While it's possible to buy ready to use tinning formulas, making your own is much less expensive. Various recipes exist for tinning copper, today I will present a simple one that uses ingredients available at online chemical stores. It's one of acid bath methods.Ingredients:
- thiourea - 12,5 grams
- tartaric acid - 8,8 grams
- tin(II) chloride - 1,3 gram
- tap water - up to 250 ml
Simply put PCB into the solution and wait a couple of seconds, the more time the PCB is in the solution, the thicker a tin layer is. It's not needed to heat up the solution - room temperature is sufficient.
The substances are irritating, if you want to apply this method at home, please use gloves and store ingredients and mixture away from children.
The first PCB that I tinned this way is presented below. Solder wets the surface easily! Next time I will use polishing paste before tinning - this should help to obtain smooth and shiny surface.
Here is the device before testing it - it's a driver for a dosimeter based on DKP-50. Not the tidiest construction, but still looks nice.
In the next post I will present PCB tinning by using Lichtenberg alloy. You may also check related previous post about galvanic copper plating.