PCB News - The main components of PCB processing process

The main components of silk screen photosensitive adhesive Shenzhen PCB processing process
The main components of the Shenzhen PCB processing process of silk-screen photosensitive adhesive are film-forming agents, sensitizers, and additives.
1. Film forming agent. The film-forming agent plays a film-forming role and is the main component of the plate film. It determines the fastness and resistance (such as water resistance, solvent resistance, printing resistance, aging resistance, etc.) of the plate film. Commonly used film-forming agents for screen printing photosensitive adhesives include: water-soluble polymer substances such as gelatin, protein, and PVA (polyvinyl alcohol). In the early days of the Shenzhen PCB processing process, the photosensitive adhesives were formulated with such a single film former, but the plate film produced had poor resistance to resistance. Later, PVA modified colloids were used, which can be divided into three categories:
1. Physically modified colloid of PVA. Emulsion of PVA+non-water-soluble polymer substance. The latter such as PVAC (polyvinyl acetate) emulsion, acrylic emulsion, PVAC and acrylic copolymer emulsion and so on. Their addition improves the resistance of the plate film.
2. The chemically modified adhesiveness of PVA. That is, chemical means are used to selectively connect groups such as vinyl acetate, acrylonitrile, and acrylic acid to the PVA bond to make the improvement of resistance more comprehensive.

3. PVA (or gelatin) + crosslinking agent. The characteristics of this system are: water-soluble polymers do not necessarily participate in photochemical reactions, and photoresist linking is mainly formed by the action of crosslinking agent and sensitizer. The crosslinking agent mostly uses vinyl monomers, polyvinyl monomers or oligomers, which are water-soluble or have good dispersibility in water-soluble polymer solutions. Once cured, it is insoluble in water. This system level adapts to more varieties of sensitizers, so it can obtain some special properties of plate making, such as indirect dry film.
2. Sensitizer. The sensitizer is a compound that can initiate a photochemical reaction under the irradiation of blue-violet light and can cause the film-forming agent to polymerize or crosslink. Sensitizer determines the spectral sensitivity, resolution and clarity of the photosensitive adhesive.
3. Additives. Film-forming agents and sensitizers are the main components of the formula, but sometimes to adjust the performance of the main components, some auxiliary agents, such as dispersants, colorants, sensitizers, plasticizers, stabilizers, etc. are still needed.
The characteristics of the PCB manufacturing process of Shenzhen PCBA
Compared with traditional physical methods and chemical methods, the use of circuit board making machines to quickly produce circuit boards has the following distinctive features:
Efficient: It only takes a few minutes to tens of minutes to make an ordinary circuit board.
Automatic: Abolish the "film, photosensitive, fixing, corrosion, cleaning, drilling" process of traditional circuit board production. The production of a circuit board only needs to complete the PCB file design of PROTEL, and the other is automatically completed by the machine.
Accurate: CNC drilling error is less than 1mil, multi-pin components can be easily positioned, avoiding plug-in difficulties caused by manual drilling.
Convenient: The operation process is as simple as a printer.
Cheap: The raw materials used in the production process of the circuit board production machine are cheap (only a small amount of blank copper clad laminate and electricity costs), which can greatly reduce the R&D expenditure of electronic projects.
Environmental protection: abolish the chemical pollution caused by traditional methods to the environment. At present, the country has higher and higher requirements for environmental protection and greater efforts in link governance. This is a challenge but also an opportunity for PCB factories. If PCB factories are determined to solve the problem of environmental pollution, then FPC flexible circuit board products can be at the forefront of the market, and PCB factories can get opportunities for further development.