JPS62186382A - Pin arrangement inspection system for object having plural pins - Google Patents

Abstract

PURPOSE:To attain the check at high speed by providing a lighting means lighting the pin pattern of an object, an image pickup means picking up the pin pattern and a picture processing means processing an image pickup signal so as to automate the pitch inspection of the pins of the object. CONSTITUTION:The picture processing section 2 consists of a digitizing circuit 21 for an analog picture signal Vi and a processing circuit 22 for a digital signal Di and processes the picture signal from an image pickup section 1. First a ring-shaped lighting device 15 gives an incident light Li to an LSI 10, and a reflected light Lo from the LSI 10 is condensed by the lens of a television camera 16 to obtain the picture signal (analog signal) of the LSI. The analog picture signal Vi is digitized by the digitizing circuit 21, that is, binary-coded (black/white level) to extract the digital picture signal Di. Then a digital signal processing circuit 22 processes the digital picture signal properly and whether or not the pins of the LSI are arranged correctly at a prescribed pitch interval from the result is discriminated.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention uses an image processing device comprising an imaging means such as a television camera and an imaging signal processing circuit to determine whether the external appearance of an article such as an electronic component is good or bad. Regarding inspection methods.

[Conventional technology]

With recent advances in automatic mounting technology for printed board electronic components,
An image processing device consisting of an imaging means such as a television camera and an imaging signal processing circuit measures the position and orientation of both the electronic component and the printed circuit board, performs accurate alignment, and automatically attaches the electronic component to the printed circuit board. Many implementation devices have been proposed. For example, the applicant also filed a patent application in 1986-6
No. 3221 proposes a position measurement method for a pin grid array type LSI.

A specific example of such a pin grid array type LSI is shown in FIG. In the figure, (a) is a plan view of the LSI, and (b) is a plan view of the LSI.
is the same side view, (c) is the same back view, LSllo
It can be seen that it consists of an integrated circuit section 11 and many pins 13.

By the way, when automatically mounting such a pin grid array type LSI, the appearance of the LSI must satisfy predetermined standards as a prerequisite for automatically measuring the position. In particular, the condition that a large number of pins planted in an LSI package are correctly arranged at predetermined pitch intervals is very important for correct mounting.

[Problem that the invention seeks to solve]

However, at present, most inspections of such pin arrangements are left to visual inspection by inspectors. Therefore, oversights and errors in judgment due to inspecting a large number of pins are unavoidable, and the inspection speed is significantly slower than the mounting speed of automatic mounting equipment, which is a bottleneck in work.

Therefore, it is an object of the present invention to provide a high-speed and highly reliable pin arrangement inspection method that can replace human visual inspection.

[Means for solving problems]

An illumination means for illuminating the pin pattern of the article, an imaging means for taking an image of the pin pattern, and an image processing means for processing the imaging signal of the pin pattern are provided.

[Operation] By using an illuminator with an appropriate optical path design,
The pin pattern of an article such as an electronic component is input as a clear image to a television camera, and the analog signal from the television camera is digitized by the analog signal digitization circuit in the image processing means, and the analog signal is digitized by the analog signal digitization circuit in the image processing means. The signal processing circuit performs effective calculations for determining whether the pin pitch interval is correct or incorrect for the pin pattern, thereby performing pin pitch inspection with high precision and high speed.

[Embodiments of the invention]

First, the overall configuration of the embodiment will be explained, and then its operation will be explained in sequence.

1) Overall configuration FIG. 1 is a schematic diagram showing the overall configuration of an embodiment according to the present invention. The broken frame indicates a hardware-like group, one of which is the imaging section 1 and the other of which is the image processing section 2. The imaging unit 1 includes a ring-shaped illuminator 15 and a television camera 1.
6 and pin 13 of LSI10, which is the target image to be inspected.
Take an image. The image processing unit 2 includes a digitization circuit 21 for the analog image signal Vi and a processing circuit 2 for the digital signal Di.
2, and processes the image signal from the imaging section 1.

First, the ring-shaped illuminator 15 receives the LS1101C incident light Li.
When the reflected light Lo from the LSI 10 is focused by the lens of the television camera 16, an image signal (analog signal) of the LSI is obtained from K. This analog image signal Vi is digitized by an analog signal digitizing circuit 21, that is, converted into white and black binary values, and a digital image signal Di is extracted. After that, the digital signal processing circuit 22 processes the digital image signal appropriately, and from the result, it is determined whether the pins of the LSI are correctly arranged at predetermined pitch intervals.

2) Measuring the center position of each pin In order to correctly inspect the pitch of the pins, the center position of each pin must first be measured correctly. This is a process in which an analog image signal is formed by the imaging section 1, digitized (binarized) by the analog signal digitization circuit 21, and the center position of the pin is calculated by the digital signal processing circuit 22.

In addition, if necessary regarding this process, please refer to the above-mentioned patent application 60.
See No.-63221. As a result, in Figure 2
As shown by the mark, the point set (ps
)(t-1tz, . . . , N; number of points) is obtained. The figure shows a set of points corresponding to about a quarter of one LSI. The most important point is the pitch interval t
For example, the point PH
There are some, such as G, that deviate from the correct pitch interval.

The next step is to determine this as defective. Note that the field of view of the television camera is the first quadrant of FIG. 2, which is within the range of the heel (see reference numeral 5).

6) Pitch inspection Follow the steps below.

(2) Obtain the outermost point sequence (Pi), (Pi) from the extraction point set (Pi) of the outermost point sequence as follows.

(P, ): A predetermined number N of points, starting from the one with the largest y value.
(for example, 7) are adopted (i-L2+...
・,N).

(P early) Predetermined in order of the two points with the largest X value! Adopt N pieces (for example, 7 pieces) (t-LL...
..., N).゛The results extracted in Fig. 2 are shown in Fig. 3.

■ Calculation of corner position and slope average value Fit a straight line to each of the point sequences (P, ), (Pi), and find the intersection point P of both straight lines. (xOt>'o) and the slope average value a are determined. The calculation formula is as follows, which is 0 or more. However, PF = (x・, y・), P・−(X Ht Y,)
It is. This calculation consists of a point sequence (Pi).

Find the straight line that best fits each of +pP:)! This is determined by the least squares method, and the intersection point PO of the two straight lines is determined as the corner position. However, it differs slightly from the general least squares method in that it imposes a constraint that two straight lines are orthogonal.

FIG. 4 shows the calculation results of Pa in FIG. 3.

Further, the average inclination value a is expressed as an inclination angle θ from the relationship θ-tu''a (incidentally, θ in the case of FIG. 4 is a negative value).

■ Coordinate transformation Po becomes the origin, and the two orthogonal helices mentioned above become the coordinate axes.
Coordinate transformation is performed as follows. As a result, (Pi)(')
The output coordinate value (xHlYH) of each point Pi becomes a new coordinate value (x+'*y1') as shown below.

It is expressed as,
Then, x-'='(x'+ayl')l 1 yi'''r('Ii' a x i').

■ Determining the quality of each pin As is clear from Figure 5, if K is a point that exists at the correct pitch in the new coordinate system, then both the x, iZ, and yYi' values are equal to an integral multiple of the predetermined pitch interval t. If the amount of deviation from that value exceeds a certain limit, it can be determined to be defective (PNG is an example of such a case). The determination procedure for each point Pi is shown in FIG. 6 in the form of a flowchart.

First, to find out how many times (integer) x i/ is closest to t, subtract t from x, /, and when it becomes negative, calculate its size and the size of the previous positive value. Let the smaller one of the two values be the deviation amount ΔXi (from an integral multiple of t) of x and / (see Fig. 6).

For example, FIG. 7 shows how the search is performed when X, / is closest to 4 times t. Next, in the same way, y・′
Find the amount of deviation ΔYi (see Fig. 6, ■, ■, ■). Next, find the square value Δ2 of the deviation amount from ΔX・, Δy・(
(See Figure 6). Finally, if Δ2 is less than a predetermined limit value α squared α2, it is judged as “good”, otherwise it is judged as “bad” (Fig. 6, ①, ②).

(See [Phase]). The pitch inspection is completed in this way.

What should be noted in the above procedures ① to ② is that the two straight lines on which the coordinate transformation depends are obtained from the set of inspection points themselves. Therefore, if the outermost circumferential point sequence adopted to obtain the two straight lines includes a point with a poor pitch, it is conceivable that the coordinate transformation according to the obtained 2@heddle will be inappropriate. However, this is not a problem as explained below. This is because if the number of defective pitch points and the degree of defectiveness are small, the reliability of the two straight lines found is high due to the effect of the least squares method. If the number of pitch defective points or the degree of defect is large, the subsequent coordinate transformation will be greatly incorrect, and the originally correct points will be considered defective during the pass/fail determination in (■), and the point set as a whole will still be considered defective. I can judge.

In any case, defects will not be overlooked. Incidentally, since the procedures ① to ② do not require particularly complicated processing, the digital signal processing circuit 22 of FIG. 1 can be processed at a sufficiently high speed by using a simple microprocessor system or the like.

〔Effect of the invention〕

According to the present invention, by providing an illumination means for illuminating a pin pattern of an article, an imaging means for taking an image of this pin pattern, and an image processing means for processing this imaging signal, an article that has conventionally relied exclusively on human labor can be manufactured. The advantage is that the pin pitch inspection can be performed automatically. Further, since no particularly complicated procedures are required for image processing, inspection can be performed at high speed using a simply configured image processing means.

[Brief explanation of drawings]

Fig. 1 is a configuration diagram showing an embodiment of the present invention, Fig. 2 is an explanatory drawing showing a set of points at the center position of each pin, Fig. 3 is an explanatory drawing showing a sequence of points on the outermost periphery, and Fig. 4 is an explanatory drawing showing corner positions. FIG. 5 is an explanatory diagram showing the result of coordinate transformation, FIG. 6 is a flowchart showing the procedure for determining whether the pin is good or bad, and FIG.
The figure is a supplementary explanatory diagram showing a procedure for determining whether a pin is good or bad, and FIG. 8 is a structural diagram showing a general pin grid array type LSI. Code explanation 1... Imaging unit, 10... Electronic component, 1
1...Integrated circuit section, 13...Pin, 1
4...Pin base, 15...Ring illuminator, 16...TV camera, 2...
Image processing section, 21... Digitization circuit, 22
...Digital signal processing circuit, 3...
Viewing range, Vi... Image signal, Di...
・Digital image signal, Li... Incident light, Lo
...Reflected light, Pi...Point, PIG...
...Failure point, t...Pitch interval, (P,)
, (P,)... Outermost point sequence, PO...
Corner position, θ...Inclination angle, x i/...
...X new coordinate value, yi'...X new coordinate value, Δ
X...X deviation amount, Δyi...y deviation amount, Δ1... deviation amount squared value, α...limit value. Agent Patent attorney Akira Namiki, attorney's right - μ Akame Hidden Lightning 1 Drawing a, Yoshiwa 2, Figure 3, Atmosphere 4, Figure 5, Figure No. 7, Drawing No. b (:shi + Te11 Chi△2.L 1 Mushi Bee

Claims (1)

[Claims] An inspection method that inspects the pin pattern of an article by imaging an article having a plurality of pins with an imaging device and processing the image signal with a processing device, the processing device inspecting the pin pattern obtained through the imaging device. A plurality of pins characterized by digitizing an image, measuring the center position of each pin from the digitized image signal, and inspecting whether each position is correctly arranged at a predetermined pitch interval. Pin arrangement inspection method for products with