Cadence Introduces Thermal Solver for PCB Design

Heat kills. No one knows this better than electrical engineers, where a hot spot can kill like a heart attack. With every design, power requirements get bigger while the design envelope shrinks. The result: too much heat produced and too little dissipated. Think of the laptop too hot for your lap, a smartphone so skinny it can’t have any air flow and lithium batteries that light up from overcharging.

For this, Cadence, best known for its EDA software, has announced the Celsius Thermal Solver, a stand-alone analysis program that uses FEA and CFD to detect overheating in chips, boards and enclosures.

Cadence celsius screenshot
The devil is in the details. A gold lead (lower, left) turns red hot, the maximum temperature on this IC, shown here with dielectric material removed. The hairs breadth detail is possible because the exact geometry of the chip is provided by Cadence design software.

The Demo

As you might expect, Celsius is able to get a lot of data from the Cadence EDA tools.

Most impressive was the level of detail. The thin gold leads on an integrated circuit (IC) appear as fine gold threads until you zoom in to see they are modeled with a rectangular section. As the current is applied, one turns red to show it is overheated. Consider the entire detailed geometry of a chip—including hundreds of leads, the circuits in the die, etc. What would take weeks to model, the microscopic detail drops out of the Cadence part library as current courses through the circuits. It’s just I2R, or Joule heating, said CT Kao, product management director at Cadence, who smoothly and effortlessly conducts the demo over the Web. The resulting temperatures can be seen from the outside, inside with sections or with parts removed.

The chip can be dissected, part by part, layer by layer. The chip junction, often a place where heat builds up, was shown with a hot spot getting hotter over time. Its location was pinpointed to within a millimeter.

Celsius seems perfect for IC designers that have to contend with more and more power in smaller and smaller die sizes. CT points out that Celsius is also capable of board level and  system level thermal analysis. With FEA, CFD, transient and steady state, Multiphysics, etc., Celsius itself packs a lot into the box.

A sample smartphone analysis took only seconds after the geometry was imported from a STEP file. Cadence claims the solver is 10 times faster than “existing solutions,” a maximum 67 degrees Celsius. Given the product name, I wonder if temperatures in Fahrenheit is an option. It’s conduction only, which is fair enough since convection plays a minor role in the cramped quarters of a smart phone, but it does contribute to low solve time with less calculation than with a multi-mode thermal solution.

Celsius integrates seamlessly with the Cadence suite of electrical design software, Voltus, Virtuoso, Innovus and Allegro. Cadence component and board geometry is read in native format. The 3D geometry of the system in the boards and components relies on neutral file formats like STEP, literally making an extra step for CAD users and detaching geometry from the current design—a potential problem if the design changes. Celsius does read in data directly from “standard chip, package and PCB design tools,” according to Cadence literature.

Celsius can react to time dependent input, like surges in current or temporal responses of operation modes and power profiles, fresh from the electrical design software. The ability to receive electrical resistance and power dissipations with push-button ease directly into a thermal analysis, plus detailed geometry of components and their physical placement, should make for accurate results and great convenience.

The FEA solver is of Cadence’s own making. The CFD solver is code licensed from a third party.

Postprocessing is built on ParaView, an open source data analyzer/visualizer that has its roots in Los Alamos National Labs.

A Multitasker

Graphic showing the flow Cadence Celsius follows.
Ten times. The massively parallel, multithreaded architecture of Celsius should be advantageous with GPU laden cards in local workstations, as well as HPC and cloud computing environments (Image courtesy of Cadence.)

Not shown in the online demo was Celsius’ claim of being able to solve really big (as in number of elements, not the size of the part) problems. Celsius takes advantage of a massively parallel, multi-threaded distributed architecture that can scale to hundreds of CPUs, such as those found in HPC centers, to claim speed increases of over 10 times that of single-threaded solvers.A No

No Brainer for Cadence Users

Screenshot of results in PCB design from Celsius
Celsius can do transient E-T “co-simulation” with temporal responses of various operation modes and power profiles, including Joule heating. (Image courtesy of Cadence.)

Celsius fills out the product suite for Cadence. It should be a no-brainer for electrical engineers doing electronics design with Cadence software. Those are many because Cadence is a leading EDA vendor and counts many top electronics companies as customers.

For those who are not Cadence users, Celsius will have stiff competition from established simulation vendors, many of whom have been doing thermal analysis forever. Most CAD companies have simulation applications, including thermal. Perhaps the stiffest competition comes from Mentor, a neck-to-neck competitor to Cadence in the EDA race. Mentor was acquired by Siemens Software giving it pole position with Siemens AG’s many electronics facilities and companies doing business with Siemens.

Cadence will need to sell Celsius based on ease of use, quickness of solution and perhaps cost. Most robust thermal solvers on the market, especially those that use CFD, fail on ease of use, tend to be prohibitively priced and may be slower to solve, saddled with legacy solvers.