Hi John Wallace,
I would like to follow up questions for UV light effect. I saw your reply statement you believe UV light will not impact the silicon after you consulted your packaging experts. Could you explain why you believe so in technical perspective? The competitor part we use is a plastic package.
We seen ard 2% out of a few hundreds units going thru UV conveyor process with latch circuit(mosfet) turned on issue. The UV light we use for conformal coating curing is UVA with intensity 200mW/cm2. This UVA process comes with UVA light and heat. We did competitor mosfet characterization with temperature chamber by measuring leakage current flow vs temperature to confirm heat would cause leakage current increased and trigger mosfet on at certain temperature. It did at temperature above 100degC in this temperature chamber testing.
We also measured mosfet leakage current and temperature going thru UVA process but found out package top side max temperature went up to ard 70degC for a few boards tested and leakage current quite similar with temperature chamber testing data at 70degC. All tested boards latch circuit did not turn on because measured package top side temperature thru UV process was ard 70degC which would not trigger mosfet on.
As with measured data thru UV process could not conclude heat is main factor in UVA process to turn on mosfet, is UVA light would have effect to plastic package mosfet?
We did try a few samples of this MPN: CSD19538Q2 in our boards but did not seen mosfet triggered thru normal UVA process as well. It would trigger only with overstress condition under long UVA exposure time which was not normal UVA process in production.
Thanks,
SF
