JP3123342B2 - Apparatus and method for cleaning workpiece electrode - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus and a method for cleaning a workpiece electrode such as a printed circuit board or a lead frame, or a workpiece electrode such as a chip mounted thereon. Things.

[0002]

2. Description of the Related Art In wire bonding in which electrodes of a substrate and electrodes of a chip mounted on the substrate are connected by wires, if the electrodes on the surface of the substrate or the chip are contaminated with an oxide film or an organic substance, a bonding failure occurs. Cheap. Therefore, the present applicant has proposed a plasma cleaning apparatus for cleaning electrodes on the surface of a substrate or a chip prior to wire bonding (Japanese Patent Application Laid-Open No. 4-123430).

In this plasma cleaning apparatus, a substrate on which a chip is mounted is housed in a casing, and plasma is generated in the casing so that ions are bombarded on the surface of the electrode to clean the substrate. The advantage is that the substrate can be cleaned with good workability.

[0004]

However, in the above-described conventional plasma cleaning apparatus, since ions collide not only with the electrodes but also over the entire surface of the substrate or chip, the surface of the substrate or chip other than the electrodes is easily damaged by cleaning. There was a problem. Further, this plasma cleaning apparatus is a rather large facility, requires a large installation space, and is considerably expensive.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an apparatus and a method for cleaning a work electrode, which can easily clean only electrodes of a substrate or a chip.

[0006]

Means for Solving the Problems] The present invention To this end, word
A positioning portion for positioning the workpiece, a first probe for applying a voltage to the electrode of the work, and a lower end portion which is a needle-like electrode which approaches the electrode and generates a discharge between the electrode and the first probe.
Cleaning the electrode of the workpiece from a second probe having the first probe, a voltage applying means for applying a voltage to each of the first probe and the second probe, and a moving means for moving the second probe relative to the substrate. This is a device configuration.

[0007]

According to the above construction, when a voltage is applied to the electrode of the substrate by the first probe and a voltage is applied by bringing the second probe close to this electrode, a discharge is caused between the electrode and the second probe. Are generated, and electrons generated by the discharge collide with the surface of the electrode to clean the surface of the electrode.

[0008]

Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a side view of an apparatus for cleaning an electrode of a work according to a first embodiment of the present invention, FIG.
FIG. 4 is an enlarged sectional view of the main part, and FIG. In FIG. 1, reference numeral 1 denotes a cleaning unit, which holds a probe unit 3 at the tip of an arm 2. Next, the structure of the cleaning unit 1 will be described with reference to FIG.

The arm 2 is formed of a conductive material such as copper. The probe section 3 includes a first probe 4 and a second probe 5. The first probe 4 is a hollow body having a lower elongated cylindrical shape, made of an insulating material such as ceramic, and has an outer surface and a lower surface coated with a conductive film 6 (see also FIG. 3). This conductive film 6 is, for example, nickel plating.

In FIG. 2, the first probe 4 is held at the tip of the arm 2. The second probe 5 has a pin shape and is disposed vertically inside the first probe 4, and has a sharp needle-like electrode at the lower end. The material of the second probe 5 is, for example, tungsten.
There is a distance D between the lower ends of the first probe 4 and the second probe 5. As described above, by housing the second probe 5 inside the first probe 4, the structure of the cleaning unit 1 can be made compact.

An insulator 7 is mounted on the upper end of the arm 2, and a conductive screw 8 is screwed inside the insulator 7. A washer 9 is provided on the upper surface of the insulator 7. The second probe 5 penetrates the screw 8 and the washer 9, and the upper end thereof is held by a split holder 10. Reference numeral 11 denotes a ring for holding the holder 10.
The outer shape of the holder 10 is a tapered shape with a small diameter. When the ring 11 is pushed up, the holder 10 is tightened inward to hold the second probe 5 firmly, and when the ring 11 is pushed down, the holder is held. The tool 10 is loosened outward, and the holding state of the second probe 5 is loose. Therefore, by raising and lowering the second probe 5, the size of the distance D can be adjusted. By adjusting the distance D, the optimum distance for discharge can be adjusted.

A first lead wire 12 is connected to the arm 2. Reference numeral 13 denotes a set screw of the first lead wire 12.
A second lead wire 14 is connected between the washer 9 and the insulator 7. First lead wire 12 and second lead wire 1
4 is connected to the voltage applying means. The conductive film 6 of the first probe 4 is in contact with the arm 2, and when a voltage is applied to the arm 2 from the first lead wire 12, a voltage is also applied to the conductive film 6. When a voltage is applied from the second lead wire 14 to the washer 9 and the screw 8, a voltage is also applied to the second probe 5. The arm 2 and the second probe 5 are insulated by an insulator 7. A positive potential is applied to the conductive film 6 of the first probe 4 and a negative potential is applied to the second probe 5.

Next, referring to FIG.
Will be described. Reference numeral 18 a denotes a power supply circuit for generating a high DC voltage, and the negative side is connected to the second probe 5 via the second lead wire 14. A constant current circuit 18b is connected to the positive side of the power supply circuit 18a and generates a constant current. Reference numeral 18d denotes a timer which turns on / off the switching circuit 18c for a certain period of time by a trigger signal Tr from an external control unit (not shown). Reference numeral 18e denotes a ballast having a resistance for stabilizing discharge. The ballast and the conductive film 6 of the first probe 4 are connected to the first lead wire 1.
2 and so on.

In FIG. 2, the arm 2 is hollow,
A suction passage 15 is perforated in the inside. This suction path 15 communicates with the inside of the first probe 4. In FIG. 1, the suction path 15 of the arm 2 is connected to a vacuum device 17 via a tube 16. Therefore, when the vacuum device 17 is driven, the air inside the first probe 4 is sucked (see the arrow in FIG. 2).

In FIG. 1, reference numeral 21 denotes a positioning portion on which a substrate 37 is placed and positioned, and a cylinder 22 is provided on a side surface thereof. The substrate 37 is a printed board made of glass epoxy, ceramic, or the like, and a chip 39 is bonded to an upper surface thereof. As shown in FIG.
An electrode 38 is formed on the surface of the substrate 37, and an electrode 40 is formed on the surface of the chip 39. In FIG. 1, a rod 23 of a cylinder 22 holds a mask 24. When the rod 23 of the cylinder 21 is pulled in, the substrate 37 is pressed against the positioning portion 21 by the mask 24 and fixed.

The base end of the arm 2 is supported by a frame 25. A cam follower 2 is provided at the rear end of the frame 25.
The cam followers 26 and 27 hold the cam 28 therebetween. When the cam 28 rotates by being driven by the motor 29, the frame 25 swings up and down around the pin 30, the arm 2 also swings in the same direction, and the probe unit 3 moves up and down (see arrow N). When the probe section 3 descends, the first probe 4 lands on the electrode 38 of the substrate 37 or the electrode 40 of the chip 39 and comes into contact therewith (see the chain line in FIG. 2 and FIG. 3). That is, the frame 25, the cam followers 26 and 27, the cam 28, the motor 29, etc.
Up and down movement means. In FIG. 3, dirt K such as an oxide film or an organic substance is attached to the surface of the electrode 38.

In FIG. 1, reference numeral 31 denotes a table device, which is constructed by stacking an X table 32 and a Y table 33. The frame 25 has a bearing 36 on a Y table 33.
Are mounted on pins 30. When the drive motor 34 for the X table 32 and the drive motor 35 for the Y table 33 are driven, the frame 25 and the arm 2 move horizontally in the X direction and the Y direction, and move the probe unit 3 to a predetermined cleaning position (electrodes 38, 40). Position). Arm 2
The swing mechanism and the mechanism such as the table device 31 are the same as those of the wire bonding apparatus described in, for example, JP-A-4-291735.

The apparatus for cleaning an electrode of a work is constructed as described above. Next, the overall operation will be described. In FIG. 1, when the table device 31 is driven, the probe unit 3 horizontally moves in the X direction and the Y direction, and stops above a predetermined electrode 38 or an electrode 40 of the substrate 37. Next, when the motor 29 is driven to rotate the cam 28, the arm 2 swings downward, and the first probe 4 is grounded on the upper surface of the electrode 38 (see FIG. 3).

Then, a positive voltage is applied to the first probe 4 and a negative voltage is applied to the second probe 5. When a positive voltage is applied to the first probe 4, a positive voltage is also applied to the electrode 38 to which it is grounded. Therefore, a potential difference occurs between the second probe 5 and the electrode 38, and the discharge A occurs.
The electrons generated by this discharge collide with the surface of the positive electrode 38, and remove the stain K by heat. At this time, the vacuum device 17 is also driven to suck the dirt K removed from the electrode 38. When the cleaning by the discharge is completed, the application of the voltage to the first probe 4 and the second probe 5 is stopped, the suction by the vacuum device 17 is also stopped, and the arm 2 is moved upward by rotating the cam 28. The probe unit 3 is also swung up and the series of operations is completed. Then, the table device 31 is driven again, and the probe unit 3 moves above the next electrode 38, and the above-described operation is repeated. The electrode 40 of the chip 39 is also cleaned by the same method. After all the electrodes 38 and 40 of the substrate 37 and the chip 39 have been cleaned as described above, the chip 39 is then cleaned by a wire bonding apparatus.
Wire bonding for connecting the electrode 40 of the substrate 37 and the electrode 38 of the substrate 37 with a wire is performed.

According to the apparatus for cleaning an electrode of a work, the following excellent operational effects can be obtained. That is, as shown in FIG. 3, only the upper surfaces of the electrodes 38 and 40 can be spot-wise and effectively cleaned.
The surface of the substrate 37 and chip 39 other than 8, 40 is not damaged. Most of the configuration other than the cleaning unit 1 is the same as that of an existing wire bonding apparatus. Therefore, if the cleaning unit 1 and the suction device 17 are set in place of a bonding tool such as a horn or a capillary tool of the wire bonding apparatus. Often,
Equipment costs can be significantly reduced. It is also possible to use software of a computer for wire bonding, in particular, software for controlling the table device 31 for moving the probe unit 3 to a predetermined position, and the cost can be reduced from this point as well. If the electrode cleaning device for the workpiece and the wire bonding device are arranged in parallel, the wire bonding can be performed immediately after the electrodes 38 and 40 are cleaned and the fresh surface of the surface is exposed. By shortening the interval, the fresh surface exposed by the cleaning can be prevented from being recontaminated.

FIG. 5 is a side view of a main part of an apparatus for cleaning a workpiece electrode according to a second embodiment of the present invention. A second probe 5 ′ is held at the tip of the arm 2 ′, and is applied with a negative voltage via the first lead wire 12. Also, the first probe 4 ′ is separate from the second probe 5 ′,
It is in contact with a lead frame 42 made of a conductive metal plate, and a positive voltage is applied through the second lead wire 14.
Reference numeral 43 denotes a nozzle, which is connected to the vacuum device 17 and sucks air near the upper surface of the electrode 41 of the lead frame 42. Other configurations such as the table device 31 are the same as those of the first embodiment.

Accordingly, the table device 31 is driven to position the second probe 5 'above the electrode 41, and to apply a positive voltage to the first probe 4' and a negative voltage to the second probe 5 '.
By applying a voltage, a discharge A is generated between the second probe 5 ′ and the electrode 41 to remove the stain K, and the removed stain substance K is sucked into the nozzle 43. Further, by controlling the height of the second probe 5 ', the distance D to the electrode 41 is adjusted, and the optimal discharge distance is adjusted.

The present invention allows various design changes,
For example, in the above-described embodiment, the probe unit 3 is moved in the X direction or the Y direction with respect to the workpiece such as the substrate 37 and the chip 39.
The work such as the probe 39 and the tip 39 may be moved in the X direction or the Y direction with respect to the probe unit 3 or the probe unit 3
May be moved in the X direction, and a workpiece such as the substrate 37 or the chip 39 may be moved in the Y direction.
To a predetermined electrode 3 of a work such as a substrate 37 or a chip 39.
What is necessary is just to move above 8,40,41. In the above embodiment, the vacuum K is used to suck the air to suck the dirt K removed from the electrodes 38, 40, and 41. May prevent oxidation of the electrode. Further, the present invention can be applied not only to electrode cleaning performed before wire bonding but also to electrode cleaning performed before bonding a bump (protruding electrode) to a substrate or chip electrode.

[0024]

As described above, according to the present invention, only the electrodes of the work can be spot-cleaned, so that the surface of the work other than the electrodes is not damaged. Most of the components other than the cleaning unit can use the existing wire bonding equipment as it is,
Equipment costs can be reduced, and wire cleaning can be performed immediately after the electrode is cleaned and its fresh surface is exposed by installing it in parallel with the wire bonding device, so the interval time from cleaning to wire bonding can be shortened. It is possible not only to improve the working efficiency but also to prevent the exposed fresh surface from being exposed to air and being oxidized, thereby causing the contamination again.

[Brief description of the drawings]

FIG. 1 is a side view of an apparatus for cleaning a workpiece electrode according to a first embodiment of the present invention.

FIG. 2 is a sectional view of a main part of the apparatus for cleaning an electrode of a work according to the first embodiment of the present invention;

FIG. 3 is an enlarged sectional view of a main part of an apparatus for cleaning a work electrode according to the first embodiment of the present invention;

FIG. 4 is a block diagram of a voltage applying circuit of the apparatus for cleaning an electrode of a work according to the first embodiment of the present invention;

FIG. 5 is a side view of a main part of a device for cleaning an electrode of a work according to a second embodiment of the present invention.

[Explanation of symbols]

 4, 4 'First probe 5, 5' Second probe 17 Vacuum device (air flow means) 18 Voltage applying circuit 25 Frame 26, 27 Cam follower 28 Cam 29 Motor 31 Table device 37 Substrate (work) 38, 40, 41 electrode 39 chip (work) 42 lead frame (work)

Claims (5)

(57) [Claims] 1. A positioning part for positioning a work, a first probe for applying a voltage to an electrode of the work, and a needle-like member for approaching the electrode and generating a discharge between the electrode and the first probe.
A second probe which is an electrode, voltage applying means for applying a voltage to each of the first probe and the second probe, and a first probe and / or a second probe which are relative to the workpiece. And a moving means for moving the workpiece electrode. 2. The method according to claim 1, wherein the first probe is an insulating hollow body having a conductive film formed on an outer surface thereof, and the second probe is provided inside the first probe. 2. The apparatus according to claim 1, further comprising an up-and-down moving unit for performing an up-and-down operation to ground the first probe to the substrate. 3. The method according to claim 1, wherein the work is a lead frame made of a conductive plate, the first probe and the second probe are separate from each other, and the first probe contacts the lead frame. The apparatus for cleaning an electrode of a work according to claim 1, wherein the apparatus is disposed. 4. The apparatus for cleaning an electrode of a work according to claim 1, further comprising gas flow means for sucking air near the electrode of the work or blowing gas to the vicinity of the electrode. 5. A method according to claim 1, further comprising: moving one probe having a lower end, which is a needle-like electrode, with respect to the work, bringing the one probe closer to an electrode of the work, applying a voltage to the one probe, By applying a voltage to the electrode of this work by the other probe, a potential difference is generated between this one probe and this electrode, and this voltage is applied.
A method for cleaning an electrode of a workpiece, comprising: generating a discharge between the electrode and a surface of the electrode by causing ions generated by the discharge to collide with the electrode.