Electronics Assembly Knowledge, Vision & Wisdom
Dissolution of Metal Foils in Common Beverages
In this study the dissolution of aluminum, copper, gold, iron, lead, nickel, SAC305 solder, silver, tin and zinc was examined.
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Corrosion, Contamination, Data Acquisition, ESD and EOS, Inspection, Measurement, Profiling, Reliability, R&D, RFID, Solder Defects, Test, Tombstoning, X-ray and more.
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Authored By:
Bev Christian, Nancy Wang, Mark Pritzker, Daniella Gillanders, Gyubok Baik, Weiyi Zhang, Joanna Litingtun and Brian Kim
Blackberry and the University of Waterloo
Waterloo, Ontario, CANADA

Summary
How susceptible are the metals used in modern electronics manufacturing to corrosion by common beverages? This is a question of interest, especially to manufacturers, retailers and to a certain extent end customers. In this study the dissolution of aluminum, copper, gold, iron, lead, nickel, SAC305 solder, silver, tin and zinc was examined. Individual foils of these materials were fully immersed in one of sixteen chosen beverages and heated for 3 days at 40 degrees C. The resulting solutions were analyzed using ICP-OES. The data were examined in light of the known pH, conductivity and ionic contents of the beverages, determined in previous work. Conclusions about the relative susceptibility to corrosion of the various metals and the corrosive power of the different beverages are made.

Conclusions
Although the attempt to develop one master predictive equation for dissolution of the metals studied has failed, some general trends can be made from the observed results.

Two keys factors are pH and the concentration of carboxylic acids. Both must be taken into account to understand why juices were usually more corrosive than carbonated beverages.

Tomato juice is more like orange juice in terms of the order of solubilities of metals in each beverage. Among the carbonated beverages the following similar pairs were found: beer and Pepsi, ginger ale and Sprite and last, Coke and Dr. Pepper. Not surprisingly tea and coffee, both fairly high pH and low concentrations of anything were fairly similar in their dissolving power.

The only metal ions that would normally be expected to be in beverages are zinc and iron. Iron is found in Pepsi and tomato juice at 156 and 10 mg/mL, respectively. Zinc is in some carbonated beverages at about 20 mg/mL, while only at 4 to 10 mg/mL for other beverages. [12] As a result, only the initial iron concentration in Pepsi has been subtracted from the value measured for the dissolved zinc. This revised value is what is shown in Table 6. None of the other amounts are enough to influence the trends discussed and thus have been ignored with respect to the values in Table 6.

In decreasing likelihood of dissolution, the following overall trend was observed: Zn>Fe>Pb>Ni>Cu>Al>Sn>Ag>Au. Except for aluminum, the trend more or less follows the oxidation EMF values for metal to lowest oxidation state.

Initially Published in the IPC Proceedings

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