What are Planar Microvoids?

Also referred to as "champagne voids," planar microvoids have a devastating impact on solder joint strength because they are actually a planar group of "empty bubbles" within a solder joint. Although no consistent, definitive root cause has yet been found responsible for planar microvoid formation, microvoids are most prevalent in cases where the underlying substrate copper has a very rough topography and excessive immersion silver plating thickness. Microvoid occurrence seems to be related to the extent and composition of organic matter co-deposited in the silver deposit.

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Microvoids Are:		Microvoids Can:
A layer of voids in the ball-to-board interface Located immediately above the intermetallic compound (IMC) layer Less than two mil (50 µm) in diameter Differ from voids that can appear below the IMC layer after reflow More prevalent on solder mask defined pads		Vary depending upon the immersion silver (ImAg) chemistry supplier, the PWB supplier and even from batch-to-batch from a single PWB supplier