There are many factors that affect the expansion and contraction of PCB boards, including the symmetry of graphic design, the characteristics of core board materials, the dimensional stability of film, operational problems in the production process, environmental problems, etc. The following PCB board factory will briefly summarize the influence of the residual copper rate in the inner layer of the circuit board on the expansion and shrinkage of the board as an example.
1. For the expansion and contraction of the core board after the circuit board is etched (the pressing structure of the ordinary four-layer PCB board)
1. The thickness is 0.1mm, and the surface copper thickness Hoz core board has a larger etching expansion and contraction than the surface copper thickness of 2oz core board;
2. When other conditions are the same, the surface copper Hoz core plate has a large warp expansion and contraction, while the surface copper 2oz core plate shrinks in the warp direction;
3. The residual copper rate of the circuit board has a significant impact on the Hoz core board of the surface copper. The lower the residual copper rate, the greater the expansion and shrinkage, and the warp direction changes are more significant.
2. For the expansion and contraction of the core board after lamination (the lamination structure of the ordinary four-layer PCB board)
1. When other conditions are the same, the latitudinal shrinkage of the surface copper thickness 2oz core plate is more obvious than the surface copper thickness Hoz core plate;
2. For the core board of the same circuit board type, the expansion and contraction in the warp direction are larger than the expansion and contraction in the weft direction, and this phenomenon is more obvious with the increase of the surface copper thickness;
3. When other conditions are the same, the higher the residual copper rate in the inner layer of the circuit board, the better the dimensional stability of the lamination, and the dimensional stability in the weft direction is better than that in the warp direction;
4. When other conditions are the same, the higher the residual copper rate in the inner layer of the circuit board, the smaller the compression expansion and shrinkage of the core board, tending to a linear relationship, and the warp direction changes more significantly;
5. Residual copper rate in the inner layer of the circuit board When the residual copper rate is less than 40%, the core board with a thickness of 0.1mm and a surface copper thickness of 2oz is larger than that of a core board with a surface copper thickness of Hoz, and vice versa when it is greater than 40%.
