JPH05256619A - Measuring method for coat quantity of cream solder - Google Patents

Abstract

PURPOSE:To provide a method capable of simply measuring the coat quantity of the cream solder coated on a substrate with a line sensor. CONSTITUTION:A line sensor 5 is used in place of an area type CCD camera as an optical system. A substrate 1 coated with cream solder 2 is conveyed by a conveyor 3, light is radiated from slant above to generate a shade section 6 behind the cream solder 2, and the length of the shade section 6 is detected by the line sensor 5. The plane area of the cream solder 2 is obtained based on the image data having the intensity received by the line sensor 5, and the obtained plane area is multiplied by thickness to determine the volume of the cream solder 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for measuring the amount of cream solder applied, and more particularly to a method for easily determining the volume of cream solder applied to a substrate by a line sensor.

[0002]

2. Description of the Related Art For electronic parts such as ICs, LSIs, capacitor chips, and resistance chips, cream solder is applied to a substrate by a screen printing machine, electrodes are landed on the cream solder, and then the cream solder is heat-treated. It is mounted by solidifying it.

In this case, if the amount of cream solder applied is too large, a solder bridge is likely to occur to cause a short circuit in the circuit, and if the amount of cream solder applied is too small, the electrodes cannot be firmly adhered to the substrate, There will be poor continuity. Therefore, after applying the cream solder to the substrate by the screen printing machine, an inspection is performed to determine whether the application amount of the cream solder is good or bad.

As a means for automatically inspecting the amount of cream solder applied, a method using a camera equipped with an area CCD is known. This method irradiates the substrate with light and observes it with a camera, obtains the plane area of the cream solder from the luminance distribution of the planar image captured by the camera, and determines the application amount of the cream solder from the size of this plane area. The quality was judged by a computer.

[0005]

However, since the area CCD camera collectively captures the luminance distribution of the substrate as plane information and performs image processing by a computer,
There is a problem that the image processing requires a considerable time and the inspection speed is slow.

The area type CCD camera can obtain the plane information, that is, the plane area of the cream solder, but cannot obtain the height information, that is, the thickness of the cream solder. Therefore, the volume (plane area × thickness) of the cream solder is obtained. However, since the quality of the coating amount must be determined based on the plane area, there is a problem that the reliability of the determination result is not high.

[0007] Therefore, an object of the present invention is to provide means for accurately and promptly obtaining the application amount of cream solder.

[0008]

To this end, the present invention uses a line sensor instead of an area CCD camera as an optical system. Then, while the substrate coated with the cream solder is being conveyed by the conveyor, light is radiated obliquely from above to form a shadow portion behind the cream solder, and the length of the shadow portion is detected by the line sensor. Further, the plane area of the cream solder is obtained from the image data of the luminance taken into the line sensor as the substrate is transported, and the obtained plane area is multiplied by the thickness to obtain the volume of the cream solder.

[0009]

According to the above structure, while the substrate is being conveyed by the conveyor, the thickness and the plane area of the cream solder are obtained by the line sensor, and the volume of the cream solder, that is, the application amount is obtained from the product of the thickness and the plane area, and the application is performed. The quality of the quantity can be determined.

[0010]

Embodiments of the present invention will now be described with reference to the drawings. FIG. 1 is an overall perspective view of an apparatus for measuring the amount of cream solder applied. Reference numeral 1 is a substrate on which cream solder 2 is applied by a screen printing machine. Cream solder 2
The shape is usually box-shaped as shown. 3 is substrate 1
Is a conveyer that conveys to the right.

Above the conveyor 3, a rod-shaped light source 4 (4
a, 4b) and the line sensor 5 (5a, 5b) are arranged with their longitudinal directions oriented in a direction orthogonal to the conveying direction of the conveyor 3. As will be described in detail later, while the substrate 1 is being conveyed by the conveyor 3, light is radiated toward the substrate 1 from obliquely above, and the shadow portions 6 (6a, 6b) generated behind the cream solder 2 are detected by the line sensor 5. Detect and
The volume of the cream solder 2 is measured. 7 is a mutual light source 4
This is a screen for blocking the light of a and 4b. In this embodiment, two sets of the light source 4 and the line sensor 5 are provided on the left and right,
The light source 4a on the left side and the line sensor 5a measure the shadow portion 6a on the front side in the traveling direction, and the light source 4b on the right side and the line sensor 5b measure the shadow portion 6b on the rear side.

FIG. 2 shows a left light source 4a and a line sensor 5a.
FIG. 6 is a side view showing a state where the shadow portion 6a on the front side of the cream solder 2 is being measured by. The light emitted from the light source 4a is blocked by the cream solder 2, and a shadow portion 6a is formed on the front side of the cream solder 2. Therefore, the length of the shadow portion 6a is detected by the line sensor 5a. θ is the irradiation angle of light.

FIG. 3 shows the image data A of the luminance of the area including the cream solder 2. 8 is a line sensor 5a
Is a light receiving element. Since the cream solder 2 is a whitish metallic material and has a high light reflectance, strong light is incident on the line sensor 5a, resulting in bright brightness. Moreover, almost no light is incident from the shadow portion 6a, and the brightness thereof is extremely low. The substrate 1 around the cream solder 2 has intermediate brightness. 4 and 5 show that the light source 4b on the right side and the line sensor 5b
The state where the shadow portion 6b on the rear side of the cream solder 2 is being measured and its image data B are shown. The image data A and B are obtained by receiving the reflected light by the line sensors 5a and 5b while the substrate 1 is being conveyed by the conveyor 3.

Next, how to obtain the volume of the cream solder 2 will be described. In FIG. 3, the coordinate X where the cream solder 2 should be
i, Yi, and the lower limit value Pa and the upper limit value Pb of the brightness of the cream solder 2 are set. Further, a reference value Pd which is a threshold value for detecting the shadow portion 6 is set.

Next, the number S of pixels having a brightness of Pa or more and Pb or less
i is counted and the plane area of the cream solder 2 is obtained. In addition, the average value L of the number of pixels in the X direction of the area of Pd or less (that is, the shadow portion 6a) that is adjacent to the cream solder 2 in the X positive direction is L
Find i.

Similarly, from the image data B shown in FIG. 5, the number of pixels Si ′ of Pa or more and Pb or less is counted to obtain the plane area of the cream solder 2, and the area of Pd or less (adjacent to the X negative direction) That is, the average value Li ′ of the number of pixels in the shadow portion 6b) in the X direction is obtained. Then, the volume Vi of the cream solder 2 is given by the following equation.

Vi = a (Si + Si ′) (Li + Li ′) This equation is obtained from the equation 1.

[0018]

[Equation 1]

This number 1 is the plane area Si of the cream solder 2.
And Si 'average value, and the thickness of cream solder 2 Litan
The product is obtained by multiplying the average value of θ and Li'tan θ. By comparing the volume Vi of the cream solder 2 thus obtained with a preset determination value,
The quality of the applied amount of cream solder 2 is determined. It should be noted that the above-described calculation and pass / fail judgment are performed by a computer.

In this method, the line sensor 5 can obtain the image data A and B necessary for obtaining the volume Vi of the cream solder 2 while the substrate 1 is being conveyed by the conveyor 3.
Moreover, the volume Vi can be obtained by a simple calculation. Further, the volume may be obtained from the image data of one set of the light source 4 and the line sensor 5.
Obtain two image data A and B, and as shown in the equation 1, the average value of the plane area of the cream solder 2 is 1/2 (Si + Si ′).
If the average thickness 1/2 (Li + Li ') tan θ is calculated, the volume Vi of the cream solder 2 can be calculated more accurately. According to this method, as shown in FIG.
Even if the upper surface of the cream solder 2 is inclined and has a trapezoidal shape, its volume can be accurately obtained.

According to this method, the volume can be accurately obtained even when the cream solder 2 applied by the screen printing machine is improper and its shape becomes irregular. Next, an example thereof will be described. The cream solder 2 shown in FIG. 7 has a triangular pyramid shape. FIG. 8 shows image data A of the cream solder 2 by the light source 4a on the left side and the line sensor 5a shown in FIG. 1, and FIG. 9 shows image data B by the light source on the right side and the line sensor 5b. Image data A has a triangular shadow 6
Although a occurs, the image data B does not have a shadow. Figure 1
0 indicates three calculation methods (a), (b), and (c) of the volume Vi. First, (a) no division will be described. in this case,
Si = Si ′, and the average length Li = L / of the shadow portion 6a
2, Li = 0. Therefore, the volume Vi = 0.25 × SiLtan θ can be obtained by the calculation formula shown in the figure. Here, the theoretical volume V of the triangular pyramid cream solder 2
Is the number 2.

[0022]

[Equation 2]

Therefore, the error becomes the equation 3.

[0024]

[Equation 3]

If the volume Vi is obtained without dividing in this way, the error will be considerably large and the quality judgment will be incorrect. The (2) division into two in FIG. 10 shows a calculation method for reducing this error. In this case, Si is S
1 and S2, and the average length L of each shadow part 6a
1 = 3 / 4L and L2 = 1 / 4L are obtained, and then the volumes V1 and V2 are obtained, and the sum thereof is obtained. As shown in the figure, Vi = V1 + V2 = 0.31 × SiLtan θ. Therefore, the error V−Vi = 0.02 × SiLt
It becomes anθ, which is considerably smaller than the case without (a) division. (C) If divided into three, the error becomes 0.01 × SiLtan θ, as shown in FIG. 10, and becomes smaller.
By dividing the region in the Y direction in this way and calculating and summing the volume for each divided region, the error can be reduced and appropriate pass / fail judgment can be performed.

[0026]

As described above, according to the present invention, while the substrate is being conveyed by the conveyor, the shadow area formed behind the cream solder is detected by the line sensor. It is possible to detect the quality by a simple method, obtain the coating amount, and properly judge the quality.

[Brief description of drawings]

FIG. 1 is a perspective view of an apparatus for measuring the amount of cream solder applied according to the present invention.

FIG. 2 is a side view during measurement according to the present invention.

FIG. 3 is an image data diagram according to the present invention.

FIG. 4 is a side view during measurement according to the present invention.

FIG. 5 is an image data diagram according to the present invention.

FIG. 6 is a side view during measurement according to the present invention.

FIG. 7 is a perspective view of cream solder according to the present invention.

FIG. 8 is an image data diagram of cream solder according to the present invention.

FIG. 9 is an image data diagram of cream solder according to the present invention.

FIG. 10 is an explanatory diagram of volume measurement of cream solder according to the present invention.

[Explanation of symbols]

 1 substrate 2 cream solder 3 conveyor 4 light source 5 line sensor

Claims (1)

[Claims] 1. A substrate coated with cream solder is conveyed by a conveyor while irradiating light obliquely from above to form a shadow portion behind the cream solder, and the length of this shadow portion is defined as the length above the conveyor. Detected by a line sensor disposed in the longitudinal direction of the line sensor in a direction orthogonal to the transport direction, the thickness of the cream solder is obtained based on the length of the detected shadow portion, and by the conveyor. It is characterized in that the plane area of the cream solder is obtained from the image data of the brightness taken in by the line sensor during transportation, and the volume of the cream solder is obtained by multiplying the obtained plane area and the thickness. How to measure the amount of cream solder applied.