Contact Resistance Measurement Method Research Articles

High-Accuracy Contact Resistance Measurement Method for Liquid Metal by Considering Current-Density Distribution in Transfer Length Method Measurement.

Liquid metals (LMs) are used as stretchable conductors in various stretchable electronic devices. Moreover, such devices using Ga-based LMs have attracted considerable attention. Herein, we propose a method for accurately determining the contact resistance (Rc) between galinstan and Cu electrodes by considering the current-density distribution in transfer length method (TLM) measurement. Conventional TLM measurements assume that the sheet resistance of the metal electrode (Rshe) is negligible compared with that of the object (Rsho), such as Si. However, this assumption may be problematic because the Rsho of Ga-based liquid metals (LMs) is close to the Rshe. Therefore, we developed a method of applying current to each measuring electrode and compared it with the conventional method of applying current to the outer electrodes. Simulation results indicated that Rshe cannot be ignored for galinstan, and the measured resistance in the contact area (RcTotal) included <10% of the Rc component when current was applied to the outer electrodes. In contrast, RcTotal included the entire Rc component when current was applied to each electrode. Furthermore, we found that the volume resistances of the object and electrode included in RcTotal cannot be ignored. Therefore, for accurate measurement, current must be applied to each electrode, and Rc must be determined from the intersections of the measured and simulated RcTotal. The obtained contact resistivity (ρc), i.e., the contact resistance per unit contact area, was 0.115 mΩ·mm2. The maximum error was 0.085 mΩ·mm2, which was lower than the ρc of the solders (≥10-1 mΩ·mm2) with the lowest ρc among the electrical interface materials between the electronic components and wiring. This study provides valuable insight into the Rc measurement of LMs, along with new opportunities for the development of stretchable electronics using LMs.

Experimental Study on the Accuracy of the Proposed LFAC Method for Measuring the Contact Resistance of NI HTS Coils

No-insulation (NI) winding technique provides high thermal stability, and the turn-to-turn contact resistance is an important factor to characterize the thermal stability and charging delay of NI HTS magnets. Therefore, a method that can accurately measure the contact resistance between turns of NI HTS magnets was required. We have previously proposed a turn-to-turn contact resistance measurement method using a low frequency AC current. The proposed low-frequency-AC-current (LFAC) can accurately evaluate the contact resistance between turns only when the whole AC current flows in the radial direction of the NI HTS pancake coil (there is almost no coil inductance). In addition, the AC current flowing in the radial direction needs to have a uniform current distribution in the plane of winding wire (REBCO wire). Therefore, in this study, an experimental study was conducted to prove the reliability of the proposed LFAC method. In the experiment, three NI test coils with different winding tension (0.5, 1 and 2 kg) were prepared, and four pickup coils were placed under each test coil to evaluate the radial current bypass characteristics. The contact resistance of each test coil was decreased from a few percent to several tens of percent by multiple cooling cycles from room temperature to liquid nitrogen temperature. Although it is a qualitative observation, the validity of the LFAC method was proved by the prepared pickup coils, and it was shown that even a small change of contact resistance in NI coils can be measured.

Turn-to-Turn Contact Resistance Measurement of No-Insulation REBCO Pancake Coil at DC Current Operation

No-insulation (NI) (RE)Ba $_2$ Cu $_3$ O $_y$ (REBCO) magnets are very promising for practical applications to generate high magnetic field. The NI winding technique provides high thermal stability so that quench protection is unnecessary. However, the turn-to-turn contact resistance (sometimes called characteristic resistance) is an important factor to characterize the thermal stability and charging delay of NI REBCO pancake magnets. Although the conventional sudden-discharging method is widely used to measure the turn-to-turn contact resistance, it is not applicable to various conditions; e.g., the change of DC operating current and temperature. Therefore, we have previously proposed a turn-to-turn contact resistance measurement method using a low-frequency AC (LFAC) current. In this paper, we measured the contact resistance for different DC operating currents or change of DC current to confirm the validity of LFAC method. In addition, by heating a test coil, the contact resistances were also measured during the change of DC operating current. Since the electromagnetic stress is small enough not to change the contact condition, the change in contact resistance is negligible. The measured contact resistance was unchanged, so we could conclude that the LFAC method is effective in measurement of the contact resistance when DC operating current was applied.

Characteristics of Metal-Metal Nano-Area Contact Resistance for Less Than 5 nm Technology Node.

Recently, better understanding of nano-area is required for 5 nm or less technology node. In particular, the high contact resistance generated in a nano-area significantly degrades the device performance. In this study, we propose a direct contact resistance measurement method without a test structure by separate processes to improve the nano-area contact resistance. The nano-area contact resistance of Ti-Ti and Cu-Cu decreased from 6.46 MΩ to 1.08 MΩ and from 3.78 MΩ to 1.48 MΩ, respectively, when the metal line and native layer formed on the surface were removed. In addition, it is confirmed that the contact resistance decreased with an increase in bonding strength in the case of nano-area homo-metal contact. However, the contact resistance is affected by the tunneling effect and bond energy according to the distance between the first layers of atoms in the case of nano-area hetero-metal contact.

An experimental study on contact resistance of coated galvanized steel sheet

A contact resistance measurement system was developed based on a four-wire contact resistance measurement method. A series of experiments were conducted on four kinds of coated galvanized steel sheets using the contact resistance measurement system at different pressures and temperatures. The results showed that pressure and temperature had great effect on contact resistance. The contact resistance was not stable during the initial period when the pressure was changeless and subsequently decreased with the increase of pressure. The contact resistance did not always decline with the temperature at low temperatures because of the joint effects of the electrical and mechanical properties of base metal and the films. However, the contact resistance decreased when the temperature rose within a certain temperature range.

Observation of the Contact Formation of PV Frontside Pastes by in-situ Contact Resistance Measurement

A large number of solar cell front side contacts is still produced by printing and firing of glass containing silver pastes. The role of the glass frit in the short firing cycles is not fully understood so far. To overcome this, an in-situ contact resistance measurement method was introduced. This examination method allows a time correlation of phase transport and reaction related phenomena and can be used as a basis for specific operations in the paste development. Thereby, the in-situ contact resistance curves of glass-containing silver metallization could be assigned to microstructural phenomena such glass melting, silver solution, ARC etching and silver precipitation. The results of the correlations between electrical characteristics and the formed microstructures confirmed the decisive importance of the glass phase in the silver metallization for contact formation processes.

Practical electrical contact resistance measurement method for bulk thermoelectric devices

ABSTRACTAs thermoelectric (TE) element length decreases, the impact of contact resistance on TE device performance grows more significant. In fact, for a TE device containing 100-μm tall Bi2Te3TE elements, the figure of merit ratio (ZTDevice/ZTMaterial) drops from 0.9 to 0.5 as the contact resistivity increases from 5 x 10-07 to 5 x 10-06 Ω-cm2. To understand the effects of contact resistance on bulk TE device performance, a reliable experimental measurement method is needed. There are many popular methods to extract contact resistance such as Transmission Line Measurements (TLM) and Kelvin Cross Bridge Resistor method (KCBR), but they are only well-suited for measuring metal contacts on thin films and do not necessarily translate to measuring contact resistance on bulk thermoelectric materials. The authors present a new measurement technique that precisely measures contact resistance (on the order of 5 x 10-07 Ω-cm2) on bulk thermoelectric materials by processing stacks of bulk, metal-coated TE wafers using TE industry standard processes. One advantage of this technique is that it exploits realistic TE device manufacturing techniques and results in an almost device-like structure, therefore representing a realistic value for electrical contact resistance in a bulk TE device. Contact resistance measurements for metal contacts to n- and p-type Bi2Te3 alloys are presented and an estimate of the accuracy of the measurements is discussed.

ESTABLISHMENT OF MEASUREMENT METHOD OF CONTACT RESISTANCE WITH PALMS AND HANDS

The purpose of this study is to present the evaluation method of contact resistance of building elements and members with palms and hands from the view point of motion support and posture control. First, sensory tests to make evaluation scales from the view point of motion support and posture control with palms and hands were carried out. Next, the contact resistance meter with palms and hands that could measure the contact resistance of samples were developed. Then, coefficients of contact resistance of the samples were searched with the contact resistance meter. Also, the relations were investigated between contact resistance and evaluation scales from the view point of motion support and posture control. As a result, the measurement method of contact resistance of building elements and members with palms and hands were presented.

THE EVALUATION METHOD OF CONTACT RESISTANCE OF BUILDING ELEMENTS AND MEMBERS WITH FINGERS FROM THE VIEW POINT OF MOTION SUPPORT AND POSTURE CONTROL

The purpose of this study is to present the evaluation method of contact resistance between fingers and building elements from the view point of motion support and posture control.First, sensory tests to make evaluation scales from the view point of motion support and posture control with fingers were carried out. Next, the contact resistance meter that could measure the contact resistance of samples was developed.Then, coefficients of contact resistance of samples were searched with the contact resistance meter by various pull angle and vertical loads.Also, the relations were investigated between contact resistance and evaluation scales from the view point of motion support and posture control.As a result, the measurement method of contact resistance of building elements and members with fingers was presented.