JP2805948B2 - Connection structure of IC chip - Google Patents

Description

The present invention relates to an IC chip connection structure.

[Prior art] As the most common method of connecting an IC chip to a substrate,
There is a method by soldering. In recent years, the pitch of the bump portion has been reduced in accordance with the improvement in the integration degree of the IC chip, and the soldering method has been considerably advanced in response to this demand. With the latest equipment and careful attention, soldering can be applied to connections with a pitch of about 200 μm. In this connection structure by soldering, it is necessary to fill a sealing resin between the IC chip and the substrate to protect the joint portion between the bump portion and the connection terminal and ensure the joint strength after the joint. However, since the gap between the IC chip and the substrate is very small with the amount of protrusion of the bump (about 20 to 30 μm), bubbles are mixed in when the sealing resin is poured, and the sealing resin is reliably filled. There is a problem that you can not.

Therefore, conventionally, a method of connecting an IC chip and a substrate using an anisotropic conductive adhesive has been studied. The anisotropic conductive adhesive is obtained by dispersing and mixing conductive fine particles in an insulating adhesive. When connecting an IC chip to a substrate using this anisotropic conductive adhesive, the anisotropic conductive adhesive is applied not only on the connection terminals of the substrate but also on the substrate between the connection terminals.
Then, when the connection terminals of the substrate and the bumps of the IC chip are thermocompression-bonded with an anisotropic conductive adhesive therebetween, the connection terminals of the substrate are
The insulating adhesive and the conductive fine particles interposed between the bumps of the IC chip flow between the connection terminals, and the connection terminals of the substrate and the bumps of the IC chip directly contact the conductive fine particles. At this time, as long as the conductive fine particles are sufficiently separated and dispersed so as not to conduct with each other, adjacent connection terminals or adjacent bump portions will not be short-circuited. In other words, the anisotropic conductive adhesive has conductivity in the thickness direction in the joined state, but exhibits insulating properties in the plane direction, and is an adhesive having a directional conductivity. Therefore, in the connection structure using the anisotropic conductive adhesive, when the anisotropic conductive adhesive is applied on the connection terminals of the substrate, no alignment is required, so that the connection can be efficiently performed, and the connection can be performed efficiently. Since the insulating adhesive is interposed between the terminals, the bonding strength can be secured without filling the sealing resin after the bonding.

[Problems to be Solved by the Invention] In the connection structure of the IC chip using the anisotropic conductive adhesive described above, the anisotropic conductive adhesive has conductivity in the thickness direction,
It is an absolute condition to exhibit insulation in the plane direction. In order to have conductivity in the thickness direction, at least one (only theoretically) one conductive fine particle needs to be interposed between the connection terminal of the substrate and the bump portion of the IC chip. In order to exhibit insulating properties in the plane direction, it is ideal that each conductive fine particle is separated from an adjacent conductive fine particle by an insulating adhesive so as to be electrically disconnected. Assuming that the adjacent conductive fine particles happen to be insulated from the adjacent connection terminal or the adjacent bump portion, conduction between the conductive fine particles is allowed only under that condition. However, there is no guarantee that such conductive fine particles are insulated from adjacent connection terminals or bumps. Therefore,
It is necessary that any conductive fine particles have a structure that does not conduct with adjacent conductive fine particles.

However, in the anisotropic conductive adhesive, the distance between the conductive fine particles dispersed in the insulating adhesive is determined only by stirring. Therefore, the distribution of the conductive fine particles is, of course, not uniform and has a dense portion and a sparse portion. Therefore, the conductive fine particles do not conduct with each other even in a dense part, and one or more conductive fine particles must be positioned for one connection terminal or one bump part even in a sparse part. Conditions arise.

With the fine pitch of the connection terminals and the bumps, it becomes difficult to satisfy the above-described conditions in proportion to the narrowing of the widths of the connection terminals and the bumps. The number of conductive fine particles located between one connection terminal and the bump portion decreases as the connection terminal and the bump portion become narrower. In order to avoid this, by increasing the number of conductive fine particles located between the connection terminal and the bump portion and increasing the ratio of the conductive fine particles mixed in the insulating adhesive, the conductivity of dense portions can be improved. The density of the fine particles is further increased. This, needless to say, the dense portion of the conductive fine particles fills between the narrow connection terminals and short-circuits the circuit.

Because of this structure and function, the connection structure of the IC chip using an anisotropic conductive adhesive can be applied to the case where the pitch of the connection terminals and bumps is about several times the diameter of the conductive fine particles. Nevertheless, in reality, this was far from it. As an example, when conductive fine particles having a diameter of about 10 to 20 μm are used, the limit of the connection terminal pitch is 200 to 300 μm.
As far as this connection structure is concerned, the application is theoretically impossible when the pitch of the connection terminals or bumps is smaller than the diameter of the conductive fine particles.

The present invention has been made in view of the above-described circumstances, and an object thereof is applicable to a case where the pitch of the bump portion and the connection terminal is much smaller than before.
IC with excellent connection reliability and sufficient bonding strength
An object of the present invention is to provide a chip connection structure.

[Means for Solving the Problems] The means of the present invention are as follows.

The fine particles for connection, in which the outer peripheral surface of the fine conductive particles is covered with a resin layer composed of a large number of insulating fine powders, are mixed in an insulating adhesive to form a conductive binder. An agent is interposed between the IC chip and the substrate, and each bump portion of the IC chip and each connection terminal of the substrate are thermocompression-bonded, so that the connection fine particles located between the bump portion and the connection terminal A portion in the thickness direction of the resin layer is destroyed, and a portion in the plane direction remains, and the conductive fine particles of the connection fine particles connect each bump portion of the IC chip to each connection terminal of the substrate. .

[Operation] The operation of the present invention is as follows.

The fine particles for connection of the conductive binder are mixed at a high density into the insulating adhesive because the outer peripheral surface of the conductive fine particles is covered with a resin layer composed of a large number of insulating fine powders. Also do not conduct with each other. In addition, since the connection fine particles are broken in the thickness direction of the resin layer by thermocompression bonding and the surface direction portions remain, the adjacent connection fine particles in the bonding state of the bump portion of the IC chip and the connection terminal of the substrate are removed. Even if they come into contact with each other, the conductive fine particles do not conduct with each other. Therefore, in the connection structure using the conductive bonding agent, even if the pitch between the bumps and the connection terminals is much finer than before, the connection between the bumps and the connection terminals can be made without short-circuiting the adjacent bumps or connection terminals. Terminals can be securely connected, and connection reliability is extremely high. In addition, since the IC chip and the substrate are bonded with an insulating adhesive, sufficient bonding strength can be secured without filling with a sealing resin or the like.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows a connection structure in which an IC chip is connected to a liquid crystal display panel. In the liquid crystal display panel 1, transparent electrodes 4 and 5 made of ITO (Indium Tin Oxide) or the like are formed on opposing surfaces of a pair of upper and lower glass substrates 2 and 3, and a sealing material 6 is provided between the transparent electrodes. The liquid crystal 7 is sealed. In this case, of the upper and lower glass substrates 2, 3, the lower glass substrate 3 is formed larger than the upper glass substrate 2, and is provided to protrude rightward of the upper glass substrate 2. On the upper surface of the protruding portion of the lower glass substrate 3, connection terminals 8 are arranged and formed over almost the entire area in the width direction. The connection terminals 8 are made of the same material as the transparent electrodes 4 and 5, and are connected to the transparent electrodes 4 and 5, respectively. In addition, a part of the connection terminal 8 is simply extended to the right end side of the glass substrate 3. IC chip 9 has transparent electrodes 4
A drive signal is supplied to the lower surface 5, and a large number of bump portions 10 (only two are shown in the figure, but there are actually many) are arranged at predetermined intervals on the lower surface. In this case, the bump
Numeral 10 is formed as a straight bump protruding straight from the lower surface, and its lower end surface is formed as a flat surface. The bumps 10 of the IC chip 9 and the connection terminals 8 of the liquid crystal display panel 1 are connected to the IC chip 9 and the liquid crystal display panel 1 by a conductive bonding agent 11.

FIG. 2 shows the structure of the conductive binder 11. Conductive binder
Reference numeral 11 denotes a conductive fine particle formed by forming a conductive film 13 on the surface of the insulating fine particle 12 and covering the outer peripheral surface of the conductive fine particle conductive film 13 with a resin layer 14 that electrically isolates the conductive fine particle. Fifteen
Are formed in such a manner that the connecting fine particles 15 are mixed with each other in the insulating adhesive 16 in a state of being arranged in a planar manner by being in contact with each other. In this case, the insulating fine particles 12 are made of silicon oxide (Si
The particles are made of an inorganic material such as O ₂ ), titanium oxide (TiO ₂ ), metal oxide, or ceramic, or an organic material such as an acrylic resin. The conductive film 13 is formed by coating a metal such as gold, silver, copper, nickel, and aluminum by plating or vapor deposition. The resin layer 14 is for electrically isolating the outer peripheral surface of the conductive film 13 and has a low melting point (about 100 to 300 ° C.) having an insulating property.
This is a configuration in which the fine powder is adsorbed on the outer peripheral surface of the conductive film 13 by static electricity. Note that the fine powder is much smaller than the insulating particles 12. The connecting fine particles 15 in which the conductive film 13 of the insulating fine particles 12 is covered with the resin layer 14 have a diameter of about 10
It can be formed to a size of about μm. Also,
The insulating adhesive 16 is preferably a hot-melt type belonging to a hot-melt type made of a thermoplastic resin, but is not limited thereto.
It may be made of a thermosetting resin.

FIG. 3 shows a connection terminal 8 and a bump portion made of a conductive bonding agent 17.
10 shows the joined state. The conductive binder 17 is disposed between the connection terminal 8 of the glass substrate 3 of the liquid crystal display panel 1 and the bump portion 10 of the IC chip 9 and is thermocompression-bonded by a heater chip (not shown). Then, the glass substrate 3 and the IC chip 9 are adhered to each other by the insulating adhesive 16, and at the same time, the opposing connection terminals 8 and the bump portions 10 are connected by the connection fine particles 15. That is, the connection fine particles 15 located between the connection terminal 8 and the bump portion 10 are vertically pressed and heated by the connection terminal 8 and the bump portion 10, so that the connection terminal 8 and the bump portion 10 are heated.
The resin layer 14 at the portion where the layer 10 comes into contact (the section in the thickness direction) is melted and washed away, and the conductive film 13 provided on the surface of the insulating fine particles 12 is exposed to contact the connection terminal 8 and the bump section 10. To conduct. In this case, since the lower end surface of the bump portion 10 is a flat surface, the connection microparticles 15 do not easily escape from the bump portion 10 during pressurization. Therefore, the connection fine particles 15 are reliably pressed between the connection terminals 8 by the bump portions 10. However, connection terminal 8
The portion of the resin layer 14 where the bumps 10 do not contact the surface (the portion in the surface direction) has a smaller pressing force than the portion in the thickness direction, and thus remains as it is. Since the connecting fine particles 15 arranged between the adjacent connection terminals 8 and 8 or the bumps 10 and 10 are not pressed by the connection terminals 8 and the bumps 10, the resin layer
14 remains as it is. Therefore, the conductive film 13 provided on the surface of the insulating fine particles 12 does not conduct in the direction in which the connection terminals 8 and the bumps 10 are arranged, but contacts only the opposing connection terminals 8 and the bumps 10 to conduct. As a result, the adjacent connection terminals 8 and the bump portions 10 do not conduct with each other, and only the opposing connection terminals 8 and the bump portions 10 are reliably connected. In this case, even if the pitch between the opposing connection terminal 8 and the bump portion 10 is about twice the size of the fine particles 15 for connection, the adjacent bump portion 10 and the connection terminal 8 are not short-circuited, and It is possible to connect only the part 10 and the connection terminal 8. Hereinafter, this will be described.

FIG. 4 shows the electrical connection between the bumps 17 and the connecting fine particles 15. In this figure, a circular contact region 18 indicated by a dotted line at the center of each connection fine particle 15 is a portion of the resin layer 14 that is melted during thermocompression bonding.
And a connection terminal (not shown here). The bump 17 indicated by a two-dot chain line corresponds to the bump 10 in FIG. 1, and the connection terminals have the same width as the bump 10 and have the same width.
It is formed longer. Here, the vertical and horizontal lengths of the bumps 17 are about twice the outer diameter of the connecting fine particles 15, and the pitch is about twice the width (length in the horizontal direction) of the bumps 17. . The connecting fine particles 15 are arranged without gaps so as to be in contact with adjacent ones. This is the same not only in the pitch direction of the bumps 17 but also in the length direction (vertical direction). Therefore, about seven connection fine particles 15 are arranged in the area of the bump portion 17 indicated by the two-dot chain line. Among them, conductive film of insulating fine particles 12
The contact of the bump 13 with the bump portion 17 is in the hatched portion shown in the contact region 18, and the number of the connection fine particles 15 with which the conductive film 13 actually contacts is five. Moreover, three of them make contact in the entire contact area 18 and the other two make contact in a part of the contact area 18. Further, since the pitch between the adjacent bump portions 17 is approximately twice the width of the bump portions 17, the connecting fine particles 15 disposed therebetween are expected to be substantially the same as or larger than the above. The bump portions 17 do not conduct with each other.

As described above, even if the width and pitch of the bumps 17 are about twice as large as the fine particles 15 for connection, it is necessary to connect only the bumps 17 facing the connection terminals without conducting the adjacent bumps 17. Becomes possible. Actually, since the vertical and horizontal widths of the bump portion 17 are larger than twice the connecting fine particles 15, the connecting fine particles 15 are arranged in the area of the bump portion 17 more than the above-described number. The connection is more secure. For example, the vertical and horizontal size of the bump 10 is 30 ×
If the diameter of the connecting fine particles 15 is about 10 μm, which is 30 μm, sufficient conduction reliability can be obtained. Moreover, the bump part 10
Even if the pitch is about twice the width of the bump section 10, the pitch is about 60 μm, and even this fine pitch can be reliably connected. Theoretically, even if the size of the bumps 10 in the pitch direction is equal to or less than the diameter of the connecting fine particles 15, at least one connection is required if the length of the bumps 10 is equal to or greater than the diameter of the connecting fine particles 15. The fine particles for use 15 are interposed between the bump portion 10 and the connection terminal, and therefore, can be applied to any fine pitch.

In such a connection structure of the IC chip 9, the conductive film 13 provided on the surface of the insulating fine particles 12 of the connecting fine particles 15 is formed.
Since the resin layer 14 that covers and electrically isolates is made of a low-melting material, low-temperature bonding is possible. Therefore, the present invention can be applied to inexpensive connection terminals and substrates. For example, the present invention can be applied not only to the glass substrate 3 of the liquid crystal display panel 1 described above but also to a film substrate, a printed wiring board, and the like.

The present invention is not limited to the embodiment described above. For example, the conductive binder may have a structure as shown in FIG. 5 or FIG. That is, the conductive binder 20 shown in FIG. 5 forms the conductive fine particles 21 with metal particles such as gold, silver, copper, nickel, and aluminum, or carbon particles. In the same manner as described above, the connection fine particles 22 are formed by covering the surface with the resin layer 14,
Are connected to each other and mixed in the insulating resin 16. The conductive binder 23 shown in FIG. 6 is formed by coating the outer peripheral surface of the conductive film 13 of the insulating fine particles 12 with a low-melting resin layer 24 having insulating properties in the form of a film to form the connecting fine particles 25. The connecting fine particles 25 are made to contact each other and mixed in the insulating resin 16. Even in such conductive binders 20, 23, the resin layer 14 or 24 in the thickness direction is broken by thermocompression bonding to expose the conductive fine particles 21 or the conductive film 13, and the resin layer in the plane direction orthogonal to the conductive fine particles 21 or the conductive film 13 is exposed. 14
Or 24 is not destroyed, so the conductive binder 11 described above
Has the same effect as.

[Effects of the Invention] As described in detail above, according to the connection structure of an IC chip of the present invention, the present invention can be applied sufficiently even when the pitch between the bumps and the connection terminals is much smaller than in the past. In particular, the fine particles for connection of the conductive binder are not necessarily insulated by the insulating adhesive, and the fine particles for connection themselves have an insulating layer. And the connection reliability is extremely high. In addition, since the IC chip is bonded to the substrate with the insulating adhesive of the conductive binder, the bonding strength can be sufficiently secured without filling the sealing resin after the bonding.

[Brief description of the drawings]

1 to 4 show an embodiment of the present invention, and FIG.
FIG. 2 is an enlarged sectional view of a connection structure in which an IC chip is connected to a liquid crystal display panel; FIG. 2 is an enlarged sectional view showing a structure of a conductive binder;
FIG. 3 is an enlarged sectional view of a main part in a state where the IC chip is bonded with a conductive adhesive, FIG. 4 is a plan view for explaining a conductive state of the bump portion and the connecting fine particles, and FIGS. FIG. 4 is a cross-sectional view showing a modified example of the conductive binder. 3 ... glass substrate, 8 ... connection terminal, 9 ... IC chip,
10, 17 ... bump part, 11, 20, 23 ... conductive binder, 12
... insulating fine particles, 13 ... conductive film, 14, 24 ... resin layer,
15, 22, 25: fine particles for connection, 16: insulating adhesive, 21
... Conductive fine particles.

Claims (1)

(57) [Claims] 1. An IC chip provided with a large number of bump portions on one surface, a substrate provided with connection terminals to which each bump portion of the IC chip is connected, and an IC chip interposed between the IC chip and the substrate. And a conductive binder obtained by mixing the connecting fine particles in which an outer peripheral surface of the conductive fine particles is covered with a resin layer composed of a large number of insulating fine powders in an insulating adhesive. By interposing the conductive binder between the IC chip and the substrate and thermocompression-bonding each bump portion of the IC chip and each connection terminal of the substrate, between the bump portion and the connection terminal A portion in the thickness direction of the resin layer of the connecting fine particles located is destroyed and a portion in the surface direction remains, and the conductive fine particles of the connecting fine particles are connected to each bump portion of the IC chip and each connecting terminal of the substrate. IC characterized by connecting
Chip connection structure.