.. _groundscrew:

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Soldering ground screws
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Solder a length of wire (we use stainless steel) to a mill-max connector, or any type of connector that fits into your drive's ground connector. We recommend using insulated wire to make it easier to ensure that there is no skin contact to the ground later, and to make it easier to embed the wire into the dental cement around the drive base (thin wires are more likely to work their way out of the cement before it fully cures). The length of the ground wire depends on the desired location and layout of the drive.

Solder the free end of the wire to the top of the ground screw. Use an appropriate stainless steel flux and use the same precautions as when soldering the spring. The easiest method is to solder to one half of the top of the screw head, so that the slot for the screwdriver remains open. Alternatively, the wire can be wrapped around the screw just under the head and soldered there, but this method brings a risk of accidentally filling the threads of the screw with solder.

Meticulously clean the screw of remaining flux with ethanol and/or acetone, and sterilize the screw before the implant.

Skull screws are used for 2 basic functions, to provide mechanical stability to the drive, and as ground/reference electrodes.
For instructions for fabricating the ground screws, see the relevant page in the drive building instructions.

In order to minimize the space taken up by screws, as well as the impact on the animal, small screws are preferable. The most important parameter though is that the thread diameter must match the diameter of the drill bit used to make the burr holes. We got good results using a screw thread diameter of 6.5mm for #1/4 round carbide dental bits (0.5mm OD).