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晶片级封装器件的可靠性
晶片级封装(倒装芯片和UCSP)代表一种独特的封装外形,它和利用传统的机械可靠性测试的封装产品有所不同。封装的可靠性主要和用户的装配方法、电路板材料以及使用环境有关。用户在考虑使用WLP型号时应认真考虑这些问题。必须进行工作寿命测试和抗潮湿性能测试,这些性能主要由晶片制造工艺决定。
机械压力性能对WLP而言是较大的问题,倒装芯片和UCSP直接焊接后,与用户的PCB连接,从而缓解了封装产品铅结构的内部压力。因此,必须考虑焊接触点的完整性。Dallas Semiconductor的晶片级封装装配指南14提供电路板布板考虑、装配工艺流程、焊接层丝网印刷、元件布局、回流焊温度曲线要求、环氧封装以及视觉检测标准等方面的详细信息。应用笔记189115介绍了Maxim的限定规格和测试数据的详细信息。快速浏览页提供Maxim器件的可靠性信息;公司网站提供Dallas Semiconductor器件的可靠性报告,见表4。
表4. Dallas Semiconductor倒装芯片和UCSP的可靠性报告 DeviceApplicable Reliability Reports with URLDS2431http://www.maxim-ic.com/reliability/dallas/Dallas-8in_CSP20_RDL_3x3.pdfDS2401http://www.maxim-ic.com/reliability/dallas/DS2401.pdf
http://www.maxim-ic.com/reliability/dallas/Dallas_Backgrind_FC-RDL.pdfDS28E01http://www.maxim-ic.com/reliability/dallas/Dallas-8in_CSP20_RDL_3x3.pdfDS1804http://www.maxim-ic.com/reliability/dallas/Bump%202%20layer%20underfill.pdf
http://www.maxim-ic.com/reliability/dallas/Bump%202%20layer%20w-redistribution%20underfill.pdfDS1845http://www.maxim-ic.com/reliability/dallas/Bump%202%20layer%20underfill.pdf
http://www.maxim-ic.com/reliability/dallas/Bump%202%20layer%20w-redistribution%20underfill.pdfDS2406http://www.maxim-ic.com/reliability/dallas/Bump%202%20layer%20underfill.pdf
http://www.maxim-ic.com/reliability/dallas/Bump%202%20layer%20w-redistribution%20underfill.pdfDS2411http://www.maxim-ic.com/reliability/dallas/DS2411A1Bump-8in.pdfDS2415http://www.maxim-ic.com/reliability/dallas/Bump%202%20layer%20underfill.pdf
http://www.maxim-ic.com/reliability/dallas/Bump%202%20layer%20w-redistribution%20underfill.pdfDS2417http://www.maxim-ic.com/reliability/dallas/Bump%202%20layer%20underfill.pdf
http://www.maxim-ic.com/reliability/dallas/Bump%202%20layer%20w-redistribution%20underfill.pdfDS2430Ahttp://www.maxim-ic.com/reliability/dallas/FlipChip_RDL_8in.pdfDS2432http://www.maxim-ic.com/reliability/dallas/Dallas-8in_CSP20_RDL_3x3.pdfDS2433http://www.maxim-ic.com/reliability/dallas/Bump%202%20layer%20underfill.pdf
http://www.maxim-ic.com/reliability/dallas/Bump%202%20layer%20w-redistribution%20underfill.pdfDS2502http://www.maxim-ic.com/reliability/dallas/DS2502Bump.pdf
http://www.maxim-ic.com/reliability/dallas/Dallas_Backgrind_FC-RDL.pdf
http://www.maxim-ic.com/reliability/dallas/FlipChip_RDL_8in.pdfDS2760http://www.maxim-ic.com/reliability/dallas/FlipChip_RDL_8in.pdfDS2761http://www.maxim-ic.com/reliability/dallas/FlipChip_RDL_8in.pdfDS2762http://www.maxim-ic.com/reliability/dallas/FlipChip_RDL_8in.pdf
结论
目前的倒装芯片和CSP还是新技术,处于发展阶段。正在改进的措施将采用背面叠片覆层技术(BSL),保护管芯的无源侧不受光和机械冲击的影响,提高激光标识在光照下的可读性。除了BSL,还会有更小的管芯厚度,保持装配总高度不变。Maxim UCSP尺寸(参见表1)说明了2007年2月产品的封装状况。依照业界一般的发展趋势,这些尺寸有可能进一步减小。因此,设计人员在完成电路板布板之前,应该从各自的封装外形上确定设计的封装尺寸,这一点非常关键。此外,了解焊球管芯WLP合金的组成也很重要,特别是器件没有声明或标记为无铅产品时。带有高铅焊球(Pb95Sn5)的某些器件通过了无铅电路板装配回流焊工艺测试,不会显著影响其可靠性16, 17。采用共晶SnPb焊球的器件需要同类共晶SnPb焊接面,因此,不能用于无铅装配环境。
参考
- Analog Devices, 应用笔记617 (PDF, 414kB)
- National Semiconductor, 应用笔记1281 (PDF, 225kB)
- National Semiconductor, 应用笔记1412 (PDF, 828kB)
- STMicroelectronics, 应用笔记1235 (PDF, 328kB)
- STMicroelectronics, 应用笔记2348 (PDF, 333kB)
- Maxim Integrated Products, FCHIP封装图
- Maxim Integrated Products, UCSP封装图
- Dr. Philip Garrou, IEEE Components, Packaging and Manufacturing Technologies Society, Semiconductor International, October 2000, http://www.reed-electronics.com/semiconductor/index.asp?layout=articlePrint&articleID=CA47705
- Michael Töpper, Fraunhofer Institute for Reliability and Microintegration (Fraunhofer-IZM); Philip Garrou, IEEE Components, Packaging and Manufacturing Technology Society, Semiconductor International, 2004年10月, http://www.reed-electronics.com/semiconductor/index.asp?layout=articlePrint&articleID=CA456679
- M. Töpper, V. Glaw, K. Zoschke, O. Ehrmann, H. Reichl, Fraunhofer IZM - TU Berlin Microperipherics Center, Advancing Microelectronics - 2006年1月/2月, http://www.imaps.org/adv_micro/2006jan_feb/2006jan_feb_full.pdf (PDF, 6.73MB)
- Amkor Technology, Wafer Level Packaging Data Sheet (PDF, 164kB)
- Maxim Product命名规则
- Topmark Cross-Reference Table (PDF, 265kB) (200页以上)
- Maxim晶片级封装安装指南
- 晶片级封装(WL-CSP)封装基础
- 采用无铅(Pb)装配流程装配高含铅的DS2502倒装芯片
- 在无铅装配流程中安装含铅的DS2761倒装芯片
*术语“共晶”在冶金行业用来说明由两种以上材料构成、在共晶点有一定浓度关系的合金。当非共晶合金从液态变到固态时,合金的一种材料在某一温度结晶,另一材料在另一温度结晶。而共晶合金则在一个温度点固化,而且有明显的熔点。这和非共晶合金形成了对比,后者有类似于塑料的熔解范围 (摘自http://www.answers.com/topic/eutectic-point)。
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