Articles from CALCE News© August 1999 issue

Legal Issues of Uprating

CALCE continues to provide guidance on how to avoid the legal risks of part use outside the manufacturer's specified temperature range through its member reports, publications and workshops. CALCE has reported the type of product liability theories that a company which uses parts outside the manufacturer's specified temperature range may face should death, injury, or property damage arise from the use. CALCE has detailed the basic parameters of a product liability prevention program for companies that uprate parts, emphasizing the acute need for "top to bottom" education and training of company personnel--from program mangers to test technicians to hazard analysts. The basic axiom of the CALCE position is clear: unless the company is well-trained in the identified legal "hot spots" and has developed a well-managed product liability prevention program, an injured party's lawyer will be able to exploit the facts concerning uprating activities in any future production liability action.

Most recently, CALCE released an article entitled, "Tipping the Scales in Your Favor When Uprating," which is the feature article in the July issue of the IEEE's Circuits and Devices magazine (Vol. 15 No. 4), co-authored by Margaret Jackson and Michael Pecht, in conjunction with two lawyers from the international law firm, McKenna and Cuneo. In addition, CALCE is hosting a workshop on October 11 in which the legal risks and mitigation methods of part use outside the manufacturer's specifications will be presented.

For more information about CALCE research regarding the use of parts outside the manufacturer's specified temperature range, or the legal issues associated with such use, please contact Dr. Michael Pecht at (301) 405-5323, or pecht@calce.umd.edu.
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Optoelectronics Faculty Receive NSF Industry Matching Award for LED Reliability Project

The CALCE Optoelectronics effort was recently boosted by the approval of a National Science Foundation matching grant to supplement research projects related to physics of failure modeling of plastic-packaged light emitting diode components. The matching program is one feature of the Faculty Early CAREER Development Award that has been received by Dr. Patricia Mead.

The CAREER award is the contemporary replacement for the Presidential Young Investigators program, and is one of the most prestigious recognitions offered to junior engineering faculty. Dr. Mead received the award for her work in the development of physics based failure modeling of semiconductor optical devices and her integrated approach to combining research and education. The matching award also includes an undergraduate fellowship and will allow the participation of a talented undergraduate student in the project. For further information, contact CALCE EPSC at (301) 405-5323.
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CALCE Conducts Virtual Qualification on AAAV

CALCE and ERS, Inc. received a Phase I STTR award titled, Technology for Advanced Amphibious Assault Vehicle (AAAV) Affordability, from the Navy. Under this contract, CALCE and ERS, Inc. will conduct physics-of-failure virtual qualification of selected electronic modules on the AAAV being built for the U.S. Marine Corps, by General Dynamics Land Systems in Woodbridge Virginia. The objective of this project is to develop innovative technologies that will reduce the manufacturing and/or repair costs, reduce weight, or increase efficiencies of the AAAV, but not adversely impact performance.

Plans for accelerated stress testing will be formulated in the Phase I to assess the quality and impact of the manufacturing process. The electronic modules being analyzed consist of VME cards built by General Dynamics, DY4 and Vista Controls.

For further information about this award, please contact Dr. Michael Osterman at (301) 405-8023 or via email at osterman@calce.umd.edu.
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CALCE Awarded Contract to Study Embedded Passives

CALCE has been awarded a three-year contract by Nu Thena Systems as part of the Advanced Embedded Passives Technology Consortium. The Consortium, consisting of NCMS and ITRI, and a broad array of industrial partners: 3M, Compaq Computer, Delphi Delco Electronics, DuPont Photopolymer & Electronic Materials, DuPont High Performance Films, HADCO Corporation, MacDermid, Merix Corporation, Nortel Networks, Nu Thena Systems, and ORMET Corporation, has been formed to manage and execute a NIST ATP project focused on developing the materials, design, and processing technology for embedding passive devices into printed wiring boards.

Consortium members on this program will develop the technology and manufacturing expertise needed to:

CALCE is the cost analysis lead for the program and will perform all cost modeling activities. The specific objectives of the CALCE work are:

For further information, contact Dr. Peter Sandborn at (301) 405-3167 or sandborn@calce.umd.edu.
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Benchmarking Activities with Lucas Aerospace

In April, Lucas Aerospace invited Margaret Jackson and Peter Sandborn to their Birmingham, England site, to benchmark their parts selection and management processes. Lucas asked CALCE to offer process improvement suggestions and identify current strengths of their processes. Lucas was particularly interested in obtaining an understanding of how their parts selection and management processes ranked in comparison with those of their competitors.

The CALCE researchers followed their time tested approach to benchmarking, and began the process by requesting and reviewing several internal Lucas parts selection and management documents. The document review was conducted to gain an understanding of the Lucas processes prior to an onsite visit. With this understanding in place, Margaret and Peter then spent three days at Lucas in Birmingham, conducting interviews of purchasing, design, component, manufacturing, testing, and reliability engineers concerning Lucas' parts selection and management processes.

At the conclusion of the third day, Lucas management was presented with immediate feedback in the form of a two hour synopsis of CALCE findings; strengths of the Lucas parts selection and management process, with respect to other companies in the industry, were identified and process improvement suggestions were offered. Upon their arrival back at CALCE, Margaret and Peter prepared a formal report in which the objectives of the benchmarking activity were discussed, the findings obtained during the internal document review and the on-site visit were presented, strengths of the current process were identified, and process improvement suggestions were offered. The results of the benchmarking activity were used to enhance the Consortium's work with respect to its soon-to-be-released parts selection and management guidebook.

To learn more about CALCE benchmarking activities, or to have CALCE benchmark your company's parts selection and management processes, please contact CALCE EPSC at (301) 405-5323.
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Litton-AMECON Digital MCM Trade-off Analysis

The CALCE EPSC performed manufacturability, cost, and reliability (thermal, mechanical and corrosive) analyses and trade-off of ceramic and plastic ASIC-multichip modules in a ball grid array package format for Litton-AMECON. The MCM-board assembly was analyzed for Litton-AMECON's specified environmental conditions and profiles. CADMP and calcePWA software, which are based on the physics-of-failure approach, were used for reliability analysis and SavanSys was used for routing analysis and for manufacturing cost estimation. Design inputs were verified and fine-tuned during interactions with Litton-AMECON, and the modifications were incorporated in the design. Results showed that the plastic MCM-board assembly was found to have a better life as compared to the ceramic MCM-board assembly. The package life of both the plastic and ceramic packages was assessed to be longer than the board life. For more information, contact Dr. Peter Sandborn at (301) 405-3167 or via email at sandborn@calce.umd.edu.
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CALCE Study on Plastic Packaged GaAs and AlGaAs LED’s Enters Analysis Stage

The CALCE Photonics Group has been involved in a study to identifiy dominant failure mechnanisms in plastic packaged GaAs and AlGaAs LED packages. Low-cost, GaAs based LED structures are often employed in optical switches, optoisolators and other information carrying applications. Packaging of these structures typically includes a wire bonding operation, application of a stress absorbing conformal coating layer (often silicone coating), and final encapsulation using a plastic molding material. In many cases, the molding encapsulant is optically transparent, and includes a lensed geometry to direct the optical signal toward an appropriate detection device, or toward a predetermined direction. Some packages employ a side mounted (also known as flip-chip) geometry. For this case, the LED electrodes are located on a single horizontal plane, and the wire bonding operation is eliminated. Finally, non-hermiticity issues are always involved where plastic packaging is employed. The stress relieving buffer coat is seen as an increased barrier to moisture ingress. However, corrosion protection will only occur if polymer chains from the coating material form chemical bonds with the semiconductor die. Voids in the coating material, or delaminations at the die surface allow moisture driven corrosion processes to occur.

A total of over 700 LED packages have been involved in the CALCE Center study, and a subset of the packages have been prepared without the silicone buffer coating layer to assess the performance of these non-coated devices. Several analytical techniques including electron beam induced current (EBIC) analysis, Raman analysis, FTIR analysis, and photo-, electroand cathodoluminescence will be utilized in the study.

Initial findings point to significant differences in the optical performance for non-coated structures. Non-coated packages typically exhibit rapid optical decay during accelerated testing, and a characteristic blue-shift in the LED emission toward shortened wavelengths occurs prior to accelerated testing. Another measurable was noted in the increased leakage rates of these devices. For THB testing parts, development of a surface oxide material is observed in high aluminum content regions of the LED structure. However, the oxide material is generally not observed when no current bias is applied to the device, so that the mechanism is also driven by the galvanic potential of the substrate. Finally, a measurable shift is observed in THB tested LED’s. However, it is not yet clear if the shift is related to an induced stress on the die (as is the case for non-coated die), or the shift may be related to leaching of As from the AlGaAs substrate.

Extensive failure analysis will continue as the analysis phase of the project continues. It is hoped that a comprehensive degradation model that accounts for the complex relationships between die stress, ambient temperature, ambient humidity and current (or voltage) bias of the LED structure can be composed using the data from this study. For more information regarding this study, contact CALCE EPSC at (301) 405-5323.
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Study on Variable Frequency Microwave Cure Process for Electronic Packages is Completed

Variable Frequency Microwave (VFM) cure of underfill encapsulant materials for flip-chip applications has recently been touted as a rapid alternative to slower, infrared (IR) oven curing techniques. VFM cure can save hours in manufacturing time, as compared to IR-oven techniques and the VFM process also results in lower stresses to the board substrate, due to selective heating of materials. Each of these advantages makes VFM technology an attractive proposal for process engineers. However, questions continue to persist regarding the effect of VFM radiation on the electrical performance of semiconductor IC’s.

A series of tests have been performed to assess the electrical performance of several microelectronic technologies following VFM radiation cycles that are similar to cure profiles for flipchip with underfill applications. Overall, the use of VFM can be a safe alternative to IR cure techniques. However, it is recommended that a program to characterize the electrical performance of all IC’s exposed during cure be implemented to insure reliable operation of these devices. The qualification program should be used to identify safe operating thresholds for general VFM parameters, such as forward power, bandwidth and package heating rates. Once these thresholds are established, we anticipate little significant difference between VFM and IR processed packages. Additional information regarding this work can be obtained by contacting CALCE EPSC at (301) 405-5323.
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Fiber Sensors Used in CALCE Studies on Fiber Connector Pistoning

As the use of fiber optics increases, the reliability of that infrastructure is becoming more critical. To begin addressing the issues involved with fiber optic connector reliability, infiber Bragg grating sensors have been used to study the mechanical state in terminated optical fibers. We have measured strain conditions in room temperature and thermally cured ST (single fiber) and ribbon (multiple fibers) connectors. Termination results in compressive strain conditions, with slightly lower strain in room temperature cured connectors. The strain offset between the room and thermal cure can however be reduced by performing anneal treatments.

The Bragg grating sensors will now be used to study mechanical conditions associated with fiber optic pistoning, a failure mechanism that may best be described as movement of the optical fiber relative to the connector structure. This condition will lead to excessive mechanical stress on the fiber and increased optical loss. We have observed pistoning during dormant storage of the connector, as well as in applications where extreme temperature changes occur. The degree of pistoning is associated with material properties of the epoxy and connector ferrule. The goal of our study will be to identify general guidelines for materials selection and termination procedures in single and multiple fiber connector structures. For additional information, please contact CALCE EPSC at (301) 405-5323.
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Failure Analysis for the Next Millennium

Rapid innovation in the materials and technology used in electronic packaging requires users to stay updated on how these changes can affect the reliability of their products. Ball grid arrays, flip chips, chip-scale packaging, underfill, high density interconnects, and elastomeric sockets, all require new approaches and new equipment in order to analyze material and system behavior under various operational loads. If problems do arise, finding the root cause of failures is fundamental to mitigating risks and to improving product quality and reliability.

CALCE has recently expanded our failure analysis capabilities through the use of state-of-the-art equipment, including an ISIS Infrared Imaging System, a Neocera Scanning Magnetic Microscope, and a JEOL Scanning Probe Microscope.

Over the next six months, additional acquisitions will include a complete surface mount fabrication laboratory with flip chip bonder and underfill dispenser, a next generation environmental electron microscope with full functionality EDS systems, and automated sample preparation.

Details on all the facilities and services offered by CALCE can be found here.

For additional information, please feel free to contact Dr. Keith Rogers, Director of Laboratory Services, at (301) 405-5316 or via email at krogers@calce.umd.edu.
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