Mu-Tao Chu

Failure and degradation mechanisms of high-power white light emitting diodes

The investigation explores the factors that influence the long-term performance of high-power 1 W white light emitting diodes (LEDs). LEDs underwent an aging test in which they were exposed to various temperatures and electrical currents, to identify both their degradation mechanisms and the limitations of the LED chip and package materials. The degradation rates of luminous flux increased with electrical and thermal stresses. High electric stress induced surface and bulk defects in the LED chip during short-term aging, which rapidly increased the leakage current. Yellowing and cracking of the encapsulating lens were also important in package degradation at 0.7 A/85 °C and 0.7 A/55 °C. This degradation reduced the light extraction efficiency to an extent that is strongly related to junction temperature and the period of aging. Junction temperatures were measured at various stresses to determine the thermal contribution and the degradation mechanisms. The results provided a complete understanding of the degradation mechanisms of both chip and package, which is useful in designing highly reliable and long-lifetime LEDs.

Thermal transient characteristics of flip chip high power light emitting diodes

The die-attached quality and the thermal transient characteristics of high power flip chip light emitting diodes (LEDs) are investigated using thermal transient tester. Various die-attached materials were utilized to compare the difference in their thermal resistances and long term performance. By applying accelerated aging stress, the deterioration rates at the die-attached layers were obtained. Numerical simulation provided further understanding of LED device temperature distribution and also revealed that the thermal variance at the die-attached interface can be recognized within only few milliseconds for the flip chip structure. The effects of bump arrangement and material were analyzed to achieve high temperature uniformity and low thermal resistance for high power LEDs.

High manufacturability and thermal stability mini-flat transmitter for 10Gb/s Ethernet applications

In this paper, the authors have demonstrated a low cost, highly manufacturable and thermally stable mini-transmitter for 10 Gb/s Ethernet applications. A novel two lens semi-passive alignment structure of 10 Gb/s 1310 nm SC receptacle or pigtail type optical mini-flat transmitter are designed and demonstrated to exhibit about 35% coupling efficiency with a /spl plusmn/5 /spl mu/m accuracy flip chip bonder general silicon optical bench process (SiOB) and packaging flow. Moreover, a high resistivity SiOB (1k/spl Omega//cm) and pressure-free bonding technique, using electroplated gold-tin solder, are also adopted to guarantee the transmitted performance in high speed operation. The eye diagram of the transmitter shows an excellent quality, passing the 10 Gb/s Ethernet mask test with 30% margin. The extinction ratio of the transmitter is also proved to above 6 dB at room temperature. The optical eye diagram shows excellent eye quality, passing the 10 Gb/s Ethernet mask test from 0/spl deg/C to 80/spl deg/C. Finally, the reliability of the transmitter is also evaluated in this paper.

Low cost package of 30Gbps pluggable parallel optical transmitter module

This paper describes a 12-channels parallel optical transmitter module with a MPO-Connector designed for a very short reach OC-192 and SNAP 12 specifications. It is important to design the micro array lens for better couple efficiency of array optical transmitter module. The authors design the high accuracy micro array lens for injection modeling to reduce the price and suit for further mass production. In this 12-channel parallel optical transmitter module, it is very difficult to posit the chip on correct position according to guide pin or guide pin hole. Therefore, the authors develop the method of two steps flip chip bonding to release the difficulty of chip alignment on ceramic substrate without two guide pin holes. The performance of the module is demonstrated to fulfill the requirements of SNAP 12[1]. The extinction ratio of the 12-channels array transmitter module is tested above 6dB, respectively. The optical shift by heat is an important factor affecting the performance of the array module. Thermal analysis of 12-channel parallel optical transmitter module is used to improve the effect of optical shift by heat in this paper. And the temperature among the case of transmitter module is greatly reduced from 52.7 degree to 31.9 degree. In this paper, a 12-channel array transmitter module package and thermal simulation are discussed and tested. This is a low cost package design and is suitable for mass production.

Low-cost and highly manufacturable 10Gb/s mini-flat transmitter for ethernet applications

The key issues of local-area-network (LAN) and storage-area-network (SAN) applications are to improve cost, manufacturability and reliability of optoelectronic devices in high speed transmission. The authors have demonstrated highly manufacturability, reliability and thermal stability mini-transmitter for 10Gb/s Ethernet applications in this paper. Passive alignment technology is a way to improve manufacturability of optoelectronic devices in the future. However, the assembly yield rate of conventional LD chip on silicon optical bench to fiber is quite limited due to restricted optical alignment tolerance (< 1μm). In this study, a novel two lens structure of 10Gb/s LC receptacle type optical mini-flat transmitter is designed and demonstrated to exhibit above 20% coupling efficiency with less than ±6um aligned deviation. Moreover, a high resistivity silicon optical bench (1kΩ/cm) and pressure-free bonding technique using the electroplated AuSn solder are also adopted to guarantee the transmitted performance in high frequency operation. The eye diagram of 10Gb/s mini-flat transmitter developed in this study showing the excellent quality obtained passing 10Gb/s Ethernet mask test with 20% margin. And the extinction ratio of transmitter is also proved to above 6dB at room temperature. The response of monitor PD is also examined up to 80% by mirror coating on silicon V-groove. Thermal stability of 10Gb/s mini-flat transmitter is another critical issue in high speed transmission. The performance of temperature stabilized transmitter over wide case temperature range is also evaluated in this study. The optical eye diagram of 10Gb/s transmitter developed in this paper showing excellent eye quality passing 10Gb/s Ethernet mask test between 0°C to 80°C. Finally, the reliability of transmitter is also performed. The reliability data indicate that the optical alignment of these modules are stable and observed essentially low variations in optical coupling as results of 1000 hours damp heat and 1000 temperature cycling durations.

Low-cost and highly reliable optoelectronic devices for 10-Gb/s ethernet applications

With the drastic expansion of internet usage, the demand of 10Gbps transmission optoelectronic devices for local-area-network (LAN) and storage-area-network (SAN) are increasing. The key issues of these applications are to improve cost, manufacturability and reliability of optoelectronic devices in high speed transmission. The authors have demonstrated highly manufacturable and reliable optical front end and trasneiver module for 10Gbps Ethernet applications in this paper. TO-Can package is a way to reduce cost of 10Gbps optical assembly. However, the signal integrity of high speed transmitter optical sub-assembly (TOSA) and receiver optical sub-assembly (ROSA) are limited due to the mismatched characteristic impedance, parasitic inductance and spread capacitance of conventional TO-Can package. In this paper, high performance and high sensitivity of 10Gbps TOSA and ROSA with TO-Can package are discussed and demonstrated to overcome the critical issues mentioned, respectively. In order to improve the signal integrity and manufacturability of 10Gbps OSA in 10Gigabit Ethernet small form factor transceiver module assembly. The authors also integrate high speed flex board and OSA package to extend the signal path, and to minimize the effect of crosstalk in module. The high speed transceiver modules with TO-Can package embedded compliant with XFP multi-source agreement (MSA) are also demonstrated in this paper. The performance of temperature-stabilized transceiver module over awide case temperature range is tested. The optical eye diagram of 10Gbps transmitter developed in this study shows an excellent quality passing the 10Gbps Ethernet mask test between 0 degrees Centigrade and to 70 degrees Centigrade. Finally, the reliability tests regulated by Telcordia GR-468-CORE and MIL-STD-883 are also performed and certified to pave the ways of highly manufacturable and reliable XFP transceiver modules for 10Gbps Ethernet applications.

Low-cost and highly manufacturable 30-Gb/s parallel optical transmitter module

This paper describes a 12-channels parallel optical transmitter module with a MPO-Connector designed for a very short reach OC-192 and SNAP 12 specifications. It is important to design the micro array lens for better couple efficiency of array optical transmitter module. The authors design the high accuracy micro array lens for injection modeling to reduce the price and suit for further mass production. In this 12-channel parallel optical transmitter module, it is very difficult to posit the chip on correct position according to guide pin or guide pin hole. Therefore, the authors develop the method of two steps flip chip bonding to release the difficulty of chip alignment on ceramic substrate without two guide pin holes. The performance of the module is demonstrated to fulfill the requirements of SNAP 12[1]. The extinction ratio of the 12-channels array transmitter module is tested above 6dB, respectively. The optical shift by heat is an important factor affecting the performance of the array module. Thermal analysis of 12-channel parallel optical transmitter module is used to improve the effect of optical shift by heat in this paper. And the temperature among the case of transmitter module is greatly reduced from 52.7 degree to 31.9 degree. In this paper, a 12-channel array transmitter module package and thermal simulation are discussed and tested. This is a low cost package design and is suitable for mass production.