Weekend Wire #15: Thermal Design Basics for Integrated Circuits

March 1st, 2025

👋 Happy Saturday! This weekend’s highlights include notes on the basics of thermal design for integrated circuits, a chart on various semiconductor chip bonding methods, and a test flight in the U-2 spy plane to the edge of space.

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📝 Lecture Notes: Thermal Design Basics for Integrated Circuits

Every component generates heat, and managing that heat is critical to reliability and performance. From Analog Devices, a primer on thermal design basics for integrated circuits. To understand the basics, the operating constraints really boil down to two variables: the junction temperature (Tj, temp. within the semiconductor die) and glass transition temperature (Tg, temp. at which plastic case softens and changes its mechanical properties). All design decisions—heat transfer strategies, output current, component placement—are designed for safe operation within the two temperatures.

A note on modern ICs: As package sizes shrink, thick copper traces are increasingly used to dissipate heat over a larger area.

More generally however, modern ICs don't use commercially available heat sinks. Instead, when significant power needs to be dissipated, such as ≥ 1 W, low thermal resistance copper PCB traces are used as the heat sink. In such cases, the most useful form of manufacturer data for this heat sinking are the boundary conditions of a sample PCB layout, and the resulting θJA for those conditions.

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Interesting Chart: Inside an Integrated Circuit

The two most common methods for connecting a semiconductor die (the “chip”) to a substrate. Interconnections are on the scale of micrometers, around 15–40 µm wide.

Flip Chip Bonding:

• Die is flipped so its active surface faces the substrate, and tiny solder bumps on the die’s pads melt to form electrical and mechanical connections.

• Applications: High-speed, high-performance chips like GPUs and smartphone processors.

Wire Bonding:

• Fine wires (gold or aluminum) connect the die’s pads to the package leads or substrate.

• Applications: Less demanding chips like analog devices, sensors, and legacy microcontrollers.

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Manufacturing & Startup News

More leftovers from our weekly research in hardware and manufacturing news:

Manufacturing & Startup News

• Lumotive raises $45M to expand sales of its programmable optical semiconductors.

• Ignis H2 Energy raises $12.5M in Series A to advance its geothermal exploration projects.

• AheadComputing raised $21.5M in Seed funding to develop a new microprocessor architecture for AI and general-purpose computing.

• Kapta Space exits stealth mode with plans for space-based target tracking, having secured $5M in seed funding and $1.8M SBIR contract.

• CorPower Ocean was awarded up to $18.2M from EIC Accelerator to commercialize wave energy technology.

• Cambridge GaN Devices raised a $32M Series C to drive global growth in the power semiconductor industry.

• Augury raised $75M in Series F funding, maintaining a $1B valuation, to expand its industrial AI solutions.

• Everstar raises $4M in pre-seed funding to develop AI solutions for nuclear compliance.

• Metcycle raised a $14.7M Series A to expand its digital platform for global metal recycling.

• Hylio raised $2M to expand production of made-in-America ag spray drones.

• SemiQon raised $18.2M to develop cryogenic CMOS technology for quantum computing.

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