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ANSI/EIA-977-2016 Approved: EIA-977 EIA STANDARD Test Method – Electronic Passive Components Exposure to Atmospheric Sulfur EIA-977 2016 Electronic Components Industry Association NOTICE EIA Engineering Standards and Publications are designed to serve the public interest through eliminating misunderstandings between manufacturers and purchasers, facilitating interchangeability and improvement of products, and assisting the purchaser in selecting and obtaining with minimum delay the proper product for his particular need. Existence of such Standards and Publications shall not in any respect preclude any member or nonmember of ECIA from manufacturing or selling products not conforming to such Standards and Publications, nor shall the existence of such Standards and Publications preclude their voluntary use by those other than ECIA members, whether the Standard is to be used either domestically or internationally. Standards and Publications are adopted by ECIA in accordance with the American National Standards Institute (ANSI) patent policy. By such action, ECIA does not assume any liability to any patent owner, nor does it assume any obligation whatever to parties adopting the Standard or Publication. This EIA Standard is considered to have International Standardization implications, but the International Electrotechnical Commission activity has not progressed to the point where a valid comparison between the EIA Standard and the IEC document can be made. This Standard does not purport to address all safety problems associated with its use or all applicable regulatory requirements. It is the responsibility of the user of this Standard to establish appropriate safety and health practices and to determine the applicability of regulatory limitations before its use. (From Standards Proposal No. 5317, formulated under the cognizance of the P-1 Committee on EIA National Resistive Devices Standards). Published by ©Electronic Components Industry Association 2016 EIA Standards & Technology Department 2214 Rock Hill Road, Suite 265 Herndon, VA 20170 PLEASE! DON'T VIOLATE THE LAW! This document is copyrighted by the EIA and may not be reproduced without permission. Organizations may obtain permission to reproduce a limited number of copies through entering into a license agreement. For information, contact: Global Engineering Documents 15 Inverness Way East Englewood, CO 80112-5704 or call USA and Canada (1-800-854-7179), International (303-397-7956) Contents 1. SCOPE .................................................................................................................................................................1 2. REFERENCED DOCUMENTS ........................................................................................................................1 3. APPARATUS AND MATERIALS ....................................................................................................................1 4. GENERAL PROCEDURE ................................................................................................................................3 5. SPECIFIC TEST PROCEDURES ....................................................................................................................5 6. DETAILS TO BE SPECIFIED ..........................................................................................................................7 7. DOCUMENTATION ..........................................................................................................................................7 Table 1 – Resistance to Environmental Sulfur Test Conditions ..............................................................................4 Figure 1: Typical Test Setup .......................................................................................................................................3 i DRAFT – Rev 10 – 13JUN2016 EIA-977 Page 1 Test Method – Electronic Passive Components Exposure to Atmospheric Sulfur (From EIA Standards Proposal No. 5317, formulated under the cognizance of the P-1 Committee on EIA National Resistive Devices Standards). 1. SCOPE This standard defines options for testing electronic components for susceptibility to the effects of environmental sulfur. Such susceptibility results in the corrosion of elemental metals, such as silver, in the presence of sulfur compounds in a liquid or gaseous state, potentially leading to component failure. 2. REFERENCED DOCUMENTS The current revision of the referenced documents in effect at the date of agreement to the test plan shall be used. Subsequent test plans will automatically use the latest revision of these referenced documents. 2.1. ASTM B 809: Standard Test Method for Porosity in Metallic Coatings by Humid Sulfur Vapor (“Flowers of Sulfur”). 3. APPARATUS AND MATERIALS 3.1. Test Specimen – The component to be tested, typically surface mount resistors or other components containing silver. 3.2. Control Sample – A silver coupon to be suspended in the test container by means of a non-corroding material such as nylon line. This control sample is used to confirm the presence of a sulfur vapor in the test container. 3.3. Dish – A Petri or other shallow dish approximately 15 cm (6 in) in diameter to hold powdered sulfur. If a large test vessel is used and the silver control coupon does not blacken (tarnish) from exposure to sulfur within 24 hours, a larger diameter shallow container may be needed to accommodate additional sulfur. 3.4. Reagent – Sulfur, Sublimed (“Flowers-of-Sulfur”) powder, CAS No. 7704-34-9, N.F. or laboratory grade. 3.4.1. Sulfur placement in Petri dish – A layer of sulfur approximately 10 mm (approx. 0.39 in) thick shall be placed in the Petri dish such that it covers the entire bottom surface of the container. 3.4.2. Reuse of reagent – It is recommended that the sulfur be replaced with fresh material each test, however, the reagent may potentially be used for multiple tests DRAFT – Rev 10 – 13JUN2016 EIA-977 Page 2 by using the corrosion of the silver control specimen as an indicator that the reagent must be replaced. If the control specimen does not blacken (tarnish) from sulfur exposure within 24 hours (per the definition in Section 4.5), the reagent must be replaced. 3.5. Test Container – Any conveniently-sized vessel of glass, polycarbonate, stainless steel (or any other material) that is not affected by sulfur vapor and elevated temperatures may be used as the test container. The size of the test samples will dictate the required size of the container. For small components such as chip resistors, a glass desiccator of 9 to 10L capacity will be sufficient. The vessel does not need to be hermetically sealed and may have a small vent opening (1 to 4 mm diameter hole) to allow equalization of pressure when elevated temperatures are present. 3.5.1. Large test containers – Larger vessels may be required to accommodate test boards and Printed Circuit Board Assemblies (PCAs). If a large test container is used and the silver coupon does not blacken (tarnish) from sulfur exposure within 24 hours (per the definition in Section 4.5), a larger diameter Petri dish and additional sulfur may be needed (Sections 5.1 and 5.2). 3.6 Convection Oven or Hot Plate– A convection oven or hot plate may be used to maintain the required temperature inside the test container. 3.7 Thermocouples – Thermocouples are used to monitor and control the temperature inside the test container. 3.8 DC Resistance Test Setup – A resistance bridge or multi-meter and appropriate test probes capable of providing resistance measurements within specified tolerances. This setup shall not apply a voltage greater than a value that exceeds the smaller of 50 mW of power or 5% of the test sample’s rated power. 3.9 Microscope – An optical microscope capable of up to 50X magnification. DRAFT – Rev 10 – 13JUN2016 EIA-977 Page 3 Figure 1: Typical Test Setup 4. GENERAL PROCEDURE 4.1. Choice of test procedure – The user and supplier must agree as to which of the two sets of test conditions will be applied, A or B. 4.2. Mounting – Unless otherwise specified in the individual specification or by customer request, samples shall be mounted to a printed wiring test board. If the components are to be placed as loose samples inside the test container, the surface of interest (typically those containing silver) should have unobstructed exposure to the sulfur environment. 4.3. Test sample documentation – All relevant parameters from the component placement and soldering operation shall be recorded, including but not limited to: solder and flux materials, soldering temperature or profile, and component placement method. 4.4. Test sample cleaning – After the components are soldered to the printed wiring board, the test specimens shall be cleaned in order to remove contamination that might affect the corrosion resistance results of the component itself. Cleaning requirements and conditions shall be adequate to remove all residual flux and ionic contamination. The cleaning requirements and conditions may be AABUS (as agreed by user and supplier). 4.5. Control sample – A silver coupon sample shall be suspended in the test container by a nylon line or other non-corroding material during the test to confirm the severity of the environment. DRAFT – Rev 10 – 13JUN2016 EIA-977 Page 4 4.6. Initial Measurements – Unless otherwise specified, initial measurements of the samples to be tested shall be made and recorded. It is expected that the initial measurement of each sample unit will be within the specified nominal tolerance. 4.7. Exposure – The samples shall be placed in the test container and subjected to the test conditions according to Condition A (Section 5.1) or B (Section 5.2) chosen from Table I below. The parameters given for each test condition are default parameters. Deviations to the given parameters shall be as agreed by user and supplier and shall be documented in the test report. Table 1 – Resistance to Environmental Sulfur Test Conditions Test Conditions Test Parameters Temperature Humidity Duration Reagent Amount of Reagent Component Sample Size Sample Nominal Resistance Value Sample Tolerance Mounted on PCB Failure Criteria 1. A1 60 ± 2°C (140°F±3.6°F) Not applicable 480 Hours Sulfur, Sublimed (Flowers of Sulfur, or FoS). The sulfur shall be placed on a tray at the bottom of the chamber or on the base of the chamber. Cover the tray or base of the chamber with a bed of sulfur to 10 mm depth minimum. The greater the amount of sulfur placed in the chamber, the faster the sulfur in the chamber air will reach equilibrium. 22 units. The case size to be qualified will be 0402 or smallest size available larger than 0402 or AABUS (As Agreed By User and Supplier). B 105°C ± 2°C (221°F±3.6°F) Not applicable 750 hours Sulfur, Sublimed (Flowers of Sulfur, or FoS). The sulfur shall be placed on a tray at the bottom of the chamber or on the base of the chamber. Cover the tray or base of the chamber with a bed of sulfur to 10 mm depth minimum. The greater the amount of sulfur placed in the chamber, the faster the sulfur in the chamber air will reach equilibrium. 15 units each from 3 different production lots (of the same style, termination design and manufactured under the same process and conditions with the same materials. ) The case size to be qualified will be 0402 or smallest size available larger than 0402 or AABUS (As Agreed By User and Supplier). Lowest available resistance value for the series being qualified or AABUS Nominal tolerance to be qualified. Yes Lowest available resistance value for the series being qualified or AABUS Nominal tolerance to be qualified. Yes A) Using 50X magnification, any Ag2S growth present at the interface between any end termination and the protective Shift in resistance (ΔR) greater than nominal tolerance. overcoat, OR B) Shift in resistance (ΔR) greater than Thus a resistance shift of > ±1% for a 1% tolerance nominal tolerance. Thus a resistance shift of > ±1% for a component or > ±5% for a 5% tolerance component . 1% tolerance component or > ±5% for a 5% tolerance component . Test conditions based on modification of ASTM B 809. DRAFT – Rev 10 – 13JUN2016 EIA-977 Page 5 5. SPECIFIC TEST PROCEDURES 5.1. Test Condition “A” 5.1.1. Test Container Temperature Control 5.1.1.1. It is recommended that the test container temperature be controlled by placing it in a larger convection oven. 5.1.1.2. Thermocouples connected to the temperature controller should be placed in close proximity to the test samples. 5.1.1.3. Properly placed flat heating elements (hot plate heaters) may be used on the exterior of the test container if the test container temperature can be controlled to ±2°C consistently throughout the test container. 5.1.1.4. It is highly recommended that proportional temperature controllers with safety temperature limit shutoff be used for heating larger test containers. 5.1.2. Test container humidity is not actively controlled because the formation of silver sulfide (Ag2S) occurs independent of the relative humidity. 5.1.3. Samples shall be exposed for 480 hours in the test container maintained at 60°C±2°C (140°F±3.6°F). 5.1.4. Monitoring control sample 5.1.4.1. The silver coupon control sample shall be visually inspected (if possible, from outside of the test container) 24 hours after a test is begun. 5.1.4.2. The silver coupon must blacken (tarnish) from exposure to sulfur within 24 hours. 5.1.4.3. If the silver coupon does not completely blacken (tarnish) from sulfur exposure within 24 hours, additional or fresh sulfur shall be added and the test shall be restarted. 5.1.4.4. The silver coupon shall remain in the test container for the duration of the test to avoid disrupting the equilibrium within the container. 5.1.5. Applied bias 5.1.5.1. Bias shall not be applied to any test sample during the test. 5.1.5.2. If resistance measurements are being used for sample monitoring and/or inspection, the applied voltage must not cause local heating of the test component because of the strong effect of temperature on the sulfuration chemical reaction and local sulfur vapor concentration. The applied voltage shall not be greater than a value that exceeds the smaller of 50 mW of power or 5% of the test sample’s rated power. 5.1.6. Sample Inspection and Testing 5.1.6.1. After exposure, components shall be examined using a microscope with adjustable magnifications to 50X. DRAFT – Rev 10 – 13JUN2016 EIA-977 Page 6 5.1.6.1.1. Higher magnifications may be necessary, including the use of scanning electron microscope, for more critical applications. 5.1.6.1.2. Any observable growths of silver sulfide crystals (Ag2S) must be recorded. 5.1.6.2. All components shall be tested for DC resistance and the measurements recorded. 5.1.6.3. Failure criteria 5.1.6.3.1. Microscopic inspection at 50X reveals the presence of any amount of Ag2S crystals at the interface between any end termination and the protective overcoat, or 5.1.6.3.2. The change in DC resistance is greater than the nominal tolerance. (For instance, a resistance shift (ΔR) of > ±1% for ±1% tolerance component, or a shift of >±5% for ±5% tolerance.) 5.1.6.3.3. A change in resistance due to printed wiring board degradation shall not be considered a failure and shall be confirmed by directly measuring the resistance of the test sample. 5.2. Test Condition “B” 5.2.1. Test Container Temperature Control 5.2.1.1. It is recommended that the test container temperature be controlled by placing it in a larger convection oven. 5.2.1.2. Thermocouples connected to the temperature controller should be placed in close proximity to the test samples. 5.2.1.3. Flat heating elements (pancake heaters) may be used on the exterior of the test container if the test container temperature can be controlled to ±2°C consistently throughout the test container. 5.2.1.4. It is highly recommended that proportional temperature controllers with safety temperature limit shutoff be used for heating larger test containers. 5.2.2. Test container humidity is not actively controlled because the formation of silver sulfide (Ag2S) occurs independent of the relative humidity. 5.2.3. Samples shall be exposed for 750 hours in a test container maintained at 105°C±2°C (221°F±3.6°F). 5.2.4. Monitoring control sample 5.2.4.1. The silver coupon control sample shall be visually inspected (if possible, from outside of the test container) 24 hours after a test is begun. 5.2.4.2. The silver coupon must blacken (tarnish) from exposure to sulfur within 24 hours. DRAFT – Rev 10 – 13JUN2016 EIA-977 Page 7 5.2.4.3. If the silver coupon does not completely blacken (tarnish) from sulfur exposure within 24 hours, additional or fresh sulfur shall be added and the test shall be restarted. 5.2.4.4. The silver coupon shall remain in the test container for the duration of the test to avoid disrupting the equilibrium within the container. 5.2.5. Applied bias 5.2.5.1. Bias shall not be applied to any test sample during the test. 5.2.5.2. If resistance measurements are used for sample monitoring and/or inspection, the applied voltage must not cause local heating of the test component because of the strong effect of temperature on the sulfuration chemical reaction and local sulfur vapor concentration. The applied voltage shall not be greater than a value that exceeds the smaller of 50 mW of power or 5% of the test sample’s rated power. 5.2.6. Sample Inspection and Testing 5.2.6.1. All components shall be tested for DC resistance and the measurements recorded. 5.2.6.2. Failure criterion 5.2.6.2.1. The change in DC resistance is greater than the nominal tolerance. (For instance, a resistance shift (ΔR) of > ±1% for ±1% tolerance component, or a shift of > ±5% for ±5% tolerance.) 6. DETAILS TO BE SPECIFIED The following details shall be specified in the referencing document: 6.1. Test condition to be used (A or B) 6.2. Number of samples 6.3. Sample nominal resistance value 6.4. Sample tolerance 6.5. Mounted on PCB or not 6.6. Failure criteria 7. DOCUMENTATION Documentation shall contain the details specified and any exceptions: 7.1. Title of the test 7.2. Specimen description, including test fixturing if applicable (photographs may be used) DRAFT – Rev 10 – 13JUN2016 EIA-977 Page 8 7.3. Test equipment used, and date of last and next calibration 7.4. The test condition used 7.5. Values and observations 7.6. Name of operator and test date ECIA Document Improvement Proposal If in the review or use of this document, a potential change is made evident for safety, health or technical reasons, please fill in the appropriate information below and mail or FAX to: Electronic Components Industry Association EIA Standards & Technology Department 2214 Rock Hill Rd., Suite 265 Herndon, VA 20170 FAX: (571-323-0245) Document No.: Document Title: Submitter’s Name: Telephone No.: FAX No.: e-mail: Address: Urgency of Change: Immediate: At next revision: Problem Area: a. Clause Number and /or Drawing: b. Recommended Changes: c. Reason/Rationale for Recommendation: Additional Remarks: Signature: FOR ECIA USE ONLY Responsible Committee: Chairman: Date comments forwarded to Committee Chairman: Date: Electronic Components Industry Association 2214 Rock Hill Road, Suite 265 * Herndon, VA 20170 * tel 571-323-0294 * fax 571-323-0245 www.ecianow.org