Updated: Sep 28, 2020
Conformal coating is a protective chemical coating that is applied to parts of or all of the topography of the printed circuit board (PCB) and components.
Examples of conformal coating:
Type AR - Acrylic resin, including lacquers and varnishes
Type ER - Epoxy resin
Type SR - Silicone resin
Type UR - Polyurethane resin
Type XY - Paraxylylene
How is conformal coating applied?
Four main types of application methods used for conformal coatings:
Selective coating by machine
Why is conformal coating applied?
Conformal coating provides protection against:
What does this mean for digital forensics?
The use of conformal coating on a PCB presents an additional hurdle to reaching data directly from an integrated circuit (IC or chip). It can also impact the ability to communicate with the integrated circuit in-situ on the PCB by directly connecting to the PCB (e.g. UART, SWD, or JTAG).
At VTO Labs, we specialize in chip-off processes for those instances when an electronic device is too damaged to extract data via cable connection between the intact device and forensic software.
If we see coating, our initial step is to do a scratch test to determine what type of conformal coating we're dealing with. The hardness and opacity of the coating give us clues to identify the coating material.
Once we narrow in on a potential coating type, we can try methods of removal. Some types of coating can be carefully scraped away to reveal the chip more clearly and inform next steps. Some coatings can be removed using heat or chemicals, and others actually peel off.
Careful removal of conformal coating allows for direct access to the chip, which can then be physically removed from the PCB using additional heat or tools.