The present method used by industry for placing and attaching solder balls to wafers and BGA packages produces unacceptable production yields because the existing process requires the use of flux. When the flux liquefies during 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 created. Also, flux residues are not always completely removed during post solder cleaning processes due to these voids and high resistance shorts and/or corrosion may result.
The demand for flip chip technology and BGA devices has steadily increased and more efficient high volume manufacturing assembly methods need to be developed to keep pace. Ball attachment production yields also need to be improved so that the cost of manufacturing can be reduced. In response to this challenge, SST has developed a new and more cost effective method of placing and attaching solder balls to wafers, to plastic and ceramic packages for BGA application. The new method virtually eliminates the problems associated with the currently used methods.
The SST process utilizes specially designed tooling for loading and precisely holding solder balls in the required position during processing. The soldering operation is performed without flux in a controlled atmosphere. As a result, presolder paste screening and post solder cleaning operations are not required. The SST ball attachment process for wafers is performed at the wafer level prior to singulation thereby maximizing production capability. The ball attachment process for BGA packages is also very efficient.
Richard Ramos is the Executive Vice President and Division General Manager of Scientific Sealing Technology. Richard brings over 40 years experience in the design of process control equipment and instrumentation systems. Richard received his BS/MS EE from Brown Engineering College and an MBA from Rutgers University.
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