Papers by Keyword: Warpage

Abstract: This work investigates the formation and control of residual deformations in composite L-shaped parts manufactured by autoclave curing. An experimental study is first conducted to characterize spring-in for different stacking sequences. Dimensional measurements are performed using stereo digital image correlation to quantify spring-in and to assess the presence of warpage along the flanges. A numerical study is then carried out to develop a simulation method for process-induced deformation prediction. The influence of the main mechanisms involved is analyzed, and a modeling strategy for the tool-part interaction is proposed. Finally, compensated mould design is addressed. The convergence of the optimization problem is investigated, and an optimized mold geometry is determined for each part considered in this study.

Abstract: Fan-out wafer-level package is a very promising packaging technology with good thermal and electrical performance. The fan-out wafer-level package exhibits beneficial features such as low profile, high I/O density, low cost, and efficient computing. The package experiences large temperature variations in the assembly phase which causes internal stresses. In particular, the mismatch between the coefficient of thermal expansion of the epoxy molding compound and the substrate due to the cool down phase of the cure process causes the internal stresses in the package. These internally induced stresses result to interfacial delamination. In this study, the interfacial delamination on a fan-out wafer-level package right after post mold cure of glass wafer was evaluated using the stress-based damage index through the finite element analysis in the ANSYS software package. The model was validated by comparing the simulation result of the glass wafer warpage to the existing experimental result from literature. From the warpage simulation of the glass wafer, the region on the package with high stress level was located and examined which may cause interfacial delamination. The maximum shear stress and principal stress at the epoxy molding compound and the Silicon chip interface was found to exceed the adhesion strength. This indicates that the interfacial delamination is inevitable. The information obtained from the stress analysis of molded wafer provides insight for the possible interfacial failure of fan-out wafer-level package in the individual package when subjected to thermomechanical loads.

Abstract: In this research, the effect of the colling channel design on the warpage of a thin-wall injection molding plastic product has been numerically simulated. Three cooling channel with different designs are considered. The results indicate that the total displacement of warpage on product significantly depends on cooling channel layout. Using a cooling channel with conformal form, the heat accumulation inside the box is released. Therefore, the maximum total displacement dramatically reduces from 1.05 mm in the original design to 0.19 mm. Though increasing conformal cooling channel length will even decrease the maximum displacement to 0.09 mm, the jump of coolant pressure to 86.7 MPa is a big drawback. Therefore, the final suitable design for this system is the short conformal cooling channel.

Abstract: Polypropylene (PP) is a promising material for extrusion-based additive manufacturing due to its low cost, chemical resistance, good mechanical properties, versatile, and can be applied in various industrial applications. Recent research has focused on addressing the warpage issue in 3D printing of PP filaments. The effect of environmental conditions and loading of nanoprecipitated calcium carbonate (NPCC) in the pristine polypropylene to decrease warpage using the Fused Deposition Modelling (FDM) printing technology was studied. PP-NPCC composite filaments containing 5, 10, and 15 NPCC (wt%) were prepared using the twin-screw extruder. The printability, physicochemical, and mechanical properties of the PP-NPCC blends were determined. Based on the results, the incorporation of NPCC has contributed to the improvement of 3D printability and warpage in the PP-NPCC composite. At controlled environmental conditions, the filament was printable and the warpage was decreased by 44% at 10% NPCC loading. At the same concentration, there was a 30% increase in compressive strength and 43% increase in elastic modulus of the 3D printed parts.

Abstract: In this work the relationship between changes in wafer center bow after thinning process and the wafer morphology has been shown. KOH wet etching allowed the observation and counting of dislocation in 4H-SiC substrate. In deep a correspondence between changes in wafer center bow and the dislocation density of the SiC substrate has been observed. By using a counting software, a relationship with the basal plane dislocation and center bow has also been observed.

Abstract: It is commonly thought that, in the development of SiC power devices with low on-state resistance (R_on), several critical processes in the device fabrication line can strongly impact the final warpage of wafers. High warpage would lead to bad definition of masks, preventing uniform deposition of resist materials and disturbing the normal handling procedures. All these factors would then result in a potential decrease of the electrical yield of the devices, especially for MOSFETs. This study reveals the lack of correlation between critical line processes such as epitaxial growth, oxidations, ion implantations, annealing processes with the final bending of wafers. Conversely, a strong dependence with the resistivity of the substrates is observed. A new parameter defined as RMR (Resistivity Modulation Rate) is taken proposed and, together with the starting value of ingot resistivity, this parameter shows a strong relationship with the final warpage after wafer thinning. A safe region having warpage low enough to allow the workability of the wafers is found.

Abstract: Electricity generation at Mae Moh Power Plant in Lampang, Thailand, uses lignite as fuel. The output is 3.0 to 3.5 million tons of fly ash per year and 1.5 to 2.0 million tons of bottom ash per year. Fly ash is widely used in concrete application but for bottom ash, it is not very useful. When considering the phase of bottom ash containing quartz, anorthite and hematite, it was found that there are suitable chemical compositions for replacement of raw materials in ceramic tile. Generally, the stoneware tiles are composed of quartz, mullite, feldspar, and glass phase. Water absorption of stoneware ceramic tiles is below 5%, high strength, fire resistance, and low warpage. Firing or sintering at rather high temperature as 1000-1250 °C is the manufacturing process for this type of tile. The changes in crystal structure and glassy phase formation in tile texture during sintering will be often result the tile to warpage or bent. The more or less lean depends on the viscosity of the glassy phase that occurs at high temperatures in the tile if less viscosity will cause higher warping rate that effect on the shape, and quality of the workpiece. The research has reported that anorthite phase improves the viscosity of a liquid phase or glassy phase when the tile is sintering at high temperatures and lead to high density and low water absorption. This research is interested in studying the effect of using lignite bottom ash as an ingredient in ceramic tile texture to produce low water absorption type by analyzing the effect of percentage of lignite bottom ash to warpage and important properties of ceramic tiles.

Abstract: The effect of mould temperature on warpage using water and oil as coolant fluid was studied using flow software analysis. Mould temperature was controlled using two types of coolants; where cold mould was controlled by water and hot mould was controlled by oil. The simulation analysis was performed using flow software analysis Moldflow Plastics Insight (MPI). Taguchi method was used to design the planning matrix and to find the optimum levels of input variables. Then, to find the percentage contribution of input variables on output variables, analysis of variance (ANOVA) was used. It is found that mould temperature controlled by water shows less warpage analysis compared to oil. The minimum and maximum percentage of warpage analysis between cold mould and hot mould are 3.1% and 7.1% respectively. In addition, ANOVA analysis shows that the most significant parameters affected the warpage analysis for both moulds using oil and water are melt temperature (255°C) followed by mould temperature (water 15°C and oil 70°C) and cooling time (water 8s and oil 6s). Thus, it shows that coolant medium used in mould cooling system contributes the quality of plastic parts.

Abstract: This study focuses on the analysis of plastic injection moulding process simulation using Autodesk Moldflow Insight (AMI) software in order to correlate between process parameters as an input and warpage as an output for single and dual gates mould design. Nessei NEX 1000 injection moulding machine and P20 mould material details are incorporated in this study on top of Acrylonitrile Butadiene Styrene (ABS) as a moulded thermoplastic material. Coolant inlet temperature, material melt temperature, packing pressure and packing time are selected as a variable parameter. Design Expert software is obtained as a medium for analysis and optimization of input variables in order to minimize the warpage. RSM method as well as Analysis of Variance (ANOVA) has been applied in this study. The results of ANOVA show that some interactions between factors are significant towards warpage existence, which is coolant inlet temperature, material melt temperature and packing pressure. Furthermore, the model created using RSM can be used for warpage prediction and improvement due to a minimum value of error. From this study, the dual gate is the best solution which able to improve the warpage up to 80% instead of single.

Abstract: The application of Taguchi method to reduce warpage in an injection moulding process is studied. The objective of this paper is to analyze the effect of injection moulding parameters, i.e., injection time, packing time, melt temperature and mould temperature, on the warpage defect in dumbbell plastics part. Optical comparator horizontal type was used to measure the difference of warpage value on each part. L9 orthogonal array with 3 replications was done with 27 totals of specimens. The result collected was optimized using Taguchi method and percentage of contribution was calculated using analysis of variance (ANOVA). According to the analysis, it is found that the significant factors affected warpage are injection time (32.01%), packing time (29.73%), mould temperature (24.39%) and melt temperature (13.87%). The optimum parameters for minimizing the warpage were injection time (1s), packing time (5s), melt temperature (270 °C) and the mould temperature (21 °C). By using Taguchi method and ANOVA analysis, optimum parameters and the percentage of contribution of parameters can be obtained. Thus, it shows that design of experiment method is the good quality tools to get the best quality for production.