Pressure Cooker Test Research Articles

Effect of hydrolysis stabilizers on anti-aging performance of PET under pressure cooker test

Polyethylene terephthalate (PET) is extensively utilized in various industries due to its good properties. However, as a kind of polyester, PET is apt to hydrolysis when exposed to moisture and heat, which severely affects its performance and service life. Hence, the incorporation of hydrolysis stabilizers is a common mitigation method. In this work, the PET specimens modified by two types of hydrolysis stabilizers were subjected to the pressure cooker test to evaluate the improvement effect, and the resultant changes in appearance, mechanical properties, and thermal characteristics were studied. Additionally, the crystallinity and infrared peaks were detected to assess the effectiveness of the hydrolysis stabilizers and to reveal the aging mechanisms of PET. The results indicated that PET underwent three distinct aging processes during the pressure cooker test, including crystallization, water plasticization and hydrolysis, and the inhibitory effect of the hydrolysis stabilizers mainly reflected in the crystallization and hydrolysis processes while the effectiveness depended on their types and concentrations.

Influence of interfacial interaction on the reliability of the bond between encapsulation epoxy and copper substrate

The need for power modules has been promoted by the emergence of electric vehicles. The requirements of small volume, high integrity, and high reliability for the next-generation power module lead to the change of encapsulation method from previous gel encapsulation to epoxy encapsulation. Efforts have been made to enhance epoxy materials, and commercialized high-end epoxy has shown excellent properties, but power module failures still exist. The possible reason may lie in the interfacial interaction between encapsulation epoxy and substrate, which is less noticed previously. This paper seeks to unveil the influence of interfacial interaction on the bonding reliability between encapsulation epoxy and copper substrate. Three reliability tests were performed: high-temperature storage test (HST), temperature cycling test (TCT), and pressure cooker test (PCT). The bonding strength after these reliability tests was evaluated, and the bonding interface and fracture surface were analyzed in a nanoscale. Our study discovered that interfacial interaction plays a vital role in encapsulation reliability. Copper can diffuse into the epoxy and catalyze epoxy thermal oxidative degradation, which results in bonding strength reduction after HST and PCT. The surface structure change caused by copper oxidation after HST and PCT also reduced the bonding strength. These findings will greatly benefit future power module design.

Comparative study of the aging degradation behaviors of PET under artificially accelerated and typical marine environment

The aging degradation behaviors of the most common PET plastics in the marine environment were investigated in different conditions, with the combination of "real-world sample/outdoor simulation/aging box accelerated simulation". By obtaining data on the morphology, biological and microbial distribution, mechanical properties, viscosity, color difference, thermal properties, and chemical composition of marine plastics after aging, the influence of typical environmental factors such as light, temperature, high pressure, salinity, moisture, and marine life on the aging degradation behavior of PET plastics were discussed. Among them, light, high pressure heat and humid environment have the most significant effects on degradation, while the high-salt environment has less effect on degradation. In addition, the Pressure Cooker Test (PCT) results showed that the ordinary cleaning process is not enough to remove the inorganic substances that penetrated into the interior of marine plastics, which will have a negative impact on the performance of marine plastics. Therefore, it is necessary to select appropriate recycling methods and processes. This study provides a new idea for the study of the aging degradation behavior of marine plastics, which is important for analyzing the environmental factors affecting the degradation behavior of marine plastics in the marine environment.

Novel EPE co-extruded encapsulating films with UV down-conversion power gain effect for highly efficient solar cells

How to maintain or even improve the performance of solar cells under the influence of high temperature, high humidity and intense ultraviolet light has always been a challenging research topic. Here, we propose a novel and effective solution by combining the benefits of EVA (ethylene vinyl acetate), POE (polyolefin) and UV down-conversion (UV-DC) fluorescent nanomaterial (Sr2-xMgSi2O7-x: Eu2+, Dy3+) to construct the first commercially available UV-DC EPE co-extruded encapsulating film with a three-layer composite structure. On the one hand, the UV-DC EPE incorporates the high adhesive strength of EVA and the strong weather resistance of POE. On the other hand, the UV-DC EPE can also convert the UV irradiation, inefficient for power generation and easily cause damage to solar cells, into visible light range with high quantum efficiencies. Therefore, we discover that the UV-DC EPE not only shows higher stability than other encapsulation films under potential-induced degradation (PID), pressure cooker test (PCT), UV and natural sunlight aging tests, but also enhances the power generation efficiencies by 0.3% and 2.3% compared with the UV-transmitting and the UV-filtering EPE films, respectively. The progress in this work breaks the stereotypical definition of encapsulation that only slows down attenuation, but integrates the advantages of power gain effect, high stability, and low cost into the novel encapsulation material and technology, which is expected to be promoted and industrialized in the near future.

Effect of NdCoGa alloy addition to waste wind turbine magnets to enhance the characteristics of recycled sintered NdFeB permanent magnets

Neodymium (NdFeB) permanent magnets play a key role in motors and other devices, and are important to both defense and civilian industrial uses; however, due to the limited rare earth resources, the issue of recycling waste NdFeB magnets to achieve sustainable development has attracted much attention. An innovative and valid method for the recycling of waste NdFeB magnets is demonstrated in this study. Recycled sintered NdFeB permanent magnets were prepared on a large scale up to 100 kg per batch by adding NdCoGa ternary rare earth alloy to waste wind turbine NdFeB magnets, and their magnetic properties, corrosion resistance and high temperature aging characteristics were evaluated. The recycled magnets were manufactured by mixing waste magnets A, B, and NdCoGa alloy according to weight percentage ratio of 90:7:3 respectively. Through BH Curve measurement and FE-EPMA qualitative element analysis, the differences in the magnetic properties and microstructure before and after adding the NdCoGa elements were observed. The results show that the magnetic properties of waste magnet A are Br = 12.60 kG, iHc = 18.92 kOe and (BH)max = 39.19 MGOe; the magnetic properties of waste magnet B are Br = 12.77 kG, iHc = 18.15 kOe and (BH)max = 40.25 MGOe. In contrast, the magnetic properties of the recycled magnets prepared in this study are Br = 12.63 kG, iHc = 18.72 kOe, and (BH)max = 39.95 MGOe, indicating that the proposed process restores the magnetic properties of the recycled magnets to the level of the original waste magnet. Also, a brand new commercial N40H magnet is further used as a control group, where the corrosion resistance and high temperature aging characteristics of bare materials were evaluated by Pressure Cooker Test (PCT), and oven/flux meter respectively. The results show that the average corrosion weights per unit area are 0.89 mg/cm2 and 1.23 mg/cm2, as well as the demagnetization rate of the high temperature aging is less than 0.4%. Compared with the new magnet, the recycled magnet has the same level of high temperature aging resistance, and 28% higher corrosion resistance. As a result, adding only 3% NdCoGa alloy to the waste magnet is beneficial to restore the magnetic properties and high temperature aging resistance, up to the level of new magnets, and also greatly enhances its corrosion resistance and reduces the cost of magnet remanufacturing. This result indicates that the recycled NdFeB permanent magnets developed in this research are more suitable for offshore wind turbine generators and electric vehicle motors operating at high temperatures and high humidity for a long period of time.

The preparation of anisotropic conductive paste and its application in FOB interconnection

PurposeThe purpose of this study is to investigate the reliability of flex-on-board (FOB) interconnection connected with an anisotropic conductive paste (ACP), which is prepared by dispersing nickel balls in the epoxy-curing system.Design/methodology/approachDifferential scanning calorimetry was used to evaluate the curing characteristics of the paste. And the contact resistances of bonding joints and 90º peel adhesion were tested before and after high temperature and high humidity test (85°C, 85% humidity), thermal cycling (−45°C∼125°C, 30min/cycle) and pressure cooker test (PCT, 121°C, 100% humidity 2 atm) to evaluate the flex on board (FOB) interconnection reliability.FindingsIt is found that FOB test vehicles have been successfully bonded by using ACP for the first time. And the ACP bonding joint of FOB has good reliability and can meet the requirements of FOB interconnection. Compared with conventional anisotropic conductive film (ACF), this ACP interconnection provides higher adhesion strength, higher joint current carrying capability and higher reliability performance and lower cost for FOB interconnection.Originality/valueACP is applied in the interconnection of FOB. It has the higher reliability performance and lower cost for than the conventional ACF.

Impact of specimen preparation method on photovoltaic backsheet degradation during accelerated aging test

AbstractIn this study, we highlight some important factors in the specimen preparation methods for evaluating photovoltaic backsheet properties after accelerated aging. Two different sequences are considered: Method (I) cut‐then‐age: cut into 1‐cm wide strips and then expose to stress, and Method (II) age‐then‐cut: expose a larger sheet to stress and then cut into 1‐cm widths for mechanical property measurements. We also compare the effect of three cutting methods, (a) tensile specimen punch, (b) paper cutter, and (c) fresh razor blade. Several commercial backsheets were evaluated, with stress exposures including (a) pressure cooker test (PCT), (b) dry ultraviolet (UV) radiation exposure, and (c) UV combined damp heat tests. Fourier transform infrared spectrometer (FTIR) and intrinsic viscosity (IV) were used to analyze the materials on unstressed materials and samples exposed to PCT. The results show that both the cutting method and the time of cutting have an impact on the backsheet mechanical properties. Under UV exposure, Method II, age‐then‐cut, generally resulted in a higher average value, with more variation than Method I; however, if the side strips from Method II were excluded, the variation dropped to the same level. This is because the specimens at the sides of the sheet get additional damage from UV light from the exposed sides of the sample. In contrast to UV exposure, PCT specimens prepared by Method II result in lower average values and higher variability. This is attributed to embrittlement through the bulk of the sample where the cutting of embrittled specimens appears to result in more edge defects which can then initiate a break at smaller strains. The data suggest that for UV exposures, the specimens should be cut after aging and the exposed side specimens discarded, and that for PCT exposures, the specimens should be cut before the exposure.

Degradation studies of epoxy coatings on printed circuit boards after pressure cooker test

AbstractThe present work focuses on the investigation of the degradation of screen‐printed epoxy coatings on printed circuit boards under multiple corrosion loads realized by the pressure cooker test (PCT). Since methods like the common mechanical shear strength tests are destructive and limited in information, the authors' approach used electrochemical impedance spectroscopy to study the change of their electrochemical behavior and the state of degradation. Complementarily, the Fourier‐transformed infrared spectroscopy was used to investigate the possible molecular change of the polymer due to the exposition. The experiments were carried out after different times of load. It could be shown that the complex conditions of the PCT initiate a controversial mechanism. The harsh corrosion load already results in a degradation of the polymer after 8 h but simultaneously the enhanced test temperature leads to ongoing curing processes consuming the remaining parts of resin and curing agents. As a result, the degradation kinetic seems to be delayed and after the test time of 96 h, the epoxy is less degraded than it was expected based on the results after a shorter time exposition.

A Study on Polyvinylidene Difluoride (PVDF) Anchoring Polymer Layer (APL) Solder Anisotropic Conductive Films (ACFs) for Fine-Pitch Flex-on-Flex (FOF) Interconnection

Fine-pitch flex-on-flex (FOF) assembly has been introduced for various electronic packaging applications because electronic products require higher functionality, flexibility, and I/O density. In this article, novel polyvinylidene difluoride (PVDF) anchoring polymer layer (APL) solder anisotropic conductive films (ACFs) were investigated for fine-pitch FOF applications. The capture rates of conductive particles and the insulation rates between neighboring electrodes have been significantly enhanced using PVDF APL solder ACFs as a result of suppressing the movement of conductive particles by the high tensile strength of the PVDF APL layer. For good solder wetting on electrodes, flux activators were added into the PVDF APL layer to remove the solder oxide layer. However, the tensile strength of the PVDF layer decreased as the flux activator content in the APL increased. The capture rates of conductive particles decreased as more flux activators were added because of the lower tensile strength of PVDF. Furthermore, optimized flux activator content in ACFs with 0.5 wt% in the APL and 2-wt% flux activators were also added in non- conductive films (NCFs) to obtain good solder wetting. Using the optimized APL solder ACFs, excellent contact resistances and insulation resistances were obtained before and after a pressure cooker test (PCT) and 85 °C/85% relative humidity (RH) reliability tests. As a conclusion, the PVDF APL solder ACF assembly can provide an excellent interconnect solution for fine-pitch FOF assemblies used for portable electronic product applications.

Investigation of Degradation Mode Spreading Interconnectors by Pressure-Cooker Testing of Photovoltaic Cells

We investigated the mechanism of the degradation mode spreading from interconnectors, a phenomenon that is frequently observed for crystalline silicon photovoltaic modules after damp heating or pressure-cooker testing (PCT). Modules tabbed by soldering or conductive film (CF) with glass–backsheet or glass–glass structure were subjected by the PCT at 110 °C and 85% relative humidity for 1000 h, then evaluated by means of current–voltage measurements, electroluminescence imaging, cross-sectional scanning electron microscopy, and energy-dispersive x-ray analysis, whereas tabbing of interconnectors with solder showed the degradation spreading from interconnectors, tabbing with a CF or the use of glass–glass structures suppressed the degradation. In the degraded area, cross-sectional observations revealed the degradation of the interfacial glass layer between the electrode and the silicon, the precipitates on inside walls of pores in the electrode, and the presence of deposits composed of tin and oxygen on the surface of the silver finger electrode. On the basis of these results, in this article we discuss the degradation mechanism in terms of preferential corrosion of the interfacial glass layer under the silver finger electrode covered by deposits.

Low-Temperature Bonding of PZT (PbZrTiO3) and Flexible Printed Circuits Using Sn52In Solder Anisotropic Conductive Films for Flexible Ultrasonic Transducers

Solder anisotropic conductive films (ACFs) consist of conductive solder particles, polymer resin, and flux activator. The flux activator removes solder oxide of solder particles by generated acid for the solder wetting during a thermocompression bonding process. In this article, eutectic Sn52In solder (Tm = 118°) particles were used as the conductive solder particle in the solder ACFs to reduce <130° ACFs’ bonding temperature. Novel Sn52In solder ACFs were fabricated using a comma-roll film coater and used to interconnect Au-coated PZT (PbZrTiO3) and flexible printed circuits (FPCs). PZT and FPCs interconnects using Sn52In solder ACFs were successfully demonstrated with the formation of good solder joints and reliable electrical resistances. According to the energy-dispersive spectrometer (EDS) line scan analysis, excellent solder wetting was confirmed by the presence of Au–In and Ni–Sn intermetallic compounds (IMCs) at the PZT and FPCs interface. Sn52In solder ACFs’ joints showed no open-circuit failure due to the excellent metallurgical bonding during a pressure cooker test (100% relative humidity and 2 atm at 121°) and a dynamic bending reliability test (the minimum bending radius of 7 mm). Therefore, Sn52In solder ACFs’ bonding can provide excellent metallurgical interconnection for flexible ultrasonic transducer packaging.

Piezoelectric Ceramics and Flexible Printed Circuits’ Interconnection Using Sn58Bi Solder Anisotropic Conductive Films for Flexible Ultrasound Transducer Assembly

Interconnection technology using Sn58Bi solder anisotropic conductive films (ACFs) has been chosen to assemble piezoelectric ceramics on flexible printed circuits for ultrasound imaging applications. The bonding and dicing processes were performed, and the bending of test samples was evaluated. The results showed excellent integrity of solder ACFs’ interconnects compared with other Ni-/Au-coated polymer ball and Ni ball-based ACFs’ interconnects. The metallurgical interconnects of the solder ACFs produce lower electrical resistances after pressure cooker and bending reliability tests. Moreover, the solder ACFs with a high-speed bonding process resulted in more electrically conductive, more reliable, and finer-pitch bonding for producing higher process yield and higher density ultrasound transducer arrays.

The Effect of Double-Layer Nonconductive Films on the Solder Sidewall Wetting and the Reliability of 40-$\mu$ m Cu-Pillar/SnAg Microbumps for Chip-on-Chip Interconnection

Cu-pillar/SnAg microbumps have been used for the latest 3-D through silicon via chip stacking. This microbumps flip-chip interconnection method can significantly further reduce the dimensions of the package and enhance the electrical performance by reducing interconnection path. As the pitch of the Cu-pillar/SnAg microbumps becomes extremely smaller, nonconductive films (NCFs) have recently been introduced to solve interconnection problems induced by the fine size microbumps. However, the applied pressure and heat during the thermo-compression (TC) bonding processes deform the SnAg solder and cause SnAg solder wetting on the sidewall of the Cu-pillar. The SnAg solder sidewall wetting causes rapid Sn consumption at the interface between the Cu-pillar and solder and decreases the joint gap heights of the SnAg solder joints. In this paper, the effects of the new double-layer NCFs (D-NCFs) were investigated for 40- $\mu \text{m}$ pitch chip-on-chip interconnection. The D-NCFs consisted of two NCF layers. The bottom NCF layer behaves as a conventional single NCF layer, and the top NCF layer, covering the Cu-pillar, prevents the movement of molten SnAg solder to the sidewall of Cu-pillar during the TC bonding process. As a result, the gap height of SnAg solder joints was doubled without SnAg solder sidewall wetting of Cu-pillar using the D-NCFs. SnAg solder joints using D-NCFs showed excellent reliability during thermal cycle tests up to 3000 cycles and pressure cooker test up to 72 h because of the significantly remaining Sn at the SnAg solder joint interface and increased joint gap height.

Galvanic Aluminum Bond Pad Corrosion in Copper Wire Bonded Device Assembly – Mechanism and Prevention

The explosion of microelectronics use in automobiles has made the microelectronic corrosion control more critical over the past decade. Wire bonded devices form an integral part of the microelectronic systems used in automobiles. With the reliability requirements of automobile microelectronics pushing towards ppb levels of failure, halide induced corrosion issues have to be controlled to achieve such high reliability goals. The corrosion of Aluminum bond pads in slightly acidic chloride solutions (ppm level) has been one of the main modes of wire-bonding failure in wire bonded devices. Earlier researches pointed out the possibility of intermetallic compound formation as the main reason for this corrosion. However, our investigation of the electrochemical nature of the corrosion led to the discovery that bimetallic contact of the aluminum bond pads with copper wires is the main reason for this type of corrosion. Copper and Aluminum being apart in the galvanic series can act as a galvanic corrosion cell under suitable conditions. Furthermore, the presence of halides causes de-passivation of Aluminum oxide layer making the Aluminum bond pad more susceptible to corrosion. In this report we introduce corrosion screening as a mimicking platform for studying wire-bond device corrosion. For the first time we reported that Hydrogen evolution is the cathodic reaction and is responsible for the explosive nature of this bond pad corrosion. By selective surface treatment of the Cu wires (cathodic part), we were able to prevent the corrosion by blocking the cathodic reaction and thereby stopping the electron flow required for the corrosion cycle to continue. The prevention treatment was then applied to commercial wire-bonded device and excellent corrosion prevention was observed. The corrosion inhibition coating exhibited high thermal stability up to 260 O C. We also report a novel testing method for corrosion testing of molded wire-bonded device with internal chloride ion contamination. Electrical continuity and delamination analysis showed that the chosen method of inhibition treatment was able to prevent corrosion even in cases of high chloride contamination and severe delamination. The results of the Pressure Cooker Test showed that the inhibitor coating is suitable for prevention of corrosion in even 100% Relative Humidity environments. Work is now in progress to apply these treatments to Palladium coated Copper wire bonded devices to check corrosion prevention ability of the reported corrosion prevention treatment.

Investigation of UV and hygrothermal stress on back side of rack-mounted photovoltaic modules

When discussing the reliability of backsheet of PV modules, it is important to accurately determine the amount of stress it receives. In this study, the UV irradiation dosage on the back side of a rack-mounted module, which has been estimated from multiplication of the UV irradiation dosage on the front side and the UV albedo, was actually measured. It was found that the measured value was 1.4 kW h/m2/y, which was almost 1/3 of the estimated value of 4.2 kW h/m2/y. The environmental stress on the back side of the PV module was also investigated by comparing changes in the molecular weight distribution of transparent poly(ethylene terephthalate) films subjected to outdoor exposure or indoor acceleration test. It is shown that UV and hygrothermal stress can be separated by analysis of the molecular weight distribution peak height and shift so that the extent of UV dose in fielded modules can be estimated. It was found that the stress on the back side of the PV module, exposed for 5.5 years using asphalt with 6% UV albedo as the flooring material, was close to that of 8 kW h/m2 after a UV irradiation test, a subsequent 6 h pressure cooker test, or a subsequent 200 h damp heat test. Acceleration tests that reproduce stress itself rather than deterioration phenomena should be developed, and for that, it is important to measure the amount of stress in various cases with reference to this measurement and separation method of stress.

Sequential Acceleration Tests with Pressure Cooker Test (PCT) and UV for Backsheets of PV Modules

The long-term reliability of backsheets for photovoltaic (PV) modules in floating systems are important due to the higher ultraviolet (UV) reflection from the water surface and the higher humidity in reservoirs or lakes. However, single tests over a long time, such as UV tests or damp heat (DH) tests for backsheets, cannot reproduce outdoor failures such as micro-cracks. Therefore, sequential acceleration tests for photovoltaic modules have been proposed, which combine DH and UV tests to reproduce multi-environment stresses. Nevertheless, DH tests usually take up to 1000–3000 h to cause degradation effects. Therefore, a pressure cooker test (PCT) is also considered as a substitute for extended DH tests since it provides test conditions with higher humidity and temperature. In this work, DH tests or PCT (121 °C /100 %Rh, 100 h), combined with UV tests, are adopted to investigate three different kinds of backsheets. The accelerated-aging test results according to different sequential test conditions are compared. The yellowing index change, peeling test, and cross-section of backsheets are also measured to evaluate the degree of degradation for different kinds of backsheets. Our results show that micro-cracks could be reproduced in sequential tests with PCT for one kind of backsheet while the other kind of backsheet did not change. This may provide an indicator to evaluate the durability of backsheets for the floating PV system application quickly.

Acceleration test using combined stresses for flexible solar modules

Production technologies of large-area, light-weight flexible thin film silicon solar cells and modules using 1-m-wide and 3,000-m-long heat-resistant plastic film substrates were developed. A unique monolithic device structure having through-hole contacts formed on a flexible plastic film was also developed. The unique solar cell device structure enables us to cut and connect flexible film cells in order to easily customize the voltage and current specifications of products. Durable solar cell and module designs and effective acceleration tests were established. In particular, an acceleration test that combines damp heat and a current injection test was established. Approximately 3,000 h of damp heat and current injection corresponds to 20 years of outdoor exposure in Japan. In this paper, we propose a pressure cooker and current injection test to achieve a much faster acceleration test. 300 h of pressure cooker and current injection test is approximately equivalent to 3,000 h of damp heat and current injection test and 20 years of outdoor exposure in Japan.

VIA Reliability Evaluation of Embedded MLCC through Pressure Cooker Test

A via reliability test of PCB board using embedded MLCC was evaluated by HALT and Pressure Cooker Test PCT. The reliability of HALT was evaluated at 125 , 4Vr, and 12Hr. The purpose of this test was to verify the stability of the MLCC by predicting the lifetime of the PCB. The PCBT conditions were measured at 85% humidity and 2 atm, and the reliability of the PCBs under severe conditions than HALT was evaluated. The basic characteristics of MLCC size are 0603 (600x300um), Capacitance 100nF, thickness 150µm. The initial electrical characteristics of the MLCC size are 0603 (600 x 300 um), Capacitance 100 nF, thickness 150 um. The initial electrical characteristics of the MLCC were measured at a rated voltage (10V) with a capacitance value of 98 ~ 103 nF, a loss rate of 0.048%, and an insulation resistance of 1.08 x 1010 (omega). The HALT test results showed that all the measured samples showed a value of 1 x 107 (omega) or more, and passed for the HALT test. The PCBT test resulted in failure, and the first sample fell below the poor insulation resistance at the start of the PCBT test. In the case of the second sample, the insulation resistance dropped to less than the defective insulation resistance for more than 30 hours, and the third sample has an appropriate insulation resistance of 1.0x106 even for more than 60 hours. It is confirmed that there is the greatest the possibility of failure in the part between the embedded chip and via that Cu plating is performed to form via by fill plating. Therefore, it is necessary to optimize the plating thickness and size conditions because the embedded MLCC has a high probability that defects mainly occur in VIA crack or delamination

A Study on the Optimization of Anisotropic Conductive Films for Sn-3Ag-0.5Cu-Based Flex-on-Board Application at a 250 °C Bonding Temperature

Although cationic epoxy was optimized for low-melting SnBi58 solder ACF joints with the lowest coefficient of thermal expansion (CTE) in terms of reliability, cationic epoxy also showed a faster curing property than any other types of adhesives. In fact, solder joint shapes at 250 °C bonding are very different from those shapes at 200 °C bonding. In this paper, four adhesive film types were investigated in terms of Sn-3Ag-0.5Cu solder ACF joint shapes on the electrical performances and reliability in a pressure cooker test (PCT). Thermal stability of adhesive films was tested to be first. Resin curing speeds were measured in a 250 °C isothermal mode differential scanning calorimetry, resin viscosities were checked by a parallel-plate rheometer, and adhesive thermomechanical properties, such as modulus and CTE, were characterized. Then, four different types of ACF resins containing the same weight percentages of Sn-3Ag-0.5Cu solders were assembled by the same thermocompression bonding parameter (250 °C 10s 2MPa on bump) on a 500- $\mu \text{m}$ -pitch flex-on-board (FOB) application, and different solder joint morphologies were verified. Various bonded solder ACFs joints were compared in terms of solder wetting areas, electrical performances by a four-point-probe method, and the reliability of PCT (121 °C 100% humidity 2atm) for 120 h. This paper aims at optimizing the best adhesive film candidate for SAC305 solder ACF joints of FOB application.

Sintering process of inkjet-printed silver patterns using a heated inert gas

In this study, we introduce a thermal sintering process using a heated inert gas as a new sintering method. The heated gas flow is formed by passing nitrogen (N2) gas through a heating head of 300 to 700°C, and the desired substrates are then exposed to the heated gas flow through a 400mm long and 5mm wide slit-nozzle. Sintering performance of Ag films was characterized by analyzing the electrical resistivity and metallographic structures according to the temperature change of the heating head. The temperature distribution of the heating region is analyzed by infrared (IR) thermal imaging and surface temperature measured by thermo-label tape. To test the feasibility of the proposed method for application to printed circuit board (PCB) manufacturing, we performed a reliability evaluation using the printed Ag patterns under the standard of the Institute for Interconnecting and Packaging Electronic Circuit (IPC), TM650. Various reliability test patterns were created by Ag inkjet-printing on both a rigid flame retardant 4 (FR4) substrate and a flexible polyimide (PI) film substrate. The reliability evaluation includes withstanding voltage, adhesive strength, thermal shock, pressure cooker, and bending tests. The surface wettability of the substrates was controlled to obtain high quality fine and uniform patterns by UV/O3 treatment after coating a fluoropolymer thin film.