In-Bi-Sn低熔點合金熱界面材料之熱性、微結構與界面反應研究

Abstract

近年來，電子產業蓬勃發展，消費性電子產品亦不斷朝向高效能、高功率、低能耗等方向前進，帶動IC元件之散熱需求提高。傳統熱界面材料之散熱效能，面臨高頻、高瓦數之挑戰。本研究遂採用低熔點合金In-32.5Bi-16.5Sn作為熱界面材料，利用合金高熱傳導性之優點，降低積存於晶片與均熱片界面之熱量。實驗探討In-32.5Bi-16.5Sn與金屬基板之界面反應，計算介金屬成長動力學以及不同基板之溶解速率差異。金屬基板之選擇以實際均熱片性質為考量：銅基板擁有高熱傳導係數，電鍍鎳常作為擴散阻擋層，金常作為氧化保護層及潤濕層。最後，針對低熔點合金在高熱傳導率之銅基板下做熱阻性質測量。 實驗結果顯示，低熔點合金In-32.5Bi-16.5Sn與銅基板反應之界面生成物為Cu6(In, Sn)5，屬於擴散控制，其活化能為2.86 kJ/mole；與銅電鍍鎳基板反應之界面生成物Ni3(Sn, In)4相，活化能為52.15 kJ/mole；與金基板反應之界面生成物在80℃時，生成AuIn2與薄層AuIn，反應溫度100℃以上，介金屬分為三層，AuIn2、AuIn、Au7In3，其中AuIn2活化能為37.64 kJ/mole，Au7In3活化能為79.69 kJ/mole。此外，電鍍鎳層最大消耗厚度約3-4 μm，是銅基板消耗厚度的1/5倍。低熔點合金In-32.5Bi-16.5Sn之熱阻抗在100 W之情況，與介金屬厚度之增加趨勢相似，都有上升現象。

As the developing of electronic industry and consuming electronic products proceeding toward high performance、high power and low power dissipation, the demand of the heat dissipation of IC component have been promoted. The heat dissipation of conventional thermal interface materials is challenged by the increasing demand for higher frequency and higher power. Therefore, this study adopts Low-melting point alloy In-32.5Bi-16.5Sn as thermal interface material, and tries to make use of the high thermal conductivity of metal to deduce the thermal budget at the interface between ship and intergraded heat spreader. This investigation includes the interfacial reaction between In-32.5Bi-16.5Sn alloy and metal substrates, calculating the kinetic of intermetallic compounds and dissolution rates of different substrates. Metallic substrates are chosen for real condition: Cu substrate processes high thermal conductivity, Ni-electroplated layer uses as a diffusion barrier, Au usually uses as an oxidation protective player or a wetting layer. Finally, according to the high conductivity of Cu substrate, the thermal resistance of Cu/In-32.5Bi16.5Sn/Cu is measured. The results show that the intermetallic compound formed at the interface of In-32.5Bi-16.5Sn/Cu is Cu6(In, Sn)5. The growth of Cu6(In, Sn)5 compound is diffusion-controlled, and the activation energy for the growth of Cu6(In, Sn)5 compound is calculated to be 2.86 kJ/mole. The intermetallic compound formed at the interface of In-32.5Bi-16.5Sn/Ni is Ni3(Sn, In)4, and the growth of Ni3(Sn, In)4 compound is diffusion-controlled. The activation energy of Ni3(Sn, In)4 intermetallic compound is calculated to be 52.15 kJ/mole. The intermetallic compound formed at the interface In-32.5Bi-16.5Sn/Au could be divided by temperature: (1) AuIn2、AuIn intermetallics are formed respectively at 80℃(2) AuIn2、AuIn、Au7In3 intermetallics are observed respectively above 100℃. The growths of AuIn2 and Au7In3 compounds are diffusion-controlled, and the activation energies for AuIn2 and Au7In3 compounds are calculated to be 37.64 kJ/mole and 79.69 kJ/mole, respectively。In addition, the maximum consuming thickness of Ni-electroplated layer is about 3~4 μm, which is one fifth of the maximum consuming thickness of Cu substrate. The thermal impedance of Cu/In-32.5Bi-16.5Sn/Cu at 100W has similar increasing trend with the growth of Cu6(In, Sn)5 compound.