Here is the abstract you requested from the IMAPS_2007 technical program page. This is the original abstract submitted by the author. Any changes to the technical content of the final manuscript published by IMAPS or the presentation that is given during the event is done by the author, not IMAPS.
|Preflowed Gold/Tin for Hermetic Packages and Die Attach|
|Keywords: Hermetic Package Sealing, Preflowed Gold/Tin, Void Free|
|Historically the method of sealing hermetic packages has been accomplished using a gold/tin preform that is tack welded to a gold plated kovar lid. New technology has been developed whereby the gold/tin solder is pre-deposited and wetted to the outside area of the lid. This technique offers the following advantages: a) Cost – since the only material required is the gold/tin actually placed on the lid the cost of alloying, casting, rolling, stamping and welding of the preform is eliminated. Less gold can be used generating a large cost savings. b) Yield – often the gold/tin preform that is tack welded develops cracks or slivers that cause non-hermetic seals and thus a yield loss occurs. This new process provides a fully bonded interface between the lid and the gold/tin with optimal uniformity of solder. c) Void free bonding – the pre-wetted gold/tin forms a metallurgical bond on the lid that is free of voids and dewet areas which insures hermeticity. The Gold-N-Flo process has been approved for use in space level devices. d) Process repeatability – the process to pre-wet the gold/tin eliminates placement errors of a tack welded gold/tin lid in the x, y and theta axis which is sometimes a problem. The paper will show by X-ray technology, as well as cross-section analysis, the absence of voiding, the consistency of the solder thickness and the exactness of the solder location in the x and y axis. We will also demonstrate by slide presentation, using this unique system for pre-positioning gold/tin can aid in multiple die bonding, multi level soldering of components and special MEMS soldering applications. Using the same technique we will demonstrate the possibilities of depositing gold/germanium for die attach. We will also discuss the applicability of placing brazing alloys, especially silver/copper eutectic, onto lead frames. This can eliminate the need for inlayed material greatly affecting the cost of the package. Questions regarding other yet unexplored areas of interest will be addressed.|
|K. Huth, Consultant
Semiconductor Packaging Materials Co. (SPM)
Armonk , NY