How to weld SMD LED_SMD manual welding tutorial
manual welding
1. It is recommended to use reflow soldering under normal circumstances and perform manual soldering only when repairs are required.
2. The maximum power of the soldering iron used for manual welding should not exceed 30W, the welding temperature should be controlled within 300°C, and the welding time should be less than 3 seconds.
3. The soldering iron tip must not touch the SMD LED lamp bead colloid to avoid high temperature damage to the LED lamp bead.
4. When the pin is heated to 85°C or higher than this temperature, the SMD LED lamp bead must not be stressed, otherwise the gold wire will easily break.
Reflow soldering
1. Reflow soldering peak temperature: 260°C or lower than this temperature value (lamp bead surface temperature).
2. The time required for the temperature to rise above 210℃: 30 seconds or less.
3. Reflow soldering is generally done once and no more than twice at most.
4. After reflow soldering, the LED lamp beads need to be cooled to room temperature before touching the LED colloid surface.
Welding essentials
(1) The contact method between the soldering iron tip and the two parts to be welded
Contact position: The soldering iron tip should contact two parts to be welded (such as solder legs and pads) at the same time. The soldering iron is generally tilted at 45 degrees and should avoid contact with only one of the parts to be welded. When the heat capacity of two parts to be welded is very different, the tilt angle of the soldering iron should be adjusted appropriately. The smaller the tilt angle between the soldering iron and the welding surface, the greater the contact area between the part to be welded and the soldering iron with the larger heat capacity, and the stronger the heat conduction capability. For example, the inclination angle is about 30 degrees when welding LCDs, and the inclination angle when welding microphones, motors, speakers, etc. can be about 40 degrees. The two parts to be welded can reach the same temperature in the same time, which is considered an ideal heating state.
Contact pressure: When the soldering iron tip is in contact with the workpiece to be welded, a slight pressure should be applied. The strength of heat conduction is proportional to the amount of pressure applied, but the principle is to not cause damage to the surface of the workpiece to be welded.
(2) Supply method of welding wire
The supply of welding wire should control three key points, namely supply time, location and quantity.
Supply time: In principle, the solder wire is supplied immediately when the temperature of the workpiece to be welded reaches the melting temperature of the solder.
Supply position: should be between the soldering iron and the parts to be soldered and as close to the soldering pad as possible.
Supply quantity: It should depend on the size of the parts to be welded and the pad. After the solder covers the pad, the solder should be higher than 1/3 of the diameter of the pad.
(3) Welding time and temperature settings
A. The temperature is determined by actual use. It is most suitable to solder a tin point for 4 seconds, and the maximum should not exceed 8 seconds. Observe the soldering iron tip at ordinary times. When it turns purple, the temperature is set too high.
B. For general direct-plug electronic materials, set the actual temperature of the soldering iron tip to (350~370 degrees); for surface mount materials (SMC), set the actual temperature of the soldering iron tip to (330~350 degrees)
C. Special materials require special setting of soldering iron temperature. FPC, LCD connectors, etc. must use silver-containing tin wire, and the temperature is generally between 290 degrees and 310 degrees.
D. When welding large component pins, the temperature should not exceed 380 degrees, but the power of the soldering iron can be increased.
