二极管短路失效原因分析

[{"attributes":{"size":"small"},"insert":"半导体工程师 icfalab 2022.10.29"},{"attributes":{"header":1},"insert":"\n"},{"attributes":{"bold":true},"insert":"一、案例背景"},{"attributes":{"align":"justify"},"insert":"\n"},{"insert":"   使用半年多的灯具陆续出现不亮现象，经判断是二极管失效导致灯具不亮。现进行测试分析，查找失效原因。"},{"attributes":{"align":"justify"},"insert":"\n\n"},{"attributes":{"bold":true},"insert":"二、分析过程"},{"attributes":{"align":"justify"},"insert":"\n\n"},{"attributes":{"bold":true},"insert":"1.外观检查"},{"attributes":{"align":"justify"},"insert":"\n"},{"insert":"   对不良灯具上的二极管以及单体二极管不良样品进行外观检查。结果未发现外观上的明显缺陷，比对丝印信息，失效二极管丝印型号与良品灯具线路板上的二极管不同，与单体良品二极管相同。后续只将失效二极管与单体良品二极管进行对比分析。"},{"attributes":{"align":"justify"},"insert":"\n\n\n"},{"attributes":{"bold":true},"insert":"2.电学性能测试"},{"attributes":{"align":"justify"},"insert":"\n"},{"insert":"   使用万用表对样品二极管的管压降进行测量，NG#1和OK#1二极管在板测量，NG#2来样为单体，直接测量。结果显示NG二极管压降为0V，即短路。OK#1二极管压降与OK#2 压降有差异，为型号上的原因。"},{"attributes":{"align":"justify"},"insert":"\n\n\n"},{"attributes":{"bold":true},"insert":"3.X-ray检查"},{"attributes":{"align":"justify"},"insert":"\n"},{"insert":"   通过X-ray对解焊后的NG二极管进行透视检查。二极管是无键合结构，正负极都是粘结到引线框架上的。发现NG二极管晶圆侧边有明显的阴影，疑似为金属附着；OK二极管晶圆侧边也有阴影。"},{"attributes":{"align":"justify"},"insert":"\n"},{"insert":{"image":"https://community-1252773949.cos.ap-guangzhou.myqcloud.com/2032/b95a42a17050c535.png"}},{"attributes":{"align":"center"},"insert":"\n"},{"attributes":{"color":"#4e4d4d"},"insert":"图1.NG二极管解焊后X-ray检查"},{"attributes":{"align":"center"},"insert":"\n"},{"attributes":{"align":"justify"},"insert":"\n"},{"insert":{"image":"https://community-1252773949.cos.ap-guangzhou.myqcloud.com/2032/b9c8ca3e866ad616.png"}},{"attributes":{"align":"center"},"insert":"\n"},{"attributes":{"color":"#4e4d4d"},"insert":"图2.OK二极管单体X-ray检查"},{"attributes":{"align":"center"},"insert":"\n"},{"attributes":{"align":"justify"},"insert":"\n\n"},{"attributes":{"bold":true},"insert":"4.IV曲线测试"},{"attributes":{"align":"justify"},"insert":"\n"},{"insert":"   再次通过IV测试确认NG二极管为短路。"},{"attributes":{"align":"justify"},"insert":"\n"},{"insert":{"image":"https://community-1252773949.cos.ap-guangzhou.myqcloud.com/2032/8ef274b4ab1eebc6.png"}},{"attributes":{"align":"center"},"insert":"\n"},{"attributes":{"color":"#4e4d4d"},"insert":"图3.样品二极管IV曲线（红色：NG样品；蓝色：OK样品）"},{"attributes":{"align":"center"},"insert":"\n"},{"attributes":{"align":"justify"},"insert":"\n\n"},{"attributes":{"bold":true},"insert":"5.开封晶圆分析"},{"attributes":{"align":"justify"},"insert":"\n"},{"insert":"   取NG和OK单体二极管进行开封取出晶圆观察。可以看到NG二极管有源区并没有烧毁，因此可以排除过电应力（EOS）。NG二极管晶圆边缘有附着物残留，观察晶圆侧边有疑似附着物痕迹。OK二极管晶圆表面没有发现附着物残留，观察晶圆侧边也有疑似附着物痕迹。因为二极管晶圆正负极都是通过粘结料连接到引线框架上的，在NG二极管晶圆边缘的附着物残留中检测到Ag，因此推测附着物与晶圆粘结料有关。"},{"attributes":{"align":"justify"},"insert":"\n"},{"insert":{"image":"https://community-1252773949.cos.ap-guangzhou.myqcloud.com/2032/f79138382663732d.png"}},{"attributes":{"align":"center"},"insert":"\n"},{"attributes":{"color":"#4e4d4d"},"insert":"图4.NG二极管开封后晶圆形貌"},{"attributes":{"align":"center"},"insert":"\n\n"},{"insert":{"image":"https://community-1252773949.cos.ap-guangzhou.myqcloud.com/2032/f67c1809d865fefb.png"}},{"attributes":{"align":"center"},"insert":"\n"},{"attributes":{"color":"#4e4d4d"},"insert":"图5.OK二极管开封后晶圆形貌"},{"attributes":{"align":"center"},"insert":"\n\n"},{"insert":{"image":"https://community-1252773949.cos.ap-guangzhou.myqcloud.com/2032/7a4cae56a5790779.png"}},{"attributes":{"align":"center"},"insert":"\n"},{"insert":{"image":"https://community-1252773949.cos.ap-guangzhou.myqcloud.com/2032/ae44e94567c9683b.png"}},{"attributes":{"align":"center"},"insert":"\n\n"},{"attributes":{"color":"#4e4d4d"},"insert":"图6.NG二极管晶圆开封后SEM形貌与EDS成分分析（Pt为制样喷涂）"},{"attributes":{"align":"center"},"insert":"\n"},{"attributes":{"align":"justify"},"insert":"\n\n"},{"attributes":{"color":"#333232","bold":true},"insert":"6.切片分析"},{"attributes":{"align":"justify"},"insert":"\n"},{"insert":"   取X-ray检查发现有明显阴影的NG和OK二极管进行纵向切片观察。发现NG 晶圆侧边光学显微镜暗场下侧边有亮线，即存在界面分层，明场下有金属连接路径，晶圆粘结底部塑封界面有大空洞。OK晶圆侧边有金属颗粒，但未形成正极到负极的连通路径。"},{"attributes":{"align":"justify"},"insert":"\n\n"},{"insert":"   电子显微镜（SEM）下观察NG二极管晶圆侧边连接路径上分布有金属颗粒，侧边晶圆界面可见分层，经过EDS成分分析，金属颗粒成分为Pb/Sn/Ag，与粘结料成分相同。OK二极管晶圆侧边金属颗粒成分Pb/Sn，与粘结料主成分一致。"},{"attributes":{"align":"justify"},"insert":"\n\n"},{"insert":"   综合可知，NG二极管因为晶圆侧边粘结料形成了连通，构成了短路。"},{"attributes":{"align":"justify"},"insert":"\n"},{"insert":{"image":"https://community-1252773949.cos.ap-guangzhou.myqcloud.com/2032/c6c7ecac27007b23.png"}},{"attributes":{"align":"center"},"insert":"\n"},{"attributes":{"color":"#4e4d4d"},"insert":"图7.NG 二极管纵向切片光学显微形貌"},{"attributes":{"align":"center"},"insert":"\n"},{"attributes":{"align":"justify"},"insert":"\n"},{"insert":{"image":"https://community-1252773949.cos.ap-guangzhou.myqcloud.com/2032/bb3a21f417caa318.png"}},{"attributes":{"align":"center"},"insert":"\n"},{"attributes":{"color":"#4e4d4d"},"insert":"图8.OK二极管纵切光学显微形貌"},{"attributes":{"align":"center"},"insert":"\n"},{"attributes":{"color":"#4e4d4d"},"insert":"  "},{"attributes":{"align":"center"},"insert":"\n\n"},{"insert":{"image":"https://community-1252773949.cos.ap-guangzhou.myqcloud.com/2032/e97f8a985c3b9df3.png"}},{"attributes":{"align":"center"},"insert":"\n"},{"insert":{"image":"https://community-1252773949.cos.ap-guangzhou.myqcloud.com/2032/b43cfa5c4204b2eb.png"}},{"attributes":{"align":"center"},"insert":"\n\n"},{"attributes":{"color":"#4e4d4d"},"insert":"图9.NG二极管纵切SEM形貌与EDS成分分析（Pt为制样喷涂）"},{"attributes":{"align":"center"},"insert":"\n"},{"attributes":{"color":"#4e4d4d"},"insert":{"image":"https://community-1252773949.cos.ap-guangzhou.myqcloud.com/2032/d324dfa5d1ef6c2d.png"}},{"attributes":{"align":"center"},"insert":"\n"},{"insert":{"image":"https://community-1252773949.cos.ap-guangzhou.myqcloud.com/2032/3c800e8d50cc969b.png"}},{"attributes":{"align":"center"},"insert":"\n\n"},{"attributes":{"color":"#4e4d4d"},"insert":{"image":"https://community-1252773949.cos.ap-guangzhou.myqcloud.com/2032/e804d999627770c0.png"}},{"attributes":{"align":"center"},"insert":"\n"},{"attributes":{"color":"#4e4d4d"},"insert":"图10.OK二极管纵切SEM形貌与EDS成分分析（Pt为制样喷涂）"},{"attributes":{"align":"center"},"insert":"\n"},{"attributes":{"align":"justify"},"insert":"\n\n"},{"attributes":{"bold":true},"insert":"7.验证试验"},{"attributes":{"align":"justify"},"insert":"\n"},{"insert":"   取NG二极管，从正极向下平面研磨，待露出晶圆轮廓后，进行热点定位，定位结果显示热点在晶圆一侧边缘。将晶圆热点位置表面研磨掉，然后用万用表测量二极管的管压降，此时显示二极管已经不再短路，压降与正常样品接近。此验证试验结果进一步说明NG二极管短路的原因是在晶圆表面和侧面从正极到负极形成了金属连通的路径。"},{"attributes":{"align":"justify"},"insert":"\n"},{"insert":{"image":"https://community-1252773949.cos.ap-guangzhou.myqcloud.com/2032/06d95e5ac684688e.png"}},{"attributes":{"align":"center"},"insert":"\n"},{"attributes":{"color":"#4e4d4d"},"insert":"图11.NG二极管热点定位"},{"attributes":{"align":"center"},"insert":"\n"},{"attributes":{"align":"justify"},"insert":"\n"},{"attributes":{"bold":true},"insert":"三、总结分析"},{"attributes":{"align":"justify"},"insert":"\n"},{"insert":"   外观检查不良灯具上的二极管和单体不良二极管未发现外观上的明显缺陷。失效二极管丝印型号与良品灯具线路板上的二极管不同，与单体良品二极管相同。后续只将失效二极管与单体良品二极管进行对比分析。"},{"attributes":{"align":"justify"},"insert":"\n\n"},{"insert":"   电学测量证实失效二极管都是短路。X-ray检查发现二极管是无键合结构，正负极都是粘结到引线框架上的。NG二极管晶圆侧边有明显的阴影，疑似为金属附着， OK二极管晶圆侧边也有阴影。"},{"attributes":{"align":"justify"},"insert":"\n\n"},{"insert":"   开封取出NG二极管晶圆观察发现有源区并没有烧毁，因此可以排除EOS。但二极管晶圆边缘有附着物残留，观察晶圆侧边有疑似附着物痕迹。OK二极管晶圆表面没有发现附着物残留，但晶圆侧边也有疑似附着物痕迹。因为二极管晶圆正负极都是通过粘结料连接到引线框架上的，在这颗NG二极管晶圆边缘的附着物残留中检测到Ag，因此推测附着物与晶圆粘结料有关。"},{"attributes":{"align":"justify"},"insert":"\n\n"},{"insert":"   取X-ray检查发现有明显阴影的NG和OK二极管进行纵向切片观察。发现NG晶圆侧边光学显微镜暗场下侧边有亮线，即存在界面分层，明场下有金属连接路径，晶圆粘结底部塑封界面有大空洞。OK晶圆侧边有金属颗粒，但未形成正极到负极的连通路径。"},{"attributes":{"align":"justify"},"insert":"\n\n"},{"insert":"   SEM下观察NG二极管晶圆侧边连接路径上分布有金属颗粒，侧边晶圆界面可见分层，经过EDS成分分析，金属颗粒成分为Pb/Sn/Ag，与粘结料成分相同。OK二极管晶圆侧边金属颗粒成分Pb/Sn，与粘结料主成分一致。因此可知NG二极管因为晶圆侧边粘结料形成了连通，构成了短路。"},{"attributes":{"align":"justify"},"insert":"\n\n"},{"insert":"   取NG二极管，从正极向下平面研磨，待露出晶圆轮廓后，进行热点定位，定位结果显示热点在晶圆一侧边缘。将晶圆热点位置表面研磨掉，然后用万用表测量二极管的管压降，此时显示二极管已经不再短路，压降与正常样品接近。此验证试验结果进一步说明NG二极管短路的原因是在晶圆表面和侧面从正极到负极形成了金属连通的路径。"},{"attributes":{"align":"justify"},"insert":"\n\n"},{"attributes":{"bold":true},"insert":"四、结论与建议"},{"attributes":{"align":"justify"},"insert":"\n"},{"insert":"   综上所述，可知NG二极管短路是因为晶圆表面和侧面从正极到负极形成了金属连通的路径。二极管晶圆本体未发现烧毁，电性正常，排除EOS。良品未使用的二极管晶圆侧边也存在粘结料颗粒，但未形成短路的通路。"},{"attributes":{"align":"justify"},"insert":"\n\n"},{"insert":"   随着二极管使用过程中当晶圆侧面塑封界面发生分层，尤其是在存在空洞的情况下，粘结料中的金属原子发生迁移（Ag/Sn/Pb都是容易发生迁移的，其中Ag原子的迁移能力最强），就导致短路通路形成。因为晶圆封装后侧边就存在散落的粘结料颗粒，迁移路径已经被大大缩短，二极管短路也就在短期使用过程中陆续出。"},{"attributes":{"align":"justify"},"insert":"\n\n"},{"attributes":{"italic":true,"bold":true},"insert":"   建议："},{"insert":"鉴于二极管物料存在封装不良的缺陷，建议加强二极管来料检验和破坏性物料分析（DPA）。"},{"attributes":{"align":"justify"},"insert":"\n"},{"insert":"来源："},{"attributes":{"color":"#576b95"},"insert":"电子制造资讯站"},{"attributes":{"align":"justify"},"insert":"\n"},{"insert":"\n"}]