JPH02171603A - Apparatus for inspecting height shape of linear object - Google Patents

Abstract

PURPOSE:To automatically and correctly inspect height of an IC wire irrespective of background conditions by a method wherein depth of field of a camera is made coincide with an allowable height range of a linear object, and whether or not a recorded image is focused is detected. CONSTITUTION:When depth of field of a camera is aligned with allowable height ranges ha, hb, hc of an IC wire, a wire having normal height is recorded in focus and a defective wire is recorded out of focus. With height data stored in a controller 19, a camera 14 is sequentially moved in a range of ha to hc while an aperture 13 is driven by a driver 17 to control a lens diameter so that depth of field is a specified value. By recording images sequentially in this state, video signals are AD-converted 20 and stored in an image memory 21, and an inspection circuit 22 is used to inspect whether or not the image is in focus according to gradient profile to judge whether an object is good or defective.

Description

[Detailed Description of the Invention] [Summary] Regarding an apparatus for three-dimensionally inspecting the height shape of a linear object, the height shape of a bonding wire, etc. connected between the pad and lead of an IC chip, etc. The purpose is to automatically and accurately inspect objects regardless of the situation. an image memory in which image data of the inspection object is stored;
By making the depth of field of the imaging device match the permissible height range of the linear object using the aperture control device, it is stored in the image memory as to whether or not the linear object is within the permissible height range. The linear object is inspected by detecting whether the captured image of the linear object is in-focus or de-focused.

(Industrial Application Field) The present invention relates to an apparatus for three-dimensionally inspecting the appearance, particularly the height and shape, of linear objects, and is suitable for inspecting the height and shape of bonding wires connected between the pads and leads of IC chips. Suitable for use.

[Conventional technology]

In semiconductor manufacturing processes, not only circuit electrical tests but also visual inspections performed at each step are important from the standpoint of improving reliability.

Visual inspection is also important in the wire bonding process. FIG. 4 shows the bonding state. A bonding wire 1 is connected from a pad 2 of an IC chip 4 to a lead 3. FIG. 5 shows a normal wire loop shape. FIG. 6 also shows a defective wire loop. 6th
In the figure, (a) shows the wire 1 hanging down, (b) shows the wire 1 with excess length and slack, and (C) shows the wire 1 stretched without any slack. In the case of FIG. 6(a), for example, there is a risk of contact with the frame part, and also in the case of FIG. 6(b), there is a risk of the wire falling over the adjacent wire.
In the case shown in FIG. 6(C), there is a risk of breakage during resin sealing of the package. Therefore, it is necessary to inspect the appearance of the bonding wire, especially its height and shape.

Conventionally, in the industrial field, the "light cutting method" has been used to inspect height.
is used. Figure 7 shows the principle.

In other words, as shown in FIG. 7(b), when the target object 51 is irradiated with a slit light at an angle of θ from the horizontal and the image is taken from directly above with the TV camera 52, the position where the slit light hits the inspected object 5 and its location are shown. The position where it hits the base surface differs by a distance d, as shown in FIG. 7(a). Therefore, the object 51
The height h is determined by h=dtanθ.

[Problem to be solved by the invention]

However, when the optical cutting method is applied to the above IC wire,
As shown in Fig. 8, the part without lead frame 3,
Adhesive member 6 for bonding IC chip 4 to lead frame 3
There is a problem in that the height of the wire 1 cannot be inspected at the portion (2) that is exposed to light.

The present invention was made to solve such problems,
The purpose is to automatically and accurately inspect the height shape of the IC wire, etc., regardless of the situation behind it.

[Means to solve the problem]

In order to solve the above problems, the present invention provides an imaging device that images a predetermined inspection object including a linear object, an aperture control device that controls the aperture of the imaging device, and an aperture control device that controls the aperture of the imaging device. Check whether the linear object is within the permissible height range by matching the depth of field of the imaging device with the permissible height range of the linear object using the image memory in which image data is stored and the aperture control device. Provided is a height and shape inspection device for a linear object, characterized in that the inspection is performed by detecting whether the first most image of the linear object stored in the image memory is in-focus or de-focused. be done.

[For production]

According to the above configuration, by matching the depth of field of the imaging device to the permissible height range of the linear object, the normal wire stretched in the normal height range is in an in-focus state and the normal wire is in the normal height range. A defective wire that is out of the range can be imaged in a defocused state, and therefore it is possible to determine whether the height and shape of the wire are good or bad depending on whether the wire image in the image memory is in the in-focus state or in the de-focused state.

〔Example〕

Figure 1 explains the basic principle of the present invention.
An example of the inspection standard for the height shape of the IC wire is shown in a). From the original drawing, it can be seen that if the height range of the wire is within a certain predetermined height range hmrhb, the height shape of the wire can be determined to be normal.

Figure 1(b) shows the basic principle of the device of the present invention for inspecting the height and shape of the wire.If the blur diameter of the image is δ, and the F number of the lens is F, then the depth of field of the imaging optical system is (sum of front depth of field and rear depth of field) is ±Fδ
The above inspection is performed using what can be done.

In other words, each normal height range shown in Figure 1 (a), h
, , and hc are the depth of field of the lens 9 of the imaging optical system (
tm, tb, and tc), the normal wire stretched in each normal height range is in an in-focus state (in focus), and the defective wire stretched outside the normal height range is in an in-focus state. is imaged in a defocused state (out of focus). Therefore, by inspecting whether the wire image stored in the image memory is in an in-focus state or a de-focus state, it is possible to determine whether the height and shape of the wire are good or bad.

In FIG. 1(b), 7 is an image plane (corresponding to the position of the imaging device), 8 is an aperture for the lens 9, and 10 is an imaging plane that is a predetermined distance a from the lens 9. The predetermined front depth of field tl and rear depth of field t are around 100! is determined.

Here, the front depth of field tl and the rear depth of field t2 are respectively (where f is the focal length of the lens and a is the object distance), and the above depths of field f+l+Lb and tc are This is the sum of the front depth of field 1+ and the rear depth of field t2 determined by each equation. Note that the front and rear depths of field are set to predetermined values by controlling the aperture 8 to change the F number. Note that the image plane 7, that is, the position of the imaging device (for example, an image sensor), ■, O
is set by automatically moving the imaging device according to the position of the wire instructed by a predetermined control device, and the diaphragm 8 is sequentially stopped in accordance with each of the positions (i.e., The F number of the lens gradually decreases), and the depth of field t
, tb, and tc are sequentially set to larger values.

FIG. 2 shows one embodiment of the apparatus of the present invention, in which an IC to be inspected is sequentially conveyed by a transport device 11 directly below an illumination device 12 and an imaging device (for example, an image sensor) 14.

At this time, the control device 19 drives the XYZ moving mechanism 15 in three axial directions using its drive device 16 to sequentially move the position of the imaging device 14 (corresponding to ■ and O above) to a predetermined inspection position. . That is, the control device 19 knows the normal height data corresponding to each position from the bonding start point to the bonding end point for each bonding wire 1, and based on the data, the control device 19 A predetermined position command is transmitted from the drive device 16 to the drive device 16 . Further, based on the grasped data, the control device 19 controls the aperture 13 (corresponding to the aperture 8 in FIG. 1) attached to the imaging device 14 so that it has a predetermined diameter D using the aperture drive device 17. . (See Figure 1 above). Further, in order to adjust the amount of increase or decrease in the amount of light entering the imaging device 14 due to the diaphragm 13 and make it constant, the control device 19 controls the illumination device 12 with its drive device 18 to increase or decrease the amount of illumination light.

The video signal captured under the above conditions is sent to the A/D converter 20.
The image is digitized and stored in the image memory 21.

Next, the height inspection circuit 22 reads data corresponding to the wire image located at the position in the image memory 21 specified by the control circuit 19 (address position of the image memory specified by the control circuit 19), and performs the following inspection. do.

FIG. 3 is a diagram illustrating the principle of inspection by the height inspection circuit 22 shown in FIG. 2, and FIG. 3(a) shows image data in the image memory 21.

Straight line AB is an inspection position (crossing the wire image) corresponding to a predetermined address instructed by the control circuit 19. When the gradation profile (the vertical axis is the brightness intensity and the horizontal axis is the position) of the video signal read from the inspection position (address position) AB is determined, the wire image is in an in-focus state (that is, the wire is in focus). In the case of a normal wire), the gradation profile is as shown in FIG. 3(b). On the other hand, when the wire image is in a defocused state (that is, a defective wire that is out of focus), its gradation profile becomes as shown in FIG. 3(C).

Therefore, if the formula used to evaluate whether or not the above focus is correct is E = (where b is the peak value of the video signal and W is its half width), if E≧st, then (
However, st is a predetermined inspection standard), the height shape of the wire at the relevant position is determined to be normal, and E<st
In this case, the defect can be detected as the height shape of the wire is not normal. The height inspection circuit 22 outputs the above inspection results as a pass/fail signal. In this way, the quality of the height shape of each wire from the bonding start point to the bonding end point is inspected.

(Effects of the Invention) According to the present invention, the height shape of an IC wire or the like can be automatically and accurately inspected regardless of the situation behind it, so that its reliability can be improved.

In addition, since height inspection is performed by controlling the depth of field, inspection can be performed in a shorter time than other methods such as autofocus methods.

[Brief explanation of the drawing]

Figures 1 (a) and (b) are diagrams explaining the basic principle of the device of the present invention, Figure 2 is a diagram showing the configuration of one embodiment of the device of the present invention, and Figures 3 (a) and (b). ), (c) is a diagram explaining the principle of inspection by the height inspection circuit shown in FIG. 2, FIG. Figures 6(a) and 6(b) showing the normal wire shape of the bonding wire shown.
, (c) is a diagram showing the shape of a defective wire in the bonding wire shown in FIG. 4, FIG. 7 is a diagram showing the principle of height inspection using the optical cutting method as a conventional technique, and FIG. FIG. 5 is a diagram illustrating a problem when inspecting the height shape of the inspection object shown in FIG. 4 by a light cutting method. (Explanation of symbols) 1... Bonding wire, 2... Pad, 3... Lead (lead frame), 4... IC chip, 6... Adhesive member, 13...
・Aperture, 9...lens,...imaging device,
19...control device,...image memory, 22...
・Height inspection circuit 2, Lb, Lc...depth of field,...front depth of field,...rear depth of field. (Q)

Claims (1)

[Claims] 1. An imaging device that images a predetermined inspection target including a linear object; an aperture control device that controls the aperture of the imaging device; an image memory that stores image data of the inspection target captured by the imaging device; By matching the depth of field of the imaging device with the permissible height range of the linear object using an aperture control device, whether or not the linear object is within the permissible height range is stored in the image memory. An apparatus for inspecting the height and shape of a linear object, characterized in that the inspection is performed by detecting whether a captured image of the linear object is in focus or defocused.