JPH06163549A - Metal bump and formation thereof - Google Patents

Abstract

PURPOSE:To realize high density connecting terminal while enhancing safety in metal bump. CONSTITUTION:The metal bump for connecting between terminals is formed on a bump forming substrate 25 such that a pointed protrusion 23 projects upward from a terminal 2 when the bump is transferred thereto. A pointed recess 27 is made at a predetermined part in the surface of the base body 26 of the bump forming substrate 25. The recess 27 is then filled up and coated with a conductive film 28 having thickness insufficient for planarization. Thereafter, a plating mask 29 is formed such that the recess 27 coated with the conductive film 28 is exposed and then the exposed conductive film 28 is subjected to electroplating thus forming a metal bump 22.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metal bump and a method of forming the same, for example, to mount a bare chip on a liquid crystal display panel or to connect a bare chip mounting film substrate, it is formed on a bump forming substrate and transferred to a glass substrate of the display panel. The present invention relates to a metal bump and a method for forming the metal bump.

[0002]

2. Description of the Related Art Conventionally, in a liquid crystal display panel or the like, a metal bump is attached to one terminal to connect a substrate to a semiconductor chip and a substrate to a film for mounting a semiconductor chip.
It is formed by one bump, the solder adhesive force is used for the solder bump, and the insulating resin (adhesive) is used for the bump using gold etc.
A connecting method using the above method and a connecting method using an anisotropic conductive resin (film) containing conductive particles in an insulating resin (adhesive) are generally used.

FIG. 7 is an explanatory view of a conventional connecting method using a metal bump and an insulating adhesive, FIG. 8 is an explanatory view of a conventional metal bump forming method, and FIG. 9 is a conventional connecting method using an anisotropic conductive film. It is explanatory drawing of a connection method.

In FIG. 7, an electrode terminal 2 for connection is formed on the lower surface of the IC chip 1, and an electrode terminal 4 formed on a glass substrate 3 of a liquid crystal display panel and an electrode terminal 2 of the IC chip 1 are formed.
Means that the electrode terminals 2 (or 4) are electrically connected to each other by the metal bumps 5 previously attached, and the connection is maintained by the adhesive force and the contracting stress of the adhesive agent 6.

In FIG. 8 (a), generally, in the metal bump forming substrate 7, a transparent conductive film 9 made of ITO is formed on the surface of the glass substrate 8 and a plating mask 10 exposing a predetermined portion of the conductive film 9 is formed. After that, a photoresist pattern 11 is laminated on the mask 10, and then the substrate 7 is immersed in an electrolytic solution to form bumps 5 made of, for example, gold on the exposed portions of the conductive film 9.

Next, after removing the photoresist pattern 11, the heated heads of the bumps 5 are pressed against the terminals 2,
When the substrate 7 is removed, as shown in FIG. 8B, the IC chip 1
The bump 5 is left (transferred) on the terminal 2 of
Like

In FIG. 9, the electrode terminal 2 of the IC chip 1
And the electrode terminal 4 of the glass substrate 3 are electrically connected by the conductive particles 12 sandwiched therebetween, and the connection is maintained by the adhesive force and the contracting stress of the adhesive 13.

For the connection with the conductive particles 12, an adhesive resin film containing a large number of conductive particles 12 is generally used. Therefore, a large number of conductive particles 12 that do not contribute to the electrical connection of the terminal 2 come to float in the adhesive 13.

The connection method using solder bumps has not been used so much because it cannot follow the miniaturization and high density of the terminals 2 and 5.

[0010]

In the conventional connecting method described above, the method of using the bumps 5 of gold or the like requires that the adhesive 6 be applied to the substrate 3 in advance, and therefore the bumps 5 and the terminals 4 are used. It is easy to form a thin film of adhesive 6 between
The electrical connection may become unstable.

On the other hand, in the method of using the conductive particles 12, if the conductive particles 12 are separated from between the terminals 2 and 4 facing each other, they will not be electrically connected. Therefore, if the content rate of the conductive particles 12 is increased, the conductive particles 12 floating in the adhesive 13
Due to the risk of short-circuiting between terminals 4,
It is difficult to further miniaturize.

[0012]

According to the present invention, which is intended to stabilize electric connection by transfer metal bumps and to increase the density of connection terminals, a bump forming substrate 25 for connecting terminals is shown in FIG. And a bump forming substrate 25, characterized in that, when formed on the terminal 2, and transferred to a predetermined terminal 2, a projection 23 having a sharp tip is formed toward the upper side of the terminal 2.
A concave portion 27 having a sharp tip is formed in a predetermined portion of the surface of the base body 26, and then the conductive film 28 is deposited on the surface of the base body 26 to a thickness that does not flatten by filling the recess 27. Recessed recess 27
After forming a plating mask 29 on the conductive film 28 so that the metal bumps are exposed, the metal bumps 22 are formed by electroplating on the conductive film 28 deposited on the recesses 27 and exposed. 22 is a forming method.

[0013]

According to the above means, when the metal bump is transferred to the first terminal and the first and second terminals are connected through the metal bump, the second terminal first has the protrusion of the metal bump. By contacting the tip and applying a predetermined pressure, the protrusion is crushed and the electrical connection is completed.

Therefore, the initial pressure between the protrusion and the second terminal becomes much larger than that when the conventional bump is used, and the adhesive adhered to the surface of the second terminal is surely pushed out.

As a result, the stability for electrical connection is increased, the fear of short-circuiting to adjacent terminals is eliminated, and the connection area (metal bumps) can be reduced, so that the density of connection terminals can be increased.

Further, the method of forming the metal bumps with protrusions by forming a concave portion with a sharp tip on the substrate of the bump forming substrate facilitates the formation of the connection protrusions and mass-produces the metal bumps with protrusions. It is possible.

[0017]

1 is a schematic side view of a metal bump according to a first embodiment of the present invention (a) and an explanatory view of a method for manufacturing the bump.
(B) and (c), FIG. 2 is an explanatory view (a) of a method for manufacturing a metal bump according to a second embodiment of the present invention and a schematic side view of the state where the bump is transferred.

In FIG. 1A, the upper surface of the IC chip 1 to be mounted on the glass substrate of the liquid crystal display panel (the lower surface at the time of mounting).
An aluminum terminal 2 connected to an electrode terminal of the glass substrate and a protective film 21 for exposing a predetermined portion of the terminal 2 are formed on the substrate, and a metal bump 22 is bonded to the exposed portion of the terminal 2.

The metal bump 22 made of gold, for example, has a plurality of protrusions 23 having a conical shape with a sharp tip protruding on the upper surface connected to the electrode terminal of the glass substrate. In Figure 1 (b),
A bump forming substrate for forming the metal bumps 22 by plating
25 is a glass substrate (base) 26 with a large number of conical recesses on its surface.
After forming 27 to a depth of about 5 to 10 μm, a transparent conductive film having a thickness of about 2000 Å, for example, an ITO film 28 is deposited on the entire surface, and a plating mask having a thickness of about 0.5 to 1 μm is formed on the ITO film 28. 29 is laminated.

In order to form a large number of bumps 22 on a single substrate 25 by plating, a large number of through holes are formed in the plating mask 29 to expose a part of the ITO film 28.
In order to form a plurality of protrusions 23 on the mask 29, a plurality of recesses 24 are provided in each through hole of the mask 29.

Then, as shown in FIG. 1C, a photoresist pattern 30 having an appropriate thickness is formed on the mask 29, and bumps are formed on the exposed ITO film 28 by electroplating.
Form 22.

Then, the resist pattern 30 is removed, and the bumps 22 are transferred (heated and pressed) onto the terminals 2 in the same manner as in the conventional method.
The result is the metal bump 22 shown in FIG. Figure 2
In (a), the bump forming substrate 31 is similar to those described with reference to FIG. 1 after forming one recess 33 corresponding to the metal bump 34 to be plated on the glass substrate (base) 32. An ITO film 28 and a plating mask 29 are formed on the substrate.

The bumps 34 made of gold, for example, are formed by forming a photoresist pattern 30 on the plating mask 29 and electroplating the exposed ITO film 25.
Therefore, when the bumps 34 are transferred to the terminals 2, one protrusion 35 is formed on the upper surface of the bumps 34 as shown in FIG.
Will be projected.

As described above, the metal bump according to the present invention
22,34, the projections 23,35 project toward the connection partner,
Therefore, when the metal bumps 22 and 34 are pressed toward the connection partner, the protrusions 23 and 35 come into contact with the connection partner (for example, the terminal 4 shown in FIG. 7) with a much stronger initial pressure than the conventional bump 5 and then are crushed. Thus, the terminals 4 are electrically connected to each other with an appropriate area.

The bump 34 having the protrusion 35 is the protrusion 35.
Since it requires only a small area for forming, it can be made smaller than the bump 22 having the protrusion 23, and is applicable to the connection of the terminals 2 and 4 having a finer width and a finer spacing than that using the bump 22, specifically, Has made it possible to reduce the bump pitch, which was difficult to reduce to 50 μm or less by the conventional method, to about 10 μm.

Next, a bump forming substrate according to the present invention will be described. FIG. 3 is an explanatory view of an embodiment in which a recess is formed by using a laser beam, and FIG. 4 is a metal bump completed after forming the recess. 5 is a cross-sectional view of an example of a forming substrate, FIG. 5 is a cross-sectional view of another example of a metal bump forming substrate completed after forming a recess, and FIG. 6 is a bump forming substrate and a metal bump in which a recess is formed by etching. FIG. 3 is an explanatory diagram of an example of FIG.

In FIG. 3 (a), the surface of the glass substrate 26 is coated with a resin 41 (which may be a normal positive photoresist which is lightly colored) colored so as to absorb the laser light.
After applying about 0.3 to 1 μm, laser light 42 is irradiated to a predetermined portion to form a recess 27 shown by a broken line.

Then, the laser light 42 is absorbed in the laser light irradiation region of the resin 41, and the recess 27 having a depth of about 5 to 10 μm is formed on the substrate 26. In Figure 3 (b),
On the surface of the glass substrate 26, a resin that absorbs laser light (photoresist) is formed in a region where a recess 27 is formed, which is indicated by a broken line.
After forming the pattern 43, laser light 44 is irradiated.

Then, the laser beam 44 applied to the resin pattern 43 is absorbed by the resin pattern 43 and the depth of the substrate 26 becomes 5 degrees.
While forming a recess 27 of about 10 μm, the resin pattern 43
A part of the laser beam 44 emitted off the plane is transmitted without damaging the substrate 26.

Therefore, the method described with reference to FIG. 3B is different from the method described with reference to FIG.
However, the irradiation with the laser light 44 is easier than the irradiation with the laser light 42.

In FIG. 4, an ITO film 28 having a thickness of about 2000Å is formed on the surface of the substrate 26 having the recess 27 formed by the method described with reference to FIG. 3, and then the formation portion of the recess 27 is exposed. A plating mask 29 is formed on the bump forming substrate 25 to complete, and a photoresist pattern 30 indicated by a two-dot chain line is formed on the plating mask 29 prior to the formation of the metal bump 22 indicated by a one-dot chain line. Prior to the transfer of the bumps 22, the resist pattern 30 will be removed.

The metal bumps 22 using the bump forming substrate 25 have a pitch of about 30 μm, that is, a pitch of 20
Enables high density with a reduction of about μm. In FIG. 5, the bump forming substrate 45 has a recess 27 formed on the surface of a glass substrate (base) 46, and then an ITO film 28 is formed thereon, and a plating mask 29 is formed so as to cover a part of the recess 27. Formed.

In the bump forming substrate 45, the pitch of the bumps to be formed can be changed by forming the plating mask 29 so that all the recesses 27 are exposed if necessary, in other words, the glass substrate. A recess 27 is formed on the entire surface of 46, and a plating mask is formed so that the recess 27 is exposed at a required pitch.
It means that 29 should be formed.

In FIG. 6A, a glass substrate (base) 51
A flat-bottomed recess 52 is formed on the surface of, for example, by an etching process. Next, when an ITO film is directly formed on the recess 52 formed by etching and bumps are formed on the ITO film, the bump separation becomes worse, so that the recess as shown in FIG.
A flattening layer 55 having a thickness of about 1 μm is formed by silicon-based thermosetting resin when the depth of the recess 52 is 5 to 10 μm. It
The ITO film 28 of about 2000 Å and the plating mask 29 are formed to complete the bump forming substrate 50.

Therefore, a resist pattern is formed on the mask 29.
By forming 30 and performing electroplating, the metal bumps 53 shown in FIG. 6B are formed. Similar to the bump 22 described above, when the metal bump 53 is transferred to the terminal 2 of the IC chip 1 as shown in FIG. 6C, the protrusion 54 is projected upward from the upper surface. However, the tips of the protrusions 54 are rounder than those of the protrusions 23 and 33 described above.

[0036]

As described above, the metal bump with a projection according to the present invention has improved stability against electrical connection using the metal bump, eliminates the fear of short-circuiting to an adjacent terminal, and has a connection area (metal bump). Therefore, there is an effect that it is possible to increase the density of the connection terminals, for example, to reduce the terminal spacing to about 10 μm, which was difficult to reduce to 50 μm or less in the past.

Furthermore, the method of forming a metal bump with a projection in which a tip-shaped recess is formed on the substrate of the bump forming substrate is similar to the conventional metal bump, and it is possible to mass-produce a metal bump with a new structure. to enable.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a metal bump according to a first embodiment of the present invention and a method for manufacturing the same.

FIG. 2 is an explanatory diagram of a metal bump and a method for manufacturing the same according to a second embodiment of the present invention.

FIG. 3 is an explanatory diagram of an example in which a recess is formed in a glass substrate by laser light.

FIG. 4 is an explanatory diagram of an example of a bump forming substrate completed after forming a recess.

FIG. 5 is an explanatory diagram of another embodiment of another bump forming substrate completed after forming the recess.

FIG. 6 is an explanatory diagram of a bump forming substrate and a metal bump according to still another embodiment.

FIG. 7 is an explanatory diagram of a conventional metal bump connection method.

FIG. 8 is an explanatory diagram of a conventional metal bump forming method.

FIG. 9 is an explanatory diagram of a conventional connection method using anisotropically conductive particles.

[Explanation of symbols]

 2 is a terminal for transferring a metal bump 22,34,53 is a metal bump with a projection 23,35,54 is a projection formed on the metal bump 25,31,45,50 is a bump forming substrate 26,32,46,51 Is the base of the substrate for forming bumps (glass substrate) 27, 33 is the recess with a sharp tip 28 is the conductive film (ITO film) 29 is the plating mask 41 is the laser light absorption layer 42, 44 is the laser light 43 is the laser light absorption Body pattern 52 is flat bottom recess 55 is flattening layer

Claims (5)

[Claims] 1. A bump forming substrate (2) for connecting terminals.
5,31,45,50) and transferred to a predetermined terminal (2), a projection (23,35,54) with a sharp tip is formed toward the upper side of the transfer terminal. Metal bump to do. 2. A substrate (26, 31) of a bump forming substrate (25, 31, 45)
A concave portion (27, 33) having a sharp tip is formed at a predetermined portion of the surface of the substrate (32, 46), and then a conductive film (28) is coated on the surface of the substrate to a thickness that does not flatten the concave portion. And a plating mask (29) on the conductive film so that the recesses of the conductive film exposed are exposed.
After forming the metal bumps, the metal bumps (22, 34) are formed by electroplating on the conductive film that is deposited and exposed in the recesses. 3. The recess in the base body (26) made of glass.
When forming (27), a laser light absorption layer is formed on the surface of the substrate.
(41) is provided, the laser light (42) on a predetermined portion of the laser light absorption layer
3. The method of forming a metal bump according to claim 2, wherein the laser light absorption layer is removed after the recess is formed by irradiating the laser beam. 4. The recess in the base body (26) made of glass.
When forming (27), a laser beam absorber pattern (43) is provided on a predetermined portion of the surface of the base, and the laser beam (44) is irradiated to the laser beam absorber pattern to form the recess. 3. The method of forming a metal bump according to claim 2, wherein the laser light absorption layer is removed. 5. A recess (5) is formed in a base body (51) of a bump forming substrate (50).
2) and when forming the conductive film (28), the recess (52) having a flat bottom is formed in a predetermined portion of the surface of the substrate (51), and the recess has a thickness to form a recess. A flattening layer (5
3) is formed, and the conductive film (28) having a thickness that does not flatten the recess by filling the recess is formed on the flattening layer so that the recess where the conductive film is deposited is exposed. After forming a plating mask (29) on the conductive film, a metal bump (53) is formed by electroplating on the conductive film exposed in the recess. Forming method.