High-Speed PCB Material Equivalent & Comparison Chart
Understanding Material Equivalence
A high-speed PCB material equivalent chart helps engineers identify alternative laminate grades by comparing dielectric constant (Dk), dissipation factor (Df), thermal stability, moisture absorption, and manufacturing compatibility. Materials with closely matched electrical properties may be suitable replacement candidates, but a qualified equivalent must also meet the original stackup, impedance, insertion-loss, and reliability requirements.
For a high-speed PCB, material substitution is more complex than replacing one FR-4 brand with another. A change in resin chemistry, glass reinforcement, copper foil treatment, or prepreg thickness can alter signal propagation and production behavior even when published Dk and Df values appear identical.
This comparison separates material equivalence into three practical categories:
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Priority Equivalent Candidate: Closely matched nominal electrical properties and a reasonable starting point for qualification.
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Conditional Alternative: Similar application or loss category, but meaningful electrical, thermal, or construction differences require engineering review.
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Not Established: Insufficient comparable data to identify a defensible substitute.
No designation implies automatic drop-in approval. For critical HDI PCB and low-loss PCB material applications, the final decision must be supported by electrical modeling, fabrication capability, and test results.
Properties to Evaluate
Dielectric Constant (Dk)
Dielectric constant influences characteristic impedance and signal propagation delay.
High-speed digital laminates commonly have Dk values between approximately 3.0 and 4.2, while selected PTFE microwave materials have Dk near 2.2.
In an ideal homogeneous dielectric, propagation delay varies with the square root of Dk. Replacing Dk 3.64 with Dk 3.66 changes the theoretical propagation delay by approximately 0.27%.
However, finished impedance also depends on trace width, copper thickness, dielectric spacing, and the glass-resin distribution.
A material replacement therefore requires a new field-solver calculation using the actual core and prepreg constructions.
Dissipation Factor (Df)
Df describes dielectric energy dissipation and is a primary consideration for long high-speed channels.
| Material category | Typical screening Df | Application |
|---|---|---|
| Standard loss | 0.015–0.025 | General digital multilayers |
| Mid loss | 0.008–0.012 | Moderate-speed digital designs |
| Low loss | 0.005–0.008 | Servers and networking |
| Very low loss | 0.0025–0.005 | Longer SerDes channels |
| Ultra-low loss | 0.001–0.0025 | Advanced high-speed systems |
| Specialty microwave | Below 0.0015 | Selected RF applications |
These ranges are practical screening categories, not formal IPC classifications.
Changing from Df 0.0095 to 0.0060 reduces nominal loss tangent by approximately 36.8%. This does not establish the same percentage reduction in total insertion loss, which also includes conductor loss and discontinuities.
Copper Roughness
At 10 GHz, copper skin depth is approximately 0.66 µm. At 28 GHz, it decreases to approximately 0.39 µm.
Rougher copper increases effective conductor resistance at high frequencies. Consequently, a laminate with excellent Df can still produce excessive insertion loss when paired with unsuitable copper foil.
Critical specifications include:
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Standard, reverse-treated, low-profile, or very-low-profile copper.
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Copper surface roughness and treatment.
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Finished copper thickness.
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Copper adhesion and peel-strength requirements.
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Conductor-loss modeling assumptions.
A material substitution should preserve the copper profile used in the original channel simulation or require the model to be updated.
Glass Weave Effect
PCB laminates are composite dielectrics containing glass fibers and resin.
Because glass and resin have different dielectric constants, two conductors in a differential pair may experience different propagation delays.
Glass styles such as 106, 1080, 1086, and 2116 differ in reinforcement geometry.
Spread-glass constructions can reduce localized dielectric variation. Routing critical pairs at approximately 10–15° relative to the weave may also reduce alignment-related skew, although the result depends on the actual fabric construction.
For high-speed differential signaling, material qualification should include glass style, resin content, and timing-skew evaluation.
Thermal and Mechanical Properties
Electrical similarity alone does not guarantee reliable multilayer manufacturing.
The principal thermal parameters are:
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Tg: Glass transition temperature of the resin system.
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Td: Thermal decomposition temperature under the specified test method.
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Z-axis CTE: Expansion through the board thickness.
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Moisture absorption: Water uptake that may affect processing and dielectric behavior.
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Lamination compatibility: Resin flow, cure behavior, and registration stability.
A 2.40 mm board with a 0.20 mm finished plated hole has a nominal finished-hole aspect ratio of 12:1.
At this geometry, plated-hole reliability and thermal expansion become important material-substitution considerations.
High-Speed PCB Material Families
Standard and Low-Loss FR-4
Standard epoxy-glass laminates remain economical for shorter channels and less demanding digital applications.
Materials such as 370HR and 185HR provide high-Tg epoxy constructions but have relatively high dielectric loss compared with modern low-loss systems.
FR408HR, I-Speed, and Shengyi S7439 represent lower-loss alternatives.
For example, I-Speed and S7439 have nominal Dk values of 3.64 and 3.66, respectively, with Df 0.0060. Their electrical similarity makes them a useful cross-brand substitution pair for further investigation.
Polyimide and Advanced Laminates
Polyimide materials are generally selected for thermal performance rather than minimum dielectric loss.
P95 and P96 have historical Tg values around 260°C, but their loss factors are considerably higher than those of advanced digital laminates.
Low-loss thermoset and PPE-based systems such as I-Tera MT40, Tachyon 100G, and Astra MT77 offer different tradeoffs between dielectric loss, thermal behavior, and multilayer processing.
A high-temperature material should not be assumed to be a high-speed, low-loss equivalent.
Ultra-High-Frequency Materials
Panasonic MEGTRON 6, 7, and 8 serve demanding high-speed digital applications.
MEGTRON 6 R-5775(N) has published Dk 3.35 and Df 0.0040 at 12 GHz.
MEGTRON 8 R-5795(N) has Dk 3.13 and Df 0.0016 at 14 GHz, while R-5795(U) has Dk 3.08 and Df 0.0012 at the same frequency.
The differences between MEGTRON variants demonstrate why material-family names alone are insufficient for substitution approval.
High-Frequency RF Materials
RO4003C and RO4350B are hydrocarbon-ceramic RF laminates with nominal Dk values of 3.38 and 3.48.
Taconic TLY-5 and RT/duroid 5880 have nominal Dk around 2.20 and very low loss factors.
These materials may be selected for microwave circuits, antennas, and RF sections of a hybrid PCB.
Their processing behavior differs from conventional digital epoxy systems, particularly in bonding, drilling, dimensional stability, and multilayer integration.
High-Speed PCB Materials Comparison & Equivalent Chart
The following integrated chart places electrical properties, thermal characteristics, and equivalent candidates in the same row.
Data interpretation: Values are nominal catalog or historical comparison figures. The test-frequency column identifies the measurement basis where available. “Historical” and “Catalog” entries require confirmation against the current manufacturer datasheet. Dashes indicate unestablished comparable values.
Equivalence interpretation: Priority Equivalent Candidate means a strong preliminary screening match. Conditional Alternative means additional differences must be resolved. Neither status constitutes an approved material substitution.
| Material Grade | Dk | Df | GHz | Tg °C | Td °C | Equivalent Material | Status |
|---|---|---|---|---|---|---|---|
| Isola 370HR | 3.92 | 0.0250 | 10–12 | 180 | 340 | Isola 185HR | Conditional Alternative |
| Isola 185HR | 3.88 | 0.0236 | 10–12 | 180 | 340 | Isola 370HR | Conditional Alternative |
| Isola IS415 | 3.68 | 0.0138 | 10–12 | 200 | 370 | — | Not Established |
| Nelco N4000-29 | 4.00 | 0.0170 | 10–12 | 185 | 350 | — | Not Established |
| EMC EM-827 | 4.20 | 0.0190 | Historical | 175 | 350 | — | Not Established |
| Isola FR408HR | 3.65 | 0.0095 | 10–12 | 180 | 360 | Nelco N4000-13EP | Conditional Alternative |
| ITEQ IT-170GRA1 | 3.90 | 0.0100 | 10–12 | 180 | 380 | EMC EM-888 | Conditional Alternative |
| EMC EM-888 | 3.80 | 0.0080 | 10–12 | 170 | 380 | EMC EM-888(S) | Priority Equivalent Candidate |
| EMC EM-888(S) | 3.80 | 0.0080 | 10–12 | 170 | 380 | EMC EM-888 | Priority Equivalent Candidate |
| Nelco N4000-13EP | 3.60 | 0.0090 | 10–12 | 210 | 350 | Isola FR408HR | Conditional Alternative |
| Nelco N4000-13EPSI | 3.20 | 0.0080 | 10–12 | 210 | 350 | — | Not Established |
| Isola I-Speed | 3.64 | 0.0060 | Catalog | 180 | 360 | Shengyi S7439 | Priority Equivalent Candidate |
| EMC EM-888(K) | 3.20 | 0.0060 | 10–12 | 170 | 380 | — | Not Established |
| ITEQ IT-968 | 3.66 | 0.0050 | 10–12 | 185 | 400 | Shengyi S7439 | Conditional Alternative |
| ITEQ IT-968 SE | 3.34 | 0.0038 | 10–12 | 175 | 400 | MEGTRON 6(N) | Conditional Alternative |
| TUC TU-883 | 3.57 | 0.0046 | 10–12 | 170 | 420 | MEGTRON 6(N) | Conditional Alternative |
| TUC TU-883SP | 3.22 | 0.0029 | 10–12 | 170 | 420 | Doosan DS-7409DV(N) | Conditional Alternative |
| Shengyi S7439 | 3.66 | 0.0060 | 10 | 200 | 383 | Isola I-Speed | Priority Equivalent Candidate |
| Shengyi S7439G | 3.74 | 0.0060 | 10 | 189 | 405 | Shengyi S7439 | Conditional Alternative |
| Isola I-Tera MT40 | 3.45 | 0.0031 | Catalog | 215 | 360 | MEGTRON 6(N) / Synamic 6N | Conditional Alternative |
| Isola Tachyon 100G | 3.02 | 0.0021 | Catalog | 215 | 360 | Isola Astra MT77 | Priority Equivalent Candidate |
| ITEQ IT-988G | 3.63 | 0.0029 | 10–12 | 190 | 405 | — | Not Established |
| ITEQ IT-988G SE | 3.24 | 0.0014 | 10–12 | 190 | 405 | MEGTRON 8(N) | Conditional Alternative |
| EMC EM-890K | 3.00 | 0.0022 | 10–12 | 170 | 430 | Tachyon 100G | Conditional Alternative |
| Doosan DS-7409DV(N) | 3.26 | 0.0025 | 10–12 | 180 | 400 | TUC TU-883SP | Conditional Alternative |
| Nelco Meteorwave 2000 | 3.40 | 0.0040 | 10–12 | 215 | 390 | MEGTRON 6(N) | Conditional Alternative |
| Shengyi Synamic 6N | 3.35 | 0.0026 | 10 | 205 | 405 | Isola I-Tera MT40 | Conditional Alternative |
| Panasonic MEGTRON 6(N) | 3.35 | 0.0040 | 12 | 185 | 410 | ITEQ IT-968 SE | Conditional Alternative |
| Panasonic MEGTRON 6(K) | 3.40 | 0.0040 | 12 | 185 | 410 | MEGTRON 6(N) | Conditional Alternative |
| Panasonic MEGTRON 7(N) | 3.40 | 0.0010 | 1 | 200 | 400 | — | Not Established |
| Panasonic MEGTRON 8(N) | 3.13 | 0.0016 | 14 | 220 | 370 | MEGTRON 8(U) | Priority Equivalent Candidate |
| Panasonic MEGTRON 8(U) | 3.08 | 0.0012 | 14 | 220 | 370 | MEGTRON 8(N) | Priority Equivalent Candidate |
| Isola Astra MT77 | 3.00 | 0.0017 | Catalog | 200 | 360 | Tachyon 100G | Priority Equivalent Candidate |
| Isola TerraGreen 400G | 3.15 | 0.0017 | Catalog | 200 | 380 | TerraGreen 400G2 | Conditional Alternative |
| Isola TerraGreen 400G2 | 3.10 | 0.0015 | Catalog | 200 | 380 | TerraGreen 400G | Conditional Alternative |
| Rogers RO4003C | 3.38 | 0.0027 | 10 | — | — | Rogers RO4350B | Conditional Alternative |
| Rogers RO4350B | 3.48 | 0.0037 | 10 | — | — | Rogers RO4003C | Conditional Alternative |
| Rogers RO4360G2 | 6.15 | 0.0038 | 10 | — | >350 | — | Not Established |
| Rogers RO4533 | 3.30 | 0.0025 | 10 | — | — | — | Not Established |
| Taconic TLY-5 | 2.20 | 0.0009 | Historical | — | — | RT/duroid 5880 | Priority Equivalent Candidate |
| Taconic RF35 | 3.50 | 0.0018 | Historical | — | — | — | Not Established |
| Taconic RF35TC | 3.50 | 0.0011 | Historical | — | — | — | Not Established |
| Taconic TSM-DS3 | 3.00 | 0.0011 | Historical | — | 526 | — | Not Established |
| Rogers RT/duroid 5880 | 2.20 | 0.0009 | Historical | — | 500 | Taconic TLY-5 | Priority Equivalent Candidate |
| Rogers RO3003 | 3.00 | 0.0010 | Historical | — | 500 | — | Not Established |
| Isola P95 | 3.73 | 0.0179 | 2–3 | 260 | 416 | Isola P96 | Conditional Alternative |
| Isola P96 | 3.73 | 0.0210 | 10–12 | 260 | 396 | Isola P95 | Conditional Alternative |
| Ventec VT-901 | 4.05 | 0.0120 | Historical | 250 | 395 | Arlon 85N | Conditional Alternative |
| Arlon 85N | 4.00 | 0.0100 | 0.001 | 250 | 407 | Ventec VT-901 | Conditional Alternative |
| Arlon 85HP | 4.00 | 0.0080 | 0.001 | 250 | 430 | Arlon 85N | Conditional Alternative |
Priority Replacement Candidates
The following pairs deserve particular attention during procurement and engineering review.
Isola I-Speed versus Shengyi S7439
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Nominal Dk: 3.64 versus 3.66.
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Nominal Df: 0.0060 versus 0.0060.
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Tg: 180°C versus 200°C.
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Dk difference: approximately 0.55%.
This is a promising cross-brand candidate for low-loss digital multilayers. Its electrical similarity is stronger than that of many alternatives, although the published test conditions must first be aligned.
Isola Tachyon 100G versus Astra MT77
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Nominal Dk: 3.02 versus 3.00.
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Nominal Df: 0.0021 versus 0.0017.
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Dk difference: approximately 0.66%.
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Nominal Df difference: approximately 19% relative to Tachyon 100G.
These materials are useful comparison candidates for demanding digital channels. Their similar Dk does not eliminate the need to verify insertion loss and copper profile.
Panasonic MEGTRON 8(N) versus MEGTRON 8(U)
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Dk: 3.13 versus 3.08.
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Df: 0.0016 versus 0.0012.
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Test frequency: 14 GHz.
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Tg: 220°C for both.
Both are advanced low-loss materials, but they are distinct product variants. The difference in glass construction and dielectric behavior requires a separate stackup and skew evaluation.
Taconic TLY-5 versus RT/duroid 5880
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Nominal Dk: 2.20 versus 2.20.
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Nominal Df: 0.0009 versus 0.0009.
The matching historical electrical values make these PTFE materials useful RF substitution candidates. However, reinforcement, available thickness, copper bonding, and thermal expansion must be reviewed before approval.
Practical Selection Tips
Match the Frequency Tier
The required laminate depends on signal frequency, channel length, and insertion-loss budget.
For NRZ signaling, the Nyquist frequency is half the bit rate. A 25 Gb/s NRZ channel therefore has a Nyquist frequency of 12.5 GHz.
A 112 Gb/s PAM4 interface operates at approximately 56 GBd, corresponding to a 28 GHz Nyquist frequency.
A practical selection sequence is:
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Define the signaling standard, channel length, and insertion-loss budget.
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Identify the frequency range used in channel simulation.
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Compare Dk and Df at compatible measurement frequencies.
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Include copper roughness, via transitions, and connector losses.
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Verify impedance and insertion loss on representative test structures.
A 50 mm channel and a 400 mm channel operating at the same data rate may require different material grades.
Check Stackup and Hybrid Designs
A hybrid PCB combines different laminate systems within a single multilayer structure.
For example, a 12-layer hybrid circuit may use RO4350B for RF structures and a low-loss epoxy system for digital routing.
The main manufacturing challenges include:
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Different resin cure and bonding behavior.
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Thermal expansion mismatch.
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Registration during multilayer lamination.
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Drilling and desmear compatibility.
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Plated-hole reliability across material interfaces.
Hybrid construction can reduce the consumption of specialty RF laminates, but additional manufacturing operations may offset the material savings.
Verify DFM and Availability
A substitute must be available in the exact dielectric construction required by the approved stackup.
For an advanced HDI PCB, representative requirements may include:
| Manufacturing parameter | Example requirement |
|---|---|
| Layer count | 16 |
| HDI construction | 1+14+1 |
| Finished thickness | 2.40 mm |
| Minimum line/space | 75/75 µm |
| Laser microvia | 100 µm |
| Finished plated hole | 0.20 mm |
| Differential impedance | 100 Ω ±7% |
| Copper foil | Qualified low-profile construction |
These are illustrative design targets, not guaranteed capabilities of every material or PCB manufacturer.
Material qualification must confirm core thickness, prepreg availability, copper treatment, and panel dimensions before fabrication release.
Factory Engineering Case
Sixteen-Layer Network PCB
The following example illustrates a factory material-substitution workflow using representative engineering parameters. It is not presented as a verified customer production record.
A 16-layer network PCB carries 25 Gb/s NRZ differential signals and uses a 1+14+1 HDI construction.
The initial material has nominal Df 0.0092. A lower-loss candidate has nominal Df 0.0031.
The nominal loss-tangent reduction is approximately 66.3%, but that value does not represent measured total insertion-loss improvement.
Manufacturing Problems
The initial fabrication package contains three material-related risks.
First, the stackup assigns one generic Dk value to multiple core and prepreg constructions.
Second, the signal-integrity model assumes smooth copper, while the production process specifies treated foil.
Third, the proposed replacement is selected by Df alone without confirming the available dielectric thicknesses.
The board also has a nominal finished-hole aspect ratio of 12:1, increasing the importance of plating quality and thermal reliability.
Engineering Corrections
The factory engineering workflow is revised:
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Identify every core and prepreg by exact manufacturer grade.
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Confirm the finished dielectric thickness after lamination.
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Recalculate controlled impedance using the actual construction.
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Incorporate copper roughness into insertion-loss simulation.
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Verify laser microvia and mechanical drilling processes.
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Produce impedance and insertion-loss coupons.
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Inspect plated-hole and microvia cross-sections.
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Complete specified thermal and electrical qualification.
Validation Results
The engineering release criteria are:
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Differential impedance within 100 Ω ±7%.
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Insertion loss within the approved channel budget.
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Acceptable plated-hole copper and microvia interfaces.
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No unacceptable delamination after specified thermal testing.
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Verified layer registration and dielectric thickness.
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Documented approval of the alternative material.
These are acceptance criteria rather than claimed production measurements. Actual improvement in yield or insertion loss requires first-article test records.
Common Design Errors
Comparing Df at Different Frequencies
A Df value measured at 1 GHz cannot be ranked directly against a 14 GHz measurement.
The same-frequency comparison should use compatible test methods and actual laminate constructions.
Assuming Similar Dk Means Equivalence
Two materials with nearly identical Dk can have different Df, Tg, CTE, moisture absorption, and copper compatibility.
Material substitution requires a complete engineering review.
Ignoring Copper Treatment
Changing copper roughness without updating the loss model can invalidate predicted channel performance.
Overlooking Prepreg Construction
Different resin contents and glass styles can change finished dielectric thickness, impedance, and differential skew.
Releasing Unqualified HDI Materials
A material that performs well in a conventional multilayer board may not be qualified for sequential lamination, laser drilling, or copper-filled microvias.
Omitting Electrical Test Coupons
Continuity testing alone cannot demonstrate controlled impedance or acceptable insertion loss.
High-speed production requires appropriate electrical test structures and clearly defined acceptance limits.
Frequently Asked Questions
Q1. What PCB material is best for high-speed design?
The best material depends on the channel-loss budget, signal frequency, stackup, and manufacturing requirements. I-Speed and S7439 are low-loss candidates, while I-Tera MT40, Tachyon 100G, and advanced MEGTRON grades may be evaluated for more demanding high-speed channels. Final selection requires simulation and qualification testing.
Q2. What is considered a high-speed PCB?
A PCB requires transmission-line design when interconnect delay becomes significant relative to signal rise time. A common screening criterion is that trace delay exceeds approximately one-quarter of signal rise time. High-speed behavior therefore depends on electrical edge rate and trace geometry, not a single clock-frequency threshold.
Q3. What are the different types of PCB materials and high-speed design guidelines?
Common material types include standard epoxy-glass, modified epoxy, low-loss thermoset, polyimide, hydrocarbon-ceramic, and PTFE composites. Important design guidelines include controlled impedance, continuous return paths, suitable copper roughness, glass-weave management, minimized via stubs, and verified insertion loss.
Q4. What is MEGTRON 6, and can another material replace it?
MEGTRON 6 is a low-loss laminate and prepreg family used in high-speed digital multilayers. The R-5775(N) grade has published Dk 3.35 and Df 0.0040 at 12 GHz. Alternative materials must be evaluated for electrical performance, dielectric construction, copper compatibility, lamination behavior, and thermal reliability before substitution.
Conclusion
A high-speed PCB material equivalent chart should do more than compare laminate names.
By combining Dk, Df, thermal properties, test frequencies, and equivalent candidates in one table, engineers can identify promising replacement materials and understand the risks associated with each substitution.
I-Speed and S7439, Tachyon 100G and Astra MT77, and selected MEGTRON variants are useful examples of material pairs worth evaluating. Their final interchangeability depends on the complete stackup, channel performance, fabrication process, and documented qualification.
For high-speed PCB, HDI PCB, and hybrid circuit applications, the most reliable substitution process begins with comparable material data and ends with verified electrical and manufacturing performance.
