JPS6276529A - Method for detecting bending of lead wire in flat-pack type ic - Google Patents

Abstract

PURPOSE:To enable a bending state of lead wires to be easily judged, by emitting light from a flat-pack type IC side to a semitransparent plate side and comparing information, which is obtained by picking up shadows of the lead wires generated on the semitransparent plate from its back, with reference information, which corresponds to a normal flat-pack type IC with no bending state of lead wires. CONSTITUTION:IC 28 is positioned at an prescribed position of a semitransparent plate 16 by a holding head 30 and is pressured with force prescribed in advance, and then light is emitted from a lighting fixture 18. Because only free terminal parts of the lead conductors 82 make a close contact with the semitransparent plate 16 by pressure, the shadows are divided into unclear shadows and dense and clear ones. The shades of the IC 28 generated on the semitransparent plate 16 are picked up by a TV camera 22. When the output signals of this TV camera 22 are binary-coded so that the signals corresponding to densely shaded parts are made O and those corresponding to thinly shaded and shadowless parts are made 1, a series of binary-coded signals, in which images of the free terminal parts in the lead conductors 82 of IC 28 are shown, can be obtained. Information related with the inspection object IC 28, obtained in this way, is compared with reference information which is supplied from a reference information set-up device 70 through a bending-judged device 68.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for detecting bends in lead wires of an IC when a flat pack type IC is mounted on a printed circuit board.

Conventional ICs are usually mounted on a printed circuit board using a mounting machine, but in dual-in-line packaged ICs, it is normal to have bends in the lead wires that result in uneven spacing between the lead wires. Cannot be implemented. For this purpose, as described in Japanese Patent Application Laid-Open No. 139699/1989, a device is used to determine the bending of lead wires by measuring the distance between the lead wires using a -dimensional image sensor for mounting dual in-line packaged ICs. Conventionally, defective lead wires are determined before mounting to prevent defective products from being passed on to subsequent processes.

Problems to be Solved by the Invention However, the lead wires of flat pack type ICs are DIP type I.
Unlike the lead wire in C, its free end extends parallel to the printed circuit board, and during mounting, the lead wire is bent so that it is floating above the surface of the printed circuit board, causing problems in the soldering process. There are many things.

Since such bending does not appear as unevenness in the spacing between lead wires, the technology described in the above publication, which measures the spacing between lead wires to determine pass/fail, cannot be applied. .

Against this background, the present invention has been made in order to provide a simple and inexpensive method for determining the bending of lead wires of flatback type ICs.

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention makes the free ends of the lead wires translucent by pressing the main body of a flat bank IC toward a translucent plate. Information obtained by placing the lead wire in close contact with the board, irradiating light from the flat pack mold 1c side toward the semi-transparent board side, and imaging the shadow of the lead wire appearing on the semi-transparent board from the back side of the semi-transparent board; Comparing the standard information with the standard information corresponding to a normal flat-pack IC with no bends in the lead wires, it was found that there was a lead wire whose free end did not come into close contact with the translucent plate when pressed against the translucent plate, and there was a clear shadow of the lead wire. Since this does not occur on the semi-transparent plate, if the two pieces of information do not match, it is determined that the lead wire is bent.

Action: An object is pressed against the translucent plate, and light is irradiated from the object side to the translucent plate side. When viewed from the back of the translucent plate, the parts of the object that are in close contact with the translucent plate are clearly illuminated. A shadow is cast, but the shadow becomes thin and blurry in the areas that are raised from the translucent plate. Therefore, it is possible to determine whether an object is in close contact with the translucent plate depending on whether the darkness or clarity of the shadow is above a certain level. The present invention automatically performs this shadow determination using an imaging device.

Effects of the Invention According to the method of the present invention, bends in lead wires are detected prior to mounting a flatback type IC, and defective ICs having bent lead wires are eliminated, thereby preventing printed circuit boards from being damaged when mounting is completed. The defective rate can be significantly reduced.

In addition, since bends in the lead wires are detected while the main body of the flat bank IC is pressed against the translucent plate, soldering only detects bends that may cause defects when the flat back IC is mounted. can be detected. - Even though the lead wire is bent, there are cases where it is bent downward from the normal position and cases where it is bent upward.If the lead wire is bent downward, it may occur when the IC body is pressed against the printed circuit board. It returns to its normal position due to elastic deformation, and there is no risk of defective soldering. However, if the soldering is bent upwards, elastic deformation as described above cannot be expected and the soldering is defective. Therefore, it is desirable to be able to reliably detect only such bends.

Also, the lead wire bends in the direction perpendicular to the IC body, not from the direction parallel to the RC body as is usually thought.
Another feature of the present invention is that it is detected by imaging from a direction perpendicular to the IC body. When detecting lead wire bends by imaging from a direction parallel to the IC body, it is difficult to detect only bends that may cause soldering defects as described above.
While it is difficult to focus an imaging device on all of the many lead wires that are lined up parallel to the IC body, the method of the present invention allows you to easily correct only the inconvenient bends in the lead wires. It can be detected.

EXAMPLE Hereinafter, a method according to an embodiment of the present invention will be described along with an apparatus that can be suitably used for carrying out the method.

FIG. 1 is a diagram schematically showing a lead wire bending detection device, and 10 in the figure is a main body frame.

A support plate 12 extends horizontally from the main body frame 10,
An opening 14 is formed in the center thereof.

A semi-transparent plate 16 is arranged to cover the opening 14 and is supported by the support plate 12. As the translucent plate 16, for example, a commercially available product made of acrylic resin can be used.

An illuminator 18 is arranged above the semi-transparent plate 16. The illuminator 18 is attached downward to an arm 20 extending horizontally from the main body frame 10, and is configured to irradiate light that passes through the semi-transparent plate 16 from the upper side to the lower side. A television camera 22 as an imaging device is disposed below the semi-transparent plate 16, and is attached to the main body frame 10 facing the illuminator 18 with the semi-transparent plate 16 in between.

The object to be inspected is the flat-punk IC2B (hereinafter referred to as
The IC2B (simply referred to as IC2B) is held by a holding hood 30 and is carried into a lead wire bending detection device while being conveyed from the component supply device onto the printed circuit board. Holding head 30
As shown in FIG. 2, the head body 34 is attached to a movable body 32 so as to be movable up and down, and is moved up and down by an air cylinder 33. The movable body 32 can be moved any distance in the X-axis direction and the Y-axis direction, which are perpendicular to each other, in a horizontal plane by an X-direction servo motor and a Y-direction servo motor (not shown).
The head main body 34 can be accurately positioned at any position within the XY plane.

A rotary cylinder 36 is attached to the head body 34 so as to be rotatable around a vertical axis, and a gear 38 formed integrally with the rotary cylinder 36 is meshed with a pinion 40 . The pinion 40 is fixed to the output shaft of a servo motor 42, so that the servo motor 42 can rotate the rotary cylinder 36 at any angle. Two glass plates 44 and 46 are arranged parallel to each other at a certain distance in the axial direction in the direction extending through the center of the rotary cylinder 36.

The glass plates 44 and 46 are coated with an antireflection coating to allow good light transmission in the axial direction of the rotary cylinder 36. Further, the space surrounded by the glass plates 44 and 46 and the rotating cylinder 36 is an airtight chamber 48.
is adapted to maintain communication with the vacuum hose 50 regardless of the rotational position of the rotating cylinder 36. The vacuum hose 50 is connected to a vacuum source via an electromagnetic control valve (not shown).

A suction tube 52 is attached to the center of the lower glass plate 44. The suction tube 52 includes a first tube 54 fixed perpendicularly to the glass plate 44 and a second tube 56 slidably fitted inside the first tube 54 . The second tube 56 is always maintained at a position protruding from the first tube 54 by a certain amount by a spring (not shown), and is pulled into the second tube 54 when a pushing force greater than the biasing force of this spring is applied. It is being done. This means that the main holding head 30 is
This measure is taken to avoid applying excessive force to the IC 28 and the printed circuit board when the IC 28 is brought into contact with the IC 28 to attract it or when the IC 2B is mounted on the printed circuit board. A suction passage that communicates with the airtight chamber 48 and opens at the lower end of the second tube 56 is formed in the adsorption tube 52, and when the airtight chamber 48 is brought into communication with a vacuum source, I
It is designed to be able to adsorb and retain C2 days.

The holding head 30 is attached to the head body 3 by an air cylinder 33.
4 is lowered to press the IC 28 held in the suction tube 52 against the semi-transparent plate 16. The pressing force at this time is the same as that applied to the IC 28 by the pressing device when the IC 28 is soldered to the printed circuit board. It is desirable that the pressure be equal to the applied pressing force. Therefore, the head main body 34 is lifted upward by a spring 60, and a pressure regulating valve is provided in the air passage to the air cylinder 33, so that the pressing force can be set to a desired value by adjusting the pressure regulating valve.

As shown in FIG. 3, the television camera 22 is connected to a binarization circuit 66, and the shadow of the IC 28 that is imaged by the television camera 22 is converted into a series of binary signals. The binarization circuit 66 is connected to a bend determination device 68,
A reference information setting device 7p is connected to this determination device 68. The reference information setting device 70 has I
Information in which the shadow imaged by the television camera 22 is binarized when all the lead wires of C28 are normal is set in advance, and the bending determination device 68 is set in advance by the reference information setting device 70.
Compare the reference information supplied from the binarization circuit 66 with the binarized information of the shadow of the IC 28 to be inspected supplied from the binarization circuit 66,
If these pieces of information differ by more than a predetermined criterion, it is determined that the lead wire of the inspection target C28 is bent, and a defect detection signal is supplied to the mounting machine control section 72. ing.

Next, a method of detecting lead wire bending using this lead wire bending detection device will be explained.

The holding head 30 holds the IC2 at a predetermined position on the translucent plate 16.
8 is positioned and pressed with a predetermined force, light is emitted from the illuminator 18. Even though the IC 28 is pressed against the semi-transparent plate 16, as is clear from FIG.
The C main body 80 and the base end portion of the lead wire 82 near the IC main body 80 are separated from the semi-transparent plate 16, and only the free end portion of the lead wire 82 is in close contact with the semi-transparent plate 16. Therefore, when light is irradiated from the illuminator 18, the shadows 84 that appear on the semi-transparent plate 16 at the base ends of the IC body 80 and the lead wires 82 become blurred as shown by broken lines in FIG. Become something. On the other hand, since the free end portion of the lead wire 82 is in close contact with the translucent plate 6, the shadow 86 thereof becomes dark and definite as shown by the solid line in FIG. As shown in FIG. 4, if there is a lead wire 82a whose free end is bent upward, the shadow 86a of the free end of this lead wire 82a will be blurred like the shadow 84 of the IC body 80, etc. becomes.

Therefore, the shadow of the IC 28 appearing on the semi-transparent plate 16 is imaged by the television camera 22, and among the output signals of the television camera 22, the signal corresponding to the dark portion of the shadow is 0, and the signal corresponding to the thin portion and the portion without the shadow is 0. If the corresponding signals are binarized to 1, a series of binarized signals representing the image of the free end of the lead wire 82 of the IC 28 is obtained. In this way, the threshold value of the binarization circuit 66 is determined in advance.

The information regarding the IC 2B to be tested obtained as described above is sent to the reference information setting device 70 by the bending determination device 68.
In this embodiment, since the IC 28 is accurately positioned at a predetermined position on the translucent plate 16 by the holding head 30, both It is extremely easy to compare whether the information matches or not. If even one of the many lead wires 82 does not have a free end that is in close contact with the semi-transparent plate 16, the above two pieces of information will clearly disagree, so the bend determination device 68 will determine whether the lead wire 82 is bent. It is determined that there is. Further, even when the lead wire 82 is bent in a plane parallel to the IC body 80, the lead wire 82
Since the information on the shadow 86 of the free end of the curve does not match the reference information supplied from the reference information setting device 70, the bending determination device 68 also performs a lead-in when the degree of discrepancy exceeds a predetermined criterion. It is determined that the line 82 is bent.

When the bend determination device 68 determines that the lead wire 82 is bent, it supplies a defect detection signal to the mounting machine control section 72, so the mounting machine control section 72 eliminates defective ICs 28 based on this defect detection signal. However, the mounting machine is controlled so that it does not mount on the printed circuit board. Therefore, it is possible to prevent a defective IC 28 with a bent lead wire 82 from being mounted on a printed circuit board, resulting in defective soldering, or from the lead wire 82 being connected to an unintended circuit, resulting in a defective product. That will happen.

In this embodiment, the shadow of the lead wire 82 appearing on the semi-transparent plate 16 is imaged by the television camera 22, and the entire information obtained as a result is compared with the reference information set in the reference information setting device 70. Because it is designed to be
Even if the shape and dimensions of the IC 28 to be inspected change, the reference information only needs to be changed, and the detection work can be performed without changing the setup of the mechanical part such as changing the position of the imaging device. Even if the shadow 86 does not completely match the reference information, there is an advantage that detailed detection can be performed, such as passing the test as long as it does not interfere with soldering.

However, for example, in FIG.
Since bending of the lead wires 82 lined up along this straight line A-A can be detected just by looking at the state of the part A, the lead wires of each group lined up along each side of the IC body 80 can be detected. It is possible to detect a bend in the lead wire 82 by comparing information about a portion along one or more straight lines of the lead wire 82 with the corresponding reference information. In this case, it is possible to use a television camera as the imaging element, extract only the information along each straight line from the information obtained from the television camera, and compare it with reference information. It is also possible to image only the shadow of the portion along each straight line of the lead wire 82 using an image sensor and compare the information obtained as a result with reference information. Furthermore, it is not essential that the information itself includes information regarding the position and width of the shadows; for example, it is also possible to use the number of shadows clearly appearing on the semi-transparent plate 16 as the information.

Furthermore, in the embodiment described above, the IC 28 was pressed against the semitransparent plate 16 by the holding head 30 itself that conveys the IC 2B from the component supply device onto the printed circuit board. to IC2
After positioning and placing 8, a dedicated pressing device is activated to
It is also possible to press C28 toward the translucent plate 16.

Furthermore, in the above embodiment, the mounting machine that mounts the IC on the printed circuit board is equipped with a lead line image detection device, and the bending of the lead wire is detected immediately before the IC is mounted on the printed circuit board. As a result, there is almost no risk of the lead wires bending due to contact with other parts after bending is detected. It is also possible to provide a lead line drawing detection device separately.

The direction in which the IC 28 is pressed against the translucent plate 16 is not limited to the downward direction, but it is also possible to press the IC 28 upward or sideways.

Although other examples will not be given, it goes without saying that the present invention can be implemented with various modifications and improvements based on the knowledge of those skilled in the art.

[Brief explanation of drawings]

FIG. 1 is a front view (partially in cross-section) schematically showing an example of a lead wire drawing edge detection device used to carry out the method of the present invention. FIG. 2 is a front cross-sectional view of a holding head that constitutes a part of the lead line edge detection device. FIG. 3 is a block diagram showing the information processing section of the lead line drawing edge detection device. FIG. 4 is a front view showing a state in which a flat back type IC is pressed against a semi-transparent plate, and FIG. 5 is an explanatory diagram showing a shadow of the IC formed on the semi-transparent plate. 16: Transparent plate 18: Illuminator 22: TV camera 28; Flat pack IC 30: Holding head 32: Moving body 52: Suction tube 80: IC body 82: Lead wire 84: Shadow of IC body 86: Half of lead wire Shadow 86a of the part of the lead wire that is in close contact with the transparent plate: Shadow of the part of the lead wire that is not in close contact with the semi-transparent plate (Fig. 1n)

Claims (1)

[Claims] By pressing the main body of the flat-pack IC toward the translucent plate, the free ends of the lead wires are brought into close contact with the translucent plate, and light is directed from the flat-pack IC side toward the translucent plate. The information obtained by imaging the shadow of the lead wires on the semi-transparent board from the back side of the semi-transparent board was compared with the reference information corresponding to a normal flat pack IC with no bends in the lead wires. , If the two pieces of information do not match because there is a lead wire whose free end does not come into close contact with the translucent plate and its clear shadow does not appear on the translucent plate when pressed against the translucent plate, the lead wire A lead wire bend detection method for a flat pack type IC, characterized in that it is determined that the lead wire is bent.