March 2007

Ceramic Injection Molding Produces Complex Parts with Tight Tolerances
By Paul Manison, project manager, Morgan Advanced Ceramics

Recent advances in ceramic injection molding (CIM) make it technically feasible and economical to produce medium to large volumes of complex, ultra-high precision ceramic components. Engineers can now combine the intricate geometry, which has long been the domain of plastic and metal parts, with the superior performance characteristics of ceramics.

The well-known benefits of ceramic material include high hardness and mechanical strength, wear and corrosion resistance, dimensional stability over a wide range of temperatures, ability to withstand high working temperatures, good electrical insulation and excellent dielectric properties. However, until recent advances in CIM technology, production engineers and product designers did not view ceramics as a viable option for complex parts requiring tight dimensional tolerances.

Limitations of Earlier Technology

Manufacturing small, intricate shapes in volume before the advent of CIM had significant limitations. The obvious challenge for ceramics is the inherent fragility of parts prior to sintering and the hardness of the material, which makes machining processes difficult and expensive post sintering.

Commonly used manufacturing processes, such as dry pressing or extrusion, are well suited for high volume production, but they can produce only relatively simple shapes. For example, blind holes and undercuts are not possible. For more complex shapes, tight tolerances and improved surface finish, secondary machining is generally required.

Ceramic injection molding allows for features such as re-entrant angles, multi-shaped blind holes, screw threads, surface profiles, perpendicular holes, undercuts and intricate cavities. Unfortunately, until recently, CIM did not provide the tight tolerances and high repeatability that is required for many applications. Achieving precise dimensional control has been difficult for CIM because the manufacturing process involves significant shrinkage of the component.

The Ceramic Injection Molding Process

The CIM process begins with very fine ceramic powders. The powders are compounded with polymer binders to produce a pelletized feedstock. During molding, binders melt to form a liquid medium that carries the ceramic powders into the mold during the injection stage.

Using an injection molding machine similar to that used in conventional plastic molding, the feedstock is forced into a mold cavity forming a net shape part. Molds can be single-cavity or multi-cavity configurations.

After forming, the part goes through a two-stage process. First, it goes through pyrolysis, debinding, to remove the binder, followed by sintering in a high temperature kiln to form a fully dense ceramic component. Sintering is the process of heating the material to a temperature below the melting point but high enough to allow fusion of individual particles and densification of the material.

During sintering, the component shrinks by as much as 20 percent while retaining the original geometric shape. With good process control, it is possible to achieve a uniform and repeatable shrinkage leading to tight tolerances, obviating any need for machining of the part afterwards

Advances in CIM

Morgan Advanced Ceramics, a manufacturer of innovative ceramic, glass, metal and engineered coating solutions, has introduced several refinements to the CIM process to control shrinkage. These techniques achieve tolerances of ±0.3 percent of nominal (e.g., 1.000" = ±0.003") with excellent batch-to-batch repeatability and Cpk’s in excess of 1.66.

The high degree of dimensional control comes from process improvements implemented by Morgan Advanced Ceramics at all stages of production.

First, during the design phases, Morgan Advanced Ceramics conducts mold flow simulation and analysis in order to optimize the part and mold design. On the computer, adjustments are made to gate positions, wall thickness and cooling parameters to help achieve success. By performing this analysis early in the design process, prior to commissioning the injection mold, many problems can be addressed and improvements can be implemented quickly at low cost and without causing expensive delays in the production schedule.

A second key factor in achieving tight tolerances and high repeatability is quality control during the mixing process to create a homogeneous pelletized feedstock. The ceramic particles must have a consistent size and they must be distributed evenly in the polymer binder. Morgan Advanced Ceramics’ engineers have implemented sophisticated processes to achieve uniform mixing and eliminate minute air pockets that could cause distortion or cracking in the final product. The use of sub-micron powders allows for smaller features that would otherwise not be possible with larger granulate-based forming methods such as dry pressing.

The third critical refinement that Morgan Advanced Ceramics has implemented is cavity pressure containment and control. Cavity pressure is the process variable that correlates most directly with part quality. Morgan Advanced Ceramics uses pressure transducers inside the mold tool cavity to provide process control as the feedstock flows into the cavity. The transducers gives the system an “eye” inside the cavity, allowing Morgan Advanced Ceramics’ engineers to closely control part weight and dimensions and eliminate flash, sinks, shorts and warp. In today’s world of Six Sigma, the standards are rising – “just fine” and “good enough” are not acceptable any more. Jobs with high volume and tight tolerances demand a level of capability that can only be achieved with cavity pressure containment and control.

Trend Toward Net-Shape Fabrication

Engineers bring parts to Morgan Advanced Ceramics and are amazed that the ceramic injection molding process can now produce similar geometries to those available in plastic and metal. Morgan Advanced Ceramics’ tolerances are typically within 25 microns on anywhere from 10 to 200 different dimensions. This new process is attractive because it is repeatable. Customers receive highly consistent quality with little part-to- part variation that enables Cpk’s in excess of 1.66. With fewer rejects and proven statistical process control, incoming inspection by the customer is no longer required.

The advanced CIM process gives engineers more versatility in the use of ceramics when designing new products and replacing plastic and metal components that fail to perform adequately.

In fact, the wider use of CIM is part of an overall philosophic trend in component manufacturing. There is a discernible move away from the energy-inefficient and wasteful practice of machining off material, toward more efficient net-shape fabrication, which takes advantage of computer-driven technology. This trend, in turn, has allowed production engineers and product designers to improve productivity, lower manufacturing costs and improve product performance.

Joint Sales and Distribution Agreement of Electronic Materials for Wafer Level Packaging

Dynaloy LLC and BASF AG have entered into an expanded sales and distribution agreement for strippers and cleaners used in the IC (integrated circuit) industry for wafer level packaging and bumping steps. This agreement will benefit BASF’s product portfolio for the semiconductor industry and will give Dynaloy access to key markets in Asia and Europe.

The new agreement is another step in BASF’s expanding activities in the electronic materials markets. It targets the area of wafer level packaging, which is one of the final steps in microchip production that uses contact pads, rather than pins or wires, to connect integrated circuits. Dynaloy has developed a broad portfolio of innovative and specialized chemical formulations for this process.

“With Dynaloy, BASF has a partner that can adjust its product offering to the ever-changing requirements of the industry and is able to customize products to meet the latest requirements,” said Dr. Karl-Rudolf Kurtz, group vice president of BASF’s Global Business Unit Electronic Materials. Donn Detzler, president of Dynaloy added, “BASF is the ideal partner for Dynaloy to provide the necessary technical support associated with our products with fast response to customer issues due to local presence and lab capabilities.”

BASF has a long-standing experience in the area of high purity chemicals and tailor-made formulations for the semiconductor and flat panel display industry. Dynaloy has advanced technology and specific products in the field of wafer level packaging.

Applied Coating Systems, Inc. has entered into an exclusive technical agreement with Nippon Fusso to provide fluoropolymer coating services to its US-based customers. Nippon Fusso recently closed its Hayward, Calif., plant and will consolidate its fluoropolymer operations in Japan and Korea.

With the signing of this agreement, Nippon Fusso has transferred the technology and materials necessary for Applied Coating Systems to effectively serve its US client base.

“Nippon Fusso-Japan has had a longstanding personal and professional relationship with Applied Coating Systems, Inc., a leader in the fluoropolymer applications business,” said Satoru Toyooka, president of Nippon Fusso. “We're confident of their ability to continue to provide the level of quality, expertise and professionalism our clients have come to expect.”

“We've already begun to work with some of Nippon Fusso's US-based clients and anticipate expanding the list throughout the coming year,” said Ronald L. Kaufmann, president of Applied Coating Systems. “Our experienced technicians will ensure a smooth transition for former Nippon Fusso clients.”

Applied Coating Systems offers a full range of services to provide total production continuity and quality assurance, from initial design consultation to surface preparation and from coating application to assembly and final inspection.

The company's 65,000-square-foot plant includes high quality robotic equipment and task-specific facilities.

Aluminum Heat Treating in Vacuum

Solar Atmospheres has recently completed solution aging 6061 aluminum from 0 to a T6 condition. This task was accomplished because of the plant’s 12-foot furnace and its Advanced Quenching capability.

Advances in vacuum furnace gas quenching processing continue to expand the materials that benefit from this technology. Fabricators of aluminum are discovering the benefits of minimized distortion and clean parts that vacuum processing offers.

Airwolf Helicopters manufactures aluminum booms for crop dusting. The 12-foot booms included smaller tubing, 1 3/8 inch dia. by .058 wall thickness, and larger tubing that ranged from 1 5/8 inch to 2 1/2 inches dia. by 0.058 wall thicknesses. Because of the thin wall and long length, water quenching would cause extreme distortion and contamination. Solar’s large furnaces and Advanced Quenching capability were the best alternative to attain material specifications while minimizing distortion.

To put the aluminum in solution, Solar uses a nitrogen partial pressure atmosphere in the vacuum furnace and gradually heat treats the aluminum up to 985°F. The material is held at this temperature and then a two bar, helium quench is performed. This brought the material to a T4 condition. While still in the furnace, age hardening is done in a nitrogen partial pressure environment. The aluminum is heated up to 350°F and held at that temperature for eight hours. The tubing is quenched in nitrogen. Required properties of the TE condition is an ultimate tensile strength of 42 KSI with yield strength of 35 KSI. Actual results attained were UTS of 42.1 KSI and yield strength of 38.6 KSI.

A significant factor that contributed to the success of this job was the thin wall tubing. Solar’s Advanced Quenching is continually improving and becoming more effective in cooling to achieve material specifications while minimizing distortion for oil and water quench materials.

CPS Technologies Offers Hermetic Microelectronic Packages for Military, Electronics, Satellite and Aerospace Markets

CPS Technologies, a company focused on design and production of metal matrix composites, now offers hermetic microelectronic packages. Made from materials such as Kovar, aluminum, and steel, CPS’ highly engineered hermetic microelectronic packages enable successful communication for military, electronics, satellite and aerospace markets.

CPS operates in a vertically integrated 38,000-square-foot manufacturing facility in Norton, Mass., which is certified to ISO:9001:2000, and offers assurance testing to MID-STD 883 and MIL-STD 202. CPS is compliant to DFARS clause 252.225-7014 ALT.1.

CPS’ test and plating capabilities include Electrolytic Nickel per QQ-N-290 and ASTM B-689, Electroless Nickel per Mil-C-26074E and ASTM B-733 and Gold per ASTM B-488 and Mil-G-45205C.

NuSil Technology Introduces Low Outgassing, Dielectric Gels Products For Electronic Packaging Applications

NuSil Technology, a silicone-based materials manufacturer for healthcare, aerospace, electronics and photonics, has announced the addition of three low outgassing, dielectric gels to its Electronic Packaging Materials line.

NuSil's EPM-2480, EPM-2481 and EPM-2482 were designed for the encapsulation of chip packages in devices where outgassing-related contamination poses a problem. These products cure into a soft, compliant silicone, which helps reduce stress on electronic assemblies during temperature cycling and protect against environmental factors and shock.

"The addition of the dielectric gels to the EPM product line offers engineers more options when it comes to protecting the chip" said Brian Nash, vice president of Marketing and Sales.

EPM-2480 and EPM-2481 are based on dimethyl silicone systems, while the EPM-2480 is a lower viscosity, firmer gel than the EPM-2481. Both are two-part systems and are supplied in 50-gram and 50-milliliter, side-by-side kits. The EPM-2482 is based on a diphenyl dimethyl silicone system for added temperature stability. The EPM-2482 is supplied in 50-gram and 50-milliliter, side-by-side kit.

Pfeiffer Vacuum Releases New Mass Spectrometer with the Added Sensitivity, Stability and Intelligent Operation

Pfeiffer Vacuum, a vacuum products and services producer, now offers PrismaPlus, a new mass spectrometer for qualitative and quantitative gas analysis and leak detection.

Pfeiffer Vacuum has earned experience in the field of mass spectrometry throughout the past 40 years. The combination of high sensitivity, stability and intelligent operation is the added “Plus” in the PrismaPlus mass spectrometer. In routine operation, the user benefits from its robust, compact design and simple systems integration.

With the ability to select mass ranges, detectors, ion sources and interface options, this mass spectrometer can be used in areas including industrial and analytical environments, research and development, leak detection and semiconductor production as well as coating technology.

The PrismaPlus delivers precise and stable results in three different mass ranges, 1 to 100 amu, 1 to 200 amu and 1 to 300 amu, down to a detection limit of 1x10 to 14 mbar. With available Faraday and electron multiplier detectors, even low level contamination in the vacuum system can be quickly identified. In addition to displaying scan data and selectable partial pressures, direct attachment of a pressure gauge enables the PrismaPlus to also accurately monitor total pressure.

The Quadera software offers an easy-to-read platform for capturing and visualizing all measured data and parameter records. Together, with a wide selection of interfaces such as Ethernet, digital and analog inputs and outputs, integration into any system is easily achieved. Custom application-specific routines may be created via a Visual Basic macro programming module.

Teijin, Ltd. has developed a highly durable fire-resistant fabric and a cold-weather insulation material for fiber optic cables, both of which incorporate high-strength aramid fibers.

Aramid fibers are more than 10 times as expensive as regular fibers like polyester, but Teijin believes it can cultivate profitable applications by playing to the fiber’s special features.

The new fire-resistant material, which is to be used in clothing, weaves together meta-type fibers that resist heat and para-type fibers that are hard to break. Para-type fibers account for 40 percent of the total, which is four times as high as conventional materials, and the cloth is wove into meshwork with spacing of 5 mm.

When the cloth is exposed to the heat of a fire, it stretches taut because the two types of aramid fibers have different thermal contraction coefficients. At the same time, countless air-filled pockets form within the meshwork, providing a heat-insulating effect.

Teijin plans to use this material in products in fiscal 2007, while striving to develop better fibers that can yield fire-resistant clothing of even lighter weight within two years.

The insulation material is designed for optical cables used in extremely cold environments like Russia. The aramid fibers are coated with a powdered polymer material that absorbs moisture and expands, preventing water from penetrating the cable. This is important in cold environments because any water that gets inside the cable can freeze and damage the optical fibers. Teijin also projects the material will be used for power cables and fuel pipes of machinery used on ocean oil-drilling rigs.

The company has also developed a rubber additive that reduces tire deformation and boosts fuel efficiency. The additive combines two chemicals that boost heat resistance so the tire experiences less deformation due to road friction. The agent can be used in tires for large vehicles that weigh more than 10 tons. Teijin officials expect a foreign tire maker to begin using the product this year.

Taking the Measure of the Seebeck Effect Might Reduce Global Warming

One side of an organic molecule trapped between two gold surfaces is heated, and the temperature difference induces an electrical current to flow. The phenomenon is an example of the Seebeck effect.

The Seebeck effect is a physical phenomenon discovered about two centuries ago that may hold the key to meeting future energy needs, while reducing global warming.

It involves the direct conversion of temperature differences into electricity. Thomas Johann Seebeck observed that a temperature difference between two ends of a metal bar created an electrical current in the space between, with the voltage being directly proportional to the temperature difference (the Seebeck coefficient).

Scientists have long recognized that the Seebeck effect could be exploited as an environmentally clean way of producing electricity, but the inefficient process and expensive materials have prevented practical commercial applications. The situation may soon be changing.

Arun Majumdar, mechanical engineer, and Rachel Segalman, chemical engineer, who both hold joint appointments at Lawrence Berkeley National Laboratory and the University of California at Berkeley, have recorded the first measurements of the Seebeck effect in inexpensive organic molecules.

Working with Pramod Reddy, a graduate student, and Sung-Yeon Jang, a postdoctoral fellow, Majumdar and Segalman trapped electron-conducting organic molecules between a pair of gold electrodes, and then measured the thermopower (voltage) at room temperature with their own technique of scanning tunneling microscopy (STM). This study was done on nanoscale materials, but it opens the door to a new field of thermoelectrics, which, could lead to a new generation of low-temperature solar cells and thin films as well as low-cost plastic power generators.

“This is a significant step and major departure from traditional inorganic semiconductor materials,” Majumdar said. “For the past 50 years, researchers have been working to improve the efficiency of thermoelectric materials, but progress has been extremely hard to come by, mainly due to the coupling between various properties of the material like electrical conductivity, thermal conductivity and the Seebeck coefficient, which determines the efficiency of the device. Recently, through nanotechnology, the efficiency has been increased — but only with expensive semiconductor materials that require high-temperature processing.”

Nearly all the world's electrical power, approximately 10 trillion watts, is generated by heat engines, giant gas- or steam-powered turbines that convert heat to mechanical energy, which, in turn, is converted to electricity. In accordance with thermodynamics, however, much of the heat isn't converted but released into the environment instead. To generate 10 trillion watts of electricity means wasting another 15 trillion watts as heat.

In the experimental setup, Majumdar, Segalman and their students used an STM with a gold stylus that tapers off to a single atom at its tip. The STM features a customized control circuit that moves the gold tip at a constant speed toward a gold substrate. While the STM gold tip is maintained at ambient temperature, an electric heater is used to warm the gold substrate. This creates a temperature difference between the tip and the substrate. Using chemical handles, the experimenters trap a molecule in the gap between tip and substrate and then measure the Seebeck effect.

The researchers worked with the benzenedithiol family for organic molecules. The electronic properties of these chemicals are well known, and they are easy to use.

“I am sure most conducting molecules will display the Seebeck effect when sandwiched in a metal junction,” Majumdar said. “We will be measuring a number of thiol-terminated molecules in metal/molecule/metal junctions, and we will also be looking into ways to tune the thermopower, such as introducing various chemical moieties in the molecule, or controlling the metal/molecule chemical bond.”

The ability to measure the Seebeck effect in metal/molecule junctions offers promise that extends beyond the field of energy, according to Majumdar and his coauthors. For example, in the emerging arena of molecular electronics, a key issue has been the alignment of electronic energy levels when new chemical bonds are formed. This is a critical factor in the operation and performance of a device, but until now it has been difficult to determine such energy alignments at metal/molecule junctions.

“The ability to measure the Seebeck effect resolves this important issue and can be directly used to estimate the energy levels of the junction,” Majumdar said. “This is a fundamental step in the design and understanding of molecular electronic devices for information processing and storage, and of molecular solar cells for converting sunlight to electricity.”

MIT Model Could Aid Design of Nanomaterials

Researchers from Massachusetts Institute of Technology, Georgia Institute of Technology and Ohio State University have developed a new computer modeling approach to study how materials behave under stress at the atomic level, offering insights that could help engineers design materials with an ideal balance between strength and resistance to failure.

When designing materials, there is often a tradeoff between strength and ductility (resistance to breaking) properties that are critically important to the performance of materials. Recent advances in nanotechnology have allowed researchers to manipulate a material's nanostructure to make it both strong and ductile. Now, the MIT-related team has figured out why some nano-designed metals behave with that desirable compromise between strength and ductility.

The team, led by Subra Suresh, the Ford professor of engineering in the Department of Materials Science and Engineering, developed a simulation method derived from experimental data that allows them to visualize the deformation of materials on a timescale of minutes. Previous methods allowed for only a nanosecond-scale glimpse at the atomic-level processes.

“It's a method to look at mechanical properties at the atomic scale of real experiments without being bogged down by limitations of nanosecond timescales of the simulation methods such as molecular dynamics,” Suresh said.

Using the new method, the researchers found that the ductility and strength of materials are greatly influenced by a special kind of interface known as the twin boundary. It is an abrupt internal interface each side of which is a precise mirror reflection of atoms of the other side. Twin boundaries can be introduced in various densities, in a controlled manner, inside a nanocrystalline metal.

For many years, engineers have been able to tinker with the structure of metals to make them stronger. Metals are traditionally made from micrometer-scale "building blocks" called grains, which each contain many millions of atoms. About two decades ago, materials engineers discovered that when they made the grains smaller, typically tens of nanometers in average size, metals become stronger. Known as nanocrystalline metals, they are several times stronger than conventional microcrystalline metals.

However, as nanocrystalline metals become stronger, they also become more brittle (less ductile). For example, copper with a grain size of 10 micrometers may have a ductility of about 50 percent (depending on exact composition), but at a 10 nanometer grain size, the ductility is below 5 percent, according to Suresh.

A few years ago, researchers at the Shenyang National Laboratory for Materials Science in China synthesized a novel form of nanostructured metal, nano-twinned copper. The material was created by introducing controlled concentrations of twin boundaries within very small grains of the metal using a technique known as pulsed electrodeposition.

The Shenyang group, working in collaboration with Suresh's group at MIT, demonstrated in the past two years that nano-twinned copper has many of the same desirable characteristics as nano-grained copper, and resulted in a good combination of strength and ductility. By controlling the thickness and spacing of twin boundaries inside small grains to nanometer-level precision, they were able to produce copper with different "tunable" combinations of strength and ductility.

Internal interfaces such as grain boundaries (which occur between grains) and twin boundaries play a critical role in the strength and ductility of metals. Smaller grains in the metal structure, and more grain boundaries for a given volume allow more interaction between the boundaries and dislocations, or string-like defects in the material that move inside and between grains during mechanical deformation. The larger proportion of these boundaries contributes to the brittleness of the metal.

Adding nano-scale twin boundaries, which effectively subdivide the grains, has a similar strengthening effect, but the twin boundaries do not promote the same level of brittleness as grain boundaries do.

"You can trick the material and optimize both strength and ductility by modifying the interactions between dislocations and these nano-scale twin boundaries inside the grain," Suresh said.

The new study reveals that the ductility of nano-twinned copper can be attributed to changes in the atomic structure of the twin boundaries as the material is deformed. Metals with more twin boundaries also maintain their electrical conductivity better than metals with more grain boundaries, making them potentially more useful for applications such as computer chip components. Nanocrystalline metals that are both strong and ductile could also be useful for many wear-resistant thin-film coating applications and MEMS (micro-electro-mechanical systems) devices, Suresh said.