By Joe Joroski, ST Assembly Test Services Ltd. (STATS) Director of Worldwide Technology Div., Singapore, and Philip Wingate, Design Center Manager, STATS, Tempe, Ariz.
With an increasing demand for next generation BGA packages featuring smaller footprints, greater functionality and higher chip speeds, substrate packaging designers are faced with issues of increased complexity in many areas. Key among these are physical layout, thermal performance, assembly and test. Specialized software tools and processes are available for designing advanced BGAs. Constraints arise, however, in the ability to transfer the design information effectively to substrate suppliers. Design Software Although substrate design software provides flexible file formats, such as DFX, Gerber 274D, 274X and GDSII, it does not allow for documentation to be generated directly in AutoCAD, the documentation format used by most substrate suppliers. This lack of integration between the tools used by substrate suppliers and those required for advanced substrate design results in a high level of manual labor. The labor-intensive nature of the traditional design process often results in cycle times extending over several days, well over the 24-48 hour design cycle times that customers expect. To reduce design cycle time, we examined the traditional substrate design methodology and identified areas in the design documentation process where the manual flow of information could be automated, redundant tasks removed and the skills of its designers more efficiently utilized. After examination, we determined that the design process could be improved by automating the input and output of data and interconnecting key software programs involved in substrate design. Customized Applications The company developed a set of custom-ized applications collectively called "Documentation Generator" that strengthens and automates the traditional substrate design process. Moreover, we achieved these useable, scaleable programs in only six months. Documentation Generator addresses four key areas:
When substrate subcontractors receive design input-such as the netlist-from customers, it can average 2-3 hours to manipulate and enter the data into a design software tool. We recognized the benefit of developing a flexible entry point into the substrate design program, one that would allow improved entry of customer information into the Avanti Encore Packager, as well as provide the ability to run "what if" design scenarios quickly for customers. Feasibility Tests Design feasibility tests can be run on new designs as well as on variations of existing designs. Our designers can now initiate designs in 2-3 minutes as opposed to 2-3 hours. The next area we identified to reduce cycle time was in the generation of customer review drawings or layer stackup files. Normally layer stackup files are manually created in AutoCAD, based on information provided from a substrate design program. The Documentation Generator extracts data from the substrate design program and automatically uploads it into AutoCAD for generation of layer stackup files. These files are then emailed to customers for review. Upon completion of a design, bond diagrams and substrate drawings must be generated. Although the specifications for these documents are contained within the substrate design program, designers must manually recreate the documentation in the appropriate file format for substrate fabrication and manufacturing purposes. STATS' custom interface accesses the necessary information within the substrate design system's database and automatically uploads the appropriate data into AutoCAD for automatic generation of bond diagrams and substrate drawings. As a result, we can create bond diagrams in 20 minutes as opposed to the previous 2-hour average time. Substrate drawings that used to take 2-3 hours to generate can now be produced within 30-40 minutes. Summary Our proprietary integrated process leverages the strengths of advanced substrate design software and AutoCAD while automating the documentation process. Benefits realized include:
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