Optimization of the profile and material of wire contacts for an IR photodetector

The study is devoted to the influence of the choice of geometry and materials of wire contacts on the reflection coefficient and thermal characteristics of the photodetector and the quality of the device design. The process of diffusion of materials of wire contacts and contact pads on a photodetector crystal is investigated. The studies were carried out on samples that are rather small in size (250x250x400 um). During the experiment, 4 main types of loop geometry were selected (main loop, reverse loop, double reverse loop, long loop). The loops were formed using a gold wire 25 μm in diameter. The quality of microwelds was investigated in 3 ways: shear and pull-off tests, optical observation using a scanning electron microscope (SEM), and contact resistance measurement. The aim of the work is to create a high-quality design of an IR photodetector, which allows achieving a high sensitivity (at least 0.5 A / W), a large dynamic range (at least 40 dB) and low indicators of dark current values. The developed technology ensures high quality of the photodetector design. Due to the low costs of this technological process (wire material, the number of operations required for installation), relative to other technologies, which allows maintaining high performance in the technical component of the photodetector, the installation method may be of practical interest in production.

The kapok petal: superhydrophobic surface induced by microscale trichomes

The Kapok petal is reported for the first time that it shows a superhydrophobic characteristic with a static water contact angle higher than 150°. Intriguingly, there exist single-scale micro-trichomes and no more nanocrystals on a kapok petal in contrast to most natural superhydrophobic surfaces with hierarchical morphologies, such as lotus leaf and rose petal. Experiment results show that kapok petal has an excellent self-cleaning ability either in air or oil. Further scanning electron microscope characterization demonstrates that the superhydrophobic state is induced by densely-distributed microscale trichomes with an average diameter of 10.2 μm and a high aspect ratio of 17.5. A mechanical model is built to illustrate that the trichomes re-entrant curvature should be a key factor to induce the superhydrophobic state of the kapok petal. To support the proposed mechanism, gold-wire trichomes with a re-entrant curvature are fabricated and the results show that a superhydrophobic state can be induced by microstructures with a re-entrant curvature surface. Taking the scalability and cost-efficiency of microstructure fabrication into account, we believe the biomimetic structures inspired by the superhydrophobic kapok petal can find numerous applications that require a superhydrophobic state.

Solid-Contact Ion-Selective Electrodes for Histamine Determination

Solid-contact ion-selective electrodes for histamine (HA) determination were fabricated and studied. Gold wire (0.5 mm diameter) was coated with poly(3,4-ethlenedioxythiophene) doped with poly(styrenesulfonate) (PEDOT:PSS) as a solid conductive layer. The polyvinyl chloride matrix embedded with 5,10,15,20-tetraphenyl(porphyrinato)iron(iii) chloride as an ionophore, 2-nitrophenyloctyl ether as a plasticizer and potassium tetrakis(p-chlorophenyl) borate as an ion exchanger was used to cover the PEDOT:PSS layer as a selective membrane. The characteristics of the HA electrodes were also investigated. The detection limit of 8.58 × 10−6 M, the fast response time of less than 5 s, the good reproducibility, the long-term stability and the selectivity in the presence of common interferences in biological fluids were satisfactory. The electrode also performed stably in the pH range of 7–8 and the temperature range of 35–41 °C. Additionally, the recovery rate of 99.7% in artificial cerebrospinal fluid showed the potential for the electrode to be used in biological applications.

Design and Fabrication of Leadless Package Structure for Pressure Sensors

Silicon piezoresistive pressure sensors can only operate below 125°C due to the leakage current of the PN junction. However, SOI high temperature pressure sensors use SiO2 for full dielectric isolation to solve this problem. At present, SOI high temperature pressure sensors mostly use lead bonding package structure, with gold wire to lead the electrical signal and silicone oil as the protection medium, but the working temperature of silicone oil is limited to about 150?. In this paper, the leadless package structure is designed by using pressure conduction on the back side of the chip and replacing the gold wire with conductive silver paste, and the materials and dimensions of the leadless package structure are determined. The reliability of the leadless package structure was verified by finite element analysis, and the results showed that the thermal stress caused by high and low temperature cycles in the leadless package is very small and does not affect the sensitivity of the pressure-sensitive chip. The size of the leadless package structure was optimized by Taguchi orthogonal method, and the maximum thermal stress was effectively reduced. Also, the key factors affecting the thermal stress of the leadless package in the package structure were identified by the variance number analysis method. The electrical signal conduction of the pressure sensor is achieved by a silver paste sintering process, and the data show that the sensitivity of the pressure sensor is 30.82 mV/MPa with a nonlinearity of less than 0.4% FS.

MODEL ANALYZING FOR REUSING GOLD WIRE CAPILLARY IN THE GOLD WIRE BONDING PROCESS

Manufacturing process improvement is necessary for manufacturers to gain business advantages. Re-using or increasing the useful lives of machine parts is considered to be a process of performance improvement. To re-use parts, the manufacturers must know the effects of the factors related to workpieces' qualities to prevent defects. This research study aims at presenting the results of analysing the effects of the factors and mathematical models for bond shear strength when reusing gold wire bonding capillary in the gold wire bonding process of integrated circuit (IC) products using design experiment. The operation factors in the reference experiment, including bond force, bond time, USG current, EFO current and EFO gap, are investigated. The Fractional Factorial Design was used to determine five factors that affect the bond shear strength. The analysis of the results show that the bond force is a significant factor where increasing bond force factors leads to increasing bond shear strength. In the end, a Regression model of bond shear strength is obtained to show the result between the bond shear strength and effect of factors. ABSTRAK: Proses pembaharuan pengilangan adalah penting untuk para pengilang bagi memperoleh keuntungan bisnes. Guna-semula atau menambah jangka hayat pada bahagian-bahagian tertentu pada mesin adalah dianggar sebahagian proses penambahbaikan prestasi mesin. Bagi mengguna semula bahagian-bahagian ini, pengilang mesti mengetahui akibat sesuatu faktor berkaitan kualiti bahan bagi mengelak kecacatan. Kajian ini bertujuan menyampaikan dapatan kajian melalui kesan faktor dan model matematik pada kekuatan ricihan ikatan apabila mengguna semula wayar emas melalui proses kapilari ikatan wayar emas pada produk litar bersepadu melalui rekaan eksperimen. Faktor operasi melalui rujukan eksperimen dari daya ikatan, masa ikatan, arus USG, arus EFO dan jarak EFO dikaji. Rekaan Faktorial Pecahan digunakan bagi mendapatkan lima faktor yang mempengaruhi kekuatan ricihan ikatan. Dapatan kajian menunjukkan daya ikatan merupakan faktor penting di mana, pertambahan faktor daya ikatan menguatkan ricihan ikatan. Akhirnya, model Regression kekuatan ricihan ikatan diperoleh bagi menjelaskan dapatan kajian antara kekuatan ricihan ikatan dan kesan faktor.

Protoporphyrin IX Based All-Solid-State Ion-Selective Electrodes for Choline Determination In Vitro

Protoporphyrin IX-based all-solid-state choline (Ch) ion-selective electrodes (ISEs) were fabricated and characterized. Poly (3,4-ethylene dioxythiophene) doped with poly (styrene sulfonate) (PEDOT/PSS) functioning as an ion-to-electron transducer was electropolymerized on the gold wire (0.5 mm diameter). The conductive polymer was covered with a Ch selective membrane containing protoporphyrin IX as an ionophore, which exhibited a lower detection limit of 0.49 μM with the potentiometric method. The Ch sensor performed a wide linear range from 1 μM to 1 mM, a fast response time of less than 5 s, and a decent selectivity of common inorganic and organic ions in the human body. Characteristics such as pH and temperature stability, life span, reproducibility and repeatability were also investigated to be satisfied. With the background of artificial cerebrospinal fluid, the recovery rate in 10−5 M of Ch solution was measured by the standard addition method, revealing the potential for biological application.

An Early Bronze Age Burial with a Golden Spiral Ring from Ammerbuch-Reusten, Southwestern Germany

A women’s burial of the Early Bronze Age that was uncovered near Ammerbuch-Reusten, Tübingen district in autumn 2020 shows clear relations to burial rites of the Final Neolithic in central Europe. The only grave good was in the rear of the burial. A small spiral ring made of gold wire at the left side of the burial at hip level, which can be considered to be the earliest securely dated precious metal find in southwestern Germany. The find fits into a small series of early spiral rings made of gold wire, which are among the oldest precious metal finds in central Europe. Its composition with c. 20 % silver and less than 2 % copper as well as traces of platinum and tin indicates the use of a naturally occurring gold alloy, most likely from so-called alluvial deposits obtained by panning from rivers. The trace element pattern strongly suggests that this type of gold derives from Cornwall, specifically from River Carnon. The burial matches a group of other burials from the Bronze Age on the plateau and is apparently related to a hilltop settlement on the nearby Kirchberg of Reusten.