Applications requiring femtoampere-level performance are extremely sensitive to contamination. Contaminants in the form of solder flux, salts, oils, organic acids, and more can form conductive paths over PCB traces that allow small currents to leak into input traces or other sensitive nodes, thus degrading performance. For best possible performance, make sure to keep the OPA928EVM as clean as possible.

The following list of best practices helps prevent the EVM from becoming contaminated:

• Always wear a fresh, clean pair of powder-free gloves or finger cots when handling the OPA928EVM.
• When handling the EVM, always hold the board by the edges.
• Avoid touching the surface of the PCB, especially near sensitive nodes or input traces.
• Be cautious when breathing, speaking, sneezing, and so on, to prevent moisture or saliva from contacting the EVM.
• Do not allow direct airflow from cooling fans or ionizers onto the board. Moving air can blow dust and moisture onto sensitive nodes. Additionally, airflow introduces moving charges that present as a small current at the input.
• When not in use, place the EVM in ESD bag or other enclosure to prevent dust and other contaminants from settling on the board.
• When configuring through-hole components in the TIA feedback path, handle the components by the wire leads only. Avoid touching the component package.

The OPA928EVM undergoes a rigorous cleaning protocol before shipping to customers, providing femtoampere-level performance directly out of the box. Follow the cleaning procedures detailed in Section 5 to maintain best performance. The EVM must be cleaned per these instructions anytime the board is soldered or modified near sensitive nodes, or if these nodes become contaminated by other means.