1,800 Commercial Fish Finder Boards Shipped with Zero Saltwater Corrosion Failures
An Oslo marine tech startup needed PCBs that survive Norwegian trawler conditions — saltwater spray, hull vibration, and −20°C to +65°C thermal swings. After one assembler's boards failed salt spray testing, they came to Queen EMS.
A Seed-Stage Marine Tech Startup, Oslo, Norway
This 11-person team builds compact commercial fish finders for professional Nordic fishing vessels — combining CHIRP sonar, GPS chart plotting, and AIS receiver into a single ruggedised unit designed for wheelhouse mounting on trawlers and coastal fishing boats.
Product Type
CHIRP fish finder / sonar unit for commercial fishing vessels. 3 boards: sonar processing board, GPS/AIS RF board, and power management board. All rated for IP67 ingress protection.
Operating Environment
Norwegian fjords and North Sea: saltwater spray, condensation, diesel exhaust, continuous hull vibration, −20°C winter cold starts, and summer wheelhouse temperatures above 50°C
Production Volume
150 units per quarter scaling to 600/quarter — sold through Norwegian maritime distributors and direct to fishing vessel operators across Scandinavia and the Faroe Islands
What They Needed
A PCBA partner experienced in conformal coating for saltwater environments, selective potting for IP67 subassemblies, vibration-resistant THT soldering, and salt spray testing validation before production release
What Went Wrong with Their Previous Supplier
The team's first assembler had never built for marine environments. They treated conformal coating as an afterthought — applied once, by hand, with no process control. The North Sea disagreed.
Salt Spray Test Failed at 24 Hours — Entire Pre-Production Batch Rejected
IEC 60068-2-11 salt spray testing at 35g/L NaCl for 96 hours is standard for commercial marine electronics. The previous assembler applied a single pass of acrylic conformal coating by brush — coverage was uneven, with holidays (uncoated voids) at component edges and connector bases. 24 hours into salt spray testing, the sonar processing board's power regulator pads showed visible copper oxide. The full pre-production batch of 60 units failed. The team lost their first production window ahead of the Norwegian autumn fishing season.
THT Connector Joints Cracking Under Hull Vibration
The fish finder uses 12 through-hole connectors for sonar transducer cables, power, and external sensors. On vessels, these connectors carry plug-unplug cycles and constant engine vibration. The previous assembler used a wave solder profile calibrated for consumer electronics — inadequate hole fill and excess flux residue wicking into the joint. After 3 months of sea trials, 8 of the 30 connectors showed cracked solder fillets visible under 10× magnification. IPC-A-610 requires minimum 75% hole fill on THT joints for marine-grade assemblies; the failed joints were at 40–55%.
Potting Compound Delamination Voided IP67 Rating
The power management board is potted in polyurethane inside the housing to achieve IP67 sealing. The previous assembler used a two-part urethane without pre-baking the PCB to remove absorbed moisture. During curing, the trapped moisture created micro-bubbles in the potting layer — visible on cross-section as a honeycomb structure near the board surface. The voids created a capillary path for saltwater ingress, voiding the IP67 rating. One unit installed on a trawler showed visible water inside the potting within 6 weeks of deployment.
Coating Contaminated RF Keep-Out Zones on GPS/AIS Board
The GPS/AIS RF board has strict keep-out zones around the patch antenna and LNA input — conformal coating applied within these zones changes the local dielectric constant and degrades antenna gain. The previous assembler applied coating across the entire board without masking. GPS acquisition time increased from 45 seconds to 4 minutes on coated boards, and AIS receiver sensitivity dropped by 6 dB. Both problems were invisible to visual inspection but immediately apparent during RF performance testing.
No Environmental Test Capability — Defects Discovered by the Customer
The previous assembler had no in-house salt spray chamber, thermal shock capability, or vibration test fixture. Every environmental defect was discovered either by the client's own test team or — in three cases — by fishing vessel operators in the field. For a product sold to professional mariners who depend on fish finding equipment for their livelihood, field failures are a direct business liability and a reputational crisis in the small Nordic marine electronics market.
"Commercial fishermen don't call customer service when their fish finder fails in the middle of the Barents Sea. They call their distributor and tell everyone they know. We needed an assembler who understood that marine-grade isn't a marketing label — it's a commitment to the worst conditions a North Sea trawler will actually see."
Why They Chose Queen EMS
After the salt spray failure and vibration joint cracks, the team needed a partner with marine-specific process knowledge — not a generic CM willing to add "conformal coating" as a line item.
Three-Pass Conformal Coating with Robotic Application
Queen EMS applies conformal coating in three controlled passes using selective robotic dispensing — masking RF keep-out zones, connector contacts, and test pads to within 0.5 mm. Thickness is verified by UV fluorescence inspection and cross-section coupon at the start of each batch. No brush, no hand application, no holidays.
Marine-Grade THT Soldering with IPC Class 3 Hole Fill
Connector THT joints are soldered with a selective soldering process optimised for ≥75% hole fill — verified by cross-section on sample joints at the start of each production run. No-clean flux residue is fully removed from connector joints to eliminate wicking under vibration. Joint cross-sections are photographed and included in the shipment documentation.
Pre-Baked PCB Potting with IP67 Validation
Before potting, all PCBs are baked at 105°C for 4 hours to drive out absorbed moisture — eliminating the bubble formation that voided the previous assembler's IP67 claim. Queen EMS performs water immersion testing at 1m depth for 30 minutes on 3 samples per batch per IEC 60529 IP67 protocol before releasing production.
"Queen EMS was the first assembler we spoke to who mentioned pre-baking PCBs before potting without us asking. That one detail told us they had actually done this before. Every other supplier just listed 'urethane potting' as a capability — Queen EMS described the process step by step. That's what earned the order."
How We Engineered the Build for Marine Deployment
Three boards. Three distinct protection strategies. One unified production process validated to North Sea conditions before a single production unit was shipped.
Triple-pass silicone coating + salt spray validation
Three robotic coating passes at 50 µm per pass, verified by UV fluorescence inspection between passes. Board edges coated to prevent ingress at the PCB perimeter — the most common coating holiday location. Salt spray coupon tested to 96 hours per IEC 60068-2-11 before each new batch release. Coating thickness report included per shipment.
Selective coating with GPS/AIS antenna masking
Patch antenna keep-out zone and LNA input masked to ±0.5 mm by robotic dispenser program. AIS receiver sensitivity and GPS acquisition time tested on 5 boards per batch using a calibrated RF signal generator — pass criteria ≤60s acquisition, RSSI within 3 dB of nominal. Boards outside tolerance are re-masked and re-coated, not shipped.
Moisture-purged urethane potting at IP67
PCB pre-baked at 105°C for 4 hours. Two-part polyurethane degassed under vacuum before dispensing. Potting applied in a temperature-controlled environment (23°C ±2°C) to ensure consistent viscosity. Cured assemblies tested per IP67: 1m immersion for 30 minutes. Three samples per batch validated; any failure triggers root-cause and re-validation before production release.
Selective soldering with IPC Class 3 verification
All 12 THT connectors soldered by selective soldering with a dedicated thermal profile for connector body mass. Hole fill measured by cross-section on 3 connector samples per batch — minimum 75% required per IPC-A-610 Class 3. Flux residue fully cleaned from all THT joints. Results photographed and archived per batch for customer field service reference.
Random vibration test per IEC 60068-2-64
Assembled boards tested on a vibration table at 5–500 Hz, 0.04 g²/Hz spectral density for 1 hour per axis. This simulates the power spectral density profile of a diesel trawler engine at 1,200–1,800 RPM. Post-vibration AOI and connector contact resistance measurement confirm no joint degradation. Test data included in documentation for insurance and certification purposes.
Cold start validation at −20°C
3 boards per batch thermally cycled from −20°C (Norwegian winter cold start) to +65°C (wheelhouse summer) for 50 cycles per IEC 60068-2-14. Solder joint integrity verified by electrical continuity test before and after cycling. ENIG surface finish specified to prevent intermetallic whisker growth at cold-cycle temperatures.
From Gerber Upload to Boards in Oslo
13-day turnkey delivery including saltwater-proof coating, IP67 potting, vibration testing, and thermal shock validation — all documented for maritime certification.
DFM + Marine Review
Day 1–2
BOM Sourcing
Day 1–4
SMT + Selective THT
Day 5–7
3-Pass Coating + Potting
Day 7–9
Salt Spray + IP67 Test
Day 9–11
Vibration + Thermal
Day 11–12
Ship DDP Oslo
Day 13
Measurable Impact After 12 Months at Sea
1,800 units deployed on Norwegian, Faroese, and Icelandic commercial fishing vessels — including 40 trawlers operating in the Barents Sea in winter conditions.
| Metric | Before Queen EMS | After Queen EMS |
|---|---|---|
| 📋 First-Pass Yield | 71% (salt spray + joint failures) | 99.2% (validated process + in-process testing) |
| 🌊 Salt Spray (96h IEC 60068-2-11) | Failed at 24h (brush-applied coating) | 100% pass — 3-pass robotic coating |
| 💧 IP67 Potting Integrity | Delamination in 1 of 5 units (moisture bubbles) | 100% pass — pre-baked + vacuum-degassed urethane |
| 🔩 THT Connector Hole Fill | 40–55% (cracked joints after 3 months) | ≥75% IPC Class 3 — selective solder + cross-section |
| 📡 GPS/AIS RF Performance | GPS 4 min acquisition / AIS −6 dB degraded | ≤60s acquisition / AIS within 3 dB nominal |
| ⚙️ Vibration Test (IEC 60068-2-64) | Not tested | Pass — 1h per axis, 5–500 Hz random |
| 🐟 Field Corrosion Failures | 9 returns from first 60 field units | 0 returns in 12 months / 1,800 units |
"During BOM review for our third production batch, Queen EMS flagged that a replacement capacitor our buyer had sourced had a silicone-coated body — a common issue with certain MLCC suppliers. Silicone body coatings inhibit conformal coating adhesion, creating delamination points. We hadn't caught it; neither did our previous supplier on the first batch. Queen EMS substituted a compatible part number before any boards were built. That catch alone prevented a coating adhesion failure across 300 units."
Is This Approach Right for Your Project?
This engagement model works best for teams building marine electronics, outdoor industrial sensors, offshore energy equipment, or any product where saltwater, humidity, or immersion is a real-world operating condition.
✅ Good Fit If You…
- Build electronics for marine, offshore, or waterfront industrial environments
- Need IP67 or higher ingress protection with validated potting process
- Require conformal coating with RF antenna keep-out masking
- Use through-hole connectors that must survive continuous vibration
- Need salt spray testing to IEC 60068-2-11 as part of production release
- Require thermal shock validation for cold-start operating conditions
🔍 What You Should Ask Us
- How many coating passes do you apply, and how do you verify coverage?
- Do you pre-bake PCBs before potting to eliminate moisture bubbles?
- How do you mask RF antenna keep-out zones during conformal coating?
- What THT hole fill percentage do you achieve on marine-grade connectors?
- Can you provide salt spray and IP67 test reports with each production shipment?
- What vibration test profile do you use, and how is it documented?
Building Electronics for Harsh Marine Conditions?
Send us your Gerbers and operating environment spec. Our engineering team will review your conformal coating requirements, potting approach, and connector strategy — with a detailed quote within 24 hours.