In this interview, individuals from H.C Starck Solutions talk to AZOM about the demands of the mobile device market on touch screen technology, and how their speciality alloys for sputtering targets help to improve the performance and reliability of touch screen devices.
What materials does H.C. Starck Solutions supply for touch screen manufacturing?
H.C. Starck Solutions offers sputter targets from molybdenum (Mo) and molybdenum alloys such as molybdenum-tungsten (MoW), molybdenum-niobium (MoNb) and DynaMo Alloys, our newest family of molybdenum-based alloys. These alloys are utilized in Touch Screen Panel (TSP) applications for mobile device displays.
What components of the panels are these materials used in?
The wiring and touch sensor electrodes in touch screen devices are created by sputtering thin layers of Mo alloys using physical vapour deposition techniques.
Specifically, H.C. Starck Solutions' MoNb sputter targets produce the thin films for barrier, capping and conducting layers. Our MoW alloy is applied in forming the gate and touch sensor layers for TFT- LTPS (thin film transistors - low temperature poly silicon) and in-cell type touch panels.
There are different types of touch sensors including on-cell, in-cell and one glass solution (OGS). The latest innovation in OGS, removes one of the glass layers and replaces it with a thin film layer of insulating material to reduce the thickness of the LCD display.
Developments in touch screen technology have led to requirements for faster electrical response and reduced power consumption, which initiated the development of lower resistivity materials with etch compatibility and improved corrosion resistance. Image Credits: YanLev/shutterstock.com
What are the characteristics of these metals that make them so well suited for these applications?
Molybdenum’s thermal expansion (which matches the thermal expansion of glass) and low resistivity, combined with good adhesion to glass and optical coating layers like indium tin oxide (ITO), make H.C. Starck Solutions' sputter targets ideal for touch screen applications.
Because of the smaller thermal expansion mismatches between materials, stresses are lower, leading to the creation of more reliable thin film devices.
The low resistivity provides faster electrical response time and lower power consumption. A feature of DynaMo alloys is the lower reflectivity compared to pure Mo, which results in a reduction in the amount of glare on the mobile display surface.
What are the key properties of these thin films that affect the performance of the device?
H.C. Starck Solutions' molybdenum alloys have excellent corrosion resistance properties, essential for advanced automotive, mobile communication and industrial applications. Pure molybdenum film has lower corrosion resistance than H.C. Starck Solutions' proprietary Dynamo alloys, and thus touch screens made with pure molybdenum films have poor performance when exposed to harsh environments.
Low resistivity is also important, as it provides faster electrical response, and helps to extend the battery life of the mobile device.
How does H.C. Starck Solutions' technology help to achieve these ideal properties?
H.C. Starck Solutions' core competency materials, such as molybdenum (Mo), niobium (Nb), tantalum (Ta) and tungsten (W), and extensive processing knowhow, enables us to manufacture products with a high level of consistency that enables our customers to produce thin film devices that can meet the stringent requirements of the electronic industry.
We can also customize the elemental composition of our DynaMo alloys to deliver better electrical performance and corrosion resistance. We can also tune the etching rates of the alloy, to match the customer’s process, which helps improve the patterning process for features on the touch sensor.
H.C. Starck Solutions, with application development resources in Asia, is able to communicate directly with product development teams at customers and custom develop products through rapid prototyping, thereby, delivering product with appropriate features and value to the market place thus giving our customers a competitive-edge.
How long has H.C. Starck Solutions been actively developing metals specifically for this application?
H.C. Starck Solutions has a long history of developing high quality materials and processes since the company’s founding in 1920. We have been specifically working with customers in thin film technology in the flat panel display industry for well over 15 years.
How have the requirements for touch screen materials changed as the technology has evolved over that time?
We have seen faster electrical response requirements, and reduced power requirements, which initiated the development of lower resistivity materials, multi-layered wiring, and electrode materials with etch compatibility and improved corrosion resistance. The development of our new alloys were driven by these requirements.
What developments do you foresee in the near future as touch screen technology develops further?
New touch screen designs on the horizon will push towards even faster touch response, even lower battery power consumption, and finer pixels for higher screen resolution. These refinements are being embedded in display devices to further drive requirements for smaller line width, and etch compatibility.
Also, the development of flexible display devices is adding a new set of mechanical requirements for the materials, pushing the technology potentially into a whole new set of touch screen applications.
Contact H.C. Starck Solutions for more information about thin film sputtering applications
About H.C. Starck Solutions
The H.C. Starck Group is a leading global supplier of technology metals and advanced ceramics. The company operates modern manufacturing facilities in Europe, America, and Asia and serves growing industries such as the electronics, chemicals, automotive, medical technology, aerospace, energy technology, and environmental technology industries, as well as engineering companies and tool manufacturers.
On December 31, 2017, the H.C. Starck Group had 2,600 employees in the United States, Canada, Great Britain, Germany, China, Japan, and Thailand.
H.C. Starck’s products are predominantly based on technology metals: Tantalum, Niobium, Tungsten, and Molybdenum.
The Fabricated Products Division converts technology metal powders into customized semi-finished and finished products through pressing, sintering, rolling, melting and thermo-mechanical processing and surface treatment.
The Tungsten Division provides high performance products for the mechanical engineering and tool making, automotive and energy industry, aviation industry, and the chemical industry, for example:
- tungsten carbides for carbide tools and wear parts
- tungsten and cast tungsten carbides for oil and gas drilling
- tungsten metal powders for heavy metal alloys
- tungsten chemicals as precursors for catalysts
The Advanced Ceramic Components (CER) Division manufactures specialized technical ceramic parts and films. CER produces engineering parts such as sealing rings, functional parts including fuel cells for solid oxide fuel cell (SOFC) systems and products for dental applications as well as for armor and wear protection. Furthermore, CER focuses on technological developments to expand the portfolio toward product applications in the semiconductor industry.
In 2018 H.C. Starck sold the division Surface Technology & Ceramic Powders to the Swedish Höganäs Group, effective March 1st and the division Tantalum and Niobium to the JX Nippon Mining & Metals Group, effective July 1st.
The group is led by a two-member Executive Board: Dr. Jens Knöll (Chairman of the Executive Board), Dr. Jan Lösch (Member of the Executive Board).
H.C. Starck was founded in Berlin in 1920. Since 2007, the company is owned by financial investors Advent International and The Carlyle Group.
H.C. Starck is registered in Goslar (Germany) and the Group’s headquarters is located in Munich (Germany).
This information has been sourced, reviewed and adapted from materials provided by H.C. Starck Solutions.
For more information on this source, please visit H.C. Starck Solutions.
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