We would like to make a normally-open solder jumper between two 50x50mil unmasked square pads. I've seen this kind of thing by others and would like to replicate it in our layout. We tried a simple layout with ~10mil spacing between 50x50mil pads, each with a solder mask expansion of 1.5mil. The result was surprisingly difficult to bridge.
Ultimately these are the goals:
- The jumper should not bridge with a "normal" amount of solder paste. (We are not using a stencil, but for example's sake, lets consider a "normal amount" to be that which would be deposited with a 5-mil thick stainless stencil.)
- It should bridge with even more solder paste, but (subjectively) we want to balance accidentally bridging vs needing a large solder blob.
- When we bridge, we wish to bridge by manually placing a larger amount of solder paste (by syringe) over the jumper and heat it with hot air.
This is approximately they layout we are thinking, but are unsure of the spacing and stub sizes. Both the stub and the 50x50mil pads are unmasked:
- What would be an ideal solder mask spacing between the stubs that protrude from the 50mil pads?
- Should there be solder mask expansion around the pad, and if so, how big?
- Should there be a negative solder mask expansion?
- How wide should the stub be in the vertical direction as pictured above?
- How far should each stub protrude toward the other in the horizontal direction?