JPH03257305A - Inspecting method of mounting of chip parts - Google Patents

Abstract

PURPOSE:To judge whether a chip is defective, improperly erect, acceptable or improperly shifted by a method wherein a laser distance sensor is equipped with a function to detect the amount of the reflecting light, a reference surface is set for every chip and the height of the chip from the reference surface is measured. CONSTITUTION:A laser distance sensor 1 mounted on an XY table 2 emits a laser beam L to scan a printed circuit board 9 to be measured which is placed onto a fixed stage 8. A stable surface with the reflecting light amount not smaller than a preset reference amount is set as a reference surface. The height of a chip 10 to be measured from the reference surface is measured. When the height of the chip is smaller than a value V1 obtained by subtracting a predetermined value from the thickness of the chip, the chip is judged to be defective. If the height of the chip exceeds a value V2 obtained by adding a preset value to the thickness of the chip, the chip is judged to be improperly erect. Moreover, when the height of the chip is between V1 and V2 and within the allowance of the positional shift, the chip is judged to be acceptable. When the height is outside the range between V1 and V2 and exceeds the allowance of the positional shift, the chip is judged to be improperly shifted.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a chip component mounting inspection method for inspecting for incorrect chip mounting after chip components are mounted in a printed circuit board manufacturing process.

[Conventional technology]

Mass production lines for circuit boards that mount large numbers of chips are equipped with machines that automatically mount chips.

According to this automatic chip mounting machine, not all chips are always mounted on the board in the correct position and in the correct posture, and the following mounting failures often occur.

(1) The chip is not installed in the correct position (missing item). (2) The chip is not installed in the correct position (misalignment). (3) The chip is installed so that it stands on the side. Many of these mounting defects are discovered at some point in the inspection process as the board manufacturing process progresses, but as the process progresses, it becomes more difficult to correct them, so they should be fixed immediately after chip mounting. All products must be inspected to remove such defective products. This inspection method includes visual inspection and inspection using an automatic inspection machine.

The automatic inspection machines currently on the market are as follows.

(1) 3D data obtained by scanning the board with multiple laser beams (usually 3 beams) and receiving the reflected light with a single CCD camera is compared with pre-input reference data to determine pass/fail. something to inspect.

(2) A device that inspects quality by comparing image data captured from the board surface with multiple CCD cameras (usually 3 or 4) and reference data input in advance.

[Problem to be solved by the invention]

However, visual inspection cannot be easily adopted because the reliability of the inspection is low and the number of personnel increases in proportion to the number of products produced. Therefore, it is necessary to rely on an automatic inspection machine, but there is a problem in that it is difficult to employ the above-mentioned automatic inspection machines that are commercially available because they are all expensive.

As mentioned above, these inspection machines require multiple laser beams and a high-density CCD camera or a processor for processing multiple data captured from multiple CCD cameras due to their structure. It's expensive.

Normally, these inspection machines require a few to a dozen or more machines due to the configuration of the printed circuit board manufacturing line, so the equipment investment amount exceeds tens of millions of yen, and although it is necessary, it is difficult to adopt it easily. The problem is that there is no.

The present invention has been made to solve the above-mentioned problems, and aims to provide a chip component mounting inspection method that can inspect all chip components to be inspected, does not require inspection time, and is inexpensive. It is something.

[Means to solve the problem]

In order to achieve the above object, the present invention is a laser distance measuring device that can measure the height of an object by emitting a laser beam to the object and measuring the height of the object based on the difference in the angle of reflection of the laser beam from the object. A laser distance measuring device equipped with a function to detect the amount of light reflected from an object is prepared, and the laser distance measuring device emits a laser beam to sequentially scan a printed circuit board and receive the reflected light from the printed circuit board, while , a reference amount of reflected light corresponding to the amount of reflected light from a predetermined reference surface is set for each chip mounting position on the printed circuit board, and a surface where the amount of reflected light due to the scanning is stable at or above the reference amount of reflected light is set. Measure the chip height at the chip mounting position from the reference surface as a reference surface, and if the measured chip height does not reach the value (1) obtained by subtracting a predetermined value from the chip thickness, it is determined that the chip is out of stock; When the measurement chip height exceeds the value v2, which is the sum of the chip thickness and a predetermined value, it is determined that there is a failure in standing, and when the measurement chip height exceeds the predetermined chip position deviation tolerance distance range, the measurement chip height exceeds the value V1. from V
Provided is a chip component mounting inspection method characterized in that when the chip position deviation is within 2, it is determined to be a pass, and when the chip position deviation exceeds the allowable distance and is still outside the range of the value V1 to V2, it is determined to be a deviation defect. do.

According to a preferred embodiment of the present invention, when using the measuring device, as described above, the surface of the printed circuit board is used as the measurement reference surface, and a dimension α (arbitrarily set in advance) is set slightly compared to the chip thickness. The "chip thickness ±α" is used as a criterion for determining the chip mounting height, and the "chip position deviation allowable distance" is set in advance as described above.

The substrate surface is set as follows. In other words, a commercially available laser distance measuring device is equipped with a function that captures analog data of the intensity of reflected light that reaches the light receiving surface, and this analog data is A/D converted to calculate the amount of light that corresponds to the amount of reflected light from a preset reference surface. A reference amount of reflected light is set, and a surface with a stable amount of light equal to or greater than this reference amount of reflected light is set as a reference surface. In this way, the laser beam is scanned while irradiating vertically downward from just above the substrate, and when it approaches the chip to be measured, the laser distance is measured from a certain distance calculated from the center of the chip until it passes the center point of the chip. The device data is taken into a controller (for example, a personal computer) and stored in its memory.

In this way, when the laser beam is moved by the XY table based on the chip mounting drawing and the height measured at the position where the chip should be mounted does not reach (11 "chip thickness - α") is determined to be “out of stock” or defective.

(2) “Standing” when exceeding “chip thickness + α”
Determined as defective.

(3) If the “chip thickness ±α” is reached within the “chip position deviation allowable distance” range, it will be passed, but if the “chip position deviation allowable distance” is exceeded, the “chip thickness ±α” If it does not reach this value, it is determined that there is a "defective misalignment".

[For production]

According to the chip component mounting inspection method of the present invention, the height of each chip on a printed circuit board from a reference plane set for each chip is measured, and based on the measured height, defects such as missing parts, standing defects, passing, and misalignment defects are detected. It is determined that either.

〔Example〕

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

In this embodiment, an inspection apparatus shown in FIG. 1 is prepared.

That is, a device is prepared that includes the following parts that are generally commercially available or that have been slightly improved.

a. Laser distance measuring device 1 b. XY table 2 C. Controller 3 c' adds a function that can detect the amount of light reflected from the object to be measured, to a commercially available product that can emit a laser beam to the object and measure the height of the object based on the difference in the angle of reflection of the laser beam from the object. A laser beam emitting section that emits laser light, a sensor section that receives reflected light from the object to be measured and obtains distance data and the amount of reflected light, and a sensor section that processes the distance data taken in from the sensor section. A calculation unit that calculates the distance (chip height), and an A/D that converts the analog reflected light amount taken from the sensor unit into digital.
Contains a converter.

The XY child table is installed on the fixed frame F,
It includes a table 2a driven in the X-axis direction by a pulse motor 21 and a table 2b driven in the Y-axis direction perpendicular to the X-axis by a pulse motor 22, and each motor is driven by pulses based on instructions from the controller 3. be driven. The amount of movement per pulse is set to 0.04 mm for both the X and Y axes, so the current position of the X and Y tables is
It can be calculated by counting the number of pulses using a pulse counter. The laser distance measuring device 1 is mounted on this XY child table and can scan a printed circuit board 9 to be measured placed on a fixed base 8 within a necessary range.

In this embodiment, the entire measuring instrument 1 is mounted on the table 2, but it is sufficient that at least the laser beam emitting section and a part of the sensor of the measuring instrument 1 are mounted.

In this embodiment, a personal computer (hereinafter referred to as a "personal computer") is used as the controller 3, and this is equipped with a floppy drive 31.

The system disk 4 is for controlling the progress of testing of the apparatus, and is in the form of a floppy disk in this embodiment.

The data disk 5 is a chip above the print 54.

It has component mounting position data and was created separately on a computer etc. based on the chip mounting diagram page 0.
In this embodiment, it is in the form of a 7-speed disk.

These floppy disks 4.5 are inserted into the floppy drive 31 of the controller 3.

The display device 6 is a CRT display in this embodiment, and can display the chip position based on instructions from the controller 3, and also displays chips before pass/fail judgment in blue, bad chips in red, and good chips in white. can.

The printer 7 prints out the test results based on instructions from the controller 3.

As shown in Fig. 2, the reflected light of the laser beam emitted perpendicularly from above the printed circuit board 9 to be measured from the laser distance measuring device 1 is captured by the light receiving surface C of the sensor part S, but the reflection angle is Due to the difference, the light-receiving point of the reflected light from surface A, which is closer to sensor part S than surface B (higher than surface B), moves to point a on light-receiving surface C. At this time, if the surface B is set as the reference surface, the moving distance 1 from the point to the point a is converted and calculated by the calculation section to obtain the height from the surface B to the surface A. Therefore, if surface B is the reference surface and surface A is the chip surface, the height of the chip surface can be measured, and whether this height can be observed or not, and if it can be observed, whether it is within the allowable error range. The installation state of the chip can be determined by whether or not the chip is installed.

However, if the measurement reference plane is always a flat plane, accurate measurements can be made as described above, but since the measurement target of the present invention is a printed circuit board, the board surface is not normally a flat plane and changes in a complicated manner. In many cases, there are irregularities that exceed the height of the chip. For this reason, it is not possible to accurately measure the chip height using the initially set reference plane.

Therefore, in this embodiment, when measuring the chip height, the inspection is carried out while resetting the substrate surface immediately in front of the chip as the reference surface for each chip.

The method of setting this reference plane will be explained.

In Fig. 3, the laser beam is read out from the data disk 5 and according to the data, the pulse is sent to the pulse motors 21 and 22 on the XY child table at a constant speed along the D line passing through the center of the chip. Although it moves,
In this embodiment, the moving distance of one pulse is 0.04 mm. As an example below, width W1.25, height Ho, 5t
It is described that m chips are to be inspected.

For each chip, calculate backwards from the center point P of the chip to be measured, read from the data input to the data disk in advance, and calculate 4.
The data acquisition start position is 8 pulses before, and 2 pulses after that.
With 4 pulses, the substrate surface is used as a reference surface, and the next 24 pulses are used to judge the chip surface.

The data for a total of 48 pulses is taken in and stored in the memory of the controller 3. When a total of 48 pulses are completed in the above steps, 2 pulses are required to start measuring the next chip.
Counting backwards from the center point Q of the th chip, data acquisition is started 48 pulses before. This process is thus repeated for each chip to continue measurement.

As described above, in this embodiment, the reference plane is reset for each chip, so that measurement errors do not occur due to irregularities on the substrate surface.

Next, the method of determining the test will be explained in more detail.

The way the amount of reflected laser light changes during 48 pulses is shown in Figure 3, where the y-axis is the amount of reflected light and the x-axis is the distance traveled, it shows a curve like β, but if β is divided into 11 to 14, To explain, j! l: Part of the single material of the board where most of the laser light passes through and the amount of reflected light is extremely weak E2 resist part, W4 foil pattern part where the amount of reflected light is large and relatively stable, and this amount of reflected light is used as the standard amount of reflected light When the amount of light greater than the reference amount of reflected light is stable for 5 pulses or more, it is set as the reference plane for measurement.

13: E3 is almost constant if the laser spot diameter is extremely small, but in this example, the laser spot diameter is set to about 0.2.
Since it is n+, it is tilted around f as shown in the figure.

14: When a chip is attached, the reflection from the chip surface is generally good, so the amount of reflected light increases and becomes stable.

In this example, instead of determining whether the chip is present or absent based on the presence or absence of the 14 parts with a large amount of reflected light and stable, the height from the reference plane set at the 7!2 parts is measured and the height is determined. It is determined whether the chip is installed correctly by whether or not the chip height is within the range of "chip height ±α" (α can be set freely).In other words, the measurement reference plane is determined by the amount of reflected light. The presence or absence of a chip is determined by measuring the height of the chip.The stability of the measurement reference plane and the chip surface is set to 5 pulses or more.Therefore, data acquisition is started 48 pulses before the center of the chip to be measured.
The surface that is stable for 5 pulses or more with a preset reference reflected light amount or more for 24 pulses is memorized as the reference surface, and the height measured for the next 24 pulses is stable for 5 pulses or more within the range of "chip thickness ± α". When it was detected that there was a chip, it was determined that there was a chip.
The color of the tested chip position displayed on RT5 is changed from blue to white, which indicates passing. When the height is less than “chip height α”
If the chip height is 5 + α or more, it is considered to be a “standing” defect, and both CRT6
Change the chip color to red.

Next, even if the chip height is not observed at the position that should naturally be the chip surface, if the chip height is observed within the preset deviation allowable number of pulses and is stable for 5 or more pulses, it is determined that there is a chip. ”, and if not, the chip color of the CRT 6 is changed to red to indicate that it is defective as a “misalignment” defect.

The defective chip is then stored in the memory of the controller 3.

As mentioned above, when the amount of laser reflected light from the substrate surface is equal to or greater than the preset reference amount of reflected light, the reference surface is defined as the reference surface.If the current judgment method is used, if there is no amount of reflected light equal to or greater than the reference amount of reflected light over the entire surface of the substrate, the reference surface is determined. cannot be set, so measurement becomes impossible and the inspection device will not function. However, with multi-layer substrates, the amount of reflected light varies depending on the material and surface reflection state, and it is not possible to always expect a constant amount of reflected light. Therefore, stable inspection cannot be continued using only the reference surface determination method described above.

6 In this embodiment, the following measures are taken to prevent such problems. Set the standard reflected light amount of 172, which is set each time on the program, as the minimum reflected light amount,
If 12 does not reach the standard amount of reflected light while the measurement is in progress, immediately reread the final data and redo the judgment on the condition that 7!2 is at least the minimum amount of reflected light and stable for 3 pulses or more. Problems are prevented.

At this time, it may be possible to use the minimum amount of reflected light and 3 or more pulses as the criteria for judgment from the beginning, but if you do that, if the amount of laser light transmitted in the 11th part is small and exceeds the minimum amount of reflected light, then it will be considered as the criterion. The procedure described above is necessary because incorrect surface settings can lead to inspection errors.

However, despite such measures to prevent inspection errors, there are a few cases where the minimum amount of reflected light is not reached on many substrate surfaces, and there is a risk that inspection errors may occur.

Therefore, in this embodiment, in such a case, the inspection is continued to the final stage, and after the inspection is completed, a part of the measuring instrument sensor is returned to the chip position stored as defective, and the data is transferred from the chip surface to the board. Read it out, and if there is a surface on which 5 or more pulses are stable regardless of the amount of reflected light in part 12, reset that surface as the reference surface and measure the height again at the position corresponding to the chip surface. Make a judgment.

In this embodiment, the inspection program includes a procedure to prevent such inspection errors, so even though the inspection equipment is a combination of extremely simple elements, it is possible to perform highly reliable and error-free inspections. It is possible to do this.

Now, before actually inspecting mass-produced products, the following preparatory work is performed.

Preparatory work follows the preparatory work chart shown in FIG.

That is, in step 1, a data disk is created on another personal computer by manually inputting the data of all the chips, using the xY data of each chip position and the chip symbol as 1 cent from the chip mounting drawing.

In step 2, the data disk and system disk are inserted into the floppy drive, and the power is turned on to start the inspection device. In step 3, the shortest inspection path (order) for the chip is automatically determined according to the program.
Set.

Note that this inspection device has the following three modes for proceeding with the inspection.

■ Manual progress mode (used for preparation work, etc.) 2 Full automatic mode (proceeds automatically until the end of inspection even if there is a defect) 3 Stop mode when defective (stops the chip mounting line when a defect is found) Step ゛In step 4, the entire set of raw boards is automatically inspected in automatic mode, and all of them are found to be defective (C
Check that all chips displayed on RT turn red.

In step 5, the sample board is set on a fixed stand and automatically inspected to confirm that all the chips on the CRT 6 are in good condition (all chips on the CRT 6 are white).

If step 4.5 above is satisfied, the preparation work is completed, but if not, return to step 1 again, make corrections, and repeat until step 4.5 is satisfied.

Next, the inspection process for the substrate to be inspected is performed according to the inspection process chart of FIG.

In step 1, insert both the system and data disks into the drive and turn on the power to the testing equipment.In step 2, set the board to be tested on the fixed stand, and in step 3, press the start key on the controller 3 to test the equipment. Start.

In step 4, the inspection device starts automatic inspection according to the program. In step 5, the test results are displayed on the CRT each time. In step 6, all chips are inspected, and if there are no defects, the next board is inspected in step 7.

If there is a defect, the defective part is automatically re-inspected in step 8, and if there is no defect, the process moves to step 7. If there is a defect, the defective chip is displayed on the CRT in step 9, the defective data is printed out in step IO, and the inspection is stopped in step 11.

According to the embodiment described above, there are the following advantages.

0 ■ Since 100% is automatically inspected according to the programmed order based on the chip mounting drawing, there are no inspection omissions due to oversights or inspection errors due to misidentification during visual inspection, and there is no need to use a large number of personnel for inspection.

2. Furthermore, since the device for carrying out the inspection can be a few fractions of the price of commercially available devices, it is easy to install and carry out the inspection.

The inspection device is extremely inexpensive because most of its components are a combination of commercially available products, and is about a fraction of the price of commercially available inspection machines, so it can be easily adopted in a printed circuit board manufacturing line.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to provide an inexpensive chip component mounting inspection method that allows chip components to be inspected to be inspected without any omissions with little effort, without any inspection errors.

[Brief explanation of drawings]

Fig. 1 is a schematic configuration diagram of an example of an inspection device used in an embodiment of the present invention, Fig. 2 is a diagram explaining the principle of a laser distance measuring device, and Fig. 3 is a diagram illustrating the principle of a laser distance measuring device.
FIG. 4 is a flowchart showing the inspection preparation work, and FIG. 5 is a flowchart of the inspection process. 1...Laser distance measuring device 9...Printed circuit board IO...chip

Claims (1)

[Claims] (1) A laser distance measuring device that can measure the height of an object by emitting a laser beam to the object and detecting the amount of light reflected from the object. A laser distance measuring device is equipped with a function that allows the laser distance measuring device to emit a laser beam to sequentially scan a printed circuit board and receive the reflected light from the printed circuit board. A reference amount of reflected light corresponding to the amount of reflected light from a predetermined reference surface with respect to the chip mounting position is set, and a surface on which the amount of reflected light due to the scanning is stable at a light amount equal to or greater than the reference amount of reflected light is set as a reference surface and from the reference surface. When the measured chip height does not reach the value V1 obtained by subtracting a predetermined value from the chip thickness, it is determined that the chip is out of stock. If it exceeds the value V2, which is obtained by adding a predetermined value to the above, it is determined to be a failure, and if the measured chip height is within the predetermined chip position deviation tolerance range and within the value V1 to V2, it is passed. A chip component mounting inspection method characterized in that if the chip position deviation exceeds the allowable distance and is still outside the range of the value V1 to V2, it is determined that the deviation is defective.