Teru Nakanishi

Solder joint reliability of indium-alloy interconnection

Recent high-density very large scale integrated (VLSI) interconnections in multichip modules require high-reliability solder interconnection to enable us to achieve small interconnect size andlarge number of input/output terminals, and to minimize soft errors in VLSIs induced by α-particle emission from solder. Lead-free solders such as indium (In)-alloy solders are a possible alternative to conventional lead-tin (Pb-Sn) solders. To realize reliable interconnections using In-alloy solders, fatigue behavior, finite element method (FEM) simulations, and dissolution and reaction between solder and metallization were studied with flip-chip interconnection models. We measured the fatigue life of solder joints and the mechanical properties of solders, and compared the results with a computer simulation based on the FEM. Indium-alloy solders have better mechanical properties for solder joints, and their flip-chip interconnection models showed a longer fatigue life than that of Pb-Sn solder in thermal shock tests between liquid nitrogen and room temperatures. The fatigue characteristics obtained by experiment agree with that given by FEM analysis. Dissolution tests show that Pt film is resistant to dissolution into In solder, indicating that Pt is an adequate barrier layer material for In solder. This test also shows that Au dissolution into the In-Sn solder raises its melting point; however, Ag addition to In-Sn solder prevents melting point rise. Experimental results show that In-alloy solders are suitable for fabricating reliable interconnections.

RF power dependence of microstrip disk resonators with YBCO films for 4 GHz band

High-Tc superconducting (HTS) power filters have an attractive possibility of being applied to the base stations of the- future mobile-communication systems. In the microstrip structure, disk-shape-patterned HTS resonators are considered potential candidates for the HTS power filters. In order to research the application feasibility of disk resonators, the resonator samples were fabricated with different quality YBCO thin-films, and the power handling and third intermodulation-distortion (IMD3) of the samples were then examined for the incident continuous wave power of up to about 10 W around 4 GHz at cryogenic temperatures. We discuss the results on the relationship between the RF power dependence and the YBCO film qualities.

RF Power Properties of YBCO-Film/LAO Microstrip Disk Resonators for 4 GHz Band

This paper presents RF power properties of YBCO films on LaAlO 3 substrate examined using microstrip disk shape-patterned resonators for around 4 GHz. Characterization of the YBCO films for the resonators was carried out. For input-output power measurement, the resonators with the condition of strong I/O couplings were designed and fabricated. The RF power properties of the resonators at cryogenic temperatures were measured. The resonator condition to obtain the handling power over 10 W at 30 and 70 K was confirmed. The temperature dependence of the break-down powers at 4GHz for the resonators showed two broad peaks. We discuss the unique phenomenon with magnetic flux model, as referred to the YBCO films characteristics results.

Precise Measurement of IMD Behavior in 5-GHz HTS Resonators and Evaluation of Nonlinear Microwave Characteristics

The intermodulation distortion (IMD) of a 5-GHz HTS resonator is precisely measured and a nonlinear analysis is conducted. When designing a radio communication system that uses an HTS microwave device, the devices IMD characteristic is one of the most important problems that must be quantitatively evaluated. The amplitudes of third-order IMD (IMD3) and higher-order IMD, which are generated in an HTS resonator given a two-tone fundamental signal, are measured in detail using a fundamental signal cancellation circuit. Moreover, the relative phase of IMD3 is obtained by using a novel measurement system constructed around a reference IMD3 generator. The measured IMD3 phase shows a drastic change in a relatively low IMD3 amplitude region. In addition, the measured resonator exhibits strong higher-order IMD. A nonlinear evaluation using complex power series representation confirms that the drastic phase change may be due to the higher-order distortions present in IMD3.

HTS microstrip disk resonator with an upper dielectric layer for 4GHz

We propose HTS microstrip disk resonator with an upper dielectric layer as a candidate resonator structure of HTS compact power filter for 4GHz band. The electromagnetic simulations on the upper dielectric layer examined the current distributions of the HTS resonators that had TM11 mode resonance of about 4 GHz. By the simulations, it is evaluated that of the maximum current density near the end portion of the disk-shape pattern of the resonator with the thick upper-layered structure decreases by roughly 30-50 percent, as compared with that of the resonator without it. Then, we designed and fabricated the resonator samples with and without the upper dielectrics. The RF power measurement results indicated that the upper dielectric layer leads to an increase in handling power.

Novel dual mode disk-shaped resonator filter with HTS thin film

We propose a novel dual mode disk-shaped resonator filter with high temperature superconductor (HTS) thin films. The 5 GHz-band YBa2Cu3O7-x (YBCO) microstrip dual mode disk resonator filter on an MgO (100) substrate keeps a perfect circle shape and a waveguide line of about a half-wavelength that is capacitively-coupled with the disk resonator to generate a dual mode. The fabricated filter had an equivalent frequency response of a two-pole filter with two attenuation poles. The coupled coefficient of two orthogonal modes can be controlled by the length of coupled waveguide line and the gap space between feeder and disk resonator. The fabricated filter showed very low third-order intermodulation distortion (IMD3) of -73 dBc with an output power of 10 W at a temperature of 65 K. In addition, the proposed structure can be fabricated using a side lithography and etching processes. This is an advantage for multi-stage filter applications. We believe this filter is a promising candidate structure for RF transmit system applications.

High-Tc Superconducting Dual-mode Disk Resonators with Attenuation Poles using Ground-slot

In order to meet stringent requirements on transmit filters, high-Tc superconducting dual-mode disk resonators with attenuation poles have been designed, fabricated, and measured. Using a ground-slot perturbation along the asymmetric plane from the feeder lines, the resonator fabricated with YBCO superconducting double-sided films showed high performance with attenuation poles at the both sides of the passband resulting in higher selectivity. From the experimental results, a design concept focusing on phase responses was found to be applicable to the appearance method of the attenuation poles.

Film-thickness dependence of the microwave properties of YBCO films

Abstract We examined the film-thickness dependence on the microwave properties and microstructure of c-axis oriented YBCO films with thickness up to approaximately 1 μm on MgO(100) substrates by pulsed laser deposition, using different growth conditions. The surface roughness that was caused by Cu compound outgrowths allowed misoriented grains to form in the thicker films resulting in higher resistance Rs. By lowering growth rate, the thick films with higher orientation were obtained, and exhibited lower Rs and unloaded Q of 8E+4 at 70 K in a 2 GHz microstrip line resonator.

HTS Reaction-Type Transmitting Filter Based Upon Split Open-Ring Resonators with Surface Current Density Reduction Technique

An high-temperature superconducting reaction-type transmitting filter (HTS-RTF) based upon split open-ring resonators with novel surface current density reduction technique is proposed. Since reaction-type resonators do not resonate with high-power fundamental signals, an HTS-RTF enables both high-power handling capability and steep skirt property compared to existing planar-type HTS transmitting filters. However, fundamental signals in the passband induce a current in their resonators. Firstly, to reduce induced currents in the passband, novel split open-ring resonator (SORR) structures that reduce maximum current densities while offering both high-unloaded Q-factors and low radiations are numerically investigated for 5-GHz band operation. Secondly, to further improve the current density dispersion effect, additional slits are introduced to the resonator surface. Then, to validate the analysis results, fabrications and measurements of the resonators are carried out. Measurements confirm an unloaded Q-factor of 68,000 and third intermodulation-distortion of -82 dBc at 30 dBm input power. Finally, design and fabrication of a 5-GHz three-pole reaction-type filter with bandwidth of 1.5 MHz (FBW = 0.03 %) is conducted. The measurement results confirm the fundamental performance of the filter.

4 GHz band HTS receiving-filters for a compact cryogenic receiver front-end

We report on the development of 4 GHz band high-temperature superconducting (HTS) filters for a compact cryogenic receiver front-end. For the application to the next-generation communications system with higher bit rate data transmission, 9-pole and 15-pole microstrip hairpin bandpass filters with a center frequency of 4 GHz and a relatively wide bandwidth of 100 MHz were designed and fabricated. A 9-pole bandpass filter using YBCO superconducting films on MgO dielectric substrate performed the frequency responses corresponding closely to the simulated results. By using LaAlO/sub 3/ substrate with higher dielectric constant, a compact, more poles, 15, bandpass filter with steeper skirt frequency characteristics was obtained. However, the measured less return loss response around the center frequency of the in-band implies that a precise coupling-control between adjacent resonators and also non-adjacent resonators is required. Moreover, the receiving-circuits comprising each fabricated YBCO bandpass filter sample and a 4 GHz band cryogenic low-noise amplifier were measured at 70 K in terms of S-parameters and noise figure (NF). The results which reflect each of the filter performance indicated high selectivity, high gain, and low NF.