All PCB fabrication companies have standardized procedures in transforming a blank PCB into a valid electronic product. They also have the capability to transform multiple PCBs into one small, but working product. This product has the advantage of fitting itself in a limited amount of space, like computers or phones.
This article contains a series of PCB fabrication procedures, which companies use to transform a blank PCB into a patterned and holed one. You can use these techniques for home or business use. Some of the subtopics found here, however, require you to have sophisticated knowledge of the steps, or expensive equipment to accomplish the tasks. It is therefore suggested to find a partner firm instead, so that they will be the ones to cater to your fabrication needs.
1. Undergo Photoengraving Process
Before you can start transforming a PCB, preparations must first be done. You must purchase copper clads, coat the inner layer circuits with photoresist chemicals, and prepare the artwork.
The inner layered artworks and the photoresist coated PCBs then need to undergo photoengraving procedures. An inner-layer board must be exposed to ultra-violet light. This light causes the polymerization or hardening of the photoresist film.
A negative film is used for the inner layers. This film contains opaque marks that are used to prevent specific areas of the coated PCB from hardening. On the other hand, the transparent portions of the photoresist that hardened are those patterns that belong to the PCB layout.
2. Etch the Electronics Circuitry
The printed circuit board will now undergo another major step in the PCB fabrication process. This is basically the start of the physical transformation of your PCB.
The procedure is called chemical etching. This procedure removes all the unwanted copper thru the introduction of an acid-based chemical. The standard chemical used in etching is Ferric Chloride. The areas that were not exposed in the photoengraving process will be eaten away by the acid. The copper located on the protected areas, on the other hand, will be protected from the chemical etch.
It is better not to do the chemical etch, if the requirement are not yet final. Once the etching procedure is completed, it cannot be undone.
3. Strip the remaining photoresist
After etching, the remaining photoresist must be removed by using another chemical. Stripping must be done to wash off the remaining photoresist. This will leave only the copper circuit pattern.
4. Inspect the Inner Layers against Customer Specification
The etched layers are then inspected for conformity based on customer’s specifications and design rules. The inspector will consult the customer submitted Gerber files for any inconsistencies with the actual output.
It is also possible that a machine can do the automatic inspection for the project. It is called Automated Optical Inspection. The machine which does the inspection usually has a camera that autonomously scans boards for defects, such as scratches and stains, open and short circuits. Other visible and physical problems can also be reported by the machine.
Inspection must be done to determine the obvious defects, and to use pre-emptive measures that can fix these problems.
5. Bond the multi-layered boards
The panels are treated with chemicals to make the copper surface more adhesive. Since the circuit involves multiple layers of copper, then the etched multiple layered boards must be assembled as one. A procedure called layup is done.
Multiple layers, also called laminates, are stacked in the order of the design. Pin holes are used as guides to prevent stacking and positioning mistakes. There also should be a predefined and standard thickness in between these laminates.
6. Laminate the Panel
Lamination usually is done in a high temperature and high pressure environment. It is typically performed in a vacuum space. The dielectric and resin will liquefy from the extreme heat. The liquefied resin of multiple layers will now bond with each other. After the bonding, the stacked up boards will then be cured back to solid form.
The lamination process will fabricate the multiple layers as one panel. Thus, another major PCB fabrication step has been completed.
The things discussed here are done by a PCB fabrication company to transform a blank PCB into a panel that contains multiple layers of PCB. The PCB manufacturer you choose should be able to create the PCB itself, and not only analyze and design it.