Main Differences Between Lead and Lead-Free Processes in PCBA Processing

PCBA, SMT processing generally have two kinds of process, one is lead-free process, the other is lead process, we all know that lead is harmful to human beings, so lead-free process meets the requirements of environmental protection, is the trend of the times, the inevitable choice of history.

Below, the differences between lead process and lead-free process are briefly summarized as follows. If global technology SMT chip processing analysis is not complete, we hope you can make more corrections.

1. The composition of the alloy is different: 63 / 37 of tin and lead are common in lead process, while sac 305 is in lead-free alloy, that is, SN: 96.5%, Ag: 3%, Cu: 0.5%. Lead free process can not absolutely guarantee that there is no lead at all, only contains very low content of lead, such as lead below 500 ppm.

2. Melting points are different: lead tin melting point is 180 ° to 185 ° and working temperature is about 240 ° to 250 °. The melting point of lead-free tin is 210 ° to 235 ° and the working temperature is 245 ° to 280 ° respectively. According to experience, every 8% – 10% increase in tin content, the melting point increases about 10 degrees, and the working temperature increases by 10-20 degrees.

3. The cost is different: tin is more expensive than lead, and when the equally important solder changes lead to tin, the cost of solder increases dramatically. Therefore, the cost of lead-free process is much higher than that of lead process. Statistics show that the cost of lead-free process is 2.7 times higher than that of lead-free process, and the cost of solder paste for reflow soldering is about 1.5 times higher than that of lead-free process.

4. The process is different: there are lead and lead-free processes, which can be seen from the name. But specific to the process, that is to use solder, components and equipment, such as wave soldering furnace, solder paste printing machine, soldering iron for manual welding, etc. This is also the main reason why it is difficult to process both lead-free and lead processes in a small-scale PCBA processing plant.

The differences in other aspects, such as process window, weldability and environmental protection requirements are also different. The process window of lead process is larger and solderability is better. However, because lead-free process is more in line with environmental protection requirements, and with the continuous progress of technology at any time, lead-free process technology has become increasingly reliable and mature.


Post time: Jul-29-2020