Coplanarity analysis and validation of PBGA and T-BGA packages

Plastic BGA (PBGA) has recently been extensively used in microelectronics package. However, its heat-dissipating capacity is limited to below 2 or 3 W, and thus fails to satisfy the requirement of high heat dissipation and improved electrical performance. This work offers a finite element analytic methodology to predict the coplanarity of T²-BGA (Turbo thermal ball grid array) and PBGA, using ANSYS software. T²-BGA involves inserting a heat slug into the molding compound of a PBGA. The material of the heat slug can be either aluminum or copper. Surface mount technology (SMT) of BGA is limited mainly by the coplanarity due to coefficient of thermal expansion mismatch, since the structure of BGA is asymmetric. The coplanarity is limited below 0.2 mm (8 mil) by the Joint Electron Device Engineering Council (JEDEC) standard (JEDEC Design Standard, No. 95-1, Section 14, Ball Grid Array, June 2000). Coplanarity analysis is performed for both PBGA and T²-BGA, using ANSYS. Finally, a coplanarity experiment is conducted on the constructed specimens of PBGA and T²-BGA, to confirm the analytic results. The results in this work establish the effectiveness of T²-BGA in improving coplanarity. Moreover, the analytic results differ slightly from the experimental results, by 1.53–10.50%. The FEM model proposed here can be extended to optimize the structure of T²-BGA.     

Polyamide-Silica Gel Mixed Layer Chromatography of Antipyretics

Nine antipyretics are well separated on a polyamide-silica gel G (1:5.2) mixed layer with four solvent systems. The mixed layer is firmly bonded and easy to handle and store. The method is applicable for the identification of A. P. C. tablet and the detection of free salicylic acid in aspirin.     

Magnetic field induced residual resistivity in quasi-one-dimensional Hg3−δAsF6

The â-b? plane resistivity of the Hg-chain compound, Hg_3?δAsF₆, has been measured as a function of temperature and magnetic field using a contactless ac technique. The data imply a magnetic field dependent residual resistivity which goes to zero as the field is reduced to zero. The results are discussed in terms of the quasi-one-dimensional electronic and structural features of this novel linear chain compound.     

A shadow-moiré method with two discrete sensitivities

A shadow-moiré method using a composite grating with two discrete pitches is proposed whereby the range of measurable deflection is enlarged as compared to the ordinary shadow-moiré method.     

Nonpolar a-plane GaN grown on r-plane sapphire using multilayer AlN buffer by metalorganic chemical vapor deposition

Mirror-like and pit-free non-polar a-plane (1 1 −2 0) GaN films are grown on r-plane (1 −1 0 2) sapphire substrates using metalorganic chemical vapor deposition (MOCVD) with multilayer high-low-high temperature AlN buffer layers. The buffer layer structure and film quality are essential to the growth of a flat, crack-free and pit-free a-plane GaN film. The multilayer AlN buffer structure includes a thin low-temperature-deposited AlN (LT-AlN) layer inserted into the high-temperature-deposited AlN (HT-AlN) layer. The results demonstrate that the multilayer AlN buffer structure can improve the surface morphology of the upper a-plane GaN film. The grown multilayer AlN buffer structure reduced the tensile stress on the AlN buffer layers and increased the compressive stress on the a-plane GaN film. The multilayer AlN buffer structure markedly improves the surface morphology of the a-plane GaN film, as revealed by scanning electron microscopy. The effects of various growth V/III ratios was investigated to obtain a-plane GaN films with better surface morphology. The mean roughness of the surface was 1.02 nm, as revealed by atomic force microscopy. Accordingly, the multilayer AlN buffer structure improves the surface morphology and facilitates the complete coalescence of the a-plane GaN layer.     

A six-dimensional gauge-Higgs unification model based on E6 gauge symmetry

We construct a six-dimensional gauge-Higgs unification model with the enlarged gauge group of E₆ on S²/Z₂$S^2/Z_2$ orbifold compactification. The standard model particle contents and gauge symmetry are obtained by utilizing a monopole background field and imposing appropriate parity conditions on the orbifold. In particular, a realistic Higgs potential suitable for breaking the electroweak gauge symmetry is obtained without introducing extra matter or assuming an additional symmetry relation between the SU(2) isometry transformation on the S²$S^2$ and the gauge symmetry. The Higgs boson is a KK mode associated with the extra-dimensional components of gauge field. We also compute the KK masses of all fields at tree level.     

Millijoule intracavity OPO driven by a passively Q-switched Nd:YVO<Subscript>4</Subscript> laser with AlGaInAs quantum-well saturable absorber

We originally demonstrate the use of an AlGaInAs periodic quantum-well absorber to achieve a quasi-continuous-wave (QCW) diode-pumped passively Q-switched Nd:YVO₄ laser with an intracavity optical parametric oscillator (OPO). With a diode-pumping energy of 35 mJ, the output pulse energy and the pulse width at 1573 nm are found to be 1.58 mJ and 26 ns, respectively. The pulse repetition rate can be up to 100 Hz with the overall OPO beam quality M² factor to be better than 1.5.     

Highly efficient Nd:Gd0.6Y0.4VO4 laser by direct in-band pumping at 914 nm and observation of self-mode-locked operation

A highly efficient Nd:Gd_0.6Y_0.4VO₄ laser by direct in-band pumping at 914?nm is demonstrated for the first time. With an absorbed power of 3.7?W, a maximum output power of 2.65?W at 1064?nm was obtained, corresponding to an optical conversion efficiency of 72%. We also experimentally observed that the laser system could be efficiently operated in the self-mode-locked state in the range of 0.9?C3.3?GHz. The pulse width was measured to be 16 ps at a repetition rate of 1.75?GHz.     

Intrinsic optical properties and divergent doping effects of manganese(II) on luminescence for tin(II) phosphite grown from a deep-eutectic solvent

This is the first study on the ionothermal synthesis, intrinsic photoluminescence (PL), and dopant effects for tin(II) phosphite, a stereochemically active 5s(2) lone-pair-electron-containing compound, the fundamental properties of which have rarely been explored before. In a new deep-eutectic solvent, single-phased products of SnHPO(3) (1) and Sn(1-x)Mn(x)HPO(3) (2) have been achieved in high yield. The crystalline powder of 1 is nonenantiomorphic, with an intense second-harmonic generation comparable to that of potassium dihydrogen phosphate. Under UV excitation, it unexpectedly emits white PL, an important intrinsic property never discovered in tin(II) oxysalts. Electron paramagnetic resonance hyperfine splitting characteristic of manganese has been detected on 2 and a three-pulse electron-spin-echo envelope modulation technique implemented to locate its corresponding location in the inorganic host. On the basis of temperature-dependent PL and lifetime measurements, the incorporated Mn(2+) uncommonly acts as a sensitizer in enhancing white emission until extremely low temperatures, in which it would resume its normal role as an activator to give out characteristic orange light.     

Regioselective assembly of 3,4-dihydroisoquinoline derivatives

A facile two-step sequence (9→10→1) of regioselective assembly of 3,4-dihydroisoquinoline derivatives 1 is reported. The halogen derivatives provide opportunity for Suzuki, Buchwald, and related coupling reactions useful for expanding the scaffold and lead optimization in drug discovery.