JPH03229439A - Wire-bonding apparatus capable of wiring inspection - Google Patents

Abstract

PURPOSE:To contrive to improve the working efficiency by automatically determining whether the loop-form of a wire and a wire connection are good, through automatic inspection of the state of wiring during a wire-bonding process. CONSTITUTION:When the whole wire-bonding process has ended, a lead frame and pellet 14 are already positioned and the deviation between a normal bonding point preset on the pellet 14 side and lead 16 side and an actual bonding point is computed for the purpose of conducting a correcting calculation. According to this correcting calculation, an XY table 1 is driven to the middle point on a line segment passing the lead 16 and the center of a pad 15, that is, the line segment of a wire 17 and a camera 2 is moved to the origin A. The center of the camera 2, that is, the center of an optical lens 3 lies in the origin A. Around this origin coordinate A as a center, respective coordinates or the wire 17 on the line segment passing the lead 16 and the center of the pad 15 are obtained and when there are any place, where respective coordinate points are not continuous, etc., an abnormality is judged to exist due to breaking of the wire 17, a wire short or the like.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a wire bonding device for assembling semiconductor integrated circuits (I), etc., and in particular to an automatic wiring inspection device for automatically inspecting the wiring after wire bonding. The present invention relates to a wire bonding device equipped with a wire bonding device.

[Background Art] When manufacturing semiconductor integrated circuits (ICs) and large-scale integrated circuits (LSIs), after positioning a lead frame on which semiconductor pellets are arranged on a conveying device, a tool for holding wires is moved to the lead frame. By displacing the wires relative to the frame and the semiconductor pellet, the wires are guided and bonded to the leads provided on the lead frame and the pads of the semiconductor pellet, respectively. Inspection of the shape of the wire loop and whether the wires are securely connected to the leads of the lead frame and the pads of the semiconductor pellet that have been bonded through such a process has conventionally been carried out by sampling immediately after wire bonding. Alternatively, the electrical inspection using a tester or the like is not carried out immediately after the wire bonding, but after the process has progressed to a state close to that of the product.

In this inspection by sampling immediately after wire bonding, the inspector stops the wire bonding equipment and carefully takes out the lead frame stored in the magazine from the magazine and uses a microscope to check whether the wires are bonded correctly. This is done through inspection.

[Problems to be Solved by the Invention] However, in the conventional visual inspection method for wire bonding, the inspector stops the wire bonding device to inspect the lead frame, and then takes the lead frame out of the magazine and inspects it. Since the lead frame is then returned to the magazine for storage, there are drawbacks such as the lead frame being subjected to impact or coming into contact with other objects, which may destroy the wire shape during transport. Such an inspection method has the disadvantage that the wire bonding apparatus must be stopped for inspection, which reduces work efficiency. In addition, when using a multi-bin lead frame with a large number of bins, human errors and variations in judgment between workers are likely to occur (there is also the disadvantage that it takes a lot of time to work). During inspection, losses occur as defective products mix with non-defective products and flow into subsequent processes, which can delay the discovery of problems and create a large number of defective products.This is the cause of which process caused the defective products. The disadvantage is that it is difficult to clarify.

The present invention has been developed in view of the above-mentioned drawbacks of the prior art, and there is no need to take out the lead frame from the magazine for inspection, and the condition of the wiring is automatically inspected during the wire bonding process to determine the loop shape of the wire. An object of the present invention is to provide a wire bonding device that can automatically determine whether a wire connection is good or bad.

[Means for Solving the Problems] A wire bonding device capable of inspecting wiring according to the present invention includes a conveying means for conveying a lead frame to a bonding stage, and a positioning means for positioning the lead frame conveyed by the conveying means to hold a wire. bonding means for guiding and bonding the wire to a lead provided on the lead frame and a pad on the semiconductor pellet, respectively, by displacing a tool relative to the lead frame and the semiconductor pellet; an imaging means that is placed on an XY table driving means that is movable and capable of imaging wires connected between the leads and pads of a positioned lead frame; and information captured by the imaging means is stored and calculated. The control means calculates the amount of deviation from the regular bonding point stored in advance, and the line segment of the wire connected to the calculated lead position and the pad position is The bonded state of wires can be monitored by detecting multiple wires.

[Example] Next, an example of the present invention will be described in detail using the drawings.

FIG. 1 shows a wire bonding apparatus used in this embodiment.

In FIG. 1, an XY table 1 is moved in the X and Y directions to position it, and a bonding head (a bonding head) that uses a tool to make a wire bonding connection between the lead of the lead frame and the pad (electrode) on the semiconductor pellet.
(not shown). Also, this XY table 1
An imaging device is mounted above to take images of semiconductor components such as semiconductor pellets. This imaging device has an XY table 1
It consists of a camera 2 attached to the tip of a support frame 8 fixed above, an optical lens 3, a coaxial illumination 4, and a parallel plane plate 5 made of a glass plate or the like.

The camera 2 converts the image captured through the optical lens 3 into a video signal by generating horizontal and vertical synchronization signals at predetermined timing using a synchronization signal generation circuit built into the camera 2, and outputs the video signal to the image processing unit 1o. . This image processing section 1
o amplifies the video signal input from the camera 2 and processes it using a binarization circuit or the like. This binarization circuit, for example, brightens the read part and sets the part to be read as "1",
The other parts are darkened and digitized to read as an "o". Further, this binarized image can be written and stored in an image storage unit such as a frame memory, and the image stored in this image storage unit is read out and reproduced on a reproduction device (not shown) such as a monitor. It is configured so that it can also be used. Since the image storage unit includes a plurality of memories that can be written to and read from at any time, it is possible to store a plurality of images. Further, this image processing section is configured so that information can be calculated and operated by an external operation means (not shown) of the bonding apparatus. In addition, optical lens 3
A lens that can change the optical field of view by changing the magnification of the lens is used, and it is possible to capture an entire image or a partially enlarged image of the semiconductor component. This optical lens 3 is provided so as to be positioned above the transfer surface of the transfer device 7, that is, the bonding stage where bonding work is performed, and is provided in a direction perpendicular to the transfer surface of the transfer device 7 shown in FIG. . A parallel plane plate 5 is arranged at the tip of the optical lens 3 so as to be inclined with respect to the central axis of the optical lens 3. A coaxial light source 4 serving as a light source is attached close to the parallel plane plate 5 in a direction orthogonal to the central axis of the optical lens 3. The parallel plane plate 5 is arranged with an inclination so that the light emitted from the coaxial illumination 4 passes through an optical path that coincides with the central axis of the optical lens 3, and the light emitted from the coaxial illumination 4, That is, the light consisting of a non-parallel light beam is reflected by the plane-parallel plate 5 and irradiates onto the lead frame positioned and mounted on the conveyance device 7.

This irradiated light irradiates the leads of the lead frame and the semiconductor chip, but since the parts other than the leads and the semiconductor chip are formed by punching, those parts are transmitted. Then, the lead frame conveying surface of the conveying device 7,
A recess is formed along the direction orthogonal to FIG.

A reflecting plate 9 is attached to the bottom surface of this recess so as to be slidable along the conveying direction. Further, the reflector plate 9 may be of any type as long as it has a substantially mirror surface state. Although this reflector plate 9 is provided at the bonding stage portion where bonding is performed, it may also be provided along the conveyance surface. In addition, this reflector plate 9 is configured so that the heater that heats the parts to be bonded is raised and lowered by a lifting mechanism (not shown), so that it can be slid onto the bonding stage when inspecting the wiring. It is composed of The light transmitted from parts other than the leads and the like is reflected by the reflecting plate 9 and returns along the optical path passing through the central axis of the optical lens 3. When this returned light passes through the plane-parallel plate 5, it is not reflected but passes through the optical lens 3 and is received by the light receiving element of the camera 2. When a wire bonded between the lead of the lead frame and the pad on the pellet is imaged with such a configuration, light is transmitted through areas other than the metal parts of the lead frame, and the return light reflected by the reflector plate 9 causes the wire to be Light is blocked in this part, allowing the camera 2 to clearly image the wire. Further, in this embodiment, in addition to the coaxial illumination 4, epi-illumination 6 is provided, and this illumination is attached to the device side (not shown). Although this epi-illumination 6 is not intended for automatic inspection of wiring, it is installed because it can sometimes clearly image bullets and the like. Next, the XY stage control section 11 drives and controls the XY table 1 in the X direction and the Y direction. Since a plurality of semiconductor chips, etc. are normally arranged on one lead frame, the conveyance control unit 12 intermittently controls the positioning of the lead frames placed on the conveyance device 7 to be fed one frame at a time onto the bonding stage. It is something to do.

In order to automatically inspect the wiring of a lead frame in which a wire bonding connection is made between the leads of the lead frame and the pads on the semiconductor chip using the device configured as described above, conditions such as self-teach must be set. There is a need.

To set these conditions, first, set the coordinates of the regular bonding points on the XY table in advance for the position of the bullet on the lead frame, the leads, and the pads on the bullet, for which automatic inspection of the wiring of the bonded lead frame is to be performed. The calculated image processing unit 1o is stored in a storage unit built into the image processing unit 1o.

Next, the positions of the leads and pellets of the lead frame to be inspected placed on the bonding stage, which is an inspection stage, are shifted from predetermined regular bonding points by the camera 2.

For example, correction of the deviation amount of this regular bonding point is done as follows.
In the pellet, two fixed points are determined in advance, and the actual positional deviation between these two fixed points is detected to calculate and correct the actual bonding position. By calculating this amount of deviation, the amount of deviation of the bullet is determined, so the amount of deviation of each pad is also determined, and these amounts of deviation are calculated and stored in the image processing section 10.

When such a deviation amount is calculated, the deviation amount from the actual bonding position is known, so the image processing unit 10 corrects it and performs bonding.

Here, FIG. 2(a) shows a diagram in which the wire 17 is bonded between the beam part 16 and the pad 15 on the bellet 14, and FIG. 2(b) shows the beam 16 (16
a, 16b, 16c) and pad 15 (15a, 15b
, 15c) and the wires 17 (17a, 17b, 1
7c) is a diagram showing a state in which they are connected by bonding, and FIG. 2(c) is a diagram showing a state in which FIG. 2(b) is viewed from the side.

Pad 15 on pellet 14 calculated by the above method
The midpoint on the line segment of the wire 17 is determined from the center position of the wire 17 and the center position of the lead frame glue 16 in the width direction. This midpoint is defined as the origin A as shown in FIG. 2(a). This origin A is calculated as a coordinate point on the XY table 1 and stored in the image processing unit 10. The wire 17 is image-transferred and the wire 1 is processed by the image processing unit 1o.
Detect multiple points on 7 and calculate AI ()C+ + y+)-A2 (Xi-,
Y2) −・AI (XI, y +,)
. . . A11CXn, :Jn) and the respective coordinates are determined, and a straight line approximation of the wire 17 is performed from each of these points.

To illustrate the general formula for this linear approximation, y=a+bx
Then, a==Ym-b *
"-((ΣY)"Jn)Sxy=ΣXY-(fΣx
)(ΣYi/n)Xm=ΣX/n Ym=ΣY/n.

Next, a case will be described in which automatic inspection of wiring of a bonded lead frame is performed using the apparatus having the above configuration.

This will be explained using the flowchart in FIG. Note that FIG. 3 explains a case where automatic inspection of wiring is performed by a bonding device.

First, a lead frame stored in a magazine (not shown) is sent out onto the transport device 7 and transported, and the lead frame, which is the object to be inspected, is positioned on the bonding stage and wire-bonded (step S).

In step S2, it is determined whether all the wire bonding has been completed. If not, the wire bonding is repeated, and if it has been completed, the lead frame and pellet 14 have already been positioned, so step S2 is performed. Then, the correction calculation is performed by calculating the amount of deviation between the lsi side bonding point, that is, the regular bonding point preset by self-teaching on the bullet 14 side, etc., and the actual bonding point. Next, 2. ．． Also for the bonding point on the 6th side, that is, on the lead 16 side, the amount of deviation between the preset regular bonding point and the actual bonding point is calculated to perform correction calculation (step S4). These correction calculations and the like are performed by the image processing section 10. With this correction calculation, the center of the lead 16 and the pad 15 are determined as shown in FIG.
Since the center coordinates of the wire 17 are determined, the XY table 1 is driven to the midpoint on the line segment passing through the center of the lead 16 and the pad 15, that is, the line segment of the wire 17, and the origin A shown in FIG. 2(a) is determined.
Camera 2 is moved to (step S). This origin A is the center of the camera 2, that is, the center of the optical lens 3, and this origin, tqA, is determined as a coordinate point on the XY table 1. Next, lead 1 is centered on this origin dust IA.
6 and the center of the pad 15, tWA, (xl, y+), A2 (x2.y
2),...A, (xy+)...An
(Xn, yn) is determined (step S6). If there is a location where the obtained coordinates are not continuous, it is determined that there is an abnormality due to a break in the wire 17, a wire short, or the like. Further, the image processing unit 10 calculates a linear correlation coefficient (step S, , ).

The value of this linear correlation coefficient is expressed as a state close to 1 if the connected wire 17 is straight, and on the contrary, a state close to 0 if there is a bend such as a curl.

Therefore, it is possible to determine whether the wire 17 is curled by appropriately setting the value of this linear correlation coefficient using an external operating means (step S).

If this linear correlation coefficient is determined to be within the set range, the actual bonding position between the lead 16 and pad 15 and the straight line distance of the wire 17 are calculated (step 5Il). , the bonding position is determined in step S9. Since the coordinate points of the center of the lead 16 and the center of the pad 15 to be bonded have been determined in advance, the straight line distance connecting them can be calculated and determined. Therefore, actually bonded lead 1
6 and the coordinate point of the pad 15 position, and the distance connecting them is calculated, and this calculated value is compared with the distance to determine whether or not it is within a predetermined range. can be determined. This incorrect wiring beam part 1
6 and the corresponding pad 15, but the amount of deviation is large, or the case is bonded to the adjacent pad 15, etc. Incidentally, since the lead width, the distance between leads 16a and 16b, the distance between pads 15a and 15b, etc. as shown in FIG. 2(b) are determined in advance at the design stage, external These conditions may be stored in the storage section using the operating means. Moreover, the setting range for determining whether or not wiring is incorrect can be set separately for the lead 16 side and the pad 15 side using external operating means. If the bonding position is within the set range according to the above determination, it is determined in step 310 whether all the wires 17 have been completed, and if not completed, proceed to step S, and repeat the subsequent steps, and if completed, proceed to step S. Forward the lead frame one frame (step S, , ), step S
, and repeat the steps described above.

Through the steps described above, it is possible to automatically inspect the wiring condition of the wire 17 that has been wire-bonded.

Therefore, according to this embodiment, the calculated veret 14 side,
If the bonding point on the lead 16 side exists within a certain range on the extension of this straight line, the corresponding pad 15 and lead 1
It can be determined that it is wired to 6.

Even if there is contact between the wires 17 due to breakage or curling of the wires 17, determination can be made by determining the continuity of detection points on the wires 17. Further, by checking the continuity of the detection points and the predetermined wire width, it is possible to reliably determine whether the wire 17 is disconnected or not.

Furthermore, in the linear approximation, since the linear correlation function r indicates the linearity of the wire 17, a wire with a low linear correlation function can be considered to be defective wiring. The setting range for determining whether the product is good or bad can be appropriately set by the image processing unit 10 in consideration of the distance between the leads 16, the distance between the pads 15, etc.

Further, according to this embodiment, since the image taken during wiring inspection can be reproduced and displayed on a reproducing device, visual inspection is also possible.

In this embodiment, an automatic inspection device that automatically inspects wiring is configured integrally with the wire bonding device, but an independent automatic wiring inspection device other than the wire bonding device having the same function as this embodiment can be used. May be used. Furthermore, the wiring may be automatically inspected on a conveying device other than the bonding stage by using an automatic inspection device in which an imaging device other than the one used in this embodiment is mounted on another moving table. . In addition, the configuration is not limited to this embodiment, and may be modified and configured as appropriate within the scope of the spirit of this embodiment.

[Effects of the Invention] As explained above, according to the present invention, the position, direction, and direction of the wiring can be determined by monitoring the condition of the wire between the bonded lead frame lead and the pad during the wire bonding process. This has the advantage that by detecting linearity, it is possible to automatically determine the presence or absence of incorrect wiring, the presence or absence of contact with nearby wires, etc. Therefore, according to the present invention, there is no need to stop the wire bonding apparatus, take out the lead frame from the magazine, inspect it, and then return it to the magazine to store it. This has the effect of improving work efficiency without damaging the shape of the wire by contacting it with other objects.Also, according to the present invention, the state of the wiring can be automatically determined even in multi-bin lead frames, etc. This has the effect of improving work efficiency by eliminating human errors and variations in judgment between workers.Furthermore, according to the present invention, since it is determined whether the wiring is good or bad during the bonding process, defective products can be produced. Another effect is that there is no possibility that the product will be mixed with non-defective products and flow into the subsequent process.

[Brief explanation of drawings]

FIG. 1 is an embodiment of the present invention, and is a diagram showing a wire bonding apparatus used in the present invention. FIG. 2(a) is a diagram showing a wire bonded between a lead and a pad on a pellet. FIG. 2(b) is a diagram showing a state in which wires are bonded and connected between leads and pads, FIG. 2(c) is a diagram showing a state in which FIG. 2(b) is viewed from the side, and FIG. The figure is a flowchart for automatically detecting the state of wiring according to the present invention. DESCRIPTION OF SYMBOLS 1...XY table, 2...Camera, 3...Optical lens, 4...Coaxial illumination, 5...Parallel plane plate, 6...
... Epi-illumination, 7... Transport device, 8... Support frame, 9... Reflector, 1o... Image processing section, 11...
・XY stage control section, 12...Transportation control section, 14.
・・Bellet, 15・ ・・Pad, 16・ ・ ・
Lead, 17...wire.

Claims (1)

[Claims] A conveying means for conveying the lead frame to the bonding stage, and a tool for positioning the lead frame conveyed by the conveying means and holding the wire, are displaced relative to the lead frame and the semiconductor pellet, thereby transferring the wire to the lead frame. bonding means for guiding and bonding the leads provided on the semiconductor pellet and the pads on the semiconductor pellet, respectively, and the leads and pads of the lead frame placed and positioned on an XY table driving means movable in the X direction and the Y direction. It is equipped with an imaging means that can take an image of the wire connected to the wire, and a control means that stores and performs arithmetic control on the information taken by the imaging means. Wiring characterized in that the bonded state of the wire can be monitored by detecting a plurality of line segments of the wire connected to the calculated lead position and the pad position calculated by the control means. Inspectable wire bonding equipment