The difference between lead-free soldering iron and lead soldering iron
The preferred lead-free soldering iron tip is compared to lead soldering iron tips. Lead soldering iron tips contain lead, cadmium, mercury, and hexavalent chromium with a content ratio of more than 1%. Some harmful substances have been banned by the EU ROHS list. Compared to lead soldering iron tips, the content of some harmful substances remains at 0.1%.
Secondly, the use of lead-free soldering iron tips produces high-quality products, while the use of lead soldering iron tips results in poor product quality and a longer lifespan. The products themselves contain toxic substances that pose a significant threat to human health.
Comparison between lead containing process and lead-free process
Lead based technology has a development history of over a hundred years. After extensive research on lead based technology, it has excellent welding reliability and stability, and mature production process technology, which mainly depends on the characteristics of lead based solder alloys.
Lead solder alloys have low melting points, low welding temperatures, and minimal thermal damage to electronic products; Lead solder alloys have a small wetting angle, good weldability, and a low possibility of "false welding" in product solder joints; The toughness of solder alloys is good, and the vibration resistance of the formed solder joints is better than that of lead solder joints.
The lead-free soldering process has explored alternative alloys with melting points higher than existing tin lead alloys based on current research results. For example, from the widely accepted "tin silver copper" alloy in the industry, the melting point is 217 ℃, which will greatly reduce the process window in the welding process. In theory, the reduction of the process window is from 37 ℃ for tin lead solder to 23 ℃. In fact, the reduction of the process window is much larger than the theoretical value. Due to the inaccuracy of our temperature measurement method in practical work, coupled with the limitations of DFM and the need to take good care of the "appearance" of solder joints, the reflow soldering process window is actually only about 14 ℃. Tongxinda has lead tin wire
Not only does the reduction of the process window bring huge challenges to the process personnel, but the increase in welding temperature also makes the welding process more difficult. One of them is the oxidation phenomenon during high-temperature welding process. We all know that the oxide layer can make welding difficult, cause poor wetting, and result in virtual welding. The degree of oxidation is determined not only by sufficient control over the incoming components themselves, but also by the supported inventory conditions and time, pre-treatment (such as dehumidification and baking), and the heat energy (temperature and time) experienced during the preheating (or constant temperature) stage of welding.
