JPH0255903A - Measuring method and device for position of object to be tested - Google Patents

Abstract

PURPOSE:To measure the position in X and Y directions at the same time and to improve an efficiency by deflecting a laser beam within the range of a specified angle in the manner of rotating a rotary polygonal mirror and making a reflection mirror to move on the optical axis of an image formation lens. CONSTITUTION:The laser beam is deflected within the specified angle range by rotating the rotary polygonal mirror 10, and the lead end surface of a semiconductor device 22 is scanned with a laser spot by making the reflection mirror M1 to move on the optical axis of the image formation lens 20. A light reflected from the lead end surface is received by a photosensor 28, and the received light signal is amplified by an amplifier 32 and inputted to a comparator 34, then if the signal with the level more than a reference level is found, rising and falling edges of the reflected light are stocked in a memory 36 as pulse signals fro a counter 38 and taken-out to a CPU, wherein arithmetically processed. The position in the X direction of the object to be measured is made to be the position corresponding to a middle point of the rising and falling edges on each lead.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method and apparatus for measuring the position of a subject;
In particular, the present invention relates to a method and apparatus for measuring the position of a subject suitable for measuring bending and floating of leads of semiconductor devices.

(Prior art and its problems) Semiconductor devices are becoming more and more highly integrated, and therefore semiconductor devices formed by incorporating them into packages also have a large number of leads for electrical continuity with the outside. ing. Furthermore, there is a strong demand for miniaturization of semiconductor devices themselves in order to increase packaging density, and therefore lead widths and lead spacings are inevitably becoming smaller. For example, in recent years, devices with a lead width of about 200 μm and a lead spacing of about 300 μm have appeared.

These semiconductor devices are mounted on a board by soldering or by being inserted into a socket to establish electrical continuity on the board, but if the leads are bent or loose, it may interfere with soldering or mount the device. This results in defects and a highly reliable mounting board cannot be obtained.

Therefore, before incorporating these semiconductor devices into automatic mounting equipment, we use a measuring device to detect bent or loose leads.
It is necessary to eliminate defective products.

Conventionally, as the above-mentioned measuring device, a video recognition device incorporating a camera is known, and the bending or floating of the lead is detected by performing video processing.

(Problems to be Solved by the Invention) However, when image processing is performed using a camera, there are the following problems.

That is, two cameras are required to measure lead bending and floating, that is, in both X and Y directions, which increases the size of the device. For example, in the case of a quad-type semiconductor device in which leads extend in all directions, a total of eight cameras are required.

Furthermore, image analysis using a camera has a limit due to the resolution of the camera, and as mentioned above, for semiconductor devices with small lead widths and lead spacing, accurate measurements cannot be performed or measurements cannot be made. A situation may also occur.

Furthermore, the video processing time also requires a long time of about 2.5 seconds.

Therefore, the present invention has been made to solve the above problems, and its purpose is to provide a measuring device that can be miniaturized, has high resolution, and can perform accurate measurements. be.

(Means for solving problems) The above objective is achieved by the following means.

In other words, a laser spot is scanned parallel to the object surface at high speed so that the scanning lines are spaced apart at a predetermined interval, a light receiving element receives the reflected light from the object surface, and a position detection sensor detects the laser spot on the object surface. The position of light incident on the surface is detected, and the arithmetic and control unit calculates the X-direction position of the object surface and the X-direction position perpendicular thereto based on the light reception signal from the light receiving element and the position detection signal from the position detection sensor. It is characterized by

In addition, there is a laser device, a rotating polygon mirror that reflects the laser light from the laser device and swings the reflected light within one plane, and a rotating polygon mirror that focuses the reflected light from the rotating polygon mirror on the surface of the object to be examined as a laser spot. a reflecting mirror and a half mirror arranged in the optical path of the lens to guide the reflected light from the rotating polygon mirror outside the optical axis of the lens to enter the object surface; moving means for moving the reflecting mirror and/or half mirror while maintaining a constant angle with respect to the incident light beam so as to deflect the incident light in a plane perpendicular to the plane deflected by the rotating polygon mirror; , a light-receiving element placed behind the half mirror to receive reflected light from the object surface; and a light receiving element placed near the object surface to detect the incident position of a laser spot scanned on the object surface. The present invention is characterized by comprising a position detection sensor, and an arithmetic and control device that calculates the X-direction position and the X-direction position of the subject surface based on the light reception signal from the light receiving element and the position detection signal from the position detection sensor.

(Function) A laser spot is scanned on the surface of the object to be examined, and the light reflected from the surface of the object is detected by the light receiving element. Positional information such as the width (X direction) and position of the subject can be calculated from the time during which this reflected light is obtained and the scanning speed of the laser spot. This laser spot can be scanned by a rotating polygon mirror that rotates at high speed.

On the other hand, by scanning the laser spot parallel to the surface of the object so that the scanning lines are spaced at a predetermined interval, and detecting the incident position of the laser spot with a position detection sensor, the laser spot can be scanned in the height direction (X) of the object. Positional information such as the position (direction) and thickness can be calculated. This laser spot scanning is performed by placing a reflecting mirror and/or half mirror in the optical path of the reflected light from the rotating polygon mirror, and keeping the reflecting mirror and/or half mirror at a constant angle with respect to the incident light beam. This can be done by moving. As a result, the scanning line obliquely scans the surface of the subject, and position information in the width direction and height direction can be calculated simultaneously.

When a rotating polygon mirror is used, the resolution is approximately 10 μI, making it possible to measure bending, floating, etc. of leads of semiconductor devices with high precision and at high speed.

(Embodiment) A preferred embodiment of the present invention will be described in detail below with reference to the accompanying drawings.

In FIGS. 1 and 2, 10 is a rotating polygon mirror, and in this embodiment, a six-sided mirror is used. This rotating polygon mirror 10 is rotated about a rotating shaft 12 at a constant high speed of about 7600 PPM. Note that the rotation device is not illustrated.

A semiconductor laser device 14 is placed on the side of the rotating polygon mirror 10, and irradiates a laser beam onto the mirror surface of the rotating polygon mirror 10 via a collimator 16. Therefore, when the rotating polygon mirror 10 is rotated at high speed, the laser beam reflected by the mirror surface travels within a predetermined angular range while being swung from one mirror surface to another.

Reference numeral 18 denotes a photosensor, which is placed at the end of the range where the laser beam is radiated, and when the laser beam is received, it issues a reset signal to reset the signal processing system, which will be described later.

Reference numeral 20 denotes an imaging lens, which is disposed within the travel range of the reflected laser beam and forms an image of the laser beam onto the lead end face of the semiconductor device 22 to be measured as a laser spot with a diameter of approximately 30 μm.

That is, the semiconductor device 22 is positioned and placed on the focal plane of the imaging lens 20.

Ml is a reflecting mirror that reflects the laser beam emitted from the imaging lens 20 in the right angle direction. Ml is a half mirror that further reflects the reflected light from the reflecting mirror M1 in the right angle direction and guides it onto the lead end face of the semiconductor device i22.

The reflecting mirror M1 is capable of reciprocating on the optical axis of the imaging lens 20 at a constant speed. This moving device can be configured to reciprocate the reflecting mirror M1 by means of a screw rod that is precisely driven by a servo motor, for example (not shown). The moving distance of the reflecting mirror M1 varies depending on the size of the subject. If the object to be examined has a small area, such as a lead of the semiconductor device 22, it is sufficient to be able to move it forward and backward by about 4+ nm. Movement speed is 4
The distance of IIlffi was made to move in about 0.5 seconds.

As the reflecting mirror M1 moves back and forth on the optical axis of the imaging lens 20 in this manner, the position at which the reflected light from the reflecting mirror M1 enters the half mirror Ml changes in the vertical direction of the plane of the drawing in FIG. As a result, it can be seen that the laser spot introduced to the lead end face of the semiconductor device 22 is also swayed in the vertical direction of the top page of FIG. 1, that is, in the thickness direction of the lead.

Reference numeral 24 denotes a position detection sensor, which is placed on the side of the semiconductor device 22, which is the object to be tested, and allows the light from the half mirror Ml to be reflected by a reflection mirror (not shown) and enters the lead, as described above. Detects the position of the laser spot traveling in the thickness direction and outputs a position signal.

Reference numeral 26 denotes a condenser lens disposed behind the half mirror M2, which condenses the reflected light reflected from the lead end face of the semiconductor device 22 and passed through the half mirror M2, and outputs the light to the photosensor 2.
Let the light enter at 8.

Next, the operation will be explained.

By rotating the rotating polygon mirror 10 to swing the laser beam within a predetermined angle range, and by moving the reflecting mirror M+ on the optical axis of the imaging lens 20, the laser spot scans the lead end face of the semiconductor device 22. do. That is, each time the rotating polygon mirror 10 rotates, the laser spot travels in the direction perpendicular to the plane of the paper in FIG. It runs in the thickness direction of the lead (referred to as the Y direction) as shown in FIG. Therefore, as shown in FIG. 3, if the speed at which the leads 30 travel in the arrangement direction (X direction) is SX, and the speed at which the leads travel in the thickness direction (Y direction) is sy, then θ=jan -' SY The laser beam will travel obliquely on the lead end face at an angle of /Sx.

However, if the rotating polygon mirror 10 rotates at 7600 RPM, the time for one scan of the laser spot reflected by the rotating polygon mirror 10 to travel on the lead end face is approximately 1.3 m.
It takes 5ec, and it travels a distance of several cII+ during this time, so it is extremely fast. For example, the mileage is 5co+
Then, Sx #3846cn+/sec.

On the other hand, the time for the reflection mirror M1 to move is approximately 0.5 seconds, as described above, and during this time the laser spot is
Since it runs about Il111, it is slow, and SY
= 0.8 cm/see.

Therefore, θ= jan-'0.8/3846#0
．． 01 degrees.

Therefore, the laser spot may traverse the lead end face almost parallel to the lead surface with almost no angle.

Note that the laser spot travels approximately 385 times in the direction in which the leads are arranged in 0.5 seconds when it travels once in the thickness direction of the leads.

To be more precise, the trajectory of the laser spot is an extremely gentle sine curve, but it can be seen as a straight line.

When the reflecting mirror M1 is moved, the laser spot focal position shifts slightly from the lead end face, but since the lead thickness is about 0.2 to 0.3 mm, the change in spot diameter can be ignored.

FIG. 3 is a schematic diagram showing an example in which a laser spot travels on a lead end face. The interval in the Y direction between the scanning lines running in the X direction is approximately 10 μm.

The reflected light from the lead end face is received by the photosensor 28, and the received light signal is amplified by the amplifier 132 (FIG. 4) and input to the comparator 34. If there is a signal above the reference level, the signal is sent to the memory (FIFO) 36. The rising edges and falling edges of the reflected light are stored as pulse signals in the counter 38, taken out by the CPU, and subjected to arithmetic processing.

FIG. 5 shows a time chart.

FIG. 2A shows a state in which reflected light is received by the photosensor 28. FIG.

FIG. 2B shows a reset signal from the photosensor 18.

Figures (c) and (d) show pulse signals of the counter 38, which are stored in the memories 36a and 36b, and correspond to the rising and falling edges of the reflected light.

Standard lead foot position information is stored in memory.

The position of the lead of the subject in the X direction corresponds to the midpoint between the rising edge and the falling edge of each lead.

In other words, the midpoint between the positions of point a and point b is the position of the first beam gate 30, and the midpoint between the position of point C and point d is the position of the second beam gate 30. This midpoint position is determined by averaging several scanning lines. The difference between the position information of each lead and the foot position information of a standard lead stored in the memory in advance is calculated to detect bending of the lead. If the bending of the lead is within the allowable range, it is determined to be a good product, and if it is outside the allowable range, it is determined to be a defective product.

Note that the actual position of each lead from a certain reference position can be easily calculated from the X-direction velocity of the laser spot and the time information of the rising edge and falling edge. This reference position may be set anywhere.

Note that the width of each lead can be easily calculated.

The position of the lead in the Y direction is detected by the position detection sensor 24. That is, the scanning line of the laser spot rises at intervals of about 10 μm as described above. By setting the position of the first reflected light generated on each lead as the sole of the foot, the position of the lead in the Y direction can be easily detected. There are various types of position detection sensors 24, but for example, one that outputs a received light current from terminals at both ends, and the output current from each terminal changes depending on where the light is received between the terminals, is used. By comparing the voltage between both terminals, the light receiving position, that is, the position of the lead in the Y direction can be detected.

The actual position in the Y direction from a reference point is determined by the time required from the reference point to the point where the reflected light is obtained, Δt, and the speed in the X direction, S.
When ×, it can be calculated by Δ■=Δt−3x tan θ.

This is calculated through arithmetic processing by the CPU.

The thickness of the lead can also be easily calculated.

Further, if the lead end face is rectangular, the area of this end face can be easily calculated.

The resolution when using the above rotating polygon mirror 10 is approximately 10μ
m, and position measurement can be performed with extremely high precision. Further, the signal processing time is only about 0.4 seconds, and position measurement can be performed efficiently.

The term "position" in the present invention is a concept that includes all of the position from the reference point, width, height (J!X), area, etc.

In the above embodiment, the position measurement of a semiconductor device has been described as an example, but it is needless to say that the present invention is not limited to this.

Although the present invention has been described above with reference to preferred embodiments, it goes without saying that the present invention is not limited to the above embodiments.
For example, the half mirror M2 may be moved, and many other modifications can be made without departing from the spirit of the invention.

(Effects of the Invention) As described above, according to the method and apparatus of the present invention, the position of the subject in the X direction and the Y direction can be measured simultaneously, and efficient position measurement can be performed.

In addition, by using a rotating polygon mirror and providing a means for moving the half mirror 1 reflecting mirror, the laser spot can be easily scanned diagonally on the surface of the object with a simple device, and the above-mentioned efficient position measurement can be achieved. At the same time as you can
It has good resolution and is effective in accurately measuring the position of minute objects, such as detecting the lead position of semiconductor devices.

[Brief explanation of the drawing]

FIGS. 1 and 2 are schematic diagrams showing an example of the device of the present invention, and FIG.
The figure is a schematic diagram showing the laser spot scanning on the lead end face, and Figure 4 is an explanatory diagram showing the essentials of the signal processing system.
FIG. 5 shows a time chart. DESCRIPTION OF SYMBOLS 10... Rotating polygon mirror, 12... Rotating shaft, 14... Semiconductor laser device, 16... Collimator, 18... Photo sensor, 20... Lens for imaging, 22... Semiconductor device, 24... Position detection sensor 26... Condensing lens, 28... Photo sensor 30...
Lead, 32...Amplifier, 34...Comparator,
36...Memory, 36a, 36b...Memory, 38...Counter

Claims (1)

[Claims] 1. A laser spot is scanned parallel to the surface of the object at high speed so that the scanning lines are spaced apart by a predetermined distance, and a light receiving element receives the reflected light from the surface of the object. The incident position of the laser spot on the object surface is detected, and the arithmetic and control unit determines the X direction position of the object surface and the Y direction perpendicular to this based on the light reception signal from the light receiving element and the position detection signal from the position detection sensor. 1. A method for measuring the position of a subject, characterized in that the directional position is calculated. 2. A laser device, a rotating polygon mirror that reflects the laser light from the laser device and swings the reflected light within one plane, and a rotating polygon mirror that focuses the reflected light from the rotating polygon mirror on the surface of the object to be examined as a laser spot. a reflecting mirror and a half mirror disposed in the optical path of the lens to guide the reflected light from the rotating polygon mirror outside the optical axis of the lens to enter the surface of the object to be examined; a moving means for moving the reflecting mirror and/or the half mirror while maintaining a constant angle with respect to the incident light beam in order to deflect the incident light in a plane perpendicular to the plane deflected by the rotating polygon mirror; , a light-receiving element that is placed behind the half mirror and receives reflected light from the object surface; and a light receiving element that is placed near the object surface and detects the incident position of a laser spot scanned on the object surface. The object is characterized by comprising a position detection sensor, and an arithmetic control device that calculates an X-direction position and a Y-direction position of the object surface based on a light reception signal from the light receiving element and a position detection signal from the position detection sensor. Specimen position measuring device. 3. Claim 2, wherein the object to be inspected is a lead leg position of a semiconductor device.
The object position measuring device described above.