JPH11326935A - Anisotropic conductive film and its connection method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to join one member to be connected formed with a two-stage projection connecting member and another member to be connected with high joining reliability. SOLUTION: The anisotropic conductive film 20 has ball bumps 2 formed to two stages of projections on at least one member to be connected and is formed by electrically connecting and mechanically fixing the two opposite members 1 to be connected. The film 20 has an insulating layer 3 formed of a resin having insulatability and adhesiveness and a particle layer 4 dispersed and arranged with many conductive particles for effecting electrical conduction into the resin having the insulatability and adhesiveness. The insulating layer 3 and the particle layer 4 are laminated and are formed like a film. The thickness of the particle layer 4 is formed lower than the amt. of the projection constituting the step at the front end of the ball bump 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an LCD (Liquor).
The present invention relates to an anisotropic conductive film used as a connecting agent between an id Crystal Display (liquid crystal display) and a flexible substrate, and a method for connecting the anisotropic conductive film.

[0002]

2. Description of the Related Art Anisotropic conductive films used as conductive connecting agents-Anisotropic Conductu
live Film- (hereinafter, referred to as “ACF”)
Is a conductive film in which metal-coated plastic particles and metal particles are dispersed in a resin such as a thermosetting resin, and is widely used for electrical connection between electronic components and substrates by utilizing its anisotropic conductivity and adhesiveness. Have been.

[0003] A conventional ACF and ACF connection technology will be described below. Here, FIG. 4 is a cross-sectional view showing a conventional ACF, FIG. 5 is a process diagram continuously showing a mounting process by the ACF of FIG. 4, and FIG. 6 is a process of forming a ball bump (two-step projection connecting member) on a semiconductor chip. 7 is a comparative view showing the configuration of plated bumps and ball bumps formed on a semiconductor chip, and FIG. 8 is a view showing a semiconductor chip on which ball bumps are formed.
It is sectional drawing which shows the state connected to the printed circuit board by F.

First, the configuration of the ACF will be described with reference to FIG. As described above, the ACF 6 is an adhesive film in which conductive particles 5 such as metal-coated plastic particles and metal particles are dispersed and arranged in an adhesive 7 having both insulating properties and adhesiveness such as a thermosetting resin. Further, from the relationship between the filling amount of the conductive particles 7 in the ACF 6 and the conductivity, the conductivity with respect to the filling amount of the conductive particles in the ACF 6 has anisotropy. In other words, the ACF 6 has a feature that it has high conductivity in the thickness direction, but has high insulating properties in the plane direction because the conductive particles 5 are isolated from each other.

Next, a process for connecting the conventional semiconductor chip 1 to the printed wiring board 8 using the ACF 6 will be described with reference to FIG.

First, using the temporary mounting tool 9, the printed wiring board 8 and the ACF 6 which are one of the members to be connected are temporarily compressed by applying heat and a load (5 sec at about 80 ° C., several tens g / bump). (FIG. 5 (a)).

Next, in the chip final step, the semiconductor chip 1, which is the other connection target member on which the gold plating bumps 10 are formed, is positioned on the chip mounting portion of the printed circuit board 8 to which the ACF 6 has been temporarily pressed, and heat is applied. Temporarily mount only by applying load without applying. The plating bump 10 is made of, for example, Pt, N as a barrier metal for preventing formation of an intermetallic compound, such as Ti, Cr, etc., as a connection metal under the plating.
i, Cu and the like are laminated, and a bump is formed on the uppermost layer by gold plating (FIG. 5B).

[0008] Finally, a heating tool 11 for thermocompression bonding
Is applied (approximately 200 ° C., 20 sec, several tens g / bump) to perform the final pressure bonding. At this time, while the adhesive 7 in the ACF 6 is melted by heating and pressing, it flows out from between the patterns of the plating bumps 10 and the printed circuit board 8 (FIG. 5C), and the dispersed conductive particles 5 are plated. Electrical continuity is obtained by being captured between the bumps 10 and the pattern of the printed circuit board 8. The mechanical contact between the conductive particles 5 and the plating bumps 10 and the mechanical contact between the conductive particles 5 and the pattern of the printed circuit board 8 are ACF.
6 is held by the curing shrinkage force of the adhesive 7 and the high adhesive force of the adhesive (FIG. 5D).

Here, as described above, most of the bumps are formed by plating in the current ACF bonding. However, recently, because of low cost and high versatility, the use of ball bumps (two-step projection connection members) 2 formed by the process shown in FIG. 6 has been increasing.

In a specific process for forming the ball bump 2, first, an initial ball 13 is formed at a tip of a gold wire 12 protruding from a capillary 14. Next, the initial balls 13 are bonded to the electrodes on the semiconductor chip 1 by applying an ultrasonic wave, a load and a temperature. Then, the capillary 14 is pulled up and the gold wire 1
Cut 2 Finally, the ball tip 2 is formed by pressing the cut end against a flat plate.

However, such a ball bump 2
There are several problems in realizing ACF bonding with the above. That is, as shown in FIG. 7, unlike the plating bump 10,
Due to the nature of the ball bump 2 having a two-stage shape, there is a problem that the bonding area with the semiconductor chip 1 is reduced.
This leads to a decrease in the number of conductive particles 5 involved in the electrical connection essential for ensuring the reliability of the ACF junction, causing a decrease in reliability.

In the future, as the pattern pitch of the printed circuit board 8 becomes narrower as the pattern pitch becomes narrower, the possibility of short-circuit between the patterns due to the conductive particles 5 is increased as shown in FIG. Come out.

Here, if the number of conductive particles 5 in the ACF 6 is reduced to avoid the problem of insulation failure, the shape of the ball bump 2 is reduced in size due to the further narrowing of the pitch, that is, the joint area is reduced. As a result, a vicious cycle occurs in which the number of trapped particles at the joint that maintains the joint reliability of the ACF 6 is reduced, and the reliability is reduced.

[0014]

As described above, the conventional A
In a CF, when a semiconductor chip is mounted on a printed circuit board using ball bumps, the joint area is reduced due to the reduction of the joint area due to the two-step projection structure of the ball bump and the narrower pattern pitch, that is, the joint area. Due to the miniaturization of the ACF, the number of conductive particles in the joint that maintains the joint reliability of the ACF is reduced, and the joint reliability is reduced.

[0015] In addition, due to the narrow space between the bumps due to the narrow pitch, there arises a problem of poor insulation such as short between bumps due to conductive particles. When the number of conductive particles in the ACF is reduced in order to avoid the problem of the poor insulation property, the number of conductive particles in the joint that maintains the joint reliability of the ACF is further reduced, and the reliability is reduced. become.

Accordingly, the present invention provides an anisotropic conductive film capable of joining one connection target member formed with a two-step projection connection member and the other connection target member with high joining reliability. It is intended to provide a connection method.

[0017]

In order to solve this problem, an anisotropic conductive film according to the present invention has at least one member to be connected having a two-stage projection connecting member formed in a two-stage projection. Anisotropically conductive film that electrically connects and mechanically fixes two opposing connection target members,
An insulating layer formed of a resin having an insulating property and an adhesive property,
Having a particle layer in which a large number of conductive particles that electrically conduct in a resin having an insulating property and an adhesive property are dispersed and arranged, and the insulating layer and the particle layer are laminated and formed into a film shape. The thickness of the particle layer is set to be equal to or less than the amount of protrusion forming the step at the tip of the two-step projection connecting member.

Thus, it is possible to join one connection target member having the two-step projection connection member and the other connection target member with high joining reliability.

Further, the method for connecting an anisotropic conductive film according to the present invention is characterized in that an insulating layer formed of a resin having an insulating property and an adhesive property is electrically connected to a resin having an insulating property and an adhesive property. Using an anisotropic conductive film having a particle layer in which a large number of conductive particles are dispersed and arranged, at least one of the connection target members has a two-stage protrusion connection member formed in two-stage protrusions, and A method for connecting an anisotropic conductive film that electrically connects and mechanically fixes two connection target members to be connected, wherein the connection target member having a two-step projection connection member and an insulating layer of the anisotropic conductive film are connected. It is arranged so as to face each other, and heats and presses the anisotropic conductive film via the connection target member to electrically connect and mechanically fix the two opposing connection target members. Is what you do.

[0020] Thus, it is possible to join one connection target member formed with the two-step projection connection member and the other connection target member with high joining reliability.

Furthermore, the method for connecting an anisotropic conductive film according to the present invention is characterized in that an insulating layer formed of a resin having an insulating property and an adhesive property is electrically connected to a resin having an insulating property and an adhesive property. Using an anisotropic conductive film having a particle layer in which a large number of conductive particles are dispersed and arranged, at least one of the connection target members has a two-stage protrusion connection member formed in two-stage protrusions, and A method for connecting an anisotropic conductive film that electrically connects and mechanically fixes two connection target members to be connected, wherein the connection target member having a two-step projection connection member and an insulating layer of the anisotropic conductive film are connected. Heating and pressing the anisotropic conductive film via the connection target member so as to electrically connect and mechanically fix the two opposing connection target members. Reduce the thickness of the particle layer of the conductive film Formed to be equal to or less than the amount of protrusion constituting the step of the tip of the step projection connection member, or alternatively, the amount of protrusion constituting the step of the tip of the two step projection connection member to be equal to or greater than the thickness of the particle layer of the anisotropic conductive film It is characterized by having been formed.

Thus, it is possible to join one connection target member having the two-step projection connection member and the other connection target member with high joining reliability.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS According to the first aspect of the present invention, at least one connection target member has a two-stage projection connection member formed in a two-stage projection, and two opposing connection target members are provided. Is an anisotropically conductive film that electrically connects and mechanically fixes the insulating layer, the insulating layer formed of a resin having an insulating property and an adhesive property, and an electric insulating film formed of a resin having an insulating property and an adhesive property. A particle layer in which a large number of conductive particles for electrically conducting are dispersed and arranged, an insulating layer and a particle layer are laminated to form a film, and the thickness of the particle layer is a two-step projection connecting member. An anisotropic conductive film characterized by being formed not more than the amount of protrusion that constitutes the step of the tip of the one, and the one to be connected and the other to be connected where the two-step projection connection member is formed It is possible to join with high joining reliability Having an iodine.

Further, the invention according to claim 2 of the present invention provides:
An insulating layer formed of a resin having an insulating property and an adhesive property,
Using an anisotropic conductive film having a particle layer in which a large number of conductive particles that electrically conduct in a resin having an insulating property and an adhesive property are dispersed and arranged, at least one member to be connected is a two-stage member. A method of connecting an anisotropic conductive film having a two-stage projection connection member formed on a projection, electrically connecting and mechanically fixing two opposing connection target members, wherein the two-stage projection connection member is The member to be connected and the insulating layer of the anisotropic conductive film are disposed so as to face each other, and the two members to be connected are electrically heated by heating and pressing the anisotropic conductive film via the member to be connected. A method for connecting an anisotropic conductive film, characterized in that it is connected and mechanically fixed, wherein one connection target member formed with a two-step projection connection member and the other connection target member have high bonding reliability. Can be joined under It has the effect of becoming.

The invention described in claim 3 of the present invention particularly provides
The invention according to claim 2, wherein the relationship between the thickness of the particle layer of the anisotropic conductive film and the amount of protrusion forming the step at the tip of the two-step projection connecting member is specified. A method for connecting an anisotropic conductive film, wherein a thickness of a layer is formed to be equal to or less than a protrusion amount constituting a step at a tip portion of a two-step projection connection member, wherein the two-step projection connection member is formed. This has the effect that it becomes possible to join the member to be connected and the other member to be connected with high joining reliability.

The invention described in claim 4 of the present invention particularly provides
The relationship between the thickness of the particle layer of the anisotropic conductive film and the amount of protrusion forming the step at the tip of the two-step projection connecting member is specified. A method for connecting an anisotropic conductive film, characterized in that the projecting amount constituting the step of the portion is formed to be equal to or greater than the thickness of the particle layer of the anisotropic conductive film, wherein the two-step projection connecting member is formed. This has the effect that it becomes possible to join the member to be connected and the other member to be connected with high joining reliability.

Hereinafter, an embodiment of the present invention will be described with reference to FIG.
This will be described with reference to FIG. In these drawings, the same members are denoted by the same reference numerals, and duplicate description is omitted.

FIG. 1 shows an ACF according to an embodiment of the present invention.
FIG. 2 is a cross-sectional view showing two members to be joined together, and FIG.
FIG. 3 is an explanatory diagram showing the configuration of the ACF that has led to the ACF of FIG. 2, and FIG. 3 is an explanatory diagram showing the state of electrical connection by the ACF of FIG.

As shown in FIG. 1, the ACF according to the present embodiment
Numeral 20 electrically and mechanically connects the two connection target members, that is, the semiconductor chip 1 and the printed circuit board 8, and includes an insulating layer 3 and a particle layer 4 having a laminated structure together with the insulating layer 3. I have.

Here, the insulating layer 3 is made of, for example, an epoxy resin having an insulating property and an adhesive property. Further, the particle layer 4 has an insulating property and an adhesive property. For example, it is composed of a number of conductive particles 5 dispersed in an epoxy resin. As the conductive particles 5, for example, metal-coated plastic particles or metal particles are used. Note that the resin of the insulating layer 3 and the particle layer 4 is not limited to an epoxy resin, and may be a thermosetting or thermoplastic resin. Then, the material of the resin of the insulating layer 3 and the material of the resin of the particle layer 4 may be different.

When the ACF 20 is pressed in the film thickness direction, the conductive particles 5 are bonded to each other by the pressing force,
These cooperate to generate electrical conduction only in the film thickness direction.

Note that a ball bump (two-step projection connection member) 2 as a two-step projection connection member formed on a two-step projection is formed on the semiconductor chip 1 as one connection target member. Here, as the material of the ball bump 2, gold, aluminum, or the like can be used. An electrode 8a is formed on the printed circuit board 8, which is the other member to be connected. Here, the substrate of the printed circuit board 8 is made of, for example, ceramic. The electrode 8a is made of, for example, copper or tungsten, and is preferably subjected to a surface treatment by gold plating.

When pressure is applied to the ACF 20 so that the insulating layer 3 of the ACF 20 is directed toward the semiconductor chip 1 on which the ball bumps 2 are formed and the particle layer 4 is directed toward the printed circuit board 8 on which the electrodes 8a are formed, the ball is pressed. Bump 2 and electrode 8
is electrically connected, and the semiconductor chip 1 and the printed circuit board 8 are mechanically connected.

As shown in the figure, the thickness of the particle layer 4 of the ACF 20 is t1, the total thickness is t2, and the tip of the ball bump 2 (ie, the side closer to the printed circuit board 8 which is the member to be connected) is projected. The amount is t3, and the total protrusion amount is t4
In this case, the thickness t1 of the particle layer 4 is equal to or smaller than the protrusion amount t3 of the tip.

Here, the reason why the ACF 20 has the two-layer structure including the insulating layer 3 and the particle layer 4 as described above will be described with reference to FIGS.

In FIG. 2, in the adjacent ball bumps 2, the distance between the bump bases is G1 and the distance between the tip ends is G2.
, The relationship of G2> G1 is established. Therefore, if it is attempted to increase the number of particles involved in bonding by increasing the number of conductive particles 5 in the ACF 6, G1
The occurrence rate of short-circuits in the part increases. In contrast,
The G2 section has a larger space than the G1 section, so that the short-circuit occurrence rate is inevitably reduced.

In such bonding of the ACF 6, in FIG. 3, first, the ACF 6 starts to melt from the ball bump 2 side, that is, the semiconductor chip 1 side by tool heating. Then, the conductive particles 5 located below the ball bump 2 are pushed out to the periphery of the ball bump 2 by the pressure. As heating and pressurization further progress, the printed board 8 side begins to melt, and the conductive particles 5 are similarly pushed out to the periphery of the ball bump 2. And finally, the printed circuit board 8
When the closest conductive particles 5 begin to flow, these conductive particles 5 are pressed between the ball bump 2 and the printed board 8 by pressurization.

Therefore, the conductive particles 5 involved in the bonding are the conductive particles 5 located closest to the printed circuit board 8 side, and most of the conductive particles 5 on the semiconductor chip 1 side flow during the bonding. Therefore, it is not involved in joining.

If so, as shown in FIG. 1, an insulating layer 3 containing no conductive particles 5 is formed in a portion which hardly participates in the bonding.
Is formed, and a particle layer 4 containing the conductive particles 5 is formed in a portion involved in the bonding. In such a two-layer structure, the thickness t1 of the particle layer 4 including the conductive particles 5 is set to be equal to or less than the protrusion amount t3 of the tip of the ball bump 2.

The ACF 20 controls the thickness of the particle layer 4 corresponding to each of the ball bumps 2 having a different shape.

With the ACF 20 having such a configuration, it is possible to maintain high insulation properties in the G1 portion where the short-circuit occurrence rate is high.

In the particle layer 4 containing the conductive particles 5, the ACF 6 composed only of the layer containing the conductive particles 5 shown in FIG.
Since the conductive particles 5 are agglomerated, the number of conductive particles 5 involved in bonding is improved. For example, 50 μm thick,
When the ACF 20 having 40,000 conductive particles / mm ² has a two-layer structure having a particle layer thickness of 25 μm including the conductive particles 5 and an insulating layer thickness of 25 μm not including the conductive particles 5, the number of conductive particles in a portion involved in bonding is obtained. Is doubled. In addition, when a two-layer structure having a particle layer thickness of 18 μm including the conductive particles 5 and an insulating layer thickness of 32 μm not including the conductive particles 5 is used, the number of conductive particles in a portion involved in bonding is approximately tripled. Therefore, it is possible to increase the number of conductive particles 5 involved in bonding without increasing the number of entire conductive particles 5.

At this time, there is a concern that the number of particles in the particle layer 4 containing the conductive particles 5 may increase, thereby deteriorating the insulating property of the G2 portion. The number of conductive particles 5 does not change regardless of the state or the two-layer structure, and since the ACF 20 flows by heat at the time of joining, the conductive particles 5 flow entirely without collecting only in the G2 portion. Therefore, it is possible to obtain good reliability with respect to insulation. Furthermore, the problem of the reduction in the number of conductive particles at the joint due to the narrowing of the pitch is also a problem with the conductive particles 5.
The problem can be solved without increasing the number.

Thus, the semiconductor chip 1 which is one of the connection target members having the two-step projection connection member and the printed board 8 which is the other connection target member can be joined with high joining reliability. Will be possible.

Although the above description is for controlling the thickness of the particle layer 4, it is possible to cope with any thickness of the particle layer 4 including the conductive particles 5 of the ACF 20 having a two-layer structure. For this purpose, the conditions for forming the ball bump 2 are controlled. At this time, the protrusion amount of the tip of the two-step projection of the ball bump 2 is processed to be equal to or larger than the thickness of the particle layer 4 of the two-layer structure ACF 20.

More specifically, the adjustment is performed by controlling the flattening load in the flattening process in order to adjust the height variation and the shape of the tip of the ball bump 2, or by controlling the shape using a capillary (FIG. 6). reference). Thereby, the number of particles trapped at the joint portion relating to the joint reliability is sufficiently ensured without being influenced by the thickness of the particle layer 4 in the two-layered ACF 20, the insulation reliability is improved, and the joint reliability is improved. It becomes possible.

[0047]

As described above, according to the present invention, one connection target member having the two-step projection connection member and the other connection target member can be joined with high joining reliability. An effective effect that it becomes possible is obtained.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an ACF according to an embodiment of the present invention together with two members to be joined.

FIG. 2 is an explanatory diagram showing the configuration of an ACF that led to the ACF of FIG. 1;

FIG. 3 is an explanatory diagram showing a state of electrical connection by the ACF of FIG. 2;

FIG. 4 is a sectional view showing a conventional ACF.

5 is a process chart continuously showing a mounting process by the ACF in FIG. 4;

FIG. 6 is a process chart continuously showing a process of forming a ball bump (two-step projection connection member) on a semiconductor chip.

FIG. 7 is a comparative diagram showing a configuration of a plated bump and a ball bump formed on a semiconductor chip;

FIG. 8 shows a semiconductor chip on which ball bumps are formed.
Sectional view showing the state connected to the printed circuit board by the ACF shown in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Semiconductor chip (connection target member) 2 Ball bump (two-step projection connection member) 3 Insulating layer 4 Particle layer 5 Conductive particle 8 Printed wiring board (connection target member) 20 Anisotropic conductive film (ACF)

Claims (4)

[Claims] At least one connection target member has a two-stage projection connection member formed in a two-stage projection, and electrically connects and mechanically fixes two opposing connection target members. An electrically conductive film, in which an insulating layer formed of a resin having an insulating property and an adhesive property, and a large number of conductive particles electrically conducting in a resin having an insulating property and an adhesive property are dispersedly arranged. A particle layer, wherein the insulating layer and the particle layer are laminated to form a film, and the thickness of the particle layer is a protrusion amount constituting a step at a tip end of the two-step projection connection member. An anisotropic conductive film formed below. 2. An insulating layer formed of a resin having an insulating property and an adhesive property, and a particle layer in which a large number of conductive particles for electrically conducting the resin having an insulating property and an adhesive property are dispersed. Using an anisotropic conductive film having, at least one connection target member has a two-step projection connection member formed in a two-step projection, and electrically connects two opposing connection target members and A method for connecting an anisotropic conductive film that is mechanically fixed, wherein the connection target member having the two-step projection connection member and the insulating layer of the anisotropic conductive film are arranged to face each other, A method of connecting an anisotropic conductive film, comprising heating and pressing the anisotropic conductive film via a member to electrically connect and mechanically fix two opposing connection target members. . 3. The anisotropically conductive film according to claim 2, wherein the thickness of said particle layer of said anisotropic conductive film is formed to be equal to or less than a projection amount which constitutes a step at a tip portion of said two-step projection connection member. Connection method for conductive film. 4. The projection according to claim 2, wherein the projection amount forming the step at the tip of the two-step projection connection member is formed to be greater than the thickness of the particle layer of the anisotropic conductive film. Connection method for conductive film.