5,000 CE-Certified Wallbox Units with Zero High-Voltage Isolation Failures
An Amsterdam cleantech startup needed power boards handling 230VAC/32A with reinforced isolation, heavy copper thermal management, and CE certification support — delivered in 11-day production cycles.
A Series A Cleantech Startup, Amsterdam, Netherlands
This 12-person company designs smart EV wallbox chargers for residential and small commercial installations across the EU. Their 22kW three-phase charger features dynamic load balancing, solar PV integration, and OCPP 2.0 connectivity — targeting the rapidly growing European home charging market where installations grew 48% year-over-year.
Product Type
Smart Level 2 AC wallbox charger (7kW single-phase / 22kW three-phase) with WiFi, 4G, and OCPP 2.0 backend connectivity for managed charging
Technical Complexity
3 board types: power board (4-layer 2oz copper, 230/400VAC mains, 32A switching with IGBT bridge), control board (MCU + metering IC + relay drivers), and connectivity board (WiFi/4G/BLE + OCPP stack)
Production Volume
Scaling from 200 field trial units to 5,000 units for B2B distribution — with quarterly batch orders timed to EU subsidy approval cycles
What They Needed
A PCBA partner experienced with high-voltage power electronics, reinforced insulation layout verification, 100% hipot production testing, CE/IEC 61851 documentation support, and heatsink integration
What Went Wrong with Their Previous Supplier
The team's first two assembly attempts treated the wallbox power board like a standard LED driver. For a product carrying 230VAC mains voltage inside a consumer's garage, the consequences were severe.
Creepage Violation Found During CE Testing — Entire Batch Rejected
The IEC 61851 standard requires minimum 8mm creepage between primary (mains) and secondary (SELV) circuits on the power board. The previous assembler's standard panelization added a breakaway tab that reduced the effective creepage gap at one board edge to 5.4mm. The CE test lab rejected the entire submission. The team lost 8 weeks re-fabricating panels with correct clearances — and the first production window for EU subsidy-eligible installations.
IGBT Solder Joints Failed Under Thermal Cycling
The IGBT power switching devices dissipate 15W each at full load. The previous assembler soldered them with a standard consumer reflow profile on 1oz copper — but the power board uses 2oz copper that requires adjusted thermal parameters. X-ray inspection after field failures revealed 35–45% voiding under the IGBT thermal pads. Under repeated charge/discharge thermal cycling, the voids grew into cracks, causing thermal runaway and IGBT failure in 23 field units during the first summer.
Heatsink Mounting Torque Not Controlled — Thermal Interface Failed
The power board mounts directly to an aluminum heatsink via thermal interface material (TIM). The previous assembler hand-tightened mounting screws with no torque specification. Over-tightened screws cracked the FR4 around mounting holes; under-tightened screws left air gaps in the TIM layer. Both scenarios degraded thermal transfer, pushing junction temperatures 20–30°C above design limits. The client discovered this when two chargers triggered thermal shutdown during a heatwave in Southern France.
No Hipot Testing — Safety Defect Shipped to Customers
The previous assembler did not perform high-potential (hipot) testing on production boards. A solder splash bridging the primary-to-secondary isolation barrier went undetected through visual inspection and AOI. The defect was discovered by the client's own safety screening — on a board that had already been invoiced and would have shipped to an installer if the client hadn't caught it internally. For a 230VAC consumer product, this was a potential product liability crisis.
CE Documentation Gaps Blocked Market Entry
When the team compiled their CE technical file for the notified body, the previous assembler couldn't provide production test records, creepage verification data, or material declarations for the PCB laminate. The notified body returned the file with 14 open items — each requiring weeks of back-and-forth with a supplier who didn't understand what CE conformity documentation actually requires.
"We're putting 230 volts on a circuit board that gets mounted in someone's garage, next to their car, accessible to their children. 'Close enough' on creepage isn't close enough. 'Skip the hipot' isn't an option. When our assembler treated this like another LED driver project, we knew we had to find someone who understood what high-voltage consumer safety actually means."
Why They Chose Queen EMS
After the CE rejection and field thermal failures, the team needed a partner who treats every high-voltage board as a safety-critical assembly — not a best-effort build.
High-Voltage DFM with Creepage Verification
Our DFM review includes automated creepage and clearance measurement on every primary-to-secondary boundary — checked against IEC 61851 and IEC 62368 before panelization begins. Breakaway tabs, fiducials, and tooling holes are positioned to never encroach on isolation barriers.
100% Hipot Testing on Every Board
Every power board undergoes 3.75kVAC hipot testing between primary and secondary circuits before release. No sampling — 100% production testing. Hipot results logged per board serial number and included in the CE technical file documentation package.
Power Electronics Thermal Expertise
Validated reflow profiles for 2oz copper power boards. X-ray inspection targeting ≤25% voiding under IGBT thermal pads. Heatsink mounting with calibrated torque drivers and TIM thickness verification. Every thermal interface documented and photographed.
"Queen EMS was the only supplier who asked to see our CE technical file checklist before quoting. They mapped their production documentation to our certification requirements and told us exactly which test records they would generate at each production stage. That conversation gave us confidence we wouldn't face another 14-item rejection from the notified body."
How We Engineered the Build for Their Application
Three board types — one carrying lethal mains voltage — each requiring a distinct safety and thermal strategy for a product installed in consumer homes.
2oz copper with validated IGBT thermal profile
Dedicated reflow profile with extended preheat for heavy copper. X-ray inspection on every IGBT and rectifier pad verifying ≤25% void area. Solder paste volume controlled by SPI to ensure consistent thermal pad wetting. Failed profiles are re-profiled and re-validated — never run on a "close enough" basis.
Creepage slot routing with post-fabrication verification
Routed isolation slots between primary and secondary circuits verified at ≥8mm effective creepage after depaneling. Automated optical measurement confirms no conductive residue in slot walls. Any board with creepage below spec is rejected regardless of other test results.
Torque-controlled mounting with TIM verification
Power board mounted to aluminum heatsink using calibrated torque driver at 0.5 Nm ±10%. Thermal interface material applied by dispensing robot with thickness verification via pressure-sensitive film. Assembly photographs archived per unit serial number for field service reference.
Metering IC calibration and relay driver verification
Energy metering IC calibrated at production using reference current source. Calibration coefficients written to on-board EEPROM and verified. Relay driver outputs tested under rated contactor load to confirm switching thresholds match firmware parameters.
Multi-radio RF verification with OCPP connectivity test
WiFi, 4G, and BLE radios tested individually for transmit power and receiver sensitivity. OCPP 2.0 stack verified by automated connection to a test backend server. Antenna keep-out zones verified during DFM review — same discipline applied to IoT and wireless boards across all our projects.
100% hipot + ground continuity on every unit
3.75kVAC hipot test between all primary and secondary circuit groups. Ground continuity verified at 25A test current. Results logged per board serial number with pass/fail threshold automation — no operator judgment in the safety test loop. Test records formatted for direct inclusion in CE technical file.
From Gerber Upload to Chargers on the Wall
11-day turnkey delivery including component sourcing, assembly, heatsink integration, hipot testing, and CE-ready documentation for all 3 board types.
DFM + Creepage
Day 1–2
BOM Sourcing
Day 1–4
SMT + THT
Day 5–7
X-Ray + AOI
Day 7–8
Hipot + Heatsink
Day 8–9
Functional Test
Day 9–10
Ship DDP
Day 11
Measurable Impact After 10 Months
From the first CE-compliant production batch to 5,000 wallbox units installed across the Netherlands, Germany, and France.
| Metric | Before Queen EMS | After Queen EMS |
|---|---|---|
| 📋 First-Pass Yield | 88.6% (isolation + thermal issues) | 99.5% (validated profiles + 100% hipot) |
| ⚡ Hipot Pass Rate | Not tested (defects shipped) | 100% tested, 100% pass rate |
| 🌡️ IGBT Thermal Failures | 23 field failures in first summer | 0 thermal failures (10 months) |
| 📄 CE Submission | 14 open items, 8-week delay | Passed on first submission |
| ⚙️ Heatsink Integration | Hand-tightened, no TIM control | Torque-calibrated, TIM verified per unit |
| 📈 Production Scale | 200 units (with field recalls) | 5,000 units across 3 EU countries |
"On our fourth production batch, a new procurement team member sourced a non-safety-rated optocoupler for the isolation feedback circuit — same pinout, missing the reinforced insulation rating. Queen EMS caught the part number discrepancy during incoming inspection and flagged it before a single board was populated. That one check prevented 800 chargers from shipping with a component that would have failed CE re-testing."
Is This Approach Right for Your Project?
This engagement model works best for teams building EV chargers, power conversion equipment, solar inverters, or any consumer-accessible product that handles mains voltage on the PCB.
✅ Good Fit If You…
- Build EV chargers, inverters, or power supplies handling 230VAC/400VAC
- Need reinforced insulation with verified creepage and clearance
- Require 100% hipot testing on every production board — no sampling
- Use heavy copper boards with IGBT or MOSFET power switching devices
- Need heatsink integration with controlled torque and TIM application
- Require CE/IEC 61851 documentation support for market certification
🔍 What You Should Ask Us
- How do you verify creepage and clearance after depaneling?
- What hipot voltage and test protocol do you use for EV charger boards?
- How do you control IGBT thermal pad voiding during reflow?
- Can you integrate heatsink mounting with calibrated torque and TIM verification?
- What CE technical file documentation do you provide with each production batch?
- How do you verify safety-rated components during incoming inspection?
Ready to Build with Confidence?
Upload your EV charger Gerber files and BOM. Our engineering team will review your high-voltage design for isolation compliance, thermal management, and CE readiness — with a detailed quote within 24 hours.