The most important part of the OLED production process is to apply the organic layer to the substrate in accordance with the requirements of the driving matrix to form a key light-emitting display unit. OLED is a solid material, and the development of high-precision coating technology is the key to restricting the productization of OLED. There are three ways to do this generally:
1. Vacuum deposition or vacuum thermal evaporation (VTE)
The organic molecules located in the vacuum chamber are slightly heated (evaporated) and then the molecules are condensed in the form of a film on the lower temperature substrate. This method is applicable to a wide range of applications, and can grow almost all compounds and alloy semiconductors. It is very suitable for growing various heterostructure materials, can grow ultra-thin epitaxial layers, and can achieve very steep interfacial transitions. Growth is easy to control and can grow purity. Very high material, the epitaxial layer has good uniformity over a large area and can be mass-produced, but it is less efficient for OLED products.
2. Organic vapor deposition (OVPD)
OVPD (Organic Vapor Deposition) was developed by Axon, Germany, and the process design has improved manufacturability, which reduces manufacturing costs compared to evaporation technology. The technology is a look at the upgrade of VTE. Excellent repeatability and process stability, as well as significant film uniformity and precise control of doping, which lays the foundation for high-yield mass production while reducing maintenance and cleaning requirements, thereby reducing material consumption and improving material utilization. The huge potential of the rate.
OVPD is in a low-pressure hot-wall reaction chamber, and the carrier gas transports the evaporated organic molecules to the low-temperature substrate, and then the organic molecules condense into a film. The use of carrier gas can increase efficiency and reduce the cost of OLEDs. However, this technology cannot break through many bottlenecks in the production of large-area glass substrates and color OLEDs.
3. Emerging technologies such as inkjet printing and indexing
The coating of OLED layers is traditionally based on vapor deposition techniques, and the emerging approach is based on transfer and printing techniques. For example, inkjet technology can be used to spray an OLED onto a substrate, just as ink is sprayed onto the paper as it is printed.
In the emerging mode, transfer technology was jointly developed and developed by Samsung and 3M; printing technology was mainly developed and developed by Epson. The biggest advantages of these two methods are to improve the material usage rate and simplify the production process, but the technology and materials have a certain monopoly.
In the printing technology, there are different types of technologies. For example, laser induced thermal imaging (LITI) technology, which mainly uses a retraced near-infrared laser to image exposure of thermal transfer film. LITI transfer is a laser-addressed high-resolution graphics processing method with unique advantages, extremely uniform transfer thickness, multi-layer transfer capability and large-size motherboard glass with scalability.
In short, the new OLED layer coating technology based on various printing technologies is becoming an important technical power and equipment route for the growth of the industry. These technologies have greatly reduced the cost of OLED production, and can also print OLEDs onto very large surface areas for large displays such as 80-inch large-screen TVs. The breakthrough of these technologies will become the basis for large-scale practical application of OLED products.
Edit: Nizi
Via In Pad PCB
What is Via In Pad? In shortly,via in pad is the via holes are at the SMD pad.The vias are very small,usually under 0.3mm.Why and how? First is there is no enough space to layout,you have to put the vias and holes closer even together.Second it helps thermal management and for high frequency boards,it may help improve signals.
Because the SMD pads are for SMD components loading,so the solder can not flow to inner layer or the other side when assemble.That is the most important for via in pad board.
How PCB manufacturers like us to do via in pad board? We will fill all vias with non-conductive epoxy and plate copper over it ,so the vias are flat same as others. Many PCB factories are unable to do such capability.
The key technology is how we fill vias and guarantee there is no any solder (surface finishing) in the holes.
Filled via in pad is a way to achieve intermediate density with an intermediate cost compared to using blind/buried vias. Some of the key advantages associated with using the via in pad technology are:
.Fan out fine pitch (less than .75mm) BGAs
.Meets closely packed placement requirements
.Better thermal management
.Overcomes high speed design issues and constraints i.e. low inductance
.No via plugging is required at component locations
.Provides a flat, coplanar surface for component attachment
Via in big pads are not a big problem.but for BGA,that is technology.As BGA pads are very small,10mil or 12mil,and there is no enough space.Manufacturing is not easy as other boards.
Via In Pad PCB
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Storm Circuit Technology Ltd , http://www.stormpcb.com