JPH03165535A - Lead height detector - Google Patents

Abstract

PURPOSE:To enhance the efficiency and accuracy of measurement by a method wherein the reflected light of a laser beam from each lead of a semiconductor element is condensed on a one-dimensional sensor by two cylindrical lenses. CONSTITUTION:A laser beam 2a is rotationally scanned by a galvanomirror 3 and reflected light 2b from individual leads 21 of a semiconductor device 20 is condensed by two cylindrical lenses 5 and 6 provided in such a way that the directions of the radii of curvature of the convex surfaces of the lenses 5 and 6 intersect orthogonally each other, is imaged on a one-dimensional sensor 7 as a beam spot 7a and is condensed on one point. A fine spot condensed on leads of an abnormal height is imaged at a position lower than that of the beam spot 7a to be imaged when the height of leads is a normal height. Thereby, the height of the individual leads can be measured at high speed and with high accuracy.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a lead height detection device, and more particularly to a lead height detection device that can be applied to detecting the lead height of a semiconductor element having a plurality of leads.

[Conventional technology]

Generally, a semiconductor element has a structure in which a plurality of leads 21 for external wiring are provided in a package 22 in which a semiconductor pellet is sealed, as shown in FIG. 3(a). This lead 21 is connected and fixed to an electrode of a printed circuit board or the like by soldering. At that time, if a part of the lead 2I is bent as shown in FIG. 1(b), and the leads 21a and 21b are deformed and have uneven heights, the melted solder may not be absorbed sufficiently. It will not flow and normal soldering will not be possible. Therefore, it is necessary to measure the height of the lead 21 to detect defects and correct τ.

Conventionally, the lead height has been measured visually using a microscope, a magnifying projector, or the like.

Therefore, the work requires a great deal of time and effort, and since the judgment is performed visually, there are variations in the judgment criteria, which limits the improvement of measurement accuracy.

[Problem to be solved by the invention]

The conventional lead height measurement described above is a visual process, which takes a lot of time and effort and is inefficient.
Measurement accuracy is said to be poor due to variations in judgment criteria.
There were drawbacks.

[Means to solve the problem]

The lead height detection device of the present invention includes a laser device that emits a first laser beam, a mirror that scans the first laser beam in one direction, and a mirror that focuses the scanned first laser beam. A projection lens that scans a second laser beam parallel to the leads of the semiconductor element at an oblique angle, and a scanning direction of a third laser beam obtained by reflecting the second laser beam on the leads, and a convex surface. A first cylindrical lens provided perpendicular to the direction of the radius of curvature, and the scanning direction of the fourth laser beam obtained by the third laser beam passing through the first cylindrical lens and the curvature of the convex surface. A second cylindrical lens provided with radial directions parallel to each other, and a beam spot obtained by converging the fourth laser beam with the second cylindrical lens is received and the position thereof is detected. It consists of a one-dimensional sensor.

〔Example〕

Next, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a perspective view showing an embodiment of the present invention.

The lead height measuring device shown in FIG. 1 includes a laser device 1 that emits a laser beam 2, a galvanometer mirror 3 that scans the laser beam 2 in one direction, and one focus on the center of scanning of the galvanometer mirror 3. A projection lens 4 that makes the scanned laser beam 2 incident on the leads 21 of the semiconductor element 20 at an angle of approximately 45° and focuses it on the leads 21 in a spot shape; The reflected laser beam 2b is incident on a cylindrical lens 5 provided with the radius of curvature of the convex surface oriented perpendicular to the scanning direction of the laser beam 2b, and the laser beam 2c obtained by passing through the cylindrical lens 5 is incident on the cylindrical lens 5. A cylindrical lens 6 provided with the radius of curvature of the convex surface oriented parallel to the scanning direction of the laser beam 2c and a laser beam 2d obtained by passing through the cylindrical lens 6 provided at the focal position of the cylindrical lens 6 are combined. It consists of a one-dimensional sensor 7 that detects the position of the imaged beam spot 7a.

Next, the operation will be explained with reference to FIG. 2.

The laser beam 2 emitted from the laser device 1 is scanned in one direction by the galvanometer mirror 3, and the center of scanning is at the focal point of the projection lens 4, so the laser beam 2a that has passed through the projection lens 4 is Converged and scanned in parallel. This converged and parallel scanned laser beam 2a is transmitted to the lead 21 of the semiconductor element 20 installed at the focal position of the projection lens 4.
Since the light is irradiated at an angle of approximately 45 degrees, the light is focused on a minute spot on the lead 21, and since the surface of the lead 21 is nearly mirror-like, it is regularly reflected by the surface.

The reflected laser beam 2b will be explained separately as reflection from a normal lead and reflection from a lead whose height is deformed and is not normal.

First, considering the laser beam 2b reflected from the abnormal lead, as shown in FIG. 2, the minute spot focused on the abnormal height lead 21a is reflected and becomes the laser beam 12b. This laser beam 12b is refracted by the convex surface of the cylindrical lens 5 to become a laser beam 12c, which passes through the cylindrical lens 6 and is imaged on the one-dimensional sensor 7.The position calculation circuit (
(not shown) to detect the position. In this way, the beam spot 17a formed on the one-dimensional sensor 7 is focused at a position below the beam spot 7a that is formed when the lead 21 is at a normal height, so the beam spot 17a is focused on the lead 21a.
It is detected that the height is not normal.

Next, considering the laser beam 2b reflected from a normal lead, as shown in FIG.
The laser beam 2b reflected from the laser beam itself becomes a diffused beam, but remains scanned in parallel. The cylindrical lens 5 is a laser; since the scanning direction of the light 2b and the radius of curvature of the convex surface are perpendicular to each other, the laser light 2b passes through as it is and becomes the laser light 2c which is itself scanned into a flat light. Next, the direction of the radius of curvature of the convex surface of the cylindrical lens 6 is the direction of the laser beam 2c.
Since the beam is parallel to the scanning direction, it is refracted and focused on one point on the one-dimensional sensor 7 provided at the focal point of the cylindrical lens 6 regardless of scanning. That is, as shown in FIG. 2, specularly reflected light from each lead 21 of the semiconductor element 20 forms an image as a beam spot a on the one-dimensional sensor 7 and is focused at one point.

As explained above, the laser beam is rotated and scanned by a galvanometer mirror, and the reflected light from each lead of the semiconductor element is focused by two cylindrical lenses whose radii of curvature of the convex surfaces are orthogonal to each other. Since the image is formed on a one-dimensional sensor, the height of each lead can be measured at high speed and with high precision.

In the above description, a galvanometer mirror was used to rotate and scan the laser beam, but the same implementation can be achieved by using a method such as a polygon mirror.

〔Effect of the invention〕

The lead height detection device of the present invention rotates and scans a laser beam, instead of visual inspection, and detects the reflected light from each lead of a semiconductor element by using two cylindrical plates arranged so that the directions of the radius of curvature of the convex surfaces are orthogonal to each other. The normal and abnormal heights of each lead can be detected by focusing them on a one-dimensional sensor using a lens, which improves the efficiency of lead height measurement and also increases the accuracy of measurement. be.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing one embodiment of the present invention, and FIG. 2 is a perspective view showing one embodiment of the present invention.
FIGS. 3(a) and 3(b) are a perspective view and a partially cutaway side view of the semiconductor element shown in FIG. 1, respectively, for explaining the operation of the embodiment shown in the figure. l... Laser device, 2... Laser light,
3... Galvano mirror 4... Light projection lens, 5, 6... Cylindrical lens, 7...
...One-dimensional sensor, 7a. 17a...Beam spot, 20...
Semiconductor element, 21...Lead.

Claims (1)

[Claims] a laser device that emits a first laser beam; a mirror that scans the first laser beam in one direction; and a mirror that focuses the scanned first laser beam and parallels it to a lead of a semiconductor element at an oblique angle. a projection lens configured to scan a second laser beam on the lead, and a scanning direction of a third laser beam obtained by reflection of the second laser beam on the lead, and a direction of the radius of curvature of the convex surface provided so as to be orthogonal to each other. the first cylindrical lens, and the third laser beam is provided so that the scanning direction of the fourth laser beam obtained by passing through the first cylindrical lens and the direction of the radius of curvature of the convex surface are parallel to each other. and a one-dimensional sensor that receives a beam spot obtained by condensing the fourth laser beam with the second cylindrical lens and detects the position of the beam spot. Lead height detection device.