Printed circuit board options?

DanK

Member
2001-08-30 5:05 pm
I'm sick and tired of sticking components on
vector board "perf. board", and hand wiring
everything.

What are my options for getting a more "professional"
printed circuit board? Are there any diy
circuit board kits? How about printed circuit
board shops -- are there any companies out there that are
low cost, and don't mind handling very small
quantity runs?

Thanks in advance,

Dan
 
Basic printed board

You will need at least an etching machine (cold perchloride is not very efficient). There is some "low cost" ones which are really usable (I have one). It uses some aquariophily parts for heating and air pump. Don't do it yourself, perchloride is really difficult to clean if there is a leak!

For making etch resist, you can use direct method. The traces and pads are adhesive symbols, directly put on bare copper board. It is convenient for simple board, but very long for big board or series.

Photo method is better, but needs more work. I use a PCB software (for example: http://www.ultiboard.com ), then I print it on a high quality paper (not glossy), then use white spirit to make it translucent. I invert the drawing to make the ink touch the photoresist (this is very important to avoid blurry edges).
I use two 15W UV tubes, not dark UV like in discos, but specials ones (dangerous for the skin and eyes!). It takes about 8/10 mins exposure. Then I use standard revelator. I made myself the UV machine (just a box with a thick glass and foam on the cover to ensure good contact).

In all case, you need to be very carefull, perchloride is a poison, it is impossible to clean on most materials. Photoresist revelator is very caustic.
Photoresist exposure needs to have a rigourous method to avoid burning too much board. The total cost for photobased system should be between 100$ and 200$.

Once you know well your system, it takes less than half an hour to have a very professional finish.
 
Dan,
It need not be complicated, nor particularly dangerous. Another etchant that you can use is ferric chloride. It'll stain your clothes, but it won't jump out of the bath and eat you alive.
There are various options for how to do the layout. By hand with sticky appliques, with an etch resistant pen (I don't recommend this, but it can be done), on a computer--then either use special paper to print and transfer to the raw PC board, or use the optical method mentioned above.

Grey
 
There are some cheaper alternatives also,

I use photo etching, but instead of a light box I just
lay the transfer and PCB under a peice of glass in the sun.
It takes a bit longer (30 mins) and it can be inconsistant (depends on weather).

As far as etching goes, I just use a flat platic container
full of etchant and then put the whole thing in a tub of
hot water. You need to occasionly shake or move the container to move the etchant around, and if the etchong takes a while you may need to replace the hot water.

Regards,
Tim.
 

cp642

Member
2001-08-17 6:00 pm
Another real 'cheap' alternative is to use an OHP tranparency film ( photocopier compatible ), get the copper side track photocopied and have it " iron on " with a hot iron an a piece of PCB. The dark and glossy toner tracks that has been transferred should be etchant resistant enough ( may need some minor touch up ).

Read it somewhere that a combination of hydrochloric acid + hydrogen peroxide makes a better etchant than ferric chloride.

..regards, cp
 
I have found the simplest way to make PCB is to print the Artwork and iron it to the board, there are a few tricks though

I use a paper made of Bagasse fibre, this is derived from sugar cane waste (<a href="http://www.abc.net.au/science/news/enviro/EnviroRepublish_257520.htm">link</a>), when I was experimenting with papers I was lucky enough to have some bagasse samples sheets from Raleigh Paper Co. this is great for transferals as it totally disintegrates in water.

The laser printers has to be 600dpi or better, turn the density up and turn any dithering off (eg RET on HPs)
If you have some areas where track clearance is tight, the thick toner might flow a little when you iron it to the board, so experiment and use the best setting you find.

Clean the Copper Very well
I use scotchbrite to get little sworls (technical term :)) in the Copper, then polish with Isopropal Alcohol (not rubbing Alcohol as they can contain oils) until the cloth stops getting discoloured. The slightly rough and clean surface holds the toner very well.
Try not to touch the surface as you might get oils on it.

Iron on the toner
I use the Wool setting and no steam on my Iron. Place the artwork toner side down, press firmly with face of the iron the toner should melt and stick the paper to the surface. The PCB should get to hot to hold, rub the traces with the tip of the Iron just to be sure they have all melted

After you feel its bonded to the PCB let it cool, then place it in some water, I have tried adding a little dishwashing liquid but can't say it made any difference, and leave over night. You should notice the paper start to bubble as it absorbs the water.

Next day just rub the paper off with you finger and give it a light scrub with a soft toothbrush, this cleans out the eyes in the pads. The toner is quite tough.

I etch in Ammonium Persulphate, I find it's cleaner than Ferric Chloride but needs to be keep warm (I take the PCb out and stick the plastic etching tub in the microwave). With Persulphate you can tell when it taken up a lot of Copper as it turns blueish, if you stick a Iron nail (take this out before using the microwave!) in the solution it will be coated by the Copper and the solution will remain stronger (I think?)

If you stuff up while experimenting, turpentine will remove the toner.

The problems I have had are mainly the component pads eyes tend to close up from toner flow and the sides of traces seem to be slightly wavery.

Some of the newer Laser printer use a low melt toner, this may be easier, havent tried one yet.

If you cannot get the Bagasse paper you could try some of the Tee-shirt transfer papers, just follow their instuctions.

<a href="http://www.al-williams.com/wd5gnr/pcb.htm">Here</a> is very similar to what I do but uses "Avery "Remove 'em" labels"


<center><font size="1" face="times new roman">Hope this helps
Regards
James</font></center>


Raleigh Paper Co P/L
1 Beaumaris Parade
Highett, Victoria
Australia 3190
 
I tried several times with the toner transfer method, but with very limited success... the toner always seemed to smush around, and there were usually gaps and plenty of touch-up afterwards. High resolution traces are also very difficult with the toner method.

So, then I went to home depot and picked up a standard light switch and two small flourescent lamp fixtures. That was cheap... the more expensive part was the two UV lamps, but even they weren't too bad. A few scraps of plywood and the glass front off a cheapo photo frame, and I had a UV light box. Now, the trick to doing photo resist is making sure you use a mylar sheet that won't shrink in the heat of your laser printer. If you use overhead transparencies, don't expect accurate dimensions on your final board. Mylar isn't clear, its hazy, but lets the UV through, which is all we care about. You print the image in reverse, and put the toner side against your photo-sensitized board, and stack a book or two on top to flatten it all against the glass. Developing is quick and easy, and you'll get very good results.

But alas, I eventually got sick of waiting for the ferric chloride to work, even with a hot water bath to speed it up. And, I got really tired of drilling all the holes (my God, the thousands of holes!!!), even after I built a mini drill press for my dremel tool. Besides, I really just wanted to build the circuit, not watch a brown fluid slowly dissolve copper... it's about as exciting as watching paint dry.

So, in the end, I've gone back to good-ol proto board for quick prototyping, or I'll go to a professional board maker for nice boards. I feel the time and effort it saves is worth the money, and the finished product looks great! The house I have used most is AP Circuits out of Calgary, AB, Canada (www.apcircuits.com). They have a real slick email order system. Now, I'm down in California, and I do more layers, so I've started using Advanced Circuits (www.4pcb.com). 4pcb may not be the cheapest, but they come with all the goodies (silkscreen, LPI solder mask, multi-layer etc...). They have a $33 deal on where you get any size board, two layer plated thru, with solder mask and silkscreen at $33 (USD) per board. If you go with a pro board maker, be prepared to generate the gerber files with a decent layout package. I use Protel 98 at home...

Incidentally, I also use a lot more SMD parts now. Despite what you might think, with a little practice, they're actually much quicker to work with than through-hole parts, and will reduce your hole-count and board size considerably. There's a nice DIY pick-n-place rig you can build - go to the library and look in the 2000 edition of the ARRL handbook.

Good luck,
 
DanK:

For my last project, I used the free software from AND had boards made by Express PCB (www.expresspcb.com). They have a MiniBoard service:

- Quantity three(3) of the same board
- Double-sided boards
- Plated-through holes
- No silkscreen or solder masks
- Board size must be 3.8 x 2.5 inches
- Shipped the next business day
- Delivery by US Priority Mail

for $59, including shipping in the US. Probably not the lowest price, the software doesn't do schematics, rule checking, auto-routing, etc. But for what we do here in DIY land, this is one way to get something quick and easy without the chemical mess. I have a buddy who's always willing to take whatever leftover board I have if I don't use all three.

I've had one board through these folks. Looks great, delivered on time, no problems.

Just my 2 cents :)
Michael
 
I use very simple, cheap and efficient method - print the board out on paper (depending on quality of the laser printer you may enhance it by making copy on copy machine). And than iron it on the board. With water resistant marker you may improve the "imprint".
I tried combination of H2O2 and HNO3, very aggresssive one. It corrodes more than you want. I can not recommend.
 
Better than Tinnit

Product called "Liquid Tin" -- Newark Electronics carries it (I believe). Because of HAZMAT rules there is a surcharge if shipped by UPS (and FedEx won't carry it at all.) The composition is such that it uses a member of the fluoric acid family (fluoroboric acid) and stannous fluoborate (by the way, hydrofluoric acid is used to etch glass!) family to clean the board and plate at the same time. On the other hand, tinnit has to be heated to work properly, it gets all clumpy, (which means that it is difficult to funnel it back into the container) and you have to clean the board afterward with ammonia.

here's a link to MG Chemicals (they carry a lot of PCB stuff):
http://www.mgchemicals.com/products/421.html

Again, there is a DIY Printed Circuit Board forum on Yahoo :

http://groups.yahoo.com/group/Homebrew_PCBs/