Two More NMEA WiFi Bridge Boards

If I could only learn to take good photos

I etched two more of the NMEA WiFi Bridge boards. After only a week of messing with the layout in Eagle, I finally decided I had a valid rev x.3. It seems I left a Vcc trace off the x.2 board.

Printing the inkjet transparency went well this time, marking solid and black in eagle print, although the color came out greenish. I exposed the pre-sensitized board 1 minute 15 seconds in the 1:30 afternoon equatorial sun then immediately developed them in caustic soda from last year for about 3 minutes. Then etched in new peroxide and muriatic acid for about the same 3 minutes. They looked really nice for a change.

I then exposed them to the sun again for 2 minutes and used the caustic to get the rest of the green photo-resist off the traces so I could solder.

I tried to coat all the copper with solder, but the very fine letters just pealed off the board. I had levf a +, -,  G and Rx in copper near those pins.

It took less than 3 hours to print, etch and populate the 2 boards. Of course that doesn't count the week fussing with the layout!

I decided to leave the voltage regulator off these because I have a number of $2 Chinese buck converters that have good regulation in the 3.3v range to pair them with.

More Homemade PCBs

Fail! Fail! Fail!
After numerous failures I think I may have a board I can use.I thought I had made good enough notes when I made the LEDTester board a while back, but???

This time I am trying to make the Sparkfun's Serial Enabled LCD Kit. They have posted the eagle files so I can change them if necessary. I didn't notice the trace width until after the first PCB failure.

The target, used w/o permission from Sparkfun.

I am using the presensitized positive photo resist boards with inkjet on transparencies for artwork still. And exposing in the direct sunshine which is just fine here near the equator. Kinda limits me to daytime PCB work though.

A weeks worth of failure from right to left. The left may be good.

The one on the right looked good, but I had forgotten what they looked like when finished etching. I took it out too soon and cleaned the resist off. The traces were too thin and were being eaten away anyway. After a lot of googling, I found how to increase the trace width, fix the errors this caused and get ready to try again.

The second board from right I noticed wasn't exposed enough, so I trird to re-expose it and develop it some more. Bad idea! I also got it out of the etch too quick. For each of these I had printed black grayscale from the default colors of eagle. this did not turn out to be opaque enough in the UV range to work but I blamed it on the other steps.

The second board from the left also failed. I printed it as color photo on photo paper. I also found a reference to a script(drill-aid.ulp) to run in eagle that makes all the holes smaller so it is easier to start the drill when hand drilling the holes for the parts. It draws a small circle with crosshatch in the middle of the hole to be drilled. Between it and the light color of the pads, when I printed the transparency, the pads pretty much disappeared. I etched it anyway to see for sure I could.

Top and bottom artwork taped like a hinge with tiny registration marks.

So the right answer seems to be, check the boxes for black and solid in the eagle print dialog, print photo color to photo paper even though it is a transparency. Then expose to sun 2 minutes per side covering the back side. Develop about 3 minutes in warm (not too hot, board 2) caustic soda until the extra resist washes off. Then etch in warm muriatic/peroxide till you see the board. You can take it out, rinse and check along the way.

Another view of the art and the board.

It looks better in person, I guess it is not very photogenic! HA.

Next to try to drill the holes by hand without destroying it.

My First Etched PCB for SMD

Ok, so I really wanted to try some SMD or surface mounted devices. I have ordered some parts for an amp-hour meter that are only available as SOIC. That's a little hard here cause I am renting an apartment in Carmen, Cebu Island, Philippines while my live aboard sailboat is being repaired in Republic Dry Dock, Danao, Cebu Is, PI.

Cebu is 45KM away and the second largest city in the Philippines apparently has no SMD component outlet. I see young people on the sidewalk in front of grocery stores with hot air reflow stations repairing cell phone circuit boards, but no parts. Could be I just haven't asked the right question. I did find a guy selling the hot air stations and standard DIP parts, but no small ones or unusual parts. He says everyone orders their own. I got blank board from him and the parts below.

The circuit I chose to copy for my first board was: LED Tester from the Robot Room

Since I couldn't find SMD parts, I opted for surface mounting some standard parts. No drill handy. My dremel is stored with most of the stuff from the boat.

The top of the board. I laid out the parts on a small piece of perf board then copied the paths with a Sharpie. Then I tried to touch up the lines with a really fine point one.The more I messed the worse it got. The dried ink seemed to make the Sharpie point act dryer than it was and rub off what I had prior.

The bottom, just to save the etch. All I had was a double sided blank.

Ready to roll! I've got the peroxide, the HCL and a baggie just bigger than the board.
I pour in a couple cap-fulls of peroxide, cause it says Always Add Acid. That means put other stuff before the acid. Then add a cap-full of Muriatic. Notice it says "PURE" on the label.

Then slip in the board.

That's not working very fast. What could be wrong. Maybe the acid isn't very strong. So I see the "Duck" in the bathroom has only one ingredient on the label, HCL. Maybe it is a little stronger.

On a second trip to the local Gaisano (grocery store here in the Philippines) I discover that Muriatic Acid comes in 29% or 19% or mild. I now have a bottle of the 29% for the next board.
So I add an equivalent cap-full of DUCK. Much better action and turns green like the others say it should.

Looks like 5 minutes or so and I have a reasonable facsimile of a DIY PCB.



Cleaned up and I see that my lettering is not so good, but the 1/16 traces(if you can call them that ) are ok. There is a "V" and an "A" at least I thought I drew them.

The finished board. I(t doesn't look so bad with components and at a distance.


My "Workstation"! Ha! I have to share the small plastic table with my wife and her hobbies, currently sewing a quilt(but that's another story).