JPH0715127A - Inspection method of detecting foreign material to soldering printed circuit board - Google Patents

Abstract

PURPOSE:To judge at a glance whether or not a generated solder ball is to be picked out and removed by forming an index that is comparable instinctively with the tolerance of diameter of a solder ball and comparing the generated solder ball with it. CONSTITUTION:Around leads 2 of an electronic component 1 or pads 4 of a printed circuit board 3 with which electrodes are soldered, an index pattern 7 that can be compared instinctively with the tolerance of diameter of a foreign material (a solder ball) 6 that is generated during soldering formed by a similar method of forming other wiring patterns. Comparing the generated solder ball 6 with the index pattern 7, acceptability for the tolerance of diameter of the solder ball 6 is judged. For example, a disc type index pattern 7 of a diameter d similar to the tolerance of the diameter of the solder ball is provided so that the solder ball 6 can be judged whether larger or smaller than it easily and instinctively in a field of vision of a microscope visually.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a foreign substance (solder ball) generated in soldering a printed circuit board and an electronic component.
It is related to the improvement of the efficiency of inspection. When mounting and soldering electronic components such as surface-mount type ICs and chip components on the printed circuit board, the melted solder is released into a ball shape depending on the soldering conditions and adheres to the flux at an indefinite place on the printed circuit board. To do. Since this solder ball has a limit to the flux adhesion depending on the size,
It is necessary to remove it beforehand because it may be released from the printed circuit board and cause electromechanical damage.
The allowable diameter of the solder ball to be removed is generally set in the standard or the like. The inspection is performed with a microscope, but it was necessary to separately measure whether the solder ball diameter found through the microscope was larger or smaller than the set tolerance. Therefore, in the present invention, an index pattern corresponding to the allowable diameter of the solder ball is provided on the printed circuit board for each field of view of the microscope, and the diameter of the generated solder ball is compared with the index pattern to remove the solder ball. Whether or not it can be easily determined.

[0002]

2. Description of the Related Art FIG. 2 shows an SOP (S
FIG. 3 is a perspective view showing a case where the mall outline package) 1 is mounted on the printed circuit board 3. The solder balls 6 generated by soldering are visually inspected by a microscope. The allowable value of the diameter of the generated solder ball is generally determined by standards and the like. However,
Whether or not the diameter of the solder ball found through a microscope was within the allowable value could not be determined without separate measurement because the index pattern 7 of the present invention was not available in the past.
This measurement was performed using a scale built into the lens of the microscope or a measuring instrument such as a tool microscope separately. For this reason, it takes a lot of time for measurement, which is a bottleneck from the viewpoint of productivity improvement. This was exactly the same in electronic parts other than the above-mentioned SOP.

[0003]

The above-mentioned drawbacks of the prior art are caused by the additional work of measurement for determining the size of the solder ball. Therefore, if there is a standard solder ball in the same field of view of the microscope that serves as a reference for judgment, the human eye has excellent contrasting power, so it is possible to easily and intuitively judge pass / fail by comparing with this. The present invention applies this principle. That is, an index pattern having the same size as the allowable limit value of the solder hole is previously formed on the printed circuit board, and the diameter of the solder ball to be inspected is compared with this index pattern to remove the solder ball to be removed. It is possible to immediately determine whether or not

[0004]

[Means for Solving Problems] As described above, in order to solve this problem, it is important that the size of the index pattern is correct and that the index pattern and the solder ball to be inspected are visible on the same screen of the microscope. is there. For this reason, it is necessary to form the index pattern by the same method as the wiring pattern when a printed circuit board is manufactured, that is, by etching the copper foil by a photographic method, and to dispose it for each field of view of the microscope of the board to be inspected.

[0005]

According to the above, the sizes of the solder balls to be inspected and the index patterns can be easily and intuitively compared for each visual field. Therefore, it can be reasonably determined in a short time whether or not the solder ball should be removed from the printed board.

[0006]

1 to 4 show an embodiment of the present invention. That is, FIG. 1 shows the SOP1 as an example of the electronic component of FIG.
3 is a plan view showing a part of a perspective view showing a part mounted on the printed circuit board 3. FIG. The pad 4 of the printed circuit board 3, the lead 2 of the SOP 1, and the solder 5 are soldered. Now, if there is a solder ball 6 that has been separated from the solder 5, the allowable value of the outer shape of the solder ball φ in the field of view of the microscope.
If the index pattern 7 of d is visible, it can be easily and intuitively visually determined whether the solder ball is larger or smaller than this. The electronic parts are not limited to the SOP of this example, but QFP (Quart. Flat Package)
Needless to say, the same can be applied to other electronic components such as chip components. Further, FIG. 3 shows an example when these are arranged on a printed circuit board. That is, 1
1 is a QFP, 12 is its lead, and 8 is a chip component. (The pattern of the printed circuit board is omitted because the figure becomes complicated.) In this way, the field of view of the microscope is provided near the lead 2 of the SOP 1, the lead 12 of the QFP 11, or the electrode 9 of the chip component 8. If the index patterns 7 are appropriately arranged together, the solder balls can be inspected extremely efficiently.

Further, the index pattern may be of any type as long as the allowable diameter value d of the solder ball is known at a glance. FIG. 4 shows an example thereof. That is, 7 is an index pattern in which the copper foil of the printed circuit board is left in a disk shape having a diameter d equivalent to the allowable solder ball diameter, which has been described with reference to FIGS.
Is a square, 72 is a space in which the vertices of two triangles facing each other are d, 73 is a linear index pattern having a length of d, and 74 is a rectangle in which the diameter φd is omitted. Although the usage and the effect are the same, if it says forcibly, 7 is similar to the shape of the solder ball, so it is easy to use.

[0008]

As described above, according to the present invention, it is possible to easily inspect a solder ball generated when soldering an electronic component to a printed circuit board and to reasonably judge the standard. it can.

[Brief description of drawings]

1 is a plan view showing a part of a perspective view showing a SOP 1 mounted on a printed circuit board 3 as an example of the electronic component shown in FIG.

FIG. 2 is a perspective view showing a SOP 1 mounted on a printed circuit board 3 as an example of an electronic component.

FIG. 3 is an index when electronic components are not limited to SOP as in the example of FIGS. 1 and 2, but are similarly applied to other electronic components such as QFP and chip components, and are arranged in a composite manner on a printed circuit board. The top view which shows an example of arrangement | positioning of the pattern 7.

FIG. 4 is a plan view showing types of index patterns.

[Explanation of symbols]

 1 SOP 2 SOP lead 3 printed board 4 pad 5 solder 6 solder ball 7 index pattern 8 chip part 9 chip part electrode 11 QFP 12 QFP lead 71 to 74 It is an example other than index pattern 7.

Claims (2)

[Claims] 1. An index pattern, which can be intuitively compared with a diameter allowable value of a foreign substance (solder ball) generated during soldering, is provided near a pad of a printed circuit board to which a lead / electrode of an electronic component is soldered. Foreign matter to be soldered on a printed circuit board, characterized in that it is formed by a method similar to that of the wiring pattern, and whether the generated solder balls are compared with this index pattern is used to judge whether the diameter of the solder balls is acceptable or not. Inspection method. 2. A disk-shaped index pattern having a diameter equivalent to a solder ball diameter allowable value is used.
Foreign matter inspection method described in.