In PCB proofing, what is the difference between lead and lead-free?

I believe that those who have made boards in various PCB sample factories know that there are many kinds of common proofing processes, mainly including spray tin, immersion gold, gold-plated OSP , etc., and the spray tin is also divided into lead spray tin and non-lead spray tin. Lead spray tin, so what is the difference between the two ?

PCB Proofing

1. First of all, the lead content of lead-free tin should not exceed 0.5% , and the lead content of lead-tin tin should reach 37 % . Therefore, in terms of environmental protection properties, lead-free tin spraying belongs to the environmental protection process, and lead does not belong.

Second, from the surface, the lead-sprayed tin will be brighter, while the lead-free sprayed tin will be dim.

3. Difference in melting point: the melting point of lead-free is about 218 degrees; the temperature of the tin furnace should be controlled at 280-300 degrees; the temperature of wave soldering should be controlled at about 260 degrees; the temperature of reflow soldering should be controlled at about 260-270 degrees. The melting point of lead is about 183 degrees; the temperature of the tin furnace should be controlled at 245-260 degrees; the temperature of over-wave soldering should be controlled at about 250 degrees; and the temperature of over-reflow soldering should be controlled at about 245-255 degrees.

Fourth, due to the relationship between the melting point, the solderability of the two is also different. Generally speaking, lead-free > lead. The solidity of the lead-containing process is relatively poor, and it is prone to false soldering during welding. However, due to the relatively low temperature, it will damage electronic products. smaller. 

5. Lead will improve the activity of the tin wire in the soldering process, and the lead tin wire is easier to use than the lead-free tin wire .

6. As for the cost issue that everyone is most concerned about, in the lead-free process, the lead-free process has more lead-free auxiliary materials and lead-free printed electrode cost requirements than the lead-based process. In the lead-free process, wave soldering uses Tin bars and wires used for hand soldering, so the board with lead-free process will be higher in the final price.  

 

Jiepei PCB is committed to the rapid and free proofing of single and double panels, and the research and development of service engineers. With multi-layer board proofing ability. Industrial Internet 4.0+ has no extreme data center, which helps PCB factories generate continuous orders and refine production management.

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