Hello, Does anyone here know why you expose the PCB board to light during the process of PCB board making? Regards, Peter 1 pt
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Peter Perseverance will always prevail

Hi Peter, You expose the pcb to UV light, with the negative overlaying the pcb. The UV goes through the areas on the negative which are clear, thus hardening the photosensitive material which covers the copper on the pcb substrate. The areas where the negative is black - and the UV light doesn't reach the photosensitive material on the copper (on the pcb) - means that it stays soft, and is easy to remove. You would then rub or wash the surface of the pcb with some type of developer material (depending upon the pcb type), which removes the soft photosensitive material, and leaves the hardened stuff. You would now have exposed, shiny copper and bluish hardened tracks and pads patterns on the pcb. Now you would etch the pcb - i.e. the acid copper eating process (but this doesn't reach the tracks and pads which are protected by the hardened material. Then you put the pcb into a solution to remove the hardened material that was protecting the tracks and pads. (Could be very diluted caustic soda.) Then you drill, tin and assemble your board! Hope this helps (and wasn't too much "overkill"). Liane.
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