Materials for Automotive Applications: Thermal Management Issues

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Alun_Morgan_Thermal_Chart.jpgListing the thermal conductivities of a wide range of materials—including air at 0.024W/mK, epoxy at 0.35 W/mK, glass at 1.05 W/mK, silicon at 149 W/mK, aluminium at 250 W/mK, and copper at 400 W/mK—Morgan gave a simple example of how even a basic 1W/mK IMS material dissipated hotspots and distributed heat far more uniformly that an equivalent assembly on a standard FR-4 substrate.

At a more advanced level, Ventec continued to work closely with their customers’ engineers to analyse and model specific thermal management challenges and either select appropriate IMS materials from their product range or quickly develop bespoke IMS solutions with the exact thermal properties needed by the OEM. Morgan showed examples of modelling calculations for real applications, illustrating how Ventec’s agility had enabled OEMs to bring new designs to market with reduced development timescales.

Failure analysis was a related topic for discussion. Morgan reviewed two case histories, identified the failure mechanisms, and described how Ventec had provided technical solutions. The first was an automotive headlamp assembly that had failed electrical function test on thermal cycling, exhibiting conductor fractures and solder-joint cracking. The second was a ceramic packaged LED unit that showed similar failures, although under different test conditions. In both case studies, thermal expansion mismatch proved to be the root cause. In the first example, the problem had been resolved by selecting a low-expansion aluminium alloy; in the second, by reducing the elastic modulus of the IMS dielectric.

On the subject of test methods, there was consensus among automotive suppliers that there should be standardised test methods and conditions. The problem was that every supplier had their own methods and agreed that theirs should be the ones to be used!

Although Alun Morgan focused this presentation on materials for thermal management, he made it clear that these only represented one specialist category of Ventec’s extensive range of base material solutions for automotive electronics. And he commented that the industry, in general, was ready for a change from categorising materials based on their structure and chemistry on definitions developed in the 1960s.

Ventec was working toward grouping materials appropriate to particular industry sectors and introduced autolam—a base material solutions set specifically curated for the diverse and unique requirements of automotive applications, or in Morgan’s words, “To relieve the designer of the laborious task of scrutinising 130 IPC slash sheets to find the product they need.”

Editor’s note: To read more about thermal management, download “The Printed circuit Designer’s Guide to Thermal Mangement With Insulated Metal Substrates” by Didier Mauve and Ian Mayoh from Ventec International Group.



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