Structured approach to requesting, measuring, and qualifying network transformer samples before production commitment.
Sample Request Specification Template
pythonSAMPLE_REQUEST = {
"speed_grade": "1000BASE-T", # or "10/100BASE-TX"
"package": "SMD-16", # SMD-8 / SMD-16 / THT
"poe_rating": "802.3at", # None / 802.3af / 802.3at / 802.3bt
"temp_grade": "industrial", # commercial (0/+70) or industrial (-40/+85)
"isolation_vac": 1500, # V AC minimum; 4000 for medical 2MOPP
"quantity_pcs": 10, # 5-20 for evaluation
"footprint_ref": "H1102NL-compatible", # or None if no compatibility requirement
"required_docs": [
"Datasheet (latest revision)",
"OCL vs DC bias characterization (if PoE-rated)",
"Reflow profile (peak temp, ramp rate)",
"Reel/tape spec (carrier pocket dimensions)",
"RoHS/REACH compliance declaration",
"Application schematic / reference design",
]
}
Pre-Solder Measurement Protocol
pythonimport time
def pre_solder_evaluation(sample_id: str, speed_grade: str) -> dict:
"""
Run before soldering samples onto test PCB.
Returns pass/fail dict with measured values.
"""
MIN_OCL = {
"10/100BASE-TX": 350e-6, # 350 µH
"1000BASE-T": 1000e-6, # 1000 µH
}
results = {}
print(f"[{sample_id}] Step 1: Measure footprint vs. datasheet land pattern")
print(" → Check: pin pitch, pad dimensions, body keepout")
print(" → Mismatch here = redesign before production — catch it NOW")
results["footprint_ok"] = input(" Footprint matches? (y/n): ") == "y"
print(f"\n[{sample_id}] Step 2: OCL — LCR meter @ 100kHz / 0.1V RMS / 0A bias")
ocl_measured = float(input(" Measured OCL (µH): ")) * 1e-6
ocl_min = MIN_OCL[speed_grade]
results["ocl_measured_uH"] = ocl_measured * 1e6
results["ocl_pass"] = ocl_measured >= ocl_min
results["ocl_margin_pct"] = round((ocl_measured / ocl_min - 1) * 100, 1)
print(f"\n[{sample_id}] Step 3: DCR — 4-wire method, both windings")
dcr_pri = float(input(" DCR primary (Ω): "))
dcr_sec = float(input(" DCR secondary (Ω): "))
results["dcr_primary_ohm"] = dcr_pri
results["dcr_secondary_ohm"] = dcr_sec
results["dcr_total_ohm"] = round(dcr_pri + dcr_sec, 3)
print(f"\n[{sample_id}] Step 4: Hipot — 1500V AC, 60 seconds")
results["hipot_pass"] = input(" Pass (zero breakdowns)? (y/n): ") == "y"
results["overall_pass"] = all([
results["footprint_ok"],
results["ocl_pass"],
results["hipot_pass"],
])
return results
Functional Test Protocol
After pre-solder checks PASS → solder onto test PCB, then:
Test 1: Link establishment
Scope: Connect to GbE switch at rated speed (100M or 1G)
Pass: Link up within 5 sec, no auto-negotiate fallback
Test 2: Traffic throughput (1 hour sustained)
Tool: iperf3 / RFC 2544 test
Pass: Zero packet errors, no link drops
Test 3: Cable length sensitivity
Test: 1m / 50m / 100m cable lengths
Pass: Stable link at all three lengths
Test 4: PoE power delivery (if applicable)
Test: Apply max rated current (350mA / 600mA / 960mA) for 30 min
Measure: Transformer temperature rise (IR camera or thermocouple)
Pass: Tj ≤ (rated Tmax − 15°C)
Test 5: Temperature (industrial grade parts)
Test: Repeat Test 1+2 at +70°C ambient
Pass: Link up and stable at temperature
Multi-Source Comparison Matrix
python# Record results from parallel supplier evaluation
sources = {
"Supplier_A": {
"part_no": "VT-GE100AT-SMD",
"ocl_measured_uH": 1150,
"ocl_margin_pct": 15.0,
"dcr_pri": 0.72,
"dcr_sec": 0.68,
"hipot": "PASS",
"link_1m": "PASS", "link_50m": "PASS", "link_100m": "PASS",
"price_usd_per_pc": 0.85,
"lead_time_days": 7,
"moq": 50,
},
"Supplier_B": {
"part_no": "HX-GBE-16P",
"ocl_measured_uH": 1010, # barely above 1000µH minimum
"ocl_margin_pct": 1.0, # low margin — temperature risk
"dcr_pri": 0.91,
"dcr_sec": 0.88,
"hipot": "PASS",
"link_1m": "PASS", "link_50m": "PASS", "link_100m": "FAIL", # ← issue
"price_usd_per_pc": 0.65,
"lead_time_days": 14,
"moq": 500,
},
}
Sample-to-Production Checklist
Week 1: [ ] Send complete sample request with spec sheet
[ ] Receive samples + documentation package via DHL
Week 2: [ ] Dimensional check (footprint match)
[ ] OCL / DCR / Hipot measurements on all samples
Week 3: [ ] Solder onto test PCB, functional tests 1-3
Week 4: [ ] PoE thermal test (if applicable), temperature test
Week 5: [ ] Compare multiple sources, select primary + alternate
Week 6: [ ] BOM update with approved part numbers
Week 7: [ ] Supplier qualification docs (ISO cert, CoC, test report)
Week 8+: [ ] First production order (confirm lead time for required quantity)
Voohu Technology — www.voohuele.com
Samples from stock | MOQ 50pcs | DHL 3–5 days | Japan / Korea / SE Asia | OCL bias data included