Different levels of PCB substrate used in different, such as 3 to 4 laminates to use prefabricated composite materials, double-sided panels are mostly used glass-epoxy materials. Lead-free electronic assembly process, due to the temperature rise, the printed circuit board bending occurs when the degree of heat increase, so in the SMT required to minimize the degree of bending of the plate, such as FR-4 and other types of substrates. Due to substrate expansion and shrinkage after heat stress on the impact of the device will cause the electrode stripping, reducing reliability, it should also pay attention to material selection in PCB copy engineering coefficient of expansion, especially when the component is greater than 3.2 × 1.6mm to pay special attention.

(150 ℃, 60min) and solderability (260 ℃, 10s), high copper foil adhesive strength (1.5 × 104Pa or more) and bending strength (25), high temperature resistance, high thermal conductivity, × 104Pa), high conductivity and small dielectric constant, good blanking (accuracy ± 0.02mm) and compatibility with the cleaning      The other requirements of the appearance of smooth, not warping, cracks, scars and rust and so on.

Printed circuit board thickness of 0.5mm, 0.7mm, 0.8mm, 1mm, 1.5mm, 1.6mm, (1.8mm), 2.7mm, (3.0mm), 3.2mm, 4.0mm, 6.4mm, 0.7mm and 1.5 Mm PCB thickness for double-sided design with cheat, 1.8mm and 3.0mm for the non-standard size. PCB size from the production point of view, the minimum veneer should not be less than 250 × 200mm, the general ideal size (250 ~ 350mm) × (200 × 250mm), less than 125mm long side or less than 100mm wide edge PCB, The use of puzzle way.

    Surface assemblyPCB copy technology for the thickness of 1.6mm substrate bending requirements for the upper warping ≤ 0.5mm, lower warping ≤ 1.2mm. Normally, the allowable bending rate is 0.065% or less.