N4000-13 SI PCB Laminate: Properties and Design Guide

N4000-13 and N4000-13 SI are high-Tg, modified-epoxy laminate and prepreg systems used in multilayer printed circuit boards that need better signal-loss and thermal performance than ordinary FR-4. The material family is associated with Nelco and is now listed within AGC's electronic materials portfolio.

The important engineering decision is not simply whether a fabricator “supports N4000-13.” Designers must identify the exact variant, glass style, resin content, copper profile and finished construction used in the impedance model. Those details influence dielectric constant, loss, thickness, skew and manufacturability.

What Is N4000-13?#

N4000-13 is a multifunctional epoxy laminate system developed for high-speed digital, RF-adjacent and high-reliability multilayer boards. It combines a high glass-transition temperature with lower dielectric loss than conventional general-purpose FR-4. Typical applications include backplanes, server and storage hardware, switching and routing equipment, wireless infrastructure, dense BGA designs and other controlled-impedance assemblies.

N4000-13 SI is the signal-integrity version. AGC describes it as using SI glass to support precise impedance control and improved loss performance. It is not a different schematic technology; it is a material and reinforcement option intended to make the physical channel more predictable.

N4000-13 vs. N4000-13 SI#

These are representative product-family values published by AGC, not universal values for every fabricated stack-up. The technical data sheet also reports test-method-dependent figures. Your impedance solver should use construction-specific values supplied or approved by the board manufacturer.

Key Published Material Properties#

AGC's N4000-13 SI technical data sheet gives typical dielectric-constant values of 3.4 at 2.5 GHz using a split-post-cavity method and 3.2 at 10 GHz using a stripline method, both at 50% resin content. It lists a typical dissipation factor of 0.008 under both stated conditions. These values demonstrate why frequency, test method and resin content must accompany any Dk or Df number.

The same data sheet reports a DMA Tg of 240°C, a degradation temperature of 350°C at 5% weight loss, T-260 greater than 30 minutes and T-288 greater than 10 minutes. AGC's product-selection table lists the family Tg as 210°C. The apparent difference is not a contradiction: Tg changes with the measurement method and reporting convention. Always compare materials using the same method and use the fabricator's qualified process data.

Published typical values also include 3.5% Z-axis expansion from 50°C to 260°C and 0.1% moisture absorption. Those indicators are relevant to plated-through-hole reliability and repeated lead-free reflow, but they do not replace a board-level reliability assessment.

Why Dk Is Not One Fixed Number#

The dielectric constant seen by a trace depends on resin content, glass weave, cured thickness, frequency, moisture, copper roughness and the measurement method. A laminate data-sheet value is therefore a starting point, not a complete field-solver model.

For controlled impedance, request the fabricator's proposed stack-up before final routing. It should define core and prepreg part numbers, glass styles, target resin content, pressed dielectric thickness, copper type and finished copper thickness. Use those values to calculate the trace geometry, then let the fabricator adjust the artwork only through an agreed impedance-control process.

If a previous design used generic FR-4, do not copy its trace widths into an N4000-13 SI stack-up. The lower Dk and different dielectric thicknesses can change impedance even when layer count and overall board thickness remain the same.

Signal Loss and Copper Roughness#

Channel loss is not determined by Df alone. At high data rates, conductor loss, copper surface roughness, trace geometry, vias, connectors and discontinuities can rival or exceed dielectric loss. A low-loss laminate paired with rough copper can miss the expected insertion-loss target.

Specify the copper profile as part of the material callout and confirm which foil is available for the selected core thickness. AGC notes that the family can be supplied with multiple copper types, including very-low-profile options. Model the actual foil treatment when the channel budget is tight.

For long links, define an insertion-loss mask or channel budget rather than relying only on a laminate trade name. Our guide to PCB insertion loss explains how dielectric, conductor and discontinuity losses combine.

Glass Weave, Skew and the SI Option#

Woven glass creates local areas with different resin and glass proportions. A differential pair routed so that its two traces encounter different weave patterns can develop phase skew. The SI construction is intended to improve signal-integrity behavior, but the complete stack-up and routing still matter.

When skew is critical, ask which glass styles are used on every signal layer and whether spread-glass or other weave-management options are available. Route differential pairs consistently, avoid unnecessarily long straight runs aligned with the weave, and consider a small routing angle where your design rules permit it. Verify the final approach against the interface timing margin rather than applying a generic rule to every pair.

Thermal Performance and Lead-Free Assembly#

High Tg helps the laminate retain mechanical stability across elevated process temperatures, but Tg does not describe every failure mechanism. Review degradation temperature, Z-axis expansion, T-260/T-288, moisture absorption and the number of assembly cycles. The distinction is covered in more detail in our PCB Tg guide.

The current N4000-13 SI data sheet states compatibility with lead-free assembly up to 245°C and notes that suitability depends on the design. Older family literature discusses acceptable results at higher reflow conditions for some constructions. Do not turn either statement into a universal peak-temperature allowance. Qualify the exact board construction, thickness, via structure and reflow profile with the manufacturer.

N4000-13 SI's thermal conductivity is still close to that of other glass-reinforced organic laminates. For high-power components, heat spreading depends mainly on copper planes, thermal vias, component attachment and the mechanical heat path—not the high Tg label.

Stack-Up and Impedance Planning#

1. Define the electrical targets. Record impedance, data rate, maximum route length, loss budget and skew limit for each critical interface.
2. Choose the exact material variant. State N4000-13, N4000-13 SI, or another approved material rather than writing only “high-speed FR-4.”
3. Request available constructions. Core thickness, prepreg glass style and cured resin content depend on the fabricator's qualified inventory.
4. Model finished copper. Include base foil, plating and copper roughness rather than using nominal copper weight alone.
5. Calculate traces from the proposed stack-up. Do not finalize controlled-impedance geometry before the dielectric construction is known.
6. Control substitutions. Require approval before the manufacturer changes material family, glass style or copper profile.
7. Use impedance and SI coupons. Define the coupon, test frequency or method, reporting and acceptance limits in the fabrication notes.

If layer count is still open, use the PCB layer-count guide to organize return paths, reference planes and routing density before requesting material quotations.

Fabrication and Supply Considerations#

N4000-13 processes similarly to high-Tg FR-4, but a fabricator still needs a qualified lamination cycle, drilling parameters, desmear chemistry and registration strategy. AGC's product literature describes a 90-minute press at 193°C and 275–350 psi as a reference process. Board shops qualify their own cycles for press loading, panel size and construction; designers should not place a generic resin recipe on the drawing.

Before releasing production data, confirm:

• whether the exact laminate and prepreg variants are stocked or require a minimum order;
• available core thicknesses, glass styles, resin contents and copper profiles;
• the manufacturer's controlled-impedance calculation method and tolerance;
• maximum qualified layer count, board thickness, aspect ratio and sequential-lamination capability;
• UL recognition and IPC-4101 slash-sheet requirements for the delivered construction;
• lead time and the rules for equivalent-material substitution;
• coupon design, test equipment and the data supplied with each lot.

When N4000-13 SI Is a Good Fit#

The material is a practical candidate when a multilayer board needs moderate low-loss performance, tight impedance control and high thermal robustness while retaining processing closer to high-Tg FR-4 than PTFE-based laminates. It can suit backplanes, networking equipment, data-storage systems, test hardware and dense digital boards with meaningful channel lengths.

It may be unnecessary for short, slow connections where ordinary qualified FR-4 meets signal and thermal margins. At the other extreme, very long or very high-frequency channels may need a lower-loss material family. Use a channel simulation or loss budget to place the design on that spectrum.

Common Specification Mistakes#

• Calling out only “N4000-13.” The SI variant, reinforcement and copper option may be electrically significant.
• Using a single Dk without context. Resin content, frequency and method change the reported value.
• Ignoring copper roughness. Df alone cannot predict total channel loss.
• Free substitution. An “equivalent” laminate can require different trace geometry and may change loss or skew.
• Confusing high Tg with high thermal conductivity. The material withstands heat better than it transports heat.
• Reusing an old stack-up. Available prepregs and pressed thicknesses may differ by supplier and factory.
• Skipping coupon requirements. A nominal impedance note does not define how compliance will be measured.

Design Release Checklist#

1. Name the exact laminate and prepreg family on the fabrication drawing.
2. List approved substitutions or require written approval for any change.
3. Approve a stack-up with glass styles, resin content and finished dielectric thickness.
4. Use the fabricator's construction-specific Dk in the impedance model.
5. Include copper profile and finished copper in loss and impedance calculations.
6. Check via structures and reflow cycles against thermal-reliability targets.
7. Define impedance, insertion-loss or skew coupons where the channel risk requires them.
8. Review artwork for reference-plane continuity and return-path transitions.
9. Inspect the released fabrication files with the online Gerber viewer.
10. Archive the approved stack-up and test results with the product revision.

Official Engineering References#

• AGC N4000-13 SI Technical Data Sheet
• AGC Electronic Materials Product Selection Table

Final Takeaway#

N4000-13 SI can provide a useful balance of controlled impedance, reduced loss and high-Tg epoxy processing, but the name on the purchase order is only the beginning. The final electrical behavior comes from the exact resin-and-glass construction, copper profile, pressed thickness and fabrication process.

Start with a channel budget, obtain a manufacturer-approved stack-up, model construction-specific values and lock substitutions. That workflow is more reliable than selecting the material from one attractive Dk, Df or Tg number.

N4000-13 SI FAQ#

Is N4000-13 SI the same as standard FR-4?

It is a glass-reinforced modified-epoxy PCB material that processes similarly to high-Tg FR-4, but it is engineered for improved high-speed electrical and thermal performance.

What is the difference between N4000-13 and N4000-13 SI?

Both use a high-Tg modified-epoxy system. The SI version uses a signal-integrity glass option and is listed with lower typical Dk and slightly lower Df for tighter high-speed design requirements.

What Dk should I use for N4000-13 SI?

Use the value supplied for the proposed glass style, resin content, frequency and test method by your fabricator or laminate supplier. Published typical values range because the measurement conditions differ.

Is N4000-13 SI suitable for lead-free reflow?

AGC lists lead-free assembly compatibility, but the allowable profile depends on the board construction. Confirm the peak temperature, number of cycles, moisture handling and via reliability with the fabricator.

Does N4000-13 SI solve all insertion-loss problems?

No. Copper roughness, route geometry, vias, connectors and reference-plane discontinuities also contribute loss. Validate the complete channel against its budget.

Can a fabricator substitute another low-loss laminate?

Only through an approved engineering change. A substitute may have different Dk, Df, prepreg thickness, glass weave and processing behavior, which can require new impedance geometry and qualification.