solution of tinnig pcb - Page 1
Forum section: electronics / general

author: mov-jump
author_rank: Contributor
timestamp: April 11, 2016, 07:37:29 pm
content: HelloI am gonna tin my pcb pad. so what is the chemical materials for the tinning solution as like as this video:Is this method a good way to tin pcb and avoiding to oxide or it's better to tin pads with melted tin? notice that I am going to make pcb in advance and there are about 500 pcbs which must be have tinny pads.

author: Unknown
author_rank: Unknown
timestamp: April 28, 2016, 10:49:23 am
content: NOTE: This message has been deleted by the forum moderator Simon for being against the forum rules and/or at the discretion of the moderator as being in the best interests of the forum community and the nature of the thread.If you believe this to be in error, please contact the moderator involved.An optional additional explanation is:

author: Ian.M
author_rank: Super Contributor
timestamp: April 28, 2016, 11:44:18 am
content: Seehttp://pcbhowto.com/articles/tin-plating-copperUnfortunately electroless tin is a very thin coating that oxidises readily. You *may* get acceptable long term solderability if a thin coating of liquid R or RMA rosin flux is applied as soon as possible then thoroughly dried.The other approach (usually used commercially) is electroplated tin, which can build up much thicker coatings, but all areas to be plated must be electrically connected, so, unless you are just plating an edge connector or similar where you can have a commoning track along the edge that will be cut off when the board is trimmed to final dimensions, that has to be done while the copper is still one solid sheet, before the PCB is etched, selectively with a resist to define the areas to be tinned, either using the tin as the etch resist, which requires very fussy chemistry, or stripping the resist after plating then applying a new resist to define the areas to be etched. Electroplating in general can be rather tricky, especially when you need a bright smooth finish with excellent adhesion.HASL isn't practical without specialist equipment.

author: wraper
author_rank: Unknown
timestamp: April 28, 2016, 12:12:39 pm
content: It's fine for avoiding bare copper oxidation. As of solderability, better to solder it right away after plating without storing in the meantime. If you vacuum seal them, they might be fine. But why would you need to make 500 PCBs by yourself anyway? At such quantity it would be cheaper to order them from china with HASL (lead or lead free) or ENIG.

author: rgawron
author_rank: Contributor
timestamp: April 28, 2016, 02:31:41 pm
content: I tried a couple of methods and the best was tinning using acid bath (thiourea ,tartaric acid, tin(II) chloride):clickThere are also a methods of alcaline bath (sodium hydroxide, Tin(II) chloride, metalic tin), but alcalines are quite dangerous, so I would avoid them.clickAll above chemicals may by bought online, buying them separately and then making a mixture is much less expensive than buying ready to use product.In addition, this is nice way too using Lichtenberg's alloy but from what I checked it may be difficult to get it in some countries:click

author: Ian.M
author_rank: Super Contributor
timestamp: April 28, 2016, 03:09:39 pm
content: Acid tinning uses thiourea which is rather toxic, with nasty long term effects.Alkaline tinning uses hot approximately 0.8 molar Sodium Hydroxide. With appropriate eye protection and immediately available washing water, the risk of serious chemical burns is manageable.Lichtenberg's alloy is totally unsuitable for PCB tinning because Lead + Bismuth contamination of a solder joint can form an extremely weak layer that will fail when temperature cycled.

author: ion
author_rank: Regular Contributor
timestamp: April 28, 2016, 04:00:43 pm
content: I've made tinning baths for my home made PCBs using Tin (II) Chloride, Thiourea and Sulfamic Acid. While it did plate the copper, I found it actually made it harder to solder - I had to dip one PCB in acid to remove the plating before the pads would wet!Now I probably messed up the process somewhere - storing the powdered chemicals already mixed was probably not a good idea - but I haven't put much effort into making it work. If you do try to make a tinning bath make sure you test it on some scrap pcb first.And as Ian.M said - Thiourea is pretty toxic. If you're not comfortable handling dangerous chemicals it's probably best to avoid formulas using it.

author: M4trix
author_rank: Frequent Contributor
timestamp: April 28, 2016, 04:50:47 pm
content: QuoteHeck, there is no warning about liver tumors on those tinning products. What does 'enough exposure' mean ? Drinking the stuff or what ? I have 8 unused bottles of this for some projects and this warning scares the sh*t out of me !http://www.tme.eu/gb/details/seno-3211/materials-for-pcb-production/

author: ion
author_rank: Regular Contributor
timestamp: April 29, 2016, 05:33:27 pm
content: Quote from: M4trix on April 28, 2016, 04:50:47 pmThe oral LD<sub>50</sub> for rats is 125mg/Kg (wikipedia), so I'm guessing not much is enough if you ingest the stuff.However, it seems to take a long time to have negative effects through skin contact:http://www.inchem.org/documents/cicads/cicads/cicad49.htmOf course if you want scary, IIRC my bottle of Thiourea has a 'suspected carcinogen' warning on it ( among a seemingly enless list of toxicity warnings)!

author: M4trix
author_rank: Frequent Contributor
timestamp: April 29, 2016, 05:52:57 pm
content: * M4trix is looking for a hazmat suit on the net...I already have the mask, gloves...

author: chris_leyson
author_rank: Super Contributor
timestamp: April 29, 2016, 05:55:56 pm
content: Used tinning solution before, can't remember what it was but I think it had Cyanide compounds in there and a thin layer of electroless tin oxidizes pretty quickly, I wasn't impressed. Went back to using a thin layer of flux and a soldering iron, I even made a soldering iron from a large piece of brass for ground planes, heat it on gas burner.I wouldn't mess with this stuff, get a professional to do it.

author: KL27x
author_rank: Super Contributor
timestamp: May 02, 2016, 10:04:40 am
content: Solderwick wets just fine for years, and it's not plated. Coating the entire board with liquid rosin flux will keep the pcb ready to solder for a good while. It dries on like a lacquer. Just brush it on and don't touch it until it's dry.I've tried silver plating solutions/powders and tinning solutions. I would suggest the tinning solution. The silver is very tricky. Tinning solution not super easy, eihter. But since you have so many boards to do, it might be worth the hassle of messing with.

author: ElectricGuy
author_rank: Regular Contributor
timestamp: May 02, 2016, 03:19:20 pm
content: I use this from MG Chemicals;It works really well;http://www.mgchemicals.com/products/prototyping-and-circuit-repair/prototyping/liquid-tin-421/Youtuber Mr Carlson's Lab, also uses it too.

author: charlespax
author_rank: Regular Contributor
timestamp: May 05, 2016, 06:25:47 am
content: I've used Liquid Tin on hand etched PCBs and was pleased with the results. Much better than just leaving bare copper. However, the cost and hassle of working with pretty toxic stuff isn't worth it for me. Next time I would do a rosin flux as KL27x suggested.