SMT缺陷及防范措施之二

四、Misalignment 偏位

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: Solderability 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致吹偏了元件

五、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

Countermeasure/对策

1、Component lead bent before placement : Sort the defective part  and return it to vendor.
      贴片前元件引脚变形：挑选出缺陷元件
2、Manual placement the loose part : Inspect the part before pass it to reflow.
     手放散料：回流前目检

五、Solder ball 锡珠
Solder balls are spheres of solder that remain after the soldering process. Solder balls violate minimum electrical clearance.
    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.

Countermeasure/对策
    1. Stencil Aperture do not focus to pad: improve 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 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 (波峰焊接).

六、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 leave 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.
• 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 leave 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

1、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) 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

七、Cold solder 冷焊

complete reflow of solder paste.
　焊锡回流不完全

InCountermeasure/ 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 reflow profile：典型的回流曲线

Countermeasure/对策
    2. The component in some location covered with reflow pallet (Peak temperature is too low or reflow time (dwell time) is not enough): Enlarge the pallet open window for the defect locations to reduce the ΔT.
    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（ΔT）

八、Solder hole/锡洞
Blow holes, pinholes, voids
   吹孔、 针孔、空洞

Countermeasure/对策
    1、Insufficient preheat: Reflow profile optimize.

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、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.
九、Disturbed Solder/焊锡紊乱
 •Disturbed solder joint characterized by stress lines from movement in the connection.
   在冷却时受外力影响，呈现紊乱痕迹的焊锡

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．
十、Solder Projections/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.

Countermeasure
1、 Less flux on board : Increase the flux spray rate 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.
十一、No Solder/ 无锡
No solder to the land or termination where solder is required.
    　焊点无锡

1、 Missing printing/ 漏印
         Root cause: a) Stencil aperture was 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) Contamination 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 wave height is low : proper height (wave solder).
           波峰高度过低: 调整到适当高度 (波峰焊)

十二、Insufficient Solder/少锡

Insufficient solder  焊锡不足

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: 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

十三、Excess Solder 多锡

Solder fillet extends on to the top of the component body.
　焊锡接触元件体

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: standardize 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 5~7 degree and soldering time to 3~5 second.
       传送带角度过小, 波峰焊接时间变长: 校正传送带角度到5~7度, 焊接时间3~5秒
       b) High preheat temperature to 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

十四、Wrong Orientation/Polarity 反向、极性反

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

 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 placement 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 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

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．