JPH0719825A - Substrate inspection apparatus - Google Patents

Abstract

PURPOSE:To make it possible to perform inspection by changing the irradiation angle of light, projecting the light on a material to be measured of cream solder, and precisely measuring the material to be measured. CONSTITUTION:The projecting angle of the optical pattern of lattice fringes, whose phase is changed, is substantially changed, and the optical pattern is projected on a printed board 11, on which cream solder 11a is printed. The printed position, area, thickness, weight and the like of the cream soder 11a are measured and detected based on a plurality of image signals outputted from a CCD camera 14.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is intended to mount small electronic components (1005 chips, etc.) and narrow lead pitch ICs on a wiring board with high density, such as a headphone stereo, a cordless telephone and a video with a built-in camera. The present invention relates to a board inspection device for measuring a three-dimensional shape represented by a cream solder amount inspection device, a visual inspection device, etc. printed on a printed circuit board.

[0002]

2. Description of the Related Art In the case of automating the surface mounting of electronic parts on a printed circuit board, for example, cream solder is printed at each predetermined position on the printed circuit board, and then the electronic parts are temporarily fixed to this printed circuit board by the viscosity of the cream solder. After that, it is soldered through a reflow furnace. Then, the soldering condition of the printed circuit board was inspected after the soldering process by the reflow furnace was completed. However, in order to realize high-density mounting of the printed circuit board, for example, an L having a J lead is used.
Those in which electronic components such as SI are soldered on the back side have come to be used, and in this case, it becomes difficult to perform an inspection after the soldering process is completed.

Since the soldering condition of electronic parts is greatly affected by the quality of the printed condition when cream solder is printed on a printed circuit board, an inspection is performed by a printing condition inspection device before the soldering process by the reflow furnace. It was being appreciated.

The above-mentioned device is composed of a projection unit consisting of a light source and a projector for generating lattice stripes by a liquid crystal shutter, and an image pickup unit for observing the state of an object to be measured such as a printed circuit board. The image pickup unit is installed in the projector, and the projection unit is installed at a certain angle with respect to the axis of the image pickup unit. Explaining the measurement principle of this inspection device, when the light of the lattice fringe pattern 1 shown in FIG. 8 (a) whose luminance distribution is sinusoidal is projected from the projection unit in an oblique direction onto the target surface of the measured object, As the lattice fringe pattern, a modulation fringe pattern 2 which is subjected to phase modulation according to the height of the object to be measured is obtained.
The luminance distribution of the m-plane of the grid pattern 1 shown in FIG. 8A is a sine wave of the solid line shown in FIG. 8B, and the luminance distribution of the n-plane is shown from the solid line to the broken line and the broken line of FIG. 8B. A sine wave with a phase shift in the middle of the solid line (broken line portion). Therefore, as shown in FIG. 8C, by measuring the phase modulation component Δφ at an arbitrary point Xo on the target surface of the object to be measured, the height of that point can be obtained. By utilizing this, the image entering the imaging unit is instantly processed, and the three-dimensional shape of the measured object is measured.

[0005]

In the substrate inspection apparatus as described above, as shown in FIG. 9A, the DUT 4 having a sharper angle than the irradiation angle of the projection light 3 by the projection unit is measured. In this case, the back is shaded and the measurement cannot be performed, or, as shown in FIG. 9B, when the projection light 3 is one, the projection light 3 is irregularly reflected due to the shape of the DUT 5, and erroneous measurement is performed. There was a problem such as a spot.

[0006]

SUMMARY OF THE INVENTION In order to solve the above problems, the board inspection apparatus of the present invention has an XY table on which a printed board is placed, a light source, and a plurality of slits obliquely from above in the printed board. A projection unit configured to irradiate a projection light having a lattice fringe pattern that changes in phase in a circular pattern, an imaging unit disposed substantially vertically above a printed circuit board, a spectroscope for separating the light from the projector, and the spectroscope. A plurality of reflecting mirrors for reflecting the light dispersed by the spectroscope to the object to be measured on the printed circuit board, and a plurality of blankers for blocking the spectrally separated light between the spectroscope and the reflecting mirror, respectively. The board is inspected by a plurality of image signals output from the image pickup unit.

Data relating to the printed board such as the printing position, area, thickness and quantity of the object to be measured obtained from the above image signal,
It is characterized in that it is provided with a judging means for judging the state of the printed circuit board by comparing with predetermined reference data of the printed circuit board such as a printing position, an area, a thickness and an amount of the measured object. is there.

Further, a reversing table on which the printed circuit board is placed, a table controller for moving the reversing table in the X and Y directions, a light source and a lattice striped pattern in which the phase is changed obliquely from above the printed circuit board into a plurality of slits. A projection unit including a projector that emits projection light, and an imaging unit in which the printed circuit board is arranged substantially vertically above the substrate surface, and the object to be measured on the printed circuit board is inverted by reversing the inversion table. It is characterized in that the substrate is inspected by a plurality of image signals output from the image pickup unit.

Data relating to the printed circuit board such as the printing position, area, thickness and quantity of the object to be measured obtained from the above image signal,
It is characterized in that it comprises a judging means for judging the condition of the printed circuit board by comparing predetermined reference data of the printed circuit board, such as printing position, area, thickness and quantity of the measured object. .

[0010]

Since this apparatus has the above-described configuration, it projects a plurality of phase-changing light patterns onto the object to be measured while changing the irradiation direction, and outputs a plurality of phase-changing image data. Since it is used, the object to be measured can be completely measured and inspected.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the substrate inspection apparatus of the present invention will be described below with reference to the drawings.

In one embodiment of the present invention, as shown in the schematic overall configuration diagram of FIG. 1, an XY table 12 on which a printed circuit board 11 is mounted, and a light source and a printed circuit board 11 are obliquely provided via a liquid crystal shutter (not shown). As a result, a projection unit 15 composed of a CCD camera 14 for irradiating a projection light of a lattice fringe pattern whose phase is changed in a plurality of slits, a CCD camera 16 for picking up an image of the printed circuit board 11 from substantially above the substrate surface, and a projector 14 A spectroscope 17 for splitting the light from the spectroscope, and reflecting mirrors 18 and 19 for reflecting the light split by the spectroscope 17 to the object to be measured,
Between the spectroscope 17 and the reflection mirror 18, and between the spectroscope 17 and the reflection mirror 19, there are provided blankers 20 and 21 for blocking the separated light. Cream solder 11a is printed on the printed circuit board 11.

The XY table 12 drives the pulse motors 12a and 12b of the XY table 12 in response to a command from the computer device 43 and the controller 44 via the XY table controller 48, thereby placing the printed circuit board 11 on the X-table. This is a device that moves the device to any position in the Y direction. The projection unit 15 includes a controller 44
Of the printed circuit board 1 via the lighting controller 45
1 is a device for irradiating the light whose phase is changed by a quarter pitch from diagonally above, and by irradiating the light from the light source 13 through the liquid crystal optical shutter, the X direction or the Y direction.
The printed circuit board 11 is irradiated with a lattice-stripe pattern in which the illuminance changes sinusoidally along the direction. At this time, the spectroscope 17 splits the light into, for example, two directions orthogonal to each other, one of the optical paths is blocked via the blankers 20 and 21, and the reflection mirrors 18 and 19 focus the light on a desired portion of the DUT 11. The appropriate light is emitted. Further, the light of the lattice fringe pattern has a fringe pattern in which the phase is changed by a quarter pitch in the X direction or the Y direction as described above by controlling the liquid crystal optical shutter and arbitrarily moving the phase. Is generated.

The detailed construction of the projection unit 15 is as shown in the sectional view of FIG. 3, and light from a light source (not shown) passes through the optical fiber 22 to the condenser lenses 23, 2.
4, a filter 25 is inserted between the condenser lenses 23 and 24. Condenser lens 23,
It is collimated by 24 and guided to a projection lens 27 via a liquid crystal element 26 which is a liquid crystal shutter. In this projection unit 15, the condenser lenses 23 and 24 and the projection lens 2
7, a constant temperature control device 28 is provided, and the liquid crystal element 26 is arranged in the constant temperature control device 28. Since the liquid crystal element 26 is arranged in the constant temperature controller 28, the temperature drift of the liquid crystal element is prevented and the contrast of the lattice pattern is stabilized.

The detailed structure of the liquid crystal element 26 is as shown in FIG. 4, in which one transparent electrode is provided over the entire surface and the other transparent electrode is divided into strips in one direction.
, 29 are provided, and terminals 31, 31, are connected from the plurality of strip-shaped electrodes 29 via the corresponding connection wires 30, 30 ,.
Derived to ... Liquid crystal element 2 which is the liquid crystal shutter
Reference numeral 6 is a twisted nematic liquid crystal, and polarizing plates (not shown) are attached in front of and behind the liquid crystal element 26.

Further, in the method of driving the liquid crystal element 26, as shown in FIG. 5, the strip electrodes 29 are driven so as to be shifted by a quarter pitch and an optical pattern in which the phase is changed into four phases is generated. That is, FIG. 5 (a), (b), (c), (d)
As shown in, each of the two strip-shaped electrodes is sequentially driven so as to be in an ON state in which light is transmitted. The shift cycle, direction, and drive division number of the strip-shaped electrodes can be arbitrarily set by the drive circuit.

The advantage of using a liquid crystal shutter for the projection unit 15 is that, first, due to the light transmission characteristics of the liquid crystal, the illuminance when a lattice fringe pattern is created is close to an ideal sine wave. The measurement resolution of three-dimensional measurement is improved. Next, since the phase shift of the lattice fringe pattern can be electrically controlled, the control system can be made compact and the phase shift can be performed accurately at high speed. In addition to this, in constructing the substrate inspection apparatus of the present embodiment, it plays an important role in facilitating the system configuration, reducing the size of the apparatus as a whole, and making it an inline-compatible high-speed inspection apparatus.

The board inspection apparatus having the above structure operates as follows.

When the printed circuit board 11 is placed on the XY table 12, the computer device 43 first sends an instruction signal to the XY table controller 48 together with data such as the amount of movement, so that the printed circuit board 11 is moved to the first inspection area (initial position). ) To. The inspection area is, for example, the printed circuit board 11 with the size of the field of view of the CCD camera 16 as a unit.
Is divided and set in advance. next,
The controller 44 sends an instruction signal to the illumination controller 45 together with data such as a checkered pattern to cause the projection unit 15 to start illumination of the checkered pattern.
As shown in (4), the phase of this checkered pattern is shifted by a quarter pitch and four types of illumination are sequentially switched. While the illumination in which the phase of the checkered pattern is shifted is performed in this manner, the CCD camera 16 images the inspection area for each of these illuminations and sequentially outputs image signals for four screens.

The image memory 46a sequentially stores the image signals for four screens sent through the distributor 47. The stored image signal is sent to the computer device 5. While the computer device 43 processes the image stored in the image memory 46a, the XY table 12 moves to the next inspection area, and the distributor 47 stores the inspection image in the image memory 46b. On the other hand, when the computer device 43 finishes the image processing of the memory 46a, the computer device 43 already has the memory 46a.
Since the next image signal has already been input to, the next image can be processed immediately. That is, test 6, whereas the next inspection area in Step S ₁ in (n + 1
Image input from S. ₂ ) and S _{3 on} the other hand
In step S ₄ , the comparison determination is performed in parallel processing from the nth image processing. Hereinafter, the same parallel processing is alternately repeated until the inspection of all the inspection areas is completed. As a result, the board inspection apparatus of the present embodiment performs the image processing sequentially while moving the inspection area under the control of the computer device 43 and the controller 44, thereby achieving high-speed printing of the cream solder 11a on the printed board 11. Can be surely inspected.

Next, the image processing and comparison judgment performed by the computer device 43 will be described.

Images of the inspection area when the phase of the striped pattern is shifted by a quarter pitch are shown in FIGS.
It becomes like (d). As is clear from FIG. 7, the checkered pattern projected on the printed circuit board 11 has a phase difference depending on the height difference between the surface of the printed circuit board 11 and the cream solder 11a. A gap occurs. Therefore, the computer device 43 calculates the height of the reflecting surface of each portion in the inspection area based on the image signals of these four screens by the phase shift method (fringe scanning method). In the calculation of the height of the reflecting surface of each part in the inspection area by the means as described above, the light from the spectroscope 17 is blocked by the blanker 21 on the other side, and the spectroscope 17 is bypassed by the blanker 20 on the other side. Is reflected by the reflection mirror 18,
The focused light l ₁ is applied to the cream solder 11a on the printed circuit board 11. At this time, the part of the cream solder 11a having a sharp angle with respect to the irradiation angle of the light l ₁ is diffused and reflected. If there is a place, above blanker 2
The measurement is performed by switching between 0 and 21 and the other light l ₂ having different incident angles.

In another embodiment of the present invention, the same portions as those in FIG. 1 are designated by the same reference numerals as in the schematic overall configuration diagram shown in FIG. The inversion table 12 ′ uses the instructions from the computer device 43 and the controller 44 for the θXY table controller 4
180 ° from the fixed position through the reversing table 12 '
(Degree) Rotate to the right or left while maintaining the horizontal position, and the reversing table 12 'includes pulse motors 12a' and 12a.
By driving b ', the printed circuit board 11 placed
Is a device for moving the X-Y direction to an arbitrary position.
The CCD camera 16 is installed vertically with respect to the printed circuit board 11, which is the object to be measured, and the projection unit 15
The light from is installed at a certain angle obliquely above the printed circuit board 11.

The other basic inspection apparatus having the above structure operates as follows.

When the printed circuit board 11 is placed on the reversing table 12 ', first, the computer device 43 is moved to θXY.
An instruction signal is sent to the table controller 49 together with data such as the amount of movement to move the printed circuit board 11 to the first inspection area (initial position). Next, the controller 44
Sends an instruction signal to the illumination controller 45 together with data such as a checkered pattern to start illumination of the checkered pattern to the projection unit 15, and shifts the phase of the checkered pattern by a quarter pitch as shown in FIG. Then, the four types of illumination are sequentially switched. In this way, while the illumination in which the phase of the checkered pattern is shifted is performed, the CCD camera 16 images the inspection area for each of these illuminations and sequentially outputs the image signals for four screens. The light projected onto the cream solder 11a, which is the object to be measured on the printed circuit board 11, is usually measured from one direction, but when the projection light is diffusely reflected and erroneous measurement occurs, or the object to be measured is measured. When the measurement cannot be performed due to a shadow in the back because the shape of the object has a sharper angle than the irradiation angle of the projection light, an instruction signal from the θXY table controller 49 causes the reversing table 12 ′ to move 180 ° right or left. Rotate to and measure accurately.

[0026]

As described above, the board inspection apparatus according to the present invention changes the irradiation direction of a plurality of phase-changing light patterns on a measured object of a printed board placed on an XY table or an inversion table. Since the inversion table is inverted to project the light pattern by substantially changing the irradiation direction of the light pattern and a plurality of image data having phase changes are used, the object to be measured can be completely measured and inspected.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an entire substrate inspection apparatus according to an embodiment of the present invention.

FIG. 2 is a schematic configuration diagram of an entire board inspection apparatus according to another embodiment of the present invention.

FIG. 3 is a configuration diagram of a projection unit of an optical system embodying the present invention.

FIG. 4 is a configuration diagram of a liquid crystal element embodying the present invention.

FIG. 5 is a diagram illustrating a method of driving a liquid crystal element according to the present invention.

FIG. 6 is a flowchart of the operation of the board inspection apparatus of the present invention.

FIG. 7 is a diagram showing each image obtained by a light pattern whose phase changes.

FIG. 8 is a diagram showing an image, a luminance distribution, and a phase obtained by a light pattern that changes in phase.

FIG. 9 is a diagram showing a relationship between an object to be measured and projected projection light.

[Explanation of symbols]

 11 printed circuit board 11a cream solder 12 XY table 12 'reversal table 14 projector 16 CCD camera 17 spectroscope 20, 21 blanker 23, 24 condenser lens 26 liquid crystal element 27 projection lens 41 host computer 42 data conversion machine 43 computer device 44 controller 45 Lighting controller 46a, 46b Image memory 47 Distributor 48 XY table controller

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location G06T 1/00 7/00 G12B 5/00 T 6947-2F G06F 15/64 320 C 8837-5L 15 / 70 455 B

Claims (4)

[Claims] 1. An XY table on which a printed circuit board is mounted, a projection unit including a light source, a projector for irradiating the printed circuit board from a diagonally upper direction with projection light having a lattice-stripe pattern in which a plurality of slits change phases, and a printed circuit board. In contrast, an image pickup unit arranged substantially vertically above, a spectroscope for splitting the light from the projector, and a plurality of reflecting mirrors for reflecting the light split by the spectroscope to an object to be measured on a printed circuit board. A substrate inspection device having a plurality of blankers for blocking the separated light between the spectroscope and a reflection mirror, and inspecting the substrate by a plurality of image signals output from the imaging unit. 2. Data relating to a printed circuit board such as a printing position, an area, a thickness and an amount of an object to be measured obtained from the image signal,
The determination means according to claim 1, further comprising: a determination unit that compares the predetermined printing position, area, thickness, amount, etc. of the measured object with reference data of the printed circuit board to determine the state of the substrate. Substrate inspection device. 3. A reversing table on which a printed circuit board is mounted, a table controller for moving the reversing table in the X and Y directions, a light source and a lattice striped pattern on the printed circuit board, the phases of which change in a plurality of slits obliquely from above. The imaging unit includes a projection unit configured by a projector that emits projection light, and an imaging unit disposed substantially vertically above the printed circuit board, and the object to be measured on the printed circuit board is inverted by the inversion table. A board inspection device that inspects a board by a plurality of image signals output from the board. 4. Data concerning a printed circuit board such as a printing position, an area, a thickness, and a quantity of an object to be measured obtained from the image signal,
4. The board according to claim 3, further comprising a judging means for judging the state of the board by comparing reference data of the printed board such as a predetermined printing position, an area, a thickness and an amount of the object to be measured. Inspection device.