conductive film 1. In such a state, a structure (hereinafter, sometimes referred to as “semiconductor device 15”) including the semiconductor element 11, the anisotropic conductive film 1, and the circuit board 12 is provided.
Heat for a certain time. At this time, as will be described later, in some cases, the pressing is performed along the thickness direction Z of the film 1.

In the anisotropic conductive film 1 of the present invention, as described above, the conduction path 3 has the protrusion 4 having a specific average protrusion height, and the protrusion 4 is most separated from the film surface 2a. A solder layer 6 is provided at an end portion. As described above, the present invention has a structure in which the solder layer 6 intended to be welded to the semiconductor element 11 and the circuit board 12 respectively protrudes from the film surface 2a. The solder layer 6 can be firmly bonded to various material surfaces irrespective of the type of metal or resin by being melted and solidified, and sufficient reliability can be obtained by bonding between the conductive path and the electrode with the solder layer 6. Electrical connection can be made. Thus, the solder layer at a position facing the electrode of the semiconductor element and the electrode of the circuit board is bonded to the electrode, and the solder layer at a position not facing the electrode is formed on the protective film (passivation film) on the surface of the semiconductor element and / or the substrate of the circuit board. By joining to a surface or the like, the members of the semiconductor device 15 can be easily and firmly joined with high reliability.

As described above, in the present invention, since only the solder layer 6 can be used for easy and strong bonding, unlike the case of bonding only by bonding the film substrate, only the heating for a shorter time is required. The above bonding can be performed. When bonding is performed using only the solder layer 6 using the anisotropic conductive film 1 of the present invention, usually, 230 ° C. to 300 ° C.,
Preferably at a temperature of 230 ° C to 280 ° C for 3 seconds to 40
Suitable bonding can be realized under the conditions of seconds, preferably 5 seconds to 30 seconds.

As will be described later, when a resin material that exhibits adhesiveness at least by heating or by heating and pressing is used as the material of the film substrate 2, in addition to the joining by the solder layer 6, The above bonding can also be performed by bonding the film substrate 2. FIG. 2 shows a case where the above-described bonding is performed not only by melting and solidifying the solder layer 6 but also by bonding with the film substrate 2. When a resin material showing adhesiveness only by heating is used as the film base material in the present invention, compared with a configuration in which similar bonding is performed only by bonding the film base material by heating,
Stronger bonding can be performed in a shorter time of about 60 seconds to 60 seconds. Further, even when a resin material showing adhesiveness by heating and pressing is used as the film substrate in the present invention, it is compared with a configuration in which similar bonding is performed only by bonding the film substrate by heating and pressing. And 0.2MPa
A lower pressure of about 1.5 MPa, and 5 seconds to 30
A stronger bonding can be performed in a shorter time of about seconds. Thus, the anisotropic conductive film 1 of the present invention
By using, while exposing to the temperature of the above degree,
In the case where pressure is also applied under shorter time conditions than in the conventional case, lower pressure may be used, so that damage to the semiconductor element and the circuit board due to bonding can be suppressed.

In the present invention, the film surface 2 of the projection 4
The average protrusion height from a is 0.1 μm to 7 μm, preferably 0.1 μm to 4 μm. The average protrusion height is
If the thickness is less than 0.1 μm, it may be difficult to perform bonding at a low pressure when connecting to a chip and a substrate, which is not preferable. On the other hand, if the average protrusion height exceeds 7 μm, a short circuit occurs between the conductive paths when the solder layer is thick, and a connection may be difficult when the solder layer is thin. When the anisotropic conductive film 1 of the present invention is used for mounting a semiconductor element having a protective film formed of a resin such as polyimide around an electrode except for an end face of the electrode as described below, the average protrusion height is , Among the above ranges, especially 0.1
It is preferable to select from μm to 4 μm. The average projecting height of the projecting portion 4 is one of Z1 in the thickness direction of the film substrate 2.
Side and the other Z2 side may be the same, or may be different from each other within the above range. In the present invention, it is preferable that the protruding heights of the protruding portions on the same side are formed to be substantially the same.

As described above, the solder layer 6 in the present invention
Film surface 2a at an average protrusion height of 0.1 μm to 7 μm
Is formed at an end portion of the protruding portion 4 protruding from the film surface 2a farthest from the film surface 2a. Thereby, even if the same solder layer is formed, the solder layer does not protrude from the film surface (the end surface of the solder layer forms the same surface as the film surface, or is depressed from the film surface) 3) Unlike the case where an anisotropic conductive film is used, a reliable electrical connection can be easily performed with the solder layer 6 protruding from the film surface. As a result, even when compared with the above case, conditions such as pressure and time required for bonding can be relaxed, and therefore, damage when bonding the semiconductor element and the circuit board can be further suppressed.

The thickness of the solder layer 6 in the present invention is preferably from 0.1 μm to 5 μm, more preferably from 0.4 μm to 5 μm.
More preferably, it is 4 μm. The thickness of the solder layer 6 is 0.
When the thickness is less than 1 μm, metal bonding between the chip and the substrate electrode cannot be performed, and sufficient electrical conduction may not be obtained, which is not preferable. The thickness of the solder layer 6 is 5 μm.
If it exceeds m, the solder layer flows and a short circuit may occur between the conductive paths, which is not preferable. The thickness of each solder layer 6 is also different from one Z1 side and the other Z2 in the thickness direction of the film base 2.
And the same may be different from each other within the above range.

As described above, the amount of solder in the solder layer 6 is
By selecting the minimum necessary amount for the above-mentioned welding, it is possible to reliably prevent a problem that the solders of the solder layers 6 in the protruding portions 4 adjacent to each other are welded to each other to cause a short circuit when the solder is welded. Bonding of the semiconductor element 11 and the circuit board 12 with high connection reliability using welding can be realized.

In this specification, "semiconductor element"
It means a chip separated from the wafer. Such a chip is a kind of circuit including a semiconductor crystal layer and an electrode, which has a simple structure such as a light emitting element, a CPU, a memory, a processor in which various arithmetic circuits are integrated, and the like. Is mentioned. The chip may be a crystal substrate capable of growing a semiconductor crystal layer or the like, such as a sapphire crystal for growing a GaN-based semiconductor, in addition to a semiconductor crystal such as Si or GaAs.

Examples of the circuit board 12 include a package base for a semiconductor element and a general printed circuit board for mounting the semiconductor element on another device.

In FIG. 2, the semiconductor element 11 shows a bare chip state (a state of a bare chip including a passivation film), and the internal structure of the element is omitted. In addition, the circuit board 12 is shown with wirings on the surface of the board omitted for convenience.

The shape, size, and number of the cross section (cut perpendicular to the passage direction) of the conductive path 3 of the anisotropic conductive film 1 can be appropriately selected according to the electrode of the semiconductor element, but the pitch is 50 μm. In order to cope with the following fine pitch electrode arrangement pattern, the outer diameter is preferably 5 μm to 30 μm. As long as the above conditions are satisfied, the cross-sectional shape of the conduction path 3 may be any shape such as a circle or a polygon. When the size of one electrode of the semiconductor element is, for example, 100 μm × 100 μm, it is preferable that one electrode of the semiconductor element has a plurality of approximately 1 to 25 conductive paths. Further, the arrangement pattern of the conductive paths 3 when viewed from the film surface may be any of a close-packed shape, a square matrix-like shape, and a random dense state. preferable.

As described above, in the configuration in which the amount of solder in the solder layer 6 is minimized, the outer diameter of the conductive path is reduced in accordance with the fine pitch of the semiconductor element, and the number of conductive paths per unit area is reduced. This is particularly useful when using an anisotropic conductive film having an increased amount of. In this configuration, even when an anisotropic conductive film having a conductive path pitch (arrangement interval) of 25 μm or less is used, electrical conduction (short circuit) due to solder between adjacent conductive paths is reliably prevented. can do.

As a material for forming a conductive path of the anisotropic conductive film, a known conductive material can be cited, but a metal material such as copper, gold, aluminum, and nickel is preferable in terms of electric characteristics. In terms of properties, copper and gold are more preferable. The outer diameter of these metal conducting paths is 5 μm to 10 μm.
0 μm, preferably 12 μm to 30 μm.

Although the material of the conductive path 3 is as described above, various characteristics such as conductivity and elastic modulus are different depending on the method of forming the conductive path 3 even if the same metal material is used. The conducting path 3 may be obtained by depositing a metal material in a through-hole formed in the film base material by plating. preferable. Among the metal wires, for example, a metal copper wire manufactured to conduct electricity, such as a copper wire specified in JIS C 3103, is preferable, and is most excellent in terms of electrical characteristics, mechanical characteristics, and cost. It becomes a conduction path.

In order to obtain the above-mentioned metal wire penetrating the film substrate, a large number of insulated conductors formed by coating the conductors with a resin material are tightly bundled and fixed so that they cannot be separated from each other. Then, there is a method of slicing to a desired film thickness using a surface forming an angle with each insulated conductor as a cut surface. The anisotropic conductive film of such an embodiment and a method for producing the same are described in International Publication WO98 / 072.
16 "Anisotropic conductive film and method for producing the same".

Further, a plurality of blocks are cut out from a resin material bonded to each other by tightly winding an insulated conductive wire around a core material and heating, and in some cases, heating and pressurizing, and these are cut into a desired anisotropic conductive material. The anisotropic conductive film may be obtained from the joined product by appropriately stacking and joining them according to the size of the film.

The remaining portion of the projecting portion excluding the solder layer (hereinafter referred to as the
As a method of forming the “projecting conductive portion 7”, a conventionally known method of depositing a metal by plating or vapor deposition on the end surface of the conductive path 2 exposed on the film surface 2a can be used. Examples of such a metal material include copper, nickel, gold, palladium, and chromium.

Further, the protruding conductive portion 7 may be formed by performing etching on the film surface 2a where the end face of the conductive path 2 is exposed to selectively remove only the film base material. . As an etching method, a method such as wet etching, plasma etching, dry etching such as an argon ion laser and a KrF excimer laser can be used alone or in combination. The etching solution in wet etching is selected in consideration of the material of the film base material and the material of the conduction path,
For example, dimethylacetamide, dioxane, tetrahydrofuran, methylene chloride and the like can be mentioned.

In the present invention, a configuration in which only the solder layer protrudes from the film surface without forming the protruding conductive portion 7 (that is, a mode in which the solder layer itself is a protruding portion) may be used. From the viewpoint of securely and firmly performing the electrical joining of the above, it is preferable that the electrical connection is realized so as to have a projecting conductive portion.

The thickness of the anisotropic conductive film 1 in the present invention is preferably from 10 μm to 200 μm, and more preferably from 25 μm to 100 μm. The thickness is 10μ
If it is less than m, voids are generated at the time of connecting the chip and the substrate because the amount of resin is small, and there is a possibility that sufficient connection reliability may not be obtained, which is not preferable. On the other hand, if the thickness exceeds 200 μm, the conductive path may be inclined when connecting the chip and the substrate, which is not preferable.

The coefficient of linear expansion and the modulus of elasticity of the anisotropic conductive film affect the bonding properties (adhesive strength and conductivity) with the semiconductor element and the circuit board. The coefficient of linear expansion of the anisotropic conductive film differs between the thickness direction and the in-plane direction of the film.
The coefficient of linear expansion in the in-plane direction in the temperature range of ５０50 ° C. is preferably 10 ppm to 150 ppm, more preferably 1 ppm.
When the content is in the range of 0 ppm to 80 ppm, better bonding properties can be obtained. The coefficient of linear expansion is determined by thermomechanical analysis (T
MA) can be suitably measured using an apparatus.

The elastic modulus of the anisotropic conductive film is also different between the thickness direction and the in-plane direction of the film.
The elastic modulus in the in-plane direction in a temperature range of ° C is preferably 1
GPa to 5 GPa, more preferably 1 GPa to 4 GPa
Within this range, better adhesiveness can be obtained. Here, the linear expansion coefficient and the elastic modulus are values relating to the in-plane direction of the anisotropic conductive film (the direction in which the film surface expands) in a state where the conductive path has a solder layer at the tip. In addition, the said elastic modulus can be measured suitably using a dynamic viscoelasticity measuring device.

The factors that determine the elastic modulus of the entire structure of the anisotropic conductive film include the material of the conductive path, the cross-sectional shape and the total length of the conductive path, the density and pattern of the conductive path, and the like.
The material of the film base, the thickness of the film base, and the like.
What is necessary is just to select these elements and make it into the said elastic modulus range.

As the insulating resin used for the film substrate 2 of the anisotropic conductive film 1 in the present invention, various conventionally known resin materials can be used. In particular, polyester resin (softening point: 180 ° C to 220 ° C), polyamide resin (softening point: 150 ° C to 210 ° C), polycarbodiimide resin (softening point: 140 ° C to 180 ° C), phenoxy resin (softening point: 130 ° C) To 160.degree. C.), epoxy resin (softening point: 100.degree. C. to 150.degree. C.), and a material exhibiting adhesiveness when heated and pressed.

[0036] The softening point in the present specification is measured by thermomechanical analysis (TMA) under the following conditions.
The temperature at the inflection point of the chart. Mode: tensile mode, sample size: 4 mm width, distance between chucks: 10 mm, tensile load: 1 g, temperature rising rate: 1
0 ° C / min

In the anisotropic conductive film 1 of the present invention, as described above, only the solder layer 6 at the tip of the protruding portion 4 provides a sufficiently strong and high connection reliability between the semiconductor element and the circuit board. Can be joined. As described above, as the material of the film substrate 2, a resin material having an adhesive property when heated and pressed as described above is used, and the film substrate 2 is also joined to the solder layer 6 by bonding, whereby a semiconductor element is formed. And / or more secure and strong bonding to the circuit board is possible.

In the case where the above-mentioned joining is also performed using the film substrate 2, it is preferable to perform the following procedure. First, as shown in FIG. 2A, the semiconductor element 11, the anisotropic conductive film 1, and the circuit board 12 are arranged such that the solder layer 6 is in contact with the electrode 14 of the semiconductor element 11 and the electrode 13 of the circuit board 12. Align the 12 members.

Next, the above structure is heated at a temperature lower than the melting temperature of the solder, and in some cases, is heated and pressed. As a result, only the film substrate 2 is flow-solidified without flowing the solder of the solder layer 6, and the semiconductor element 11 and the circuit board 12 are bonded via the anisotropic conductive film. When the film substrate 2 is fluidized and solidified, the resin forming the film substrate 2 flows into the space between the protrusions 4 and solidifies. Thus, after the above-mentioned bonding, the solder layer 6 can be surrounded by the wall of the film substrate 2.

The heating temperature at the time of the above-mentioned bonding varies depending on the type of solder and the type of resin forming the film substrate, but is preferably 140 ° C. to 220 ° C., and more preferably 140 ° C. to 180 ° C. If the temperature is lower than 140 ° C., the semiconductor elements 11 and / or
Alternatively, the adhesive strength to the circuit board 12 may not be sufficiently obtained, which is not preferable. If the temperature exceeds 220 ° C., the solder may flow during the bonding, which is not preferable. In addition, when pressurizing with heating, the pressure is:
0.3 MPa to 3.0 MPa is preferable, and 0.5 MPa
-2.5 MPa is more preferable. The pressure is 0.3MPa
When the pressure is less than 3.0 MPa, it is not preferable because the adhesive strength cannot be expected to be improved by pressurization. When the pressure exceeds 3.0 MPa, collapse (inclination) of the conduction path occurs during the heat fusion. It is not preferable because there is a fear.

Next, by further heating, the solder layers 6 on the front side and the back side of the film are melt-bonded to the electrode 14 of the semiconductor element 11 and the electrode 13 of the circuit board 12, respectively. At this time, since the solder layer 6 at the end of each conduction path 3 is surrounded by the wall of the film base material 2, the solder layers adjacent to each other are melted and solidified without contact (fusion). To melt-bond to the electrode 14 of the semiconductor element 11 and the electrode 13 of the circuit board 12.

By using the anisotropic conductive film of the present invention and performing bonding by the above-described method, an electrically insulating state is maintained between adjacent conductive paths of the anisotropic conductive film, and A highly reliable semiconductor device in which a short circuit does not occur between electrodes and / or electrodes of a circuit board can be formed.

As a heating device used for bonding the film base of the anisotropically conductive film and melting and joining the solder layer, for example, an IR reflow device is used. In addition, as a heating / pressing device when the bonding of the film substrate is performed by heating and pressing, for example, in addition to an autoclave, a flip chip bonder, and the like, a pressing device (desired heating means (heater means, hot air blower, etc.)) Are added).

Usually, it is preferable to provide the solder layer at the ends of all the conductive paths protruding from the front and back surfaces of the anisotropic conductive film, but it is possible to obtain a sufficient bonding strength to a semiconductor element, a circuit board and the like. Therefore, as long as the desired conductivity can be obtained, it is not always necessary to provide a solder layer on all the conduction paths. For example, a solder layer may be provided only on one protruding portion, or a solder layer may be selectively provided only on a part of each protruding portion protruding from the same surface of the film.

When a solder layer is provided only on one end of the conductive path of the anisotropic conductive film on either the semiconductor element side or the circuit board side, the end of the conductive path on which the solder layer is not provided is connected to the semiconductor layer. An electrical conduction state is created by directly contacting the electrodes of the element or the electrodes of the circuit board.

[0046]

EXAMPLES The following semiconductor elements (chips), circuit boards and anisotropic conductive films were prepared. Chip: a silicon chip 11 having an outer shape of 8 mm × 8 mm and a thickness of 300 μm, as shown in FIGS. 3A and 3B, a silicon base layer 15, a 1 μm thick silicon nitride layer 16 on a circuit forming surface, and 3 μm thick polyimide layer 17
Are laminated. The size of the electrode pad 14 is 100 μ
The electrode pad arrangement is mx100 μm, and the electrode pad array is arranged on the periphery of the chip 11 at a pitch of 200 μm. The surface of the pad 14 is subjected to Ni / Au plating and has the same height as the polyimide layer 17. Circuit board: A wiring pattern having a thickness of 15 μm is formed on a polyimide having an outer shape of 40 mm × 40 mm and a thickness of 25 μm, and the surface of the wiring pattern is subjected to Ni / Au plating. Anisotropic conductive film: A conductive path (outer diameter: 0.03 mm copper wire) is formed on a 70 μm thick film base made of polycarbodiimide resin, which is prepared by the method described later, and has a thickness of 50 μm.
8.2mm ×
Solder (Sn) to the end of the copper wire exposed from the film surface of the 8.2 mm anisotropic conductive film by electroless plating.
What formed a layer. Height of protrusion: 3 μm, thickness of solder layer: 2 μm, linear expansion coefficient in the in-plane direction in a temperature range of 30 ° C. to 50 ° C .: 73.3 ppm (Thermo-mechanical analyzer (T
MA / SS100, measured by Seiko Instruments Inc.), in-plane elastic modulus in a temperature range of 25 ° C. to 40 ° C .: 3.4 GPa (dynamic viscoelasticity measuring device (D
MS210, manufactured by Seiko Instruments Inc.).

[Method of producing anisotropic conductive film] Outer diameter 30 μm
m of polycarbodiimide resin (softening point: 6)
5 [deg.] C.) to form a coating layer having a thickness of 25 [mu] m and producing an insulated wire having a total outer diameter of 55 [mu] m. The insulated wire was wound with a winding device to have a total length (winding width) of 210 mm and a cross-sectional shape of 160 mm * 160 mm. Is wound around the square prism plastic core material in a close-packed manner, and the average number of windings per layer is 98.5 turns and the number of winding layers is 130 (=
Layer thickness: about 15 mm) to form a wound coil,
While heating the wound coil to about 130 ° C, 0.94
Pressurized with MPa to fuse the polycarbodiimide resin,
After cooling to room temperature, a wound coil block in which the wound wire was integrated was obtained. The core material is removed from the wound coil block to make a square tube, which is 80 mm x 30 mm x 15 mm
Cut into rectangular parallelepiped blocks. This cuboid block,
A laminate in which five wires are stacked so that they are in the same direction,
While heating to about 160 ° C., pressurizing at 1.96 MPa, 8
A composite block of 0 mm × 30 mm × 75 mm was obtained. This block was sliced to obtain an anisotropic conductive film having a size of 80 mm × 75 mm and a thickness of 0.070 mm.

First, the above-mentioned circuit board was adsorbed on a stage heated to 150 ° C., and then the above-mentioned chip was adsorbed on a flip chip bonder (manufactured by Shibuya Kogyo). After aligning the chip and the circuit board,
An anisotropic conductive film is placed on a circuit board, and the pressure is set to 0.
The bonding was performed by heating and pressing under the conditions of 49 MPa, a temperature of 335 ° C., and a time of 30 seconds.

The initial connection resistance value of the sample of the embodiment manufactured by the above method immediately after the bonding was 1.5 mΩ. After measuring the resistance value, the sample was set in a pressure cooker, the temperature was set to 121 ° C. and the humidity was set to 100%, and a connection reliability test was performed. There was little change. It has been found that the production method of the present invention is sufficiently useful.

Comparative Example For comparison with the example, the same anisotropic conductive film was used as in the example except that the end face of the solder layer did not protrude from the film surface, and bonding was performed under the same conditions. The resistance value was 4 mΩ. Using the sample of this comparative example,
A connection reliability test was performed using a pressure cooker device in the same manner as in the example, but peeling occurred between the chip and the anisotropic conductive film, and conduction could not be confirmed.

[0051]

As is apparent from the above description, according to the present invention, at least between the electrodes with the semiconductor element and / or between the electrodes with the circuit board can be easily and firmly joined with high reliability. In addition, it is possible to provide an anisotropic conductive film that can minimize damage to the semiconductor element and the circuit board during this bonding.

[Brief description of the drawings]

FIG. 1 shows a preferred example of an anisotropic conductive film 1 of the present invention.
FIG.

FIG. 2 is a simplified diagram showing an example of joining a semiconductor element 11 and a circuit board 12 using the anisotropic conductive film 1 of the present invention shown in FIG.

FIG. 3 is a simplified diagram showing an example of a semiconductor element 11 bonded to a circuit board using the anisotropic conductive film 1 of the present invention. FIG. 3 (a) is a front view, and FIG. b) is an enlarged sectional view.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Anisotropic conductive film 2 Film base material 3 Conductive path 4 Projecting part 5 Part of conductive path in film base (conductive part in base material) 6 Solder layer 7 Projecting conductive part

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Yuji Hotta 1-2-1, Shimohozumi, Ibaraki-shi, Osaka Nitto Denko Corporation F-term (reference) 5E085 BB08 BB28 DD01 EE15 FF19 GG12 HH01 JJ06 JJ31 JJ35 JJ38 5F044 LL04 LL09 LL13

Claims (4)

[Claims] 1. A film base made of an insulating material, and a plurality of conductive bases which are insulated from each other in the film base, are arranged in an axis direction substantially parallel to a thickness direction of the film base, and penetrate therethrough. A conductive path, wherein the conductive path has a protrusion protruding from the film substrate surface on at least one side in the axial direction, and the protrusion has a thin-film solder layer at its tip. Anisotropic conductive film. 2. The projecting portion has an average projecting height of 0.1 μm or less.
The anisotropic conductive film according to claim 1, wherein the thickness is 7 μm. 3. The anisotropic conductive film according to claim 1, wherein the thickness of the solder layer is 0.1 μm to 5 μm. 4. The anisotropic conductive member according to claim 1, wherein the conductive path includes a projecting portion projecting from both surfaces of the film substrate, and the projecting portion has a thin-film solder layer at an end thereof. Conductive film.