高功率發光二極體晶片級封裝應用金屬薄膜封裝技術改善散熱

Abstract

在應用發光二極體（LED）的固態照明中，隨著晶片溫度的升高，發光效率將降低。因此，散熱是熱管理的關鍵因素，特別是大功率LED應用。從LED封裝結構分析，散熱主要是藉由熱傳導模式從LED晶片載體基板，焊錫，系統板,到外界環境。諸如MCPCB和Al 2O3陶瓷等散熱基板經常用於LED晶粒承載基座中加強散熱。然而，當LED晶片封裝尺寸接近晶片時，上述散熱基板在散熱效率將因接觸面積縮小而降低，而且其中使用的絕緣金屬基板（IMS）有較高熱阻,這時反成為散熱瓶頸。為了改善上述問題，本論文提出以金屬薄膜封裝（TMP），取代傳統的LED載體基板，將LED透過金屬薄膜與系統板連接，移除傳統散熱基板，將LED晶片的廢熱快速導至外界。熱逸散系統中，熱阻是檢查材料導熱能力的重要指標。在本研究中，對TMP和其他散熱基板的熱阻進行了研究和比較。從實驗結果可以看出，所提出的TMP與傳統散熱基板相比，具有更好的散熱性能和更低的熱阻，從而大幅降低了LED結溫升高時的相對光通量衰減和光學特性偏移。

In solid state lighting, such as light emitting diode (LED), the light emission efficiency will decrease with the temperature increase. Therefore, the heat dissipation is one of the key factors in thermal management, in particular, for high power LED applications. From the LED package structure, the contact mode is the major heat dissipation path that is from LED chips, LED grain carrier substrate, and solder board to ambient. The thermal substrates, such as MCPCB and Al2O3 ceramic substrate, are frequently used in LED grain carrier substrate for heat dissipation. However, when LED chip scale package (LED CSP) is close to the chip size, the efficiency of the above thermal substrates on heat dissipation is insufficient, and the higher thermal resistance of the insulated metal substrate (IMS) used in thermal substrate will also become the bottleneck of heat dissipation. In order to improve the above issue, thin metal package (TMP) substrate was proposed to replace the conventional LED grain carrier substrate to connect LED electrode to solder board, and quickly dissipate the heat. In thermal system, the thermal resistance is one important index to check the thermal conduction ability of materials. In this study, the thermal resistances of TMP and other substrates were investigated and compared. From the experimental results, the proposed TMP exactly provided better heat dissipation performance and lower thermal resistance than that of conventional thermal substrate to greatly reduce the loss of the relative luminous flux and optical characteristic shift with the increase of LED junction temperature.