From Electronics Manufacturing: With Lead-Free, Halogen-Free, and Conductive-Adhesive Materials



Experimental results in Chap. 19 strongly indicate that metal oxide formation resulting from galvanic corrosion of a nonnoble metal at the interface between an electrically conductive adhesive (ECA) and the metal was the main mechanism for the unstable contact resistance of conductive adhesives. In this chapter, various approaches will be used to stabilize the contact resistance.

Several factors, such as moisture absorption and concentration of electrolyte, can affect the rate of galvanic corrosion. One of the critical requirements for galvanic corrosion is the presence of electrolyte solution. Without aqueous solutions, galvanic corrosion does not happen. An ECA formulation with lower moisture pickup should have less condensed water at the interface between the ECA and the nonnoble metal. Such an ECA is expected to show less serious galvanic corrosion at the interface and less increase in contact resistance.

Electrolytes provide electrical conductivity, which is also required for a galvanic corrosion process. Without electrolytes, galvanic corrosion is very slow. The electrolytes in this case mainly come from impurities in the resin. Therefore, purer resins should provide ECAs with better resistance to galvanic corrosion.


Oxygen Scavengers.

Oxygen scavengers are chemicals that are added to water solutions to inhibit oxygen corrosion. As their name implies, they react with dissolved oxygen in aqueous solution. However, to assume that they act as inhibitors of oxygen corrosion by scavenging the oxygen from the water is too simple a view. Their reactions with oxygen are...

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Rust preventives and corrosion inhibitors are lubricants, greases, oils or fluid additives that form a protective film or barrier to prevent corrosion or rust formation.
Dissolved Oxygen Sensors
Dissolved oxygen sensors are used to measure the amount of oxygen dissolved in a unit volume of water. In water quality applications, such as aquaculture (including fish farming) and wastewater treatment, the amount of dissolved oxygen (DO) must be kept high.
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Chemical water treatment equipment mitigates the formation of scale, calcium carbonate deposits, in process water systems such as cooling towers, boilers and heat exchangers by controlled chemical addition and system monitoring.
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Galvanizing services involve the application of a protective zinc coating on metals such as steel or iron. The zinc layer forms a barrier that protects the underlying steel by providing sacrificial or galvanic corrosion protection on the steel surface.

Topics of Interest

4.3 GALVANIC CORROSION 4.3.1 DEFINITION Galvanic corrosion occurs when two metals with different electrochemical potentials or with different tendencies to corrode are in metal-to-metal contact in a...

Four conditions must be present for galvanic corrosion to occur: o Cathode - the more noble or least active metal. This metal has current discharge properties and will be protected from corrosion by...

What piping materials, black steel piping with cast iron/malleable iron fittings vs. galvanized pipe and fittings, have the lowest corrosion rate when used with softened water? Corrosion can occur...

4.3.8 METHODS OF PREVENTION OF GALVANIC CORROSION Select metals, close together, as far as possible, in the galvanic series. Do not have the area of the more active metal smaller than the area of...

Gasket compression and seam contact pressures To achieve a successful gasket joint with little radio-frequency (RF) leakage, low contact resistance between the gasket and flange is an important...

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