PCB solder ink development

In order to improve the welding efficiency and avoid damage to parts that do not need to be welded during PCB production, these parts need to be protected with blocking ink. The development of PCB ink is closely related to equipment technology, welding conditions and line requirements. With the further high-density PCB and the appearance of lead-free welding technology, new requirements are put forward for diluent to adjust ink viscosity and make it meet the requirements of ink jet printing sticky solder ink. PCB solder ink has four stages of development, from the early dry film type and thermosetting type gradually developed to ULTRAVIOLET (UV) light fixation type, and then appeared photographic developing solder ink.

1. Low viscosity can be ink-jet welding ink

With the development of electronic industry, a full printed electronic technology with addition method emerges at the right moment. Addition method process has the advantages of material saving, environmental protection, simplified process, etc. Due to its use of inkjet printing as the main technical means, there are new requirements for the properties of ink and body materials, mainly manifested as:

(1) control the ink viscosity, to ensure that it can be sprayed continuously through the nozzle, to prevent the plug to meet

(2) control the curing reaction speed, achieve fast initial solid, prevent ink in the substrate due to infiltration and spread;

(3) Adjust the ink thixotropy to ensure the quality and repeatability of the printing line. For the development of low viscosity solder ink, the main use of traditional solder material modification, supplemented by active or inactive degree requirements.

2. FPC welding ink

With the development of PCB industry, the demand of FPC grows rapidly, and new requirements are put forward for corresponding materials. Because the copper wire on flexo plate is easy to oxidize, the welding resistance material of flexo copper wire has become a research hotspot. The traditional epoxy resistance film shows high brittleness after curing and is not suitable for flexography. Therefore, the key to solve the problem is to introduce flexible chain segment into the traditional resin structure and keep the original resistance welding performance. The ink has good storage stability, can be well soluble in sodium carbonate solution, ammonia solution, curing film mechanics, thermal, acid and alkali corrosion properties meet the relevant requirements.

3. Water-soluble alkali development photographic solder ink

In order to reduce the emissions of organic solvents in PCB manufacturing process and reduce the impact of solvents on the environment, solder blocking ink has gradually developed from organic solvent development process to dilute alkaline water development, and in recent years, it has developed to water development technology. At the same time, in order to meet the requirements of lead-free welding technology for resistance film, improve the resistance to high temperature performance.

4. LED with high reflection white solder ink

TaiyoInk first demonstrated its white solder blocking ink for LED packaging in 2007. Compared with traditional solder ink, white solder ink needs to solve the problems of discoloration and accelerated aging caused by long-term exposure to light source. Traditional epoxy solder ink due to molecular structure containing benzene ring, long-term light is easy to cause discoloration. For LED light source, solder resistance coating is coated below the luminescent material, so it is necessary to improve the reflective efficiency of solder resistance coating to light, and then enhance the brightness of the light source. This presents a new challenge to the research of resistance welding materials.

Conclusion

The research of solder ink is always a difficult point in PCB industry. With the printing circuit from the subtraction method gradually to the addition method, inkjet printing as the main technical means of addition process, the viscosity of solder ink, thixotropy and reactivity put forward higher requirements; The popularization of lead-free welding technology has put forward new requirements for the high temperature resistance of solder film, the development of new solder flux urgently needs a large number of researchers, and the research of solder ink is in the rise, which has great potential.