The flexural characteristic of FPC is very important in PCB design, and the elements that endanger it can be seen from two aspects:
FPC raw materials themselves appear to have the following key hazards to the flexure characteristics of FPC.
One. Molecular formula and orientation of copper foil (i.e. type of copper foil)
The tear resistance of injection copper is significantly better than that of electrolytic copper foil.
Second, the thickness of copper foil
For the same species, the thinner the copper foil is, the higher its tear resistance will be.
Third, the type of sheet commonly used glue
Generally speaking, the epoxy resin glue is more flexible than the acrylic glue.Therefore, epoxy resin system is dominant in the selection of highly flexible raw materials.And the glue with high tensile modulus (tensilemodulvs) can improve the flexural property.
Fourth, the thickness of commonly used glue
The thinner the thickness of the glue the higher the flexibility of the raw material.FPC can improve the flexibility.
Fifth, insulating layer plate
The thinner PI of the insulation layer is, the higher the flexibility of the raw material will be, the better the flexural property of FPC will be enhanced, while the flexural property of FPC will be enhanced by using low tensile modolos PI.The key hazards of raw materials against flexure are summarized as two key levels: the type of raw materials used;The thickness of the raw material
From the processing technology of FPC, the harm of its flexure is analyzed.
First, symmetry of FPC composition
After the plate conforms to the covering film, the higher the symmetry of the double-sided copper foil material can improve its flexural property.Because the ground stress that it needs to suffer when flexing is consistent.The THICKNESS of PI on both sides of PCB tends to be the same, and the thickness of glue on both sides of PCB tends to be the same
Second, the manipulation of pressing process
For Coverlay compaction, the glue should be completely filled in the middle of the line without any layers (cut into slices for inspection).If there are layers equal to bare copper in flexure, the flexure frequency will be reduced.
Post time: Sep-09-2020