KGD Myth #3: Die must be "burned-in" to be considered KGD.
KGD Myths Contents
Burn-in is a manufacturing screening method in which the lot of devices is subjected to excessive stress prior to shipping to a customer in order to cause weak devices to fail within the factory rather than in the field.
Figure 3: The so-called "bath-tub" reliability curve shows the three distinct periods of a products lifetime. The curves show the failure rate that can be expected for new and mature products. New products exhibit a high infant mortality rate which shows up as early life failure rate in a customers application if the devices are shipped. Operating the devices at high temperature and voltage accelerate the weakness in the device to become a failure that can be detected by subsequent testing.
Burn-in is done by applying abnormally high voltage and elevated temperatures to the device, usually about the limits specified in the data sheet for normal operation. The elevated temperature and voltage are maintained while the device are operated in some manner. Modern burn-in equipment is capable of applying stimulus to the inputs of devices and monitoring the outputs -to provide a test during burn-in operation, which offers advantages to devices that may have long test cycles, such as DRAM
As figure 3 illustrates, the need for burn-in lessens as the device technology becomes more mature. Effective yield management and reliability learning bring the "bath-tub" curve down, reflecting a lower failure rate for all phase of product life. Reliability goals may then be met without a manufacturing burn-in on all devices in the lot. The supplier of bare die will be able to state an estimate for the infant mortalities to be expected in a lot of bare die, based on experience with the product.
Suppliers of IC's in general, not only those who participate in the bare die markets, are keenly interested in developing novel reliability screens that can be applied quickly and simply at the wafer level. These novel screens may have the effect of enabling the device to meeting reliability targets without burn-in, especially for today's high volume, low cost consumer and mobile markets.