If you have read our image circuit layer article, either image outer circuit layer or image inner circuit layer process require in the yellow room.
The yellow room, or named clean room.
This paper Emma wants to focus on some important tips that Provos did not discuss during the inner circuit process.
Only under the black area copper, will remove
We know the inner image process is used photosensitive material.
And we want to reserve the circuit and remove other area.
The photosensitive film through UV light expose, the surface color will change.
4MCPCB experts told us that only under the black area that the copper will be removed.
This means that the circuit, trance areas are not black.
Then consider unhardened resist area circuit manufacturing
Above we have known the black areas are very hard area.
But if you have visited a rigid PCB factory, you will find that there were some area unhardened resist area also need circuits.
Usually the workers will spray with a powerful alkali solution in those areas.
Of course outside of the photosensitive film and unhardened resist areas.
The the powerful alkali solution will use chemical methods to create circuits.
Then the inner circuit layer board should be clean.
Most of rigid PCB manufacturers use pressure-washed automotive machines.
Some advantages automatic machines have an auto dried function.
Or the workers should dry them by manual method.
You will find the copper pattern we want is now covered by the hardened resist.
