EAGLE 6.2.0, Windows 7.
Hi all. Anyone see potiential problems with this work around to the vias in pad delima? I have not had a board manufactured using this package yet but the Gerbers do look good and EAGLE does not generate any DRC errors.
Example library file included: QFN.zip
Steps used to create pad:
Assumes package centered on 0,0 coordinate with symetrically placed vias.
1.) Determine overall pad dimension for top layer. In this example, it is 2.1mm square.
2.) Determine number of vias. In this example, 4.
3.) Create 4 pads with the properties of square and the drill size preferred. "Mirror", "Thermals", "Stop" and "First" properties Off (not checked).
The "Stop" property could be left on. I chose to turn it off and create the stops myself in each layer.
4.) Calculate the individual pad diameters (strange name for a square pad) for a 2x2 arrangement.
This example:
2.1mm (desired overall pad dimension) divided by 2 ( number of vias required in the X and Y axis) = 1.5mm
Change Pad "Diameter" property to 1.5mm
5.) Calculate the positions of the 4 pads.
This example:
2.1mm (pad dimension) divided by 4 (number of vias in the X and Y axis times 2) = 0.525mm
Change each pads "Position" property to the following:
(-0.525, 0.525) For the top left pad.
(0.525, 0.525) For the top right pad.
(-0.525, -0.525) For the bottom left pad.
and
(0.525, -0.525) For the bottom right pad.
6.) Most of the time, these pads you just created will connect to another pad on the package. So name the pads the same using the @ symbol.
This example:
Pin/Pad 12, which I have named VEE@12 (pin description and pin#)
Change Pad 1 "Name" property to VEE@2.
Change Pad 2 "Name" property to VEE@3.
Change Pad 3 "Name" property to VEE@4.
Change Pad 4 "Name" property to VEE@5.
I wanted the bottom layer pad to be a bit larger than the top so I added an SMD and assigned the following properties:
Name: VEE@1
Position: 0,0
Angle: 0
Mirror: Off (not checked)
SMD Size: 2.5mm x 2.5mm
Layer 16 Bottom
Roundness: 0 %
Thermals: Off (not checked)
Stop: Off (not checked)
Cream: Off (not checked)
7.) In the Device, I made the following connections. Note the multiple VEE's connected to G$1.VEE@12.
8.) On the board, I connected all of the VEE@ pads by routing traces as you would any airwire net.
I also created this QFN using the same methods:
Let me know what you think.
ADMsystems
