KB-6169GT represents Kingboard's most electrically advanced production-ready laminate within the halogen-free platform. Positioned between KB-6167GLD (low-loss, Df ~0.006) and KB-3200G (very-low-loss, Df ~0.004), it targets the critical 56G PAM4 design space where every fraction of a dB in the channel insertion loss budget determines compliance margin. The "GT" designation indicates the premium tier within Kingboard's Green Technology lineup—ultra-low loss with halogen-free compliance and high-Tg thermal reliability in a single material.
The 56G PAM4 design challenge is fundamentally different from 25G NRZ. PAM4 modulation uses four amplitude levels instead of two, making the signal 3× more sensitive to attenuation and noise. A channel that passes 25G NRZ compliance can fail 56G PAM4 with identical physical dimensions simply because the reduced eye opening demands tighter loss control. KB-6169GT addresses this by providing approximately 17% lower dielectric loss than KB-6167GLD (Df ~0.005 vs ~0.006 at 1 GHz) with proportionally flatter Dk dispersion across the 1–28 GHz band that PAM4 signaling requires.
In This Guide
- How KB-6169GT Fits Between Low-Loss and Very-Low-Loss Material Tiers
- KB-6169GT Technical Specifications and Dielectric Characterization
- 56G PAM4 Channel Loss Requirements and Material Impact
- KB-6169GT vs KB-6167GLD vs KB-3200G: Choosing the Right Ultra-Low-Loss Grade
- Copper Foil Selection: Why HVLP Is Mandatory at This Performance Tier
- Data Center, AI Accelerator, and 400G Optical Module Applications
- Manufacturing Process Control for Ultra-Low-Loss PCB Fabrication
- How to Order KB-6169GT PCBs from APTPCB
How KB-6169GT Fits Between Low-Loss and Very-Low-Loss Material Tiers
The PCB material market divides into well-defined dielectric performance tiers, and KB-6169GT occupies a narrow but commercially significant position between the established low-loss and very-low-loss categories:
| Material Tier | Kingboard Product | Df @10GHz | Dk @10GHz | Target Data Rate | Cost vs Std FR-4 |
|---|---|---|---|---|---|
| Mid-Loss | KB-6167GMD | ~0.013 | ~4.1 | ≤10 Gbps | 1.2× |
| Low-Loss | KB-6167GLD | ~0.008 | ~3.8 | ≤25G NRZ / 56G PAM4 | 1.5× |
| Ultra-Low-Loss | KB-6169GT | ~0.006 | ~3.6 | 56G PAM4 optimized | 1.8× |
| Very-Low-Loss | KB-3200G | ~0.005 | ~3.4 | ≤112G PAM4 | 2.0× |
| Ultra-Low-Loss (external) | Megtron 7 | <0.003 | ~3.3 | 112G+ PAM4 | 3.0×+ |
The 0.002 Df gap between KB-6167GLD and KB-3200G may appear small, but in insertion loss terms it represents approximately 25% less dielectric attenuation. KB-6169GT captures half of this improvement at a lower cost increment, making it the optimized choice for 56G PAM4 designs that need better performance than KB-6167GLD but don't require KB-3200G's full very-low-loss capability.
KB-6169GT Technical Specifications and Dielectric Characterization
KB-6169GT specifications are estimated from Kingboard's published product tier positioning. No standalone official datasheet PDF has been independently verified; values are cross-referenced against comparable ultra-low-loss materials in the Df ~0.005 class. Specimen condition: 1.0 mm.
Thermal and General Properties
| Property | Estimated Value | Test Method |
|---|---|---|
| Glass Transition (Tg, DSC) | >170°C | IPC-TM-650 2.4.25 |
| Decomposition Temperature (Td, TGA 5%) | >340°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) | <2.5% | IPC-TM-650 2.4.24 (TMA) |
| Moisture Absorption | ≤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 | ~3.7 | IPC-TM-650 2.5.5.9 |
| Dk @10 GHz | ~3.6 | IPC-TM-650 2.5.5.9 |
| Dk @20 GHz | ~3.55 | — |
| Df @1 GHz | ~0.005 | IPC-TM-650 2.5.5.9 |
| Df @10 GHz | ~0.006 | IPC-TM-650 2.5.5.9 |
| Df @20 GHz | ~0.007 | — |
| Dk Variation (1–20 GHz) | <3% | — |
The Dk variation of <3% across 1–20 GHz is critical for PAM4 performance. At 28 Gbaud (56G PAM4), signal energy extends to approximately 28 GHz. Dk dispersion across this range causes differential group delay that distorts the four-level eye pattern. KB-6169GT's <3% variation provides tighter eye closure margin than KB-6167GLD's estimated <5% variation.
Data Confidence Note: KB-6169GT is a newer product with limited published data. Specifications are estimated from Kingboard's product family hierarchy and cross-referenced with comparable materials. Contact Kingboard or APTPCB for the latest characterization data.
56G PAM4 Channel Loss Requirements and Material Impact
56G PAM4 (28 Gbaud) creates unique channel requirements that distinguish it from lower-speed NRZ signaling. The four amplitude levels reduce the voltage margin between adjacent levels to one-third of the total swing, making the signal approximately 9.5 dB (20×log(3)) more sensitive to attenuation than 28G NRZ at the same baud rate.
For a typical 56G PAM4 channel with 4-inch trace length on 4-mil dielectric:
| Loss Component | KB-6167GLD | KB-6169GT | KB-3200G |
|---|---|---|---|
| Dielectric Loss @14 GHz (Nyquist) | 2.9 dB | 2.1 dB | 1.5 dB |
| Conductor Loss (HVLP, Rz <1.0 µm) | 2.0 dB | 2.0 dB | 2.0 dB |
| Total Trace Loss (4 inches) | 4.9 dB | 4.1 dB | 3.5 dB |
| Via Transitions (2 vias, backdrilled) | 1.0 dB | 1.0 dB | 1.0 dB |
| Total Channel Loss | 5.9 dB | 5.1 dB | 4.5 dB |
The 0.8 dB improvement from KB-6167GLD to KB-6169GT may appear modest, but in PAM4 terms it translates to approximately 10% wider eye opening at the receiver—often the difference between marginal and robust compliance. For channels longer than 4 inches or designs with additional via transitions, the cumulative improvement becomes more significant.
The practical boundary: KB-6169GT supports compliant 56G PAM4 channels up to approximately 5 inches of trace length, versus approximately 4 inches for KB-6167GLD. For trace lengths beyond 6 inches at 56G, KB-3200G becomes necessary.
KB-6169GT vs KB-6167GLD vs KB-3200G: Choosing the Right Ultra-Low-Loss Grade
| Parameter | KB-6167GLD | KB-6169GT | KB-3200G |
|---|---|---|---|
| Df @1 GHz | ~0.006 | ~0.005 | ~0.004 |
| Df @10 GHz | ~0.008 | ~0.006 | ~0.005 |
| Dk @1 GHz | ~3.9 | ~3.7 | ~3.5 |
| Dk Stability (1–20 GHz) | <5% | <3% | <3% |
| Primary Target | 25G NRZ / 56G short | 56G PAM4 optimized | 112G PAM4 |
| Maximum Trace @56G PAM4 | ~4 inches | ~5 inches | ~7 inches |
| Cost vs Std FR-4 | 1.5× | 1.8× | 2.0× |
| Copper Requirement | VLP minimum | HVLP recommended | HVLP mandatory |
Choose KB-6167GLD when: 25G NRZ is the fastest interface, or 56G PAM4 traces are short (<4 inches). The 1.5× cost position provides the best value for designs that don't need KB-6169GT's incremental improvement.
Choose KB-6169GT when: 56G PAM4 is the primary high-speed interface with moderate trace lengths (4–5 inches). The 0.002 Df improvement versus KB-6167GLD provides the compliance margin that 56G PAM4 demands, at 20% lower cost than KB-3200G.
Choose KB-3200G when: 112G PAM4 interfaces are present, or 56G PAM4 traces exceed 6 inches. The very-low-loss performance tier is necessary for next-generation 800G switch fabric and PCIe Gen 6 applications.
Copper Foil Selection: Why HVLP Is Mandatory at This Performance Tier
At the KB-6169GT performance level, copper surface roughness becomes the dominant contributor to total conductor loss, and foil selection can add or negate the material's dielectric advantage.
| Copper Type | Surface Roughness (Rz) | Conductor Loss @14 GHz (per inch) | Compatible Materials |
|---|---|---|---|
| Standard HTE | 5–8 µm | 0.55 dB/inch | Standard FR-4 only |
| RTF (Reverse Treated) | 3–5 µm | 0.42 dB/inch | Mid-loss and below |
| VLP (Very Low Profile) | 1.5–2.5 µm | 0.35 dB/inch | Low-loss |
| HVLP (Hyper VLP) | 0.8–1.2 µm | 0.30 dB/inch | Ultra-low-loss |
| Ultra-Low Roughness | <0.8 µm | 0.27 dB/inch | Very-low-loss and above |
Using standard HTE copper on KB-6169GT would add approximately 0.25 dB/inch of unnecessary conductor loss at 14 GHz—more than negating the 0.8 dB total channel improvement over KB-6167GLD. HVLP copper (Rz <1.2 µm) is the minimum recommendation; for the most demanding 56G channels, ultra-low roughness foils provide additional margin.
Specify the copper foil grade explicitly in your fabrication drawing. Many fabricators default to RTF or standard HTE unless instructed otherwise—this is adequate for mid-loss materials but unacceptable at the KB-6169GT performance tier.
Data Center, AI Accelerator, and 400G Optical Module Applications
56G PAM4 Switch Fabric: 400G switches use 8×56G PAM4 lanes per port. KB-6169GT enables compliant SerDes channels across the switch ASIC's full ball map, including the longest routes that reach 4–5 inches. Our telecom and networking PCB capability handles KB-6169GT in 16+ layer switch designs with controlled impedance and insertion loss testing.
400G Optical Module Host Boards (QSFP-DD, OSFP): The host board channels between the switch ASIC and cage must support 8×56G PAM4 with minimal signal degradation before the optical module's retimer. KB-6169GT's low Dk dispersion preserves PAM4 eye quality across all 8 lanes.
AI Accelerator Interconnect: GPU-to-GPU and GPU-to-HBM communication in AI training systems operate at 56G per lane with hundreds of parallel channels. HDI structures with KB-6169GT deliver the trace density and signal quality these designs demand.
Next-Generation Automotive Radar: Digital backend processing for 77 GHz FMCW radar at 56G data rates between ADC and DSP. KB-6169GT provides automotive-grade thermal reliability with the signal integrity performance these next-generation modules require.
800G Development Platforms: Early 800G (8×112G PAM4) development boards can use KB-6169GT for intermediate-speed channels while reserving KB-3200G or higher-grade materials for the 112G lanes.
Manufacturing Process Control for Ultra-Low-Loss PCB Fabrication
KB-6169GT fabrication requires the highest level of process discipline in the FR-4-compatible material family:
HVLP copper handling: HVLP foils are more delicate than standard copper. Handling procedures must prevent surface contamination and mechanical damage that would increase roughness. Store in controlled environments and minimize handling between lamination and imaging.
Backdrilling precision: Via stub length target below 5 mils (versus 8 mils for KB-6167GLD). At 56G PAM4, a 10-mil stub creates a resonance notch near 20 GHz that falls within the signal bandwidth. Our fabrication process achieves consistent backdrill depth control within ±2 mils.
Glass weave mitigation: At frequencies above 15 GHz, differential signals can experience skew from the dielectric constant variation between glass fiber bundles and resin channels. For the most critical 56G layers, specify spread-glass (NE-glass) or rotated routing angle (7–15° from glass weave axis) during DFM analysis.
Insertion loss testing: S-parameter measurement up to 25 GHz minimum (40 GHz preferred) on dedicated test coupons is mandatory for every production lot. Our quality system includes VNA-based insertion loss testing with SPC tracking across production runs.
Etch profile control: Fine differential traces (3–4 mil width) require tight etch factor control. Trapezoidal etch profiles affect impedance and loss differently than rectangular profiles—verify with cross-section measurement during first article.
How to Order KB-6169GT PCBs from APTPCB
Submit your high-speed design with channel specifications including SerDes data rate, trace lengths, and loss budget requirements. Our SI-aware engineering team evaluates insertion loss budgets, recommends KB-6169GT versus KB-6167GLD (for lower speeds or shorter traces) or KB-3200G (for 112G interfaces or longer channels), and provides comprehensive DFM feedback covering HVLP copper selection, backdrill requirements, and glass weave considerations. For complete fabrication and assembly quotes, we include all materials, specialty copper foils, and insertion loss testing in a single project price.