Detection methods and skills of faulty soldering of electronic components

Date：2022-02-14 18:07:00Views：1784

The false soldering of components is that there are only a small number of tin welding posts at the solder joint, resulting in poor contact, on and off. Both false welding and false welding refer to that the surface of the weldment is not fully coated with tin, and the weldment is not fixed by tin. It is caused by the unclean surface of the weldment, too little flux and too short welding time.

False soldering is mainly caused by oxides and dirt on the surface of the metal to be welded. Its solder joints become the connection state with contact resistance, resulting in abnormal operation of the circuit, unstable phenomena of good and bad, increased noise and no regularity, which brings major hidden dangers to the debugging, use and maintenance of the circuit. In addition, there are also some false solder joints that remain in good contact for a long time after the circuit starts to work, so it is not easy to find. However, under the selection of environmental conditions such as temperature, humidity and vibration, the contact surface is gradually oxidized, and the contact slowly becomes incomplete. The contact resistance of the false solder joint will cause local heating, and the local temperature rise will further worsen the incomplete contact solder joint, and finally even make the solder joint fall off, and the circuit can not work normally. This process can last for one or two years.

The detection methods and skills of faulty soldering of electronic components are introduced as follows:

1. Visual inspection method

Generally, first look for heating components, such as power tubes, high-current diodes, high-power resistors, integrated circuits, etc. these components are prone to false soldering due to heating, which can be seen directly in serious cases, and can be viewed with a magnifying glass in slight cases. Generally, the newly welded pins are very smooth. When the edge is affected, it will become rough and dull due to continuous extrusion and stretching, and gray circles will appear around the solder joint. When viewed with a high-power magnifying glass, you can see the small crack group in the shape of crack, and in serious cases, it will form a ring crack, that is, desoldering. Therefore, even if there is no desoldering in the place with circular black circle, it will be a hidden danger in the future. Large area repair welding of integrated circuits and heating element pins is one of the solutions.

2. Current detection method

Check whether the current setting complies with the process regulations and whether the current setting does not increase accordingly when the product load changes, resulting in poor welding due to insufficient current during welding.

3. Shaking method

It is to shake the low-voltage components one by one with your hand or camera to feel whether the components are loose. This is mainly to shake the larger components. In addition, before using this method, the fault range should be compressed. Determine the approximate range of the fault, otherwise it is unrealistic to face the shaking of many components one by one.

4. Vibration method

When the phenomenon of false soldering is encountered, it can be confirmed by knocking. Gently tap the circuit board with a screwdriver to determine the position of the false soldering point. However, when the percussion method is adopted, the personal safety and the safety of the equipment shall be ensured to avoid expanding the fault range.

5. Repair welding method

Repair welding is a maintenance method when the fault can not be found after careful inspection, that is, welding the components within the fault range one by one. In this way, although no real fault point is found, the purpose of maintenance can be achieved.

False soldering is a major hidden danger of the circuit. It is easy for users to cause faults due to poor conductivity after using for a period of time, and then cause high repair rate and increase production cost. Therefore, the problem of faulty welding should be found in time to reduce losses. According to statistics, nearly half of the electronic machine product failures are caused by poor welding. However, it is not easy to find the faulty solder joint from an electronic device with thousands of solder joints. Pay special attention to manual welding during work.