Through-Hole Stencils print Solder Paste in and around a Through-Hole. The device is placed into the holes and reflowed along with the Surface Mount Devices thus eliminating a Wave-Soldering operation.
Three Stencil Designs to achieve the objective:
- Overprint Stencil - Overprint Step Stencil - Two-Print Stencil
Overprint Stencils have apretures larger than the Through-Hole Pads to provide sufficient solder paste to fill the hole and form solder filltes after reflow.
The Two-Print Stencil uses two separate print operations. SMD paste is printed with a normal SMT Stencil. While the paste is still tacky the thicker Through-Hole (15 to 30 mil thick) is used to print the Through-Hole Paste.
Relief etch pockets on the back side of the stencil in the SMD pad area prevents smearing of the SMD paste already on the board.
