Integra Technologies Brings Low-Cost NAND Flash Testing to the Mil/Aerospace Marketplace

Integra Technologies has announced that they have put into production High Parallel NAND flash testing for 512Gb NAND flash devices in support of Military/Defense & Space/Satellite application use. The extreme and rugged environments of this specialized niche group of customers requires their devices to be tested up to -55°C to 125°C temperature extremes. For NAND flash testing this introduces a unique set of obstacles in order to achieve cost-effective high-test integrity due to the extreme long test execution times of over 3-hours per insertion pass on an industry standard 512Gig-bit SLC NAND flash device. This test time translates into ~10-hour total time to test 1 group of devices!  From a test-cost standpoint testing 1 device at a time, which is often the case for small volume Military Temp High density memory devices, the cost is astronomically high due to the stringent requirements to test every single memory cell for both data states of storage and pseudo-random patterns to exercise the periphery logic. Yet more problems to overcome here is the expensive cost of high-parallel ATE’s and the subsequent efforts of applying the extreme temperatures to the test head directly. 

NAND-benchtop-tester1Integra engineers solved both of these problems by employing low-cost Benchtop test system (see figure 1) that is used to test the long data patterns of every memory cell, and elevating the test platform (see figure 2) away from the test head electronics in which a pure dry-air purge is applied to the chamber between the test head and the load board where the sockets hold the individual devices. In addition, very low noise, high thermal resistance, high precision BGA sockets are used to secure the devices during test. For noise immunity and high signal integrity, the device contact is made through pogo-pins specially designed for long use and high speed in which connection back to the test head electronics is via coaxial cables that enable up to 400Mhz operation. To insure the D/C & ICC parameters are measured with high precision, these parameters are additionally tested on ATE to validate their performance to specifications and to catch the test windows after Burn-in and other stress events. This 2-pass test approach provides the stringent test coverage that the Mil/Aero customer base demands.

On a NAND flash, an important aspect of test is to collect and manage the bad block occurrence and verification against a defined ECC condition. In the 512Gb example, the industry device here is Micron (part# redacted) that requires 24-bit per 1100bytes of data. Using Integra’s test system, the block management data is retained for every temperature point and VCC voltage tested setting (i.e. min/max VCC) NAND-benchtop-tester2, in which an invalid block is one that contains at least one page that has more bad bits than can be corrected by the minimum required ECC. This fail data will be provided the customer for their final determination of device selection to meet their Reliability needs. Since the devices can go through many test steps (defined as multiple temperature test flows at 25°C, -55°C, and 125°C) in conjunction with multiple Burn-in steps (Mil-Std-883 160/240hr dynamic B/I & static bias B/I) with pre and post electrical test after each, and each test pass performed at min and max VCC voltage for both data states, the automatic data management of the bad blocks is a very critical aspect of NAND test and the Integra NAND Flash test system excels at this paramount task. 

To achieve this parallel test, one of the most grueling engineering tasks was the thermal characterization of the temperature response of the DUT in each socket relative to the other DUTs and the thermal stream temperature.  Using RTD’s and thermocouple, a correlation was established for each corner socket relative to the other sockets in the parallel formation. This data meets the Military Mil-Std-883 requirement of +/3°C and is maintained through-out the long test time in which hybrid devices are allowed +6°C/-3°C.  The test doesn’t start until thermal stability is achieved for the given customer requirement. 

Contact Integra Sales to discuss your extended temperature NAND flash test requirements and how Integra engineers can help support Mil/Aero/Space test solutions for the future.