John Robert Campbell

Assembly and reliability of flip chips with a nano-filled wafer level underfill

The assembly and packaging of electronic devices today is becoming increasingly challenging and demanding because of requirements for smaller, faster and lighter products that provide increasing functionality at low cost. These requirements continue to place greater demands on the electronics industry and mandate improved packaging technology. In part, flip chip packaging technology is the response to these demands and provides a solution to these challenges. While flip chip packaging provides a solution to evolving device requirements, underfill materials are required to improve flip chip device reliability. These resins overcome poor device reliability issues resulting from the mismatch of coefficient of thermal expansion (CTE) between the silicon die and the organic substrate. However, offsetting the gains in device reliability are additional processing steps that adversely affect manufacturing productivity. To compensate for this adverse effect on manufacturing productivity, several new processes, such as wafer level underfill, have been developed. In this paper, we describe the assembly and reliability of flip chips with a nanofilled wafer level underfill (WLU). This approach allows application of the underfill material on the entire wafer, such that many chips can be underfilled simultaneously. Assembly is then carried out with a compatible epoxy flux material. Air-to-air thermal shock (AATS) results and failure mechanisms are described for this novel approach

Development of a novel filled no-flow underfill material for flip chip applications

Flip chip package design has a significant drawback related to the mismatch of coefficient of thermal expansion (CTE) between the silicon die and the organic substrate. This CTE mismatch creates stress on the solder joints during thermal excursions, which reduces the fatigue lifetime of the solder joints. This leads to premature failures of the package. However, package reliability can be improved by the application of an underfill material. In this communication, we report the development of a novel filled no-flow underfill material utilizing proprietary filler technology, which provides a previously unobtainable balance of low CTE, high glass transition temperature (Tg), and good solder joint formation. The fluxing parameters and effect of catalyst level on assembly yield are presented. Assembly results (yield, void area) are presented and compared with commercially available no-flow underfill materials.

The generation and reactions of some diaryl-dihalomethylcarbonium ions☆

Abstract Previously unknown diaryl-dihalomethylcarbonium ions, formed in high yield from the respective alkenes in trifluoromethanesulfonic acid (triflic acid) undergo facile rapid equilibration of aryl groups in triflic acid with a second added aryl component.