FAQ
What makes a PCB suitable for high-frequency applications?
High-frequency pcbs require low dielectric loss materials (such as Rogers RO4003C or Megtron 6), controlled impedance traces, and tight dimensional tolerances to maintain signal integrity above 1 GHz.
What is the difference between HF PCB materials?
HF pcb materials like Rogers RO4003C offer lower dissipation factor (Df < 0.004) compared to standard FR4 (Df ~ 0.02). Lower Df reduces signal attenuation and insertion loss in high-speed designs.
How do I design microstrip for HF applications?
Microstrip design for high frequency requires calculating trace width for 50 ohm impedance using the substrate dielectric constant and thickness. Tools like a pcb impedance calculator help verify dimensions before fabrication.
What is DK in PCB materials?
Dielectric constant (DK) measures a material's ability to store electrical energy. Higher DK values increase trace capacitance and affect pcb impedance control, making material selection critical for rf and high-speed digital designs.
Do high-frequency PCBs need special surface finishes?
ENIG is preferred for hf pcbs due to its flat surface and consistent impedance performance. HASL can introduce surface irregularities that affect high-frequency signal propagation, especially above 10 GHz.
Selecting a halogen-free PCB laminate is no longer only an environmental compliance decision. Modern automotive, telecom, server, and industrial designs require engineers to balance thermal endurance, Z-axis expansion, signal performance, CAF resistance, and manufacturing compatibility.
Kingboard HF-140 and HF-170 are both halogen-free FR4 PCB laminate platforms designed for reliable lead-free assembly and environmentally compliant electronics. HF-140 targets cost-sensitive high-reliability designs, while HF-170 increases thermal margin for demanding multilayer, automotive, and infrastructure applications.
This guide converts laminate specifications into an engineering decision framework: when to select HF-140, when HF-170 is justified, and which parameters matter for long-term PCB reliability.
Which material should I choose: HF-140 or HF-170?
| Design requirement | Recommended material | Reason |
|---|---|---|
| Standard halogen-free FR-4 replacement | HF-140 | Tg 141°C, low CTE, lead-free compatible, IPC-4101E/127 |
| Automotive ECU and harsh thermal cycling | HF-170 | Tg 180°C, lower Z-axis expansion, T-288 >60 min |
| High-layer-count multilayer PCB | HF-170 | Better thermal stress margin and lower expansion |
| Consumer electronics requiring EU compliance | HF-140 | Balanced performance and cost |
| Server, telecom, and networking hardware | HF-170 | Higher thermal reliability and lower dielectric loss |
| Fine-pitch via structures requiring CAF resistance | HF-140/HF-170 | Both provide anti-CAF capability |
What are the key differences between HF-140 and HF-170?
The primary difference is thermal reliability margin.
HF-140 is a normal-Tg halogen-free laminate with Tg 141°C and Z-axis expansion of 3.3% from 50–260°C.
HF-170 increases Tg to 180°C and reduces Z-axis expansion to 2.2%, improving reliability during repeated lead-free reflow cycles and thermal excursions.
| Property | HF-140 | HF-170 |
|---|---|---|
| Tg (DSC) | 141°C | 180°C |
| Tg (DMA) | — | 190°C |
| Td (TGA) | 350°C | 385°C |
| Z-CTE alpha 1 | 45 ppm/°C | 45 ppm/°C |
| Z-CTE alpha 2 | 254 ppm/°C | 220 ppm/°C |
| Z-axis expansion (50–260°C) | 3.3% | 2.2% |
| T-260 | >60 min | >60 min |
| T-288 | >5 min | >60 min |
| Dk @1 GHz | 4.6 | 4.6 |
| Df @1 GHz | 0.013 | 0.011 |
| CTI | >175V | ≥200V |
| IPC classification | /127 | /127/128/130 |
| Halogen-Free | Yes | Yes |
| Anti-CAF | Yes | Yes |
What failure modes do HF-140 and HF-170 help prevent?
| Reliability concern | Important parameter | Material advantage |
|---|---|---|
| Via barrel cracking after thermal cycling | Z-axis CTE, T-288 | HF-170 provides lower expansion and higher thermal endurance |
| Delamination during lead-free assembly | T-260/T-288, Td | Both support lead-free processing; HF-170 provides additional margin |
| Conductive Anodic Filament (CAF) growth | Anti-CAF resin system | Both materials are designed for CAF resistance |
| Signal loss at higher frequencies | Dk/Df | HF-170 provides lower Df at 1 GHz |
| Environmental compliance requirements | IEC 61249-2-21 | Both eliminate bromine/chlorine flame retardants |
What is a halogen-free PCB?
A halogen-free PCB is a board built on laminate and prepreg whose flame retardant does not rely on bromine or chlorine compounds. It still has to reach UL 94 V-0 flammability, usually through phosphorus- or nitrogen-based chemistry. "Halogen-free" is a material declaration with numeric limits (below), not a separate board type: the same stackup, drilling, plating, and finishes apply, though drilling and lamination parameters are tuned to the resin system.
Why are halogen-free PCB laminates required?
Halogen-free laminates are increasingly specified for global electronics markets because manufacturers require materials with reduced environmental impact while maintaining flame resistance.
IEC 61249-2-21 defines halogen-free requirements including:
- Bromine <900 ppm
- Chlorine <900 ppm
- Total bromine plus chlorine <1500 ppm
HF-140 and HF-170 use halogen-free flame-retardant chemistry while maintaining UL 94 V-0 performance and compatibility with standard PCB manufacturing processes.
What are the verified HF-140 specifications?
HF-140 is designed for engineers who need halogen-free compliance without moving to higher-cost ultra-high-Tg materials.
HF-140 Thermal and electrical properties
| Test Item | Condition | Typical Value |
|---|---|---|
| Tg (DSC) | E-2/105 | 141°C |
| Z-axis CTE alpha 1 | TMA | 45 ppm/°C |
| Z-axis CTE alpha 2 | TMA | 254 ppm/°C |
| Z-axis expansion | 50–260°C | 3.3% |
| Td | TGA | 350°C |
| T-260 | TMA | >60 min |
| T-288 | TMA | >5 min |
| Dk @1 GHz | IPC-TM-650 2.5.5.2 | 4.6 |
| Df @1 GHz | IPC-TM-650 2.5.5.2 | 0.013 |
HF-140 is suitable for industrial controls, consumer electronics, LED systems, and products where environmental compliance is required but extreme thermal cycling is not the dominant requirement.
What are the verified HF-170 specifications?
HF-170 is the higher-performance selection for applications where thermal reliability is critical.
HF-170 Thermal and electrical properties
| Test Item | Condition | Typical Value |
|---|---|---|
| Tg (DSC) | DSC | 180°C |
| Tg (DMA) | DMA | 190°C |
| Z-axis CTE alpha 1 | TMA | 45 ppm/°C |
| Z-axis CTE alpha 2 | TMA | 220 ppm/°C |
| Z-axis expansion | 50–260°C | 2.2% |
| Td | TGA | 385°C |
| T-260 | TMA | >60 min |
| T-288 | TMA | >60 min |
| Dk @1 GHz | IEC 61189-2-721 | 4.6 |
| Df @1 GHz | IEC 61189-2-721 | 0.011 |
| Dk @10 GHz | IEC 61189-2-721 | 4.4 |
| Df @10 GHz | IEC 61189-2-721 | 0.013 |
HF-170 is designed for automotive electronics, servers, telecom infrastructure, and complex multilayer boards requiring additional thermal margin. With a DSC Tg of 180°C it falls into the range normally quoted as high Tg PCB material, so it is the halogen-free option when a design already calls for high-Tg FR-4.
How does HF-140/HF-170 compare with other Kingboard materials?
For the full Kingboard family, see the Kingboard PCB laminate comparison. The table below places the two halogen-free grades next to their closest neighbors.
| Property | HF-140 | KB-6164 | HF-170 | KB-6167F | KB-6165G |
|---|---|---|---|---|---|
| Tg | 141°C | 140°C | 180°C | 175°C | ~150°C |
| Td | 350°C | 330°C | 385°C | 349°C | ~340°C |
| Z-axis expansion | 3.3% | 3.5% | 2.2% | 2.6% | ~3.0% |
| Dk @1 GHz | 4.6 | 4.6 | 4.6 | 4.6 | ~4.6 |
| Df @1 GHz | 0.013 | 0.016 | 0.011 | 0.016 | ~0.014 |
| Anti-CAF | Yes | Yes | Yes | Yes | Yes |
| Halogen-Free | Yes | No | Yes | No | Yes |
HF-140 provides a direct halogen-free migration path from standard mid-performance materials.
HF-170 provides a higher reliability alternative to traditional high-Tg materials with improved thermal endurance and lower dielectric loss.
What prepreg data matters for HF-140 and HF-170 stackups?
Impedance-controlled designs should use prepreg-specific Dk/Df values rather than relying only on laminate core values.
PP-HF140 Prepreg Dk/Df examples
| Glass Style | Resin Content | Dk @1 GHz | Df @1 GHz |
|---|---|---|---|
| 106 | 74±2% | 4.2 | 0.017 |
| 1080 | 65±2% | 4.2 | 0.014 |
| 3313 | 55±2% | 4.4 | 0.013 |
| 7628 | 45±2% | 4.6 | 0.012 |
Use prepreg-specific values like these in the PCB impedance calculator for a first estimate, then confirm the final stackup with the fabricator.
How should suppliers quote HF-140 and HF-170 PCB projects?
Provide the following information during material selection:
| Supplier information requirement | Why it matters |
|---|---|
| Exact laminate grade | Prevents material substitution |
| Finished board thickness | Affects CTE and impedance |
| Copper weight | Impacts thermal and electrical behavior |
| Prepreg glass style | Required for accurate impedance |
| Dk/Df test method | Ensures frequency correlation |
| Compliance documentation | Confirms environmental requirements |
| Thermal reliability targets | Matches material to application |
For production designs, request material certificates, stackup review, and DFM validation before fabrication.
How do I order HF-140 or HF-170 PCBs?
Upload your design files with your thermal, impedance, and compliance requirements. Our engineering team evaluates HF-140/HF-170 suitability, verifies stackup parameters, and provides DFM analysis for reliable manufacturing.
For projects requiring complete environmental documentation, fabrication and assembly support, our one-stop service includes material selection, manufacturing coordination, and compliance verification.
Frequently Asked Questions
What PCB materials are recommended for HF-140 and HF-170?
Both materials are halogen-free and RoHS compliant. HF-140 uses phenolic-cured resin and is suited for standard multilayer applications with moderate signal integrity requirements. HF-170 uses higher crosslink-density resin for improved thermal resistance and is recommended for higher-frequency and higher-layer-count builds.
How does HF-140 compare to HF-170 in DK andDf?
HF-140 provides a Dk of approximately 4.2-4.4 and Df of 0.018-0.022 at 1 GHz. HF-170 delivers lower loss with Dk approximately 3.9-4.1 and Df of 0.010-0.014 at 1 GHz. The difference is most noticeable above 5 GHz.
What thermal properties does HF-170 offer over HF-140?
HF-170 has a higher Tg (180°C vs 140°C), better thermal stability during lead-free reflow, and superior Z-axis expansion control for multilayer boards with PTH barrels. This reduces barrel cracking risk during thermal cycling.
Are HF-140 and HF-170 compatible with lead-free assembly?
Yes, both materials are fully lead-free assembly compatible. HF-170's higher Tg makes it more robust during the higher peak temperatures required for lead-free solder processes.
What board types and layer counts work best with HF-140?
HF-140 is compatible with standard multilayer builds up to 8 layers, flex-rigid constructions, and metal-backed boards. For boards above 8 layers or with high aspect ratio PTH, HF-170 is the preferred choice.