Megtron 6 & Megtron 7 PCB
Low-Loss for High-Speed. No MOQ.

Megtron 6 (R-5775): The High-Speed Workhorse

Megtron 6 has been the go-to low-loss laminate for high-speed digital since the 25G era, and it remains the volume leader for good reason. Key properties at a glance:

• Dielectric constant (Dk): 3.71 @ 1GHz (approximately 3.4 @ 10GHz depending on glass style and resin content)
• Dissipation factor (Df): 0.004 @ 10GHz — this is the critical insertion-loss driver
• Glass transition temperature (Tg): 185°C (DSC method)
• Decomposition temperature (Td): 400°C — handles lead-free reflow with margin
• CTE Z-axis: 2.4% (50-260°C) — good via reliability for standard aspect ratios
• Copper peel strength: 0.8 N/mm (after thermal stress) — no delamination concerns

Megtron 6 processes on the same equipment as standard high-Tg FR-4 with no parameter changes. Same drill speeds, same plating chemistry, same lamination cycle. This processability is why it dominates the "better than FR-4" segment — factories can run it without qualification headaches.

Megtron 7 (R-5785): For 112G PAM4 and Beyond

Megtron 7 represents a generation jump in loss performance, driven by T-Glass reinforcement (lower Dk glass fiber) and an optimized resin system:

• Dielectric constant (Dk): 3.37 @ 1GHz (approximately 3.3 @ 10-28GHz) — lower Dk than Megtron 6 means slightly higher impedance for the same geometry, or narrower traces for the same impedance
• Dissipation factor (Df): 0.002 @ 28GHz — half the loss of Megtron 6, which translates to roughly 1.5-2.0 dB less insertion loss per 10 inches at 14 GHz (Nyquist for 28 Gbaud)
• Glass transition temperature (Tg): 200°C (DSC method) — higher than Megtron 6
• T-Glass reinforcement: Low-Dk glass fiber that reduces the fiber-weave effect on signal propagation
• Spread-glass option: Flat-fiber weave that further reduces Dk variation across the trace width (important for skew-sensitive PAM4 links)

The T-Glass reinforcement is what makes Megtron 7 supply-constrained: AGC (the glass manufacturer) has limited T-Glass production capacity, and demand from hyperscaler AI server boards has grown faster than supply. This is why lead time can vary.

When Megtron 6 Is Enough

For many high-speed designs, Megtron 6 provides sufficient loss performance at a significantly lower cost point. Megtron 6 is the right choice when:

• 25 Gbps NRZ links: At 12.5 GHz Nyquist frequency, Megtron 6's Df of 0.004 keeps channel loss well within budget for traces up to 12 inches
• PCIe Gen4 (16 GT/s) and Gen5 (32 GT/s): Both generations specify loss budgets that Megtron 6 can meet comfortably for standard trace lengths (under 10 inches)
• 56G PAM4 with short traces: At 28 Gbaud, channels under 6-8 inches on Megtron 6 typically stay within the -20dB insertion loss budget that most 56G SerDes can equalize
• 100G Ethernet (4x25G NRZ): Standard server-to-switch links at 25G per lane are well-served by Megtron 6
• Cost-sensitive production: When the design has margin and the BOM needs optimization, Megtron 6 at roughly half the material cost of Megtron 7 makes economic sense

When You Need Megtron 7

Megtron 7 becomes necessary when the link budget is tight and Megtron 6 cannot close the eye diagram. Specific scenarios:

• 112G PAM4 (56 Gbaud): At 28 GHz Nyquist, the halved Df of Megtron 7 gives you approximately 3-4 dB more link budget than Megtron 6 over a 10-inch channel. For PAM4 signaling with its reduced noise margin, those decibels are often the difference between an open eye and a closed one.
• Traces longer than 6 inches at 56G+: Even if Megtron 6 works for short 56G channels, longer backplane traces (8-20+ inches in switch fabric applications) need the lower Df to stay within equalizer capability.
• Loss budget below -3dB at Nyquist per inch: When your channel simulation shows the loss budget requires below -0.3dB/inch at the signaling Nyquist frequency, Megtron 6 cannot deliver — its 0.004 Df at 10 GHz translates to approximately -0.4 to -0.5 dB/inch at 14 GHz for typical geometries.
• AI/ML accelerator backplanes: GPU-to-GPU and switch-to-switch links in modern AI server clusters run at 112G PAM4 per lane, with 224G on the roadmap. These boards are the primary demand driver for Megtron 7.
• PCIe Gen6 (64 GT/s PAM4): The upcoming generation specifies channel loss budgets that essentially mandate ultra-low-loss materials for anything beyond shortest-reach connections.

Cost Comparison: The Real Numbers

Megtron 7 material costs approximately 2-3x more than Megtron 6 per sheet of prepreg or core. For a full-Megtron-7 build at 16-20 layers, that material premium translates to roughly 60-100% increase in total board cost compared to an all-Megtron-6 build of the same layer count.

However, most designers do not need — and should not pay for — a full Megtron 7 stackup. The mixed-dielectric approach (Megtron 7 on the 4-8 signal layers where high-speed pairs run, standard FR-4 or Megtron 6 elsewhere) brings the total material premium down to 25-40% over all-Megtron-6, while delivering the critical insertion loss performance where it matters.

For reference: a typical 16-layer all-Megtron-6 board might cost $45-65 per piece at 50-piece prototype quantity. The same design in all-Megtron-7 would be $85-130. Mixed-dielectric (Megtron 7 on 4 signal layers, Megtron 6/FR-4 elsewhere): $60-85. These are rough reference points — actual pricing depends on board size, hole count, and surface finish.

Mixed Stackup Strategy in Practice

The mixed-dielectric approach works because signal integrity only depends on the dielectric immediately surrounding the signal trace (the prepreg above and below the signal layer). Power and ground planes do not carry high-frequency signals — they only need to be low-impedance at DC and provide stable reference planes. Standard FR-4 does this perfectly.

A typical mixed stackup for a 20-layer AI accelerator board might look like: layers 1-3 use Megtron 7 prepreg (top signal pairs + adjacent reference planes), layers 4-17 use IT-180A or Megtron 6 (power, ground, low-speed I/O), layers 18-20 use Megtron 7 prepreg (bottom signal pairs). This puts ultra-low-loss material only on the 4-6 prepreg layers that carry 112G differential pairs.

Important: when mixing dielectrics, the impedance calculation must account for different Dk values at different layers. A trace that gives 100 ohms differential on Megtron 7 (Dk 3.3) will not give 100 ohms on Megtron 6 (Dk 3.7) with the same geometry. We run full impedance modeling for mixed stackups and provide trace width tables for each signal layer.

Processing Differences: Megtron 7 Fabrication Notes

While Megtron 6 processes identically to standard FR-4, Megtron 7 has specific fabrication requirements that our process engineers manage:

• Lamination pressure: Reduced by 15-20% compared to standard FR-4 cycle. The T-Glass weave is less conformable than E-Glass, and excessive pressure causes resin squeeze-out at panel edges, leading to resin-starved areas with Dk variation.
• Cure cycle: Extended by 10-15 minutes to ensure full cross-linking of the low-Df resin system. Under-cure leads to higher-than-specified Df and moisture absorption.
• Drill parameters: Standard — no changes needed. Megtron 7 drills cleanly with the same feeds, speeds, and bit life as Megtron 6.
• Desmear: Standard permanganate desmear cycle. T-Glass does not require modified chemistry.
• Solder mask: Standard LPI process. No adhesion concerns with Megtron 7's resin system.

These adjustments are well-documented by Panasonic and are part of our standard process library. You do not need to specify lamination parameters — just tell us the material and we handle the rest.

How Megtron Compares to Competitors

Megtron is not the only low-loss laminate family. Here is how it stacks up against the most commonly specified alternatives:

• Isola I-Speed (Df 0.0035 @ 10GHz): Slightly lower loss than Megtron 6 but higher than Megtron 7. Good alternative when Panasonic material is unavailable. We stock I-Speed and can substitute in mixed stackups.
• Isola I-Tera MT40 (Df 0.0028 @ 10GHz): Competitive with Megtron 7 on loss, uses spread-glass construction. Availability varies by region; Megtron 7 typically has better supply chain in Asia-Pacific.
• Panasonic R-5670 (Megtron 4, Df 0.005): The previous generation — still adequate for 10-25G designs but outclassed by Megtron 6 for anything faster. We have phased it out of new designs in favor of Megtron 6 at similar pricing.
• Nelco N7000-2 HT (Df 0.004 @ 10GHz): Similar performance class to Megtron 6. Limited availability outside North America. We can source it but recommend Megtron 6 for equivalent performance with better supply chain.
• Tachyon 100G (Df 0.002 @ 10GHz): AGC's direct competitor to Megtron 7, also uses T-Glass. Performance is comparable; choice often comes down to which material your channel simulation was validated against.

For most high-speed digital applications in our factory, Megtron 6 is the default recommendation unless the link budget specifically requires Megtron 7. We are material-agnostic — if your channel simulation specifies I-Speed or Tachyon, we build with that material. But for new designs where you are choosing, Megtron 6/7 has the best combination of performance data, supply availability (in Asia), and process maturity in our factory.