二、 Open Cross-Section常见案例

7.Socket775 Solder Ball不共面(下陷)

    1.Foxocnn Sn.Ag 工艺CPU Socket775 Normal Housing Height SPEC为0um +/-50um;

    2.Foxconn Sn.Ag.Cu工艺CPU Socket775 Normal CPU Socket775 Housing Height SPEC为200um +/-50um.

    3.Socket775 Housing高度决定socket775 Ball共面度.

    4.Socket775 Housing Height高出Normal Height上限会导致Solder Ball与Solder Paste不能相溶产生open. 

    5.Socket775 Housing Height低于Normal Height下限会导致Socket775插槽Pin针不能与CPU相通(open).

8.CPU Socket478 Ball下陷

    1.Normal cpu socket478 Ball其Pad端子夹角应呈90˚，着装时socket478 ball平面于pcb pad solder paste，以确保焊接良好.

    2.socket478 ball下陷使socket端子pad夹角变形，socket478 Ball无法接触PCB Pad solder paste，导致焊接open.

9.CPU Socket结构不良：CPU Socket478卡口太宽不能接触CPU Pin针(open).

10.BGA Socket歪球：BGA Ball歪球造成不能平面于pcb pad solder paste而拉近其旁bga ball间距，易导致焊接产生open/short.

11.Solder Paset活性不强&Solder Ball与PCB PAD污染

    1.BGA Ball与Solder Paste已形成Cu/Sn IMC层并形成鼓形;

    2.因BGA Ball/PCB Pad杂质污染/Solder Paste活性不强，造成solder paste不能完全清除BGA Ball杂质及氧化层，导致焊接BGA Ball与Solder Paste间产生open

12.PCB PAD拒焊：PCB Pad表面杂质污染产生拒焊，造成无法与Solder Paste焊接，Reflow过程中，Solder Paste被BGA Ball吸附产生open.

13.Solder Mask上PAD（阻焊膜侵入焊盘）：Solder Mask覆盖PCB Pad表面产生拒焊,导致焊接OPEN.

14.PCB变形：CPU Socket775 Housing Height在一道平行线上，PCB材质在高温下发生热胀冷缩变化产生翘区，导致BGA焊接open.

三、分析方法

1.测量CPU Socket Housing四边高度有无超出Normal值;

2.测量Housing Solder Ball高度有无超出Normal值;

备注﹕CPU Housing高度不在Normal值﹐说明CPU Socket本体发生变化导致不良；如果Housing正常﹐但Solder Ball高度不在Normal范围﹐说明PCB发生翘曲变形;