The uneven copper surface area on the circuit board will worsen the bending and warping of the board. The circuit boards are mostly multi-layer boards, and there will be vias between the layers. The vias are divided into through holes, blind holes and buried holes.
The places where there are vias will limit the effect of the expansion and contraction of the board, and also cause the board to bend and warp indirectly.
Generally, a large area of copper foil is designed on the circuit board for grounding purposes. Sometimes there is also a large area of copper foil designed on the Vcc layer.
When these large-area copper foils cannot be distributed on the same circuit board evenly , it will cause uneven heat absorption and heat dissipation. Of course, the circuit board will also expand and contract.If the expansion and contraction cannot be done at the same time, it will cause different stress and deformation.
At this time, if the temperature of the board has reached the upper limit of the TG , the board will begin to soften and cause deformation.
The vias of each layer on the circuit board will also limit the expansion and contraction of the board.
Post time: Jul-30-2020