Juding Circuit Technology brings you a deep understanding of printed circuit boards: Introduction to Copper Etching in PCB Fabrication Process

2019-09-18 15:40:57 461

Printed circuit board production and manufacturing process introduction:

With the continuous development of printed circuit board production processes, there are more and more manufacturing methods, so there are many classifications. The manufacturing process includes photolithography, image migration, etching, drilling, hole metallization, surface metal coating and coating of organic chemical raw materials. Although there are many production and processing methods, most of the processing techniques are divided into two categories, namely, "reduction method" (also called "copper etching process") and "addition method" (also called "addition method"). In these two categories, it can be divided into several manufacturing processes. The following sections detail the important categories in them.

Subtraction method:

In this way, the photochemical method or the metal screen printing method or the electroplating method is generally applied to the copper surface layer of the copper clad plate to transfer the necessary power circuit pattern, and the pattern is composed of necessary anti-corrosive materials. Subsequent organic etching is used to etch away the excess portion, leaving the necessary power circuit pattern.

Now introduce the following types of representative processing techniques:

1. Photochemical etching process

A layer of light-sensitive adhesive or resist dry film is uniformly coated on the cleaned copper-clad plate, and a power circuit image is obtained according to the photographic substrate exposure, development, solid-film, and etching processes. After the film is removed, the necessary mechanical processing and manufacturing process is carried out, and finally the surface coating is carried out, and the printed printed text and the mark become finished products. The characteristics of this type of processing technology are high precision graphics, short manufacturing cycle time, suitable for mass production, and various types of manufacturing.

2. Metal screen printing and etching process

A template prepared in advance and having a pattern of a power supply circuit is placed on the copper surface of the cleaned copper clad plate, and the resist material is smeared on the surface of the copper foil by a squeegee to obtain a printed pattern. After drying, an organic chemical etching process is performed to remove a portion of bare copper that is not covered by the printing material, and finally the printing material is removed, which is a required power circuit pattern. This type of method can carry out large-scale specialized manufacturing, with large production volume and low cost, but the precision is not comparable to the photochemical etching process.

3. Graphic plating etching process

The photo-sensing film for pattern migration is a dry-resist film, and its production process is roughly as follows:

Cutting→turning hole→hole metallization→pre-plated copper→pattern migration→pattern plating→de-filming→etching process→electroplating power plug→hot melt→design and production processing→inspection→screen printing solder resist→screen printing letter symbol.

This type of processing has now become a typical process for the production of two-sided circuit boards or multi-sided circuit boards. Therefore, it is also called the "normative law."

4. Full-plate plating masking method

Similar to the “Graphic Plating Etching Process”, the key difference is that this method uses this unique feature of the masking dry film (soft and thick), covering the holes and the pattern, and using it as a resist film during the etching process. The production process is roughly as follows:

Cutting→turning hole→hole metallization→full-plate electroplating copper→filming with photosensitive masking→pattern migration→etching process→de-filming→electroplating power plug→design and production processing→inspection→screen printing solder resist→welding material coating Apply → screen printed letter symbol.

5. Super book to copper foil rapid etching process

Also known as "differential etching process", applied to laminates of thin copper foil. The key processing is similar to the pattern plating etch process. Only after the copper plating of the pattern, a part of the power circuit pattern and the copper material of the hole side metal material are about 30 μm thick, and the copper foil which is not part of the power circuit pattern is still thin and thin (5 μm) of the copper foil. For its rapid etching process, a part of the 5μm thick non-power circuit is etched away, leaving only a small part of the etched power circuit pattern. This type of method can produce high-precision, dense circuit boards, which is a development. A promising new production process.

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