CEM-1 Single-Layer PCB Fabrication

Cost-Optimised Rigid Boards and CEM PCB 1 (Single-Layer PCB) for Home Appliances, LED Drivers & General Electronics

What Is a CEM-1 PCB?

CEM-1 (Composite Epoxy Material, type 1) is a hybrid laminate consisting of:

Woven-glass cloth on the copper side (for dimensional stability)
Cellulose paper core (for punchability and low cost)
Epoxy resin system bonding the layers

Because CEM-1 is glass-reinforced on only one face, it bridges the gap between full FR-4 (all-glass) and phenolic (all-paper) substrates, delivering moderate mechanical strength at roughly 70 % of FR-4 cost.

Property	Typical Value*	Design Impact
Dielectric constant (εr, 1 MHz)	≈ 4.5	Impedance control to ~100 MHz is feasible
Loss tangent (1 MHz)	0.02	Acceptable for low-to-mid-frequency digital/analog
Glass-transition temperature (Tg)	~110 °C	Survives tin-lead wave solder; marginal for Pb-free reflow
Coefficient of thermal expansion (Z)	70–85 ppm / °C	Slightly higher than FR-4; manage via aspect-ratio ≤ 6 : 1
Thermal conductivity	0.32 W/m·K	Better heat spreading than phenolic

Always confirm with the laminate datasheet supplied for production.

Why Choose Single-Layer CEM-1 PCBs?

Ultra-competitive BOM

~30 % cheaper than FR-4 at volume without sacrificing safety ratings (UL 94 V-0 available).

Good Electrical Insulation

CTI ≥ 175 V supports appliance Class I & II requirements.

Excellent Punchability

Tabs, slots and IO cut-outs can be punched in one hit—no costly routing.

Reasonable Thermal Headroom

Tg ≈ 110 °C handles wave solder and selective-solder processes.

Low Warpage

Glass layer on the copper side minimises bow/twist during soldering.

Typical Applications

Coffee-machine & microwave oven control boards
CFL / LED bulb driver boards (< 25 W)
Low-frequency audio amplifiers (≤ 50 kHz)
IR remote transmitters & sensor keypads
Small SMPS primary-side boards (≤ 50 kHz switching)

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Manufacturing Workflow (Single-Layer CEM-1)

Step	Process Note	Best-Practice Parameter
Panel CAM	Gerber & netlist DRC, punch-tool map	Min clearance 0.25 mm
Drilling / Punching	Use carbide bits for holes < 1 mm; punch larger slots	Hit-rate ≤ 200 hits/bit
Copper Patterning	Dry-film or LDI; cupric chloride etch	Min trace/space 0.20 mm
Solder Mask	LPI epoxy, UV cure	Mask opening ≥ 80 µm
Surface Finish	OSP for cost; Sn > 8 µm for long shelf life	Pb-free HASL only if profile < 245 °C
Depanelisation	Steel rule punch or singulation	Burr ≤ 0.05 mm
Electrical Test	Flying probe 50–100 pts/s	HiPot 250 V, isolation ≥ 10 MΩ

Design Guidelines (Engineers’ Quick Reference)

Board thickness: 1.0 mm (handheld) or 1.6 mm (appliance)
Copper weight: 35 µm standard; 70 µm for ≥ 2 A traces
Single-sided PTH: Avoid; if jumpers needed, use solder bridges or rivets
Min hole Ø (NPTH): 0.80 mm (to suit punch tooling)
V-cut: 30° blade, residual web 0.25 mm
Thermal relief: For pads > 3 mm keep spoke width ≥ 0.25 mm to avoid cold joints

Thermal Tip: For LEDs or TO-220 devices, add an external aluminium slug or thick-copper jumper on the component side to compensate for CEM-1’s modest 0.32 W/m·K conductivity.

Comparing CEM-1 vs FR-4 vs Phenolic (1-Layer)

Metric	FR-4	CEM-1	Phenolic
BOM cost (relative)	1.0	0.7	0.4
Punchability	Moderate	Excellent	Excellent
Pb-free reflow	✔	Borderline	✖
Wave solder	Excellent	Good	Fair
Mechanical strength	High	Medium	Low
UL 94 rating	V-0	V-0	HB / V-0

CEM-1 delivers the sweet-spot for appliance-grade cost savings without dropping below UL V-0 safety.

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Material Deep-Dive: Single-Layer Budget Substrates

1 CEM-1 PCB – 1 Layer

Structure: glass-cloth (copper side) + cellulose paper, epoxy bonded.
Electrical: εr ≈ 4.5; suitable to ~100 MHz digital.
Thermal: Tg ≈ 110 °C → wave solder yes; Pb-free reflow marginal.
Processing: punches cleanly; V-cut 30°; use peelable mask for test pads.
Use-cases: coffee-machine controllers, CFL/LED bulb drivers, audio amps ≤50 kHz, remote-control keypads.

2 Phenolic PCB – 1 Layer (FR-1 / FR-2)

Structure: paper core + phenol-formaldehyde resin (SRBP). No glass.
Electrical: εr ≈ 5.1; good to ~30 MHz analog.
Thermal: Tg 100 – 105 °C → wave/hand solder only; reflow not recommended.
Processing: carbide tooling, punch/rout; vias via rivets or jumpers.
Use-cases: toy circuits, analog TV tuner modules, wall-charger primaries, disposable medical testers.

Design Rules (Cost-Optimised 1-Layer Rigid Boards)

Parameter	CEM-1	Phenolic
Min track / gap	0.20 / 0.20 mm	0.25 / 0.25 mm
Min NPTH drill	0.80 mm	0.90 mm
Copper weight	35 µm standard	35 µm (50 µm for >1 A)
Board thickness	1.0 / 1.6 mm	1.2 / 1.6 mm
Max punched panel	450 × 600 mm	350 × 450 mm

Engineering tip: on phenolic boards, keep continuous currents >1 A on ≥2 mm tracks or add external Cu jumpers / Al heat-sinks.

Cost & Performance Snapshot

Property	FR-4	CEM-1	Phenolic
Relative cost	1.0×	0.7×	0.4×
Punchability	Moderate	Excellent	Excellent
Wave-solder survival	Excellent	Good	Fair
Pb-free reflow	✔	Borderline	✖
Mechanical strength	High	Medium	Low
UL-94 rating	V-0	V-0	HB (> some grades V-0)

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Why Source CEM-1 Boards from HighPCB?

Hybrid tooling – CNC + high-speed steel-rule punch lines for perfect edge finish.
Process-controlled wave profiles for epoxy/paper laminates (ΔT < 3 °C across panel).
3-day quick-turn prototypes; mass production within 7–10 days.
End-to-end service – stencil, assembly, functional test at IPC-A-610 Class 2.

Ready to slash PCB cost without compromising safety?
Request your instant CEM-1 quotation from HighPCB today and accelerate your next appliance or LED design to market.