Multilayer PCB image process needs several photosensitive film.
From our 4MCPCB experience, we should make one film per PCB layer at least.
Even some of the special multilayer PCB have a similar layer circuit, also require separate the image phontosentive film.
This point may confuse by most green PCB designers.
The importance of aligning photosensitive film with copper panel
In multilayer PCB manufacturing, the align precision is the important factor.
This rule also some with the image circuit process.
So the films are registered with each other and align with the pins.
This means the different layers of multilayer PCB will be perfectly aligned.
The aligned steps of photosentive film
First of all the workers should registration hole in the film.
Because every circuit layer should be made one film, so every film should be Registrate align holes.
Most of China PCB manufacturers will use punching methods to Registrate.
Also other factors may use the different Registrate method.
But the punching registrant is the more effective economy method.
Use the punching machine to Registrate align the hole
The workers should push precise registration hole in each sheet of film
This means the holes in one film should be precise, but also keeping precise holes each photosensitive film.
Here are some tips for this process.
Firstly, puts the film on the table of the punch.
This table is very small but suited for the film size.
Then align the film with the punching.
Also the worker should micro-adjusts the table, to make sure the targets on the film are exactly lined up with the targets on the film Puch.
Only follow above rule can Registrate high precise hole.