Ag 合金線在IC 與LED封裝打線接合之銲墊界面反應

Abstract

摘 要 電子構裝工業打線接合技術在直徑20μm 等級的第一級封裝中，過去大部分主要是使用Au 作為打線接合的材料。而隨著Au 價格從2001 年每盎司不到300美元，成長到2011 年達到每盎司超過1800 美元，未來製造成本只會更加提升。除了原料成本因素，Au wire 與Al pad 容易產生過多的介金屬化合物(IMC)造成接點可靠度降低。本研究使用價格只有Au wire 三分之一的Ag alloy wire， 直徑20μm 等級與Al pad 上進行各種可靠度測試(HTS TCT PCT)。經本研究發現因為Ag alloy wire 的硬度跟Au wire 相近，因此不會有像Pd-coated Cu wire 會損傷Alpad 造成接合強度不佳的問題。Ag alloy wire 與Al pad 的接合界面都非常的完整。熱時效試驗使用溫度100℃到200℃;時效時間0hr 到1000hr 作接合強度測試與界面反應觀察。使用dage 4000 對第一銲點做ball shear 測試後再經由電子顯微鏡的觀察可以明顯發現Ag alloy wire 與Al pad 的接合界面非常的緊密，所以測試結果都會斷在wire 內；而Pd-coated Cu wire 與Al pad 產生的介金屬化合物(IMC)很薄，接合強度不高。在經由200℃ 1000hr 熱時效測試可以發現，Au wire 與Al pad的接合強度會因為過度厚的介金屬化合物(IMC)造成接點脆化與產生大量孔洞而造成接點強度降低；而Ag alloy wire 與Al pad 則是因為生成的介金屬化合物(IMC)成長適中，即使在200℃1000hr 的時效下，接合強度仍然很高。使用Ag alloy wire除了可以降低成本，經由本實驗研究發現Ag alloy wire 在熱時效200℃1000hr後與Al pad 的接合強度測試更強於Au wire 與Al pad 的接合強度，因為Ag alloy wire與Al pad 有著特殊適中的界面反應機制。

Abstract Electronic packaging industry wire bonding technology in the first stage of diameter 20μm level package, in the past most of the major is to use as an Au wire bonding material. With Au Price from less than $ 300 per ounce in 2001, growing to 2011 reached one ounce more than 1800 U.S. dollars,the future will be more improved manufacturing costs.In addition to raw material cost factor, Au wire and Al pad prone to excessive intermetallic compound (IMC) cause joint reliability decreases.In this study, the price is only one third of the Au wire Ag alloy wire, diameter 20μm level and Al pad on a variety of reliability testing (HTS TCT PCT). The present study found that because of the hardness of Ag alloy wire with Au wire similar, so there is no like Pd-coated Cu wire will damage Al pad causing the problem of poor bonding strength, Ag alloy wire and Al pad bonding interface is very complete. And make more use of the thermal aging test temperature 100 ℃ to 200 ℃; aging time 0hr to 1000hr for bond strength test and interfacial reactions observed. Use dage 4000 made the first solder ball shear test and then observed through an electron microscope can obviously find Ag alloy wire and Al pad bonding interface is very close, so the test results are broken inside the wire; while the Pd-coated Cu wire the Al pad intermetallic compound produced (IMC) is thin, the bonding strength is not high. Via the 200 ℃ 1000hr thermal aging tests can be found, Au wire bonding strength with the Al pad thickness because of excessive intermetallic compound (IMC) cause embrittlement and produce large amounts of the contact holes caused by the contact strength decreases; while Ag alloy wire and Al pad is because the generated intermetallic compound (IMC) growth is moderate, even at 200 ℃ 1000hr the timeliness, the bonding strength is still high. Using the Ag alloy wire in addition to reducing costs, by the experimental study Ag alloy wire after the heat aging and the Al pad is much stronger than the bonding strength test of Au wire bonding strength with the Al pad, since Ag alloy wire and Al pad has a special medium the interfacial reaction mechanism.