CN103954241A - IC pin coplanarity measuring system and measuring method based on structured light - Google Patents

Abstract

The invention discloses an IC pin coplanarity measurement system based on structured light and a measurement method thereof, comprising: a graphics projector, a goniometer, a diffuse ceramic calibration plate, A telecentric lens, B telecentric lens, and a CCD Camera and computer; the graphics projector is connected to the A telecentric lens, and fixed on the vibration isolation test bench through the clamping device. The light of the graphics projector is perpendicular to the plane of the vibration isolation test bench, and the IC chip to be tested is placed directly under the graphics projector. The B telecentric lens is connected to the CCD camera and fixed on the vibration isolation test bench through the clamping device. The light of the CCD camera forms a certain angle with the plane of the vibration isolation test bench. The device can transform the measurement of the coplanarity of IC pins into an intelligent measurement based on machine vision, and the coplanarity measurement of the pins is mapped on the image as the height difference between the grating stripes on the surface of the chip and the surface of the pins. The cost of equipment is low, the technical means are simple and easy to implement, omitting cumbersome formula derivation and calculation, and improving the efficiency of testing.

Description

An IC pin coplanarity measurement system and its measurement method based on structured light

technical field

The invention relates to the field of integrated circuit packaging, in particular to a system for measuring the coplanarity of IC pins based on structured light and a measuring method thereof.

Background technique

With the development of the electronic information industry, integrated circuit electronic components have achieved rapid development. In the production line of electronic integrated circuit components, controlling and improving the surface quality of products has always been the content of the electronics industry's great attention, so the detection of product quality is particularly critical, among which the coplanarity of IC pins is the most important factor affecting the quality of circuit board assembly an important factor. The distance deviation between the lowest pin of an IC device, that is, the lowest pin of an integrated circuit electronic device, and the plane formed by the three highest pins that are not on the same straight line is defined as a coplanarity error, usually referred to as coplanarity. In the surface mount (SMT) production process of circuit boards, in order to ensure the quality of mounting, the mounting process puts forward quite high requirements on the coplanarity of the pins. When the coplanarity of the pins exceeds a certain range, the device Some pins of the PCB cannot be in close contact with the surface of the PCB pad, that is, the pad of the printed circuit board, and it is easy to cause the melted solder to not touch the bottom of the pin during soldering, and the solder cannot connect these pins to the pad. Together to form a good solder joint, it may lead to defects such as solder joints, missing solder joints and virtual joints.

The coplanarity of the pins of IC devices is one of the key indicators to measure the packaging technology of IC devices. It indicates the degree of contact between the pins of IC devices and the surface of PCB pads. If the coplanarity between the device pins and the PCB is not good, it is easy to lack solder paste, resulting in weak soldering of the device, or too much solder paste, resulting in short circuit of components. Conversely, the better the coplanarity, the better the complete contact between the pins of the IC device and the surface of the PCB pad, so that the best soldering quality can be obtained during the soldering process.

The traditional detection method is detected by human eyes. This method has many problems: the detection efficiency is not high; the detection results are easily affected by human subjective factors; the labor intensity of the detection personnel is high. With the improvement of production speed of manufacturers and the improvement of upstream assembly manufacturers' requirements for pin coplanarity accuracy, the disadvantages of manual visual inspection are becoming more and more prominent. Industrial product inspection based on machine vision can overcome the above difficulties, so it is widely used Automatic monitoring of the surface quality of IC chips. High-precision automatic detection systems for IC surface appearance have been developed at home and abroad.

The existing coplanarity detection methods can generally be divided into four commonly used measurement methods: metallographic section analysis method, three-dimensional coordinate instrument measurement method, three-dimensional image measurement method, and contact three-dimensional coordinate instrument measurement method. Although the metallographic section analysis method is intuitive and accurate, its measurement efficiency is low and it is a destructive measurement; although the three-dimensional coordinate instrument measurement method is non-destructive and repeatable, its accuracy is low, and the measurement results of different surveyors vary greatly; Although the measurement results of the image measurement method are intuitive and easy to process, it is also a destructive measurement. The measurement results are greatly affected by the surface condition of the sample (substrate/copper surface color, surface treatment); the accuracy of the contact three-dimensional coordinate instrument measurement method High efficiency The probe has a physical size, and the positioning error is large when measuring tiny samples;

Contents of the invention

In order to overcome the disadvantages and deficiencies of the existing coplanarity measurement device, such as complex structure, bulky volume, high equipment manufacturing cost, slow detection speed and low detection accuracy, the present invention provides a coplanarity measurement of IC pins based on structured light Compared with the prior art, the system and the measuring method thereof have simple measuring equipment and improved measuring precision.

The present invention realizes through following technical scheme:

A system for measuring the coplanarity of IC pins based on structured light, including a graphic projector 1, a goniometer, a circular line grating, a diffuse ceramic calibration plate, A telecentric lens 2, B telecentric lens 4, and a CCD A camera 5 and a computer 6; the circular line grating sheet is placed in a graphic projector 1; the graphic projector 1 adopts an LED graphic projector.

The graphics projector 1 is connected to the A telecentric lens 2, and fixed on the vibration isolation test bench through a clamping device, the light of the graphics projector 1 is perpendicular to the plane of the vibration isolation test bench, and the IC chip to be tested is placed on the graphics projector 1 on a horizontal plane directly below;

The B telecentric lens 4 is connected to the CCD camera 5, and is fixed on the vibration isolation test bench by the clamping device. Go to the computer 6, display the IC chip image with grating stripes captured by the CCD camera 5 on the computer 6, adjust the angle of the CCD camera 5 to make the grating stripes in the image appear as horizontal straight lines.

The light of the CCD camera 5 preferably forms an included angle of 45° with the plane of the vibration isolation test bench.

Adopting above-mentioned measuring system to measure IC chip pin coplanarity measuring method, comprises the following steps:

Step 1: adjust the pose of the graphics projector 1 and the IC chip so that the grating stripes are vertically projected onto each pin of the IC chip, and then adjust the angle of the CCD camera 5 so that the grating stripes captured by it become a horizontal straight line;

Step 2: Utilize the goniometer to measure the angle θ formed by the CCD camera 5 or the telecentric lens 4 and the horizontal line;

Step 3: Carry out image morphology processing to the image of the IC chip pin with the grating stripe captured by the CCD camera 5, extract the skeleton of the IC chip pin grating stripe, and do the straight line fitting of the least squares method to the skeleton , calculate the pixel distance S between the straight line fitted by the grating stripes on the surface of the IC chip and the straight line fitted by the grating stripes on the surface of the pin;

Step 4: use the CCD camera 5 to perform camera calibration on the diffuse ceramic calibration plate, and calculate the proportional relationship k between the pixel distance and the actual physical distance;

Step 5: Each pin of the IC chip is processed through the above steps 3 and 4 one by one, and the vertical distance H between the pins of the IC chip and the surface of the IC chip is obtained by the formula H=k S/cosθ;

Step 6: Calculate the height difference H _i from each pin of the IC chip to the surface of the IC chip, and the coplanarity L is expressed by the difference between the maximum value H _max and the minimum value H _min of the actual height difference between the IC pin and the surface of the IC chip , that is, L=H _max -H _min , and L is the coplanarity of IC pins.

Compared with the prior art, the present invention has at least the following advantages and effects:

The invention can transform the measurement of the coplanarity of IC pins into intelligent measurement based on machine vision, and the coplanarity measurement of the pins is mapped on the image as the height difference between the grating stripes on the surface of the chip and the surface of the pins.

Due to the use of sub-pixel digital image processing technology based on machine vision and high-precision testing instruments, the detection accuracy can be improved.

The equipment used in the invention has low cost, does not need complex and huge testing instruments, and has simple and easy technical means, saves cumbersome formula derivation and calculation, and improves the efficiency of testing.

Description of drawings

Fig. 1 is a schematic diagram of the measurement system of the present invention.

Fig. 2 is a schematic diagram of projection of grating onto IC chip.

Fig. 3 is a schematic diagram of the height difference of grating pixels.

Detailed ways

The present invention will be described in further detail below in conjunction with specific embodiments.

Example

As shown in Figures 1 to 3. The invention discloses an IC pin coplanarity measurement system based on structured light, which includes:

Graphics projector 1, goniometer, circular line grating sheet, diffuse ceramic calibration plate, A telecentric lens 2, B telecentric lens 4, CCD camera 5 and computer 6; the circular line grating sheet is placed on the graphic In the projector 1; the graphic projector 1 is an LED graphic projector.

The graphics projector 1 is connected to the A telecentric lens 2, and fixed on the vibration isolation test bench through a clamping device, the light of the graphics projector 1 is perpendicular to the plane of the vibration isolation test bench, and the IC chip to be tested is placed on the graphics projector 1 on a horizontal plane directly below;

The B telecentric lens 4 is connected to the CCD camera 5, and is fixed on the vibration isolation test bench by the clamping device. Go to the computer 6, display the IC chip image with grating stripes captured by the CCD camera 5 on the computer 6, adjust the angle of the CCD camera 5 to make the grating stripes in the image appear as horizontal straight lines.

The light of the CCD camera 5 and the plane of the vibration isolation test bench form an angle of at least 45°.

The method for measuring the coplanarity of IC chip pins by the above measurement system can be realized through the following steps:

Step 1: adjust the pose of the graphics projector 1 and the IC chip so that the grating stripes are vertically projected onto each pin of the IC chip, and then adjust the angle of the CCD camera 5 so that the grating stripes captured by it become a horizontal straight line;

Step 2: Utilize the goniometer to measure the angle θ formed by the CCD camera 5 or the telecentric lens 4 and the horizontal line;

Step 3: Carry out image morphology processing to the image of the IC chip pin with the grating stripe captured by the CCD camera 5, extract the skeleton of the IC chip pin grating stripe, and do the straight line fitting of the least squares method to the skeleton , calculate the pixel distance S between the straight line fitted by the grating stripes on the surface of the IC chip and the straight line fitted by the grating stripes on the surface of the pin;

Step 4: use the CCD camera 5 to perform camera calibration on the diffuse ceramic calibration plate, and calculate the proportional relationship k between the pixel distance and the actual physical distance;

Step 5: Each pin of the IC chip is processed through the above steps 3 and 4 one by one, and the vertical distance H between the pins of the IC chip and the surface of the IC chip is obtained by the formula H=k S/cosθ;

Step 6: Calculate the height difference H _i from each pin of the IC chip to the surface of the IC chip, and the coplanarity L is expressed by the difference between the maximum value H _max and the minimum value H _min of the actual height difference between the IC pin and the surface of the IC chip , that is, L=H _max -H _min , and L is the coplanarity of IC pins.

As described above, the present invention can be preferably carried out.

The implementation of the present invention is not limited by the above examples, and any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods, and are all included in within the protection scope of the present invention.

Claims (4)

1. the IC pin coplanarity measuring system based on structured light, is characterized in that comprising:

Graphic projection's instrument, angular instrument, round wire lenticular lenses, diffusion pottery scaling board, A telecentric lens, B telecentric lens, CCD camera and computing machine; Described round wire lenticular lenses is positioned in graphic projection's instrument;

Described graphic projection instrument connects A telecentric lens, by clamping device, is fixed on vibration isolation testing table, and the light of graphic projection's instrument is perpendicular to the plane of vibration isolation testing table, and IC chip to be measured is positioned on the surface level under graphic projection's instrument;

Described B telecentric lens is connected to CCD camera, by clamping device, be fixed on vibration isolation testing table, the plane of the light of CCD camera and vibration isolation testing table is 15 °～60 ° angles, CCD camera is connected to computing machine, show on computers the IC chip image with grating fringe being photographed by CCD camera, the angle of adjusting CCD camera makes the grating fringe in image be shown as horizontal linear.

2. the IC pin coplanarity measuring system based on structured light according to claim 1, is characterized in that: Yi Wei LED graphic projection of graphic projection instrument.

3. the IC pin coplanarity measuring system based on structured light according to claim 1, is characterized in that: the plane of the light of described CCD camera and vibration isolation testing table is 45 ° of angles.

4. in employing claims 1 to 3, described in any one, measuring system is measured an IC chip pin coplanarity measuring method, it is characterized in that comprising the steps:

Step 1: adjust the pose of graphic projection's instrument and IC chip, grating fringe is vertically projected on each pin of IC chip, then adjusts the angle of CCD camera, the grating fringe that makes it to photograph becomes horizontal linear;

Step 2: utilize angular instrument to measure CCD camera or telecentric lens and horizontal line angulation θ;

Step 3: the image of the IC chip pin with grating fringe that CCD camera 5 is photographed carries out the processing of morphological image, extract the skeleton of IC chip pin grating fringe, and skeleton is done to the fitting a straight line of least square method, calculate by the pixel distance S between the straight line of IC chip surface grating fringe matching and the straight line of pin surface grating striped matching;

Step 4: do camera calibration with 5 pairs of diffusion pottery scaling boards of CCD camera, calculate the proportionate relationship k between pixel distance and actual physics distance;

Step 5: each pin of IC chip is processed by above-mentioned steps 3,4 one by one, shown that by formula H=kS/cos θ the pin of IC chip is to the vertical range H between IC chip surface;

Step 6: calculate each pin of IC chip to the height difference H of IC chip surface _i, the maximal value H that coplane degree L use IC pin and IC chip surface true altitude are poor _maxwith minimum value H _mindifference represent, i.e. L=H _max-H _min, L is IC pin coplanarity.