Christopher M. Greene and Krishnaswami Srihari
Environmental concerns over hazardous materials being placed in landfills have caused many countries to enact legislation to limit and/or eliminate the use of lead in electronic…
Abstract
Purpose
Environmental concerns over hazardous materials being placed in landfills have caused many countries to enact legislation to limit and/or eliminate the use of lead in electronic devices. As a result, the electronics manufacturing industry has undertaken efforts to comply with the legislation. Solder paste is typically used as the joining material between boards and components. The standard solder paste alloy has traditionally been a tin/lead eutectic. Lead‐free should, in theory, have the same functionality as the standard pastes to be utilized as a drop‐in replacement. Typically, solder paste is deposited on to a land pattern site by a stencil printer. In the manufacturing environment, speed and accuracy are desirable characteristics of the stencil printing operation. The purpose of this paper is to determine how fast a selection of lead‐free pastes can be successfully printed.
Design/methodology/approach
A representative sample of four lead‐free solder pastes containing different alloys was selected. A series of experiments at an increasing print speed was used to deposit these solder pastes on to printed circuit boards and the printed solder volumes were measured. The maximum print speed for each paste was observed and noted for future use.
Findings
Of the four alloys selected for experimentation, one emerged to have the most superior performance in terms of high‐speed printability. The speeds for each paste were observed and noted for future use.
Research limitations/implications
Experimentation was performed in an electronics service provider's environment using equipment and materials that were normally used in production.
Practical implications
The parameters obtained can be used on the manufacturing floor assembling lead‐free products.
Originality/value
The results offer a suggestion (in the form of the parameters that can be utilized) as to what parameters to use in the stencil printing of lead‐free solder paste at high speeds.
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Keywords
Girish S. Wable, Quyen Chu, Purushothaman Damodaran and Krishnaswami Srihari
Historically, tin‐lead solder has been a commonly used joining material in electronics manufacturing. Environmental and health concerns, due to the leaching of lead from landfills…
Abstract
Purpose
Historically, tin‐lead solder has been a commonly used joining material in electronics manufacturing. Environmental and health concerns, due to the leaching of lead from landfills into ground water, have necessitated legislation that restricts the use of lead in electronics. The transition from tin‐lead solder to a lead‐free solder composition is imminent. Several alternative solder alloys (and their fluxes) have been researched for electronics assembly in the last few years. The objective of this research was to develop a systematic selection process for choosing a “preferred” lead‐free solder paste, based on its print and reflow performance.
Design/methodology/approach
After a detailed study of industry preferences, published experimental data, and recommendations of various industrial consortia, a near eutectic tin‐silver‐copper (SAC) composition was selected as the preferred alloy for evaluation. Commercially available SAC solder pastes with a no‐clean chemistry were extensively investigated in a simulated manufacturing environment. A total of nine SAC pastes from seven manufacturers were evaluated in this investigation. A eutectic Sn/Pb solder paste was used as a baseline for comparison. While selecting the best lead‐free paste, it was noted that the selected paste has to perform as good as, if not better than, the current tin‐lead paste configuration used in electronics manufacturing for a particular application. The quality of the solder pastes was characterized by a series of analytical and assembly process tests consisting of, but not limited to, a printability test, a solder ball test, a slump test, and post reflow characteristics such as the tendency to form voids, self‐centring and wetting ability.
Findings
Each paste was evaluated for desirable and undesirable properties. The pastes were then scored relative to each other in each individual test. An aggregate of individual test scores determined the best paste.
Originality/value
This paper summarizes a systematic approach adopted to evaluate lead‐free solder pastes for extreme reflow profiles expected to be observed in reflow soldering lead‐free boards.
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Venkatesh Arasanipalai Raghavan, Sangwon Yoon and Krishnaswami Srihari
This paper aims to focus on integrating a lean framework in a high-mix-low-volume (HMLV) printed circuit board assembly (PCBA) environment to enhance current assembly processes…
Abstract
Purpose
This paper aims to focus on integrating a lean framework in a high-mix-low-volume (HMLV) printed circuit board assembly (PCBA) environment to enhance current assembly processes and facility layouts. An HMLV PCBA environment is characterized by stochastic demands, a variety of products in terms of shapes and sizes and different sequences of assembly and test operations, in addition to long cycle times and high fall-out rates.
Design/methodology/approach
Preliminary analysis indicates that the push inventory control system led to the longer cycle times, such that various lean methodologies have been applied to enhance the assembly operations. In this research, Kanban sizes for different assembly lines are also estimated to integrate and implement a “pull-system” into the lean framework. In addition, material movement and facility layout have been studied to minimize work-in-process travel time. An “iterative-MAIC” approach has been applied to implement lean principles.
Findings
As a result, a lean manufacturing pilot line has been implemented to evaluate the effectiveness of the lean principles before rolling them out across the manufacturing floor. It has been shown that the cycle times of the pilot line products are decreased by 40 per cent and the number of defects decreased by 10-30 per cent, depending on different assembly processes, after the lean implementation.
Originality/value
There is limited literature that addresses lean transformation in an HMLV electronics manufacturing service provider handling several product types with different testing methodologies, frequent product revision changes and higher fall-out rates. Hence, in this research, lean manufacturing has been implemented in an HMLV PCBA environment, which has the challenges of varying demand with a mix of assembly and test operations for different product families.
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Deepak Manjunath, Satyanarayan Iyer, Shawn Eckel, Purushothaman Damodaran and Krishnaswami Srihari
The leaching of lead from electronic components in landfills to ground water is harmful to health and to the environment. Increasing concern over the use of lead in electronics…
Abstract
Purpose
The leaching of lead from electronic components in landfills to ground water is harmful to health and to the environment. Increasing concern over the use of lead in electronics manufacturing has led to legislation to restrict its use as a joining material. Consequently, significant recent research efforts have been geared to identification of suitable lead‐free solder pastes. Typically, lead‐free solder pastes contain a very active flux in an effort to improve wetting. These aggressive fluxes have the tendency to explode (or burst) and create flux spatter, causing many process problems with sensitive electronic components. The purpose of this paper is to propose solution procedures to minimize/eliminate these flux spatters, particularly, on gold fingers in memory modules when lead‐free solder pastes are used.
Design/methodology/approach
Four no‐clean, lead‐free Sn‐Ag‐Cu (SAC) alloy‐based solder pastes consisting of four different flux systems from three different vendors were evaluated. Two types of reflow profiles (linear and ramp‐soak‐ramp) were also evaluated. Experiments were also conducted to optimise the soak temperature and soak time to determine a broader process window for lead‐free volume production with minimal flux spatter on the contact fingers of memory modules. In order to validate our findings the recommended profile and paste was adopted in production. Additional experiments on a board with a different surface finish were also carried out to validate the recommendations.
Findings
Flux spatter can be reduced/eliminated through proper selection of flux chemistry and reflow profile optimisation. The experimental study conducted indicates there is a reduction in the occurrence of flux spatter when a ramp‐soak‐ramp profile is used with lead‐free solder pastes.
Originality/value
Demonstrates that flux spatter can be reduced/eliminated by carefully choosing a soak profile and appropriate flux chemistry.