Megtron 4 (MEGTRON 4) is Panasonic’s mid-loss laminate (R-5725) and prepreg (R-5620) for high-speed multilayer boards that need lower loss and better heat resistance than standard FR-4, without the cost of Megtron 6, 7 or 8. On Panasonic’s datasheet it has a Tg of 176°C (DSC), a Td of 360°C, and a Dk of 3.83 with a Df of 0.005 at 1 GHz. This page brings the official values together, shows how Dk and Df change with the construction, explains where Megtron 4 sits in the Megtron family, and lists what to write on a PCB order. For other laminates, see our PCB materials guide.
1. What Is Megtron 4?
A Panasonic MEGTRON-series high-speed laminate system:
| Item | Megtron 4 |
|---|---|
| Laminate (core) | R-5725 |
| Prepreg | R-5620 |
| IPC-4101 slash sheet | /91 (primary), /102 (secondary) |
| Flammability | UL 94 V-0 |
| Not to be confused with | MEGTRON 4S (R-5725S) and MEGTRON M (R-5735), which have their own datasheets |
Panasonic lists the slash sheets as typical correspondence, not a quality guarantee; the product specification is the one agreed in the supply contract (Panasonic IPC-4101 sheet, October 2024).
Is Megtron 4 FR-4? It is processed much like FR-4 and is often used where a better FR-4 would be the alternative, but it is a different resin system with lower loss, and it is ordered by its own part numbers.
2. What Does the Megtron 4 Datasheet Say?
Typical values for R-5725, 0.8 mm test laminate (3313 glass × 8 plies):
| Property | Megtron 4 (R-5725) | Method |
|---|---|---|
| Tg | 176°C (DSC), 170°C (TMA), 210°C (DMA) | As received |
| Td | 360°C | TGA |
| T288 | 30 min with copper; > 120 min without | IPC-TM-650 2.4.24.1 |
| X / Y CTE below Tg | 12–14 / 13–15 ppm/°C | IPC-TM-650 2.4.24 |
| Z-axis CTE below / above Tg | 35 / 265 ppm/°C | IPC-TM-650 2.4.24 |
| Dk at 1 MHz / 1 GHz | 3.89 / 3.83 | IPC-TM-650 2.5.5.9 |
| Df at 1 MHz and 1 GHz | 0.005 | IPC-TM-650 2.5.5.9 |
| Dk / Df at 13 GHz | 3.68 / 0.0074 | Balanced-type circular disk resonator |
| Water absorption | 0.14% | IPC-TM-650 2.6.2.1 |
| Peel strength (1 oz copper) | 1.2 kN/m | IPC-TM-650 2.4.8 |
| Flammability | 94V-0 | UL |
Sources: Panasonic R-5725 / R-5620 datasheet (April 2022) and MEGTRON 4 summary sheet (October 2024). Values are typical, not guaranteed. Note that the 1 GHz and 13 GHz figures come from different test methods, so do not mix them in one calculation.
Panasonic also shows a reliability example: a 28-layer, 3.8 mm thick board with 0.3 mm drills passed 10 reflow cycles at 260°C on R-5725.
3. How Do Dk and Df Change With the Construction?
Each core is a different mix of glass and resin, so Dk varies by construction. Panasonic’s tables for R-5725 at 2 GHz include:
| Core construction | Resin content | Thickness | Dk at 2 GHz | Df at 2 GHz |
|---|---|---|---|---|
| 106 × 1 | 72% | 0.050 mm | 3.38 | 0.006 |
| 1078 × 1 | 68% | 0.090 mm | 3.47 | 0.006 |
| 1080 × 2 | 63% | 0.140 mm | 3.65 | 0.006 |
| 3313 × 1 | 57% | 0.100 mm | 3.82 | 0.006 |
| 2116 × 2 | 47% | 0.200 mm | 4.10 | 0.006 |
| 7628 × 1 | 45% | 0.190 mm | 4.16 | 0.006 |
Source: Panasonic R-5725 datasheet, construction tables.
The range is wide, from about 3.4 to 4.2 depending on resin content. For controlled impedance, use the Dk of the constructions actually in your stackup, or let the fabricator propose the constructions and calculate impedance from them. Our controlled impedance PCB guide covers the stackup side.
4. Where Does Megtron 4 Sit in the Megtron Family?
| Material | Typical role | Loss level |
|---|---|---|
| Standard / high-Tg FR-4 | General boards | Highest (e.g. Isola 370HR Df 0.0161 at 1 GHz) |
| Megtron 4 | Mid-loss high-speed digital, servers, network equipment | Df 0.005 at 1 GHz |
| Megtron 6 / 7 | Lower-loss high-speed digital | Lower |
| Megtron 8 | Ultra-low loss, 800GbE-class | Df 0.0012–0.0016 at 14 GHz |
Values come from each maker’s datasheet with different methods and frequencies, so use the table to place the materials, not to calculate loss. For the FR-4 values, see our FR-4 material guide.
5. When Should You Specify Megtron 4?
When standard FR-4 loses too much signal for your channel, but the loss budget does not need Megtron 6 or higher. It suits mid-speed server, storage and network boards, and it can serve as the lower-cost material in a hybrid stackup whose fastest layers use a lower-loss laminate, if the fabricator confirms the two are compatible. It is also a good fit for thick, high-layer-count boards that go through lead-free assembly, given its Tg, Td and the Panasonic 28-layer reflow example.
Make the decision with numbers: model the channel with Megtron 4’s construction-specific Dk and Df and your copper roughness. If the margin is thin, quote a lower-loss material alongside it.
6. How Do You Specify Megtron 4 on a PCB Order?
| Item | What to write |
|---|---|
| Material | “Panasonic MEGTRON 4: R-5725 laminate / R-5620 prepreg” |
| Specification | IPC-4101 /91 |
| Substitutes | “No substitution without written approval,” or an approved list |
| Stackup | Layer order, dielectric thickness and glass style per layer |
| Copper | Foil type and weight |
| Impedance | Targets, tolerance, reference layers and test method |
“Megtron 4 or equivalent” needs a definition of equivalent. Our article on PCB material substitution approval explains what to compare before approving an alternative.
How Can We Help?
Send your stackup with the material you specified and your Gerber files, and we will confirm Megtron 4 availability and constructions and calculate impedance from them in the quote; bare-board quotes come back within 2 hours. We build multilayer PCBs, up to 24 layers as standard and higher layer counts after engineering review.
Conclusion
Megtron 4 is Panasonic’s mid-loss high-speed laminate (R-5725 / R-5620): Tg 176°C (DSC), Td 360°C, Dk 3.83 and Df 0.005 at 1 GHz, and Dk 3.68 / Df 0.0074 at 13 GHz by resonator. Its Dk ranges from about 3.4 to 4.2 depending on construction, so design impedance from the constructions in your stackup. Use it when FR-4 is too lossy and Megtron 6 or higher is more than you need. Contact us with your stackup for a quote.
FAQ
What is Megtron? Panasonic’s family of low-loss laminates and prepregs for high-speed boards, including MEGTRON 4, 6, 7 and 8.
What is the Dk of Megtron 4? 3.83 at 1 GHz on the main datasheet (3.89 at 1 MHz), 3.68 at 13 GHz by resonator, and about 3.4 to 4.2 depending on construction.
What is the Tg of Megtron 4? 176°C by DSC, 170°C by TMA and 210°C by DMA.
Is Megtron 4 the same as FR-4? No. It processes similarly but is a lower-loss material ordered by its own part numbers.
Is Megtron 4 enough for high-speed boards? For mid-loss budgets, often yes; for the fastest, longest channels, Megtron 6, 7 or 8 or other ultra-low-loss laminates are used.
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