PCB Manufacturing Methods

Conventionally, all methods of manufacturing printed circuit boards can be grouped into four groups:

• additive;
• subtractive;
• semi-additive;
• combined.

Subtractive

These processes involve the removal of specific areas of the conductive foil by etching. Most often chemical. They are used, as a rule, when one-sided dielectric bases are manufactured, which are characterized by selective protection of the conductor pattern. It can be used to create an inner layer of multi-layer products.

What are the stages of the future payment in this case?

• Nibbling the workpiece.
• Drilling holes.
• Preparation of the foil surface, elimination of protrusions, surpluses.
• Pattern application of acid-resistant paint on foil fragments that cannot be etched.
• Actually, deleting open fragments.
• Drying.
• Solder mask overlay.
• Formation on open parts of the metal layer by melting the solder (tinning).
• Marking imprint.
• Examination.

The advantages of chemical actions can be considered the possibility of maximum automation of the above procedure and high productivity at low cost.

Among the shortcomings, the first to highlight is the environmental factor (considerable volumes of waste harmful liquids). Also, this technique cannot boast of an impeccable bond density.

Instead of chemical etching, gaps between electrically conductive substances can be created by mechanical action (with a special cutting tool). If we are talking about one-sided products , then it is enough to have one specialized machine with software control available, which allows you to form through holes and grooves of a given depth.

Blind cuts (scribing) are created with diamond cutters. This procedure must be carefully adjusted because even a slight deviation in its parameters can lead to inaccuracies in the width of the gap.

The advantages of the method include low capital intensity, the absence of environmental pollutants. It is good for making experimental prototypes, but for mass production, it is better to choose another one. After all, the board takes longer to create, and at the same time, its cost is more expensive than using reagents.

After exposure to the cutter, the plates require protection of the exterior from external factors, therefore, it is covered with a solution, impregnation that does not interfere with the soldering process or varnish after installation.

In order to minimize the damage caused to the dielectric , lasers are used that engrave the contours of the conductors. The laser method is highly productive, but at the moment it is very expensive for mass distribution.

Additive

Such technologies are gaining more and more popularity, and have a great chance of gaining a dominant position in the mass production of printed dielectric bases. In this case, the initial material is non-foil, on which the image is applied.

The advantages of the method (when compared with the previous one) are:

• high reliability;
• homogeneous compounds;
• complete elimination of etching;
• no need for protective substances during the removal of selective sites, respectively, saving on raw materials and disposal of wastewater;
• simplicity of the technological process.

Both the photoadditive technique and the application of a photoresist at the very beginning go through the same stages: formation of the base, making recesses for metallization and treatment of the entire surface with a catalyst.

Photoadditive technologies activate it using a negative photomask, after which it happens:

• thick copper plating;
• washing;
• thorough drying;
• solder mask overlay;
• circumcision;
• examination;
• obtaining a certificate.

Their undoubted advantage is the application of a thin pattern. The disadvantage is the long-term interaction of the metalworking solution with the dielectric, which requires additional cleaning steps.

In the case of using a photoresist, it is applied through the positive of a photomask. The next steps are:

• its manifestation with exposure of areas with a catalyst;
• metalworking of grooves and conductors with the formation of a thick layer;
• marking;
• shaping;
• testing;
• certification.

A light-sensitive polymer material serves as a protective coating on the insulation. Of the minuses, the duration of the metallization process can be noted .

Semi-additive technologies

This method combines the advantages of subtractive and additive: the use of non-foil materials and the ability to produce thin conductive lines. What does his scheme look like?

• Creating a blank.
• Making holes.
• Thin-layer metallization.
• Thin layer compaction.
• Exposing the photoresist using a photomask.
• Galvanic metallization.
• Metal resist overlay.
• Removing the polymer photosensitive source.
• Etching.
• Fusion of metal resist using tin.
• The deposition of contact coatings on the end plates.
• Cleaning.
• Drying.
• Application of a heat-resistant protective agent.
• Coating treatment.
• Marking.
• Perimeter trimming.
• Examination.
• Acceptance.

Combined

Combine individual details or whole stages of all described techniques. There are:

• positive;
• negative.

They use positive templates and negative templates, respectively.