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Article
Publication date: 25 September 2007

Sunil Gopakumar, Peter Borgesen and K. Srihari

The objective of this research is to address issues that relate to the assembly of Sn/Ag/Cu bumped flip chips.

Abstract

Purpose

The objective of this research is to address issues that relate to the assembly of Sn/Ag/Cu bumped flip chips.

Design/methodology/approach

Flip chips bumped with Sn/Ag/Cu bumps were assembled onto different lead‐free surface finishes at lead‐free soldering temperatures. Sensitivity to fluxes, reflow profiles, pad finishes and pad designs were all investigated and the potential consequences for assembly yields were calculated numerically.

Findings

Soldering defects, such as incomplete wetting and collapse and poor self‐centring were observed in the assemblies. Defect levels were sensitive to contact pad metallurgy and flux type, but not to flux level and reflow profile within the ranges considered. Owing to a particularly robust substrate‐pad design, defects observed in this work were limited to incomplete wetting and collapse, as well as poor self‐centering.

Research limitations/implications

The scope of this work is limited to the lead‐free fluxes available at the time of research. A switch to lead‐free solder alloys in flip chip assemblies raises concerns with respect to the compatibilities of materials and the quality of soldering that is achievable. While this may be less of an issue in the case of larger area array components, such as ball grid arrays and chip scale packages, it is more of a concern for applications that use flip chips due to the smaller size of the solder spheres. Assembly yields tend to become more sensitive to the reduced collapse of the joints. More work is essential to investigate the potential benefits of more active lead‐free fluxes, both no‐clean tacky and liquid fluxes, in reducing or eliminating soldering defects.

Originality/value

The paper offers insights into assembly issues with Sn/Ag/Cu bumped flip chips.

Details

Soldering & Surface Mount Technology, vol. 19 no. 4
Type: Research Article
ISSN: 0954-0911

Keywords

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Article
Publication date: 25 September 2009

Qiang Su, Lei Liu and Shengjie Lai

The purpose of this paper is to focus on the assembly quality of copier products, specifically, concentrating on the prediction of the operator‐induced assembly defect.

Abstract

Purpose

The purpose of this paper is to focus on the assembly quality of copier products, specifically, concentrating on the prediction of the operator‐induced assembly defect.

Design/methodology/approach

Based on the Shibata model, the design‐based assembly complexity is redesigned. And the Sony Standard Time is replaced by the Fuji Xerox Standard Time in the calculation of the process‐based assembly complexity. Furthermore, different correlation functions are attempted and comparatively studied in the regression analysis. Thereby, a new defect rate prediction model is proposed and validated with three copier assembly cases.

Findings

The new proposed model is much more accurate and stable in the human‐induced assembly defect prediction in copier production.

Practical implications

The proposed model can be used to ensure the assembly quality by removing potential defects at the structure and process design stages. Meanwhile, with this model, the interactions between the engineers and designers can be more effective.

Originality/value

This paper presents a novel assembly defect rate prediction model for copier assembly quality management.

Details

Assembly Automation, vol. 29 no. 4
Type: Research Article
ISSN: 0144-5154

Keywords

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Article
Publication date: 13 February 2007

Yueli Liu and R. Wayne Johnson

To optimize the printed circuit board design and assembly processes to minimize defects in the assembly of 01005 size chip resistors.

Abstract

Purpose

To optimize the printed circuit board design and assembly processes to minimize defects in the assembly of 01005 size chip resistors.

Design/methodology/approach

A test board was designed with a range of pad sizes, pad shapes, pad spacings and pad orientations. This test board was used in a series of designed experiments to optimize the printing, placement and reflow processes. Assembly defects were analyzed as a function of board design and assembly processes.

Findings

An electroformed, 76 μm stencil yielded a robust paste printing process and higher process capability indices (Cp) compared to a 102 μm stencil. Nitrogen reflow was required to achieve good solder wetting due to the high surface‐to‐volume ratio of the solder deposits. With regard to bridging defects, no defects were observed if the pad‐to‐pad spacing for parallel resistors was 150 μm or larger. Rectangular pads with no vias‐in‐pad and designed at 90 percent of nominal pad size (pad size type 2) with the ramp profile, independent of 0° or 90° resistor orientation yielded the lowest number of defects. Given the undersized pads on the actual board, the 90 percent pad average width was 170 μm (versus a design value of 183 μm) and the measured width of the 01005 chip resistor was 180 μm. Thermal cycle reliability testing of the solder joints with this pad size showed no failures after 1,000 thermal cycles.

Originality/value

The results of this work provide a set of design and assembly processes recommendations for those who must implement 01005 size component assembly in production.

Details

Soldering & Surface Mount Technology, vol. 19 no. 1
Type: Research Article
ISSN: 0954-0911

Keywords

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Article
Publication date: 2 April 2019

Yunyong Li, Yong Zhao, Haidong Yu and Xinmin Lai

A new deviation propagation model considering the form defects in compliant assembly process is proposed. The purpose of this paper is to analyze the deviation propagation…

Abstract

Purpose

A new deviation propagation model considering the form defects in compliant assembly process is proposed. The purpose of this paper is to analyze the deviation propagation by using the basic deviation fields. In particular, each basic deviation field is defined with a generalized compliance matrix of part.

Design/methodology/approach

First, the form defects of parts may be decomposed into a linear combination of basic deviation fields, which are constructed by the eigen-decomposition of the structure stiffness of parts with ideal dimensions. Each basic deviation field is defined with a generalized compliance of part. Moreover, by analyzing the relationship between the basic deviation fields before and after assembling process, a new sensitive matrix is obtained in which each value expresses the correlation of a basic deviation field between the parts and the assembly.

Findings

This model may solve the deviation propagation problems of compliant assembly with considering form defects. Here, one case is used to illustrate the deviation propagation in the assembly process. The results indicate that the proposed method has higher accuracy than the method of influence coefficient when the entire deviation fields of parts are considered. Moreover, the numerical results with the proposed method basically agree with the experimental measurements.

Research limitations/implications

Owing to the hypothesis of linear superposition of basic deviation fields, the research in this paper is limited to the parts with linear elastic deformation. However, the entire form defects of parts are considered rather than the deviations of the local feature points. It may be extended to analyze the three-dimensional deviations of complex thin-walled parts.

Originality/value

A deviation propagation model considering parts form defects is developed to achieve more accurate predictions of assembly deviation by using the basic deviation fields.

Details

Assembly Automation, vol. 39 no. 1
Type: Research Article
ISSN: 0144-5154

Keywords

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Article
Publication date: 1 January 2006

Sanka Ganesan and Michael Pecht

To present and discuss open trace defects uncovered in an FR4 assembly during electrical testing.

Abstract

Purpose

To present and discuss open trace defects uncovered in an FR4 assembly during electrical testing.

Design/methodology/approach

This paper presents open trace defects observed in FR4 assemblies and analyses the distribution of defects. The paper also discusses possible root causes for their occurrence.

Findings

The open trace defects that occurred during printed circuit board (PCB) fabrication should have been observed by the board manufacturer. It appears that the PCB manufacturer did not perform automatic optical inspection (AOI) and electrical testing during the manufacturing of the boards. The cost due to the rejected PCBAs was approximately 3x times that of the PCB cost.

Originality/value

The paper highlights the costly impact of uncovering a PCB defect after assembly. Based on the results of this study, the implementation of electrical testing and AOI for PCBs is recommended.

Details

Circuit World, vol. 32 no. 1
Type: Research Article
ISSN: 0305-6120

Keywords

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Article
Publication date: 20 September 2011

Yong‐Won Lee, Keun‐Soo Kim and Katsuaki Suganuma

The purpose of this paper is to optimize assembly processes in order to minimize defects in the assembly of 01005 chip components.

Abstract

Purpose

The purpose of this paper is to optimize assembly processes in order to minimize defects in the assembly of 01005 chip components.

Design/methodology/approach

During the study, solder paste printing process‐related variables, such as solder paste type, stencil type, and stencil opening ratio, and pick and place process‐related methods, such as vision camera type and vacuum pickup nozzle type were evaluated with the goal of achieving a high‐yield assembly solution for 01005 chip components. A test board was used in a series of designed experiments to optimize the solder paste printing, pick and placement, and reflow processes. Assembly defects were analyzed as a function of the stencil design and the assembly processes.

Findings

The results of the study indicated that both electroformed and electropolished laser‐cut stencils had a comparable print quality with respect to the solder volume delivered to the pads. In terms of assembly yield performance, type 4 (size range: 20‐38 μm) solder paste with a smaller sphere size gave a better overall yield and better paste deposition on the pad, if used on a 0.08‐mm thick electroformed stencil with a 90 per cent aperture. Temperature cycling between −65 and 150°C, with up to 1,500 cycles, showed that no cracks were observed at the solder joints due to temperature cycling. The process and design change required for achieving a robust manufacturing process have been indicated and reported.

Originality/value

The results of this work provide process recommendations for the implementation of 01005‐sized chip components assembly in mass production processes.

Details

Soldering & Surface Mount Technology, vol. 23 no. 4
Type: Research Article
ISSN: 0954-0911

Keywords

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Article
Publication date: 1 January 1989

R. Nameth

The initial excitement over increased solder joint densities, higher manufacturing throughput, and superior electrical performance brought forth by surface mount…

Abstract

The initial excitement over increased solder joint densities, higher manufacturing throughput, and superior electrical performance brought forth by surface mount technology (SMT) has been replaced by frustrations over lower yields and the inherent difficulties of inspecting hidden solder joints. In the plated through hole (PTH) process, rework and inspection tasks were not only relatively easier tasks, but also less costly. The high cost of inspecting and reworking SMT assemblies dictates a rethinking of the assembly process. Increasing first time yields becomes the key to reducing SMT inspection and rework costs. In a high volume facility, a 100% visual inspection process is not feasible because of the high cost of inspection and rework. However, if a company intends to remain competitive, inspection and rework must be reduced without a sacrifice to final product quality. Realising that it is not possible to ‘inspect’ quality into a product, improved yield must result from a controlled process environment. By maintaining a controlled environment, one will be provided with lower inspection costs, lower rework costs, lower scrap and, in the final analysis, improved product quality. At the heart of any process control environment should be a real‐time process control system designed specifically to accommodate SMT process defects. Process monitoring is accomplished by locating and identifying SMT process flaws. These flaws will then be reported to a host system for statistical analysis. These are statistical data used to make timely adjustments to the various stages of the assembly process in a real‐time manner. Being able to monitor the production process objectively in real time, and detect hidden flaws accurately, are the keys to having a successful process inspection system. Automated X‐ray Inspection is gaining acceptance as a viable process monitoring tool, capable of detecting and reporting SMT process flaws, including those hidden flaws not reported with typical visual inspection systems. The purpose of this paper is to show how an Automated X‐ray Inspection system can be integrated into the SMT production process as a cost‐effective method for improving SMT yield.

Details

Soldering & Surface Mount Technology, vol. 1 no. 1
Type: Research Article
ISSN: 0954-0911

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Article
Publication date: 1 April 1998

Volker‐Ekkehart Koch

A ball grid array (BGA) is a surface‐mount device and is processed in a standard surface‐mount (SM) assembly line. However, there are some special features which make it…

Abstract

A ball grid array (BGA) is a surface‐mount device and is processed in a standard surface‐mount (SM) assembly line. However, there are some special features which make it different from other assemblies. The peculiarities of PCB layout, screen printing, placement, soldering, and inspection in BGA processing are presented. The failures of BGA assembly during ramp up and series production start‐up are analysed in detail. An assembly quality better than 1dpm was achieved. The scale of repair is determined by the electrical quality of the devices. If small packages with higher pincount and better electrical performance are required, the µBGA is a sound choice. Compared with other high pincount packages with a small formfactor as TAB, flip‐chip and chip on board, the µBGA may be processed in a standard SM assembly line. The results of µBGA‐assembly feasibility studies are discussed.

Details

Soldering & Surface Mount Technology, vol. 10 no. 1
Type: Research Article
ISSN: 0954-0911

Keywords

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Article
Publication date: 15 October 2019

Yicong Gao, Chuan He, Bing Zheng, Hao Zheng and Jianrong Tan

Complexity is the main challenge for present and future manufacturers. Assembly complexity heavily affects a product’s final quality in the fully automated assembly

Abstract

Purpose

Complexity is the main challenge for present and future manufacturers. Assembly complexity heavily affects a product’s final quality in the fully automated assembly system. This paper aims to propose a new method to assess the complexity of modern automated assembly system at the assembly design stage with respect to the characteristics of both manufacturing system and each single component to be mounted. Aiming at validating the predictive model, a regression model is additionally presented to estimate the statistic relationship between the real assembly defect rate and predicted complexity of the fully automated assembly system.

Design/methodology/approach

The research herein extends the S. N. Samy and H. A. ElMaraghy’s model and seeks to redefine the predictive model using fuzzy evaluation against a fully automated assembly process at the assembly design stages. As the evaluation based on the deterministic scale with accurate crisp number can hardly reflect the uncertainty of the judgement, fuzzy linguistic variables are used to measure the interaction among influence factors. A dependency matrix is proposed to estimate the assembly complexity with respect to the interactions between mechanic design, electric design and process factors and main functions of assembly system. Furthermore, a complexity attributes matrix of single part is presented, to map the relationship between all individual parts to be mounted and three major factors mentioned in the dependency matrix.

Findings

The new proposed model presents a formal quantification to predict assembly complexity. It clarifies that how the attributes of assembly system and product components complicate the assembly process and in turn influence the manufacturing performance. A center bolt valve in the camshaft of continue variable valve timing is used to demonstrate the application of the developed methodology in this study.

Originality/value

This paper presents a developed method, which can be used to improve the design solution of assembly concept and optimize the process flow with the least complexity.

Details

Assembly Automation, vol. 39 no. 5
Type: Research Article
ISSN: 0144-5154

Keywords

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Article
Publication date: 28 December 2020

Weibin Lan, Shouwen Fan and Shuai Fan

This paper aims to propose an elementary approach toward the identification of assembly defects of a cam curved groove mechanism.

Abstract

Purpose

This paper aims to propose an elementary approach toward the identification of assembly defects of a cam curved groove mechanism.

Design/methodology/approach

A numerical analysis method for identifying the assembly defects of the cam curved groove mechanism is proposed by resorting to Hertz contact theory. A general mathematical model is established to analyze the kinematic and dynamic characteristics with an interference fit between the main roller and cam curved groove, including the contact points of the external and internal ring.

Findings

The analysis method of the contact point characteristics of the cam curved groove mechanism is given in this paper, and the kinematic and dynamic characteristics of the main roller can be analyzed. The numerical examples presented in this paper are implemented in MATLAB, feasibility and validity of the above algorithm are verified by the finite element method.

Originality/value

Regarding the defects of the interference fit, the findings of this paper can serve as a reference for researchers in reducing the defects in the design process of the cam mechanism.

Details

Assembly Automation, vol. 41 no. 1
Type: Research Article
ISSN: 0144-5154

Keywords

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