Seno Immerse Tin Crystals 90g for 1ltr

I bought this product to make life easier when finishing off printed circuit boards. Having carefully read the safety instructions first,and taking care not to shake the container I mixed the solution with warm water. As the powder is toxic you need to ensure your skin does not come into contact with the powder or you breath in the dust during mixing the powder. My first attempt was not a success, because I failed to thoroughly clean the board. The second attempt did result with a decent tinned surface on the board. I achieved this by cleaning the board with scouring powder first, then applying a tin coating to the board. I then used some fine wet and dry sandpaper to clean the surface of the board and re immersing the board into the tinning solution for 20-30 minutes followed by thoroughly washing the board with hot and then cold running water. To remove the board from the solution I used plastic board grippers so I did not come into contact with the liquid.

Tin plating can be a fantastic option for any home made PCB for improving soldering as well as protection from tarnish and oxides. But unless you are a hardcore PCB maker (such as myself), the contents of these tinning solution is a complete mystery and its about time that someone revealed the truths as well as the safety concerns. For those who are not aware this solution contains a chemical called Sulfamic Acid (this is a derivative of sulphuric and ammonia). What makes sulfamic acid special is that it comes in powdered form and thus very safe to handle (as the powder is not acidic). When this solution is made the pH sits around 1.2 to 1.8 which may sound dangerous however is only slightly more strong that vinegar! But why do you need to heat the solution to 50 degrees and then use at room temperature? Firstly, you need to heat it up as sulfamic acid and stannous chloride take some time to dissolve in solution (this stuff is essentially sulfamic, stannous chloride and thiourea). Once they are all dissolved it is VITAL to keep the solution cold because sulfamic acid hydrolyses slowly in water to form ammonium bi-sulfate. While this substance is still acidic it stops the tinning solution from even working. This is why you need to keep this solution at room temperature (as it takes a while for the sulfamic acid to break down). It also explains why the solution only lasts 6 months. At higher temperatures the solution will break down...quickly. I would go as far to say this: Try mixing the solution without using any heat first because I have done this and got the solution to work! A second overlooked factor is that the solution needs to be kept very clean. This is easily done by ensuring that you wash all PCBs before the tinning process. Now for some safety: For those who are not aware this product contains thiourea which is not something you want in your body (hence why it is not available for export). Constant exposure will lead to potential tumors on the liver as well as causing thyroid issues but this is all very easy to avoid by simply wearing gloves! To summarise: Also called liquid tin, this stuff is expensive and thus not suitable for those making a few PCBs UNLESS you are clever enough to measure the powder, divide the contents into smaller amounts and only ever make up small solutions for individual projects. If however you are PCB mad like myself this is an item that you should be adding to your basket...now...go on! Robin Mitchell MitchElectronics

I have a problem the solder paste it dose not take to the tin plating I dont know weather or not if the temp is to high can this damage the molecules I have polished the copper on the pcb then place it in the tin plating then apply the solder paste, I use a hot air unit but it dose not take to the tin plating proplery hope you can help thanking you.