Showing papers by "Fred Barlow published in 1999"

UBM Formation on Single Die/Dice for Flip Chip Applications

Abstract: Flip Chip bonding is well known to have many advantages and it has been used for many applications in the electronic packaging industry to achieve high I/O count and high electrical performance. Currently, Under Bump Metallurgy (UBM) is one of the most important methodologies to obtain reliable connections in the solder bump structure of the Flip Chip. UBM can be deposited on wafers through various techniques such as sputtering, evaporation, or electroless plating. However, these processes are only suitable for very high volume production, but in general, they are not practical for use in prototyping stages or in low volume production, especially where the entire wafer is not readily accessible. This paper reports a low cost UBM deposition process for use on a single die or a number of dice. This new technique will allow Flip Chip bonding to be based on a single die and will be suitable for low volume applications. The UBM deposition process on aluminum pads of a single die consists of two major processing steps. Firstly, step one temporarily attaches the die to a substrate using an amorphous thermoplastic adhesive. Such adhesives may be cleanly removed from the die backside, with suitable solvents, after the UBM deposition is achieved. The second step is to deposit the UBM layer using nickel electroless plating. A zincation process is performed to pretreat the aluminum surface prior to the plating process. This paper will discuss in details the procedures used in each process step as well as the experimental results and the analysis of data for the newly developed process.

The utilization of polymer thick film (PTF) and flex technologies for low cost Power electronics packaging of DC/DC down converters

Abstract: Electronic power converters have been designed, produced, and disseminated to the market in mass quantities utilizing a number offabrication techniques; ranging from standard Printed Circuit Board (PCB) technologies for low cost applications, to conventional thick film on ceramic, to Direct Bond Copper (DBC) approaches for high power, higher cost applications Each of these approaches holds a share of the power packaging market, but they all demonstrate a limitation to conventional 2D flat board thinking PCBs, thick films, and DBCs are all technologies which restrict, for the most part, circuit and package designs to two dimensional boards The one potential pathway into the third dimension is through the use of multilayers ; an approach which becomes increasingly difficult with each additional layer added beyond the first, and with the exception of high performance solutions is typically cost prohibitive for the majority of applications This paper will demonstrate the feasibility and viability of an alternative low cost power packaging option which utilizes familiar industry technologies in a unique manner; flexible polymer substrates Flex technology employs industry standard PCB and/or thick film processes, offers the lower cost, higher performance solutions inherent with the majority of polymer plastics, and as a final bonus, essentially frees the designer to more efficiently utilize all three dimensions of space The researchers have demonstrated the feasibility of this low cost alternative solution through the fabrication and testing of Integrated Power Modules (IPMs) which utilize flexible polymer substrates in conjunction with both surface mount and bare dice These DC/DC power converters transform 120V/240V inputs to 9V, 7 Watt outputs, and illustrate through their unique geometrical design the miniaturization advantages of fully utilizing the 3D space offered by flex circuitry