Chip Resistors Research Articles

Wideband absorptive frequency‐selective reflector based on split‐ring resonator embedded with chip resistor

AbstractHere, a wideband absorptive frequency‐selective reflector (AFSR) based on a split‐ring resonator (SRR) embedded with chip resistors is proposed. The wide absorption band is achieved by the multimode resonances of two dipoles, and the insertion of SSRs is able to bypass the losses in the passband, thus allowing to open a wide window in addition to achieving broadband absorption performance. The upper structure consists of a dipole in series with two SSRs, while the lower dipole connects one SSR. The upper and lower structures are grouped together and rotated by 90° around the Z‐axis to form the final dual‐polarization 3D‐AFSR. The simulated results demonstrate that reflection coefficients below −10 dB are seen between 6.74–9.31 and 16.91–19.61 GHz under normal incidence, with a total fractional bandwidth of 46.8%. It also has a wide 3 dB reflection band which is obtained from 10.69 to 15.44 GHz, and the entire profile is 0.17λL, where λL is lowest operating frequency.

Research on Low-Insertion-Loss Packaging Materials for DC-6 GHz Attenuation Chips

Research on Low-Insertion-Loss Packaging Materials for DC-6 GHz Attenuation Chips

A high sensitivity planar electric–magnetic isolated sensor for full characterization of magneto-dielectric materials

Magneto-dielectric (MD) materials have received much attention due to their applications in design of high-performance antenna and microwave components. Usually, their permittivity and permeability are key parameters in design of these components. Unfortunately, full characterization of these parameters faces challenge of measurement coupling between permittivity and permeability. To address this issue, an electric and magnetic isolated sensor based on a planar resonance structure is proposed and verified. Several shorting pins are used to separate the electric and magnetic regions, which effectively reduces the measurement coupling between permittivity and permeability. These shorting pins form a magnetic cavity pins (MCP) structure. The resonance structure is used for permittivity measurement, and the MCP structure is designed for measuring permeability with enhanced sensitivity. Moreover, to further improve the quality factor, a metal patch and two 50 Ω chip resistors are integrated on the microstrip line. To extract the imaginary part, the quality factor calculated from S21 will be used. By integrating these techniques, the sensor developed in this paper provides possibility of full characterization of MD materials with high sensitivity. Moreover, the magnetic cavity provides more space than the original design, allowing measurement in the Ultra-Wideband (UWB) range possible. Two sensors are designed and fabricated for validating the sensitivity and accuracy. Several materials with different permittivity and permeability are measured. The extracted measurement values show high agreement with the reference values. The permeability errors for real and imaginary parts are smaller than 3% and 4.5%, respectively. And the permittivity errors are smaller than 2.6% and 6.4%.

Convolutional Attention Network with edge supervision for void and spot segmentation in chip resistors based on X-ray images

The presence of voids inside solder joints in chip resistors can affect the stability and reliability of the product. Therefore, accurate void and spot segmentation is crucial for performance evaluation. In this study, we propose Convolutional Attention Network (CA-net) with edge supervision for void and spot segmentation based on X-ray images of chip resistors. First, CA-net has an encoder-decoder architecture and use skip connections to aggregate low-level features and high-level features. Second, the multi-scale convolutional attention modules (MSCA) are employed at each encoder and decoder to capture multi-scale feature maps of voids and spots. Finally, adding edge-supervised branch to the encoder allows the network to focus more on edge information, so that the response area of the network will be more focused on pads and empty areas. Experimental results show that CA-net outperforms other methods in void and spot segmentation, achieving 96.56 % MIOU and 97.44 % mean DIC. These results indicate that CA-net is a promising approach for accurate void and spot segmentation in chip resistors based on X-ray images.

A Comprehensive Study on Failure Modes and Mechanisms of Thin Film Chip Resistors

Usually, resistors and capacitors populate majority portion of a common electrical circuit, hence miniaturization drive of any package or subsystem starts with miniaturized resistor and capacitors. In this context, thin film chip resistors are the most sought-after components for any electronic/electrical circuit due to their small size, wide range of values, military temperature range, stringent tolerance, low TCR value (recognised with PPM). Increased use of thin-film surface mount chip resistors in military and space application has led to an increased awareness of its potential failure modes in harsh environments. Thin film resistor with lower TCR (5PPM, 10PPM and 25PPM) are most preferable and widely used because of very low temperature coefficient of resistance (TCR) and high resistivity, which suits for high precision measurement application. Low temperature coefficients characteristics of thin film resistors also makes them stable and reliable. Because of their high-volume usage in recent times, failure in thin film resistor with lower TCR/PPM (Parts per Million) are also being seen more predominantly. In general, there are two types of thin film chip resistors, one is discrete type and the other is die type or wire bondable type. Discrete type chip resistor are used directly on cards, whereas, die type/wire bondable type chip resistors used in hermetically sealed HMC packages. Standard failure mode of a resistor is open mode or high resistance mode, whereas short mode failure has a very low probability. Hence in this paper, failure modes and mechanisms of both types of thin film chip resistors, with respect to common failure causes such as EOS, ESD are discussed, which is in continuation to Fabrication/Workmanship related failures discussed in our earlier technical paper. With this, all possible failure modes and mechanism related thin film chip resistors are explained. Discussion in totality always provide in depth analysis on a subject of concern, which in turn facilitate reliability assessment of the component and corrective action, if any.

The study of heat characteristics for micro pin-fin heat sinks with different structures

Heat flux in electronic devices has increased dramatically with the development of advanced IC technology, facing the demand for effective thermal management technology. Micro pin-fin heat sink (MPFHS) has been demonstrated to be capable of improving the heat transfer capability and suppressing temperature rise effectively. In order to elaborate the discrepancy of heat dissipation of the MPFHS due to the cross-section shapes of pin-fin structures a set of heat sink samples with four different shapes, including the circle-MPFHS, the square-MPFHS, the crisscross- MPFHS, and the octagon-MPFHS, are fabricated with micromachining technology. Then, the thermal characteristics are tested by integrating the heat sinks with a Pt film resistor chip as the heating source, and nucleate boiling phenomenon was observed with a high-speed camera. Results showed that concave corners in pin-fin structures increased the specific surface area, but generated low velocity vortexes in back flow regions, reducing the heat transfer capability. The heat transfer coefficients of the octagon-MPFHS, the crisscross-MPFHS, and the circle- MPFHS was increased by 161.9 %, 152.4%, and 85.7 %, respectively, relative to the square-MPFHS at the flow rate of 147 kg/m2s. The heat transfer coefficients of the octagon-MPFHS, the crisscross-MPFHS, the circle-MPFHS, and the square- MPFHS was increased by 7.27%, 11.32%, 2.56%, and 4.76% when the mass-flow rate was increased from 147 kg/m2s to 295 kg/m2s. The nucleate boiling phenome-non in the crisscross-MPFHS showed periodicity and positive feedback effect, resulting in local dry-out and consequent heat transfer capability deterioration. This study will contribute to the design and modification of MPFHS.

Solder Joint Degradation and Electrochemical Metallic Ion Migration Property of Solder Joints with Surface Finish

To confirm the degradation property of solder joints by substrate surface finish, chip resistors are reflow soldered to organic solderability preservative (OSP) and electroless nickel immersion gold (ENIG) finish substrate in a nitrogen atmosphere using the type 6 Sn-3.0Ag-0.5Cu (SAC305) solder paste. To confirm the electrochemical metallic ion migration (ECM) sensitivity with and without photo solder resist (PSR) ink-coated printed circuit board (PCB), comb patterned test vehicles were prepared by the hot air reflow soldering process in nitrogen atmosphere, and the SAC305 solder paste was printed on the conductor of the ECM test PCB. The ECM test was conducted under high temperature and high humidity conditions of 85℃ and 85% RH, respectively. As a result of measuring the void content of the 2012 chip resistor, the average void content of the OSP substrate was higher than that of the ENIG substrate. The thermal shock test (TST) indicated that the degradation rate of the OSP substrate was higher than that of the ENIG substrate. Microstructure analysis showed that the OSP substrate had more crack propagation and thicker intermetallic compound (IMC) thickness than the ENIG substrate. The ECM test revealed that the substrate with PSR-coated PCB coupon generated more dendrites than that without PSR-coated coupon. Because the PSR coated substrate decreased the moisture absorption into the substrate, moredendritesweredeterminedtobe generated.

Effect of Differently Shaped Solder Joints of Chip Resistor on Fatigue Life

Abstract As surface mount components shrink in size, smaller apertures on stencils during solder paste printing can lead to uneven solder volume on a single resistor. This can result in the formation of irregular solder shapes, which are often deemed acceptable criterion depending on assembly house. However, such irregularities can potentially introduce variations in the fatigue life of the surface mount component. This study employs experimental and numerical approaches to investigate the reliability of differently shaped SAC305 solder joints on a single chip resistor. Four distinct solder shapes, concave, straight, tiny convex, and convex, are generated using varying volumes of solder paste controlled by uniquely designed apertures on a stencil. Eight pairs of differently shaped solder joints are assembled to hold a chip resistor in place. The test assembly involves R1005 and R0402 soldered with SAC305 and undergoes thermal shock cycling. As a single chip resistor assembly consists of two solder joints connecting termination and pads, the effect of solder volume difference between two solder joints are investigated. The fatigue life corresponds to decrease as the solder volume difference increase as 40%, 80%, and 120%. Conversely, total volume of two solder joints in a single chip resistor increases in scenarios with the same volume difference between two solder joints. Experimental data and finite element analysis lead to a new set of Darveaux's constants specific to this assembly. This study provides guideline to control the solder paste volumes in relation to fatigue life and enables numerical solution using a new Darveaux's constants.

Enhanced solder fatigue life of chip resistor by optimizing solder shape

As surface-mounted components get smaller, especially passive components such as chip resistor or chip capacitor, small apertures on a stencil are required, which generates higher variations in the printed solder paste volume and solder joint shape. In this study, the board-level fatigue life of chip resistor assemblies with SAC305 was investigated. Different volumes of solder paste are printed, which varies the shape of solder joints. Four solder joint shapes are compared: concave, straight, tiny convex, and convex, which are achieved using a stencil with differently sized openings. Thermal shock cycling shows that the convex shape exhibits the best thermal shock reliability while the concave shape has the shortest fatigue life. Additionally, different sizes of chip resistor package are compared. A comparison of the size of components concludes that the R0402 chip resistor has relatively better thermal shock resistance than the larger chip resistor, R1005 due to larger change in length of R1005 during thermal cycling. Based on the experimental results of fatigue life, the parameters of a constitutive equation are calculated to evaluate the fatigue life of the solder joint. This study provides criteria manufacturers can use to improve the reliability of chip assemblies though inspecting solder paste volumes and shapes.

Study on the Solder Joint Reliability of New Diamond Chip Resistors for Power Devices

New diamond chip resistors have been used in high-power devices widely due to excellent heat dissipation and high-frequency performance. However, systematic research about their solder joint reliability is rare. In this paper, a related study was conducted by combining methods between numerical analysis and laboratory reliability tests. In detail, the shape simulation and thermal cycling finite element simulation for solder joints with different volumes were carried out. The optimized solder volume was 0.05 mm3, and the maximum thermal cycling stress under the optimized shape was 38.9 MPa. In addition, the thermal cycling tests with current and high temperature storage tests were carried out for the optimized solder joint, which showed good agreement with the simulation results, clarified the growth and evolution law of intermetallic compound at the interconnection interface, and proved the optimized solder joint had great anti-electromigration, temperature cycling and high temperature storage reliability. In this work, an optimized solder joint structure of a diamond chip resistor with high reliability was finally obtained, as well as providing considerable reliability data for the new type of diamond chip resistors, which would boost the development of power devices.

Broadband Metasurface Absorber Based on an Optimal Combination of Copper Tiles and Chip Resistors

In this study, a broadband metasurface absorber composed of an optimal combination of copper tiles connected with four chip resistors is designed and experimentally verified. After fixing the locations of the chip resistors and setting their resistances to 100 Ω, the genetic algorithm (GA) is utilized to design the optimal copper tile pattern for broadband absorption. The optimal combination of the copper tiles is identified by determining the states of the square tile pairs between copper or air, depending on the one or zero states of the bit sequence created by GA, respectively. The full-wave simulation results of the optimized metasurface absorber confirmed a -10 dB reflectance bandwidth within the frequency range of 6.57 to 12.73 GHz for the normal incidence condition, with the fractional bandwidth being 63.83%. The accuracy of the metasurface absorber was verified through an experimental result that matched well with the full-wave simulated one.

Effects of Reflow Profile and Miniaturisation on the Integrity of Solder Joints in Surface Mount Chip Resistors

Effects of Reflow Profile and Miniaturisation on the Integrity of Solder Joints in Surface Mount Chip Resistors

Reconfigurable phase-modulated metasurfaces via rotating adjustable resistor

Reconfigurable metasurfaces have enriched metasurface design with a wide range of application prospects. However, traditional reconfigurable phase-modulated metasurfaces primarily rely on active devices such as diodes to change the resonant response, which means that many feeders and external circuitry are additionally loaded on the metasurface, thus leading the increasing complexity for metasurfaces design. In this paper, a reconfigurable phase-modulated metasurface based on adjustable chip resistor is proposed to control the reflected phase by rotating the knob of the rheostat. The designed metasurface can realize the functional reconstruction without external circuitry. As an example, a reconfigurable digital coding metasurface is fabricated, which is verified through both the simulation and experimentation. All the results show that the designed sample can customize the far-field scattering mode. This work provides a new idea for reconfigurable metasurfaces, which will lay the foundation for the intelligent control of metasurfaces.

Ultrathin Broadband Dual‐Ring Metamaterial Absorber Based on Chip Resistance

Herein, an ideal metamaterial absorber with broadband, ultrathin, and wide incidence angle is proposed. The absorption unit of the proposed metamaterial absorber consists of two double rings. And, eight chip resistors are loaded between them to increase the absorption bandwidth. It is showed in the simulation results that the structure absorbs more than 90% in the range of 8.6–17.4 GHz at vertical incidence. The total thickness of the absorber is 2.4 mm (0.069 λL), where λL is the lowest‐absorption frequency, smaller than the absorber structure of the same type of bandwidth. To understand the broadband absorption performance of this absorber, the effects of design parameters such as substrate thickness and resistive resistance are investigated. In addition, herein, to investigate the absorption mechanism of this absorber, the normalized impedance, electric field distribution, and surface current density are demonstrated. Finally, the absorber is fabricated and measured at vertical incidence, and the experimental results are in good agreement with the simulation results.

Mutual coupling reduction for monopole MIMO antenna using l-shaped stubs, defective ground and chip resistors

In this paper, a symmetrical and compact monopole multiple input multiple output (MIMO) antenna is designed with two feeding ports. To reduce the mutual coupling between antenna elements, the l-shaped stubs and the defective ground structure (DGS) are used, and additionally the chip resistors are loaded. By optimizing the length of stub, the elements isolation can be improved remarkably. Then, two rectangular slots are etched on the metal ground as DGS to change the path of electric current so as to enhance the isolation further. Also, through loading the chip resistors to control the coupling current on the stubs, the isolation can be strengthened once more. The simulation and measurement results show that this antenna has the mutual coupling of −36 dB, the envelope correlation coefficient (ECC) of 0.002 and the diversity gain (DG) of 9.99 dB at resonance along with the radiant peak gain of 4.03 dBi.

Adaptive Hybrid Framework for Multiscale Void Inspection of Chip Resistor Solder Joints

Adaptive Hybrid Framework for Multiscale Void Inspection of Chip Resistor Solder Joints

A dual-transmission-bands rasorber with improved absorption and oblique incidence performance

In this paper, a high-absorption and dual-transmission-bands rasorber (HADTR) was proposed. Different from the reported designs, a foam layer and a FR4 layer are added as top layers in HADTR to improve its absorption and oblique incidence performance. The unit cell of resistive layer is concentric metallic rings loaded with chip resistors based on absorption enforced design to ensure its dual-transmission-bands at the same time. The unit cell of band-stop frequency selective surface (BS-FSS) is double metallic square loops loaded with chip inductors on both sides of FR4 substrate, which expands its reflection band (|S11|≥ − 1.0 dB) without destroying its dual-transmission-bands effectively. At normal incidence, for TE and TM polarization, the HADTR has a low-frequency passband up to 1.34 GHz (|S21|≥ − 1.5 dB), a high-frequency passband from 16.04 to 18.00 GHz (|S21|≥ − 1.5 dB) and a wide 90% absorption band from 5.01 to 10.56 GHz; and the reflection coefficient below − 10 dB and − 20 dB is in the range of 4.48–11.70 GHz and 5.48–9.96 GHz, respectively. For TE/TM polarization, the 90% absorption of oblique incidence stability is 40° and 30° respectively. Strong association between measurement and simulation results validates the design method and the HADTR.

Effect of temperature on vibration durability of lead-free solder joints

Safety critical electronics in automotive, avionic or military applications have to work reliably in a range of harsh conditions, including simultaneous mechanical and thermal loads (Gromala, 2021; Qi et al., 2009 [1, 2]). The durability of electronics, more specifically their board level interconnects, under vibration and thermal loads must be investigated and understood for interconnects assembled with lead-free solder alloys. In this study, isothermal vibration fatigue tests have been carried out at −40 °C, 25 °C and 125 °C. A novel test specimen, specifically designed for combined vibration and temperature cycling experiments, was used for this study. The test PCB contains leadless chip resistor (LCR) components, soldered using the SAC105 solder alloy (Sn98.5Ag1.0Cu0.5). Failed specimens at each temperature were subjected to destructive physical analysis (DPA) for root cause analysis (RCA) of the observed failures. Dynamic finite element analysis (FEA) was carried out and combined with the experimental results in order to generate fatigue strain-life (SN) curves. Two opposing effects of increasing temperature - viz. decrease of fatigue strength for high-cycle fatigue (HCF) and increase of fatigue ductility for low-cycle fatigue (LCF) - are hypothesized to be responsible for this non-monotonic behavior.

A high absorptance wide-band metamaterial absorber with metasurface and low-permittivity dielectric slabs

In this paper, a new wide-band and high-absorption metamaterial absorber (WHMA), consisting of a metasurface (MS), three low-permittivity dielectric slabs, and a metal backplane, is proposed and fabricated. The unit cell of MS is concentric rings loaded with chip resistors. This structure exhibits excellent absorption property and improved stability of oblique incidence, which are difficult to be achieved in previous radar absorbing materials. The functions of MS and different dielectric slabs are analysed. At normal incidence, the simulated results indicate that −10 dB absorption and −20 dB absorption bands cover a bandwidth of 4.8–14.3 GHz and 5.70–13.57 GHz, respectively. The measured results show that −10 dB and −20 dB absorption are achieved with the bandwidth of 4.6–16.3 GHz and 5.5–14.4 GHz respectively at normal incidence; below 50° angle of oblique incidence, WHMA can still have wide-band −10 dB absorption. The agreement between simulation and measurement validates the proposed design. Finally, since the structure is made of foam and thin dielectric layers, the area density is relatively low.

An Ultrawideband and High-Absorption Circuit-Analog Absorber With Incident Angle-Insensitive Performance

This work presents an ultrawideband and high-absorption structure (UHAS) obtained by a fast design method. The proposed analytic approach can simply design single-FSS-layer absorber with ideal performance stability under oblique incidence. With this method, a composite material reinforced circuit-analog (CA) absorber is designed, which unit cell of CA sheet is a square ring loaded with chip resistors. At normal incidence, both TE and TM polarization simulation results demonstrate that the reflection coefficient below −10 dB is from 5.8 to 22.2 GHz; meanwhile, the reflection coefficient less than −20 dB covers a bandwidth of 7.4–19.1 GHz; also, there is a −30 dB absorption band in 8.6–17.2 GHz. Furthermore, under TE polarization, experimental results indicate that UHAS can maintain a −20 dB absorption band from 7.4 to 18.0 GHz within 40° oblique angle of incidence; −10 dB absorption is from 6.1 to 18.0 GHz within 50° oblique angle of incidence. The good agreement between simulation and measurement validates the proposed method and UHAS. Finally, the UHAS, with a protective layer, will be more stable in practical applications.