General-purpose
Glass-reinforced epoxy prepreg dielectric with modest conductivity (around 1 W/m·K). Low cost; used for automotive and office electronics, power supplies and lower-power LED boards.
Guide · Metal-core PCB material
Aluminium Base Copper Clad Laminate (Al-CCL)
Aluminium base copper clad laminate (Al-CCL), also called insulated metal substrate (IMS), is the raw board used to make metal-core PCBs. It bonds a copper circuit foil to an aluminium plate through a thin, thermally conductive but electrically insulating dielectric, so heat from LEDs and power devices flows straight into the metal. This guide explains the layer build, the grades of dielectric, how to choose the aluminium alloy and thickness, and what to check on a datasheet.
- Base
- 1060 · 5052 · 6061 aluminium
- Copper
- 18 – 350 µm (0.5 – 10 oz)
- Dielectric
- ≈ 1 – 5 W/m·K, 75 – 150 µm
- Use
- LED, power, automotive
What is an aluminium base copper clad laminate?
A standard FR-4 circuit board is a poor conductor of heat: its glass-epoxy core conducts only about 0.3 W/m·K. When a board carries high-power LEDs, MOSFETs or IGBTs, that heat has to go somewhere. An aluminium-base laminate replaces most of the FR-4 with an aluminium plate, which conducts heat hundreds of times better and also acts as a built-in heat spreader.
The laminate has three layers. On top is copper foil, later etched into the circuit. In the middle is a dielectric, typically an epoxy or other polymer filled with ceramic particles such as alumina or boron nitride, which insulates the circuit electrically while passing heat. At the bottom is the aluminium base, usually 0.5 – 3.0 mm thick, which spreads heat sideways and passes it into a heat sink, housing or chassis.
The thermal performance of the whole stack is dominated by the dielectric, because it is the layer with the lowest conductivity. Choosing an Al-CCL is therefore mostly a choice of dielectric grade and thickness, with the aluminium alloy and copper weight chosen to suit the mechanical and electrical design.
Typical layer build
- Copper foil
- 18, 35, 70, 105, 140 µm (0.5 – 4 oz); up to about 350 µm (10 oz) for high-current boards
- Dielectric layer
- About 50 – 200 µm, most often 75 – 150 µm; thermal conductivity ≈ 1.0 – 5.0 W/m·K, higher grades available
- Aluminium base
- 0.5, 0.8, 1.0, 1.5, 2.0 and 3.0 mm in 1060, 1100, 3003, 5052 or 6061
- Panel sizes
- Common panels include 330 × 380, 500 × 600, 500 × 1200 and 1000 × 1200 mm
Why aluminium base boards run cooler
Heat crossing a thin layer meets a resistance per unit area of thickness ÷ conductivity. Comparing a 1.6 mm FR-4 board with a 100 µm Al-CCL dielectric makes the advantage obvious:
| Layer | Thickness | Thermal conductivity | Area-specific thermal resistance |
|---|---|---|---|
| FR-4 board | 1.6 mm | ≈ 0.3 W/m·K | ≈ 53 K·cm²/W |
| Al-CCL dielectric, standard grade | 100 µm | 1.0 W/m·K | 1.0 K·cm²/W |
| Al-CCL dielectric, high grade | 100 µm | 2.0 W/m·K | 0.5 K·cm²/W |
| Al-CCL dielectric, very high grade | 100 µm | 5.0 W/m·K | 0.2 K·cm²/W |
| Aluminium base (1060) | 1.5 mm | ≈ 230 W/m·K | ≈ 0.07 K·cm²/W |
Calculated from thickness and conductivity only; contact resistance at interfaces and spreading effects are ignored. Use manufacturer datasheet values (often measured to ASTM D5470) for design.
Two lessons follow. First, every step up in dielectric conductivity, or down in dielectric thickness, lowers device junction temperature, which directly extends LED life and power-device reliability. Second, the aluminium base adds very little resistance, so the choice of alloy matters more for flatness, strength and cost than for heat flow. Thinner dielectrics, however, reduce breakdown voltage, so thermal and electrical requirements must be balanced.
Types of aluminium base laminate
High thermal conductivity
Ceramic-filled epoxy or polymer dielectric, typically 1.5 – 5 W/m·K. For high-power LED street and flood lights, power modules, motor drives and EV chargers.
High-frequency
Low-loss dielectric resins for RF and microwave circuits, such as power amplifiers and radar modules, where dielectric constant and loss must be controlled.
Bendable / formable
Thin, flexible dielectrics on soft aluminium so the board can be bent once during assembly into 3D shapes for lamps and compact housings.
Double-sided and multilayer
Two copper layers or a multilayer circuit on an aluminium base, for more complex routing; more costly and harder to make.
Prepreg for lamination
Separate thermally conductive prepregs (often 75 – 125 µm pressed) for board makers who build their own metal-core stacks; match prepreg grade to the laminate grade.
| Dielectric grade (typical) | Thermal conductivity | Typical use |
|---|---|---|
| Standard | ≈ 1.0 W/m·K | Indicator LEDs, low-power drivers, general electronics |
| Enhanced | ≈ 1.5 – 1.6 W/m·K | Mid-power LED modules, lighting strips |
| High | ≈ 2.0 – 2.2 W/m·K | High-power LED lamps, power supplies |
| Ultra-high | ≈ 3.0 – 5.0 W/m·K and above | COB LEDs, power modules, automotive headlamps, chargers |
Choosing the aluminium base alloy
The base plate is usually supplied anodised or chemically treated on the back and pretreated on the bonding face for adhesion. Typical properties of the common base alloys are below (handbook values for the stated temper).
| Alloy / temper | Thermal conductivity (W/m·K) | Tensile strength (MPa) | Yield (MPa) | Character |
|---|---|---|---|---|
| 1060-H14 | ≈ 230 | ≈ 100 | ≈ 90 | Highest conductivity, soft, economical |
| 1100-H14 | ≈ 220 | 125 | 115 | High conductivity, slightly stronger than 1060 |
| 3003-H14 | ≈ 160 | 150 | 145 | Moderate strength, good formability |
| 5052-H34 | 138 | 262 | 214 | Stronger and stiffer; resists bending during punching |
| 6061-T6 | 167 | 310 | 276 | Highest strength; machinable for precise mounting features |
Typical values from Aluminum Association and ASM data; values vary by temper. Order to a specific alloy and temper and check the certificate.
- Best heat spreading at lowest cost: 1060 or 1100, common for LED boards.
- Thin, large or punched boards: 5052-H32/H34 stays flat and resists denting during routing and V-scoring.
- Boards with machined features or structural duty: 6061-T6.
- Outdoor or automotive use: 5052 or 6061 for corrosion resistance and stiffness.
Metline supplies the base aluminium itself as sheet and coil, for example 1060 sheet and 5052 sheet, as well as finished Al-CCL panels to specification.
How to read an Al-CCL datasheet
| Property | Typical range for aluminium IMS | Why it matters |
|---|---|---|
| Thermal conductivity of dielectric | 1 – 5 W/m·K (ASTM D5470 or laser flash) | Main driver of device temperature |
| Thermal resistance of stack | Stated in °C/W or K·cm²/W for a test size | Compare only values measured on the same method and sample size |
| Dielectric breakdown voltage (AC) | Roughly 3 – 6 kV for 75 – 150 µm layers | Safety margin for mains-connected drivers |
| Peel strength of copper | Often ≥ 1.0 – 1.5 N/mm, measured as-received and after solder float at 260 °C | Resistance to pad lifting during rework and thermal cycling |
| Glass transition (Tg) | ≈ 100 – 150 °C, higher grades above | Stability at operating and soldering temperatures |
| Flammability | UL 94 V-0 for most grades | Required by most lighting and power product standards |
| Volume and surface resistivity | Reported as-received and after humidity conditioning | Insulation reliability in damp service |
| Dielectric constant / loss (1 MHz) | Dk ≈ 4 – 7, Df ≈ 0.01 – 0.03 | Relevant for switching noise and RF designs |
Always compare grades on the same test conditions: thermal resistance figures measured on different sample sizes, or conductivity measured by different methods, are not directly comparable. Ask for a test report for the batch, including Hi-Pot (high-voltage) results if the product will be mains-connected.
Standards and compliance for aluminium base laminates
Common references
- IPC-4101
- Specification for base materials for rigid and multilayer printed boards; many IMS datasheets reference it for test methods
- IPC-TM-650
- Test methods used for peel strength, Tg, thermal stress and dielectric properties
- ASTM D5470
- Steady-state method for measuring thermal impedance and conductivity of thin thermal interface materials
- UL 94 / UL 796
- Flammability rating of the laminate and recognition of the finished printed board
- RoHS and REACH
- Restriction of hazardous substances; many grades are also halogen-free for lead-free assembly
UL recognition is held by the laminate formulation and by each board fabricator's process, so check that the specific grade and your PCB maker are listed if your end product requires it.
From laminate to metal-core PCB
- Panel preparationLaminate panels are cut to working size; the aluminium face stays protected by film or anodising.
- ImagingPhotoresist is applied and exposed by photolithography or laser direct imaging to define the circuit.
- EtchingUnprotected copper is etched away; the aluminium must be shielded from etchants that attack it.
- Solder mask and finishWhite or black solder mask is printed, and pads receive HASL lead-free, ENIG, immersion silver or OSP.
- ProfilingBoards are routed, punched or V-scored. Harder bases (5052, 6061) give cleaner edges; punching needs sharp, well-maintained tools.
- TestingElectrical test, Hi-Pot test between circuit and base, and visual and dimensional checks.
Common mistakes include specifying a very thin dielectric for heat without checking breakdown voltage, choosing soft 1060 for large thin panels that then bow during routing, and comparing thermal resistance figures from different test methods.
Where aluminium base laminates are used
- LED lighting: street and tunnel lights, floodlights, high-bay industrial lights, architectural and bridge lighting, automotive headlamps and tail lamps
- Power conversion: inverters, rectifiers, DC-DC converters, motor drives, solid-state relays and voltage regulators
- Automotive electronics: power management, ignition, lighting and battery-system control boards
- EV charging and renewable energy: charger power stages and solar inverters
- Industrial electronics: power transistors, heaters and high-reliability control circuits
- Audio and consumer: amplifier output stages and display driver modules
References and standards
- IPC-4101 – Specification for Base Materials for Rigid and Multilayer Printed Boards
- ASTM D5470 – Thermal Transmission Properties of Thermally Conductive Electrical Insulation Materials
- UL 94 – Standard for Tests for Flammability of Plastic Materials for Parts in Devices and Appliances
- The Aluminum Association – Aluminum Standards and Data (properties of 1060, 1100, 3003, 5052, 6061)
- ASM International – Properties of Wrought Aluminum and Aluminum Alloys
Aluminium base copper clad laminate: frequently asked questions
What is the difference between an aluminum PCB and Al-CCL?
Al-CCL is the raw laminate: unpatterned copper foil bonded to an aluminium plate through a dielectric. An aluminium PCB (metal-core PCB) is that laminate after imaging, etching, solder mask, finishing and profiling.
Which thermal conductivity grade should I choose?
Match it to power density. Around 1 W/m·K suits low-power and general electronics; 1.5 – 2.2 W/m·K covers most LED lamps and power supplies; 3 W/m·K and above is used for COB LEDs, power modules and automotive lighting.
Is 1060, 5052 or 6061 better as the base?
1060 conducts heat best and costs least, so it is the usual LED board base. 5052 is stiffer and stays flat on large or thin panels. 6061-T6 is strongest and suits boards with machined features or structural duty.
Does a thinner dielectric always mean better cooling?
It lowers thermal resistance but also lowers breakdown voltage. For mains-connected drivers, keep enough dielectric thickness for the required Hi-Pot test and choose a higher-conductivity grade instead.
What copper thickness is standard?
35 µm (1 oz) is most common, with 18 – 140 µm widely available and thicker foils up to about 350 µm (10 oz) for high-current power boards.
What panel sizes are available?
Common panel sizes include 330 × 380, 500 × 600, 500 × 1200 and 1000 × 1200 mm, with base thicknesses from 0.5 to 3.0 mm. Other sizes can be cut on request.
Need aluminium base laminate or base sheet?
Tell us the dielectric grade, copper weight, base alloy and thickness, panel size and quantity, and we will reply with options and pricing.
