Discrimination between lead-free process and lead-free process for PCB board proofing

Date：2022-08-31 17:19:03 Views：1012

With the continuous development of the electronic industry, the technical level of PCB is also improving. I believe those who have printed boards in various PCB sample factories know that there are many kinds of common Proofing processes, mainly including tin spraying, gold deposition, gold-plated OSP, etc. among them, tin spraying is also divided into lead-free and lead-free tin spraying. How can we distinguish lead-free and lead-free processes for PCB board proofing?

1. From the surface of tin, lead-free tin is bright, while lead-free tin (SAC) is dim. The wettability of lead-free is a little worse than that of lead-free.

2. Lead in lead is harmful to human body, but lead-free does not. The eutectic temperature with lead is lower than that without lead. The specific amount depends on the composition of the lead-free alloy. For example, the eutectic temperature of SnAgCu is 217 ° C, and the welding temperature is the eutectic temperature plus 30 ~ 50 ° C. It depends on the actual adjustment. The eutectic with lead is 183 degrees. Mechanical strength, brightness, etc. lead is better than lead-free.

3. The lead content of lead-free tin shall not exceed 0.5, and that of lead-free tin shall reach 37.

4. Lead will improve the activity of tin wire in the welding process. Lead tin wire is relatively easier to use than lead-free tin wire. However, lead is toxic, and long-term use is not good for human body. Moreover, lead-free tin will have a higher melting point than lead tin, so the welding point is much stronger.

5. Lead will increase the activity of tin during welding. Lead tin wire is better to use than lead-free tin wire, and lead-free tin spraying has a higher melting point than lead tin spraying, and the welding point will be much stronger.

6. The price of lead-free and lead-free tin spraying for PCB board proofing is the same, and there is no difference.

PCB has the difference between lead and lead-free

1. Weldability

The melting point of the lead-free process is 218 degrees, while the melting point of the lead spraying tin is 183 degrees. The solderability of the lead-free soldering is higher than that of the lead soldering. The process with lead is relatively poor in firmness, and it is easy to have false soldering. However, due to the relatively low temperature of lead, the thermal damage to electronic products is small, and the PCB surface is brighter.

2. Cost variance

In the lead-free process, the tin bar used for wave soldering and the tin wire used for manual soldering have increased the cost by about 3 times; The use cost of solder paste in reflow soldering is increased by about 2 times.

3. Security

As a toxic substance, long-term use of lead will cause harm to human health and the environment.

From the perspective of composition, the main elements of lead-free solder are tin and lead, while the lead-free solder contains less than 500ppm. The lead-free solder generally contains tin, silver or copper metal elements. Considering that the lead-free solder is not 0 lead, but the lead content is very small, reaching the standard content of environmental protection. In terms of use, lead solder is used for the welding of lead products, and the tools and components used are all lead. Lead free solder is used for welding lead-free products exported to Europe, America and other countries. The tools and components used must be lead-free.

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