Types of PCB Materials: PCB Board Components and Understanding with Details

These are MADPCB internal technical data about basic knowledge about Types of PCB Materials this will be the PCB raw materials . The purpose is the understanding of the commonly used specifications and performance parameters of rigid PCB Copper Clad Laminate, Prepreg, Copper Foil, Solder Mask, and Silkscreen ink. Here I will discuss with details about Types of PCB Materials.

Here are almost all PCB materials with their details and pictures.

Prepreg 

Prepreg (PP) is “pre-impregnated” composite fibers where a matrix material, such as epoxy, is already present.

1. Main Function: as the matrix material among the inner layers of multilayer PCBs and is used to adjust the PCB thickness.
2. Main Feature: The resin flows and cures in a certain pressure and temperature. The curving thickness differs from different PP model, which is used to adjust the PCB thickness.
3. Storage: Constant Temperature (21+/-2°C), Constant Humidity (55+/-8%).

 

The resin in Prepreg (PP)

Resin type includes phenolic resin, epoxy resin, PTFE, polyimide (PI), triazine resin or/and bismaleimide and etc. The most commonly used is epoxy resin at present. Resin can be thermosetting material, which can happen macromolecule polymerization, with function and feature as following:

• Electrical insulation.
• As matrix material between copper foil and reinforcement material (glass fiber fabric).
• Feature: Electrically resistance, heat resistance, chemical resistance, water resistance.

 

E-Glass Fiber Fabric Specifications: 106, 1080, 3313, 2116, 7628

Specification	Theoretical Thickness	RC (%)
106	0.0513mm (2mil)	72.5
1080	0.0773mm (3mil)	66
3313	0.1034mm (4mil)	57
2116	0.1185mm (5mil)	54
7628	0.1951mm (8mil)	46

 

Prepreg Sizes

Prepreg has standard sizes, including:

• 16”x18”
• 16”x21”
• 18’’x24”
• 12”x18”
• non-standard sizes can be customized

 

Copper Foil

• Main Function: be the conductive tracks on the top and bottom layer of a multilayer PCB.
• Main Feature: Cohered with PP at a certain pressure and temperature.
• Storage: Constant temperature and constant humidity.

 

The Classification of Copper Foil as per IPC-4562

Code	Industrial Code	Metric		English
		Basic weight (g/m²)	Nominal thickness(μm)	Basic weight (oz/ ft²)	Basic weight (g/ in²)	Nominal thickness (mil²)
Q	1/4oz(9μm)	75.9	8.5	0.249	12.5	0.34
T	1/3oz(12μm)	106.8	12.0	0.350	17.5	0.47
H	1/2oz	152.5	17.1	0.500	25.0	0.68
M	3/4oz	228.8	25.7	0.750	37.5	1.01
1	1oz	305.0	34.3	1	50.0	1.4
2	2oz	610.0	68.6	2	100.0	2.70
3	3oz	915.0	102.9	3	150.0	4.05
4	4oz	1220.0	137.2	4	200.0	5.40

*We commonly used thickness including 1/3oz(12μm), 0.5oz, 1oz, 2oz, 3oz and 4oz.

 

Copper Clad Laminate

 

Copper clad laminate (CCL) is the main raw material of printed circuit boards, made of copper foil and PP in the certain temperature and pressure, with different thickness.

 

Classification by Resin

• Phenolic CCL (such as FR-2)
• Epoxy Resin CCL (FR-4, such as IT-180A)
• High Temperature Resistance CCL (such as FR-5)
• Polyimide CCL (such as PI, PET)
• Polytetrafluorethylene (PTFE or TEFLON) CCL (such as Taconic TLX-8)
• Bismaleimide Triazine (BT) CCL (such as Isola GI-180)
• Cyanide Ester (CE) CCL (such as CCL-HL950)

 

Classification of Copper Clad Laminates

 

Classification by Application	Specifications	Representation Material
Common CCL: FR-4	Common Tg: ≥135℃	S1141
	Medium Tg: ≥145℃	S1141 150
	High Tg: ≥170℃	IT180A
High Frequency	High Performance FR-4	N4000-13
	PTFE	Arlon RF-35
	Ceramic Filled (not PTFE)	RO4350B
High Temperature Resistance	PI CCL	Arlon 85N
Other Special Application	Halogen-free and CAF resistant	S1155, IT180A

 

Common FR-4 Copper Clad Laminates Parameter Table

 

Capability Property	Standard	Typical Value of S1141	Standard	Typical Value of IT158	Standard	Typical Value of IT180A
IPC4101B		/21		/99		/126
Tg (°C)	≥135	140	150-200	155	≥170	180
Td (°C)	—	310	—	345	≥340	345
Dicy/PN		Dicy		PN		PN
Filler		No		Yes		Yes
Dk @1MHz	≤5.4	4.6	≤5.4	4.8	≤5.4	4.8
Df @1MHz	≤0.035	0.015	≤0.035	0.016	≤0.035	0.013
CTE (Z axis) (50-260°C)	—	4.5	≤3.5	3.3	≤3.0	2.8
T288 (min)	—	2	≥5	20	≥15	20
Moisture Absorption	≤0.8	0.15	≤0.5	0.08	≤0.5	0.1

 

Four Main Considerations of Selecting Copper Clad Laminates

• Processability
• Material Acquisition in Time
• Cost Factor
• The practicality of laws and regulations

 

Specific Aspects Upon Above Consideration Factors:

 

– Tg Value (consideration of Lead free);

– Td Value or T260, T288 (consideration of Lead free);

– Er (/Dk) and Tanδ (Dk and Df);

– Halogen Content (whether it is a halogen-free material);

– Other consideration aspects: CAF, IST, Q1000, UL level, CTI and moisture absorption.

 

Selecting Common Tg or High Tg CCL

 

• For common PCBs ≤ 10 layer, and the finished copper of inner and outer layer ≤ 2 oz,
• Material Selection: S1141, S6018 (RCC) (common Tg)

 

To meet one of the following conditions, material selection: IT180A, LDPP (high Tg)

• As per Acceptance Standards of Nation and Military;
• The finished copper thickness of inner and outer layer ≥ 3 oz;
• Layer Count ≥ 12 layer;
• The finished PCB thickness ≥ 3.0mm;
• The high-density heat dissipation hole distance < 1.2mm after hole diameter compensated.

 

High Frequency PCB CCL Selection

 

• Dk (/Er): it’s up to specific circuit design and function, which has directly effect on PCB stack-up structure, especially for PCB thickness and impedance control; (Signal transfer rate is inversely proportional to the square of Er. Lower Dk PCB has faster transfer rate.)
• Df: generally, wish the smaller Df, the better. The Df stands for signal loss in the PCB circuit;
• Variation in thickness: the substrate is mainly determined to characteristic impedance, and affects signal interference between the layers;
• The Dk consistency of the up and down dielectric of the signal tracks;
• Material Processability;
• TCK of dielectric constant.

 

Soldermask & Silkscreen Inks

• Soldermask provides solder resist and protection for conductor
• Silkscreen acts as identification role

 

Ink Properties

Chemical Properties	Solder Mask Ink Electrical Properties	Silkscreen Ink Properties
Acid Resistance ≥ 30minutes (10% H2SO4, 20℃) Alkali Resistance ≥30minutes (10% NaOH, 20℃) Solvent Resistance≥30minutes (CH2ClCHCl2, 20℃)	Voltage Resistance: 1000V DC/mil Volume Resistance: 1×10^15Ω*cm Surface Resistance: 1×10^14Ω Dielectric Loss: 0.025 @1MHz Dielectric Constant: 3.4 @1MHz	Insulation Resistance: 1×10^14Ω Heat Resistance: 270°C /10 seconds*3 times Flammability: UL 94V-0

 

Commonly Used Solder Mask Color

Ink Acceptance Common Criteria