JP2005197417A - Capillary and capillary regenerating method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a capillary regenerating method for regenerating a capillary by removing a substance with which the capillary is filled in short time, and to provide the capillary. <P>SOLUTION: It is judged whether the capillary 100 can be regenerated or not from a tip 100a of the capillary 100. When it is judged that the capillary can be regenerated, the substances 200 and 400 existing in a through hole 100d inside the capillary 100 are dissolved, and the substances 200 and 400 are removed. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a hard brittle capillary used in a wire bonding apparatus that electrically connects terminals of a semiconductor element using a wire, and a method for regenerating the capillary.

  In semiconductor assembly, a thin metal wire is generally used to connect a package terminal and an integrated circuit terminal. A device for connecting terminals using metal wires is called a wire bonder device. The types of metal wires used in the wire bonder device can be broadly divided into aluminum wires and gold wires. In recent years, as a tendency of the metal wire used, the case of using a gold wire tends to increase. In addition, the diameter of the wire bonder apparatus is also increasing, and wire bonder apparatuses using a gold wire having a diameter of 20 microns or less are increasing.

  In conventional capillaries, joints are stacked on the side of the capillary. A conduit having the other end connected to a gas source is inserted into the joint. The gas injected from the gas source passes through the capillary and reaches the wire at the tip of the capillary. This is to prevent the wire from clogging in the capillary (see, for example, Patent Document 1).

  Moreover, the capillary 100 of the wire bonder apparatus using the gold wire used normally which does not spout gas is shown in FIG. 1 and FIG. The material of the capillary 100 is generally made of a hard and brittle material such as ceramic or ruby. The capillary 100 includes a front end portion 100a, a slope portion 100b, and a body portion 100c, and the outer diameter decreases from the body portion 100c toward the front end portion 100a. The capillary 100 has a through hole 100d in order to pass the gold wire 200 therein. The through hole 100e is tapered, and the diameter of the through hole 100e increases from the distal end portion 100a toward the body portion 100c. The reason why the diameter is increased is to facilitate insertion of the gold wire 200 into the capillary 100. Further, a chamfered portion 100e having a flat surface is provided at the tip of the tip portion 100a.

Next, a case where the two terminals are electrically connected using the metal wire 200 will be described with reference to FIG. When electrically connecting both terminals using the metal wire 200, first, the gold wire 200 is passed through the through hole 100e of the capillary 100. The tip of the gold wire 200 coming out from the tip 100a is melted by discharge to form a gold ball 200a. The resulting gold ball 200 a is pressed against the first joining location 310 of the element 300. The gold ball 200a and the first joining location 310 are joined while applying ultrasonic vibration. Next, the capillary 100 moves to the second joining location 320 while extending the gold wire 200. The capillary 100 presses the gold wire 200 at the second joining location 320. Ultrasonic vibration is applied to bond the gold wire 200 and the second bonding location 320. Finally, the gold wire 200 is torn by clamping 200b. Bonding is performed by repeating this operation.
Japanese Patent Laid-Open No. 5-47824 (2nd page, FIG. 1)

  However, when such foreign matter adheres to the gold wire, the gold wire drags the dust, so the diameter of the gold wire entrance at the capillary is large, so even if dust can pass through the gold wire, Since the diameter of the outlet narrows, dust is clogged, and the result is that a gold wire cannot pass through and eventually breaks. Even when a capillary in which gas is blown onto a gold wire is used, the gold wire may be clogged in the capillary. There are various types of foreign substances that cause clogging of the gold wire in the capillary in addition to the gold wire for bonding. For example, various foreign matters such as organic foreign matters such as fats and oils and fibrous foreign matters, and inorganic foreign matters such as metal pieces and stones enter the capillaries and prevent the movement of the gold wire.

  When the gold wire is clogged, it takes time and effort to remove the money, so the capillary is positioned as a consumable item and has not been reclaimed by removing the money.

  The capillary regeneration method of the present invention includes a step of determining whether or not the capillary can be regenerated from the tip state of the capillary, and a step of dissolving the substance existing in the capillary and removing the substance when it is determined that regeneration is possible. Consists of.

  In the capillary regeneration method of the present invention, the determination as to whether or not the regeneration is possible is that the capillary is regenerated when the wear of the tip of the capillary is ¼ or less of the height of the unused tip of the capillary. It is supposed to be possible.

  In the capillary regeneration method of the present invention, the substance is dissolved using aqua regia after being immersed in an organic solvent.

  In the capillary regeneration method of the present invention, when the substance is dissolved using the aqua regia, the aqua regia is dissolved by applying ultrasonic vibration.

  In the capillary regeneration method of the present invention, the substance is further dissolved using a strong acid.

  In the capillary regeneration method of the present invention, the aqua regia is placed in a container subjected to fluorine processing to dissolve the substance.

  In the capillary regeneration method of the present invention, after the substance is dissolved, a gas under pressure is ejected onto the capillary to remove the substance. A part of the substance is dissolved without completely dissolving the substance, and then the substance is removed by jetting a gas such as air or nitrogen under pressure.

  The capillary of the present invention is regenerated using the above capillary regeneration method.

  According to the present invention, the gold wire clogged in the capillary can be removed in a shorter time than in the prior art. Thereby, the capillaries that have been discarded can be efficiently regenerated.

  For wire bonders that use gold wires that operate for 24 hours, the capillaries are often replaced at a rate of one per day. As a result of classifying the used capillaries replaced when the present invention was carried out, almost 70% were classified into the reproducible capillaries of the present invention. The capillary regenerated according to the present invention does not have the same life as a new product due to wear of the tip, etc., but by regenerating, the originally discarded capillary can be reused. Because it is inexpensive, it has the effect of contributing to lowering the production cost of the semiconductor post-process.

  Embodiments of the present invention will be described with reference to the drawings.

  In Example 1, a method for regenerating a capillary in the case where a gold wire is clogged in the capillary with oil or fat will be described with reference to FIGS.

The shape before use of the capillary 100 used for regeneration in Example 1 is shown in FIG. The tapered portions 100a and 100b in the outer portion of the capillary 100 are divided into two stages. The capillary 100 used in Example 1 is made of a ceramic in which alumina and zirconia are mixed. The diameter of the gold wire outlet 100d is 25 microns, and the diameter of the gold wire 200 to be used is 20 microns. Looking at the appearance of the used capillary 100 for which regeneration was attempted, it is roughly divided into two. First, the capillary 100 has a shape (hereinafter, referred to as “shape 1”) in which the tip 100a is slightly shaved on the slope 100f. A side view of the shape 1 is shown in FIG. The other is a capillary having a shape in which the tip 100a is worn to near the second taper 100b (hereinafter referred to as “shape 2”).
A side view of the shape 2 is shown in FIG. Most of the capillaries 100 showing the shape 2 are those in which the tip 100a is damaged in the bonding process. It is not impossible to polish the tip 100a on the capillary 100 having the shape 2 and to join only the tip 100a by bonding or other methods. However, the strength of the tip 100a can be sufficiently secured. The joining work is quite difficult. In addition, the amount of processing associated with it was high, and these were taken into consideration from the viewpoint of recycling, and in Example 1, it was treated as a non-recyclable product.

  FIG. 5 is a view of the capillary 100 as viewed from the tip side 100a. FIG. 5A shows the state of the tip 100a of the capillary 100 before use. In many cases, the inner surface of the tip portion 100a is chamfered 100e for preventing burr, and the inside thereof is a cavity 100d. The cavity 100d has a tapered shape inside and is hollow up to the opposite side, that is, the portion into which the gold wire is inserted. However, the tip 100a of the capillary 100 having the shape 1 is in a state where the metal wire 200 is cut and clogged as shown in FIG. Alternatively, as shown in FIG. 5C, there may be a state in which the fracture surface of the metal wire 200 is not visible and the substance 400 in which dust is hardened with oil or fat is clogged.

  In the case of FIG. 5B and FIG. 5C, a physical force is applied to the gold wires 200, 400 from the tip 100a of the capillary 100 in order to remove the gold wires 200, 400. It is packed so hard that the gold wires 200 and 400 cannot be removed easily. The clogging of the metal wire 200 is caused by clogging of the gold wire 200 used for wire bonding at the outlet portion 100d of the capillary 100 where the taper is thinned by entraining dust such as floating dust, and as a result, the gold wire 200 is damaged. As a result, it is most likely that the gold wire 200 is clogged. In order to remove the clogging material including the gold wire 200, the mechanical pressure from the tip 100 a of the capillary 100, for example, a method of piercing with a needle with a thin tip or a metal wire or a method of injecting compressed air is added to the eye. A method of pushing out the clogging can be considered. However, with this method, the tip may be damaged, and the work of applying a needle to a very small hole of 25 microns is not efficient and is not suitable for mass production reproduction. On the other hand, the gold wire 200 can be judged from the state of gloss or fractured surface by microscopic observation. Therefore, a method of chemically melting the gold wire 200 is used.

  The capillary regeneration process will be described with reference to the flowchart of FIG. First, a used capillary 100 is prepared (step 201). It is determined whether the prepared capillary 100 can be regenerated (step 202). First, the reproducible capillary 100 has the appearance shown in FIG. 4B, and the inside of the capillary 100 is clogged by the gold wires 200 and 400 as shown in FIGS. 5B and 5C. It is a thing. In other words, the used capillary 100 determined to be recyclable is a capillary having no damage other than the wear of the tip 100a, and the tip wear 100f is not more than a quarter of the first taper portion 100a. The reason that the wear of the first taper portion 100a is regulated to a quarter or less is that the internal cabbage of the capillary 100 has a tapered shape that becomes narrower toward the tip of the capillary 100a, and is aimed at when the inner diameter of the tip is increased. This is because there is a problem that the wire cannot be struck at the same place.

  Next, the capillary 100 determined to be regenerated is immersed in an organic solvent for degreasing (step 203). The organic dust 400 clogged with the metal wire 200 inside the capillary 100 usually contains oil and fat. Since this oil and fat prevents the erosion of the solvent used to dissolve the gold wire 200 to be performed next, removing the oil and fat accelerates the dissolution of the gold wire 200 and promotes work efficiency. As the organic solvent, alcohols such as acetone and IPA and aromatic organic solvents such as benzene can be used. In this example, acetone was used as the organic solvent. Further, in order to accelerate degreasing, the capillary 100 was placed on cotton and degreased by applying ultrasonic vibration for 6 hours.

  Next, the capillary 100 that has been degreased is dried and the organic solvent component is removed (step 204). Since acetone was used in this example, it was highly volatile and was naturally dried. Next, aqua regia 720 is produced by mixing at a ratio of nitric acid 1 and hydrochloric acid 3 (step 205). Next, the aqua regia 720 produced in the previous step is transferred to the container 710 (step 206), and the degreased capillary 100 is placed in the container 710 (step 206). An ultrasonic vibration is applied to the container to melt the gold wire (step 207). The container 710 used in this example was made of fluorine processing. When the aqua regia 720 melts the gold wire 200, the addition of ultrasonic vibration 740 increases the dissolution rate. However, if the capillary 100 jumps in the aqua regia 720 by the ultrasonic vibration 740, the capillary tip 100a may be damaged, so a buffering agent on which the capillary 100 is placed is necessary. However, there are few buffering agents that show durability against the highly reactive aqua regia 720, and by using a fluorine-processed container 710, it was possible to provide both functions of the container and the buffering agent. It is possible to increase the dissolution rate of the gold wire 200 by heating the aqua regia 720, but it is preferable to keep the solution temperature within 50 degrees Celsius. In this example, aqua regia was used at room temperature. Since the melting time of the gold wire 200 differs depending on the clogged state inside the capillary, it takes two days and nights in this embodiment, although it differs depending on the individual.

  After completion of the metal wire melting operation, the capillary is washed with water to wash away the aqua regia component 720 (step 208). When the gold wire 200 is released from the clogging inside the capillary 100, the clogging substance is removed due to the influence of ultrasonic vibration. If the clogging substance is not removed, the clogging substance is pushed out by blowing compressed air from the tip end side of the capillary (step 209). Normally, it is not necessary to push out clogging substances, but clogging substances can be removed. Next, it wash | cleans using alcohol (process 210). In this example, ethanol was used. The capillary 100 is dried (step 211) and packed (step 212). For packaging, a vinyl chloride box was used to form a packaging box.

  When the capillary 100 is clogged only with the gold wire 200, the step of degreasing the capillary 100 with an organic solvent (step 204) and the step of drying the capillary 100 (step 205) can be omitted.

  Next, a method of regenerating the capillary 100 when the cause of clogging of the capillary is other than the gold wire 200 and the organic dust 400 will be described with reference to FIG. Many causes of clogging of capillaries can be assumed in addition to the gold wire 200 and the organic dust 400. For example, the movable part of the wire bonder device wears out to give a metal piece that becomes clogged, or the lubricating oil is solidified, which may cause clogging. In this embodiment, the case where the metal type cannot be specified will be described.

  The capillary 100 is prepared (step 301). The prepared capillary 100 may be a capillary that could not be clogged in Example 1. Further, in the determination step (step 202) of the first embodiment, the capillary 100 may be determined that the cause of the clogging is not soluble in an organic solvent other than the gold wire 200 and the organic dust 400.

Next, the capillary 100 is put in a container containing a solvent for dissolving metal (step 302).
Generally, a strong acid such as hot concentrated sulfuric acid, cyanic acid or hot concentrated phosphoric acid is used as the solvent for dissolving the metal. In this example, cyanic acid was used. Ultrasonic vibration is applied to the container to dissolve the metal clogging (step 303). As the cyanic acid container, a fluorine-treated container as in Example 1 was used. The working time was two days and nights.

  The solvent is washed away (step 304). As in Example 1, when the metal portion is dissolved but the clogging substance is not removed, compressed air is blown from the tip side of the capillary (step 305). In this way, clogging substances can be removed.

  Next, it wash | cleans using alcohol (process 306). In this example, ethanol was used. The capillary is dried (step 307), and the capillary 100 is packed (step 308).

  Next, a method for regenerating the capillary 100 when the tip 100a of the capillary 100 is deformed will be described with reference to FIGS. The deformation of the capillary tip 100a is caused by wear because the capillary tip 100a is pressed against the bonding surface during wire bonding. As shown in FIG. 4B, the worn capillary tip has a generally reduced shape. When this half reduction is an extremely acute angle, the regenerated capillary 100 may not be able to normally hit the wire, so the wear surface 100f needs to be processed flat.

Since wear is a very small part of the tip, correction is generally performed by chemical polishing. Since the capillary is generally made of ceramic or alumina single crystal, a colloidal silica-based abrasive is suitable as the abrasive. Unlike the mechanical polishing method, the chemical polishing method has the feature that it is difficult to cause chipping around the polishing surface, and the polishing edge is rounded like a chamfer, so when the capillary tip is chemically polished, flattening and chamfering are not possible. There is an advantage that can be done at once.
Based on the flowchart shown in FIG. 12, the chemical polishing process performed in the present embodiment will be described. First, the capillary 100 whose tip is deformed is prepared (step 401). The prepared capillary 100 is a capillary having no damage other than the wear of the tip 100a, and the tip wear 100f is not more than a quarter of the first taper portion 100a. The reason that the wear of the first taper portion 100a is regulated to a quarter or less is that the internal cabbage of the capillary 100 has a tapered shape that becomes narrower toward the tip of the capillary 100a, and is aimed at when the inner diameter of the tip is increased. This is because there is a problem that the wire cannot be struck at the same place.
The capillary is mounted on the set jig 900 (step 402). The jig 900 prevents overcutting of the tip of the capillary 100 and keeps the capillary 100 perpendicular to the polishing surface 100f.
Next, the polishing disk 910 with the polishing pad 920 stretched is rotated, and the tip of the capillary is polished while pressing the capillary set on the jig 900 against the polishing pad while flowing the polishing agent 930 (step 403). Chemical polishing is usually performed with a combination of a chemical polishing agent and a polishing pad. An alkaline aqueous solution of colloidal silica having a central particle size of 40 nanometers was used as the polishing agent, and a hard nylon polishing pad was used as the polishing pad. In addition, a circulating polishing method was used in which the polishing agent was heated to 50 degrees Celsius at the part to be processed and polished while circulating the polishing agent.

  The polished capillary is washed with alcohol (step 404) and dried (step 405). In this example, ethanol was used. The tip of the capillary that has been polished is inspected (step 406). The inspection is an appearance inspection, and the appearance shape is observed using a stereomicroscope. The observation contents are the parallelism of the capillary tip, the chipping state around the tip, cracks, and the like.

It is the figure showing the shape of the capillary for gold wire wire bonders, (A) is the external appearance shape figure of a capillary, (B) is the figure which looked at the capillary from the tip. It is a figure which shows the internal structure of a capillary, and the shape of a gold wire. It is the figure showing the method of wire bonding by a gold wire, (A) is the state which forms a gold ball by heating, (B) is the 1st bonding state, (C) is the drawing state of a gold wire, (D) Is the second bonding state, and (E) is the gold wire cutting and the completion state of the work. It is a figure showing a capillary, its breakage, and a wear state, (A) is an outline drawing of a capillary before use, (B) is a capillary outline drawing with slight wear of a tip, and (C) is a tip breakage or excessive wear. It is an external view of a capillary. It is a figure which shows the clogging of a capillary and its state, (A) is the state of a capillary before use, (B) is the clogged state of a metal wire, (C) shows the clogged state with organic dust. It is an external view of a reproducible capillary. It is a schematic diagram of the dissolution process of the gold wire by aqua regia. It is a flowchart which shows a capillary regeneration process. It is a flowchart when melting substances other than a gold wire. It is an external view of the capillary tip calibration jig and its mounting method, (A) is a side view of the calibration jig, and (B) is a view of the calibration jig as seen from below. It is a schematic diagram of capillary tip calibration polishing processing. It is a flowchart of capillary tip calibration.

Explanation of symbols

100 Capillary 200 Gold wire 400 Organic dust 710 Container 720 Aqua regia 730 Electric heater

Claims (8)

  A method for regenerating a capillary comprising the steps of determining whether or not the capillary can be regenerated from the state of the tip of the capillary, and dissolving and removing the substance present in the capillary when it is determined that the capillary can be regenerated.   The determination as to whether or not the regeneration is possible is that the capillary can be regenerated when the wear of the tip of the capillary is ¼ or less of the height of the unused tip of the capillary. The capillary regeneration method described.   3. The capillary regeneration method according to claim 1, wherein the substance is dissolved using aqua regia after being immersed in an organic solvent.   The capillary regeneration method according to claim 3, wherein when the substance is dissolved using the aqua regia, the aqua regia is dissolved by applying ultrasonic vibration.   The capillary regeneration method according to claim 3 or 4, wherein the substance is further dissolved using a strong acid.   6. The capillary regeneration method according to claim 3, wherein the aqua regia is placed in a fluorine-processed container to dissolve the substance.   The capillary regeneration method according to any one of claims 1 to 6, wherein after the substance is dissolved, a gas to which pressure is applied is jetted onto the capillary to remove the substance.   A capillary which is regenerated using the capillary regeneration method according to any one of 1 to 7 above.

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