Electrochemically Neutral PA Compounds
Corrosion of the contacts on integrated circuits (ICs) is a major reason for the failure of electronic assemblies. Such contact corrosion occurs when two meals with different electrochemical potential are connected in a conductive manner by an electrolyte (e. g. water of humid air).
In the automotive industry, the housing and components of control units and connectors are usually made of polyamide (PA). To stabilize the PA, systems containing copper iodide or potassium iodide are used. Use of these halogen-containing stabilizers, however, has a major drawback – the iodine and/or bromine ions undergo a complex interaction with the intermetallic phases. Even the copper content of the inorganic stabilizers can cause contact corrosion and attack components made of magnesium or zinc. When such a reaction occurs between plastic and metal, the electronic assembly can fail. In addition to copper-halogen compounds, metal soaps are frequently used as stabilizers in electronics. They, too, can dissociate into ions that migrate in an electric field to the corresponding pole.
To prevent such corrosion phenomena, Akro-Plastic has developed a new product line of electrochemically neutral PA compounds. They contain heat stabilizers and lubricants that contain neither halogens nor metal soaps.
In addition to development of a formulation, verification of the absence of halogens is the decisive point, since carryover during the manufacturing process can result in unwanted contamination of the compound. The cooling water for the extruded strand can be a source of impurities. It has been determined that cooling water with copper iodide or potassium iodide impurities actually contaminates what is intrinsically an electrically neutral product, making it unusable. This source of contamination can be ruled out if each system has its own closed cooling water circuit.
Article: Preventing Galvanic Corrosion Reliably, Kunststoffe International 2015/10
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