Emerging Technologies Conference Proceedings


FLUX-FREE PROCESS FOR PLACEMENT AND ATTACH OF SOLDER BALLS TO WAFERS, FLIP CHIPS AND ALL BGA PACKAGES

Author: RICHARD RAMOS
Company: SCIENTIFIC SEALING TECHNOLOGY
Date Published: 11/16/1998   Conference: Emerging Technologies


Abstract: 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.



Members download articles for free:

Not a member yet?

What else do you get when you join SMTA? Read about all of the benefits that go along with membership.

Notice: Sharing of articles is restricted to just your immediate work group. Downloaded papers should not be stored on an external network or shared on the internet.


Back


SMTA Headquarters
6600 City West Parkway, Suite 300
Eden Prairie, MN 55344 USA

Phone +1 952.920.7682
Fax +1 952.926.1819