Abstract:There are very few studies that have investigated directly the effect of an oxide film on tin whisker growth, since the 'cracked oxide theory' was proposed by Tu in 19941 . The current study has investigated the effect of an electrochemically produced oxide on tin whisker growth, for both Sn-Cu electrodeposits on Cu and pure Sn electrodeposits on brass. X-ray photoelectron spectroscopy (XPS) has been used to investigate the effect of the applied electrochemical oxidation potential on the oxide film thickness. … Show more
“…For the thermally treated sample, the intermetallic compound was relatively uniform in thickness, whilst that present in the untreated control sample was much less regular and varied greatly in thickness, which is consistent with previous analyses of Sn-Cu deposits stored at room temperature. 30,31 The morphology of the IMC present within the ALD processed Sn-Cu coating from batch 4 (Fig. 12c) was similar to that of the thermally processed sample.…”
Section: Thermally Treated Control Samples (Batch 13)mentioning
confidence: 63%
“…These results suggest that the ALD coating itself may act as a physical barrier to impede whisker growth, as shown by previous studies that have investigated the influence of applied surface oxides on whisker growth. 31,35,36 ALD processing may, therefore, provide greater long-term whisker mitigation than thermal treatment alone, which may simply retard the onset of whisker growth. Longer-term monitoring of whisker growth will more clearly elucidate the benefits of the ALD coating.…”
Section: Summary Of Whisker Growth Trialsmentioning
This paper presents the results of a research program set up to evaluate atomic layer deposition (ALD) conformal coatings as a method of mitigating the growth of tin whiskers from printed circuit board assemblies. The effect of ALD coating process variables on the ability of the coating to mitigate whisker growth were evaluated. Scanning electron microscopy and optical microscopy were used to evaluate both the size and distribution of tin whiskers and the coating/whisker interactions. Results show that the ALD process can achieve significant reductions in whisker growth and thus offers considerable potential as a reworkable whisker mitigation strategy. The effect of ALD layer thickness on whisker formation was also investigated. Studies indicate that thermal exposure during ALD processing may contribute significantly to the observed whisker mitigation.
“…For the thermally treated sample, the intermetallic compound was relatively uniform in thickness, whilst that present in the untreated control sample was much less regular and varied greatly in thickness, which is consistent with previous analyses of Sn-Cu deposits stored at room temperature. 30,31 The morphology of the IMC present within the ALD processed Sn-Cu coating from batch 4 (Fig. 12c) was similar to that of the thermally processed sample.…”
Section: Thermally Treated Control Samples (Batch 13)mentioning
confidence: 63%
“…These results suggest that the ALD coating itself may act as a physical barrier to impede whisker growth, as shown by previous studies that have investigated the influence of applied surface oxides on whisker growth. 31,35,36 ALD processing may, therefore, provide greater long-term whisker mitigation than thermal treatment alone, which may simply retard the onset of whisker growth. Longer-term monitoring of whisker growth will more clearly elucidate the benefits of the ALD coating.…”
Section: Summary Of Whisker Growth Trialsmentioning
This paper presents the results of a research program set up to evaluate atomic layer deposition (ALD) conformal coatings as a method of mitigating the growth of tin whiskers from printed circuit board assemblies. The effect of ALD coating process variables on the ability of the coating to mitigate whisker growth were evaluated. Scanning electron microscopy and optical microscopy were used to evaluate both the size and distribution of tin whiskers and the coating/whisker interactions. Results show that the ALD process can achieve significant reductions in whisker growth and thus offers considerable potential as a reworkable whisker mitigation strategy. The effect of ALD layer thickness on whisker formation was also investigated. Studies indicate that thermal exposure during ALD processing may contribute significantly to the observed whisker mitigation.
“…In previous studies by the current authors [24,25], it was observed that an electrochemically formed tin oxide greatly reduced the growth of whiskers and that increasing the thickness of the tin oxide film promoted further reductions in whisker growth.…”
Section: Introductionmentioning
confidence: 73%
“…All surface modification treatments were carried out immediately after electrodeposition of the Sn or Sn-Cu coating using, if required, a Solartron SI 1286 Electrochemical Interface potentiostat and the 3-electrode cell described previously [24,25].…”
Section: Surface Modification Treatmentmentioning
confidence: 99%
“…The thickness of the conversion coating and the microstructure of the electroplated Sn-Cu coating was investigated using a FEI Nova 600 Nanolab Dual Beam focussed ion beam milling scanning electron microscopy (FIB-SEM) using the method previously described [25].…”
Section: Characterisation Of Conversion Coatingsmentioning
There are very few studies that have investigated directly the effect of an oxide film on tin whisker growth, since the 'cracked oxide theory' was proposed by Tu in 1994. The current study has investigated the effect of both a molybdate conversion coating and a tungstate conversion coating on tin whisker growth from Sn-Cu electrodeposits on Cu, and compared it with that from an electrochemically-formed oxide produced from a potassium bicarbonate-potassium carbonate electrolyte. X-ray photoelectron spectroscopy (XPS) has been used to investigate the effect of both immersion time and applied potential on the thickness and composition of the oxide film. The XPS studies show that the oxide film formed using either of the conversion coating baths is significantly thicker than that produced from the potassium bicarbonate-potassium carbonate bath.Initial observations suggest that both the tungstate-based conversion coatings and the molybdate-based conversion coatings significantly reduce whisker growth by over 80 % for all conversion coating systems compared with a native air-formed oxide and provide improved mitigation compared with the electrochemically formed oxides previously investigated.
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