氬氣電漿活化對晶片與軟性基板以非導電膜接合強度與可靠度之研究

The Effect of Argon Plasma Activation on the Die-Shear Force and Reliability of Chips and Flex Substrates Assembly Using a Non-conductive Film

陳俊佑(Jun-you Chen)

指導教授 ： 莊正利

中山醫學大學/健康管理學院/職業安全衛生學系碩士班/碩士(2015年)

https://doi.org/10.6834/CSMU.2015.00173

摘要

本研究以非導電膜(non-conductive film)結合熱音波覆晶接合製程將植金凸塊之晶片接合於軟性基板銅電極，接合過程中以不同接合溫度、固化溫度與固化時間探討晶片與軟性基板之接合強度。為提升晶片以非導電膜接合於軟性基板之接合品質，軟性基板先經氬氣電漿處理後，再將非導電膜貼合於軟性基板表面，隨後進行晶片與軟性基板之接合，並施以高壓蒸煮、高溫儲存以及恆溫/恆濕可靠度試驗探討氬氣電漿活化製程對接合試片之可靠度。晶片與軟性基板接合後以及經可靠度測試後，以電子顯微鏡(SEM)與光學顯微鏡(OM)觀察晶片及軟性基板與非導電膜之接合品質，以剪力試驗檢測晶片與軟性基板之接合強度，並觀察剪力試驗後之破斷面，判斷晶片與軟性基板之破裂機制，以座滴法量測氬氣電漿處理後，軟性基板表面之潤濕性。晶片與軟性基板與軟性基板之接合強度主要來自非導電膜與晶片及軟性基板三者之黏著力，較高固化溫度與固化時間有助於非導電膜之固化強度，故可提高晶片與軟性基板之接合強度。比較氬氣電漿活化處理對接合試片強度之影響，其接合強度均高於未經氬氣電漿活化處理者，軟性基板經氬氣電漿活化處理後其表面接觸角大幅下降，顯示其表面潔淨度較佳，具較佳潤濕性，可有效提高金凸塊與軟性基板之接著性，為晶片與軟性基板之接合強度提升之主因，並可形成有效電訊通路之封裝，但氬氣電漿活化製程對接合試片之高壓蒸煮可靠度測試及恆溫/恆濕可靠度測試並未具有明顯之效益，原因為隨兩者之測試時間增加，測試環境之水氣侵入晶片及軟性基板與非導電膜之接合界面，導致接合試片之接合強度大幅下降；反觀氬氣電漿活化製程對接合試片之高溫儲存可靠度測試具有較明顯之效益，原因為氬氣電漿活化製程能使晶片金凸塊與軟性基板直接接著，使兩者間受長時間之高溫環境產生材料之鍵結，因此其接合強度隨高溫儲存可靠度測試時間延長並無明顯下降，此一實驗驗證氬氣電漿活化對高溫儲存可靠度之效益。

關鍵字

熱壓覆晶接合 ； 非導電膜 ； 電漿活化 ； 可靠度試驗

並列摘要

A non-conductive film (NCF) and the thermal compression bonding process were combined to assemble chips and flex substrates. Two purposes of this study are expected to achieve chips bonded on flex substrates directly and to verify the reliability of chips and flex substrates assembly. Flex substrates subjected to argon plasma activation prior to assemble the chips and flex substrates with different activated parameters. The effects of cured parameters on the bonding strength were also investigated, cured temperature and cure durations. For flex substrates activated with argon plasma, the NCF placed on the surface of flex substrates and then chips were flip-bonded on the flex substrates using thermal compression. A subsequent die-shear test was carried out to evaluate the bonding strength of chips and flex substrates assembly. Scanning electron microscopy (SEM) was conducted to confirm the morphology and elucidate the bonding interface between chips and flex substrates. After chips bonded on flex substrates using NCF, the reliability of pressure cooker test (PCT), high temperature test (HTS) and high humidity/high temperature (HH/HT) test was evaluated according JEDEC standards. For flex substrates with argon plasma activation, the NCF can be removed away from bonding interface between gold bumps and copper electrodes during thermal compression bonding. Accordingly, gold bumps were directly bonded onto copper electrodes to form an active electrical path between chips and flex substrates. A low contact angle can be obtained for flex substrates activating with argon plasma, indicating the containments on the surface of flex substrates were removed, and a good wettability on the bonding surface can be actieved. The sound bonding interface with sufficient bonding strength was achieved, since neither delamination nor porosity was found at bonding interface between the NCF and flex substrates. The argon plasma activation has a significant improvement on bonding strength of chips and flex substrates assembly using NCF. This process was potentially to be applied to the packaging of chips and flex substrates assembly. After specimen subjected to PCT and HT/HH test, the delamination can be found due to the moisture penetrated to the bonding interface among gold bumps, NCF, and flex substrates. The die-shear force of chips and flex substrates assembly is thus degraded. Similarly, the delamination that occurred at the bonding interface between NCF and flex substrates after HTS test of 1000 hr durations, and then deteriorated the die-shear force slightly.For flex substrates subjected to argon plasma activation, the gold bumps bonded on copper electrodes directly and the metallurgical bonding was formed after HTS test. This experimental result showed that the argon plasma activation was effective scheme to improve the reliability of HTS test.

並列關鍵字

thermal compression bonding ； non-conductive film ； plasma cleaning ； reliability

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