Understanding Lapping Film: Formula, Coating, Specs, Grits, Applications, and Polishing Process

Lapping film is a precision-coated abrasive product designed for the controlled polishing and finishing of surfaces to tight tolerances. It plays a critical role across industries like fiber optics, electronics, aerospace, medical device manufacturing, and automotive systems. This guide explores the fundamentals — from material formulas to polishing procedures — to help you fully understand lapping film technology.

1.Formula of Lapping Film

lapping films achieve ultra-precision material removal and superb surface finishes through a proprietary three-layer construction: a high-loading, micron-graded abrasive layer; a robust, waterproof resin bond; and a dimensionally stable polyester backing (with optional PSA). Together, these engineered layers deliver consistent cutting action, minimal particle fallout, and flatness tolerances within microns—ideal for everything from coarse stock removal to final optical polishing.

1. Abrasive Grain Layer

• Precisely Graded Minerals: Diamond, aluminum oxide (Al₂O₃), silicon carbide (SiC), silicon dioxide (SiO₂), cerium oxide (CeO₂), and specialty oxides are coated on the film.

• Micron/Grit Range: Available in 0.01–120 µm grades to suit rough to ultra-fine applications.

• High Loading Density: Typically 18–30 g/m² per side, depending on grit and coating method.

• Coating Method: Slurry coating is common for uniform deposits, while electrostatic or shot-pin techniques may be used for specialized films (e.g., final polishing).

2. Resin Bond (Binder)

• Waterproof, Oil-Resistant: Thermoset resin systems (urethanes or acrylic polyols) that resist water, alcohols, oils, and solvents ensure the abrasive remains fixed through multiple uses.

• Controlled Resin Thickness: Thin-film resin layers (~2–5 µm) minimize build-up while securely anchoring particles.

• Customizable Formulations: Resin options can be tailored (hardness, flexibility) to match specific process requirements.

3. Film Backing & Adhesive System

• Polyester (PET) Backing: Standard backing is 3 mil (75 µm) or 5 mil (125 µm) PET, flat to ±0.005 mm and tear-resistant (>45 N/mm).

• Optional PSA: Pressure-sensitive adhesive backing (peel strength ~300–500 g/cm) with color-coded release liners enables rapid film changes on flat platens or rotating fixtures.

• Operating Range: Backing remains dimensionally stable from –20 °C to +150 °C, suitable for a variety of lapping environments.

4. Key Performance Benefits

• Flatness & Consistency: Uniform abrasives and precise backing deliver reproducible µ-inch planarity across batches.

• Long Life & Predictable Wear: High abrasive loading and strong resin bonds extend usable film life with minimal glazing.

• Versatility: Compatible with water, oil, or dry polishing; suitable for metals, ceramics, optics, fiber-optic connectors, semiconductors, and more.

• Process Control: Tight particle-size distribution (±10 %) and controlled resin-to-abrasive ratios yield consistent material‐removal rates and surface finishes.

2. Coating Technologies in Lapping Film

The way abrasive particles are deposited and bonded to the polymer backing has a decisive impact on cutting efficiency, wear rate, and final surface finish. XYT employs three primary coating methods—each optimized for specific grit ranges, removal rates, and finish requirements.

1. Slurry (Flood) Coating

• Process
  A viscous suspension of abrasive grains and resin is “flooded” over a continuously moving polyester web. Excess slurry is squeegeed off, then the film is cured to lock in the particles.

• Key Features

  • High Coating Weight: 25–30 g/m² per side, suited for coarser grits (> 30 µm)

  • Uniform Resin Distribution: Minimizes bare spots and loose grains

  • Thickness Control: Typical dried coating thickness of 3–5 µm

• Best Use Cases
  Heavy stock removal, coarse shaping, and applications where cost per unit area is critical.

2. Electrostatic Coating

• Process
  Abrasive grains are tribo- or corona-charged before being applied to a grounded, resin-primed backing. The electric field aligns particles upright, maximizing their cutting edges.

• Key Features

  • Low to Moderate Coating Weight: 18–22 g/m² per side, ideal for medium to fine grits (5–30 µm)

  • Particle Orientation: Upright grains cut more aggressively and wear uniformly

  • Sharp Initial Cut: Outperforms slurry-coated films in removal rate for the same grit

• Best Use Cases
  Intermediate lapping, connector pre-polishing (e.g., LC/SC ferrules), glass and ceramic stock removal.

3. Precision (Shot-Pin) Coating

• Process
  A thin base resin layer is applied and pre-cured, then abrasive particles are “pinned” into the tacky surface at controlled density. A final resin top coat is added to lock grains in place.

• Key Features

  • Ultra-Low Coating Weight: 12–18 g/m² per side, for fine to ultra-fine grits (0.02–5 µm)

  • Tight Density Control: ±5 % variation in particle count per unit area

  • Minimal Resin Overlay: Ensures maximum grain exposure for supreme finish

• Best Use Cases
  Final polishing of optical connectors, semiconductor planarization, mirror-grade finishes.

Comparative Overview

By matching the coating technology to your application’s removal rate and surface-finish targets, lapping films deliver predictable performance—from rapid material removal to the finest optical-grade polish.

3.Abrasive Types & Key Characteristics

1. Synthetic Diamond

• Hardness: Mohs 10 (highest)

• Particle Shape: Blocky to “semi-blocky” for uniform cutting edges

• Typical Micron/Grit Range: 0.02 µm (8 000#) up to 120 µm (80#)

• Best Applications:

  • Ultra-hard substrates (sapphire, SiC, Al₂O₃ ceramics)

  • Final optical-grade polishing of fiber-optic ferrules and connectors

  • Semiconductor wafer planarization

• Pros/Cons:

  • • Extremely long life and consistent removal rate

  • – Higher cost; sensitive to ferrous-metal contamination (leads to graphitization)

2. Silicon Carbide (SiC)

• Hardness: Mohs ~9.5

• Particle Shape: Sharp, angular

• Typical Micron/Grit Range: 1 µm (3 000#) to 100 µm (100#)

• Best Applications:

  • Aggressive stock removal on glass and ceramics

  • Intermediate pre-polishing of hard plastics and metals

• Pros/Cons:

  • • Fast cut rate and good toughness

  • – Friable (breaks down), so tends to “self-sharpen” but can leave finer debris

3. Aluminum Oxide (Al₂O₃)

• Hardness: Mohs ~9

• Particle Shape: Blocky to friable (depending on grade)

• Typical Micron/Grit Range: 0.3 µm (5 000#) to 100 µm (100#)

• Best Applications:

  • General-purpose lapping of metals, plastics, PCBs

  • Pre-polishing before diamond or ceria stages

• Pros/Cons:

  • • Cost-effective and versatile

  • – Less sharp than SiC; slower cut in very hard materials

4. Silicon Dioxide (SiO₂, “Silica”)

• Hardness: Mohs ~7

• Particle Shape: Spherical to irregular

• Typical Micron/Grit Range: 0.05 µm to 5 µm

• Best Applications:

  • Fine polishing of glass optics, lenses, and displays

  • Chemical–mechanical polishing (CMP) slurries for glass‐substrate finishing

• Pros/Cons:

  • • Extremely smooth finishes; minimal subsurface damage

  • – Very slow removal rate; used only in final polishing

5. Cerium Oxide (CeO₂)

• Hardness: Mohs ~6.5

• Particle Shape: Irregular, blocky

• Typical Micron/Grit Range: 0.5 µm to 5 µm

• Best Applications:

  • Optical-grade polishing of glass, crystalline lenses, and fiber-optic endfaces

  • Final stage to achieve mirror finish (Ra < 0.01 µm)

• Pros/Cons:

  • • Chemical activity on silica glass yields very low subsurface damage

  • – Limited to silica-based substrates; not for metals

6. Specialty & Emerging Abrasives

• Zirconia (ZrO₂): Tough, used in heavy-duty metal lapping; Mohs ~8.5

• Magnesium Oxide (MgO): Ultra-fine finishing on polymers; Mohs ~5.5

• Aluminum Fluoride-doped Garnet: Ultra-hard, blocky, for sub-micron finishing

Comparative Summary

By choosing the proper abrasive—and matching its hardness, particle shape, and removal characteristics to your substrate—you can optimize material-removal rates, achieve target surface-roughness (Ra), and extend film life across every stage of your polishing process.

4.Specifications (Specs) of XYT Lapping Film

The performance and selection of a lapping film hinge on a set of precise specifications. Below are the key parameters you should consider when specifying or choosing an XYT lapping film for your application.

1. Abrasive Material

• Type: Diamond, SiC, Al₂O₃, CeO₂, SiO₂, etc.

• Purity: ≥ 99 % (for synthetic diamonds and specialty oxides).

• Particle-Size Distribution: ± 10 % tolerance around nominal grit.

2. Grit / Micron Size

• Range: 0.02 µm (≈ 20000#) to 120 µm (≈ 60#)

• Standard Grades:

  • Ultra-fine: 0.02–0.3 µm (20000#–12000#)

  • Fine: 0.5–3 µm (10000#–4000#)

  • Medium: 5–15 µm (3000#–240#)

  • Coarse: 30–120 µm (120#–60#)

3. Film Backing

• Material: Polyester (PET), Polycarbonate (PC)

• Thickness: 3 mils (75 µm), 5 mils (125 µm), or custom

• Flatness Tolerance: ± 0.005 mm across the roll

• Tear Strength: ≥ 45 N/mm

• Temperature Rating: –20 °C to +150 °C

4. Coating & Loading

• Coating Method: Slurry, Electrostatic, Precision (Shot-Pin)

• Abrasive Loading: 12–30 g/m² per side, dependent on method and grit

• Resin Layer (Binder) Thickness: 2–5 µm

• Total Coating Thickness: 5–8 µm (abrasive + resin)

5. Adhesive System

• Options:

  • Plain Film: Non-adhesive, for fluid or mechanical fixturing

  • PSA (Pressure-Sensitive Adhesive):

    • Peel strength: 300–500 g/cm

    • Release liner color-coded by grit for quick identification

6. Physical & Mechanical Properties

• Tensile Strength: ≥ 100 MPa (backing only)

• Elongation at Break: ≥ 100 %

• Hardness of Binder: Shore A 80 after cure

• Chemical Resistance: Water, alcohols, light oils

7. Identification & Packaging

• Color Coding: Industry-standard film colors tied to grit size

• Labeling: Lot number, grit, coating method, backing, batch date

• Roll Length: Standard 20 m, 50 m, or custom lengths

• Width Options: 10 mm to 610 mm (custom slitting available)

Summary Specification Table

By matching these specifications to your process requirements—whether it’s coarse stock removal or final optical polishing—you ensure consistent, high-precision results and optimal lapping-film performance.

5.Grits vs Microns Chart, Surface-finish and Common Application

Here’s a concise grits-vs-microns reference chart for lapping films, showing approximate grits, typical surface-finish (Ra) ranges, and common applications:

Quick Explanations:

• Ra (Roughness Average) indicates the average deviation of surface peaks and valleys, measured in micrometers (µm).

• Common Applications move from heavy cutting and sanding at high micron values to optical-grade polishing at sub-micron levels.

6.Applications of Lapping Film

Lapping film’s precision, consistency, and flatness control make it indispensable across a wide range of industries. Below are the primary application areas and how lapping film is used in each:

1. Fiber-Optic Connector Polishing

• Use Case: Endface finishing of ferrules (LC, SC, FC, ST, MPO/MTP, TMT etc) to ensure low insertion loss and high return loss.

• Typical Grits: 30 or 15µm → 9 µm → 3 µm → 1 or 0.5 µm → 0.02 µm

• Benefits: Uniform microscopic flatness; minimal subsurface damage; reproducible optical performance.

2. Semiconductor & Electronics

• Wafer Planarization: Final polishing of silicon, GaAs, InP wafers for CMP processes.

• PCB Deburring & Edge Rounding: Removal of micro-burrs and sharp edges on multilayer boards.

• Grits Used: 0.5–3 µm for CMP; 15–30 µm for PCB prep.

• Benefits: Controlled material removal; high throughput; compatibility with automated fixtures.

3. Metalworking & Aerospace Components

• Valve Seats & Fuel System Parts: Surface finishing for sealing faces and high-precision mating surfaces.

• Bearings & Hydraulic Components: Flatness tuning for ultra-tight tolerance fits.

• Grits Used: 30–80 µm for bulk removal; 6–15 µm for final metrology prep.

• Benefits: Consistent pressure distribution; elimination of chatter; long service life on hard alloys.

4. Medical Devices

• Surgical Instruments & Implants: Polishing of stainless steel, titanium, and cobalt-chrome parts to reduce bacterial adhesion.

• Catheter & Cannula Tips: Achieving mirror finishes on polymer or metal components.

• Grits Used: 3–9 µm for initial smoothing; 0.5–1 µm for final polish.

• Benefits: Biocompatible finishes; reproducible surface roughness; improved fatigue resistance.

5. Glass, Ceramics & Optics

• Lens & Prism Polishing: Final finishing of optical elements to achieve nanometer-scale surface roughness.

• Ceramic Components: Surface preparation for bond coating or sealing.

• Grits Used: 0.02–0.5 µm (ceria, diamond); 1–6 µm (SiC).

• Benefits: Low subsurface damage; excellent edge control; high removal uniformity.

By selecting the appropriate grit sequence, coating technology, and film backing, lapping films deliver consistent, high-precision surface finishes tailored to each of these demanding applications.