Good QFN, Good QFN Paste Layer
I write a lot here about things that go wrong with various layouts. Hopefully by doing that, I can help some of you avoid common pitfalls. But I should probably write about more good things though to balance it out.
So, here's a decent example. This is a good way to specify the solder paste layer for your QFN parts. Notice that the center thermal area is segmented to give about 50% paste coverage. This will lead to a secure and reliable placement with minimal voiding underneath.
There are a lot of different ways to segment the stencil for good paste coverage. This is one is easy to do and will work well. Note that this QFN doesn't have any thermal vias so here we don't have to worry about any via in pad issues. If you do need thermal or grounding vias in the pad, check out our section on via-in-pad for guidelines to help properly deal with the.
All we are is paste on the pcb
Just a drop of solder on an endless stencil