IR Susceptibility of WLCSP Package

I'm looking to understand the IR Susceptibility of the WLCSP. I've seen some post talking about direct IR light causing issues, but not how much of an issue it actually is.

Our project is for use in a hospital environment so only used indoors and will be in an ABS plastic housing, which I'm aware does not block IR. I'm trying to understand if we need to shield the nRF MCU or if there is little risk of there being adverse effects to the part.

It would be also good to understand exactly what effect IR has on the nRF part specifically, is it just increased current draws or single event failures?

Any info would be appreciated.

Yours,

Cameron

0 Hung Bui 10 months ago

Hi Cameron,

The general recommendation is stated in the product's specification:

8.1 WLCSP light sensitivity
All WLCSP package variants are sensitive to visible and close-range infrared light. This means that a final
product design must shield the chip properly, either by final product encapsulation or by shielding/coating
of the WLCSP device.
Some WLCSP package variants have a backside coating, where the marking side of the device is covered
with a light absorbing film, while the side edges and the ball side of the device are still exposed and need
to be protected. Other WLCSP package variants do not have any such protection.
The WLCSP package variant CKAA has a backside coating.

As you may find in other tickets discussing this, the IR doesn't do permanent damage to the chip but it affect the current consumption and the analog parts. This includes the radio. So our recommendation is to have protection over the WLCSP chip.

light sensitive of nRF52832 WLCSP package

Coating WLCSP for Light Sensitivity

52810 WLCSP Light Sensitive