The picture shows a “Dispensing Component Kit”. I find this is extremely helpful in quickly verifying your powder/needle combination. This particular kit is put together by EFD.
由于间距和焊料量随整体封装尺寸的减小而减小，锡膏沉积量也随之减小。您可能会考虑使用较小的粉末尺寸或针头尺寸。我列出了一些指导原则，希望对您的工作有所帮助（请记住，如有具体问题，您可以随时致电或发送电子邮件给我）：
23 号针头或更大 3 型粉末（25-45 微米）
25 号针头 4 型粉末（20-38 微米）
27 号针头 5 型粉末（15-25 微米）
30 号针头或更小 您可以尝试 6 型粉末（5-15 微米），但有时比较困难，而且费用较高。
The problem with finer particle sizes relates to surface area. Smaller particles have more surface per volume of paste, which is more challenging for a flux. A flux vehicle needs to reduce oxides on the backside of the die, the leadframe surface, as well as each paste alloy particle. It is best practice to use the largest powder diameter that will still be around 1/7th of the needle’s inner diameter. I generally use a needle that is 2/3 the desired deposit diameter.
这些计划步骤将为您指引正确的方向，但如果您使用的焊膏仍有堵塞现象，那么您所选择的针的尺寸应该可以通过焊膏：
1) Lower the pressure, 30psi is the max. pressure I’d ever think about subjecting a paste to.
2) Review storage suggestions and check for flux separation.
3) Use a larger needle tip if possible.
4) Try a conical needle. These are generally plastic, and tapered to help the paste flow properly through the equipment.
5) Double check the dispensing equipment, verify all the internal parts are working properly.
