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The electronics used in such automotive, aerospace, and military vehicles are subjected to more challenging application environments than those present in the computer and telecommunication sectors. The CAVE3 Center is built around commonality of themes related to electronic systems in the automotive, military, defense, aerospace and space-based applications. The focus of the center research is on innovation in design, reliability, prognostics, and manufacturability of electronics for future emergence of cost-effective, damage tolerant electronic systems.
The NSF Industry/University Cooperative Research Center for Advanced Vehicle and Extreme Environment Electronics (CAVE3, also known as CAVE) was established at Auburn University in 1999 to develop and implement new technologies for the packaging and manufacturing of electronics, with emphasis on the harsh environment, reliability, prognostics and cost. Today, the Center is a premier research world-class organization in the area of harsh environment electronics. The center provides an ideal forum in which academia and industry work in partnership on identification of key road blocks relevant to electronics in harsh environments and development of innovative technologies for enabling cost-effective solutions. The Center membership is vertically integrated to include OEMs as well as their supply infrastructure including manufacturers of components, printed wiring boards, and electronics materials. The focus of the center research is on innovation in design, reliability, prognostics, and manufacturability of electronics for future emergence of cost-effective, damage tolerant electronic systems. Electronics in harsh environments typical of automotive, military, defense, aerospace and space-based applications may be subjected to severe high and/or low ambient temperatures; extreme temperature changes; moisture and high humidity; exposure to dirt, contaminants, chemicals, and radiation; and excessive transient loadings, shock/drop, and vibration. EMI/RFI (Electro Magnetic Interference /Radio Frequency Interference) shielding from internal and external noise, and ESD (Electro Static Discharge) are also critical factors. Commercial off-the-shelf technologies may not address the reliability and life-cycle needs of the extreme environment applications. These themes provide the motivation for the Center’s strategic directions related to technology development and research resource allocation.
CHIP-LEVEL INTERCONNECTS, FLIP-CHIP AND UNDERFILLS
In this research area, materials and processes are being explored for flip chip on laminate, flip chip BGA packaging, CSP (redistributed die, Ultra-CSP, etc.) assemblies deployed in extreme thermal cycling environments. The primary objective is to develop a fundamental understanding of the reliability of flip chip applications in harsh environment applications and High End Microprocessor Packaging. Study next-generation materials (Nano-structured underfills, High-Reliability STABLCOR Substrates, Thermal Interface Materials, Chip-Level Interconnects). Project deliverables include design and material guidelines for flip chip packages used in the automotive thermal cycling environment; material properties and adhesion characteristics of underfill encapsulants; flip chip thermal cycling reliability data; assembly and manufacturing processing recommendations; and finite element and material models for application to future package designs.
COMPONENTS, PARTS AND ASSEMBLIES
In this research area, reliable component packaging technologies (BGA, CSP, 3D Packaging, QFN, etc.) are being developed for harsh environments such as automotive under-the-hood and aerospace applications and also for portable electronic products such as cell phones. The major goal is to develop fundamental knowledge on the interactions between component design and material selection on package reliability and thermal performance in harsh thermal cycling and vibration environments. Develop guidelines on the selection and use of components in harsh environments. Develop accelerated Test Data on Electronic Structures including but not limited to - metal backed boards, high Tg laminates subjected to extreme environments. Deliverables include crack propagation and damage models; thermal cycling reliability data; algorithms for prognostication; computational models for reliability and thermal performance; design guidelines and decision support tools; and models for shock, drop, and vibration.
CONNECTORS AND SYSTEM-LEVEL INTERCONNECTS
In this research area, the effects of vibration and environment on the performance of automotive and other harsh environment connectors are being evaluated. The primary goals are to examine connector interconnection options for next generation extreme environment applications and to establish the reliability and failure mechanisms. A basic understanding of the causes of fretting corrosion is being established, and then utilized to develop strategies for the accelerated testing of connectors. In addition, the growth of tin whiskers is being studied on connector pins with lead free plating finishes. The ongoing tin whisker research includes both fundamental studies on the origin of whisker growth and experimental test matrices to examine next generation connector designs. Deliverables from our Connector Reliability research include design guidelines, modeling tools, reliability data, and processing recommendations.
LEADFREE SOLDERS ALLOYS CONSTITUTIVE AND WETTING BEHAVIOR
In this research area, potential lead-free solder alloys and corresponding lead-free surface finishes (board and component) are being identified to replace eutectic 63Sn-37Pb solder in harsh environment applications. The primary goal is to develop a fundamental unde rstanding of alternate solder alloys that will meet the high reliability, and high volume low cost manufacturing needs of the vehicle industry. Deliverables include recommended solder alloys; solderability (wetting) measurements; thermal cycling reliability data, stress-strain and creep results as a function of temperature, constitutive and solder fatigue models; and processing recommendations.
PROGNOSTICS HEALTH MANAGEMENT SYSTEMS
Leading indicators-of-failure are being developed for interrogation of material state significa ntly prior to appearance of any macro-indicators. The research focus is on determination of residual life of electronic systems via on-board sensing, damage-detection algorithms and data processing. Environments being studied include single, sequential, simultaneous thermo-mechanical, hygro-mechanical and dynamic loads. PHM is a key enabling technology with applications to avionic, automotive, and bio-implantable electronic systems.
The Center has developed an online software interface for the reliability and prognostics of harsh environment electronics. The tool-sets have been created in the two general areas including finite element tool add-ons for high-end simulation of electronic assemblies on commercial FE platforms, and closed-form modeling tool-set for the turn-key assessment of part reliability, risk-informed technology assessment, and part life-cycle management. The software tools are intended to operationalize the results from center research and put it in the hand of the industry practitioners and product development teams.
Auburn University has a demonstrated research focus on electronics reliability. Extreme Environment Experimental research capabilities include several laboratories including a surface-mount assembly line. It is believed that these facilities are among the best available at any university in the nation in the areas of electronic assembly, packaging, and reliability. A description of these and other facilities is given below.
MODELING AND SIMULATIONS TOOLS: The laboratory has a full suite of computer-aided design, and high-end simulation tools. Computer-aided design tools include Pro-Engineer and Solid Edge. Simulation tools include, ANSYS, LS-DYNA, ABAQUS, ABAQUS/Explicit, NASTRAN, and MATLAB. The laboratory is well equipped with dual-processor Pentium-class workstations, and Unix multi-processor compute server.
TRANSIENT DYNAMICS LABORATORY: The laboratory is equipped with state-of-art facilities for measurement of high-speed, high strain rate transient dynamic events such as shock and vibration. Equipment includes, high speed data acquisition systems, Vision Research Phantom-Series high-speed camera capable of 275,000 fps, SAI 3D image tracking software for high-speed image analysis and measurement, oscilloscopes, HP Spectrum Analyzers, vishay instruments 2311 high-speed wide-band strain-gage amplifier, motion-control drop tower, LDS v700 Series vibration system. Full-field strain measurement capabilities using digital image correlation.
LABORATORY DESIGN AND ARTWORK: The laboratory has capability of complete set of electrical design and layout tools. Specific software and hardware includes, SUN Workstations and PCs, Complete Mentor Graphics Suite, ORCAD PWB Layout & Simulator, IntelliSuite MEMS CAD software, Lavenir, CAM View, AutoCAD, Optronics Film Master 2000 Laser Photoplotter
SURFACE MOUNT ASSEMBLY: This laboratory includes a state-of-the-art high volume surface mount assembly line capable of flip chip assembly, as well as other equipment for advanced electronics packaging including manual and automated wire bonders, encapsulant dispense systems, facilities for thick/thin film hybrid circuit fabrication on ceramic substrates, and a vacuum solder sealing system for MEMS and SiC packaging. The surface mount assembly line can be used for prototype creation, fabrication of test structures, development of manufacturing processes or new product launch platform. In addition, in-line inspection capabilities enable x-ray, acoustic and laser profilometry based inspections. In addition, the laboratory has semi-automatic placement machines and rework stations. Specific equipment includes, MPM AP Solder Paste Printer with Vision System, Agilent SP1 Solder Paste Inspection System, Asymtek Flux Jetting System, Siemens SIPLACE 80F5 Pick and Place Machine, VISCOM VPS 6053 Automated Optical Inspection System, Heller 1800 Solder Reflow Conveyer Oven with Nitrogen Capability, Slim-KIC 2000 Thermal Profiling System, CAM/ALOT 3700 Encapsulant Dispense System.
ELECTRONIC PACKAGING: Air Vac DRS24 Solder Rework Station, Semiconductor Equipment Corporation 4150 Split Optics Alignment System for Die Placement, Karl Suss Thermocompression Flip Chip Bonder, Yield Engineering YES-R3 Plasma Etch System, Palomar Products Model 2460-V Automatic Thermosonic Wire Bonder, K & S Model 2071 VFP Automatic Wedge Bonder, Asymtek Model 402 Dispensing System, Fisher Scientific Programmable Cure Oven, ATV Model PEO 601 Programmable Brazing Furnace, SST 3150 Vacuum Sealing Furnace. The assembly and packaging resources are supported by inspection and failure analysis equipment including a Phoenix micro-focus x-ray system, Sonix C-mode scanning acoustic microscopy (CSAM) system, WYCO wafer inspection system, Tencor surface profilometer, Brookfield viscometer, Dage PC2400 pull and shear tester, and optical and scanning electron microscopes.
ACCELERATED TESTING LABORATORY: Laboratory includes capabilities for imposing various steady-state and cyclic temperature and humidity stresses. Chambers includes 3 Blue-M thermal cycling ovens, two liquid to liquid thermal shock systems, a Ransco air-to-air thermal shock system, two humidity chambers, and an Express Test HAST chamber.
MATERIAL CHARACTERIZATION: Major equipment includes Instron 3367 with several load cells, LVDTs, Blue-Hill Software, micro-scale mechanical testing system, facilities for calibration and application of stress and thermal test chips, and an environmental vibration system, an infrared thermal imaging system, and several custom-built apparatuses for characterizing thermal resistance of materials and assemblies.
SURFACE ANALYSIS LABORATORY: The Surface Science Laboratory includes several Scanning Electronic Microscopes (SEMs) with heating capabilities, and a Transmission Electron Microscope (TEM). Method capabilities include Energy Dispersive X-Ray Spectroscopy (EDS), X-Ray Photoelectron Spectroscopy (XPS), Scanning Auger Spectroscopy (SAS), and Rutherford Backscattering Spectroscopy (RBS).
MICRO-FABRICATION LABORATORY: CHA Mark 50 dual E-beam/sputter/ion gun deposition system, plasma reactive ion etcher, Applied Materials 8130 metal etcher, Applied Materials 8110 oxide etcher, Applied Materials 8110 oxide etcher, Matrix 103 asher, Matrix 303 etcher, Karl Suss MA/BA 6 frontside/backside mask aligner, Wet benches, Thermco oxidation and diffusion furnaces, Tempress LPCVD system, nickel and gold plating, STS ASE 100 DRIE, STS AOE 100 DRIE, CO2 critical point dryer, room temperature ion deposition/milling system. For advanced MEMS fabrication, the microfabrication facility has an STS ASE 100 for silicon DRIE and an STS AOE 100 for silicon dioxide DRIE.