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Thermal Simulation Reduces Cost of Stacked Module Potting Compound 50%

C-MAC Reduces Cost of Stacked Module Potting Compound by 50% Using FloTHERM Thermal Simulation Software

July 2008

C-MAC MicroTechnology used Flomerics' FloTHERM thermal simulation software to determine that the thermal requirements of a stacked module could be met with a potting compound that cost only half the amount of the default choice. "Our engineer simulated the junction temperatures of the devices in the stacked modules while using three different potting compounds," said Bob Hunt, Head of Engineering for C-MAC. "Simulation was much faster and less expensive than the alternative of building and testing prototypes."

C-MAC, an electronics design and manufacturing company based in SouthDenes, Great Yarmouth, United Kingdom, recently developed a stacked module for a critical defense application. Prior to building prototypes, C-MAC engineers performed thermal simulation on the initial concept design and discovered that junction temperatures on the module ranged up to 125°C, well above the 100°C maximum. They realized they needed a potting compound to reduce thermal resistance and wanted to select the least expensive formulation that would meet the thermal requirements of the application.

"Without simulation we would have been faced with two unattractive alternatives," said C-MAC senior engineer Jonathan Crossley. "We could have undertaken a much lengthier and more expensive physical testing process to identify the potting compound that provided the best mix of performance and price. Or we could have foregone this process and used the best potting compound because we were fairly confident that it would have delivered acceptable thermal performance."

Instead, Crossley performed thermal simulation on the initial design using FloTHERM software. "We use FloTHERM because it provides many built-in functions that reduce the time required to module complex stacked module designs," Crossley said. "The most important of these is the FloTHERM.PACK web-based wizard, which quickly produces accurate models of integrated circuits and other components."

Crossley used the Flomerics FloTHERM.PACK web-based wizard to generate models of each of the components. "Using the FloTHERM.PACK wizard all I had to do was enter basic design parameters such as the die size, die flag size and lead frame clearance. FloTHERM.PACK generated models of the components that were almost complete. I was able to create a thermal model for this stacked module with FloTHERM.PACK in a tenth of the time that would have been required using conventional modeling methods."

Compound type Simulated junction temperature Standard 110°C Enhanced 85°C Best 75°C
Crossley ran thermal simulations of the stacked module with three different potting compounds which are referred to here as: standard, enhanced and best. "Simulation demonstrated that both the enhanced and best potting compounds brought the core temperature down to acceptable levels with ample safety margin on the die junction temperatures," Hunt concluded. "So we were able to specify the enhanced potting compound at a cost of about half of the best potting compound. Thermal simulation helped us engineer an optimized solution while minimizing our engineering costs and leadtime."

About C-MAC MicroTechnology
C-MAC MicroTechnology ( is a world leader in high-reliability electronic systems, modules and components for harsh environments such as extremes of temperature, vibration and shock. C-MAC operates primarily within the defence, aerospace, automotive, space, medical and specialised industrial sectors. The head office is in Wooburn Green, UK and the company has design and manufacturing facilities in the UK, France, Belgium and Canada, with additional dedicated sales and customer support teams throughout Europe and the USA. C-MAC has an extensive intellectual property portfolio and considerable electronics design and manufacturing expertise geared to its target industries.

For further information, please contact:

Nazita Saye
Head of Marketing
Mentor Graphics Mechanical Analysis, UK
81 Bridge Road
Hampton Court
Surrey, KT8 9HH

Tel: +44 (0)20 8487 3000
Fax: +44 (0)20 8487 3001

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