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Developing a green product development strategy

Posted: 01 Aug 2008 ?? ?Print Version ?Bookmark and Share

Keywords:green electronics? green design and manufacturing?

These low-technology suppliers represent a greater risk to the green supply chain. They tend to be unregulated, with greater focus on cost than on quality or green. They might purposely substitute specified green materials, which might be more expensive, with nongreen components or processes. A very effective system of quality and due diligence has to be in place to prevent this tendency. Recent examples of pet food and toy finish poisoning from China show the large negative impact of unregulated foreign suppliers.

The electronics supply chain is also performing warranty and repair of the customer products. For green products and processes, the repair process of electronic circuits has to be developed and tested, since these processes might have different characteristics from nongreen ones. Other chapters in this book explore how to develop and test repair processes for electronic circuits and PCBs.

Improper adoption of green processes

The obvious concerns in adopting green materials and processes are the quality and reliability issues. The book features several chapters with many examples of case studies on how to properly test green materials and processes for quality and reliability, using either mathematical or physical environmental conditions to simulate life-cycle material behavior. These tests can be performed by either comparing the properties of green materials and processes to a baseline of nongreen materials, or to study the life cycle through testing to failures. These techniques will result in calculating a quantifiable risk level for green alternatives, or lack thereof.

Most of the green materials and process verifications in this book and in the general literature are based on the performance of the green materials, and not on the consequences of adopting new green materials on the functional performance of the products. New products can be based on either existing designs that have been converted to green or an improvement on the technology of an earlier generation of nongreen products. In the case of converting current products to green, some product performance verification tests will have to be repeated to ensure compliance with advertised specifications, especially when PCB designs are re-layed because of lack of green replacement components with the same footprints. In the case of newly designed green products, verifications tests will uncover any hidden problem when using fresh green materials and processes in the design.

While a company might perform a very thorough set of tests and analysis of green materials and processes, the green products using them might exhibit different functionality than expected in the nongreen predecessor products. Refer to Sec. 7.2 for more insight into the green material conversion consequences in design. These potential adverse consequences could be as follows:

1. RF and wireless circuits!These circuits are susceptible to changes in the shielding provided by changes in the metallic or plating of shield metals (such as the removal of hexavalent chrome coating) or by changing of the PCB surface finish [from tin lead hot air solder leveling (HASL) to immersion silver, for example]. These new green materials might cause a frequency shift in the tuners of these circuits. This is especially serious if there are no adjustments available to tune the RF or wireless oscillators. Redesign or relayout of the electronics circuits might be required.

2. Clock speeds and propagation delays!In very high speed circuits, clock speeds and propagation delays through the electronics circuits and components might be affected by changes to the surface finish of the PCBs or to the materials used in the interconnecting traces on the outer layer surface and through the inner layers of multilayer PCBs and connectors. Electronic race conditions might also be increased due to these conditions.

3. Transmission line reflections. When the electronics on the PCBs are connected directly to outside connectors or to other PCBs or products in a digital communications mode, the impedance match between them is very critical to sustain digital transmission over specified connector cable lengths. Changes to green materials might offset this impedance balance, rendering communications less effective. The communications system might work for shorter distances than specified, engendering a serious customer satisfaction issue. A simple PCB test would be the standard Time Domain Reflectrometry (TDR) test, where a coupon with a specified parallel trace length is used for the PCB laminate to ensure transmission line conformance to specification. This test can be performed at the PCB fabricator location and specified as part of the quality audit.

4. PCB surface features!In some electronic designs, PCB surface features are used for electrical, magnetic or charge coupling in the electronics circuits. Examples would be the use of filled-in surface pads or rings to generate proportional feedback for a position control circuit. Changing the PCB surface finish to green materials might change the electrical or electromagnetic properties, rendering the circuit inoperable or out of control.

5. Surface resistance and cleanliness: With new green materials for soldering and fluxing of electronic PCBs, the cleanliness properties of the PCB after soldering or reflow might change. These changes can be easily measured with a variety of instruments such as surface insulation resistance (SIR) meters.

Green design implementation
The conversion of electronics manufacturing processes to comply with RoHS regulations provides a great opportunity of process improvement for efficient as well as environmentally friendly design and manufacturing processes. Six Sigma and quality techniques for process measurement, analysis and improvement can be used to select optimum RoHS-compliant processes that will increase quality and reduce cost. The methodologies outlined in this section were used by the New England Lead Free Consortium of companies created by the author and jointly supported by funding and resources from member companies, the Toxics Use Reduction Institute (TURI), and the EPA.

An unintended consequence of the RoHS directive began when the components suppliers implemented their RoHS compliance by eliminating banned substances such as lead in the component finishes. As a result, some suppliers decided not offer the components with the original lead finishes, since they did not want to keep two versions of the same component. The exempted industries are finding that they cannot easily obtain their traditional leaded components and therefore are being forced to make necessary changes to their components and processes to be RoHS-compliant. It appears that an unintended impact of the RoHS regulation is a universal switch away from the banned substances for all industries, giving all companies the opportunity to make optimum material and process improvements as they switch into new materials and processes because of RoHS compliance.

Implementation of RoHS offers several opportunities as well as dilemmas for companies. This is because of the myriad alternatives being proposed by their suppliers with conflicting claims, as well as the pace of technological progress in material technologies. What is a hot RoHS material substitute today might become out of favor because of subsequent developments. Examples include such developments as bismuth-based solders, which were attractive because of their lower melting temperature that have fallen out of favor since they have contamination problems with lead, while tin-based solders and finishes were suspect as Pb-free replacements because of their higher reflow temperatures and the dreaded tin whiskers. In addition, technological developments in material technology, as in any other, tend to produce leapfrog effects: a supplier that claims to have the best results for their materials might be overtaken by another supplier with a newer technology. So what is a company to do that is trying to implement RoHS?

The larger companies developed their own research program, with a multitude of talent and resources brought to bear, to solve the problems of material and process conversion for RoHS compliance. They might work with their contractors and material suppliers to implement RoHS compliance using a variety of reliability and test methods, as well as complex analytical tools such as vibration platforms, long-term environmental testing to failure, and electronic scanning microscopes to see the interfacing layers of RoHS-compliant materials. These sophisticated analysis tools and extensive DoE matrices were used to evaluate a large number of candidate material replacement and process parameters.

Medium and smaller companies could not afford these massive programs, but could develop cost-effective green conversion programs using Six Sigma principles for RoHS conversion projects. A set of simple guidelines to effectively manage a successful conversion could be as follows:

1. Avoid the NIH (not invented here) syndrome!There are many resources available for identifying successful materials and process replacements for RoHS-prohibited materials. These include national consortia and standards-setting organizations for electronic products such as NEMI, SMTA, and IPC. However, these organizations might recommend the general composition of the replacement materials, but not the specific process parameters to handle the local complement of equipment and product mix that the company uses.

2. Use standard performance criteria and test methods for the RoHS materials whenever possible!Standards for reliability testing using temperature and humidity cycling, vibrations, electrical conductivity, and mechanical stress exist for many materials from the same sources mentioned in the preceding paragraph. In addition, use testing methods that are standardized in industry, either by using techniques that are outlined in the standards or using commonly available commercial testers to perform the test.

3. When standardized or commonly used testing methods are not available, the current processes could be used as the baseline when comparing RoHS-compliant materials to the current process!Comparing to the baseline can also be used when there is not enough time or resources to properly conduct the testing for the RoHS materials. This could be the case for shorter-term environmental testing. Examples would be to use fewer temperature cycles and not test to failure, but to compare pull tests of RoHS materials to baseline leaded counterparts. Vibration testing could be on specific spectrum lines and not the full spectrum of frequencies. Statistical significance testing could be used to compare Pb-free results to the current product leaded manufacturing process baselines.

4. Use the latest green material selection available, from leading material suppliers, realizing that today's RoHS material champion might not be the champion tomorrow, and that the tests might have to be repeated down the road as the material technology keeps improving. Avoid proprietary or patented materials.

5. Realize that the RoHS conversion effort might not be performed in one single large continuum project, but might be a succession of smaller projects that builds on the knowledge acquired in the previous project. For example, in Pb-free soldering, there might be an initial project to deal with SMT components, with a distinct portion for BGA/mini BGAs, and then follow on projects for through hole and rework.

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