EMI/RFI Shielding: Autosplice
Notes:
- Limited number of insertion cycles, clips will loose retention strength after the shields are pulled off and replaced.
- Pads and soldermask need to be tightly defined to accurately register the clips during reflow soldering.
- Place covers on after testing and rework have been completed to minimize insertion cycles.
Here is an interesting statement about soldermask.
"By the way, don't assume that putting fingers of resist between pads on an otherwise bare board might help overcome bridging, because most bridging occurs between component leads above the board. You are just adding to the cost by using a more expensive process, and gaining little."
Source: PCB Solder Mask Design Basics - Standards, Materials and Processes:
Some points to consider:
Solder mask thickness is typically ~ 0.5mil thick.
Copper pads on outer layer are typically 1.4 to 2.0 mil thick.
Solder paste thickness is typically ~ 5mil thick.
The copper pads are 3 to 4 times thicker (taller) than the soldermask.
The 5mil thick solder paste on top of copper pad is 10 times thicker (taller) than the soldermask.
And the paste is sitting top of the copper pads.
click on image to view
Does soldermask between the pads really help prevent solder bridging ?
For fine pitch QFPs you may want to use ganged soldermask.
Something to think about.
Close up of solder paste on two adjacent pins.
That's It !
