JP2565274B2 - Height measuring device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a height measuring device, and more particularly to measuring the height of leads of a semiconductor element placed on a transparent and flat glass surface, that is, the amount of floating of the leads from the glass surface. The present invention relates to a height measuring device.

[0002]

2. Description of the Related Art A conventional height measuring device for measuring the height of a lead of a semiconductor device is a light projecting lens for focusing a laser beam and a light reflected from an object to be measured placed at a focusing point. The light receiving lens for condensing the light and the one-dimensional light spot position detector arranged at the image forming point of the light receiving lens are provided, and the height is measured from the output.

FIG. 3 is a perspective view showing an example of a conventional height measuring device, and FIG. 4 is an explanatory view of its operating principle.

The height measuring apparatus shown in FIG. 3 has a light projecting lens 33 that collects a laser beam 32 from a laser 31 on a lead 21 of a semiconductor element 20 and a light receiving lens 34 that collects a reflected light from the lead 21. And the height signal H and the light amount signal P obtained from the one-dimensional light spot position detector 35 and the one-dimensional light spot position detector 35, which determine the height of the lead 21. And a height detection circuit 36 for measuring.

When the height of the lead 21 changes, as shown in FIG. 4, the reflection points of the laser light 32 change like A, B and C, and the images of the reflection points A, B and C change. Thus, images are formed at the positions A ', B', and C'on the one-dimensional light spot position detector 35, respectively. The one-dimensional light spot position detector 35 is
P is a detector that outputs signals P1 and P2 according to the distance from the tip to the center of the imaged light spot at both ends.
1 + P2 becomes the light quantity signal P of the light spot, and (P1-P2) /
(P1 + P2) becomes the height signal H indicating the position of the light spot, that is, the height of the lead.

The height signal H usually does not change even if the light quantity signal P of the light spot changes, but when the light quantity signal P is extremely small, it is affected by electrical noise and the error becomes large.
Therefore, when actually obtaining the lead height, the height signal H is made effective only when the light amount signal P is larger than the specified output P0, and the height detection circuit 36 displays the measured value. .

[0007]

In the above-mentioned conventional height measuring device, the package portion of the semiconductor element is held by suction or the like, and each lead is measured in a free state without any restraint. However, the height of the leads in a practical state in which the semiconductor element is placed on the flat substrate is important, and it is desirable to perform the measurement in this state.

In order to measure in a practical state, when a semiconductor element is placed on a transparent glass substrate and measured from the lower side through the glass substrate, in addition to the reflected light from the lead, which is the object to be measured, the specularly reflected light on the glass surface. However, since the image is formed on the one-dimensional light spot position detector through the light receiving lens, there is a drawback that the conventional height measuring device cannot obtain an accurate height.

An object of the present invention is to provide a height measuring device capable of accurately measuring the height of leads in a practical state in which a semiconductor element is mounted on a glass substrate.

[0010]

The height measuring apparatus of the present invention comprises a transparent and flat glass substrate on which an object to be measured is placed, and a laser and a lens for condensing the laser light, which is obliquely below the glass substrate. A projection optical system that irradiates a surface to be measured with laser light, and a first cylindrical lens that has a curvature in a measurement plane including a laser optical axis and a height measurement axis and that collects reflected light from the surface to be measured. And a second cylindrical lens having a curvature in a plane orthogonal to the measurement plane and condensing light reflected from the surface to be measured, and reflection condensed by the first and second cylindrical lenses. A one-dimensional light spot position detector arranged at an image forming point of light, a light shielding plate arranged in front of this one-dimensional light spot position detector to block specularly reflected light from the upper surface of the glass substrate, and the primary Height signal obtained from original light spot position detector and A height measuring circuit that measures the height of the surface to be measured from the quantity signal, and an alarm is generated when the height signal is detected from the one-dimensional light spot position detector when there is no object to be measured on the glass substrate. And a foreign matter detection circuit.

[0011]

Embodiments of the present invention will now be described with reference to the drawings.

FIG. 1 is a perspective view of an embodiment of the present invention, FIG. 2 is an operation explanatory view of this embodiment, (a) is a plan view seen from above,
(B) is a side view.

As shown in FIG. 1, the height measuring apparatus of this embodiment irradiates a laser beam 2 obliquely onto a lead 21, which is a surface to be measured and is composed of a laser 1 and a lens 3 for condensing the laser beam 2. A projection optical system 4, a first cylindrical lens 5 having a curvature in a measurement plane including a laser optical axis and a height measurement axis and condensing reflected light, and a curvature in a plane orthogonal to the measurement plane. And a one-dimensional light spot position detector 7 arranged at the image forming point of the reflected light condensed by the second cylindrical lens 6
And the specularly reflected light 11 on the surface of the glass substrate 25 which is arranged in front of the one-dimensional light spot position detector 7 and holds the semiconductor element 20.
A light-shielding plate 8 for shutting off the light, a foreign matter detection circuit 9 for detecting a foreign matter on the glass substrate 25 from the height signal H obtained from the one-dimensional light spot position detector 7, and a read from the height signal H and the light amount signal P. And a height detection circuit 10 for measuring the height of 21.

Next, the operation will be described with reference to FIG.
The laser light 2 emitted from the laser 1 is condensed by the lens 3 and is applied to the leads 21 of the semiconductor element 20 placed on the glass substrate 25. At this time, a part of the laser light 2 is emitted from the glass substrate 25. Is specularly reflected on the surface of. The laser beam 2 transmitted through the glass substrate 25 is reflected by the surface of the lead 21, but the surface of the lead 21 is somewhat rougher than the surface of the glass substrate 25 and causes irregular reflection. The reflected light 12 at the lead has a larger beam spread than the reflected light 11. The first cylindrical lens 5 which receives the reflected light has a curvature in a measurement plane including the laser optical axis and the height measurement axis, and the second cylindrical lens 6 has a curvature in a plane perpendicular to the measurement plane. Are arranged as follows. The operation will be described below by dividing it into a measurement plane and a plane perpendicular thereto.

First, when considered in a plane perpendicular to the measurement plane, the first cylindrical lens 5 can be considered as a simple glass plate. Therefore, the specular reflection light 11 on the glass surface and the reflection light 12 on the leads diffuse with a certain spread, respectively, but the second cylindrical lens 6
Each becomes a converging light. Then, the specularly reflected light 11 on the glass surface is blocked by the light shield plate 8 and does not reach the one-dimensional light spot position detector 7, but the reflected light 12 at the lead has a wide beam divergence angle at the reflection point, so the light shield plate. Although a part of the light is blocked by 8, the part that spreads to the outside reaches the one-dimensional light spot position detector 7.

Next, when considered in the measurement plane, the second cylindrical lens 6 can be considered as a simple glass plate. Therefore, the spot condensed on the lead 21 is imaged on the one-dimensional light spot position detector 7 by the first cylindrical lens 5. Here, when the height of the lead 21 changes, the image forming position on the one-dimensional light spot position detector 7 changes, and this change can be detected as a height signal H of the one-dimensional light spot position detector 7. Actually, the height detection circuit 10 validates the height signal H and displays the measured value only when the light amount signal P is larger than the specified output P0.

As described above, the function of the pair of first and second cylindrical lenses 5 and 6 and the light shielding plate 8 blocks the specularly reflected light 11 on the glass surface and the reflected light 12 on the leads. By collecting only the ones on the one-dimensional light spot position detector 7, the height of the lead 21 of the semiconductor element 20 placed on the glass substrate 25 can be accurately measured. The specular reflection from the lower surface of the glass substrate 25 can be easily made out of the effective range of the one-dimensional light spot position detector 7 by appropriately selecting the glass thickness.

Further, when the semiconductor element 20 is not placed on the glass substrate 25, the light amount signal P is zero and the height signal H has a value that is deviated to + or −. However, if there is a foreign substance on the glass substrate 25, a light quantity signal P is generated due to the diffused reflection component from the foreign substance, and the height signal H is + or −.
The height of the surface of the glass substrate 25 is shown instead of the state of swinging. Therefore, if the glass substrate 25 is moved and the height signal H indicates the height of the surface of the glass substrate 25, an alarm is issued by the foreign substance detection circuit 9 so that the position of the foreign substance on the glass substrate 25 is detected. I can know.

[0019]

As described above, the height measuring device of the present invention uses one set of the cylindrical lens and the light blocking plate to block the specularly reflected light on the glass surface and efficiently reflect the reflected light on the leads. Since the light can be collected well, there is an effect that the height of the lead can be accurately measured in the same state as the actual use state in which the semiconductor element is mounted on the glass substrate. Further, since an alarm can be issued by detecting a foreign substance on the glass substrate which causes a measurement error, there is an effect that an accurate measurement can be guaranteed even in continuous operation by an automatic machine.

[Brief description of drawings]

FIG. 1 is a perspective view of an embodiment of a height measuring device of the present invention.

FIG. 2 is an explanatory diagram of an operation of this embodiment.

FIG. 3 is a perspective view of an example of a conventional height measuring device.

FIG. 4 is an operation explanatory view of a conventional height measuring device.

[Explanation of symbols]

 1,31 Laser 2,32 Laser light 3 Lens 3 4 Projection optical system 5 First cylindrical lens 6 Second cylindrical lens 7,35 One-dimensional light spot position detector 8 Light shield 9 Foreign matter detection circuit 10,36 High Detection circuit 11 Regularly reflected light on the glass surface 12 Reflected light from the lead 20 Semiconductor element 21 Lead 25 Glass substrate 33 Light emitting lens 34 Light receiving lens H Height signal P Light intensity signal

Claims (1)

(57) [Claims] 1. A projection optical system for irradiating a surface to be measured with laser light obliquely below the glass substrate, which comprises a transparent and flat glass substrate on which an object to be measured is placed, and a lens for condensing laser and laser light. And a first cylindrical lens having a curvature in a measurement plane including a laser optical axis and a height measurement axis and condensing reflected light from a surface to be measured, and a curvature in a plane orthogonal to the measurement plane. A second cylindrical lens for collecting the reflected light from the surface to be measured, and a one-dimensional light spot arranged at the image forming point of the reflected light collected by the first and second cylindrical lenses. A position detector, a light blocking plate arranged in front of this one-dimensional light spot position detector to block specular reflection light from the upper surface of the glass substrate, and a height signal obtained from the one-dimensional light spot position detector, and Height to measure the height of the measured surface from the light intensity signal A height comprising: a measurement circuit; and a foreign matter detection circuit that generates an alarm when a height signal is detected from the one-dimensional light spot position detector when there is no object to be measured on the glass substrate. measuring device.