Smart Solder Paste

[shangaoren]

Hello Everyone,

I was wondering if altium has a smart way to make solder paste pad array for big pads ?

Today for big pads i use negative paste mask expansion and then i add by hand paste fills, is there a smarter way ?

Thanks a lot =)

[ajb]

I've taken to using PCB Library Expert Lite to generate footprints for Altium; it has settings for paste percentage and automatically generates suitable apertures.  Does Altium's footprint generator not have those options?  I haven't looked in a while.  Library Expert's defaults seem to work well enough for the prototypes we assemble in-house.  For production, though, that's the sort of thing I let the assembler worry about.  I include a note in the assembly package that the paste apertures are nominal and they should adjust them as needed to suit their process.  After all, that's what I'm paying them for!  You might have unusually specific (or just unusual) requirements for the paste application, but even then I'd prefer to tell the assembler the results I need and let them figure out the process.

[DerekG]

Normally the supplier of the solder paste stencil will "grid the large pad into smaller a number of smaller squares" automatically for you. Talk to them if you have a particular need or have particular concerns.

The thickness of the stencil also needs to be carefully chosen.

If the large SMD pads are used as heatsinks, consider not only using a vapour phase oven but a vacuum vapour oven.

Vapour phase will normally ensure a better solder joint for larger pads & the vacuum will suck out the air under the component which then provides the best heat transfer to the pad itself.

This can be very important when using power mosfets that generate considerable heat.

In some of our designs we have have no choice but to move back to through hole mosfets for heat dissipation reasons.