A Novel Test Strategy for Fine Pitch Wafer-Level Packaged Devices

This paper describes an innovative test strategy comprising a compliant elastomer mesh for testing fine pitch wafer-level package (WLP) devices. The test probe, hardware, and sample preparation processes are detailed. The components of the test hardware socket such as the SMA connectors, coplanar transmission lines on the PCB, via, off-chip interconnect, and elastomer mesh probe have been modeled. A complete system-level model, with off-chip interconnects on the WLP device pads, has been developed. The measurement and model demonstrate that the prototype test socket performs at 5 GHz with an insertion loss of about 3 dB. WLP device with Bed-of-Nail interconnects are characterized. Functional test features of the system are also addressed.     

Analysis and control of a buck DC-DC converter operating with constant power load in sea and undersea vehicles

Power-electronics-based zonal direct current (dc) power distribution systems are being considered for sea and undersea vehicles. The stability of the dc power-electronics-based power distribution systems is a significant design consideration because of the potential for negative-impedance-induced instabilities. In this paper, the dynamic properties and control of a buck converter feeding a downstream dc-dc converter are studied. The controller in this system combines an instantaneous current feedback loop using hysteresis with a proportional-integral (PI) algorithm to regulate the output voltage of the converter. Based on a large-signal-averaged model of the converter, the stability-in-large around the operation point is presented. The complete analysis is carried out considering a buck dc-dc converter operating with a constant power load (CPL). Simulations and experimental results are provided to verify the analysis.     

Studies on polyurethane potting compound based on HDI-TMP adduct for fabrication of haemodialyzer

Polyurethane potting compounds based on hexamethylene diisocyanate-trimethylol propane (HDI-TMP) adduct (Component A) and polypropylene glycol, polyethylene glycol and castor oil (Component B) were prepared as potential compounds for the fabrication of haemodialyzer. The setting characteristics of the potting compounds having isocyanate index 2.0 are better than those compounds having 1.35. The aging stability of PEG and PPG based potting compounds are poorer than those of castor oil based potting compounds. Appreciable hydrolytic, oxidative and chemical stability could be observed with castor oil based potting compounds of HDI-TMP adduct.     

Nanomaterial-based ionic polymer metal composite insect scale flapping wing actuators

Small size actuators (8 mm × 1 mm), IPMNC (RuO₂/Nafion) and IPMNC (LbL/CNC) are studied for flapping at the frequency of insects and compared to Platinum IPMC-Pt. Flapping wing actuators based on IPMNC (RuO₂/Nafion) are modeled with the size of three dragonfly species. To achieve maximum actuation performance with Sympetrum Frequens scale actuator with optimized Young's modulus, the effect of variation of thickness of electrode and Nafion region of Sympetrum Frequens scale actuator is studied. A trade-off in the electrode thickness and Young's modulus for dragonfly size IPMNC-RuO₂/Nafion actuator is essential to achieve the desirable flapping performance.     

Modelling and analysis of selective assembly using Taguchi's loss function

An assembly is the integrative process of joining components to make a completed product. It brings together the upstream process of design, engineering and manufacturing processes. The functional performance of an assembled product and its manufacturing cost are directly affected by the individual component tolerances. But, the selective assembly method can achieve tight assembly tolerance through the components manufactured with wider tolerances. The components are segregated by the selective groups (bins) and mated according to a purposeful strategy rather than being at random, so that small clearances are obtained at the assembly level at lower manufacturing cost. In this paper, the effect of mean shift in the manufacturing of the mating components and the selection of number of groups for selective assembly are analysed. A new model is proposed based on their effect to obtain the minimum assembly clearance within the specification range. However, according to Taguchi's concept, manufacturing a product within the specification may not be sufficient. Rather, it must be manufactured to the target dimension. The concept of Taguchi's loss function is applied into the selective assembly method to evaluate the deviation from the mean. Subsequently, a genetic algorithm is used to obtain the best combination of selective groups with minimum clearance and least loss value within the clearance specification. The effect of the ratio between the mating part quality characteristic's dimensional distributions is also analysed in this paper.     

Studies on inherently radiopaque acrylate copolymers for biomedical applications

Poly(glycidyl methacrylate-co-ethyl methacrylate) and poly(glycidyl methacrylate-co-butyl methacrylate) random copolymers (with 50–50 mol % of monomers) were made radiopaque by grafting iodine moieties through the ring opening reaction of the epoxy groups. The percentage weight of grafted iodine in the copolymers was found to be as high as 19%. The iodinated copolymers showed higher glass transition temperature and thermal stability in comparison with the parent copolymers. Iodinated copolymer of poly(glycidyl methacrylate-co-ethyl methacrylate) has improved glass transistion temperature than iodinated poly(glycidyl methacrylate-co-butyl methacrylate). Radiographic analysis of these iodinated copolymers showed excellent radiopacity. The in vitro cytotoxicity tests revealed cytocompatibility with cells. These radiopaque copolymers are expected to find application as dental and orthopedic cements. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Synthesis and characterization of biodegradable poly (ethylene glycol) and poly (caprolactone diol) end capped poly (propylene fumarate) cross linked amphiphilic hydrogel as tissue engineering scaffold material

Biodegradable poly (caprolactone diol-co-propylene fumarate-co-ethylene glycol) amphiphilic polymer with poly (ethylene glycol) and poly (caprolactone diol) chain ends (PCL-PPF-PEG) was prepared. PCL-PPF-PEG undergoes fast setting with acrylamide (aqueous solution) by free radical polymerization and produces a crosslinked hydrogel. The cross linked and freeze-dried amphiphilic material has porous and interconnected network. It undergoes higher degree of swelling and water absorption to form hydrogel with hydrophilic and hydrophobic domains at the surface and appreciable tensile strength. The present hydrogel is compatible with L929 fibroblast cells. PCL-PPF-PEG/acrylamide hydrogel is a candidate scaffold material for tissue engineering applications.     

Effect of process parameters of pulsed current tungsten inert gas welding on weld pool geometry of titanium welds

The effects of pulsing current parameters on weld pool geometry namely front height, back height, front width and back width of pulse current gas tungsten arc welded (GTAW) titanium alloy was analysed. Four factors, five levels, central composite design were used to develop empirical relationships, incorporating pulsed current parameters and weld pool geometry.     

表面活性剂对镁合金基体上的非铬化镀镍涂层的腐蚀特性的作用

在镁合金AZ91D化学沉积了镍涂层,研究了非铬化预处理及表面活性物质对涂层腐蚀特性的影响。通过盐水试验(1mol/L HCl)和电化学极化试验(3.5%NaCl)检测了腐蚀性能。试验表明:化镀镍溶液中添加的表面活性剂可提高镁合金镍涂层上的抗腐蚀能力。此外,表面平整均匀的纳米和非晶相涂层提高了其抗腐蚀能力。极化试验表明,其腐蚀电位向正方转移,且腐蚀电流密度减低。浸泡试验和电化学极化试验都表明阳离子表面活化剂具有更好的提高抗腐蚀性能的作用。     

A scaling technique for partial element equivalent circuit analysis using SPICE

A scaling technique for partial element equivalent circuit (PEEC) analysis using SPICE is introduced in this letter. The perturbation series based scaling is applied to the component values extracted by the standard PEEC method to get up to an order of magnitude improvement in relative accuracy of scattering parameters with SPICE simulation. The effectiveness of the technique is verified by using the numerical example of a stripline structure and comparing the results with that of the method of moments (IE3D).