What causes the circuit board to deform easily?

1.When the copper surface on the circuit board area is not uniform, it is easy to deteriorate, plate bending and plate warping. 1, general circuit boards will be designed with a large area of copper foil for grounding, sometimes Vcc layer has designed a large area of copper foil, when these large areas of copper foil can not evenly distributed in the same circuit boards, will cause uneven heat and cooling speed, circuit boards, of course, also can heat bilges cold shrink, if increases and cannot at the same time can cause different stress and deformation, the temperature of the board at this time if the Tg has reached the upper limit value, the board will start to soften, causing permanent deformation. 

2. Each layer of the circuit board connection point (vias, through the hole) will limit the board expansion and contraction.Today's circuit board is mostly multi-layer board, and between the layer and the layer will have the same connection to the rivet point (vias), the connection point is divided into through hole, blind hole and buried hole, there is a connection point place will limit the effect of the board to rise cold contraction, will also indirectly cause bending and plate warping.