The "OFweek2020 (6th) China Laser Online Exhibition" hosted by OFweek, the portal of China's high-tech industry, and undertaken by OFweek Laser, was held as scheduled. During the exhibition, MKS/Spectra-Physics held an online seminar on the theme of "UV ps laser processing polymer OLED materials for the next generation of 5G and foldable consumer electronic devices." The identity of the speaker was shared with everyone. The live broadcast review is as follows:
During the seminar, the audience was enthusiastic and enthusiastically asked questions. Here are some questions and answers as follows:
Around OLED applications:
1. What are the current application cases of laser technology used in OLED?
The specific application cases are now very extensive. As early as a few years ago when Samsung and LG in South Korea launched OLED screens, lasers have been deeply involved. Several major domestic manufacturers are now introducing equipment for the production of OLED screens. Therefore, the application of lasers in this area has been Very extensive.
2. Why is picosecond laser suitable for OLED polymer processing?
It depends on the overall process requirements. For OLED, its polymer materials are particularly sensitive to thermal effects. In addition, the size and spacing of the current cells are very small, and the remaining processing size is also very small. The traditional die-cutting process is no longer suitable for today. The demand for production is higher, and now there are application requirements for special-shaped screens and perforated screens, which are beyond the capabilities of traditional craftsmanship. In this way, the benefits of lasers are reflected, especially picosecond ultraviolet and even femtosecond lasers, which have a small heat-affected zone and are more suitable for more flexible applications such as curve processing.
3. Is the femtosecond laser of Spectra-Physics also suitable for OLED processing? What are the similarities and differences compared with picoseconds?
Femtosecond lasers can also be used in OLED processing. We have done a corresponding comparative test. Because the femtosecond laser has a shorter action time, it produces a smaller heat-affected zone than a picosecond laser under the same parameters. In fact, some domestic manufacturers have already used femtosecond lasers for OLED processing in their production lines.
4. At present, both UV picoseconds and femtoseconds can be applied to OLED module cutting, and screen manufacturers tend to UV femtoseconds. What are the advantages of UV picoseconds over femtoseconds?
For now, the advantage of picoseconds over femtoseconds is in price. Screen factories tend to be femtoseconds, and are more demanding in terms of processing quality.
5. What are the difficulties and trends in OLED laser processing?
When it comes to difficulties, especially in small-size processing, the common ones are mainly heat-affected zone and processing efficiency. The current trend is towards solving these two problems. One is to develop in the femtosecond direction, and the other is higher frequency and higher power. Major laser manufacturers are also working hard in this direction.
6. How to improve the precision of laser in OLED processing?
Machining accuracy is a system problem: the accuracy of the controller and the motion platform itself is the foundation, and installation and adjustment will also affect the accuracy!
7. How to improve the thermal effect of materials? How to solve the problem of overheating in the corner?
There are a lot of relevant discussions about the public information in this area, in two aspects in theory: 1. Minimize the heat input, such as using a narrower pulse width laser or shorter wavelength; 2. Make a fuss on the processing parameters, such as multiple rapid scans, if it is a large area with multiple patterns, you can use the time-sharing cross-processing method.
The current mainstream methods at the corner: 1. Use a galvanometer with a faster speed (if it is processed by galvanometer); 2. Position synchronization trigger (PSO); 3. If it is a sharp corner, the platform (galvanometer) is often used to'circumnavigate'-at the sharp corner, the platform/galvanometer slides out at the original speed along the extension line of the trajectory and then turns back along the extension line of the other side of the sharp corner. Turn off the laser in time at sharp corners.
8. Will there be dust, air intake, stratification, etc. during cutting?
This can be controlled by processing parameters. OLED materials will definitely generate dust during processing, and a good dust removal system is required. The delamination is mainly caused by the heat-affected zone, and the processing parameters need to be well controlled to avoid delamination.
9. What is the smallest heat-affected zone of laser processing?
This is related to the material and processing parameters. In theory, the femtosecond laser can achieve almost no heat-affected zone, or it can't be detected by ordinary detection methods (such as a microscope).
10. What is the production stability and yield rate of UV ps laser processing polymer OLED materials in mobile phone industry applications?
There are two main aspects to the stability of production. One is the stability of the laser itself. Relatively speaking, the lasers of foreign manufacturers are more stable, and domestic manufacturers are also constantly catching up; the yield is related to the quality of the laser itself, and is related to processing. Parameter control and the precision of the integration of the entire system are related.
11. What is the most difficult aspect of OLED laser peeling (referring to the process)?
In terms of equipment integration, the more difficult thing to do is beam shaping. Now if the laser is also provided, there is no problem.
12. What is the cutting thickness of polyimide?
In the femtosecond test, we mentioned that its thickness is 75 microns; in actual applications, there are many thicknesses. For example, it is commonly used in flexible circuit boards. The thickness is about 12 microns. The connection layer It is about 20 microns, and the total thickness is more than 30 microns.