PCB stencil, hand assembly

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Joyce Taylor
Posts: 6
Joined: 12 Jul 2020, 22:22

PCB stencil, hand assembly

#1 Post by Joyce Taylor » 21 Jul 2020, 06:37

I have ordered some boards in a PCB manufacturer recently and was a little dismayed at the amount of extra solder I managed to get on TQFP parts and the bridging I ended up with. I am also due to redo a design with VQFN on it where much trouble has had on the first version.
So other than picking the thinnest stencil, how can I try to correct mine over pasting in prototyping without affecting manufacturing? I can obviously pick the thinnest stencil available which is usually 100μm versus the usual 120-127μm but that does not take much off.
For example, the 64 pin 7x7mm TQFP in Kicad has stencil apertures the same size as the pad. I thought usually some clearance was given? what I can do is to use the back solder past layer to set custom hand assembly apertures.

Technical Support
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Joined: 14 Jun 2010, 06:43

Re: PCB stencil, hand assembly

#2 Post by Alex » 21 Jul 2020, 08:16

Right click on TQFP pad, open "Mask/Paste Settings", enable "custom paste mask shrink" and enter the value. Positive value means the slot hole in the stencil will be smaller than the pad. Then apply the change to similar pads. You can preview result on design area (in version 4).

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