October 1, 2005
By Sherman Ikemoto
| Web-based model development means sensitive IC design never leaves the company.
Agilent has long used thermal simulation tools to produce detailed models of packages that accurately predict the temperature of various elements within the design for a variety of conditions. More recently, the company has found it can save a considerable amount of time by using Flomerics’s new Internet-based process for developing behavioral compact models. The process helps predict temperatures at critical points such as the junction, case, and board.
“We can produce accurate, validated compact models of our new components in a matter of minutes,” said Scott Burton, package analysis engineer for Agilent’s Imaging Solutions Division in Fort Collins, CO. “The result is that we can generate simulated thermal characterization data based on JEDEC standard tests in much less time than was required with previous approaches. As an added feature, we can now provide our customers with models that they can drop into a full thermal design simulation. This allows them to model the behavior of the component in their system environment with minimal effort.”
Need to Supply Thermal Design Information For three decades, Agilent has designed and manufactured complex, high-performance application-specific integrated circuits (ASIC) for applications including networking, computing, and imaging. Agilent offers state-of-the-art hierarchical design methodology and design-for-test capability, and has an outstanding track record of first-pass success in the design and manufacture of these chips. These strengths, combined with an extensive IP portfolio, facilitate rapid integration of quality ASICs. Burton says that thermal data is required for most of the company’s products because it’s useful for engineers to have access to thermal characterization data based on standard tests such as EIA/JEDEC standard JESD51-6 (the integrated circuit thermal test method of environmental conditions–forced convection). In the past, the majority of Agilent’s networking and computing ASICs were supplied to customers who were involved in the design process from start to finish, and those customers had complete access to component design information and decisions. This close relationship, in many cases, eliminated the need to provide standardized thermal design information. However, Agilent is now addressing a broader group of customers and needs to provide thermal design information in a more universal format. Boundary Condition-Independent ModelsAgilent engineers have used Flomerics’s Flotherm simulation for system- and component-level thermal analysis. At Agilent, detailed package models are used to generate simulated standard thermal characteristics and the thermal design information needed by customers integrating Agilent components into their systems.
“Creating this design information has its difficulties,” Burton said. “Detailed models can often be difficult for customers to use because the ‘conduction only’ software models cannot be easily integrated into computational fluid dynamics (CFD) system simulations and even when they can, the complexity of detailed models can often computationally overwhelm system simulations. Distilling information from these detailed models into something simple and useful for customers can create its own problems,” Burton continued. “Simple resistor models are not universally useful since each customer may need this information tailored to their own system and boundary condition information.” “Flomerics has introduced a very easy and simple method of creating either detailed or Delphi models from what they call JEDEC Library Wizards,” Burton said. “One can simply select the appropriate JEDEC package outline from a dropdown list, input the power and the die size and occasionally a few additional pieces of information for certain package sizes. The website then generates a compact or detailed thermal model of the component.”
The JEDEC library wizard on Flomerics’ Flopack website contains built-in common industry manufacturing and design rules used by most IC component suppliers. These results will generate package models from a reduced set of input parameters. A detailed Flotherm study that correlated Delphi models to physical testing results showed that it yields less than 10 percent error for the wide range of environments that were examined, including single bare package in natural convection, single package with heatsink in natural convection, single bare package in forced convection at two meters per second, single bare package under impingement flow with a jet velocity of one meter per second, and package with neighboring components at forced convection at two meters per second. In each case a four-layer (2S2P—two signal, two power plane) PCB with a size of 100mm by 100mm was used. The ambient temperature was +30°C for the natural convection environments and +25°C for the forced convection environments. Implementing Flopack as a Web application makes it possible to implement new package models or update older ones by simply changing a single copy of code on a central Web server. Flopack supports all major package styles, sockets, PCBs and heatsinks. Further validation of Flopack models is ongoing at Flomerics. The Power of the Model “When we create a new product, whether it is designed for the general market or a single customer, we always start with a detailed model,” Burton said. “We’re developing a process to validate these models by importing them into Flotherm and adding them to a model of the board that we use for electrical testing. The validated models are then added to a model of the board specified in EAI/JEDEC standard EAI/JESD51-3. The boards specified in this standard have very specific requirements for stock material, board outline, and trace design.” Using a model of the board that it has previously validated, Agilent can accurately simulate standard tests that determine parameters (i.e., junction-to-top-center of package or junction-to-board) that it provides to customers on a data sheet. It saves both the expense and lead time that would otherwise be required to build, assemble, and test JEDEC standard boards. “The value of creating a compact model goes far beyond the ability to create data sheets more quickly and inexpensively,” Burton continued. “If all we provided to our customers was data sheets, in many cases they would come back to us with questions such as: ‘how did you obtain this particular number?’ or ‘can I use this number in my application environment?’ ” Burton explained Agilent can now provide customers that use Flotherm with the boundary condition-independent compact model for insertion into the system model. It saves time and allows them to obtain information under any conditions as opposed to the “limited information provided by the JEDEC standard tests.” “While the compact models that we create are specific to Flotherm,” Burton concluded, “a large part of the industry uses them, including all Agilent customers, so up to now there has been no compatibility or data translation issues. Finally, another advantage of this approach is that by providing nearly every significant piece of thermal information, the need to share sensitive IC design information, in most cases, is eliminated.” Sherman Ikemoto is the business development manager at Flomerics. He has 6 years of electronics physical design experience at General Dynamics and 10 years of sales, marketing and business development experience at Flomerics. He has a BS in mechanical engineering from San Jose State University and a MS in mechanical engineering from the University of Santa Clara. You can send an e-mail about this article clicking here. Please reference “Thermal Design, November 2005” in your message. Product Information Agilent Technologies | |||||||||
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