1. PCB Key Performance Indicators
Chemical properties: Tg/Td/Z-CTE Electrical properties: dielectric constant/dielectric loss/flame retardancy Environmental properties: water absorption rate/CAF resistance/CTI
2. Glass transition temperature Tg
3. IPC standard classification:
Greater than or equal to 130 degree C low Tg Greater than or equal to 150 degree C medium Tg Greater than or equal to 170 degree C high Tg has an impact on PCB usage: Tg can affect the Z-CTE, high-temperature deformation, dimensional stability, and other properties of the material.
3. Coefficient of thermal expansion
The coefficient of thermal expansion (CTE) of PCB is an important parameter for measuring the dimensional stability of materials under temperature changes. The thermal expansion coefficient is divided into X-axis, Y-axis, and Z-axis thermal expansion coefficients, generally referring to the Z-axis expansion coefficient, as it has the greatest impact on material reliability. Specifically, CTE describes the ratio of the change in material length per unit temperature change to the original length. For PCB materials, the linear coefficient of thermal expansion is usually used to measure the linear change in size during temperature changes.
4. Thermal decomposition temperature Td
5. Copper foil peel strength
Peel strength is a measure of the bonding force between a conductor and the substrate material. The thickness of copper foil will affect the peel strength value of the test, defaulting to 1oz thick copper. The peel strength of copper foil is one of the important indicators for evaluating the quality of PCB. The peel strength test generally refers to the bonding strength test between copper foil and substrate or between copper foil and browning film. By using a universal tensile testing machine to vertically stretch copper foil at a certain rate, the force value during the peeling of copper foil from the substrate is detected, and the peeling strength is calculated.
6. Water absorption and hygroscopicity
7. Flame retardancy
The flame retardancy of PCB is an important performance indicator used to evaluate the combustion characteristics of materials after flame ignition. According to the different flame retardant properties, PCBs can be divided into three levels: V-0, V-1, and V-2.
8. Dielectric constant
9. Loss factor
10. CAF resistance performance
11. Leakage resistance index CTI
PCB leakage resistance index (CTI) refers to the highest voltage value at which a solid insulation material surface can withstand 50 drops of electrolyte without forming leakage marks under the combined action of an electric field and electrolyte, expressed in V. The anti leakage trace tester used for CTI testing consists of a voltage supply device, two rectangular electrodes with a cross-section of 2mm x 5mm made of platinum, a 30 degree angled slope at one end of the electrode, and a droplet needle for adding electrolyte.