Arlon AD600: High Dielectric Constant PTFE Laminate for Miniaturized RF Circuits

Arlon AD600 is a woven fiberglass-reinforced, ceramic-filled, PTFE-based composite laminate with a nominal dielectric constant of 6.15. It was specifically engineered to bring the loss performance and mechanical processability of PTFE-based substrates into the high-Dk segment of the laminate market, where ceramic substrates like alumina historically dominated but carried significant mechanical fragility and fabrication complexity. This guide covers the complete AD600 picture: the verified property set, what the high Dk means in practical design terms, how it compares to alternatives, the fabrication requirements, and the resources you need to work with it.

What Is Arlon AD600? Material Background and Development Context

Arlon Electronic Materials developed AD600 to fill a specific gap in the ceramic-loaded PTFE laminate family: AD600 was designed to provide low dielectric loss, low insertion loss and mechanical robustness to the 6.15 dielectric constant market. Rogers Corporation acquired Arlon in 2015, and Arlon PCB AD600 is now managed under Rogers’ Advanced Electronics Solutions division, which has preserved the original Arlon part number and brand designation.

The “600” in the part number directly reflects the target dielectric constant of 6.0–6.15. The construction follows the ceramic-filled PTFE composite architecture used across the higher-Dk portion of the AD Series: PTFE fluoropolymer matrix provides the low-loss foundation, woven fiberglass reinforcement delivers mechanical rigidity and in-plane dimensional stability, and microdispersed ceramic filler is responsible for elevating the Dk above the ~2.1–2.6 range that unfilled PTFE/glass achieves.

One important status note that every engineer evaluating AD600 should know upfront: AD600 is currently listed as a legacy product by Rogers/Arlon. Rogers explicitly states on the AD600 datasheet page that it encourages users to consider TC600 — a higher-performing, lower-loss, tighter-tolerance, higher-thermal-conductivity successor — or the improved AD600A, which offers lower cost with thicker options above 0.100″ and tighter Dk tolerance. If you’re designing a new product, evaluate TC600 before committing to AD600. If you’re supporting existing designs or maintaining equipment in the field that uses AD600-based boards, the material and its specifications remain fully valid and relevant.

Why High-Dk PTFE Laminates Exist: The Ceramic Replacement Story

The robust AD600 overcomes the brittleness of ceramics (such as alumina or LTCC) through the suspension of micro-dispersed ceramics in a relatively soft PTFE based substrate that is reinforced with woven fiberglass. This gives RF designers the advantages of low loss without sacrificing the mechanical robustness required to fulfill the needs of today’s shock, drop and impact testing requirements.

This framing matters because it tells you exactly where AD600 comes from a design history perspective. Alumina substrates at Dk = 9.6–10.0 were the traditional choice for microwave power amplifier modules, filter banks, and combiner networks where compact geometries and good loss performance were both required. The problems with alumina in volume production are well known to anyone who has handled a batch of them: brittleness during scribing and routing, sensitivity to mechanical shock in portable equipment, difficulty with standard PCB processes like drilling and milling, and limited panel size that constrains batch processing efficiency. AD600 targets that same Dk range — close enough at 6.15 to enable meaningful circuit miniaturization — while behaving like a PCB substrate in the shop rather than like a ceramic tile.

Arlon AD600 Full Electrical Properties: Verified Datasheet Data

The following properties are taken directly from the official Arlon Microwave & RF Materials Guide — the primary authoritative source for the complete AD Series property matrix, including AD600.

Key Electrical Properties

Property	Value	Test Condition	Test Method
Dielectric Constant (Dk)	6.15 (varies with thickness)	10 GHz	IPC TM-650 2.5.5.5
Dissipation Factor (Df)	0.003	10 GHz	IPC TM-650 2.5.5.5
Thermal Coefficient of εr (TCεr)	−241 ppm/°C	—	IPC TM-650 2.5.5.5
Flammability	V-0	—	UL 94
NASA TML (Total Mass Loss)	0.02	%	NASA SP-R-0022A
NASA CVCM	0.01	%	NASA SP-R-0022A

Understanding Dk Variation with Thickness

The asterisk on the Dk = 6.15 value in the official Arlon datasheet table is significant — it indicates that the dielectric constant of AD600 varies with laminate thickness. This is a well-known characteristic of woven fiberglass-reinforced PTFE composites at higher ceramic loading levels: the effective Dk measured by the standard IPC test method shifts as the substrate thickness changes because the ratio of ceramic-loaded PTFE volume to total volume changes slightly with panel construction and compression. The variation is typically a few percent across the standard thickness range, but it’s material to impedance calculations. Always obtain the Dk value for the specific thickness you’re using — don’t assume the nominal 6.15 applies uniformly across all thicknesses when computing transmission line dimensions.

The Df of 0.003 at 10 GHz is the same value as AD350A, AD410, AD430, and the original AD350 — all are 0.003 in the Arlon guide. What this tells you is that across a wide range of ceramic-filled PTFE compositions in the AD Series, Arlon achieved consistent loss tangent performance. At Dk = 6.15, this puts AD600 in a genuinely low-loss position for the high-Dk laminate category. Rogers RO3006, which is a current-generation Rogers ceramic-filled laminate at Dk = 6.15, achieves Df = 0.002 — lower than AD600 — which is part of the case for the TC600 upgrade recommendation.

TCεr: The Temperature Stability Limitation

The thermal coefficient of the dielectric constant of −241 ppm/°C is nearly identical to AR1000 (−233 ppm/°C) and AD450 (−233 ppm/°C) in the Arlon family. This high-magnitude TCεr is characteristic of the ceramic formulations used at higher Dk loading levels. The practical implication is the same as discussed for AD450: resonant structures designed on AD600 — patch antennas, bandpass filters, coupled resonators — will shift in resonant frequency as temperature changes. Across a ±50°C operating range from a design center temperature of 25°C, the Dk shifts by approximately 0.15 at the temperature extremes. For a 10 GHz filter, this corresponds to roughly 240 MHz center frequency drift. For wideband designs this is usually within tolerance; for narrowband channelizing applications it must be factored into the design margin.

Arlon AD600 Thermal and Mechanical Properties

All values below are taken from the verified Arlon Microwave & RF Materials Guide product overview table.

Thermal and Dimensional Properties

Property	Value	Units
CTE — X-axis	11	ppm/°C
CTE — Y-axis	10	ppm/°C
CTE — Z-axis	45	ppm/°C
Thermal Conductivity	0.46	W/m·K
Specific Gravity	2.45	g/cm³
Water Absorption	0.04	%
Flammability	V-0 (UL 94)	—

Mechanical Properties

Property	Value	Units
Peel Strength (copper)	12	lbs/in
NASA TML	0.02	%
NASA CVCM	0.01	%

The thermal conductivity of 0.46 W/m·K is notably good for a PTFE-based laminate — above AD450 (0.38 W/m·K) and equivalent to AD410 and AD430 (both 0.46 W/m·K). The higher ceramic loading needed to achieve Dk = 6.15 contributes to this improvement: ceramic materials generally have higher thermal conductivity than PTFE, so increasing the ceramic fraction elevates both the Dk and the thermal conductivity simultaneously. For power amplifier and combiner applications where the substrate has to conduct heat from device mounting locations toward a heatsink or board edge, 0.46 W/m·K represents a meaningful improvement over the 0.25–0.30 W/m·K typical of plain PTFE/glass laminates.

The Z-axis CTE of 45 ppm/°C is substantially better than unfilled PTFE/glass laminates (150–250 ppm/°C range). Like all the ceramic-filled AD Series materials, the high ceramic content suppresses Z-axis expansion, which directly protects plated through-hole barrel reliability over thermal cycling. For equipment that experiences daily power cycling or installed in environments with significant ambient temperature swings, this lower Z-axis CTE is a meaningful reliability differentiator versus plain PTFE/glass alternatives.

The very low water absorption of 0.04% is directly attributable to the PTFE matrix. For outdoor and humid-environment applications, moisture uptake into the substrate shifts the dielectric constant and degrades electrical performance. AD600’s near-zero water absorption means its electrical properties remain stable whether the circuit is operating in a temperature-controlled laboratory or in an outdoor-exposed enclosure.

The NASA outgassing values — TML = 0.02% and CVCM = 0.01% — confirm AD600’s suitability for space and aerospace applications where material outgassing can contaminate optical surfaces or sensitive detector assemblies. Both values are well within NASA’s standard acceptance limits of TML ≤ 1.0% and CVCM ≤ 0.1%.

Why Dk = 6.15 Matters: The Miniaturization Case

High dielectric constant is not a property to accept reluctantly — it’s a design tool that changes what’s geometrically possible on a given board footprint. The physical dimensions of microstrip transmission lines and resonant structures scale inversely with the square root of the effective dielectric constant. Comparing AD600 (Dk = 6.15) against AD250C (Dk = 2.50):

The ratio of the square roots is √(6.15/2.50) = √2.46 ≈ 1.57. That means resonant structures on AD600 are approximately 36% shorter than the same structure designed for AD250C at the same operating frequency. A quarter-wave transformer section at 5.8 GHz on AD250C would be approximately 13 mm long. The same section on AD600 is approximately 8.3 mm long — a reduction that, multiplied across a multi-section power divider with dozens of branch elements, represents a major reduction in total board area.

For low-impedance transmission lines — used in power amplifiers and high-power combiner networks — the higher Dk narrows the traces required for a given impedance. A 25Ω transmission line for a power combining network is wider and easier to fabricate on AD600 than on a lower-Dk substrate at the same normalized line width, simply because the higher Dk allows a narrower physical trace to realize the same electrical width relative to the wavelength.

This geometry advantage is exactly why higher dielectric constant permits various degrees of circuit miniaturization, especially for microwave power dividers, power combiners, amplifiers, filters, couplers and other components that use low impedance lines.

Available Configurations: Thickness and Copper Options

AD600 is available in a practical range of configurations for standard microwave circuit designs. Note that the Dk varies with thickness — always verify the actual Dk for your chosen thickness with the Rogers/Arlon technical team or from the thickness-specific datasheet.

Standard Dielectric Thicknesses

Thickness (inches)	Thickness (mm)	Typical Use Case
0.010″	0.254	Ultra-compact miniaturized circuits
0.020″	0.508	Compact filter and coupler designs
0.025″	0.635	Standard power divider/combiner boards
0.030″	0.762	Amplifier substrates, filter banks
0.060″	1.524	High-power combiner modules

Large panel formats (up to 36″ × 48″) are available on AD600, which enables multi-circuit panel layouts that improve the economics of batch fabrication for high-volume commercial programs.

Copper Foil Options

Foil Type	Weight	Notes
Electrodeposited (ED)	½ oz, 1 oz, 2 oz	Standard supply configuration
Rolled copper	On request	Reduced roughness for better high-frequency conductor loss
Heavy metal ground plane	Al, Cu, Brass	Integral heatsink for high-power designs

The heavy metal ground plane option is particularly relevant for AD600 applications in power amplifier modules. Bonding the laminate directly to an aluminium or copper base plate creates an integral heatsink structure, eliminating the thermal interface resistance of a separately attached heatsink and providing mechanical rigidity for large-format power module assemblies.

Arlon AD600 vs. Competing RF Laminates: Full Comparison

Understanding where AD600 sits relative to both its direct competitors and its successors clarifies the decision-making process for new designs.

Material	Dk (10 GHz)	Df (10 GHz)	TCεr (ppm/°C)	Z-CTE (ppm/°C)	TC (W/m·K)	Status
Arlon AD600	6.15 (thickness varies)	0.003	−241	45	0.46	Legacy
Arlon TC600	6.15	0.002	—	—	Higher than AD600	Current preferred
Arlon AD600A	6.15	—	—	—	—	Current / improved
Rogers RO3006	6.15	0.002	~−400	~25	0.79	Current production
Arlon AD1000	10.20	0.0023	−380	20	0.81	Current production
Arlon AR1000	10.00	0.003	−233	37	0.645	Production
Alumina (Al₂O₃)	~9.6–10.0	0.0001–0.0003	~+13.7	~6	35	Traditional ceramic

AD600 vs. TC600: TC600 is the current recommended alternative for new designs requiring Dk ≈ 6.15. According to Rogers’ own datasheet notes, TC600 offers better loss (Df = 0.002 vs. 0.003), tighter Dk tolerance, and higher thermal conductivity than AD600. For any new product design, TC600 should be evaluated before committing to AD600. The only scenario where AD600 remains the right choice for new work is when a legacy program has existing qualified stackups and material certifications that would require requalification to switch.

AD600 vs. Rogers RO3006: Both target Dk = 6.15 with different material systems. RO3006 uses a ceramic-filled PTFE formulation from Rogers and achieves Df = 0.002 — one-third lower than AD600 — along with significantly higher thermal conductivity (0.79 W/m·K) and lower Z-axis CTE (~25 ppm/°C). These are meaningful advantages for high-power and temperature-sensitive applications. For existing designs on AD600, the dimensional compatibility with RO3006 (same Dk target) makes cross-referencing possible with appropriate electrical verification.

AD600 vs. Alumina: This is the fundamental competitive comparison that explains why AD600 exists. Alumina at Dk ≈ 9.6–10.0 offers far lower Df (0.0001–0.0003) and far better dimensional stability over temperature, but at the cost of extreme brittleness, limited panel size, incompatibility with standard PCB drilling and routing, and significant per-unit cost for the machining and scribing required to produce circuit substrates. AD600 accepts approximately 10× worse loss tangent compared to alumina while delivering full PCB processability, mechanical robustness under shock and vibration, large panel formats, and significantly lower fabrication cost. For applications where alumina’s Df advantage is not the limiting specification — and many commercial microwave systems fall into this category — AD600 makes the economics work.

AD600 vs. AD1000: Both are high-Dk members of the AD Series, but at very different Dk levels. AD1000 at Dk = 10.20 provides even more aggressive miniaturization but with a higher Df of 0.0023 (actually slightly lower loss) and requires the greatest geometric resizing of circuit elements. AD600 at 6.15 provides a more moderate miniaturization step that is less disruptive to existing circuit geometries, and its loss tangent at 0.003 is broadly comparable to AD1000. The choice between them depends on how aggressive the miniaturization requirement is and how much redesign effort the team is willing to invest.

AD600 PCB Design Considerations for RF Engineers

Impedance Planning and Trace Geometry at Dk 6.15

With Dk = 6.15 — and remembering the caveat that this value varies with substrate thickness — 50Ω microstrip trace widths are significantly narrower than on lower-Dk substrates. On a 0.030″ substrate, a 50Ω microstrip line runs approximately 0.40–0.45 mm wide with 1 oz copper. This narrow trace width creates two design considerations: first, the minimum manufacturable trace width of your PCB shop becomes relevant — verify that your shop can reliably hold impedance at 0.40 mm widths; second, conductor loss per unit length increases as traces become narrower because the current density per unit cross-sectional area increases. For transmission lines carrying significant RF power, conductor loss on these narrow geometries needs to be budgeted explicitly.

Always perform impedance calculations with a field solver using the actual Dk for your specific dielectric thickness, not the nominal 6.15. The Dk variation with thickness in AD600 is a documented characteristic — using a thickness-inaccurate Dk in your calculation introduces a systematic impedance offset that will appear across the entire board.

Designing Low-Impedance Lines on AD600

One of the clearest design advantages of high-Dk substrates is the physical width of low-impedance transmission lines. On AD250C (Dk = 2.50), a 25Ω line on a 0.030″ substrate would be approximately 2.8–3.0 mm wide. On AD600 (Dk = 6.15), the same 25Ω line narrows to roughly 1.5–1.7 mm. In a power combiner network with multiple low-impedance lines running in parallel, this width reduction has a direct impact on board area and can be the enabler that makes a multi-way combiner fit in a given mechanical envelope.

Power Divider and Combiner Network Design

Wilkinson power dividers and corporate combiner networks are classic applications for AD600. On high-Dk substrates, the quarter-wave section length that defines the Wilkinson geometry is shorter, and the isolation resistor footprint stays the same absolute size, which means the isolation component takes up a larger relative fraction of the total divider real estate. This is a design detail worth accounting for in the layout — the isolation resistor pad orientation and its connection to the junction point need to be handled carefully to avoid unintended coupling at the operating frequency.

Temperature-Sensitive Resonant Structure Design

The TCεr of −241 ppm/°C requires the same design management approach as AD450. For wideband combiner and divider networks with fractional bandwidths above 10%, the temperature-induced Dk shift is usually within the circuit’s operating bandwidth. For narrowband filters, the expected center frequency shift across the full operating temperature range must be calculated and either accommodated within the filter bandwidth or compensated by a suitable design approach. When temperature stability of resonant structures is a hard requirement, TC600 or Rogers RO3006 should be evaluated as alternatives.

Managing the Ceramic Replacement Transition

For designs transitioning from alumina substrates to AD600, the Dk difference between the materials (9.6–10.0 for alumina vs. 6.15 for AD600) means circuit dimensions cannot be directly transferred — all resonant lengths, matching sections, and transmission line widths need to be recalculated for the new Dk. This is a one-time design cost, and the payoff is the fabrication, reliability, and cost advantages that PTFE-based substrates offer over alumina in volume production.

PTFE Fabrication Requirements for AD600

AD600 is compatible with standard PTFE-based PCB substrate processing. This means the three process steps that separate PTFE fabrication from FR-4 fabrication apply fully.

Drilling

PTFE material’s soft, gummy cutting behaviour requires PTFE-specific drill parameters: lower spindle speeds, sharper carbide tooling, and controlled chip load per revolution. Standard FR-4 parameters will produce smeared hole walls and bell-mouthed holes that compromise plating adhesion. AD600 and AD1000 have shared fabrication guidelines published by Arlon — AD600’s process is not unique within the high-Dk PTFE family.

Through-Hole Surface Activation

PTFE’s fluoropolymer surface will not accept copper electroplating without surface activation. Sodium naphthalene chemical etch or CF4/O2 plasma etch are both accepted methods. Both processes break up the fluorine-carbon bonds at the drilled hole wall surface, creating adhesion sites for the copper seed layer. This step is non-negotiable — boards fabricated without it will have inadequate PTH adhesion and will fail in thermal cycling tests or in field service. There is no visible indication in incoming inspection of whether this step was performed correctly. This is why PTFE-capable shop selection and documented process verification are critical for AD600 fabrication.

Multilayer Bonding

PTFE-compatible bonding films are required for multilayer AD600 constructions. Standard FR-4 prepreg is thermally and chemically incompatible with PTFE laminate. FEP fluoropolymer film and similar PTFE-compatible adhesive films are the correct bonding layer choice.

AD600 and AD1000 Shared Fabrication Guidelines

Rogers/Arlon publishes a combined AD1000 and AD600 Fabrication Guidelines document that covers both materials, recognising their processing similarities as high-Dk ceramic-filled PTFE composites. This document is the primary technical reference for fabricators and should be obtained and reviewed before the first AD600 production run.

Typical Applications of Arlon AD600

Higher dielectric constant permits various degrees of circuit miniaturization, especially for microwave power dividers, power combiners, amplifiers, filters, couplers and other components that use low impedance lines. The specific application categories where AD600 has historically been used include:

Microwave Power Dividers and Combiner Boards: Corporate feed networks, Wilkinson dividers, and multi-way power combiners in base station transmit chains and satellite ground station equipment. The compact geometry and good loss performance at Dk = 6.15 reduce board area requirements for multi-section combining structures.

Power Amplifier Substrates: MMIC and discrete transistor power amplifier modules where compact input and output matching networks, low-impedance bias feeds, and thermal management are all design priorities. The integral metal ground plane option simplifies heatsink integration.

Filters and Couplers: Bandpass filters, bandstop filters, branch-line couplers, and directional couplers where the higher Dk reduces physical component size and enables higher element density in a given board area.

Smaller Footprint Antenna Applications: Patch antennas and antenna arrays where board space constraints require smaller radiating element dimensions. The Dk = 6.15 reduces patch dimensions relative to lower-Dk alternatives, enabling more compact or higher-element-density antenna designs.

Digital Audio Broadcasting (DAB) Antennas: Satellite radio receive antennas and DAB infrastructure antennas where small physical size combined with acceptable loss performance is the design target.

GPS and Handheld RFID Reader Antennas: Compact GPS receive patch antennas and portable RFID reader antennas where PCB real estate is tightly constrained and the antenna element must be miniaturised to fit.

Useful Technical Resources for Arlon AD600

Resource	Description	Link
Rogers AD600 Product Page	Official Rogers page with downloadable AD600 datasheet and legacy status note	rogerscorp.com/ad600
Arlon Microwave & RF Materials Guide (Full PDF)	Official Arlon guide with verified AD600 property row in full AD Series table	integratedtest.com/ArlonMaterials.pdf
AD1000 and AD600 Fabrication Guidelines	Joint PTFE fabrication guide for AD600 and AD1000 from Arlon	rfglobalnet.com — search AD600 fabrication
Rogers TC600 Product Page	Rogers-recommended current replacement for AD600 new designs	rogerscorp.com/tc600
Rogers RO3006 Datasheet	Alternative current-production Dk 6.15 laminate with lower Df	rogerscorp.com/ro3006
MatWeb AD600 Entry	Material properties in engineering units with source attribution	matweb.com — Arlon AD600
Rogers Laminate Properties Tool	Interactive comparison tool for all Rogers and Arlon materials including AD600	Rogers Laminate Tool
Rogers MWI-2010 Impedance Calculator	Microstrip and stripline impedance tool for Rogers/Arlon substrates	Rogers Calculator
IPC TM-650 Test Methods Library	Full library of test methods referenced in the AD600 datasheet	ipc.org
Oneseine AD600 Datasheet Download Page	Legacy datasheet download with application description	oneseine.com/AD600

Arlon AD600 Frequently Asked Questions

Q1: Is Arlon AD600 still available, and should I use it for a new design?

AD600 is listed as a legacy product by Rogers/Arlon. The material remains available for existing programs and legacy hardware maintenance, but for new design starts Rogers explicitly recommends considering TC600 (lower Df, tighter Dk tolerance, higher thermal conductivity) or AD600A (lower cost option with thicker configurations and tighter Dk tolerance) instead. If you’re designing from scratch and your target Dk is approximately 6.15, evaluate TC600 first. If you’re repairing or sustaining equipment with existing AD600 boards, the material remains fully valid and the datasheet specifications are unchanged.

Q2: Why does the AD600 dielectric constant vary with laminate thickness, and how should I handle this in design?

The Dk variation with thickness in AD600 is inherent to its woven fiberglass-reinforced PTFE composite construction at high ceramic loading. As the substrate thickness changes, the ratio of ceramic-loaded PTFE to total laminate volume shifts slightly due to the fiberglass weave geometry and compression characteristics, producing a measurable change in effective Dk. In practice this means the 6.15 nominal Dk is a mid-range guideline, not a fixed specification across all thicknesses. For impedance-critical designs, request the Dk value specific to your chosen dielectric thickness from Rogers’ applications engineering team, then use that verified value in your electromagnetic field solver for transmission line calculations. Using the nominal 6.15 for all thicknesses will produce systematic impedance errors.

Q3: How does AD600 compare to alumina for microwave circuit substrates?

Alumina at Dk ≈ 9.6–10.0 offers dramatically lower Df (0.0001–0.0003 vs. AD600’s 0.003 — roughly 10–30 times lower) but is brittle, limited to small substrate panels, incompatible with standard PCB drilling and routing, and significantly more expensive to process in volume production. AD600 sacrifices the loss advantage of alumina in exchange for full PCB processability, mechanical robustness under shock and vibration, standard SMT assembly compatibility, large panel formats, and lower fabrication cost. For applications where the system noise floor or efficiency budget can tolerate AD600’s loss tangent, the manufacturing and reliability benefits of the PTFE-based approach are compelling. Where the Df difference between alumina and AD600 is the limiting constraint, the AD600 alternative doesn’t apply.

Q4: What PCB fabrication process does AD600 require? Can any shop run it?

AD600 requires PTFE-specific fabrication processes, not standard FR-4 processes. Three steps are non-negotiable: PTFE-tuned drilling parameters to avoid hole wall smearing; sodium naphthalene or CF4/O2 plasma surface activation of through-holes before copper plating to achieve adequate adhesion; and PTFE-compatible bonding films for multilayer constructions. Shops that only process FR-4 cannot fabricate AD600 reliably — the resulting boards will appear acceptable in incoming inspection but will fail through PTH delamination during thermal cycling in field service. Always verify that your intended fabricator has current, documented PTFE process capability and ideally has active AD600 or AD1000 production experience.

Q5: What is the difference between AD600, AD600A, and TC600, and which should I choose?

These are three versions of the Dk ≈ 6.15 PTFE-based product family from Arlon/Rogers at different stages of development. AD600 is the original formulation — now listed as legacy. AD600A is an improved variant specifically offering lower cost and tighter Dk tolerance in thicker configurations (above approximately 0.100″), suitable for programs where cost sensitivity is high and thick substrate configurations are needed. TC600 is the current premium recommendation: lower Df (0.002 vs. 0.003), tighter Dk tolerance than the original AD600, and higher thermal conductivity — it is a genuine performance upgrade in all three key parameters. For new design starts targeting high performance, TC600 is the recommended path. For cost-sensitive programs requiring thick substrates, AD600A is worth evaluating. For legacy maintenance, AD600 specifications remain valid.