SMT 缺陷.pdf - 第14页
23 Time 时间 Temp. 温度 230°C 250°C tc1 – small SMD tc1 – medium SMD tc3 – large SMD 20 °C 20 °C Too Hot! Too Cold! Peak: 230 – 250°C Cold solder/ Cold solder/ 冷焊 冷焊
22
Cold solder/
Cold solder/
冷焊
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 reflow profile:/ 典型的回流曲线
Preheat
stage
Soak stage
Reflow stage
Peak temp.
Cool
down
<4
o
C/s
23
Time
时间
Temp.
温度
230°C
250°C
tc1 – small SMD
tc1 – medium SMD
tc3 – large SMD
20
°C
20
°C
Too Hot!
Too Cold!
Peak: 230 – 250°C
Cold solder/
Cold solder/
冷焊
冷焊
7、焊点缺陷(SOLDER POINT DEFECT)
9 焊点处有裂纹、针孔、吹孔等现象
¾ 锡膏质量缺陷
¾ 环境恶劣
¾ 回流缺陷
裂纹
吹孔
针孔
STENCIL对SMT工艺的影响
2-2、常见SMT工艺缺陷分析: