JPH03238132A - Cutting method for extremely five metallic wire - Google Patents

Abstract

PURPOSE:To efficiently massproduce the objective wire tip with high cutting accuracy by arranging plural extremely fine metallic wires parallely on the plane surface plate and cutting them by using the cutting jig attached with the blade being aligned at a fixed interval. CONSTITUTION:The extremely fine metallic wires 1 of the blank material are arranged on the upper surface of the flat base plate 3, and fixed by sticking the adhesive tape at both end parts. All the extremely fine wires on the base plate 3 are cut to the wire tips of the prescribed length by moving the cutting jig 10 of cylindrical type being fixed with the disk type blade 11 at the prescribed pitch from the one end of the base plate 3 to the other end. All the wire tips after cut are entered in the graphite crucible of flat bottom so as not to contact each other and heated with the high frequency, so the golden ball for bump of clean free from impurities and with acceptable size can be obtained.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention is directed to the production of bumps in order to make metal protrusions called bonding bumps that are used to connect the electrodes of an IC chip with external leads. This invention relates to a method for cutting ultra-fine metal wire as a raw material into a certain length.

[Conventional technology]

Various methods are used to connect the electrodes of the IC chip and external leads. There is a method of connecting using ultra-thin wiring wire (bonding wire), but a method of thermocompression bonding by sandwiching a metal protrusion called a bump between the chip electrode and the lead is also becoming widely used.
TA, B (Tape Automated Bon
ding) method is a technique that is attracting attention as a representative method of the latter. In this method, a bump is formed in advance on either the electrode part of the IC chip or the lead tip on the rAB tape, and then the IC chip electrode part and the TAB tape having the lead are connected via the bump. The two are joined together by placing them one on top of the other. Also T
In addition to the AB method, the flip-chip method also uses IC chips with bumps formed on the electrode portions.

Up until now, the method of making bamboo provided for such uses has mainly been based on the method of making bamboo sticks.

In other words, the mainstream methods are to directly plate the electrodes of the IC chip with metal to serve as bumps, or to transfer bumps formed by plating on a glass substrate or the like to the lead tips of the T A and B tapes. ing.

However, the plating method requires large equipment and has the disadvantage of being restricted by the composition of the metal used as the hump. In addition, if bumps were to be formed by directly plating the electrode portions of IC chips, the chip itself would have to go through a plating process, which would deteriorate the yield of the chips.

As a method to overcome these drawbacks, methods of forming bumps that do not involve plating have also been studied. The inventors of the present application first processed the metal that would be the material for the bump into wires as thin as possible, then cut the ultra-fine metal wires to a specified length, separated them separately, and then melted and solidified them into spherical shapes. proposed a method for obtaining bumps (Japanese Patent Application No. 1-320296). The spherical bump thus produced is used by being thermocompression bonded to the tip of the lead, etc. (Japanese Patent Application No. 1-234917). Hitherto, the most common metal used for such bumps has been high purity gold. Although gold is certainly an effective metal for bumps, it seems that there were also restrictions on the process of forming bumps by plating, which made it difficult for other metals to be considered as targets.

On the other hand, by realizing a new method of melting any piece of metal wire to make bumps without relying on plating, it is possible to use any metal with characteristics suitable for a bonding member as bumps. It has expanded greatly.

Similarly, when using gold to form bumps with plating, it was difficult to stably obtain an alloy with the desired composition, so it was necessary to use high-purity gold that was close to pure gold. However, according to the method of melting the wire piece, it is possible to create a bump having any composition as long as it is possible to draw the wire. In addition to gold, copper, roots, and various alloys based on them can now be easily molded into humps.

[Problem to be solved by the invention]

By the way, when creating bumps using this method, in order to obtain bumps of uniform size, it is first important to make the cutting length of the ultra-fine metal wire uniform. Needless to say, in order to increase the cutting accuracy of the length, it is advantageous to use a material with a wire diameter as small as possible so that the cutting length can be made longer. The size of the bump is generally smaller than 100 microns in diameter, so even if the metal wire used is made thinner, the cutting length will range from 0.5 m or less to longer.
It has to be a short amount of time. Moreover, since the metals generally used for bumps are often soft, metal wires processed into ultra-thin pieces are extremely susceptible to deformation, such as bending under their own weight.

When it comes to wires made of soft metal with a diameter ranging from several tens of microns to as thin as 10 microns, it is naturally unstable, so it is extremely difficult to create a device that can feed them accurately without bending.

Therefore, when attempting to accurately cut such ultra-fine metal wires for bump materials with an existing cutting machine that has a feeding mechanism with a constant pinch, it is necessary to bundle multiple ultra-fine metal wires or arrange them in parallel on a tape. Therefore, it is necessary to cut the material after taking measures to ensure that it does not interfere with feeding. The method of the previous Japanese Patent Application No. 1-320296 is based on this idea.

Although this method is extremely effective in principle, from an industrial standpoint based on large-scale production, there have been strong expectations for the establishment of a simpler and more efficient cutting method.

The object of the present invention is to use 50
A large amount of soft material metal wire such as gold, which is drawn to an ultra-fine diameter of about microns or less, is cut efficiently and with high cutting accuracy using a method that leaves no room for the adhesive or paulownia material for alignment to be mixed in as impurities. It is an object of the present invention to provide a cutting method capable of cutting wire pieces of 11 layers or less, preferably 0.6u or less.

[Means to solve the problem]

The present invention involves arranging a plurality of ultra-fine metal wires in parallel on a flat base, and then cutting the ultra-fine metal wires using a cutting jig with cutting edges lined up at regular intervals. This is a method for cutting ultra-fine metal wire, characterized by manufacturing metal wire pieces.

In order to efficiently cut ultra-fine metal wires, it is necessary to cut multiple ultra-fine metal wires at the same time, or to cut individual trees one by one, a method with extremely high cutting speed must be used. That is clear. The present invention is based on the premise that a plurality of ultra-fine metal wires for bumping are bundled in advance or arranged in parallel, and then cut at the same time. However, if a coating material, adhesive, tape, etc. is used over the entire length of the ultra-fine metal wires in order to arrange them in parallel, these will be cut together with the ultra-fine metal wires, making it difficult to separate them. In order to avoid this problem, in the present invention, a fixing material such as a covering material, adhesive, or tape is used only at both ends of the parallel-arranged ultra-fine metal wires, and the ultra-fine metal wires supported by these ends are fixed. No fixing material was used in the middle part.

However, because we decided to arrange the ultra-fine metal wires in this way, it became impossible to cut the arranged ultra-fine metal wires to a certain length by cutting them sequentially from one end. Ta.

Because the arrangement is only established by support at both ends,
This is because if the end portions are cut off even on one side, the arrangement will instantly become disorganized. A similar problem naturally occurs when the top surface of the substrate is not sufficiently flat, so the top surface of the substrate should be flat and clean without any fine dust or the like. In order to cut the ultra-thin metal wires arranged in such an unstable manner into a constant length, it is effective to cut all the wires at the same time.

Therefore, in the present invention, various studies have been conducted on methods that can simultaneously cut the entire length of the intermediate portion of ultra-fine metal wires arranged in parallel. As a result, it was confirmed that the purpose could be easily achieved by employing a special cutting jig made by stacking multiple blades with disc-shaped or linear cutting edges.

In other words, as mentioned above, an ultra-fine metal wire stretched over a flat base of hard rubber or the like is shaped like a disk or a straight line, and the cutting edge is inserted at regular intervals according to the length of the target metal wire piece. By using side-by-side cutting jigs, ultrafine metal wires can be cut to desired lengths in a short period of time.

Next, points to be noted when implementing the present invention will be explained.

When arranging ultra-fine metal wires on a flat base, if the arranged wires are not kept parallel to each other, this will cause a large error in the length of the cut wire pieces. In addition, arranging ultra-fine metal wires in multiple layers of two or more on a base will deform the cut end and impair cutting accuracy, so it is important to avoid excessive It is necessary to avoid stacking too many pieces.

In any case in the method of the present invention, the cutting jig must be in contact with the cutting edge at any position along the length of one ultra-fine metal wire at the same time. It must be noted that if the timing of the contact of the cutting edge differs depending on the lengthwise position of the ultra-fine metal wire, the entire wire will jump up as soon as the first cutting edge cuts the gold wire, making it impossible to cut normally. .

Therefore, it is necessary that the height of the cutting edge be at a constant level. Furthermore, when using a cylindrical cutting jig, make sure that the axis of the jig remains parallel to the length direction of the ultra-fine metal wire, and when using a flat cutting jig, make sure that the top surface of the flat base Care should be taken to ensure that the plane formed by the cutting jig and the cutting jig are parallel to each other, or at least maintain parallelism between the length direction of the ultra-fine metal wire and the direction in which the cutting jig's cutting jig is lined up. It is necessary.

[Effect]

In the method of the present invention, the ultrafine metal wires to be cut are first arranged on the surface of a flat base in the same number as the number to be cut. To fix the arrangement, only use adhesive, tape, coating material, etc. on both ends of the ultra-fine metal wires.
These alignment aids were not used at all in the middle part of the ultra-fine metal wire.

For this reason, the alignment aid does not get mixed into the ultra-fine metal wire pieces after they are cut, and there is no need to worry about impurities having an adverse effect on melting in the subsequent process.

Furthermore, since the entire middle part of the ultra-fine metal wire is cut at the same time by a cutting jig with multiple disc-shaped or straight cutting edges, it is necessary to arrange the wire using a simple method that only fixes both ends. This means that a large number of ultra-fine metal wire pieces of a fixed length can be manufactured at the same time.

In addition, as a flat base on which to arrange the ultra-fine metal wires to be cut, it is desirable to use a material that is dense, has a certain degree of elasticity, and is softer than a knife, such as hard rubber or various plastics. The cutting jig can be used repeatedly over a long period of time without causing unnecessary damage.

〔Example〕

Hereinafter, the present invention will be explained in more detail according to examples.

Example 1 FIG. 1 is a schematic diagram showing an outline of a first example according to the present invention. The diameter of the ultra-fine metal wire 1 is 30μ.
M gold wires were arranged in parallel on the upper surface of a hard rubber plate used as a flat base 3, and fixed by adhering adhesive tape 2 to both ends. From one end of this hard rubber plate, a disc-shaped cutting edge 1
By moving the cylindrical cutting jig 10, which was fixed with 0.55 mm pinches to the other end so that the cutting edge traced the upper surface of the hard rubber, cut the ultra-fine gold wire on the hard rubber by 1 mm. Cut into length wire pieces.

The cut gold wire pieces were placed in a flat-bottomed graphite crucible so as not to touch each other, and by high-frequency heating, it was possible to obtain clean, impurity-free gold balls for bumps of uniform size.

Example 2 This embodiment will be explained with reference to FIG. 2, which shows the concept of this embodiment.

Small protrusions 5 are provided at regular intervals on both ends of the hard rubber plate used as the flat base 3, and the ultrafine metal wires are arranged at a constant pitch by passing alternately between the small protrusions 50 at both ends. I made it so that it would be done.

In this example, the ultrafine metal wire has a diameter of 25 μm.
gold wire was used. A small amount of adhesive was applied to the portion where the ultrafine metal wire was folded back and bent along the small protrusion 5 for temporary fixation.

2. This ultra-fine gold wire was cut using a cutting jig 15 made of a large number of razor blades 16 stacked one on top of the other so that the cutting edge portion was flat. The spacing between the razor blades was set to 0.4 mm. From above the hard rubber plate 3 covered with gold wire 1,
This cutting jig 15 was lowered while keeping it horizontal, and brought into contact with the ultrafine gold wire so that the entire length of the wire was cut almost simultaneously.

The cut gold wire piece of fixed length was melted in the same manner as in Example 1, and clean fine gold balls for bumps could be produced.

Example 3 In FIG. 3, a large number of ultrafine metal wires l (gold wires with a diameter of 25 μm) are bundled and both ends are fixed with adhesive. This was placed on a polypropylene plate of a flat base 4 so as not to sag, and the adhesive tape 2 was attached to the parts hardened with adhesive at both ends to fix it to the base.

While rotating the cutting jig 0, which is the same as that used in Example 1 and has a plurality of disc-shaped cutting edges 11 stacked on top of each other at a pitch of 1 mm, a horizontal plane was cut from above the polypropylene plate to which the bundled ultra-fine gold wire was fixed. I lowered it while holding it.

The cut gold wire piece of fixed length was melted in the same manner as in Example 1, and fine gold spheres suitable for use as bumps could be produced.

〔Effect of the invention〕

It is now possible to cut a large amount of standard-sized ultra-fine metal wire pieces of bump metal, which are required when manufacturing humps required by the TAB method etc. by melting, without contaminating impurities. This eliminates the need for impurity removal work when melting ultrafine metal wire pieces during the process, making it possible to efficiently manufacture bumps.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram showing a first embodiment of the present invention, Fig. 2 is a schematic diagram showing a second embodiment of the invention, and Fig. 3 is a schematic diagram showing a third embodiment of the invention. It is. 1... Ultrafine metal wire, 2... Adhesive tape, 3.4...
・Flat base, 5...Small protrusion, 10...Cylindrical cutting jig, 11...Disc-shaped cutting edge, 15...Flat-shaped cutting jig, 16...Straight line shaped cutting edge.

Claims (1)

[Claims] After arranging a plurality of ultra-fine metal wires in parallel on a flat base, the ultra-fine metal wires are cut using a cutting jig with cutting edges lined up at regular intervals to produce ultra-fine metal wire pieces of minute regular length. A method for cutting an ultra-fine metal wire.