https://devzone.nordicsemi.com/f/nordic-q-a/12335/how-to-solve-wlcsp-light-sensitivity-problemHi, all Recently I use nrf51822 CEAA, WLCSP package to develop a project on UV (ultraviolet), the UV sensor must be exposed to the sunlight. When we take the product board outside and expose it to the sunlight, it cannot work any more, while it worksen-USTelligent Community 13Mon, 07 Mar 2016 02:36:52 GMThttps://devzone.nordicsemi.com/thread/46670?ContentTypeID=1Mon, 07 Mar 2016 02:36:52 GMT137ad170-7792-4731-bb38-c0d22fbe4515:556f44a7-8527-4864-b186-4e8cd9e9cf64Frank<p>Thanks for your answer. I think I&#39;ve found out the reason. It&#39;s not the nRF51822 problem. Actually, it&#39;s another chip that causes this problem.</p><div style="clear:both;"></div>https://devzone.nordicsemi.com/thread/46669?ContentTypeID=1Fri, 04 Mar 2016 12:16:46 GMT137ad170-7792-4731-bb38-c0d22fbe4515:5175adab-fa28-4730-8da7-aafe481da6c2H&#229;kon Alseth<p>Hi,</p> <p>The light sensitivity can only be a problem if you operate the transmitter with IR light present. Silicon is translucent for IR light and the photons can open a transistor, just like a photo diode. The analog parts are sensitive for this, especially the TX. The carrier drift can in some cases become too high, but no damage will occur on the nRF due to this phenomenon.</p> <p>Our recommendation is to cover the sides of the WLCSP package with a IR blocking coating. The top of the package has already a IR blocking coating.</p> <p>If you have a casing that will block IR light, then that is also sufficient.</p> <p>If your program does not work on devices that are already coated properly, then this points to a issue in firmware. Are you able to see where the device fails in firmware?</p> <p>Cheers, Håkon</p><div style="clear:both;"></div>