Homebrew PCB tips?

Question

At home, I etch single and double sided PCBs but there are a few of areas I've always had trouble with. Can anyone help?

Tinning

The PCBs I make are useless for hot air rework or skillet reflowing. Once the copper heats up it oxidises, then I'm unable to solder anything else to the board.

Rubbing wet solder wick over the PCB helps, but I usually just end up damaging the tracks. Will a tinning solution solve this?

Is there any other way?

Vias and plated through hole

So long as I keep vias big and away from components I can solder short pins or wires through the board. But, these vias are too raised to go under a chip, which is often where they're needed.

Is through hole plating possible/practical at home?

Are there other ways?

Cutting

I buy presensitised FR4. It's not cheap, so I like to cut up the sheets to avoid waste. Strong scissors can cut it, but they sometimes curl the edges which makes it hard to get a good contact with the transparency when exposing.

What's a cheap way to cut PCB?

Coating

There's no soldermask, so I have a lot of exposed copper. Is there something inexpensive I could use for a better finish than hotglue?

Thanks.

Answer 1

For tinning, my cheap home method is to coat the traces with a flux pen as soon as the board is finished etching, then run all over them with the thinnest coat of solder from my iron. I've drilled them before and after the flux and or tin process and usually prefer to drill before fluxing.

I too use tin snips for cutting my boards, sometimes sanding the edges with 600 grit wet and dry paper with water and a little soap to get a nice smooth edge.

Conformal coating is available to coat and protect your board. I'm planning to give polyurethane varnish a try on my next project.

Answer 2

I use a room temp tin plating solution to get an evenly tinned surface, it seems expensive at first, but the solution lasts a long time and can be stored and reused if you make too much up. It comes in the form of crystals that are dissolved in hot water, it smells of eggs really bad! - I really recommend it tho - I use it all the time and it's pretty no-nonsense.

As for solder mask, you can get a peelable soldermask that works well for protecting your board and components, it's not the prettiest of finishes but can be easily removed by hand afterward, it's certainly cheaper and less difficult than working with a DIY solder masking kit.

:)

With regards to DIY vias - have you tried connecting the two sides with just solder, leaving the wire out? Not sure how effective this would be - but it might allow you to make them with a much lower profile so they can fit under a chip.

Answer 3

Regarding the cutting of PCBs, I've found that tin snips do a good job. I haven't had a problem with the remnants curling so far.

Answer 4

There's a question with 15 answers here which discusses cutting PCBs.

I may have to dig out my tile cutter (a miniature circular saw with a reservoir for water cooling) and find some PCB to cut as a result of that question.

Answer 5

I use the photo-etch technique and find that the small residue of resist remaining on the board after resist removal protects the copper. It's very thin so it doesn't impede soldering. I have some tin-plating compound, but haven't tried it yet.