A brief discussion on the material structure and design suggestions suitable for laser soldering

　　Before analyzing the above points, let us briefly review the principle of laser wire welding. Generally speaking, it goes through three stages: preheating-welding-cooling.

　　Preheating: In the preheating stage, the laser emits light to preheat the solder pad position to heat up the solder joints.

　　Welding: In the welding stage, the tin feeding device delivers the tin wire to the pad. Under the action of the laser and the heat of the pad, the tin wire

　　Cooling: In the cooling stage, the tin wire is withdrawn and separated from the solder joint, the laser gradually weakens to stop, and the solder joint forming and cooling is completed.

　　In the 3C5G consumer electronics industry, there are many customer groups for laser wire soldering. The main reason is that laser wire soldering has a wide range of applications and is compatible with pads of different sizes. The cost is compared with laser soldering and laser soldering. Welding will be lower.

　　Laser solder ball welding: non-contact welding, no flux, good tin quantity consistency, high welding efficiency, suitable for high-precision welding

　　Laser tin wire welding: non-contact welding, no loss of soldering iron tip, suitable for welding of devices in small spaces where the soldering iron is prone to interference

　　Laser solder paste welding: non-contact welding, suitable for special application welding such as small solder joints, easily oxidized materials, laser penetration through-hole burn devices, etc.

　　Laser soldering suitable materials

　　Of course, laser soldering is not omnipotent, and some materials cannot be welded, as shown in the figure below:

　　Illustration of suitable materials for laser soldering

　　Among them, gold-plated, silver-plated, and tin-plated pads are most suitable for laser soldering. The above-mentioned three soldering processes are applicable, while copper/nickel pads are easily oxidized in the air. The wettability is poor, and laser heating will accelerate oxidation. You can try the laser solder paste welding process. The last mentioned iron/aluminum/stainless steel pad is not solder-resistant, so it is not built.It is recommended to use laser soldering.

　　Laser soldering is suitable for structures

　　The common structures of laser soldering generally include the following six types (as shown in the figure), namely Corner, Overlap, Sandwich, Lap, Insert, and Bridge.

　　Laser soldering design suggestions

　　The daily soldering process will come into contact with a variety of products during the proofing process. The following four suggestions are summarized for special samples:

　　1. Enameled wire + terminal

　　Suggestion: Enameled wire does not stick to tin. Increasing the laser power will cause the enameled layer to oxidize and turn black, resulting in a strong laser absorption effect and burning out the solder joints. The welding can be tested by removing the enameled layer or using direct welding enameled wire.

　　2. The pad ring width is too small

　　Recommendation: Pad ring width B=((D-d)/2)0.5mm.H

　　3. Easily oxidized materials

　　Recommendation: When the upper material is thin metal or thin wires, laser heating will cause the upper material to oxidize first and not be stained with tin. It is recommended that the thin sheets/thin wires be tinned to increase the wetting effect, and solder balls or solder pastes are used to test welding.

　　4. Narrow plastic space

　　Suggestion: Solder joints and molten tin will reflect laser light and cause burns to the surrounding plastic. It is recommended that the distance between the edge of the solder pad and the plastic should be greater than 0.8mm. If conditions permit, a protective cover should be added around the solder joint during welding.

　　Summarize

　　As an enterprise that has been deeply involved in the field of laser soldering for more than 20 years, Songsheng Optoelectronics is well aware of the wide application and irreplaceable advantages of laser in industrial production and processing. We independently developed a constant-temperature laser precision soldering system. This constant-temperature laser precision soldering system adopts a number of innovative designs and integration technologies to achieve excellent performance and high reliability.

　　From a technical point of view, this equipment uses the most stable semiconductor laser as the energy source, ensuring the high stability of the laser energy; through the latest optical technology, the four points of laser, CCD, temperature measurement, and indicator light are coaxial, perfectly It solves the overlapping problem of solder joints, guide light, imaging points and solder joints to avoid complicated debugging, making it more suitable for precise welding of highly precise microelectronics. The unique feature positioning method further ensures the mass production welding yield of precision microelectronics. It can better cooperate with the processing on large production lines.

　　The above is the specific content of Wuhan Songsheng Optoelectronics’ brief discussion on the suitable material structure and design suggestions for laser soldering. If you have any questions, please call or add WeChat for detailed inquiries. We will continue to update more relevant instructions for you. You can follow our website Learn more.