Evaluating the Performance of 2-Mercapto-5-Benzimidazolesulfonic Acid in Controllable Electro-Healing Cracks in Nickel

Abstract

The performance of 2-Mercapto-5-benzimidazolesulfonic acid (MBIS) in a Watts bath in crack electro-healing was investigated. Potentiostatic and galvanostatic voltammetry, current efficiency measurements were performed for electrochemical investigation. The morphology of the healed crack indicates that the healing crystals grow in a controllable manner with the addition of MBIS under forced convection with the healing crystals fill preferentially in the crack tip to the crack sidewalls. No obvious defects were observed along the interface between the substrate and the healing crystals, which is attributed the much higher current efficiency of MBIS. Annual-ring like defects are observed but with a much longer width compared with PEI. The formation mechanism of annual ring is discussed. Possible approach to get defect-free crack healing is also prospected.

The Combination Addition of 2-Mercapto-5-benzimidazolesulfonic Acid and Thiourea to Watts Bath in Controllable Electro-Healing Cracks in Nickel

“…6b), which is analogous to the active growth in the intervals between the "rings" with the only addition of MBIS. 8 It is deduced from EDS results that there are additive inclusion in the passive growth, as the case when only MBIS is added to the healing solution. 8 This additive inclusion has also been reported during Cu damascene process.…”

“…8 It is deduced from EDS results that there are additive inclusion in the passive growth, as the case when only MBIS is added to the healing solution. 8 This additive inclusion has also been reported during Cu damascene process. 22 The EDS results support our partition on the healed crack morphology.…”

“…5a for comparison. 8 Generally speaking, the healing crystals all grow following a controllable growth mode by either the addition of only MBIS or MBIS + TU. Further, no defects are observed along the interface between the healing crystals and the substrate with the additional addition of TU to the MBIS-added healing solution as it is expected.…”

“…7 A few inhibitors, including polyethyleneimine (PEI), PEI + saccharin and 2-Mercapto-5-benzimidazolesulfonic acid (MBIS) have been added to the conventional Watts Bath to explore their behavior in controllable electro-healing cracks in pure nickel. [7][8][9] It is deduced that with the single addition of inhibitor (MBIS) or inhibitors (PEI + saccharin), the growth mode of healing crystals is controlled by the magnitude (intensity) of inhibition of the inhibitor(s). When the magnitude is small, as the case for PEI under natural convection, the healing crystals will follow a general growth mode; when the inhibition magnitude is strong (forced convection for PEI or PEI + Saccharin), controllable growth mode will be achieved.…”

“…Although at a given concentration, the cathodic current efficiency with the addition of MBIS is significantly higher than that of PEI, therefore eliminates the formation of visible defects along the interface between the healing crystals and the substrate, annual-ring like defects still exist. It is believed 8 that with the addition of single inhibitor or inhibitors, the formation of annual-ring like defects is unavoidable.…”