Browsing by Author "Chen, KS"

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A Bayesian-like estimator of C-pk
(1996)
Pearn, WL
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Chen, KS
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工業工程與管理學系
;
Department of Industrial Engineering and Management
Bissell (1990) proposed an estimator for the process capability index C-pk assuming the knowledge whether the process mean mu < m or mu greater than or equal to m is available, where m is the mid-point between the upper and lower specification limits. Kotz, Pearn and Johnson (1993) showed that for the index C-pk, the natural estimator gives values for the standard deviation smaller than those of Bissell's. In this paper we show that by adding a well-known correction factor to Bissell's estimator, we obtain an unbiased estimator of C-pk whose standard deviation is smaller than those given in Kotz, Pearn and Johnson (1993). In addition, we propose a Bayesian-like estimator which relaxes Bissell's assumption on the process mean. The distribution of the new estimator is shown to be identical to that of Bissell's estimator.
A gold-free fully copper-metallized InP heterojunction bipolar transistor using non-alloyed ohmic contact and platinum diffusion barrier
(2005)
Chang, SW
;
Chang, EY
;
Lee, CS
;
Chen, KS
;
Tseng, CW
A gold-free, fully Cu-metallized InP heterojunction bipolar transistor using non-alloyed Ti/Pt/Cu and Pt/Ti/Pt/Cu ohmic contacts and platinum diffusion barrier has been successfully fabricated. The InGaAs/Ti/Pt/Cu ohmic structure was stable after annealing up to 350 degrees C as judged from the Auger depth profiles. A current-accelerated stress test was conducted on the device with a current density J(C) = 80kA/cm(2) for 24h, and the current gain showed no degradation after the current stress. The devices were also thermally annealed at 200 degrees C for 3 h and showed almost no change in the electrical parameters after the heat treatment. The results show that the Au-free, fully Cu-metallized InP heterojunction bipolar transistor (HBT) can be realized using non-alloyed ohmic contacts and Pt diffusion barrier.
A low noise composite-channel metamorphic HEMT for wireless communication applications
(2003)
Lu, CY
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Chen, KS
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Lee, HM
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Chang, EY
;
Chen, SH
A composite-channel Metamorphic high electron mobility transistor (MHEMT) was developed for low noise high linearity application. The MHEMT was grown by Molecular Beam Epitaxy (MBE) on GaAs substrates with InAlAs graded buffer. The composite-channel layers in the MHEMT include a top In0.55Ga0.45As layer, a middle In0.67Ga0.33As layer, and a bottom In0.55Ga0.45As layer. The design of this structure provides better electron confinement in the channel with less impact ionization as compared to conventional dual delta doped MHEMTs. This results in devices with higher linearity and drain to gate voltage as compared to the conventional metamorphic HEMTs. The 0.25x160 mum(2) device with the novel channel structure exhibits a maximum frequency of oscillation f(max) of 290 GHz and a current gain cut-off frequency f(t) of 110 GHz. The noise figure of the device at 6 GHz is 0.23 dB and the associated gain was 15.06 dB. The IP3 of the device at 6 GHz is 19.67 dBm. The composite channel metamorphic HEMT shows great potential for high linearity and low noise application at high frequencies.
A practical implementation of the incapability index C-pp
(2002-12-01)
Pearn, WL
;
Chen, KL
;
Chen, KS
;
工業工程與管理學系
;
Department of Industrial Engineering and Management
Process capability index C-pp has been introduced to measure process performance. In practice, since sample data must be collected in order to calculate the index value, then a great degree of uncertainty may be introduced into capability assessments due to sampling errors. In current practice, the practitioners would simply look at the index value calculated from the sample data then make a conclusion on whether the given process meets the capability requirement. This approach is not reliable since the sampling errors are ignored. In this paper, we take into account the sampling errors and develop a simple procedure using the UMVUE (uniformly minimum variance unbiased estimator) of C-pp, for practitioners to use in determining whether a process meets the capability requirement. The decisions made based on the proposed procedure are, of course, more reliable.
An application of non-normal process capability indices
(1997-11-01)
Chen, KS
;
Pearn, WL
;
工業工程與管理學系
;
Department of Industrial Engineering and Management
Numerous process capability indices, including C-p, C-pk, C-pm, and C-pmk, have been proposed to provide measures of process potential and performance. In this paper, we consider some generalizations of these four basic indices to cover non-normal distributions. The proposed generalizations are compared with the four basic indices. The results show that the proposed generalizations are more accurate than those basic indices and other generalizations in measuring process capability. We also consider an estimation method based on sample percentiles to calculate the proposed generalizations, and give an example to illustrate how we apply the proposed generalizations to actual data collected from the factory. (C) 1997 John Wiley & Sons, Ltd.
Behavior and surface energies of polybenzoxazines formed by polymerization with argon, oxygen, and hydrogen plasmas
(2004-11-15)
Chen, JK
;
Lin, IK
;
Ko, FH
;
Huang, CF
;
Chen, KS
Polybenzoxazine (PBZZ) thin films can be fabricated by the plasma-polymerization technique with, as the energy source, plasmas of argon oxygen or hydrogen atoms and ions. When benzoxazine (BZZ) films are polymerized through the use of high-energy argon atoms, electronegative oxygen atoms, or excited hydrogen atoms, the PBZZ films that form possess different properties aid morphologies in their surfaces. High-energy argon atoms provide a thermodynamic factor to initiate the ring-opening polymerization of BZZ and result in the polymer surface having a grid-like structure. The ring-opening polymerization of the BZZ film that is initiated by cationic species such as oxygen atoms in plasma, is propagated around nodule structures to form the PBZZ. The excited hydrogen atom plasma initiates both polymerization and decomposition reactions simultaneously in the BZZ film and Results in the formation of a porous structure on the PBZZ surface. We evaluated the surface energies of the PBZZ films polymerized by the action of these three plasmas by measuring the contact angles of diiodomethane and water droplets. The surface roughness of the films range from 0.5 to 26 nm, depending on the type of carrier gas and the plasma-polymerization time. By estimating changes in thickness, we found that tie PBZZ film synthesized by the oxygen plasma-polymerization process undergoes the slowest rate of etching in CF(4) plasma. (C) 2004 Wiley Periodicals, Inc.
Capability evaluation of a product family for processes of the larger-the-better type
(2002)
Chen, KS
;
Li, RK
;
Liao, SJ
;
工業工程與管理學系
;
Department of Industrial Engineering and Management
Process capability indices (PCIs) have been widely used in manufacturing industry, but most of the studies associated with analysing the quality and efficiency of a process are limited to discussing one single quality specification. Practically, a product family is usually composed of several models, which result in different specifications. Generally, the quality characteristics of a product can be classified into three types; the nominal-the-best, the smaller-the-better and the larger-the better types. This paper introduces one simple and applicable method to evaluate the process capability of a product family. The process is of the larger-the-better type and consists of several models with different specifications. For practical applications, a simple step-by-step procedure is established to determine whether the total process capability of the product family meets the preset target. Finally, an example is given and a procedure for a hypothesis test is provided for easy application.
Capability indices for non-normal distributions with an application in electrolytic capacitor manufacturing
(1997-12-01)
Pearn, WL
;
Chen, KS
;
工業工程與管理學系
;
Department of Industrial Engineering and Management
Process capability indices C-p(u, v), which include the four basic indices C-p, C-pk, C-pm and C-pmk as special cases, have been proposed to measure process potential and performance. C-p(u,v) are appropriate indices for processes with normal distributions, but have been shown to be inappropriate for processes with non-normal distributions. In this paper, we first consider two generalizations of C-p(u, v), which we refer to as C-Np(u, v) and C-Np(u, v), to cover cases where the underlying distributions may not be normal. Comparisons between C-Np(u, v) and C-Np'(u, v) are provided. The results indicated that the generalizations C-Np(u, v) are superior to C-Np'(u, v) in measuring process capability. We then present a case study on an aluminum electrolytic-capacitor manufacturing process to illustrate how the generalizations C-Np(u, v) may be applied to actual data collected from the factories. (C) 1997 Elsevier Science Ltd.
Capability indices for processes with asymmetric tolerances
(2001-09-01)
Chen, KS
;
Pearn, WL
;
工業工程與管理學系
;
Department of Industrial Engineering and Management
Process capability indices (PCIs) for processes with symmetric tolerances have received substantial research attention. But, PCIs for processes with asymmetric tolerances have been comparatively neglected. Recently, Boyles (1994) reviewed the existing PCI literature and proposed several new indices to handle processes with asymmetric tolerances. In this paper we analyze PCIs based on various process characteristics., then introduce a new class of capability indices to handle processes with asymmetric tolerances. The proposed new indices are compared with existing PCIs in terms of process yield, process centering, and process characteristic related to loss functions. The results indicate that the new indices are superior to the existing capability indices, and provide greater accuracy in current applications using PCIs to measure process potential and performance.
Capability measures for processes with multiple characteristics
(2003-03-01)
Chen, KS
;
Pearn, WL
;
Lin, PC
;
工業工程與管理學系
;
Department of Industrial Engineering and Management
Process capability indices, such as C-p, C-a, and C-pk, have been widely used in the manufacturing industry providing numerical measures on process precision, process accuracy, and process performance. Capability measures for processes with a single characteristic have been investigated extensively. However, capability measures for processes with multiple characteristics are comparatively neglected In this paper, we consider a generalization of the yield index S-pk proposed by Boyles, for processes with multiple characteristics. We establish a relationship between the generalization and the process yield. We also develop a control chart based on the proposed generalization, which displays all the characteristic measures in one single chart. Using the chart, the engineers can effectively monitor and control the performance of all process characteristics simultaneously. Copyright (C) 2003 John Wiley Sons, Ltd.
Characterization and conductive coating of phosphors for improved brightness
(2005-04-30)
Chang, CH
;
Chiou, BS
;
Chen, KS
;
Ho, JC
;
電子工程學系及電子研究所
In this study, the phosphors used in CRTs are coated with In2O3 conductive layer derived from the hydrolysis of indium chloride. The conductive coating retards/eliminates charging-up on the phosphor surface during the bombardment of the electrons and improves the cathodoluminescent brightness of the phosphor. However, the non-emissive conductive coating also degrades the cathodoluminescent brightness when it is too thick. The cathodoluminescent brightness increases initially with the amount of coating, reaches a maximum at 10 wt.% InCl3, and decreases with further increase of coating. It is found that with a 10 wt.% InCl3 coating, the brightness of phosphor increases by 20% at 500 V and 1 mu A. (c) 2004 Published by Elsevier B.V.
Contract manufacturer selection by using the process incapability index C-pp
(2005-09-01)
Chen, KS
;
Chen, KL
;
Li, RK
;
工業工程與管理學系
;
Department of Industrial Engineering and Management
In the competitive global business environment, enterprises should effectively respond to and satisfy customer needs. Outsourcing manufacturing is an effective method of adjusting the flexibility of production capability. To ensure final product quality, evaluating and selecting a contract manufacturer is essential. Process capability indices are extensively adopted in manufacturing to determine whether a process meets capability requirements. This study attempts to determine the score index R-i and then apply it to assess the process performance of contract manufacturer by using the process incapability index C-pp. The formulae for C-pp and R-i are simple to understand and to apply. The procedure developed in this paper is also an easy and convenient tool for practitioners to assess contract manufacturer quality performance and make more reliable decisions regarding contract manufacturer.
Distributional and inferential properties of the process accuracy and process precision indices
(1998)
Pearn, WL
;
Lin, GH
;
Chen, KS
;
工業工程與管理學系
;
Department of Industrial Engineering and Management
Process capability indices such as C-p, k, and C-pk, have been widely used in manufacturing industry to provide numerical measures on process potential and performance. While C-p measures overall process variation, k measures the degree of process departure. In this paper, we consider the index C-p and a transformation of k defined as C-a = 1 - k which measures the degree of process centering. We refer to C-p as the process precision index, and C-a as the process accuracy index. We consider the estimators of C-p and C-a, and investigate their statistical properties. For C-p, we obtain the UMVUE and the MLE. We show that this UMVUE is consistent, and asymptotically efficient. For C-a, we investigate its natural estimator. We obtain the first two moments of this estimator, and show that the natural estimator is the MLE, which is asymptotically unbiased and asymptotically efficient. We also propose an efficient test based on the UMVUE of C-p. We show that the proposed test is the UMP test.
Estimating process capability index C"(pmk) for asymmetric tolerances: Distributional properties
(2001)
Pearn, WL
;
Lin, PC
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Chen, KS
;
工業工程與管理學系
;
Department of Industrial Engineering and Management
Pearn et al. (1999) considered a capability index C"(pmk), a new gener alization of C-pmk, for processes with asymmetric tolerances. In this paper, we provide a comparison between C"(pmk), and other existing generalizations of C-pmk PM on the accuracy of measuring process performance for processes with asymmetric tolerances. We show that the new generalization C"(pmk) is superior to other existing generalizations of C-pmk. Under the assumption of normality, we derive explicit forms of the cumulative distribution function and the probability density function of the estimated index (C) over cap "(pmk). We show that the cumulative distribution function and the probability density function of the estimated index (C) over cap "(pmk) can be expressed in terms of a mixture of the chi-square distribution and the normal distribution. The explicit forms of the cumulative distribution function and the probability density function considerably simplify the complexity for analyzing the statistical properties of the estimated index (C) over cap "(pmk).
Gold-free fully cu-metallized InGaP/GaAs heterojunction bipolar transistor
(2005-01-01)
Chang, SW
;
Chang, EY
;
Biswas, D
;
Lee, CS
;
Chen, KS
A gold-free, fully Cu-metallized InGaP/GaAs heterejunction bipolar transistor using platinum as the diffusion barrier has been successfully fabricated. The HBT uses Pd/Ge and Pt/Ti/Pt/Cu for n-type and p(+)-type ohmic contacts, respectively, and Ti/Pt/Cu for interconnect metals with platinum as the diffusion barrier. The Ti/Pt/Cu structure was stable during annealing up to 350degreesC judging from the X-ray diffraction (XRD) data and sheet resistance. A current-accelerated stress test was conducted on the device with a current density J(C) = 140 kA/cm(2) for 24 h, and the current gain showed no degradation. The devices were also thermally annealed at 250degreesC,for 24 h and showed little change. We have successfully demonstrated that an Au-free, fully Cu-metallized HBT can be realized using Pt as the diffusion barrier and Pd/Ge and Pt/Ti/Pt/Cu as the ohmic contacts.
Graphical analysis of capability of a process producing a product family
(2005-10-01)
Huang, ML
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Chen, KS
;
Li, RK
;
工業工程與管理學系
;
Department of Industrial Engineering and Management
Statistical techniques are effective and powerful means of quantifying the variability of processes, analyzing this variability with reference to product requirements, and eliminating this variability in product manufacturing. Many process capability indices have been effectively and widely used to determine whether the quality of a process meets preset targets. However, conventional process capability indices cannot be applied to assess the entire process capability of a product family with nominal-the-best specifications. This work presents a novel process capability index (C-pp(T)), which takes into account all family members. The index C-pp is a simple transformation from index C-pm, and C-pp(T) provides additional, individual information concerning the accuracy and precision of a process. Vannman's (delta, gamma)-plot [Vannman and Deleryd, Quality and Reliability Engineering International 15(3): 213-217 (1999)] is revised to compare the process capabilities of family members under both 100% inspection and sampling plans. Examples are provided to demonstrate the method's practical application.
Making decisions in assessing process capability index C-pk
(1999-07-01)
Pearn, WL
;
Chen, KS
;
工業工程與管理學系
;
Department of Industrial Engineering and Management
Process capability indices C-p, C-pk and C-pm have been used in manufacturing industries to provide a quantitative measure of process potential and performance. The formulae for these indices are easy to understand and straightforward to apply. However, since sample data must be collected in order to calculate these indices, a great degree of uncertainty may be introduced into capability assessments owing to sampling errors. Currently, most practitioners simply look at the value of the index calculated from the sample data and then make a conclusion on whether the given process meets the capability (quality) requirement. This approach is not reliable, since sampling errors are ignored. Cheng (Qual. Engng., 7, 239-259 (1994)) has developed a procedure involving estimators of C-p and C-pm for practitioners to use to determine whether a process meets the capability requirement or not. However, no procedure for C-pk was given, because difficulties were encountered in calculating the sampling distribution of the estimator of C-pk. In this paper we use a newly proposed estimator of C-pk to develop a procedure for practitioners to use so that decisions made in assessing process capability are more reliable. Copyright (C) 1999 John Wiley & Sons, Ltd.
New generalization of process capability index C-pk
(1998-12-01)
Pearn, WL
;
Chen, KS
;
工業工程與管理學系
;
Department of Industrial Engineering and Management
The process capability index C-pk has been widely used in manufacturing industry to provide numerical measures of process potential and performance. As noted by many quality control researchers and practitioners, C-pk is yield-based and is independent of the target I: This fails to account for process centering with symmetric tolerances, and presents an even greater problem with asymmetric tolerances. To overcome the problem, several generalizations of C-pk have been proposed to handle processes with asymmetric tolerances. Unfortunately, these generalizations understate or overstate the process capability in many cases, so reflect the process potential and performance inaccurately. In this paper, we first introduce a new index C-pk", which is shown to be superior to the existing generalizations of C-pk We then investigate the statistical properties of the natural estimator of C-pk", assuming that the process is normally distributed.
New generalization of process capability index C-pk
(1998-12-01)
Pearn, WL
;
Chen, KS
;
工業工程與管理學系
;
Department of Industrial Engineering and Management
The process capability index C-pk has been widely used in manufacturing industry to provide numerical measures of process potential and performance. As noted by many quality control researchers and practitioners, C-pk is yield-based and is independent of the target I: This fails to account for process centering with symmetric tolerances, and presents an even greater problem with asymmetric tolerances. To overcome the problem, several generalizations of C-pk have been proposed to handle processes with asymmetric tolerances. Unfortunately, these generalizations understate or overstate the process capability in many cases, so reflect the process potential and performance inaccurately. In this paper, we first introduce a new index C-pk", which is shown to be superior to the existing generalizations of C-pk We then investigate the statistical properties of the natural estimator of C-pk", assuming that the process is normally distributed.
Performance assessment of processing and delivery times for very large scale integration using process capability indices
(2002)
Chen, KS
;
Chen, HT
;
Tong, LI
;
工業工程與管理學系
;
Department of Industrial Engineering and Management
Process quality and delivery time have received increasing attention in the highly competitive electronics industry. Many studies have proposed process capability indices (PCIs) to assess process effectiveness. However, methods to assess the performance in terms of processing and delivery times of products have seldom been discussed. The conventional PCIs can no longer assess the processing time (PT) and delivery time (DT) performance objectively or identify the relationship between PCIs and the non-conformance rate of PT or the conformance rate of DT. Lacking an effective performance index or an objective testing procedure to assess process/product performance will lead to inefficiency or a high manufacturing management overhead cost. Therefore, this study offers effective performance indices (i.e., PCIs) to assess the PT and DT performance for very large scale integration (VLSI). The uniformly minimum variance unbiased (UMVU) estimators of the proposed PCIs are derived under the assumption of a normal process distribution. The PCI estimators are then employed to construct a one-to-one relationship between the PCIs and the conformance rate of DT or non-conformance rate of PT, respectively. Finally, hypothesis testing procedures for the proposed PCIs are also developed. The testing procedure can be used to determine whether DT or PT can satisfy a customer's requirements.