Global Citizenship: What I’ve Learned About the American PCB Business
Global Sourcing Spotlight: The Best Products to Buy Offshore Through Global Sourcing
Nolan's Notes: The Rise (and Risk) of Data
How to Streamline PCB Thermal Design
April 1, 2015 | John Parry, Mentor Graphics CorporationEstimated reading time: 2 minutes
Thermal issues with a PCB design are mostly determined during the component selection and layout phases. After this point, only remedial actions are possible if components are found to run too hot. Addressing thermal issues early in PCB design, starting at the system or enclosure level to understand the flow environment critical for air-cooled electronics, can streamline the process. Assumptions about the airflow uniformity in early design that subsequently prove unachievable can have a disastrous effect on the commercial viability of the product and meeting the market window.
Begin Before Placement and Layout
Substantial work can be done well before layout is completed within the electrical design flow. A simple representation of the enclosure can provide information about the air flow profile over the board. Start by smearing the total board power over the total board surface, which will provide a temperature map that will show any hot regions that are caused by a badly distributed air flow. Treat the board as a block with an isotropic conductivity of between 5 W/mK and 10 W/mK to optimize enclosure-level air flow ahead of the PCB design.
Components inject heat locally into the board so the heat flux density into the board below a component will be higher than the average for the board. As a result, the local board temperature will be higher than that predicted in the simulation. Refine the model before using the board temperature to estimate component temperatures. If the board temperature at any point is close to the maximum component case temperature, this limit will be exceeded once the component heat sources are represented discretely.
Guesstimate Component Power
At this stage, make a best-guess estimate of the individual power budgets for the main heat dissipating components that will be used in the design and the approximate size of those packages. This will enable describing them as footprint heat sources in the simulation, smearing the remainder of heat uniformly over the board surface.
Before Selecting the Package, Use 3D Component Models
Include some form of 3D component model in the simulation before the component selection is finalized. By feeding the thermal results back before this milestone is reached, the thermal performance will more likely be considered in the package selection criteria. Some ICs are available in more than one package style, and not all package styles perform equally well from a thermal point of view. The need for a heatsink later may be eliminated by appropriate package selection.
Component temperature, either in the form of a case temperature or junction temperature depending on how the manufacturer has specified the component, is the key measure used to indicate whether the design is thermally acceptable.
Editor's Note: This article originally appeared in the March issue of SMT Magazine.
Share on:
Suggested Items
Rules of Thumb for PCB Layout
11/21/2024 | Andy Shaughnessy, I-Connect007The dictionary defines a “rule of thumb” as “a broadly accurate guide or principle, based on experience or practice rather than theory.” Rules of thumb are often the foundation of a PCB designer’s thought process when tackling a layout. Ultimately, a product spec or design guideline will provide the detailed design guidance, but rules of thumb can help to provide the general guidance that will help to streamline the layout process and avoid design or manufacturing issues.
PCB Design Software Market Expected to Hit $9.2B by 2031
11/21/2024 | openPRThis report provides an overview of the PCB design software market, detailing key market drivers, challenges, technological advancements, regional dynamics, and future trends. With a projected compound annual growth rate (CAGR) of 13.4% from 2024 to 2031, the market is expected to grow from USD 3.9 billion in 2024 to USD 9.2 billion by 2031.
KYZEN to Spotlight KYZEN E5631, AQUANOX A4618 and Process Control at SMTA Silicon Valley Expo and Tech Forum
11/21/2024 | KYZEN'KYZEN, the global leader in innovative environmentally friendly cleaning chemistries, will exhibit at the SMTA Silicon Valley Expo & Tech Forum on Thursday, December 5, 2024 at the Fremont Marriott Silicon Valley in Fremont, CA.
Flexible Thinking: Rules of Thumb: A Word to the Wise
11/20/2024 | Joe Fjelstad -- Column: Flexible ThinkingIn the early days of electronics manufacturing—especially with PCBs—there were no rules. Engineers, scientists, and technicians largely felt their way around in the dark, making things up as they went along. There was a great deal of innovation, guessing, and testing to make sure that early guidelines and estimates were correct by testing them. Still, they frequently made mistakes.
Cadence Unveils Arm-Based System Chiplet
11/20/2024 | Cadence Design SystemsCadence has announced a groundbreaking achievement with the development and successful tapeout of its first Arm-based system chiplet. This innovation marks a pivotal advancement in chiplet technology, showcasing Cadence's commitment to driving industry-leading solutions through its chiplet architecture and framework.