All About PCB Materials of CCL, PP, Core & Foil

 

Copper Clad Laminate (CCL)

CCL is an abbreviation of Copper Clad Laminate, which is a type of substrate material of rigid printed circuit boards with a thin layer of copper laminated on either one side or both sides, and we call it as single-sided CCL or double-sided CCL. In rigid PCB production, manufacturers use rigid CCL with rigid base materials, like resin epoxy (FR4), Aluminum, Copper, CEM, PTFE and ceramic. In flex circuit production, manufacturers use flex CCL (FCCL) with materials, like polyimide (PI) and polyester (PET).


Rigid Copper Clad Laminate (CCL)

FR-4 CCL

FR-4 (or FR4) copper clad laminate (CCL) is a rigid PCB substrate material with copper clad on either one side or both sides of FR4 base, which is a composite material composed of woven fiberglass cloth with an epoxy resin binder that is flame resistant. FR4 does not specify material, but instead of a grade of material.

FR stands for flame retardant, and does not denote that the material complies with the standard UL 94V-0 unless testing is performed to UL 94, Vertical Flame testing in Section 8 at a compliant lab. The designation FR-4 was created by NEMA (National Electrical Manufacturers Association) in 1968.

Properties of our FR-4 CCL:

Low Glass Transition Temperature (Tg) (Tg130oC – Tg140oC)

Mid Glass Transition Temperature (Tg) (Tg150oC)

- High Glass Transition Temperature (Tg) (Tg170oC)

- High Decomposition Temperature (Td) (Td>345oC)

- Dielectric Constant (Dk or Er) (@1GHz): 3.66-4.5

- Dissipation Factor (Df) (@1GHz): 0.016

- High UL Rated Flammability: 94V-0

- Low Coefficient of Thermal Expansion (CTE) (2.5%-3.8%)

- High Comparative Tracking Index (CTI): (CTI >=600V)

- Halogen-free

- Compatible with standard and lead-free assembly

- FR4 CCL thickness available from 0.2mm to 3.2mm

- Copper thickness available form 1/3oz to 3oz


Metal Core CCL

Aluminum Core or Aluminum Base Copper Clad Laminate (CCL) is made of aluminum plate, dielectric layer and copper foil by high temperature hot pressing. The alminum layer(s) are with high thermal conductivity, and the overall conductivity of the aluminum core laminate is decided by the dielectric layer. With high thermal conductivity, the dielectric may be filled with ceramic. Most aluminum PCB boards are built with single-sided CCL, while double-sided CCL for double-sided metal core PCB and multilayer hybrid aluminum core PCB manufacturing are possible at MADPCB

Properties of our Aluminum Core CCL:

- Thermal Conductivity: 1.0W/m·K, 1.5W/m·K, 2.0W/m·K, 3.0W/m·K, 4.2W/m·K, 5.0W/m·K, 7.0W/m·K

- Aluminum (Al) Alloy Style: 1060 (138 W/m·K) and 5052 (220 W/m·K)

- Copper (Cu) Style: C1100 (386 W/m·K)

-  Copper thickness available from 0.5oz to 2oz

- Glass Transition Temperature (Tg): Tg100oC, Tg120oC, Tg130oC

 - Dielectric Constant (Dk or Er) (@1MHz): 4.8

- Halogen-free

- Compatible with standard and lead-free assembly

- High UL Rated Flammability: 94V-0

- Aluminum Core CCL thickness available from 0.8mm to 2.0mm


Copper Core CCL

Similar to Aluminum Core CCL, Copper Core CCL is made of copper plate, dielectric layer and copper foil. The thermal conductivity is mainly decided by the dielectric layer and whether you your board has thermal dissipation design.

Copper Core PCB, also referred to copper substrate PCB, copper based PCB or copper clad PCB, which has 3 main design types:

1. Common copper core PCB: (with circuitry on copper layer without PTH)

2. Chip on Board (COB) copper PCB

3. Direct thermal path copper-based PCB (no insulator under the thermal path pad)

Properties of our Copper Core CCL:

- Thermal Conductivity: 3.0W/m·K, 5.0W/m·K, 7.0W/m·K

- Copper (Cu) Style: C1100 (386 W/m·K)

 - Copper thickness available from 0.5oz to 2oz

- Glass Transition Temperature (Tg): Tg100oC, Tg120oC, Tg130oC

- Dielectric Constant (Dk or Er) (@1MHz): 4.8

- Halogen-free

- Compatible with standard and lead-free assembly

- High UL Rated Flammability: 94V-0

- Aluminum Core CCL thickness available from 0.8mm to 2.0mm

 

Radio Frequency (RF) /Microwave PCB Copper Clad Laminate (CCL)

When your PCB boards designed at microwave frequencies, the key characteristics that define CCL and prepreg (PP) performance for microwave/RF printed circuit boards include dielectric constant (Dk), dissipation factor (Df), coefficient of thermal expansion (CTE), thermal coefficient of dielectric constant (TCDR), and thermal conductivity.

The high-frequency material perhaps most familiar to designers and manufacturers is PTFE (Polytetrafluoroethylene), which is a synthetic thermoplastic fluoropolymer that has excellent dielectric properties at microwave frequencies. Below is a brief outline of the major material suppliers that we have experience with as every material is processed a bit differently and it is critical to know exactly how the materials will respond to every process.

There are 4 copper clad laminate companies manufacture high-frequency materials.

 Isola High Performance PCB laminates: since their founding in 1912, Isola has been the industry leader in developing and manufacturing copper-clad laminate products used to fabricate advanced multilayer printed circuit boards (PCBs). They have an optimal balance between cost and performance when selecting base materials. Key factors microwave and millimeter wave designers must consider when choosing a high-speed RF or microwave laminate include dielectric thickness, dielectric constant and dissipation factor, and maintaining tight tolerance within a batch as well as batch-to-batch. RF high-frequency PCB designs require extremely precise controls on dielectric constant, trace widths, and dielectric thickness.

Rogers Advanced Lminates for RF/Microwave Designs: As one of the oldest public companies in USA, Rogers has a rich legacy of innovative and collaborative problem-solving techniques with our customers. In 1949, Rogers introduced the first RT/duroid® material for electronic applications and today the RT/duroid® family of high frequency PTFE laminates is the leader in the industry for high speed RF/microwave PCB designs. Most PTFE PCB laminates require special equipment and processes to manufacture the highest reliability PCBs along with significant expertise in the material properties as many of the materials behave differently during PCB processing. The best-known brand name of PTFE-based formulas is Teflon, which is used in non-stick cooking pans which means that this material can be difficult to work with if you don’t have the proper experience.

Taconic Advanced PCB Dielectric Laminates: Taconic has been a world leader in the PTFE products sine 1961. Today they provide PTFE and silicon coated fabrics, tapes, and laminates for a range of high-performance application. Thermally stable, low Dk, low Z axis CTE PTFE laminates are the focus for the Taconic materials used in the manufacturing of RF/microwave PCB boards. Many of the Taconic products are designed with ultra-low fiberglass content to achieve world class insertion loss properties and a homogeneous dielectric constant throughout the laminate. The uniform dispersion of ceramic throughout the laminate yields extremely low X and Y coefficients of thermal expansions. Taconic has materials for every application and a partial list of their offering.

Panasonic MEGTRON 6: MEGTRON 6 from Panasonic is an advanced printed circuit board (PCB) laminate material designed for high-speed applications such as network equipment, mainframes, IC testers, and high frequency measuring instruments. MEGTRON 6 material is best-known for low dielectric constant and dielectric dissipation factors, as well as low transmission loss and high heat resistance.

 

Flexible Copper Clad Laminate (FCCL)

Polyimide (PI) CCL

Flexible copper clad laminate (FCCL) is a core component of flexible printed circuits (FPCs) (also referred to flexible printed circuit boards, FPCBs), which are used mainly in areas that require or repeated curves. FCCL comprises layers of copper foil and polyimide (PI), which are used as an electrical conductor and insulator, respectively. Single-sided FCCL has copper foil on one side, while double-sided FCCL has foil on both sides. This kind of FCCL is adhesiveless FCCL. And FCCL has another kind -adhesive FCCL, in which there is an extra layer of adhesive in-between the copper foil(s) and polyimide layer. At MADPCB, our mainly used flexible copper clad laminates (FCCLs) are from Dupont (Kapton), Zhengye and ITEQ.

  • FCCL with ED (Electro Deposit) Copper

  • FCCL with RA(Rolled & Annealed) Copper


Prepreg (PP)

Prepreg (PP), or Pre-preg, is a shorthand expression for Pre-Impregnated, also referred to B-stage, Bonding sheet, or simply Preg, which is composited of fiberglass fabric impregnated with resin. The resin has been partially cured but not hardened during the Prepreg coating operation. When heating the PCB stack-up in pressing process, the resin in Prepreg will follow, stick and bond the PCB core with copper foil or other materials, like cover-lay and stiffeners.

The name of each prepreg derives from the type of fiberglass used. Prepreg (PP) 106, 1080, 2116, 7628 are glass fabric types, and each number has different parameters, including Resin Content, Cured Thickness, Standard Size (Roll Type), Weight and etc. From the Prepreg parameter chart, you can see the resin contents and cured thicknesses of the same glass fabric type can be different.

The resin material encases a glass weave, and the manufacturing process for this glass weave is very similar to that used to manufacture yarns. The glass weave can be quite tight (e.g. 7628 PP) or loose (e.g. 106 PP), which is controlled with a loom during manufacturing. Any gaps and the overall homogeneity of the yarn will determine the electromagnetic properties, which is then responsible for dispersion, losses, and any fiber weave effects seen by signals in the PCB board.

PCB Prepreg (PP) 106, 1080, 2116 and 7628

  • PP 106: thickness 50μm, Er=2.8-3.7, resin content ~70%

  • PP 1080: thickness 60-70μm, Er=3.2-3.7, resin content ~60%

  • PP 2116: thickness 90-110μm, Er=3.6-3.8, resin content ~50%

  • PP 7628: thickness 170-190μm, Er=4.1-4.6, resin content ~45%

 

PCB Core

PCB cores and laminates are similar and, in some ways, they are quite different. Printed circuit board (PCB) cores are pre-pressed layers according to the pattern: copper foil – prepreg – copper foil. The core is effectively one or more prepreg laminates that are pressed, hardened, and cured with heat, and the core is plated with copper foil on each side. The prepreg material is impregnated with a resin, where the resin is hardened but left uncured. Most PCB board manufacturers describe the prepreg as the glue that holds core materials together; when two cores are stacked on each side of a prepreg laminate, exposing the stack to heat causes the resin to being bonding to the adjacent layers. The hardened resin slowly cures through crosslinking, and its resulting material properties start to approach those of the core layers.

 

Core Thickness

Initial Copper Thickness (/Weight)

50µm

18µm/18µm;

100µm

18µm/18µm; 35µm/35µm

150µm

18µm/18µm; 35µm/35µm; 70µm/70µm; 105µm/105µm;

200µm

18µm/18µm; 35µm/35µm; 70µm/70µm; 105µm/105µm;

300µm

18µm/18µm; 35µm/35µm; 70µm/70µm; 105µm/105µm; 140µm/140µm;

350µm

18µm/18µm; 35µm/35µm; 70µm/70µm; 105µm/105µm; 140µm/140µm; 210µm/210µm

400µm

18µm/18µm; 35µm/35µm; 70µm/70µm; 105µm/105µm; 140µm/140µm; 210µm/210µm

500µm

18µm/18µm; 35µm/35µm; 70µm/70µm; 105µm/105µm; 140µm/140µm; 210µm/210µm

550µm

18µm/18µm; 35µm/35µm; 70µm/70µm; 105µm/105µm; 140µm/140µm; 210µm/210µm

600µm

18µm/18µm; 35µm/35µm; 70µm/70µm; 105µm/105µm; 140µm/140µm;

700µm

18µm/18µm; 35µm/35µm; 70µm/70µm; 105µm/105µm; 140µm/140µm;

800µm

18µm/18µm; 35µm/35µm; 70µm/70µm; 105µm/105µm; 140µm/140µm;

900mm

18µm/18µm; 35µm/35µm; 70µm/70µm; 105µm/105µm;

1000µm

18µm/18µm; 35µm/35µm; 70µm/70µm; 105µm/105µm;

1200µm

18µm/18µm; 35µm/35µm; 70µm/70µm; 105µm/105µm;

1500µm

18µm/18µm; 35µm/35µm; 70µm/70µm; 105µm/105µm;

2000µm

18µm/18µm; 35µm/35µm; 70µm/70µm; 105µm/105µm;

2400µm

18µm/18µm; 35µm/35µm; 70µm/70µm; 105µm/105µm;

3200µm

18µm/18µm; 35µm/35µm; 70µm/70µm; 105µm/105µm;

*Special cores may also be pressed for a particular project, like constantan PCB.

PCB core and PP materials can have somewhat different dielectric constants (Er), depending on the resin content, type of resin, and glass weave. This can be a problem when designing PCB boards that require very precision impedance matching as the effective dielectric constant seen by a signal on a trace depends on the dielectric constants of the surrounding materials. Not all prepreg and core materials are compatible with each other, and core or prepreg stacks with very different dielectric constants make it difficult to predict exact dielectric constants and losses in an interconnect.


Copper Foil

Copper foil is the base copper thickness applied on outer and inner layers. The copper foil can be pre-attached by the copper clad laminate manufacturer to a base material core or it can be introduced in a multilayer board as copper foil before processing. On inner layers, the final copper thickness remains that of the base copper foil. On outer layers, we deposit extra 20-30μm copper on the traces during the copper plating process for plating through the vias and microvias.

The copper for the out layers of multilayer boards is in the form of copper foil and pressed together with the prepregs or cores. For use with microvias in high density interconnect (HDI) printed circuit board (PCB), the copper foil is replated by RCC (resin coated copper) foil. At MADPCB, we have copper foil with copper thicknesses, including 12μm (1/3oz), 18μm (1/2oz, or Hoz), 35μm (1oz), 70μm (2oz), 105μm (3oz) and 210μm (4oz) for your options.