Introducing you to different types of Printed Circuit Boards

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Steps Involved in PCB Fabrication

Modern technology has streamlined the process of PCB fabrication. Almost all tasks are conducted by machines. This guarantees that you get a perfect and high functioning product each and every time. But if you have ever wondered what exactly goes on in the fabrication process, then keep on reading because today you are going to know about the process of creating multilayer PCB, step by step.  

Schematics

The designer of the board uses the CAD system (Computer Aided Design) to create the schematics. CAD system uses its own internal data format. The PCB industry had developed its own standard output format to transfer the layout data of the manufacturer referred to as the gerber file. This file defines the copper lines in the schematics, as well as the soder mask and the location of the components. The designer of the schematic conducts the DFM review after the initial design is complete. This is done to check the trace lift widths; the space between the traces and the size of the holes to make the design fit the manufacturing capabilities. Once this task is complete, the file data is sent to the appropriate machines for the next step.

Photo Plotting

The laser photo plotting machines create the film that will be used to make the PCBs in a temperature and humidity controlled darkened environment. The data from the gerber file is converted into an image file here and the laser photo plotter cuts it onto the film. The machine then automatically develops the film and unloads it.

Inner Layer Lamination

This process starts with cleaning the copper sheets. This is done in a clean environment to make sure that no dust can get it in, because otherwise it might cause a short or open circuit. After the cleaning, the sheet is coated with a photo sensitive material called the photo resist. After that the previously created film is placed in the printer. Over that the copper sheet with photo resist is placed and the layers are precisely aligned. This time the printer uses powerful UV lamps, which harden the photo resist on top of the copper sheet.

Etch Strip Developing

The hardened resist remains on the copper sheets while the rest of the resist needs to be cleaned away. A powerful alkaline solution is used to etch away (dissolve) the unwanted copper. After that the film, that protected the remaining copper, is stripped away. Later, to align the inner and outer layers, holes are punched in the layer.

Automatic Optical Inspection

Flaws in the layers cannot be detected once the PCB is assembled. That is why the AOI (Automatic Optical Inspection) machine is used to compare the produced copper layer with the original image created by CAD. The machine displays the flaws on the screen. Once they have been corrected, the oxide treatment of the sheet begins. This is done to protect the copper sheets from oxidizing. For this process the brown or black oxide is used.

Multilayer Lamination

The multilayer lamination process starts with placing copper foil at the base. On top of which, two prepreg sheets are placed. The copper sheet, fresh from the oxide treatment is placed in the middle, again followed by prepreg sheets and copper foil. However, the aluminum plate is added at the top this time. This stack is sent to the pressing machines, where it is laminated together using heat. The aluminum plate is placed on top to protect the copper foils and it is later removed. The prepared panels are sent to another machine where excess material is cut off very carefully.

Drilling

The drilling machines are prepared with exit material, on which the panels would be placed. On top of the panel, an aluminum plate is placed to make sure that the panels don’t tear up during the drilling. The computer operated machine drills precise holes in the panel according to the original schematics. The drilled panels again go through a cleaning process to remove the excess debris. Finally the boards are electroplated with copper and stacked automatically.

Jet Scrub Cleaning and Soder Mask Application

This is done to remove oxidation from the surface of the copper, as well as to create topography to enhance the doer mask adhesion about to be applied soon. The process also makes the panels go through anti tarnish. Most boards have soder mask printed on to each side to protect the copper surface and to prevent soder shorting between components during assembly. A coating of soder mask is applied using machine machines to spray it on the surface of the panel. Soder mask is also called Liquid Photo Imageabel (LPI). Afterwards, the panel is covered with protecting platting. An inkjet printer is used to plot the location of the components that will be placed on the board.

Electrical Testing and Inspection

The prepared panels are all tested for any open and short circuit. Once it’s declared flaw free, the panels are rigorously tested by both machine and human operators. Only when they have been cleared by both, are the panels sent for final inspection and testing. The panels are tested against the original design, and checked to see if they will fit the components and operate within the parameters they were designed. The boards which pass each and every test are made ready for the shipment.

If you are interested in the fabrication process, or if you are looking for that specializes in developing prototypeprinted circuit boards, then contact the leading PCB developers, Super PCB right now to get a quote. Or you can visit http://superpcb.com