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How are printed circuit boards made?
How are printed circuit boards made?

PCBs have been manufactured for more than 80 years, and their complexity has increased with the steady growth of the electronics industry. Materials have also changed due to applications and regulations. Thus, in the design of the panels, the end use will have as much impact on the way the panel is manufactured and its overall cost as the choice of a specific component.

All printed circuit boards (commonly known as PCBs) are unique and custom. They are a solution for having to wire components in a circuit. They form a platform on which to organize elements for specific circuit design.

Their printed circuit board assembly companies involves many techniques and disciplines, the interaction of which must be understood and controlled to produce reliable and consistent results. Only one defect on 100 processes used to make a printed circuit is necessary to cause a fault.

First stage

All PCBs start with a CAD file or Gerber file that must be "Tooled," each manufacturer working with different machines and a different set of tool holes to position the panels for process alignment to the other. Photographic tools will also have to be produced for several stages of production. This is the "tooling load" often cited.

Second step

The raw material used is a mixture of glass fibers coated with copper and double-sided epoxy. There are different qualities of other materials also available, depending on the requirements of the final application. Some of them require special treatment, which is usually neither stored nor accessible.

The most common is FR4 1.6mm thick with 1 oz of copper. (FR4 refers to the degree of fire resistance, 1 oz of copper has a thickness of 36 microns)

This raw material is precut in sheets of different sizes, easy to handle by the processing machines. Pre-production will determine the best yield to reduce waste and therefore, the best sheet size for each custom build.

The panel is then drilled with holes required for the circuit and tool holes or slots for production.

Third step

All previously drilled holes are non-conductive. Thus, to connect them (by allowing interconnection between the upper and lower copper layers on the base substrate panel), the entire panel undergoes a series of wet chemical processes to "metalize" the whole surface, which adds: 1-5 microns of copper on all surfaces.

Fourth stage

The panel is then covered on both sides with a film of photoresist which, using the photographic tool, will give a resistant resin. For areas where copper tracks are needed and to reinforce the plated holes, are now galvanized with copper and a thin layer of tin. Tin is there to form a strong etch for the next step.

Step five

The plating resistor is then removed, and the panel is then passed through an etching solution. This will burn the copper, but not in the areas where the tin acts as a resist resistant to etching, leaving behind "conductive tracks."

Step Six

The tin is removed, and the copper etched and cleaned before applying a layer of electrically insulating protective mask ink for the photo. With a photo tool, an image is generated, leaving a hard coating on the entire circuit, going exposed copper studs to interconnect the components.

Step Seven

At this stage, a weldable surface finish is applied, which may be of the HASL (Hot Air Welding Leveled) or Gold (ENIG) type with electrolytic nickel immersion (EN), depending on the application and complexity of the card design.

Other surface finishes are available, but these two applications cover the majority of the application and are the most commonly used.

Step eight

Printed Circuit Board can be applied at this stage, by photo-imaging or screen printing. This facilitates the placement of components and is a help in the field if repairs/upgrades are needed.

The circuits are now ready to be routed as simple circuits or left in a panel before testing the bare board.

Once tested for breaks and shorts, they are visually inspected before shipping.

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PCB, PCB, printed circuit boards, printed circuit boards, PCB companies, PCB companies,

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