Pan Pacific Symposium Conference Proceedings


Methods of Micro Ball Bumping for Wafer Level and 3-Dimensional Applications Using Solder Sphere Transfer and Solder Jetting

Authors: Thomas Oppert, Andrew Strandjord, Thorsten Teutsch, Ghassem Azdasht, and Elke Zakel
Company: Pac Tech
Date Published: 2/14/2012   Conference: Pan Pacific Symposium


Abstract: The miniaturization in electronics is driven by size reduction and cost, however by increasing the technical performance of the device. In regard to wafer level applications flip chip technology is still one of the interconnection methods with the potential of highest integration and cost savings. For applications other than on wafer level, 3-dimensional packages like e.g. camera modules, read-write heads for hard disk drives and various other applications a solder jetting method using solder ball diameters down to 30µm is used.

To explore this potential, cost-efficient solder bumping technologies for the processing of flip chips on wafer level as well as for 3-dimensional devices have been developed and qualified. The research has shown that the underfill process is one of the most crucial factors when it comes to Flip Chip miniaturization for high reliability applications. Therefore, high performance underfill material was qualified initially [1].

Wafer level solder application has been done using wafer level solder sphere transfer process against what solder sphere jetting technology was used for other applications than wafer level. Wafer level solder sphere transfer technology uses a patterned vacuum tooling fixture to simultaneously pick up preformed spheres and transfer them all over the wafer at once. The latter is a technique that drops a preformed solder sphere onto the bond pad while simultaneously reflowing the ball in-place using a laser. This tool has been used for many years in the industry, it is commonly known in the industry as a solder ball bumping tool. For the described work the process was scaled down for processing solder spheres with a diameter down to 30 µm.

Besides presenting the above described methods in detail various applications as well as reliability data of assembled flip chips with micro solder bumps according to MIL-STD883G will be shown.

Key Words: 

Solder Sphere Transfer, Solder Bumping, Solder Jetting, Flip Chip



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