Up to a 0.0008" reduction in copper (Cu) barrel plating was found with multiple exposure thermal stress testing in accordance with IPC-TM-650, Method 2.6.8, modified. A typical original equipment manufacturer (OEM) specification for printed circuit board specimens specifies 3 or 6 thermal stress cycles. For boards with an initial Cu plating thickness of 0.0010" to 0.0015", this reduction of 0.0008" is significant and may contribute to cracking in Cu plating, especially at the through-hole and pad intersection. This report is the first in a series required to determine if copper dissolution does indeed occur in thermal stress testing and furthermore, to determine if this dissolution has any direct relevance to printed circuit board performance and reliability. The ramifications of this research may ultimately require specification changes.
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