新型封装材料与大功率LED封装热管理

高效散热封装材料的合理选择和有效使用是提高大功率LED(发光二极管)封装可靠性的重要环节。在分析封装系统热阻对LED性能的影响及对传统散热封装材料性能进行比较的基础上,阐述了金属芯印刷电路板材料、金属基绝缘板材料、陶瓷基板材料、导热界面材料和金属基复合材料结构特点、导热性能及其封装应用实例。指出了封装材料的研究重点和亟待解决的问题。     

大功率LED低热阻封装技术进展

散热是大功率LED封装的关键技术之一,散热不良将严重影响LED器件的出光效率、亮度和可靠性。影响LED器件散热的因素很多,包括芯片结构、封装材料(热界面材料和散热基板)、封装结构与工艺等。文章具体分析了影响大功率LED热阻的各个因素,指出LED散热是一个系统概念,需要综合考虑各个环节的热阻,单纯降低某一热阻无法有效解决LED的散热难题。文中还对国内外降低LED热阻的最新技术进行了介绍。     

COB封装对LED光学性能影响的研究

针对LED高光效、低功耗的要求,文章在分析LED光学性能的基础上,采用了COB(ChipOn Board)即板上芯片封装技术。研究了不同封装工艺和材料,分析比较其对LED光通量、光效和色温的影响。研究首先介绍COB封装的结构、优点及其实用性,然后分析影响LED光学性能的因素,最后进行测试。在实验过程中,发现COB封装结构除了具有保护芯片的功能外,还可以提高出光效率,并实现特定的光学分布。实验结果表明:文章提出的封装工艺对于提高光通量和光效、调节色温有良好的效果。     

中国LED封装技术与国外的差异

本文从封装设备、LED芯片、辅助封装材料、封装设计、封装工艺、LED器件性能等方面描述了当今中国LED封装技术与国外技术的差异,既肯定了中国LED封装技术长足的进步,也找出了与国外技术之间的差距。     

功率型白光LED封装设计的研究进展

综述了功率型白光LED封装的研究现状和存在的问题,着重从LED封装结构和封装材料两个方面进行了详细的评述,在现有蓝光芯片激发钇铝石榴石(YAG)荧光粉来实现节能、高效的白光LED照明的基础上,介绍了可以提高功率型白光LED的取光效率和空间色度的均匀性的各种封装结构和材料.指出新的封装结构、封装材料和封装工艺的有机结合以获得高取光效率,延长功率型白光LED的使用寿命,节约整体封装结构的成本,从而推进LED同体光源的应用是今后功率型白光LED研究的重点.     

浅议EMC在LED封装中的应用

环氧模塑料（EMC）作为一种常见的封装材料,具有可规模化生产和高可靠性等特点,被广泛应用于微电子封装领域。随着LED半导体照明技术的迅速发展,EMC作为一种新型支架塑封材料被引入到LED封装行业,成为第三代LED封装支架。与传统的PPA材料相比,EMC具有低膨胀系数、高热导率、更好的耐热性等优势。由于EMC支架是一种高度集成化的支架,具备更好的封装性能和可靠性,可进一步提升LED器件的可靠性并降低LED器件的成本。文章主要介绍EMC支架的主要特点、优势及其制作工艺,同时也总结了EMC在LED封装应用过程中还存在的一些问题。     

功率型LED封装技术

随着LED芯片输入功率的提高,带来了大的发热量及要求高的出光效率,给LED的封装技术提出了更新更高的要求,使得功率型LED的封装技术成为近年来的研究热点.首先介绍了几种主要的功率型LED封装结构,对功率型LED封装过程的关键技术,如荧光粉涂覆技术、散热技术、取光技术、静电防护技术等及未来发展方向进行了描述.指出功率型LED封装应选用新的封装材料,采用新的工艺和新的封装理念来提高LED的性能和光效,延长使用寿命,以推进LED固体光源的应用.     

基于COB技术的LED散热性能分析

当前,散热问题已成为影响LED寿命、光效、光衰和色温等技术参数的重要因素。文章在综合分析散热技术和LED封装对散热性能影响的基础上,利用COB(板上芯片)封装技术,将LED芯片直接封装在铝基板上,研制成了一种基于COB封装技术的LED。与SMD封装LED进行比较,分析了其散热性能。分析结果表明:基于COB封装技术的LED减少了LED器件的结构热阻和接触热阻,使其具有良好的散热性能。     

高光效LED灯丝球泡灯的光学性能研究

基于板上芯片(COB)封装技术,提出了一种360°出光的新型发光二极管(LED)灯丝球泡灯,其封装基板采用透明基板.研究了不同封装材料及芯片对其LED光通量、光效和色温的影响.首先介绍了LED灯丝球泡灯的结构、优点,然后分析了影响LED光学性能的因素,最后进行相关性能测试.测得采用玻璃/蓝宝石基板封装的LED灯丝的光通量分别为467.29和471.69 lm;光效分别为110.06和111.79lm/W;显色指数分别为84.1和81.9.测试结果表明,采用透明基板封装的LED灯丝球泡灯不仅能有效调节色温,而且能显著提高LED的光通量、光效和显色指数.     

大功率LED用封装基板研究进展

LED被称为第四代照明光源及绿色光源,近几年来该产业发展迅猛.由于LED结温的高低直接影响到LED的出光效率、器件寿命和可靠性等,因此散热问题已经成为大功率LED产业发展的瓶颈.文章阐述了大功率LED基板的封装结构和散热封装技术的发展状况,从基板的结构特点、导热性能及封装应用等方面分别介绍了金属芯印刷电路基板、覆铜陶瓷...     

Status and prospects for phosphor-based white LED packaging

The status and prospects for high-power, phosphor-based white light-emitting diode (LED) pack-aging have been presented. A system view for packaging design is proposed to address packaging issues. Four aspects of packaging are reviewed: optical control, thermal management, reliability and cost. Phosphor materials play the most important role in light extraction and color control. The conformal coating method improves the spatial color distribution (SCD) of LEDs. High refractive index (RI) encapsulants with high transmittance and modified surface morphology can enhance light extraction. Multi-phosphor-based packaging can realize the control of correlated color temperature (CCT) with high color rendering index (CRI). Effective thermal management can dissipate heat rapidly and reduce thermal stress caused by the mismatch of the coefficient of thermal expansion (CTE). Chip-on-board (COB) technology with a multi-layer ceramic substrate is the most promising method for high-power LED packaging. Low junction temperature will improve the reliability and provide longer life. Advanced processes, precise fabrication and careful operation are essential for high reliability LEDs. Cost is one of the biggest obstacles for the penetration of white LEDs into the market for general illumination products. Mass production in terms of CoB, system in packaging (SIP), 3D packaging and wafer level packaging (WLP) can reduce the cost significantly, especially when chip cost is lowered by using a large wafer size.     

基于倒装焊芯片的功率型LED热特性分析

对LED的导散热理论进行了研究,推导出了倒装焊LED芯片结温与封装材料热传导系数之间的关系。通过分析倒装焊LED的焊球材料、衬底粘结材料和芯片内部热沉材料对芯片结温的影响,表明衬底粘结材料对LED的结温影响最大,并且封装材料热传导系数的变化率与封装结构的传热厚度成反比,与传热面积成正比。该研究为倒装焊LED封装结构和材料的设计提供了理论支持。     

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 of passive thermal management of LED module

Recently, the high-brightness LEDs have begun to be designed for illumination application. The increased electrical currents used to drive LEDs lead to thermal issues. Thermal management for LED module is a key design parameter as high operation temperature directly affects their maximum light output, quality, reliability and life time. In this review, only passive thermal solutions used on LED module will be studied. Moreover, new thermal interface materials and passive thermal solutions applied on electronic equipments are discussed which have high potential to enhance the thermal performance of LED Module.     

A statistical study to identify the effects of packaging structures on lumen reliability of LEDs

The development of high-power light-emitting diode (LED) devices has been bedeviled by the reliability problems. And most reliability issues are caused by the packaging materials rather than the chips. However, which packaging material is the most influential remains unrevealed. To answer this question, a statistical method was introduced in this paper. Optical simulations were conducted to calculate the optical output power of LED package according to the orthogonal experimental design. Range and variance analyses were carried out to determine the significance of the relevant factors on the LED's light output. The results showed that the dome lens among the non-luminescent packaging materials had the most significance in affecting the light output. It is concluded that this method is useful in detecting the most significant part of LED packaging materials during the development of new packaging structures and is beneficial for enhancing the whole reliability of LED package effectively.     

A review of passive thermal management of LED module

Recently,the high-brightness LEDs have begun to be designed for illumination application.The increased electrical currents used to drive LEDs lead to thermal issues.Thermal management for LED module is a key design parameter as high operation temperature directly affects their maximum light output,quality,reliability and life time.In this review,only passive thermal solutions used on LED module will be studied.Moreover,new thermal interface materials and passive thermal solutions applied on electronic equipments are discussed which have high potential to enhance the thermal performance of LED Module.     

LED结温、热阻构成及其影响

LEDPN结温上升会引起LED光学、电学和热学性能的变化,甚至过高的结温还会导致封装材料(例如环氧树脂)、荧光粉物理性能变坏,LED发光衰变直至失效,因此分析LED结温、热阻构成,如何降低PN结温升,是应用LED的重要关键所在。