Three Functions in One Enclosure
In September 2026 a Chinese automotive supplier disclosed two developments that point in the same direction. Its semi-solid state battery had been nominated by a leading domestic customer for a supply position with production expected in the fourth quarter of 2026, and an integrated power product aimed at electric aircraft had been nominated by an overseas customer. That product combines battery management, DC/DC conversion and power distribution into a single system, with production planned for the first quarter of 2027. The same company is developing power conversion units and immersion-cooled power cabinets for data centres.
The common thread is integration. Battery management, voltage conversion and power distribution have historically been separate units connected by cables and contactors. Combining them into one enclosure removes connectors, reduces weight and simplifies the vehicle or aircraft architecture, all of which are valuable in electrified platforms where every kilogram matters.
For the printed circuit board inside that enclosure, integration changes the requirements substantially. Current that was previously distributed across several boards now passes through one, and the copper that carries it has to be correspondingly heavier while the control electronics around it remain fine-featured.
What Thick Copper Means in Manufacturing
Thick copper generally refers to foil above two ounces per square foot, and high-power boards may use four, six or more. The benefit is straightforward: a heavier conductor carries more current with less resistive loss and spreads heat more effectively across the board.
The manufacturing consequences are less obvious. Etching thick copper accurately is difficult because the etchant must remove material through the full thickness, and the resulting sidewalls tend to be less vertical than in thin foils. Minimum feature size therefore increases with copper weight, which reduces routing density and forces additional layers or larger boards.
Plating follows the same pattern. Filling vias in thick material requires more copper deposition, and drilled holes in heavy boards present a high aspect ratio that is harder to plate uniformly. Poor plating in a high-current via produces local heating, which degrades the joint further, which increases resistance again. This is a failure mode that develops over time, so it does not appear in a first-article inspection or in a short functional test, and it is one of the main reasons power assemblies are validated by endurance testing rather than by a single measurement.
Mechanical mounting deserves attention equal to the electrical design. A power module is heavy, often mounted to a cooling structure, and subject to vibration. The board inside must tolerate the resulting stress without flexing enough to crack solder joints or fracture heavy copper features, which usually means the enclosure carries the load and the board is mounted with compliant elements rather than rigidly clamped at many points.
Mixed Technology on One Board
A combined unit contains both high-current paths and sensitive control circuitry. The control section includes a microcontroller, isolation barriers, current and voltage sensing, and communication interfaces. The power section includes busbars, switching devices, gate drivers and bulk capacitance.
The two sections have opposite physical requirements. The power section wants thick copper, wide traces and large thermal masses. The control section wants fine features, controlled impedance and short return paths. Putting them on one board produces a design where half the layout rules differ from the other half.
The usual solution is a hybrid construction, sometimes with copper inlay or copper pillar features that place heavy copper only where current flows, leaving the rest of the board at conventional weight. This preserves density in the control area while providing a low-resistance path in the power area, but it requires a fabrication process that can combine both in one stackup. That is a specialised manufacturing capability rather than a standard offering.
Isolation Is a Design and Manufacturing Requirement
High-voltage battery systems require galvanic isolation between the power path and the control electronics, and between the high-voltage domain and anything a user might touch. Isolation is achieved through creepage and clearance distances, through isolation components, and sometimes through slots in the board that break the surface path.
Clearance requirements interact directly with the layout. Increasing the spacing between high-voltage conductors consumes board area, and the required spacing changes with pollution degree and altitude. In an aviation application, reduced air pressure lowers the breakdown voltage of air, which means clearances must increase again.
Manufacturing then has to preserve those distances. Solder mask over a high-voltage region is not a substitute for physical separation, and contamination, flux residue or moisture can reduce the effective insulation distance. Processes for cleaning, coating and inspection therefore become part of the electrical safety argument, not merely cosmetic steps.
Another consideration is serviceability. Battery management and power distribution units may need to be replaced during the life of a vehicle or aircraft, and the connectors, mounting points and software configuration all influence how long that takes. Designing for replacement influences the board layout through connector placement and through the accessibility of test and configuration interfaces.
Thermal Behaviour Under Load
Power electronics generate heat in concentrated locations, and the heat has to travel to a cooling surface. In a thick copper board, the copper itself is part of the thermal path, which is one of the reasons heavy copper is used in the first place. Metal core and copper inlay constructions extend that idea by providing a low-resistance route directly beneath the switching devices.
Thermal cycling then becomes the dominant reliability concern. Power devices heat and cool with every operating cycle, and the solder layer between a device and the board experiences the greatest strain because the two materials expand at different rates. Large devices with large pads generate the largest forces, so the attachment method becomes a reliability decision rather than a manufacturing preference.
Designers address this with copper balancing, with thermal vias distributed under the device rather than concentrated, and with joint geometries that accommodate expansion. Each of those measures has a cost in routing area or process complexity, and each of them is best evaluated with the manufacturer rather than specified in isolation.
Testing High-Current Assemblies
Functional test for a power unit must exercise the current path, which requires equipment capable of delivering high current and dissipating the resulting heat. That is a different test environment from a signal-level assembly, and it usually means dedicated fixtures and a defined duty cycle for the test itself.
In-process inspection matters as much. Solder joint quality on heavy copper is hard to verify optically, and the failure modes that matter, such as voiding in a thermal pad or incomplete via fill, are internal features. X-ray inspection and, for critical joints, destructive sampling provide the evidence that the process is under control.
Combining those methods into a repeatable routine is what makes assembly testing meaningful for power products. A test plan that verifies function but not joint integrity will pass units that fail in the field, and in high-current applications those failures tend to be dramatic.
Sourcing Power Electronics in 2026
Demand for power electronics is rising in several directions at once: electric vehicles, electric aviation, energy storage and data centre power conversion. These applications compete for the same specialised fabrication capacity, particularly for heavy copper and metal core constructions.
The practical implication for a programme is that power board capability should be secured early. A factory that can produce heavy copper with fine-feature control in the same stackup is not common, and its capacity is allocated on the basis of existing relationships rather than on the basis of a first enquiry.
Component sourcing follows a similar pattern. Wide-bandgap devices, current sensors and isolation components have their own supply dynamics, and combining them into one integrated unit concentrates that risk. This is where component procurement support and a documented quality system provide practical value, because they convert a scheduling problem into a managed one.
Standards compliance frames much of the design work. High-voltage systems are covered by functional safety requirements, and the resulting architecture must demonstrate that a single fault cannot lead to a hazardous condition. Achieving that with integrated functions requires redundancy in sensing and in the isolation path, which adds components and board area that a non-safety design would not need.
Where Power Integration Goes Next
Integration will continue, following the path already visible in automotive power electronics and now in aviation and data centre equipment. Each step moves more current through fewer boards, raises thermal density and narrows the range of fabrication processes that can deliver the result.
Suppliers who invest in thick copper, inlay, metal core and mixed-technology assembly capability are positioning themselves for that demand. For customers, the corresponding action is to involve the fabricator earlier, when the power architecture is still flexible and when a change in construction can still be accommodated within process planning rather than after tooling.
The electrification trend does not reduce the importance of the printed circuit board. It changes what the board must do, from carrying signals to carrying current, and the companies that can manufacture that transition reliably will serve every one of these markets.
