PCB materials types included HB sheet and V0 sheet
HB sheet has low flame retardancy and is mostly used for single-layer PCB. VO sheet has high flame retardancy. It is mostly used in double-sides and multi-layer boards. This type of PCB sheet meets V-1 fire rating requirements and becomes FR-4 sheet. V-0, V-1, V-2 are fire rated.
The flammability of the material, also known as flame retardancy, self-extinguishing flame resistance, flame retardancy, fire resistance, flammability, etc., is a measure of the resistance of the material to resistance to combustion.
The flammable material sample is ignited by the required flame, the flame is removed after the specified time, and the flammability grade is evaluated according to the degree of combustion of the sample. The flammability grade is divided into three levels, and the sample is horizontally placed into a horizontal test method, which is divided into FH1, FH2. , FH3 three-stage, the sample is placed vertically for vertical test method is divided into FV0, FV1, VF2.
The circuit board must be flame resistant, cannot burn at a certain temperature, and can only soften. The temperature point at this time is called the glass transition temperature (Tg point), which is related to the dimensional stability of the PCB.
What types of PCB boards are there?
According to the grade level, from bottom to top are divided as follows:94HB – 94VO – 22F – CEM-1 – CEM-3 – FR-4 is described in detail as follows:
- 94HB: ordinary cardboard, not fireproof (minimum material, die punching, can not be used as power board)
- 94V0: flame retardant cardboard (mode Punching)
- 22F: single-sided semi-glass fiberboard (die punching)
- CEM-1: single-sided fiberglass board (must be drilled by computer, can not be punched)
- CEM-3: double-sided semi-fiberglass board (except double-sided The outermost part of the double-panel material is made of cardboard. The simple double-panel can use this material, which is a little bit cheaper than FR-4.
- FR-4: double-sided fiberglass board
What is high Tg PCB?
High Tg refers to high heat resistance. With the rapid development of the electronics industry, especially the electronic products represented by computers, the development of high functionality and high multi-layer requires the higher heat resistance of PCB substrate materials as an important guarantee. The emergence and development of high-density mounting technology represented by SMT and CMT makes PCBs more and more inseparable from the high heat resistance of substrates in terms of small aperture, fine wiring and thinning.
Generally, Tg degrees are above 130 degrees, high Tg is generally greater than 170 degrees, and medium Tg is greater than about 150 degrees. A PCB printed board with a typical Tg ≥ 170 ° C is called a high Tg printed board. The Tg of the substrate is improved, and the heat resistance, moisture resistance, chemical resistance, and stability resistance of the printed board are improved. The higher the TG value, the better the temperature resistance of the sheet, especially in the lead-free process, where high Tg is applied.
What are the advantages of high Tg PCB boards and the use of high Tg PCBs?
High Tg printed board When the temperature rises to a certain area, the substrate will change from “glass state” to “rubber state”, and the temperature at this time is called the glass transition temperature (Tg) of the plate. In other words, Tg is the highest temperature at which the substrate remains rigid.
So the difference between the general FR-4 and the high Tg FR-4:
It’s in the hot state, especially after moisture absorption.Under heat, there are differences in mechanical strength, dimensional stability, adhesion, water absorption, thermal decomposition, and thermal expansion of materials. High Tg products are obviously better than ordinary PCB substrate materials. In recent years, customers demanding the production of high Tg printed boards have increased year by year.