大功率白光LED封装工艺技术与研制 毕业论文外文翻译.doc

a research&fabrication of packaging technology for high power white ledcomparing with the traditional incandescent and fluorescent lighting, the high power white led has many significant incomparable advantages such as energy saving, envirorunental protection, long life and so on. it represents the development direction of green lighting, and is moving into the field of lighting rapidly. from the packaging technology of 1 w high-bower white led, the cost and performance of several methods were analyzed and compared for white light led. based on this, using the“blue chip&yag phosphor for producing white light led is the final selection with its good perfounance and proper price. the results show that in improving the light emitting efficiency, unilounity and stability of high-power white led, it needs further development of new materials and new technology.introductionled use semiconductor chips of solid as light emitting materials, the use of electric light-emitting. as a light source, leds advantages is in energy saving, environmental protection and long-lived three aspects. led does not depend on heating filament to light-emitting, energy conversion efficiency is very high, in theory only 10% of the energy consumption of incandescent. compared with fluorescent, led can be up to 50% of the energy saving effect. special survey showed that the annual electricity consumption of chinas lighting is more than 300 billion, to replace all incandescent lamps with led or in part or to replace the fluorescent lamp, can save 1 / 3 of the lighting electricity, means that the saving of 1 000 billion kwh, representing the full-years generating capacity of three gorges project which investment of more than 200 billion. using led to replace fluorescent lamps, bamboo lamps to avoid the breakdown of a spill of mercury pollution, moreover waste and manufacturing backplane led (copper clad aluminum) reuse can be recycled. led by solid package, the structure is deep-set , life expectancy can be up to h. in addition, led also has a low operating voltage, power consumption in small, high luminous efficiency, response time is very short (ns-grade), pure light color, light weight, small size, such as a series of characteristics of rapid development, especially high-power high-brightness white light led of the invention, by the insider as the lighting the area of the third revolution.following make fire lighting, after edison invented the lamp .white led production methodat present, the way to product white light with led chips show in the table1.tab.1 preparation principle of“blue chip&yag phosphorthe way of the white light production methodadvantagesdisadvantagescan single grain blue light led +fluorescent materialsingle grain production method, low cost, electronic circuit, designed is simpleluminous efficiency is low; of poor color; fluorescent material is not easy to find; limited phosphor coating, so thewhite light is not evenuv led (375nm) + fluorescent materialphosphor material is not easy to find, will enable the conversion efficiency higher than the yag fluorescent material, light-emitting efficiency of space; good colorluminous efficiency is low; packaging materials are easy to produce ultra-violet by uv light ; limited phosphor coating, so thewhite light is not evenznse single grainblue led + znse substrate single grain product white light, low cost; low drive voltage (2.7); without the use of phosphorluminous efficiency is 50% lower than can, about 8lm / w; short life, only 8000hdual-wave single grainwhite lightsingle grain product white light,other to be done to be donemulti-graingreen, blue & red, green and blue multi-color combinationshigh luminous efficiency; can be dynamically adjusted color-temperature; of good color; natural colorthe needs of three grains, the grain of the need for individual electronic circuit design, high cost; poor of the close-up color; multi-color led light-emitting efficiency is not evenas a result of blue light chips + yag phosphor have a white led production method of the lowest cost, practicalitys characteristic has become the mainstream products on the market. therefore, the experiment chosen this method to product white led.key processes and technical measures compared with the ordinary white-light led, the high-power (w-class power) white led has a higher power and more heat, therefore, in the packaging process, be considered light, electricity, heat and other factors.flip-chip technology installed in the traditional way of led chip package, because of p-type doped gan difficulties, the current widely used in the preparation of p-type gan metal transparent electrodes on the ways in which even the spread of current in order to achieve the purpose of light-emitting uniformity. p-type gan on the transparent electrode metal to absorb 30% to 40% of a light, while n-type electrode and the lead will block some of the revealing light, which severely affect the chip led light efficiency. in the manufacturing process, in order to improve light efficiency, generally transparent electrode metal thinning methods, so that in turn limits the current in the h-gan surface evenly spread the impact of the products reliability, constraint of the led chip operating current . at the same time, such a structure is installed through the pn junction calories derived sapphire substrates, sapphire is the thermal conductivity 35 w / (mk) (worse than the metal layers), a larger thermal resistance, resulting in bamboo core temperature rise, thus affecting the device the performance.this experiment, to take advanced flip chip (flip-chip) technology, through the p-chip and n very very bottom of the production of ultrasonic gold wire leads to solder joint as the electrode structure and the outside of the si chip on the production floor gold lead, to overcome the above-mentioned led chips are mounted in a light efficiency and the shortcomings of current constraints; chip pn junction from the heat generated by gold wire solder through a direct transfer to the si substrate and heat sink, the heat transfer is far superior to the effect of sapphire is mounted cooling structure; flip chip solder ball structure of the gold wire to shorten the path, avoiding the chips installed in the traditional structure is a result of a long wire path phenomenon resulting from high fever; at the same time, the production of si substrate reverse bias the pn junction, the realization of si substrate and the cu heat sink electrical isolation between; thus increased product life led, so that package greatly enhance the reliability.optical design techniques1. to improve the refractive indexhigh-power white light led chip refractive index of n = 2-4, much higher than the lens plays a role in the refractive index of packaging materials (generally of the refractive index of epoxy resin at about 1.4-1.5). therefore, when the light after the chip packaging materials, in a total reflection from the interface effect occurred, resulting in about 50% of the light reflection back to the chip itself, can not be effectively exported to become ultra-high brightness led chips from low light efficiency underlying causes. how different materials will be among the internal refraction, reflection of light energy to be consumed in use, the design of optical systems is the key. therefore, taking flip-chip technology to enhance the efficiency of the light at the same time, through on-chip light-emitting layer and si increase the reflective layer between the bottom of the chip to heat sink side mirror processing methods, the rate of increase in light-emitting devices. in addition, flip-chip in the sapphire substrate surface and between the combination of epoxy resin to increase the si layer of plastic material as a buffer layer, to reduce stress due to thermal expansion caused by the phenomenon of delamination, chip out to improve and enhance the refractive index of light product reliability.2. optimization of spherical optical lenshigh-power led devices at the top of the spherical lens design, led light to improve the efficiency of market applications, also plays an important role. in the lens materials, select a high transmittance of the glass or acrylic and other synthetic materials to improve light efficiency; applications in the market, according to lighting differences in optical design of the needs of the market demand for the companys largest spherical lens structure basis, taking into account a variety of other lens design. thermal packaging technology cooling for the power type led devices is critical, if not the current heat generated by the shed in time to maintain the pn junction to allow the junction temperature in the range will not be able to obtain a stable light output and maintenance of the normal life of the device. thermal materials are usually used, although the best thermal conductivity of ag, but the high cost of the radiator not suitable for general-purpose. and cu close to the thermal conductivity of ag, and low cost compared with ag. although the thermal conductivity of al is lower than cu, but its integrated the lowest cost, is conducive to large-scale manufacturing. after the experimental contrast, the approach is: to connect the chip part of the use of cu or ag-based matrix for the heat sink, and then the heat sink connected to the a1-based radiator, shed heat (or air-cooled heat transfer mode).this approachs advantages are: cost-effective full account of the radiator, the radiator will be a different combination of features to achieve efficient heat dissipation, and the rationalization of cost control head. in addition, cu-based heat sink to connect with the material between the chips is also very important to choose the general led used as a connecting material silver plastic. however, due to the thermal resistance of plastic ag high thermal conductivity in the 10-25 w / (mk), using ag glue to connect the material, it means that people in between the chip and heat sink with a layer of thermal resistance.to this end, the introduction of a new solid materials technology, welding technology that is a total of goods: the goods sn films as tablets of welding and connecting material between the heat sink. sn for the thermal conductivity of 67 w / (mk), its cooling effect and physical properties far superior to ag glue, so to obtain a more ideal thermal effects (thermal resistance coefficient of about 16( c / w).the production process and analyzes finallysplit - blue light chip testing-the blue light chip sticks the piece-the vacuum dries-eutectic welds-wire solder yga luminous powder-vacuum drying-point scattering medicinal preparation-vacuum drying-fills the rubber-vacuum drying-drawing of patterns-partly cuts-test-all cuts-long roasts-separation-packing-warehousing based on the above technology means 1w completed the development of high-power white led to work with a advanced company, 1w high power white led packages, compared to the parameters of performance, the laboratory developed 1w high power white light led products, and its light-emitting efficiency close to the similar products abroad.specific test results as shown in table 2.tab.2 comparison of measurement results with similar foreign products搜索i/mathis experiments 1w high power white ledadvanced company 1w high power white led/w/v/w/v30065.413.493783.533although high efficiency white light led develops successfully, but to achieve and surpass the international advanced level, and realizes the batched production, but also has the following question to need to solve: a. color uniformity is not highthis experiment selects “the blue light chip +yag luminous powder” to have the white light led manufacture method, because of using the manual spot rubber, will cause the luminous powder to be uneven distribution inevitably, causes in various directions, the yellow light colour blending allocated proportion not to be inconsistent blue, thus t influencing products illumination luster and the uniformity, the white light color temperature change fluctuation which send out by it will be big, initiates the so-called facula effect. the chromaticity uniform enhancement also depends on the new technological development.b. color rendering property index is insufficient the development of high-power white light led products is the ultimate goal for general lighting, and therefore the color index is very important evaluation. this experiment using blue, yellow blending methods produce white led, so the performance of red is bad, causing part of the spectrum is not continuous, the spectrum can not be part of reflection to the human eye, which will feel the objects in the human eye color distortion. at present, the insider has been trying to use ultra-violet light-emitting chip make up rgb luminous powder, to fill the existing lack of red performance deficiencies of led white light , but because ultraviolet luminous energy, extremely easy to destroy many seal materials, if works as when epoxy resin ultraviolet ray long-term illumination, its structure in contains under the oxygen environment the very easy broken bond deterioration, produces the color machine group, causes the seal material yellow stain, then largely influence the white light led brightness and white homogeneity. therefore, the development of anti-ultraviolet transparent materials as a package become enhances the colored index uniform new challenge. coclusion in brief, high-power white light led package is a multi-disciplinary involved, such as optical, electrical, thermal, materials and other study. from a certain perspective, high-power white light led package is not only a manufacturing technology, but also a constant innovation in the development of basic sciences. the need for good packaging technology of optical, electrical, thermal, materials and other physical nature of the understanding and use of the package to be introduced to update the structural design and process technology.附录b 大功率白光led封装工艺技术与研制与传统的白炽灯、荧光灯照明相比，由于大功率白光led具有显著的节能、环保、使用寿命长等一系列不可比拟的优势，代表着新型绿色、环保照明的发展方向，正迅速进军照明领域。从1w大功率白光led的封装工艺技术出发，在分析比较了几种产生白光led方法的成本、性能的基础上，最终选取性价比相对较高的“蓝光芯片+yag荧光粉”产生白光led的制作方法。实践证明，在提高大功率白光led发光效率、均匀性和稳定性等方面，还需要进一步开发新材料，采用新工艺。引言led是利用固体半导体芯片作为发光材料，采用电场发光。作为光源，led优势体现在节能、环保和长寿命三个方面。led不依靠灯丝发热来发光，能量转化效率非常高，理论上只需要白炽灯10%的能耗，相比荧光灯，led也可以达到50%的节能效果。专项调查表明，我国照明用电每年在3000亿度以上，用led取代全部白炽灯或部分取代荧光灯，可节省1/3的照明用电，意味着节约1000亿度，相当于一个总投资超过2000亿三峡工程全年的发电量。用led替代荧光灯，避免荧光灯竹破裂溢出汞的一次污染，而且制造led的废弃底板(铝基覆铜板)可以回收重复利用。led采用固体封装，结构牢固，寿命可达h。此外，led还具有工作电压低、耗电量小、光效高、响应时间极短(ns级)、光色纯、重量轻、体积小等一系列特性，发展突飞猛进，尤其是大功率高亮度白光led的发明，被业界称为继取火照明、爱迪生发明电灯之后的“照明领域的第三次革命”。白光led的制作方法 目前，用led芯片产生白光的方法见表(1)由于“蓝光芯片+yag荧光粉”产生白光led的制作方法，其成本最低，实用性强，已经成为目前市场产品的主流。因此，本实验选用该方法制作白光led。表1白光led产生方法的比较白光产生方式优点缺点can单晶粒蓝光led+荧光材料单一晶粒产生白光,成本低,电子回路,设计简单发光效率低；显色性不佳；荧光材料不易寻找；限于荧光粉涂布，使白色光不够均匀紫外光led（375nm）+荧光材料荧光粉材质不容易寻找，可使转换效率高于yag的荧光材料，发光效率有提高空间；显色性佳发光效率低；封装材料被紫外光照射易产生老化；限于荧光粉涂布，使白色光不够均匀znse单晶粒蓝光led+znse基板单粒产生白光，成本低；低驱动电压（2.7）；不需使用荧光粉发光效率较can低50%，约8lm/w；寿命短，仅8000h双波长叠层单晶粒白光单晶粒产生白光；其他待研究待研究多晶粒绿、蓝&红、绿、蓝多种色光组合发光效率较高；可动态调整色温；显色性佳；颜色自然需要三颗晶粒，各晶粒需有个别的电子回路设计，成本高；近距离混色性不佳；多色led发光效率不均关键工艺及技术措施相对于普通白光led而言，大功率(w级功率)白光led具有更高的功率和更大的发热量，因此，在封装过程中，需要综合考虑光、电、热等多方面因素。倒装芯片技术在传统的正装led芯片封装方式中，由于p型gan掺杂困难，当前普遍采用在p型gan上制备金属透明电极的方法，使电流均匀扩散，以达到发光均匀性的目的。p型gan上的金属透明电极要吸收30%-40%的光，同时h型电极和引线也会遮挡部分光线的透出，这严重地影响着led芯片的出光效率。在制造过程中，为改善出光效率，普遍采取减薄金属透明电极的方法，这样反过来又限制了电流在h型gan表面的均匀扩散，影响了产品的可靠性，制约着led芯片的工作电流。同时，这种正装结构的pn结热量通过蓝宝石衬底导出，蓝宝石的导热系数为35 w/ (mk)(比金属层要差)，热阻较大，导致竹芯温度上升，从而影响器件的各项性能。本实验中，采取先进的flip chip(倒装芯片)技术，通过在芯片的p极和n极下方制作超声波金丝球焊点作为电极的引出结构，并在芯片外侧的si底板上制作金丝引线，克服了上述正装led芯片在出光效率与电流制约方面的缺点;从芯片pn结产生的热量通过金丝球焊点，直接传导至si基板和热沉，其传热效果远优于正装蓝宝石的散热结构；flip chip的金丝球焊结构缩短了导线路径，避免了在传统正装芯片结构中因导线路径较长而产生的高热现象；同时，在si基板上制作反向偏置的pn结，实现si基板与cu热沉之间的电隔离;从而提高了led产品寿命，使封装的可靠性得到极大提升。光学设计技术1. 折射率的改善大功率白光led的芯片折射率n= 2-4，远高于起着透镜作用的封装材料的折射率(一般环氧树脂的折射率约在1.4-1.5)。因此，当芯片发出的光经过封装材料时，在一者界面处发生全反射效应，造成约50%的光线反射回芯片内部，无法有效导出，成为超高亮度led芯片取光效率很