IEC 60749-4:2017 pdf download

IEC 60749-4:2017 pdf download.Semiconductor devices – Mechanical and climatic test methods – Part 4: Damp heat, steady state, highly accelerated stress test (HAST)
1 Scope
This part of IEC 60749 provides a highly accelerated temperature and humidity stress test (HAST) for the purpose of evaluating the reliability of non-hermetic packaged semiconductor devices in humid environments.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes requirements of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. IEC 60749-5, Semiconductor devices – Mechanical and climatic test methods – Part 5: Steady state temperature humidity bias life test
3 Terms and definitions
No terms and definitions are listed in this document. ISO and IEC maintain terminological databases for use in standardization at the following addresses: • IEC Electropedia: available at http://www.electropedia.org/ • ISO Online browsing platform: available at http://www.iso.org/obp
4 HAST test – General remarks
The HAST test employs severe conditions of temperature, humidity and bias which accelerate the penetration of moisture through the external protective material (encapsulant or seal) or along the interface between the external protective material and the metallic conductors which pass through it. The stress usually activates the same failure mechanisms as the “85/85” steady-state temperature humidity bias life test, IEC 60749-5. As such the test method may be selected from IEC 60749-5 or from this test method. When both test methods are performed, test results of the 85 °C/85 % RH steady-state temperature humidity bias life test, IEC 60749-5, take priority over HAST. This test method shall be considered destructive.
5 Test apparatus
5.1 Test apparatus requirements The test requires a pressure chamber capable of maintaining a specified temperature and relative humidity continuously, while providing electrical connections to the devices under test in a specified biasing configuration. 5.2 Controlled conditions The chamber shall be capable of providing controlled conditions of pressure, temperature and relative humidity during ramp-up to and ramp-down from the specified test conditions. 5.3 Temperature profile A permanent record of the temperature profile for each test cycle is recommended so that the validity of the stress can be verified. 5.4 Devices under stress Devices under stress shall be mounted in such a way that temperature gradients are minimized. Devices under stress shall be no closer than 3 cm from internal chamber surfaces, and shall not be subjected to direct radiant heat from heaters. Boards on which devices are mounted should be oriented to minimize interference with vapour circulation. 5.5 Minimize release of contamination Care shall be exercised in the choice of board and socket materials, to minimize release of contamination and to minimize degradation due to corrosion and other mechanisms. 5.6 Ionic contamination Ionic contamination of the test apparatus (card cage, test boards, sockets, wiring storage containers, etc.) shall be controlled to avoid test artefacts. 5.7 De-ionized water De-ionized water with a minimum resistivity of 1 × 1 0 4 Ωm at room temperature shall be used.
6 Test conditions
6.1 Test conditions requirements Test conditions consist of a temperature, relative humidity, and duration in conjunction with an electrical bias configuration specific to the device. Unless otherwise required by the detailed specification the test conditions shall be selected from Table 1 .6.2 Biasing guidelines Apply bias according to the following guidelines: a) Minimize power dissipation. b) Alternate pin bias as much as possible. c) Distribute potential differences across chip metallization as much as possible. d) Maximize voltage within operating range. NOTE The priority of the above guidelines depends on mechanism and specific device characteristics. e) Either of two kinds of bias can be used to satisfy these guidelines, whichever is more severe: 1 ) Continuous bias The DC bias shall be applied continuously. Continuous bias is more severe than cycled bias when the die temperature is ≤1 0 °C higher than the chamber ambient temperature or, if the die temperature is not known when the heat dissipation of the DUT is less than 200 mW. If the heat dissipation of the DUT exceeds 200 mW, then the die temperature should be calculated. If the die temperature exceeds the chamber ambient temperature by more than 5 °C, then the die temperature rise above the chamber ambient should be included in reports of test results since acceleration of failure mechanisms will be affected.