Reliability test and failure analysis of high power LED packages

A new type application specific light emitting diode(LED) package(ASLP) with freeform polycarbonate lens for street lighting is developed,whose manufacturing processes are compatible with a typical LED packaging process.The reliability test methods and failure criterions from different vendors are reviewed and compared.It is found that test methods and failure criterions are quite different.The rapid reliability assessment standards are urgently needed for the LED industry.85℃/85 RH with 700 mA is used to test our LED modules with three other vendors for 1000 h,showing no visible degradation in optical performance for our modules,with two other vendors showing significant degradation.Some failure analysis methods such as C-SAM,Nano X-ray CT and optical microscope are used for LED packages.Some failure mechanisms such as delaminations and cracks are detected in the LED packages after the accelerated reliability testing.The finite element simulation method is helpful for the failure analysis and design of the reliability of the LED packaging.One example is used to show one currently used module in industry is vulnerable and may not easily pass the harsh thermal cycle testing.     

A review on discoloration and high accelerated testing of optical materials in LED based-products

Reduction of intensity of light output is one of the most common degradation modes in light-emitting diode (LED) systems. It starts from the failure of the various components in the system, including the chip, the driver, and optical components (i.e. phosphorous layer). The kinetics of degradation in real life applications is relatively slow and in most cases it takes several years to see an obvious deterioration of optical properties. Highly Accelerated Stress Testing (HAST) set-up and a methodology to extrapolate the results to real time applications are therefore needed to test the reliability of LED packages and lens materials. Using HAST concept in LED industry is inevitable due to the necessity of assessing the reliability of new products in a short period of time. This paper aims at briefly clarifying the degradation mechanisms of optical components in LED packages and explaining how they contribute to the depreciation of light output of the LED systems. The concept of HAST and the way the reliability of LED packages can be evaluated will also be discussed.     

Low-cost and low-electromagnetic-interference packaging of optical transceiver modules

The low-cost and low-electromagnetic-interference (EMI) packaging of optical transceiver modules employing housings of plastic composites are developed and fabricated. Optical transceiver modules fabricated by the plastic composites with transmission rates of 1.25 and 2.5 Gb/s are tested to evaluate the electromagnetic (EM) shielding against emitted radiation from the plastic packaging. The results show that these packaged optical transceiver modules with their high shielding effectiveness (SE) are suitable for use in low-cost and low-EMI Gigabit Ethernet lightwave transmission systems. By comparison of cost, weight, and shielding performance for optical transceiver modules fabricated by the housings of nylon and liquid-crystal polymer with carbon fiber filler composites, woven continuous carbon fiber (WCCF), and nanoscale hollow carbon nanocapulses (HCNCs) epoxy composites, the WCCF composite shows lower cost, lighter weight, and higher EM shielding than the other types of composites. Future studies may develop the low-cost and low-EMI optical transceiver modules using nanoscale HCNCs that have the combination of excellent physical and mechanical properties, light weight, and thinness compared with the conventional fabrication techniques.     

Technology development of a high-density 32-channel 16-Gb/s opticaldata link for optical interconnection applications for theoptoelectronic technology consortium (OETC)

A parallel, 32-channel, high density (140 μm pitch), 500 Mb/s NRZ, point-to-point, optical data link has been fabricated using existing GaAs IC, silicon optical bench (SiOB), and multichip module (MCM-D) technologies. The main components of the transmitter and the receiver modules are a GaAs-based vertical cavity surface emitting laser (VCSEL) array at 850 mn with its IC driver array chip and an integrated metal-semiconductor-metal (MSM) receiver (photodetector and signal processing circuits) array at 850 nm. The package module uses a modified 164 I/O JEDEC premolded plastic quad flat pack (PQFP) in combination with a polymer film integrated circuit (POLYFIC) chip carrier. The electrical input and output are 500 Mb/s NRZ binary signals. The optical I/O in both modules consists of a directly-connectorized (nonpigtail) fiber array block that plugs into the 32×1 optical fiber ribbon directly on one side and accepts 32 optical signals from the SEL array or delivers them to the MSM receiver array via a gold-coated 45° polished fiber array mirror. The MACII-32 ribbon cable is an enhanced version of the standard MACII connector ribbon cable. This paper characterizes key components of the optical data link, describes its package design, and discusses preliminary component and optical data link test results     

一种并行多路数字光模块的设计与实现北大核心CSCD

并行多路数字光模块在短距离光通信中有广泛应用,并行多路数字光模块的电芯片、光芯片大都采用裸芯片,针对非气密封装会使裸芯片暴露在空气中导致氧化、可靠性不高的问题,本文提出了一种全气密封并行多路数字光模块的设计方法,采用LTCC基板四周设置焊环及管壳设计环框的新型结构,实现了数字光模块基板与管壳的直接焊接,从而实现了并行多路数字光模块的全气密性设计,解决了数字光模块非气密封设计难题。以12路收发一体数字光模块为例,本文不仅介绍了并行多路数字光模块的设计原理、并行多路光路耦合的设计方法,而且给出了全气密封并行多路数字光模块的完整结构和实现方法,试验表明,气密性(最大漏率)为5×10~(-9)P·m~3·s~(-1)。本文提出的设计结构对并行多路数字光模块的全气密性设计具有重要的参考价值。     

Hermetic-equivalent packaging of GPS MCM-L modules for highreliability avionics applications

Results are presented of comparative reliability testing of multichip modules (MCM's) fabricated with laminate substrates, and protected with various bare-die coatings. The demonstration MCM's included two design versions (flip-chip and wire-bond) of the digital portion of global positioning system (GPS) receiver multichip modules. This paper summarizes the results for the wire-bonded constructions. Standard encapsulants and new inorganic coatings (Dow Coming's ChipSeal(R) hermetic coating materials') were evaluated in environmental stress exposures corresponding to high reliability avionics applications. Full wafer probe testing was performed both before and after the supplemental ChipSeal processing and dip-chip wafer bump processing steps. ChipSeal and flip-chip wafer processing steps were shown to cause no yield degradation on wafer lots of five different IC types used in the overall program. The environmental test results demonstrate that MCM-L units with bare die packaging can be designed for very robust reliability applications such as military and other high reliability avionics     

Fabrication of semiconductor optical switch module using laser welding technique

The 4/spl times/4, 1/spl times/2, and 1/spl times/4 semiconductor optic-switch modules for 1550 nm optical communication systems were fabricated by using the laser welding technique based on the 30-pin butterfly package. For better coupling efficiency between a switch chip and an optical fiber, tapered fibers of 10-15 /spl mu/m lens radius were used to provide the coupling efficiency up to 60%. The lens to lens distance of the assembled tapered fiber array was controlled within /spl plusmn/1.0 /spl mu/m. A laser hammering technique was introduced to adjust the radial shift, which was critical to obtain comparable optical coupling efficiencies from all the channels at the same time. The fabricated optical switch modules showed good thermal stability, with less than 5% degradation after a 200 thermal cycling. The transmission characteristics of the 4/spl times/4 switch module showed good sensitivities, providing error free transmissions below -30 dBm for all the switching paths. The dynamic ranges for the 4/spl times/4 and 1/spl times/2 switch modules were about 8 dB for a 3 dB penalty and about 17 dB for a 2 dB penalty, respectively.     

Components for optical communications systems: A review

Current trends in research and development of components for optical communication are reviewed. Emphasis is placed on active components for fiber-optic systems which have undergone recent major advances. Basic properties of optical fibers and recent technological improvements in splices, connectors, and source/detector-fiber couplers are presented first. This background information serves as a basis for describing recent developments in optical sources (e.g., device reliability, LED's and laser diodes) and photodetectors. Developments in both the 0.8-0.9-µm and 1.0-1.7-µm wavelength regions are covered. Also surveyed are results of research in areas of potential interest for optical communications: novel fiber-optic components, integrated optics (sources and modulators/switches), novel device fabrication methods, and integration of optical components.     

Hybrid optical switch using passive polymer waveguides andsemiconductor optical amplifiers

Optical switching can be performed by using optical amplifiers combined with a passive waveguiding network. Recently, most of the effort in optical amplifier switch modules have been focused on monolithic switches in which the entire device is fabricated on an InP substrate together with the semiconductor optical amplifiers (SOA's). In this paper, we investigate the use of SOA's with passive polymer waveguides to make hybrid switches of varying sizes. The optical amplifiers serve dual purposes, gating the signal and amplifying the signal. Amplification is needed in order to offset the losses associated with the passive waveguide elements as well as the losses from component misalignments in the switch module. Our analysis finds the largest switch module size that can be made with the architecture used. We also calculate the maximum number of switch modules which can be cascaded in order to retain a bit-error rate (BER) under 10^-9     

Embedded TiNxOy thin-film resistors in a build-up CSP for 10 Gbps optical transmitter and receiver modules

Integral passive components provide efficient circuit miniaturization while maintaining high performance and reducing assembly costs. The development of practical integral passive components, however, requires advances in the areas of materials, low-cost processes, and structural design. We have developed new TiNxOy thin-film resistors, as well as a termination resistor-embedded CSP, and a process for fabricating integral passive components. Our TiNxOy films exhibit a sheet resistivity in the range of 30-5k /spl Omega//square. To keep costs low, we have made the fabrication process compatible with that for MCM-D/L. Resistors as small as 25 /spl mu/m square have been successfully produced with this process. The chip scale package (CSP) with embedded resistors has been designed for 10 Gbps optical transmitter and receiver modules. A fabricated version shows excellent return loss for its termination resistor, less than -20 dB in the frequency range of 50 MHz-14 GHz, and its resistors showed high reliability in constant voltage stress tests, with less than 5% change in resistance at 800 mW/mm/sup 2/ over 1000 hours.     

Degradation mapping in high power IGBT modules using four-point probing

An electrical four-point probing approach is used to estimate local degradation in high power insulated gate bipolar transistor modules subjected to power cycling. By measuring electrical parameters of selected units and components the possibility of mapping the degradation is demonstrated. The development of failures is put in accordance with physical phenomena and materials fatigue. These results are directly usable for reliability purposes with a focus on geometry optimization and enhanced lifetime prediction methods.     

High reliability optical splitters composed of silica-based planarlightwave circuits

The environmental and mechanical reliability of a planar lightwave circuit (PLC)-type optical splitter modules is investigated with reference to the Bellcore requirements. The module is composed of Y-branching silica-based waveguides on Si connected to optical fiber with UV-curable adhesives and is packaged in a metal case which is filled with humidity-resistant resin. High optical performance such as low loss, low reflection, and thermal stability are obtained through the use of this fiber connection technique. Ten reliability tests including long-term environmental and mechanical tests were carried out for more than ten PLC splitter modules. Under one of the most severe sets of conditions (75°C and 90% RH), all the 19 samples we tested were stable for more than 5000 hours. Other tests confirmed that the PLC splitters offer long-term stability and that their optical characteristics have sufficient mechanical strength. These results indicate that the PLC splitters can be used for practical applications     

Design and implementation of an optical burst-switched network testbed

Optical burst switching has been receiving increased attention as a promising technology for building the next-generation optical Internet. This article presents the design and discusses the implementation of an overlay mode optical burst-switched network testbed. A flexible "transceiver + forwarding" edge node architecture is proposed to perform both electronic burst assembly/disassembly and optical burst forwarding. It is designed to provide class of service and wavelength selection for locally generated bursts, and transparency to cut-through bursts. The functional modules of the control plane and related key design issues are presented. In particular, we discuss a scheduling mechanism that efficiently combines two different contention resolutions in space and wavelength domains. Experimental results show the effectiveness of this scheme in reducing burst blocking probability. Furthermore, the performance of the network testbed and corresponding methods of improving it are discussed.     

Multigigabit multichannel optical interconnection module forbroadband switching system

This paper describes optical transmitter and receiver modules for package-to-package interconnection in broadband switching networks such as an asynchronous transfer mode switch fabric. These modules, which include the multiplexer and demultiplexer, can reduce the number of connections and the problem of skew between links. Five-channel optical transmitter and receiver modules were fabricated and demonstrated at 2.8 Gbit/s with a power dissipation of 4.5 W per channel. Moreover, temperature-insensitive optical interconnection was successfully demonstrated by driving a laser with a constant bias current over the threshold and by deducting the optical signal offset. The output power of the transmitter module was -4.2 dBm. Nonuniformity of the transmitter output powers across the range of optical channels was <2.1 dB. Receiver sensitivity for a bit error rate of 10^-11 was -9.3 dBm. Nonuniformity of the receiver sensitivities was <1.5 dB. The power penalty of the receiver sensitivity due to crosstalk was 1 dB. The connection distance was >250 m     

Differentiated reliability in optical networks: theoretical and practical results

This paper presents both theoretical and experimental studies carried on wavelength-division multiplexing (WDM) networks with arbitrary (mesh) topology that provide optical circuits with differentiated reliability (DiR). Reliability is obtained by means of a modified shared path protection (SPP) switching scheme-here referred to as SPP-DiR. As explained in the paper, SPP-DiR networks provide multiple degrees of circuit reliability that satisfy client-specific reliability requirements in a cost-effective way. The theoretical study first defines the problem of optimally designing SPP-DiR WDM networks. It then presents a time-efficient suboptimal algorithm that determines the routing and the reliability degree of each demand in the given traffic matrix by applying both the conventional SPP and the SPP-DiR scheme. When compared to dedicated path protection switching, results obtained for the pan-European network using the proposed algorithm indicate cost reductions of about 16% when SPP is applied, and up to 34% when SPP-DiR is applied. The experimental study describes the /spl Omega/ testbed-a WDM optical circuit-switched mesh network with an IP control plane-which is believed to be the first testbed ever built that makes use of the SPP-DiR scheme. Experimental results performed on the /spl Omega/ testbed report restoration times of the optical circuits-disrupted by a fiber fault-that are few tens of milliseconds.     

A 2-Gb/s optical transceiver with accelerated bit-error-ratio test capability

Accelerated bit-error-ratio (BER) measurement techniques using specialized test equipment are widely used for rapidly verifying the low BER (<10/sup -12/) of high-performance optical links. However, once these links are deployed in the field, it takes days to weeks to complete such BER measurements using a conventional testing method. This paper describes an optical transceiver architecture with on-chip accelerated BER measurement mechanics that reduces "in the field" BER testing time to minutes. The approach described in this paper uses an integrated interference generator to degrade receiver performance and raise the BER to a range that allows a substantially reduced measurement time. Values of BER versus the amount of interference are then extrapolated to the point of zero artificial degradation for actual BER. A 0.5-/spl mu/m complementary metal-oxide-semiconductor, 2-Gb/s, four-channel optical transceiver chip was designed, fabricated, and tested to serve as a vehicle for verifying the concept. The experimental results show excellent agreement between the extrapolated and actual BER values. The architecture described here points to a practical built-in self-test capability for optical links within high-performance digital systems, specifically in board- and backplane-level interconnections.     

低电压驱动的MEMS F-P可调光学滤波器研究

基于微机电系统（MEMS）技术,研制了一种新颖的光学腔与静电驱动器分离的Fabry-Pérot（F-P）可调谐滤波器。从光学设计、MEMS结构设计、制造工艺与器件测试等开展了F-P可调谐滤波器的研究,成功制备了工作在以1550 nm波长为中心、调谐范围为40 nm和驱动电压低于30 V的MEMS F-P可调滤波器。测试...     

Agilent technologies' singlemode small form factor (SFF) moduleincorporates micromachined silicon, automated passive alignment, andnon-hermetic packaging to enable the next generation of low-cost fiberoptic transceivers

Agilent Technologies (formerly Hewlett-Packard) are currently manufacturing a range of multimode and singlemode (SM) SFF transceivers with data rates from 125 Mb/s to 1.25 Gb/s (higher data rates are being developed). This paper will address the singlemode module design, assembly techniques and performance. The SFF transceivers offer the same functionality as SC duplex transceivers but utilize the mini MT-RJ optical interface in order to achieve twice the port density. Test results that demonstrate the performance of the mini MT-RJ optical interface will be presented. The SFF modules are price competitive with SC duplex modules, and are designed to enable low cost, high volume manufacture. In order to meet the size constraints and achieve low manufacturing costs, the SM SFF transceiver utilizes silicon as a base to support the optical fibers and active components, and as an aid to passively align of the active components to the fibers. Most other passively aligned modules require the use of a more expensive expanded mode region laser diode (LD). But Agilent Technologies have developed a unique passive align and attach system that can easily achieve the required coupling power for fast ethernet, OC3 and gigabit ethernet using a standard 1300 mn Strained Multiquantum Well (SMQW) LD. The module design and the methods used for passive align will be discussed, as will the precision die attach (PDA) equipment. All precious Agilent Technologies/Hewlett-Packard SM modules relied on an Hermetic cavity around the active devices to achieve the reliability assurance, e.g., as defined in Bellcore TA-NWT-000983, but this type of Hermetic design has limited potential for cost reduction. The SM SFF module is designed to meet the same assurance levels, but uses silicone encapsulation in place of Hermeticity, and the results of the qualification testing will be presented     

Real‐time reliability test for a CPV module based on a power degradation model

Models based on degradation are powerful and useful tools to evaluate the reliability of those devices in which failure happens because of degradation in the performance parameters. This paper presents a procedure for assessing the reliability of concentrator photovoltaic (CPV) modules operating outdoors in real‐time conditions. With this model, the main reliability functions are predicted. This model has been applied to a real case with a module composed of GaAs single‐junction solar cells and total internal reflection (TIR) optics. Copyright © 2010 John Wiley & Sons, Ltd.     

Near hexagonal close-packed optical fiber array for parallel optical interconnection

In conventional optical fiber based two-dimensional (2-D) parallel optical interconnection (POI), optical fiber arrays are aligned to 2-D light sources and detectors using precisely fabricated hole-plate or stacked V-groove plates. All these structures have problems in making positioning components and assembly with high accuracy. For polymer optical fibers with large diameter, the whole dimension of the array will be too large if they are positioned using V-grooves or hole-plate. This paper proposes a 2-D near hexagonal close-packed (NHCP) optical fiber array for 2-D POI. NHCP array has a cross-sectional profile of near-hexagonal lattice and with fibers precisely positioned at each node of lattice. Compared with perfect HCP lattice, NHCP lattice is slightly stretched in one dimension and still have all fibers with nonuniform diameter packed tightly with high packing fraction. The position of fibers in NHCP array is very important when aligned to 2-D light sources and detectors. This paper deduce the analytically expression for the probability distribution of fiber position which is related to variance of fiber diameter and structure parameters of NHCP array, and verified it by computer simulation. Experiment samples of NHCP array have been made showing that NHCP array is easy to be fabricated.