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Title: | 以燒結銀銦為材料的高溫高功率晶片接合技術開發 Development of Die Attachment Technology for High Power and High Temperature Application by Sintered Silver-Indium Bonding Material |
Authors: | Chun-An Yang 楊淳安 |
Advisor: | 高振宏 |
Keyword: | 高溫封裝材料,奈米銀燒結接合技術,銀銦暫液態相接合法,銀銦合金,高溫可靠度,功率模組晶片接合法, High temperature packaging material,Nano-silver sintering,Silver-Indium transient liquid phase (TLP) bonding,Silver-Indium alloy,High temperature reliability,Power module die attachment, |
Publication Year : | 2018 |
Degree: | 博士 |
Abstract: | 新一代的功率積體電路模組在電動車、航太等產業中對於功率和工作溫度將有更高且更嚴峻的要求。在半導體材料部分,寬能帶半導體材料已被發現在高功率、高溫300度以上擁有極佳的性質,已經逐漸在功率裝置中取代傳統矽晶的角色。然而,在封裝材料部分,傳統的錫基焊料之最高使用溫度卻無法突破250度。因此,能夠耐高溫且具有良好性質的封裝材料急需被開發。在過去十幾年間,奈米銀燒結接合法(Nano-silver sintering technology)被視為最具潛力之高溫高功率模組晶片接合技術之一。然而,燒結奈米銀接點仍然存在一些棘手的問題,例如:高孔洞率、界面潤濕性差、高溫可靠度不佳(180度以上會有嚴重氧化問題)、銀的硫化特性以及電化學遷移問題。奈米銀燒結接合技術需要克服以上這些棘手的問題,才能真正為業界所大量採用。此研究之目的在於解決燒結奈米銀接點之各項問題,並且為新一代的功率模組發展一個更理想的晶片接合技術以及封裝材料。我們所提出的接合方法為在奈米銀燒結系統中添加金屬銦,透過結合銀銦暫液態相接合法(Transient liquid phase bonding)和燒結奈米銀接合法兩種方法之概念及優點,我們成功解決燒結奈米銀接點之各項問題。我們嘗試以三種不同添加銦之方法來接合:銦粉末、銦薄片和電鍍銦層,而其中最有效的添加方式為銦薄片。在我們開發的接合系統中,奈米銀膠和銦薄片之厚度比例對於製造理想銀銦接點之經驗式已被建立。透過在奈米銀膠上放置特定厚度之銦薄片可以將兩電鍍銀之晶片和基板接合良好,形成燒結銀銦接點。此技術除了可以大幅降低接點孔洞率(從體積比20%降至5%)、改善界面潤濕性,還克服了高溫銅基板氧化之問題,且在300度有極佳之高溫可靠度。此外,燒結銀銦接點還具有良好之機械強度,並且在300度時效100小時後,因為接點成分從銀銦介金屬Ag7In3轉變為固溶銀(Ag),使得強度上升到40 MPa以上,且具有良好之延展性。固溶銀接點相當穩定,在300度時效2000小時後仍然維持高強度。燒結銀銦接點的熔點高達600度以上,表示此接點具有在高溫下使用之能力。
在此研究中,我們也針對燒結奈米銀接點和燒結銀銦接點進行溫度循環可靠度及硫化性質之測試。結果皆顯示燒結銀銦接點具有較佳之溫度循環可靠度和抗硫化性質之表現。最後,我們針對銀銦合金材料進行Water Drop Test (WDT)的電化學遷移性質評估,而結果顯示在銀銦合金中,含銦之成分越高抗電化學遷移之能力亦越高。總而言之,本研究提出之燒結銀銦接合法能夠製造出具有良好高溫可靠度、機械性質、溫度循環可靠度以及極佳抗硫化性質之燒結銀銦接點。此外,燒結銀銦接點中之銀銦合金材料亦具有傑出之抗電化學遷移能力。因此,此接合技術和銀銦封裝材料將能夠提供新一代功率模組以及其他高溫應用一極具潛力之理想晶片接合技術和封裝材料。 New generation power IC modules in electric vehicles, aerospace or other industries require higher power and higher service temperature. Fortunately, wide band gap semiconductors exhibit excellent properties at high power and high temperatures above 300°C, and have gradually replaced the role of silicon in power electronic chips. However, the maximum operation temperatures of conventional packaging materials like tin-based solders are limited to around 250°C due to low melting temperatures. Thus, a high temperature packaging material with competitive properties must be developed. In the past few years, nano-silver sintering has been regarded as one of the most promising die attachment technologies for high power and high temperature applications. Nevertheless, some critical issues still exist in the sintered nano-silver joints such as high porosity, poor wettability at interfaces, poor high temperature reliability above 180°C (oxidation problem) and silver tarnishing issue. These serious issues cannot be neglected before this technology steps to practical application. The purpose of this research is to resolve the drawbacks of sintered nano-silver joint and develop a feasible die attachment technology and packaging material for high power and high temperature applications by introducing indium into nano-silver sintering system. The proposed method combines the concepts and advantages of the Ag-In transient liquid phase (TLP) bonding and nano-silver sintering, and has successfully improved some significant properties of sintered nano-silver joint. We have tested three different addition methods of indium: indium powder, indium foil and indium electroplating layer, and the most viable one is by adding indium foil. An empirical law of the thickness ratio between nano-silver paste and indium foil for producing an ideal sintered silver-indium joint was established. By placing an indium foil over the nano-silver paste between silver-plated die and substrate with a specific thickness ratio of silver over indium, we could considerably lower the porosity (from 20 vol.% to 5 vol.%), improve the wettability at interfaces, and overcome the oxidation problem of copper substrate and exhibit excellent high temperature reliability at 300°C. Moreover, the sintered silver-indium joint had competitive shear strength in as-bonded Ag7In3 state, and even increase to above 40 MPa with high ductility after aging for 100 h and transformed into silver-indium solid solution (Ag) joint. The silver-indium solid solution (Ag) joint was stable and remained high shear strengths over 2000 h at 300°C. In addition, the melting temperature of sintered silver-indium joint can reach up to 600°C, showing the capability of high operating temperature. We also evaluated the temperature cycling reliability, anti-tarnishing property of both the sintered joints with and without indium addition. The results showed that sintered silver-indium joints have much better reliability and anti-tarnishing performance than the sintered nano-silver joints. Finally, the electrochemical migration (ECM) property of silver-indium alloys was investigated by Water Drop Test (WDT), and the results showed that the resistance to ECM increases with increasing indium concentration in silver-indium alloys. In conclusion, the sintered silver-indium joints produced by our sintered silver-indium bonding method exhibit excellent high temperature reliability at 300°C, competitive mechanical properties, good temperature cycling reliability, and extraordinary anti-tarnishing property. In addition, the silver-indium alloys inside the joint also possess remarkable anti-ECM property. Therefore, it is expected that our proposed bonding method and the sintered silver-indium bonding material can provide a feasible solution of die attachment technology and ideal packaging materials for the new generation power IC modules and high temperature applications. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/77774 |
DOI: | 10.6342/NTU201801819 |
Fulltext Rights: | 有償授權 |
Appears in Collections: | 材料科學與工程學系 |
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ntu-107-F02527019-1.pdf Restricted Access | 8.69 MB | Adobe PDF |
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