PHOTO RESIST

 

PHOTO-RESIST BOARD is a piece of glass reinforce plastic. One of the sides is copper clad and this copper has a photosensitive coating. When the plastic film is peeled back this sensitive coating is revealed.
After processing this will be the PCB.

 

PCB MASK

 

The PCB mask (now on a transparency) is placed underneath the photo-resist board, touching the sensitive surface. Remember the plastic film must be removed. PCB mask and board are then transferred to the UV light Box.

You must be careful to ensure that the PCB mask is the right way up, otherwise when the circuit is etched you will discover that the tracks are also the wrong way round.

 

UV EXPLOSURE

 

The lid is shut and the box switched on. The photo-resist board, with PCB mask are left underneath the lid for 2 ½ minutes. The photo-resist board is then placed in a tank filled with developer (using plastic tongs)
It is important that the board is only left in the developer for approximately ten seconds.

 

ETHICNG

 

When the board is taken out of the developer it must be washed in clean water before transferring to the etching tank. Always use plastic tongs.

DEVELOPER TANK

 

The etchant is held in a ‘bubble etch tank’ and is heated. This solution slowly etches away the unwanted copper, leaving the tracks only. At this stage it is important to keep checking that the PCB is completed (time – 15 to 45 minutes). If it is left in the tank too long the copper tracks will also be removed or damaged.

ERASING

 

When removed from the etching solution, the PCB is washed and a PCB eraser is used to remove any film from the tracks. This must be done carefully because the film will prevent good soldering of the components to the PCB. The tracks can be checked using a magnifying glass. If there are gaps in the tracks, sometimes they can be repaired using wire but usually a new PCB has to be etched.

 

DRILLING

 

The last stage is drilling the holes for the components. A small PCB drill is used for this purpose.

Again care is needed as a good PCB can be ruined by careless drilling.

 

COMPLETION

 

 

This completed Printed Circuit Board (PCB) has all its components soldered in position. It has been manufactured through the processes described in the information sheets.
PCBs manufactured in industry are designed on a computer and then manufactured on an production line controlled by computers. Usually there is very little human contact.