华为工艺可靠性设计方法与实践

HUAWEI TECHNOLOGIES CO., LTD.,Page,*,单击此处编辑母版标题样式,单击此处编辑母版文本样式,第二级,第三级,第四级,第五级,HUAWEI Confidential,HUAWEI TECHNOLOGIES Co., Ltd.,HUAWEI Confidential,Security Level:,单击此处编辑母版标题样式,单击此处编辑母版文本样式,第二级,第三级,第四级,第五级,HUAWEI TECHNOLOGIES CO., LTD.,HUAWEI Confidential,单击此处编辑母版标题样式,单击此处编辑母版文本样式,第二级,第三级,第四级,第五级,Thank You,工艺可靠性设计方法与实践,华为公司工艺可靠性研究业务介绍,工艺基础研究部工艺可靠性研究组,20061124,Page,2,目录,工艺可靠性业务的需求分析,工艺可靠性业务行业分析,工艺可靠性业务组织流程,工艺可靠性业务技术内容,工艺可靠性技术在产品中的应用案例,Page,3,产品中工艺可靠性需求,High Performance Systems,10,25,年的使用寿命对工艺可靠性设计的要求；,高频、高速信号；,热可靠性问题,高复杂度单板；,封装技术的极限化发展带来的失效。,Mid Range Performance Electronics,5,年以上使用寿命；,混合组装；,无铅可靠性问题。,Hand-held/Wireless Electronics,4,年以上使用寿命；振动、冲击等特殊应用环境；,高密；,无铅可靠性问题；,低成本问题。,Page,4,工艺可靠性行业分析业界趋势分析：,ECTC,、,SMTA,近年来在工艺可靠性领域的研究,1,、不同表面处理条件下的脆性断裂问题；,2,、快速可靠性评估方法研究；,3,、无铅、密间距焊点可靠性研究；,4,、腐蚀与迁移失效机理研究；,5,、无损分析和故障诊断技术。,业界采用仿真、可靠性试验以及失效机理的研究方法对典型的板级互连可靠性问题进行研究，包括：,Page,5,Reliability Engineering,FEM,Page,6,业界常见可靠性业务流程,Design Verification,Failure analysis,Root cause analysis,results,Predictions /,failures,Manufacture &,Market product,Field,failures,Component count reliability analysis,Long term life test & group testing,Design “rules”,Product Qualification,Product design,results,Parametric,distribution,yield,analysis,Demonstration of target reliability,SHIP,BETA,ALPHA,FEM,Page,7,工艺可靠性业务内容,工艺对象,环境,可靠性研究方法,结论,焊点,PCB/PTH,辅料,器件,基于,POF,仿真分析工具,可靠性试验标准,失效分析方法,工作热循环,工作机械应力,功率循环,组装热过程,组装机械应力,存储,运输,气候,环境气氛,设计方法,可靠性规格,DFR,设计流程,技术积累,Page,8,工艺可靠性研究内容,挑战,:,高密高速、小型化、低成本的市场需求,新技术、新工艺、新材料的不断应用,研发周期不断缩短,新型法律法规出台,/,环保政策的推行,工艺可靠性研究就是从工艺的角度，控制工艺风险，保证产品的质量波动在允许的范围之内,工艺可靠性研究的主要课题：,PCBA,的环境适应性,电气互连可靠性。,PCB,可靠性；,连接器互连的可靠性。,Page,9,工艺可靠性分析测试和评估能力,无损分析技术,微观组织结构分析,表面形貌分析技术,材料力学性能测试,有限元模拟和仿真技术,Page,10,工艺可靠性设计与产品开发,有限元仿真分析技术,采用,Ansys,仿真技术对板级热、机械应力进行分析，评估各种工艺对象包括焊点、封装、,PCB,的热机械可靠性问题，并进行优化设计。,Page,11,工艺可靠性技术与产品开发,工艺失效分析,失效现象,失效模式,失效机理,根本原因,改进预防,芯片级,器件级,单板级,系统级,开路,断路,时断时续,物理,化学,电学,热学,力学,材料学,可靠性设计,物料,制造过程,应用环境,人为损坏,DFM,DFR,来料监控,Page,12,工艺可靠性设计与产品开发,新材料,/,新工艺,/,新封装工艺可靠性认证与评估,Influence of Ni-Sn-Cu ternary intermetallic compound on,solder joint reliability,Page,14,PRESENTATION,OUTLINE,Overview,Experiments results,Discussion,Conclusion,Page,15,Overview,As we all know, Cu-Sn or Ni-Sn binary compound forms at the interface of pad and solder material after soldering.,Scallop Cu6Sn5,1,thin Ni3Sn4,2,Cu6Sn5,Page,16,Overview,But sometimes, things don,t happened exactly like this.,Ni-Sn-Cu,Ni,-Sn,SAC+NiAu BGA after soldering,3,Page,17,Overview,Somebody found solder joint brittle fracture between two layer IMC and then attributed to ternary compound.,Ni,Cu,Ni-Sn,Ni-Sn-Cu,Solder joint open case in Qualcomm,4,Page,18,Experiments,Assembly: PCB,（,HASL / OSP / IAg / NiAu / ENIG,）,solder,（,SnPb eutectic / SAC,）,BGA,（,NiAu,）,Etch: 5%HNO3 + alcohol to remove solder without cross-section,SEM & EDS,Solder joint fracture case analysis,Page,19,Results,NiSn binary IMC formed in,NiAu/SnPb/NiAu,Solder joint,granular sand-like,6000x,Solder joint after solder removed,Ni-Sn only,NiSn binary IMC,Page,20,Disconnected rock formed upon sand in,HASL/SnPb/NiAu,Rock like column lies upon sand like granules,Just change PCB finishing from NiAu to HASL, things become different at BGA side?,Results,2000x,Page,21,5000x,Sand-like mainly still Ni-Sn,（,contains a little copper,）,; rock-like column mainly,Contains Ni-Sn-Cu,Results,EDS indicates,Ni-Sn-Cu ternary compound,They do exist!,Page,22,If copper exist in ether side of solder joint or inside of solder joint, ternary compoud will form upon nickel layer!,PCB pad finishing,Solder,BGA pad finishing,BGA side exist ternary compound?,NiAu,SnPb,NiAu/ENIG,No,NiAu,SAC,NiAu/ENIG,Yes,HASL,SnPb,NiAu/ENIG,Yes,OSP,SnPb,NiAu/ENIG,Yes,OSP,SAC,NiAu/ENIG,Yes,Results,They even exist in almost all kinds of solder joint!,Page,23,Results,It seems like this:,SnPb,NiAu,HASL/OSP,SAC,NiAu,Any, even NiAu,reflow,Ni-Sn(Cu),Ni-Sn-Cu,Page,24,Discussion,Why copper can migrate so long distance?,Copper is so active with much solubility in tin.,Copper can form Cu-Sn IMC more easily and quickly than Ni-Sn.,At the touch second, great many copper diffuse into melt solder even exceed stable solubility,Due to unstable, some copper atom come back to decrease energy,Copper migration,Touch melt solder,reflow,Cooling begin,IMC nucleate at interface and ternary IMC forms,Page,25,1000x,3000x,Hollow hexagon,Hollow hexagon Cu6Sn5,3000x,2000x,solid trigon,solid hexagon,Discussion,Variable morphology of ternary compound, sometimes like Cu6Sn5,Looks similar!,Page,26,So the column can be identified as (CuNi)Sn5,(a),(b),Diffraction pattern of (a) Cu6Sn5 binary compound (b) column-like ternary compound found in solder joint,5,Discussion,The crystal structure of rock-like column is close to Cu6Sn5,Page,27,Field failure of BGA solder joint crack , found trigon and hexagon rock at fracture surface without any etching,Discussion,Some solder joint failure cases show abnormal brittle fracture,1000x,Can ternary compound be so terrible?,Page,28,Top side BGA solder joint crack after wave solder, found more strong trigon and hexagon rock at fracture surface.,Some solder joint failure cases show abnormal brittle fracture,Discussion,1000x,Is ternary compound a trouble maker?,Page,29,Discussion,It seems that crack develop between two IMC layers, Ni-Sn(Cu) and Ni-Sn-Cu,！,Yes, there do exist micro cracks in IMC layer!,Ni-Sn(Cu),Ni-Sn-Cu,5000x,Page,30,Discussion,Failure joint ternary compound didnt show any difference to others,But,there also exist evidence to prove his innocence.,Fracture didnt occur in IMC but at interface between solder and IMC,Page,31,Discussion,Source,Experiments results or failure case,conclusion,publication,Qalcomm,CSP ball off during ball attach; Ni-Sn/Ni-Sn-Cu interfacial brittle fracture,Ternary compound caused fracture,；,can be avoid by decrease heat in reflow,4,2004,Solectron,BGA Ni-Sn/Ni-Sn-Cu interfacial brittle fracture,Ternary compound caused fracture and dewet,6,2004,Siemens,BGA Ni-Sn/Ni-Sn-Cu interfacial IMC spalling,Ternary compound can lead reliability risk due to interfacial weakness,7,2004,UIC,Ni-Sn/Ni-Sn-Cu interfacial brittle fracture during ATC,Ternary compound can lead reliability,8,2005,Sungkyunkwan University,Shear strength didnt decrease when formed Ni-Sn-Cu ternary IMC,No problem,3,2004,Philips,Gold brittle alleviated by ternary IMC,Can avoid gold brittle problem,9,2003,How about other companies ?,Page,32,Discussion,How about other companies ?,Interfacial failure,by S company,dewet failure,by S company,Interfacial failure,by UIC,Page,33,Conclusion,when copper exist inside or at ether side of solder joint, Ni-Sn-Cu ternary compound will form at interface between nickel and solder.,The Ni-Sn-Cu ternary compound have two layers, Ni-Sn(Cu) and,（,CuNi,）,6Sn5, the former is continuous and dense granular sand-like, and later is discontinuous column like.,the bonding strength of the two layer compound might not good enough, and sometimes can lead to micro crack, but almost never cause solder joint open in this way.,Some company found solder joint brittle fracture and attributed it to ternary compound, but there do exist,contrary opinions,and many experiment result dont show any weakness of ternary compound. UIC plan to do a full research and we can participate.,Assessment on Reliability of 1.0mm pitch BGA Package double-side assembly,HUAWEI TECHNOLOGIES Co., Ltd.,Process Reliability Research Group of AATC,Board Design Engineering Dept.,20061124,Page,35,OUTLINE,Overview,Reliability Test,Sample Design,Reliability Test results,Simulation Analysis,Conclusion,Page,36,Overview,Advantage:,layout simple, Optimum routing, noise isolation, shorten line length,Problem:,rework, long reliability,Page,37,Reliability Test,BGA Package and PCB Test board,1.0mm pitch,2525mm,256 solder balls,1.6mm PCB,OSP surface finish,Common Tg material,Page,38,Reliability Test,BGA Assembly,Double-side mirror assembly,Double-side offset assembly,Page,39,Reliability Test,Test sample,Assembly,Solder joint,Numbers,Peak Temp,240C,Page,40,Reliability Test,Thermal Cycle condition,1hour per cycle, 15min dwell time, 200,failure criterion,Page,41,Reliability Test,Reliability results,Single side SnAgCu solder joints have the strongest reliability,Double-side mirror assembly decrease the life by half,Double-side offset assembly will improve the reliability, but depend on the distance of offset,Page,42,Reliability Test,Failure analysis,Crack initial from the solder joints of corner,Red means solder joint open entirely,Green means solder joint fail in electric function, but not separate from PCB,Page,43,Simulation Analysis,Material Property,Implicit Creep Model,Parameter,C1,(1/sec),C2,(1/Pa),C3,C4,(,o,K),Sn63Pb37,926(508-T)/T,1/(37.78x106-74414T),3.3,6360,SnAgCu,277984,0.02447,6.41,6500,Page,44,Simulation Analysis,Crack growth model,For Sn63Pb37, Darveaux model:,a1,b1,a2,b2,71900,cycle/MPa,-1.58,1.16e-7,mm/cycle/MPa,1.,58,1.21,For SnAgCu, Syed model:,Page,45,Simulation Analysis,Finite Element Model,diagonal,Geometry sketch,Single side assembly,Page,46,Simulation Analysis,Finite Element Model,Double side mirror assembly,Double side offset assembly,Page,47,Simulation Analysis,FEM Results-dangerous points,Single side,Double side,Initial crack location have different for single side and double side,Page,48,Simulation Analysis,FEM Results-Estimation life,Sample,Test results, cycle,Prediction life,cycle,Single- SnAgCu,1014cycle No Failure,2432,Mirror- SnAgCu,318,501,481,Offset- SnAgCu,320,510,703,Single- SnPb,8551136,1870,Mirror- SnPb,/,247,failure location by FEM prediction is same to experimental results,prediction life have a good correlation with experimental results,Page,49,Conclusion,For PCBA structure using in ATC experiments, we found:,for all assembly shape, the first crack will initialize from solder joint of corner;,for SnAgCu alloy, double side mirror will reduce life by over 3 times compared with single-side whether by using experiment or FEM; while for SnPb alloy, FEM analysis show the reduction degree will increase more;,Double side offset assembly shape will increase the solder joints reliability to some extent which depend on the distance of offset,Reasons of solder joints reliability reduction for BGA double-side assembly maybe include package structure, solder alloy, PCB thickness, offset distance, and so on,，,these factors will interact.,Page,50,DSP C6203器件工艺失效分析,整机测试功能信号时断时续，用手轻轻按压或者开机一段时间故障现象会暂时消失,之前曾经出现过此类失效，二者的故障现象和失效定位几乎完全一致，当时的给出的结论是在拿板的时候该处,DSP,器件是承受外力最大的位置，从而容易造成失效。如此相似的失效现象重复出现，有必要进行更加深入的分析，以确定起失效的根本原因。,Page,51,无损检测分析,XRay,分析,最初的故障定位在,U21,位置芯片的,A1,角附近，对该芯片,A1,附近区域进行,X,Ray,分析，结果如图,1,所示。发现除了存在较多的气孔，没有其他的异常现象。,Page,52,无损检测分析,IV,曲线,重点对,BGA,器件的四边引脚进行分析,AA19,和,W22,开路，,AB21,和,W21,时断时续。,Page,53,无损检测分析,ERSASCOP,分析,芯片,AB22,位置角附近存在多处焊点的开裂现象，裂纹产生在器件侧焊盘同焊料球之间，当在该芯片处施加外力或者热应力的情况下，裂纹可能会暂时的愈合或者断开，因此，功能测试表现出时断时续的现象。,Page,54,有损检测分析起拔试验,几乎所有焊点的断裂面都在器件侧焊盘与焊料球之间,断面光滑平整，属于脆性断裂,AB22,角部分焊点端面颜色发暗，应该为断裂面在空气中曝露,Page,55,SEM,显示断口为脆性断口,Page,56,韧性断口图象（推力试验）,Page,57,一个正常焊点起拔后的各种断面位置,一般断面在焊料球中间或者是由于器件侧和,PCB,侧的焊盘从基板脱离,Page,58,有损检测分析切片,器件侧焊盘为,ENIG,镀层,个别焊点器件侧出现的裂纹,裂纹产生在,Ni,层,/IMC,之间，并几乎贯穿整个界面。,裂纹的宽度为,2,4,微米左右。,裂纹在,Ni,层,/IMC,之间产生并扩展,Page,59,有损检测分析切片,时断时续焊点器件侧出现明显裂纹,所有焊点,PCB,侧连接正常,Page,60,SEM,时断时续焊点器件侧裂纹背散射图象,所有焊点,PCBIMC,背散射图象,Page,61,有损检测分析,SEM,和,EDX,能谱分析的结果显示了断面,Ni,层的,P,含量过高。一般来说业界通用的标准认为,ENIG,焊盘,Ni,层中,P,的含量在,9wt,10wt,左右为宜。而从图中可以看出该批次器件样品的,P,含量已经达到了,20wt,25wt,。,断面,P,含量超高,Page,62,有损检测分析线扫描,Page,63,有损检测分析线扫描,从线扫描的结果看出，在,Ni/SnPb,的界面位置出现了大约一个微米厚度的,P,的峰值，说明在该层面存在着,P,富集的现象,解释,：在焊点服役过程中界面处,IMC,不断生成和长大，会不断的消耗界面附近两侧的,Ni,和,Sn,，这就使原本,P,含量偏高的,Ni,（,P,）层在靠近,IMC,的地方形成含量更高的富,P,层；同理，,IMC,的另一侧会形成一个富,Pb,的区域。富,P,层的形成会造成焊点界面的严重弱化，在工艺操作或运输过程中即使是受到一些微小的应力，也容易导致器件焊盘从焊点脱离。,Page,64,改进措施,短期解决措施：,尽量减少单板加工过程中的热过程（比如减少回流焊液态以上温度时间，降低峰值温度等）,减小扣板在装配环节的受力，如规范操作、使用工装,后续新单板设计使用到该器件，需要确认不能布局在高应力区域，例如螺钉附近、扣板连接器附近、板边等。,根本解决措施,敦促加强,DSP ENIG,镀层工艺过程的控制,敦促尽快进行,DSP,基板表面处理方式的改进（由,ENIG,镀层工艺转变为,OSP,镀层工艺）,Page,65,附：黑盘判断依据,4,X,方法,外观检查：焊点裂纹,起拔试验：脆性断口,可焊性试验：起拔后失效断口润湿不良,切片分析：断面在,Ni/IMC,之间,EDX,分析：起拔断口,P,含量过高（,15wt,以上）,SEM,分析：起拔断口存在,Mud Crack,黑盘失效,切片分析：裂纹旁边存在“牙缝”现象,黑盘失效发生必然伴随以上现象，如果其中一条不满足则可认为不是黑盘失效,三种现象发生一种或者多种，都可以判定为黑盘失效,失效现象表现为电信号时断时续可以作为失效分析时一个参考，但不可以作为判断黑盘的准则,Y,Y,Y,Y,Page,66,外观检查,市场返回单板异物腐蚀分析,来源：市场运行近一年返修,失效现象：复位频繁，可能为某处短路导致,外观检查： 从外观上看比较明显的现象是有异物流过的痕迹,Page,67,失效分析,外观观察,如果流体导电的话完全可以造成器件引脚之间的短路,Page,68,失效分析,IC,分析（离子色谱）,从返修样品上取少量异物，进行,IC,检测，结果显示为异物中含有较多的硫根离子。,EDX,分析,对图中的,1,，,2,，,3,位置进行了,EDX,分析，结果见后页,Page,69,失效分析,EDX,分析,Processing option : All elements analyzed (Normalised),SpectrumCOSCaTotal,117.7759.3112.4310.50100.00,217.4460.4411.5510.57100.00,312.7662.8612.9011.48100.00,Max.17.7762.8612.9011.48,Min.12.7659.3111.5510.50,All results in Atomic Percent,EDX,结果显示异物中含有较多的,C,，,O,，,S,等物质,Page,70,失效分析,FTIR,分析,用红外光谱分析表明，该痕迹的含,N-H,C=O,C-N,O-S,等基团。而且其中,NH,的含量很多。没有检验出,C-H,，表明里面含有其他有机成分的可能性不大。,尿素的结构分子式为,O,|,H2N- C NH,由此可以判断该痕迹中有尿素。,O-S,的存在应该是空气中的,SO2,溶解造成的。,Page,71,结论和改进措施,结论：,该痕迹为鼠尿的遗留痕迹。,鼠尿流过使器件内部和器件之间部分短路，造成失效。,该失效属于个别现象。,改进措施：,敦促局方加强机柜的防鼠措施,Thank You,联系人：刘桑,0755,89651218 28780808,知识回顾,Knowledge Review,谢 谢！,放映结束,感谢各位的批评指导！,让我们共同进步,