Critical issues of wafer level chip scale package (WLCSP) withemphasis on cost analysis and solder joint reliability

Some of the critical issues of wafer level chip scale package (WLCSP) are mentioned and discussed in this investigation. Emphasis is placed on the cost analysis of WLCSP through the, important parameters such as wafer-level redistribution, wafer-bumping, and wafer-level underfilling. Useful and simple equations in terms of these parameters are also provided. Furthermore, the effects of microvia build-up layer on the solder joint reliability of WLCSP on printed circuit board (PCB) through the creep responses such as the deformation, hysteresis loops, and stress and strain are presented. Only solder-bumped with pad-redistribution WLCSPs are considered in this study     

Structural and Rheological Properties of Aerated High Sugar Systems Containing Egg Albumen

ABSTRACT: Structural and rheological properties have been investigated for an aerated system containing a high content of invert sugar and 2 to 10 wt% egg albumen. The specific gravity and the overrun were found to be influenced by the protein concentration and the whipping time. The systems exhibited rheopexy and shear-thinning at high shear rate, with flow data fitted to a power-law model. At small deformations, viscous character was found to dominate over elastic character over the frequency range 10⁻² to 10 Hz. Images taken from confocal microscopy indicated that mean bubble size and concentration varied systematically with protein concentration and whipping time, and that more protein accumulated on the bubble surfaces as whipping proceeded. The study of this model system illustrates how the texture of a high sugar content aerated food depends on protein content and whipping conditions.     

Abnormal gastro-oesophageal reflux in Chinese with atypical chest pain

Although atypical chest pain has been well described in the Western population, its frequency in Chinese is unknown. Over a period of 42 months, we studied 521 Chinese patients with chest pain and identified 108 patients (20.7%) whose pain was not related to cardiac causes, as determined by exercise ECG or cardiac catheterization. Using 24 h ambulatory pH monitoring and baseline oesophageal manometry, 28.7, 19.4 and 5.6% of these patients were found to have abnormal reflux parameters, abnormal manometric findings or both, respectively. There were significantly more patients complaining of chest pain during the study in the gastro-oesophageal reflux disease (GERD) group than in the non-GERD group (16/31 vs 20/77; P < 0.001). The lower oesophageal sphincter pressure was lower in those with abnormal reflex parameters than in those with normal reflux parameters (12.7 +/- 5.4 vs 17.8 +/- 5.8 mmHg; P < 0.05). There was no significant difference in symptoms, such as heartburn (54.8 vs 42.9%), regurgitation (38.7 vs 35.1%) and dysphagia (19.4 vs 24.7%), among the two groups. Non-specific changes were the most frequent baseline motility pattern. In conclusion, atypical chest pain and gastro-oesophageal reflux disease are not uncommon in Chinese and this deserves special emphasis as the continuation of anti-anginal drugs may aggravate their condition.     

Deposition of carbon nitride films by filtered cathodic vacuum arc combined with radio frequency ion beam source

Atomically smooth carbon nitride films were deposited by an off-plane double bend filtered cathodic vacuum arc (FCVA) technique. A radio frequency nitrogen ion source was used to supply active nitrogen species during the deposition of carbon nitride films. The films were characterized by atomic force microscopy (AFM), XPS and Raman spectroscopy. The internal stress was measured by the substrate bending method. The influence of nitrogen ion energy (0–1000 eV) on the composition, structure and properties of the carbon nitride films was studied. The nitrogen ion source greatly improves the incorporation of nitrogen in the films. The ratio of N/C atoms in the films increases to 0.40 with an increase in the ion beam energy to 100 eV. Further increase in the ion beam energy leads to a slight decrease in the N/C ratio. XPS results show that nitrogen atoms in the films are chemically bonded to carbon atoms as C---N, C=N, and CN bonds, but most of nitrogen atoms are bonded to sp² carbon. The increase in nitrogen ion energy leads to a decrease in the content of nitrogen atoms bonded to sp² carbon, and an increase in the content of nitrogen atoms bonded to sp³ and sp¹ carbon. Raman spectra indicate an increase in the sp² carbon phase in carbon nitride films with an increase in nitrogen ion energy. The increase in sp² carbon fraction is attributed to the decrease in internal stress with increasing nitrogen ion energy.     

Synthesis of novel tri- and tetrasubstituted C<Subscript>18</Subscript> furan fatty esters

A methylene-interrupted C₁₈ keto-acetylenic fatty ester (methyl 12-oxo-9-octadecynoate) was obtained from methyl ricinoleate by bromination-dehydrobromination followed by oxidation. Reaction of methyl 12-oxo-9-octadecynoate with bis(benzonitrile) palladium(II) chloride, allyl bromide, or methyl-allyl bromide furnished methyl 8-[5-hexyl-3-allyl-furan-2-yl]-octanoate (1, 56%) or methyl 8-[5-hexyl-3-(2-methyl-allyl)-furan-2-yl]-octanoate (2, 55%). Reaction of methyl 12-oxo-11-chloro-or 11-fluoro-9-octadeyynoate (prepared from methyl santalbate-methyl 11-E-9-octadecynoate, found in sandalwood, Santalum album, seed oil) with bis(benzonitrile) palladium(II) chloride gave methyl 8-(4-fluoro-5-hexyl-furan-2-yl)-octanoate (3, 50%) or methyl 8-(4-fluoro-5-hexyl-furan-2-yl)-octanoate (4, 50%), respectively. And when methyl 12-oxo-11-chloro- or 11-fluoro-9-octadecynoate was treated with a mixture of bis(benzonitrile) palladium(II) chloride, allyl bromide, or methyl-allyl bromide, the reaction yielded tetrasubstituted C₁₈ furan derivatives, viz, methyl 8-(3-allyl-4-chloro-5-hexyl-furan-2-yl)-octanoate (5, 54%), methyl 8-[4-chloro-5-hexyl-3-(2-methyl-allyl)-furan-2-yl)-octanoate (6, 54%), methyl 8-(3-allyl-4-fluoro-5-hexyl-furan-2-yl]-octanoate (7, 10%), and methyl 8-[4-fluoro-5-hexyl-3-(2-methyl-allyl)-furan-2-yl]-octanoate (8, 10%). The presence of a fluorine atom in the furan derivatives 4, 7, and 8 was readily characterized by the appearance of doublets for carbon nuclei, which were coupled to the fluorine atom in the ¹³C NMR spectra. All furan fatty derivatives from this work were characterized by NMR spectroscopic and mass spectrometric analyses. The yields of compounds 7 and 8 were very low (10%) despite attempts to improve the procedure by increasing the amounts of the reactants and catalyst.     

Nutritional constituents and antioxidant properties of indigenous kembayau (Dacryodes rostrata (Blume) H. J. Lam) fruits

The nutritional and antioxidant properties of peels, pulp and seeds of kembayau (Dacryodes rostrata) fruits were evaluated. Kembayau seeds and pulp were rich in fat, while peels had the highest ash contents. Potassium was the most prevalent mineral in peels (380.72-1112.00 mg/100 g). In kembayau fruits, total flavonoid content (1012.74-28,022.28 mg rutin equivalent/100 g) was higher than total phenolic and total monomeric anthocyanin contents. Kembayau seeds exhibited high flavonoid and phenolic contents compared to the contents in peels and pulp. Antioxidant capacities were also higher in seeds as typified by trolox equivalent antioxidant capacity assay (51.39-74.59 mmol TE/100 g), ferric reducing antioxidant power assay (530.05-556.98 mmol Fe²⁺/100 g) and by 1,1-diphenyl-2-picryl hydrazyl radical scavenging activity (92.18-92.19%) when compared to peels and pulp. Pulp and peels of kembayau fruit may be an important source of energy and minerals for human consumption, while seeds have a good potential as antioxidants.     

Application of Matrix Solid-Phase Dispersion and Liquid Chromatography–Ion Trap Mass Spectrometry for the Analysis of Pesticide Residues in Fruits

This study presents an application of rapid and sensitive multiresidue method for the analysis of acephate, acetamipride, atrazine, carbendazim, carbaryl, carbofuran, dimethoate, imidacloprid, linuron, malathion, monocrotophos, monuron, propazine, simazine, and tebufenozide in fruits. The method involves an extraction procedure based on matrix solid-phase dispersion using diatomaceous earth as a dispersant and dichloromethane as the eluent. The target pesticides were determined using liquid chromatography–ion trap mass spectrometry. Quantification of the analytes was carried out using the most sensitive ion transition. Ion trap parameters, like activation q and time, were found to have a prominent influence on method sensitivity for some pesticides and they were optimized accordingly. The confirmation of residues detected in real samples was performed by repeated injection and acquiring additional ion transitions besides the ones used for quantification. The method was validated for accuracy, linearity, reproducibility, and sensitivity. Mean values for recoveries were in the range of 70–120 % for all tested matrices. Repeatability of the method, expressed as the relative standard deviation, was in general lower than 20 %. The applicability of the method to routine analysis was tested in real fruit samples with good performance.     

Study of Low-Temperature Thermocompression Bonding in Ag-In Solder for Packaging Applications

Low-temperature solders have wide applications in integrated circuits and micro-electromechanical systems packaging. In this article, a study on Ag-In solder for chip-to-chip thermocompression bonding was carried out. The resulting joint consists of AgIn₂ and Ag₉In₄ phases, with the latter phase having a melting temperature higher than 400°C. Complete consumption of In solder into a Ag-rich intermetallic compound is achieved by applying a bond pressure of 1.4 MPa at 180°C for 40 min. We also observe that the bonding pressure effect enables a Ag-rich phase to be formed within a shorter bonding duration (10 min) at a higher pressure of 1.6 MPa. Finally, prolonged aging leads to the formation of the final phase of Ag₉In₄ in the bonded joints.     

Polyester composite based on betelnut fibre for tribological applications

A polyester composite based on betelnut fibres was fabricated and its adhesive wear and frictional performance studied using a block on disk machine at different applied loads and sliding distances at 2.8 m/s sliding velocity under dry/wet contact conditions. SEM was used to study worn surface morphology. The results revealed that betelnut fibre reinforced polyester (BFRP) composite had better wear and frictional performance under wet contact condition compared to dry. The wear mechanism of the BFRP composite was predominated by micro and macro-cracks in the polyester regions and debonding of fibres.