Avoiding Microvoids - Several variables interact to create microvoids: flux chemistry, plating thickness, surface roughness, and reflow temperature

摘要

Microvoids are numerous small voids at the interface of a solder joint. Also known as champagne voids, microvoids are less than 40 microns in diameter. They are typically found just above the inter-metallic layers between the copper from the circuit board and the tin from the solder paste. Like all solder voids, microvoids are troublesome when they exist in sufficient number to reduce the cross-sectional area of the joint. In extreme cases, a solder joint can have thousands of microvoids, causing the joint to fail physically and electrically. Engineers have known about microvoids for years. However, the widespread use of high-resolution X-ray inspection equipment has raised awareness of the problem. Indeed, it's possible that microvoids have always been present in solder joints, and inspection methods were simply insufficient to detect them.