JPH03178146A - Inspecting equipment for wire bonding state - Google Patents

Abstract

PURPOSE:To improve the inspection precision of bonding state by distance- transforming a binary-valued monochromatic image of an inspection region, searching each pixel value of the above obtained image, from the direction opposite to a wire, setting the center of pixel position of the firstly detected maximum value as the center position of a bonding ball, and detecting the minimum radius of the image subjected to distance transformation. CONSTITUTION:A monochromatic image obtained by a threshold value calculating means 13 is subjected to distance transformation by a distance-transforming means 14. Out of the values of the pixels of the monochromatic image subjected to distance transformation, the maximum value is detected from the direction opposite to a wire 4 by using a center detecting means 15. The center of the pixel position of the firstly detected maximum value is set as the center position of the bonding ball 5. By a shape inspecting means 16, the distance between the above center position and the pixel position of a specified value out of each pixel of the image subjected to distance transformation is calculated, and the shape of the bonding ball 5 is inspected. Thereby the ball shape can be inspected without the influence of wire image and ball shape, and the state of the bonding ball 5 can be inspected with high precision.

Description

[Detailed Description of the Invention] (Installed into a wire bonding condition inspection device equipped with a visual function that automatically inspects the wire bonding condition of IN integrated circuits, etc., the wire bonding condition can be accurately bonded without being affected by wire formation or ball deformation. The purpose of detecting the center of the ball and inspecting the wire bonding state is to include an imaging means for imaging the bonding ball at the tip of the wire bonded to the pad, and digital processing of all output video signals of the imaging means. a pixel generation means for generating pixels; an m-light gray scale image memory for storing pixels in an inspection area of a predetermined size among the pixels generated by the pixel generating means; Threshold value calculation means for calculating a threshold value by an automatic binarization calculation method and converting the image in the inspection area into 2iflj using the threshold value; and distance conversion means for distance converting the binary image obtained by the threshold value calculation means; center detecting means for searching the value of each pixel of the distance-converted fi image from a direction opposite to the wire and detecting the center of the first detected pixel position of the largest spear as the center position of the bonding ball; The apparatus comprises a shape inspection means for inspecting the bonding ball shape by calculating the distance between the center position detected by the center detection means and a predetermined lead pixel position among each pixel of the distance-converted image.

[Industrial application field]

The present invention relates to a wire bonding condition inspection device, and more particularly to a wire bonding condition inspection device having a visual function for automatically inspecting the wire bonding condition of integrated circuits and the like.

In recent years, integrated circuits (IC) and large-scale integrated W1 circuits (LSI)
Since wire bonding devices have come to be used widely and in large quantities, the visual inspection of wire bonding conditions in ICs and LSIs has been automated. In this visual inspection of the wire bonding state, it is necessary to accurately detect the center position of the bonding ball.

[Conventional technology]

FIG. 10 shows a configuration diagram of an example of a conventional wire bonding condition inspection device. In the figure, 1 is a lead frame, on which an IC chip 2 is placed. A pad 3 is formed on the IC chip 2. 4 is a wire, and -S is fixed to form a bonding ball 5 on the pad 3.

The lead frame 1 is connected to a frame feeder 6 which is a conveying device.
As a result, the mushrooms are transported directly below the illumination device 7 and the II imaged mushrooms 8. As a result, the bonding ball 5 is illuminated by the illumination device d7 and imaged by the m* device 8. The video signal taken out from the IIm device 8 is sent to the information processor 3g! The image is supplied to the device 9, where the shading is corrected by ab-ogg processing or digital processing to make the image uniform! gA automatically obtained after changing to a 2-light state (converted to 211i with llI and lc
The wire bonding condition of the image is inspected.

Here, in the conventional wire bonding condition inspection metal,
Above information center 1! ! As the process in step 9, after detecting the pad 3, the diameter of the bonding ball 5 is calculated from the largest chain of line segments that cross the part of the pad 3 excluding the wire 4, and the center position of the bonding ball 5 is calculated from this diameter. (for example, Japanese Patent Laid-Open No. 57-172746), or assuming that the planar shape of the bonding ball 5 is a perfect circle, detecting the contact point where the bonding ball image changes to the pad image in each of the X direction and the y direction. , a method of drawing perpendicular lines in the x and y directions through the contact point and detecting their intersection as the ball center position (for example, special R[53-
124066) is known.

[Problem to be solved by the invention]

However, although the former Conventional II requires the location excluding the wire 4, since the bonding ball 5 is the end point of the wire 4, the wire image is fiP! in the bonding ball image. iy, it is actually difficult to remove only the wire 4, which limits the accuracy of bonding state inspection.

Further, in the latter conventional device, the planar shape of the bonding ball 5 is assumed to be a perfect circle, but since the planar shape of the actual bonding ball 5 is not a perfect circle in most cases,
If the ball center ta cannot be detected accurately and the bonding ball 5 is deformed, a position extremely deviated from the ball center placement will be detected as the ball center position.

The present invention has been made in view of the above points, and provides a wire bonding condition inspection 'IAE' that can accurately detect the center of the bonding ball and inspect the wire bonding condition without being affected by the wire image or ball deformation. The purpose is to

[Means to solve the problem]

FIG. 1 shows a block diagram of the principle of the present invention, in which 10
is a va image means, flII! the bonding ball at the tip of the wire bonded to the pad! do. 11 is a pixel generation means, and 12 is a gray scale image memory, which generates pixels from the video signal from the imager means 10 and stores pixels in an inspection area of l front window size.

Reference numeral 13 denotes a threshold value calculation means which calculates a threshold value using an automatic binarization calculation method from all pixels read out from the gray scale image memory 12, and uses the threshold value to convert the image in the inspection area to 2f+! to obtain a grayscale image.

14 is a distance conversion means that performs distance conversion on the gray scale image.

Reference numeral 15 denotes a center detecting means which searches for the spear of each pixel of the distance-converted h image from the direction opposite to the wire and detects the center of the pixel position of the first detected maximum value as the center position of the bonding ball. Furthermore, 16 is a shape inspection means, which calculates the distance between the detected center position and a predetermined pixel position of each pixel of the distance-converted gray image 11 to inspect the shape of the bonding ball.

[Effect]

In the present invention, the density image obtained by the mItix output means 13 is subjected to separation conversion by the separation conversion means 14, and the value of each pixel of the distance image is set to "1" at the outermost periphery (contour part), and the value of the center pixel is Then, among the pixel values of this distance-converted grayscale image, the center detection means 15 detects the maximum value from the opposite direction of the wire, and the pixel position of the first detected maximum value is detected. By setting the center of the bonding ball as the center position of the bonding ball, the bonding ball center 1 ftF can be detected without being affected by the wire image or ball deformation.

In addition, since the maximum value itself becomes the maximum radius of the bonding ball, in the present invention, the shape inspection means 16 detects the minimum radius of the distance conversion image based on the detected center position, so that wire images and ball deformation can be detected. The ball shape can be inspected without being affected by the

〔Example〕

FIG. 2 shows a configuration diagram of an embodiment of the present invention. In the figure, the same components as those in FIG. 10 are denoted by the same reference numerals, and the explanation thereof will be omitted. In FIG. 2, the lighting device 7 and the camera 11ff
8 constitutes the imaging means 10 shown in FIG. Second
In the figure, an image input circuit 21 constitutes the pixel generating means 11 and digitally processes an input video signal. 2
2Lt image memory and 23&i image processing memory, which constitute the above-mentioned 'a;alj* memory 12.

Further, 24 is an image processing processor, and the product value calculating means 13. Distance conversion means 14. It constitutes a center detection means 15 and a shape inspection means 16, and calculates the m value according to a flowchart shown in FIG. 3, which will be described later. 25 is an image display circuit that causes a display 26 to display an image. The above image input circuit 219 image copying memory 222 image processing memory 23° image processing processor 24 and image table 7j, @Route 2
The pixel data transfer between 5 and 4G uses the image bus 27/? 6 will be held.

Further, 28 is a program memory which stores 10 grams for performing TSM on the entire wire bonding condition inspection device. A system processor 29 supervises the circuits of the entire wire bonding condition inspection apparatus according to the program from the program memory 28.

30 is the camera controller, Ill! I! The operation of the device 8 is controlled. 31 is a lighting controller, which is a lighting device W
The amount of illumination light for the 17 IC chips 2 is adjusted to optimize the S/N of the video signal. Reference numeral 32 denotes a frame feeder controller that transports the frame feeder 6 at the transport \A position. 33 is the I10 controller, keyboard and joystick 34. It provides an interface between the printer 35 and the system processor 29.

The keyboard and joystick 34 are used to set test conditions, and the printer 35 is used to print out test results.

It is connected to a floppy disk 37 and a hard disk 38 by a disk controller (FCC) and a hard disk controller (HDC). The floppy disk 37 and hard disk 38 store test results, test standards, and the like. Furthermore, 39 is a system bus, which is a bus for data transfer between the above-mentioned circuits.

Next, the operation of this embodiment will be explained.
m-images the bonding ball 5 formed at the end of the wire ψ4 on the IC chip 2 side bonded to the tC chip 2, and supplies the resulting video signal to the image input circuit 21. The image input circuit 21 digitally processes the human power ffi signal g to generate image data in which the pixel groups are bottomed out in time series, and stores the ta data in the image memory 22 via the image bus 27. system processor 29
from the gl image memory 22 to a predetermined [, size area w1. D
The pixels (image data) are cut out and stored in the image processing memory 23.
Store in.

Using all the pixels in the above-mentioned area stored in the image processing memory 23 in this way, the image processing processor 24 sends the data from the IIIti calculation means 13 to the shape inspection means 16 according to the O-chart (shown in FIG. 3). Perform each process.

First, as shown in FIG. 3, the image processor 24 cuts out all the pixels of the region 1tLo (step 41). Next, the image processing processor 24 performs gradation compensation m (sub-vixel generation) on each of the read 1s (
Step 42 in FIG. 3).

This pixel! 1st Gradation Complementary I&I As shown in FIG. Pixel N value is P+=f'(i,j), Pz=f
' (i+1.j), Pal = f' (i, j+
1), P4-f' (i+1.j+1), the method generates a sub-vixel at the position indicated by the white circle SP with the gradation value of f (x, y) expressed by the following formula % formula % (1) be. However, in the above formula, α represents the horizontal distance from P+, and β represents the vertical distance from Pl.

With this pixel floor A supplementary 1 field, the above 4 pixels P+”P
4, sub-vixels are generated in the same manner as above at each position indicated by a white circle in FIG. As a result, the above image 1k
The image of the bonding ball 5 before the aW adjustment surface is shown in Figure 5 (
As shown in A), the jaggedness of the diagonal 11th image part was large, but by performing the rewetting of the above image IA, the image I& of the bonding ball 5 became as shown in (8) of the same figure. The diagonal jaggedness is significantly reduced, and an image in which the aF conversion error caused by digitization is significantly reduced can be obtained.

Next, picture f11! l! The L processor 24 calculates the binarized low value from the complete recovery 1 (including sub-vixels) of the inspection area by automatic 2m conversion processing (step 43 in FIG. 3).
>, automatic 2Wi conversion here refers to, for example, adaptive binarization (
This refers to an automatic binarization lIr1 calculation method such as Adaptive B 1nariZation). This adaptive binarization reduces the total number of pixels within the inspection area to N.

When f (x, y)·γ is a predetermined ratio for the pixel level 1 chain, the binarization threshold filT is calculated based on the following formula.

After calculating the above binarization threshold T, the image in the inspection area VtD is set to "O" for pixels with a gradation value greater than T and "1" for pixels with a gradation value less than or equal to T. This is a 2WI image as schematically shown in FIG.

However, in FIG. 6, illustration of each pixel with the value "O" is omitted. This 2iU image is converted into an IC as shown in FIG.
The shape of the wire 4 and the bonding ball 5 in the inspection area [0], which have a lower video signal strength than the chip 2 and the pad 3, is shown. The data of this binarized image is stored in the image processing memory 23 in an area different from the pixel storage area.

Next, the image processing processor 24 performs distance conversion on the above-mentioned halved image (step 44 in FIG. 3). In this distance conversion, the value of the outermost pixel forming the outline of the 2fB image is set to "1", and each time the pixel advances one by one toward the center of the 2fB image, the value of the four lines is changed to 1. This is a process to increase the number by one. In other words, this distance transformation transforms the two-dimensional image into 41
Ii is a process of assigning to each pixel a value indicating which pixel it is from the contour. Therefore, by this distance J11 conversion, the distance of each pixel constituting the above 2(a) image is set as shown in FIG.

Next, the image processing processor 24 reaches the pixel values in the direction toward the wire 4 from the f-d facing the wire 4 for the above-mentioned image within the inspection area after the distance conversion, and The position is detected (step 45 in FIG. 3). That is, the 8th Fj! As shown in I, the button of each pixel constituting the image after the above distance conversion is detected from the direction opposite to the position of the wire 4, and
The center of the pixel (indicated by diagonal lines in FIG. 8) where fI (here "6") is located is defined as the center position C of the bonding ball 5.

Here, since there are two pixels in the same row with the maximum detection value "6" indicated by diagonal lines in FIG.
X is assumed to be 6.5. Note that the detection direction from the position of the bonding ball 5 facing the wire 4 to the wire 4 is I
l & ICC foot for device 8 2. Bad 3. wire 4
Since the position and direction of the pounding ball 50 are known in advance, it can be identified.

Next, the image processing processor 24 determines the shape of the bonding ball 5 by calculating the distance from the center position dC to each pixel forming the contour whose value is "1" in the image after distance conversion. Inspect (step 46 in FIG. 3). That is, in step 46, the distance between the center position C shown by the arrow in FIG. Value RH1N
represents the minimum radius of the bonding ball 5 of 41N.

Thereafter, the image processor 24 determines whether the bonding ball 5 is good or bad. This pass/fail judgment U, S? Tsu1
Center position 1iff of bonding ball 5 detected at 45
The positional deviation of the bonding ball 50 is inspected based on the deviation between C and the center position of the pad 3, and it is determined whether the position f is within the allowable range, and the minimum value (R small ball radius) R detected in step 46 is determined. ,,N, the maximum value (maximum ball radius) RHAX detected in step 45, and the reference ball diameter R
310 (for example, 35 μm to 65 μl), it is determined whether the ball deformation determined from the ratio is within an allowable range.

The 71 constant that affects the ball deformation of one player is, for example, that the minimum ball radius RHIM is 70% or more of the reference ball diameter R81D, and the maximum ball radius RHAX is within the allowable range of 130% or less of the reference ball t\R3TD. It is definite whether or not it is.

Therefore, according to this embodiment, the center IC of the bonding ball 5 can be detected with high accuracy without being affected by the wire 4 or the ball deformation.

Note that the present invention is not limited to the above-mentioned embodiment. For example, the sub-vixel generation process in step 42 in FIG. 3 can produce more accurate inspection results than 1! ! Although this is a desirable process in terms of performance, it can be omitted in principle.

〔Effect of the invention〕

In contrast to the above, according to the present invention, the ball shape can be inspected without being affected by the wire image or ball deformation.
This method has the advantage of being able to inspect the condition of the bonding ball with a higher accuracy than the conventional method.

[Brief explanation of drawings]

FIG. 1 is a block diagram of the principle of the present invention, FIG. 2 is a configuration diagram of an embodiment of the present invention, FIG. 3 is a flow chart for explaining the operation of an embodiment of the present invention, and FIG. 4 is a pixel sNa Figure 5 is a diagram showing an example of images before and after pixel interpolation, Figure 6 is a diagram showing a binary image of a rainbow bonding ball, and Figure 7 is a diagram showing bonding ball distance conversion 11! FIG. 8 is an explanatory diagram for detecting the bonding ball center position, FIG. 9 is an explanatory diagram for bonding ball shape inspection, and FIG. 10 (q) is a configuration diagram of an example of a conventional V device. In the figure, 2 is the Lt IC chip, 3 is the pad, 4u wire, 5 is the bonding ball, 1 (HJ [m means, 11 is i! ii elementary school kaite generation 12L1 density clear tone southern image memory, 13 is the threshold value 14 is a distance conversion means, 15 is a center detection means, 16 is an LL shape inspection means, and 24 is an image processing processor.

Claims (1)

[Claims] An imaging means (10) for imaging a bonding ball at the tip of a wire bonded to a pad;
pixel generation means (11) for digitally processing the output video signal of step 10) to generate pixels; and a gray scale for storing pixels in an inspection area of a predetermined size among the pixels generated by the pixel generation means (11). an image memory (12); and a threshold calculation means for calculating a threshold from all pixels read from the gray scale image memory (12) by an automatic binarization calculation method and binarizing the image in the inspection area using the threshold. (13
), distance converting means (14) for distance converting the binary image obtained by the threshold value calculating means (13), and searching for the value of each pixel of the distance-converted image from the direction opposite to the wire. center detection means (
15), and shape inspection means for inspecting the bonding ball shape by calculating the distance between the center position detected by the center detection means (15) and a pixel position of a predetermined value among each pixel of the distance-converted pixels. (16) A wire bonding condition inspection device comprising: