Thermal Analysis Techniques to Improve Performance of High-Density Semiconductor Systems

Thermal problems are often overlooked in semiconductor Thermal Analysis Techniques to Improve Performance of High-Density Semiconductor Systems, which can lead to failures. While thermal problems can be understood and avoided through sound design, building new systems with improved thermal performance takes time and money.

Today's need to manage energy consumption, avoid failures due to component overheating, and avoid costly over-design necessitates the full potential of thermal modeling tools for semiconductor electronic systems.semiconductor system In this context, a semiconductor electronic system is defined as multiple PCB assemblies in an enclosure, a single board with multiple heat-generating ICs, or even a single IC in a package, mounted on a substrate.

In order to design for optimal thermal performance and avoid the previously mentioned problems, thermal design optimization techniques are needed to manage the way heat flows in electronic systems.

Thermal Analysis Techniques

Using the concepts of thermal resistance and capacitance,semiconductor test system it is simple to analyze simple systems with a single active heat source generating heat on the substrate in an environment. Designers can use thermal resistance to estimate the junction temperature of a device at steady state, or they can combine the resistance concept with capacitance and model the transient response.

The difficulty of thermal analysis quickly becomes complicated when adding several (> four components) more heat-generating devices to the model and trying to fit them all in a small space. Thermal coupling between multiple heat-generating devices can be a significant factor affecting the individual temperatures of each device, which is very complex to model.

Engineers will model heat transfer similar to electronic circuit designers modeling voltage and current in an electronic system, except replace these concepts with temperature and power. Borrowing concepts of resistance and capacitance from electronic devices and converting them to thermal and power concepts is the basis for many custom huge spreadsheets populated with thermal resistors that model all thermal relationships between all nodes of interest.

Many engineers will build complex spreadsheets, ostensibly based on actual measurements, crafted by turning on one device at a time and recording heat transfer to all the other points and adding these up. The assumption is that the principle of superposition will hold, and a simple linear analysis will give a reasonable idea of how the heat transfer will conclude when all devices are running at the same time. This spreadsheet approach lacks the ability to accomplish all but the simplest thermal modeling tasks, leaving system designers searching for more efficient modeling methods.

CFD Simulators

The next level of thermal modeling is usually to find a suitable 3D model-based CFD (Computational Fluid Dynamics) simulator that can simulate any 3D geometry for any thermal condition, as well as steady state and transient situations. Depending on the modeling needs, CFD simulators can model all thermal solid-solid and solid-fluid heat transfer interactions, provided the right options are selected.

The CFD simulator approach is not an avenue for the faint of heart, nor is it a natural tool workflow for electronics engineers striving to build systems without thermal issues (as this is not their primary area of expertise.) CFD tools require the following to be an effective strategy for heat transfer modeling:

1. proficiency in the use of CAD tools

2. mechanical model preparation for the simulator (the model must not be too detailed or the simulation will not be completed quickly enough to be usable, and it must not be too simple or the results will be inaccurate).semiconductor solutions It is a common requirement for simulation engineers to judiciously "de-feature" existing mechanical components so that the original heat transfer details are not lost). 3.

3. Assign materials and boundary conditions to match the conditions of interest.

4. reasonably fast iterations for intelligent trade-offs.

Passing these requirements is usually an insurmountable task for most electronic system designers (probably chip designers or electronic assembly designers), who have to rely on fellow mechanical/packaging engineers who have mastered these tools to build their thermal models them. This is the downside of adopting CFD methods too early in the design process.

System designers are not CFD experts and therefore rely on the company's overloaded CFD experts. CFD specialists are often so overwhelmed with company requests that much of the work can be in the queue for weeks, and the results shared throughout the design are often not systematic or robust.

System design details have to be handed off to engineers from different disciplines, and there is always some information "lost in translation" between the electronics engineers running the CFD tool and the packaging engineers. In addition, this situation hardly lends itself to an iterative optimization process or encourages the exploration of different design architectures. Ideally, the original system designer should be empowered to optimize their heat transfer design in a simple manner.Early Architectural Experiments and Feasibility Analysis

It is obvious from the above that there is a need for something that can handle the modeling of the thermal coupling between the many components in a system in a way that is more robust than a spreadsheet linear analysis, but not so complex that it takes all the engineering time to learn the nuances of using an advanced CFD simulator tool to begin modeling.Electrical engineers and electronic system designers must have access to this process, which means that training to a useful skill level must be done very quickly.The modeling process should encourage collaboration among team members and make optimization and design iteration easy.One possibility is to work with the team at AnemoiSoftware, which has built a thermal solver tool that is based primarily on the conduction method of heat transfer, and is therefore ideally suited to high-density packages containing many ICs in all types of packages.It is a cloud-based tool that comes with at least three licenses, so users are encouraged to easily share designs and collaborate between their accounts. The solver is optimized to run small and very large designs containing thousands of components extremely fast (compared to full-mesh CFD designs).Fast solution speeds are essential to inspire designers to experiment creatively with different architectures.Since thermal solving is not a fully meshed CFD simulation, there are some tradeoffs in accuracy using these tools. These can be discussed in detail with the Anemoi team.