SMT 缺陷.pdf - 第4页
17 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 typica lly small balls of the origin…
1、锡珠（SOLDER BALLS）
¾ PCB、元件可焊性差
¾ 焊膏移位或量过多
¾ STENCIL脏
¾ 焊膏质量缺陷
¾ 过大的贴片力
¾ 温度曲线设定不合理
¾ 环境、操作、传输等
2-2、常见SMT工艺缺陷分析:
STENCIL对SMT工艺的影响
17
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.
18
Solder ball 锡珠
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).