SMT 缺陷.pdf - 第6页

2 、桥连 (BRIDGE ） 9 焊锡在导体间的非正常连接 ¾ 焊膏质量缺陷如过稀等 ¾ 焊膏移位或量过多 ¾ 不合理温度曲线 STENCIL 对 SMT 工艺的影响 2-2 、常见 SMT 工艺缺陷分析:

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).

2、桥连(BRIDGE）

9 焊锡在导体间的非正常连接

¾ 焊膏质量缺陷如过稀等

¾ 焊膏移位或量过多

¾ 不合理温度曲线

STENCIL对SMT工艺的影响

2-2、常见SMT工艺缺陷分析:

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 stencil 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