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Final Report: Enabling Commercialization of a Lead-Free Coating Manufacturing ProcessEPA Contract Number: EPD09021
Title: Enabling Commercialization of a Lead-Free Coating Manufacturing Process
Investigators: Garich, Holly
Small Business: Faraday Technology, Inc.
EPA Contact: Manager, SBIR Program
Project Period: February 1, 2009 through July 31, 2009
Project Amount: $69,982
RFA: Small Business Innovation Research (SBIR) - Phase I (2009) RFA Text | Recipients Lists
Research Category: Small Business Innovation Research (SBIR)
This Phase I SBIR project addresses the need for a manufacturing process that enables high reliability lead-free tin coatings for electronics manufacturing. Because of legislation enforced in the European Union (EU) as of July 1, 2006 (namely Directive 2002/95/EC [ROHS]), lead, which has been the most commonly used solder material for connecting electronic components to the base printed circuit boards (PCBs), has been phased out of tin-lead solders. The global trend to eliminate lead from electronic devices is driven by legislative and marketing pressures based on environmental, health, and social concerns about the cumulative effects of lead in waste streams. The occurrence of tin whiskers, resulting from the use of lead-free tin solders, is a strong technical barrier that currently prohibits the use of lead-free tin solders in some electronic applications, such as aerospace and automotive applications, where failures are unacceptable. The growth of tin whiskers from lead-free, tin-rich deposits may cause short-circuits or metal vapor arcing in the electronics components, ultimately leading to device failure. For lead-free tin solders to become a commercial reality, and for the environmental benefit of lead-free electronics to be realized, technical barriers such as the growth of whiskers must be overcome.
Faraday Technology, Inc. is developing a non-steady state electrochemical process (termed the Faradayic Process) for deposition of pure tin solders in electronic manufacturing applications with controlled deposit properties such as internal stress and grain size. The Faradayic Process is based on the use of non-steady state electric fields to control the deposition process and, as a consequence, the physical properties of the tin deposit. This will ultimately enable the development of a pure tin solder electrodeposition process with minimal to no whisker growth, facilitating the wide-spread implementation of a lead-free, pure tin technology, which is anticipated to reduce the environmental lead exposure associated with: (1) disposal of plating baths containing lead, and (2) disposal of leaded electronic products as well as lead-free electronic products suffering from faulty components as a consequence of tin whisker growth.
The purpose of this Phase I SBIR project was to demonstrate the ability to control the stress in pure tin electrodeposits with non-steady state electric fields. Compressive stress within the tin deposit is thought to be a driving force and necessary precursor for the development of tin whiskers. The Faradayic Process is a proven tool for the control of deposit properties such as grain size, internal stress, and preferred grain orientation. In this project, Faraday explored the relationship between pulse and pulse reverse waveform parameters and internal stress. This Phase I project demonstrates the feasibility of reproducibly depositing pure tin coatings with controlled stress properties with pulse and pulse reverse waveforms. Internal stress of pure tin deposits was shown to be dependent upon the waveform conditions of the deposition process. Faraday Technology demonstrated that it could deposit pure tin coatings of tensile, compressive, or zero internal stress. These stress states may be reproducibly deposited through the use of pulse and pulse reverse waveforms. SEM images and XRD characterization further support the evidence that pulse and pulse reverse waveforms enable control of pure tin electrodeposits. Control of properties would enable pure tin coatings to be tailored for specific applications.
Characterization tests conducted during this Phase I feasibility effort demonstrate that the physical properties of pure tin electrodeposits may be controlled with applied electric field parameters in a simple, non-toxic plating chemistry. Control of the deposit’s physical properties is achieved with sophisticated electric fields engineered to deliver a specific set of deposit properties, rather than through the use of exotic or toxic chemical additives that currently dominates industrial electrodeposition processes. Development of such a process is anticipated to improve the green nature of electronics manufacturing through: (1) the elimination of lead with equivalent performance characteristics, and (2) the replacement of a lead-tin process with a pure tin process that is environmentally benign and compatible with existing post-processes.
The elimination of lead from tin-lead solders has lead to a global effort to identify a material compatible with current processes and hardware while providing equivalent or improved reliability/performance. The issue of tin whiskers limits the widespread adoption of a single technology and, as such, the marketplace it littered with various alternatives that, in general, do not provide equivalent or improved reliability characteristics. Furthermore, the tin-rich alloy alternatives that currently are commercially available require higher processing temperatures, which result in an increase in the energy necessary for the manufacturing process. Implementation of a pure tin manufacturing process would address these key factors if not for tin whiskers. Development of a pure tin process with properties that mitigate whisker growth is anticipated to offer a manufacturing advantage to tin-rich alternatives. To identify a commercial partner to bring the technology to the market, reliability of the pure tin deposit must be demonstrated.
Faraday Technology currently is working to identify commercially relevant industrial partners who will aid in the qualification of pure tin deposits with controlled physical properties deposited with pulse and pulse-reverse processes. Additionally, the technology must be scalable, robust, and mature, and the complexity must be equivalent or less than currently available lead-free solder deposition technology. A pure tin process will be less complex than the tin-rich solders that currently are available. Faraday Technology has a great deal of experience in scaling processes to manufacturing scale in addition to its competency in the design and building of electrochemical processing hardware. These factors are expected to enhance the commercialization efforts for a pure tin solder deposition process. Currently, there is little competition in the development of a pure tin solder deposition process; most competing technologies are based on tin-rich deposits that create their own set of environmental problems because of the higher processing temperatures required for these coatings. Faraday Technology's approach is centered on control of the deposition process through the use of sophisticated waveforms engineered to deliver controllable deposit properties, rather than the use of exotic and toxic chemicals that traditionally dominate electrodeposition processes. Therefore, in addition to the environmental benefit of the development of a pure tin solder deposit, the Faradayic approach is environmentally benign.