Looking at China's silk screen printing ink development from the PCB ink sales war (1)

With the continuous advancement of reforms and the development of science and technology, China has leapfrogged from an underdeveloped PCB producer to a world leader in the world. In 2003, China’s total PCB output value ranked second in the world, and the development of the PCB industry quickly led the periphery. Development of industries and related industries. Nowadays, whether it is high-end cutting-edge equipment, instruments, meters, or materials used in PCBs, there has been rapid development. It has also changed from an importing country to an exporting country. The technical indicators of some equipment and materials have also reached international standards, especially PCB screen printing ink has reached the highest in the world.

I. Historical review and application status

The first printed board in China was introduced in 1959 and was used for mass production in the early 1960s. The mask originally used as a pattern for manufacturing a printed board is a colloid with a dichromate as a sensitizer.

1. The three development stages of the photomask

1 Shellac Photomask: This oldest technology was introduced from the former Soviet Union and was quickly eliminated due to the complexity of the ethanol development process.
2 Gummy Photoreceptor Mask: This technology is transplanted from the process of plate making and sign making, and it is economical and practical. Later, technicians further developed physical solid film and chemical solid film technologies, which were quickly promoted but could not be stored for a long time at high temperatures.
3 PVA Photomask: This mask can be used for more than one month, and its physical and chemical properties are stable. It has made great progress compared with bone glue mask.

None of the above three masks can meet the growing market demand. Given that the lines of printed board graphics are mostly above 1.5 mm at that time, a new process method is urgently needed instead.

2. Self-made screen printing resist ink

At that time, silk screens were used for silk screens, and mesh specifications were less. Platemaking methods used “engraved red film” and “etched pattern painting reversal”. At the time, there were about two types of screen printing resist ink formulations:

1 air dry type:

Bitumen 200～300g
Talc 50～200g
Dry oil 10 ~ 15ml
Solvent gasoline up to 1000ml

2 drying type:

Thick lacquer 150～200g
Talc 20～50g
Color material 0.5 ~ 1g
Rosin 20～30g
Turpentine oil to 1000ml
Conditions: 130°C, 30min

Although there are many inadequacies in self-made screen printing resist inks, it is also a leap in China's PCB manufacturing graphics.

3. Commercialization of screen printing resist ink

Ink printers saw a strong business opportunity in China's PCB ink market. They soon introduced screen printing resist inks of various types and different properties, forming a printing plate ink market. Hong Kong, Japan, and the United States also pushed our company's PCB screen printing resist ink to China as quickly as possible, and established a joint venture company. These brands have stable ink properties and are easy to use. The most prominent feature is the fading ink process. There has been a great improvement - the use of alkaline solution to remove ink, eliminating the need for solvent cleaning and solvent pollution. With the increase in the number of TV boards and recorder boards, UV-cured resist screen printing inks have come out, which has significantly accelerated the production speed of PCB boards. The 100% solids content of this ink is solvent-free and is the material of choice in circuit board graphic processing. It quickly spread to the entire country in 1 to 2 years. There has been a situation of oversupplied supply at one time, creating unlimited business opportunities for ink manufacturers.

4. Optical imaging resist plating ink

With the expansion of the PCB material market, a corrosion-resistant electroplating ink for pattern plating (also called counter plating) has also been introduced to China. The most prominent advantage is that it can be used as a general resist ink (acid resistance Etching and alkaline resistance under certain conditions), can also be resistant to Cu, PbSn, Sn-plated, and NiNi-plated, with a resolution of 0.05mm/0.05mm (line pitch/linewidth). The processing of circuit boards has created the conditions.

It has become one of the main materials for the manufacture of graphics. Because no special equipment is required, large and small enterprises that are widely used in the PCB industry have now become the most used ink in the PCB industry.

Second, solder mask ink

The solder resist ink should be permanently left on the surface of the printed circuit board to protect the circuit and provide insulation. It can also protect the circuit when Sn is blown (Sn and the hole wall are coated with Sn), and only the components can be inserted at the peak. Welding disk welding.

1. Development of solder resist ink

The surface of the printed circuit board coated with solder mask ink originated in the late 1960s, and China's printed circuit board solder mask ink began in the late 1970s and began to transfer from imports to domestic production. At the same time, thermosetting characters also appeared. Ink. After being limited by the heat-resistant conditions of TVs, tape recorders, and recording boards, UV-cured solder mask inks were also available. After a few years, there has been an increase in variety: In addition to different colors, bright, matt, textured, wrinkled, etc. are also available for users to choose.

2. Optical imaging solder mask ink

Whether it is a thermosetting solder resist ink or a UV solder resist ink, the coating method is that the screen printing pattern exposes the printed circuit board pad. However, as the spacing between the printed circuit board pattern and the land line of the pad gradually becomes smaller and denser, the method of using the pump to print the pattern is no longer sufficient. Although the solder mask method has been popular for several years, due to its expensive materials, the manufacturing technology of the special vacuum laminator is not popular, the operation procedures are complicated, and the yield is low. This technology has now been eliminated. Today's high-density printed boards are light-imaging solder masks. In addition to their thermosetting and UV-blocking properties, the most prominent is their resolution advantage (essentially comparable to photoimprint resists).

From the printed circuit board ink market, optical imaging resist plating resist inks and photoimageable solder mask inks are not only the main products in printed board inks, but also the main materials in the production of high-precision printed boards.