Elementary Mr. Watson: Running the Signal Gauntlet
The Shaughnessy Report: Winning the Signal Integrity Battle
Connect the Dots: How to Avoid Five Common Causes of Board Failure
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:
Testimonial
"The I-Connect007 team is outstanding—kind, responsive, and a true marketing partner. Their design team created fresh, eye-catching ads, and their editorial support polished our content to let our brand shine. Thank you all! "
Sweeney Ng - CEE PCBSuggested Items
Staying on Top of Signal Integrity Challenges
09/16/2025 | Andy Shaughnessy, Design007 MagazineOver the years, Kris Moyer has taught a variety of advanced PCB design classes, both online IPC courses and in-person classes at California State University-Sacramento, where he earned his degrees in electrical engineering. Much of his advanced curriculum focuses on signal integrity, so we asked Kris to discuss the trends he’s seeing in signal integrity today, the SI challenges facing PCB designers, and his go-to techniques for controlling or completely eliminating SI problems.
ASM Technologies Limited signs MoU with the Guidance, Government of Tamilnadu to Expand Design-Led Manufacturing capabilities for ESDM
09/15/2025 | ASM TechnologiesASM Technologies Limited, a pioneer in Design- Led Manufacturing in the semiconductor and automotive industries, announced signing of Memorandum of Understanding (MoU) with the Guidance, Government of Tamilnadu whereby it will invest Rs. 250 crores in the state to expand its ESDM related Design-Led Manufacturing and precision engineering capacity. ASM Technologies will acquire 5 acres of land from the Government of Tamilnadu to set up a state-of-the-art design facility in Tamil Nadu's growing technology manufacturing ecosystem, providing a strong strategic advantage and long-term benefits for ASM.
Variosystems Strengthens North American Presence with Southlake Relaunch 2025
09/15/2025 | VariosystemsVariosystems celebrated the relaunch of its U.S. facility in Southlake, Texas. After months of redesign and reorganization, the opening marked more than just the return to a modernized production site—it was a moment to reconnect with our teams, partners, and the local community.
Deca, Silicon Storage Technology Announce Strategic Collaboration to Enable NVM Chiplet Solutions
09/11/2025 | Microchip Technology Inc.As traditional monolithic chip designs grow in complexity and increase in cost, the interest and adoption of chiplet technology in the semiconductor industry also increases.
I-Connect007 Launches New Podcast Series on Ultra High Density Interconnect (UHDI)
09/10/2025 | I-Connect007I-Connect007 is excited to announce the debut of its latest podcast series, which shines a spotlight on one of the most important emerging innovations in electronics manufacturing: Ultra-High-Density Interconnect (UHDI). The series kicks off with Episode One, “Ultra HDI: What does it mean to people? Why would they want it?” Host Nolan Johnson is joined by guest expert John Johnson, Director of Quality and Advanced Technology at American Standard Circuits (ASC).