IMS, thermal vias, and embedded copper change different path segments. Define sources, heat outlets, and electrical isolation before comparing local conduction/external cooling. If the heatsink/contact already dominates, more internal copper/vias may provide limited improvement.
Confirm temperature targets and heat dissipation paths first
Define the target as junction, case, or pad temperature, recording worst-case dissipation, duty, and ambient. Input power is not necessarily all heat; distinguish load energy from component loss. Outlets may be backside heatsinks, enclosures, planes, or air; orientation and airflow are boundary conditions.
Map component internals, joints, board structures, interfaces, heatsinks, and air. List parallel paths separately instead of forcing everything into series. Establish target measurement locations and heat outlets before material selection if either is missing.
Where do the three structural types take effect
| Structure | Primary Modification | Matching Check |
|---|---|---|
| IMS Metal Substrate | Transfer heat through insulating dielectric to a metal base | Dielectric thickness, thermal resistance, insulation, and backside contact |
| Thermal Vias | Connect different copper layers and backside hot zones | Hole-wall copper, density, filling, soldering, and heat outlet |
| Copper Embeds | Locally increase current or thermal conduction cross-section | Embedding location, interfaces, insulation, and lamination |
| Expand Copper Area | Improve planar spreading and local heat distribution | Potential, layout, available area, and environment |
Würth's thermal-management overview provides structural directions for technical selection, not evidence that a company offers every process. Manufacturing review must confirm the specific chosen combination.
Why series thermal resistance helps locate bottlenecks
Assume board, interface, and heatsink-to-ambient resistances of 2, 1, and 7 °C/W: total 10 °C/W. At 3 W, temperature difference is approximately 30 °C. Reducing the board segment from 2 to 1 °C/W gives 9 °C/W and approximately 27 °C, only 3 °C lower. Improving external cooling too changes the outcome.
This shows total-path limits on local improvement, not actual resistance for any board. Real devices have multiple condition-dependent paths; use suitable models/measurements. Junction-to-ambient and case-to-ambient refer to different objects and cannot be added indiscriminately.
Thermal target and electrical isolation defined together
Embedded copper and thermal vias may carry a potential, while IMS bases often require circuit isolation. Product inputs must define isolation interfaces, continuous conditions, and tests; breakdown values do not establish working voltage. Interface materials can provide both electrical and thermal functions; record thickness, compression, and installation.
Fastening can introduce metal contact, dielectric damage, or gap changes. Review screws, enclosures, heatsinks, and PCBs together rather than fixing electrical issues after assembly. If thermal structures alter references/copper, check signal/current loops too.
- Identify potentials of conductive structures and required isolation points.
- List thermal contact area, flatness, interface materials, and fastening.
- Define thermal, electrical, and mechanical verification objects separately.
- Test actual assemblies and retain contact conditions after disassembly/reassembly.
Structural selection also affects assembly and manufacturing
Thermal vias under pads can affect drainage, voiding, and flatness; embedded copper's thermal mass/height affect fabrication/assembly; metal bases affect machining/backside mounting. A highly conductive simulation block needs a defined manufacturing/soldering method too.
| Solution | Manufacturing Input | Assembly Inspection |
|---|---|---|
| Thermal Vias | Hole groups, hole-wall copper, fill, and caps | Paste printing, solder joints, and backside contact |
| Copper Embeds | Three-dimensional dimensions, location, and connection | Local heating process, surface, and flatness |
| IMS | Dielectric, metal substrate, and outline | Interface materials, fixation, and insulation status |
Check structure and thermal results together on first articles. Lower hot spots do not justify release if joints or insulation fail agreed requirements.
How to maintain comparability with reference samples
Hold source, dissipation, copper, heatsink, airflow, and orientation constant; record ambient/stabilization criteria. Measure near components, backside, both interface sides, and heatsink. Account for infrared emissivity/reflections and thermocouple attachment; do not directly compare bare-metal and plastic readings.
Compare structures first, then repeated assembly to separate board design from contact repeatability. If dissipation differs, calculate apparent temperature difference/power and retain raw values instead of choosing the coolest board. Boundary conditions make conclusions reusable.
Segment troubleshooting by temperature difference when temperature rise remains high
Hot components with cool backsides suggest checking internal-to-pad, solder, and board paths. Hot backsides with cooler heatsinks suggest gaps, interface materials, bow, and fastening. Uniformly hot structures suggest total dissipation/external cooling. Electrical anomalies after local copper changes require potential/reference checks too.
Deliver thermal paths, structural selection matrices, measurement maps, and verification records, identifying improved and remaining bottlenecks. Compare cost/space when changes are needed instead of jumping directly from vias to metal substrates.
Sensitivity-check model inputs too. Vary uncertain contact resistance, interface thickness, and air conditions separately to identify dominant effects. If an undefined interface dominates, measure or define its assembly before fine-tuning internal board structures.
Distinguish thermal-image displays, quantitative temperatures, and inferred junction temperatures. State internal-sensor or parameter-based methods where used; backside thermocouple readings cannot be renamed junction temperature. Methods can corroborate one another while retaining objects and conditions for later selection.
How to avoid viewing only steady state for pulse loads
Continuous and pulsed dissipation have different responses. Large copper masses may delay heating through capacity without improving final outlets, and repeated cycles can accumulate heat. Retain time-varying loads and target definitions before choosing transient/steady-state comparisons; one startup-temperature ranking is insufficient.
Align power/temperature time axes and specify sensor locations, response, and sampling. Slow backside response does not establish low internal peaks. Use junction methods appropriate to the device/task, keeping junction, case, and substrate terminology accurate.
Evaluate initial heating, stabilized differences, and shutdown cooling together. Initial-only improvements need actual-duty assessment; steady-state improvements with internally limited peaks may need other measures. Limit conclusions to supported phases.
Repeat critical conditions after external mounting changes, especially interfaces, fastening, and airflow. Multiple parts form the thermal path; board success does not extend to every enclosure. Retain installation conditions so later changes have defined rechecks.
Frequently Asked Questions
Can three structures be used simultaneously?
It can be a candidate combination, but review connections, insulation, fabrication, and assembly together.
Is more copper and more holes always better?
Heat outlets, layout, and soldering also constrain it. See Metal substrate dielectric, Thermal Vias, Manufacturing Combination and Delivery List.
Source material and applicable scope
- Würth Elektronik, “Thermal Management — Heat Dissipation and Management PCB Solutions”; current official technical webpage with no fixed revision stated; checked on 2026-10-17; relevant sections: Thermal Vias, IMS, and Copper structures. Supports classification and path selection. Resistance examples/prototype methods are engineering guidance, not transferred supplier capabilities.
