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Etching Your Own PCBs

Posted by 3:37 
Etching Your Own PCBs
July 03, 2010 01:52PM
Hello, I'm getting ready to make a RepRap and I would like to keep my costs as low as possible. Seeing as Maker Bot Industries do not sell the bare PCBs for the motherboard and such I was wondering if it is possible to etch your own PCBs for those electrical components or are the tolerances for the SMT components too high for an amateur job.

Thanks
Re: Etching Your Own PCBs
July 03, 2010 05:28PM
A great resource for etching PCB's at home is [tech.groups.yahoo.com]
I have used toner transfer to make boards with components having a pin spacing as small as .4mm pitch.
Photoresist is my preferred method now.

If you plan to only etch just for this project, then you probably will not save that much in money or time versus just buying. However if you are a serious electronics hobbyist, then I think it is worth while to get equipped and become proficient in making your own boards.
Re: Etching Your Own PCBs
July 05, 2010 05:00PM
Thanks for the help, also does anyone know if the RepRap PCBs are double sided. If anyone has made PCBs for a RepRap and has any tips to share they will be appreciated.
Re: Etching Your Own PCBs
July 05, 2010 09:05PM
Search my posting history. I had some left over PCB and toner transfer paper, which I used to make a USB cable from the arduino layout. My experience with home etching has been mixed. This is something I have done off and on for over 30 years. Usually I find the toner does not stick to the edges. Better results from photo etching, but the overhead is a lot more and the chemicals are nasty.

While pricey I like the expressPCB service. This requires dedicated layout software and is as closed as it gets. Advantage, small quantities arrive in a bit less than a week. Send the design on Sunday, have the board on Thursday. One can get 3 Arduino sized boards for about $60USD. or about $20USD per board. I have been using this service for over 10 years. Have a lot of layouts in that format.

Eventually myself or someone else will make up some express PCB files. Mostly that is time and effort, which I seem to be rather short of these days.

-julie
VDX
Re: Etching Your Own PCBs
July 06, 2010 03:02AM
... i've given avay my PCB-etching tools to a friend and use my CNC-mill for singelecounts of PCB's - single- and doublesided ... sometimes populated with SMD's.

For higher counts or multilayer-PCB's it's much easier with comercial services ...


Viktor
--------
Aufruf zum Projekt "Müll-freie Meere" - [reprap.org]
Call for the project "garbage-free seas" - [reprap.org]
Re: Etching Your Own PCBs
July 06, 2010 05:46AM
@3:37
The Gen3 boards are double-sided.
I started making these boards some months back, and it is possible but I should point out the following:
1. You need to clean your double-sided copper board, thoroughly. There must be absolutely no finger-print marks or any dust on the board. You can hold the board at an angle and watch for clear reflection from the surface. If you can, wear gloves while polishing.
2. I use photo-resist (positive-20), to spray on the copper board. Make sure that you do this in poor lighting condition. Spray from a distance of about 20cm and make sure that the coating is even on the board surface. Note the following:
2.1.If you hold the spray-can too close to the board surface, the some liquid will "bounce off" the board surface, and the chemical application will be uneven.
2.2.If you did not clean the board properly in step 1 above, the photoresist chemical will adhere to impurities and form pot-marks on board surface.
3. After spraying the board, you have two options:
3.1. You can store the board in a dark, dry cupboard for 24 hours at average temperature of 23C
3.2. You can put the board in oven at 80C. If using this method, you will have to experiment to find the right amount of time inside the oven. My test results revealed the following:
3.2.1. Before inserting the board into the heated oven, I had to switch off power in order for the heating element to stop glowing red. I suspect that the light given off by the element was enough to interfere with the photosensitive chemical.
3.2.2. For double-sided board, best oven-time (with oven power off) was 30min per side i.e. put board in while oven temp at 80C, wait 30min, remove board, re-heat oven to 80C, remove oven power, wait for element glow to recede, and insert board again (flipped over)
3.2.3. When working with positive-20, wear gloves, and protective eye-wear.
4.Once the copper board is removed from oven, then it is photo-sensitive, and can now be exposed to UV (approx wavelength 370nm, if I remember correctly). For this purpose, I bought a "black light" from a local lighting store. I rigged a big box, with white A4 paper glued on the inside, and stuck the black-light through the top.
5. You are not ready to use the black-light yet. First you have to make the "book".
5.1. If you have a pdf-format of your PCB layout, then print out top layout and its left-right mirror, on a laser printer on transparency. Print out the bottom-layer board layout, and its left-right mirror, as well. Make sure that the toner density is at least 600dpi.
5.2. Take two top layer printouts, and align such that toner is on "outside" i.e. toner-sides face away from each other. You can determine the toner-side of the transparency by looking for reflection off transparency surface. Toner-side will be dull, and not reflect light. Duck-tape or glue transparencies together.
5.3. Align the bottom layouts, same as above.
5.4. Align top layout (in 5.2) to bottom layout (in 5.3). Duck-tape them together, such that you can slide copper board between.
6. Slide photosensitive copper in-between transparencies, and place between two glass surfaces. If needed, duck-tape glass surfaces together, with transparencies and copper inside.
7. Put UV box (made in 4), over glass surface, and expose for 30min per side.
8. Once exposure is complete, you can develop photo-sensitive copper in solution of sodium-hydroxide (NaOH) and waterglass. You can make the solution in the following way:
8.1. Dissolve a teaspoon of sylicate (chrystal cat-sand) and one teaspoon of NaOH in a cup of hot water. Stir while cooling.
8.2. Dissolve between one and one-and-a-half teaspoons of NaOH (drain cleaner) in 1000ml water.
8.3. Add waterglass made (in 8.1) to NaOH solution.
9. Exposure time may vary. I have had exposure times ranging between 5min and 10min.
10. Once exposure is complete, rinse with water and dry with kitchen-roll paper.
11. At this point, it is better to drill via holes, first. Since tracks will become unstuck while drilling after etching.
12. Also, make sure that all track definitions are well developed i.e. remove all photoresist between tracks with a sharp knife, if necessary.
13. You may also want to increase definition of certain "over-etched" tracks with sharpie or other etch resistant marker.
14. Once all vias have been drilled, it is time to etch the board;
15. Etching can be done in various solutions of your choice eg. FeCl (iron chloride/ferric chloride). I use a prepared solution of CuCl and water. Prepare CuCl solution in following way:
15.1. Add 100ml of HCl (Hydrochloric Acid aka pool acid) to 700ml of water. Add 20ml-40ml of peroxide-40. Add a "throw-away" copper board into the solution - not the board you will develop!!!
15.2. The solution will turn green after a while as the HCl reacts with Cu. If the solution turns dark brown, you have dissolved too much copper, so just add HCl until the green colour returns.
15.3. Remove the "throw-away" copper board. The solution that remains behind, can now be re-used for successive etching i.e. same solution can be stored and re-used to etch many boards.
15.4. The next step is to aerate the CuCl solution by letting a fish-tank pump push air through.
15.5. Add the board that you wish to develop, while the pump is pushing air through the solution.
15.6. Monitor the etching process frequently. The colour of the CuCl solution will proceed from light green to dark green to brown, depending on how much Cu needs to be etched.
15.7. The speed of the etching process can also be increased by heating the CuCl solution.
16. When etching, make sure that you wear protective hand and eye gear at all times. Also make sure that the area where the etching happens, is well ventilated. Use plastic tweezers to remove/ and insert board as needed.
17. Once etching is complete, remove board and wipe with acetone.

These suggestions above was sufficient for me to build a sanguino and V2.3 stepper boards for Mendel. YMMV.

Regards
Marius Botha
Pretoria, South Africa
[mariushermanbotha.wordpress.com]
VDX
Re: Etching Your Own PCBs
July 06, 2010 06:30AM
... uh ... oh - what a long checklist confused smiley

This was one of the reasons too, i've gone away from etching spinning smiley sticking its tongue out


Viktor
--------
Aufruf zum Projekt "Müll-freie Meere" - [reprap.org]
Call for the project "garbage-free seas" - [reprap.org]
Re: Etching Your Own PCBs
July 08, 2010 05:53PM
I found cleaning with acetone not adequate. The green foil stuff would simply move to somewhere else on the board and make it look dark and muddy. I finally gave in and used MEK, which is nasty stuff but cleaned the board nicely.

Yes, the only complex double sided board I have done took LOTS of care to get it close to working, much time between masking and etching to check for shorts and opens, more time after etching to repeat the same, and then hand bridging EVERY via, and some component through holes, with little strands of copper. It is expensive, but nice to have the commercially made boards with no shorts, no opens, and all the holes plated through!

Mike
Re: Etching Your Own PCBs
July 10, 2010 12:16PM
Thanks guys, this is really helpful
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