FR4 Machining Services

DEK's FR4 machining service produces test fixtures, probe plates, insulators and spacers from UL 94 V-0 glass-epoxy laminate to ±0.01 mm. Diamond tooling, backing plates and dust extraction prevent delamination.

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±0.01 mm
Features Under 100 mm
3–5 days
Prototype Lead Time
UL 94 V-0
Flammability Rating

FR4 machined insulator plate on dark workshop table

ISO 9001:2015 Certified AS9100D and ISO 13485 certified

Why FR4 CNC Machining Suits Test Fixtures

FR4 is the same flame-retardant glass-epoxy laminate as the printed circuit boards it sits next to, rated UL 94 V-0, with dielectric strength of 20 kV/mm and stiffness no unfilled plastic matches. It is one of the laminates in our plastic CNC machining services.

It is also abrasive, dusty and quick to delaminate under dull tooling. We machine it on the same 3-, 4- and 5-axis mills as your metal parts, with PCD and diamond tooling, sacrificial backing and vacuum extraction. Background is in our FR4 and G10 machining guide.

FR4 machining since 2002
ISO 9001:2015, ISO 13485 and AS9100D
Engineer-reviewed quote within 6 hours
Batches from 1 to 10,000+ pieces

Assorted machined plastic parts in green and yellow

FR4 Grades We Machine

Glass-epoxy laminates chosen by flame rating and service temperature. Standard FR-4 runs to 130 °C continuous with 0.10% water absorption.

FR-4 NEMA grade
UL 94 V-0, 0.4–50 mm sheet
The standard natural yellow-green laminate for fixtures, insulators and spacers; 275–310 MPa tensile strength lengthwise and 1.85 g/cm³ density.
High-Tg FR-4
Tg 170–180 °C
For fixtures used in hot testing, reflow tooling and parts that sit near heat sources, where standard FR-4 at 130 °C continuous is not enough.
FR-5 / G-11
155–180 °C continuous
Higher-temperature epoxy laminates for insulating parts that must keep stiffness above the service limit of standard FR-4 grades.

CNC milling cutter machining FR4 laminate with dust extraction

±0.01 mm
Features under 100 mm
±0.02 mm
Long plates and true position
Ra 1.6–3.2
As-machined finish, µm

FR4 Machining Capabilities at DEK

Milling, drilling, turning and profiling of laminate sheet, rod and tube, with in-plane expansion of 11–15 µm/m·K close to steel.

1

CNC Milling

CNC milling on 3-, 4- and 5-axis machines for fixture plates, probe plates, insulator barriers, brackets and enclosure panels.
2

High-Density Drilling

Probe and pin arrays drilled with PCD drills at 0.5–3 mm diameter, holding ±0.02 mm true position across 500 mm plates. See CNC drilling.
3

CNC Turning

CNC turning of rod and tube into standoffs, bushings, coil forms and insulating spacers for electrical assemblies.
4

Profiling & Slotting

FR4 sheet machining from 0.4 mm with compression routers, followed by edge sealing, ultrasonic cleaning and press-fit metal bushings and pins.

Design & Machining Tips for FR4

What our engineers check on every laminate drawing to avoid delamination, fraying and bowed plates.

1

Delamination Avoidance

Plies separate at hole exits and routed edges under dull tools or deep step-downs. We drill onto sacrificial backing, take light final passes and chamfer edges 0.3 mm.
2

Abrasive Tooling

FR4 wears carbide within a few parts. We use PCD and diamond-coated tools, track tool life per hole count and include tool consumption in the quote.
3

Dust Extraction

Glass and epoxy dust is a respiratory hazard and abrasive to machine ways; parts are cut with vacuum extraction or filtered flood coolant, then ultrasonically cleaned.
4

Flatness on Thin Plates

Cutting one face releases lay-up stress and bows thin fixture plates. We machine both faces evenly; flatness of 0.1 mm per 300 mm is realistic on 5 mm sheet.
5

Corners, Walls and Webs

Specify 0.5 mm internal radii and avoid features thinner than 1 mm. Keep 1.0 mm between adjacent probe holes, 1.5 mm on plates over 200 mm.
6

Threads and Inserts

Tapped FR4 threads hold light loads only. Specify press-fit metal inserts for cyclic loads and oversize clearance holes by 0.1 mm.

When to Choose FR4 vs G10, Ultem or Aluminum

FR4 is the default near electrical equipment or wherever a flame rating is specified; most test fixtures pair an FR4 probe plate with an aluminum frame.

Criteria	This MaterialFR4	G10	Ultem (PEI)	Aluminum
Choose it for	Fixture plates	Cryogenic	Medical, sockets	Frames
Flame rating	UL 94 V-0	None	UL 94 V-0	–
Max temp	130 °C	–	170 °C	–
Tolerances	±0.01 mm	Near-identical	Tighter	Tighter
Insulates	Yes	Yes	–	No
Cost	Lower	–	Far higher	–

Where Machined FR4 Parts Are Used

From bed-of-nails probe plates to battery pack insulators, FR4 parts insulate, stay stiff and keep alignment with steel pins.

Finishing Options for Machined FR4 Parts

CNC machining plus finish for FR4: anodizing, plating and vapor polishing do not apply to glass-epoxy laminate.

FR4 Finishes

As-machined
Bead blasting
Edge sealing
Painting
Laser marking & engraving

Need another finish or a flame rating? Ask our engineers.

FR4 Machining FAQs

Common questions about flame retardant laminate machining, delamination and tolerances.

Can FR4 be CNC machined?

Yes. FR4 mills, drills and turns accurately with PCD or diamond-coated tooling, backing plates and dust extraction. The failure modes are tool wear, delamination at hole exits and routed edges, and dust, all of which a laminate-ready process controls.

Is FR4 flame retardant?

Yes. FR4 is rated UL 94 V-0, meaning it self-extinguishes within 10 seconds of flame removal without dripping. That rating is the main reason to specify FR4 over G10 for parts in or near electrical equipment.

How do you prevent delamination in FR4 CNC machining?

Sharp diamond tooling, sacrificial backing under every drilled hole, compression routers on sheet, light final passes and a 0.3 mm edge chamfer. Dull tools and heavy step-downs are what pull plies apart.

What tolerance can you hold on machined FR4 parts?

±0.01 mm on features under 100 mm, ±0.02 mm on long plates and on hole-pattern true position across probe fields. In-plane expansion is close to steel, so FR4 fixtures stay aligned with steel pins and aluminum frames.