Abstract
The presence of solder flux residue on the Printed Circuit Board Assembly (PCBA) surface compromises the corrosion reliability of electronics under humid conditions and can lead to degradation of the device’s lifetime.
In this work, the effect of solder mask morphology and hygroscopic residues were studied towards assessment of their influence on the water film formation on the PCBA surface. The in-situ observations of water layer build-up was studied on the solder mask substrates as a function of surface finish and residue type (adipic and glutaric acids). The effect of solder flux residues was described in terms of their varying hygroscopicity defined by chemical structure and test temperature. The climatic testing of two acids was performed under relative humidity (RH) conditions varying from 30% to ~99% at 25˚C and 40˚C using gravimetric water vapour sorption/desorption and electrochemical impedance methods. The corrosivity of WOAs was evaluated via leakage current measurements using surface insulation resistance (SIR) comb patterns. The corrosion studies were correlated with the hygroscopicity studies.
The results show that the water layer formation depends on the PCBA surface topography and the type of post-production residue present on the surface. Moreover, the hygroscopic nature of typical flux residue depends on its chemical structure and temperature. An increase of temperature shifts the critical RH level for water vapour absorption towards lower RH range accelerating the formation of well-conductive electrolyte and the occurrence of ionic-induced electrochemical migration (ECM).
In this work, the effect of solder mask morphology and hygroscopic residues were studied towards assessment of their influence on the water film formation on the PCBA surface. The in-situ observations of water layer build-up was studied on the solder mask substrates as a function of surface finish and residue type (adipic and glutaric acids). The effect of solder flux residues was described in terms of their varying hygroscopicity defined by chemical structure and test temperature. The climatic testing of two acids was performed under relative humidity (RH) conditions varying from 30% to ~99% at 25˚C and 40˚C using gravimetric water vapour sorption/desorption and electrochemical impedance methods. The corrosivity of WOAs was evaluated via leakage current measurements using surface insulation resistance (SIR) comb patterns. The corrosion studies were correlated with the hygroscopicity studies.
The results show that the water layer formation depends on the PCBA surface topography and the type of post-production residue present on the surface. Moreover, the hygroscopic nature of typical flux residue depends on its chemical structure and temperature. An increase of temperature shifts the critical RH level for water vapour absorption towards lower RH range accelerating the formation of well-conductive electrolyte and the occurrence of ionic-induced electrochemical migration (ECM).
| Original language | English |
|---|---|
| Title of host publication | Proceedings of the European Corrosion Congress (EUROCORR 2017) |
| Number of pages | 12 |
| Publication date | 2017 |
| Article number | 98145 |
| Publication status | Published - 2017 |
| Event | European Corrosion Congress (EUROCORR 2017) - Prague, Czech Republic Duration: 3 Sept 2017 → 7 Sept 2017 |
Conference
| Conference | European Corrosion Congress (EUROCORR 2017) |
|---|---|
| Country/Territory | Czech Republic |
| City | Prague |
| Period | 03/09/2017 → 07/09/2017 |
Keywords
- Water layer formation
- Flux residue
- Surface morphology
- Humidity
- Reliability of electronics