JPH1172316A - Measuring apparatus for flatness of ic lead - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a flatness measuring apparatus by which the flatness of a lead ball at a ball grid array(BGA), a ship-scale package(CSP) or the like can be measured in a short time. SOLUTION: In this apparatus 1, one pair of parallel luminous fluxes 15a, 16a from right and left symmetric directions are shone at parts near top parts of respective lead balls 3(n) at an IC package BGA through linear slits 52(n), for light transmission, which the formed in a slit plate 5, and one pair of light spots are formed. An image on the surface of every lead ball on which the light spots are formed is imaged by a CCD camera or the like, and the center distance between the pair of light spots is found on the basis of the obtained image. The height of every lead ball 3(n) is found on the basis of the conter distance, and the flatness of every lead ball can be computed on the basiso f every height. The time required for an inspection can be shortened sharply as compared with a case in which the respective lead balls are scanned sequentially by a laser beam so as to measure the height of the respective lead balls.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an IC lead flatness measuring apparatus for measuring the flatness of an IC lead.
More particularly, the present invention relates to an IC lead flatness measuring apparatus suitable for measuring the flatness of an IC package having a configuration in which spherical IC leads are arranged in a grid on the back surface of a package in which an IC chip is sealed. It is.

[0002]

2. Description of the Related Art There are known IC packages of a type called a CSP (chip scale package) or a BGA (ball grid array). In this type of IC package, a bare chip of an LSI is placed on a printed wiring board and sealed, and lead terminals formed of spherical solder arranged in an area array (two-dimensional matrix) form from the back side of the board. This is a surface mount type package.

As a method of measuring the flatness of an IC lead, that is, a lead ball in an IC package of this type, a method is performed by measuring the position (ie, height) of the apex of each lead ball using a laser displacement meter. It has been known. There is also known a method of irradiating a lead laser beam with a linear laser beam, capturing an image of each lead ball with a CCD camera, and processing the obtained image to measure the height of each lead ball.

[0004]

A disadvantage of these commonly used methods is that they do not allow rapid measurements. That is, in any of the above methods, since a point or linear laser beam is used,
In order to inspect the dimensions of all lead balls, it is necessary to sequentially scan each lead ball with a laser beam. In an IC package such as a CSP or BGA, a large number of lead balls are arranged in a matrix (grid shape). Therefore, in the conventional dimensional inspection method in which all lead balls need to be sequentially scanned by a laser beam, the inspection time is short. Hang on. Further, as the number of lead balls increases, the required inspection time also increases proportionately.

An object of the present invention is to provide an IC lead flatness measuring apparatus capable of shortening the time required for flatness measurement, focusing on the problems of such a conventional dimension inspection method.

[0006]

In order to solve the above-mentioned problems, an apparatus for measuring flatness of an IC lead according to the present invention comprises a plurality of linear slits for transmitting light which are arranged in parallel at equal intervals. A slit plate, a parallel light source for irradiating the slit plate with a parallel light from a direction inclined at the same angle to the opposite side along the arrangement direction of the linear slits with respect to a normal line of the slit plate, and the slit plate A work stage for holding an IC package to be measured at a position on the light emitting side such that a lead ball forming surface thereof is parallel to the slit plate; and a surface of each lead ball arranged on the lead ball forming surface. Image pickup means for picking up an image, and a distance between centers of light-receiving points formed on the surface of each lead ball is obtained based on the image obtained by the image pickup means. It employs a configuration having a measuring means for measuring the flatness of each lead ball on the basis of the center-to-center distance.

Here, it is desirable to have a positioning means for adjusting the position of the slit plate so that a pair of light-receiving points is formed near the apex of the lead ball.

In a typical flatness measuring device of the present invention, the pitch of the linear slit is n times (n: a positive integer) the pitch of the lead ball. In this case, each of the linear slits and each vertex of the two lead balls onto which a pair of parallel light beams passing through the linear slit are projected is positioned at each vertex of an isosceles triangle. What is necessary is just to align a slit and each lead ball.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a schematic configuration diagram of an IC lead flatness measuring apparatus to which the present invention is applied. Referring to FIG. 1, an IC lead flatness measuring apparatus 1 according to the present embodiment includes a work stage 2 on which an IC package BGA to be measured is installed.
The C-lead formation surface, that is, the lead ball formation surface 3 is set on the work stage 2 so as to face downward.

Immediately below the work stage 2, a slit plate 5 held by a slit plate positioner 4 is located. This slit plate 5
Are arranged parallel to the lead ball forming surface 3 of the IC package BGA. This slit plate 5
Below, an optical system 6 including an imaging lens and an imaging unit 8 including a CCD camera 7 are arranged. This imaging means 8
The optical axis 8a coincides with the center normal 3a of the lead ball forming surface 3 of the IC package BGA set on the work stage 2. Therefore, it coincides with the center normal line of the slit plate 5 arranged parallel to the lead ball forming surface 3.

A surface image of each lead ball 3 (n) (n is a positive integer) obtained by the CCD camera 7 is supplied to a data processing device 12 via an image processing device 11, and is described below. The height of 3 (n) of each lead ball is calculated, and the flatness is obtained based on the calculation result. The obtained flatness measurement value is output via the input / output device 13.

On the other hand, a pair of parallel light sources 15 and 16 are arranged on both sides of the image pickup means 8. These parallel light sources 15 and 16 are connected to the center normal 3 a of the lead ball forming surface 3.
Are arranged at symmetrical positions with respect to the center. Also,
The parallel light beams 15a and 16a emitted from these parallel light sources 15 and 16 irradiate the slit plate 5 from directions inclined at the same angle to the left and right with respect to the center normal 3a. A typical inclination angle is a value within a range of 30 to 40 degrees, and is set to, for example, an angle of 30 degrees in this example. Note that an LED illumination light source 17 is disposed below the slit plate positioner 4.

FIG. 2 is an explanatory view showing the slit plate 5 and its peripheral portion in an enlarged manner. The slit plate 5 includes a transparent glass substrate 51 and a plurality of linear slits 52 (n) for light transmission formed on the surface thereof. Each linear slit 52 (n) is parallel to each other,
They are formed at the same pitch p1. In this example, the pitch is the same as the pitch p2 of the lead ball 3 (n).
Each linear slit 52 (n) is defined by a pair of light shielding masks 53 (n) formed in parallel at regular intervals. As can be seen from the figure, a wide slit 54 (n) through which light passes is also formed between the linear slits 52 (n).

Here, each linear slit 52 (n) and two adjacent lead balls 3 (n) and 3 (n + 1) on which a pair of parallel light beams 15a and 16a passing therethrough are projected.
Are positioned at each vertex of the equilateral triangle.
Is positioned by As a result, via the wide slit 54 (n) between each linear slit 52 (n),
From the lower side of the slit plate 5, each lead ball 3
A surface portion including the vertex of (n) can be desired.

The operation of measuring the flatness of a lead ball by the flatness measuring apparatus 1 of the present embodiment thus configured and its principle will be described. First, the IC package BGA to be measured
On work stage 2. Next, based on the information obtained from the CCD camera 7, the attitude of the slit plate 5 is corrected by the slit plate positioner 4 in accordance with the attitude of the IC package BGA, and the fine light passing through each linear slit 52 (n) is corrected. Correctly each lead ball 3
(N) is set so as to irradiate the vicinity of the vertex. In this correction operation, the LED illumination light source 17 is turned on and CC
The posture of the IC package BGA is confirmed by the D camera 7.

After the posture of the slit plate 5 is adjusted, the LED illumination light source 17 is turned off, and the pair of parallel light sources 15 and 16 are turned on instead. As can be seen from FIG. 2, the light sources 15, 1 passing through the respective linear slits 52 (n).
The fine light of the parallel light fluxes 15a and 16a from 6 irradiates the vicinity of the vertex of each lead ball 3 (n). As a result, near the apex of each lead ball 3 (n), the parallel luminous flux 15a, 16
A pair of light spots (lighting points) are formed by the pattern a. Therefore, for example, if the height of the lead ball whose vertex is located at a position where the pair of light spots coincides is set as the reference height, the height of each lead ball 3 (n) is determined based on the distance between the centers of the pair of light spots. The height difference with respect to the reference height can be calculated, and the flatness of the lead ball can be obtained based on the calculated height difference.

FIG. 3 is an explanatory diagram showing a method of calculating the height of the lead ball. In the lead ball 3 (n) having the reference height, a pair of parallel light beams 15a, 16a
Just irradiates the apex 31 of the lead ball 3 (n) to form light spots 15c and 16c that are overlapped therewith. On the other hand, in the case of the lead ball 3 (n-1) lower than the reference height, a pair of light spots 15c 'and 16c' centering on the vertex 32 are formed.
In the figure, the distance between the centers of the light spots 15c 'and 16c' is indicated by C '. Conversely, in the case of the lead ball 3 (n + 1) higher than the reference height, the top 3
3, a light spot 16c "is formed on the right side, and a light spot 15c" is formed on the left side. In the figure, these center-to-center distances are indicated by C.

The radius of the lead ball is R, the distance from the light spots 15c ', 16c' formed on the surface of the lead ball 3 (n-1) lower than the reference height to the reference height position is H ', Light spot 15c 'from vertex 32, 1
If the distance to 6c ′ is h ′, the lead ball 3 (n
The distance from the vertex 32 of (-1) to the reference height position is (H ′)
−h ′). Here, the distances H ′ and h ′ are represented by Expressions (1) and (2).

[0019]

(Equation 1)

Accordingly, it is possible to calculate how low the vertex 32 of the lead ball 3 (n-1) is from the reference height position.

Similarly, in the case of the lead ball 3 (n + 1) higher than the reference height position,
The light spot 15 formed on the surface of the lead ball 3 (n + 1) having a radius of (n) smaller than R and having a radius lower than the reference height.
Let H be the distance from c ″, 16c ″ to the reference height position,
Assuming that the distance from the vertex 33 to the light spots 15c ″ and 16c ″ is h, the distance from the vertex 33 of the lead ball 3 (n + 1) to the reference height position is (H + h). Here, the distances H and h are represented by Expressions (3) and (4).

[0022]

(Equation 2)

Therefore, it is possible to calculate how high the vertex 33 of the lead ball 3 (n + 1) is from the reference height position.

Here, even if the distances C and C 'between the centers of the light spots 15c and 16c are the same, the light spot 1
The formation positions of 5c 'and 16c' are light spots 15c ",
Since the left and right sides are reversed with respect to the formation position of 16c ″, for example, by turning on the parallel light sources 15 and 16 alternately, it is possible to determine whether the lead ball is higher or lower than the reference height position.

Next, in the above flatness measuring device, the pitch P2 of the lead ball 3 (n) and the linear slit 52 (n)
Have the same pitch P1. However, in this case, as the pitch of the lead balls becomes smaller, it is necessary to make the slit pattern of the slit plate 5 to be formed finer accordingly, which makes the production difficult. In such a case, the pitch P1 of the linear slits 52 (n) may be set to an integral multiple of the pitch P2 of the lead balls 3 (n).
For example, as shown in FIG.

By doing so, the lead ball 3 (n)
Even if the pitch P2 of the linear slit 52 is small.
The pitch P1 of (n) can be widened. In this case, the measurement is performed in the state shown in the figure, and then the slit plate 5 is moved laterally by the pitch P2 of the lead balls, and the measurement is performed again, whereby the measurement for all the lead balls can be performed. .

Also, as described above, the linear slit 52 (n)
Is widened, the width w of the wide slit 54 (n) formed therebetween can be made sufficiently wider than the lead ball diameter D. As a result, two-dimensional measurement (planar measurement) of the lead ball can be performed at the same time.

[0028]

As described above, according to the apparatus for measuring flatness of an IC lead of the present invention, a pair of light spots formed by a parallel light flux formed near the apex of each lead ball is subjected to CC.
If an image is taken by an imaging means such as a D camera and the distance between the centers is calculated, the height of each lead ball can be obtained, and the flatness can be obtained based on the obtained height of each lead ball. Therefore, the time required for the inspection can be greatly reduced since the scanning time of the laser beam is not required as compared with the case where the height of the lead balls is measured by sequentially scanning the lead balls with the laser beam.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an IC lead flatness measuring apparatus to which the present invention is applied.

FIG. 2 is an explanatory diagram showing an enlarged view of a slit plate of FIG. 1 and a peripheral portion thereof;

FIG. 3 is an explanatory view showing a principle of calculating a height of a lead ball by the apparatus of FIG. 1;

FIG. 4 is an explanatory diagram of a main part showing a modification of the flatness measuring device of FIG. 1;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Flatness measuring device of IC lead 2 Work stage 3 Lead ball forming surface 3 (n) Lead ball 3a Center normal of lead ball forming surface 4 Slit plate / positioner 5 Slit plate 6 Optical system 7 CCD camera 8 Imaging means 15, Reference Signs List 16 parallel light source 15a, 16a parallel light 15c, 16c light spot 11 image processing device 12 data processing device 13 input / output device

Claims (4)

[Claims] 1. A slit plate having a plurality of linear slits for light transmission arranged in parallel at equal intervals, and opposed to a normal line of the slit plate along an arrangement direction of the linear slits. A parallel light source that irradiates a parallel light beam to the slit plate from a direction inclined by the same angle to the side, and an IC package to be measured at a position on the light emission side of the slit plate, where a lead ball forming surface thereof is parallel to the slit plate. A work stage to be held, imaging means for imaging the surface of each lead ball arranged on the lead ball forming surface, and a work stage formed on the surface of each lead ball based on an image obtained by the imaging means. Measuring means for determining the distance between the centers of the light-receiving points and measuring the flatness of each lead ball based on the distance between the centers. IC lead flatness measuring device. 2. The flatness of an IC lead according to claim 1, further comprising positioning means for adjusting a position of the slit plate so that a light spot is formed near a vertex of the lead ball. Degree measuring device. 3. The IC lead flatness measuring device according to claim 1, wherein a pitch of the linear slit is n times (n: a positive integer) of a pitch of the lead ball. 4. The device according to claim 3, wherein one of the linear slits and each vertex of the two lead balls onto which a pair of parallel light beams passing through the linear slit are projected are each vertex of an isosceles triangle. Each linear slit and each lead ball are aligned so as to be positioned.
C-lead flatness measuring device.