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Alright so I'm learning the PCB manufacturing process.

I have seen many professional PCB manufactures use "Tin" to be used as an "etch resist" which protects the copper traces which makes the circuit. Then the "etchant" will only remove the unwanted copper but will not have any affect on the copper traces since it is "tinned". This will give a better etched product since the etchant will not remove any of the copper traces of the circuit. Seems like a great idea, can easily be done at home. I haven't seen anyone on the "DIY" internet that follows this process.

What I don't understand is that the PCB manufacturers remove the tin after the etching process. Isn't it better to just keep the plated tin rather than removing it? I know a solder mask will be applied to protect the PCB circuit traces after the removal of tin.

Does it make any difference to just keep the tin traces and put a solder mask on top and not remove the tin?

Does the etchant changes the chemical properties of the tin, is this why the PCB manufactures remove it?

I know many people Tin their PCB so that it protects the copper traces and then add a solder mask on top.

Here is a reference video, scroll to video time 19:22: youtube.com/watch?v=sIV0icM_Ujo

Edit, answer to the question: I just spoke with a PCB manufacturer technical team from "sfcircuits.com", I was told the reason why PCB manufacturers remove "Tin" from copper traces is so that "Tin Whiskers" will be avoided. So basically after applying "Tin" to your PCB traces and over time will grow "Tin Whiskers" and can potentially cause a short between traces...

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  • \$\begingroup\$ Can you post a reference to such process? How is tin added in the layout pattern? \$\endgroup\$
    – Wesley Lee
    Commented Dec 23, 2020 at 19:37
  • \$\begingroup\$ youtube.com/watch?v=sIV0icM_Ujo Scroll video time at: 19:22 \$\endgroup\$
    – S To
    Commented Dec 23, 2020 at 19:45
  • \$\begingroup\$ Listen to the narrator carefully. He said Tin added, then later it is removed. For some reason they skipped that video of adding Tin. \$\endgroup\$
    – S To
    Commented Dec 23, 2020 at 19:51
  • \$\begingroup\$ The tin would melt during the solder process, stripping the soldermask. \$\endgroup\$
    – RJR
    Commented Dec 23, 2020 at 19:56
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    \$\begingroup\$ I just spoke with a PCB manufacturer technical team from "sfcircuits.com", I was told the reason why PCB manufacturers remove "Tin" from copper traces is so that "Tin Whiskers" will be avoided. So basically after applying "Tin" to your PCB traces and over time will grow "Tin Whiskers" and can potentially cause a short... \$\endgroup\$
    – S To
    Commented Dec 23, 2020 at 20:15

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