Does anybody have experience of creating components where the manufacturer's datasheet requires several vias within the area of the central package pad? I have come across this for the Analog Devices AD9513, and the Texas TPS796xx, where additionally it is recommended that the solderpaste is windowed over the central pad area. (Data sheet recommendations can be found at http://www.fpgasics.co.uk/Pads.htm)
I have had this - the PAD i have created in the centre had 3 x 3 vias for heat dissipation in the square central PAD which was ground also.
So if the IC is 8 pads x 4 sides - i created a 33rd PAD which was ground, then 9 extra PADs which were Through holes - and listed them as connecting to the GND connection of one of the 32 PADS on the IC side.
The PCB library component/footpront design layout looks messy - but this works. Placing the component ensures all vias and PADS are connected to ground - and you don't see the long string as per PCB fottprint design.
I did ask - did not receive a response- so am not sure if you can list in the PCB footprint design 33-42 the extra GND connections, or as i did list them individually - 32,33,34.. to 42 etc. in the existing ground connection.
You can (if there is a standard footprint), in the PCB layout editor simply add the central pad and vias ... remember to add them to the appropriate net as required.
Unusual PCB footprints
Posted - 21 Feb 2011 : 13:52:42
