JP2002296014A - Printed circuit board inspection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To finely measure the amount of displacement and enhance detection accuracy without saturation in detection at a light receiving part even in the case of a printed circuit board with a large difference in reflectivity level. SOLUTION: A printed circuit board P is irradiated with S-polarized laser beam outgoing from a light source 1 and the amount of displacement is outputted from a light receiving element 7. By using the S-polarized beam, the detection signal values of reference mark portions having high reflectivity on the circuit board can be lowered to reduce differences in detection values from soldered portions having high reflectivity, thus enabling fine measurement. The detection output of the receiving element 7 is amplified by an amplifying means 21. A processing means 22 optimally sets the amplification factor of the amplifying means 21 by varying its gain so that the detection output outputted from the receiving element 7 increases to an unsaturated maximum value when light is received from the reference marks.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printed circuit board inspection apparatus capable of measuring a displacement amount on a printed circuit board in a non-contact manner, and more particularly, to accurately measuring a displacement amount on a printed circuit board having a greatly different reflectance. The present invention relates to a printed circuit board inspection device that can be used.

[0002]

2. Description of the Related Art FIG. 4 is a block diagram showing a displacement measuring device. The displacement amount of the measurement surface of the measured object 54 can be measured by irradiating the measured object with the measuring light to the displacement measuring device. The laser light emitted from the light source 51 of the light emitting unit 50 is
The light is irradiated on the measurement surface via the light projecting lens 53. The light reflected from the measurement surface is incident on the light detecting element 62 via the light receiving lens 61 of the light receiving section 60.

[0003] The light detecting element 62 outputs a detection signal corresponding to the image forming position on the light receiving surface. The laser light applied to the reference height O forms an image at a substantially central position of the light detection element 62, and the laser light applied to the low height A forms an image at an end position of the light detection element 62. The detection signal output from the light detection element 62 is output to a calculation unit (not shown), and the displacement of the surface of the object to be measured is calculated and output based on the detection signal.

This displacement measuring device is incorporated in a printed circuit board inspection device arranged on a printed circuit board manufacturing line, for example, and inspects the state of solder formation (position shift, height, defect, etc.) on the printed circuit board.

As described above, when detecting displacement on a printed circuit board, a signal corresponding to an image forming position on a light receiving surface is expressed by:
It is affected by the reflection state of the device under test. FIG. 5 is a view showing a printed circuit board. On the printed board P, a reference mark M for determining a reference position at the time of manufacturing such as solder printing, a solder H on a metal pad, and the like are provided. The reference mark M is a metal surface and has a high reflectance of the irradiated laser beam.
On the other hand, the material of the printed circuit board P is translucent in the case of glass epoxy or the like, and a part of the irradiated laser light does not reflect on the surface but penetrates inside the printed circuit board P (diffuse reflection inside) and has a low reflectance. . In addition, the cream printed solder portion also has a low reflectance.

FIG. 6 is a diagram for explaining the characteristics of the reflectance of a dielectric with respect to the polarization of laser light. FIG. 6A is a diagram showing the state of incidence of laser light, and FIGS. 6B and 6C are characteristic diagrams between air and glass. The vertical axis of (b) is the reflectance, and the horizontal axis is the incident angle. The case where the plane of polarization of the incident angle (the plane containing the direction of the electric vector and the incident light) is parallel to the plane of incidence (the plane containing the incident light and the normal to the incident point) (P-polarized light) and perpendicular ( (S-polarized light) indicates a state in which the reflectance changes depending on the incident angle. (B) shows the case where the laser beam enters the glass from the air, and (c) shows the case where the laser beam enters the glass from the air.

For example, in the displacement measuring device described in Japanese Utility Model Publication No. Hei 7-26648, the light projecting unit 50 is provided with a wavelength plate 52 for adjusting the ratio of S and P polarization of laser light. Thereby, the reflectance of the laser light on the glass surface can be measured in a substantially constant state at an incident angle in a predetermined range, so that there is no difference in the measured value between the measurement of the glass substrate and the measurement of the metal surface. .

[0008]

However, conventionally, the direction of polarization of laser light for measurement on a printed circuit board has not been defined in consideration of reflectance. The difference in reflectance due to polarized light greatly differs depending on the medium on the reflection surface.

FIG. 7 shows the amount of light received when the light reflected from each part on the printed circuit board P is received by the light receiving element (since the amount of projection light is constant, it can be regarded as the reflectance.
FIG. 4 is a characteristic diagram showing the reflectance in the following description. The vertical axis indicates the amount of light received by the photodetector 62, and the horizontal axis indicates the distance (position of each part) on the printed circuit board P.

As shown in FIG. 7, the reflectivity of P-polarized light is lower on the resist surface. The same applies to P and S polarized light in the solder H portion. However, at the reference mark M, the reflectance itself is much higher, and the reflectance of the P-polarized light is higher than that of the S-polarized light. The reflectivity of the gold pad portion was lower due to the influence of the adjacent solder, but the reflectivity of the P-polarized light was higher.

In general, the setting of the dynamic range (measurement span) in the light detecting element 62 is set based on the maximum amount of received light and the minimum amount of received light. Conventionally, the light receiving amount is set based on the light receiving amount of the resist portion having the highest light receiving amount and the light receiving amount of the solder H portion having the lowest light receiving amount. Was saturated and could not be used.

For this reason, conventionally, in the case where the laser beam is irradiated to the reference mark M portion while using the P-polarized light, the dynamic amount is considered in consideration of the light reception amount of the reference mark M portion having the maximum light reception amount. A range must be set.
If the dynamic range is expanded on the premise of the same performance, a problem arises in that the S / N of the displacement output (detected value) in the solder H portion on the lower light receiving amount side is reduced.

In particular, when a displacement measuring device is incorporated in a printed circuit board inspection device to detect the displacement of the solder H portion, if the displacement output on the low light receiving side becomes inaccurate, the displacement of the solder H (projection The position of the solder determined from the height, the area, etc.) and the displacement cannot be accurately obtained. The printed board P has a lower displacement than the actual one and is easily detected due to the light transmitting component of the glass epoxy used. However, the accuracy cannot be improved and the error component increases.

In the configuration in which the displacement measuring device is incorporated in the printed board inspection apparatus, the reference mark M is used as a reference position for matching the position of the printed board fixed by the inspection apparatus with the design coordinates used for the pass / fail judgment. Is being used.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and the detection at the light receiving section is not saturated, and the displacement can be measured precisely even on a printed circuit board having a large difference in reflectance. It is another object of the present invention to provide a printed circuit board inspection device capable of improving detection accuracy.

[0016]

In order to achieve the above object, a printed board inspection apparatus of the present invention provides a printed board provided with a metal part (M) having a high light reflectance and a solder (H) having a low light reflectance. A printed board inspection apparatus for irradiating a substrate (P) with a laser beam for measurement to measure a displacement amount on the printed board using triangulation, and emits S-polarized laser light to the printed board. A light projection unit (10) for causing the light to be emitted.

Further, according to the present invention, a printed circuit board (P) provided with a metal part (M) having a high light reflectivity and a solder (H) having a low light reflectivity is irradiated with a laser beam for measurement. What is claimed is: 1. A printed circuit board inspection apparatus for measuring a displacement amount on a substrate by using triangulation.
A light projecting unit (10) for emitting polarized laser light, a light receiving unit (11) for receiving reflected light from the printed circuit board,
Dynamic range changing means (22) capable of changing a light receiving dynamic range in the light receiving section.

The light receiving section (11) includes a light receiving element (7) for receiving light reflected from the printed circuit board (P).
Amplifying means (21) for amplifying the detection output of the light receiving element at a predetermined amplification rate, wherein the amplifying rate is variable, and the dynamic range varying means (22) is adapted to reflect light from the metal part (M). A configuration may also be adopted in which the amplification factor of the amplifying means is variably set so that the detection output output from the light receiving element when light is received has a maximum value that does not saturate.

The light projecting section (10) has a light source (1) for emitting S-polarized laser light to the printed circuit board (P) and a variable light emission power of the laser light emitted from the light source. Flexible light emission driving means (20) is provided, and the dynamic range variable means (22) is provided with a maximum value at which a detection output output from a light receiving element when light reflected from the metal portion (M) is received is not saturated. The light emission power of the light emission drive means may be variably set.

The light source (1) provided in the light projecting section (10) is a laser diode, and the light emitted from the laser diode may be arranged to be S-polarized light.

Further, the light projecting section (10) may be provided with a λ / 2 plate (2) for converting a laser beam for measurement on the printed circuit board (P) into S-polarized light.

According to the above configuration, the measurement light of the light projecting unit 10 is irradiated to the printed circuit board P as S-polarized light, and the light receiving element 7 outputs the displacement amount. By using S-polarized light, the value of the detection signal of the metal portion M having a high reflectance on the printed circuit board P can be reduced. This allows
The difference in the detection value from the portion of the solder H having a low reflectance can be reduced, and fine measurement can be performed. In addition, the reflectivity of the glass epoxy surface increases, and the amount of light penetration decreases. As a result, the displacement measurement accuracy of the glass epoxy surface can be improved. Further, the detection output of the light receiving element 7 can be set to an optimum state by the dynamic range changing means 22. The dynamic range setting on the light receiving section 11 side variably sets the amplification factor of the amplifying means 21 so that the detection output output from the light receiving element 7 at the time of receiving the metal portion M becomes the maximum value that does not saturate. On the other hand, the dynamic range setting on the light projecting unit 10 side is such that the light emission driving means 20 is set so that the detection output output from the light receiving element 7 at the time of receiving the metal portion M becomes the maximum value which does not saturate.
The light emission power of the light source 1 is variably set.

[0023]

(Embodiment 1) FIG. 1 is a configuration diagram showing a displacement measuring device which is a main part of a printed board inspection device of the present invention. This displacement measuring device includes a light projecting unit 10 that irradiates the object W with measurement light and a light receiving unit 11 that receives light reflected by the object by a light receiving element. Measure using the principle of surveying.

The structure of the light projecting section 10 will be described. Light having an S-polarized component is emitted from the light source 1 such as a laser diode. The S-polarized light means that the plane of polarization of incident light with respect to the device under test W (the plane containing the direction of the electric vector and the incident light) is the plane of incidence (the plane containing the incident light and the normal set to the incident point). Light perpendicular to

The light source 1 adjusts the angle in the rotation direction about the optical axis so that the object to be measured W is irradiated with S-polarized light. Generally, P-polarized light and S-polarized light can be changed to the other side by changing the direction of the laser diode by 90 degrees with respect to the rotation direction about the optical axis. The S-polarized light is collimated by the collimator lens 3, and then is radiated to the measurement surface of the workpiece W via the light projecting lens 4.

The structure of the light receiving section 11 will be described. An image is formed on the light receiving surface 7a of the light receiving element 7 via the light receiving lens 5 provided on the optical axis of the reflected light and the image forming lens 6. Then, the position of the imaging point on the light receiving surface 7a moves in the X direction in accordance with the amount of displacement of the surface of the workpiece W (the amount of movement in the height direction Z in the figure). The light receiving element 7 outputs a signal corresponding to the position of the light imaging point, and a calculation unit (not shown) executes a predetermined calculation based on the signal to output the displacement of the workpiece W.

The object to be measured W is the above-described printed circuit board P, which is made of glass epoxy and has a solder H, a metal pad, and a reference mark M. Fiducial mark M
Is a metal member made of copper, for example.

FIG. 2 is a diagram showing the amount of light received by the device under test W detected on the light receiving element 7. The amount of light received (reflectance) of the reference mark M and the solder H provided on the workpiece W is the detection value of the reference mark M and the detection value of the solder H for the P-polarized light shown in FIG. Although the difference L1 is large, the difference L2 between the detection value at the reference mark M and the detection value at the solder H can be reduced for the S-polarized light shown in FIG.

FIG. 3 is a block diagram showing the electrical configuration of the displacement measuring device. The light source 1 is driven to emit light by the light emission driving means 20. The light emission driving means 20 is an LD of the light source 1.
Is variably controlled. The amplification unit 21 amplifies and outputs the signal level of the displacement signal output from the light receiving element 7 at a predetermined amplification factor. The processing unit 22 measures the amount of displacement of the workpiece W based on the displacement signal output from the light receiving element 7 and outputs the displacement signal to the outside. Also, the light emission driving means 20
Has a function of adjusting the light receiving dynamic range by changing the output power of the amplifying means and the amplification factor of the amplifying means 21.

In this embodiment, the amplifying means 21
Optimum dynamic range is set by changing the amplification factor of. As shown in FIG.
By irradiating the laser beam with S-polarized light on the reference mark M, the amount of light received at the reference mark M can be reduced and the difference L2 can be reduced, so that saturation of the light receiving element 7 when the reference mark M is detected can be prevented. The amplification factor of the amplifying unit 21 is set to be the maximum amplification factor under the condition that the amplifying unit 21 does not saturate when the reference mark M is detected.

As a result, as shown in FIG. 7, the light receiving element 7 does not saturate even in the part of the reference mark M having an extremely high reflectance, and the dynamic range can be optimally set. Therefore, it is possible to improve the measurement accuracy of the displacement amount of the solder H, which is particularly necessary. At the same time, since the measurement accuracy can be improved, the printed circuit board P having a material transmitted light component such as glass epoxy can be used.
The displacement of the portion can also be accurately detected.

A modification of the above configuration will be described. In the above embodiment, the dynamic range is set by changing the amplification factor of the amplification unit 21. Instead, the light emission power may be varied with respect to the light emission drive means 20. In this case, the light emission power of the light source 1 by the light emission drive means 20 may be set to be the maximum light emission power under the condition that the amplification means 21 does not saturate when the reference mark M is detected. The effect can be obtained. Further, the dynamic range may be set by combining the variable amplification factor and the variable emission power.

Further, when the S-polarized laser beam is irradiated, the light receiving element 7 whose output is not saturated when the reference mark M is detected may be appropriately selected. After the selection, a configuration in which the above-described amplification factor and emission power are variably controlled as necessary can be adopted.

(Embodiment 2) Embodiment 2 of the present invention
1 is different from that of FIG. 1 only in that a λ / 2 plate 2 is additionally arranged on the optical axis of the laser light emitted from the light source 1. The λ / 2 plate 2 is disposed between the collimator lens 3 and the light projecting lens 4 (a place of parallel light) as shown in the figure. This λ / 2 plate 2 is
Is applied to emit P-polarized light to the device under test W. The λ / 2 plate 2 converts the P-polarized light from the light source 1 into S-polarized light and irradiates the object to be measured W. Also in the second embodiment, the optimal dynamic range can be set by executing the variation of the amplification factor and the light emission power described in the first embodiment.

[0035]

According to the printed board inspection apparatus of the present invention, the measurement light of the light projecting section is irradiated as S-polarized light onto the printed board, so that the value of the detection signal at the reference mark portion having a high reflectance can be reduced. Can be. This makes it possible to reduce the difference between the detection value of the solder portion having a low reflectance and the precision of the measurement.

A configuration for setting a dynamic range when irradiating S-polarized light onto the reference mark, that is, detecting the light emission power of the light source in the light projecting unit or the amplification factor in the light receiving unit, is output from the light receiving element. By variably setting the output to the maximum value that does not saturate,
Fine measurement can be performed, and measurement accuracy can be improved.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an embodiment of a main part of a printed board inspection apparatus of the present invention.

FIG. 2 is a diagram showing a change state of a light receiving amount on a printed circuit board.

FIG. 3 is a block diagram showing an electrical configuration of the present invention.

FIG. 4 is a diagram for explaining the principle of displacement detection.

FIG. 5 is a view showing a printed circuit board.

FIG. 6 is a diagram for explaining a reflectance for each polarization state.

FIG. 7 is a view for explaining a difference in the amount of received light in each part on the printed circuit board.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Light source, 2 ... λ / 2 plate, 3 ... Collimator lens, 4 ...
Light-emitting lens, 5: light-receiving lens, 6: imaging lens, 7: light-receiving element, 7a: light-receiving surface, 10: light-emitting section, 11: light-receiving section,
20: emission driving means, 21: amplification means, 22: processing means.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H05K 3/34 512 H05K 3/34 512B (72) Inventor Eiji Tsujimura 5-10 Minamiazabu, Minato-ku, Tokyo No. 27 F-term in Anritsu Corporation (reference) 2F065 AA06 AA16 AA24 BB02 BB23 BB27 CC01 CC26 DD04 EE09 FF01 FF09 FF44 FF49 GG04 GG07 GG22 HH04 HH09 HH12 JJ01 JJ08 LL35 NN02 NN06 QQ014 AU02 AB01 AB11 BB20 CA00 CB01 CB05 CD01 EA24 EA25 5E319 AA01 AC01 BB05 CD53 GG03 GG09 GG15

Claims (6)

[Claims] 1. A printed circuit board (P) provided with a metal part (M) having a high light reflectivity and a solder (H) having a low light reflectivity is irradiated with a laser beam for measurement to displace on the printed board. What is claimed is: 1. A printed circuit board inspection apparatus for measuring a quantity by using triangulation, comprising: a light projecting unit (10) for emitting S-polarized laser light to the printed circuit board. 2. A printed circuit board (P) provided with a metal part (M) having a high light reflectivity and a solder (H) having a low light reflectivity is irradiated with a laser beam for measurement to displace on the printed circuit board. A light emitting unit (10) that emits S-polarized laser light to the printed circuit board, and a light receiving unit that receives reflected light from the printed circuit board. Department (1
1) and a dynamic range changing means (22) capable of changing a light receiving dynamic range in the light receiving section. 3. The light receiving section (11) includes a light receiving element (7) for receiving reflected light from the printed circuit board (P), and an amplification factor for amplifying a detection output of the light receiving element at a predetermined amplification factor. A variable amplification means (21) is provided, and the dynamic range variable means (22) has a maximum value at which a detection output output from the light receiving element is not saturated when light reflected from the metal part (M) is received. 3. The printed circuit board inspection apparatus according to claim 2, wherein the amplification factor of the amplification unit is variably set so as to satisfy the following. 4. A light source (1) for emitting S-polarized laser light to the printed circuit board (P), and a light emission power of the laser light emitted from the light source is variable in the light projecting section (10). Flexible light emission driving means (20) is provided. The dynamic range variable means (22) is provided with a maximum value at which a detection output output from a light receiving element when light reflected from the metal part (M) is received is not saturated. 3. The printed circuit board inspection apparatus according to claim 2, wherein the light emission power of said light emission drive means is variably set. 5. The light source according to claim 2, wherein the light source provided in the light projecting section is a laser diode, and the light emitted from the laser diode is arranged to be S-polarized light. Printed circuit board inspection equipment. 6. The print according to claim 2, wherein the light projecting section is provided with a λ / 2 plate for converting a laser beam for measurement on the printed circuit board to S-polarized light. Board inspection equipment.