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LML Metal Products Ltd.No. D309, Yunchuang E Valley, No. 3 Huanshi West Road, Tangxia Town, Dongguan City, Guangdong,China
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Materials

CNC Machining in FR4

FR4, a fiberglass-reinforced epoxy laminate, boasts superior electrical insulation, high mechanical strength (bending resistance ≥340MPa), and thermal stability (-100°C to 130°C). Its CNC machinability enables precision-machined PCB substrates and insulating components via optimized tooling—tungsten carbide cutters at 100-200 m/min

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FR4

Designers and engineers frequently choose FR4 for CNC machining and CNC milling parts. Makes sense. This all-purpose metal has been proven to offer:
  • * Excellent machinability
  • * High strength
  • * Hardness
  • * Heat tolerance
  • * Corrosion resistance
  • * Superior electrical insulation
  • * Low weight
  • * Low cost
  • * Overall versatility

Description

Applications
PCB substrates ∙ Electrical insulators ∙ Switchgear components ∙ Test jigs ∙ RF microwave circuits
Strengths
Superior electrical insulation ∙ High mechanical rigidity ∙ Flame retardant (UL94 V-0) ∙ Excellent dimensional stability ∙ Moisture resistance
Weaknesses
Brittle fracture tendency ∙ Anisotropic properties (weak Z-axis) ∙ High tool wear during machining ∙ Limited high-frequency performance (>1 GHz)
Process compatibility
CNC machining ∙ Laser cutting ∙ Waterjet cutting ∙ Punch pressing
Surface Treatment
Solder mask application ∙ Immersion gold/ENIG ∙ HASL finishing ∙ Silkscreen printing

Characteristics

Price
$5-15/sheet (1.6mm thickness) ∙ High machining cost (requires diamond-coated tools)
Lead Time
CNC: 3-7 days (depending on layer complexity) ∙ No thermal curing required
Wall Thickness
Standard: 0.4-3.2mm (Min. machinable: 0.2mm for ≤50mm² areas)
Tolerances
Drilling: ±0.05mm ∙ Outline machining: ±0.1mm ∙ Layer alignment: ±0.075mm
Max part size
500 × 600mm (standard panel size) ∙ Custom panels up to 1200 × 1000mm

FR4 Material Processing Technologies

Process TechnologyProcess CharacteristicsFR4 TypeApplications
High-Temperature LaminationHigh pressure (300-500 psi) at 170-190°CAll typesMultilayer PCB construction
Precision Drilling±0.05mm accuracy with carbide bitsStandard, High TgThrough-hole vias, component mounting
Laser MicromachiningUV laser ablation (355nm), 20-100μm precisionAll typesMicrovias <0.15mm, HDI PCBs
PhotolithographyLDI/contact exposure, chemical etchingCopper-cladCircuit pattern definition
Surface FinishingElectroless nickel immersion gold (ENIG)All typesSolderable surfaces, contact pads
CNC Routing±0.1mm dimensional accuracyStandard, Lead-freePCB outline cutting
Solder Mask ApplicationUV-curable epoxy LPI coatingAll typesInsulation, protection

Key Technical Points

  • High-Temperature Lamination: Core process for FR4, ensures complete curing of epoxy resin under heat and pressure.
  • Precision Drilling: Critical for multi-layer PCBs requiring ±0.05mm hole position accuracy.
  • Laser Micromachining: Essential for creating microvias less than 0.15mm in high-density interconnect (HDI) designs.
  • Surface Finishing: ENIG (Electroless Nickel Immersion Gold) provides optimal soldering surface and oxidation resistance.
  • FR4 Type Differences:
    • Standard FR4: Glass transition temperatureTg 130-140°C, general purpose
    • High Tg FR4: Heat deflection temperature>170°C, for lead-free reflow processes
    • Lead-free FR4: Compliant with RoHS requirements, halogen-free formulations

FR4 for Machining

​Material Properties & Machining Relevance​ FR4—a flame-retardant (UL94-V0) composite of woven fiberglass and epoxy resin—combines high mechanical strength (bending resistance ≥340 MPa) and exceptional electrical insulation . Its anisotropic structure provides stability in the XY plane but demands careful toolpath planning to prevent Z-axis delamination during cutting or drilling . Operating temperatures from -100°C to 130°C ensure reliability in electronics, though its brittleness requires specialized tooling to avoid edge chippingMachining Challenges & Best Practices​ CNC machining FR4 necessitates diamond-coated carbide tools due to rapid wear from abrasive glass fibers; optimal parameters include spindle speeds of 18,000–24,000 RPM and feed rates of 100–200 m/min . Critical processes like drilling sub-0.5mm holes or routing thin walls (<0.2mm) require peck cycles and minimized cutting forces to reduce micro-crackingPost-Processing & Precision Control​ Achieving tight tolerances (drilling: ±0.05mm; outline: ±0.1mm) relies on temperature-controlled environments to mitigate resin expansion . Surface treatments like ENIG (Electroless Nickel Immersion Gold) or solder masking enhance conductivity and corrosion resistance for PCB applicationsGET INSTANT QUOTE

Gallery of FR4 Parts Made by LML

The color of anodized finishes may exhibit some degree of variation due to standard alloy tolerance differences. Please refer to the color scheme below to observe the range of available colors.

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FAQs

LML takes the stress out of manufacturing by guaranteeing the quality and consistency of every part. Each order is dimensionally and visually inspected by our in-house quality control team to make sure it meets the LML Standard. If you’re not satisfied with your order, we’ll remake your parts as fast as possible, free of charge, or refund you - whichever you prefer.
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    "5-Axis" generally refers to the ability of a CNC machine to move the tool in five directions, which belongs to a high precision production technology.
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  • Could I have a look at your production facility for sliver contacts?
    Cold Heading & Stamping Workshop

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