1、JEDEC STANDARD Accelerated Moisture Resistance - Unbiased HAST JESD22-A118B (Revision of JESD22-A118A, March 2011) JULY 2015 JEDEC SOLID STATE TECHNOLOGY ASSOCIATION NOTICE JEDEC standards and publications contain material that has been prepared, reviewed, and approved through the JEDEC Board of Dir
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7、 for alternative contact information. Published by JEDEC Solid State Technology Association 2015 3103 North 10th Street Suite 240 South Arlington, VA 22201-2107 This document may be downloaded free of charge; however JEDEC retains the copyright on this material. By downloading this file the individu
8、al agrees not to charge for or resell the resulting material. PRICE: Contact JEDEC Printed in the U.S.A. All rights reserved PLEASE! DONT VIOLATE THE LAW! This document is copyrighted by JEDEC and may not be reproduced without permission. For information, contact: JEDEC Solid State Technology Associ
9、ation 3103 North 10th Street Suite 240 South Arlington, VA 22201-2107 or refer to www.jedec.org under Standards-Documents/Copyright Information. JEDEC Standand No. 22-A118B Page 1 Test Method A118B (Revision of Test Method A118A) TEST METHOD A118B ACCELERATED MOISTURE RESISTANCE - UNBIASED HAST (Fro
10、m JEDEC Board Ballot JCB-00-56, JCB-11-17, and JCB-15-25, formulated under the cognizance of the JC-14.1 Subcommittee on Reliability Test Methods for Packaged Devices.) 1 Scope This test method applies primarily to moisture resistance evaluations and robustness testing, and may be used as an alterna
11、tive to unbiased autoclave. Samples are subjected to a noncondensing, humid atmosphere, similar to the JESD22-A101, “Steady-State Temperature, Humidity and Bias Life Test“, but with a higher temperature. For the temperature limits defined by this procedure, the test will typically generate the same
12、failure mechanisms as those in an unbiased “85 C/85% RH“ Steady-State Humidity Life Test, but caution must be used if higher temperatures are considered since non-realistic failure modes can be generated. The use of a noncondensing environment avoids many irrelevant external failures, e.g., pin-to-p
13、in leakage or lead corrosion. However, because absorbed moisture typically decreases glass transition temperature for most polymeric materials, the combination of high humidity and high temperature ( Tg) may produce unrealistic material failures. Thus, caution is needed if and when Unbiased HAST is
14、required for reliability or qualification purposes. The Unbiased HAST is performed for the purpose of evaluating the reliability of nonhermetic packaged solid-state devices in humid environments. It is a highly accelerated test that employs temperature and humidity under noncondensing conditions to
15、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 that pass through it. Bias is not applied in this test to ensure the failure mechanisms potentially oversh
16、adowed by bias can be uncovered (e.g., galvanic corrosion). This test is is used to identify failure mechanisms internal to the package and is destructive. 2 Apparatus The test requires a pressure chamber capable of maintaining a specified temperature and relative humidity during ramp-up to, and ram
17、p-down from, the specified test conditions. JEDEC Standand No. 22-A118B Page 2 Test Method A118B (Revision of Test Method A118A) 2 Apparatus (contd) 2.1 Records A permanent record of the temperature profile for each test cycle is recommended, so the stress conditions can be verified. Calibration rec
18、ords shall verify that the equipment avoids condensation on devices under test (DUTs) hotter than 50 C during ramp-up and ramp-down for conditions of maximum thermal mass loading. Calibration records shall verify that, for steady-state conditions and maximum thermal mass loading, test conditions are
19、 maintained within the tolerances specified in Table 1. 2.2 Devices under stress Devices under stress must be placed in the chamber to minimize temperature gradients. Devices under stress shall be no closer than 3 cm from internal chamber surfaces, and must not be subjected to direct radiant heat fr
20、om heaters. If devices are mounted on boards, the boards should be oriented to minimize interference with vapor circulation. 2.3 Ionic contamination Care must be exercised in the choice of any materials introduced into the chamber in order to minimize release of contamination, and minimize degradati
21、on due to corrosion and other mechanisms. Ionic contamination of the test apparatus shall be controlled to avoid test artifacts. 2.4 Distilled or deionized water Distilled or deionized water with a minimum resistivity of 1 M-cm at room temperature shall be used. JEDEC Standand No. 22-A118B Page 3 Te
22、st Method A118B (Revision of Test Method A118A) 3 Test conditions Test conditions consist of a temperature, relative humidity, and duration. Table 1 Temperature, relative humidity and pressure Test condition3,4Temperature1dry-bulb C Relative humidity1%Temperature2wet-bulb, C Vapor pressure2kPa (psia
23、) A 130 2 85 5 124.7 230 (33.3) B 110 2 85 5 105.2 122 (17.7) NOTE 1 Tolerances apply to the entire usable test area. NOTE 2 For information only. NOTE 3 The test conditions are to be applied continuously except during any interim readouts. For interim readouts, devices should be returned to stress
24、within the time specified in 4.4 NOTE 4 The unbiased HAST duration is intended to meet or exceed an equivalent field lifetime under use conditions. The duration is established based on the acceleration of the stress (see JEP122). The stress duration is specified by internal qualification requirement
25、s, JESD47 or the applicable procurement document. Typical test durations are: Condition Duration A 96 hours (-0,+2) B 264 hours (-0, +2). CAUTION: For plastic-encapsulated microcircuits, it is known that moisture reduces the effective glass transition temperature of the molding compound. Stress temp
26、eratures above the effective glass transition temperature may lead to failure mechanisms unrelated to operational use. 4 Procedure The test devices shall be mounted in a manner that exposes them to a specified condition of temperature and humidity. Exposure of devices to conditions that result in co
27、ndensation on them, particularly during ramp-up and ramp-down, shall be avoided. While devices are above 30 oC, R.H. must be 40% to ensure their moisture content is not reduced, i.e., inadvertant moisture bake out. JEDEC Standand No. 22-A118B Page 4 Test Method A118B (Revision of Test Method A118A)
28、4 Procedure (contd) 4.1 Ramp-up 4.1.1 The time to reach stable temperature and relative humidity conditions should be less than 3 hours. 4.1.2 Condensation shall be avoided by ensuring that the test chamber (dry-bulb) temperature exceeds the wet-bulb temperature at all times, and that the rate of ra
29、mp up shall not be faster than a rate which ensures that the temperature of any DUT does not lag below the wet bulb temperature. 4.1.3 The dry- and wet-bulb temperature set points shall be maintained so that the relative humidity is not less than 50 % after significant heating begins. In a dry labor
30、atory, the chamber ambient may initially be drier than this. 4.2 Ramp-down 4.2.1 The first part of ramp-down to a slightly positive gauge pressure (a wet bulb temperature of about 104 C) shall be long enough to avoid test artifacts due to rapid depressurization, but should be less than 3 hours. 4.2.
31、2 The second part of ramp-down from a wet bulb temperature of 104 C to room temperature shall occur with the chamber vented. There is no time restriction, and forced cooling of the vessel is permitted. 4.2.3 Condensation on devices shall be avoided in both parts of the ramp down by ensuring that the
32、 test chamber (dry-bulb) temperature exceeds the wet-bulb temperature at all times. 4.2.4 Ramp-down should maintain the moisture content of the molding compound encapsulating the die. Therefore, the relative humidity shall not be less than 50 % during the first part of the ramp-down, see 4.2.1. 4.3
33、Test Clock The test clock starts when the temperature and relative humidity reach the set points, and stops at the beginning of ramp-down. JEDEC Standand No. 22-A118B Page 5 Test Method A118B (Revision of Test Method A118A) 4 Procedure (contd) 4.4 Readout Electrical test shall be performed not later
34、 than 48 hours after the end of ramp-down. Note, for intermediate readouts, devices shall be returned to stress within 96 hours of the end of ramp-down. The rate of moisture loss from devices after removal from the chamber can be reduced by placing the devices in sealed moisture barrier bags, the ba
35、gs should be non-vacuum sealed without a N2 purge and without dessicant. When devices are placed in sealed bags, the “test window clock“ runs at 1/3 of the rate of devices exposed to the laboratory ambient. Thus the test window can be extended to as much as 144 hours, and the time to return to stres
36、s to as much as 288 hours by enclosing the devices in sealed moisture barrier bags. NOTE 1 The electrical test parameters should be chosen to preserve any defect (i.e., by limiting the applied test current). NOTE 2 Additional time-to-test delay or return-to-stress delay time may be allowed if justif
37、ied by technical data 4.5 Handling Suitable hand-covering shall be used to handle devices, boards and fixtures. Contamination control is important in any highly accelerated moisture stress test. 5 Failure criteria A device will be considered to have failed if parametric limits are exceeded, or if fu
38、nctionality cannot be demonstrated under nominal and worst-case conditions as specified in the applicable procurement document or data sheet. 6 Safety Follow equipment manufacturers recommendations and local safety regulations. 7 Summary The following details shall be specified in the applicable pro
39、curement document: (a) Test duration (b) Test conditions (c) Measurements after test. JEDEC Standand No. 22-A118B Page 6 Test Method A118B (Revision of Test Method A118A) Annex A (informative) Differences between JESD22-A118B and its predecessors These tables briefly describe most of the non-editori
40、al changes made to entries that appear in this standard, JESD22-A118B, compared to its predecessors, JESD22-A118A (March 2011) and JESD22-A118 (December 2000, Reaffirmed June 2008). A.1 Differences between JESD22-A118B and JESD22-A118A Clause Description of change 1 Changed “which” to “that”, 2 time
41、s. 3 Changed “psia/kPa” to “kPa (psia)”. 4.1.1 Changed the phrase “shall be less than 3 hours” to “should be less than 3 hours”. 4.2.1 Changed the phrase “shall not exceed 3 hours” to “should be less than 3 hours”. A.2 Differences between JESD22-A118A and JESD22-A118 Clause Description of change 1,
42、2 Combined to align with JEDEC Sytle Manual, JM7. All Renumbered accordingly. 4.4 Readout: Added two notes. Standard Improvement Form JEDEC JESD22-A118B The purpose of this form is to provide the Technical Committees of JEDEC with input from the industry regarding usage of the subject standard. Indi
43、viduals or companies are invited to submit comments to JEDEC. All comments will be collected and dispersed to the appropriate committee(s). If you can provide input, please complete this form and return to: JEDEC Attn: Publications Department 3103 North 10thStreet Suite 240 South Arlington, VA 22201
44、-2107 Fax: 703.907.7583 1. I recommend changes to the following: Requirement, clause number Test method number Clause number The referenced clause number has proven to be: Unclear Too Rigid In Error Other 2. Recommendations for correction: 3. Other suggestions for document improvement: Submitted by Name: Phone: Company: E-mail: Address: City/State/Zip: Date:
