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Solutions and precautions to problem of PCBA manual welding



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By : Lily Hathaway    19 or more times read
Submitted 2019-10-15 07:55:21
Things to be aware of when performing manual PCBA soldering:

1. It must be operated by an electrostatic ring. The human body can generate static electricity of more than 10,000 volts, and ICs above 300V will be damaged. Therefore, the static electricity of the human body needs to be discharged through the ground wire.

2. When wearing gloves or finger sleeve operation, bare hands can not directly contact the parts of the machine board and gold fingers.

3. When welding, correct welding temperature, welding angle, welding sequence, and proper welding time should be noticed.

4. Take the PCB correctly: When taking the PCB, hold the edge of the PCB correctly. Pcba processing SMT and DIP are ways to integrate parts on the PCB. The main difference is that SMT does not need to drill holes in the PCB. In DIP, the PIN pin of the part needs to be inserted into the drilled hole. Do not touch the components on the board.

5.Try to use low temperature welding: High temperature welding will accelerate the oxidation of the iron head, reducing the life of the iron head. If the iron head temperature exceeds 470 °C. Its oxidation rate is twice that of 380 °C.

6. Do not apply too much pressure to the welding: do not apply too much pressure when welding, otherwise the iron head will be damaged and deformed. As long as the iron head is in full contact with the solder joint, heat can be transferred. Different iron heads can be selected according to the size of the solder joints, which can also make the iron heads have better heat transfer.

7. Do not tap or shake the iron nozzle during welding: tapping or swinging the iron nozzle will damage the heating iron core and the splashing tin beads, shortening the service life of the heating iron core. If the tin beads are splashed on the PCBA, a short circuit may occur, resulting in a short circuit. Poor electrical performance.

8. Remove the iron oxide and excess tin slag with a wet sponge. PCBA uses a placement machine to mount some tiny parts onto a PCB. The production process is: PCB board positioning, printing solder paste, placement machine placement, over-reflow oven and inspection. With the development of technology, SMT can also carry out the placement of some large-sized parts. The water content of the cleaning sponge should be appropriate, which not only does not completely remove the solder chips on the iron head, but also because the temperature of the iron head drops sharply (this thermal shock affects the heating elements and the soldering iron in the iron head). If the water on the iron head sticks to the circuit board, such as corrosion and short circuit of the circuit board, the water volume is too small or not treated with wet water, the damage is great), the welding is poor, such as leakage welding, cold welding, and the like. The water on the iron head sticks to the circuit board, such as corrosion and short circuit. It can cause damage to the iron head, oxidation can lead to tin, and it is easy to cause poor welding, such as virtual welding. Always check the moisture content of the sponge and wash the dross and other debris in the sponge at least 3 times a day.

9. The amount of tin and flux should be appropriate during the soldering process. Too much solder can easily cause soldering defects or cover soldering defects. The solder is too small, not only has low mechanical strength, but also the surface oxide layer gradually deepens with time, which easily leads to solder joint failure. Excessive flux can contaminate and corrode PCBA, which can cause electrical defects such as electrical leakage, and too little flux will not work.

10, often put tin on the iron head: This can reduce the oxidation of the iron head, making the iron head more durable.

11. Flux splash and solder ball generation are related to soldering proficiency and tip temperature. Flux Splash Problem: When the solder wire directly melts the wire, the flux splashes quickly. During the welding process, the welding wire does not directly contact the soldering iron, which can reduce the flux splash.

12. When soldering, please be careful not to iron the surface of the plastic insulation layer and the components of the surrounding welding wire, especially for products with compact welding structure and complicated shape.

13. When welding, self-testing is required: a. Whether there is leakage in the welding. b. Whether the solder joint is smooth, full and smooth. c. Whether there is residual flux around the solder joint. d. There is no connection. e. Regardless of whether the mat is gone or not. f. Whether the solder joint has cracks.

How to solve the PCBA manual welding problem:

1.The appearance of the pcba sample inspection. The QC visually inspects the appearance of the solder joints on the board, and the board can be carefully inspected with a microscope.

2. Test the response of the board. At room temperature, test the resistance on the board with a multimeter and test the surrounding solder joints to see if there is any fault.

3. AOI checks. X-ray inspection of the board, especially check whether there are abnormal connections near the resistor, whether the connector on the board is abnormal, whether the internal copper wire is abnormal, or whether the resistor is abnormal.

4. The fault reappears. In order to verify the board failure mode, look for the cause of the failure and perform a constant hot flash test with and without resistance.
Author Resource:- editor from Kynix semiconductor electronic blog: http://www.apogeeweb.net/
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