Complete engineer’s guide to Arlon IsoClad 933 โ why its non-woven structure delivers true X-Y-Z isotropy, full datasheet specs, conformal antenna applications, comparison with DiClad 870 and CuClad 233, and PTFE fabrication requirements.
Most RF PCB laminates are flat. They sit in a press, get copper etched onto them, and live their useful lives in rigid planar assemblies. That covers the vast majority of microwave circuit applications, and the DiClad and CuClad product families serve those designs well. But a meaningful subset of real-world RF designs โ conformal antennas that wrap around aircraft fuselages, wrap-around radar apertures, curved satellite terminal elements, missile seeker radomes โ cannot be built on rigid substrates. You need a laminate that can be shaped.
Arlon IsoClad 933 fills exactly that role. It is a non-woven fiberglass/PTFE composite laminate that brings together Dk 2.33, a Df of 0.0016 at 10 GHz, and a non-woven random fiber architecture that delivers both conformability and true three-dimensional isotropy. For RF engineers who have never worked outside the flat-laminate world, IsoClad 933 opens a design dimension that woven-glass PTFE substrates simply cannot access.
This guide covers the full technical story on Arlon IsoClad 933 โ material construction, complete specifications, what the non-woven isotropic architecture actually means in practice, where it fits versus DiClad 870 and CuClad 233 at the same Dk, and how to fabricate with it reliably.
What Is Arlon IsoClad 933?
Arlon IsoClad 933 is a non-woven fiberglass/PTFE composite laminate originally developed by Arlon Materials for Electronics and now produced under the Rogers Corporation brand following their acquisition of Arlon LLC. It belongs to the IsoClad product family, which is distinctly different in construction from both the DiClad (parallel-plied woven glass) and CuClad (cross-plied woven glass) families.
The defining characteristic of the entire IsoClad family is the non-woven reinforcement structure. Rather than PTFE-coated woven fiberglass cloth โ where glass fibers run in defined warp and fill directions โ IsoClad materials use longer random fibers in a non-woven, randomly oriented mat structure embedded in a PTFE matrix. Two important consequences follow directly from this architecture.
First, because the fibers have no preferred orientation, there is no directional anisotropy in the laminate plane or through the thickness. The electrical and mechanical properties are genuinely isotropic in X, Y, and Z โ not just in the XY plane as claimed by cross-plied CuClad products, but in all three axes. This full three-dimensional isotropy is unique to the IsoClad family and is not achievable with any woven fiberglass construction.
Second, the non-woven structure is inherently less rigid than woven glass reinforcement. This is what enables the conformability that makes IsoClad 933 attractive for curved and wrap-around antenna applications. The laminate can be formed to a radius that a woven-glass board cannot match without cracking or delaminating.
Within the two-product IsoClad family, IsoClad 933 is the higher-reinforcement variant. Its higher fiberglass-to-PTFE ratio compared to IsoClad 917 delivers better dimensional stability, higher mechanical strength, and a Dk of 2.33 โ traded against the lower Dk 2.17 of IsoClad 917. Engineers building conformal antennas who can live with Dk 2.33 will generally prefer IsoClad 933 for its better dimensional behavior through fabrication.
For the full context of how IsoClad 933 fits in the broader Arlon portfolio, Arlon PCB manufacturers with PTFE experience can advise on both the material and fabrication process requirements.
Arlon IsoClad 933 Full Specification Table
The table below presents the typical electrical, mechanical, and environmental properties for Arlon IsoClad 933. These are typical values โ always verify against the current Rogers/Arlon datasheet for your specific application and thickness.
| Property | Value | Test Method |
| Dielectric Constant (Dk) @ 10 GHz | 2.33 | IPC TM-650 2.5.5.5 |
| Dissipation Factor (Df) @ 10 GHz | 0.0016 | IPC TM-650 2.5.5.5 |
| Thermal Coefficient of Dk (TCDk) | -132 ppm/ยฐC | IPC TM-650 2.5.5.7 |
| Volume Resistivity | > 10^7 Mฮฉยทcm | IPC TM-650 2.5.17 |
| Surface Resistivity | > 10^6 Mฮฉ | IPC TM-650 2.5.17 |
| Dielectric Breakdown Voltage | > 45 kV | IPC TM-650 2.5.6 |
| Moisture Absorption | 0.05% | IPC TM-650 2.6.2 |
| NASA Outgassing (TML / CVCM) | Meets requirements | NASA SP-R-0022A |
| UL Flammability Rating | UL94-V0 | UL94 |
| Reinforcement Type | Non-woven random fiberglass | โ |
| Isotropy | True X-Y-Z isotropic | โ |
| Ply Orientation | Random (non-directional) | โ |
| Standard Panel Sizes | 36″ร48″, 36″ร72″ | โ |
The Df of 0.0016 at 10 GHz is worth putting in context. It is slightly higher than DiClad 870’s 0.0013, which reflects the different reinforcement architecture and higher fiberglass content. However, 0.0016 is still well below any thermoset high-frequency laminate and is competitive with the best PTFE materials at Dk 2.33. For the applications where IsoClad 933’s conformability and isotropy are required, this Df represents entirely adequate performance.
Available Thickness Options for Arlon IsoClad 933
IsoClad 933 is available from very thin substrates through moderate thicknesses. The non-woven construction means even the thinner gauges retain useful flexibility.
| Thickness (inches) | Thickness (mm) | Notes |
| 0.005″ | 0.127 | Ultra-thin; maximum flexibility for tight radius applications |
| 0.010″ | 0.254 | Thin; strong conformability |
| 0.015″ | 0.381 | Standard thin option; ยฑ0.0030″ tolerance |
| 0.020″ | 0.508 | Balanced flexibility and circuit robustness |
| 0.031″ | 0.787 | Standard thickness; ยฑ0.0030″ tolerance |
| 0.045″ | 1.143 | Moderate thickness |
| 0.060″ | 1.524 | Thickest standard option; reduced flexibility |
Copper cladding is available in ยฝ oz, 1 oz, and 2 oz electrodeposited copper. As with other IsoClad laminates, the product can also be ordered bonded to a metal backing plate (aluminum, brass, or copper) for applications requiring both microwave substrate performance and a structural support layer. When ordering, specify the Dk, thickness, cladding weight, panel size, and any special requirements.
The Non-Woven Architecture: Why It Matters for RF Design
This is the section most articles on IsoClad 933 either miss or underexplain. Understanding what non-woven really means โ and why it produces isotropy โ is the difference between selecting this material for the right reasons and being surprised by its behavior.
In a woven fiberglass laminate, glass fibers are interlaced in a defined textile pattern. The warp fibers run in one direction, the fill fibers run perpendicular. Even in a cross-plied construction like CuClad, where alternating layers are rotated 90ยฐ, the isotropy achieved is a spatial average of two perpendicular directions โ true isotropy in the XY plane, but still a layered construction with fiber-direction-dependent properties.
In IsoClad 933, the fiberglass reinforcement is non-woven. Longer fibers are distributed randomly in all orientations within the PTFE matrix using Arlon’s proprietary process. There is no warp direction and no fill direction. When you measure Dk along the X-axis, the Y-axis, or the Z-axis of an IsoClad 933 laminate, you get the same value. This three-dimensional isotropy is not a marketing approximation โ it is a direct physical consequence of the random fiber architecture.
For RF circuit design, this has three practical implications. First, circuits laid out in different orientations on the board perform identically โ a microstrip running east-west has the same characteristic impedance as one running north-south. Second, the dielectric constant is consistent through the substrate thickness, which improves the accuracy of EM simulations and reduces impedance uncertainty in multilayer builds. Third, for conformal antenna elements where the circuit is bent around a structure, the dielectric properties do not change as a function of the bend axis โ you are not creating a mechanically anisotropic laminate when you form IsoClad 933 around a radius.
Additionally, Arlon’s proprietary process for IsoClad materials produces better dielectric constant uniformity across the panel than competitive non-woven fiberglass/PTFE laminates of similar dielectric constants. This panel-level Dk uniformity directly supports impedance control yields in production.
IsoClad 933 vs. DiClad 870 vs. CuClad 233: Choosing the Right Dk 2.33 Material
Three Arlon/Rogers materials share a nominal Dk of 2.33: IsoClad 933, DiClad 870, and CuClad 233. Engineers frequently ask how to choose among them. The answer is primarily architectural rather than electrical.
| Parameter | IsoClad 933 | DiClad 870 | CuClad 233 |
| Dk @ 10 GHz | 2.33 | 2.33 | 2.33 |
| Df @ 10 GHz | 0.0016 | 0.0013 | 0.0013 |
| Reinforcement Type | Non-woven random | Woven parallel | Woven cross-plied |
| 3D Isotropy (X-Y-Z) | Yes | No (parallel-plied) | XY only |
| Conformability / Flexibility | Yes โ unique property | No | No |
| Moisture Absorption | 0.05% | 0.02% | < 0.10% |
| TCDk (ppm/ยฐC) | -132 | -161 | ~-130 |
| Best Application Fit | Conformal antennas, curved assemblies, 3D isotropic circuits | Flat-board, low-loss radar & base station | Flat-board, XY-isotropic phased arrays |
The critical insight from this comparison is that if your design is flat and rigid, you should not be choosing IsoClad 933. DiClad 870 will give you better Df (0.0013 vs. 0.0016) and lower moisture absorption (0.02% vs. 0.05%) with no disadvantage for your planar layout. If X-Y isotropy on a flat board is specifically required โ phased array, balanced circuit, or precision coupler โ then CuClad 233’s cross-plied construction is the right answer.
IsoClad 933 is the right material when conformability is required, when true X-Y-Z three-dimensional isotropy matters (versus just XY), or when the specific non-woven architecture’s Dk uniformity across the panel provides a process advantage for your impedance control yield.
Typical Applications for Arlon IsoClad 933
The application set for IsoClad 933 is shaped directly by the two properties that make it unique: three-dimensional isotropy and conformability from its non-woven construction.
| Application Category | Specific Use Cases |
| Conformal & Wrap-Around Antennas | Aircraft fuselage antennas, missile body conformal patches, vehicle-mounted wrap antennas |
| Military RF Systems | Radar feed networks requiring full 3D isotropy, missile guidance RF front ends |
| Phased Array Systems | Commercial and military phased array networks where 3D isotropy improves array element uniformity |
| Base Station Antennas | Low-loss base station antenna circuits in flat or curved form factors |
| Satellite & Aerospace | Uplink/downlink circuits meeting NASA outgassing requirements |
| Passive Microwave Components | Filters, couplers, LNAs for high-frequency systems |
| Digital Radio Systems | Antenna circuits for DAB and satellite radio |
| Curved Assembly Electronics | Any RF sub-assembly that must conform to a non-planar housing or structure |
The conformal antenna application deserves more explanation because it represents a design scenario that most engineers haven’t encountered in standard PCB work. A conformal antenna integrates the antenna structure flush with the surface of the platform it’s mounted on โ an aircraft skin, a missile body, a ship’s hull. The radiation pattern, impedance, and electrical phase of the antenna elements are all determined by the substrate’s dielectric properties. When that substrate is IsoClad 933, the design can proceed knowing that bending the laminate to the surface radius does not change the Dk or Df values โ the isotropic non-woven structure is mechanically invariant to the forming operation in a way that a woven-glass laminate is not.
Arlon IsoClad 933 vs. IsoClad 917: Within-Family Comparison
Engineers who need to choose between the two IsoClad variants face a straightforward trade-off that mirrors the choice seen across the DiClad and CuClad families.
| Parameter | IsoClad 917 | IsoClad 933 |
| Nominal Dk | 2.17 โ 2.20 | 2.33 |
| Fiberglass/PTFE Ratio | Lower glass | Higher glass |
| Mechanical Strength | Lower | Higher |
| Dimensional Stability | Lower | Better |
| Available Thicknesses | 0.005″ โ 0.062″ | 0.005″ โ 0.060″ |
| Best Fit | Lowest Dk & loss in non-woven PTFE | Better stability + 3D isotropy |
IsoClad 917 uses a low fiberglass-to-PTFE ratio to achieve the lowest dielectric constant and dissipation factor available in non-woven PTFE laminates โ making it the right choice when Dk 2.17 is specifically required and mechanical strength can be lower. IsoClad 933 uses a higher fiberglass-to-PTFE ratio for improved dimensional stability and mechanical strength, at the cost of raising the Dk to 2.33. In most conformal antenna production environments, the better mechanical robustness of IsoClad 933 through forming and assembly operations makes it the preferred variant.
Design Considerations for Arlon IsoClad 933
Trace Width, Impedance, and the Dk 2.33 Design Point
With Dk 2.33, IsoClad 933 produces wider traces for a given impedance than materials with Dk 3.0 or above. For a 50-ohm microstrip on 0.031″ IsoClad 933, the trace width will be significantly wider than on a thermoset substrate at the same thickness. This width increase is generally beneficial โ wider traces have lower conductor resistance per unit length, which reduces resistive loss. For conformal antenna feed lines where trace routing may follow curved paths, wider traces are also more tolerant of minor angular deviations from the design centerline.
The isotropic Dk of IsoClad 933 simplifies one aspect of conformal antenna simulation. Because the Dk does not change with bend direction, the electrical model of a transmission line running across a formed substrate surface uses the same Dk value throughout โ you do not need to apply directional Dk corrections to segments of trace that run in different orientations on the curved surface.
Dk Stability Across Frequency
IsoClad 933 exhibits the inherently stable Dk-versus-frequency behavior characteristic of all PTFE-based materials. The dielectric constant remains consistent from low MHz through the microwave and millimeter-wave ranges. For wideband conformal antenna designs โ particularly blade antennas or wideband patch arrays โ this stability eliminates frequency-dependent impedance drift and simplifies the simulation-to-measurement correlation process.
TCDk and Temperature Performance
The TCDk of -132 ppm/ยฐC means IsoClad 933’s Dk decreases slightly as temperature rises. For conformal antennas integrated into aircraft or missile skins, operational temperature swings of 100ยฐC or more are routine. At -132 ppm/ยฐC, a 100ยฐC swing shifts the Dk by about 0.031 โ from 2.33 to approximately 2.30. For broadband antenna designs this is generally negligible. For narrowband resonant elements (patch antennas for GPS, for instance), the resonant frequency shift should be estimated in design simulation and verified during thermal qualification testing.
Handling the Conformability โ Minimum Bend Radius
IsoClad 933 can be formed to a radius, but there is a practical minimum. Thicker substrates require a larger minimum bend radius to avoid copper foil cracking or substrate delamination. As a general rule, consult your fabricator’s experience with the specific thickness you are using and perform qualification bend tests before committing to a minimum radius in the structural design. The thinnest available substrates (0.005″โ0.010″) are most amenable to tight-radius applications.
Fabrication Guidelines for Arlon IsoClad 933
Storage and Panel Handling
Store IsoClad 933 panels in a clean, controlled-humidity environment. Although moisture absorption at 0.05% is low, surface contamination degrades plating adhesion. Handle with clean gloves and inspect panels for any surface damage before processing. The non-woven structure is somewhat more susceptible to surface fiber damage from rough handling than woven-glass laminates.
Drilling
Use sharp carbide drill bits at low stack heights โ one to two panels maximum. The non-woven fiber structure drills somewhat differently from woven glass, with a tendency for fiber pullout if tooling is dull. Use appropriate entry and backup materials to support clean hole entry and exit. Inspect hole walls for fiber pullout and smear before proceeding to surface activation.
PTFE Hole Wall Activation
As with all PTFE-based laminates, IsoClad 933 requires hole wall activation before electroless copper deposition. Sodium naphthalate chemical etch or plasma etch processes are the standard approaches. This step is non-negotiable โ PTFE will not bond to electroless copper without activation, and skipping or under-performing this step produces plated through-holes with poor adhesion that will fail under thermal cycling. Confirm with your fabricator specifically how they perform and verify PTFE activation before awarding production work.
Forming and Conformal Assembly
When IsoClad 933 is used for conformal applications, the forming operation typically happens before or after copper etching, depending on the circuit topology. Pre-etching forming allows the circuit to be chemically processed flat and then formed to shape. Post-etching forming is used when precise circuit geometry is needed at the formed radius. The choice depends on how tightly the final formed geometry affects the circuit’s electrical dimensions. In either case, forming should be done slowly and at controlled temperature to avoid cracking the copper traces at bend locations. Verify minimum copper bend radius for your specific copper weight and trace geometry before forming.
Assembly and Soldering
IsoClad 933 is compatible with standard SMT reflow processes. The 0.05% moisture absorption means minimal outgassing risk during reflow. For conformal assemblies, component placement on a curved substrate may require custom fixtures to hold component orientation during reflow. Ensure your oven conveyor and reflow fixtures are compatible with the three-dimensional shape of the assembly.
Common Pitfalls with Arlon IsoClad 933
Selecting IsoClad 933 for a flat, rigid design. If your board is flat and you just want low loss at Dk 2.33, DiClad 870 gives you Df 0.0013 (versus 0.0016) and lower moisture absorption. Use IsoClad 933 when you specifically need conformability or full 3D isotropy.
Underestimating the minimum bend radius. IsoClad 933 is flexible compared to woven-glass laminates, but it is not infinitely bendable. Exceeding the minimum bend radius for your specific thickness and copper weight will crack traces and cause delamination. Qualify the minimum radius with test coupons before production.
Not validating PTFE activation on non-woven structure. PTFE activation is essential, and the non-woven fiber structure can behave differently from woven glass during the plasma or chemical etch activation step. Confirm with microscopy or pull-test that activation is achieving adequate hole wall coverage before committing to production plating.
Assuming Dk uniformity without verifying lot data. While Arlon’s proprietary process delivers superior Dk uniformity versus competitive non-woven PTFE laminates, for precision narrowband circuits, request actual panel Dk data for your specific lot before fabricating tuning-sensitive circuits on that material.
Useful Resources for Arlon IsoClad 933 Engineers
| Resource | Description | Link |
| Rogers IsoClad 933 Product Page | Official Rogers product page with data sampling | rogerscorp.com |
| Arlon Microwave & RF Materials Guide | Full IsoClad thickness chart and family comparison | integratedtest.com PDF |
| IsoClad Datasheet (Midwest PCB) | IsoClad 917 and 933 datasheet with full property tables | midwestpcb.com PDF |
| MatWeb IsoClad 933 Entry | Third-party property database with unit conversions | MatWeb |
| RF Global Net IsoClad Page | Product overview with download links | rfglobalnet.com |
| Hughes Circuits IsoClad Page | Fabricator perspective on IsoClad materials | hughescircuits.com |
| Rogers Laminate Properties Tool | Interactive laminate comparator across Rogers product families | rogerscorp.com tools |
| IPC TM-650 Test Methods | Standard test methods referenced in the IsoClad 933 datasheet | ipc.org |
| RayPCB Arlon PCB Resource | Practical resource for Arlon PCB manufacturing | RayPCB Arlon PCB |
5 Frequently Asked Questions About Arlon IsoClad 933
1. What makes Arlon IsoClad 933 isotropic when other PTFE laminates are not?
The isotropy of IsoClad 933 comes entirely from the non-woven random fiber structure. In woven-glass PTFE laminates like DiClad or CuClad, the fiberglass runs in defined directions (warp, fill, or cross-plied alternating). These defined fiber directions create measurable anisotropy in both electrical and mechanical properties. IsoClad 933 uses longer random fibers distributed without a preferred orientation, which produces the same dielectric constant and mechanical properties in all three axes. This is true X-Y-Z isotropy โ not just XY-plane isotropy.
2. Can Arlon IsoClad 933 be bent or formed without damaging the circuit?
Yes, within limits. IsoClad 933’s non-woven structure is specifically less rigid than woven-glass laminates, enabling conformal and wrap-around antenna applications. Thinner substrates (0.005″โ0.020″) tolerate tighter bend radii; thicker substrates require a larger minimum radius to avoid cracking copper traces or causing delamination at the copper-PTFE interface. Always characterize the minimum bend radius for your specific substrate thickness and copper weight using test coupons before committing to a product design that depends on forming.
3. How does Arlon IsoClad 933 compare to Rogers RT/duroid 5870 at the same Dk range?
Rogers RT/duroid 5870 is also a PTFE-based substrate targeting the Dk ~2.33 range, but it uses a non-woven microfiber (not random chopped fiber) reinforcement rather than the longer random fibers in IsoClad 933. RT/duroid 5870 achieves a slightly lower Df (~0.0012 at 10 GHz) than IsoClad 933’s 0.0016. However, RT/duroid 5870 is designed as a flat, rigid substrate and does not offer the conformability or the specific three-dimensional isotropy that Arlon’s longer-random-fiber IsoClad 933 process produces. For flat-board, lowest-loss applications at Dk 2.33, RT/duroid 5870 or DiClad 870 may be preferable. For conformal antenna and true 3D-isotropic applications, IsoClad 933 is the appropriate material.
4. Does Arlon IsoClad 933 meet aerospace and satellite outgassing requirements?
IsoClad 933 meets NASA outgassing requirements, qualifying it for use in space-adjacent and aerospace applications where outgassing poses a risk to optical surfaces, sensors, or adjacent materials. The 0.05% moisture absorption โ while slightly higher than DiClad 870’s 0.02% โ remains very low by any reasonable standard and supports reliable long-term performance in vacuum and aerospace environments. For programs with specific outgassing thresholds, verify the actual TML and CVCM values against your program specification using the current Rogers/Arlon datasheet data.
5. What copper foil options are available with Arlon IsoClad 933, and which is best for microwave performance?
IsoClad 933 is available in standard ยฝ oz, 1 oz, and 2 oz electrodeposited (ED) copper as the standard offering. For microwave designs operating above 10 GHz โ where surface roughness of the copper foil becomes a significant contributor to conductor loss โ consider specifying rolled annealed (RA) copper if available for your specific thickness. RA copper has a smoother surface profile than standard ED copper, which reduces the roughness-induced insertion loss that increasingly dominates total circuit loss at X-band and above. For conformal antenna applications at lower microwave frequencies (1โ6 GHz), standard ED copper is generally adequate.
Final Thoughts on Arlon IsoClad 933
Arlon IsoClad 933 is a material with a specific and well-defined purpose: it enables RF and microwave circuit designs that a rigid woven-glass PTFE laminate cannot support. Its non-woven random fiber architecture delivers genuine three-dimensional isotropy โ not the XY-plane isotropy approximation of cross-plied woven materials โ and the physical flexibility to conform to curved structures without degrading the dielectric properties the circuit depends on.
For the large majority of flat-board microwave designs, IsoClad 933 is not the right choice โ DiClad 870 or CuClad 233 at the same Dk 2.33 will give you lower Df and better moisture performance. But for conformal antennas, wrap-around apertures, or any application where full three-dimensional dielectric isotropy is a real design requirement rather than a nice-to-have, IsoClad 933 is in a category by itself among commercially available PTFE-based laminates.
The fabrication requirements are the same as for all PTFE laminates โ PTFE hole wall activation is non-negotiable, and a fabricator with genuine PTFE processing capability is essential. Add the forming operation for conformal builds, qualify your minimum bend radius early, and work with a material-knowledgeable fabricator who has handled non-woven PTFE substrates before. Do those things, and IsoClad 933 will deliver exactly the performance its datasheet promises in applications that no flat laminate can serve.
