Mechanical Shock Testing Research Articles

Integrated design of a compact magneto-optical trap for space applications

In this Letter, we describe an optical assembly that is designed for the engineering application of the atomic laser cooling techniques. Using a folded optical path scheme, we have built a miniaturized, compact magneto-optical trap (CMOT) for an Rb87 atomic fountain clock. Compared with the conventional magneto-optical traps used in other clocks, our system is more robust, more compact, more stable, and saves about 60% laser power. This optical setup has operated for about a year in our fountain system, passed the thermal cycle tests and the mechanical vibration and shock tests, and maintained a high performance without a need for realignment.

Evaluation of silicon tuning fork resonators under mechanical loads and space-relevant radiation conditions

This work reports on mechanical tests and irradiations made on silicon bulk-acoustic wave resonators. The resonators were based on a tuning fork geometry and actuated by a piezoelectric aluminum nitride layer. They had a resonance frequency of 150 kHz and a quality factor of about 20,000 under vacuum. The susceptibility of the devices to radiation-induced degradation was investigated using Co60γ-rays and 50 MeV protons with space-relevant doses of up to 170 krad. The performance of the devices after irradiation indicated a high tolerance to both ionizing damage and displacement damage effects. In addition, the device characteristics were evaluated after mechanical shock and vibration tests and only small effects on the devices were observed. In all experiments, no significant changes of the resonance characteristics were observed within the experimental uncertainty, which was below 100 ppm for the resonance frequency. The results support the efforts toward design and fabrication of highly reliable MEMS devices for space applications.

Varactor-Tuned Narrow-Band High Temperature Superconducting Notch Filter

A tunable narrow band high temperature superconducting (HTS) notch filter is presented. HTS folded square open loop resonator loaded with hyper-abrupt GaAs varactor is used to reach high tunability and avoid the via-hole grounding. Measured results show that the notch frequency can be tuned from 286 to 485 MHz (tuning range of 51.6%), and the attenuation from 26 to 70 dB when the bias voltage of the varactors is from 1 to 20 V. The -3 dB bandwidth is between 6.9 and 7.9 MHz, and the out-of-band insertion loss is less than 0.2 dB. Furthermore, the reliability of manufacture techniques of the filter is proved by mechanical vibration and shock tests.

Development, qualification, and performance validation of an optical differential pressure sensor for downhole permanent monitoring applications

This paper describes the development, qualification, and performance validation of an optical differential pressure (DP) sensor for the high-pressure and high-temperature downhole environment. The current implementation of measuring DP in downhole applications is based on the calculated difference between two static pressure sensor measurements with high uncertainties. A true DP sensor is superior in comparison due to the decreased uncertainty both in measurement and component levels. This translates to better performance in system level measurements such as flow. A development program was launched in 2007 to build an optical DP sensor targeted for two main applications: standalone use in single-phase or auxiliary use in multiphase flow measurement systems. Several prototypes have gone through multiple design phases and qualification test programs including mechanical shock and vibration tests, thermal tests, hot vibration tests, short-term stability and long-term endurance tests. The sensor was then integrated with a Venturi and tested in a single-phase flow loop to validate its performance against an electronic DP sensor and an electromagnetic flowmeter. Results suggest that optical DP sensor performs better than the electronic DP sensor in measuring differential pressures, and is on a par with the electromagnetic flowmeter.

Micro-integrated extended cavity diode lasers for precision potassium spectroscopy in space

We present a micro-integrated, extended cavity diode laser module for space-based experiments on potassium Bose-Einstein condensates and atom interferometry. The module emits at the wavelength of the potassium D2-line at 766.7 nm and provides 27.5 GHz of continuous tunability. It features sub-100 kHz short term (100 μs) emission linewidth. To qualify the extended cavity diode laser module for quantum optics experiments in space, vibration tests (8.1 g(RMS) and 21.4 g(RMS)) and mechanical shock tests (1500 g) were carried out. No degradation of the electro-optical performance was observed.

The Mechanical Reliability of a Commercial MEMS Microphone

This paper describes our recent work on the mechanical reliability of a commercial MEMS microphone by performing three mechanical tests, i.e. a constant acceleration test, a mechanical shock test, and a random vibration test, according to the standard of Mil-Std-883. We find that, the studied MEMS part of the microphone can survive a stress limit above 20000g. Two failure modes, i.e. the breaking of diaphragm and the backplate and the delamination of the electrode from the backplate are revealed in the three tests.

Mechanical Shock Ability of Different Potting Materials and Packaging Processes for Electronic Components

In the paper, the mechanical shock abilities of the three potting materials of hard material, silicone and paraffin wax for the ceramic packaging capacitors and metal packaging capacitors are investigated by mechanical shock tests. Results show that the mechanical shock resistance ability of the hard epoxy resin potting material is the strongest, and the mechanical shock resistance ability of the metal packaging component is more than the ceramic packaging. The mechanical shock resistance value of the epoxy resin potting material for metal packaging capacitors is in 20000g above.

Assembly reliability assessment and life estimation for a stacked area array device

Memory module manufacturers face an ongoing challenge to incorporate more functionality and superior performance with each new generation of product offering. The growth in demand for memory capacity is surpassing the pace at which memory component manufacturers are able to cost-effectively produce the next-generation of monolithic memory devices. Stacking components helps in the transition to higher-density memory while the design and production capability for the next-generation of memory devices is being developed. However, on the other hand, the complex nature of stacked Chip Scale Package (CSP) components mandates a thorough review of the assembly processes and a detailed reliability assessment for these packages. The research objective was to study the assembly reliability of stacked CSP components assembled on a densely populated lead-free memory module utilizing mirror imaged component placements. The assessment was carried out using thermal cycling and mechanical shock tests. The data collected from thermal cycling was also used for failure modeling and life estimation. The methodology for estimating field life was established and the field life was estimated for a server application. The results proved that stacked CSP components can be reliably assembled. The module using stacked CSP components surpassed the life expectancy for server applications, which is 10 years.

Improving Copper Electrodeposition in the Microelectronics Industry

Sporadic voiding within the interfacial Cu3Sn intermetallic compound (IMC) layer-sometimes referred to as ?Kirkendall voiding?-has been found to lead to degradation of solder joint reliability in board level, mechanical shock testing. It has been suggested that the voiding phenomenon is a result of the incorporation of organic impurities in the copper (Cu) deposit during electroplating. In the present study, Cu samples were electroplated galvanostatically from a generic solution, containing Cl- ions, as well as a suppressor [polyethylene glycol (PEG)], and a brightener (bis(3-sulfopropyl) disulfide, SPS) as additives. Overpotential transients were measured during electroplating with a range of current densities (0.5-40 mA cm-2) in baths with various compositions. Effects of the bath chemistry on the Cu surface morphology, as well as on the propensity for voiding after soldering, were also investigated. Elemental analysis of selected samples was performed by SIMS. Plating at 10-20 mA·cm-2 with an optimized bath composition led to Cu with a fine-grain structure and smooth appearance. Solder joints formed from these deposits remained void free after soldering and thermal aging. Lower current densities, ran in the same plating bath, led to a significant propensity for voiding, apparently because of incorporation of, principally, SPS and its breakdown products into the growing layer. Continuous plating at 10 mA cm-2 for up to 18 hours without replenishment revealed a strong dependence on bath aging, with Cu changing from ?void-proof? to clearly ?void-prone.? These trends were attributed to the different rates of consumption for PEG and SPS and changes in the contaminants being incorporated in the deposits. In general, differences in the voiding behavior of the plated Cu could be predicted by monitoring a set of characteristic overpotential transient signatures.

Effect of Mechanical and Chemical Wear on Consistency of Conditioning in Diamonds

AbstractWe evaluated the effects of the edge degradation of diamonds in terms of their cutting ability from the viewpoint of mechanical, chemical and chemical-mechanical wear in chemical-mechanical polishing (CMP) systems for high-volume manufacturing. The results showed that both micro-chipping on the cutting edges of diamonds caused by a mechanical shock test and the rounding off of the sharp edges of diamonds in a marathon wear test degraded the pad cut rate, while no adverse effects on the cutting ability were observed during an acidic slurry immersion test. We also examined in situ coefficient of friction (COF) monitoring for use in identifying the tribology of the pad conditioning. Furthermore, we demonstrated the usefulness of measuring the height ratio of the asperity called “top surface area (TSA) ratio” as an appropriate topographical parameter to study the dependence of COF during conditioning on the decay of the tungsten removal rate. We presented a clear correlation between the pad cut rate degradation and the TSA ratio after CMP in order to elucidate an increase in the conditioning COF related to truncation of the asperity tip by wear and plastic deformation.

Second- and Third-Level BGA Solder Joint Reliability of High-End Flip Chip System in Package (FCSiP)

The major concerns posed by system-in-package (SiP) designs for network applications are the interconnection reliability between the memory plastic ball grid array (PBGA) package and the SiP module, which we refer to as 2nd-level interconnection, and between the SiP module and the system board, which we refer to as 3rd-level interconnection, induced by thermomechanical stress to the large SiP module, i.e., 55 × 55 mm2 package body size. In this paper, finite element analysis (FEA) and design of experiment (DOE) case studies were used to evaluate the 2803-pin flip chip SiP (FCSiP) and to determine the best construction of the SiP module and optimize the assembly material set. Heat spreader (lid) thickness, heat spreader material, and under-fill implementation were considered in the stress and fatigue lifetime FEA case studies and long-term solder joint reliability, which was accelerated thermal cycle (ATC) tested at operating temperatures from 0 to 100°C. Another important factor in the system-level reliability is an external heat sink, and its compressive force effect was also investigated in the ATC test. In addition, short-term mechanical reliability tests, such as the 4-point monotonic bend test based on the IPC-9702 specification and mechanical shock test based on the JESD22-B110A standard, were also evaluated for the 2803-pin FCSiP qualification. Finally, the results of these experiments were compared with the FEA data in a correlation process.

Effects of Glue on the Bend Performance of Flip Chip Packages

To combat reliability margin loss in ball grid array (BGA) packages specifically in mechanical shock and vibration testing, companies are exploring the possibility of using glue and complete underfill to mitigate risk to second-level interconnects (SLI). Though glue has been demonstrated to have a positive influence on SLI reliability margin, it can have adverse affects on the rest of the package such as substrate or first-level interconnects (FLI). This paper explains details on how glue modulates the overall reliability of the package. Finite-element modeling (FEM) along with low strain rate bend tests was done to prove the effect of glue on solder joint reliability. Further, shock testing was done to demonstrate how the glue modulates the shock performance. The improvement in SLI reliability was highly dependent on the choice of glue.

Investigation of mechanical shock testing of lead-free SAC solder joints in fine pitch BGA package

The lead-free Sn–Ag–Cu (SAC 305/405) solder that replaced the tin–lead eutectic solder tends to be more brittle in nature due to high stiffness and excessive solder interfacial reactions. This leads to higher occurrences of solder joints failure during surface mount assembly and handling operations as a result of PCB bending, shock impact and drop. In this work, mechanical tests simulating the shock impact were conducted on lead-free SAC of different weight percentages. These SAC materials were prepared for use in the solder joints of fine pitch ball grid array (BGA) components which were mounted onto the motherboard. After the mechanical shock tests, strain measurements were performed on the BGA components to gauge the solder joint integrity, which was shown to be related with the formation of intermetallics in the bulk and at the interface of the SAC solder. The ball pull tests were conducted to determine both the bulk and interfacial strength and the solder joint fracture, which was classified as either mode 1, 2 or 3. A correlation was made between the silver (Ag) and copper (Cu) weight percentages with the metallurgical reactions.

Stress–Strain Characteristics of Tin-Based Solder Alloys for Drop-Impact Modeling

The stress–strain properties of eutectic Sn-Pb and lead-free solders at strain rates between 0.1 s−1 and 300 s−1 are required to support finite-element modeling of the solder joints during board-level mechanical shock and product-level drop-impact testing. However, there is very limited data in this range because this is beyond the limit of conventional mechanical testing and below the limit of the split Hopkinson pressure bar test method. In this paper, a specialized drop-weight test was developed and, together with a conventional mechanical tester, the true stress–strain properties of four solder alloys (63Sn-37Pb, Sn-1.0Ag-0.1Cu, Sn-3.5Ag, and Sn-3.0Ag-0.5Cu) were generated for strain rates in the range from 0.005 s−1 to 300 s−1. The sensitivity of the solders was found to be independent of strain level but to increase with increased strain rate. The Sn-3.5Ag and the Sn-3.0Ag-0.5Cu solders exhibited not only higher flow stress at relatively low strain rate but, compared to Sn-37Pb, both also exhibited higher rate sensitivity that contributes to the weakness of these two lead-free solder joints when subjected to drop impact loading.

Anisotropic Conductive Adhesives for Flip-Chip Interconnects

Anisotropic conductive adhesive films consist of an epoxy adhesive with dispersed conductive particles. They are used as electrical–mechanical interconnecting materials for flip-chip to flexible substrates and flip-chip to glass substrates. Contact resistance and adhesion strength are two important features of anisotropic conductive adhesive film joints. Contact resistance is affected by the curing degree of the adhesive, the bump characteristics, the reflow process and the environmental application conditions. Adhesion strength is affected by bonding temperature, bonding pressure, bubbles in the joints and particle characteristics. To assess reliability, anisotropic conductive adhesive film joints were tested under thermal cycling tests, autoclave tests and mechanical shock tests.

Thermo-mechanical properties of ceramics: Resistance to initiation and propagation of crack in high temperature

Dense silicon nitride is investigated to determine the effect of its microstructural parameters and densification on thermo-mechanical properties as well as its thermal stress resistance to fracture initiation during a hot or cold mechanical and thermal shock testing. The different materials and microstructures are obtained by changing the parameters such as the type of the powder, additive, forming process and sintering condition. The maximum crack growth and thermal shock resistance of dense Si3N4 is achieved for the materials with higher toughness having a thick elongated grain with high aspect ratio dispersed in matrice of relatively coarse and equiaxed grains and higher grain phase boundary (glassy phase) by mechanism of pull-out and recovery of crack.

Proposal for a new technique to join CFC composites to copper

The divertor design of the ITER fusion machine comprises the joint between CFC composites and the copper alloy heat sink. The main problem of the CFC–Cu joint manufacturing is the large thermal expansion mismatch of the components and the very high contact angle of molten copper on carbon substrates. The aim of this work is to develop a new technique to join CFC composite to pure copper. In order to increase the wettability of CFC by molten copper, the composite surface was modified by direct reaction with group VI transition metals which form a carbide layer and allow a large reduction of the contact angle. A morphological analysis and the mechanical and thermal shock tests were performed to characterize the CFC–Cu joined samples.

D-band rectangular-waveguide-output uni-travelling-carrier photodiode module

A uni-travelling-carrier photodiode module with a WR-6 waveguide output port for operation in the D-band has been developed. The bandwidth with the output power above -10 dBm ranged from 104 to 185 GHz. The module stability was also confirmed under an optical input stress test, a temperature cycle test, and mechanical vibration and shock tests.

Behaviour of cordierite materials under mechanical and thermal biaxial stress

AbstractA commercial cordierite powder (< 0.17 wt-% impurities) was selected for a study of material behaviour under mechanical and thermal stresses. Disks were slip cast, sintered for 2 h at 1450°C, and indented (Vickers, 44.1 N) at the centre of the surface to be subjected to mechanical and thermal shock tests. The sintered bodies (84 wt-% cordierite, 10 wt-% mullite, 6 wt-% glass) reached 95% of theoretical density. The microstructure consisted of homogeneous, mainly equiaxed grains (mean size ≈0.5 μm) and a few elongated grains (aspect ratio ≈1.9). A glass phase was identified at triple points, and intergranular pores (< 10 μm) and a few isolated larger pores (up to 40 μm) were observed. The fracture strength σF was measured by biaxial flexure, employing a ball on discontinuous ring configuration with displacement con1 trol (0.05 mm min -1). In each thermal shock test, the indented specimen was heated to a selected temperature and the disk centre was then suddenly cooled using a high velocity air jet ...

Underfilling fine pitch BGAs

Fine pitch BGAs and chip scale packages have been developed as an alternative to direct flip chip attachment for high-density electronics. The larger solder sphere diameter and higher standoff of CSPs and fine pitch BGAs improve thermal cycle reliability while the larger pitch relaxes wiring congestion on the printed wiring board. Fine pitch BGAs and CSPs also allow rework to replace defective devices. Thermal cycle reliability has been shown to meet many consumer application requirements. However, fine pitch BGAs and CSPs have difficulty passing mechanical shock and substrate flexing tests for portable electronics applications. The fine pitch BGA used in the study was a 10 mm package with the die wire bonded. The package substrate was bismaleimide-triazine (BT) and the solder sphere diameter was 0.56 mm. Two types of underfill were examined. The first was a fast flow, snap cure underfill. This material rapidly flows under the package and can be cured in five minutes at 165/spl deg/C using an in-line convection oven. The second underfill was a thermally reworkable underfill for those applications requiring device removal and replacement. The paper discusses the assembly and rework process. In addition, liquid-to-liquid thermal shock data is presented along with mechanical shock and flexing test results.