Rework Procedures Research Articles

Intelligent Rework Process Management System under Smart Factory Environment

Rework for defective items is very common in practical shopfloors; however, it generally causes unnecessary energy consumptions and operational costs. In order to address this problem, we propose a novel approach called the intelligent rework process management (i-RPM) system. The proposed system is based on intelligent rework policy, which provides a preventive rework procedure for items with latent defects. Such items can be detected before quality tests by applying conventional classification techniques. Moreover, training sets for the classification algorithms can be collected by using modern information and communications technology (ICT) infrastructures. Items with latent defects are not allowed to proceed to the following processes under intelligent rework policy. Instead, they are returned to the preceding processes for rework in order to avoid unnecessary losses on the shopfloor. Consequently, the proposed system helps to achieve a sustainable manufacturing system. Nevertheless, misclassification by the classification model can degrade the performance of intelligent rework policy. Therefore, the i-RPM system is designed to compare rework policies based on classification accuracy and choose the best one of them. For illustration, we applied the i-RPM system to the rework procedure of a steel manufacturer located in Busan, South Korea, and our experiment results revealed that the cost reduction effect of the intelligent rework policy is affected by several input parameters.

Investigations on a standardized process chain and support structure related rework procedures of SLM manufactured components

For the successful production of high quality parts by selective laser melting, various process steps are required. Besides the SLM process itself, different pre- and rework steps are needed to produce a final component. Therefore, the first part of this paper presents a concept of a standardized process chain for carrying out the necessary planning and production procedures. For this purpose, the CAD-model is enriched with information regarding support structures, the desired surface quality and the position of tooling points. Since major steps in the reworking procedure are the removal of residual powder, the removal of support structures and the finishing operations for functional component surfaces, selected experimental results concerning these steps are presented in the second part of the paper. Based on the result, recommendations for the design of support structures are given.

Rework solution method on large size radial roller bearings

The aim of this paper is to propose and verify a new rework solution method on large size radial roller bearing. Bearing rework is developing rapidly owing to cost control and greenhouse effect. General rework procedures and rules are evaluated by relative files and executed by most famous bearing suppliers. All defective rolling elements are scrapped according to the existing rework solutions, which leads to tremendous wastage. We draw our attention to the possibility of reusing large size rollers. In the procedure, rolling contact fatigue characteristic of roller bearings is analyzed and the solution method by reusing large size rollers is obtained in the paper. In view of greatly changing the rollers, rolling bearing design method is involved in the new solution method. This is significantly different from the old methods. In addition, the rating life of reworked bearing is re-calculated for reliability.

Controlling the Genotoxins Ethyl Chloride and Methyl Chloride Formed During the Preparation of Amine Hydrochloride Salts from Solutions of Ethanol and Methanol

The genotoxins ethyl chloride (EtCl) and methyl chloride (MeCl) were generated during the preparation of the hydrochloride salts of two tertiary amines in the presence of ethanol and methanol, respectively. In EtOH five batches of a tertiary amine hydrochloride were prepared on 0.3−18 kg scale using 37% aqueous HCl; residual EtCl was detected at less than 10 ppm in each batch. The preparation of the hydrochloride salt of another tertiary amine in MeOH on a 3 kg scale produced salt with 11−12 ppm of MeCl, and these higher levels precipitated investigations into controlling the levels of residual MeCl in batches of the HCl salt of the second amine. Four rework procedures were developed to reduce the level of MeCl in one batch of HCl salt. Generating the salts at a lower temperature (10 °C) was the key parameter to minimize the concentration of these impurities in this drug candidate when HCl was charged as 37% aqueous HCl. Control of the process was demonstrated by preparing a 30 kg batch containing 1 ppm o...

Plasma Charging Damage Affecting Flash Memory Device Encountered at Pad Etch

This paper is to present plasma charging damage affecting 0.18 micron flash memory product. The affected product encountered high voltage N-MOS transistor current leakage. Correlation analysis pointed towards the passivation / pad etch step. Engineering splits were performed to isolate and understand the root cause. Several factors were suspected contributing to the current leakage. These factors are categorized by recipe, consumable kit and product technology (process flow). Further splits were performed with the consumable kits divided into three groups; quartz group, anodized aluminum group and the gas distribution plate group. The focus of this paper is to highlight the combined impact of high power radio frequency (RF) from process recipe with equipment consumable parts intrinsic defect affecting flash memory device causing plasma charging damage. This paper also investigates the effectiveness of electrical test rework procedure utilizing ultraviolet (UV) erase.

Decapsulation Method for Flip Chips with Ceramics in Microelectronic Packaging

The decapsulation of flip chips bonded to ceramic substrates is a challenging task in the packaging industry owing to the vulnerability of the chip surface during the process. In conventional methods, such as manual grinding and polishing, the solder bumps are easily damaged during the removal of underfill, and the thin chip may even be crushed due to mechanical stress. An efficient and reliable decapsulation method consisting of thermal and chemical processes was developed in this study. The surface quality of chips after solder removal is satisfactory for the existing solder rework procedure as well as for die-level failure analysis. The innovative processes included heat-sink and ceramic substrate removal, solder bump separation, and solder residue cleaning from the chip surface. In the last stage, particular temperatures were selected for the removal of eutectic Pb-Sn, high-lead, and lead-free solders considering their respective melting points.

Design of a flexible assembly and remanufacturing cell for advanced SM components: selection of cell design concept based on reflow tools

PurposeTo design a flexible integrated robotic assembly and rework (remanufacturing) cell for assembly, selective assembly and rework of advanced surface mount components (SMCs) using the generic methodology developed in this paper.Design/methodology/approachManual rework procedures are investigated for all advanced SMCs. General and specific component‐related rework considerations are obtained and necessary tooling candidates for automation are determined. This is followed by determination of the specific automated rework procedure and selection of suitable tooling for automated robotic rework and generation and evaluation of design concepts.FindingsThe developed methodology, which considers the reflow tool at the centre of the development process, has worked well in designing a flexible integrated robotic assembly and rework cell.Practical implicationsThis study identified the rework requirements for advanced SMCs, the essential features for rework reflow tools, criteria for comparing reflow tools, and a generic procedure for design and concept selection.Originality/valueIt provides valuable knowledge for designers of flexible integrated robotic assembly and rework cells for assembly, selective assembly and rework of advanced SMCs.

High frequency conductor loss impact of oxide and oxide alternative processes

PurposeTo examine the impact of oxide and oxide alternative processes on signal loss in commercial RF applications.Design/methodology/approachStripline conductors were formed using traditional oxide, oxide dissolution/reduction, and oxide alternative processes. Conductor geometry was measured and surface topography was characterized. Effective dielectric constants and characteristic impedance for each system was determined. Finally, line loss for each treatment and rework condition was charted to nearly 20 GHz. Electrical measurements were performed by taking S‐parameter measurements through 20 GHz using an agilent vector network analyzer (VNA).FindingsThe methods employed were sufficient to statistically characterize the increased loss associated with thick oxides and high‐microetch oxide alternatives. Lower etch oxide alternatives yielded benefits for signal integrity. Of importance, rework procedures gave unacceptable increases in line loss. Overall, however, the loss due to innerlayer bonding processes was not of sufficient magnitude to elevate oxides as a primary contributor to conductor loss. For the relative simple, high production system employing epoxy substrate, oxide loss was found to be far less than substrate effects, imaging quality, and foil treatment.Originality/valueElectrical engineers and printed circuit board (PCB) designers strive to focus their efforts on improving the PCB processes leading to maximum conductor loss in the electronic system. This work shows that oxide treatments are not a primary factor in affecting loss. Significant improvements in signal integrity may be achieved, however, with the use of low‐etch oxide alternatives and with restrictions on oxide rework. In addition, this paper allowed for new interpretations of VNA data for better modeling of PCB system data using non‐classical analysis.

A quantitative study of post contract award design changes in construction

The investigation reported forms part of a wider study into the applicability of design for manufacture (DFM) thinking to the total construction process, and the ways in which this could be implemented. Historical data from change order request procedures were examined for several case studies which were considered to be successful projects. These procedures are intended to capture information about design modifications, and thus can be considered to be analogous to the rework procedures used in manufacturing. It was found that in monetary terms alone, the direct cost of post contract design changes amounts to 5.1-7.6% of the total project cost. Although the case studies used here were a convenience sample, the typical financial opportunity for controlling design changes better is likely to be considerably greater than this. Frequently cited reasons for design changes included: employer has changed his requirements, designer's omission in tender documents and new information on existing site conditions. Little commonality between case studies was found at the work package level. In contrast to manufacturing, the availability and accessibility of data relating to rework is problematic.

Automated rework of printed circuit board assemblies: Methods and procedures

In the last few years, although the number of rework stations available on the market has grown considerably, the process of repair has not been fully automated due to the requirement for flexibility and because most processes are complex, unlike printed circuit board assembly (PCBA), which is concerned with dedicated processes. In order to automatically handle a variety of PCBs each of which may have different fault problems, an autonomous rework system capable of advanced sensing, in-process inspection and automatic planning is required. This paper presents automated rework methods and procedures which were developed to extend the capability of a robotic assembly cell so that it could perform rework and in-process inspection of single-sided PCBAs for a minimum batch size of one. It outlines detailed rework procedures for surface mount (SM) and through hole (TH) components, summarizes the hardware requirements and the structure of the cell and evaluates the procedures developed with regard to rework effe...

THERMAL DEFORMATIONS IN THIN CIRCULAR RINGS SUBJECTED TO LOCALIZED HEATING

This investigation examined the vertical and horizontal thermoelastic deformations of the outside diameter of a turbojet-engine roller bearing. During a rework operation, thermal loads were imparted to the bearing by the hands of a bearing technician. A worst case analysis was employed by assuming a three-minute dwell time and diametrically symmetric thermal loading. A numerical model was used together with experimentally measured contact temperature to determine the temperature fields throughout the bearing outer ring. Next, diametric displacement solutions were variationally derived for two mathematical approximations using Hamilton's principle and assuming thin ring behavior. Alternatively, diametric deflections were calculated using a finite element model (FEM) constructed for the bearing outer ring. Then the solutions yielded by the finite element and two analytic techniques were compared to diametric expansion data found experimentally. This analysis yielded vertical expansions in the bearing outer ring's diameter that would be problematic for some bearings during the rework procedure; several recommendations were given to alleviate the problem.

Flip-chip replacement within the constraints imposed by multilayer ceramic (MLC) modules

Economics often dictates that suitable module rework procedures be established to replace solder bump devices (flip chips) reflowed to multichip carriers. These operations are complicated, owing to various constraints such as the substrate's physical and mechanical properties, close proximity of surface features, etc. This paper describes the constraints and the methods to circumvent them. An order of preference based upon the degree of constraint is recommended to achieve device removal and subsequent site dress of the residual solder left on the substrate. It has been determined that rework (device replacement) can be successfully achieved in even highly constricted situations. This is illustrated by the example of utilizing a localized heating technique, hot gas, to remove solder from microsockets from which chips were previously removed. Microsockets are areas to which chips are reflowed to the top surface of IBM's densely populated multilayer ceramic (MLC) modules, thus forming the so-called controlled collapse chip connection or C-4. The microsocket patterns are thus identical to the chip footprint.

An Investigation of Production Problems Relating to the Power-Carrying Capacity of a K-Band Microwave Component

Findings are presented on the effect of various mechanical parameters, performance criteria, environmental conditions, and production techniques. Discussion centers about a K-band microwave duplexer, with particular emphasis on the hybrid ring, in an attempt to reduce breakdown rejections. Of humidity, temperature and pressure, only the latter bad a noticable effect on the breakdown measurements. Performance experiments covered pulse width, phasing, rise time and duty cycle with relation to both duplexer breakdown and magnetron life; and with rise time affecting breakdown. The mechanical aspects of dimensions, tolerances, imperfections and finish were investigated; and the latter two found to be the most important. The production techniques contributing to the determined causes were thoroughly investigated. Cleaning processes were proved to be of considerable importance. Corrective measures and effective rework procedures are described.