PCB Tech - PCB circuit board screen printing ink development

With the continuous advancement of reforms and the development of science and technology, China has jumped from a backward PCB ink producer to an advanced country in the world. In 2003, the total output value of China's PCB ranked second in the world rankings, and the development of the PCB industry quickly drove it. The development of surrounding industries and related industries. Nowadays, high-end advanced equipment, instruments, meters, and materials used for PCB have developed by leaps and bounds. They have also changed from a big importing country to a big 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.

1. Historical review and application status

The first printed circuit board in China came out in 1959 and was only used for mass production in the early 1960s. Originally used as a mask for the manufacture of printed board graphics, dichromate was used as a sensitizer colloid.

1. Three development stages of photosensitive mask

1. Shellac photosensitive mask: This oldest technology was introduced from the former Soviet Union, and was quickly eliminated due to the complexity of the ethanol development process.

2. Bone glue photosensitive mask: This technology is transplanted from the plate-making and sign-making process, which is economical and practical. Later, technicians went on to develop physical solid film and chemical solid film technologies, which were quickly promoted, but they could not be stored for a long time at high temperatures.

3. Polyvinyl alcohol photosensitive mask: This kind of mask can be used for more than one month after it is equipped, and its physical and chemical properties are stable, which is a great improvement over the bone glue mask.

None of the above three types of masks can meet the ever-developing market demands. In view of the fact that most of the lines of the printed board graphics were above 1.5mm at that time, a new process method is urgently needed to replace them.

2. Self-made screen printing anti-corrosion ink

The screens used at that time were all silk screens, and the mesh specifications were few. The plate-making methods mostly adopted the "red-engraved film" and "etched pattern spray paint reversal" methods. At that time, there were about two kinds of self-made screen printing anti-corrosive ink formulations:

1. Self-drying type:

Petroleum bitumen 200～300g

Talcum powder 50～200g

Dry oil 10～15ml

Add solvent gasoline to 1000ml

2. Drying type:

Thick paint 150～200g

Talcum powder 20～50g

Color material 0.5～1g

Rosin 20～30g

Add turpentine oil to 1000ml

Condition: 130 degree Celsius, 30min

Although the self-made screen printing anti-corrosion ink has many shortcomings, it is also a leap forward for China's PCB manufacturing graphics.

3. Commercialization of screen printing anti-corrosion ink

Ink vendors saw the strong business opportunities in China's PCB ink market, and soon launched a variety of models and different performance screen printing anti-corrosive inks, forming a printed board ink market. Hong Kong, Japan, and the United States have also promoted the company’s PCB screen printing anti-corrosion inks to China at the fastest speed, and established joint ventures. These brand inks have stable performance and easy use. The most prominent feature is the process of fading. There has been a great improvement-the alkaline solution method is used to remove the ink, which eliminates the solvent cleaning and the pollution caused by the solvent. With the increase of TV boards and tape recorder boards, UV curing type anti-corrosive screen printing inks came out, which significantly accelerated the production speed of PCB boards. The solid content of this ink is 100% solvent-free, and it is the preferred material for circuit board graphics processing. It will soon be promoted to the whole country within 1 to 2 years. There was a situation of short supply at one time, creating unlimited business opportunities for ink manufacturers.