Sunday, July 4, 2010

Making PCB's at home

I know all the Electrical, Electronics and Instrumentation engineering students in
final year would be working on some project.If your project is some hardware
implementation then you may need a to prepare a PCB.Instead of spending 1000's of rupee's
outside to get your PCB done, its better to make one at home.It would not cost you much
 and at the same time you would learn something. So let me tell you exactly how to
prepare a PCB at home.Remember by the words, 'at home' I mean making use of the things
(most of the things) that are available at home.Things you need before hand, to start

1.PCB layout software Eagle PCB/Express PCB to prepare your circuit layout.
2.A photocopy paper or any smooth surface(glossy) paper.
3.An iron box.
5.Copper clad board (size depending on your circuit).
6.A metal scrub which is used to clean vessels at home.
7.A small plastic container or may be even glass container.
8.Ferric Chloride(FeCl3).
9.A PCB hand drill or you can drill holes using the drilling machine at your
10.Solder paste, solder gun, lead.
11.All your circuit components.

This is exactly how you do it:-
1.PCB layout: 
     Express PCB is a freeware whereas Eagle PCB is not.However student version of
Eagle PCB is available.Design your PCB using the PCB layout software get a MIRROR image
 of the the layout.Print your image first as a jpeg image or a pdf file. Ensure high dpi
settings while taking the printout.

     Get xerox copy of your circuit layout on the photocopy or the glossy paper ONLY.
The more THIN(for photos it is expected to be thick) it is, the better it will be.
Get the copy only through XEROX and not any other ink. You may take a print out using
laser printer not the inkjet printer.I would highly recommend XEROX ink than the printer
 ink, its better not to use a printer. In case you don't find a xerox machine that
connects to the computer directly, first take a print out on a normal paper then get
the xerox of the same on the glossy paper. Its better not to use a printer or it ll be
difficult later to transfer the ink on to your PCB. If you have some advertisement papers
(one side of the advertise papers is usually blank) which are smooth you can use them too to take the xerox instead of spending on the glossy paper.

3. Transferring the ink on to the PCB:
     First clean your clad board for dust particles using the metal scrub. With a little glue on the edge of your paper stick the paper to the copper clad board (PCB) with the printed side sticking to the board on the copper side.Ensuring that it is firm iron it for about 10 minutes or more using high setting for your iron box. Apply pressure so that the ink gets transferred onto the PCB.Once the ink is transferred to the PCB now soak the board in cold water so as to remove the glossy paper. Gently rub the paper so that it comes away in bits.

     Once the ink is transferred, next process is Etching. This is the most important step in making the PCB. Etching means removing the unwanted copper from the board to get the exact circuit on the PCB. This requires some chemicals, I mean, just one, FeCl3. You need to be a bit cautious here. Now in the plastic bowl or container take some FeCl3 mix it with water, immerse your board in the solution then continuously stir the solution.Use hot water.Add FeCl3 to water dont add water to FeCl3.The proportion is 2:1(Water : FeCl3) or a little less FeCl3.For a faster action use HCL as a catalyst 3-4 drops(not mandatory).
  2Cu + FeCl3 ----> FeCl2 + CuCl
Don't heat to a high temperature or the solution may spill out keep your clothes away because it will make marks. Once your PCB is etched, that is, only the circuit you wanted is left on the board then it is the end of this process. Stirring continuously is very important to ensure proper etching and lower the wastage of FeCL3.Be sure to dilute or neutralize the solution with a base before you dispose it. Just add lots of water and dilute. Clean the board with water. Rub gently with a waste cloth.

5.Drilling and Soldering:
      Drill the necessary holes on the PCB using a small drill or a drilling machine at your college, if there are many holes.A small hand drill made for PCB's is available in the market. And finally solder all your components on to the PCB using solder gun.

Thats how it is done and your PCB is ready.

Estimated cost for etching a 13x9cm pcb

1.Cost of clad board:          1                   20-30 Rs
2.Cost of FeCl3:               25 grams         25 Rs
3.Cost of glossy paper        1                   5-10 Rs
4. Miscellaneous                                      25 Rs
Total                                                       75-90 Rs

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