There are various welding methods for SMD LED lamp beads, and the following is one of the commonly used methods for reference. First, use an electric soldering iron to heat some soldering tin on the positive and negative electrode pads of the lamp bead (the soldering tin must not be too much, otherwise, the positive and negative electrode pads will be connected once heated with a Heat gun), then use a Heat gun to heat the positive and negative electrode pads at the same time, after the tin is melted, use tweezers to place the positive and negative electrodes of the lamp bead on the corresponding pads.

The operation should be fast and accurate, otherwise, the Heat gun will melt the LED plastic packaging and damage it.

In the absence of Heat gun, different welding methods can be used according to the structure of LED lamp beads and the substrate used. The pins of SMD LED lamp beads are semi plastic sealed, with a small portion of the pins exposed on both sides of the lamp beads, such as commonly used 5730, 7020, 4014, etc; Some also use fully plastic packaging, where the positive and negative poles of the lamp beads are all at the bottom of the chip, such as 3030. Welding semi plastic sealed lamp beads such as 7020 is also relatively easy. Before welding, it is necessary to first apply a little tin to the solder pad (do not apply tin to the pins of the lamp beads). Use tweezers on both sides to place the positive and negative electrodes of the lamp beads on the solder pad, press the lamp beads with your fingers or a small screwdriver, and finally quickly heat the exposed electrodes with an electric soldering iron, At the same time, apply appropriate force to the fingers and press them down (during heating, the soldering iron should not be rubbed back and forth, and the pressure on the fingers should not be too high, otherwise it may damage the lamp beads).

Real time shot of 5730 lamp beads

For fully plastic sealed lamp beads (such as 3030), if the lamp strip substrate is a regular circuit board, first use a blade to scrape the paint around the lamp bead solder pad to expose the copper wire, and then heat a small amount of tin on the solder pad. First, solder the large electrode of the solder pad, and then heat the electric soldering iron on the newly scraped copper wire (cannot be placed on the solder pad). After the tin on the solder pad melts, use tweezers to slightly pressurize the corresponding electrode of the lamp bead on the solder pad, Finally, solder the electrodes with small pads. The reason why it is necessary to weld the electrode with a large solder pad first is because the required heating time is long. If this electrode is welded later, the lamp beads are prone to overheating and damage.

If the light strip substrate is aluminum substrate, the above method cannot be used because the circuits using aluminum substrate are designed very finely. When welding the lamp beads of this type of lamp strip, heat conduction can be used to weld the lamp beads. The aluminum plates on the back of the positive and negative electrode pads of the lamp beads are heated at the same time. After the tin on the pads melts, the lamp beads are placed on the pads and slightly pressurized. The heater can be purchased from Taobao or replaced with a high-power electric soldering iron (no less than 100W).

When using an electric soldering iron to weld lamp beads, the outer shell of the soldering iron must be well grounded, and it is best to also wear an anti-static bracelet to prevent induced electricity and static electricity from damaging the LED lamp beads. In addition, the soldering iron head should be ground into a horseshoe shape to increase the contact area and shorten the welding time.