Inner layer image process for multilayer rigid PCB

Photoresist material introduces

Photoresist material is a critial multilayer PCB material for multilayer rigid PCB Inner layer image process.
In the outer layer imager article, we have mentioned this type raw PCB material.
And in the clean room, the workers loaded the cleaned copper panel.
Then skillfull coat with a thin layer of photosensitive film.
Yes, the photosensitive film is main contain photoresisit material.

Use pin to align inner copper panel

There were many align method to align the inner copper panel.
And different multilayer rigid PCB factories have differed inner copper panel align method.
In China, most of them use pin to align the inner copper panel in the bed of the print ad.
The registration pins matching the holes in the potatoes and in the inner copper panel.
This may the most effective economical aligns method.

Detail steps of inner image circuit process

The worker loads the first film on the pins, make sure the photosensitive film align right position.
Then loads the coated inner copper panel on the pins.
This time the photosensitive film is under the inner copper panel layer.
Then we should go to load the second film on the pins, up the inner copper panel.
All two layers photosensitive film and the inner copper panel layer precisely aligned by the pins.

An expose of the inner image circle is a critical factor

All beginning steps of the inner image circuit process were in the yellow room.
Due to the printer’s power UV lamps should in a yellow environment working.
The photoresisit under the lamps, some parts has harden and the rest area were not.
This means the photosensitive material through the clear film to define the inner copper pattern.