Getter Material Research Articles

An Instrumented Getter for Hermetically Sealed Packages

For decades, getters have been used in vacuum sealed hermetic packaging of electronic devices to maintain high vacuum for extended periods of time. Getters work by chemically binding certain gas molecules to them as they leak into the package over time. Typically, getters are activated by exposure to high temperatures after the hermetic package has been sealed in a high vacuum chamber. The problem with using a getter is that it is assumed that the hermetic package is properly sealed and the getter binds small numbers of gas molecules that leak into the package over a long period of time. If that is not the case, the getter will eventually saturate and cease from trapping additional gas molecules that leak into the package. At this point, the pressure begins to rise inside the package. Since this is an open loop process, this problem only becomes apparent when the electronic part fails. If the getter could be instrumented, then it could be monitored to determine its operating state and the hermetic condition of the package. Recently, Alpha Advanced Materials introduced the Staydry® Hicap™ 2000 getter material, which can absorb H20 and CO2 molecules. The Hicap 2000 getter material can be deposited by stencil printing, and is cured at relatively low temperatures, 150oC to 200oC. It activates upon curing. This getter material absorbs moisture by converting calcium oxide to calcium hydroxide. Calcium oxide has a dielectric constant of approximately 11.8, while calcium hydroxide has a dielectric constant between 1.8 and 3.5. Therefore, the dielectric constant of the getter material drops between 70% and 85% as it saturates with absorbed moisture. Exploiting this electrochemical property, the Hicap 2000 getter material was deposited on top of a miniaturized interdigitated electrode fringing field capacitor structure to realize an instrumented getter that decreases in capacitance as moisture is absorbed. Prototype instrumented getter units were fabricated and tested to demonstrate their functionality. Power is only required to occasionally measure the capacitance of the device. Instrumented getters will allow the status of the getter protected hermetic packages to be monitored to determine the operating condition of the getter and the quality of the vacuum environment inside the package. By using instrumented getters, the reliability of high vacuum packaged electronic and MEMS devices will by significantly improved. This is particularly important for high risk applications such as medical electronics, aircraft, military systems, next generation wireless communication systems, and autonomous vehicles.

Effect of Adding Al on the Phase Structure and Gettering Performance of TiZrV Non-Evaporable Getter Materials.

Titanium zirconium vanadium (TiZrV) is a widely used non-evaporable getter (NEG) material with the characteristics of a low activation temperature and a large gas absorption capacity. At present, the research on TiZrV getters mainly focuses on the thin-film state, with little research on the bulk state. In this paper, a TiZrV getter was optimized by adding Al, and the phase structure, activation properties, and gettering performance were studied. With the addition of Al, the α-Zr phase and Ti2Zr phase changed into the Ti-Zr phase and Al-Zr, Al-Ti phase. The newly generated phase promoted the diffusion of hydrogen and oxygen atoms. The activation temperature decreased significantly, as shown in the in situ XPS results. The H2 and CO gettering performance of TiZrVAl samples was promoted to 2073 cm3·s-1 and 1912.8 cm3·s-1, increased by 40.7% and 40.3%. This paper provides valuable ideas for optimizing the properties of bulk TiZrV getters.

Additively Manufactured Silicone Polymer Composite with High Hydrogen Getter Content and Hydrogen Absorption Capacity.

Hydrogen getters consisting of 1,4-bis[phenylethynyl] benzene (DEB) and a carbon-supported palladium catalyst (Pd/C) have been used to mitigate the accumulation of unwanted hydrogen gas in a sealed system. Here, we report the formulation of a composite resin consisting of silicone polymer plus DEB-Pd/C as an active getter material and the additive manufacturing of silicone getter composites with a high getter content (up to 50 wt %). NMR and DSC studies suggest no reaction between the silicone polymer resin and DEB even at elevated curing temperatures (75 °C). Getter composites with varying amounts of getter and filler were formulated, and their rheological properties were studied. The two composite resins with good printability parameters and different getter contents were chosen to make 3D-printed samples. The hydrogen absorption capacity of these samples was studied at a low hydrogen pressure of 750 mTorr of pure hydrogen. The getter composite with 50 wt% of getter showed normalized DEB conversion of 83%, with the hydrogen adsorption capacity of 100.2 mL of H2 per gram of polymer getter composite.

Evolution of Getter Technology in Electronic Hermetic Packaging

Hermetic packaging is a well-established technology used for sealing electronic and optoelectronic devices. A reliable and enabling way to preserve the proper stable atmosphere conditions in hermetic packages is the integration of engineered getter solutions, specifically designed for the characteristics of different packaged systems. Getter solutions may vary from sintered, compressed or sputtered metallic alloys for vacuum sealed packages to dispensable hybrid organic-inorganic materials for gas back filled devices. The paper will present the main features of getter materials suitable for different type of packages and will show their efficiency in absorbing detrimental gases in the devices.

Characterization of a NEG cartridge under high pressure conditions

The development of advanced sintered pumping elements based on the ZAO® alloy, characterized by a high affinity towards hydrogen and its isotopes, make Non Evaporable Getter (NEG) pumps particularly appealing for applications in fusion research, which typically deal with large fluxes of these gaseous species. NEG getters show high pumping speeds and capacity, excellent reliability with ability to withstand a high number of loading and unloading cycles without showing any type of failure, ease of integration within a complex system (such as a fusion reactor) because of their high specific properties and the simplicity of the mechanism that regulates its operation. These properties make NEG technology particularly suitable for the development of compact, efficient and easily scalable solutions, which are also very safe, since the release of absorbed hydrogen is prevented in the case of power outage or subsystem failures, as it can occur only by providing an adequate amount of heat to the getter material. This paper reports the results of an experimental campaign conducted on a new type of NEG pump, aimed to obtaining an accurate characterization in response to different operating conditions. Hydrogen pumping speed was investigated in a range of pressures of particular interest for the activities of the Divertor Tokamak Test facility (between 0.1 and 10 Pa). The influence of nitrogen absorption and getter material operating temperature on the pumping performances of the NEG pump were also examined. Finally, numerical simulations have been performed to estimate the nominal pumping speed of the NEG pump, that is, the one acting at the absorbing surface, stripped of the effects of the conductance of the paths from the pump NEG to the pressure gauges.

Preliminary evaluation of NEG materials in view of CMSB replacement in HCPB TER architecture

CMSB (Cryogenic Molecular Sieve Beds) operated at 77 K is used for tritium recovery in the reference design of HCPB (Helium Cooled Pebble Bed) TER (Tritium Extraction and Removal) system. However, this technology has two main drawbacks: large consumption of liquid nitrogen and the controlling of tritium stream sent to the Tritium Plant, during the regeneration of the CMSB, in such way to avoid large variations in the gas flow rate.This paper reports on a preliminary evaluation for CMSB replacement by non-evaporable getter materials for tritium recovery. The advantages of NEG technology are the high specific pumping speed and capacity and the ability to withstand a large number of absorption/desorption cycles. In addition, NEG do not release hydrogen unless power is supplied to heat them, addressing an important safety issue related to uncontrolled release in case of power outage or subsystem failures.

A new NEG coating setup with travelling thin solenoids for the SLS 2.0 complex vacuum chambers

The 288 m long Storage Ring of Swiss Light Source 2.0 (SLS 2.0) consists of several vacuum chambers with unique geometries. Complicated features, with many changes in the cross sections, are essential to provide the best impedance matching, and to allow synchrotron light extraction under the tight geometrical constraints. In order to speed up the commissioning time, it was decided to coat most of the vacuum chambers with non-evaporable getter (NEG) material. A new magnetron sputtering setup has been developed in Paul Scherrer Institut (PSI), where the plasma length, defined by thin solenoids, is relatively small. The solenoids are continuously travelling over the entire vacuum chambers more than hundred times per coating process with an average speed of 4 mm/s to assure the best possible thickness uniformity and to limit the cathode heat up. Flexibility provided by this solution allows to coat various vacuum vessels in one assembly. This paper will describe this NEG coating setup and show results on SLS 2.0 vacuum chambers.

Determination of Hydrogen Content in Getter Material from Parabolic Trough Receivers

In this study, a procedure for analyzing the hydrogen content of used getter material is described based on mass spectrometry coupled to thermal gravimetry. It is shown that hydrogen masses per getter mass in the range of 2 – 15 mg/g can be quantified. At least three differently strong hydrogen binding situations are found with the thermal desorption program applied so far. Up to 450 °C only traces of hydrogen can be desorbed from the getter material with the applied method and up to 99% is released on heating up to 800 °C.

Nitrogen concentration control during diamond growth for NV- centre formation.

Negatively charged nitrogen-vacancy (NV-) centres formed in diamond crystals are point defects that have potential applications in various quantum devices such as highly sensitive magnetic sensors. To improve the sensitivity of magnetic sensors using NV- centres, it is essential to precisely control the nitrogen concentration in the crystals. In this paper, we demonstrated that nitrogen concentration in diamond can be controlled with high precision for the following two representative growth methods. One is the high-pressure/high-temperature (HPHT) synthesis method and the other isthe chemical vapour deposition (CVD) method. The nitrogen concentration of HPHT-grown diamond decreased semi-logarithmically with increasing contents of titanium or aluminium as nitrogen getter materials. The nitrogen concentration of CVD-grown diamond increased linearly with increasing the flow rate ratio of nitrogen to carbon. NV- centres were formed by controlling the total fluence of electron beams so that approximately 20% of the nitrogen became NV- centres. The coherence time of electron spin of NV- centres obtained by the Hahn-echo pulse sequence T2 of these diamond crystals was inversely proportional to the nitrogen concentration. A comparison of T2 of the NV- centres for HPHT-synthesized and CVD-grown diamonds showed no significant difference between them. This article is part of the Theo Murphy meeting issue 'Diamond for quantum applications'.

Study of doped Cu on adjusting the TiZrV phase structure and improving the low temperature activated gettering performance

In this paper, we focus on studying the low-temperature activated bulk TiZrV getter materials instead of thin film materials to meet the high reliability requirements of vacuum devices. The research was carried out by introduce Cu element to improve the activated characteristic and gettering performance. The XRD and in-situ XPS results showed the addition of Cu could effectively reduce the diffusion temperature and increase the diffusion rate of O atoms by modifying the phase structure of TiZrV getter. An appropriate amount of Cu was beneficial for stabilizing high-temperature β-Zr phase at room temperature, which had a larger interstitial void compared to that of the low-temperature α-Zr phase. The TiZrVCu getter with high proportion of β-Zr phase displayed 55.0% higher gettering performance than that of TiZrV with activated at 350 °C for 10 min. The proposed strategy of improving the low-temperature activated gettering performance offers promising opportunities for exploiting potential new low-temperature activated bulk getter materials.

Study of Tritium Diffusivity in Pure and Sn-Defective Zr: A First-Principles Density Functional Theory Approach

Zirconium alloys (e.g., zircaloy-4) are used as tritium (3H) getter materials in tritium-producing burnable absorber rods (TPBARs) owing to their ability to capture 3H and chemically convert them into metal hydrides. Understanding of 3H diffusion mechanisms in zircaloy is crucial for the optimal design of material performance in nuclear technology. Here, we perform first-principles density functional theory calculations to study the 3H diffusion mechanism in pure and impure Zr with a low concentration of tin (Sn) atoms to determine the impact of the presence of Sn on the movement of 3H atoms through the material. First, we calculated the diffusion barriers for 3H in pure Zr by taking different migration pathways. We then introduced a low concentration of Sn impurity and systematically explored the impurity effect on the diffusion barriers for 3H. Using our calculated diffusion energy barriers, we further obtained the diffusion coefficients and analyzed the results by comparing them with the experimental and previously calculated values. A diffusion coefficient of the order of 10–8 m2/s is predicted. We also found that the presence of a Sn impurity could reduce the diffusivity up to 4 orders of magnitude. Our results could serve as guidelines for further experimental investigations.

Multi-Contaminant Getter for Trace Airborne Contaminant Capture in Elevated Temperature Electrochemical Systems

Electrode poisoning in high temperature electrochemical systems from trace levels of airborne contaminants remains a critical issue, contributing to long-term irreversible performance degradation. The intrinsic and extrinsic presence of gas phase Cr, Si, B, and SOx, species in air have been reported to form detrimental secondary compounds and microstructural changes at the electrode/electrolyte interface, consuming electrochemically active sites. Herein, a novel contaminant capture method is reported that uses low-cost getter materials based on alkaline-earth metals. The getters, in benchtop transpiration tests, demonstrated the desired ability to form thermodynamically stable reaction products and reducing the gaseous contaminant partial pressures by several orders of magnitude. Consumption of the contaminants in the getter preserves the performance of solid oxide cells. The presented results have demonstrated the feasibility of the use of getter materials under operating conditions typical to elevated-temperature electrochemical systems.

Modeling of the HCPB Helium Coolant Purification System for EU-DEMO: Process Simulations of Molecular Sieves and NEG Sorbents

The Helium Cooled Pebble Bed breeding blanket of the EU-DEMO foresees continuous processing of a small fraction of the helium coolant in the coolant purification system (CPS) to counteract buildup of tritium and impurities. For this system, two different process variants are currently considered. The first is based on the conversion of all hydrogen species into water using copper oxide beds and the subsequent water adsorption over zeolite molecular sieve (ZMS) beds. The alternative process foresees the direct sorption of hydrogens onto novel ZAO® non-evaporable getter (NEG) materials. The ZMS beds and the NEG beds are operated batchwise, but alternating schemes with an absorption (operation) phase and a desorption (regeneration) phase result in a pseudocontinuous process. Transient process simulations have been developed to evaluate the performance and impact of the different variants on downstream systems in the fuel cycle. In this contribution, these process models for the preconceptual design of both variants are presented and evaluated. For the reference designs proposed for each system, they have been found to satisfy the requirements of achieving 90% efficiency. This modeling then lays the foundation for optimization of the conventional process and outlines further research demand regarding the application of NEG materials needed to progress toward the concept design of the CPS process.

Experimental Characterization of an NEG Pump of Novel Size—A Major Step toward Its Application in DEMO Neutral Beam Injectors

A future nuclear fusion plant DEMO needs neutral beam injection (NBI) systems requiring a vacuum pumping system with a very high pumping speed, in the order of several 1000 m3/s. Large customized cryopumps are actually used to meet the requirements. A promising concept for future NBI systems is based on high capacity getter materials. The ZAO® alloy, developed by SAES Getters, Italy, provides a drastically improved performance for the pumping of hydrogen compared to conventional getter materials. This paper describes the experimental characterization of a large pump of scalable size with 15 kg of ZAO® and the achieved results, in particular the systematic investigation of sorption characteristics and regeneration behaviors. Major findings include a very good repeatability of the sorption performance, a reduced pumping speed at higher pressures only above the NBI relevant level, an improved performance (+20%) with elevated getter temperature and an isotope independent sticking coefficient for hydrogen. Furthermore, improved operation experience and regeneration prediction tools have been developed. Employing the experimental results, a simulation task was performed and the sticking factor of the getter cartridge was determined with 7%.

Micromechanics of porosity of various degrees in porous permeable Ti–V30 getter made of powder

In this paper, a porous medium, microstructure, and morphology of the surface of a sheet non-sprayed getter based on a Ti–V system, obtained by cold rolling of powder into a tape and its subsequent sintering, are studied. The macro- and mesoporous structures are considered. The microporous structure is formed during the cold rolling of Ti–V30 powder into a tape, and it is a porous framework with an average capillary diameter of 5.00–8.50 μm. The mesoporous structure in the initial PTP powder is a uniformly distributed porosity on the surface of particles of the powder. During the heat treatment of the formed rolled stock, the mesoporosity qualitatively transforms into cracks on the surface of the sintered porous body. An interrelation between the parameters of the macroporous structure, which affect the formation of mesoporosity (mesocracks) on the surface of the sintered rolled stock, determining a specific sorption rate, was established. A hypothesis on the mechanisms of formation of the mesoporosity in the sintered getter during its heat treatment is formulated, and recommendations that allow obtaining getter materials having a maximum specific sorption rate are given. The necessity of performing an analysis of macro- and mesoporosity for bulk porous getters and mesoporosity in the case of film getters to explain and predict their sorption properties is shown.

Development and Characterization of Low Temperature Wafer-Level Vacuum Packaging Using Cu-Sn Bonding and Nanomultilayer Getter.

Most microsensors are composed of devices and covers. Due to the complicated structure of the cover and various other requirements, it difficult to use wafer-level packaging with such microsensors. In particular, for monolithic microsensors combined with read-out ICs, the available process margins are further reduced due to the thermal and mechanical effects applied to IC wafers during the packaging process. This research proposes a low-temperature, wafer-level vacuum packaging technology based on Cu-Sn bonding and nano-multilayer getter materials for use with microbolometers. In Cu-Sn bonding, the Cu/Cu3Sn/Cu microstructure required to ensure reliability can be obtained by optimizing the bonding temperature, pressure, and time. The Zr-Ti-Ru based nanomultilayer getter coating inside the cap wafer with high step height has been improved by self-aligned shadow masking. The device pad, composed of bonded wafer, was opened by wafer grinding, and the thermoelectrical properties were evaluated at the wafer-level. The bonding strength and vacuum level were characterized by a shear test and thermoelectrical test using microbolometer test pixels. The vacuum level of the packaged samples showed very narrow distribution near 50 mTorr. This wafer-level packaging platform could be very useful for sensor development whereby high reliability and excellent mechanical/optical performance are both required. Due to its reliability and the low material cost and bonding temperature, this wafer-based packaging approach is suitable for commercial applications.

Intermetallic Getters Reactants for Vacuum Applications

The present work continues a series of publications devoted to the study of the sorption properties of reactive alloys based on IIA metals and the development of advanced getter materials for gas and vacuum technologies. This publication attempts to answer the current challenges in the field of gas sorption associated with the emergence of new vacuum products such as vacuum insulated glasses, electronic systems, cryogenic devices, etc. An analysis of the problems that arise here, as well as the results of sorption measurements, carried out with the participation of intermetallic phases of the composition CaLi2 and Ca0.33Li0.48Mg0.19, show that the best getter support for these new hermetically sealed products can be provided by intermetallic compounds formed in systems Li-IIA metals. Intermetallic phases of this family are easy to manufacture and demonstrate outstanding service characteristics: their specific sorption capacity is recorded high, exceeding traditional gas sorbents in this respect by at least an order of magnitude; the kinetics of gas capturing is set at the stage of alloy production, i.e., is adjustable; the temporary resistance of these phases to atmospheric gases allows to install the getter at its workplace in air, without further thermal activation. The sorption superiority of reactive intermetallics is explained by their special sorption mechanism: the gas/metal interaction is formed here as a combination of two processes, continuous growth of reaction products on a metallic surface and corrosion decay of brittle intermetallic phase under mechanical forces, which feeds the chemical reaction with a fresh surface. The advantages of sorption processes of this new type are undoubted and significant: compared with the conventional sorbents, an intermetallic getter reactant solves two important problems; it reduces production costs and increases the sorption yield.

Experimental investigation of methods to reduce outgassing from core materials in the fabrication process of transparent vacuum insulation panels

The notion that modern buildings should strive to be net-zero energy buildings (NZEBs) is widely accepted. In order to improve window’s insulation in existing buildings, structured-core transparent vacuum insulation panels (TVIPs) are proposed. TVIPs mainly consist of the structured core material, the low-emissivity film, and the transparent gas barrier envelope. TVIPs have high insulation performance and are inexpensive to manufacture and can be easily installed. However, it is necessary to overcome the issue of preventing the pressure rise inside TVIP after vacuum sealing. The authors constructed an experimental setup by applying the pressure-rate-of-rise-method to establish the fabrication process for TVIPs that prevents the pressure rise. In this experiment, a gas barrier film with a straw was used as the vacuum chamber. This could reproduce the pressure increase in the TVIP after sealing and the gas flow rate in the TVIP is evaluated. The experimental results showed that the internal pressure of TVIP could be reduced to about 1 Pa after vacuuming while heating for 8 hours, coating the core material, and sealing the getter material.

Stimulated gas desorption from TiZrV, Ag and Pd coating films in response to synchrotron radiation

In order to apply coating technology to the development of accelerator components with low gas desorption under synchrotron radiation (SR) exposure, TiZrV, Ag and Pd coating films were prepared and gas desorption in response to SR were studied at KEK Photon Factory (PF). TiZrV alloy is a non-evaporable getter (NEG) material widely used to coat accelerators vacuum chambers, and low pressure under SR irradiation was observed in the TiZrV coated tubes after activation. In this study, planar Cu substrates were coated with TiZrV, Ag and Pd and their SR-stimulated desorption yields were measured. It has been identified that the desorption yield of the TiZrV coated sample was significantly lower than that of the bare Cu substrate, while Ag coating also exhibited similarly low desorption yield. In addition, the Pd coating demonstrated the possibility of further decreasing the gas desorption in response to the SR.

A Novel Packaged Ultra-High Q Silicon MEMS Butterfly Vibratory Gyroscope.

A novel three-dimensional (3D) wafer-level sandwich packaging technology is here applied in the dual mass MEMS butterfly vibratory gyroscope (BFVG) to achieve ultra-high Q factor. A GIS (glass in silicon) composite substrate with glass as the main body and low-resistance silicon column as the vertical lead is processed by glass reflow technology, which effectively avoids air leakage caused by thermal stress mismatch. Sputter getter material is used on the glass cap to further improve the vacuum degree. The Silicon-On-Insulator (SOI) gyroscope structure is sandwiched between the composite substrate and glass cap to realize vertical electrical interconnection by high-vacuum anodic bonding. The Q factors of drive and sense modes in BFVG measured by the self-developed double closed-loop circuit system are significantly improved to 8.628 times and 2.779 times higher than those of the traditional ceramic shell package. The experimental results of the processed gyroscope also demonstrate a high resolution of 0.1°/s, the scale factor of 1.302 mV/(°/s), and nonlinearity of 558 ppm in the full-scale range of ±1800°/s. By calculating the Allen variance, we obtained the angular random walk (ARW) of 1.281°/√h and low bias instability (BI) of 9.789°/h. The process error makes the actual drive and sense frequency of the gyroscope deviate by 8.989% and 5.367% compared with the simulation.