PCB Stack-Up Library: 4/6/8-Layer, HDI, Metal-Core, RF and Rigid-Flex

Construction

Example

4-layer rigid (signal / ground / power / signal)

Layers: 4L

#	Layer	Thickness
1	Silkscreen · TOP
2	Solder mask · TOP	20 µm
3	Copper · L1	35 µm
4	Prepreg · PP1	0.2 mm
5	Copper · L2 / GND	35 µm
6	Core · Core	1.2 mm
7	Copper · L3 / PWR	35 µm
8	Prepreg · PP2	0.2 mm
9	Copper · L4	35 µm
10	Solder mask · BOT	20 µm
11	Silkscreen · BOT

Applications: Consumer mainboards / industrial control / power modules

Legend

Silkscreen
Solder mask
Copper
Prepreg
Core
Dielectric
Metal core
Coverlay
Adhesive
Polyimide base film

Rigid multilayer

4-layer rigid (signal / ground / power / signal)

4L

#	Layer	Thickness
1	Silkscreen · TOP
2	Solder mask · TOP	20 µm
3	Copper · L1	35 µm
4	Prepreg · PP1	0.2 mm
5	Copper · L2 / GND	35 µm
6	Core · Core	1.2 mm
7	Copper · L3 / PWR	35 µm
8	Prepreg · PP2	0.2 mm
9	Copper · L4	35 µm
10	Solder mask · BOT	20 µm
11	Silkscreen · BOT

Applications: Consumer mainboards / industrial control / power modules

6-layer rigid (two cores, three prepreg bonds)

6L

#	Layer	Thickness
1	Silkscreen · TOP
2	Solder mask · TOP	20 µm
3	Copper · L1	35 µm
4	Prepreg · PP1	0.1 mm
5	Copper · L2 / GND	18 µm
6	Core · Core 1	0.2 mm
7	Copper · L3	18 µm
8	Prepreg · PP2	0.4 mm
9	Copper · L4	18 µm
10	Core · Core 2	0.2 mm
11	Copper · L5 / PWR	18 µm
12	Prepreg · PP3	0.1 mm
13	Copper · L6	35 µm
14	Solder mask · BOT	20 µm
15	Silkscreen · BOT

Applications: Industrial mainboards / comms modules / instrument boards

8-layer rigid (four planes, four routing layers)

8L

#	Layer	Thickness
1	Silkscreen · TOP
2	Solder mask · TOP	20 µm
3	Copper · L1	35 µm
4	Prepreg · PP1	0.1 mm
5	Copper · L2 / GND	18 µm
6	Core · Core 1	0.2 mm
7	Copper · L3	18 µm
8	Prepreg · PP2	0.2 mm
9	Copper · L4 / GND	18 µm
10	Core · Core 2	0.3 mm
11	Copper · L5 / PWR	18 µm
12	Prepreg · PP3	0.2 mm
13	Copper · L6	18 µm
14	Core · Core 3	0.2 mm
15	Copper · L7 / GND	18 µm
16	Prepreg · PP4	0.1 mm
17	Copper · L8	35 µm
18	Solder mask · BOT	20 µm
19	Silkscreen · BOT

Applications: Server boards / networking / machine vision / medical

HDI (high-density interconnect)

1-stage HDI (1+N+1, laser microvias on the outer layers)

1+N+1

#	Layer	Thickness	Note
1	Silkscreen · TOP
2	Solder mask · TOP	20 µm
3	Copper · L1	30 µm
4	Prepreg · Buildup (top)	0.1 mm	Laser-drilled buildup dielectric; the microvia penetrates this layer only.
5	Copper · L2 / GND	18 µm
6	Core · Core 1	0.2 mm
7	Copper · L3	18 µm
8	Prepreg · PP (core assembly)	0.2 mm	Mechanically drilled inner core assembly; through and buried vias are formed here.
9	Copper · L4	18 µm
10	Core · Core 2	0.2 mm
11	Copper · L5 / PWR	18 µm
12	Prepreg · Buildup (bottom)	0.1 mm	Laser-drilled buildup dielectric; the microvia penetrates this layer only.
13	Copper · L6	30 µm
14	Solder mask · BOT	20 µm
15	Silkscreen · BOT

Applications: 0.65 mm pitch BGA / wireless modules / handheld mainboards

2-stage HDI (2+N+2, two buildup cycles)

2+N+2

Silkscreen · TOP

Solder mask · TOP

20 µm

Copper · L1

30 µm

Prepreg · Buildup 2 (top)

0.1 mm

Copper · L2 / GND

18 µm

Prepreg · Buildup 1 (top)

0.1 mm

Copper · L3

18 µm

Core · Core 1

0.2 mm

Copper · L4 / GND

18 µm

Prepreg · PP (core assembly)

0.3 mm

Copper · L5 / PWR

18 µm

Core · Core 2

0.2 mm

Copper · L6

18 µm

Prepreg · Buildup 1 (bottom)

0.1 mm

Copper · L7 / GND

18 µm

Prepreg · Buildup 2 (bottom)

0.1 mm

Copper · L8

30 µm

Solder mask · BOT

20 µm

Silkscreen · BOT

#	Layer	Thickness	Note
1	Silkscreen · TOP
2	Solder mask · TOP	20 µm
3	Copper · L1	30 µm
4	Prepreg · Buildup 2 (top)	0.1 mm	Laser-drilled buildup dielectric; the microvia penetrates this layer only.
5	Copper · L2 / GND	18 µm
6	Prepreg · Buildup 1 (top)	0.1 mm	Laser-drilled buildup dielectric; the microvia penetrates this layer only.
7	Copper · L3	18 µm
8	Core · Core 1	0.2 mm
9	Copper · L4 / GND	18 µm
10	Prepreg · PP (core assembly)	0.3 mm	Mechanically drilled inner core assembly; through and buried vias are formed here.
11	Copper · L5 / PWR	18 µm
12	Core · Core 2	0.2 mm
13	Copper · L6	18 µm
14	Prepreg · Buildup 1 (bottom)	0.1 mm	Laser-drilled buildup dielectric; the microvia penetrates this layer only.
15	Copper · L7 / GND	18 µm
16	Prepreg · Buildup 2 (bottom)	0.1 mm	Laser-drilled buildup dielectric; the microvia penetrates this layer only.
17	Copper · L8	30 µm
18	Solder mask · BOT	20 µm
19	Silkscreen · BOT

Applications: 0.4 mm pitch BGA / SiP modules / camera modules / RF front end

Metal core (MCPCB)

Single-layer aluminium MCPCB (copper / thermal dielectric / aluminium base)

1L

#	Layer	Thickness	Note
1	Silkscreen · TOP
2	Solder mask · TOP	20 µm
3	Copper · L1	35 µm
4	Dielectric · Thermal dielectric	75 µm	Thermally conductive dielectric, carrying heat transfer and electrical isolation at once: thinning it lowers thermal resistance but eats into the breakdown margin. Available thermal conductivity grades are 1 / 2 / 3 / 8 / 12 W/m·K.
5	Metal core · Base	1.0 mm	The aluminium base itself, acting as both structural support and heat path; it normally mounts straight onto a chassis or heatsink.

Applications: LED lighting boards / street and high-bay luminaires / PSU heat spreaders

Double-layer aluminium MCPCB (two copper layers over dielectric and base)

2L

#	Layer	Thickness	Note
1	Silkscreen · TOP
2	Solder mask · TOP	20 µm
3	Copper · L1	35 µm
4	Core · Core	0.2 mm
5	Copper · L2	35 µm
6	Dielectric · Thermal dielectric	100 µm	Thermally conductive dielectric, carrying heat transfer and electrical isolation at once: thinning it lowers thermal resistance but eats into the breakdown margin. Available thermal conductivity grades are 1 / 2 / 3 / 8 / 12 W/m·K.
7	Metal core · Base	1.5 mm	The aluminium base itself, acting as both structural support and heat path; it normally mounts straight onto a chassis or heatsink.

Applications: Driver-on-board LED modules / automotive lamp control / motor drives

Heavy copper

4-layer heavy copper (3 oz outer, 6 oz inner)

4L

#	Layer	Thickness	Note
1	Silkscreen · TOP
2	Solder mask · TOP	20 µm
3	Copper · L1	105 µm (3 oz)	Heavy copper; etched sidewalls are sloped, so trace width tolerance is wider than for standard copper.
4	Prepreg · PP1	0.3 mm
5	Copper · L2	210 µm (6 oz)	Heavy copper; etched sidewalls are sloped, so trace width tolerance is wider than for standard copper.
6	Core · Core	0.8 mm
7	Copper · L3	210 µm (6 oz)	Heavy copper; etched sidewalls are sloped, so trace width tolerance is wider than for standard copper.
8	Prepreg · PP2	0.3 mm
9	Copper · L4	105 µm (3 oz)	Heavy copper; etched sidewalls are sloped, so trace width tolerance is wider than for standard copper.
10	Solder mask · BOT	20 µm
11	Silkscreen · BOT

Applications: Inverter and servo power stages / EV chargers / energy-storage busbars / automotive DC-DC

High-frequency hybrid

4-layer hybrid (Rogers 4350B over FR-4)

4L

#	Layer	Thickness	Note
1	Silkscreen · TOP
2	Solder mask · TOP	20 µm
3	Copper · L1	35 µm	RF laminate carrying the controlled-impedance traces. Its thermal expansion and bonding behaviour both differ from FR-4, so the lamination cycle has to suit the two materials at once.
4	Core · RF core (Rogers 4350B)	0.254 mm	RF laminate carrying the controlled-impedance traces. Its thermal expansion and bonding behaviour both differ from FR-4, so the lamination cycle has to suit the two materials at once.
5	Copper · L2	35 µm	Reference plane for the RF layer; it must sit on the opposite face of the RF dielectric. Once the reference drops to the FR-4 layer below, the controlled impedance is lost.
6	Prepreg · PP (FR-4)	0.2 mm
7	Copper · L3	35 µm
8	Core · Core (FR-4)	0.8 mm
9	Copper · L4	35 µm
10	Solder mask · BOT	20 µm
11	Silkscreen · BOT

Applications: Antenna modules / RF front end and PAs / radar and mmWave modules

Flex and rigid-flex

2-layer flex (polyimide base, copper both faces, coverlay)

2L

#	Layer	Thickness	Note
1	Coverlay · TOP	25 µm	Coverlay replaces soldermask — a polyimide film bonded with an adhesive layer, which does not crack under repeated flexing the way soldermask ink does.
2	Adhesive · TOP	25 µm
3	Copper · L1	18 µm	Copper in the flex area; thinner copper bends better, while thick copper sees markedly higher tensile stress on the outer face of a bend.
4	Polyimide base film · Base	25 µm	Polyimide base film; it sets the basic bend behaviour of the flex area and is the layer the neutral bend axis of the two copper faces runs through.
5	Copper · L2	18 µm	Copper in the flex area; thinner copper bends better, while thick copper sees markedly higher tensile stress on the outer face of a bend.
6	Adhesive · BOT	25 µm
7	Coverlay · BOT	25 µm	Coverlay replaces soldermask — a polyimide film bonded with an adhesive layer, which does not crack under repeated flexing the way soldermask ink does.

Applications: Camera and display flex / interposers in folded assemblies / medical probe leads

4-layer rigid-flex (FR-4 rigid sections over a continuous flex core)

4L

#	Layer	Thickness	Note
1	Silkscreen · TOP
2	Solder mask · TOP	20 µm
3	Copper · L1	35 µm
4	Prepreg · PP1 (FR-4, rigid area)	0.2 mm
5	Coverlay · Flex TOP	25 µm	Coverlay replaces soldermask — a polyimide film bonded with an adhesive layer, which does not crack under repeated flexing the way soldermask ink does.
6	Adhesive · Flex TOP	25 µm
7	Copper · L2	18 µm	Copper in the flex area; thinner copper bends better, while thick copper sees markedly higher tensile stress on the outer face of a bend.
8	Polyimide base film · Flex core	50 µm	Flex core; it must run continuously through the rigid-to-flex transition rather than terminating at it.
9	Copper · L3	18 µm	Copper in the flex area; thinner copper bends better, while thick copper sees markedly higher tensile stress on the outer face of a bend.
10	Adhesive · Flex BOT	25 µm
11	Coverlay · Flex BOT	25 µm	Coverlay replaces soldermask — a polyimide film bonded with an adhesive layer, which does not crack under repeated flexing the way soldermask ink does.
12	Prepreg · PP2 (FR-4, rigid area)	0.2 mm
13	Copper · L4	35 µm
14	Solder mask · BOT	20 µm
15	Silkscreen · BOT

Applications: Folding devices / automotive clusters and cameras / industrial handhelds / medical imaging probes