A reference solar inverter assembly line now ships as 50 standardized modules running 22 working stations, expanding to 50-70 modules / 22-28 stations on demand, and replacing about 40 operators per double shift on string-inverter SKUs [S1][S2][S7].
The build covers the full inverter block: SMT and DIP board load, automated screw locking, laser marking, potting and dispensing, CCD visual inspection, pressure resistance test, barcode/RFID bind, and end-of-line aging, with MES data capture on every station [S2][S3][S8].
Reference Line Architecture: 50 Modules, 22 Stations
Solar inverter automatic assembly lines from Chinese system integrators (Hymson, OKATA) and India-based Solar Techmach converge on the same envelope: 50 modules, 22 stations, modular station design that can be reconfigured without line replacement [S1][S2][S3][S7]. The module list is consistent across vendors: automatic code reading, laser marking, automatic screw locking, pressure resistance test, automatic dispensing, CCD visual detection, automatic barcode paste, and good/bad product sorting [S1][S2][S3].
Headcount economics drive the build. OKATA cites "double shift saving about 40 people" against the prior manual screw-lock workflow, and a first-pass yield lift on the downstream test session from tightened in-line CCD tolerance [S2]. RFID tagging at every station records the build history, so a failing unit on aging can be traced back to the specific screw station and torque record, not just the lot [S2]. For plant engineers comparing this envelope to other discrete-assembly builds, the closest architectural reference is the automatic molding line format: short, modular stations with server-side data logging and the ability to add or swap stations without a line rebuild.
SMT Front End: Sizing Pick-and-Place for Inverter PCBs
UPH is the gating number on the SMT side, not station count. For a medium-sized residential inverter board carrying 800 to 1,500 components, the SMT line must be configured so the pick-and-place placement speed and the cycle time of the slowest process (typically reflow or selective soldering) clear the takt time dictated by downstream assembly [S9]. The slowest process sets the line ceiling, so unbalanced machine classes will bottleneck a fast placer.
SMT placement feeds directly into the assembly line module chain, where DIP components, power modules, and magnetic parts are populated after the board exits reflow [S6][S8]. Process control on the SMT side is what determines first-pass yield at the inverter test station; the Deye line walkthrough shows SMT, DIP, conformal coating, and final assembly running as a single linked flow, with aging as the final gate [S8]. Engineers retrofitting an existing PCB shop into a full inverter line can use the SMT sizing logic from VFD production (similar IGBT gate-driver board density) as a useful upper bound for component count per board.
Test Coverage: Performance, Environmental, Safety
Large-scale photovoltaic inverter production merges three test regimes: performance (efficiency, MPPT tracking, THD), environmental adaptability (temperature, humidity, altitude, salt fog), and safety (insulation, dielectric withstand, ground continuity) [S6]. All three are run on the integrated assembly and test line, with manual stations retained for high-voltage hookup and final EOL inspection [S6].
The pressure resistance test module on the assembly line is the in-line dielectric pre-screen, isolating boards that would otherwise fail the full safety suite downstream and burning them back at the screw-lock or potted-station level [S1][S2][S3]. Aging chambers then run loaded no-load burn-in per SKU; Deye's published process shows coating, assembly, and aging as three gated stages, with each gate logging to the central server [S8]. For buyers mapping this against a conveyor sorting line downstream of EOL test, the inverter test set is the harder gate because the test itself takes minutes, not seconds, so buffer accumulation between EOL and pack-out must be sized accordingly.
Selection Criteria: Volume, Variant Count, and Traceability Depth
For residential string inverters in the 5-50 kW range running high SKU variety, the 50-module / 22-station reference line is the right size, and the modular station design lets a plant add a 23rd or 24th station for a new variant without touching the rest of the line [S1][S2]. For utility-scale central inverters above 250 kW, the station count and cabinet handling move toward heavier-payload AGV flow rather than a fixed conveyor loop, since the unit weight and HIPOT test time both push cycle time up.
CCD positioning at every screw and dispensing station is the spec that actually protects yield; without it, positional drift between stations is the dominant first-pass failure mode for hand-loaded subassemblies [S2]. RFID bind at each station is the second spec to lock in, because it is the only way to make the per-station data capture useful during an inverter field failure investigation [S2]. The line walkthrough at the Deye facility matches this, with each station logging to a central server and aging data tied back to the unit serial [S8]. Specifying these two together, CCD positioning and RFID bind, is the minimum viable build for a 2026 spec; anything less and the line is just a manual flow with robots bolted on. For adjacent process decisions on sealing and bonding, the adhesive selection for energy equipment spec path is the most directly relevant cross-reference, since potting and thermal interface compounds are set at the same dispensing station that locks the screw pattern.
Decision Matrix: 3 Inverter Line Build Profiles
Three practical build profiles cover most 2026 plant asks. Profile A, residential string (5-50 kW, 800-1,500 components/board, high SKU): 50 modules / 22 stations, single SMT line, CCD + RFID on every station, batch aging, throughput governed by EOL test [S1][S2][S9]. Profile B, commercial string (50-250 kW, denser IGBT content, longer HIPOT): 50-70 modules / 24-26 stations, dual SMT, conformal coating in-line, longer aging, AGV handoff to pack-out [S1][S6][S7]. Profile C, utility central (above 250 kW, low volume, very long test): fewer stations but heavier-payload, more manual EOL, two-shift burn-in cabinets sized for full lot [S6].
Cost-per-watt installed follows a different curve than station count. Adding stations above the 22-station reference only pays back when SKU variety is high and changeover time is the actual bottleneck, not raw throughput; for a low-mix, high-volume residential line, the smarter spend is more pick-and-place capacity at the SMT end, not more assembly stations downstream [S9]. Capacity planning for the SMT side should size to the slowest process, not the average, because a single under-spec reflow or selective soldering oven will cap the entire line at its takt [S9].
Limitations and Common Failure Modes
Three failure modes recur on automated inverter lines. First, screw-lock torque drift on the aluminum heatsink interface, which only shows up under thermal cycling and is caught late without an in-line torque-and-angle trace [S1][S2]. Second, potting voids at the IGBT module base, which a dispensing station with no vacuum or pre-degas step will produce at a rate the downstream HIPOT test cannot screen, so the line needs either a vacuum potting module or a lower-viscosity compound spec [S5][S6]. Third, RFID read failures on the metal inverter chassis, which an aluminum or steel enclosure can detune unless the tag is positioned and the antenna tuned to the cabinet material [S2].
Manual stations remain necessary for high-voltage hookup, final EOL safety signing, and rework; the assembly-test line integrates manual and automated operations rather than replacing manual work outright [S6]. Stations that look like they could be automated (labeling, final screw on the cover) are usually left manual because the cost of an error there is a full unit scrap plus a field failure, and the labor cost of doing them manually is small relative to that risk [S6]. Buyers evaluating the Solar Inverter Industry 4.0 Adoption: Spec Map, Vendor Moves, and 2026-2031 Numbers reference will see the same pattern, where the gating investment is per-station data capture and trace, not the robot count.
Two trackable signals to watch over the next two quarters: (1) whether 50-70 module / 26-28 station configurations become the default residential build instead of the 50-module / 22-station baseline, driven by SKU fragmentation in hybrid inverters; (2) whether inline partial discharge test moves from the safety lab onto the assembly line, which would add a new test module but eliminate a separate test cell downstream.