1、2019/3/12,1,SMT defects and countermeasure SMT缺陷及防范措施,2019/3/12,2,Identify SMT defects,Identify the SMT defects according to IPC-A-610 (Rev: D) 根据 IPC-A-610 (Rev: D)确定缺陷This standard is a collection of visual quality acceptability requirements for electronic assemblies. IPC-A-610是关于电子组装外观质量验收条件要求的文件
2、,2019/3/12,3,Major contributor to defects 缺陷的主要分布,Source: MPMs A users guide to more Precise SMT printing,2019/3/12,4,Know the common defect了解常见缺陷类型Analysize the possible cause分析可能的原因Countermeasure for the defects基于以上原因采取的对策,Learning Objectives 学习目的,2019/3/12,5, Chip components standing on a termina
3、l end (tombstoning).片式元件末端翘起（墓碑）,Tombstoning/ 立碑,2019/3/12,6,Countermeasure/ 对策 Mechanism: Surface tension in component terminal is uneven in reflow. 原理:在回流过程中零件两末端的表面张力不均衡.1. Component terminal heat distributed unevenly 零件两末端受热分布不均衡.Insufficient soak time: Reflow profile optimization.保温区时间太短:优化回流曲线
4、参数. 2. PCB Pad design issue (the pads distance is too big): improve PCB pad design. PCB焊盘设计问题(焊盘间距太大):改善PCB焊盘设计.,Tombstoning/ 立碑,2019/3/12,7,Countermeasure/对策3. Component terminal oxidization or contamination : Solderability test if necessary and RTV the defect material.元件末端氧化或者受污染: 根据情况做可焊性实验并且退还缺陷
5、物料. 4. Printing misalignment: adjust printing machine parameters.丝印偏位: 校正丝印机的参数. 5. Placement misalignment: Optimize the P&P machine parameters.贴片偏位: 优化贴片机的参数. 6. Stencil aperture design issue: study and improve the aperture design.钢网开孔的设计问题: 研究并且改善开孔设计.,Tombstoning/ 立碑,2019/3/12,8, A solder connect
6、ion across conductors that was joined. 焊锡在导体间非正常连接. Solder has bridged to adjacent non-common conductor or component. 焊锡桥连到相邻的非导体或元件.,Solder bridge/ 桥联,2019/3/12,9,Countermeasure/对策1. Screen printing issue/丝印问题:a) Paste height out of UCL: Adjust the printer to control the paste height.锡膏高度超出控制上线: 校正
7、丝印机, 控制锡膏高度.b) Paste printing misalignment or bridging: Fine tune printing machine. /锡膏印刷偏位或者桥联: 优化丝印机.c) Icicle printing: Fine tune printing machine or change to lower viscosity paste.丝印拉尖: 优化丝印机或者使用低粘性的锡膏. d) Solder paste collapse: change to higher viscosity paste./锡膏塌陷:使用高粘性的锡膏.e) Nonstandard ste
8、ncil aperture opening : Study and improve the aperture./不标准的钢网开孔: 研究并改善开孔.,Solder bridge/ 桥联,Icicle printing 丝印拉尖,Paste collapse 锡膏塌陷,Bridging 桥联,Misalignment 印刷偏位,2019/3/12,10,Countermeasure/对策2. Pick & Placement/贴片a) Component placing misalignment: Fine tune the P&P machine .元件贴片偏位: 优化贴片机的参数.b) Hi
9、gh pressure for placement: reduce pressure to proper value .贴片压力过大: 减少压力到适当的参数.3. Wave soldering/波峰焊a) Low conveyor ramp: Raise the conveyor ramp per actual status.传送带角度过小: 根据实际情况加大传送带角度b) Less flux on board : Increase the flux spray volume on board before going through wave soldering.板上的助焊剂较少: 波峰焊接
10、之前加大助焊剂的喷射量,Solder bridge/ 桥联,2019/3/12,11,Component damaged (Nicks, cracks, or stress fractures)/ 元件损坏,Nicks, cracks, or stress fractures. 缺口，裂纹，压痕,2019/3/12,12,Countermeasure/对策1. Raw material damaged: purge the batch material./来料损坏: 清除这批来料.2. Damaged during SMT process (Fixture or machine touch i
11、t) : Investigate and take corrective actions for nonstandard operation.在SMT流程中损坏(夹具和设备接触): 调查分析并且对不规范的操作作出矫正行动.3. Fast cooling rate on reflow process : Control the cooling rate to below 4degree per second.在回流过程中冷却速率过快: 控制冷却速度使斜率保持在每秒4度以下.Typical reflow profile/ 回流曲线典例:,Component damaged (Nicks, crac
12、ks, or stress fractures)/ 元件损坏,2019/3/12,13,Misalignment 偏位,2019/3/12,14,Countermeasure/对策1. P&P machine function unstable: Fine tune the P&P machine.贴片机性能不稳定: 优化贴片机性能参数.a) Fine tune X,Y data/ 调整X,Y坐标b) Optimize pick and placement parameters./ 校正吸料和贴片的参数.2. Component termination oxidization: Soldera
13、bility test if necessary. Purge the failed material/ 元件末端氧化: 可焊性实验, 清除不合格的来料.3. Operator touch the component prior to reflow: Standardize the operator handling (document control)/ 在回流炉前目检操作员碰到贴片元件: 标准化操作员操作(文件控制)4. Air flow rate in the reflow oven is so high that the components are moved.回流炉内空气流量太高以
14、致吹偏了元件.,Misalignment 偏位,2019/3/12,15,Component lead lifted 元件引脚翘高,One lead or series of leads on component is out of align-ment and fails to make contact with the land.元件一个或多个引脚变形不能与焊盘正常接触,2019/3/12,16,Component lead lifted 元件引脚翘高,Countermeasure/对策1. Component lead bent before placement : Sort the d
15、efective part and return it to vendor. 贴片前元件引脚变形: 挑选出缺陷元件,退回供应商2. Manual placement the loose part : Inspect the part before pass it to reflow. 手放散料: 回流前目检,2019/3/12,17,Solder ball 锡珠,Solder balls are spheres of solder that remain after the soldering process. Solder balls violate minimum electrical c
16、learance.焊锡球是焊接后形成的呈球状焊锡.Solder fines are typically small balls of the original solder paste metal screen size that have splattered around the connection during the reflow process.焊锡残渣是在回流中形成的小的球状或不规则状焊锡球.,2019/3/12,18,Solder ball 锡珠,Countermeasure/对策1. Stencil Aperture do not focus to pad: improve
17、stencil aperture opening.钢网开孔没有对准焊盘中心: 改善钢网开孔.2. Printing misalignment: Fine tune print machine.丝印偏位: 调整丝印机状态.3. Excess paste : Cpk control. 多锡: Cpk控制.4. Damp PCB : Bake the PCB before loading it to SMT.PCB焊盘受潮: SMT组装流程之前烘烤PCB.6. Stencil polluted: clean the stencil. 钢网脏污: 清洗钢网.7. Profile ramp up is
18、too fast : Optimize reflow profile.回流曲线升温速度过快: 优化回流曲线.8. Paste oxidized: exchange with fresh solder paste. 锡膏氧化: 更换新锡膏.9. Chip wave or solder wave height is too high caused excess solder to top side: adjust the wave soldering height to proper level (wave solder).波峰高度设置的太高致使多余的焊锡到顶面: 校正波峰焊设置到适当的高度 (波
19、峰焊接).,2019/3/12,19,Non-Wetting, Dewetting/ 虚焊，半润湿, Solder has not wetted to the land or termination where solder is required.虚焊: 需要焊接的引脚焊盘不润湿 Solder coverage does no meet requirements for the termination type. Dewetting as a condition results when molten solder coats a surface and then recedes to le
20、ave irregularly-shaped mounds of solder that are separated by areas that are covered with a thin film of solder and with the basis metal or surface finish not exposed.半润湿: 熔化的焊锡浸润表面后收缩,留下一焊锡薄层覆盖部分区域,焊锡形状不规则.,2019/3/12,20,Non-Wetting, Dewetting/ 虚焊，半润湿,1. Poor solderability of component or pad./元件或焊盘
21、可焊性太低Root cause: a) Old date component or PCB. /陈旧元件或PCB板b) Contamination or oxidation on component or PCB. 元件或焊盘污染或氧化Action: Purge the material for further disposition. /清除来料2. The paste out of its life time: /锡膏超出有效期Scrap the lot paste and replace it with fresh one报废有问题的锡膏更换新锡膏,2019/3/12,21,Cold s
22、older/ 冷焊,Incomplete reflow of solder paste.焊锡回流不完全,2019/3/12,22,Cold solder/ 冷焊,Countermeasure/ 对策 1. Peak temperature is too low or reflow time (dwell time) is not enough: Re-setup the profile to fulfill the paste spec or customer provided spec. requirement. 回流峰值温度太低或者回流时间不够: 重设温度曲线图.Typical reflo
23、w profile:/ 典型的回流曲线,2019/3/12,23,Time 时间,Temp. 温度,230C,250C,tc1 small SMD,tc1 medium SMD,tc3 large SMD,20C,20C,Peak: 230 250C,Cold solder/ 冷焊,2019/3/12,24,Cold solder/ 冷焊,Countermeasure/对策2. The component in some location covered with reflow pallet (Peak temperature is too low or reflow time (dwell
24、time) is not enough): Enlarge the pallet open window for the defect locations to reduce the T.某些元件位置被回流托盘遮挡造成该点峰值温度太低或回流时间不足:对缺陷位置放大托盘的开口从而减少温差（T）.,2019/3/12,25,Solder hole/锡洞, Blow holes, pinholes, voids吹孔, 针孔,空洞,2019/3/12,26,Solder hole/锡洞,Countermeasure/对策1. Insufficient preheat: Reflow profile o
25、ptimize. 预热时间不足: 优化回流曲线设置.2. Ramp up is too fast : Re-setup the reflow profile to make it optimize.升温速率太快: 重设回流曲线图使之最优化.3. Excess flux in solder paste: properly to increase preheat time and temperature.锡膏助焊剂含量过多: 适当增加预热时间和温度值.4. Damp PCB: Bake the PCB before loading it to SMT.PCB受潮: SMT组装前烘烤PCB板.5.
26、Component feet oxidation: Bake it before SMT or require vacuum packing on incoming material.元件脚氧化: 烘烤或者来料真空包装.6. Attached flux residue on component foot: Sort out the defect part.元件脚有助焊剂残渣: 挑选出缺陷来料.,2019/3/12,27,Disturbed Solder/焊锡紊乱,Disturbed solder joint characterized by stress lines from movement
27、 in the connection.在冷却时受外力影响,呈现紊乱痕迹的焊锡,2019/3/12,28,Disturbed Solder/焊锡紊乱,Countermeasure 1. Optimize reflow soldering profile especially for cooling zone. 优化冷却区回流曲线2. Conveyor shaking in PCA cooling down phase: Repair the conveyor per actual status.冷却阶段传送带震动: 根据实际情况调校传送带,2019/3/12,29,Solder Projecti
28、ons/锡尖,Solder projection violates assembly maximum height requirements or lead protrusion requirements.焊锡毛刺违反组装的最大高度要求或引脚凸出要求. Solder projection violates minimum electrical clearance.焊锡毛刺违反最小电气间隙.,2019/3/12,30,Solder Projections/锡尖,Countermeasure 1. Less flux on board : Increase the flux spray rate
29、on board before go through wave soldering (wave solder). 助焊剂不足: 增加助焊剂的喷射量 2. Low conveyor ramp: Raise the conveyor ramp per actual status (wave solder). 传送带角度过小: 根据实际情况校正传送带角度3. Excess preheat temperature and time (flux dry off): Optimize wave soldering profile. (Wave solder)预热过度（助焊剂过度挥发）: 优化波峰曲线 (波
30、峰焊)4. Caused by rework: Standardize operator handling and enhance visual inspection.返修中产生: 规范员工操作加强目检.,2019/3/12,31,No Solder/ 无锡,No solder to the land or termination where solder is required.焊点无锡,2019/3/12,32,No Solder/ 无锡,Countermeasure/ 对策 1. Missing printing/ 漏印Root cause: a) Stencil aperture wa
31、s jammed./ 钢网堵孔b) High viscosity of solder paste./ 锡膏粘性过高Action: a) Clean stencil;/ 清洗钢网b) Replace the recycled paste with fresh one./更换新锡膏c) Printing machine parameter adjustment./校正丝印机参数2. Poor solderability of component or pad./元件或焊盘可焊性太低Root cause: a) Old date component or PCB. /陈旧元件或PCB板b) Cont
32、amination on component or PCB. /元件或焊盘受污染Action: Purge the material for further disposition. /清除来料3. Insufficient flux volume: increase flux spray rate (wave solder).助焊剂量不足: 增加助焊剂喷射量 (波峰焊接)4. Preheat excess: lower preheat temperature properly (wave solder).预热过度: 适当降低预热温度 (波峰焊)5. Chip wave or solder w
33、ave height is low : proper height (wave solder).波峰高度过低: 调整到适当高度 (波峰焊),2019/3/12,33,Insufficient Solder/少锡,Insufficient solder焊锡不足,2019/3/12,34,Insufficient Solder/少锡,Countermeasure /对策1. Stencil aperture clogging cause incomplete solder printing): Automatic or manual clean the stencil.钢网孔堵塞导致锡膏不完全印刷
34、: 自动或者手工清洗钢网2. No enough solder paste volume (Paste height under LCL) : Visual inspection and Cpk control.锡膏量不足(锡膏高度在LCL以下): 目检和Cpk控制3. Solder paste print misalignment: Fine tune printing machine锡膏印刷偏位:校正丝印机使之最优,4. Poor solderability of component or PCB pad: 元件或PCB焊盘可焊性差 a) Optimize reflow profile.优
35、化回流曲线b) Exchange the poor solderability component. 更换掉低可焊性元件5. Excess glue or glue misalignment: Fine tune screen print (wave solder). 点胶过多或点胶偏位:优化丝印参数6. Less flux : Increase the flux spray on board before it pass wave soldering (wave solder).助焊剂不足: 增加助焊剂的喷射量,2019/3/12,35, Solder fillet extends on t
36、o the top of the component body.焊锡接触元件体,Excess Solder/多锡,2019/3/12,36,Excess Solder/多锡,Countermeasure /对策 1. Excess solder paste: 锡膏量过多a). Solder paste height out of UCL: Adjust printing machine to control the paste height.锡膏高度超出UCL: 校正丝印机控制锡膏高度b). Nonstandard of stencil aperture opening: standardiz
37、e the stencil aperture opening for different type components.钢网开孔不标准:为不同类型的元件设置相应钢网的开孔标准2. Wave soldering/ 波峰焊接a) Low conveyer ramp, long wave soldering time: Adjust conveyor ramp angle to 57 degree and soldering time to 35 second.传送带角度过小, 波峰焊接时间变长: 校正传送带角度到57度, 焊接时间35秒b) High preheat temperature to
38、 dry off the flux: According to flux spec to control the preheat temperature, normally the PCB surface preheat temperature should be under 100oC.高预热温度造成助焊剂过度挥发: 按照助焊剂的规格控制预热温度, 通常, PCB表面温度一般低于100oC,2019/3/12,37,Wrong Orientation/Polarity 反向, 极性反,Correct polarity/ 正确的极性,Wrong polarity/ 极性反,This mark
39、is anode of tantalum capacitor on PCB.,This mark is anode of tantalum capacitor.,Correct polarity/ 正确的极性,Wrong polarity/ 极性反,This mark is cathode direction.,This mark is cathode direction.,Wrong Polarity:/极性反,2019/3/12,38,Wrong Orientation/Polarity 反向, 极性反,Correct direction/ 正确的方向,Wrong Orientation
40、/反向,This mark is ICs direction.,This mark is ICs direction on PCB.,Wrong Orientation/ 反向: The IC is populated in inverse direction on the PCB./ IC被反方向组装在线路板上,2019/3/12,39,Countermeasure/ 对策1. Wrong placement machine program : Check and correct the machine program.贴片机程序错误: 检查和更正机器程序2. Manual placemen
41、t in reverse direction: 手工放置元件错误a) Avoid manual placement components 避免手工放置元件b) Need special inspection for the manual placement prior to reflow (document control).炉前需要特别检查那些手工放置的元件 (文件控制)3. Disordered orientation in the tray/reel of the incoming material: 卷装或盘装来料元件的不规则放置a) Inspect before loading it
42、 to SMT. 上料前检查来料 b) Feedback to vendor to take corrective actions.反馈给供应商采取改善行动,Wrong Orientation/Polarity 反向, 极性反,2019/3/12,40,a. Long lead / short lead 脚长/脚短 b. Missing component 元件丢失 c. Expose copper 露铜 d. Surface scratched 外观划伤Countermeasure /对策Take corrective action and preventive action after investigated.调查后采取相应的改善措施和预防措施,Others 其它,2019/3/12,41,Thank you,The End,
