TPH-1/2 Microwave Composite Dielectric Laminate: Properties, Applications & Design Guide

When Wangling engineers developed the TP substrate family, they built it around an adjustable-Dk PPO-ceramic composite that could be tuned from Dk 3 all the way up to Dk 25. That flexibility makes the TP series ideal for high-Dk antenna miniaturisation work. But a different problem sits at the other end of the Dk spectrum: designing low-loss microwave transmission structures — feed lines, power dividers, couplers, filter networks — where you want a substrate Dk close to 2.65, wide trace widths, low conductor loss, and the kind of mechanical machinability that sintered ceramic simply cannot offer.

That is the exact engineering niche the TPH-1/2 microwave composite dielectric laminate was designed to fill. It is the low-Dk member of the Wangling thermoplastic PPO-ceramic family, fixed at a dielectric constant of 2.65, identifiable by its distinctive black substrate appearance, and characterised by a dissipation factor at or below 0.001 — competitive with PTFE-based laminates at a fraction of the processing complexity. This article covers the full technical specification, the design engineering case for choosing TPH-1/2, how it compares to PTFE and hydrocarbon alternatives, its fabrication characteristics, and where it belongs in a microwave design toolbox.

What Is the TPH-1/2 Microwave Composite Dielectric Laminate?

Material Construction and Distinguishing Characteristics

The TPH-1/2 microwave composite dielectric laminate belongs to the same thermoplastic PPO-ceramic substrate family as the Wangling TP series. Like its higher-Dk siblings, it uses a dielectric layer composed of ceramic particles uniformly distributed in a polyphenylene oxide (PPO) resin matrix, without any glass fibre reinforcement. The absence of glass fibre means there is no glass weave effect — none of the periodic Dk variation that woven-glass laminates exhibit at higher microwave frequencies.

What distinguishes TPH-1/2 within the Wangling PPO-ceramic family is its low, fixed dielectric constant of 2.65. Where the TP series uses high ceramic loading to engineer Dk values from 3.0 upward to 25, TPH-1/2 uses a formulation optimised for the low end of the Dk range — the territory occupied by PTFE-based substrates in the wider substrate market. The result is a substrate with Dk 2.65 and a dissipation factor of tgδ ≤ 1×10⁻³ (0.001), making it directly competitive with higher-cost PTFE composites in loss performance.

The substrate colour is black — an immediately recognisable visual characteristic that distinguishes TPH-1/2 on the production line and in incoming inspection. In a world where F4BM produces brown substrates, WL-CT produces off-white boards, and Rogers RO4350B is a light tan, a black substrate stands out unambiguously.

The TPH-1/2 Naming Convention

Designation	Description
TPH	Bare substrate — no copper foil (smooth surface material)
TPH-1	Single-sided — copper foil on one side
TPH-2	Double-sided — copper foil on both sides

The suffix indicates the cladding configuration, not Dk grade. Unlike the broader TP family where the numeric suffix encodes Dk (e.g., TP1020 = Dk 10.2), TPH has a single fixed Dk of 2.65 across all cladding variants.

Core Electrical Properties of TPH-1/2 Microwave Composite Dielectric Laminate

Verified Specification Summary

Parameter	TPH-1/2 Specification	Notes
Dielectric Constant (Dk)	2.65	Fixed; consistent over temperature and frequency
Dissipation Factor (Df / tgδ)	≤ 0.001	Slight increase with frequency; not significant within 10 GHz
Operating Temperature	-100°C to +150°C	Excellent cryogenic performance
Substrate Colour	Black	Distinctive visual identifier
Glass Fibre Reinforcement	None	PPO-ceramic composite only
Resin System	PPO (thermoplastic)	Polyphenylene oxide matrix
Copper Adhesion	Superior to vacuum-metallised ceramic	More reliable peel strength
Layer Count	1 (TPH-1) or 2 (TPH-2) sides	Multilayer not recommended
Machinability	Drill, punch, grind, cut, etch	All standard methods; ceramic cannot match
Weight	Low specific gravity	Lighter modules than alternative materials

Why Dk 2.65 and Df ≤ 0.001 Matter Together

A Dk of 2.65 places TPH-1/2 in the same electrical neighbourhood as several well-established PTFE substrates — Wangling’s own F4BM series at its lowest Dk variants, Rogers RT/duroid 5870 (Dk 2.33), and various PTFE composites in the 2.2–2.65 range. At this dielectric constant, microstrip trace widths for 50 Ω impedance on a given substrate thickness are significantly wider than on Dk 3.5 or Dk 4.0 materials. Wider traces mean lower conductor resistance per unit length and reduced sensitivity to fabrication tolerance on trace width — both advantages for microwave transmission line designs.

The dissipation factor of ≤ 0.001 at operating frequency is the other defining merit. For comparison, standard FR4 runs Df around 0.020 at 1 GHz, rising with frequency. Rogers RO4350B publishes Df 0.0037 at 10 GHz. PTFE-based substrates like F4BM achieve Df of 0.001–0.003 depending on Dk grade. TPH-1/2’s ≤ 0.001 figure puts it at the PTFE-competitive end of the loss spectrum despite using a PPO thermoplastic matrix rather than PTFE. The loss increases slightly with frequency but remains non-significant within the 10 GHz operational band most commonly targeted for this substrate.

Academic researchers have validated TPH-1/2 alongside Rogers RO4350B in dielectric characterisation studies, confirming that its measured dielectric properties are consistent with specification and stable across the measurement frequency range. This independent characterisation provides additional confidence beyond manufacturer data sheets.

TPH-1/2 vs Competing Low-Dk Microwave Substrates

Engineers evaluating TPH-1/2 will naturally compare it to other low-Dk substrates. Here is an honest side-by-side with the most common alternatives:

Parameter	TPH-1/2	Wangling F4BM265	Rogers RT/duroid 5880	Rogers RO4350B
Dk (nominal)	2.65	2.65	2.20	3.48
Df @ 10 GHz	≤ 0.001	~0.002	0.0009	0.0037
Glass Fibre	None	Woven glass	None (random microfibre)	Woven glass
Resin System	PPO thermoplastic	PTFE	PTFE	Hydrocarbon thermoset
Plasma Activation	Not required	Required	Required	Not required
Multilayer Support	Not recommended	Yes	Yes (with PTFE prepreg)	Yes
Machinability	Excellent	Good (soft PTFE)	Good (soft PTFE)	Good
Substrate Colour	Black	Brown	White	Tan/light
Operating Temp (low)	-100°C	-50°C	-55°C	-55°C
Cost	Lower than PTFE	Moderate	High	Moderate–High
Cryogenic Performance	Excellent	Moderate	Good	Moderate

The table reveals TPH-1/2’s competitive position clearly. Its Df ≤ 0.001 at Dk 2.65 is comparable to F4BM265 (same Dk) while offering PPO thermoplastic machinability. Its cryogenic floor of -100°C beats every PTFE and hydrocarbon alternative. Its lack of glass fibre avoids the glass weave effect at higher microwave frequencies. And it requires no plasma surface activation — a significant advantage over PTFE-based substrates in fabrication shops without specialist PTFE process lines.

The limitations relative to PTFE: it does not support multilayer PCB construction in standard processes (thermoplastic matrix constraint shared with all TP-family substrates), and its Df will trend higher than PTFE above 10 GHz where PPO polymer losses become more significant.

Fabrication Guide for TPH-1/2 Microwave Composite Dielectric Laminate

Machining Advantages Over Ceramic

One of the strongest engineering arguments for TPH-1/2 versus sintered ceramic substrates at Dk 2.65 is pure machinability. Sintered ceramic cannot be compared to TPH-1/2 in this regard. Standard carbide drill bits cut TPH-1/2 cleanly without the cracking or chipping that plagues ceramic machining. The PPO-ceramic composite can be punched, ground, sheared to shape, and routed with standard CNC milling equipment. Ceramic substrates require diamond tooling for all cutting operations and crack under any tensile stress applied during drilling.

This machinability advantage translates directly to lower manufacturing cost and higher production yield. The substrate is created to offer customers easy circuit processing, a higher pass-rate of production, and manufacturing cost much lower than ceramic substrate.

Surface Activation: No Plasma Required

Unlike PTFE-based substrates that require plasma or sodium-naphthalene etching to activate the surface for copper plating adhesion, the PPO matrix in TPH-1/2 accepts standard PCB desmear and plating chemistry. This means any board house with standard FR4-line processing can plate through holes and deposit surface finishes on TPH-1/2 without specialist equipment. The peel strength between copper and the substrate is more reliable than the vacuum film coating of ceramic substrate, making copper adhesion a strength rather than a concern.

Critical Temperature Constraint: 180°C Upper Limit for Assembly

This is the most important fabrication constraint to understand before designing with TPH-1/2. When the temperature exceeds 180°C, the material may deform, the copper foil may peel off, and there may be significant changes in electrical performance. The thermoplastic PPO matrix softens above its glass transition — unlike thermoset materials that remain dimensionally stable through lead-free reflow temperatures of 255–260°C peak.

This means standard lead-free reflow soldering at 255–260°C peak is not compatible with TPH-1/2. Assembly processes must use either low-temperature solder alloys (BiSn eutectic at 138°C, InSn at 118°C), conductive adhesives, or compression bonding. This constraint is shared with the full TP series and is the fundamental trade-off of the thermoplastic matrix system. Designers evaluating TPH-1/2 for a new programme must confirm their assembly process compatibility before committing to the substrate.

Surface Finish Recommendations

Surface Finish	Suitability	Notes
ENIG	Excellent	Standard for most RF circuits; flat, reliable, compatible with low-temperature solder
Immersion Silver	Very Good	Low conductor loss above 6 GHz; assemble promptly
Pure Gold	Best for mil/aero reliability	Used in missile and aerospace sub-assemblies
OSP	Limited	Short shelf life; low-temperature assembly window
HASL	Avoid	HASL peak temperatures approach deformation threshold

Applications for TPH-1/2 Microwave Composite Dielectric Laminate

Microwave Transmission Line Substrates and Feed Networks

TPH-1/2’s Dk 2.65 combined with low Df makes it a natural substrate for the transmission line layers of microwave assemblies — power dividers, Wilkinson combiners, rat-race couplers, and branch-line hybrids — where wide trace widths reduce conductor loss and the substrate loss budget is tight. At 5 GHz, a 50 Ω microstrip line on Dk 2.65 is significantly wider than the same line on Dk 3.5, making fine-geometry etching tolerance less critical and improving power handling capability.

Lightweight Missile-Borne and Airborne Electronics

The specific gravity advantage of TPH-1/2 is explicitly called out in the original product documentation: due to the specific gravity being less, the remarkable characteristic of the module is weight lighter manufacturing by this substrate, which other materials cannot compare. In missile-borne electronics where every gram of RF module weight affects flight performance, a substrate system that delivers PTFE-competitive electrical performance in a lighter assembly has genuine engineering value. The -100°C lower operating temperature further validates TPH-1/2 for cold-soak environments encountered in high-altitude aircraft applications and missile seekers before motor ignition.

Phase-Stable Microwave Circuits Over Wide Temperature Ranges

The consistent performance over broad temperature and frequency ranges is a defining TPH-1/2 characteristic. Circuits that must maintain phase accuracy across -100°C to +150°C — such as phased-array feed phase shifter networks, temperature-compensated oscillator substrates, and radar timing circuits — benefit from the stable Dk of TPH-1/2 throughout this range. Standard FR4 shows significant Dk variation with temperature; TPH-1/2’s PPO-ceramic matrix is more thermally stable in its dielectric characteristics.

Research and Characterisation Platforms

The documented use of TPH-1/2 in academic dielectric characterisation research — including comparison studies with Rogers RO4350B — reflects a role as a characterised, reproducible substrate for microwave measurement reference structures. Researchers designing test fixtures for free-space or transmission-line dielectric measurement setups can specify TPH-1/2 with confidence in its consistent electrical properties.

Useful Technical Resources for TPH-1/2 Design Engineers

Resource	Description	Link
Wangling Official Product Page	TPH-1/2 product listing within TP-1/2 microwave substrate series	wang-ling.com.cn
iPCB TPH-1/2 Material Data	Full specification summary for TPH-1/2 from verified distributor	ipcb.com/material/397.html
Wangling PCB Manufacturing	PCB fabrication on TPH-1/2 and other Wangling substrates	pcbsync.com/Wangling-pcb
IPC-4103C	High Speed/High Frequency PCB Base Material Specification	ipc.org
IPC-TM-650	Standardised test methods for Dk, Df, peel strength	ipc.org/test-methods
Microwave Laminates Comparison Chart	Full RF laminate property comparison across manufacturers	microwaves101.com
NWES RF Material Guide	Engineering guidance on RF substrate selection	nwengineeringllc.com

Five FAQs: TPH-1/2 Microwave Composite Dielectric Laminate

FAQ 1: What exactly separates TPH-1/2 from the standard TP-1/2 series?

Both use the same PPO-ceramic thermoplastic composite without glass fibre reinforcement, and both share the operating temperature range of -100°C to +150°C. The key differences are Dk and colour. The TP series offers adjustable Dk from 3 to 25 by changing ceramic loading; TPH-1/2 is fixed at Dk 2.65 — a lower dielectric constant achieved with different formulation chemistry. Visually, TP substrates are typically off-white or beige; TPH-1/2 is distinctively black. The “H” designation marks this as the low-Dk variant optimised for transmission-line substrates rather than high-Dk antenna miniaturisation.

FAQ 2: How does TPH-1/2 Df ≤ 0.001 compare to PTFE-based alternatives at Dk 2.65?

Wangling’s PTFE-based F4BM265 (Dk 2.65, woven glass reinforced) achieves Df of approximately 0.002 at 10 GHz. Rogers RT/duroid 5880, with no glass fibre and Dk 2.20, achieves Df 0.0009 at 10 GHz. TPH-1/2 at Dk 2.65 with Df ≤ 0.001 matches or approaches PTFE-based performance at the same Dk. For most microwave circuits operating at frequencies where TPH-1/2 is specified (below 10 GHz), this loss performance is functionally equivalent to PTFE without requiring PTFE-specialist board house processes.

FAQ 3: Can standard lead-free reflow soldering be used with TPH-1/2 assemblies?

No. Standard lead-free SAC305 reflow profiles peak at 255–260°C — well above the 180°C deformation threshold of the PPO thermoplastic matrix. When the temperature exceeds 180°C, material deformation, copper foil peeling, and electrical performance changes will occur. Assembly must use low-temperature alloys (bismuth-tin or indium-tin based), conductive epoxy, or compression mounting. This is the most important process constraint when designing a TPH-1/2 PCB. It does not prevent production use, but it requires assembly process planning from the start of the programme rather than as an afterthought.

FAQ 4: Is TPH-1/2 suitable for programmes with radiation resistance requirements?

Yes. Like the broader TP and TPH substrate family, TPH-1/2 is resistant to radiation and has low outgassing. Both properties are confirmed in the product specification and are consistent with PPO-ceramic composite behaviour — the PPO backbone and ceramic filler are chemically and structurally stable under gamma and particle radiation doses typical of satellite and aerospace environments. Low outgassing is specifically relevant for space applications where volatile condensable material (VCM) contamination of optical surfaces is a programme risk. Programmes requiring formal outgassing compliance should request test data against ASTM E595 from their fabricator.

FAQ 5: What is the practical board size limit for TPH-1/2 fabrication?

As with the TP series, the thermoplastic PPO matrix and specialist pressing process constrain available panel sizes to approximately 150 mm × 220 mm maximum. This limits TPH-1/2 to compact board designs — appropriate for the RF module, microwave sub-assembly, and antenna element applications it targets, but not suitable for large-format antenna arrays or panel-level production of boards larger than around 150 × 200 mm. Designers working with larger transmission-line networks should consider WL-CT or F4BM series substrates, which come in full production panel sizes up to 915 × 1220 mm.

Summary: When to Specify TPH-1/2 Microwave Composite Dielectric Laminate

The TPH-1/2 microwave composite dielectric laminate is a focused specialist material rather than a general-purpose RF substrate. It solves a specific set of co-occurring requirements: low Dk around 2.65 for wide-trace low-loss transmission lines, dissipation factor at or below 0.001, operating temperature extending to -100°C, lower weight than competing material classes, and the machinability advantage over sintered ceramic that makes PCB-format circuit boards practical.

For programmes designing lightweight missile-borne RF modules, phase-stable microwave feed networks for wide-temperature aerospace applications, or low-loss coupler and divider circuits where Dk 2.65 traces give maximum impedance flexibility, TPH-1/2 delivers a compelling combination that no glass-reinforced PTFE substrate can match in machinability and no sintered ceramic can match in processability. The 180°C assembly temperature constraint and the single/double-sided-only construction requirement are non-negotiable trade-offs that must be designed around from the start.

Engineers ready to evaluate TPH-1/2 in production should begin with a prototype run at a board house experienced in the PPO-ceramic thermoplastic family. Wangling PCB supports TPH-1/2 fabrication within the specialist process knowledge this unique black composite substrate demands.