FR1 is basically the same as FR2. FR1 has a higher TG of 130oC instead of 105oC for FR2. Some laminate manufacturers who produce FR1 may not produce FR2 since the cost and usage are similar and it is not cost effective for having both.
FR3 is also basically FR2. But instead of phenolic resin it uses an epoxy resin binder.
FR4 (FR = Flame Retardent)is a glass fiber epoxy laminate. It is the most commonly used PCB material. 1.60 mm (0.062inch). FR4 uses 8 layers glass fiber material. The maximum ambient temperature is between 120o and 130oC, depending on thickness.
In China FR4 is the most widely used PCB base material, next is FR1 then FR2. But FR1 and FR2 are usually used for 1-layer PCBs because they are not good for passing through holes. FR3 is not recommended to bu ilding multi-layer PCBs. FR4 is the best selection. FR4 is widely used because it is good to make from one- layer to multi-layer PCBs. With only FR4, PCB companies can make all kinds of PCBs, which leaves the management and quality control much easier, and eventually it can reduce the cost!
CEM-1 and CEM -3
CEM-1 Composite material composed of woven glass fabric surfaces and paper core combined with epoxy resin. Primarily used in the printed circuit board industry. Easy punching and excellent electrical properties and higher flexural strength than paper based grades. CEM-1 provides excellent mechanical and electrical properties, and punches well up to .093″.
CEM-3 is very similar to FR4. Instead of woven glass fabric a ‘flies’ type is used. CEM-3 has a milky white color and is very smooth. It is a complete replacement for FR4 and has a very large market share in Asia. It is a kind of flame retardant epoxy copper-clad plate glass material, is generally used in electronics with double sided and multilayer pcb boards. And CEM – 3 is a new printed circuit substrate material developed based on FR – 4. In recent years, CEM-3 is used to replace FR-4 in Japan, even more than the FR – 4 dosage.
Aluminum Metal Core
As Aluminum Metal Core PCB means the base material for PCB is metal, but not normal FR4/CEM1-3, etc, and currently what the metal used are Aluminum, Copper alloy. Aluminum Metal Core PCB are used instead of traditional FR4 or CEM3 PCBs because of the ability to efficiently dissipate heat away from the components. This is achieved by using a Thermally Conductive Dielectric Layer.
Flex and Rigid-flex
Flex and Rigid-flex circuit boards have become increasing popular due to their unique applications. Flex and Rigid-flex circuit boards can do what regular standard rigid circuit boards can not do. They can fold, twist, and wrap around tight/small packaging area.
The copper clad foil polyimide film has good electrical properties, mechanical properties, flame retardancy, chemical resistance and weather resistance. The most prominent feature is high heat resistance,the glass transition temperature of Tg is higher than 220. The disadvantage is that the hygroscopicity is high, and the shrinkage rate is high and the cost is high at high temperature or after moisture absorption, Pre bake to remove moisture before PCB welding. PI is suitable for flexible printed boards for high-speed circuit microstrip or strip line signal transmission, it’s also one of the most widely used substrates in flexible substrates.
The mechanical properties of copper-clad polyester film are better in tensile strength, dielectric constant and insulation resistance. It also has good anti-moisture and dimensional stability after moisture absorption. Disadvantages are poor heat resistance, large size change after heating, and lead bad welding.The working temperature is lower (below 105 degrees C). PET is only used in printed transmission lines without welding and flat cables in electronic machines.