The manufacturing of technical ceramics has driven the development of processing equipment that is more sophisticated than conventional counterparts, both in accuracy and consistency.

Production of technical ceramics has posted record growth over the past decade; indeed, it has been the fastest growing sector of the ceramic industry. Manufacturing of these non-traditional products has driven the development of processing equipment that is more sophisticated than conventional counterparts, both in accuracy and consistency.

The core business of HED International, headquartered in Ringoes, N.J., is satisfaction of these requirements, both through specialized tape casting systems and custom solutions for high temperature/high precision firing kilns. Development of these solutions has been achieved through aggressive research, partnering with customers and collaborating with a variety of industry experts.

Tape Casting

Tape casting/coating is a process in which a slurry or slip (solvent or aqueous based) is delivered to a continuous carrier (polymer, steel or web) for application of a thin/thick film. To attain exact thickness, the slurry on the carrier goes under a knife, roll or slot die that has been set to the precise desired gap. The applied film then goes through a drying chamber and is taken up on a spool along with the carrier, or separated from the carrier and either wound on a take-up spool or cut to lengths.

Products made by tape casting and web coating produce the feedstock for several multi-billion dollar industries. Tape cast products have been a foundation for an unprecedented era of advancement in space age science and technology. Early fabrication of tape suffered from significant deviations of thickness, but as new products reliant on the tape cast materials have been developed, precision and accuracy requirements have also increased. Some of these products include integrated circuit (IC) substrates, multi-layer ceramic capacitors (MLCCs), microelectronics, fuel cells, batteries, flat panel displays and many other thick film products.

HED International’s objectives of improved and repeatable performance, reduced maintenance and simplicity have been achieved through many critical design elements. For example, the casting/coating surface plate on its tape casting machines is certified to a tolerance of ± 0.00005 in., providing a degree of accuracy not previously achieved on other commercially available casters. This tolerance level is imperative for low deviation thickness. Speed control of the carrier is also essential and is accomplished by using a specially designed tachometer closed-loop feedback system. Finally, the casting blade, or doctor blade, is structurally overbuilt to ensure that virtually no deflection takes place, regardless of load.

To provide correct drying of the cast substrate, preheated air is drawn over the cast film in a flow counter to the tape direction. This allows the solvent concentration to be controlled for safe, rapid solvent removal. Systems for solvent recovery are built in to minimize solvent costs and reduce the downstream exhaust treatments.

Control of the system includes a full supervisory control and data acquisition (SCADA) system. The human machine interface (HMI) provides an easy to use operator interface specifically designed for the tape casting/coating process. This system controls production variables such as casting/coating speed, temperature profile, solvent gradient, airflow and casting/coating thickness.

Technical Ceramic Kilns

Technical ceramics are a broad class of ceramic materials, principally processed with very high purities of alumina or zirconia. Often tape cast or iso-pressed to near theoretical density and near net shape, they are fired as accurately as possible, followed by machining to near perfection. Products produced in this way can end up in such common devices as home faucets and in such exotic applications as chip and processor manufacturing. These ceramic materials are an indispensable part of “high-tech” manufacturing.

Specialty periodic kilns to process these ceramic materials come in all shapes and sizes, but as a class, they are typically smaller than their traditional kiln counterparts. Their sizes range from relatively small front-loaded chamber kilns to bell kilns of up to 100 m3 (350 ft3). A relatively small kiln can hold $50,000 worth of products, while a large bell kiln can have a payload approaching half a million dollars of value. Consequently, the design phase is a crucial part of the kiln’s construction, since this kind of firing device must be ultra-accurate and ultra-reliable.

In addition, all kilns of this class must have several key performance characteristics, including:

• Very high temperature capability, often up to 1780?C (3236?F)
• Slow start capability, with steady state temperature operation as low as 60?C (140?F)
• Temperature uniformity capability, normally within a range of 10?C (18?F)

HED International has been a major supplier to this market area, delivering numerous kilns to this market segment. The company developed its overall product range by benchmarking the kilns available, and then offering features and performance that would exceed industry standards.

Taking kiln manufacturing a step further, HED is currently building a new kiln for its laboratories that will be the foundation for the next generation of kilns. The new kiln will employ a totally new combustion system that uses mass flow measurement of air and fuel input and controls the flow of these inputs at each burner to an accuracy within 0.3%. This mass flow system will interface with individual burner O2 monitors to control the atmosphere within the kiln at the burner level. The expected gains will be better temperature uniformity, combined with the atmospheric integrity that is essential for many technical ceramic products. The HMI control system will be further refined for clarity and scope of control, and additional features for control, maintenance reduction and energy consumption will also be a part of the finished product. HED plans to make this system available in early 2002 for specialty tests.

Delivering Solutions

James Dennis, president of HED International, sums up the company philosophy: “We are committed to providing our customers with superior technology, quality and service. The team at HED is made up of dedicated and experienced individuals who realize that success is measured by our ability to consistently deliver solutions that meet the needs of our customers and exceed their expectations. Whether we are developing new systems for a special market segment, or providing customers with alternatives to purchasing a new kiln via lease arrangement, our goal is to help our customers succeed.

“As we look forward, we are developing brand new systems and techniques through investment in research and development in our own processing equipment. At present, we are completing the manufacture of both a technical kiln and a tape caster that will incorporate many new and innovative design features. We plan to make this equipment available to our customers for toll firing and testing at our in house R&D; facility. We believe this development work is critical to our ability to continue to meet the current and future requirements of our customers.”

For More Information

For more information about HED International and its initiatives, contact the company at Route 31, Box 246, Ringoes, NJ 08551; (609) 466-3600 or (800) 433-5456; fax (609) 466-3608; e-mail info@hed.com; or visit www.hed.com.

SIDEBAR: High-Tech Bell Kiln Provides Benefits for Kyocera

Kyocera Industrial Ceramics Corp. in Mountain Home, N.C., manufactures ceramic products that span a wide range of applications. Using alumina and zirconia compositions, products as diverse as ceramic seals, brick core mandrels, pulleys for wire drawing, injection molded thread guides, insulators for automotive applications, and ceramics for semiconductor manufacturing equipment provide a wide range of manufacturing and firing challenges. HED International has provided three kilns to the Mountain Home operation in the past two years. The latest, installed in early 2001, is a large (300+ cubic feet) bell kiln, which has a capacity of several hundred thousand dollars of product value per kiln load.

The engineers at HED employed the best technology available in terms of control systems, refractory design and energy consumption. The recuperation system is a high efficiency design and is capable of achieving maximum combustion air preheating temperatures at the early stages of firing. And the SCADA system uses distributed control that provides factory floor information at the fingertips of both the kiln operator as well as the kiln manager.

John Windham, kiln engineer for Kyocera, and Jim Barrett, manager of quality, recently commented on Kyocera’s selection of HED’s technically advanced bell kiln. “The willingness of HED to form a partnership with us was extremely important. For example, initially HED built two front loaded chamber kilns in record time, on a lease arrangement, to help supplement our production prior to the completion of the large bell kiln. We had a high degree of confidence in the HED people; we knew that they would work with us to help with the firing process over and above any kiln operational issues. The kiln was started ahead of the projected timetable, and the startup was relatively trouble free. And all of this was provided at a competitive price,” said Windham.

“Our investment in a state of the art bell kiln from HED has resulted in a number of positive results, including consistent product yield improvement, reduced energy consumption owing to the use of exhaust recuperation, better service to our own customers through provision of extra capacity, and far better temperature uniformity and consistency. We use our new kiln to demonstrate our commitment to quality to our own customers,” said Barrett.

Windham and Barrett also value the data collection and analysis provided by the HED kiln. “The HMI/Cimplicity SCADA package designed by HED provides comprehensive information about our firing operations. We have better tracking of the firing process as related to our ceramic process. But it is crucial to have skilled people working with the HMI system, both for operation and support. Having more data to work with is only useful if our people can properly work with it,” Windham said.

Links

• HED International