JP2775984B2 - Cutting method of fine metal wire - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a metal wire used as a material of a bump to form a bump used for bonding between an electrode of an IC chip and a lead of a TAB tape. For cutting to a certain length.

[Conventional technology]

Various methods are used to connect the electrodes of the IC chip to the external leads.

Although there is a method of connecting using a very thin wire (bonding wire) for wiring, a method of thermocompression bonding with a metal projection called a bump interposed between an electrode of a chip and a lead is also widely used.

The TAB (Tape Automated Bonding) method is a technology that has attracted attention as a representative of the latter. In this method, a bump is formed in advance either on the electrode portion of the IC chip or on the tip of the lead on the TAB tape, and then the IC chip electrode portion is connected to the TAB tape having leads via the bump. The two are joined together so as to overlap. Also TA
Bumps are used in the flip chip method in addition to the B method.

Until now, the method of producing bumps provided for such uses has been mainly by plating. That is, IC
The mainstream method is to directly form a metal serving as a bump on the electrode portion of the chip by plating, or to transfer a bump once formed on a glass substrate or the like by plating to the tip of a lead on the TAB tape side.

However, the plating method has disadvantages in that the equipment is large and the composition of the metal used as the bump is restricted. In addition, there has also been a problem in that if the bumps are formed by directly plating the electrode portions of the IC chip, the chip itself passes through a plating process, thereby deteriorating the yield of the chip.

As a method of solving these disadvantages, a bump forming method without plating has been considered. The present inventors have previously processed metal as a material for bumps into a fine wire, cut this metal wire to a fixed size, then melted and solidified in a state where they were spaced apart from each other, and utilized surface tension. (Japanese Patent Application No. 1-320296)
issue). The formed spherical bump is used by thermocompression bonding to the lead tip or the like (Japanese Patent Application No. 1-234917). High purity gold has hitherto been the most common metal used for such bumps. Gold is a metal that is effective as a bump, but it may have been difficult for other metals to be taken up because of the process restrictions of forming the bump by plating.

On the other hand, according to a new method in which an arbitrary metal wire piece is melted into a bump without relying on plating, the possibility of using any metal having characteristics suitable for a joining member as a bump is greatly expanded. It will be. Also, even when using gold as before, when forming bumps by plating, it had to be high-purity gold close to pure gold, but according to the method of melting wire pieces, drawing It is possible to produce a bump having an arbitrary composition as much as possible. In addition to gold, copper, silver, and various alloys based on them can be easily formed as bumps.

When a bump is produced by melting a metal wire piece, it is necessary to make the cut length of the metal wire strictly constant in order to obtain a bump of uniform size. It goes without saying that it is advantageous to use a material having a wire diameter as small as possible to increase the cutting length in order to increase the cutting accuracy of the length. Nevertheless, the size of the bumps is generally small, less than 100 microns in diameter.
It must be as short as mm. In addition, since a soft metal is generally used for bumps, a metal wire formed from the soft metal is extremely difficult to handle such as being bent by its own weight. In particular, in order to increase the accuracy of the cutting length, it is necessary to send a bendable metal wire with a certain length with high precision. It is very difficult to send a single thin line without bending and with high accuracy.

Therefore, when trying to cut such a thin metal wire for a bump material accurately with an existing cutting machine having a feed mechanism at a constant pitch, a plurality of thin metal wires are bundled or arranged in parallel on a tape and fixed. Thus, it is effective to cut the sheet after the treatment so as not to hinder the feeding.
The method disclosed in Japanese Patent Application No. 1-320296 was based on such a concept.

[Problems to be solved by the invention]

It is an object of the present invention that 50
A large amount of soft material metal wire such as gold drawn with a diameter of less than a micron can be mass-produced efficiently and with high cutting accuracy by means that there is no room for adhesive or alignment material to be mixed as impurities. It is an object of the present invention to provide a method which can be cut into wire pieces having a length of not more than 1, and can be cut so that the cut wire pieces are not entangled with each other.

[Means for solving the problem]

The present invention provides (1) a method of manufacturing a fine metal piece for producing a bump used in a semiconductor device by cutting a fine metal wire, wherein an end of the fine metal wire is set on an exit side of a guide. The fine metal wire is pulled out from the guide exit side by a certain length by grasping and moving the holding portion, and then the fine metal wire is cut by a cutting blade provided near the guide side of the holding portion. (2) A method for manufacturing a fine metal piece for producing a bump used in a semiconductor device by cutting the fine metal piece into a fine metal wire. A method for cutting a fine metal wire, wherein the fine metal wire is pulled out from the guide by a predetermined length, and then the fine metal wire is cut by a cutting blade provided in proximity to the feed roll delivery side. , It is.

The present invention relates to the cutting of metal wires, but the cut metal wire pieces are then arranged and melted so as not to interfere with each other to provide a spherical bump. is there. So instead of thinking by cutting alone,
It is important to cut so that it can be easily used in the subsequent melting process.

In the melting process, care must firstly be taken to avoid contamination of the impurities. In general, the characteristics required for a bump may be significantly affected by the inclusion of a small amount of impurities. Therefore, if impurities are mixed in the cut metal wire piece in the cutting process, it is necessary to remove the impurities by some method before melting. Further, in the melting process, it is necessary that the individual metal wire pieces are separately melted without interfering with each other. This is because if the melting process is started while the plurality of metal wire pieces are in contact with each other, a large bump in which the plurality of metal wire pieces are united is obtained, and it becomes useless.

From the above, cutting of the ultrafine metal of the present invention,
First, it is a method in which impurities are not mixed. Second, it is easy to control even the interval of each of the metal wire pieces that are cut and fall into the receiver if possible, without being entangled. The method was aimed at realizing. In order to satisfy these aims, it is necessary to cut one piece at a time by cutting one piece of the bare fine metal wire as it is, so that the cut piece can be processed one by one.

When cutting a metal wire with a normal diameter to a certain length, the metal wire is intermittently sent out by a fixed length by a feed roll or the like that is rotated by a step motor, and the cutting blade is operated for each step to cut the wire. Thus, a large number of metal wire pieces having a uniform length can be easily obtained. However, in the case of a fine metal wire, there is a problem that when feeding by a feed roll, the wire is bent, so that accurate feeding itself cannot be easily realized. In order to solve this point, it has become clear that it is effective to draw a fine metal wire passing through the guide from the exit side of the guide. The following two methods were particularly effective as a method for accurately drawing a fine metal line by a fixed length.

First, there is provided a holding portion for grasping and fixing the tip portion of the fine metal wire, for example, by sandwiching all or a part of a portion to be cut next, and a fine metal wire for cutting this holding portion. In this method, the fine metal wire is drawn by moving the wire away from the guide by a length corresponding to the length of the metal wire. As another means, a feed roll is installed on the exit side of the guide, and the fine metal wire is formed by rotating the feed roll by a step motor or the like adjusted so that one step is equivalent to the length just cut. The withdrawal method was equally effective. According to such a method, there is no need to worry about the bending that tends to occur when the fine metal wire is fed from behind, and the inconvenience that the fine metal wire is clogged in the fine hole portion of the guide is also extremely unlikely to occur. It was confirmed that.

In this way, a mechanism for pulling out the fine metal wires of a fixed length at a time was realized. Next, a cutting method matching with the feeding mechanism of the fine metal wires was examined. For accurate cutting, it is necessary to operate the blade with the portion as close as possible to the cutting blade fixed. The farther the fixed portion is from the blade, the more the fine metal wire is moved by the movement of the blade itself at the time of cutting, and it is inevitable that the cutting accuracy is degraded accordingly. Moreover, it is necessary to limit the portion to be fixed to a portion as close as possible to the tip of the fine metal wire. And if possible, I would like to grab the tip of the fine metal wire that is about to be cut off, not between the guide and the blade, but outside the blade. Then, the fine metal wire deformed by the gripping is cut off, and the next position where the gripping part tries to fix is the position where the influence of the deformation by the previous gripping and cutting hardly affected, This is because the reliability when automating the method of the present invention becomes extremely high.

The present invention has been achieved by combining the above findings, and details will be described in more detail later based on embodiments.

[Action]

The fine metal wire to be cut is intermittently drawn from the exit side of the guide by a length corresponding to a fixed cut length. The extraction of the fine metal wire is based on the operation of the feed roll or the holding unit on the guide exit side. Cutting is performed by a cutting blade provided near the feed roll or the holding unit. Since the fine metal wire is drawn out from the outlet side instead of being fed into the narrow guide hole, the cutting operation suitable for mass production is performed without the fine metal wire being bent at the entrance of the guide hole or clogged inside.

〔Example〕

Embodiment 1 FIG. 1 is a schematic diagram showing a basic operation of the present invention. As the fine metal wire 1, a gold wire having a diameter of 20 μm was used.
The fine metal wire 1 is drawn downward through a guide 2 made of quartz and having a fine hole with an inner diameter of 30 μm. The distal end of the fine metal wire 1 reaches between the holding parts 3a and 3b which are being released and the cutting blades 4a and 4b which are also being released.
Also, clampers 5a and 5b are provided on the entrance side of the guide 2 to prevent the fine metal wire 1 from flowing out naturally through the guide 2 (FIG. 1 (a)).

The holding portions 3a and 3b are made of ceramics. First, the holding portions 3a and 3b were operated to grasp and fix the fine metal wire 1 so as to sandwich it from the left and right (FIG. 1 (b)). Next, the clampers 5a, 5b were released, and the holding parts 3a, 3b were moved downward by d while holding the fine metal wire 1. Razor blades were used as the cutting blades 4a and 4b, but their vertical movement was
The cutting blades 4a and 4b are also moved downward by d as a result of the downward movement of the holding portion because they are linked with the a and 3b (FIG. 1 (c)). By the operation up to this point, the fine metal wire is drawn out of the guide 2 by the length d to the output side.

Here, the clampers 5a and 5b were closed again, and the cutting blades 4a and 4b were operated in the horizontal direction to cut the fine metal wire 1 (FIG. 1 (d)). The cutting blades 4a and 4b are returned to their original standby positions immediately after cutting, and when the holding portions 3a and 3b holding the fine metal wire 1 are also released, the cut wire piece 10 falls (FIG. 1 (e). )). Finally, holding parts 3a and 3b and cutting blade 4
When a and 4b are raised together by d (FIG. 1 (f)), it can be seen that this state has been restored to a state completely equivalent to the initial state shown in FIG. 1 (a). Accordingly, by repeating the steps (a) to (f) of FIG. 1, the fine metal wire 1 is cut into line pieces having a uniform length d.

Tests were performed with the line length d of the fine metal wire being 0.3, 0.5, and 0.8 mm. In each case, cutting was possible with an accuracy of ± 0.1 mm or less.

Second Embodiment In the first embodiment, the role of the clampers 5a and 5b is that when the holding portions 3a and 3b, which hold and pull out the fine metal wire at the exit side of the guide, are released, the fine metal wire is The goal was to prevent them from coming out and back naturally. This role can be assigned by another means that does not rely on the clamper as in the first embodiment.

In this embodiment, as shown in FIG.
Is made to have a function of a clamper by making it spiral. The same holding members 3a, 3b and cutting blades 4a, 4b as in Example 1 were used. When the fine metal wire 1 passes through the inside of the spiral guide 21, the resistance given from the inner wall of the guide comes to rest at the pulled-out position, and is the same as in the first embodiment despite the absence of the clamper. High-precision cutting was performed.

Example 3 FIG. 3 is a schematic view of the apparatus used. 1 is a fine metal wire, 2 is a guide, 3a and 3b are holding parts, and 4a and 4b are cutting blades. Feed rolls 6a and 6b were installed on the exit side of the guide 2. This feed roll was made of ceramics having a diameter of 3 mm, and was set at a position 10 mm away from the exit side of the guide 2. The rotation of the roll was performed by a step motor (not shown), and the fine metal wire was intermittently drawn out to the exit side of the guide 2 by a fixed length.

In the case of the present embodiment, since the fine metal wire is automatically supplied to the position of the cutting blade by the action of the feed roll as described above, both the holding portions 3a and 3b and the cutting blades 4a and 4b are vertically moved. Need not move. When both the holding parts 3a, 3b and the cutting blades 4a, 4b are released, the feed roll rotates one step and the leading end of the drawn fine metal wire 1 is first moved horizontally by the holding parts 3a, 3b. After grasping and fixing, the cutting blade 4a,
4b is also moved in the horizontal direction to cut the fine metal wire 1.

As the fine metal wire 1, a gold wire having a diameter of 30 μm was used, and the cutting length was 0.4 mm.

Embodiment 4 Although the method of the present invention cuts a fine metal wire with high accuracy in a single wire state, in order to further improve the cutting efficiency, a plurality of cutting elements for each single wire may be combined and processed in parallel. It is possible. FIG. 4 shows an example of this case, in which four fine metal wires 1 are cut simultaneously.
The guide 2 is made of ceramics, but has a groove for passing a fine metal wire inside in a split state, and is used in a state where it is fitted from the left and right. Feed roll 6a, 6b
It is also made of ceramics and has a grooved roll to pass fine metal wires straight. The rotation of the roll uses a step motor (not shown), and the four fine metal wires 1 can be simultaneously drawn out by the same length.

The holding parts 3a, 3b and the cutting blades 4a, 4b can also act on the four fine metal wires 1 at the same time, and when both are released, the feed roll rotates to feed the fine metal wires of a certain length. After being pulled out, the holding parts 3a and 3b were closed to fix the tip of the fine metal wire, and then the cutting blades 4a and 4b were operated to cut.

With this method, a gold wire having a diameter of 20 μm could be efficiently cut into a uniform wire piece having a length of 0.8 mm.

〔The invention's effect〕

The fine metal wire can be cut accurately without contacting impurities, and the cut wire pieces can be taken out individually, so that it can be easily supplied to the subsequent melting process. is there.

[Brief description of the drawings]

FIG. 1 is a schematic view for explaining an operation situation in a cutting process in the present invention, FIG. 2 is a schematic view in which a part thereof is replaced by another means, and FIG. 3 uses a feed roll. FIG. 4 is a schematic view showing an example of the case, and FIG. 4 is a sketch showing an example of the embodiment in which the method of the present invention is more efficiently performed. 1 ... fine metal wire, 2 ... guide, 3a, 3b ... holding part, 4a, 4b ... cutting blade, 5a, 5b ... clamper, 6a, 6b ... feed roll, 10 ... cut Fine metal wire piece, 21… spiral guide.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁶ , DB name) B21F 11/00

Claims (3)

(57) [Claims] 1. A method of manufacturing a fine metal piece for producing a bump used in a semiconductor device by cutting a fine metal wire, wherein the end of the fine metal wire is placed on an exit side of a guide. The fine metal wire is pulled out from the guide exit side by a predetermined length by grasping and moving the fine metal wire, and then the fine metal wire is cut by a cutting blade provided near the guide side of the holding unit. Cutting method of fine metal wire. 2. A method of manufacturing a fine metal piece for producing a bump used in a semiconductor device by cutting a fine metal wire, wherein the fine metal wire is fixed from a guide by a feed roll arranged on a guide exit side. A method for cutting a fine metal wire, comprising cutting out the fine metal wire by a cutting blade provided close to a feed side of a feed roll after drawing the length. 3. The fine metal wire has a wire diameter of 5 μm or more and 50 μm or more.
3. The method for cutting a fine metal wire according to claim 1, wherein the length is not more than m.