PCBs are laminated in order to strongly bond together. Once the PCB panels are fixed with traces, they will undergo a process known as Automated Optical Inspection (AOI). During this process, the inside layers are examined in opposition to design rules based on the data stored in the gerber files. If it is permissible and found practical, some level of repairs and fixes can be made at this stage.
Moreover, the information pertinent to defects and irregularities is circulated among the relevant departments to work on its resolutions.
The hub which has the design pattern is now stamped in the copper and is mingled together using a fiberglass material known as prepreg. The top and bottom layer is covered using copper foil which is typically around .5 oz to 1 oz. Of course, it is very thin and is added as part of the overall stack-up. Next, the panels are placed for lamination within a lamination press. It is during this process that they go through heat and pressure in order to bond the hub, prepreg and the copper foil mutually.
The Lamination Process
Desmear
This process is quite applicable on PCBs are that composed of multiple layers. This is referred to a chemical process whereby the skinny coating of resin is removed from the inside layer produced by the warmth and movement of the drill bits as they punch holes. By eliminating the resin, this process enhances the electrical connection of the board.
To obtain consisting copper plating in the holes of the printed circuit board, a number of steps need to be concluded.
Deburr
Deburr is an coarse and sharp motorized process that eradicates the elevated ends of the metal (or burrs) neighboring the holes that crop up at some point during the process of drilling. Through deburring, any debris or grime that’s left out within the holes is exterminated simultaneously. Desmearing is repeated after deburring.
Electroless Copper Deposition
Upon the removal of the smear, a slim copper coating is deposited on all the uncovered exteriors of the board, inclusive of the hole in the walls through a chemical process. This leads to the creation of a metallic base for electroplating copper onto the surface and the holes as well. The breadth of the electroless deposited layer falls in the range of 45 & 60 millionths of an inch.
The next step involves applying and etching the copper onto the externals layers. It is important to know that this step is all about getting the traces as well as the spaces impressed into the copper.
Furthermore, the panel will undergo a copper plating bath for the copper plating to be added into the holes along with the copper on the exterior of the board. However, the time duration for copper plating highly depends upon the ultimate copper thickness needed for the board.
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