JPH0781834B2 - Chip component mounting inspection method - Google Patents

Description

The present invention relates to a chip component mounting inspection method, and more particularly, to an erroneous determination of mounting quality due to warp or undulation of a substrate or omission of determination, and an inexpensive device. The present invention relates to a chip component mounting inspection method that can be easily implemented.

[Conventional technology]

Conventionally, as a method of automatically inspecting mounting of chip components on a printed wiring board, as disclosed in, for example, Japanese Patent Laid-Open No. 62-299705, a laser beam from a semiconductor laser is passed through a component mounting portion. And two points on a path parallel to this, and the light reflected by the two points on the printed circuit board are detected by the line sensor respectively, and the minimum reference value and these detected values set uniformly over the entire printed circuit board are detected. And a binary signal obtained by directly comparing the output of the OR circuit (A bit signal) that inputs the two binary signals and the output of the two line sensors (B bit signal)
A method (hereinafter referred to as a conventional example) for inspecting the presence / absence of a component and the presence / absence of a position shift based on the above is proposed.

[Problems to be Solved by the Invention]

By the way, generally, when determining the quality of component mounting of a printed circuit board, the printed circuit board is placed on a flat surface. However, the printed circuit board is heated at the time of processing holes such as through holes and at the time of component mounting. It is well known that the substrate has waviness and warpage. And
The undulation or warpage of the printed circuit board may be higher than the height of the components mounted on the printed circuit board.

According to the above conventional example, for example, when the printed circuit board is warped or undulated, the minimum reference value is set uniformly over the entire printed circuit board, so that one or both line sensors cannot receive light. Or a light beam that should otherwise be received by the other line sensor may be received. As a result, for example, the second line sensor does not receive light, the output of the first line sensor becomes larger than the output of the second line sensor over the entire area, and no component is detected even though there is a component, It is not possible to judge the quality of the product, and there are no parts.
The first line sensor no longer receives light, and the output of the first line sensor is smaller than the output of the second line sensor as a whole, and there are parts even though there are no parts. Then, it is not uncommon for an incorrect decision to be made.

In view of the above circumstances, the present invention provides a chip component mounting inspection method capable of preventing erroneous determination of a mounting failure due to warpage or undulation of a substrate or omission of determination, and being easily implemented using an inexpensive device. With the goal.

[Means for Solving the Problems]

Chip component mounting inspection method according to the present invention, in order to achieve the above object, the printed circuit board is sequentially scanned by the laser distance measuring device, for each preset component mounting position, the received light amount of the laser distance measuring device, The surface height of the printed circuit board is measured as the reference surface height based on the reference value given individually for the specified section immediately before the component mounting position on the scanning path, and the component mounting position is subsequently measured. The surface height of the component mounting position is measured based on the amount of light received by the laser distance measuring instrument at and the reference value given individually to the component mounting position on the scanning path. It is characterized in that the quality of component mounting is determined based on the difference from the surface height.

[Action]

In the present invention, the printed circuit board is placed on a plane prior to the inspection, and the laser distance measuring machine is moved in a two-dimensional direction parallel to the plane, or the printed circuit board and the plane are moved in the plane direction. As a result, the printed circuit board is sequentially scanned by the laser distance measuring device.

The scanning path of this laser distance measuring machine is not particularly limited, but it is set to scan all the chip components mounted on the printed circuit board, and preferably the scanning path connecting all the chip components at the shortest distance is selected. It

For each preset component mounting position on this scanning path, the height of the board surface of the printed circuit board immediately before the component mounting position on the scanning path, the received light amount of the laser distance measuring device, and the component mounting position on the scanning path. Is measured as the reference plane position based on the reference value given individually to the predetermined section immediately before, and following this measurement, the received light amount of the laser distance measuring device at the component mounting position and the scanning path The surface height of the component mounting position is measured based on the reference value given individually to the component mounting position, and the difference between the surface height of this component mounting position and the reference surface position is calculated. Whether the mounting is good or bad is determined.

The quality determination method performed here is, for example, when the difference is higher than the surface height (hereinafter referred to as chip thickness) of the chip normally mounted at the component mounting position by a predetermined dimension α or more, the chip is If it is a "standing" defect that is mounted upright with the side face down, and it is smaller than the chip thickness by a predetermined dimension α (or β that is different from α), it is a "missing product" defect and the component mounting position If the difference becomes the chip thickness ± α after the “out of stock” defects continue from the end, there is a deviation from the end to the position where the difference value becomes the chip thickness ± α.
If the deviation of the end of the component mounting position is equal to or more than the allowable amount, it is determined that the "deviation" is defective, and in other cases, "pass" is determined.

The quality judgment at each component mounting position compares the height of the board immediately before the component mounting position with the height of the component mounting position, so that the printed circuit board may warp or swell at each component mounting position and its vicinity. Even if the component is positioned higher or lower than the average height, it is possible to reliably determine the mounting state of the component at the component mounting position.

In the height measurement on the scanning path, the reflectance or the light transmittance of the printed circuit board surface at that position has a great influence, but this reflectance or the light transmittance is, for example, on a bare substrate surface. , The surface of the substrate covered with the insulating layer, the surface of the substrate to which the solder is attached, or the surface of the component, that is, the certain reference value or more depending on the type of the surface. It has been known.

Each height measurement position is determined if the measurement path is determined, and the type of the surface at that measurement position and the reflectance or transmissivity of the surface are also determined.

In the present invention, for each height measurement position on the scanning path, by setting a reference value individually corresponding to the measurement position, the reflectance or transmissivity of the surface measured at each height measurement position The measurement error due to the difference is eliminated.

Here, the reference value is not particularly limited, but the surface of the printed circuit board is higher in a portion where there is warpage or undulation than in a portion where the printed circuit board is in close contact with the table upper surface that supports it. If the amount of reflected light that is reflected from the surface of the substrate when it is in close contact with the upper surface of the table supporting
At each height measurement position, the amount of light received by the laser distance measuring device becomes equal to or greater than the reference value, and the height can be measured without leakage.

Then, in the present invention, in order to increase the reliability of height measurement at each height measurement position, a large amount of reflected light than this reference value is continuously applied to the laser distance measuring device at the same light amount for a predetermined time or longer. When the state of receiving light is confirmed, it is preferable to detect the height corresponding to the amount of received light as the height at the measurement position.

Further, in the present invention, foreign matter is attached to the surface of the actual printed board, pinholes are formed,
The surface of the component may be dented, and it is preferable to consider that the amount of light received by the laser distance measuring device falls below the above-mentioned reference value at some height measurement positions due to these.

In the present invention, as one method for solving such a problem, when the amount of light received by the laser distance measuring device is lower than the above reference value during height measurement, final data,
That is, it is possible to read the measured value immediately before it becomes lower than the reference value and perform the height measurement based on the read measured value and the reference value. In this case, in order to improve the reliability of height measurement, it is preferable to use, as the final data, data that has been held at the same value continuously for a predetermined time. Further, it is preferable that the data used as the final data has a light receiving amount of a certain level or more.
It is preferably ½ or more of the reference value.

In this way, even if you take measures to prevent inspection omissions,
At some height measurement positions, the amount of light received by the laser distance measuring device may fall below one-half of the reference value. In this case, in order to shorten the overall determination time, it is necessary to make a determination. It is preferable to proceed with the quality judgment for all the subsequent parts as defective. Then, it is preferable that after the quality determination of all the components including such a determination as defective, the quality determination is performed again for the component mounting position determined to be defective.

In this case, it is considered that the reflectance or the transmittance at the height measurement position immediately before the component mounting position differs depending on the direction of the measurement path. By measuring the height of the surface and the height of the printed circuit board surface at the position immediately before that, and returning the laser distance measuring device from the position immediately before to the component mounting position to obtain the height of the printed circuit board surface at the component mounting position. Therefore, it becomes possible to determine the quality of the component mounting state at the component mounting position which has been determined to be defective.

A commercially available laser distance measuring device can be used as the laser distance measuring device used for carrying out the present invention, and the table on which the laser distance measuring device or the printed circuit board is placed is moved in a two-dimensional direction. In order to do this, a commercially available XY table may be used, so that it can be easily implemented with an inexpensive device.

〔Example〕

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

In this embodiment, the inspection device shown in FIG. 1 is prepared.

That is, an apparatus including the following parts which are generally commercially available or which are slightly improved is prepared.

Laser distance measuring device 1 b. XY table 2 c. Controller 3 c '. X, Y pulse generator 3' d. System disc 4 e. Data disc 5 f. Display device 6 g. Blinter 7 Laser distance measurement The instrument 1 has a function of emitting a laser beam to the object to be measured and measuring the height of the object to be measured by measuring the height of the object to be measured by the difference in the angle of reflection of the laser light from the object to be measured. The laser light emitting unit that emits laser light, the sensor unit that receives the reflected light from the object to be measured at the light receiving unit to obtain the distance data and the reflected light amount, and the distance data taken from the sensor unit are processed. It includes an arithmetic unit that calculates the distance (chip height) and an A / D converter that digitally converts the analog reflected light amount taken from the sensor unit.

The XY table 2 is provided on the fixed frame F and includes a table 2a driven in the X-axis direction by the pulse motor 21 and a table 2b driven in the Y-axis direction perpendicular to the X-axis by the pulse motor 22. And each motor is operated by a pulse based on an instruction from the controller 3. Since the movement amount per pulse is set to 0.04 mm for both the X and Y axes, the current position of the X and Y table can be calculated by counting the number of X and Y pulses with a pulse counter. The laser distance measuring device 1 is mounted on the XY table 2 and can scan the printed circuit board 9 to be measured placed on the fixed table 8 within a required range. In addition, in the present embodiment, the entire measuring device 1 is mounted on the table 2, but it is sufficient if at least the laser beam emitting unit and the sensor unit of the measuring device 1 are mounted.

In this embodiment, a personal computer (hereinafter, referred to as “personal computer”) is used as the controller 3, and the controller 3 includes a flippy drive 31.

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

The data disk 5 has chip component mounting position data on the printed circuit board, and is created by a personal computer or the like based on the chip mounting drawing, and is in the form of a floppy disk in this embodiment.

These floppy disks 4 and 5 are set in the floppy drive 31 of the controller 3.

The display device 6 is a CRT display in this embodiment,
The chip position can be displayed based on the instruction of the controller 3, and the chip before the pass / fail judgment can be displayed in blue, the defective chip in red, and the good chip in white.

The printer 7 prints out the inspection result based on the instruction from the controller 3.

As shown in FIG. 2, although the reflected light of the laser light L emitted from the laser distance measuring device 1 perpendicularly to the printed circuit board 9 to be measured is captured by the light receiving surface C of the sensor section S, Due to the difference, the light receiving point of the reflected light from the surface A closer to the sensor unit S (higher than the surface B) with respect to the surface B moves from the point b to the point a on the light receiving surface C. At this time, when the surface B is set as the reference surface, the moving distance from the point b to the point a is converted and calculated by the calculation unit to obtain the height from the surface B to the surface A. Therefore, if the surface B is the reference surface and the surface A is the chip surface, the height of the chip surface can be measured. Whether or not this height can be observed, and if it can be observed, is it within the allowable error range? Whether or not the chip is mounted can be determined by whether or not the chip is mounted.

However, when the measurement reference plane is always a flat plane, the measurement can be performed correctly as it is, but since the measurement object of the present invention is a printed circuit board, the board surface usually changes in a complicated manner rather than a flat plane. In many cases, there are irregularities that exceed the chip height. For this reason, the chip height cannot be accurately measured with the reference plane set initially.

Therefore, in the present embodiment, when measuring the chip height, it is devised to proceed with the inspection while resetting the substrate surface immediately before the chip as the reference surface for each chip.

A method of setting the reference plane will be described. In FIG. 3, the laser beam moves at a constant speed along the D line passing through the center of the chip by the pulse sent to the pulse motors 21 and 22 on the XY table 2 according to the data read from the data disk 5. However, in this embodiment, the moving distance of one pulse is 0.04 mm. Width W1.25m as an example below
Described as inspecting a chip with m and height H 0.5 mm.

For each chip, back-calculate from the center point P of the measured chip read from the data previously input to the data disk to obtain 48
The data acquisition start position is before the pulse, the substrate surface is the reference surface with 24 pulses thereafter, and the chip surface is determined with the next 24 pulses. The data of 48 pulses in total is fetched and stored in the memory of the controller 3. When a total of 48 pulses in the above steps are completed, in order to start measurement of the next chip, back calculation is performed from the second chip center point Q and data acquisition is started from before 48 pulses. Thus, this process is repeated for each chip to continue the measurement.

As described above, in the present embodiment, the reference plane is set again for each chip, so that a measurement error will not occur due to the unevenness of the substrate surface.

Next, the method of determining the inspection will be described in more detail. The method of changing the amount of laser reflected light is between 48 pulses. In Fig. 3, when the amount of reflected light is on the y-axis and the moving distance is on the x-axis, a curve such as l is shown, but l is divided into 1 to l4. To explain, 1: The part where the laser light is almost transmitted and the reflected light amount is extremely weak in the single part of the substrate. L2: The resist part and the copper foil pattern part have a large amount of reflected light, and the part is relatively stable. Is set as the reference reflected light amount, and when the light amount of the reference reflected light amount or more is stable for 5 pulses or more, it is set as the reference surface for measurement.

l3: If the laser spot diameter is extremely small, l3 almost stands, but since the laser spot diameter is about 0.2 mm in this embodiment, it is inclined as shown in the figure.

l4: When a chip is mounted, the amount of reflected light increases and stabilizes because the reflection on the chip surface is generally good.

In the present embodiment, the presence / absence of the l4 portion, which has a large amount of reflected light and is stable, is not used to determine whether the chip is “present” or “absent”, but the height from the reference plane set in the l2 portion is measured, Is within the range of "chip height ± α" (α can be freely set), it is determined whether or not the chip is properly mounted. That is, the measurement reference surface is determined by the amount of reflected light, and the presence or absence of the chip is determined by measuring the height of the chip. The stability of the measurement reference surface and the chip surface is set to 5 pulses or more. Therefore, data acquisition starts from 48 pulses before the center of the chip to be measured, and
A stable surface for 5 pulses or more with a reference reflection light amount set in advance for pulses is stored as a 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 there is a chip, the color of the inspected chip position displayed on the CRT5 is changed from blue to acceptable white. When the height is less than "chip height -α", it is a "missing" defect. Conversely, when the height is "chip height + α" or more, it is a "standing" defect. In both cases, the CRT6 chip color is changed to red.

Next, even if the chip height is not observed at the position which should be on the chip surface, if the chip height is observed within the preset deviation allowable pulse number and it is stable for 5 pulses or more, "chip exists" If it is not, the chip color of CRT6 is changed to red and it is displayed as defective. The defective chip is stored in the memory of the controller 3 in advance.

As described above, since the reference surface is when the laser reflected light amount from the substrate surface is equal to or greater than the preset reference reflected light amount, in the determination method as it is, if there is no reflection amount equal to or greater than the reference reflected light amount over the entire substrate surface, the reference surface Since it cannot be set, measurement becomes impossible and the inspection device does not work. However, in many substrates, the amount of reflected light varies depending on the material and the state of surface reflection, and it is not possible to always expect more than a certain amount of reflected light. Therefore, stable inspection cannot be continued only by the reference surface determination method described above.

In this embodiment, the following measures are taken to prevent such a problem. If you set 1/2 as the minimum reflected light amount of the reference reflected light amount set each time on the program and if l2 does not reach the reference reflected light amount in the middle of the measurement, immediately read the final data again and l2 becomes the minimum. The above-mentioned problem is prevented by re-determining under the condition that the amount of reflected light is equal to or more than 3 pulses and is stable for 3 pulses or more.

At this time, it is considered that the minimum reflected light amount and 3 or more pulses should be used as the criteria from the beginning. However, if the amount of laser light transmitted through one portion is too small to exceed the minimum reflected light amount, the criterion is used. Since the mistaken inspection will be made by mistakenly setting the surface, the above procedure is required.

However, despite such a measure for preventing inspection errors, there are some cases where the minimum reflected light amount is not reached on many substrate surfaces, which may cause an inspection error.

Therefore, in this embodiment, in such a case, the inspection is advanced to the end, the measuring instrument sensor unit is returned to the chip position stored as a defect after the inspection, and the data is read from the chip surface to the substrate in reverse. However, if there is a stable surface for 5 pulses or more in the l2 part regardless of the amount of reflected light, reset that surface as the reference surface, and measure the height again at the position equivalent to the chip surface for judgment. I do.

In the present embodiment, since the inspection program has such a procedure for preventing the inspection error, the inspection apparatus has a highly reliable and error-free inspection despite the combination of extremely simple elements. Can be done.

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

The preparatory work follows the preparatory work chart in FIG.

In other words, in step 1
Create XY data and chip symbol as one set, and create a data disk on which data of all chips is input on another personal computer.

In step 2, the data disk and system disk are mounted in the floppy drive, the power is turned on, and the inspection device is started. In step 3, the shortest inspection path (sequence) of chips is automatically set according to the program.

The inspection apparatus has the following three modes regarding the progress of the inspection.

1 Manual progress mode (used for preparatory work, etc.) 2 Overall automatic mode (automatically advances to the end of inspection even if there is a defect) 3 Stop mode at the time of failure (stops the chip mounting line when a defect is found) As a cross-over automatic mode, the set raw board is automatically inspected and all become defective (CRT
Check that all the chips displayed in turn red).

In step 5, the sample board is set on the fixed base and automatically inspected to confirm that all are good (all the chips on the CRT6 are white).

If the above steps 4 and 5 are satisfied, the preparatory work is completed, but if not satisfied, the procedure returns to step 1 to make corrections and repeats until steps 4 and 5 are satisfied.

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

In step 1, set both the system and data disks in the drive, turn on the power of the inspection device, and step 2
Then, the board to be inspected is set on the fixed base, and in step 3, the start key on the controller 3 is pressed to start the apparatus.

In step 4, the inspection device starts automatic inspection according to the program. In step 5, the inspection result is displayed on the CRT each time. In step 6, the inspection of all chips is completed, and if there is no defect, in step 7, the inspection of the next substrate is started.

If there is a defect, the re-inspection of the defective part is automatically performed in step 8, and if there is no defective part, the process proceeds 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 10, and step 11
Stop the inspection with.

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

Since the 100% automatic inspection is performed according to the sequence programmed by the one-chip mounting drawing, there is no inspection omission due to oversight or visual error due to misidentification in visual inspection, and it is not necessary to spend a lot of personnel for inspection.

2 As a device for carrying out the inspection, a device that is a fraction of the price of a commercially available device can be adopted, so that it is easy to install and carry out the device.

The inspection apparatus is extremely inexpensive because the constituent elements are a combination of almost all commercially available products, and the price is about a fraction of that of commercially available inspection machines. Therefore, the inspection apparatus can be easily adopted in a printed circuit board manufacturing line.

〔The invention's effect〕

As described above, the present invention measures the surface height of the printed circuit board measured immediately before each chip component and the surface height of the component mounting position of each chip component, and based on the difference in height. Since the quality is determined by the above, it is possible to prevent erroneous determination of the quality of mounting and omission of determination due to warp or undulation of the board.
Commercially available laser range finder and X-
It can be easily implemented using an inexpensive device such as a Y table.

In the present invention, particularly when the amount of light received by the laser measuring device from each point on the scanning path becomes less than the reference value at that point, the final data within a predetermined time immediately before that point is continuously divided by half the reference value. When the height is measured based on the final data within a predetermined time immediately before this condition on condition that it is 1 or more, for example, surface reflectance decreases due to adhesion of impurities, and the amount of light received by the laser distance measuring device becomes the reference. Even if the value is less than the value, it is possible to judge the quality of the component mounting, and the inspection can be continued stably.

Further, in the present invention, after the quality determination of the component mounting of all the component mounting positions is performed, the reverse scanning is performed immediately before the component mounting position where the defect determination is made and immediately before the component mounting position where the defect determination is made. The surface height of the printed circuit board is measured again as the reference surface height based on the amount of light received by the laser distance measuring device that is stably detected for a specified time or longer, and then the surface height of the printed circuit board at the mounting position is measured. However, in the case of performing quality determination of component mounting based on the difference between the reference surface height and the surface height of the component mounting position in this series of measurement,
Even when the amount of light received by the laser measuring instrument is less than one half of the reference value at the point, it is possible to re-determine the quality of component mounting, and to prevent erroneous determination more reliably.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an example of an inspection apparatus used in one embodiment of the present invention, FIG. 2 is a principle explanatory diagram of a laser distance measuring device, and FIG.
FIG. 4 is an explanatory diagram of an inspection determination method, FIG. 4 is a flowchart showing an inspection preparation work, and FIG. 5 is an inspection process flowchart. 1 ... Laser distance measuring device 9 ... Printed circuit board 10 ... Chip

Claims (3)

[Claims] 1. A printed circuit board is sequentially scanned by a laser distance measuring device, and for each preset component mounting position, the received light amount of the laser distance measuring device and a predetermined section immediately before the component mounting position on the scanning path. On the other hand, the surface height of the printed circuit board is measured as the reference surface height based on the reference value individually given, and following this measurement, the received light amount of the laser distance measuring device at the component mounting position and the scanning path The surface height of the component mounting position is measured based on the reference value given individually to the component mounting position, and the quality of the component mounting is judged based on the difference between the surface height of the component mounting position and the reference surface height. A method for inspecting chip component mounting, which is characterized by being performed. 2. When the amount of light received by the laser measuring device from each point on the scanning path becomes less than the reference value at that point, the final data within a predetermined time immediately before that point is continuously halved of the reference value. 1
The chip component mounting inspection method according to claim 1, wherein the height is measured based on the final data within a predetermined time immediately before the above condition. 3. A printed circuit board immediately before the component mounting position where a defect determination is made by performing reverse scanning immediately before the component mounting position where a defect determination is made after performing quality determination of component mounting at all component mounting positions. Measure the surface height of the printed circuit board as the reference surface height again, and then measure the surface height of the printed circuit board at the component mounting position, based on the difference between the reference surface height and the surface height at the component mounting position in this series of measurements. The chip component mounting inspection method according to claim 1 or 2, wherein the quality of the component mounting is determined by the above.