Printed Circuit Board Ink and Progress (1)

Abstract The following describes the special printing materials used in the production of printed circuit boards: anti-etching printing materials, anti-electroplating printing materials, solder resist printing materials, characters, marking materials, plug printing materials, conductive printing materials, peelable printing materials , Solder paste printing materials and other types of printing materials, technical specifications, process parameters and production and operation techniques.

Keywords circuit board, screen printing, printed material

Printed circuit board production is inseparable from screen printing and printing materials. Ink, also known as ink, is widely used in printed circuit manufacturing processes. Today, electronic products are moving toward high-precision, high-density, high-reliability, and micro-technologies, and require higher requirements for screen printing included in printed circuit manufacturing technology. With the rapid development and advancement of screen printing materials in recent years, many new types of printing materials have been developed and developed, and they have been continuously improved to meet the production process requirements for finished printed circuit boards.

At present, the printed board manufacturing industry has formed a series of special printing materials. Its types are roughly classified as follows:
(1) Anti-etching printing materials;
(2) Electroplating resist printing materials;
(3) Solder resist printing materials;
(4) characters, marking materials;
(5) plug hole printing materials;
(6) Conductive printing materials;
(7) Peelable printing materials;
(8) Solder paste printing material.

First, anti-etching printing materials

Anti-etching printing material is one of the earliest developed and used printing materials in PCB production and is used in subtractive process. Its role is to screen print on the copper foil, protecting the circuit pattern from being etched away by the etching solution. A large number of brands have been formed at present, but they are grouped into two major categories: (1) self-drying or thermosetting; (2) light-curing.

(1) Self-drying or thermosetting self-drying or thermosetting resist printing materials are one-component type printing materials composed of synthetic resins, fillers, pigments, auxiliaries and solvents.

Self-drying printing materials are dried at room temperature for one hour or less; thermosetting printing materials are required to be dried in a hot air circulation oven at 80 to 100° C. and 8 to 10 minutes (minutes). Hardness up to 2H. Some varieties are only resistant to acidic etching solutions, while others are resistant to both acidic and alkaline etching solutions. The removal of the film is usually carried out with a 1% to 3% NaOH solution. The print has a shelf life of one year and the pigment is mostly blue or black.

(2) Photo-curable light-cured resist printing materials are generally composed of a photosensitive resin, a photosensitive monomer, a photosensitive agent, a filler, an auxiliary agent, and a pigment. Its main feature is that it does not dry on the screen when it is screen printed, and it does not block the screen, but under ultraviolet (UV) light irradiation, photocrosslinking polymerization occurs within a few seconds. Rapid curing, the film layer hardness is also up to 2H, the same resistance to acidic and alkaline etching liquid; at the same time because of no solvent, it will not pollute the environment, suitable for single-sided printed circuit board automated production line. The storage period of printing materials is approximately 4 to 6 months.

The usual curing conditions for printing materials are as follows: high pressure mercury lamp 80 W/cm×3, irradiation distance 10 cm, light curing machine conveying speed 4 to 6 m/min, removing film 3% to 5% NaOH solution, temperature 30～ 50°C.

The resolution of the thermosetting and photosetting printing materials is about 200 μm, and patterns with line widths and pitches above 0.25 mm are produced.