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Mil-Std-883 Screen TestingMIL-STD-883 SCREENING OVERVIEW
The Department of Defense (DoD) has set up a quality system to provide device manufacturers an acceptable established baseline to support Government microcircuit applications and logistic programs. The DoD has empowered the Defense Logistic Agency to be the custodian of MIL-PRF 38534 (GENERAL SPECIFICATION FOR HYBRID MICROCIRCUITS), which flows down the screening requirements of MIL-STD-883 (TEST METHOD STANDARDS MICROCIRCUITS) (See Figure 1).
Figure 1 HIERARCY OF SCREENING REQUIREMENTS
MIL-PRF-38534 is a performance based specification that details the necessary quality controls required to build reliable hybrids. For example; element evaluation of all incoming materials, in process controls such as wire pull testing, screening and qualification testing etc. MIL-STD-883 is simply a collection of test methods used for microelectronic devices and is grouped along the lines of mechanical, electrical and environmental test methods. The specific test method and test conditions along with other details required in the production flow are specified in MIL-PRF-38534. (See Figure 2)
Figure 2 MIL-STD-883 PROVIDES A SERIES OF STANDARD TEST METHODS FOR ENVIRONMENTAL, MECHANICAL, AND ELECTRICAL (DIGITAL AND LINEAR) TESTING
WHAT IS SCREENING
The reliability of semiconductor, integrated circuits, hybrid and microelectronic devices is represented by the failure rate curve, which is shown in figure 3. The "bathtub curve" can be divided into the three following regions:
Figure 3 THE THREE REGIONS CREATING THE BATHTUB CURVE
- Initial failures, or early period phase, which occur within a
relatively short time after a device is put in service. This part of
the curve is known as "infant mortality".
- Random failures, which occur over a long period of time, and
- Wear-out failures, which increase as the device nears the end of its life.
To eliminate "initial failures"a process called "screening"is used to weed out those early period failures. A non-destructive test is applied to 100% of the device population to eliminate the "weak devices" and thus enter the flat portion and low failure rate period of the "bathtub curve".
Per MIL-PRF-38534, each hybrid microcircuits, multi-chip modules (MCM) and similar microelectronic devices is subjected to the applicable screening tests and inspections in accordance with the Table below from MIL-PRF-38534. . Each test must be performed in the order to eliminate infant mortality type failures and are removed from the lot.
There are two major quality classes. Class H is the standard military quality level and Class K is the highest reliability level intended for space applications.
*Per Source Control Drawing (SCD) or applicable device specification
TABLE C-IX. Device screening
DESCRIPTION OF TYPICAL MIL-STD-883 Class H TEST METHODS
MIL-STD-883 Test Method (TM) 2017 Internal Visual
The purpose of this test is to visually inspect the internal materials, construction, and workmanship of hybrid, multichip and multichip module microcircuits. There are two levels of criteria used. Class K is more stringent visual requirement than the Class H criteria. Figure 4 shows some common die defects uncovered during the Preseal ("Pre-Cap") inspection.
Figure 4 Common die defects uncovered per MIL-STD-883TM2017 Internal Visual inspection. (CLASS H)
Temperature cycling in an unbiased condition is performed to MIL-STD-883, TM 1010, Condition C, using 10 cycles from 65°C to +150°C.
For microcircuits in cavity packages, MIL-STD-883 TM2001 includes constant acceleration in its screening tests. This is carried out using a centrifuge at accelerations in the range 3,000g to 300,000g, depending on the package mass. The Y1 orientation is such as to accelerate die and bonds away from the package based as shown in Figure 5 below.
Figure 4 Orientation of Microelectronic Device to the direction of applied force.
Burn-In is performed per MIL-STD-883 TM1015 at a test temperature of 1250C for 160 hours with bias power applied per the SCD.
Final electrical tests are performed to MIL-PRF-38534. Both
Static and dynamic parameters from Group A, Subgroups 1-6,
are 100% tested to the device SCD or applicable device specification limits at 550°C, 250°C and +1250°C.
Seal Fine and Gross leak tests are performed to verify Hermeticity.
Fine leak testing is typically performed to MIL-STD-883, Method 1014, Condition A2, Flexible method, followed by the bubble test to inspect for gross leaks.
Hybrid circuits receive external visual to MIL-STD-883, TM 2009 for package body and lead defects as well as correct piece part marking.