Structured approach to requesting, measuring, and qualifying network transformer samples before production commitment.

Sample Request Specification Template

pythonSAMPLE_REQUEST = {

# Required fields — specify ALL before contacting supplier

"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

# Documents to request with samples

"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 = {}



# 1. Dimensional check

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"



# 2. OCL measurement

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)



# 3. DCR measurement

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)



# 4. Hipot test

print(f"\n[{sample_id}] Step 4: Hipot — 1500V AC, 60 seconds")

results["hipot_pass"] = input("  Pass (zero breakdowns)? (y/n): ") == "y"



# Summary

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,

},

}

→ Supplier_A: preferred. Better OCL margin, passes 100m cable, lower MOQ.

→ Supplier_B: disqualified on 100m cable test AND has very low OCL margin.

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