Common Corrosion Phenomena On PCB Boards
The corrosion of electronic products mainly includes galvanic corrosion and chemical corrosion. The corrosion caused by the electrolysis principle is called electrolytic corrosion. The common anode conductive wire failure (CAF) and the thick film circuit Ag migration failure in pcb belong to the failure phenomenon caused by corrosion caused by the electrolysis principle.
The circuit on the PCB board consists of a number of wires with potential differences between them. These adjacent wires with potential differences form the cathode and the anode. In addition, flux residues are often left on the processed PCB. They have a certain activity. When the PCB is in a humid environment, when water molecules are deposited on the board, the flux residue is dissolved in water, water and flux. The residue forms an electrolyte, and the Cu on the wire becomes positively charged Cu ions in the electrolyte, which run toward the cathode, and the cathode electrons form Cu atoms deposited on the cathode end, and thus in the shape of branches Growth from the cathode to the anode ultimately leads to product failure, which is the phenomenon of electromigration in electronic products.
2) galvanic corrosion
The galvanic reaction occurs when impure metals or different metals are in contact with the electrolyte solution. Corrosion which is oxidized by the more active metal loss of electrons is called galvanic corrosion and is a kind of electrochemical corrosion.
In the electroless silver plating process of the PCB, the exposed Cu and the Ag deposited first on the Cu surface constitute a galvanic cell in the plating solution. The lively Cu is eroded to form the famous "Jaffany effect." This is typical of galvanic corrosion and is also known as galvanic corrosion in the field of metal corrosion.
Corrosion phenomena on PCB boards are harmful. In addition to the quality damage of the circuit board itself, it will have a certain impact on human health.
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