Author: Ivano Tognetti Product Manager Cadlog Group

The automotive PCB market will explode with the widespread adoption of electric vehicle (EV) systems. As electric vehicles become a reality on the road, durability and reliability will be critical to the success of applications involving power electronics, electrical distribution, and safety-critical PCBs. Increasingly stringent security regulations are forcing companies that design and manufacture printed circuit boards to adopt development practices that are fast, efficient, sophisticated, and right the first time. PCB suppliers can turn these challenges into opportunities with a fully digitized, simulation-based development process.

Development of electronic systems safety critical for electric vehicles

The electric vehicle revolution

The use of state-of-the-art (Silicon Carbide-based) power electronics, advanced electrical distribution systems and other safety-critical PCB modules in electric vehicles is already notable: systems and operations include junction boxes, power modules, battery control, battery packs, inverters, drive motors, high current harnesses, battery cooling systems, power relay modules, HVAC and much more. Traditionally, most PCBs in automotive electronic systems had marginal reliability and functional requirements. If an instrument panel or radio circuit board failed, it required an awkward visit to the dealership for repair. The failure of the most critical electronic components for safety, such as electric motors, inverters and the battery control itself, means that the vehicle does not work.

With the advent of electric vehicle technologies, the reliability of power electronic systems and their hardware/circuit boards is quickly becoming a paramount and urgent goal in the industry. An electrolytic capacitor that overheats or a solder joint on a surface mount component that cracks due to thermal stress or vibration, for example, can cause potentially catastrophic system failure.

Today, PCB suppliers are expected to supply boards with materials that can withstand heavy use and long life cycles. The industry demands PCBs that are durable and can quickly dissipate heat; With the revolution in electric vehicle systems, the demands regarding the applications of PCBs and automotive electronics will skyrocket.

The focus on safety and durability

Safety and durability are the main requirements of electric vehicles and the most important. Just as safety and reliability remain top of mind, so too is the need to consider all aspects of electronic and electrical systems, including operating environments, power duty cycles, component tolerances, and assembly and manufacturing variants, among others.

For the industry to make electric cars a reality, suppliers of PCBs and electrical components must develop durable, robust and reliable systems, and convince a skeptical public and regulatory bodies that such systems will work 100% of the time. Traditionally, this test was carried out through physical tests in thermal cameras and vibration cells. Test failures required redesign or new components, leading to cost overruns and missed deadlines.

The traditional approach is no longer sufficient to demonstrate that electrical system and electronic circuit board design will meet these safety and robustness requirements. Today, companies want testing early in the development process to verify that designs are secure and robust. The answer to this requirement is simulation.

Simulation of all aspects of performance

Simulation these days is often limited to simulating circuits for functionality, PCB routing, and usually a basic level of thermal analysis. These limitations are aggravated by the fact that different fields of engineering (electrical and mechanical) are involved. Often, changes in one area are not taken into account or evaluated in the other. A change to an electronic component that causes increased power dissipation can trigger a thermal overload if not evaluated.

An integrated development process from start to finish

To demonstrate that the reliability, robustness, and roadworthiness of electric vehicle systems meet safety and robustness standards, suppliers of electrical PCBs and components must adopt an integrated, multi-domain, simulation-driven development process. , which evaluates all aspects of the performance of electronic and electrical systems.

Electronic and electrical design and verification

The starting point of electronic systems is the circuit schematic, which represents the functional arrangement of electronic components, including resistors, capacitors, transistors, microcontrollers, and other electrical components. Connected symbols typically represent them for each system component in an orderly format, and schematics can be simulated mathematically to assess and assess required functionality before hardware is built.

Time is of the essence as the next generation of vehicle products is the subject of intense research and development. New electronic and electrical components that provide key functionality to these systems are released on the market every day, even just before launch. It's critical to assess those changes quickly or risk a slow simulation process that prevents you from getting to market faster than a competitor.

Optimization of layout

The role of PCBs and electrical systems will be fundamental in electric vehicles. With so many components and an increased need to verify the safety and durability of the vehicle, the provision of these systems will become crucial to ensure that the vehicle has the maximum possible functionality and does so safely.

Once the schematic of the electronic or electrical system is completed, it must be transferred to the real world. The circuit board or electrical system represents the physical embodiment of the electronic configuration. The challenge is putting all the necessary electronics on a board or device and routing the essential copper traces and wires that provide the interconnects. This process becomes quite a challenge, since the copper traces and wires cannot physically touch and cross each other. For this reason, multilayers are needed that allow these traces to cross each other, deep into the layers of the circuit board or electrical system.

This stage of the process represents a critical phase in its development. There are millions of possible routings that result in a different number of plate and layer sizes. However, there are also numerous standards, guidelines, and ultimately space constraints that make optimization critical to achieving all goals.

An automation process that quickly evaluates thousands of possible routes plays an integral role in the development process. Further development can identify performance issues with the location of a capacitor or driver due to vibration or temperature. Changing the location of the components would require a new copper routing configuration. In the past, this would represent a significant investment of time. Furthermore, an increase in the number of layers and the size of the plate may not be possible.

The circuit routing process takes into account the topological structure of the copper traces and components. A 3D CAD representation is needed to assess the physical performance of a model, and this step represents a major challenge in the industry.

3D CAD modeling

Creating an accurate and detailed 3D model of the printed circuit board is a key factor in accurately predicting design behavior. Unfortunately, 3D modeling of PCBs (including all layers of the board, components, holes, traces, and vias of multilayer designs) and other electrical systems has traditionally been a time-consuming process and is a pain in the ass. luxury that few companies can afford. As an alternative, many companies have turned to simplified 3D models that can only support rough, preliminary simulations of airflow and thermal performance. Given the increased complexity and power density of integrated circuit (IC) designs, PCBs, and electrical systems today, companies need to accurately understand the temperatures, airflows, and mechanical stress of such systems to prevent failure.

Fortunately, there are advanced technologies that can automatically generate fully detailed 3D CAD models from PCB layouts and electrical systems created in electronic design automation solutions. Working directly from board design data, automatic CAD model creation makes the process faster and faster, reducing the time and effort required from days/weeks to minutes/hours.

A 3D CAD model of the electronic or electrical system enables many other critical processes such as component data management, manufacturing development, design for assembly (DFA), design for manufacturing (DFM), calculation costing and bill of materials (or BOM) management.

Thermal analysis

The software and electronic content of autonomous and electric vehicles is growing exponentially, more than that of traditional vehicles, which means that the next generation of PCBs will need to have the maximum robustness at the design level to guarantee the functionality and safety of the vehicle. vehicle. One aspect that will be key is to ensure that heat is not a problem that causes the PCB to malfunction. High temperatures reduce the life expectancy of components, solder joints, and printed circuit boards. For every 10 degrees Celsius reduction in temperature, life expectancy improves by 50%. Even small temperature reductions are important.

Component Power

Some components have a constant voltage and current and work all the time. Others turn on and off, depending on the functional need of the system. These duty cycles are unique to the electronics and have a significant impact on thermal performance. To improve simulation and performance prediction, these duty cycles should be evaluated as a time-based transient response. Some components have different technologies and packaging configurations that respond better or worse to applied voltages and currents.

New technologies can force many modifications to the system. Software is often considered the easiest way to fix a system's functional deficiencies. Although it may be easy to change lines of code, the consequences on operating temperatures can be catastrophic. Seemingly benign software modifications can trigger many problems. Changing the duty cycle from 50 to 70 percent may be easy to code, but the resulting temperature impact on the MOSFET can cause premature failure.

The environment of the electronic module

At the end of the XNUMXth century, most electronic and electrical systems in automobiles were placed in relatively stable thermal environments, such as the dashboard, inside the vehicle, or in places with good air circulation to promote cooling. However, as packaging space, wire harness lengths, and locations became more critical, these electrical and electronic systems were often placed in more inhospitable locations. In one case, an electronic module was placed near the exhaust manifold of an engine.

In the case of new electric vehicle technologies, it may not be as obvious when a location is problematic. For example, electrical junction boxes that handle high motor and system currents are mounted under the hood of a vehicle with limited access to cooling airflow.

However, you have to understand the usage scenarios. Starting and running the electric vehicle on cold mornings, for example, requires additional power to support the defrost and defrost function of the climate control system. This additional power demand scenario can cause critical components to overheat and pose problems for these systems. Likewise, desert locations can wreak havoc due to solar thermal radiation, causing high temperatures in the power electronics of the EV during operation. The first thing a driver does when getting into the car is to turn on the air conditioning and the fan of the heating and cooling system to cool the interior, which in turn consumes additional energy from the electric vehicle's system.

Traditionally, safety-critical electrical and electronic systems were designed to exceed durability and robustness targets, resulting in increased cost, mass, and time to market. However, this is no longer an option. As the industry de-mass electric vehicles to improve battery range, there is a need to optimize all electrical and electronic systems. Businesses need to achieve optimal performance at the lowest cost. Ultimately, vibration and thermal stress simulations should be performed together, as this represents real life.

Structural analysis

Performing stress analysis on electronic and electrical systems is not a new concept, but until recently it was not practical. In any electronic system that works and gets hot, changes in temperature and vibrations introduce stress. Let's see a summary of them:

thermal stress

Temperature changes and the difference in thermal growth of materials cause structural stresses.

vibration stress

Vibration stress is often not taken into account in the simulation process, but one of the main emerging challenges is the new requirements related to random vibrations.

fatigue analysis

The results of the structural simulations should be applied in fatigue and durability studies that can help to understand the overall durability and robustness over time.

Where today meets tomorrow

As the new mega trends in the automotive industry continue to evolve, so must the engineering behind them. For electric cars to become a reality, suppliers of PCBs and electrical components must develop durable, robust and reliable systems. However, the technology of the past will not be able to cope with the new challenges of tomorrow. New simulation-driven, multi-domain, integrated development processes are needed to assess all aspects of electrical and electronic system performance virtually before they are built and tested, in order to get the design right the first time and speed time to time. commercialization.

At present, there are functionalities of this type that include simulations for:

• Performance of electronic circuits and electrical systems.
• Optimization of design and architectural topology.
• 3D CAD modeling of the mechanics and PCB.
• Thermal, structural and fatigue analysis of mechanical systems and electronic and electrical components.
• Performance optimization.

Siemens Digital Industries Software provides the tools of tomorrow, today, and optimizes the development of next-generation vehicle electronics with:

• PCB domain specific data management.
• Functional block level design.
• IP reuse.
• Simultaneous design of multi-board systems, including cabling.
• Modeling and analysis.
• Industry leading thermal verification.
• Vibration and acceleration analysis.
• ECAD-MCAD collaboration.
• Verification and validation DFM and DFA.

Siemens Digital Industries Software also ensures compliance with Functional Safety, with independent verification by TÜV-SÜD and by SGS TÜV Saar (Tool Confidence Level 1 (TCL1) with ASIL certification from level A to level D). The Safety Kits (ISO 26262) is available to all current customers through the Siemens Support Center and enables suppliers to the automotive industry to meet ASIL certification documentation requirements.

Find out more at www.cadlog.es.