錫鉛銲料(Sn63Pb37)與無鉛銲料(Sn95.5Ag4Cu0.5)對熱電模組接點電性影響之研究

A study of electrical properties of Sn63Pb37 and Sn95.5Ag4Cu0.5 solder joints in thermoelectric modules

陳文進(Wen-Jin Chen)

指導教授 ： 廖建能

國立清華大學/工學院/材料科學工程學系/碩士(2006年)

https://doi.org/10.6843/NTHU.2006.00498

摘要

熱電致冷模組通常是利用銲接反應將熱電材料與金屬導線連結起來。隨著熱電模組微小化，熱電材料尺寸愈來愈小，熱電材料與電極端間的總接觸電阻將對熱電元件的致冷能力造成影響。錫鉛銲料一直是微電子封裝工業最主要且常用的銲料，然而，在WEEE與ROHS法規的限制下，錫鉛銲料勢必將被無鉛銲料所取代。本論文利用傳統錫鉛銲料與無鉛銲料Sn95.5Ag4Cu0.5分別和P、N型熱電材料接著，進而比較錫鉛銲料與無鉛銲料Sn95.5Ag4Cu0.5對P、N型熱電材料間接觸電阻值的大小與接點微結構的差異性。本研究亦研究無鉛銲料與P、N型熱電材料間，隨著接著時間不同其接觸電阻率變化情形。實驗結果發現，無鉛銲料Sn95.5Ag4Cu0.5的接觸電阻率較傳統錫鉛銲料要來的低。因此，無鉛銲料Sn95.5Ag4Cu0.5對於熱電元件的致冷能力影響較小。然而，無鉛銲料較錫鉛銲料與熱電材料間的介金屬化合物層厚度要來的大。這將是元件接點可靠度的一大隱憂。且隨著無鉛銲料與熱電材料的接著時間增長，造成其介金屬化合物層變厚，而接觸電阻率亦有增大的趨勢。根據實驗結果計算，介金屬化合物層厚度與接著時間成線性關係，推論介金層化合物的生長機制主要為反應控制。

關鍵字

接觸電阻率 ； 熱電 ； 無鉛銲料 ； 錫鉛銲料

並列摘要

Thermoelectric elements and metallic conductors are connected by soldering reaction in thermoelectric cooling module. Owing to miniaturization of thermoelectric cooling modules, the size of thermoelectric elements is also decreasing. The contact resistance between thermoelectric elements and electrodes are expected to affect the cooling performance of thermoelectric modules. Lead-tin solder is widely used in microelectronic packaging industry. However, it will be replaced by lead-free solder soon due to WEEE and ROHS regulations. In this study, p-type and n-type thermoelectric elements were jointed by lead-tin and Sn95.5Ag4Cu0.5 solders, respectively, and contact resistivity and microstructure at the solder/thermoelectric junctions were compared. Besides, this study also discussed the changes of contact resistivity with different reaction time when lead-free solder and thermoelectric material are connected. It is observed that the contact resistivity of Sn95.5Ag4Cu0.5 solder/Cu junction is lower than that of lead-tin solder/Cu junction. Therefore, Sn95.5Ag4Cu0.5 solder is expected to have smaller influences on the cooling performance of thermoelectric device. But, the thickness of IMC at the interface of Sn95.5Ag4Cu0.5 solder/thermoelectric element is thicker than that at lead-tin solder/thermoelectric element interface, which may cause an implicit reliability problem. With the increase of soldering reaction time, the IMC thickness and contact resistivity between thermoelectric material and electrode also increased. The experimental results indicate that the IMC thickness is proportional to the reaction time, and a reaction-controlled kinetic process is suggested.

並列關鍵字

contact resistivity ； thermoelectric ； lead-free solder ； lead-tin solder

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