JP2844838B2 - Center detection method for electronic components - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a detection method for determining the center of an electronic component when an electronic component having two or more leads on one side is mounted on a substrate.

2. Description of the Related Art Conventionally, when mounting an electronic component having two or more leads on one side, for example, a QFP or SOP, on a substrate, the electronic component is mounted so that a displacement between the substrate and the land does not occur after the mounting of the electronic component. In many cases, the center position of the electronic component is mechanically determined before bonding to the substrate. Recently, instead of the mechanical centering method, the number of methods of performing centering in image processing using a recognition device is increasing.

Problems to be Solved by the Invention In the method of finding the center of these electronic components, that is, the centering method, in the case of a mechanical centering, the system is simple and the control is such that the centering claw is moved. , Although it is possible to easily construct a system for all controls, on the other hand, mechanically grasping the electronic components and forcibly centering them, the leads of the electronic components may be bent, and the positional accuracy may be large depending on the quality of the mechanism. It has the drawback of being influenced by.

Also, in the method of performing centering by image processing using a recognition device, there is no mechanical damage to electronic components due to the image processing, and since the position can be determined purely electronically, the position accuracy is extremely high. It has the advantage of being high. However, in the conventional image processing method, the positions of the leads of the electronic component are measured one by one,
The center of the electronic component is calculated using the least squares method or the like from the positions of all the leads, or the center of a circumscribed rectangle formed by the straight lines is obtained by connecting the positions of the leads on each side with an approximate straight line. The former method has a problem that the memory capacity increases and the calculation time increases, and the latter method has a problem that the center position accuracy is poor.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method that solves the above-described conventional problems and has the advantage of the centering method in image processing while reducing the memory and the calculation time while increasing the position accuracy. What you want to do.

Means for Solving the Problems According to the present invention, when an electronic component having two or more leads on one side is mounted on a substrate, the number of leads and lead pitch data are converted to a theoretical pitch based on the specification of the electronic component. Register as a sequence and calculate the center value, measure all the lead positions of the electronic components to be mounted, compare the lead position of the theoretical pitch sequence with the measured lead position, calculate the respective difference, and calculate the difference Is determined so that the maximum amount of the minimum is minimized, and the center value of the theoretical pitch sequence is taken into account by taking the amount of the shift into consideration, and the center after the shift is determined. The intersection between the centers after the transition is the center of parts. Further, a measurement pitch sequence is created for each side based on the measurement data of all the lead positions of the electronic components to be mounted, and the difference between the theoretical pitch sequence and the measurement pitch sequence at the point of the lead at the end of the lead arrangement is set to zero. The difference between the superpositions is calculated, and the amount of displacement is determined so that the maximum amount of the difference is minimized.

As described above, according to the present invention, first, a fixed sequence having a lead pitch as a width (this sequence is called a theoretical pitch sequence) is created and registered in advance from the lead pitch data of the electronic component and the number of leads on each side. At the same time, the center position is calculated.

Next, the lead position of the electronic component is measured, and a sequence of lead positions is created for each side (this sequence is called a measurement pitch sequence).

Next, a specific point is determined for the above two sequences, the difference between the values at this point is set to 0, and the respective differences are calculated. Based on the sequence obtained from the lead pitch data, that is, the theoretical pitch sequence, this sequence and the read sequence are read. Is extracted, that is, the maximum difference on the plus side and the maximum difference on the minus side of the sequence of measured pitches are extracted. When the difference between the plus side and the minus side is added and halved, the shift amount of the center position is defined as the shift amount of the center position, and the shift amount is added to the center value of the theoretical pitch sequence to obtain the center after the shift. It is close to the center, and the deviation from the measured lead is minimized.

Since the center of the theoretical pitch sequence can be obtained in advance by calculation, comparison with the measured pitch sequence, plus and minus
If only the negative maximum value is obtained, the displacement can be easily calculated, and the center of each side of the electronic component can be obtained.

The center of the electronic component may be an intersection formed by connecting the center positions of the sides obtained above with the center positions of the opposing sides.

According to the above-described configuration, since the center of the electronic component is determined using the data itself of the specification of the electronic component, the input of data becomes easy, and even if there is variation in the lead pitch of the electronic component actually measured. There is no large error because each average center is determined.

In addition, it can be said that the centering accuracy is further improved by using this method and the method of eliminating the electronic components exceeding the allowable value by using the pitch error allowable value for the lead pitch test in parallel.

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 2 shows that after the QFP is imaged,
This is an example in which measurement was performed with reference to FIG.

Next, FIG. 3 shows the theoretical pitch sequence and the measured pitch sequence of the lead position measured above superimposed on the basis of the lead a. At this time, the theoretical pitch sequence and the measured pitch sequence are compared to determine whether there is a difference. In the example of FIG. 3, it can be seen that a difference of “ΔM” occurs in the lead b and a difference of “ΔP” occurs in the lead d. Difference “ΔM” generated here
Since the position where “ΔP” becomes minimum is considered to be the average center of the lead, ΔC is added to the center value of the theoretical pitch sequence.

As shown in FIG. 4, the center value of the theoretical pitch sequence is ΔC
The added one is the center C ', which is the center of this side. These are repeated on four sides, and the intersection of the line connecting the four opposite C's is defined as the center of the electronic component.

1 (a) and 1 (b) are flowcharts of the above operation.

The flow of the operation will be described based on the flowcharts of FIGS. 1 (a) and 1 (b).

First, basic data of an electronic component is inputted in steps 1 and 2, and in step 3, a theoretical pitch sequence and a center value C are calculated. Next, the electronic component to be measured is imaged, the lead position is detected in step 4, and the measured pitch sequence is calculated from the lead position in step 5. In step 6, the representative lead is determined. In the present embodiment, the lead at the end of the lead arrangement is used. In step 7, the representative read point is compared with the theoretical pitch sequence obtained in steps 3 and 5 and the measured pitch sequence is compared. In steps 8 and 9, the difference is calculated, and in step 10, the center shift amount is calculated. In step 11, the center value of the side is obtained by adding the shift amount (shift amount) to the center value of the shifted theoretical pitch sequence. In step 12, it is checked whether all the above operations have been performed, and in step 13, the center of the electronic component is calculated.

Effect of the Invention Since the present invention has the above-described configuration, the center of the electronic component can be obtained with a small memory and can be easily calculated, and the accuracy is smaller than that obtained when the average value of all the lead positions is obtained. It has the effect of being comparable.

[Brief description of the drawings]

FIG. 1 is a flowchart of a component mounting and positioning method shown as one embodiment of the present invention, FIG. 2 is an explanatory diagram of a lead position measurement of an electronic component, FIG. 3 is a comparison diagram of a theoretical pitch sequence and a measured pitch sequence, FIG. FIG. 4 is an explanatory diagram when a difference is added to the center value of the theoretical pitch.

Claims (2)

(57) [Claims] When an electronic component having two or more leads on one side is bonded to a substrate, the number of leads and lead pitch data are registered as a theoretical pitch sequence based on the specification of the electronic component and a central value is registered. Is calculated, all the lead positions of the electronic components to be mounted are measured, the lead positions of the theoretical pitch sequence are compared with the measured lead positions, and the respective differences are calculated, and the maximum amount of this difference is minimized. In this way, the amount of displacement is obtained, and the center value of the theoretical pitch sequence is added to the amount of the displacement to obtain the center after the change, and the center after this change is obtained on each side, and the centers of the opposing sides after the change are determined. A method of detecting the center of an electronic component with the connected intersection as the center of the component. 2. A measurement pitch sequence is created for each side based on measurement data of all lead positions of an electronic component to be mounted, and a difference between the theoretical pitch sequence and the measurement pitch sequence at a value of a lead point at an end of a row of leads is arranged. 2. The method for detecting the center of an electronic component according to claim 1, wherein a difference between the superimposed positions is calculated by setting 零 to zero, and a displacement amount is determined so as to minimize the maximum amount of the difference.