Must-Have Conditions for Soldering锡焊
Beijing Welding Sincerity Technology Reminds You: The physical foundation of welding is "wetting," also known as "wetting." To explain wetting, let's start with the water droplets on lotus leaves: The surface of lotus leaves has a waterproof wax layer, which causes the water to form droplets due to surface tension. These droplets roll on the lotus leaves without spreading out, and this state is called non-wetting. Conversely, if a liquid spreads out on the contact surface of a solid, fully covering and wetting the surface, it is called wetting. The soldering process involves heating to allow the lead-tin solder to solidify, flow, and wet on the welding surface, enabling the lead-tin atoms to penetrate into the surface of the copper base material (wires, pads), and form a brittle Cu6-Sn5 alloy layer on the contact surface between the two.
In the welding process, the angle formed where the solder contacts the base material is known as the wetting angle. Prior to this, when the solder does not wet the base material, it cannot form a good solder joint; whereas, when the solder wets the base material, it can create an excellent solder joint. By carefully examining the wetting angle of the solder joint, one can determine the quality of the joint.
Clearly, if there is contamination or oxidation on the welding surface that prevents wetting, or if the temperature is not high enough to allow the solder to fully solidify, the solder will not wet the alloy layer of the two metal materials. To achieve tin soldering, the following conditions must be met:
Weldments must possess excellent weldability.
Weldability refers to the ability of a metal material to form a separable alloy with solder at appropriate temperatures. Not all metals possess good weldability; some, such as chromium, molybdenum, and tungsten, have very poor weldability. Others, like copper and brass, have relatively good weldability. During welding, low temperatures can cause oxidation on the metal surface, affecting the material's weldability. To improve weldability, measures such as tin plating or silver plating can be taken to prevent oxidation of the material's surface.
The surface of the welding pieces must remain clean.
To ensure the solder and the workpiece can be separated, the welding surface must be kept clean. Even焊件 with good solderability can develop harmful oxide films and oil stains on the surface due to storage or oxidation. It is imperative to thoroughly clean off any dirt before welding, as this is essential for ensuring焊接 quality. Light oxidation on metal surfaces can be removed by the action of the flux, while severe oxidation requires mechanical or chemical cleaning methods, such as scraping or acid washing.
Utilize appropriate soldering flux
The role of flux is to remove the oxide film on the surface of the welding piece. Different welding processes require different types of flux, such as nickel-chromium alloys, stainless steel, aluminum, etc., and it is difficult to perform soldering without a specific flux. When welding delicate electronic products like printed circuit boards, a flux mainly consisting of rosin is generally used to ensure reliable and stable焊接. Typically, rosin is dissolved into rosin solvent using alcohol.
Weldments must be heated to an appropriate temperature.
During welding, the role of heat energy is to condense solder and heat the焊接object, allowing the tin and lead atoms to gain sufficient energy to penetrate the crystal lattice of the metal surface and form an alloy. An excessively low welding temperature is beneficial for the penetration of solder atoms, but it prevents alloy formation and can easily lead to false welding; conversely, an overly high welding temperature will keep the solder in a non-eutectic state, slowing down the rate of solder paste synthesis and evaporation, thus lowering solder quality, and in severe cases, may cause solder pads on the printed circuit board to fall off.
It is important to note that not only should the solder be heated to its melting point, but the component should also be heated to the temperature where the solder can melt.
Appropriate Welding Time
Welding time refers to the duration required to halt physical and chemical changes during the entire welding process. It encompasses several aspects, including the time it takes for the base metal to reach welding temperature, the solidification time of the solder, the activation time of the flux, and the alloying process of the naturally occurring metal alloys. Once the welding temperature is established, the appropriate welding time should be determined based on the shape, nature, and characteristics of the焊接 piece. Excessive welding time can easily protect components or welding areas, whereas insufficient time may not meet the welding requirements. Generally, the welding time for each soldering point should not exceed 5 seconds.
