Void-free, flux-free process for placement and attach of solder balls

摘要

As production of wafer bumping, chip scale packages (CSPs), micro ball grid array (μBGA) and flip chip packages increases, so does the need for cost-effective and high yield production. The present method can produce unacceptable yields because it requires the use of flux; when the flux liquifies during the reflow soldering operations, the bonds between the flux, balls and pads are destroyed and the balls are free to move. Defects, such as vacancies, bridging of adjacent balls, loss of positional accuracy and voids, are thus created. Flux residues are also not always completely removed during post-solder cleaning processes because of voids, and high resistance shorts and/or corrosion may result.