I have some A4988 motor drivers, green edition which I wish to use to output 2A/coil for a short duration in the ramp up period for my stepper motors (before the inductance takes over and the actual current output drops).
Reading the product page, I see that the A4988 needs a heatsink to drive this amount. Reading online, it looks like most people add a heatsink to the top of the chip, however the datasheet says that the chip is built to heatsink through the bottom and adding a heatsink to the top of the chip means that you wreck the board if you hit the heatsink. As the driver boards are small and short on copper, I am wondering if it would be a good idea to add a piece of copper to the bottom with thermal epoxy. Would I get better performance with this solution?
We do not have any specific advice for heat sinking, and we generally view adding a heat sink as an advanced modification that should only be made by those who have experience with this kind of thing. The square pad on the bottom is one location where a heat sink could be added, but we have not characterized how adding a heat sink there compares with adding one to the top of the IC.
Also, if the 2A draw is brief enough, you might not need additional heatsinking.
heat sink on the top is kind of useless for chips designed to be cooled using the bottom pad.
A heatsink on the bottom could improve it, but you have to take into consideration that you will need proper ventilation to cool it and a good way of gluing the heatsink. That means a low thermal resistance in the glue.
Ideally a copper heatsink solder to the bottom bare copper and a small fan somewhere around would a good way to go.