Due to the weight of the board with components the board will sag.This sagging will increase due to the decrease of the modules of elasticity in flexure E, with increasing temperatures. The given formulas are valid for solid boards. If a board has large holes or is a pre-cut multi-format board the sagging will be far more than calculated for a solid board.
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Note: Sagging will be considerably reduced when the board is supported on all four sides. If sagging is still too much, extra means of supporting have to be used, to ensure a well controlled soldering operation and/or to prevent solder flooding the board.
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