Thermal simulation optimises memory stack design

Staktek, a leading supplier of high-density memory stacking solutions, is using Flotherm thermal simulation software to ensure that innovative new products meet thermal management requirements.

Staktek, a leading supplier of high-density memory stacking solutions, is using Flotherm thermal simulation software to ensure that innovative new products meet thermal management requirements.

Thermal performance is critical to the design of Staktek's products, which double, triple or quadruple memory in the same physical footprint as the underlying packaged component.

One of the company's most important design challenges is ensuring that the stacked packages have superior thermal performance.

In a typical example, Staktek engineers recently examined a new design concept that reduces the height of a memory stack.

"We modeled the new design in Flotherm to obtain the junction temperatures of the devices in the stack", said Mark Wolfe, Product Development Engineer for Staktek, Austin, Texas.

"Using our Flotherm model we predicted that the low profile stack ran hotter than our baseline product".

"Then we evaluated several ideas to thermally improve the performance of the low profile stack".

"We found that by making some minor modifications to the stack we could bring the thermal performance of the low profile stack back in line with our baseline design".

Wolfe said that thermal management has become a more challenging task to the company over the last several years.

"In the past, Staktek primarily designed our stacked memory solutions around TSOP packages".

"The TSOP package geometry is standardised so Staktek didn't have to worry about many packaging variations".

"More recently, memory manufacturers have shifted to using ball grid array packages".

"The BGA packages that we work with today have a wide range of different package sizes, ball patterns, and packaging materials, all of which change the thermal performance".

"Using empirical methods for thermal design on all of these packages would be time-consuming and expensive".

"With Flotherm we can quickly model the stacked product, accurately simulate its thermal performance, and then just as quickly evaluate any design changes that may be needed to improve thermal performance".

"One major advantage of Flotherm is that our customers use it, so they are familiar with the software and can accept our models for use in their system-level simulations".

In another recent example, Staktek evaluated the effects of changing the material of the heat spreaders used in its stacks.

Staktek wanted to create a lightweight stack by using lower density heat spreaders, but it was concerned about the thermal costs associated with the change.

Flotherm allowed Staktek to determine the thermal penalty associated with the lightweight stack concept.

"Our analysis showed that the junction temperature rise wasn't as large as expected".

"Flotherm gives us the analytical information we need to make decisions", Wolfe said.

Back to top