Printed Circuits Boards Manufacturing process
Printed Circuits Boards manufacturing will go through 8 steps:
1 Printed Circuits Boards file drawing:
The majority of PCB file is draw by PCB designer, and Printed circuits boards manufacturer in order to ensure the quality when PCB manufacturing, will need to inspect and modify the PCB file, those unqualified PCB file will be re-draw to meet the requirement;
2 Printed Circuits Boards film plotting:
Plotting a PCB film onto photo and make it has the same size of PCB layout, photograph a PCB possess the same process as ordinary picture photograph, can be divided into: film cutting — exposure — developing — water rinse — dry — edition revise.
PCB film inspection should be operated before the photograph process being taken especially for those PCB film being placed for a while;
3 Printed Circuits Boards pattern transfer:
Transfer the PCB film from the plate to Copper Clad laminate (CCL), there are several ways for PCB pattern transfer, include the silk screen and photochemical method;
Install the CCL onto the base substrate and fix it through the pin-hole, printed material being placed into the fixing frame;
Use the rubber knife to scracth the surface of printed material, untill the printed material can get in touch with CCL directly, and then PCB film pattern will be printed on CCL; finally cure the plate, make necessary modification on the PCB film pattern.
4 Printed Circuits Boards circuit pattern formation:
A. Direct exposure method include CCL surface treatment — print photo-sensitive film — exposure — developing — cure — modification, modification is an necessary step before the etching through which all the burs, open circuit and node can be stripped off;
B. Photo-sensitive dry film method use a thin film as the sensitive material, the film consist of polyester film, photographic film and polyethylene film, photo-sensitive film being composed in the middle structure and the protective film should be stripped off and then use the printed film machine to press the photosensitive film onto the surface of CCL.
5 Printed Circuits Boards circuit pattern etching:
Use the chemical solution to etch the unnecessary copper and left behind the circuit pattern which is composed by PADs, circuit and symbol, the commonly used chemical solution include basic copper chloride, ferric chloride and so on.
6 Printed Circuits Boards through hole metalization:
Via hole metalization is deposited copper onto the hole wall which go through the both side circuit and pad simutaneously, so called “Plated through hole”, it is an indispensable step when the manufacture of double sided and multilayer PCB circuit board. And the working process is: drilling — desmear — acid treatment — water rinse — hole wall activation — copper deposit — copper plated and so on;
The quality of PTH is critical important for double sided and multilayer PCB circuit board, so the inspection is necessary, the hole wall should be even and completely connected with copper circuit or pad, when it comes to the HIGH DENSITY INTERCONNECTED PCB circuit board so called HDI, all the metallic via existed in the format of blind hole (hole filled with copper) in order to save the space of PCB surface and increase the density;
7 Printed Circuits Boards surface treatment:
In order to improve the performance of electric connectivity, solderability, abrasive and extend the shelf-time of PCB circuit board, PCB bare board will be treated with metal material like GOLD, SILVER and TIN-LEAD alloy.
8 Printed Circuits Boards solder resist printing:
PCB can be protected by the solder resist ( also know as SOLDER MASK ) to ensure the accuracy of welding, at the same time all the PCB circuit board pads which are need to be soldered will be exposured, the solder resist can be divided into 2 types: heating absorption curing and photo-sentitive curing, color has a wide variety of choices from green, black, red to yellow, according to customer requirement.
Tags: printed circuits boards