JPH05251453A - Formation of tab bump - Google Patents

Abstract

PURPOSE:To improve bonding quality by applying pressure to an ultra-fine particle grinding wheel of which grinding surface is formed flat while giving thereto the lateral vibration of ultrasonic wave and giving a fine cutting area to a stud bump formed on an IC chip electrode part and then grinding such cutting area. CONSTITUTION:At the lower surface of a rectangular main body 1, a grinding surface 10 is formed flat by coating the surface with ultra-fine particle grinding material 2 using a particle binding agent. While the lateral vibration is given with the ultrasonic wave to the main body, pressure is also applied toward the lower direction. Thereby a fine cutting area is formed to a stud bump 4 formed at the rear surface of an IC chip 3 placed on the working desk 7 and this area is ground. Thereby, the height of the stud bump can easily be made uniform.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a processing method for making the heights of TAB stud bumps used to mount IC semiconductor chips on a film-shaped tape carrier surface uniform. Is.

[0002]

2. Description of the Related Art Conventionally, as a method of forming bumps used for mounting an IC semiconductor on a carrier, there are a wafer bump forming method, a transfer bump forming method, and a stud bump forming method. As shown in FIG. 3, the wafer bump forming method is
The via metal layer 102 is formed on the aluminum electrode 101 formed on the back surface of the C chip 100, and the bump 10 is formed thereon.
In order to form No. 3, it is necessary to form the via metal layer 102, and there are drawbacks such that the cost does not decrease unless the number is large, but there are advantages that the dimensional accuracy of the bumps is good and there is little variation. However, since the wafer maker is requested to form the chip, there is a problem in that it is difficult to obtain the bumped chip on the corresponding surface.

In the transfer bump forming method, the bumps formed on the glass substrate are transferred to the leads of the TAB film carrier 201 as shown in FIG. 4, and the formed bumps 200 are formed. Is bonded to the aluminum electrode 101 formed on the back surface of the IC chip 100, but it has the advantage that it is not necessary to form a via metal layer and the bump dimension accuracy is good, but on the other hand, the cost is high and the bump formation is performed by a film carrier manufacturer. It is difficult to make it on your own because you ask. Therefore, there is a drawback that mass production is required to reduce the cost.

On the other hand, the stud bump forming method is
As shown in FIG. 5, a stud-shaped bump 300 is formed on an aluminum electrode 301 formed on the back surface of the IC chip 100. The conventional wire bonding device is modified,
After the 1st bonding, the wire is cut and formed. Therefore, the device is relatively inexpensive and can form bumps by itself.
There is an advantage that the formation of a via metal layer is unnecessary and the cost is low.

FIG. 6 shows the appearance of a film carrier in which such a stud bump is used. The IC chip 100 (see FIG. 5) has a device hole formed in a film carrier 400 such as a polyimide resin film. Inner leads 402 housed in 401 and formed so as to surround the periphery of the device hole 401.
Then, the stud bumps 300 formed on the back surface of the IC chip 100 are joined and mounted on the film carrier. In addition, 403 is an outer lead, 404 is a test pad for checking the terminal connection error and the operation of the IC chip after the IC chip is mounted, 405 is a tie bar for reinforcement, and 406 is a carrier film for carrying and moving. 407 is a sprocket hole for the outer lead hole, and 407 is an outer lead hole. By the way, such a stud bump forming method is suitable for high-mix low-volume production as long as the bumps have relatively low pins (200 pins or less).
The bump height tends to be non-uniform, and under the present circumstances, for example, when using a gold wire wire of 25 μm, there is a variation of about 35 to 55 μm, and a larger variation is present in the vicinity of the outer periphery other than the central portion defined by the bump height. It is easy to occur. Therefore, in the case of joining to the inner lead, the single point method is used (joining the lead portion and the IC chip electrode portion by applying ultrasonic vibration, pressurization and overheating for each lead).
The current situation is to join the leads one by one.

However, in such a stud bump forming method, if the bump height is uniform and the variation is small, a gang bonding method of collective bonding is also possible, and it is considered that the bonding quality is also improved. It has been demanded.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and relates to a method for forming TAB stud bumps, and in particular, the bump height is uniformly processed to improve the bonding quality. It is an object of the present invention to provide a bump forming method.

[0008]

In order to achieve the above object, the method of the present invention proposes an IC chip by applying pressure to an ultrafine particle grindstone having a flat polishing surface while applying ultrasonic transverse vibration. The stud bumps formed on the electrode part are characterized by making a minute cut and polishing (claim 1), and in claim 2, the polishing surface of the ultrafine particle grindstone has a plurality of minute chips. A suction hole is formed, and during cutting, air or the like is sucked through the chip suction hole to remove the chips of the bump. Further, in the claim 3, the stud bump is cut. After that, it is characterized in that pressure is further applied by a mirror surface plate.

[0009]

The method of the present invention will be described below with reference to the accompanying drawings. The stud bumps are usually formed on the back surface of the IC chip, but in the future, the stud bumps can be formed on the substrate side or the inner lead side. In the following, I
An example in which the method of the present invention is applied to a stud bump formed on the C chip side will be described.

In the method of the present invention, an ultrafine particle grindstone in which ultrafine particle abrasive grains such as diamond abrasive grains or borazon abrasive grains are mixed in the polishing surface is used, and by applying ultrasonic pressure to the grindstone while applying ultrasonic transverse vibration. , The stud bump upper surface is finely cut and polished. FIG. 1 shows an ultrafine particle grindstone A used in such a method of the present invention. An ultrafine particle abrasive 2 is applied to the lower surface of a rectangular main body 1 by using an abrasive grain binder. The polishing surface 10 is formed in a planar shape, and the stud bump formed on the back surface of the IC chip 3 placed on the work table 7 is pressed downward while laterally vibrating by ultrasonic waves. Four
A small incision is made on the surface to remove it by polishing. In this example, the workbench 7 has a structure in which an air suction hole 71 is formed in the center and the IC chip 3 is fixed by the suction force of air. The particle size of the ultrafine particle abrasive used for such an ultrafine particle grindstone A is preferably such that the abrasive grain size is about 20 to 1 μm and is formed by a bonding method such as metal bonding or electroforming, and the binder is strong and does not scatter. The type is good.

The ultrasonic transverse vibration applied to the grindstone A preferably has an amplitude of about 10 to 500 μm, and is vibrated at several tens KHz to several thousands kHz. When such an ultrafine particle grindstone A is used, as shown in FIG.
If a plurality of minute chip absorption holes 12 communicating with an air suction path 11 penetrating the main body 1 in the lateral direction are provided and chips generated from the cut stud bumps 4 are removed by using suction force such as air, It is possible to effectively prevent the chips from adhering to the back surface of the IC chip 3 and to improve the cutting work (claim 2).

If the stud bump 4 cut by the above method is pressed by a mirror surface plate (not shown) as necessary, the height of the stud bump 4 and the surface polishing accuracy can be made uniform. The bump 4 can be processed with higher accuracy (claim 3). FIG. 2 is a view showing a finished state after cutting the stud bumps by the method of the present invention,
It can be seen that the upper surface of the stud bump 4 formed on the aluminum electrode 101 formed on the back surface of the IC chip 3 is polished flat. According to the present inventors, it was confirmed that the height of the stud bumps 4 can be made uniform with a variation of about 5 μm when such a method of the present invention is carried out.

[0013]

According to the method of the present invention, the following effects can be obtained. (1) The height of the stud bump can be easily made uniform. (2) Since the upper surface of the stud bump is formed by a grindstone using ultrafine particles to which ultrasonic transverse vibration is applied, the stud bump is not separated from the base material such as an IC chip. (3) The joining method, which can be performed only by the single-point method in the past, can also be performed by the gang (collective) method, and the joining time can be significantly shortened.

[Brief description of drawings]

FIG. 1 is an example view of an ultrafine particle grindstone used in a method of the present invention.

FIG. 2 is a view showing a finished state of stud bumps after carrying out the method of the present invention.

FIG. 3 is an explanatory diagram of a wafer bump forming method.

FIG. 4 is an explanatory diagram of a transfer bump forming method.

FIG. 5 is an explanatory diagram of a method of forming a stud bump.

FIG. 6 is an external view of a film carrier in which TAB bumps are used.

[Explanation of symbols]

 A ... Fine particle grindstone 1 ... Main body 10 ... Polishing surface 2 ... Fine particle abrasive 3 ... IC chip 4 ... Stud bump 11 ... Air suction path 12 ... Chips Suction hole

Claims (3)

[Claims] 1. A method for applying pressure to an ultrafine particle grindstone whose polishing surface is formed into a flat surface while applying ultrasonic transverse vibration to I
A method for forming a TAB bump, which comprises polishing a stud bump formed on a C chip electrode portion with a minute cut. 2. The method for forming a bump for TAB according to claim 1, wherein a plurality of minute chip suction holes are formed on the polishing surface of the ultrafine particle grindstone, and the air is drawn from the chip suction holes during cutting. A method for forming a bump for TAB, which comprises removing chips from the bump by sucking the chips. 3. The method for forming a TAB bump according to claim 1, wherein after the stud bump is cut, the TAB bump is further pressed by a mirror surface plate.