Panasonic MEGTRON 7 R-578Y is the laminate designation to examine when a high-speed MEGTRON 7 PCB also needs a UL-recognized material route. It combines ultra-low-loss electrical performance with a 200°C typical Tg by DSC and a 400°C typical decomposition temperature. Those headline values are useful, but they are not enough to release a stackup.
The important purchasing and engineering questions are more specific: Do you need R-578Y rather than R-5785? Is the construction based on E-glass or low-Dk glass? Which copper profile and prepreg designation are available? At what frequency and by which test method was the quoted Dk or Df measured?
QFPCB uses those questions to turn a material callout into a manufacturable PCB proposal. We review the exact Panasonic grade, glass style, resin content, dielectric thickness, copper type, controlled-impedance geometry, registration needs, and documentation requirements before confirming a build.
What Is Panasonic MEGTRON 7 R-578Y?
R-578Y is a MEGTRON 7 copper-clad laminate for low-loss multilayer circuit boards. The matching prepreg family is R-568Y. Panasonic’s March 2026 datasheet covers two current variants:
- R-578Y(GE) / R-568Y(GE): E-glass construction.
- R-578Y(GN) / R-568Y(GN): low-Dk glass construction.
The Panasonic North America model supplied for this article is listed as R-578Y(G). Panasonic also publishes a July 2024 sheet for R-578Y(N) / R-568Y(N), a low-Dk-glass version. Because suffixes, production locations, copper options, and released constructions can change, your BOM should identify more than the base name “R-578Y.”
Panasonic notes that parenthetical letters or numbers at the end of a part number are company identification codes and are not included in the part numbers registered for UL certification. That detail matters when your drawing, UL documentation, and purchase order must agree.
R-578Y Datasheet Values That Matter to PCB Design
The following table summarizes the general-property page of Panasonic document No. 260330, dated March 2026. These are typical reference values, not guaranteed limits. The frequency, method, conditioning, sample construction, and copper profile remain part of the data.
| Property | Typical value | Test method / condition | Engineering note |
|---|---|---|---|
| Tg | 200°C DSC; 190°C TMA; 210°C DMA | As received | Always state the method with Tg. |
| Td | 400°C | TGA, as received | A material indicator, not a reflow guarantee. |
| T288 | >120 min, with or without copper | IPC-TM-650 2.4.24.1, as received | Review together with finished-board construction. |
| CTE α1 | X/Y 14–16; Z 42 ppm/°C | IPC-TM-650 2.4.24, below Tg | Relevant to registration and plated-hole strain. |
| Z-axis CTE α2 | 280 ppm/°C | IPC-TM-650 2.4.24, above Tg | Do not use alone to predict via reliability. |
| Dk, GE | 3.63 at 1 GHz; 3.60 at 13 GHz | IPC-TM-650 2.5.5.9; IEC 63185 (2020), C-24/23/50 | Values are for a 0.750 mm Core Type 30 specimen. |
| Df, GE | 0.002 at 1 GHz; 0.0034 at 13 GHz | Same methods and condition as GE Dk | Df changes with frequency and construction. |
| Dk, GN | 3.37 at 1 GHz; 3.31 at 14 GHz | IPC-TM-650 2.5.5.9; IEC 63185 (2020), C-24/23/50 | Low-Dk glass changes the laminate system. |
| Df, GN | 0.001 at 1 GHz; 0.0023 at 14 GHz | Same methods and condition as GN Dk | Use construction-specific data in modeling. |
| Water absorption | 0.06% | IPC-TM-650 2.6.2.1, D-24/23 | Typical laminate value. |
| Peel strength | 0.8 kN/m | IPC-TM-650 2.4.8, 1 oz H-VLP2, as received | Confirm the ordered copper option. |
| Flammability | UL 94V-0 | C-48/23/50 | Confirm exact grade, site, thickness, and UL file for the project. |
The 2024 R-578Y(N) sheet reports the same headline low-Dk-glass values of Dk 3.37 at 1 GHz and 3.31 at 14 GHz, with Df 0.001 and 0.0023 respectively. Its peel-strength row references H-VLP copper, while the 2026 GN/GE sheet references H-VLP2. That is a practical reason to lock the exact variant and copper before insertion-loss correlation or procurement.
R-578Y(N), R-578Y(GN), and R-578Y(GE) Are Not Interchangeable Labels
GE uses E-glass; GN and N are described as low-Dk-glass types. Their laminate Dk and Df differ because glass style, resin content, copper profile, and specimen construction all influence measured electrical behavior. Even within one variant, Panasonic’s detailed tables show different Dk and Df values across core thicknesses, cloth styles, resin contents, and frequencies.
For impedance work, “MEGTRON 7” is therefore not a complete material definition. Your fabrication data should identify the laminate, matching R-568Y prepreg, finished dielectric thickness targets, glass style or approved construction, copper weight and profile, and the frequency range that matters to the channel.
R-578Y vs. R-5785: UL Recognition Is the Key Selection Question
R-578Y and MEGTRON 7 R-5785 are closely related ultra-low-loss systems, but the part number is not a cosmetic choice. Panasonic’s product guidance directs users to R-578Y when UL recognition is required. That makes R-578Y the grade to evaluate when the finished equipment, customer specification, or compliance file requires a recognized material route.
Do not convert an existing R-5785 stackup to R-578Y by changing only the BOM text. Confirm the exact laminate/prepreg pair, released glass styles, copper option, nominal and pressed thicknesses, availability, UL recognition details, and impedance model. Conversely, if UL recognition is not required, that does not automatically make R-578Y technically wrong; it means compliance, availability, cost, and qualification should be compared rather than assumed.
Why Test Frequency and Method Change the Meaning of Dk and Df
A Dk number is not a universal constant ready to paste into every field solver. Panasonic reports 1 GHz data using IPC-TM-650 2.5.5.9 and higher-frequency data using a balanced circular disk resonance method under IEC 63185 (2020). The higher-frequency point is 13 GHz for GE and 14 GHz for GN/N in the general-property tables.
That means 3.60 at 13 GHz and 3.31 at 14 GHz are not simply “better” and “worse” values from identical constructions. They describe different glass systems and slightly different frequencies. For an actual controlled-impedance PCB, we also need the selected core/prepreg build, resin content after pressing, copper roughness, etch geometry, solder mask, and the fabricator’s process compensation.
How R-578Y Affects Channel Loss and Stackup Decisions
Material loss is only one part of the channel. Copper roughness, trace width and thickness, return-path continuity, glass-weave interaction, via transitions, connectors, and reference-plane changes can dominate a poorly controlled design. An ultra-low-loss laminate cannot compensate for an avoidable impedance discontinuity.
The GN/N low-Dk-glass route can be useful where low dielectric loss and glass effects are critical, while GE may fit projects that need MEGTRON 7 performance with E-glass constructions. The correct decision depends on insertion-loss budget, rise time and harmonic content, trace length, layer count, available foil, fabrication yield, and supply-chain qualification—not on the lowest datasheet Df alone.
For designs comparing generations, MEGTRON 6 R-5775 may remain a practical cost-performance benchmark. Qualification should use the same channel, connector, copper, stackup, and test conditions wherever possible.
Multilayer, Hybrid, and Mechanical Blind-Via Review
QFPCB can review R-578Y for high-speed multilayer PCBs, hybrid constructions, and mechanically drilled blind-via stackups. We can support stackup planning and impedance simulation calculations after checking the actual material construction, copper profile, dielectric thickness, layer transitions, lamination sequence, and drilling constraints.
For this high-frequency material content, QFPCB does not describe R-578Y as an HDI or Any-Layer HDI stackup capability. If your architecture needs blind vias, send the required layer pairs and let us assess a mechanically drilled blind-via or hybrid route. Feasibility remains project-specific.
PCB engineer Alan has more than 10 years of PCB CAM engineering experience and can support the technical review. Technical email: [email protected].
When R-578Y Is—and Is Not—the Right Material
R-578Y is worth evaluating for long, loss-sensitive channels; high-speed networking equipment; servers and switches; test and measurement hardware; and other multilayer systems where the compliance plan points to a UL-recognized MEGTRON 7 grade.
It may be unnecessary when the channel is short, the loss budget is generous, a less costly laminate already meets performance, or the assembly does not require this UL material route. It may also be a poor procurement choice if your approved stackup uses an unavailable construction or if the specified suffix cannot be supported by the selected manufacturing source.
The best material is the one that closes the electrical, thermal, compliance, manufacturability, and supply-chain requirements together.
What to Send QFPCB for an R-578Y Quote
Send the Gerber or ODB++ data, fabrication drawing, net or impedance table, layer order, finished thickness, copper weights, surface finish, quantity, panel constraints, and applicable standards. Also identify:
- Exact R-578Y suffix or whether alternates may be reviewed.
- Required R-568Y prepreg constructions and any approved glass styles.
- Target impedance, tolerance, reference layers, and critical differential pairs.
- Maximum frequency, data rate, channel-loss target, and any coupon requirement.
- UL recognition or customer-documentation requirement.
- Copper-profile requirement and whether a material substitution needs written approval.
- Mechanical blind-via layer pairs, if applicable.
QFPCB will separate confirmed material data from proposed manufacturing values and flag unresolved items before release. This is more reliable than treating a family-level datasheet value as a finished-board guarantee.
Frequently Asked Questions
Is Panasonic R-578Y the same as R-5785?
No. They are closely related MEGTRON 7 laminate families, but Panasonic points users to R-578Y when UL recognition is required. Do not substitute one by editing the material name alone. The exact laminate/prepreg pair, glass system, copper profile, construction availability, electrical model, and compliance documentation should be reviewed before changing a released stackup.
What is the Dk of R-578Y?
It depends on the variant, frequency, method, and specimen. Panasonic reports typical R-578Y(GE) Dk values of 3.63 at 1 GHz and 3.60 at 13 GHz. R-578Y(GN) and R-578Y(N) are reported at 3.37 at 1 GHz and 3.31 at 14 GHz. Use construction-specific data for impedance modeling.
What is the dissipation factor of R-578Y?
Panasonic reports typical GE Df values of 0.002 at 1 GHz and 0.0034 at 13 GHz. GN/N values are 0.001 at 1 GHz and 0.0023 at 14 GHz. These results use defined test methods and conditions, so they should not be mixed with values measured by a different method as if directly equivalent.
What are R-568Y and R-578Y?
R-578Y is the laminate designation, while R-568Y is the matching prepreg family. A multilayer PCB normally needs both cores and prepregs, but the exact cloth style, resin content, nominal thickness, and pressed dielectric thickness must be selected. Listing only R-578Y on a drawing can leave important stackup variables unresolved.
What is the difference between R-578Y(GE) and R-578Y(GN)?
GE is the E-glass type, while GN is the low-Dk-glass type. Their published dielectric values and released constructions differ. The low-Dk-glass variant may help demanding loss and glass-effect requirements, but availability, copper, resin content, thickness, impedance geometry, and qualification scope should determine the final choice.
Does UL 94V-0 mean the finished PCB is automatically UL approved?
No. The datasheet reports 94V-0 for the material under its stated condition, but finished-board recognition depends on the applicable UL file, exact grade, manufacturing site, thickness, construction, and process. Confirm the compliance route for your product instead of treating a datasheet flammability row as finished-equipment approval.
Can QFPCB build an HDI stackup with R-578Y?
QFPCB does not claim HDI or Any-Layer HDI stackup capability for this high-frequency material. We can review multilayer and hybrid R-578Y constructions and assess mechanically drilled blind-via layer pairs. Send the layer transitions, lamination sequence, dielectric targets, copper, and impedance requirements for a project-specific feasibility review.
What data does QFPCB need for R-578Y impedance simulation?
Provide the layer order, target finished thickness, copper weights and profile, exact R-578Y/R-568Y construction, reference layers, trace geometry or target impedance, solder-mask condition, and critical frequency range. QFPCB can then propose a manufacturable stackup and simulation calculation. Final values remain subject to material availability and engineering review.
Official Sources and Research Notes
- Panasonic Industry, MEGTRON 7 R-578Y(GE)/R-568Y(GE) and R-578Y(GN)/R-568Y(GN), No. 260330, March 2026: https://industrial.panasonic.com/cdbs/www-data/pdf/EMB0000/ast-ind-409310.pdf
- Panasonic Industry, MEGTRON 7 R-578Y(N)/R-568Y(N), No. 240724, July 2024: https://industrial.panasonic.com/cdbs/www-data/pdf/EMB0000/ast-ind-389553.pdf
- Panasonic North America, R-578Y(G) model page: https://na.industrial.panasonic.com/products/electronic-materials/circuit-board-materials/lineup/megtron-series/series/127604/model/151068
- Research window: March 9 to September 9, 2026; English-language US intent. No relevant recent Reddit discussion or reliable competitor click-traffic dataset was found, so no “highest-traffic” competitor voice is claimed.
