{"title":"用共晶Sn-Pb焊膏在210℃下组装共晶Sn-Ag-Cu球的BGAs的显微组织和热疲劳寿命","authors":"N. Nandagopal, Z. Mei, S. Teng","doi":"10.1109/ECTC.2006.1645759","DOIUrl":null,"url":null,"abstract":"Conventionally, it has been understood that in order to assemble BGAs with eutectic Sn-Ag-Cu solder balls in eutectic Sn-Pb solder paste, a reflow profile having a peak temperature higher than 217degC, which is the melting point of eutectic Sn-Ag-Cu, would be required to achieve complete mixing of the Sn-Pb paste and the Sn-Ag-Cu ball. Nevertheless, it was observed in this study that solder joints with uniform microstructure may be achieved with a peak reflow temperature of about 210degC. For further understanding of this phenomenon, DSC testing was performed on eutectic Sn-Ag-Cu spheres (of 0.406-0.76 mm diameters) placed over eutectic Sn-Pb solder paste of different volumes. It has been observed that the mixing of the Sn-Pb and Sn-Ag-Cu was accomplished in about 15 to 25 sees at a peak temperature of 210degC. Thermodynamic calculations published in the literature indicate that the liquidus temperature of completely mixed Sn-Pb and Sn-Ag-Cu is above 210degC. However, above 205degC the volume ratio of solid phase to liquid phase is very small, or practically negligible. The metallograph of Sn-Pb/Sn-Ag-Cu solder joints reflowed at 210degC peak temperature shows uniform microstructure. However, the distribution of Pb-rich phase inside the alpha Sn for the 210degC reflowed Sn-Pb/Sn-Ag-Cu solder joints was somewhat different from those of the 240degC reflowed Sn-Pb/Sn-Ag-Cu solder joints. Accelerated thermal cycling tests (0-100degC and -40-125degC) have been conducted on CSPs with eutectic Sn-Ag-Cu balls assembled on PCBs (of 0.093\" and 0.125\" thick) with eutectic Sn-Pb solder paste. SnPb and Pb-free control samples were also included. These parts were assembled in both single and double-sided board configurations and were reflowed with peak temperatures of 210degC and 227deg C. The ATC test results showed that the fatigue life of CSP assemblies reflowed at 210deg C and 227degC had no significant difference","PeriodicalId":194969,"journal":{"name":"56th Electronic Components and Technology Conference 2006","volume":"14 1","pages":"0"},"PeriodicalIF":0.0000,"publicationDate":"2006-07-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"21","resultStr":"{\"title\":\"Microstructure and thermal fatigue life of BGAs with eutectic Sn-Ag-Cu balls assembled at 210/spl deg/C with eutectic Sn-Pb solder paste\",\"authors\":\"N. Nandagopal, Z. Mei, S. Teng\",\"doi\":\"10.1109/ECTC.2006.1645759\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"Conventionally, it has been understood that in order to assemble BGAs with eutectic Sn-Ag-Cu solder balls in eutectic Sn-Pb solder paste, a reflow profile having a peak temperature higher than 217degC, which is the melting point of eutectic Sn-Ag-Cu, would be required to achieve complete mixing of the Sn-Pb paste and the Sn-Ag-Cu ball. Nevertheless, it was observed in this study that solder joints with uniform microstructure may be achieved with a peak reflow temperature of about 210degC. For further understanding of this phenomenon, DSC testing was performed on eutectic Sn-Ag-Cu spheres (of 0.406-0.76 mm diameters) placed over eutectic Sn-Pb solder paste of different volumes. It has been observed that the mixing of the Sn-Pb and Sn-Ag-Cu was accomplished in about 15 to 25 sees at a peak temperature of 210degC. Thermodynamic calculations published in the literature indicate that the liquidus temperature of completely mixed Sn-Pb and Sn-Ag-Cu is above 210degC. However, above 205degC the volume ratio of solid phase to liquid phase is very small, or practically negligible. The metallograph of Sn-Pb/Sn-Ag-Cu solder joints reflowed at 210degC peak temperature shows uniform microstructure. However, the distribution of Pb-rich phase inside the alpha Sn for the 210degC reflowed Sn-Pb/Sn-Ag-Cu solder joints was somewhat different from those of the 240degC reflowed Sn-Pb/Sn-Ag-Cu solder joints. Accelerated thermal cycling tests (0-100degC and -40-125degC) have been conducted on CSPs with eutectic Sn-Ag-Cu balls assembled on PCBs (of 0.093\\\" and 0.125\\\" thick) with eutectic Sn-Pb solder paste. SnPb and Pb-free control samples were also included. These parts were assembled in both single and double-sided board configurations and were reflowed with peak temperatures of 210degC and 227deg C. 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引用次数: 21
摘要
传统的理解是，为了在共晶Sn-Pb锡膏中组装具有共晶Sn-Ag-Cu锡球的BGAs，需要峰值温度高于217℃(共晶Sn-Ag-Cu的熔点)的回流曲线，以实现Sn-Pb锡膏和Sn-Ag-Cu锡球的完全混合。然而，在本研究中观察到，在210℃左右的峰值回流温度下，可以获得具有均匀组织的焊点。为了进一步了解这一现象，将直径为0.406 ~ 0.76 mm的共晶Sn-Ag-Cu球放置在不同体积的共晶Sn-Pb锡膏上，进行了DSC测试。结果表明，Sn-Pb和Sn-Ag-Cu在峰值温度为210℃时，混合时间约为15 ~ 25次。热力学计算表明，Sn-Pb和Sn-Ag-Cu完全混合的液相温度在210℃以上。然而，在205℃以上，固相与液相的体积比很小，几乎可以忽略不计。在210℃峰温回流处理下，Sn-Pb/Sn-Ag-Cu焊点的金相组织均匀。210℃回流Sn- pb /Sn- ag - cu焊点的富pb相分布与240℃回流Sn- pb /Sn- ag - cu焊点有所不同。加速热循环测试(0-100℃和-40-125℃)在csp上进行，共晶Sn-Ag-Cu球组装在pcb(0.093"和0.125"厚)上，共晶Sn-Pb焊膏。还包括SnPb和不含pb的对照样品。在210℃和227℃的峰值温度下对CSP组件进行再流处理，ATC试验结果表明，在210℃和227℃的峰值温度下再流处理的CSP组件的疲劳寿命没有显著差异
Microstructure and thermal fatigue life of BGAs with eutectic Sn-Ag-Cu balls assembled at 210/spl deg/C with eutectic Sn-Pb solder paste
Conventionally, it has been understood that in order to assemble BGAs with eutectic Sn-Ag-Cu solder balls in eutectic Sn-Pb solder paste, a reflow profile having a peak temperature higher than 217degC, which is the melting point of eutectic Sn-Ag-Cu, would be required to achieve complete mixing of the Sn-Pb paste and the Sn-Ag-Cu ball. Nevertheless, it was observed in this study that solder joints with uniform microstructure may be achieved with a peak reflow temperature of about 210degC. For further understanding of this phenomenon, DSC testing was performed on eutectic Sn-Ag-Cu spheres (of 0.406-0.76 mm diameters) placed over eutectic Sn-Pb solder paste of different volumes. It has been observed that the mixing of the Sn-Pb and Sn-Ag-Cu was accomplished in about 15 to 25 sees at a peak temperature of 210degC. Thermodynamic calculations published in the literature indicate that the liquidus temperature of completely mixed Sn-Pb and Sn-Ag-Cu is above 210degC. However, above 205degC the volume ratio of solid phase to liquid phase is very small, or practically negligible. The metallograph of Sn-Pb/Sn-Ag-Cu solder joints reflowed at 210degC peak temperature shows uniform microstructure. However, the distribution of Pb-rich phase inside the alpha Sn for the 210degC reflowed Sn-Pb/Sn-Ag-Cu solder joints was somewhat different from those of the 240degC reflowed Sn-Pb/Sn-Ag-Cu solder joints. Accelerated thermal cycling tests (0-100degC and -40-125degC) have been conducted on CSPs with eutectic Sn-Ag-Cu balls assembled on PCBs (of 0.093" and 0.125" thick) with eutectic Sn-Pb solder paste. SnPb and Pb-free control samples were also included. These parts were assembled in both single and double-sided board configurations and were reflowed with peak temperatures of 210degC and 227deg C. The ATC test results showed that the fatigue life of CSP assemblies reflowed at 210deg C and 227degC had no significant difference
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