FR4 (Glass-Epoxy Laminate)

Physical properties

Laser processing

⚠️ SEVERE HAZARD: Thermal processing (laser) and mechanical processing (milling, drilling) of FR4 generates glass fiber dust (amorphous silica) and epoxy resin particulate. Glass fibers are highly irritating to skin, eyes, and respiratory tract. Prolonged exposure poses long-term health risks. FFP3/P3 mask mandatory, non-negotiable.

CO₂: Technically cuttable with high-power CO2 laser, but strongly discouraged. The glass fiber does not vaporize and generates crystalline silica particulate highly abrasive to laser optics and extremely hazardous for the respiratory tract. Surface engraving for copper removal (PCB prototyping) is practiced industrially but requires professional HEPA extraction systems.

Diode: Not applicable.

Fiber: Fiber lasers are used industrially for cutting and marking FR4. All warnings about glass fiber dust remain valid.

CNC / milling processing

CNC milling of FR4 for PCB (isolation routing) is the quintessential maker application. Requires dedicated solid carbide (tungsten carbide) end mills — never HSS, which wears out in seconds. Glass fiber is extremely abrasive: expect very short tool life. High spindle speed (20,000–30,000 RPM), moderate feed rates, low chip loads. Dedicated extraction mandatory: the particulate is invisible and hazardous.

Post-processing

Sanding: Sanding possible with silicon carbide abrasive paper, always wet to limit airborne glass fiber dust. FFP3 mask mandatory even for manual sanding.

Gluing: Bondable with two-component epoxy adhesives after surface abrasion. The copper surface (if present) must be removed or abraded in the bonding area.

Over time: Excellent dimensional stability and moisture resistance over time. Does not degrade significantly under normal PCB operating conditions. Immune to common chemicals used in PCB etching processes (ferric chloride, ammonium persulfate).

Common defects

• Layer delamination during milling due to excessive feed rates or worn tools
• Imprecise drilling with exit burr on the back of the panel — use a sacrificial backing board
• Rapid and sudden HSS tool failure — use carbide cutters exclusively

Safety

Recommended PPE: mask_p3, eye_protection_goggles, gloves_nitrile

⚠️ CAUTION: Dust produced by mechanical or laser processing of FR4 is highly irritating and potentially harmful. Glass fibers penetrate skin and lungs. FFP3/P3 mask (not FFP1 or FFP2), sealed goggles, nitrile gloves, and dedicated HEPA-filtered extraction are non-negotiable equipment. Do not blow off residues with compressed air.

Availability and formats

Commercial formats: panels 100×160mm, panels 200×300mm, sheets 1.0 / 1.6 / 2.0mm, with copper on one or both sides (35µm or 70µm)

Related materials

Sources

• IPC-4101 — Specification for Base Materials for Rigid and Multilayer Printed Boards
• NEMA LI 1 — Industrial Laminated Thermosetting Products
• Isola Group — FR406 Laminate Datasheet