2.3.1.3 Case 1: 420-Hour Baking Time at 170°C

In this test, the MSP430 MCU is continuously subjected to this high temperature of 170°C for 420 hours. The purpose of this test is to determine data retention at higher temperatures, and then calculate expected data retention at 25°C using Equation 2.

Using T1 = 25°C and T2 = 170°C in Equation 1 gives the following AF:

Using this AF information, back substitution gives the data retention in years at 25°C (see Equation 3).

After this value has been established, different AF values can be calculated for different T2 temperatures. Similar back substitution yields data retention in years.

Figure 1 shows the data retention versus temperature for this test.

The corner cases for 85°C and 105°C are slightly over 2 years and less than 9 months, respectively. These numbers do not truly indicate the performance of the MSP430 flash. To qualify the MSP430 MCU to have better data retention, further tests are conducted on the MSP430 flash.

There are instances in which there are strict requirements for flash data retention, particularly when the device is subjected to extreme temperatures. Although, in almost all cases, the device would never be subject to extreme temperatures 24 hours a day, 7 days a week, tests are in place to achieve better numbers at the corner case temperatures. To improve data retention for corner case temperatures, bake time must be increased. One such approach is to fix the bake temperature and use Equation 1 to establish bake time for the requirements on data retention. The bake temperature has been increased from case 1 to a temperature of 250°C. This test is performed on the flash used in the MSP430 MCU.

Table 1 lists the values plotted in Figure 1.