We report on a search for non-Newtonian forces that couple to mass, with a characteristic scale of $\sim 10\mu \mathrm{m}$, using an optically levitated microsphere as a precision force sensor. A silica microsphere trapped in an upward-propagating, single-beam, optical tweezer is utilized to probe for interactions sourced from a nanofabricated attractor mass with a density modulation brought into close proximity to the microsphere and driven along the axis of periodic density in order to excite an oscillating response. We obtain a force sensitivity of $\lesssim {10}^{-16}\mathrm{N}/\sqrt{\mathrm{Hz}}$. Separately searching for attractive and repulsive forces results in the constraint on a new Yukawa interaction of $|\alpha |\gtrsim {10}^8$ for $\lambda >10\mu \mathrm{m}$. This is the first test of the inverse-square law using an optically levitated test mass of dimensions comparable to $\lambda$, a complementary method subject to a different set of systematic effects compared to more established techniques.

Silicon carbide (SiC) devices have shown definite advantages over Si counterparts in high-temperature, high-voltage, and high-frequency applications. To fully exploit the potentiality of SiC devices in high temperatures, die-attach materials that can withstand high temperatures for a long time are required in the power electronics packaging. In this article, the high-temperature die-attach materials, such as high-temperature solders and transient liquid-phase bonding materials, were reviewed first. Then, metallic (mainly Ag and Cu) nanoparticles (NPs) sintering technologies were thoroughly overviewed. The metallic NPs sintering materials, metallic NPs sintering process, and interface and reliability were analyzed, respectively. Finally, the challenges and outlook of promising Cu NPs sintering technology were discussed.

In this letter, a patch driven low-profile broadband metasurface antenna is proposed. The novel antenna is constituted utilizing an aperture coupled patch and proposed configurations of finite sized AMC. With the surrounding metasurface excited by the surface wave introduced through the center patch, an additional TM resonance is generated and a wideband impedance matching is achieved. The performance and operating mechanism of the proposed antenna are investigated and analyzed. To demonstrate the concept, a 1×4 array with an overall thickness of 0.047 λ $_0$ (λ $_0$ is the free space wavelength at 28 GHz) is successfully implemented through advanced substrate manufacturing process. The obtained impedance bandwidth for reflection coefficient below -10 dB is 27.1% with a maximum realized gain of 13.6 dBi.

A millimeter-wave (mmWave) broadband metasurface antenna with low profile is proposed. The radiator composed of four groups of coplanar patches with different dimensions has four adjacent broadside characteristic modes. Coaxial probe feeding is selected carefully to excite the four modes to broaden impedance bandwidth. Dual slots are etched on the patch fed by the coaxial probe to reduce H-plane cross-polarization levels. Characteristic mode analysis (CMA) and input impedance analysis are performed to characterize its resonance behaviors. The proposed antenna with dimension of 1.03 × 1.03 × 0.023 λ ₀ ³ (λ ₀ is wavelength at 28 GHz in free space) realizes 16% (26.1 GHz-30.7 GHz) impedance bandwidth for |S ₁₁ | ≤ -10 dB. Realized peak gain is up to 10.1 dBi and 3 dB gain bandwidth is 22% (24.4 GHz-30.5 GHz). H-plane cross-polarization levels are less than -16 dB.

In general, although abundant literature studies are available on epoxy resin systems, a complete description of the curing kinetics in epoxy-cyanate ester composites relevant to the microelectronics industry is still lacking. Herein, curing behaviors of Ajinomoto build-up films, which are epoxy/silica composites, were studied by the non-isothermal differential scanning calorimetry method, and then, three non-isothermal curing kinetics models and model-free curing methods were used to analyze curing behaviors. In addition, a copper layer was also deposited onto the surface of the build-up film, and its interfacial adhesion property was also analyzed at different pre-curing conditions. The results showed that the curing reaction of the build-up film contains two curing reaction processes, and the first curing process is suited for the autocatalytic curing model, while the other curing process is suited for the Kamal curing kinetics model. Three model-free curing methods were used to calculate the activating energy at different degrees of curing, which indicated that the activating energy is variable during the whole curing process. The interfacial adhesion strength between the build-up film and copper layer decreased with the increase in the degree of curing, which is attributed to the contribution of mechanical anchoring. This work will offer guidance in curing behaviors for improving interfacial bonding force and controlling warpage behavior for chip substrates in the future.

An antenna-in-package solution is proposed based on embedded organic substrate package. RF front-end module is integrated with an antenna considering the electrical and thermal performance, dimensions, manufacturing as well as cost. A millimeter-wave low-profile wideband antenna is designed, analyzed, and verified experimentally. The radiator of the proposed antenna consists of three groups of patches with different dimensions and it is fed by a stripline through an aperture etched on a ground plane. Input impedance analysis is utilized to accurately explore resonance characteristics of the aperture-coupled radiator. As a comparison, characteristic mode (CM) analysis is applied to calculate CMs of the source-free radiator. Different results obtained by two methods are analyzed. Over the operating band, three resonance modes, respectively, dominated by quasi-TM ₁₀ mode of different patches are excited in turn, which contributes to wideband performance. Measured results demonstrate that the proposed antenna with only 0.039λ ₀ (λ ₀ is wavelength of 28 GHz in free space) substrate thickness achieves an impedance bandwidth ( |S ₁₁ | ≤ -10 dB) of 37.5% (22.8-33.3 GHz). The peak gain is up to 10.7 dBi and 3 dB gain bandwidth is 23.7% (25.7-32.6 GHz), while 6 dBi gain bandwidth is 33.6% (23.5-33 GHz).