There are generally two processes for PCBA and SMT chip processing, one is lead-free process, and the other is lead-free process. Everyone knows that lead is harmful to people, so lead-free process meets the requirements of environmental protection, which is the general trend and the inevitable choice of history. Below, the difference between lead-free process and lead-free process is briefly summarized as follows:
1. The alloy composition is different: the composition of tin and lead with lead technology is 63/37, while the composition of lead-free alloy is SAC 305, that is, Sn: 96.5%, Ag: 3% and Cu: 0.5%. Lead-free process can't absolutely guarantee that it doesn't contain lead at all, only contains extremely low content of lead.
2. Different melting points: the melting point of lead and tin is 180 ~ 185, and the working temperature is about 240 ~ 250. The melting point of lead-free tin is 210 ~ 235, and the working temperature is 245 ~ 280. According to experience, when the tin content increases by 8%-10%, its melting point increases by about 10 degrees, and its working temperature increases by 10-20 degrees.
3. Different costs: The price of tin is more expensive than that of lead. When lead is replaced by tin as an equally important solder, the cost of solder will rise sharply. According to statistics, the lead-free process is 2.7 times higher than the lead-free process for tin bars used in wave soldering and tin wires used in manual soldering, and the cost of solder paste used in reflow soldering is about 1.5 times higher.
4. The process is different: this is the lead process and lead-free process can be seen from the name. But when it comes to the process, the solder, components and equipment used are different, such as wave welding furnace, solder paste printing machine and soldering iron used for manual welding. Other differences, such as process window, weldability and environmental protection requirements, are also different. Lead-free process has a larger process window and better solderability, but because lead-free process is more in line with environmental protection requirements, and with the continuous progress of technology, lead-free process technology has become increasingly reliable and mature.
