EC-24.7 Thermal Design, and Designing for Manufacture and Test
You can estimate a junction temperature from a power dissipation and a thermal resistance chain, design a board that an assembly line can build without hand intervention, and add the test points and structures a factory needs.
Before:EC-2. Electromagnetics and Transmission LinesEC-17. Industry and Research Experience
Two questions decide whether a good design becomes a good product: will it stay cool enough to last, and can it be built and tested by people who have never seen it. Both are answered on paper long before production. The thermal half is a resistance calculation almost identical to an electrical one; the manufacturing half is a checklist that costs nothing at design time and a great deal afterwards.
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Thermal resistance as a circuit: junction to case to ambient
Power dissipation multiplied by a chain of thermal resistances gives a temperature rise, in exactly the way current and resistance give voltage. That analogy makes the whole calculation familiar.
NPTEL: Electronic Packaging and Manufacturing (IIT Kharagpur) · CourseCopper as a heat sink: thermal vias, planes and pads
On most boards the copper is the cooling system, and an array of vias under a package moves heat into an internal plane. How much it helps depends on the plane's area and on what else is dissipating into it.
NPTEL: Electronic Packaging and Manufacturing (IIT Kharagpur) · CourseAirflow, heat sinks and the temperature the product will actually see
A calculation done at twenty-five degrees ambient is optimistic for something inside an enclosure in a warm room. The ambient used has to be the one inside the product, not the one in the laboratory.
Designing for assembly: component orientation, spacing and fiducials
A placement machine needs reference marks, adequate spacing and a consistent orientation to work without operator intervention. Violating any of them turns an automated build into a manual one.
NPTEL: An Introduction to Electronics Systems Packaging (IISc Bangalore) · CourseSolder paste, reflow and the defects that come from the layout
Pad geometry and thermal balance decide whether a part sits flat or tombstones, and the stencil aperture decides how much paste arrives. These are layout decisions with manufacturing consequences.
NPTEL: An Introduction to Electronics Systems Packaging (IISc Bangalore) · CourseTest points, test fixtures and boundary scan access
A factory needs to prove each board before it ships, which means physical access to key nets or a scan interface that reaches every pin. Adding that access after the layout is finished is rarely possible.
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