Keywords: Printed Circuits, Circuits Board

For anyone involved in the electronics industry, The PCB manufacturing process is very important. In a variety of ways, the PCB manufacturing process can be achieved and there are various variants. The main stages in the Printed Circuits manufacturing process are the same despite the many small variations.

PCB constituents

From a variety of substances, Printed circuit boards PCBs can be made. A form of glass fiber-based board known as FR4 is the most widely used. Under temperature variation, this provides a reasonable degree of stability. While not being excessively expensive, it does not break down badly. For the PCBs in low-cost commercial products, other cheaper materials are available. PTFE-based printed circuit boards can be used for high-performance radio frequency designs where low levels of loss are needed and the dielectric constant of the substrate is essential although they are quite tough to work with.

The copper-clad board is first obtained to make a PCB with tracks for the components. The substrate material, typically FR4 is present in them with copper cladding on both sides normally. Bonded to the board, a thin layer of copper sheet is present in this copper cladding. The very nature of PTFE makes this more difficult although this bonding is normally very good for FR4. To the processing of PTFE PCBs, this adds difficulty.

The basic manufacturing process of PCB

Creating the required tracks on the board and removing the unwanted copper is the next step with the bare PCB boards selected and available. Using a chemical etching process, the manufacture of the PCBs is normally achieved. With PCBs, the most common form of etch used is ferric chloride.

A photographic process is used to gain the correct pattern of tracks. Typically, with a thin layer of photo-resist, the copper is covered on the bare printed circuit boards. Through a photo mask or photographic film detailing the tracks required, it is then exposed to light. The image of the tracks is passed onto the photo-resist in this way. In a developer, the photo-resist is placed with this complete so that only those areas of the board where tracks are required are covered in the resist.

Placing the printed circuit board into the ferric chloride is the next stage in the process to etch the areas where no copper or track is required. It is placed into the etch froth required amount of time knowing the thickness of the copper and the concentration of the ferric chloride on the Circuits Board. Some definition is lost as the ferric chloride will tend to undercut the photo-resist if the printed circuit boards are placed in the etch for too long.

Other methods are also available although most PCB boards are manufactured using photographic processing. Using a specialized highly accurate milling machine is one method. To mill away the copper in those areas where the copper is not required, the machine is then controlled. From files generated by the PCB design software, the control is driven and automated.

Printings etch-resistant inks onto the PCB using a silk screening process are another method that is sometimes used for a PCB prototype.

PCB vias and holes

Holes often called vias or via holes are needed. To enable leaded components, Holes may also be needed to be mounted on the PCB. Additionally, some fixing holes may be needed.

Normally, within a PCB to connect the different layers at different points, the inner surfaces of the holes have a copper layer so that they electrically connect the layers of the board. Using a plating process, these plated through holes are produced. The layers of the board can be connected in this way.

Using numerically controlled drilling machines, Drilling is then accomplished. The data supplied from the PCB CAD design software is also accomplished. It is worth noting that the cost of the PCB manufacture is reduced by minimizing the number of different sizes of holes.

Existing within the center of the board may be necessary for some holes, for instance when board inner layers need to be connected. In the relevant layers, these "blind vias" are drilled before the bonding of PCB layers together.

PCB solder resist and solder plating

Keeping the areas that are not to be soldered protected by a layer of what is termed solder resistance is vital when a PCB is soldered. Unwanted short circuits on the PCB boards caused by the solder can be prevented by the addition of this layer. The solder protects the board from other contaminants and resists normally consisting of a polymer layer. The solder resists color is normally deep red or green.

Either SMT or led to solder to the board easily to enable the components added to the board. Exposed areas of the board are normally plated with solder or tinned. Occasionally areas of boards or boards may be gold plated. If some copper fingers are to be used for edge connections, this may be applicable. It offers a good connection at a low cost and good conductivity As the gold will not tarnish.

PCB silkscreen

It is often necessary to place other small printed indents and print text onto a PCB. To aid in fault finding, etc., this can help in marking component locations, and also in identifying the board. To add the markings to the board, a silkscreen generated by the PCB design software is used after the completion of other manufacturing processes for the bare board.

PCB prototype

Before committing to full production, it is normally advisable to make a prototype as part of any development process. PCB prototype is normally tested and manufactured before full production and it is true of printed circuit boards. To complete the hardware design phase of the product development, there is always pressure. Hence, a PCB prototype will need to be manufactured quickly typically. Using a slightly different PCB manufacturing process as only a small quantity of the PCB prototype boards will be needed is often accepted as the main purpose of the PCB prototype is to test the actual layout. In the electronics production lifecycle, The PCB manufacturing process is an essential element. Many new areas of technology are employed by PCB manufacturing.  Both the reliability of the Printed Circuits and the reduction of sizes of tracks as well as components used, this has enabled significant improvements to be made.