雅达无铅工艺知识(英文)(pdf 21页)

1. Layout Requirements
2. Machine Requirements
3. Hand Soldering Requirements
4. Soldering Materials
5. Components and PCB Surface Finish
6. Qualification Test for Lead-free Solder
7. Common Production Defect Guide
8. Inspection Criteria

1) Layout requirement for lead-free wave soldering process
(For reflow soldering, no difference between tin-lead and lead-free on layout requirement)
a) Teardrop solder resist opening for AI/RI pad (Update as general for both tin-lead and lead-free)
This is to minimize the possibility of pin hole/incomplete soldering due to high viscosity
characteristic of lead-free solder
b) No robber pad requirement (For lead-free only)
Due to higher viscosity of lead-free solder, bigger land size can pull more solder to bounce back
result in short solder
c) Double sided board PTH annular ring size on component side should be 0.3mm for all. If solder pad
is layout on big copper area, use solder resist opening to control the pad size to hole size + 0.6mm
(Update as general for both tin-lead and lead-free)
The solderability of lead-free is not as good as the tin-lead, the reduction in annular ring can
increase the flow of solder for top side fillet
d) Thermal relief for big copper area (General for both tin-lead and lead-free)……

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