Must-Read for Electronics Engineers Characteristics and Selection Guide for 7 Types of PCB Substrate Materials
Author:Jack Wang
At the failure analysis site of a 5G base station power module, we once encountered a case where an entire batch of products failed thermally due to incorrect substrate selection. This article deciphers the "genetic code" of mainstream PCB substrates based on IPC-4101 standards and tested data.
1. FR-4:The Reinforced Concrete of the Electronics Industry FR-4--HDI PCB / FR-4--High - Layer Multilayer PCB
Composition Profile
Fiberglass cloth (60%) + Epoxy resin (35%) + Flame retardant (5%), compliant with UL94 V-0 fire rating.
Performance Parameters
①Dielectric Constant (Dk): 4.2–4.8 @1MHz
②Dissipation Factor (Df): 0.018–0.025
③Glass Transition Temperature (Tg): 130–180°C
④Thermal Conductivity: 0.3 W/m·K
Design Considerations
①Use high-Tg variants (e.g., S1000-2) for multilayer boards.
②Loss increases sharply above 1 GHz.
Typical Application: Smart appliance control boards (Haier’s latest air conditioner mainboard tested at 1.6mm thickness).
2. Metal-Core PCBs: Thermal Management Experts Metal Base-PCB
Structural Anatomy
1mm aluminum layer (6061-T6) + 75μm insulation layer (epoxy resin + ceramic filler) + 35μm copper foil.
Key Metrics
①Thermal Resistance: 0.5–3.0°C·in²/W
②Breakdown Voltage: ≥3 kV
③Peel Strength: ≥1.5 kgf/cm
Selection Tips
①Use models with thermal conductivity >2.0 W/m·K for LED automotive lighting.
②EV charging piles require 3,000 thermal shock cycles.
Case Study: Tesla Model Y taillight module (operating range: -40°C to 125°C).
3. Ceramic Substrates: Survivors in Extreme Environments Alumina & AlN Ceramic-PCB
Material Comparison
Type | Alumina (Al₂O₃) | Aluminum Nitride (AlN) | Silicon Nitride (Si₃N₄) |
Thermal Cond. | 24 W/m·K | 180 W/m·K | 90 W/m·K |
Flex Strength | 400 MPa | 320 MPa | 800 MPa |
Cost Index | 1x | 5x | 8x |
Applications
①High-speed rail IGBT modules (tested at 15kV on Beijing-Shanghai line).
②Lunar spacecraft power systems (Chang'e-5 operated under 300°C temperature swings).
4. PTFE High-Frequency Boards: Runways for the Millimeter-Wave Era High- Frequency PCB
Formula Evolution
First-gen pure PTFE (Dk=2.1) → Ceramic-filled (RO3003, Dk=3.0±0.04) → LCP composite (Dk=2.9@40GHz).
Tested Data
①Loss <0.0015 @10 GHz
②Z-axis CTE: 25 ppm/°C
Fabrication Challenge: Requires plasma treatment for reliable hole metallization.
Design Case: Huawei 5G AAU antenna board (64TRx channels, 3.5GHz band).
5. High-Speed Materials: Guardians of Signal Integrity High- Speed PCB
Three Technical Routes
1.Modified epoxy (e.g., MEGTRON6, Df=0.002)
2.Hydrocarbon-based (Tachyon-100G, Dk=3.2)
3.Liquid Crystal Polymer (LCP, Df=0.0025@110GHz)
Golden Rule: For signal rates >56 Gbps, prioritize glass fabric with low dispersion (e.g., NE-glass 1037).
6. BT Resin Substrates: Invisible Wings for Chip Packaging Special - type PCB
Microstructure
Bismaleimide Triazine resin + spherical silica (0.5μm particle size).
Advanced Packaging Uses
①FCBGA substrates (20/20μm line/space).
②2.5D silicon interposers (10μm TSV diameter).
Test Result: Warpage <0.1% after 300°C reflow.
7. Halogen-Free Materials: Mandatory Course in Green Manufacturing Special - type PCB
Eco-Performance Comparison
Comparison of environmental indicators
Parameter | Traditional | Halogen-Free |
Bromine Content | >15% | <900 ppm |
Combustion Toxins | Dioxins emitted | Only CO₂/H₂O |
Decomposition | 100 years | 30 years |
Medical Application: Medtronic pacemaker PCB compliant with ISO10993 biocompatibility.
2024 Selection Decision Tree
1.Frequency >10 GHz → PTFE/High-Speed Materials
2.Power Density >50 W/cm² → Ceramic Substrates
3.Eco-Mandates → Halogen-Free
4.Cost-Sensitive → FR-4
(Data sourced from IPC standards and 2024 third-party lab reports. Cite test conditions when repurposing.)
FR-4 Laminate: Definition, Core Properties, and Engineering Application Guide
Technical Analysis of Ceramic Substrates Definition, Properties, and Engineering Applications
PCB High-Speed Material Technology Guide Key Selection Criteria and Practical Applications