KB-6167GLD pushes Kingboard's FR-4 platform toward its electrical performance frontier. With Df approximately 0.006 at 1 GHz—approaching Panasonic Megtron 4 territory—it enables 25 Gbps NRZ and 56 Gbps PAM4 serial links while retaining FR-4 compatible processing and Tg 220°C (DMA) ✓ thermal reliability. The "GLD" designation—Green Low-loss Dielectric—marks it as the low-loss counterpart to KB-6167GMD, offering 40% lower dielectric loss for applications where mid-loss performance hits its ceiling.
For data center switches, high-performance computing interconnects, and next-generation networking, KB-6167GLD eliminates the traditional choice between FR-4 processability and specialty-material dielectric performance. The critical advantage is manufacturing: KB-6167GLD laminates and drills on standard FR-4 equipment, accepts conventional plating chemistry, and co-laminates with other Kingboard high-Tg products in hybrid stackups—processing simplicity that PTFE-based alternatives cannot match.
In This Guide
- Where KB-6167GLD Fits in the Low-Loss Material Hierarchy
- KB-6167GLD Technical Specifications and Dielectric Performance
- Insertion Loss Budget Analysis for 25G and 56G Channels
- KB-6167GLD vs Panasonic Megtron 4 and Industry Equivalents
- Hybrid Stackup Strategy: Optimizing Cost in Multi-Layer Switch Designs
- Critical Manufacturing Requirements for Low-Loss PCB Fabrication
- Target Applications from Data Center to Automotive Radar
- How to Order KB-6167GLD PCBs from APTPCB
Where KB-6167GLD Fits in the Low-Loss Material Hierarchy
The PCB material market segments into clear performance tiers based on dielectric loss, and KB-6167GLD occupies the "low-loss" tier—the critical middle ground between mid-loss materials adequate for ≤10 Gbps and very-low-loss materials required for 112G+ interfaces:
| Material Class | Representative | Df @10GHz | Cost Index | Maximum Data Rate |
|---|---|---|---|---|
| Standard FR-4 | KB-6167F | ~0.020 | 1.0× | ≤2 Gbps |
| Mid-Loss | KB-6167GMD | ~0.013 | 1.2× | ≤10 Gbps |
| Low-Loss | KB-6167GLD | ~0.008 | 1.5× | ≤25–56 Gbps |
| Very Low-Loss | KB-3200G | ~0.005 | 2.0× | ≤112 Gbps |
| Ultra Low-Loss | Megtron 7 | <0.003 | 3.0×+ | 112 Gbps+ |
This hierarchy clarifies the design decision: KB-6167GLD is the sweet spot for 25G NRZ and 56G PAM4 designs that need significantly better performance than mid-loss materials but don't require (or can't justify the cost of) very-low-loss alternatives like KB-3200G.
KB-6167GLD Technical Specifications and Dielectric Performance
KB-6167GLD specifications are estimated from Kingboard's published product family data. No standalone official datasheet PDF has been independently verified; values are cross-referenced against equivalent industry materials (Megtron 4, TU-768, S7136). Specimen condition: 1.0 mm.
Thermal and General Properties
| Property | Estimated Value | Test Method |
|---|---|---|
| Glass Transition (Tg, DMA) | 220°C ✓ | IPC-TM-650 2.4.25 |
| Decomposition Temperature (Td, TGA 5%) | 409°C ✓ | IPC-TM-650 2.4.24.6 |
| T-260 (time to delamination) | >30 min | IPC-TM-650 2.4.24.1 |
| T-288 (time to delamination) | >15 min | IPC-TM-650 2.4.24.1 |
| Z-axis CTE (50–260°C) | 1.8% ✓ | IPC-TM-650 2.4.24 (TMA) |
| Moisture Absorption (D-24/23) | ≤0.15% | IPC-TM-650 2.6.2.1 |
| Flammability | V-0 | UL 94 |
| Halogen-Free | Yes | IEC 61249-2-21 |
| UL File | E123995 | — |
Electrical Properties
| Property | Estimated Value | Test Method |
|---|---|---|
| Dk @1 GHz | 3.9 ✓ | IPC-TM-650 2.5.5.9 |
| Dk @10 GHz | 3.8 ✓ | IPC-TM-650 2.5.5.9 |
| Df @1 GHz | 0.006 ✓ | IPC-TM-650 2.5.5.9 |
| Df @10 GHz | 0.007 ✓ | IPC-TM-650 2.5.5.9 |
| Dk Variation vs Frequency (1–20 GHz) | <5% | — |
| CTI | ≥175V | IEC 60112 |
The low Dk variation across frequency (<5% from 1 to 20 GHz) is a critical advantage for PAM4 signaling, where Dk dispersion causes differential group delay that distorts the 4-level eye opening. Standard FR-4 with Dk variation >10% across this range introduces measurable PAM4 degradation.
Data Confidence Note: Electrical values are estimated from Kingboard's product family positioning and cross-referenced with equivalent-tier materials from Panasonic, TUC, and Shengyi. Request the current official datasheet from Kingboard for production design verification.
Insertion Loss Budget Analysis for 25G and 56G Channels
At 25G NRZ (12.5 GHz Nyquist) and 56G PAM4 (14 GHz Nyquist for 28 Gbaud), insertion loss management becomes the primary design constraint. The total channel loss budget for a typical 25G link is approximately -15 dB at Nyquist, split between dielectric loss, conductor loss, via transitions, and connector loss.
For a 6-inch differential stripline on 4.5-mil dielectric:
| Loss Component | KB-6167F | KB-6167GMD | KB-6167GLD |
|---|---|---|---|
| Dielectric Loss @12.5 GHz | 7.5 dB | 4.7 dB | 2.8 dB |
| Conductor Loss (1oz RTF) | 3.2 dB | 3.2 dB | — |
| Conductor Loss (VLP) | — | — | 2.1 dB |
| Total Trace Loss | 10.7 dB | 7.9 dB | 4.9 dB |
| Remaining Budget for Vias/Connectors | 4.3 dB | 7.1 dB | 10.1 dB |
KB-6167GLD's advantage is twofold: lower dielectric loss AND the ability to leverage VLP copper. Standard RTF copper's surface roughness (Rz ~3–5 µm) adds significant conductor loss at frequencies above 5 GHz through the skin effect. VLP copper (Rz <1.5 µm) reduces conductor loss by approximately 30% at 12.5 GHz, but using VLP on high-Df material wastes its benefit—the copper improvement matters most when dielectric loss is already controlled.
The remaining budget of 10.1 dB (versus 4.3 dB for standard FR-4) provides the margin needed for via transitions, connector interfaces, and manufacturing variation—turning a marginal channel design into a robust one.
KB-6167GLD vs Panasonic Megtron 4 and Industry Equivalents
KB-6167GLD competes directly with the established low-loss laminate tier that has been dominated by Panasonic Megtron 4 (R-5775K) for over a decade:
| Material | Manufacturer | Dk @10GHz | Df @10GHz | Tg | Halogen-Free | Cost Position |
|---|---|---|---|---|---|---|
| KB-6167GLD | Kingboard | ~3.8 | ~0.008 | >170°C | Yes | Lower |
| Megtron 4 (R-5775K) | Panasonic | ~3.8 | ~0.008 | >175°C | Available | Higher |
| TU-768 | TUC | ~3.8 | ~0.008 | >170°C | Yes | Comparable |
| S7136 | Shengyi | ~3.8 | ~0.008 | >170°C | Yes | Comparable |
| IT-170GRA1 | ITEQ | ~3.8 | ~0.009 | >170°C | Yes | Comparable |
The dielectric performance is functionally equivalent across these materials—they occupy the same Df tier with comparable Dk stability. The competitive differentiation is primarily supply chain: Kingboard's manufacturing scale as the world's largest CCL producer provides pricing advantages and capacity assurance that smaller specialty suppliers cannot match. For designs qualified on Megtron 4 that need cost reduction or supply diversification, KB-6167GLD is a direct material-level equivalent.
Hybrid Stackup Strategy: Optimizing Cost in Multi-Layer Switch Designs
A 16-layer data center switch board with 25G SerDes lanes illustrates the hybrid approach that maximizes KB-6167GLD's value while controlling material cost:
| Layer Pair | Material | Dielectric | Rationale |
|---|---|---|---|
| L1–L2 (25G signals) | KB-6067GLD prepreg | Low-loss | Highest speed, surface routing |
| L3 (ground) | KB-6167F core | Standard | Reference plane, no SI requirement |
| L4–L5 (25G signals) | KB-6067GLD prepreg | Low-loss | Second high-speed pair |
| L6–L11 (power/ground/low-speed) | KB-6167F cores | Standard | No SI requirement |
| L12–L13 (25G signals) | KB-6067GLD prepreg | Low-loss | Third high-speed pair |
| L14 (ground) | KB-6167F core | Standard | Reference plane |
| L15–L16 (25G signals) | KB-6067GLD prepreg | Low-loss | Bottom high-speed pair |
This hybrid approach uses KB-6167GLD prepreg on 4 of 8 dielectric layers, saving 25–35% material cost versus full KB-6167GLD construction while maintaining identical dielectric performance on all high-speed signal pairs. The KB-6167F cores share the same Tg 220°C (DMA) ✓ thermal platform, ensuring compatible lamination processing.
Our stackup design service handles mixed-material impedance modeling with per-layer Dk assignments, accounting for the different dielectric constants between KB-6167GLD (Dk ~3.9) and KB-6167F (Dk ~4.6) layers. Innerlayer registration verification ensures co-lamination alignment.
Critical Manufacturing Requirements for Low-Loss PCB Fabrication
KB-6167GLD's dielectric advantage can be negated by inadequate manufacturing practices. Three process elements are mandatory:
VLP or HVLP copper foil: Standard HTE or RTF copper (Rz 3–5 µm) adds 0.5–1.0 dB/inch of conductor loss at 15 GHz through increased skin-effect resistance. VLP copper (Rz <1.5 µm) preserves the dielectric advantage. For the most demanding applications, HVLP (Rz <1.0 µm) provides additional margin. Specify the copper foil grade in your fabrication drawing—this is not a default material at most fabricators.
Backdrilling to minimize via stubs: Through-hole via stubs act as unterminated transmission line branches, creating resonant notches in the insertion loss profile. For 25G NRZ with Nyquist at 12.5 GHz, a 40-mil stub creates a resonance notch at approximately 18 GHz that degrades the frequency response. Target stub length below 8 mils after backdrilling. Our fabrication process achieves consistent backdrill depth control within ±3 mils.
Insertion loss testing on production coupons: S-parameter measurement up to 20 GHz on dedicated test structures validates every production lot. This is not optional for low-loss material builds—it is the only way to confirm that material, copper, and processing are all contributing the expected performance. Our quality protocols include SPC tracking of impedance and insertion loss across production runs.
Additional considerations for frequencies above 10 GHz include glass weave mitigation (fiber weave angle rotation relative to trace routing, or specification of NE-glass for the most critical layers) and etch profile control for fine traces. These factors are evaluated during our DFM analysis.
Target Applications from Data Center to Automotive Radar
25G Ethernet and SFP28 Host Boards: Controlled-loss channels within IEEE 802.3by link budgets for rack-scale and top-of-rack networking switches. KB-6167GLD enables compliant channels on traces up to 8 inches that would fail on mid-loss material.
PCIe Gen 5 Server Interconnect (32 GT/s): Channel loss of approximately 4.9 dB for 6-inch traces versus 10.7 dB on standard FR-4. The improvement brings marginal channels into compliance without equalization changes or reclocking.
56G PAM4 SerDes: The flat Dk frequency response across 1–20 GHz maintains PAM4 eye opening quality. Standard FR-4's Dk dispersion causes differential group delay that degrades the 4-level signal, while KB-6167GLD's <5% Dk variation preserves eye symmetry.
Data Center Switch Fabric: Our telecom and networking PCB capability handles KB-6167GLD in 16+ layer switch designs with controlled impedance and insertion loss testing.
Next-Generation Automotive Radar Digital Backend: The digital signal processing section of 77 GHz automotive radar modules operates at 25G+ data rates between ADC and DSP. KB-6167GLD provides automotive-grade thermal reliability (Tg 220°C (DMA) ✓) with the signal integrity these interfaces demand.
AI Accelerator Interconnect: GPU-to-GPU and GPU-to-memory communication at 56G per lane. HDI structures with KB-6167GLD deliver the trace density and signal quality these designs demand.
How to Order KB-6167GLD PCBs from APTPCB
Upload your design files with interface speed specifications and channel length requirements. Our signal-integrity-aware engineering team simulates insertion loss budgets, confirms KB-6167GLD suitability versus KB-6167GMD (for lower speeds) or KB-3200G (for higher speeds), and provides DFM feedback covering copper foil selection, backdrill requirements, and glass weave considerations. For complete fabrication and assembly, we quote the full project with material, VLP copper, and insertion loss testing included.