IN Brief:
- Two production lines have been installed at Astemo’s Horwich operation near Bolton.
- One line incorporates SMT assembly for power-electronics PCBs, while the other handles inverter production.
- Annual capacity is expected to exceed one million units after volume production begins in April 2027.
Astemo has installed the principal equipment for a £100 million electric-vehicle inverter expansion at its Horwich site near Bolton, keeping the manufacturing programme on course for volume production from April 2027.
Two production lines are being developed within the operation. One will assemble the main inverter system, while the second incorporates surface-mount production for printed circuit boards used in the power-electronics assembly.
Commissioning has been completed on the first line, where initial pre-production units have already been built for the associated vehicle programme. The wider redevelopment is more than 80% complete and includes the controlled manufacturing areas required for electronics assembly and inverter production.
Annual capacity is expected to exceed one million inverters once full output has been established. Alongside creating 125 positions, the investment will protect around 100 existing roles and move the Bolton site further into high-volume electrified-drivetrain manufacturing.
An automotive inverter converts direct current from the traction battery into the controlled alternating-current waveforms used by the motor. During regenerative braking, the same system manages energy flowing in the opposite direction while coordinating switching behaviour with motor position, battery limits, thermal conditions, and the wider vehicle controller.
Power-semiconductor modules, gate drivers, voltage and current measurement, DC-link capacitors, busbars, control electronics, connectors, cooling structures, and embedded software all sit within the resulting assembly. Manufacturing variation across those elements can alter electrical efficiency, electromagnetic compatibility, acoustic behaviour, and operating life.
Volume production tightens every tolerance
As output moves beyond prototype or low-volume assembly, process stability must be maintained across production shifts, component batches, operators, and maintenance cycles. Each inverter also requires traceable manufacturing and test records capable of linking field performance to the parts, equipment, software, and process conditions used during assembly.
The SMT line will produce control and driver boards operating close to high switching voltages and currents. Placement accuracy, solder-paste deposition, reflow profiles, cleanliness, insulation distances, and automated inspection influence whether those boards can withstand vibration, thermal cycling, humidity, and prolonged electrical stress.
Separation between low-voltage control circuitry and the traction-voltage domain remains critical. Measurement devices, isolators, gate drivers, and protection circuits must detect overcurrent, short-circuit, or insulation faults quickly enough to prevent damage propagating through the switching stage.
Component suppliers are integrating more of that measurement chain, with 1,200V signal paths combining functions previously distributed across several devices. Reduced board area and calibration effort can simplify production, although the resulting components still require careful layout, isolation, and thermal design.
End-of-line equipment must examine considerably more than basic operation. Insulation resistance, leakage, switching response, sensor accuracy, communications, firmware identity, thermal-interface quality, and reactions to simulated faults may all form part of the production test sequence.
Thermal interfaces are especially sensitive because small changes in material thickness, flatness, fastening force, voiding, or coolant contact can raise semiconductor junction temperature. An assembly may pass a brief functional test while carrying a defect that reduces operating life during repeated high-load cycles.
The broader Horwich redevelopment also increases UK production capacity for a component that directly affects vehicle efficiency, range, and platform cost. Local assembly, however, does not necessarily localise every semiconductor, passive component, substrate, or thermal material used within the finished inverter.
Power modules may depend on silicon carbide or silicon devices produced through international supply chains, while capacitors, magnetic components, connectors, and insulating materials carry separate capacity and qualification constraints. Automotive approval makes substitution difficult once an electrical or mechanical configuration has been validated.
Pre-production builds give the Bolton operation time to stabilise equipment, qualify processes, train operators, refine test limits, and resolve supplier variation before April 2027. The transition to volume will be judged by whether those controls preserve inverter performance repeatedly across hundreds of thousands of assemblies.
