PCB virtual welding is a common line fault. One is in the process of circuit board production, due to improper production process, the other is electrical appliances through long-term use, due to some of the more serious heat parts, the solder joint at the welding foot is very prone to aging peeling phenomenon caused.
In PCB virtual welding detection and identification, mainly divided into routine detection and X-ray inspection machine detection. Conventional detection is generally based on external forces, with the naked eye detection, and X-ray detection is the use of X-ray penetration principle for nondestructive testing, the PCB printed circuit board internal structure through the formation of images.
The visual inspection of PCB virtual welding is to apply certain external force to the welded components, observe whether loose, no loose is judged as no virtual welding. In addition, it can be judged by directly observing the solder joints. If the solder is virtually welded, it can be seen that the edge and surface of the solder cannot be well matched. If it is not easy to judge, the problem can be avoided by welding again. To avoid false welding, first of all to clean up and tin each welding surface. It is better not to use solder paste when cleaning, because it contains acid, there may be corrosion element pins, resulting in virtual welding. After removing the oxide, you can tin the welding surface first, and then welding is easy and not prone to false welding.
For the optical inspection machine in the circuit board between the component foot and solder welding, you can use the starter press solder welding edge to highlight the component foot, to check whether virtual welding. If the component foot can move, it is virtual welding. If there is a virtual welding between the solder joint and the pad, the looseness will occur when the circuit board element is pressed. In addition, there are two fundamental conditions for virtual welding in circuit boards:
1. The first condition: seam. In this case, we must use a multimeter to determine whether it is on, which is not an easy task. If the impact of external forces occurs, desoldering is likely to occur owing to the small welding surface, and this is much easier to be found.
2. The second condition: no welding. This means that solder and solder joints are not soldered, but simply touched. In this situation, the first thing we need to do is to see whether the welding surface is clean and whether the multimeter is open. However, at this time, the multimeter cannot accurately detect the virtual welding.
There is a core component in the X-ray inspection machine, namely the X-ray tube. It uses X-ray to observe the internal of the detection body through the workpiece. The X-ray inspection machine uses the X-ray tube as the ray source to penetrate the PCB printed circuit board by X-ray. The X-ray high-definition flat panel detector is used to compose the image, and then the X-ray system software is used for imaging display, which can be expanded for technicians to view the PCB virtual welding orientation. It is relatively safe to use X-ray inspection machine for PCB virtual welding detection, because X-ray inspection machine can still detect other PCB defects, such as PCB bubbles, leakage welding and a series of invisible defects.