Processes Involved in the Manufacturing of 4 layered PCBs – Part 1

The demand for 4 layer PCB boards has been on the rise owing to the fact that they offer high signal intensity. The 4 layer PCB features a top layer, inner layer 1, inner layer 2 and a bottom layer Is that all? Would you like to know how 4 layered PCBs or other multi layers boards are manufactured? This post lists the major steps involved in multilayer PCB production.

PCB manufacturers generally follow the below-listed steps in the production of a 4 layered or other multilayered boards. Let’s have a look at these major processes involved in the board making.

• Clean the Board Surface:

  The board surface must be cleaned and devoid of fingerprints, dust, oil and other contaminants. Thus, its intense cleaning is highly demanded so as to ensure a firm bonding of corrosion-resistant layer with the surface of the substrate.

• Laminating:

  Laminating a dry film, which is made of the photoresist film, polyethylene protective film and polyester film on to the copper surface is the next process in the 4-layered PCB production. The film is generally laminated to the inner layer plate via pressing and then heating.

• Image Transfer:

  To assure optimum quality and unfailing board performance, the laminate is given a layer of a photo-sensitive film called photoresist. This helps prevent the accumulation of any kind of dust or contaminants directly on the laminate.

• Copper Etching:

  Removal of unwanted copper from the board is the next step. During the etching process, the copper below the photoresist is retained, so as to form the desired circuit pattern.

• Strip Resist:

  Once the unwanted copper is removed, the existing copper present on the surface usually gets covered by electroplated tin or tin/lead, which must be cleaned. The stripping resist helps in the removal of the tin using concentrated Nitric acid. Ensure to dry the surface properly after cleaning before proceeding to other manufacturing processes.

• Lay- up with Prepeg and Copper Foil:

  A prepreg, which is also called “PP sheet” and a thin copper foil are stacked between the 2 layers of the board. The stack is then allowed to cool at a controlled rate.

• Drilling:

  The most crucial step in 4 layer PCB manufacturing is drilling to make holes at specific points. PCB manufacturers locate the position for drilling using an x-ray locator.

• Plating and Copper Deposition:

  The holes created are to be filled with copper. This is done to enable the through-holes to be conductive among the layers. A copper deposition is accomplished by chemical deposition process.   

  The processes involved in making 4 layered PCB do not end here. There are a few more to be added to the list, which will be discussed in the next post. Stay tuned!