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First etch & surface mount!

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Recently had my first go at printing a board and soldering surface-mount components. It's a straight-forward breakout for an FT230XS.

 

Technique:

On the etching side, I used a 2:1 mixture of Hydrogen Peroxide solution and Muratic Acid. Initially clear, it turned a lovely neon green when the copper started reacting! Etch took maybe 5-6 minutes.

I used an "ultra fine tip" Sharpie as the resist; learned the hard way that the 'Micron' brand of super fine tip pens doesn't work for this application  :-( . I was struggling to mark the pads with the sharpie, so instead I drew a dark box across an entire row of pins then used a type of dental pick to scratch a fine line between adjacent pads. Seemed to work pretty well!

 

I had bought a syringe of solder paste for the occasion, but ultimately I couldn't make it cooperate--globs kept bridging pins. Eventually I just put down solder on all the pads, put some flux on the pins and reflowed that way.

 

Anyhow, it was a somewhat messy learning experience, but hopefully next I'll print/mount the whole module. Will keep you posted!

post-31877-0-61527400-1369846207_thumb.jpg post-31877-0-11135600-1369846057_thumb.jpg post-31877-0-59620700-1369846067_thumb.jpg

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I do home etching fairly often.  The chinese cheapo prototype places are pretty sweet, but fairly often I just need a single board for something specific.  Usually just testing with a specific chip.  I do toner transfer and I've been doing it for years, so I've got the process pretty set down.

 

I tried out the acid/peroxide solution a few times, but it's just too harsh.  It will cut through my resist and I get a lot of pitting.

 

If you get bridges, just suck them up with some solder wick.

 

20110502-speedo-adjust-001.jpg

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Nice to see others who think it's more fun to make your own rather than send off for boards (even though I'm sure it makes sense that way).

 

I've been trying to get my first surface mount etched board done over the last few weeks but just don't seem to find the time once my son's in bed. I've CNC milled some through-hole boards before, but have just started playing around with photo-resist boards and ferric chloride as this combo seems the easiest way to etch.

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hey @@TheDirty what chemical / process steps do you use, your boards look nice and sharp.  I would like to be able to prototype y own boards just because waiting 2 to 3 weeks for turn around is kinda annoying.

 

my trick with solder paste is in realizing it is just too thick in its base form from the syringe, it is designed to stick and stay in its cutout shape in the stencil.  but since were applying it by hand, we need to change that behavior.  I use a hard plastic disc and dot my flux pen a few times on it to get a pool of flux (not too much) and then syringe some solderpaste into that pool.  I use the tip of an exacto knife to mix the two around until it is a nice smooth mixture and more flowing than the paste it started at.  you have to play a balancing act between diluting it down for workability, and too much where there isn't enough solder per volume to be usefull.

 

I take my exacto and get a small ball of the thinner paste on the tip, and "dot" the pads with it, you get a nice controlled small application of solder paste, and its very quick to just dot dot dot dot down the line then get another bit on the knife and dot dot dot ...   it works well for me

 

it takes a bit to get the feel for it, but I find it very usefull in doing the 0402 SMD things i work with mostly now.  

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with solder paste i find you need a very small amount, then i push the iron onto each pin, if im using normal solder usually precoat the pads alittle then apply flux pen then put chip down then more flux pen, then same soldering technique. dabbing flux coated desoldering braid on the bridge works abit better then the solder sucker i find, the sucker i have will remove 3 or 4 pins of all their solder. 

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hello @@TheDirty.   I agree with the others that your toner method looks great !  Better than my attempts...

I second the request for a brief outline on the details that make your boards look so good.   I'd like to try again.

 

Since most of us know about the toner method / or / can find info on the web, would you at least share your key ingredients with us :

- what toner / printer type you use, plus any printer settings to get the right toner thickness

- what type of paper you print on

- how you iron the toner onto the blank PCB (temperature / time)

- etching chemicals / temperature / time (do you use a zip-lock plastic bag, for instance?)

- last but not least - which PCB software package - and do you use 'mirror image' output to printer ?

 

I've heard of some guys turning around toner boards from layout to final product in less than an hour - is this your experience too ?

 

Cheers....

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I've helped a lot of people with this and all I can say once you get a method down you are golden, but even with the exact steps it takes experimentation and time to get it so it's quick and easy.  You may have to modify the steps to get things to work for you.  I started many years ago and got my process down.  For some people now it may not be worth it to go through the learning curve, but if I want to experiment with a board or just need a little add on, I can get a board from Eagle to etched and drilled in a couple hours when waiting for Seeed can take a month or more for 10 boards were I don't need 9 of them.

 

For my steps I use:

HP1012 printer and I still have the old Staples Glossy Photo paper that they don't sell anymore.

I use a clothes iron to iron on the resist.

 

My steps are:

  • I'll print out the design on a regular piece of paper and cut it out.
  • I use the cut out to cut a piece of copper clad to size.  File the edges down.
  • I cut out a piece of the glossy paper just bigger than the design and tape it on a regular piece of paper.
  • Print the design onto the glossy paper.
  • Iron the design onto the board.  I use high heat.  Pressure and duration need to be experimented with.  I use a paper towel on the top to help make sure I don't get heat and pressure spots.  I don't know how to describe.  I use decent pressure and put it on for a minute or two.  Rub around and turn the board a few times while doing it to make sure you are doing the pressure evenly.
  • Then need to scrub the paper off.  Let it soak first and then I use a toothbrush and my thumbs to get the paper off.
  • Etch with warmed ferric chloride.  I just use the plastic sandwich boxes and drop the board in.  I rock it back and warm it over a desk light I have.  The light shines through and you can see the etching process and when all the copper has been removed because you can see through the board.
  • Drill using a drill press I have.  You can get PCB sized drill bits from e-bay for cheap.
  • Clean using acetone.
  • ???
  • Profit

I took pictures once when I was experimenting with the fab-in-a-box paper.  This paper does a total release of the laser toner and doesn't work as well for me.  The toner on its own doesn't make a great resist.  They sell a green film that you can use after to seal the toner better for a better etch, but I never got it to work properly.  They recommend a laminator to put it on though and I've never gone through the trouble of getting a laminator.

http://higginstribe.com/uc/Stellaris/LM3S811/

 

Modifications:

The paper you use is the biggest variable.  The paper I use isn't available anymore and I don't know of any good replacements.  Many people use glossy magazine paper.  The super glossy and stiff kind you get in higher end magazines.

Many people swear by the laminators.  I haven't needed one, but they are available cheap on e-bay and there are some recommended ones if you google around.

Like I said before, I've had bad experiences with everything other than ferric chloride.  FC seems to be the most forgiving on resist.

 

I use Eagle to design the board.  If you put all your tracks on the top layer (red) you will need to 'mirror' the board when printing.  If you put all your tracks on the bottom layer (blue) you don't mirror the board when printing.

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My solder paste process.

 

Cheap solder paste from DX.

http://dx.com/p/lodestar-soldering-paste-50g-4711

 

Syringe from DX.  (just search syringes there)

 

18 gauge syringe tip from e-bay.  You can search them.  (maybe smaller gauge if you are doing smaller than 0603)

 

I mix the solder paste with some no clean flux to the correct consistency and scoop it into the syringe.

 

That's it.  I apply and use the hot air gun to set everything.

 

Syringes and tips are one use only unless you can find a way to clean them.

I use a hot glue gun to seal the tip of the syringe after every use and it keeps pretty well in the there.  A month or more.  Just make sure you don't get the glue inside the tip.

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Nice work. For "I need it now" boards, there are three options: etching your own boards with chemicals, and electro-depositing your own boards with chemicals, or machine etching.

 

Given the recent explosion of cheap 3D printers and CNC, I'm kind of surprised no one is marketing a PCB machine etcher for hobbyist (or, maybe there is one that I don't know about).

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I suppose that is it.  You can buy PCB blanks with a layer of copper on each side, and then put them through a machining process where the parts that are not copper are removed via a CNC router head.

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I sorted my own CNC mill out for significantly less than that. It was easy to do. http://0xfred.wordpress.com/2012/02/12/proxxon-mf70-cnc-mill-conversion/

 

I started because I wanted to mill PCBs, but have used it far more for other stuff. If anyone's tempted I can really recommend a CNC mill. I'd say it's far more useful than a 3D printer.

 

It does work reasonably well for PCBs, but getting a very fine consistent cut can be tricky. Copper clad boards are difficult to hold completely flat without flexing and most vary in thickness. It means that the finer SMT stuff gets tricky. I'm giving etching a go to see what I prefer.

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