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I am making a PCB with a subtractive PCB mill, and I am having difficulty soldering some components to the finished copper. The solder isn't flowing onto the traces easily, and by the time it does flow, the pad lifts.

I'm not sure if the boards need to be cleaned more, or if they need to be covered with a tinning solution (or both). What can I do to make the board easier to solder?

When should I clean my boards - just before or after milling?

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  • \$\begingroup\$ Use more flux! (15 chars) \$\endgroup\$ – Connor Wolf Dec 6 '10 at 4:52
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Immersion tinning would help, but I'd simply use a flux pen on the pads. Rubbing them lightly with Scotchbrite will also help.

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  • \$\begingroup\$ Sometimes I'll just put a thin layer of solder on the pads to "tin" them, right after etching. \$\endgroup\$ – tyblu Dec 6 '10 at 6:57
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    \$\begingroup\$ Worked like a charm. After using a Scotchbrite pad, I could easily tell that my copper had been oxidized quite a bit. Another stupid thing, the iron I had been using wasn't being kept clean and the sponge was completely ineffective. \$\endgroup\$ – W5VO Dec 9 '10 at 21:51
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Clean with wire wool after milling, then a coat of flux to prevent forther oxidisation.

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  • \$\begingroup\$ Is there a particular kind of flux that you're referring to? \$\endgroup\$ – W5VO Dec 5 '10 at 23:16
  • \$\begingroup\$ This does sound like a perfect case for flux to be used. Most solder has flux in it, but it can burn off very quickly if not careful. There are many types of flux that you can use, all should work for you, but look to see what you will need to clean the board with after soldering to remove flux. \$\endgroup\$ – Kellenjb Dec 5 '10 at 23:19
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    \$\begingroup\$ You put flux down when you are ready to solder. There is no need to worry about oxidation before you are soldering. The flux does the job then. \$\endgroup\$ – Kortuk Dec 6 '10 at 0:17
  • \$\begingroup\$ The runny liquid type that comes in flux pens - you can also buy it by the bottle. \$\endgroup\$ – mikeselectricstuff Dec 6 '10 at 0:34
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Use soft wire wool after milling and then a spray coat such as Servisol plastic seal 60

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  • \$\begingroup\$ No, you do absoltely do NOT want conformal coating! \$\endgroup\$ – mikeselectricstuff Dec 6 '10 at 0:35
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    \$\begingroup\$ Citation needed. OK - let me rephrase that..what's wrong with PS60? "Film can be soldered through to facilitate spot repairs". I have used this on many occasions for simple to complex circuit boards and have never had a problem soldering components. \$\endgroup\$ – Linker3000 Dec 6 '10 at 20:17

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