JPH0447210A - Height measuring apparatus by laser spot light - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention relates to a height measuring device using a laser spot light, in which the position of the center of gravity of the light intensity distribution received by a position detection element is averaged. It is designed to accurately measure height.

(Prior Art) As shown in FIG. 9, a laser spot light is irradiated from a laser irradiator 1 onto a solder 6 for bonding an electrode 5 of an electronic component to a substrate 4, and the reflected light is collected by a condenser 2. The height of the reflection point 7 is measured by making the light incident on the position detection element 3 such as a PSD. 8 is a condensing element for focusing on the reflection point 7.

Figures 10 (a), (b), and (c) show the distribution of brightness at the reflection point 7 when the focus is accurately set on the reflection point 7, which is shown in Figure 10 (a). , almost the entire surface of the reflection point 7 shines brightly. In this case, the center of gravity G1 of the brightly shining portion Sl almost coincides with the center A of the reflection point 7. In this case, the distribution of the amount of light received by the position detection element 3 is approximately a normal distribution, as shown in a of FIG.
By detecting the distance Z1 from the zero point O to the center of gravity position Gl', the height of the reflection point 7 can be measured almost accurately.

(Problem to be Solved by the Invention) However, when a target object is irradiated with laser spot light, the uniform brightness distribution as shown in FIG.
As shown in Fig. 10(b) and (c), bright (shining parts S2 and S3 tend to be unevenly distributed.G2.G3)
is the brightly shining part S2. The center of gravity of S3, center A
It has shifted considerably. Figure 11.
It shows the light amount distribution of Figures (b) and (C),
Distance Z2. from zero point ○ to center of gravity position G2., G3. Z
3 has an error △Z2. △Z3 is included, and this distance Z
2. The height of the reflection point 7 calculated based on Z3 also includes an error.

Such variations in the light intensity distribution are particularly likely to occur when the laser spot light is irradiated onto metal surfaces such as solder or electrodes, and furthermore, it is caused by the interference of the reflected light at the reflection point with each other. Also, measurement errors occur.

SUMMARY OF THE INVENTION Therefore, it is an object of the present invention to provide a means for accurately measuring the height of a reflection point by eliminating errors caused by variations in the light amount distribution as described above.

(Means for Solving the Problems) For this purpose, the present invention provides a laser irradiator that irradiates a laser spot light onto an object, receives the reflected light reflected by the object, and positions the center of gravity of the received light amount distribution. A height measuring device using a laser spot light is constituted by a position detecting element that detects the height of the reflection point and an averaging means that averages the center of gravity position.

(Function) According to the above configuration, by averaging the center of gravity of the light intensity distribution received by the position detection element, it is possible to eliminate errors caused by variations in the light intensity distribution and accurately measure the height of the reflection point. can.

(Example 1) Next, the present invention will be described in detail with reference to the drawings.

In FIG. 1, l is a laser irradiator, 2 is a condensing element, and 3 is a laser irradiator.
is a position detection element such as a PSD, 4 is a substrate, and 5 is a substrate 4
Electrodes of the electronic component are bonded to the electrodes by solder 6, and 7 is a reflection point of the laser spot light. Reference numeral 10 denotes a mirror, and the laser spot light emitted from the laser irradiator 1 is reflected by the mirror 10 and irradiated onto the solder 6, which is the object to be measured, and the reflected light enters the position detection element 3. Condensing element 8
The focus of the laser spot light is made to coincide with the reflection point 7 which is the measurement point.

11 is a piezoelectric element as a vibration means attached to the back surface of the mirror 10, and when a voltage is applied, it expands and contracts, and the mirror 1
0 vibrates.

When the mirror 10 is vibrated while irradiating the laser spot light, two brightness distributions are obtained as shown in FIGS. 2(a) and 2(b). The figure (a) shows the brightness distribution when the piezoelectric element 11 is contracted, and the figure (b) shows the brightness distribution when the piezoelectric element 11 is expanded. Ga and Gb are the brightly shining parts Sa and Sb.
The brightly shining parts SL and S2 are unevenly distributed. These Figures 2(a) and (b) are similar to Figure 1o(b),
This corresponds to (c).

In addition, Fig. 3 a and b show the respective light intensity distributions, Ga',
Gb' is the center of gravity position.

Therefore, the average position Gm″ of the two center of gravity positions Ga・, Gb・
By finding the distance #Zm from the zero point 0,
The accurate height of the reflection point 7 can be determined. This average position Gm・ is calculated as shown in FIG. 2(C).
It corresponds to the average position Gm of the center of gravity Ga and the center of gravity cb when the two brightness distributions of a) and (b) are superimposed,
This average position Cm almost coincides with the center A of the reflection point 7. In this way, by averaging the two luminance distributions obtained by vibrating the mirror 10, the height of the reflection point 7 can be accurately measured.

(Example 2) In FIG. 4, 12 is an X mirror and 13 is a Y mirror, which are rotated in the X and Y directions to irradiate the solder 6 with laser spot light while scanning in the XY force directions. In this case, the piezoelectric element 11 causes the mirror 1 to
By vibrating 2.13, Figure 2(a),
A brightness distribution similar to that shown in (b) is obtained. Note that when scanning in the X direction by rotating the X mirror 12, the movable X mirror 12 is not vibrated;
The fixed side X mirror 13 is vibrated. Similarly, when scanning in the Y direction by rotating the X mirror 13, the fixed X mirror 12 is vibrated.

(Example 3) In FIGS. 5 and 6, 15 is a light transmitting body provided between the laser irradiator 1 and the mirror 14, and the rotating shaft 16
Rotate around. 17 is a motor. The light transmitting body 15 is made of a transparent glass plate or a synthetic resin plate, and has a thick part 15a and a thin part 15b.

Since the laser spot light transmitted through this light transmitting body 15 is refracted, the optical path length of the laser light transmitted through the thick portion 15a is
Since there is a slight difference in the optical path length of the laser beam that passes through the thin part 15b, when the light transmitting body 15 is rotated, the optical path length changes slightly, and the optical path length changes slightly as shown in FIGS. 2(a) and 2(b). A similar brightness distribution is obtained.

Further, the light transmitting body 18 shown in FIG. 7 is formed by integrally combining light transmitting parts 18a and 18b having different refractive indexes, and can be used in place of the light transmitting body 15 described above.

(Embodiment 4) In FIG. 8, 19 is a motor that rotates the laser illuminator I. When the laser illuminator I is rotated, the laser spot light that will be illuminated from now on rotates around its optical axis, so there is no interference unevenness between the reflected lights reflected from the reflection point 7 toward the position detection element 3. The results are averaged, and the same effect as in the above embodiment can be obtained. Of course, the laser beam may be rotated around the optical axis using a rotating prism or the like.

The present invention can further include various means, such as providing a frequency shifter in the optical path of the laser spot light,
By changing the frequency, the second (a), (b)
It is also possible to obtain a brightness distribution similar to that shown in FIG. Furthermore, the object to be measured is not limited to solder, and can be applied as a height measuring means such as an electrode.

(Effects of the Invention) As explained above, the present invention includes a laser irradiator that irradiates a laser spot light onto a target object, a laser irradiator that irradiates a laser spot light onto a target object, a laser irradiator that receives the reflected light reflected by the target object, and a light beam that is reflected from the center of gravity of the received light amount distribution. Since the height measurement position is composed of a position detection element that detects the height of a point and an averaging means that averages the center of gravity position, the height of the object can be accurately measured.

[Brief explanation of drawings]

The figures show examples of the present invention, in which Figure 1 is a side view of the measuring device, Figure 2 is a luminance distribution diagram, Figure 3 is an analysis diagram, and Figures 4 and 5 are other diagrams. Side view of the embodiment, Figures 6 and 7
The figure is a perspective view of a light transmitting body, Figure 8 is a side view of another embodiment, Figure 9 is a side view of a conventional measuring device, Figure 10 is a luminance distribution diagram, and Figure 11 is an analysis diagram. be. l...Laser illuminator 3...Position detection element 6...Target 7...Reflection point (○) Figure Figure Figure Figure Figure Figure Figure A Figure Figure

Claims (4)

[Claims] (1) A laser irradiator that irradiates a laser spot light onto a target object, and a position detection element that receives the reflected light reflected from the target object and detects the height of the reflection point from the center of gravity of the received light amount distribution. and an averaging means for averaging the center of gravity position. (2) The above-mentioned claim characterized in that the above-mentioned averaging means comprises a mirror that reflects the laser spot light irradiated from the above-mentioned laser irradiator toward the above-mentioned object, and means for vibrating this mirror. A height measuring device using a laser spot light according to item 1. (3) The above claim 1 is characterized in that the averaging means is a light transmitting body that is located between the laser irradiator and the object and that slightly changes the transmission length of the laser spot light. Height measurement device using the laser spot light described above. (4) The laser spot according to claim 1, wherein the averaging means is a means for rotating the laser spot light irradiated from the laser irradiator around an optical axis. Light-based height measurement device.