Helium Leak Research Articles

Optimization of Process Parameters in Electro-Magnetic Welding of D9 Tube to SS316 L (N) Plug

In electro-magnetic welding (EMW) process, optimization of process parameters is very important aspect. Optimization process leads to generation of mechanically and metallurgically sound interface weld without overstressing tool coil and electromagnetic welding equipment. This work investigates the effect of four important process parameters (Magnetic field in coil ID, Frequency of current pulse, Taper angle of SS316 L (N) plug and Stand-off distance between D9 tube and SS316 L (N) plug) on weld quality and their optimization. Multiple experiments were conducted to arrive at optimized value of above mentioned process parameters which generated heat effected zone free, mechanically and metallurgically qualified interface weld of reasonable length. The welded interface revealed a wavy morphology of 35 - 40 μm as maximum crest height and lowest helium leak rate of 4 × 10?10 m?bar?L/s. Experimental results have proved that 27 T magnetic field is needed in coil ID to produce optimum weld quality at interface. Experimental data has proved that at higher frequency, similar quality of electro-magnetic welding can be obtained at lower bank energy. Experimental results have also proved that taper angle of 8? produces weld interface at lowest possible magnetic field in coil ID. It is also proved experimentally that 0.5 mm stand-off distance produces better weld length as compared to no stand-off distance and 1.0 mm stand-off distance.

Determining Maximum Allowable Rubber Stopper Displacement for Container Closure Integrity (CCI).

Sterile pharmaceuticals require they be developed and manufactured using suitable container closure systems to maintain sterility until product opening. Characterizing container closure integrity (CCI) in relation to rubber stopper displacement was controversially discussed during the Annex 1 revision process. An automated inspection system can reject units with displaced rubber stoppers, and the related acceptance criteria for such in-process testing can be established by adequate studies. In this manuscript, we describe a novel helium leak CCI testing method to study the relation of rubber stopper displacement and CCI. Ten different commonly used vial-rubber stopper combinations were characterized, which led to robust test results. Pronounced differences between the different vial-rubber stopper combinations were observed, clearly showing that the combination of different stoppers, vials, and caps led to significant differences in allowable stopper displacement for routine manufacture.

Experimental investigation of driver material on electromagnetic welding of alloy D9 SS tube to SS316L(N) plug

In electromagnetic welding process, for a low electrically conductive outer tube material, physical and mechanical properties of conductive drivers are important to achieve strong wavy weld. However, the technology may not be cost-effective for joining such metals. This work investigates the effect of using driver materials (Al of thickness 0.65, 1.0, 1.3, and 2.0 mm and annealed Cu (up to 650°C) of thickness 0.5, 0.75, 1.0, and 1.5 mm) on effectively achieving welding between alloy D9 SS tube and SS316L(N) solid plug. Multiple experiments were conducted to determine the preferred material and thickness of the driver tube. The welded interface revealed a wavy morphology of 35–40 μm as maximum crest height and lowest helium leak rate of 4 × 10–10 m bar L/s with annealed Cu driver having thickness 1 mm. The experimental results prove that annealed Cu (up to 650°C) should be chosen over Al as driver material. The preferred driver thickness was found to be dependent on the frequency of the current pulse.

Microwave-assisted alumina-zirconia brazed joint for microwave tubes

Alumina-zirconia joint was fabricated by microwave-assisted brazing technique at 980 °C for 15 min using TICUSIL (68.8Ag26.7Cu4.5Ti in wt%) as the brazing alloy. The brazed joints were characterized by X-ray diffraction, scanning electron microscopy, energy dispersive X-ray analysis, Vickers microhardness evaluation, brazing strength measurement, and helium leak test. X-ray diffraction analysis confirmed the formation of Ti-based compounds at the substrate-filler alloy interfaces of the brazed joints. SEM images showed the substrate-filler alloy interfaces of the brazed joints. The EDX analysis determined the elemental compositions along the joint cross-section. Vickers microhardness measurement indicated reliable joint performance for the microwave-assisted brazed joints during actual application. Brazing strength measurement and helium leak test proved the formation of sound alumina-zirconia brazed joint by both microwave and conventional heating techniques. Scratch tests were performed on the cross-sectional surfaces of the alumina-zirconia joints. Scratch test results established the strong interfacial strength of the microwave brazed joints.

Effect of Impact Velocity on Interface Characteristics of HT-9 Steel Joints Fabricated by Magnetic Pulse Welding

The weldability window in magnetic pulse welding (MPW) is proposed for the end-closure joining of HT-9 steel tubular workpieces. Based on both theoretical and experimental investigations, the impact velocity of the flyer tube at the moment of collision had a dominant effect on the bonding characteristics of the resultant joints and the optimal impact velocity was estimated to be in the range of 265–290 m/s in this alloy system. Under the optimal process conditions, no leak was detected during helium leak testing. Moreover, the integrity of the joint interface was preserved until the tube section ruptured during internal pressure burst testing. For HT-9 steel, the ductile δ-ferrite phase produced by the localized interfacial melting during MPW acted as an effective obstacle to crack propagation, thereby enhancing the fracture resistance of the joint interface. All of the results demonstrated the high integrity and durability of the HT-9 steel tube assembly fabricated by the MPW process.

Unveiling hermetic failure of ceramic tubes by digital image correlation and acoustic emission

AbstractA new, in situ hermeticity testing apparatus has been developed to allow helium leak evaluation of ceramic tubes, including nuclear‐grade SiC/SiC fuel cladding ceramic matrix composites (CMC), during four‐point bending with simultaneous monitoring of local deformation and damage, using stereoscopic digital image correlation (DIC) and acoustic emissions. The capabilities of the experimental apparatus are demonstrated using alumina, borosilicate glass, and 4130 steel tubes with representative cladding dimensions and then applied to study the deformation‐hermeticity relationship of SiC/SiC CMCs. Results of three CMCs appear to indicate that matrix cracking occurs near the deviation from linearity strain at strains ranging from 0.04% to 0.06% and is shortly followed by an initial loss of gas tightness by 0.09% bending strain. Leaking increased in distinct steps over 0.1%‐0.2% bending strain, and within this range, results indicate that prior to fiber fracture, it is likely possible to regain gas tightness upon unloading. This technique and uncovered hermetic failure behavior are intended to progress the standardization of a test methodology for nuclear reactor components and to begin to resolve the mechanisms controlling distinct steps of ceramic matrix composite failure.

Adaptive feedforward cancellation with gain and damping control system considering helium leakage in HDDs

This study developed an adaptive feedforward cancellation system with gain and damping control for hard disk drives (HDDs). The system was developed to compensate for fluid-induced vibration due to helium leakage. Helium-filled HDDs are used in data servers around the world to support the information society. One of the concerns in helium-filled HDDs is the deterioration of positioning accuracy of the control system due to helium leakage. The proposed head positioning control system can compensate for the fluid-induced vibration by updating the characteristics of the control system in real-time. Real-time simulations based on MATLAB/Simulink were performed to demonstrate that fluid-induced vibrations due by helium leakage in the head positioning control system of HDDs can be compensated. The results indicated that the characteristics of the control system were updated in real-time to compensate for fluid-induced vibrations in conformity with the variation in characteristics due to helium leakage and that the fluid-induced vibrations can be adequately compensated.

Quantifying the Vial-Capping Process: Reexamination Using Micro-Computed Tomography.

A vial-capping process for lyophilization stopper configurations was previously quantified using residual seal force (RSF). A correlation between RSF and container closure integrity (CCI) was established, and component positional offsets were identified to be the primary source of variability in RSF measurements.To gain insight into the effects of stopper geometry on CCI, serum stoppers with the same rubber formulation were investigated in this study. Unlike lyophilization stoppers that passed CCI (per helium leak testing) even with RSF of 0 N owing to their excellent valve seal, serum stoppers consistently failed CCI when RSF was <15.8 N. When the plug was removed, both types of stoppers exhibited a comparable critical lower RSF limit (19-20 N), below which CCI could not be maintained. When CCI was retested at later time points (up to 6 mo), some previously failed vials passed CCI, suggesting that CCI improvement might be related to rubber relaxation (viscous flow), which can fill minor imperfections on the vial finish.To confirm component positional offsets are the primary sources of RSF variability, a novel quantification tool-micro-computed tomography (micro-CT)-was used in this study. Micro-CT provided images for quantification of positional offsets of the cap and stopper that directly correlated with RSF fluctuations. Serum stoppers and lyophilization stoppers are comparable in RSF variations, although lyophilization stoppers are more robust in CCI. The use of micro-CT provides a nondestructive and innovative tool in quantitatively analyzing component features of capped vials that would otherwise be difficult to investigate.

Preparation of three-dimensional ceramic substrate by multiple electroforming for UV-LED hermetic packaging

In this work, preparation of three-dimensional direct plated copper (3DPC) ceramic substrate was proposed based on multiple lithography and electroforming. Firstly, the effects of current density, stirring speed and bath temperature on electrodeposition rate and residual stress were investigated. An optimal combination of parameters for high electrodeposition rate and low residual stress was the current density of 4 A/dm2, the stirring speed of 1000 rpm, and the bath temperature of 50 °C. Secondly, 3DPC ceramic substrate with 0.5 mm nickel dam was prepared through 4 times lithography and electroforming. Finally, the reliability of 3DPC substrate was evaluated by helium leak rate and bonding strength between the electroforming dam and planar DPC substrate during thermal cycle test. The 3DPC substrate exhibited excellent hermeticity and high bonding strength even after 30 thermal cycles. The UV-LED module packaged using 3DPC substrate and quartz glass exhibited excellent hermeticity and high light power. The above results suggested that 3DPC substrate prepared through multiple lithography and electroforming could be a promising candidate for UV-LED hermetic packaging.

Helium leak detection method using ambient temperature of canister top

The aging management of long-team storage of spent fuel and the monitoring method of integrity of fuel are attracting interest more than ever in the world. In a concrete cask, the loss of sealing performance of a canister, which is caused by stress corrosion cracking (SCC), is concerned in the case of the long-term storage. However, a helium leak detector is not installed to the concrete cask yet.A phenomenon that the temperature at the top of the canister decreases and the temperature at the bottom of the canister increases as helium gas in the canister leaks has been confirmed experimentally.We have proposed the helium leak detection method by using temperature difference between the top and the bottom of the canister.This method requires temperature information at two points of a canister top and bottom; therefore, depending on a flow channel structure for cooling air of the cask, there might be difficulties when temperature sensors are installed initially. To resolve such a problem, we newly devised an easier detection method using only the temperatures of the canister top and its ambient temperatures.

Sealing of glass with titanium by glass pressing at the softening point

Hermetic and mechanically strong glass-to-metal seals are required for many applications in technological fields such as aerospace engineering or medical engineering. While traditional glass-to-metal bonding technologies require melting of the glass, modern technologies such as anodic bonding use glass in its solid state. In this publication, a novel glass-to-metal bonding method with process temperatures around the softening point of the glass material is investigated. A glass window (silica based crown glass B270) in a titanium (grade 5) housing is manufactured by applying compressive force to the glass in a controlled low pressure argon atmosphere. Adherence of the glass-to-metal interface is determined with a universal testing machine. Hermeticity is measured directly with either pressure gain test or helium leak test. Experiments were performed in a full factorial design with 3 different process temperatures, 3 different process forces and 3 different methods for preparing the titanium surface. The results indicate that the bonding method is capable of producing hermetic seals with leak rates below 10−8 mbar l/s. Roughening of the metal surface generally improves both hermeticity and interface strength. Bonding strength can be further improved by increasing either processes temperature or, especially for rough surfaces, process force. For improving hermeticity either processes temperature or, especially for smooth surfaces, process force must be increased. The results indicate that successful bonding of glass and titanium with the new bonding method is influenced by the effects of mechanical interlocking and chemical reactions at the material interface.

Improved Method for Measuring the Permeability of Nanoporous Material and its Application to Shale Matrix with Ultra-Low Permeability.

Nanoporous materials have a wide range of applications in clean energy and environmental research. The permeability of nanoporous materials is low, which affects the fluid transport behavior inside the nanopores and thus also affects the performance of technologies based on such materials. For example, during the development of shale gas resources, the permeability of the shale matrix is normally lower than 10−3 mD and has an important influence on rock parameters. It is challenging to measure small pressure changes accurately under high pressure. Although the pressure decay method provides an effective means for the measurement of low permeability, most apparatuses and experiments have difficulty measuring permeability in high pressure conditions over 1.38 MPa. Here, we propose an improved experimental method for the measurement of low permeability. To overcome the challenge of measuring small changes in pressure at high pressure, a pressure difference sensor is used. By improving the constant temperature accuracy and reducing the helium leakage rate, we measure shale matrix permeabilities ranging from 0.05 to 2 nD at pore pressures of up to 8 MPa, with good repeatability and sample mass irrelevance. The results show that porosity, pore pressure, and moisture conditions influence the matrix permeability. The permeability of moist shale is lower than that of dry shale, since water blocks some of the nanopores.

Experimental study for manufacturing 316L/CuCrZr hollow structural component

In this study, a multi-step welding method combining explosive welding, laser welding, and Tungsten Inert Gas (TIG) welding was developed to manufacture 316L/CuCrZr hollow structural component. The welding parameters were selected according to theoretical calculations and preliminary tests, and the bonding qualities were evaluated by microstructure analyses and mechanical tests. The results demonstrated that this method was a feasible way to manufacture hollow structural components. All the joints exhibited good quality without micropores and cracks, and the tensile shear testing confirmed that the joining section was not the weakest element of the component. Under bending load, no separation, tearing or fracture was observed at the 316L/CuCrZr interface. The helium leak test results also proved that the welded specimens were sound. In addition, a hardening phenomenon near the 316L/CuCrZr interface was revealed by microhardness tests and fractography studies on tensile specimens.

Calibration of ultra-fine helium leak rates for leak testing of microelectromechanical systems

A novel method was developed to calibrate helium leak rates lower than 10−10 Pa m3/s. This method involves two essential points. One is the use of a leak artifact with known molecular conductance and known pressure at which molecular flow is realized. The other is that the upstream pressure of the leak artifact is determined by the static expansion method under a pressure in the range in which molecular flow is realized. In this study, a porous plug with a molecular conductance of 3.04 × 10−9 m3/s and a molecular flow realizing the pressure of 104 Pa was used as the leak artifact. The upstream helium pressure of the porous plug was determined from 133 to 10−5 Pa by repeated expansion up to five times, from which reference helium leak rates from 3 × 10−8 to 4 × 10−14 Pa m3/s were generated. The reliability of the helium leak rates so generated was examined using a cumulative helium leak detection method with a nonevaporated getter pump. The peak-to-peak data scatter including nonlinearity and repeatability was less than ±26%.

Cu–Cu Bonding in Ambient Environment by Ar/N2 Plasma Surface Activation and Its Characterization

Ar/N2 plasma surface activation in ambient environment for Cu–Cu bonding has been performed and characterized. Cu–Cu bonding occurs at room temperature and under normal atmospheric conditions. Postbonding annealing is performed at 300 °C and below to control the overall thermal budget. Shear strength and hermeticity property of samples with varying annealing temperature are investigated. Samples annealed at 250 °C demonstrate the highest average shear strength of 20.3 MPa and the lowest average helium leak rate of $8.7 \times 10^{-9}\,\,\text {atm}\cdot \text {cc}$ /s. Daisy chain structures are used to examine the electrical property of sample bonded at 300 °C, and the temperature cycling tests from −40 °C to 125 °C for 1000 cycles have been performed for the reliability assessment. It is observed that the dies are well-bonded and intact after 1000 cycles even though the exposed Cu surface is heavily oxidized.

Electroplating of 3D Sn-rich solder for MEMS packaging applications

Electroplating is a popular method to produce solders in microelectromechanical systems (MEMS) encapsulation and interconnection applications. In this work, a fabrication process is introduced for the generation of three-dimensional (3D) Sn solder microstructures. An aluminum membrane was employed as the conducting layer while electroplating. Based on the proposed method, Sn solders with different heights can be easily obtained after reflow. Taking advantage of these 3D structures, MEMS packaging, electrical interconnections, hermetic seals and metal-armoring can be formed simultaneously in one step. Metal-armoring provided by the solder–solder contact can be used at the extremes of the suspension travel, greatly increasing the capability of shock resistance. The helium leak rates of the packaged samples are lower than the reject limit (5 × 10−8 atm cc s−1 based on MIL-STD-883E standard). The bonding strength of samples is measured by a die shear strength tests with an average value of 7.4 MPa. In addition, the ohmic behavior of the Sn solder bonding is verified as well. These excellent results show an outstanding packaging quality in MEMS encapsulation applications.

Comparing Physical Container Closure Integrity Test Methods and Artificial Leak Methodologies.

The sterility of drug products intended for parenteral administration is a critical quality attribute (CQA) because it serves to ensure patient safety and is thus a key requirement by health authorities. While sterility testing is a probabilistic test, the assurance of sterility is a holistic concept including adequate design of manufacturing facilities, process performance, and product design. Container closure integrity testing (CCIT) is necessary to confirm the integrity of a container closure system (CCS), until the end of a product's shelf life. The new and revised United States Pharmacopeia (USP) General Chapter <1207> is a comprehensive guidance on CCI. Nevertheless, practical considerations including the choice of CCIT methods, the acceptance criteria, or the positive control samples (artificial leaks) must be addressed by the pharmaceutical manufacturer.This study is the first to provide a systematic comparison of four commonly used physical CCIT (pCCIT) methods [Helium (He) leak, vacuum decay, laser-based headspace analysis (HSA), and dye ingress] and four commonly used modes of creating artificial leaks (laser-drilled micro holes, copper wire introduced leaks, and two types of capillary leaks).The results from these experiments provide comprehensive data to allow a direct comparison of the capabilities of the individual methods. The results confirmed that the He leak detection method, which is considered the "gold-standard" for pCCIT regarding method sensitivity, indeed demonstrates the highest detection sensitivity (lowest detection limit). In comparison to the dye ingress method, HSA and vacuum decay also demonstrated better detection sensitivity in our study.Capillary leaks with orifice diameter (capillary leak with flow according to an ideal orifice) and micro holes yielded similar leak rates, whereas capillaries with nominal diameters yielded significantly lower leak rates. In conclusion, method sensitivity cannot be compared by means of a leak diameter, but requires the consideration of multiple impacting factors (e.g., path length, uniformity).LAY ABSTRACT: Sterility of drug products intended for parenteral administration is a critical quality attribute to ensure patient's safety and is thus a key requirement by health authorities. The absence of microbial contamination must be demonstrated by container closure integrity (CCI) of the container closure system (CCS). Currently, the revised United States Pharmacopeia (USP) General Chapter <1207> provides the most extensive guidance on how CCI should be assessed. Nevertheless, practical considerations on the choice of an appropriate CCIT method, artificial leaks or the choice of an acceptance criteria are lacking and must be addressed by the pharmaceutical manufacturer.This study provides a systematic comparison of four commonly used physical CCIT (pCCIT) methods [Helium (He) leak, vacuum decay, laser-based headspace analysis (HSA) and dye ingress] and four commonly used modes of creating artificial leaks (laser-drilled micro holes, copper wire introduced leaks, and two types of capillary leaks).

Balancing Container Closure Integrity and Aesthetics for a Robust Aseptic or Sterile Vial Packaging System.

Container closure integrity (CCI) is one of the requirements for a sterile packaging system. For vial-based systems, the capping process is a critical step in creating and ensuring an adequate seal with acceptable CCI. Container closure integrity tests (CCITs) such as the dye ingress and the helium leak rate are two methods among many that, in the appropriate scenario, help to challenge this required attribute. The use of locked-in stopper compression (compression under the crimp seal post capping) enables correlation of these methods to CCI and seal quality. In fact, the overall acceptability of a seal can be evaluated using quantitative and qualitative methods. Usually lost in these assessments is the existence of seal cosmetics as an essential additional seal quality attribute. Unacceptable cosmetic quality can have a major impact on manufacturing (reduced batch output, high yield cost, etc.) and user (perceived low quality, brand image, potential injury, etc.) experiences. Interestingly, the aesthetics of a seal is also impacted by the capping process which is quite complicated because the acceptance criteria for aesthetics of a seal is subjective. Ultimately, this affects commercial manufacturing efficiency and CCI. Here, we present a simple methodology for package selection and evaluated multiple package configurations using locked-in stopper compression (through residual seal force, RSF) measurements and seal aesthetics analyses (using a semi-quantitative aesthetics scale). The integrity of the seals was analyzed using multiple CCIT methods. We determined that component dimensions such as the seal length play a major role in obtaining proper seal aesthetics and integrity. This can ultimately enable the selection of robust packaging components that provide an adequate range of manufacturing conditions without cosmetic defects. A failure to do this could result in high rejects during drug product visual inspection culminating in low batch yield, high costs or could pose harm to patients if suitable CCI is not achieved.LAY ABSTRACT: One common container closure system for parenteral drug products includes a glass vial, rubber stopper, and aluminum crimp seal. The capping process, in which the elastomeric closure is compressed against the vial by means of an aluminum crimp seal, is key to ensuring an optimal seal from both an aesthetic and CCI perspective. Ensuring a robust capping process must include a deep and necessary understanding of the interconnection between the selected components, desired aesthetics of the seal, stopper compression, residual seal force, and CCI; the way in which the capper is configured (sealing parameters) will play a part in addition to the "style" used in manufacturing. Previous published studies have focused on capping process controls to only ensure CCI. Here, we present a useful methodology for selecting appropriate components and capping process parameters using a scaled-down approach to achieve elegant seal quality and CCI simultaneously. Dimensional analysis and capping design of experiments (DOEs) were conducted on lab-scale equipment that was representative of commercial configurations. The seals made from these studies were analyzed using residual seal force, helium leak, and dye ingress methods. The results and their implications were discussed with regard to the operating principle of the rail-type capping machine.

Development of head positioning control system of HDDs to compensate for fluid-induced vibration considering helium leakage

Development of head positioning control system of HDDs to compensate for fluid-induced vibration considering helium leakage

Micro-fabrication and hermeticity measurement of alkali-atom vapor cells based on anodic bonding

A vapor cell provides a well-controlled and stable inner atmosphere for atomic sensors, such as atomic gyroscopes, atomic magnetometers, and atomic clocks, and its hermeticity affects the stability and aging of atomic sensors. We present the micro-fabrication of a micro-electromechanical system wafer-level hermit vapor cell based on deep reactive ion etching and vacuum anodic-bonding technology. The anodic-bonding process with the voltage increasing in steps of 200 V had a critical influence on vapor cell hermeticity. Further, the silicon–glass bonding surface was experimentally investigated by a scanning electron microscope, which illustrated that there were no visual cracks and defects in the bonding surface. The leak rate was measured using a helium leak detector. The result shows that the vapor cells with different optical cavity lengths comply with the MIL-STD-883E standard (5 × 10−8 mbar·L/s). Moreover, D2 absorption spectroscopy was characterized via optical absorption. The bonding strength was determined to be 13 MPa, which further verified the quality of the vapor cells.