2,000 Soil Sensors Deployed Across 3 Countries in 9 Months
A seed-funded agtech startup needed ultra-low-power IoT boards with LoRa connectivity and IP67 protection — built to survive 5 years buried in open farmland without maintenance.
A Seed-Funded Agtech Startup, Tel Aviv, Israel
This four-person engineering team builds wireless soil monitoring sensors that measure moisture, temperature, salinity, and nutrient conductivity at three depth levels. Their data feeds a cloud-based irrigation recommendation engine used by commercial farms in Israel, Spain, and California. Each sensor is designed to operate maintenance-free for 5 years on a single lithium thionyl chloride battery.
Product Type
Wireless soil sensor with tri-depth probes, LoRa 868/915 MHz radio, and solar-assisted lithium primary battery — deployed in-ground on commercial farms
Technical Complexity
Single compact PCBA (42mm × 68mm) with ultra-low-power MCU, LoRa transceiver, 3-channel ADC for soil probes, on-board voltage regulator, and chip antenna — sleep current budget under 3µA
Production Volume
Scaling from 50 evaluation units for field trials to 2,000 units for commercial deployment — with unit cost targets that demand panelized production at high yield
What They Needed
A PCBA partner that understands ultra-low-power assembly cleanliness, RF antenna keep-out compliance, conformal coating for IP67 environments, and rapid iteration from prototype to volume
What Went Wrong with Their Previous Supplier
The team's first 200 field sensors started dying after 11 months instead of the designed 5-year lifespan. The root cause wasn't a design flaw — it was an assembly quality problem.
Flux Residue Was Silently Draining the Battery
The entire product relies on a 3µA sleep current budget. Flux residue between the MCU's fine-pitch pads created parasitic leakage paths drawing an additional 8–12µA continuously. The problem was invisible during functional testing — the board worked perfectly — but it cut battery life from 5 years to under 14 months. The team discovered this only after 47 sensors went silent in the field within the same two-week window.
LoRa Antenna Performance Degraded by 6dB
The chip antenna datasheet specifies a strict copper-free keep-out zone on the PCB. The previous assembler placed a decoupling capacitor and a test point within the exclusion area during panelization — neither was in the original layout, both were added to "improve testability." The result: a 6dB drop in radiated power, cutting communication range from 4km to under 1.5km. Sensors deployed in large open fields couldn't reach the gateway.
Conformal Coating Didn't Survive the First Rainy Season
The previous supplier applied a thin acrylic conformal coating that met basic testing requirements on the bench. But the sensors are deployed in-ground in Mediterranean and California climates — 40°C daytime heat followed by condensation at dawn, repeated daily for months. The coating delaminated at board edges after six months, allowing moisture ingress that corroded exposed copper and eventually shorted the power regulator.
Four Design Iterations, Four Separate Quotes and Setup Fees
The team needed to iterate quickly during field trials — adjusting probe ADC filtering, tuning LoRa transmit power, and modifying the sleep cycle timing. Each revision required a full re-quote, new stencil setup charge, and 3-week lead time from their supplier. For a seed-funded team with a limited runway, the accumulated NRE fees and delays consumed both budget and patience.
No Support for Scaling — "We Don't Do More Than 500"
When the pilot program succeeded and the team needed to scale from 200 to 2,000 units, their prototype-focused supplier couldn't accommodate the volume. They quoted the same per-unit price at 2,000 units as at 50 — no panelization optimization, no volume component pricing, no production engineering support. The team was stuck between a prototype shop that couldn't scale and a mass-production factory that wouldn't touch 2,000 units.
"We promised our pilot customers 5-year maintenance-free operation. When 47 sensors died in month 11, we weren't just losing hardware — we were losing the credibility that took us two years to build. The boards passed every test on the bench. The problem was invisible until it killed them in the field."
Why They Chose Queen EMS
After the field failure crisis, the team needed a partner who understood that assembly cleanliness isn't optional for ultra-low-power IoT — it's the difference between a 5-year product and a 1-year disposable.
Ultra-Low-Power Assembly Cleanliness
Post-reflow aqueous cleaning on every board, followed by ionic contamination testing verified below 0.75 µg/cm² NaCl equivalent. For a 3µA sleep budget, even trace flux residue is a reliability failure. We treat cleanliness as a functional specification, not an aesthetic preference.
RF-Aware DFM Review
Our DFM process includes antenna keep-out zone verification against manufacturer datasheets. We review panelization breakaway tab placement, fiducial locations, and test point positions to ensure nothing encroaches on the RF exclusion area — before the first stencil is cut.
Prototype-to-Volume in One Relationship
No re-quoting for minor revisions during iteration. Stencil and programming setup carried forward across board revisions. When the team was ready to scale from 200 to 2,000 units, we optimized panelization, negotiated volume component pricing, and maintained the same 8-day lead time.
"With our previous supplier, every board order was a project management exercise. With Queen EMS, I upload files, confirm the order, and boards show up on time. It sounds basic, but when you're a four-person team trying to deploy 2,000 sensors before the planting season, 'basic' is exactly what you need."
How We Engineered the Build for Their Application
A single compact PCBA that must survive 5 years in open farmland — where temperature swings, moisture, and soil chemistry test every material and solder joint on the board.
Aqueous cleaning + ionic contamination testing
Post-reflow aqueous cleaning removes all flux residue from the MCU and ADC pads. Ionic contamination measured on every production panel — boards exceeding 0.75 µg/cm² are rejected. This single process step restored the 3µA sleep current budget that the previous supplier's dirty boards couldn't achieve.
Antenna keep-out enforcement with panelization check
Chip antenna exclusion zone verified against Semtech reference design before stencil generation. Panelization breakaway tabs positioned to avoid the antenna ground plane. DFM report includes an annotated overlay showing the exclusion zone boundary relative to all nearby components.
Precision ADC with humidity-resistant conformal coating
The 3-channel 24-bit ADC measures soil conductivity at microvolt resolution. Silicone conformal coating applied to the entire analog front-end section, with masking on probe connectors only. Silicone selected over acrylic for its superior moisture resistance and flexibility across -20°C to +60°C thermal cycling.
Leakage-verified voltage regulator circuit
Ultra-low quiescent current LDO regulator with verified shutdown leakage under 0.5µA. Board-level sleep current measured on a sample from every production panel using a nanoampere-resolution current meter. Any board exceeding 4µA total sleep current is flagged and quarantined.
Silicone conformal coating for 5-year outdoor life
Full-board silicone conformal coating (MIL-I-46058C Type SR) applied by selective spray with programmed masking on battery terminals, probe connectors, and programming header. Coating thickness verified at 50–130µm using dry film measurement. UV inspection confirms continuous coverage with no pinholes or skip areas.
Panelized production with automated depaneling
4-up panelization with V-score routing designed around the antenna keep-out zone. Automated depaneling eliminates board flex stress near fine-pitch components. Panel design optimized for maximum SMT line utilization — reducing per-unit assembly cost by 32% compared to the team's previous single-board workflow.
From Gerber Upload to Sensors in the Field
8-day turnkey delivery including component sourcing, assembly, cleaning, coating, and testing — fast enough to keep up with planting season deadlines.
DFM + RF Check
Day 1
BOM Sourcing
Day 1–3
SMT Assembly
Day 3–5
Clean + Test
Day 5–6
Coat + Inspect
Day 6–7
Ship DDP
Day 8
Measurable Impact After 9 Months
From the first clean prototype batch to 2,000 sensors deployed across commercial farms in Israel, Spain, and California.
| Metric | Before Queen EMS | After Queen EMS |
|---|---|---|
| 📋 First-Pass Yield | 93.1% | 99.5% |
| 🔋 Measured Sleep Current | 11–15µA (3µA budget) | 2.7µA (within budget) |
| 📡 LoRa Range (Open Field) | 1.2–1.5km (degraded) | 3.8–4.2km (per spec) |
| 🔧 Field Failure Rate (9 months) | 23.5% (47 of 200 dead) | 0.3% (6 of 2,000) |
| 💰 Per-Unit Assembly Cost | $8.40 (single board, no optimization) | $5.70 (panelized, volume pricing) |
| 📈 Production Scale | 200 units (with 23.5% field losses) | 2,000 units across 3 countries |
"When we submitted our Rev 4 files, Queen EMS noticed we'd added a debug LED that would draw 2mA during each sensor wake cycle. They calculated the cumulative impact on battery life — it would have cut our 5-year target to 3.2 years. We removed the LED before production. That's the kind of thinking you can't get from a supplier who just builds what you send."
Is This Approach Right for Your Project?
This engagement model works best for teams building IoT devices, environmental sensors, or connected hardware that must operate reliably for years in outdoor or uncontrolled environments.
✅ Good Fit If You…
- Build battery-powered IoT devices targeting 3+ year unattended operation
- Require ultra-low sleep current verified at the board level, not just the schematic
- Deploy sensors outdoors in temperature extremes, moisture, or corrosive environments
- Use LoRa, NB-IoT, or other LPWAN radios with chip antennas requiring keep-out compliance
- Need to scale from 50 prototypes to 2,000+ production units with one supplier
- Operate on a startup budget where per-unit cost optimization matters at every stage
🔍 What You Should Ask Us
- What ionic contamination level do you guarantee after post-reflow cleaning?
- How do you verify antenna keep-out zones during panelization?
- Can you measure sleep current at the board level during production testing?
- What conformal coating do you recommend for 5-year outdoor exposure?
- How does your pricing change from 50 to 500 to 2,000 units?
- Can you carry my stencil and program setup across board revisions without re-charging NRE?
Ready to Build with Confidence?
Upload your IoT sensor Gerber files and BOM. Our engineering team will review your design for ultra-low-power assembly, RF compliance, and environmental protection — with a detailed quote within 24 hours.