UV PCB Manufacture


- SAFETY NOTICE -

It is important to follow current safety procedures and guidelines
when handling or working with the chemicals and materials mentioned below.


Making Your Own Printed Circuit Board

(A 10-step process using the photographic technique)

 

1, After you have produced your PCB layout with OnTrack's System's Designer, use a printer and clear transparent film to produce your photographic mask. You can either do this with the subsystems connected for individual work, or separated for group work (this is so the subsystem modules can be interconnected later on).

Ex. 1 - Subsystems Closed
Ex. 2 - Subsystems Open (for group work)

 

2, Using 50mm wide PCB with a "photo-resist" layer, cut a length of the board to fit between the corner marks of your mask (see above). Either use a guillotine, tin snips, or hacksaw to do this and then smooth the edges with emery cloth or a file.

PCB with photoresist layer

3, Place the mask onto an Ultra Violet (UV) light box ensuring it is the correct way up and not upside down!
Peel off the protective plastic film from the PCB and place it face down onto the mask. After closing the lid, set the UV Light Box timer for approximately 2 minutes and wait for areas of the board, not masked by the black areas on the mask, to be exposed to the U.V. light.

UV Timer Box (Remember to close the lid!)

 


4, When the time is up lift up the lid (but never look into the light box when the UV is switched on). Remove the board and keep your mask safe, just in case you need to use it again.


5, The board should now be given to a qualified technician who will place it into a suitable tank or tray containing developer or alkali solution. This will strip away the photo-resist layer that had been exposed to the UV light. The circuit tracks on your PCB will be saved, however, as they were covered by the mask's black areas. Remember the developer can be harmful and necessary safety precautions such as eye, clothing, inhalation and skin protection have to be taken. (See COSHH details associated with the products before use).

Bubble Etch Tank with 2 Compartments

 


6, Wash the board in water to remove all the chemicals used in this process.


7, The copper layer underneath can now be removed by transferring the PCB to a heated tank of etchant - ferric chloride or sodium persulphate. This acid will react more quickly with the heat and remove the exposed copper on the board. After approximately ten minutes your circuit board will be produced.

It is very important to follow the recommended safety precautions when working with these chemicals and expert help should be sought before carrying out this work - Never mix these two chemicals. As part of "Quality Assurance" procedures, it is important that the chemical solutions are made to the correct strength, maintained at the correct temperature and replaced from time-to-time after continued use.


8, Wash the finished circuit board thoroughly and rub with either a pan scourer or very fine wire wool to remove any left-over resist or residue that might still be covering the copper tracks and pads. Any contaminated water should be disposed of carefully and responsibly.


9, So that the component legs may be pushed through the board, you will now need to drill holes through the PCB pads on the circuit board (details are also shown on OnTrack's circuit legends).

PCB Legend

You can use a 1mm drill bit held in a mini-PCB drill + stand to do this - Remember to wear safety glasses as the small drill bit can easily break if the work is not done gently.

PCB Drill + Stand

 


10, To finish, visibly check with a magnifying glass that there are no breaks in the Copper tracks or short circuits. These faults can occur if the printed mask is of poor quality or the copper has been left for too short, or too long, in the developer/etchant solutions.

A multimeter set to measure resistance, or conductivity, will further help you check for continuity or breaks. These checking procedures are part of "Quality Control" and avoid unseen manufacturing errors preventing your circuit from working later on.