LCP Injection Moulding: Liquid Crystal Polymer Properties & Guide
LCP (liquid crystal polymer) is the specialist injection-moulding material for ultra-thin-wall miniature components in electronics, where no other thermoplastic can fill a 0.2 mm wall section with 260°C reflow solder stability and sub-0.01 mm dimensional precision. Its unique ordered molecular structure at melt temperature gives it exceptionally low viscosity under shear, allowing it to fill geometric features that are physically inaccessible to conventional engineering polymers. Nordmould supplies LCP-moulded components primarily for fine-pitch connectors, sensor housings, and miniaturised electronic assemblies where dimensional precision and SMT compatibility are non-negotiable.
What are the mechanical and thermal properties of LCP?
LCP forms highly ordered molecular chains during processing — similar to a liquid crystal display in structure, hence the name. This ordered orientation is responsible for both LCP's exceptional thin-wall fillability and its primary drawback: strong anisotropy between the flow direction and cross-flow direction. All property values below should be understood as flow-direction properties; cross-flow properties are significantly lower.
| Property | Unfilled LCP | 30% GF LCP | 50% GF+Mineral LCP | Test Standard |
|---|---|---|---|---|
| Tensile Strength (flow) | 170–200 MPa | 200–230 MPa | 160–200 MPa | ISO 527 |
| Tensile Strength (cross-flow) | 50–70 MPa | 80–110 MPa | 100–130 MPa | ISO 527 |
| Flexural Modulus (flow) | 9,000–12,000 MPa | 14,000–17,000 MPa | 15,000 MPa | ISO 178 |
| Izod Impact (notched) | 30–60 J/m | 45–75 J/m | 50–80 J/m | ISO 180 |
| Heat Deflection Temp (1.82 MPa) | 240–300°C | 260–300°C | 250–290°C | ISO 75 |
| Continuous Use Temp | 200–240°C | 200–240°C | 200–240°C | — |
| Density | 1.40–1.44 g/cm³ | 1.63–1.70 g/cm³ | 1.80–1.90 g/cm³ | ISO 1183 |
| Mould Shrinkage (flow) | 0.0–0.3% | 0.0–0.2% | 0.1–0.3% | ISO 294-4 |
| Mould Shrinkage (cross-flow) | 0.7–1.5% | 0.5–1.0% | 0.3–0.7% | ISO 294-4 |
| Water Absorption (24 h) | 0.02–0.04% | 0.02–0.03% | 0.02–0.03% | ISO 62 |
The near-zero flow-direction shrinkage is unique among injection-moulding materials. It directly enables the dimensional precision achievable in LCP connectors — pin-to-pin spacing can be held to tolerances that are physically impossible in nylon, PPS, or PC. The cross-flow shrinkage differential is the primary source of warp risk in flat geometries.
Where is LCP injection moulding used?
LCP's application space is tightly defined by its unique combination of properties: ultra-low flow-direction shrinkage, very thin wall capability, SMT solder compatibility, and minimal moisture-induced dimensional change.
Fine-pitch SMD connectors: Board-to-board, FPC/FFC, and high-speed data connectors at pitches of 0.3–0.8 mm are the dominant LCP application globally. LCP is specified by design as the only material capable of holding the pitch tolerances required by modern connector standards while withstanding reflow solder profiles.
Sensor and actuator housings: Miniature pressure sensor bodies, accelerometer housings, optical sensor enclosures, and precision mechanical reference components. The near-zero moisture absorption and dimensional stability over temperature and humidity cycles are the key selection drivers.
Antenna components and RF substrates: LCP's low and stable dielectric constant (approximately 2.9–3.2) and very low dissipation factor make it a substrate candidate for high-frequency antenna and waveguide components in millimetre-wave applications, including 5G infrastructure and automotive radar.
Medical miniature components: Fine-pitch connectors for implantable devices, endoscope working channel components, and miniature catheter fittings where the combination of biocompatibility (ISO 10993 grades available), sterilisability, and dimensional precision are all required.
Aerospace electronics: Lightweight, thermally stable connector and relay housings for avionics, where the combination of low weight, vibration resistance, and temperature capability justify the material cost.
What are the moulding characteristics of LCP?
LCP is one of the most technically demanding injection-moulding materials from a tooling and process design perspective — not because it is difficult to fill, but because its extreme sensitivity to gate location, injection speed, and cavity layout makes the difference between dimensionally precise parts and warped scrap.
Melt temperature: 280–380°C depending on polymer type (aromatic LCP backbone types vary widely). Temperature must be consistent; LCP can thermally degrade above its ceiling temperature, producing dark streaks and off-specification mechanical properties. The processing window is narrower than most materials; barrel temperature profiling is important.
Injection speed: Critical — LCP is highly shear-thinning. At low injection speeds, LCP behaves as a high-viscosity material and may not fill thin walls. At high injection speeds, viscosity drops sharply, filling proceeds cleanly, and weld lines are minimised. Very high-speed injection is often needed for wall sections below 0.3 mm; machine capability matters here.
Mould temperature: 70–120°C. Higher mould temperatures reduce the anisotropy gradient between skin and core and improve weld-line strength. For parts with structural weld lines, temperatures at the upper end of this range should be specified.
Drying: 120–150°C for 3–4 hours. Despite low inherent moisture absorption, LCP must be dried; any surface moisture causes defects in thin walls where there is no material volume to absorb gas.
Tooling: Hardened tool steel throughout. The very high injection speeds and pressures required for thin-wall LCP demand dimensionally stable, well-vented tooling. Gate design is critical: pin gates are standard for small parts; gate diameter and land length must be matched to the wall thickness and flow path. Inadequate venting causes burns and short shots in thin walls.
Anisotropy management: Gate location is the primary tool for controlling LCP orientation and warp. For flat parts, multiple gates or fan/film gates are used to achieve balanced fill and minimise differential shrinkage. Symmetrical gate layouts improve cross-flow shrinkage uniformity. Mould flow simulation is strongly recommended before cutting tools for complex LCP parts; correcting orientation-driven warp post-tooling is expensive.
Weld lines: LCP weld lines are mechanically weak — the ordered molecular orientation reforms along each flow front independently, creating a structural discontinuity at the knit line. Core pulls and multi-gate designs should be used thoughtfully to position weld lines away from structural or load-bearing areas.
Which LCP grades and variants are available?
| Grade | Filler / Modification | Primary Application |
|---|---|---|
| Unfilled LCP | No filler, ultra-thin wall capability | Sub-0.3 mm walls, fine-pitch connectors |
| 30% GF LCP | Reduced anisotropy, higher cross-flow strength | Structural housings, coarser connectors |
| 50% Glass + Mineral LCP | Best isotropy, reduced warp | Flat components, large-area parts |
| Carbon-fibre LCP | ESD-safe, maximum stiffness | Semiconductor handling, RF shielding |
| PTFE-blended LCP | Low friction | Miniature bearings, seal components |
| High-purity LCP | Low extractables, biocompatible | Medical implantable connectors |
LCP grade selection requires matching the filler loading and type to the minimum wall section: filler particle size must be compatible with the narrowest flow path in the tool. In gate lands or walls below 0.2 mm, unfilled LCP is the only practical choice.
What are LCP's advantages and limitations?
Advantages:
- Ultra-thin wall capability — fills below 0.3 mm where no other thermoplastic reaches
- Near-zero flow-direction shrinkage delivers dimensional precision unmatched by competing materials
- Very low moisture absorption (<0.04%) — dimensions stable across all humidity conditions
- Survives 260°C SMT reflow solder profiles without deformation
- Continuous use temperature 200–240°C
- Excellent broad-spectrum chemical resistance including strong acids and bases
- Inherent UL 94 V-0 rating in most commercial grades
- Good dielectric properties for RF and high-frequency applications
Limitations:
- Strong flow-direction anisotropy — cross-flow properties substantially lower; warp is the dominant design risk
- Mechanically weak weld lines — gate layout must keep weld lines out of structural areas
- Highest tooling and process complexity among standard engineering polymers; flow simulation is usually mandatory
- High material cost relative to PPS or PEI
- Knit-line sensitivity limits design freedom in multi-feature geometries
- Unfilled grades are brittle — handle parts with care during assembly
When should you choose LCP over alternative materials?
LCP vs PPS: Both are standard SMD connector materials. Choose LCP for wall sections below 0.4 mm, pitch below 0.5 mm, or applications requiring absolute minimum moisture-induced dimensional change. Choose PPS for structurally loaded or larger connector bodies where LCP's anisotropy would be a reliability concern and lower material cost matters.
LCP vs PEEK: PEEK offers better impact resistance, established implant-grade biocompatibility, and is less anisotropic. Choose LCP for the thinnest-wall SMD components and high-frequency dielectric applications. Choose PEEK for structural medical parts, high-impact applications, or when chemical resistance to ketones and halogenated solvents is required.
LCP vs PEI: PEI is less expensive, amorphous (no anisotropy), and reflow-solder compatible to 260°C in filled grades. Choose LCP when walls below 0.4 mm or sub-0.5 mm connector pitch is a firm requirement. Choose PEI for cost-sensitive, larger-format SMT housings or when structural loads and weld-line positions cannot be controlled.
Is LCP recyclable?
LCP is not collected in consumer or standard industrial recycling streams. Production regrind from clean, single-grade LCP scrap can be reprocessed, but the highly orientation-sensitive material properties mean that regrind use in connector applications requires qualification. Most LCP connector production runs on 100% virgin material. The material's exceptional service life in electronic assemblies — typically equal to the product lifetime — partially offsets its end-of-life limitations. Nordmould can advise on production scrap handling and whether regrind use is appropriate for specific applications.
Frequently asked questions
What makes LCP the preferred material for micro-connector housings?
LCP can fill wall sections below 0.3 mm with exceptional dimensional precision, tolerates 260°C SMT reflow soldering without deformation, has very low and stable moisture absorption (under 0.04%), and achieves extremely tight tolerances in high-cavity tooling. Nordmould positions LCP for fine-pitch connectors, sensor housings, and miniaturised electronic components where no other thermoplastic meets all four requirements simultaneously.
What is the continuous use temperature of LCP injection-moulded parts?
Most commercial LCP grades have a continuous use temperature of 200–240°C. Heat deflection temperatures for standard LCP are 240–300°C at 1.82 MPa, depending on filler content and polymer backbone. The key practical capability is dimensional stability through 260°C peak reflow solder profiles — a requirement that eliminates most competing materials.
Does LCP need to be dried before injection moulding?
Yes — LCP must be dried at 120–150°C for 3–4 hours in a dehumidifying dryer before processing. LCP's inherent low moisture absorption (0.02–0.04%) means it does not absorb moisture as aggressively as nylon or PC, but processing undried material still produces voids, surface defects, and inconsistent flow behaviour in very thin wall sections.
What are the melt and mould temperatures for LCP injection moulding?
LCP melt temperature is typically 280–380°C depending on grade. Mould temperature of 70–120°C is common. LCP is highly shear-thinning — melt viscosity drops sharply with injection speed, which is why it fills thin walls so effectively. Injection speed is a critical process variable; slow fill rates significantly increase LCP's effective viscosity.
What is the main limitation of LCP in structural applications?
LCP's highly anisotropic molecular orientation in the melt direction produces dramatically different mechanical properties along and across the flow direction. Tensile strength across the flow direction can be 30–50% of the flow-direction value. This anisotropy causes warp in flat parts and limits LCP to applications where load paths are well-defined and geometries favour flow-direction loading. Gate position must be chosen to align molecular orientation with the primary load direction.
Is LCP chemically resistant enough for harsh environments?
LCP has excellent resistance to a wide range of chemicals including concentrated acids, bases, organic solvents, and fuels. It is particularly resistant to hydrolysis — unlike nylon, it retains its properties in hot-water or steam environments. Chemical resistance is broadly comparable to PPS and often exceeds it, particularly in resistance to strong acids.
What filler grades of LCP are available for injection moulding?
LCP is most commonly processed with glass-fibre or mineral fillers at 30–50% loading to reduce anisotropy and improve dimensional stability. Unfilled LCP is used for extreme thin-wall applications where filler particles would obstruct narrow gate and wall sections. Carbon-fibre-filled LCP is available for maximum stiffness and ESD applications. Proprietary blends with PTFE are used for bearing and seal components.
How does LCP compare to PPS for electronic connector applications?
Both LCP and PPS are standard SMD connector materials. LCP achieves thinner walls, finer pitch dimensions, and lower moisture absorption — making it preferred for the most miniaturised connectors. PPS is less expensive and better suited for structurally loaded components where LCP's flow-direction anisotropy would be a reliability risk. For connectors below 0.5 mm pitch or wall thickness below 0.3 mm, LCP is effectively the only viable injection-moulding material.
Submit your STEP file to Nordmould for a free DFM review — our engineers will evaluate whether LCP is the correct specification, model the fill pattern to identify weld-line risks, and confirm gate locations before any steel is cut.