High Humidity Test Research Articles

P‐5.10: Lifetime Prediction Model for Microcapsule Electrophoretic Display Device Based on High Temperature and High humidity Test

The failure mode of electronic paper display under different temperature and humidity conditions is studied in this paper. Nine high temperature and high humidity conditions are designed for the verification, it is found that the Arrehenius accelerated life model and the Peck accelerated life model are not suitable for the lifetime prediction of Microcapsule Electrophoretic Display Device. Therefore, based on these two accelerated life models, the new model is proposed, which is a new acceleration method for Predicting the lifetime of Microcapsule Electrophoretic Display Device, and the feasibility of this model has been theoretically confirmed.

Copper electrochemical migration growth in an air HAST

High performance electronics require printed circuit boards (PCBs) with an extremely narrow pitch between adjacent copper patterns. However, copper electrochemical migration in these fine-pitch PCBs is a major source of failure. This phenomenon is typically identified using a highly accelerated temperature and humidity stress test (HAST) in which the water vapor pressure inside a chamber is increased along with the temperature and humidity. However, a side effect of this is that little air remains in the chamber despite air being required when replicating actual environments. This can be overcome by using an air HAST system that includes air inputs in its chamber. In our experiments, we analyzed the copper electrochemical migration on coupon samples with a 125 μm pitch at temperatures above 120 °C under various air pressures. We then compared the results for the air HAST, HAST, and high temperature and high humidity (85 °C/85% R.H.) tests by plotting each lifetime in the form of a Weibull distribution. Upon inspection, the cross-sectional microstructures of the copper electrochemical migration were seen to vary between the HAST and air HAST methods due to differences in the growth mechanism of the copper electrochemical migration.

Thermostability and reliability properties studies of transparent Ce:GdYAG ceramic by Gd substitution for white LEDs

Abstract Yttrium Aluminum Garnet transparent ceramics with different Gd3+ concentrations ((Ce0.001GdxY0.999-x)3Al5O12) ceramics were prepared by the conventional solid state reaction technology and vacuum sintering method, and the ceramic-based LEDs with blue LED were prepared by flip chips and Chip on board package. The extreme circumstance of −40 °C and 150 °C alternate environments, high humidity and high temperature as well as xenon lamp aging test for a long time are mentioned to explore the reliability of phosphor ceramics, respectively. And the thermostability and the effect of Gd3+ doping on the PL properties of ceramics were also investigated. What is more, the effects on the optical performance of the ceramic-based LEDs have been also investigated. As Gd3+ concentration added from 0 to 0.5, the PL spectra peaks of phosphor shifted from 542 nm to 575 nm under the excitation of 460 nm. It can be summarized that the increase of Gd3+ concentration could not improve the thermostability, but enhance the reliability when the x value is x is not greater than 0.4. What is more, the ceramics-based LED of x = 0.3 instead of x = 0.4 has the best reliability after the xenon lamp aging and thermal cycling test. And the ceramics-based LED of x = 0.45 has the best reliability after the high humidity and high temperature test. Compared with Ce:YAG and Ce:LuAG ceramics, although the increase of Gd3+ concentration decreases the thermostability and luminous efficiency, the Gd substitution can enhance the reliability and solve the lack of red light in the spectrum of Ce:YAG and Ce:LuAG ceramics, which has improved the performance of Ce:GdYAG ceramics for high-power warm white LEDs.

Effect of Air-HAST Conditions on Sn Whisker Growth

Sn whiskers are one of the major causes of failure in fine-pitch electronics because of the short distance between the leads in an electronic package. In various whisker mechanisms, it takes a long time to grow a whisker due to Sn corrosion because the temperature is limited to below 100°C in high humidity. In the highly accelerated temperature and humidity stress test (HAST), the corrosion phenomenon rarely occurred because of the little air inside the chamber. Therefore, air is needed in the whisker accelerating test to meet the same whisker mechanism under high temperature and humidity conditions. In this study, an Air-HAST with air inputs in the chamber with highly temperature and humidity was introduced. Whisker growth was accelerated with temperatures at 130°C and various air pressures using the thin quad flat package (TQFP) sample with Sn plating lead. The whisker growth in the Air-HAST, HAST, and high temperature and high humidity test (85°C, 85%R.H.) was compared by plotting each growth length and number of whiskers. The accelerated relationships of whisker growth under the various test conditions will help the electronic industry meet the short development cycles. Key words: Sn whisker, Air-HAST, 85°C/85%RH, HAST, TQFP

PRELIMINARY TECHNICAL DISCUSSION ON A NEW RADON AND ITS PROGENY CONTINUOUS MONITOR USING TWO-FILTER METHOD.

Focusing on the scalability of Two-Filter Method, we started to develop a monitor for the concentration of radon and its progeny. In this study, we investigated the influence of a high-humidity environment on measuring radon concentration, and the influence of the decay chamber of the monitor on the measurement. In the high-humidity test, the conversion factor of (Bqm-3)/(cpm) tends to raise with increasing humidity. On the measurement of radon progeny, existence of the decay chamber of the monitor makes measurement sensitivity lower under environments of little aerosols. Radon concentration measurement by the developed monitor could be influenced by environmental humidity, and that counting loss could occur due to deposition of radon progeny inside of the decay chamber. Correction relating these would be needed based on the data of calibration tests.

Influence of multi-walled carbon nanotube (MWCNT) concentration on the thermo-mechanical reliability properties of solderable anisotropic conductive adhesives (SACAs)

Abstract In the present work, the influence of multi-walled carbon nanotube (MWCNT) concentration on the thermo-mechanical reliability properties of carbon nanotube (CNT)-filled solderable anisotropic conductive adhesives (SACAs) containing low-melting-point-alloy (LMPA) fillers was investigated. To measure the reliability-related properties of SACA assemblies, six types of SACAs with different MWCNT concentrations (from 0 to 2 wt%) were formulated, and two types of reliability tests, thermal shock (TS) and high-temperature and high-humidity (HTHH) tests, were conducted on these samples. All of the CNT-filled SACA assemblies with different MWCNT concentrations showed proper and stable electrical reliability during each aging test, due to the molten LMPA fillers forming a metallurgical interconnection between the corresponding metallization regions. Although the mechanical strength of the CNT-filled SACA joints degraded after aging tests due to excessive intermetallic compound (IMC) layer growth, the CNT-filled SACAs with an MWCNT concentration below 0.1 wt% exhibited better mechanical reliability properties than those of SACAs without MWCNTs due to the initially achieved high bonding strength of the SACA joints, enabled by the reinforcing effects of the MWCNTs within the polymer composites.

Mechanical Property of SAC305 Ball-Grid Array and Epoxy Sn-58Bi Solder Joints with 85 °C/85% Relative Humidity Environmental Conditions.

The ball-grid array (BGA) is widely used to reduce component size and it had advantages such as high I/O pins and fine pitch. Typical Sn-Ag-Cu (SAC) solder alloys are used for formation of BGA because SAC solder has excellent characteristics among lead-free solders. However, the electronic components assembled by SAC solder were easily damaged by heat during manufacture process because SAC solder had high melting point of 220 °C. To prevent these thermal damages, SAC305 BGA component assembled by Sn-58Bi solder paste has been studied because Sn-58Bi solder had low melting point of 139 °C. In generally, Sn-58Bi solder was improved by additional elements or polymer such as epoxy because Sn-58Bi had a brittle property. However, the epoxy Sn-58Bi solder did not guaranteed high environmental reliability such as high-temperature high-humidity (HTHH) test. Thus, we evaluated the shear strength of solder joints assembled by SAC305 BGA components with Sn-58Bi solder paste and epoxy Sn-58Bi solder paste. The shear strength of solder joints was evaluated by die shear test after HTHH test at the 85 °C/85% RH conditions. The Cu6Sn5 intermetallic-compound (IMC) at the interface of solder joints was observed by scanning electron microscope (SEM). The IMC thickness of Sn-58Bi solder joints was smaller than that of epoxy Sn-58Bi solder. The shear strength was improved up to 20% by epoxy addition. The shear strength of epoxy Sn-58Bi solder joints dramatically decreased after HTHH test for 100 h.

Reliability of Acceleration Sensor Data Under Environmental Stresses for Remote Machine Monitoring

Remote monitoring of mechanical equipment using sensor data has been widely discussed. This type of monitoring has the risk of its sensor output changing because of environmental stresses. This means that fluctuations in the sensor data include fluctuations caused by changes in the state of the equipment and changes in the sensor output itself. However, it is hard to determine the cause of fluctuations from remote locations. It is important to first determine possible causes of fluctuations in order to ensure the reliability of the sensor data. Acceleration sensing is one effective way to monitor the failure of rotating equipment. The output of an acceleration sensor changes depending on the state of its mounting [1, 2]. Major mounting methods include fixing with screws, magnets, wax, and adhesives. Fixing with screws is the stiffest method, but necessary installation costs include that of drilling the screw hole in the equipment. Although fixing with magnets is the easiest installation method, there is the concern that the magnetic field may adversely affect the rotating equipment. Wax fixing and adhesive fixing is also easy and stiff method. The concern for these types of fixing are their weakness against heat and environmental stresses. The environmental stresses that rotating equipment undergoes during operation are: temperature cycling between room temperature and operation temperature (approximately 90° C), humidity, and the adherence of water, oil, chemicals, and salt. The long-term reliability of various mounting methods under such environmental stresses has not been sufficiently studied. We constructed a measurement setup to evaluate the transmission characteristics of mountings and investigated the influences of environmental stresses. The measurement setup was modeled as a series connection of an acceleration sensor with an internal mass m and an internal spring constant k and of a mounting with a mass M and a spring constant K (Fig. 1). The input vibration is transmitted to the sensor through the mounting. The sensor output is proportional to the acceleration of the internal mass influenced by two springs. Measurements were taken using the following procedure to identify the effect of the mounting alone. First, the input vibration of sine waves from 100 Hz to 14 kHz was measured using a laser Doppler vibrometer (LDV). Next, a metal block simulating a sensor was attached and the vibration of the metal block was measured using the LDV. The attachment corresponds to the addition of m, M and K without adding k. Transmission characteristics were determined by calculating the output/input amplitude ratio. With this method, the effect of the internal spring is eliminated and the mounting alone is evaluated. First, the transmission characteristics of fixing using a screw (M6, 6.5 mm long) was measured (Fig. 2). When the screw was tightened with a managed torque exceeding 3 Nm, the transmission characteristics were relatively flat up to 10 kHz. However, a resonance peak appeared at around 10.5 kHz when the screw was tightened by hand (< 3 Nm). Therefore, the torque should be controlled to exceed 3 Nm. Next, wax fixing was tested. There was no significant resonance peak below 14 kHz at room temperature. However, the wax detached at around 40° C. Finally, adhesive fixing was tested. The volume of the adhesive (Aron Alpha # 202, Toagosei) was adjusted to 2 μL using a micropipette. A resonance peak did not appear below 14 kHz. The following two tests were carried out to check durability against environmental stresses: a temperature cycling test, wherein a samples was exposed to 30 cycles of ˗40 to +85° C temperature cycling, and a high temperature and humidity test, wherein samples were exposed to 85° C and 85% relative humidity conditions for 10 hours (three samples) and 300 hours (one sample).The metal block detached in the temperature cycling test and in the sample tested for 300 hours in the high temperature and humidity test (Fig. 3). However, no changes in the transmission characteristics were observed before detachment for all five samples. The results are summarized in Table 1. For fixing with a screw, torque management is necessary. Wax fixing is not suitable because detachment occurs at a relatively low temperature. Adhesive fixing can be considered a good mounting method on the basis of our findings thus far. Degradation caused by further environmental stresses are under investigation. D. Marine et al. Special Topics in Structural Dynamics, 6, pp. 53–66, (2017).Z. Liu et al. 2016 3rd International Conference on Information Science and Control Engineering, pp. 862–866, (2016). Figure 1

Effect of gallium ion content on thermal stability and reliability of YAG: Ce phosphor films for white LEDs

Abstract Y 2.94 (Al 1−x Ga x ) 5 O 12 :0.06Ce (x = 0.05, 0.1, 0.15, 0.2, 0.25, 0.3) phosphors were prepared by conventional solid-state reaction. Phosphor films are prepared from the synthesized Y 2.94 (Al 1−x Ga x ) 5 O 12 :0.06Ce phosphors by a simple spin coating method. The influence of different content of Ga 3+ doping on the photoluminescence (PL) spectra, thermal stability and reliability of prepared Y 2.94 (Al 1−x Ga x ) 5 O 12 :0.06Ce (x = 0.05, 0.1, 0.15, 0.2, 0.25, 0.3) phosphor films were investigated. The emission peak of the Y 2.94 (Al 1−x Ga x ) 5 O 12 :0.06Ce (x = 0.05, 0.1, 0.15, 0.2, 0.25, 0.3) phosphor films shifted from 545 nm to 520 nm with the Ga 3+ content(i.e. the value of x) increasing from 0.05 to 0.3 excited at 460 nm. The phosphor films have excellent thermal stability, and the intensities of PL spectra decrease by about 2%, 5%, 20% and 50% at 373 K, 423 K, 473 K and 523 K, respectively. The xenon lamp aging test show that the relative PL spectra intensity of the phosphor films decreases to 95.55%, 96.24%, 96.05%, 97.67%, 95.96% and 93.22% with the x value is 0.05, 0.1, 0.15, 0.2, 0.25 and 0.3 after the xenon lamp aging test for 168 h. The high temperature and high humidity test show that the relative PL spectra intensity of the phosphor films decreases to 94.36%, 95.6%, 95.26%, 96.87%, 95.28% and 93.1% with the x value is 0.05, 0.1, 0.15, 0.2, 0.25 and 0.3 after the condition of 85 ℃/RH85% for 168 h. The thermal cycling test show that the relative PL spectra intensity of the phosphor films decreases to 90.6%, 91.4%, 93.76%, 94.38%, 91.84% and 88.81% with the x value is 0.05, 0.1, 0.15, 0.2, 0.25 and 0.3 after the condition of 120 ℃ for 1 h and −40 ℃ for 1 h by turns for eight times. So, it can be generalized that low level of Ga 3+ doping can enhance the thermal stability and reliability of Y 2.94 (Al 1−x Ga x ) 5 O 12 :0.06Ce phosphor films.

Effect of high temperature high humidity and thermal shock test on interfacial intermetallic compounds (IMCs) growth of low alpha solders

In this study, the effects of high temperature high humidity aging conditions and thermal shock tests on the growth of intermetallic compounds (IMCs) in low alpha Sn–1.0Ag–0.5Cu (LA-SAC105) solder and low alpha Sn (LA-Sn) solder have been investigated. The aging has been performed at 50, 85 and 150 °C for 30, 70 and 120 h at a relative humidity (R.H.) of 40 and 85%. The thermal shock tests of LA solders has been performed from −65 to 150 °C for 100, 200, 400, 600, 800 and 1000 thermal cycles, and the results are compared with the normal SAC105 and Sn solders. It is observed that the evolution of Cu–Sn IMCs with aging time and temperature is diffusion controlled and the IMC thickness increases linearly with square root of aging time. The thickness of IMCs of LA-SAC105 and LA-Sn is smaller than that of SAC105 and Sn solders. It is also observed that as the number of thermal cycles increased, the IMC grain coarsening occurs in case of LA-SAC105 and as well as LA-Sn solders. In addition, whisker growth is noticed in LA-Sn and Sn solders. However, the LA-Sn has the lower sensitivity towards the whisker growth. On the contrary, a rapid growth and cracking of the IMCs formed at the interface of the normal SAC105/Cu system causes the solder sample to detach from the joint after 600 cycles, as compared to the LA-SAC105/Cu which resists the fracture up to 1000 cycles. The LA-SAC105 and LA-Sn can reduce the growth of IMCs when compared with the normal SAC105 and Sn as reference solders and may improve the solder joint reliability.

Research and Development on 8-­Wavelengths Dual-Lamp Combined with Lamp and Ballast

This study was to develop the products that the Lamp and Ballast are combined for the purpose of easy installation to complement the difficulty of the installation process due to the structure of existing product which the lamp and the Ballast are separated, and that have 8-wavelengths dual-lamp structure such as solar, an advantage of more than 3 times longer life than fluorescent lamp and immediately lighting. This study developed the commercialized products that can prevent the environmental pollution caused by low efficiency and short life time of existing Lamps, and can replace the LED Lighting products which has high Glare index with high price, has also developed the variety of application for industrial, commercial, indoor and military. The applied product are Street lights, Security lights, Flood lights, Indoor lights and lights for fishing. This study solved the optimum distribution and placement of components considering the lightest weight first and thermal interference caused by combination of lamp and ballast by thermal release through applying the double bulkhead design of ballast box, and implemented the high efficiency Eco-friendly products with excellent visibility which can be applied and used for indoor and outdoor both place through high temperature and high humidity test, which has an advantage of 8-wavelengths of same spectrum of solar through the initial trial production.

Reliability of Passive UHF RFID Copper Tags on Plywood Substrate in High Humidity Conditions

The growth of the wireless world, especially the increasing popularity of the Internet of Things, has created a need for cost-effective and environmentally friendly electronics. Great potential lies especially in versatile applications of passive UHF RFID components. However, the reliability of these components is a major issue to be addressed. This paper presents a preliminary reliability study of glue-coated and non-coated brush-painted copper tags on a plywood substrate in high humidity conditions. The passive UHF RFID components presented in this paper are fabricated using brush-painting and photonic sintering of cost-effective copper oxide ink directly on a plywood substrate. The performance of the glue-coated and non-coated tags is evaluated through wireless tag measurements before and after high humidity testing. The measurement results show that the copper tags on plywood substrate initially achieve peak read ranges of 7–8 meters and the applied coating does not affect to the read range. Moisture does not prevent the coated tags from working in a tolerable way, although the tag performance slightly temporarily decreases due to the moisture absorption. However, when the moisture exposure is long, the performance degradation comes irreversible. The absorbed moisture decreases the read range of the non-coated tags and the performance does not return back to normal after drying. Hence, the coating improves the reliability of the tags in a moist environment compared to the non-coated tags. Based on our results, the plywood material and the used manufacturing methods are very potential for low-cost, high-volume green electronics manufacturing.

Effect of multi-walled carbon nanotube (MWCNT) concentration on thermomechanical reliability of MWCNT-reinforced solderable isotropic polymer nanocomposites

Multi-walled carbon nanotube (MWCNT)-reinforced solderable isotropic polymer nanocomposites (SIPNs) containing low-melting-point alloys (LMPAs) were developed to enhance the interconnection properties of solderable isotropic polymer composites (SIPCs). In this study, the reliability properties of MWCNT-reinforced SIPN assemblies with different MWCNT concentrations were investigated through thermal shock (−55–125 °C, 1000 cycles) and high-temperature and high-humidity (85 °C, 85 %RH, 1000 h) tests. In addition, the interfacial microstructure and fracture mode of the MWCNT-reinforced SIPN joint were investigated. All the MWCNT-reinforced SIPN assemblies, with different MWCNT concentrations, showed stable electrical reliability during reliability tests owing to the formation of a metallurgical interconnection between the corresponding metallization layers by molten LMPA fillers. The mechanical reliability properties of all the MWCNT-reinforced SIPN assemblies degraded owing to excessive intermetallic compound (IMC) layer growth. However, the mechanical reliability properties of MWCNT-reinforced SIPNs with a low MWCNT concentration (<1 wt%) were superior to those of the SIPNs without MWCNTs owing to the initial high bonding strength of the former due to the reinforcing effect of MWCNTs.

3-D-Stacked 16-Mpixel Global Shutter CMOS Image Sensor Using Reliable In-Pixel Four Million Microbump Interconnections With 7.6-&lt;inline-formula&gt; &lt;tex-math notation="LaTeX"&gt;$\mu \text{m}$ &lt;/tex-math&gt;&lt;/inline-formula&gt; Pitch

We have developed a 3-D-stacked 16-Mpixel, 3.8- $\mu \text{m}$ pitch, and global shutter (GS) CMOS image sensor with a 2-Mpixel 10 000-frames/s high-speed image-capturing mode, with four million reliable microbump interconnections. This sensor consists of a photodiode (PD) substrate and an in-pixel storage node substrate. The four PDs in the unit pixel circuit on the top substrate share one microbump interconnection in 7.6- $\mu \text{m}$ pitch. Each signal of the PDs is transferred to the corresponding storage node on the bottom substrate via the interconnection to achieve a GS function. The ratio of the parasitic light sensitivity of an in-pixel storage node and the light sensitivity of a PD is −180 dB, which is the best record for a CMOS image sensor with 3.8- $\mu \text{m}$ pixels. The image sensor was fabricated with a wafer-on-wafer bonding process technology. We confirmed that the bonding process did not harm the pixel or the MOS transistor characteristics and required no extra area, which means no restrictions on the layout design of microbumps or circuits. No reliability problems were observed in either a heat cycle test or a high temperature and high humidity test.

硬X 線光電子分光法による有機薄膜太陽電池の分析

Metal/organic interfaces in organic thin-layer photovoltaic cells were investigated by means of hard X-ray photoelectron spectroscopy (HAXPES). The large detection depth of HAXPES using 6 keV X-rays allowed to study the buried organic layer, poly (3,4-ethylenedioxythiophene) : polystyrene sulfonate (PEDOT : PSS), through the Ag electrode. PEDOT : PSS showed two additional S 1s peaks at the Ag electrode interface, which could be associated with thiolate-like species and Ag sulfides. The latter peak increased after the high-humidity test, indicating that the interface reaction proceeded during the test. Severe X-ray-induced damage of PEDOT : PSS layer was also observed, mainly due to the transformation of sulfonate groups of PSS to the lower oxidation-state forms. Nevertheless, HAXPES showed to be one of the powerful tools to study the buried interface of organic devices as it is.

EVA(Ethylene Vinyl Acetate) 수지가 태양전지의 장기적인 수명에 미치는 영향에 관한 실험적 연구

Abstract In this study, analysed the characteristics of power drop and surface damage in solar cell through high temperature and humidity test in the 3 case of EVA(ethylen e vinyl acetate) and 2 case ribbon thickness. The solar cells were tested during the 500hr in 85℃ temperature and 85% relative humidity conditions, that excerpted standard of PV Module(KS C IEC-61215 ). Through the EL(Electroluminescence) shots, specimen's surface have partialy damaged. Before and after high humidity and high temperature test, ribbon thickness 200㎛ EVA1 case power drop rate was 8.463%, EVA2 case was 6.667%, EVA3 case was 6.373%. In the ribbon thick ness 250㎛ EVA1 case power drop rate was 6.521%, EVA2 case was 8.517%, EVA3 case was 6.019%. EV A3 case was the lowest power and FF(fill factor) drop rate at the 2 case of ribbon thickness , because EVA3 is laerger than EVA1 and EVA2 in thickness, elongation and tensile strength.Keywords : Solar cell, EVA(ethylene vinyl acetate), High temper ature and high humidity, EL(electroluminescence)

Thermo-mechanical reliability of a multi-walled carbon nanotube-incorporated solderable isotropic conductive adhesive

Abstract Carbon nanotubes (CNTs) are considered as ideal candidates for the reinforcement of polymer composites due to their superior physical properties. In this paper, in order to investigate the influence of multi-walled carbon nanotubes (MWCNTs) on the reliability properties of solderable isotropic conductive adhesives (SICAs) with a low-melting-point alloy (LMPA), two types of SICAs (with 0.03 wt.% MWCNTs and without MWCNT) were formulated. Thermal shock (− 55 to 125 °C, 1000 cycles) and high-temperature and high-humidity (85 °C, 85% RH, 1000 h) tests were conducted on these samples. The SICA assemblies with and without MWCNTs showed stable electrical reliability properties during reliability testing; this stability was due to the formation of excellent metallurgical interconnection between corresponding metallization by the molten LMPA fillers. Although the mechanical pull strength of SICA assemblies decreased after thermal aging, due to the excessive layer growth and planarization of the IMCs, the SICA with MWCNTs showed enhanced mechanical reliability properties compared with the SICA samples without MWCNTs. This improvement in performance was caused by the enhancement effect of the MWCNTs. These results demonstrate that MWCNTs within SICAs can enhance the reliability properties of SICA joints due to their outstanding physical properties.

Carbon nanotube-silver nanowire composite networks on flexible substrates: High reliability and application for supercapacitor electrodes

Highly transparent, flexible and conductive networks of carbon nanotubes-silver nanowire networks were formed on polyethylene terephthalate (PET) substrates. The high temperature and humidity tests reveal that our CNT–AgNW composite networks maintain high durability and reliability in the electrical and optical properties under high temperature (85 °C) and relative humidity (85% R.H.). When bent and flexed over 1000 cycles; the films did not show significant degradation in sheet resistance compared to Ag films and ITOs on the same flexible substrates; demonstrating the superior mechanical stability of our CNT–AgNWs networks. The composite films on PET were employed for supercapacitor electrodes. The supercapacitors demonstrate a mass specific capacitance of 143 Fg−1 with a stable charge-discharge (3000 cycles) and low internal resistance (16 Ω). Furthermore; the supercapacitors showed high durability under harsh climatic conditions and mechanical bending. Our works indicate that the CNT–AgNWs could be promising transparent conductive electrodes for the applications in flexible optoelectronics and energy storage devices.

An investigation of the reliability of solderable ICA with low-melting-point alloy (LMPA) filler

Conductive adhesives play a major role in the electronic packaging industry as an alternative to solder due to their potential advantages that include mild processing conditions and superior thermo-mechanical performance. In a conductive adhesive interconnection, adequate mechanical and electrical performance and long-term reliability are critical. In this paper, the reliability of solderable isotropic conductive adhesive (ICA) interconnections was investigated. Reliability testing was performed via thermal shock (−55 to 125 °C, 1000 cycles) and high-temperature and high-humidity tests (85 °C, 85% RH, 1000 h). The interfacial microstructure of the solderable ICA was also investigated. Additionally, the fracture mode was investigated via mechanical pull strength testing before and after the reliability test. The electrical resistance of the solderable ICA interconnection showed improved stability compared to conventional ICAs, and similar stability to conventional solder paste (Sn–3Ag–0.5Cu and Sn–58Bi) due to the metallurgical interconnection formed by the molten LMPA fillers between the corresponding metallization layers. After the reliability tests, the grown IMC layer was composed of Cu6Sn5 (η-phase) and Cu3Sn (ε-phase), and the scallop-type IMC transformed into a layer-type IMC. The fracture propagated along the Cu–Sn IMC/SnBi interface and the fracture surface showed a semi-brittle fracture mode mixed with cleavage and ductile tear bands.

Reliability of adhesive joined thinned chips on flexible substrates under humid conditions

Abstract Thin chips are an interesting option for reducing the thickness of an electronics package. In addition to the reduced size, thinned chips are flexible and can dissipate more heat than thicker ones. Joining of the thin chips can be done using several different techniques. Of these, anisotropic conductive adhesives (ACA) are an interesting option as they have several advantages, such as low bonding temperature and capability for high density interconnections. The reliability of ACA flip chip joints under thermal cycling conditions has been found to increase when thinned chips are used. However, the effect of humidity has not been fully explored. In this study the reliability of thinned chips (50 μm) under humid conditions was investigated using thin flexible substrates. Seven test lots were assembled with thinned chips using two different ACA films and liquid crystal polymer (LCP), polyimide (PI) and thin FR-4 substrates. A high humidity and high temperature test was used to study the reliability of the interconnections. A finite element model (FEM) was used to analyse the stresses in the test samples during testing. Several failures occurred during the test and significant differences between the substrates were seen. Additionally, bonding pressure was found to be a critical factor for the reliability under the humid conditions.