Dry Phase Patterning:
New concept for the patterning of flexible substrates
staffan.nordlinder@acreo.se
A new low cost concept has been developed for the patterning of thin films on flexible substrates for applications such as RFID antennas.
Acreo’s focus on reel-to-reel production of printed electronics in standardized processes and the need of good conductors for antennas and power supply led to the development of a new technology for the patterning of flexible materials, such as laminated flex foils for the electronic industry that challenges the traditional methods and also creates new areas of applications.
The process that Acreo has developed, called Dry Phase Patterning (DPP), is up to ten times faster than traditional etching. Together with the benefit that no chemicals are used, this makes the process very cost effective and environmentally friendly. Several processes, control system and applications are patent pending.
The process makes great demands on active machine elements, the tolerances are more than ten times higher than normal for mechanical converting machinery. To meet the high mechanical demands, the development project was carried out in close co-operation with highly skilled expertise with many years of experience from precision machinery manufacturing.
Together with a production partner Acreo has a test production line with a capacity of several million square meters annually. By the end of 2005 a new specially built DDP process line will be installed at Acreo.
Technology
The process is a based on mechanical machining of the material. Tests have shown that it is possible to pattern with high precision at high speeds. This makes it possible to integrate the process in a printing line e.g. for printing organic electronics. It is possible to pattern most flexible substrates with soft materials such as metals or polymers deposited on the surface for instance by lamination or evaporation. Examples of material patterned in Acreo’s test equipment are: PE/PEDOT, Paper/Aluminium, PET/Aluminium and PET/Copper etc.
The material is patterned and machined in the same process step, unlike the etch process where a resist mask first is printed, the etching takes place in the next step, followed by removing the residuals of resist and etch liquids. In the DDP process, the residual product from the process is in a dry phase and recyclable. Thus, the method has large environmental benefits: no chemical products are used, and there is a possibility of recycling the residual products. Pattern fibrous materials or products sensible for fluids or chemicals have earlier been a problem. With the DPP method it is now possible to realize such products to a reasonable cost.
The resolution of the pattern is comparable to the resolution of etching; pattern with spacing and lines smaller than 100µm has been proved. Just as for etching the resolution of the pattern is depending on the patterned material, but the DPP resolution will not decrease with higher production speed. Tests have shown that it is possible to pattern with high precision in speeds over 150 m/min. In order to visualise the resolution of the DPP method a test pattern was made in a 22µm thick plastic foil with thin layer evaporated aluminium on top, shown in the figure above.
Field of application
The DPP method has been evaluated for a wide range of application areas; everything between display elements for electrochromic displays and heating radiators has so far been produced in the DPP laboratory. One of the largest markets for the technology is the RFID antenna market where the cost reduction of the DPP patterned antenna can make the market emerge.
The thin layout of DPP products makes them fit perfectly for inlay products such as heating elements or antennas. The method is perfectly suited for patterning organic electronic components such as display pixels or transistors, since the organic material is not processed with any chemicals. The dry process makes it possible to pattern also fibrous materials like paper.