THE MECHANICAL-BEHAVIOR OF ELECTROPLATED COPPER AT ELEVATED-TEMPERATURES

The tensile behavior of electroplated copper has been measured, using a mini-tensile tester at elevated temperatures and strain rates typical of those found in the processing of electronic components. Plating was from an acid sulfate bath that produces deposits with a columnar grain structure. An embrittlement effect was found when testing was performed at 150 and 290-degrees-C. The effect was strain-rate-dependent at the lower temperature, but not at the higher. Specimens annealed without straining at the same temperatures and then tensile tested at room temperature did not become embrittled. Microstructural studies suggest that the effect is a result of weakening of the columnar grain boundaries and inhibition of their motion. It is speculated that a vacancy mechanism, possibly resulting from chloride in the deposit, may be responsible for the embrittlement.