JP2008218789A - Wire bonding method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wire bonding method which joints a wire to a jointing member by use of a capillary mounted to a horn for moving and vibrating by means of the horn, wherein an organic substance attached to a tip of the capillary can be properly removed without dismounting the capillary from the horn for replacement. <P>SOLUTION: A plasma irradiation part 210 for a plasma irradiation is provided surrounding jointing members 10, 20, and before a bonding wire 30 is jointed to the jointing members 10, 20, a capillary 100 is moved to the plasma irradiation part 210 by the horn, and the plasma irradiation is performed on a tip 102 of the capillary 100 to remove the organic substance attached to the tip 102. Successively, the capillary 100 is moved to the jointing members 10, 20 by a horn 110 for jointing the wire 30. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a wire bonding method for bonding a wire to a member to be bonded using a capillary attached to a horn.

  Conventionally, this type of wire bonding is performed by attaching a capillary that can be pulled out while holding the wire to a horn of a wire bonding apparatus. This horn can move and vibrate the capillary.

Specifically, the wire is inserted into the capillary by vibrating the capillary with the horn in a state where the wire portion led out from the tip of the capillary is pressed against the member to be joined. It joins to a joining member. Such a wire bonding method is called a so-called ball bonding method (see, for example, Patent Document 1).
Japanese Patent Laid-Open No. 9-17817

  By the way, recent semiconductor mounting tends to perform high-density mounting having a process of combining various composite members. Here, FIG. 5 is a schematic cross-sectional view showing a semiconductor mounting structure made by the inventors of the present invention.

  In the mounting structure shown in FIG. 5, a substrate 10 made of ceramic, resin, or the like is connected to a casing 50 such as alumina die cast by a silicone adhesive 40, and the land 11 on the substrate 10 and the substrate 10 are connected. In this structure, the electrode 21 of the mounted semiconductor element 20 is connected by a wire 30 made of Au wire.

  Here, the wire 30 is inserted into the inner hole 101 of the capillary 100 formed of ceramic or the like, and is led out from the distal end portion 102 of the capillary 100. The capillary 100 is attached to the horn of a wire bonding apparatus (not shown) and can move to a desired position or vibrate.

  In the wire bonding step, the capillary 100 is applied to the electrodes 11 and 21 in the member to be bonded, and the capillary 100 is vibrated by vibration from the horn, thereby bonding the wire 30.

  In this case, since there is a step of curing the silicone adhesive 40 before the wire bonding step, the organic substance K such as a siloxane component generated from the silicone adhesive 40 on the land 11 of the substrate 10 and the electrode 21 of the semiconductor element 20 at the time of curing. Further, the organic substance K scattered when the substrate 10 is heated during wire bonding adheres to the tip 102 of the capillary 100.

  When such an organic substance K adheres to the tip portion 102 of the capillary 100, the bonding strength of the wire 30 is insufficient, or the wire bonding performance is deteriorated such that the wire 30 is not attached. Yes.

  Further, when the organic substance K adheres to the tip portion 102 of the capillary 100, the capillary 100 must be removed from the horn and replaced in accordance with the degree of adhesion, resulting in problems such as troublesome replacement. .

  Here, in Patent Document 1, a vent hole for exhausting fumes during heating is provided in a fixing jig for wire bonding in order to prevent capillary contamination. However, in this method, once the organic matter adheres to the capillary, it cannot be removed, and the above-described problem of replacement of the capillary still occurs.

  In addition to those shown in the prototype, if the member to be joined itself or the part attached to the member to be joined has an adhesive or resin part, these adhesives or It is considered that scattered matter is generated from the resin portion in the same manner as described above. For this reason, it is considered that the organic substance adheres to the tip portion of the capillary as described above, if it is a structure having such an adhesive or a resin part.

  The present invention has been made in view of the above problems, and in a wire bonding method for bonding a wire to a member to be bonded using a capillary attached to a horn, the capillary is removed from the horn without replacement. The object is to enable appropriate removal of organic substances adhering to the tip.

  In order to achieve the above object, in the wire bonding method of the present invention, a plasma irradiation part (210) for performing plasma irradiation is provided around the members to be bonded (10, 20), and the members to be bonded ( 10 and 20), the capillary (100) is moved to the plasma irradiation part (210) by the horn (110) and the tip (102) of the capillary (100) is irradiated with plasma before joining to the tip. The organic substance adhering to the part (102) is removed, and then the capillary (100) is moved to the member (10, 20) by the horn (110) to join the wire (30). And

  According to this, before bonding the wire (30) to the members to be bonded (10, 20), plasma is applied to the tip (102) of the capillary (100) with the capillary (100) attached to the horn (110). Since irradiation can be performed, organic substances attached to the tip (102) of the capillary (100) can be appropriately removed without removing the capillary (100) from the horn (110) and replacing it.

  As a result, according to the present invention, wire bonding performance can be improved. Here, oxygen radical irradiation, argon plasma irradiation, etc. are employable as plasma irradiation.

  In this case, a laser irradiation part (220) for performing laser irradiation is provided around the members to be bonded (10, 20), and before performing plasma irradiation, the capillary (100) is moved by the horn (110) to the laser irradiation part ( 220) to irradiate the tip (102) of the capillary (100) with laser, and then move the capillary (100) to the plasma irradiator (210) by the horn (110) to perform plasma irradiation. It may be.

  According to this, by performing laser irradiation on the tip (102) of the capillary (100) before plasma irradiation, the organic matter adhering to the tip (102) is thermally decomposed or the organic matter is physically removed. Since it can be scraped off, it can be easily removed by subsequent plasma irradiation.

  In this case, a cleaning member (230) to which the tip (102) of the capillary (100) is rubbed is provided around the member to be joined (10, 20), and after the plasma irradiation, the wire ( 30) Before joining the member to be joined (10, 20), the horn (110) moves the capillary (100) to the cleaning member (230) to clean the tip (102) of the capillary (100). You may make it rub against a member (230).

  According to this, it is possible to scrape off organic matter remaining on the tip (102) of the capillary (100) after plasma irradiation.

  Further, when the member to be joined (10, 20) is cured by heating and has an adhesive (40) that generates scattered matter in the air by the heating, the above-described organic capillary (100) is used. However, even in such a case, the above means are effective.

  Here, as such an adhesive (40), what consists of a silicone resin in which organic substances, such as above-mentioned siloxane, disperse | spatter is used.

  In addition, the code | symbol in the bracket | parenthesis of each means described in the claim and this column is an example which shows a corresponding relationship with the specific means as described in embodiment mentioned later.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following drawings, parts that are the same or equivalent to each other are given the same reference numerals in the drawings for the sake of simplicity.

  FIG. 1 is a schematic cross-sectional view of an electronic device S1 according to an embodiment of the present invention. In the electronic device S1, the substrate 10 is a ceramic substrate, a printed circuit board, a lead frame, a heat sink or the like, and an IC chip 20 as a semiconductor element is mounted on one surface (the upper surface in FIG. 1) of the substrate 10. Yes.

  The IC chip 20 is bonded to the substrate 10 with a die bond material or the like (not shown). The IC chip 20 is a general chip formed by forming an IC circuit using a transistor element or the like on a silicon semiconductor or the like, and has an electrode 21 made of Al, Cu or the like on the surface thereof.

  Further, a land 11 as an electrode of the substrate is provided in the vicinity of the IC chip 20 on one surface of the substrate 10. The land 11 is made of a foil such as Au or Cu, a conductor paste, or the like. The land 11 of the substrate 10 and the electrode 21 of the IC chip 20 are connected via a bonding wire 30.

  As described above, in the present embodiment, the substrate 10 and the IC chip 20 are configured as members to be bonded to which the bonding wires 30 are connected, and the land 11 and the electrode 21 are connected by the bonding wires 30 as described above. Thus, the substrate 10 and the IC chip 20 are electrically connected.

  Here, the bonding wire 30 is formed by wire bonding using a ball bonding method as described later, and is made of, for example, Au or Cu. In addition to the IC chip 20, an electronic component made of a capacitor, a resistance element, or the like (not shown) may be mounted on one surface of the substrate 10.

  A housing 50 is connected to the other surface (the lower surface in FIG. 1) of the substrate 10 via an adhesive 40. Here, the adhesive 40 is made of a material such as a silicone resin or an epoxy resin that is cured by heating, and a low-molecular component in the adhesive 40 such as siloxane is generated as a scattered matter by the heating.

  That is, in the present embodiment, the adhesive 40 is attached to the other surface of the substrate 10, so that the adhesive that generates the scattered matter is attached to the substrate 10 as a member to be joined. Yes.

  The housing 50 is not particularly limited as long as it houses or supports the substrate 10 and is bonded to the substrate 10 via the adhesive 40. Specifically, examples of the substrate 10 include a general lead frame, a bus bar, and a case made of aluminum.

  In FIG. 1, the connection by the bonding wire 30 is performed between the substrate 10 and the IC chip 20, but other than that, for example, between the substrate 10 and the housing 50 or on the substrate 10. The connection by the bonding wire 30 of this embodiment may be performed between different electrodes, and also between the IC chip 20 and the housing 50.

  In the electronic device S1 of this embodiment, the substrate 10 and the IC chip 20 are connected via the die bond material, and the casing 50 and the substrate 10 are connected via the adhesive 40, and then bonded. By forming a wire, the IC chip 20 and the substrate 10 are connected via the bonding wire 30.

  Next, a method for forming the bonding wire 30 in the electronic device S1 of the present embodiment, that is, a wire bonding method will be described with reference to FIGS. FIG. 2 is a view showing the periphery of the capillary 100 of the wire bonding apparatus for performing the wire bonding method, and FIG. 3 is a process for bonding the wire 30 to the members to be bonded 10 and 20 in the wire bonding method (wires). It is process drawing which shows a joining process.

  Here, the electrode 21 of the IC chip 20 is used as the primary bonding side, and the land 21 of the substrate 10 is used as the secondary bonding side, and both the bonding members 10 and 20 are wire-bonded by a ball bonding method.

The wire bonding apparatus in the present embodiment is a ball bonding apparatus that can perform general ball bonding. As shown in FIG. 2, the wire 30 is attached to the horn 110 that vibrates by ultrasonic waves or the like. The holding capillary 100 is attached.
The capillary 100 is moved and vibrated by the horn 110. As shown in FIG. 3, the capillary 100 inserts the bonding wire 30 into the inner hole 101 to hold the wire 30 and feeds the wire 30 to the tip portion 102.

  First, as shown in FIG. 3A, in the wire 30 inserted into the inner hole 101 of the capillary 100, a ball (which is formed into a spherical shape by electric discharge machining) is formed at the tip of the portion derived from the tip 102 of the capillary 100. Initial ball) 31 is formed.

  Next, this ball 31 is pressed against the electrode 21 of the IC chip 20 and joined while applying ultrasonic vibration, as shown by an arrow Y in FIG. 3B, to perform primary bonding. Thereafter, the wire 30 is drawn out from the tip end portion 102 of the capillary 100 and drawn to the land 11 of the substrate 10 (see FIG. 3C).

  Next, the wire 30 routed to the land 11 is pressed against the land 11 at the tip portion 102 of the capillary 100, and ultrasonic vibration is applied as indicated by an arrow Y in FIG. Bonding and secondary bonding are performed.

  Then, the capillary 100 is moved upward in the order shown by the arrows in FIG. 3E to separate the bonding wire 30 from the land 11 of the substrate 10 on the secondary bonding side. Thus, the wire bonding process in the present wire bonding method is completed.

  When the bonding wire 30 is cut off, the wire 30 protrudes from the tip 102 of the capillary 100 and remains as a tail 32. The tail 31 is again subjected to electric discharge machining in the same manner as described above to form the ball 31. . Thus, one cycle of ball bonding is completed and the next cycle is performed.

  Here, also in the wire bonding method of the present embodiment, scattered matter is generated when the adhesive 40 is heated, so that the scattered organic matter may adhere to the tip 102 of the capillary 100.

  Therefore, the wire bonding method of this embodiment further includes a step of irradiating the tip portion 102 of the capillary 100 with plasma before removing the organic substances adhering to the tip portion 102 before performing the ball bonding. . Specifically, the organic substance removing step is performed before the first cycle of the ball bonding or during each cycle of the ball bonding.

  That is, the organic matter removing step of the present embodiment is performed before and after the wire bonding step, but this organic matter removing step may be performed according to the degree of contamination of the capillary 100, that is, one cycle of the wire joining step, that is, It may be performed every one cycle of the ball bonding shown in FIG. 3 or may be performed every plural cycles.

  Therefore, the wire bonding apparatus according to the present embodiment includes an organic substance removing unit as a part for performing the organic substance removing step in addition to the above-described normal wire bonding apparatus. Here, FIG. 4 is a diagram showing a schematic configuration of the wire bonding apparatus according to the present embodiment including the organic substance removing unit 200.

  As shown in FIG. 4, the wire bonding step is performed in a state where the work is mounted and supported on the heat piece 120. The heat piece 120 functions as a fixing jig that supports the workpiece and also functions as a heater that heats the workpiece by energization, and is generally used in this type of ball bonding.

  Then, as shown in FIG. 4, the organic substance K is generated from the adhesive 40 adhering to the substrate 10 that is the member to be bonded due to heating at the time of wire bonding, and this adheres to the tip 102 of the capillary 100. .

  In this embodiment, the organic substance removing unit 200 is provided around the heat piece 120, that is, around the members to be joined 10 and 20, and after the wire joining step, the capillary 100 remains attached to the horn 110 and remains to be joined 10. , 20 to the organic substance removing unit 200.

  Here, the organic substance removing unit 200 in the wire bonding apparatus of this embodiment is for rubbing and cleaning the plasma irradiation unit 210 that performs plasma irradiation, the laser irradiation unit 220 that performs laser irradiation, and the tip portion 102 of the capillary 100. The cleaning member 230 is provided.

  The plasma irradiation unit 210 is, for example, a general atmospheric pressure plasma apparatus. In the plasma irradiation unit 210, plasma is blown out from a plasma blowing port 211.

Here, examples of the gas used in the plasma irradiation unit 210 include oxygen radical irradiation and argon plasma irradiation. The action mechanism of the oxygen radical irradiation is that the organic substance C is separated and removed in the state of CO ₂ , while the argon plasma irradiation physically removes the organic substance.

  Further, the laser irradiation unit 220 of the present embodiment is, for example, a general semiconductor laser generator, and emits an infrared laser generated from the semiconductor laser generator from the laser light guide fiber 221.

  The cleaning member 230 may be any member that removes the organic matter by rubbing the tip portion 102 of the capillary 100 against the cleaning member 230, and the material thereof is not particularly limited, such as metal, resin, or ceramic.

  Further, in this wire bonding apparatus, the heat piece 120 on which the members to be joined 10 and 20 are mounted and the organic substance removing unit 200 are arranged close to each other so as to be located within the movable range of the horn 110. As a result, the horn 110 enables the capillary 100 to move between the members to be joined 10 and 20 and the organic substance removing unit 200.

  In this wire bonding method, the organic substance removing step is performed between the cycles of the wire bonding process as described above using the organic substance removing unit 200 shown in FIG. Note that the arrows Y1 and Y2 in FIG. 4 indicate the paths along which the capillary 100 moves in this method.

  First, in this organic substance removal step, for example, after the end of one cycle of the wire bonding step, the horn 110 moves the capillary 100 from the bonded members 10 and 20 side to above the laser light guide fiber 221 of the laser irradiation unit 220. .

  Then, laser irradiation is performed from the laser light guide fiber 221 to the tip portion 102 of the capillary 100. By performing this laser irradiation, the organic matter adhering to the tip portion 102 of the capillary 100 is thermally decomposed, or the organic matter is physically removed by micro-cutting the surface of the tip portion 102.

  As a specific example of this laser irradiation, an infrared laser generated from a semiconductor laser is irradiated to the tip portion 102 of the capillary 100 from a laser light guide fiber 221 having a diameter of 0.8 mm, for example, so that it is heated to about 100 to 200 ° C. To do. Thereby, the organic matter is thermally decomposed. Here, although depending on the type of organic matter, an example of the siloxane decomposition temperature is about 130 ° C. In addition, about the temperature by this heating, when setting a temperature range in detail, what is necessary is just to employ | adopt the method of measuring temperature from general infrared rays.

  After this laser irradiation, subsequently, the capillary 100 is moved above the plasma outlet 211 of the plasma irradiation unit 210 by the horn 110. And plasma irradiation is performed to the front-end | tip part 102 of the capillary 100 from the plasma blowing outlet 211, and the organic substance adhering to the said front-end | tip part 102 is removed.

As a specific example of this plasma irradiation, oxygen radical plasma generated from a plasma apparatus is irradiated to the tip portion 102 of the capillary 100 at a speed of 30 to 50 mm / second with a spot size of φ5 to 10 mm. Thereby disconnecting the molecules of organic substances C adhering to the tip 102 can be removed in the form of carbon dioxide CO _2.

  The capillary 100 is moved to the cleaning member 230 by the horn 110 after the plasma irradiation and before the wire 30 is bonded to the members 10 and 20 to be bonded.

  Then, the distal end portion 102 of the capillary 100 is pressed against the cleaning member 230 and the horn 110 is vibrated to rub the distal end portion 102 against the cleaning member 230. This makes it possible to mechanically remove the organic matter remaining after the plasma irradiation.

  Thus, the organic substance removing step is completed, and subsequently, the capillary 100 is moved from the cleaning member 230 to the members to be joined 10 and 20 by the horn 110, and the wire 30 is joined. When a plurality of bonding wires 30 are formed, the steps of wire bonding and organic substance removal described above are repeated.

  As described above, according to the wire bonding method of the present embodiment, the plasma irradiation unit 210 is provided around the members to be bonded 10 and 20, and the capillary 100 is used by the horn 110 before the wire bonding as an organic substance removing step. Is moved to the plasma irradiation unit 210 to perform plasma irradiation, thereby removing organic substances from the tip portion 102 of the capillary 100. Subsequently, the capillary 100 is moved to the bonded members 10 and 20 by the horn 110, and the wire 30 is moved. The members 10 and 20 to be joined are joined together.

  According to this method, it is possible to irradiate the tip portion 102 of the capillary 100 with plasma while the capillary 100 is attached to the horn 110 before wire bonding, so that the capillary 100 is not removed from the horn 110 and replaced. The organic matter adhering to the tip portion 102 of the capillary 100 can be removed.

  As a result, according to the present embodiment, it is possible to ensure the bonding strength of the wire 30 and prevent non-bonding, improve the wire bonding performance, and increase the replacement interval of the capillary 100. Become.

  In the wire bonding method of the present embodiment, the laser irradiation unit 220 is provided around the members to be bonded 10 and 20, and the horn 110 is used to connect the capillary 100 to the laser irradiation unit before performing plasma irradiation in the organic substance removal step. The tip end 102 of the capillary 100 is irradiated with laser by moving to 220, and then the capillary 100 is moved to the plasma irradiation unit 210 by the horn 110.

  According to this, by performing laser irradiation on the tip 102 of the capillary 100 before plasma irradiation without removing the capillary 100 from the horn 110 and exchanging it, the organic matter attached to the tip 102 is thermally decomposed or physically Cutting is performed. Therefore, removal by subsequent plasma irradiation can be easily performed.

  Furthermore, in the wire bonding method of the present embodiment, after the plasma irradiation and before the wire bonding, the capillary 100 is moved to the cleaning member 230 by the horn 110 and the tip portion 102 of the capillary 100 is rubbed. Later, organic matter remaining on the tip 102 of the capillary 100 can be scraped off, and further cleaning becomes possible.

(Other embodiments)
In the above embodiment, the organic substance removing unit 200 includes the plasma irradiation unit 210, the laser irradiation unit 220, and the cleaning member 230. However, the organic substance removing unit 200 includes at least the plasma irradiation unit 210. It only has to be.

  For example, the organic substance removing unit 200 may be configured by only the plasma irradiation unit 210, only the plasma irradiation unit 210 and the laser irradiation unit 220, or only the plasma irradiation unit 210 and the cleaning member 230. It may be configured.

  In addition, the plasma irradiation method in the plasma irradiation unit 210 and the laser irradiation method in the laser irradiation unit 220 are not limited to the above-described examples, and may be changed as appropriate according to the type of organic substance so as to exhibit the above effects. Also good.

  Further, the cleaning member 230 may be configured such that the surface on which the tip portion 102 of the capillary 100 is rubbed is configured as a surface that is rotated by a roll or the like, so that it can be rubbed with a new surface at all times.

  Further, the members to be joined are not limited to the substrate 10 and the IC chip 20 described above, and other members may be used as long as the wires 30 can be connected by the wire bonding method described above.

It is a schematic sectional drawing of the electronic device which concerns on embodiment of this invention. It is a figure which shows the peripheral part of the capillary in the wire bonding apparatus which concerns on the said embodiment. It is process drawing which shows the wire bonding process in the wire bonding method which concerns on the said embodiment. It is a figure which shows the typical structure of a wire bonding apparatus provided with the organic substance removal part which concerns on the said embodiment. It is a schematic sectional drawing which shows the semiconductor mounting structure which this inventor made as an experiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Board | substrate as to-be-joined member, 20 ... IC chip as to-be-joined member,
30 ... bonding wire, 40 ... adhesive, 100 ... capillary,
101 ... inner hole of capillary, 102 ... tip of capillary, 110 ... horn,
210: Plasma irradiation unit, 220: Laser irradiation unit, 230: Cleaning member.

Claims (5)

A wire (30) is inserted into the inner hole (101) of the capillary (100) attached to the horn (110) and moved and vibrated by the horn (110), and led out from the tip (102) of the capillary (100). The capillary (100) is vibrated in a state in which the portion of the wire (30) pressed against the member (10, 20) to be bonded, whereby the wire (30) is moved to the member (10, 20). 20) In the wire bonding method adapted to be bonded to
A plasma irradiation part (210) for performing plasma irradiation is provided around the bonded members (10, 20),
Before the wire (30) is bonded to the members to be bonded (10, 20), the capillary (100) is moved to the plasma irradiation unit (210) by the horn (110) to move the capillary (100). ) Plasma is applied to the tip (102) to remove organic matter adhering to the tip (102),
Subsequently, the wire (30) is joined by moving the capillary (100) to the members (10, 20) to be joined by the horn (110). A laser irradiation part (220) for performing laser irradiation is provided around the bonded members (10, 20),
Before performing the plasma irradiation, the tip (102) of the capillary (100) is irradiated with laser by moving the capillary (100) to the laser irradiation part (220) by the horn (110),
2. The wire bonding method according to claim 1, wherein the plasma irradiation is performed by moving the capillary (100) to the plasma irradiation unit (210) by the horn (110). A cleaning member (230) to which the tip (102) of the capillary (100) is rubbed is provided around the member to be joined (10, 20),
After performing the plasma irradiation and before bonding the wire (30) to the members to be bonded (10, 20), the horn (110) is used to connect the capillary (100) to the cleaning member (230). The wire bonding method according to claim 1 or 2, wherein the tip (102) of the capillary (100) is pressed against and rubbed against the cleaning member (230). The member to be joined (10, 20) is characterized in that a member that is cured by heating and has an adhesive (40) that generates scattered matter in the air by the heating is used. The wire bonding method according to any one of the above. The wire bonding method according to claim 4, wherein the adhesive (40) is made of a silicone resin.

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