Hello,
Does anyone know how to create an smd pad in Eagle where the stop area is only over a small sub-section of the pad’s total area? An example can be found in the PLCC4-TOPLED-RG.pac package, located in the led.lbr library. (see screen cap below)
Thanks,
jasper
I have noticed the cited package gets around the problem by using rects instead of the smd tool. However, this method doesn’t seem to allow one to associate pads on the package with device inputs and outputs. Is this correct?
Jasper
It’s relatively straight-forward. You just have to use the group tool and select specific layers.
In the library editor, create a new package, draw your pads. Then select only the tstop layer (unselect everything else). Using the group tool, select the tstop area(s) and then delete it/them. Now, select the polygon tool, make sure you are drawing on the tstop layer and draw the area you want.
You are almost done, you’ll need to do the same with cream. Pay attention to the differential in size between the stop and cream rectangles - it looks like cream is a touch smaller than stop. You’ll have to mess with the grid size. I don’t know why they didn’t just use solder mask and paste as the layer names - probably just litteral translations from german.
Interestingly, you can draw abritrary shapes (to the limit of eagles drawing tools) in most layers.
What’s it for? Note that this will make it harder to solder the part by hand because big areas of copper tend to conduct heat away from the solder point - that’s why there are “thermals”.
Phil
Thanks for the pointers. Hadn’t noticed that about the cream, either.
This is for the Osram Multiled-6 package, used by their part LATB G66B.
It’s a tiny, rather bright surface-mount led with a 120deg viewing angle. The nice thing about it is that you can drive the colors separately. In their spec, which is painstakingly thorough, they provide a recommended PCB design, and they don’t have any thermals in there. The largest pads are 16mm^2, most of which is covered in resist, so I am hoping that they are not too hard to solder to, at least as far as melting the solder goes. It will be quite detailed work, but only the prototypes are going to be soldered by hand. Still, I am not familiar with the process of spec’ing these things and assembling them, so I am sure I have plenty to learn.
Thanks,
Jasper
