Original Date: 01/23/1995
Revision Date: 01/18/2007
Best Practice : Model Based Design and Virtual Prototyping
Sandia National Laboratories (SNL) has developed a Model Based Design team to provide engineering personnel with the capability to design products and develop or improve processes using computer generated virtual prototypes. Virtual prototyping consists of creating new products within a computer and analyzing them for form, weight, size, and critical mechanical, electrical, and thermal properties before producing a physical product. Benefits of virtual prototyping include the ability to observe the design in three dimensions, the ability to assess trade-offs within the product and processes, reduced design time, and a reduction in pre-production hardware. Model based design often requires a mesh or solid based modeling system for spatial-type analysis. One advantage of this model is that it can be used for scientific analysis as well as design.
SNL used model based design to create a virtual prototype for the output module from a Modular Adaptable Controller-based weapon programmer design. The output module consisted of eight power Metal Oxide Silicon Field Effect Transistors and a voltage level-shifting ASIC. The virtual prototype used an electronic circuit model, solids model, and a 46,000 element thermal mesh. Commercial modeling software was coupled to computer code developed at Sandia to study thermal management issues. This was used to predict the circuit behavior in reaction to internally- generated heat over an eight second operational lifetime. Trade-off analysis performed with the virtual prototyping proved that multiple substrates, including isolating the ASIC on a single alumina substrate, was preferable to a single substrate of aluminum nitride. Although this option created the added expense of intersubstrate wire bonding, it protected the ASIC from excessive heat, allowing the device to perform as desired for the entire test.
Model based design has been used in other areas to reduce costs and shorten cycle times. Sandia develops Synthetic Aperture Radar antennas using parametric and virtual prototyping methods. Traditionally this process would require almost a year of iterative prototypes and calibrations. Using model based design to create a solid model reduced this time to two to four weeks. The design was verified within the computer, and a physical solid model was then created using stereolithography. The plastic model of the radar dish was coated with copper; calibration was performed, allowing the final design to go into production in less than four weeks.
Sandia also applies model based design in the use of stress analysis tools. Allied Signal/Kansas City Division (a manufacturing partner of Sandia) analyzed certain types of lead forming to determine if tighter radius lead bends could be used to increase component density, thereby allowing for flexibility in component spacing problems.
Sandia and Allied Signal are using model based product realization to reduce costs and cycle times. They are currently using models to evaluate thermal management and stress distributions and are also programming wire bonding equipment on virtual components to reduce setup times and errors during programming.
For more information see the
Point of Contact for this survey.