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ME60 Troubleshooting Guide V1.0 (VRPv8)

This document provides the maintenance guide of the device, including daily maintenance, emergence maintenance, and typical troubleshooting.
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Huawei uses machine translation combined with human proofreading to translate this document to different languages in order to help you better understand the content of this document. Note: Even the most advanced machine translation cannot match the quality of professional translators. Huawei shall not bear any responsibility for translation accuracy and it is recommended that you refer to the English document (a link for which has been provided).
Handling Corrosion and Vulcanization Issues for devices

Handling Corrosion and Vulcanization Issues for devices

Sulfidation corrosion, also called creep corrosion, resulted from vulcanization of copper, which causes a board failure stemming from short circuits. This section describes the principles, causes, and measures of creep corrosion.

Creep Corrosion

Creep corrosion is resulted from vulcanization of copper, which causes a board failure stemming from short circuits. This section describes the appearance and principles of creep corrosion.

Creep Corrosion



Creep Corrosion Principles
  1. Exposed copper is prone to creep corrosion.

    Since PCB surface has micro holes and is prone to corrosion of water or other pollutants, the copper surface of a PCB will react with sulfur-containing materials (as shown in research reports, elemental sulfur, hydrogen sulfide, organic sulfides and sulfur alcohol can react with copper to generate cuprous sulfide) and generate sulfide.

  2. Copper oxide does not move. However, copper sulfide and chloride will because they are soluble in water. In this way, copper sulfide and chloride are extendable on surface driven by the concentration gradient and will extend from the high-density area to the low-density area.
  3. Sulfide is semi-conductive. Therefore, short circuit does not occur in a short period. However, with the increase of sulfide, the resistance decreases and finally causes short circuit. In addition, the resistance of sulfide varies with humidity and may change sharply from 10 Mohm to 1 ohm.
  4. Humidity is an important factor that aggravates the creep corrosion. When the relative humidity is 50% (or 65% as recorded in some documents), a water film is generated on the PCB surface. In this case, sulfide (such as hydrogen sulfide and sulfur dioxide) will react with the water to generate a weak acid that will decompose copper oxide and expose the copper PCB surface. In this way, the exposed copper surface will continue to be corroded. The generation of cuprous sulfide is exponentially increased with the increase of relative humidity. In other words, copper corrosion accelerates in a humid environment.

Standards and Measurement Methods for the Sulfurous Environment

The recommended PTN device running environment is that the monthly hydrogen sulfide density must be no more than 0.10 mg/m3.

Standards for the Sulfurous Environment
  1. Recommended device running environment: The monthly hydrogen sulfide density must be no more than 0.10 mg/m3.
  2. In the industry, requirements on electronic products vary with vendors. The monthly hydrogen sulfide density must be no more than 5 ppb.

    As recommended by HP, the monthly hydrogen sulfide density of the electronic product running environment must be no more than 0.0042 mg/m3 (2.8 ppb).

    As recommended by IBM, the monthly hydrogen sulfide density of the equipment room must be less than 3 ppb, that is, ISA G1.

Measurement Methods
  1. Corrosion analysis using test copper bars (recommended, low cost but long term and low precision)

    According to the ISAS71.04-1985 standard, perform a qualitative assessment on the corrosive gas in the environment. The environment result can be obtained after one month.

  2. Inspection report from a third inspection institute SGS (high cost, but short term and high precision)

    A pump with various liquids or tubes is used to absorb gas sample of the environment and different compounds are absorbed by those liquids or tubes for analysis. With the content of objective compound and the total gas volume, the density of the objective compound in the environment can be obtained.

Sulfidation Corrosion Cause

This section describes sulfidation corrosion causes.

  • The decoration materials of the equipment room contain too much sulfur, which volatilizes to corrode devices.
  • The equipment room is directly connected to the drain. For example, the equipment room floor is directly connected to the drain or the air inlets of air conditioners are near to the drain.
  • Batteries are located in the same room with cabinets and the batteries leak acid, corroding devices.
  • The external environment contains too much sulfur. For example, the equipment room is near to a large mine site, chemical plant, garbage disposal field.

Check on Sulfidation Pollutants in the Equipment Room

If sulfidation corrosion is found on any board at the site, check the environment according to the following checklist.

No.

Check Item

Check Result

Inside the equipment room

Temperature

°C

  

Humidity

Relative humidity

  

Decoration materials

Check whether the equipment room decoration project is just finished, whether the used decoration materials have sulfur risks, and whether vulcanized rubber and foaming cotton are installed inside the ceiling or floor. It is recommended to use eco-friendly materials.

  

Battery

Check whether the battery string and cabinets are located in the same room. If yes, external circulating for the equipment room should be enabled. In addition, move the battery string to another independent room and check whether battery leakage is found.

  

Drain

Check whether the equipment room is directly connected to the drain, for example, the equipment room floor is directly connected to the drain or the air inlets of air conditioners are near to the drain.

  

External environment

Large mine site

Check whether there is any large coal mine, oil field, or sulfur iron mine that is less than 15 km away from the telecommunications room.

  

Chemical plant

Check whether there are non-ferrous metal smeltery, kaolin processing plant, rubber plant, tire plant, sulph processing plant, effluent treatment plant, power plant, paper mill, and printing and dyeing mill within 5 miles of the equipment room. List the name in the case of uncertainty.

  

Large consumption of coal, diesel oil, and gasoline

Check whether there are many diesel engines, gasoline engine (such as underground parking area), or barbeque booths that use coal near the equipment room.

  

Garbage disposal field

Check whether there are effluent treatment field, garbage burning field, large garbage recycling station, and civilian cesspool/marsh gas tank near the equipment room.

  

Others

The hydrogen sulfide (H2S) often exists in the operations of marsh, ditch, tunnel, garbage clearance, and feces clearance, or exists in natural gas, volcanic exhalation, and mineral spring.

  
NOTE:
Take pictures when checking the site environment.

Sulfidation Corrosion Case

This section provides a sulfidation corrosion case and describes how to handle such a problem.

Corrosion Symptom

In July 2011, some boards were sent back from a specific site. On the board surface, all holes and exposed copper areas are black and cannot be cleaned. This symptom is determined as sulfidation corrosion after inspection.

Problem Analysis

Huawei checked the equipment room at the site and concluded that:

The equipment room used massive black rubber mat with pungent odor. Based on the material component test result, these black rubber mats contain sulfur and will volatilize sulfur gas (such as hydrogen sulfide and sulfur dioxide). Under a certain temperature and humidity, the boards are prone to sulfidation corrosion.

The following figure shows the test result of the black rubber mats.

Test results of other materials in the equipment room:
  • Fireproof mud and bricks: No sulfur is found and no sulfidation corrosion risk is involved.

  • Heat insulation cotton: No sulfur is found and no sulfidation corrosion risk is involved.

Problem Identification

To confirm whether sulfur density in the equipment room is out of limits, copper bars are used to test sulfur content in the equipment room. The following figures show the test result.



According to the test result, the sulfur content of two equipment rooms at the site severely exceeds the standard and reaches the G3 and GX levels respectively.

Solution

Replace the black rubber mats used in the equipment room.

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Updated: 2019-06-11

Document ID: EDOC1000175918

Views: 14609

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