Microchip's own reliability data show that chips made using their 0.25uM process are much more reliable than those using their 0.18uM process. This is perhaps not so surprising.
But I've failed to find a way of knowing which process is used for any particular chip, other than finding the chip mentioned in process change notifications.
Anyone know where one should expect to find this information? If it's in the datasheets, I've certainly overlooked it despite searching.
Sylvia.