Taguchi Experiment Research Articles

Reliability evaluation of CSP soldered joints based on FEM and Taguchi method

Abstract Finite element method and Taguchi method were combined and related to evaluate the reliability of CSP soldered joints with various sets of parameters under temperature cycling. Garofalo–Arrheninus model was implemented to simulate the creep behaviour of soldered joints. It is found that the maximum creep strain is located at the upper surface of the soldered joint which is under the outermost of CSP chip. Subsequently, the L9(34) orthogonal array was applied for Taguchi experiment to investigate the effects of solder alloy, height of the soldered ball, chip thickness and substrate thickness on the reliability of soldered joints, results indicate that substrate thickness and height of soldered ball possess an important effect on the reliability. Furthermore, the above parameters were selected optimally towards the improvement of reliability, and result shows that the optimal parameter settings are that the solder is Sn3.8Ag0.7Cu, the ball height is 0.18 mm, the chip thickness is 0.1 mm and the substrate thickness is 0.42 mm, which could reduce the creep strain energy density by 78.4% compared with the original parameters.

Taguchi Experiment Design for Investigation of Freshened Properties of Self-Compacting Concrete

Problem statement: The intent of this study was to apply of Taguchi Design Of Experiments (DOE) techniques in Self Compacting Concrete (SCC) freshened properties studies. Owing to a wide range of material content of Self Compacting Concrete (SCC), generally, a large number of experiments were usually required as to decide a suitable mixture for finding the needed requirements of SCC. Approach: For that purpose, Taguchi’s approach with an L18(21×37) orthogonal array and three-level factor to reduce the numbers of experiment was adopted. Six control factors, namely, contents of coarse aggregate, sand, cement, silica fume, water and superplasticizer were used. The mixtures were extensively tested in freshened state and to meet technical requirement of SCC. Four responses (slump flow, flow time, V-funnel, L-box and segregation resistance) were evaluated. Results: The result of this study showed that Taguchi method is a promising approach for optimizing mix proportions of SCC to meet several freshened concrete properties. Conclusion: This study has shown that it possible to design self compacting concrete with fulfilling the criteria. As it can be seen in the results of freshened concrete properties of produced concrete samples, they fulfilled the expected properties of SCC.

Towards rapid manufacturing of angled autoclaved composite laminates with minimised spring-in – a Taguchi experiments and finite element analysis based approach

Cure induced deformations in polymer composites lead to increased component rejection and assembly time. Warpage is generally accounted at the tool design stage, using past experience, often resulting in several trials to fabricate an exact composite tool or part. In this paper, the Taguchi design of experiments is used to minimise the spring-in of angled autoclaved composites. Three varieties (glass, carbon and Kevlar with epoxy resin matrix) of woven prepregs used in the transport aircraft program of Indian aerospace sector are investigated. The significance and optimum setting of eight process parameters for yielding minimum spring-in is obtained by ANOVA analysis. Further, the experimental results are validated using a 2-D, anisotropic, coupled thermal-displacement FEM formulation. A good agreement is obtained between the experimental and FEM results, validating the integrated approach. This approach is likely to assist in rapid composite part manufacturing meeting the requirements of a superior quality, ab-initio composite part.

Application of Taguchi Method in Light-Emitting Diode Backlight Design for Wide Color Gamut Displays

This paper utilizes the Taguchi design method to optimize the design parameters of a light-emitting diode (LED) backlight unit for wide color gamut liquid crystal displays (LCDs). In optimizing the design, the parametric analyses consider two particular regions of the backlight unit, namely, the color-mixing zone and the extractor zone. The Taguchi experiments are configured in L <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">9</sub> (3 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sup> ) orthogonal arrays and are designed to evaluate the effects of the design parameters on the color-difference, optical efficiency and luminance of the unit. The analysis of variance (ANOVA) results reveal that the optical efficiency and color-difference properties are determined primarily by the reflector design and the length of the color mixing zone, respectively, while the luminance to the LCD panel is affected principally by the taper angle of the optical microstructures in the extractor zone. The optimal design parameters of the color-mixing zone and extractor zone are estimated from the Taguchi S/N ratio data and the ANOVA results, and are verified via ray-tracing simulations. For an input flux of 1501 lm, the optimal design shows 0.01 of the color differences in CIE 1976 color space, 85% of the optical efficiency, and 10675 nits of luminance. Thus, the optimized backlight unit provides an ideal solution for the illumination of large-scale LCD display devices.

다구찌 방법을 이용한 BGA 현상 공정용 수직 습식 장비의 공정 최적화

Vertical wet equipment for the BGA develop process was newly developed substituted for conventional horizontal wet equipment. The benefits of vertical equipment are that the pattern damages generated by the collision between the patterns and transferring rollers can be eliminated because the direct contact between the equipment`s transferring units and the soft dry film patterns does not occurs. Taguchi experiment was conducted to optimize the process characteristics for the vertical equipment. The experiment was organized as the smaller the better problem which includes adequate uncontrollable factor and controllable factors. The uncontrollable factors are the 4 sides of two panels which are loaded to the equipment at the same time. By the analysis of the experiment, temperature of the develop chemicals and develop spraying time are analyzed as the main controllable factors. Finally, line pattern`s minimum width which is not damaged for the develop process was improved from for the horizontal equipment to for the vertical equipment. And dot pattern`s minimum width is improved from to .

Influence of processing parameters on micro injection molded weld line mechanical properties of polypropylene (PP)

As a hot fabrication technology for micro scale parts, micro injection molding is receiving increasing market attention. Improving mechanical properties of micro parts should be an important issue in the micro injection molding process. The relation between weld line strength in micro injection molding parts and processing parameters is investigated. A visual mold with variotherm unit is designed and constructed, in which the micro tensile specimen with weld line are prepared. Polypropylene (PP) is used as the research material in this study, and six processing parameters were chosen as investigating factors, which were melt temperature, mold temperature, injection pressure, packing pressure, ejection temperature and injection speed. In order to achieve optimized processing parameters and their order of significance, Taguchi experiment method was applied in this presented study. The prediction formulation of the strength of micro weld line was built up by multiple regression analysis based on Chebyshev orthogonal polynomial. The results showed the influencing significance order of parameters from strong to week separately are mold temperature, melt temperature, injection speed, ejection temperature, packing pressure and injection pressure. And the tolerance of micro weld line prediction formulation was found to be lower than 21% through confirmation experiments.

Robotic polishing of precision molds with uniform material removal control

In this paper, a uniform material removal (UMR) model is proposed for an automatic mold polishing system (AMPS). Free-form surfaces of mold geometry in IGES format are read and regenerated by the AMPS using the NURBS model. The normal vector, the principal curvatures, and the effective contact area are calculated at any point on the surface. The sensitivity of each factor that influences the material removal is determined by Taguchi experiments. The UMR model is based on maintaining constant velocity and contact pressure by controlling the polishing force according to the effective contact area. Three optical molds were polished using two path patterns with and without UMR control for comparison. The experimental results showed that even the conventional constant-force polishing scheme can achieve nearly the same surface roughness; the surface profile error of the mold with UMR control is less than 1/3 of the mold without UMR control. In addition, the actual material removal depth is less than 5.4% of error compared to the predicted value by the UMR model.

超硬金型の自動ラッピングシステムにおけるラップ剤の最適化とその評価(機械要素,潤滑,工作,生産管理など)

Recently the dies with cemented carbide are used for many products using its high stiffness and high wear resistance. The hand lapping is even now used as finishing process of them because of difficulty of its mechanization. The new lapping system was developed in our previous study from these reasons. And the lapping system could machine to flat surface of cemented carbide (V10) with mirror-like surface. In that case, mixture of diluted starch syrup and diamond grain was used as lapping slurry. However, this slurry can machine only flat bottom surface because of dropping the grain for lapping. So, it has to improve for the lapping to three dimensional work pieces including vertical surface, concave-convex surface. In this study, the mixture of polymer material and diamond grain was used as new lapping slurry for suspending the diamond grain using special properties of polymer. The distribution density of grain in the slurry medium was researched by experiment. Relationship between the lapping condition and the grain retention propaties on tool head was researched. Finally improving the surface roughness of large work piece was confirmed. It is concluded from the results that; (1) New lapping slurry with polymer can keep the diamond grain while enough time for machining. (2) The best lapping condition was confirmed from TAGUCHI methods and experiment. (3) New lapping slurry can be used for lapping the mirror-like surface of large or complex dies.

MODELING AND OPTIMIZATION OF REFLOW THERMAL PROFILING OPERATION: A COMPARATIVE STUDY

ABSTRACT In this study, a comparative study of optimizing the reflow thermal profiling parameters using a hybrid artificial intelligence and the desirability function approaches without/with combining multiple performance characteristics into a single desirability is presented. Reflow soldering is the key determinant for the improvement of the first-pass yields of electronics assembly. A reflow thermal profile is a time-temperature contour with multiple performance characteristics utilized to monitor the heating effects on a printed circuit board (PCB) and surface mount components (SMCs) in the reflow oven. The use of an inadequate reflow thermal profile may not only produce a variety of soldering failures, but can also result in the needs for considerable reworking and waste. An L18 (21*37) Taguchi experiment design is conducted to collect the thermal profiling data. A quick propagation (QP) neural network is modeled based on experimental data to formulate the nonlinear relationship between the thermal profiling factors and responses, and a genetic algorithm (GA) is used in the optimization of thermal profiling factors with the fitness function based on the trained QP neural network model. Alternatively, the response columns for the experimental data can be transformed into a single measure of desirability which is then optimized by the desirability function approach with the response weightings derived from an analytic hierarchy process (AHP). The empirical evaluation results show that the desirability function approach with combining the multiple performance into a single desirability delivery superior soldering performance to that obtained by the hybrid artificial intelligence method without combining the multiple performance into a single desirability, as measured by the DPMO, yield rate, and process sigma.

From value stream mapping toward a lean/sigma continuous improvement process: an industrial case study

Though lean manufacturing has been widely recognised for its effectiveness in continuously improving productivity, product quality, and on-time delivery to customers, the cost for hiring a full-time lean manufacturing engineer has kept many small businesses from implementing lean in their facilities. This paper presents a case study of lean implementation at a small manufacturer in the United States. Starting with collecting process information, a current value-stream map was created that reflected the current operation status. A future value stream map was then proposed to serve as a guide for future lean activities. Next, hurdles that kept the company from moving towards future state were identified. The ‘5 whys’ method was employed to reveal the root cause for each hurdle, followed by kaizen events proposed as solutions. In this case study, two kaizen events were proposed. For the first kaizen event, Taguchi experiment design was used to find the optimal machining parameters that reduced variation in a plasma cutting process. It consequently eliminated rework time and improved productivity. In the second kaizen event, implementation of rabbit chasing increased the system flexibility and consequently reduced inventory levels between work stations.

Optimizing tape‐burnishing/wiping process of magnetic recording media through Taguchi method

AbstractFor the ever‐increasing recording density in hard disk drives, ultra‐low gliding height media are required. It is an immense challenge for the tape‐burnishing/wiping process of media to reduce the asperities effectively and efficiently while no scratches occur. The purpose of this paper is to characterize and then optimize the tape‐burnishing/wiping process as so to minimize the asperities without leaving any scratches on the media surface. A Taguchi experiment design method is adopted to analyze the data and acquire an optimal level combination of process parameters. The resulting optimal combination is practically implemented in tape‐burnishing/wiping the several magnetic recording media, which reveals that the average pass ratio of 5 nm glide avalanche testing increases nearly doubly to a level of 96%. Copyright © 2008 John Wiley &amp; Sons, Ltd.

Manufacture of Spinnerets for Synthetic Micro-fibers by LIGA and Micro-injection Molding Technique

Abstract In the past, the capillaries of fiber-spinneret were made by micro drilling or by micro electro-discharge-machining (M-EDM). However, the productivity and uniformity of M-EDM are restricted. Hence, a new approach related to LIGA technique was developed. The micro mold of the capillaries was made by LIGA. Micro plastic cores were then duplicated by micro injection molding. With consequent treatments and electroforming, the spinneret die can be mass produced. Better process conditions for micro molding will be determined by Taguchi's experiment design method. Through a single injection molding cycle, a 48-capillary structure was formed at once. The diameters of each capillary were inspected at three locations along the longitudinal direction carefully. The results show that the accuracy of the diameters of capillaries can be controlled within 200 ± 1 μm. Capillaries die to spin ∗ and w-shaped micro-fibers were also developed in this work. Thanks to LIGA process, spinnerets with higher aspect ratios (even up to 30) can be achieved more easily. By applying micro injection molding, consequent treatments and electro-forming processes, the spinnerets can be produced in a batch and mass production way. The technology developed here can also be used in the fabrication of Micro-Electro-Mechanical (MEMS) components.

Taguchi-based Six Sigma approach to optimize plasma cutting process: an industrial case study

This case study outlines the use of Taguchi parameter design to optimize the roundness of holes made by an aging plasma-cutting machine. An L9 array is used in a Taguchi experiment design consisting of four controllable factors, each with three levels. With two non-controllable factors included in the setting, we conduct 36 experiments, compared to the 81 parameter combinations (four factors, three levels or 34) required in a traditional DOE setting. Therefore, using the Taguchi method significantly reduces the time and costs of a quality improvement process. Conducted for two response variables—bevel magnitude and the smallest diameter deviation of the hole—the Taguchi experiments gave the optimal combination A1B2C1D3 (small for tip size, 93 in/min for feed rate, 100 V for voltage, and 63A for amperage), which is verified with a confirmation run of 30 work pieces. All 30 cuts meet the quality requirement for subsequent assembly. Furthermore, statistical analysis indicates that the mean value and standard deviation of the confirmation run data are smaller than those before Taguchi parameter design is conducted.

Competitive parameter optimization of multi-quality CNC turning

Surface roughness, tool wear, and material removal rate (MRR) are major intentions in the modern computer numerical controlled (CNC) machining industry. In this paper, the \({\text{L}}_9 \left( {3^4 } \right)\) orthogonal array of a Taguchi experiment is selected for four parameters (cutting depth, feed rate, speed, and tool nose runoff) with three levels (low, medium, and high) in optimizing the finish turning parameters on an ECOCA-3807 CNC lathe. The surface roughness (Ra) and tool wear ratio (mm−2) are primarily observed as independent objectives for developing two combinations of optimum single-objective cutting parameters. Additionally, the levels of competitive orthogonal array are then proposed between the two parameter sets. Therefore, the optimum competitive multi-quality cutting parameters can then be achieved. Through the machining results of the CNC lathe, it is shown that both tool wear ratio and MRR from our optimum competitive parameters are greatly advanced with a minor decrease in the surface roughness in comparison to those of benchmark parameters. This paper not only proposes a competitive optimization approach using orthogonal array, but also contributes a satisfactory technique for multiple CNC turning objectives with profound insight.

Mixing behavior of the rhombic micromixers over a wide Reynolds number range using Taguchi method and 3D numerical simulations

A planar micromixer with rhombic microchannels and a converging-diverging element has been systematically investigated by the Taguchi method, CFD-ACE simulations and experiments. To reduce the footprint and extend the operation range of Reynolds number, Taguchi method was used to numerically study the performance of the micromixer in a L(9) orthogonal array. Mixing efficiency is prominently influenced by geometrical parameters and Reynolds number (Re). The four factors in a L(9) orthogonal array are number of rhombi, turning angle, width of the rhombic channel and width of the throat. The degree of sensitivity by Taguchi method can be ranked as: Number of rhombi > Width of the rhombic channel > Width of the throat > Turning angle of the rhombic channel. Increasing the number of rhombi, reducing the width of the rhombic channel and throat and lowering the turning angle resulted in better fluid mixing efficiency. The optimal design of the micromixer in simulations indicates over 90% mixing efficiency at both Re > or = 80 and Re < or = 0.1. Experimental results in the optimal simulations are consistent with the simulated one. This planar rhombic micromixer has simplified the complex fabrication process of the multi-layer or three-dimensional micromixers and improved the performance of a previous rhombic micromixer at a reduced footprint and lower Re.

Wetting behavior of Al–Si–Mg alloys on Si3N4/Si substrates: optimization of processing parameters

The wetting behavior of Al–Si–Mg alloys on Si3N4/Si substrates has been investigated using the sessile drop technique. Based on a Taguchi experiment design, the effect of the following processing parameters on the contact angle (θ) and surface tension (σLV) was studied: processing time and temperature, atmosphere (Ar and N2), substrate surface condition (with and without a silicon wafer), as well as the Mg and Si contents in the aluminium alloy. In nitrogen, non-wetting conditions prevail during the isothermal events while in argon a remarkable non-wetting to wetting transition leads to contact angles θ as low as 11±3° and a liquid surface tension σLV of 33± 10×10-5 kJ/m2. According to the multiple analysis of variance (Manova), the optimum conditions for minimizing the values of θ and σLV are as follows: temperature of 1100 °C, processing time of 90 min, argon atmosphere, no use of a silicon wafer, and the use of the Al-18% Mg-1% Si alloy. A verification test conducted under the optimized conditions resulted in a contact angle of θ=9±3° and a surface tension of σLV=29± 9×10-5 kJ/m2, both indicative of excellent wetting.

Microstructure Evaluation of Solid-Solution in Fe-Cu Immiscible Alloy System

The study of mechanical alloying on the Fe–Cu system, as a model system for those with positive heats of mixing, are investigated. In this research work the effects of impact force, such as increasing in the surface temperature of powders, the number of vacancies and pipe diffusion, on the strain and grain size of final powders have been studied. The aim of this research is to find the optimum condition for mechanical alloying of Cu-Fe system by the help of automatic design and analysis of TAGUCHI experiments.

On the Potential of CVD Diamond Films as Mechanical Seal Face Materials

Polycrystalline diamond coatings have been deposited by microwave plasma-assisted CVD onto silicon carbide substrates. The coating conditions and the substrate properties were varied systematically using the Taguchi method and the resulting coating morphologies were determined. A second Taguchi experiment was then used to assess the tribological performance of the coatings against a range of counterface materials in a thrust washer test rig. The results of these tests are reported here, and they confirm the excellent tribological performance that can be obtained. Consideration is also given to the role of surface texture in determining seal performance. A simple mathematical model has been developed to assist in the characterization and interpretation of the tribological results produced. The surface texture of the diamond films was identified as significant to their tribo-performance. The model demonstrated how the surface texture could contribute to interface lubrication.

Experimental investigation on electrolytic in-process dressing (ELID) grinding of die steel

Electrolytic in process dressing (ELID) grinding is drawing more and more attention for its in process dressing of the grinding wheel that not only eliminates the conventional dressing time but also increases the ground surface quality considerably. The present research focuses on the study of the effect of dressing voltage, electrolytic concentration electrolytic flow rate and depth of cut on two important machining performances, e.g., material removal rate (MRR) and surface finish of die steel. A Taguchi-based experimental investigation has been carried out to study the various process parametric effects and finally the process has been optimised. Confirmation tests were conducted to check the adequacy of Taguchi experiment. Besides, another set of experiments have been carried out to study the effect of inter-electrode gap on MRR and surface finish. A comparative study of conventional and ELID grinding of M2-hardened die steel has also been made. Under all experimental conditions, the ELID grinding process exhibited better performance compared to conventional grinding.

Optimization of cryogenic treatment to maximize the wear resistance of 18% Cr martensitic stainless steel by Taguchi method

Deep cryogenic treatment (DCT) is a one time permanent process, carried out on steel components in such a way that the material is slowly cooled down to the cryogenic temperature , after which it is held at that temperature for a specified period of time and is heated back to room temperature at a slow rate followed by low temperature tempering. The main advantage of DCT is to enhance the wear resistance. The various levels of DCT process parameters have their own influence upon the wear resistance of the material. In this study, the Taguchi method has been used to optimize the process parameters of DCT for a commercial piston ring , made up of 18% Cr martensitic stainless steel (SR34) to obtain maximum wear resistance. The DCT parameters considered for optimization are: the cooling rate, the soaking temperature, the soaking time, the tempering temperature and the tempering time. In this regard, two iterations of Taguchi design have been used to arrive at the optimum DCT parameters. During the first iteration, L 16 2 15 orthogonal array (OA) was used to conduct the Taguchi experiment so as to study the significance of these factors and the effect of their possible two-factor interactions. In the second iteration, L 9 3 4 OA was used to conduct the Taguchi experiment to arrive at the optimal levels. Wear test was conducted on a reciprocatory friction and wear monitor (RFWM) by weight loss method , as per ASTM standards G-181 and G-133. The relative importance of the controlling parameters of DCT and their interactions for enhancing the wear resistance was evaluated in terms of their percentage contributions using analysis of variance (ANOVA). The optimum levels of the significant DCT parameters for SR34 steel ring were arrived based on the maximum S/N ratio. A confirmation test was conducted subsequently, and the results were found to be within the confidence interval.