JPH06331327A - Inspection of cream solder printing state - Google Patents

Abstract

PURPOSE:To judge the bridge inferiority at the time of the printing of cream solder from the continuity of a bridged land. CONSTITUTION:The bridge inferiority at the time of the printing of solder is inspected by performing an image input processing process receiving an image from an imaging means to store the same in an image memory means, a contour tracking process 1 tracking the contour of solder with respect to the stored image, a process 2 calculating the distance (land) moved at the time of the process 1, a process 3 judging a continuous bridge by the process 2 and a process 4 moving to a next inspection land. By this constitution, this inspection method can correspond to such a phenomenon that bonding inferiority becomes hard to generate at the time of the printing of cream solder by one bridge but becomes easy to generate by a continuous bridge developed in a process using a nitrogen reflow furnace and can achieve the lowering of a line-out ratio in the inspection at the time of the printing of solder.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cream solder printing state inspection method for inspecting the print state of cream solder printed by a cream solder printing apparatus in the field of surface mounting.

[0002]

2. Description of the Related Art In recent years, a mounting inspection apparatus has been introduced while a high density mounting of a printed circuit board is progressing and it becomes difficult to inspect and correct manually. In particular, since a bridging defect in the cream solder printing process is likely to result in a bonding defect as it is, a cream solder printing inspection device equipped with an inspection algorithm for determining the bridging defect has been developed.

An example of the conventional bridging failure determination algorithm described above will be described below with reference to the drawings.

FIG. 7 is a flow chart of conventional processing, and FIG. 8 is an image diagram thereof. In FIG. 7, 26 is a measurement window installation process, 27 is a contour tracking process process, 28 is a bridge width detection process process, and 29 is a bridge defect determination process process. 8th
In the figure, 30 is an inspection start land, 31 is a measurement window, 3
2 is a contour tracing start point, 33 is an intersection between the solder contour and the measurement window 31, 34 is a margin width from the intersection 31, 35 is a lead pitch width, 36 is a bridge measurement window, and 37 is a minimum bridge width.

In the measurement window installation processing step 26, the measurement window 31 is installed on the inspection start land 30. After that, in the contour tracing processing step, the measurement window 3 is sequentially arranged from the contour tracing starting point 32.
An intersection 33 with the measurement window 31 is obtained by tracing the outline of the solder in the sample 1. If the intersection 33 is not detected, it is regarded as normal. If the intersection 31 is detected, a margin width 34 is provided in the bridge width detection processing step, and a lead pitch width 35
The bridge measurement window 36 is installed, and the minimum bridge width 37 in the window is measured. After that, the minimum bridge width 35 measured in the bridge failure determination processing step is compared with the bridge determination width, that is,

[0006]

[Equation 1]

In the case of "7", the bridge is defective.

[0008]

However, in the above-mentioned configuration, since bridge determination is made for each land, it is in a process using a recent nitrogen reflow furnace.
A bridge of one land often breaks in the reflow furnace and becomes normal, and if the lands are continuously bridged, all the bridges will not be broken and some land will become defective even after reflow. However, there is a problem in that it is difficult to match a bridge defect during printing and a bridge defect after reflow.

[0009]

In order to solve the above problems, there is provided a cream solder printing inspection method to which a function of judging a bridging defect judgment from the continuity of lands bridging is added. The purpose is to

[0010]

According to the present invention, with the above-described structure, particularly in a process using a nitrogen reflow furnace, a bridge failure of only one land at the time of solder printing does not cause a failure after reflow, and a failure of a continuous land causes a failure after reflow. It becomes possible to deal with the phenomenon that it is easy to become.

[0011]

【Example】

(Embodiment 1) Hereinafter, a bridging defect determination algorithm during cream solder printing according to an embodiment of the present invention will be described.

The inventors of the present invention have investigated the correlation between defective printing and defective bonding in the mounting process using a nitrogen reflow furnace, and found the following.

In the case of a bridge at the time of printing, if it is only one land, it often breaks during reflow and becomes a non-defective product, and if it is a bridge of continuous lands (5 to 10 lands), it all breaks during reflow. However, one of them often causes a defective joint.

Therefore, an inspection algorithm having a function of judging the bridge judgment at the time of printing from its continuity so that such a phenomenon can be inspected will be described with reference to the drawings.

FIG. 1 is a flow chart of processing in the first embodiment of the present invention, and FIG. 2 is an image diagram thereof. In FIG. 1, 1 is a contour tracking processing step, 2 is a moving distance land calculation processing step, 3 is a continuous bridge determination processing step, and 4 is a next inspection land moving processing step. In FIG. 2, 5 is an inspection start land, 6 is a contour tracking start point 7, 8 is an XY coordinate value and a Y coordinate where the Y coordinate has the maximum value among the coordinate values detected in the contour tracking processing step 1, respectively. Is the minimum X
Y coordinate value, 9 is the land pitch width, 10 is the next inspection land, 11 is the previously announced inspection start land 5
Is the center coordinate of 12 and the center coordinate of the next inspection land is known in advance.

First, in the contour tracing processing step 1, the solder contour tracing starting point 6 on an arbitrary inspection start land 5 is sequentially performed in the input image until the solder contour tracing is returned to the starting point 6. At this time, the XY coordinate value 7 (Xa, Xmax) at which the Y coordinate takes the maximum value and the XY coordinate value 8 (Xb, Ymin) at which the Y coordinate takes the minimum value are simultaneously obtained in the contour tracing points. Next, in the movement distance (land) calculation processing step, the XY coordinates 7 and 8 and the land pitch width 9 were used.

[0017]

[Equation 2]

The number of land solders traced is calculated by the following. Then, in the continuous bridge determination processing step 3, the number N of continuous bridge failure determination lands and the value of (Equation 1) are compared.

[0019]

[Equation 3]

In the case of (2), it is considered as a continuous bridge failure. If all lands have not been inspected, in the next inspection land movement processing step 4, the center position of the inspection start land is moved to the next inspection land center position where the value of (Equation 1) is added, and contour tracing processing is performed. The same process is performed from step 1.

(Embodiment 2) FIG. 3 is a flow chart of processing in a second embodiment of the present invention, and FIG. 4 is an image diagram thereof.

In FIG. 3, 13 is a measurement window setting process,
Reference numeral 14 is a bridge width detection process. In FIG. 4, 1
Reference numeral 5 is an inspection start land, 16 is a measurement window, and 16 is a bridge measurement window.

First, in the measurement window installation processing step 13,
The first embodiment is applied only to the land where the bridge failure has been detected by the conventional method of detecting the bridge failure by installing the bridge measurement window 16 in the bridge width detection processing step 14 with respect to the inspection start land 15.

(Embodiment 3) FIG. 5 is a flow chart of processing in a third embodiment of the present invention, and FIG. 6 is an image diagram thereof. In FIG. 5, 18 is a measurement window installation processing step, and 19
Is a contour tracking processing step, 20 is a bridge width and area detection processing step, 21 is a data rearrangement processing step by land number by read direction, and 22 is a continuous bridge determination processing step.
In FIG. 6, 23 is an inspection start land, 24 is a measurement window, and 25 is a bridge measurement window.

As in the conventional example, by the measurement window installation step 18,
The measurement window 24 is installed, and after the contour tracking processing step 19, the bridge measurement window 25 is installed. Then, in the bridge width / area detection processing step 20, the minimum bridge width d and the solder area measurement S in the bridge measurement window 25 are performed. When all the lands have been subjected to the above processing, data rearrangement is performed in the data rearrangement processing step described above by land number for each read direction. After that, in the continuous bridge determination processing step, the total number N of continuous lands and the bridge width of the continuous lands

[0026]

[Outer 1]

Total area

[0028]

[Outside 2]

Is obtained and compared with each criterion value, for example,

[0030]

[Equation 4]

If so, it is determined as a continuous bridge failure.

[0032]

As described above, according to the present invention, by adding the function of judging the bridge failure at the time of cream solder printing from the continuity thereof, it is possible to perform the one-time process found in the process using the nitrogen reflow furnace. Although it is difficult for a bridge to have a defective joint, it is possible to deal with a phenomenon that a continuous number of bridges are likely to cause a defective joint, and the line-out rate in the print inspection can be reduced.

[Brief description of drawings]

FIG. 1 is a process flow chart of a first embodiment of the present invention.

FIG. 2 is a plan view of a land showing a processing image of the first embodiment of the present invention.

FIG. 3 is a processing flowchart of a second embodiment of the present invention.

FIG. 4 is a plan view of a land showing a processing image of the same.

FIG. 5 is a processing flowchart of a third embodiment of the present invention.

FIG. 6 is a plan view of a land showing a processing image of the same.

FIG. 7 is a processing flow chart of a conventional example.

FIG. 8 is a plan view of a land showing a processing image of the same.

[Explanation of symbols]

1 contour tracking processing step 2 movement distance (land) calculation processing step 3 continuous bridge determination processing step 4th inspection land movement processing step 5 inspection start land 6 contour tracking start point 7 XY of solder contour part where Y coordinate value is maximum Coordinates 8 XY coordinates of the solder contour part where the Y coordinate value is the minimum value 9 Land pitch width 10th inspection land 11 Central coordinates of inspection start land 12 Central coordinates of secondary inspection land 13 Measurement window installation processing 14 Bridge width detection processing 15 Inspection Start land 16 Measurement window 17 Bridge width measurement window 18 Measurement window installation processing step 19 Contour tracking processing step 20 Bridge width, area detection processing step 21 Data rearrangement processing step by lead direction and land number 22 Continuous bridge determination processing step 23 Inspection start land 24 Measuring window 25 Bridge measuring window 26 Measuring window installation process 27 Contouring Step 29 bridging determination process 30 inspection start land 31 measuring window 32 contour intersection 34 margin width 35 land pitch of the measuring window tracking start point 33 solder contour 36 bridge measuring window 37 minimum bridge width

Claims (3)

[Claims] 1. An image input processing step in which an image is input by an image pickup means and an image is stored in an image storage means for an inspection of continuous continuous bridge defects over multiple lands that are likely to occur in electronic components with leads during cream solder printing. , A first step of sequentially tracing the contour of the cream solder, a second step of calculating a moving distance in the first step, and a third step of judging a continuous bridge failure by comparing the result of the second step with a judgment value.
A method of inspecting a cream solder printing state, which comprises performing a step and a fourth step of moving to a next inspection object based on a result of the second step. 2. A fifth step of installing a measurement window before the first step, a sixth step of sequentially tracing the contour of the cream solder in the measurement window installed in the fifth step, and a sixth step of the sixth step. From the results, the seventh step of installing the bridge measurement window and measuring the bridge width, and the eighth step of judging the single land bridge failure by comparing the result of the seventh step with the judgment value are characterized. Item 3. A method for inspecting a printed state of cream solder according to Item 1. 3. A first step of installing a measurement window after the processing step of image input by the image pickup means and image storage for storing the image in the image storage means for the inspection of a continuous bridge defect at the time of cream solder printing. A second step of sequentially tracing the contour of the cream solder in the measurement window installed in the step, and a second step
From the result of the process, install the bridge measurement window and set the bridge width,
A third step of measuring the solder area in the bridge measurement window, and a third step
It is the result of the 4th process which determines a single land bridge failure by comparing the result of a process, and a judgment value, the 5th process which rearranges the result of the 4th process by a land number, and the result of the 5th process. It is characterized by performing a sixth step of judging continuous bridges by comparing the number of consecutive land numbers, the sum of bridge widths in the consecutive lands, and the sum of areas in the bridge measurement window with respective judgment values. The method of inspecting the printed state of cream solder.