Soldering part of PCB external inspection

Soldering part of PCB external inspection

When inspecting the soldering part of the PCB board, we can use the following four methods.

1. PCB triangulation method (optical cutting method, optical structuring method)

The method of checking the three-dimensional shape is generally the triangulation method. A device for detecting the cross-sectional shape of the solder lead part using triangulation has been developed. However, because the triangulation method observes from different directions from which light is incident, this method is essentially the most suitable when the object surface is light diffusive. This method is not suitable when the solder surface is close to the mirror surface condition.

2 Light reflection distribution measurement method

The light reflection distribution measurement method is a representative inspection method using a commercially available welded joint inspection device. Light is incident from an oblique direction, and a TV camera is set up to detect it. At this time, in order to know the angle of the solder surface, it is necessary to know the angle information of the irradiated light, turn off the lights of various angles, and obtain the angle information according to the color of each lamp. Instead, the beam is irradiated from above, the angular distribution of the light reflected by the solder surface is measured, and the tilt of the solder surface is checked.

The light reflection distribution measurement method of this device can easily detect the angle of the solder surface, and the device is inexpensive. Its disadvantages are: (1) Because it is necessary to use large-angle illumination, the shadow of the components is affected by the high density, and sometimes it is difficult to detect; (2) Although the angle of the solder surface is known, the absolute height cannot be known if the integral , The height can be calculated, but it may be unstable); (3) The ratio 45 cannot be detected. Steeper surface.

3Method of inspecting images using multiple cameras with varying angles

The inspection device has multiple (5) cameras with varying angles and illumination composed of multiple LEDs. Usually multiple images are used and the inspection is performed under conditions close to the visual inspection, which can improve reliability.

4 focus detection method

The methods in Section 1 to Section 3 are all detection methods that require a wide solid angle. For high-density mounting substrates, this is not a desired condition. For example, the multi-segment focus method, because it can directly detect the height of the solder surface, it is a high-precision detection method. 10 focal plane detectors are installed, and the position of the solder surface is detected by finding the focal plane obtained by the maximum output. A fine laser beam is used to irradiate the object, and 10 focal position detectors with pinholes are staggered in the z direction to successfully check the installation of 0.3mm pitch lead wires.