JP2006058213A - Method and apparatus for inspecting terminal of electronic part - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance inspection precision by precisely extracting three points functioning as the imaginary support surface of an electronic part. <P>SOLUTION: After three-dimensional coordinates of respective representative points are calculated with respect to the respective terminals of the electronic part to be inspected, the respective representative points are successively combined by three to discriminate whether three points related to the combination satisfy first and second conditions. The first condition is a condition capable of projecting the part center part on a triangular plane of three points and the second condition is a condition wherein the triangular plane is positioned under all of representative points other than three points. When the combination of three points satisfying both conditions is found out, the distance D of the imaginary plane containing three points and each of the representative points is calculated, by using the distance D to discriminate the presence of the floating of each terminal. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention provides an electronic component (IC, QFP, etc.) of a type in which a large number of lead terminals are provided on the side surface of the package or an electronic component (BGA, CSP, etc.) of a type in which a large number of ball terminals are provided on the bottom of the package. It is related to a technique for inspecting whether or not each terminal is lifted as an inspection object.

  In order to perform the above inspection with high accuracy, it has been proposed to obtain the three-dimensional coordinates of the tip of each terminal and analyze the measurement result (see Patent Document 1).

JP-A-7-151522

  When the presence or absence of floating is determined using the three-dimensional coordinates of each terminal as in Patent Document 1, generally three points that form the lowermost surface of a virtual plane formed between the terminals are extracted. Then, the distance between the virtual plane by these three points and other points is calculated, and each distance is compared with a predetermined threshold value.

  Conventionally, after obtaining a plane that approximates the distribution of each representative point by the least square method using each three-dimensional coordinate, the distance to the plane is the largest among the representative points below this plane. Three points, the largest and the third largest, are obtained, and the virtual plane formed by these points is the bottom surface.

In order to accurately detect the floating of the terminal, it is necessary to obtain the distance from the horizontal plane to each virtual terminal that supports the entire component between the horizontal plane and each terminal when the component is placed on a horizontal plane such as the substrate surface.
In order to horizontally support the component main body at three points, it is desirable that the triangular plane formed by these three points be opposed to the portion including the center portion of the component.

  On the other hand, in the above-described conventional method, as the three points forming the lowermost surface, three points are extracted in order from the lowest one, so two or three points are selected from the terminals arranged in a row. There is a possibility that appropriate three points may not be selected, for example, three points that cannot constitute a plane are extracted, or three points that constitute a triangular plane that cannot project the center of a component are extracted.

  The present invention has been made paying attention to the above-mentioned problems, and by accurately extracting three points that function as virtual support surfaces of components from the representative points of each terminal, the accuracy required for the terminal floating inspection is accurately determined. The purpose is to increase.

  Three arbitrary points are extracted from the representative points of each terminal, and a triangular virtual plane (referred to as “triangular plane” in this specification) formed by these three points is considered. In order for this triangular plane to be a virtual support surface of a part, a condition that the center part of the part can be projected onto this plane (hereinafter referred to as “first condition”), and this triangular plane is other than the above three points. It is desirable to satisfy a condition (hereinafter referred to as “second condition”) that is located below all representative points (which means a direction opposite to the package).

  The electronic component terminal inspection method according to the present invention uses a first step of measuring the three-dimensional coordinates of the representative point for each terminal, and the three-dimensional coordinates of the representative points obtained in the first step. A second step of forming a triangular plane capable of projecting the center part of the component and extracting three representative points located below the other representative points from the representative points; Calculating a distance between the plane including the three representative points extracted in the second step and other representative points, and determining whether or not each terminal is lifted based on the calculation result; , To perform.

  In the above, in the first step, three-dimensional measurement processing based on the principle of triangulation can be performed using two cameras or the like. The representative point of each terminal is preferably selected from a portion in contact with the substrate. However, in the case of a lead terminal, a point on the upper surface side of the tip may be selected.

  In the second step, three representative points of each terminal are sequentially combined, and for each combination, it can be determined whether or not the three points related to the combination satisfy both the first condition and the second condition. . If a combination of three points satisfying both conditions is found during the series of determination processes, the determination process can be terminated at that point.

  In the second step, as a process of determining whether or not a combination of three representative points satisfies the first condition, the three representative points related to the combination are projected onto a virtual horizontal plane, and each projected point is projected. It can be determined whether or not the central part of the component can be projected within the triangle. In this way, since the relationship between the triangular plane viewed from above or below the component and the component center can be recognized, it is possible to easily determine whether or not the first condition is satisfied.

  The center part of the part is desirably a position corresponding to the center of gravity of the main body (package) of the part or the center point of the lower surface of the main body, but is not limited thereto. For example, a mark may be added to the center of the package surface in advance, and the coordinates corresponding to this mark may be measured during the three-dimensional measurement process, and used as the position of the component center. Alternatively, the coordinates of the central part of the part may be determined in advance, and the part to be inspected may be strictly positioned based on the coordinates. More preferably, an average value of the three-dimensional coordinates of all the representative points obtained in the first step is calculated and used as position data of the part center.

  The inspection apparatus according to the present invention uses a three-dimensional coordinate acquisition unit that measures or inputs a three-dimensional coordinate of a representative point of each terminal, and a three-dimensional coordinate of each representative point acquired by the three-dimensional coordinate acquisition unit. An extraction unit that forms a triangular plane capable of projecting the center of the component from the representative points and extracts three representative points located below the other representative points; and the extraction unit The distance measuring means for calculating the distance between the plane including the three representative points extracted from the other representative points and the distance calculated for each representative point by the distance measuring means are respectively compared with a predetermined threshold value. And determining means for determining whether or not each terminal is lifted, and output means for outputting the determination result of the determining means as an inspection result.

  In the above, the three-dimensional coordinate acquisition means can be a device that measures each terminal using the principle of triangulation described above. Alternatively, an input unit (including an interface circuit or the like) that inputs measurement results from a device having this type of three-dimensional measurement function, or a drive device that reads the three-dimensional results from a storage medium that stores the three-dimensional measurement results You can also

The extracting means, the distance measuring means, and the discriminating means can each be configured by a computer in which the functions of the means are set. Further, these three means can be constituted by a single computer. Further, the computer can be provided with means for measuring the amount of lifting of the terminal where lifting is detected.
The output means can include a signal generation circuit and an interface circuit for outputting the inspection result as a digital or analog signal.

  According to the present invention, it is possible to accurately determine the three points constituting the virtual triangular plane that supports the component from among the terminals of the electronic component, so that the presence or absence of the floating of each terminal can be determined with high accuracy. And high-precision inspection can be performed.

FIG. 1 shows an electrical configuration of an inspection apparatus according to the present invention.
This inspection device is for inspecting the presence or absence of lifting of each terminal with a component having a large number of lead terminals on the side surface of the package and a component having a large number of ball terminals on the bottom surface of the package as inspection targets. Two CCD cameras 1a and 1b (hereinafter simply referred to as “cameras 1a and 1b”), image input units 2a and 2b corresponding to the cameras 1a and 1b, an image memory 3, a CPU 4, a memory 5, and a work support unit 6 , Input unit 7, output unit 8 and the like.

  The workpiece support 6 includes a component package suction mechanism, and supports the component to be inspected at a predetermined height position by this suction mechanism. Each camera 1a, 1b images the components supported by the workpiece support 6 from below. The image input units 2a and 2b are configured by camera interface circuits, A / D conversion circuits, and the like.

  The image memory 3 is for storing the image data digitally converted by the image input units 2a and 2b. The memory 5 stores a program and setting data necessary for the operation of the CPU 4 and a work data storage area.

  The input unit 7 is used to input a threshold value for determining a floating state of the terminal prior to the inspection, and is configured by a keyboard and a mouse. The output unit 8 is for outputting the inspection result, and includes an output terminal to a monitor and an external device.

  In the above, the CPU 4 performs an edge extraction process or the like on each of the two images input to the image memory 3, and extracts an area corresponding to each terminal. Next, one representative point is extracted for each terminal, and each representative point is associated between images based on the relationship of the coordinate systems of the cameras 1a and 1b. Then, three-dimensional coordinates are calculated from the coordinates on the image based on the principle of triangulation for each associated representative point.

  The representative point of the terminal is selected from a portion in contact with the substrate surface during mounting. FIG. 2 shows an example of the selection. In the figure, reference numerals 10 and 12 denote parts of a package constituting the component main body, reference numeral 11 denotes a lead terminal, and reference numeral 13 denotes a ball terminal. In the component having the lead terminal 11 shown in FIG. 2A, the point P at the lower end portion of the terminal 11 is selected. In the component having the ball terminal 13 in FIG. 2B, the point Q at the lower end of the terminal 13 is selected.

  The CPU 4 extracts a virtual support surface of the part (hereinafter simply referred to as “support surface”) using the three-dimensional coordinates of each representative point obtained in the three-dimensional measurement process. Then, the distance between each representative point and the support surface is obtained, and this is compared with a predetermined threshold value to determine whether or not each terminal is lifted. For the terminals whose distance exceeds the threshold value, the distance of the representative point with respect to the support surface is extracted as the lift amount.

The details of the process of extracting the support surface of the component will be described below.
FIG. 3 shows the correspondence between the spatial coordinate system used in the three-dimensional measurement process of this embodiment and the component to be inspected (QFP in the illustrated example). In this example, the horizontal plane is expressed in the xy coordinate system, and the height direction is the z-axis, and the component package 14 is supported so as to be parallel to the xy plane, and measurement is performed. Then, when the three-dimensional coordinates of the representative points of each terminal are obtained, these representative points are combined in order, and it is determined whether or not the triangular plane formed by the three points related to the combination corresponds to the support surface.

  As described above, in order for a triangle plane with three points to function as a support surface for a component, the triangle plane is in a position where the center of the component can be projected (first condition), and the triangle plane has three points. It is desirable to satisfy the condition (second condition) of being located below all the representative points except for the above. In this embodiment, first, in order to determine whether or not the first condition is satisfied, the coordinates of the three points are respectively projected onto the xy plane, and the projection point at the center of the component is within the triangle formed by these projection points. Determine whether it is included. Note that the center of gravity of the component body and the center point of the package surface may be used as the center part of the component. It is necessary to position the parts strictly. In this embodiment, in order to eliminate the complexity of such processing, the average value of the coordinates of each representative point is used as position data indicating the part center.

4 (1) and 4 (2) show the relationship between the projected images of the three points and the component center point. In each figure, points A, B, and C are the three projected points. Point O is a projected point of a point corresponding to the average value of the coordinates of each representative point. Hereinafter, this point O is referred to as a center point O.
In this embodiment, it obtains a straight line L _A passing through the point A and the center point of O, checks whether intersects the segment BC to the straight line L _A is opposed to the point A. Similarly, for other points B and C, straight lines L _B and L _C passing through the point and the center point O are obtained, and whether or not these straight lines L _B and L _C intersect with the line segments AC and AB, respectively. To check.

When the center point O is included in the triangle ABC, as shown in FIG. 4A, any of the straight lines L _A , L _B , and L _C intersects the line segment. On the other hand, in the absence of the center point O in the triangle ABC, as shown in FIG. 4 (2), (in the illustrated example L _A, L _C) line does not intersect the line segment is present.

Here, the coordinates of the three points A, B, and C are (x _A , y _A ) (x _B , y _B ) (x _C , y _C ), and the coordinates of the center point O are (x _O , y _O ). consider the condition for straight _{L C} intersects the line segment AB.

First, if the equation of a straight line including the line segment AB (referred to as straight line M) is p1 · x + q1 · y + r1 = 0 and dx = x _B −x _A and dy = y _B −y _A , then p1 = dy, q1 = −dx, r1 = dx · y _A −dy · x _A.

Also when the expression of the straight line _{L C} and p2 · x + q2 · y + r2 = 0,
_{p2 = y C -y O, q2} = x o -x C,
r2 ₌ the _{(y O -y C) · x} O + (x C -x O) · y O.
Therefore, the straight line M and the straight line _{L C} with the intersection point (x, y) the following (1) (2) can be obtained by expression.

If the straight line _{L C} intersects the line segment AB, the (1) (2) the intersection determined by the equation (x, y) it will be located on the line segment AB. For that purpose, the following condition X or condition Y must be satisfied.
Condition X: When | dx | ≧ | dy |, if dx <0, x _B ≦ x ≦ x _A ; if dx ≧ 0, x _A ≦ x ≦ x _B
Condition Y: When | dx | <| dy |, if dy <0, y _B ≦ y ≦ y _A ; if dy ≧ 0, y _A ≦ y ≦ y _B

Therefore, the straight line _{L A,} L B, per _{L C,} the corresponding line segment BC on the basis of each (1) (2), AC, obtain the intersection of the straight line containing the AB, the intersection point the condition X or Y It is possible to confirm whether or not the center point O is included in the triangle ABC by determining whether or not it is satisfied.

In this embodiment, for the combination of representative points determined to satisfy the first condition by the above method, it is further determined whether these points satisfy the second condition. In this determination process, a virtual plane including each representative point is obtained, and it is determined whether all other representative points are above the virtual plane. Note that this virtual plane includes the above-described triangular plane formed by the three points. Assuming that the formula of this virtual plane is ax + by + cz + d = 0, the condition Z for any arbitrary representative point (x _i , y _i , z _i ) outside the combination to be located above this plane is:
ax _i + by _i + czi + d> 0.

FIG. 5 shows a processing procedure when the inspection apparatus inspects one component. This procedure starts when the parts to be inspected are imaged by the cameras 1 a and 1 b and the images are input to the image memory 3.
First, in the first ST1 (ST is an abbreviation for a step. The same applies to the following), the images input from the cameras 1a and 1b are processed to calculate the three-dimensional coordinates of the representative points of the terminals. The calculated three-dimensional coordinates are stored in the memory 5. In addition, since the x and y coordinates of the three-dimensional coordinates of the representative point are reflected on the projection point on the xy plane described above, the process for obtaining the coordinates of the projection point is unnecessary.

Next, in ST2, the average values x _O and y _O of the x and y coordinates of each representative point are obtained, and the point corresponding to the average values x _O and y _O is set as the central point O.

In ST3, arbitrary three points are selected from the representative points. In ST4, straight lines L _A , L _B , and L _C that pass through these three projection points A, B, and C and the center point O are obtained. In ST5, the coordinates of the intersection point are calculated based on the equations (1) and (2) for the straight lines L _A , L _B , L _C and the line segments BC, AC, AB corresponding to the respective straight lines.

  In ST6, it is determined whether or not each intersection calculated in ST5 satisfies the condition X or the condition Y, respectively. If any of the intersections satisfies the condition X or the condition Y, it is determined that the first condition is satisfied, and the process proceeds to ST7.

In ST7, a virtual plane including three points is obtained using the three-dimensional coordinates of the three points. If the coordinates of the three points are (x _A , y _A , z _A ) (x _B , y _B , z _B ) (x _C , y _C , z _C ), the coefficients a, b, c, and d are as follows.
_{a = (y B -y A)} (z C -z A) - (y C -y A) (z B -z A)
_{b = (x C -x A)} (z B -z A) - (x B -x A) (z C -z A)
_{c = (x B -x A)} (y C -y A) - (x C -x A) (y B -y A)
d = − (ax _A + by _A + cz _A )

  In the next ST8, it is determined whether or not each point satisfies the condition Z by using the coordinates of all the representative points other than the three points. Here, when all the representative points satisfy the condition Z, it is determined that the second condition is satisfied.

  If it is determined in ST6 that the three points do not satisfy the first condition, or if it is determined that the first condition is satisfied but the second condition is not satisfied in ST8, the process returns to ST3 via ST9 and returns to three points. Redo the selection. And the process of ST4-8 is similarly performed about three points concerning a new combination.

If it is determined that the first and second conditions are satisfied for the three points related to the predetermined combination, the process proceeds to ST11, and the distance D of each representative point to the virtual plane related to the combination is calculated. When the coordinates of the representative point are (x _i , y _i , z _i ), the calculation formula for the distance D is as shown in the formula (3).

  In ST12, the distance D for each representative point obtained in ST11 is compared with a predetermined threshold value to determine whether or not each terminal is lifted. In ST13, the determination result is output from the output unit 8, and then the process is terminated.

  When all the combinations of representative points are selected, if ST6 or ST8 is “NO”, ST9 is “YES” and the process proceeds to ST10, and an error signal is output from the output unit 8. Output. This error processing is considered to be executed when there is an obvious defect such as poor support of the component, large floating at the terminal, or bending of the terminal and tilting of the component. It is done.

It is a block diagram which shows the electric constitution of the inspection apparatus concerning this invention. It is explanatory drawing which shows the example of selection of the representative point in a terminal. It is explanatory drawing which shows the relationship between a three-dimensional coordinate system and components. It is explanatory drawing which shows the relationship between the projection point and center point of three representative points. It is a flowchart which shows the process sequence concerning a test | inspection.

Explanation of symbols

1a, 1b Camera 4 CPU
11 Lead terminal 13 Ball terminal 14 Package

Claims (4)

A method of inspecting whether or not each terminal is lifted, with an electronic component having a large number of terminals arranged on the side or bottom of the package as an inspection target,
A first step of measuring the three-dimensional coordinates of the representative point for each terminal;
Using the three-dimensional coordinates of each representative point obtained in the first step, a triangular plane capable of projecting the central part of the component is formed from these representative points, and this triangular plane is more than the other representative points. A second step of extracting three representative points located below;
Calculating the distance between the triangular planes of the three representative points extracted in the second step and other representative points, and determining whether or not each terminal is lifted based on the calculation result; A method of inspecting a terminal of an electronic component, characterized in that it is executed. The method of claim 1, wherein
In the second step, three representative points are combined in order, three representative points relating to the combination are projected onto a virtual horizontal plane, and the component center can be projected into a triangle formed by the projected points. An electronic component terminal inspection method for determining whether or not a central part of a component can be projected on a triangular plane covering the three representative points by determining whether or not the three representative points are present. The method according to claim 1 or 2, wherein
In the second step, the electronic component terminal inspection method uses an average value of three-dimensional coordinates of all representative points as the position data of the component center. A device for inspecting whether or not each terminal is lifted, with an electronic component having a large number of terminals arranged on the side or bottom of the package as an inspection target,
3D coordinate acquisition means for measuring 3D coordinates of representative points of each terminal or inputting the measurement results;
Using the three-dimensional coordinates of each representative point obtained by the three-dimensional coordinate acquisition means, a triangle plane capable of projecting the center part of the component is formed from these representative points, and this triangle plane is another representative point. Extraction means for extracting three representative points located below
Distance measuring means for calculating a distance between a plane including the three representative points extracted by the extracting means and other representative points;
A determination unit that compares the distance calculated for each representative point by the distance measurement unit with a predetermined threshold value to determine whether each terminal is lifted,
An inspection apparatus comprising: output means for outputting the determination result of the determination means as the inspection result.

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