PCB Substrates — Family Index

Reference index of printed-circuit-board (PCB) base materials: rigid epoxy-glass laminates, halogen-free, high-speed digital, RF/microwave hydrocarbon and PTFE, polyimide flex, metal-core insulated substrates, and ceramic carriers. Properties, brand exemplars, and selection heuristics. Adjacent technology families: see [[Engineering/Tier3/semiconductor-packages]], [[Engineering/Tier3/passive-components]], [[Engineering/Tier3/ceramics-taxonomy]].

1. At a glance — substrate families by application

• Rigid epoxy-glass (FR-4 family) — ~95 % of all PCBs by area. Woven E-glass cloth impregnated with brominated or phosphorus-cured epoxy resin. Standard Tg 130 °C up to 200 °C variants. Examples: Kingboard KB-6160, Shengyi S1141/S1170, ITEQ IT-180A, Isola 370HR.
• High-Tg FR-4 (lead-free reflow capable) — Tg ≥ 170 °C, decomposition (T_d) ≥ 340 °C, to survive 245-260 °C SnAgCu reflow without delamination. Shengyi S1170, ITEQ IT-180A, Panasonic R-1566W.
• Halogen-free — phosphorus-FR resins replacing Br/Cl. ITEQ IT-150GS, Panasonic R-1755V, Shengyi S1150G, Isola IS400, TUC TU-768. Driven by RoHS, OEM eco mandates.
• Mid-loss high-speed digital — Df ~0.010–0.015 at 1 GHz for PCIe 4 / DDR4 / 25 GbE backplane. Isola FR408HR, Panasonic Megtron 4, Nelco N4000-13, ITEQ IT-958G, EMC EM-285K.
• Low-loss / ultra-low-loss high-speed digital — Df 0.002–0.005 at 12 GHz for 56G/112G SerDes, 400/800 GbE, datacenter spine. Panasonic Megtron 6/7, Isola Tachyon 100G, EMC EM-528K, Shengyi S7439, Nelco N4000-13EP/SI.
• RF / microwave hydrocarbon-ceramic — Rogers RO4003C, RO4350B; Isola Astra MT77; Taconic RF-35. Cellular base station 1-6 GHz, automotive 24 GHz radar, satcom.
• RF / microwave PTFE-based — Rogers RO3003, RO5880, RO5880LZ; Taconic TLY, RF-60; Arlon AD250C. Lowest Df (0.0009-0.0017) for mm-wave 28-77 GHz, but soft and dimensionally unstable.
• Polyimide flex — DuPont Kapton (HN, PV9) plus copper-clad Pyralux LF/AP/TK. Smartphone camera and display tails, HDD head-suspensions, satellite harnesses.
• Metal-core (Insulated Metal Substrate, IMS) — Al or Cu base, thin filled-epoxy dielectric, Cu foil. Bergquist (Henkel) Thermal Clad T-Clad/HPL, Laird, Ventec VT-4B5. High-power LED, EV gate-drive.
• Ceramic substrates — Al₂O₃ (96, 99.5 %), AlN, Si₃N₄ DBC/AMB for SiC/GaN power modules. Hybrid microelectronics, RF MMIC carriers, IGBT/SiC modules.
• LTCC / HTCC — co-fired multilayer ceramic for RF front-end modules (LTCC) and high-temp / power-module packaging (HTCC).

2. Property cheat-sheet

Substrate	Dk @ 10 GHz	Df / tan δ @ 10 GHz	Tg (°C)	T_d (°C)	CTE_z (ppm/°C)	k_th (W/m·K)	Typical use	Approx. $/m²
FR-4 standard (Shengyi S1141)	4.5	0.022 @ 1 GHz	135	305	60 (<Tg)	0.4	Consumer rigid	12-25
FR-4 mid-Tg (S1150G HF)	4.4	0.018 @ 1 GHz	150	340	55	0.4	Industrial	20-35
FR-4 high-Tg (S1170, IT-180A)	4.3	0.018 @ 1 GHz	170	350	50	0.4	Lead-free reflow	30-45
Isola 370HR	4.0	0.021 @ 1 GHz	180	340	50	0.4	Auto/industrial	35-55
Megtron 4 (R-5775)	3.8	0.013 @ 1 GHz	200	380	45	0.5	PCIe 4 server	80-130
Isola FR408HR	3.7	0.010 @ 1 GHz	200	360	45	0.4	DDR4 backplane	80-130
Megtron 6 (R-5775N)	3.4	0.004 @ 12 GHz	185	410	38	0.5	56G SerDes	250-400
Megtron 7 (R-5785N)	3.3	0.002 @ 12 GHz	200	410	35	0.5	112G SerDes / 400 GbE	400-600
Isola Tachyon 100G	3.0	0.0021 @ 10 GHz	200	360	30	0.4	100/400 GbE	350-550
EMC EM-528K	3.3	0.003 @ 10 GHz	200	400	35	0.5	High-speed server	300-500
Rogers RO4003C	3.38	0.0027	280	425	46	0.71	Sub-6 cellular, radar	200-300
Rogers RO4350B	3.48	0.0037	280	390	50	0.69	5G mm-wave 28 GHz	200-350
Rogers RO3003	3.00	0.0010	(PTFE)	—	24	0.50	77 GHz auto radar	400-700
Rogers RO5880	2.20	0.0009	(PTFE)	—	237	0.20	Premium RF / satcom	500-900
Isola Astra MT77	3.00	0.0017	200	360	28	0.7	mm-wave radar	300-500
Taconic RF-35	3.50	0.0018	(PTFE-blend)	—	50	0.24	Antennas, base station	200-400
Taconic TLY-5	2.20	0.0009	(PTFE)	—	—	0.22	Antennas	400-700
DuPont Kapton HN (PI)	3.4	0.018	360 (Tg none, no melt)	520	—	0.12	Flex base film	n/a (film)
DuPont Pyralux AP	3.4	0.014	—	500	—	0.12	FPC copper-clad	100-200
Bergquist HPL (IMS)	4.5 (DK diel.)	—	—	—	50	3.0 (diel.)	LED, gate-drive	100-180
Ventec VT-4B5 (IMS)	4.5	—	130	—	50	2.2	LED	80-150
Al₂O₃ 96 %	9.8	0.0001	—	—	7.1	24	Thick-film hybrid	varies
Al₂O₃ 99.5 %	9.9	0.0001	—	—	7.4	28	Thin-film MMIC	varies
AlN	8.9	0.0005	—	—	4.6	170-220	SiC power module DBC	high
Si₃N₄	7.9	0.0007	—	—	2.7	70-90	EV traction inverter	very high
BT-epoxy (Mitsubishi CCL-HL832)	4.1	0.013	185	390	50	0.4	BGA substrate	60-120

Notes: Dk and Df vary with frequency; values are nominal at the listed frequency. T_d defined at 5 % weight-loss per IPC-TM-650 2.3.40. Prices indicative only, fluctuate with copper and resin cost cycles.

3. FR-4 family

FR-4 is a NEMA grade (NEMA LI-1, 1968): “flame-retardant grade 4” — woven E-glass cloth saturated with a brominated epoxy resin and B-staged (prepreg). The brominated chemistry achieves UL 94 V-0 burn rating. FR-4 is a class, not a single product; hundreds of commercial laminates qualify.

Standard Tg ~130-140 °C: Kingboard KB-6160, Shengyi S1141, ITEQ IT-140, Nan Ya NPG-150. Suitable for SnPb reflow (215 °C peak) but not robust for SnAgCu. Cheapest grade, 12-25 USD/m² for 1.6 mm core.

Mid-Tg ~150 °C: Shengyi S1150, ITEQ IT-158, Isola 185HR. Common in industrial and automotive infotainment. Halogen-free variants common at this Tg.

High-Tg ~170 °C: Shengyi S1170, ITEQ IT-180A, Isola 370HR (Tg 180). The workhorse grade for lead-free reflow. T_d ≥ 340 °C means ≥ 30 min above 260 °C without blistering. Required by IPC-4101 /99 spec.

Very-high-Tg ~180-200 °C: Panasonic R-1566W, Shengyi S1141B, Isola IS410 (Tg 200). For multilayer thick boards (> 16 layers) needing extra z-axis stability through repeated lamination cycles.

Mechanical: Dk ~4.2-4.6 @ 1 GHz drifting to ~4.0-4.3 @ 10 GHz (frequency-dispersive), Df ~0.020-0.025 @ 1 GHz. Glass-resin Dk anisotropy causes “fiber-weave effect” — high-speed signals over glass bundle see higher Dk than between bundles → skew. Spread-glass (low-DK) styles 1078, 1086 mitigate; 1080 / 2116 / 7628 are conventional weaves.

4. Halogen-free laminates

Driven by RoHS, JEDEC JS709, and OEM eco-labels (Sony Green Partner, Apple regulated substances). The brominated TBBPA flame retardant is replaced with phosphorus-functional resins (e.g., DOPO-cured), nitrogen synergists, or aluminum hydroxide / magnesium hydroxide fillers.

Common brands:

• ITEQ IT-150GS, IT-180GA — phosphorus-cured, halogen-free, automotive-qualified.
• Panasonic R-1755V / R-1577 — server-grade halogen-free.
• Shengyi S1150G, S1165 — high-Tg halogen-free.
• Isola IS400 — high-Tg, halogen-free, Pb-free reflow.
• TUC TU-768 — Tg 175 °C halogen-free.

Trade-offs: Df ~10-20 % higher than brominated equivalent at matched Dk; moisture absorption slightly higher; cost premium 15-30 %. Now the default for new consumer/automotive designs in EU/JP markets.

5. Mid-loss high-speed digital

Sweet-spot grade between commodity FR-4 and premium low-loss laminates. Df 0.010-0.015 at 1 GHz, sufficient for PCIe 3/4, DDR3/DDR4, 10/25 GbE backplane at moderate reach ( 0.5 m).

Exemplars: Isola FR408HR, Panasonic Megtron 4 (R-5775), Nelco N4000-13, ITEQ IT-958G, EMC EM-285K, Shengyi S7045, Nan Ya NP-175TL. Most use a filled epoxy or modified-epoxy resin (BT or cyanate-ester blend) on standard or spread E-glass.

Cost: roughly 2-3 × FR-4 high-Tg. Compatible with standard FR-4 fab processes — drill, plate, image, no special press cycles required.

6. Low-loss / ultra-low-loss high-speed digital

For 56 Gbit/s NRZ, 112 Gbit/s PAM4, 400/800 GbE, datacenter spine fabric, AI accelerator interconnect. Df < 0.005 at 12 GHz, often combined with very-low-profile (VLP) or reverse-treat (RTF) copper foil to minimize skin-effect surface roughness loss.

• Panasonic Megtron 6 (R-5775N) — Df ~0.004 @ 12 GHz. The de-facto standard for 56G server backplane.
• Panasonic Megtron 7 (R-5785N) — Df ~0.002 @ 12 GHz. Cost premium over M6 ~50 %. 112G PAM4 reach.
• Panasonic Megtron 8 (R-5575) — newer, lower Df still, aimed at 224G.
• Isola Tachyon 100G — Df 0.0021 @ 10 GHz. Spread-glass with hyper-VLP copper.
• EMC EM-528K, EM-892K, EM-528S — Taiwanese low-loss family, popular in Tier-1 ODM boards.
• Nelco N4000-13EP/SI (Park Aerospace) — long-standing aerospace and high-end server.
• Shengyi S7439, S7045G — Chinese low-loss for 5G base-station and AI.
• Showa Denko (Resonac) MCL-LZ-71G.

Cost: 3-5 × FR-4. Often constrained by glass-cloth weave skew — designs route diff-pairs at ±10° off the warp/fill direction to randomize fiber crossings (“zig-zag routing”).

7. RF / microwave laminates

Two families: ceramic-filled hydrocarbon (semi-rigid, FR-4-like processing) and PTFE-based (softer, special drill/plating).

Hydrocarbon-ceramic (rigid, easy fab):

• Rogers RO4003C — Dk 3.38, Df 0.0027 at 10 GHz. Workhorse for cellular base-station 1-6 GHz, automotive 24 GHz BSD radar. No flame retardant, but UL 94 V-0 achievable in stackup.
• Rogers RO4350B — Dk 3.48, Df 0.0037. RO4003C with brominated FR. The most-specified mm-wave laminate for 5G n257/n258/n260/n261 bands.
• Rogers RO4360G2 — Dk 6.15 — slow-wave compact phased-array radiators.
• Isola Astra MT77 — Dk 3.0, Df 0.0017 at 10 GHz. Direct RO4350B alternative, often lower cost. UL 94 V-0.
• Taconic RF-35, RF-60A — Dk 3.5 / 6.15, Df 0.0018 / 0.0028. Glass-reinforced PTFE-ceramic. UMS antennas and base station.

PTFE-based (lowest loss):

• Rogers RO3003 — Dk 3.00, Df 0.0010 at 10 GHz. CTE_x/y ~17 ppm/°C closely matched to copper; key for 77 GHz auto radar.
• Rogers RO3010 — Dk 10.2, Df 0.0022.
• Rogers RO5880 — Dk 2.20, Df 0.0009 at 10 GHz. Glass-microfiber-reinforced PTFE. Premium RF, but soft; CTE 237 ppm/°C in z requires careful PTH design.
• Rogers RO5880LZ — same family, lower-Z thickness.
• Taconic TLY-5, TLY-3, RF-30 — competitor PTFE family.
• Arlon AD250C, AD300C, AD350C — PTFE-glass, military aerospace.

PTFE laminates require sodium-naphthalenide or plasma surface activation before electroless copper plate-through-hole (PTH) — standard FR-4 epoxy desmear does not bond to PTFE.

8. Mixed-dielectric hybrid stackups

Common in radar and base-station designs: 1-2 RF layers on Rogers (top/bottom) over inner digital control layers on FR-4 or Megtron, pressed together with bonding film. Reduces cost (only RF layers carry the expensive laminate) and lets a single board carry both RF front-end and digital baseband.

Bond plies: Rogers RO4450F / RO4450T (matched to RO4003C/RO4350B), Arlon CuClad 6700, 3M FastRise FR-27, Taconic fastRise. Bonding films are B-staged thermosets cured at 180-220 °C with 250-450 psi during lamination.

Design caveats: CTE mismatch in z (Rogers ~50 vs FR-4 ~50 — close, manageable) and lateral expansion (RO5880 PTFE is much higher). Stackups with RO5880 + FR-4 are rare for this reason; RO4003C / RO4350B + FR-4 is the standard pairing.

9. Polyimide / flex

DuPont Kapton, invented 1965, is the original polyimide film: Tg 360 °C (in practice no glass transition or melt; decomposes above 520 °C). Variants: HN (heat-stabilized), PV9 (plasma-treated for adhesion), VN (low-shrink). Standard thickness 25, 50, 75 µm.

Copper-clad polyimide (flexible printed circuit, FPC) base material:

• DuPont Pyralux AP — adhesiveless, sputtered seed + plated copper on PI. Premium HDI flex.
• DuPont Pyralux LF — acrylic-adhesive copper-clad PI. Older, cheaper.
• DuPont Pyralux TK — fluoropolymer-bonded PI for low-Dk RF flex.
• Taiyo Ink TP series — Japanese FPC base.
• Sheldahl Novaclad G2300 — aerospace-grade adhesiveless PI.

Applications: smartphone camera-module ribbon, display tails (LCD/OLED-to-PCB), HDD head-stack-assembly suspensions (HDD head reads through a PI suspension carrying ~25 µm RA copper traces), satellite harnesses (radiation-tolerant — PI inherently rad-hard), wearable sensor patches.

Solder mask on flex: photo-imageable coverlay (DuPont Pyralux PC1025) replaces conventional LPI.

10. Rigid-flex

Hybrid construction: rigid FR-4 (or other) sections joined by a continuous polyimide flex strip. The flex layer extends across both rigid sections; rigid layers laminate only over the rigid-region portions.

Applications: aerospace flight-control PCBs (eliminates connectors and harness), medical implants (pacemakers — folds inside a hermetic Ti can), military handheld radios, fold-up smartphone hinges, virtual-reality headset link.

Fabrication challenge: combining different lamination temperatures (FR-4 ~180 °C, PI flex ~200 °C with acrylic adhesive at 175 °C); achieving cleanly transitioning flex-to-rigid boundary; managing the “book-binder” effect at the flex break. IPC-2223 governs design.

11. Metal-core (Insulated Metal Substrate, IMS)

Construction (bottom to top): aluminum or copper base plate (1-3 mm thick), thin (50-150 µm) thermally-conductive dielectric (filled epoxy with Al₂O₃ / BN / AlN fillers, or hybrid resin), copper foil (35-105 µm), top solder mask.

Thermal conductivity of dielectric: 1-7 W/m·K typical, with premium hybrids reaching 9 W/m·K. Overall thermal resistance to base plate: 0.3-1.5 K·cm²/W.

Brands:

• Bergquist (now Henkel) Thermal Clad T-Clad, HPL, MP, T-Lam — original IMS, mid-1980s.
• Ventec VT-4B5, VT-4A2 — IMS lineup.
• Laird Tlam — competitor IMS.
• ITEQ IT-MB-1.
• Polytronics, Doosan.

Applications: high-current LED modules (street lighting, automotive headlamp), EV traction-inverter gate-drive boards, switched-mode power supplies (SMPS), motor controllers.

IMS is single-conductor-layer (one routing plane); multi-layer aluminum-core variants exist but are rare due to drill difficulty. Through-hole drilling into aluminum requires special carbide drills and is generally avoided.

12. Ceramic substrates

For high-power-density, high-temperature, or high-frequency applications where polymer substrates cannot dissipate heat or are dielectrically lossy.

• Al₂O₃ (alumina), 96 % — workhorse hybrid substrate. k ~24 W/m·K, Dk ~9.8, CTE 7.1 ppm/°C. Thin-film MMIC carriers, thick-film resistor networks, RF circulators.
• Al₂O₃, 99.5 % — higher purity, smoother surface (Ra < 0.05 µm), used for thin-film Au/Pt resistor laser-trimmed precision networks.
• AlN (aluminum nitride) — k 170-220 W/m·K, Dk 8.9, CTE 4.6 ppm/°C. Closely matched to Si CTE — direct die-attach without solder fatigue. Used in IGBT power modules, RF power transistors. More expensive than Al₂O₃ ~3-5 ×.
• BeO (beryllium oxide) — k ~270 W/m·K, but BeO dust is toxic (chronic beryllium disease) — largely phased out; legacy in military RF.
• Si₃N₄ (silicon nitride) — k 70-90 W/m·K, fracture toughness K_IC ~6 MPa·m^0.5 (vs AlN ~3.5). Best for thermal cycling: SiC EV-traction power modules (Rogers Curamik, Kyocera Si₃N₄ DBC) where −40/+150 °C swings would crack AlN.
• BN (boron nitride) — hexagonal BN as filler in IMS dielectrics; cubic BN niche.

Metallization on ceramic: DBC (direct bond copper) — Cu foil reflowed to Al₂O₃ or AlN at 1065 °C in O₂ atmosphere; Cu thickness 0.2-0.4 mm. AMB (active metal brazing) — Ag-Cu-Ti braze bonds Cu to Si₃N₄ at 800-900 °C; preferred for Si₃N₄. DBA direct-bond-Al for AlN. Thin-film: sputtered Ti-W-Au or Ta-N. Thick-film: screen-printed Au, Ag-Pd, or PtAu pastes fired at 850 °C.

13. LTCC and HTCC

LTCC (Low-Temperature Co-fired Ceramic) — glass-ceramic mixture co-fired with Au, Ag, or Cu inner traces at 800-900 °C (low enough that gold and silver remain conductive). Multi-layer green tape lamination (10-50 layers typical) → punched vias → screen-printed conductors → co-fired stack. Dk 5-8, Df 0.001-0.005, k 2-4 W/m·K.

Brands / pastes: Murata (LTCC modules), KOA Speer, Heraeus CT-2000 series glass-ceramic tape, DuPont 951 Green Tape, Ferro A6S.

Applications: RF front-end modules for cellular and Wi-Fi (integrated filter + antenna + amplifier in one substrate), automotive radar antenna arrays, MEMS sensor packages, miniature LC filters.

HTCC (High-Temperature Co-fired Ceramic) — Al₂O₃ tape co-fired with tungsten or molybdenum at 1500-1700 °C (only refractory metals survive). Higher mechanical strength and k than LTCC. Used for IGBT module substrates, high-rel hermetic chip carriers (older mil-aero), spark-plug ceramics. Less popular for RF because W trace resistivity is higher than Cu.

14. Specialty / aerospace / space

• Arlon 33N / 35N — polyimide-glass laminates for high-temp aerospace. Tg 250 °C continuous. Down-hole oil tools, jet-engine instrumentation.
• Arlon 85N — polyimide for very-low-outgassing space applications.
• Nelco N7000-1 — polyimide-quartz. Mil-spec.
• Arlon AD250C / AD300C / AD350C — PTFE-glass for satellite RF.
• CIC (Cu-Invar-Cu) cores — controlled CTE laminate cores. Three-ply rolled stack tunes effective CTE to ~5-10 ppm/°C, matching ceramic BGA packages. Reduces solder-joint fatigue under thermal cycling. Used in mil-aero PCBs hosting ceramic BGAs.
• CMC (Cu-Mo-Cu) — similar CTE-matching role, also used as heat-spreader inserts.

Outgassing per ASTM E595: TML < 1.0 %, CVCM < 0.1 % is the NASA spec for space-qualified materials. Standard FR-4 fails outgassing; polyimide and PTFE pass.

15. Copper foils

The copper foil bonded to the laminate dictates surface roughness and therefore high-frequency conductor loss.

• ED (electrodeposited) — standard treatment, “matte side” Rz ~5-10 µm. Cheapest; OK to ~5 GHz.
• RTF (reverse-treat foil) — treatment node-side reversed; Rz ~3-5 µm. Standard for mid-loss laminates.
• VLP (very-low-profile) — Rz ~2-4 µm. Megtron 6, EM-528K default.
• HVLP (hyper-VLP) / SVLP (super-VLP) — Rz ~1.5 µm. Megtron 7, Tachyon 100G default.
• RA (rolled-annealed) — cold-rolled and annealed foil, very smooth on the roll side, ductile. Standard for flex (Pyralux AP uses sputtered/plated, but classical flex used RA).
• Nodular high-Tg — extra nodules grown on the bond side for high-peel-strength on high-Tg resins.

Conductor loss scales with √f and is amplified by surface roughness (Hammerstad-Jensen or Huray surface-roughness models). At 28 GHz, going from ED to VLP can recover 1-2 dB/m of insertion loss in a microstrip line.

16. Surface finishes

The finish on exposed copper pads at the end of fabrication.

• HASL (Hot-Air Solder Leveling), leaded — molten SnPb dipped, hot air levelled. Cheap, robust, but uneven thickness — bad for fine-pitch < 0.5 mm.
• HASL lead-free — SnAgCu or SnCuNi. RoHS-compliant; slightly worse coplanarity than SnPb HASL.
• OSP (Organic Solderability Preservative) — azole-based organic film over bare Cu. Flat, cheap, RoHS-OK; limited reflow cycles (2-3); not wirebondable.
• ENIG (Electroless Nickel / Immersion Gold) — 3-6 µm Ni, 0.05-0.1 µm Au. Flat, multi-reflow, wirebond-OK (Al only on thin Au). Risk of “black-pad” — phosphorus segregation at Ni/Au interface causing brittle solder joint.
• ENEPIG (Electroless Ni / Electroless Pd / Immersion Au) — 3-6 µm Ni, 0.05-0.2 µm Pd, 0.03-0.1 µm Au. Solves black-pad; Pd buffer prevents Ni oxidation. Wirebondable (Au ball + Al wedge). Premium finish.
• Immersion Ag — 0.1-0.3 µm Ag over Cu. Flat, good solderability, but tarnishes; needs anti-tarnish topcoat.
• Immersion Sn — 0.8-1.2 µm Sn. Flat, single-reflow risk of tin whiskers.
• Hard Gold over Ni — 0.5-1.5 µm electroplated hard Au (Ni 5-8 µm). Wear-resistant — edge connector fingers, key contacts.
• Soft Gold over Ni — wirebond pads.

IPC-4552 (ENIG), IPC-4556 (ENEPIG), IPC-4554 (Imm-Sn), IPC-4553 (Imm-Ag) define the specifications.

17. Copper weight and current capacity

Copper weight is quoted in ounces per square foot:

• 0.5 oz/ft² = 17 µm
• 1 oz/ft² = 35 µm
• 2 oz/ft² = 70 µm
• 3 oz/ft² = 105 µm
• 4 oz/ft² = 140 µm
• Heavy copper 6-20 oz/ft² (210-700 µm) for high-current bus PCBs, motor controllers, welder PCBs.

Current capacity is governed by IPC-2152 (2009, superseded IPC-2221A nomograph). For a 0.5 mm wide outer-layer 1 oz trace at 10 °C rise: ~1.4 A. Inner-layer traces de-rate ~60 % due to dielectric thermal insulation. Plane fills, board thickness, board material k, ambient airflow all modify the result — IPC-2152 provides multi-variable charts.

Heavy copper requires wider etch resist, gap, and longer plating times; typical commercial fab caps at 6 oz, specialty shops to 20 oz.

18. Selection heuristics

Quick decision guidance:

• Generic consumer rigid, SnPb reflow → standard FR-4 Tg 135 °C, halogen-OK if cost-driven.
• Consumer rigid, lead-free SnAgCu reflow → Tg 170 °C FR-4 (S1170, IT-180A, Isola 370HR). Halogen-free preferred for EU/JP.
• Automotive infotainment (85 °C op temp) → Tg 170 °C, halogen-free, AEC-Q200 listed (IT-180GA, R-1755V).
• PCIe 4 / DDR4 server backplane → Megtron 4 or ITEQ IT-958G with RTF/VLP foil and spread glass (1078, 1086 styles).
• 56G PAM4 / 100 GbE spine → Megtron 6 with VLP foil; Tachyon 100G acceptable alternative.
• 112G PAM4 / 400-800 GbE AI fabric → Megtron 7 or Megtron 8 with HVLP/SVLP foil; specify glass-skew mitigation.
• 5G sub-6 cellular front-end → Rogers RO4003C or Astra MT77 on top RF layer.
• 5G mm-wave 28-39 GHz → Rogers RO4350B or Astra MT77; hybrid stackup over FR-4 for digital baseband.
• 77 GHz automotive radar → Rogers RO3003 (CTE-matched) or Astra MT77.
• Premium satcom Ku/Ka → Rogers RO5880, with care for soft-substrate handling.
• High-power LED driver (1-10 W per emitter) → IMS aluminum-core 1.5-3 mm base, HPL or VT-4B5 dielectric.
• SiC EV traction inverter (1200 V, 100 A SiC MOSFET module) → AlN DBC for cost-sensitive or Si₃N₄ AMB for thermal-cycle-critical.
• GaN RF power amplifier (S-band, X-band) → AlN ceramic carrier with AuSn die-attach.
• Smartphone camera ribbon → adhesiveless PI (Pyralux AP) FPC, 25 µm PI core.
• HDD head-suspension → PI flex with very-thin RA copper (12 µm).
• Implantable pacemaker → rigid-flex with polyimide flex tail inside hermetic Ti can.
• Spacecraft RF subsystem → Arlon AD250C or Rogers RO4350B (rad-tolerant); polyimide flex for harness segments.
• Down-hole instrumentation (175-200 °C ambient) → Arlon 33N polyimide-glass.
• 24 GHz sensor antenna patch → Rogers RO4350B or Taconic RF-35, 0.51 mm thickness.
• High-rel mil-aero with ceramic BGAs → CIC core for CTE match.
• Wi-Fi 6E / 7 front-end module → LTCC (Murata, Kyocera) integrating filter + balun + match.

19. Cross-references

• pcb-design — board-level routing, impedance control, stack-up planning.
• semiconductor-packages — BGA, QFN, CSP packages that mount onto these substrates.
• passive-components — chip resistors / capacitors / inductors specified for SMT to these laminates.
• connector-families — board-to-board, board-to-cable connectors with matching impedance.
• rf-design — RF-specific layout: microstrip, stripline, grounded coplanar waveguide, via-stitching.
• ceramics-taxonomy — Al₂O₃, AlN, Si₃N₄ as engineering ceramics (broader properties).
• copper-alloys — RA vs ED copper metallurgy.
• polymers-taxonomy — polyimide, epoxy, PTFE as polymer chemistries.

20. Citations and standards

• IPC-4101 — Specification for Base Materials for Rigid and Multilayer Printed Boards. The master classification for laminates and prepregs.
• IPC-4202 / 4203 / 4204 — flex base materials, bond plies, copper-clad flex laminates.
• IPC-4552 / 4553 / 4554 / 4556 — surface finish specifications (ENIG, Imm-Ag, Imm-Sn, ENEPIG).
• IPC-2152 — Standard for Determining Current-Carrying Capacity in Printed Board Design (2009).
• IPC-2221 / 2222 / 2223 — generic / rigid / flex PCB design standards.
• IPC-A-600 — Acceptability of Printed Boards.
• IPC-6012 / 6013 — qualification and performance of rigid / flex PCBs.
• IPC-TM-650 2.3.40 — T_d (decomposition temperature) test method.
• JEDEC JS709 — definition of halogen-free.
• NEMA LI-1 (1968) — original FR-4 designation.
• ASTM E595 — outgassing of materials in vacuum (space applications).
• AEC-Q200 — automotive passive-component / laminate qualification.
• Coombs, C. F., “Printed Circuits Handbook,” 7th ed., McGraw-Hill, 2016 — the definitive reference text.
• Rogers Corporation product data sheets — RO4003C, RO4350B, RO3003, RO5880, RO4450F/T.
• Panasonic / Nitto Megtron product data sheets — Megtron 4 / 6 / 7 / 8.
• Isola product data sheets — 370HR, FR408HR, Tachyon 100G, IS400, Astra MT77.
• DuPont Kapton and Pyralux data sheets — polyimide film and copper-clad flex.
• Henkel Bergquist Thermal Clad — IMS data sheets.
• Rogers Curamik / Kyocera — DBC and AMB ceramic substrate datasheets.