SparkFun Forums

[jarcher]

I just noticed that my plastic stencil is cut wrong. Despite the GTP layer having all the needed holes in it, the stencil has only things that are square.

That got me thinking. All the pads for my surface mount resistors, capacitors, LEDs and such (size 0805) are round. Had they been square they would have made it to the stencil, although I think they should have anyhow.

Is there an advantage to one shape over the other for these components?

[leon_heller]

There must be something wrong with your footprints if you have round pads for 0805 components.

[jarcher]

There must be something wrong with your footprints if you have round pads for 0805 components.

Oh that's not good. Will it work?

[leon_heller]

Not very well, with solder paste and reflow. You should be able to manage with hand soldering. You could live with it for a prototype, but I'd redo the boards if they are going into production.

If the stencil has square apertures, the Gerbers were probably OK, and your round pads sound like a manufacturing error. Check the Gerbers and check with your board supplier if they are correct.

[jarcher]

No its our error. The package specified in Eagle was "0805RND." The design was copied and pasted from an Arduino design then modified. Its very easy to switch to 0805 pachage and go to square pads. These are prototype boards. They cost about $175 and I was hoping to get 3 working prototypes out of them. Well, I'll reflow one in my toaster oven and see what happens.

[NleahciM]

I just noticed that my plastic stencil is cut wrong. Despite the GTP layer having all the needed holes in it, the stencil has only things that are square.

That got me thinking. All the pads for my surface mount resistors, capacitors, LEDs and such (size 0805) are round. Had they been square they would have made it to the stencil, although I think they should have anyhow.

Is there an advantage to one shape over the other for these components?

I think rounded rectangles are the favored approach these days. A full circle will use up space inefficiently, while a full square messes up the surface tension of the solder or something (I forget the exact explanation). Thus rounding the pads slightly is the typical middle ground.

[leon_heller]

Rounded corners are better for lead-free solder paste.

[jarcher]

Okay thanks. So in Eagle, the round pads are package 0805RND while the square ones are 0805. Is there a package name for squares with rounded corners? For now, I am not doing lead free.

From what I have seen, the round pads should work. Yes?

[leon_heller]

If you want rounded corners for lead-free, just create your own footprint. It'll only take a couple of minutes.

I'd hand-solder those circular pads, as I said previously. The excess paste with the square aperture stencil might cause problems.

[jarcher]

If you want rounded corners for lead-free, just create your own footprint. It'll only take a couple of minutes.

I'd hand-solder those circular pads, as I said previously. The excess paste with the square aperture stencil might cause problems.

Oh, the stencil has apertures that match the pads. That's not a problem.

[stratosfear]

Okay thanks. So in Eagle, the round pads are package 0805RND while the square ones are 0805. Is there a package name for squares with rounded corners? For now, I am not doing lead free.

From what I have seen, the round pads should work. Yes?

jarcher,

Rounded corners are set in the Shapes tab of the DRC menu. It's not necessary to create new footprints.

Jon