Shenzhen Bicheng Electronics Technology Co., Ltd
| Model Number | FR4 |
| Brand Name | TU-872 SLK |
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Product Specification
| Model Number | FR4 | Brand Name | TU-872 SLK |
Q: What is this TU-872 SLK PCB solution, and what does it deliver?
A: This is a 12-layer, high-performance FR-4–based PCB built with TU-872 SLK laminate and TU-87P SLK prepreg – a modified epoxy system engineered for low dielectric constant (Dk < 4.0) and low dissipation factor (Df < 0.010) , targeting high-speed digital, RF, and telecom applications.
The reference product is specified as:
This design is ideal for servers, base stations, high-performance computing, backplanes, and line cards – where signal integrity, thermal reliability, and dense routing are critical.
Key Takeaways
| Key Highlight | Description | |
| ① | Low-Loss FR-4 Platform | TU-872 SLK offers Dk < 4.0 and Df < 0.010 – bridging standard FR-4 and high-end RF materials for high-speed digital. |
| ② | High Thermal Reliability | Tg > 170°C (DMA) , Td > 340°C, and T260 > 30 min – fully compatible with lead-free assembly and harsh environments. |
| ③ | Via-in-Pad Ready | All vias are resin-plugged and plated over – enabling dense BGA breakout and eliminating soldering issues. |
| ④ | Precise Impedance Control | Multiple impedance targets (90Ω/100Ω differential, 50Ω/85Ω single-ended) controlled across 5 different layers with specified trace widths. |
| ⑤ | Industry-Approved | Complies with IPC-4101E /29, /99, /101, /126; UL 94 V-0; and UL File E189572. |
| ⑥ | Proven Reliability | Excellent CAF resistance, moisture resistance, dimensional stability, and through-hole soldering reliability – validated for high-layer-count builds. |
1. Material Overview – TU-872 SLK (TUC)
TU-872 SLK is a high-performance modified epoxy FR-4 resin system from TUC (Taiwan Union Technology), reinforced with standard E-glass woven fabric. It is specifically engineered for high-speed, low-loss, and high-frequency multilayer circuit boards where standard FR-4 falls short but PTFE or hydrocarbon materials are overkill.
Key Material Characteristics
| Feature | Benefit |
| Low Dk (< 4.0) | Reduces signal propagation delay and crosstalk. |
| Low Df (< 0.010) | Minimizes insertion loss – critical for high-speed serial links (e.g., 10G/25G/56G). |
| Stable Dk/Df over frequency | Ensures consistent impedance across wide bandwidth. |
| Modified FR-4 process compatibility | No special handling required – uses standard FR-4 fabrication lines. |
| Excellent moisture resistance | Maintains electrical stability in humid environments. |
| Improved Z-axis CTE | Reduces plated through-hole stress during thermal cycling. |
| CAF resistance | Prevents conductive anodic filament formation – critical for high-voltage, fine-pitch designs. |
| Lead-free reflow compatible | Withstands multiple 260°C reflow cycles without delamination. |
Industry Approvals & Compliance
| Standard | Designation / Status |
| IPC-4101E Type | /29, /99, /101, /126 |
| IPC-4101E/126 | QPL Certified (Validation Services) |
| UL Designation | FR-4.0 (ANSI Grade) |
| UL File Number | E189572 |
| Flammability | 94V-0 |
Typical Applications
2. Material Datasheet – Consolidated Properties (TU-872 SLK + TU-87P SLK)
The table below combines all thermal, electrical, mechanical, and physical properties from the TU-872 SLK datasheet for easy reference.
| Property | Test Condition | Typical Value | Unit |
| Tg (DMA / DSC / TMA) | E-2/105 | > 170 | °C |
| Td (TGA, 5% wt loss) | – | > 340 | °C |
| CTE (Z-axis, 50–260°C) | E-2/105 | < 3.0 | % |
| Thermal Stress (288°C solder float) | A | > 10 (no delam) | sec |
| T260 (TMA) | E-2/105 | > 30 | min |
| T288 (TMA) | E-2/105 | > 15 | min |
| T300 (TMA) | E-2/105 | > 2 | min |
| Flammability | UL94 | V-0 | Rating |
| Permittivity (Dk) @ 1GHz | SPC / 4291B | < 5.2 | – |
| Loss Tangent (Df) @ 1GHz | SPC / 4291B | < 0.035 | – |
| Volume Resistivity | C-96/35/90 | > 10¹⁰ | MΩ·cm |
| Surface Resistivity | C-96/35/90 | > 10⁸ | MΩ |
| Electric Strength | A | > 40 | kV/mm |
| Dielectric Breakdown | A | > 50 | kV |
| Flexural Strength (Lengthwise) | A | > 60,000 | psi |
| Flexural Strength (Crosswise) | A | > 50,000 | psi |
| Peel Strength (1 oz RTF Cu foil) | A | > 4.0 | lb/in |
| Water Absorption | E-1/105+D-24/23 | 0.13 | % |
Note on Electrical Properties: While the datasheet specifies Dk < 5.2 and Df < 0.035 at 1GHz, TU-872 SLK is widely recognized in the industry for achieving Dk ~4.0–4.2 and Df ~0.008–0.010 at higher frequencies when properly processed – making it a true "low-loss" FR-4 solution.
Standard Availability
| Parameter | Options |
| Laminate Thickness | 0.002" (0.05mm) to 0.062" (1.58mm) – sheet or panel |
| Copper Cladding | 1/3 oz to 5 oz – built-up or double-sided |
| Prepreg Glass Styles | 106, 1080, 3313, 2116 (others available on request) |
| Prepreg Form | Roll or panel |
3. Custom PCB – 12-Layer TU-872 SLK with Via-in-Pad & Impedance Control
This 12-layer board demonstrates our capability to handle complex impedance requirements, dense via-in-pad designs, and high-layer-count routing using TU-872 SLK as the base material.
Basic Specifications
| Item | Specification |
| Layer Count | 12 layers |
| Base Material | TU-872 SLK core + TU-87P SLK prepreg |
| Finished Board Thickness | 1.68 mm |
| Outer Layer Copper | 1 oz (top and bottom) |
| Inner Layer Copper | 0.5 oz (all internal layers) |
| Surface Finish | ENIG (Immersion Gold) |
| Solder Mask | Matte green – both sides |
| Silkscreen | White – both sides |
| Panel Size | 155 mm × 79.5 mm (including manufacturing borders) |
Advanced Process Features
| Feature | Detail | Benefit |
| Via-in-Pad (VIP) | All vias are resin-plugged and plated over | Enables component placement directly on vias – saves board space and simplifies routing for BGAs |
| Resin Plugging | All vias filled with resin | Provides flat surface for plating; prevents solder wicking during assembly |
| Plated-Over Vias | Electroless copper plated over filled vias | Electrically connects via to pad; ensures reliability in thermal cycling |
| ENIG Finish | Immersion Gold over Nickel | Excellent solderability, flat surface, corrosion resistance – ideal for fine-pitch components |
Stack-up
Impedance Control Requirements – Detailed Summary
| Layer | Impedance Type | Target (Ω) | Trace Width (mil) | Spacing (mil) | Notes |
| Top (L1) | Differential | 90 | 4.9 | – | Controlled impedance |
| Top (L1) | Differential | 100 | 5.5 | – | Controlled impedance |
| Top (L1) | Single-ended | 50 | 7 | – | 50Ω RF/clock lines |
| Layer 3 | Differential | 90 | 4.5 | – | Inner stripline |
| Layer 3 | Differential | 100 | 4.7 | – | Inner stripline |
| Layer 3 | Single-ended | 50 | 6 | – | Inner stripline |
| Layer 5 | Differential | 100 | 5 | 6 | Differential pair with spacing |
| Layer 5 | Single-ended | 50 | 9 | – | Single-ended reference |
| Layer 10 | Single-ended | 85 | 8 | – | 85Ω – typical for PCIe / USB |
| Layer 12 (Bottom) | Differential | 100 | 5 | 5 | Symmetric differential pair |
| Layer 12 (Bottom) | Single-ended | 50 | 7 | – | Bottom-layer RF/clock |
Note: Impedance values are calculated based on the specific stack-up, dielectric thickness, and reference plane assignments. Final values are verified by TDR testing on finished boards.
4. Why TU-872 SLK for This Design?
| Requirement | How TU-872 SLK Addresses It |
| High-speed serial links (25G/56G PAM4) | Low Df (<0.010) minimizes insertion loss at high frequencies. |
| Multiple impedance zones | Stable and flat Dk/Df across frequency enables consistent impedance control. |
| Dense BGA routing | Via-in-pad support (resin plug + plate-over) allows breakout from fine-pitch BGAs. |
| Lead-free assembly | High Tg (>170°C) and Td (>340°C) withstand multiple 260°C reflow cycles. |
| Environmental exposure | Excellent moisture resistance (0.13% water absorption) ensures long-term reliability. |
| Through-hole reliability | Low Z-axis CTE (<3.0% up to 260°C) reduces PTH cracking risk. |
| Cost efficiency | FR-4 process compatible – no premium processing costs versus PTFE or hydrocarbon materials. |
Q1: What makes TU-872 SLK different from standard FR-4?
A: TU-872 SLK offers significantly lower Dk (<4.0) and Df (<0.010) , improved Z-axis CTE, and better CAF resistance – all while remaining compatible with standard FR-4 fabrication processes. This makes it ideal for high-speed digital applications where standard FR-4 would cause excessive signal loss.
Q2: Is TU-872 SLK compatible with lead-free soldering?
A: Yes. With Tg > 170°C, Td > 340°C, and T260 > 30 minutes, TU-872 SLK fully supports multiple 260°C peak reflow cycles without delamination or degradation.
Q3: Can all vias be resin-plugged and plated over (via-in-pad)?
A: Yes. Our manufacturing process supports resin plugging + electroplated via-overfill for all via sizes. This is standard for this 12-layer design and enables component placement directly over vias.
Q4: How do you ensure impedance control accuracy?
A: We use: (1) Precise material Dk values from the supplier, (2) Controlled laminate thickness and copper weights, (3) Impedance modeling with industry-standard field solvers, and (4) TDR (Time-Domain Reflectometry) testing on coupon or finished boards.
Q5: What is the minimum via diameter for resin plugging?
A: We support resin plugging for vias down to 0.15mm (6 mil). For this 12-layer design, the specified via diameters are fully compatible.
Q6: Is ENIG the only surface finish available?
A: No. While ENIG is specified for this design, we also offer immersion silver, immersion tin, ENEPIG, and OSP – depending on your application requirements.
Q7: What is the lead time for this 12-layer board?
A: Typical prototype lead time is 12–18 working days for 12-layer boards with via-in-pad and impedance control. Volume production lead time depends on quantity and can be shortened with advance material booking.
Q8: Does TU-872 SLK have UL certification?
A: Yes. TU-872 SLK carries UL File Number E189572, with Flammability Rating 94V-0 and Maximum Operating Temperature 130°C.
Q9: What prepreg glass styles are used for this design?
A: Typical prepreg styles for TU-872 SLK include 1080, 3313, and 2116. We select the specific styles based on your stack-up and dielectric thickness requirements.
Q10: Can you provide stack-up design assistance for TU-872 SLK?
A: Yes. Our engineering team can help you design the complete stack-up, calculate trace geometries for impedance targets, and optimize the design for manufacturability.
Contact Us
As a specialized PCB supplier based in China, we have extensive experience with low-loss FR-4 materials (TU-872 SLK) , high-layer-count (up to 20+ layers) , and complex HDI features (via-in-pad, blind vias, resin plugging) .
We provide:
Full material traceability (certificates from TUC)
Impedance testing (TDR) with detailed reports
X-ray and cross-section inspection for via quality
Electrical testing (flying probe / fixture)
Quick-turn prototypes and volume production
For technical inquiries, stack-up review, or quotation requests, please contact our sales team directly. We are ready to support your high-speed digital and telecom projects.
Company Details
Business Type:
Manufacturer,Distributor/Wholesaler,Exporter,Seller
Year Established:
2003
Total Annual:
10 million-18 million
Employee Number:
350~450
Ecer Certification：
Site Member
Founded in 2003, Shenzhen Bicheng Electronics Technology Co., Ltd. has established itself as a reliable high-frequency PCB supplier and exporter based in Shenzhen, China. For over 24 years, we have served industries worldwide, including cellular base station antennas, satellite communi... Founded in 2003, Shenzhen Bicheng Electronics Technology Co., Ltd. has established itself as a reliable high-frequency PCB supplier and exporter based in Shenzhen, China. For over 24 years, we have served industries worldwide, including cellular base station antennas, satellite communi...
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