It is easy for PCB board to bend and warping after reflow furnace. As we all know, how to prevent PCB board from bending and warping after reflow furnace is described as follows:
Since “temperature” is the main source of plate stress, so as long as reduces the temperature of the reflow furnace or slows the rate of heating and cooling of the plate in the reflow furnace, the occurrence of plate bending and warping can be greatly reduced. But there may be other side effects, such as a solder short circuit.
Tg is the glass transition temperature, that is, the temperature at which the material changes from the glass state to the rubber state. The lower the Tg value is, the faster the board begins to soften after entering the reflow furnace, and the longer the time it takes to become the soft rubber state, and the more serious the deformation of the board will be. The circuit board with higher Tg plates can increase its ability to withstand stress and deformation, but the price of relative materials is also relatively high.
Many electronic products in order to achieve the purpose of the thinner, the thickness of the board have the 1.0 mm and 0.8 mm, and even do the thickness of 0.6 mm, the thickness of this to keep the board with no deformation after welding furnace back, really stand, suggested that if there are no frivolous demands, board * can use 1.6 mm thickness, can greatly reduce the risk of plate bending and deformation.
Since most of the back weld furnace use chain to drive circuit board, the larger the size of the circuit board will be because of the weight of its own, concave deformation in the welding furnace back, so try to put the long side of the circuit board as an edge on the chain back to soldering furnace, can reduce weight sag deformation caused by the circuit board itself, to reduce the number of the makeup is also, for this reason, that is to say, a furnace, as far as possible with narrow edge perpendicular to the direction of the furnace, can reach to low sag deformation.
If the above methods are difficult to achieve, * is used oven tray (reflow carrier/template), to reduce the deformation of a furnace tray can reduce the plate bending plate become warped because both thermal and cold, all hope that the tray can hold the circuit board to wait until the temperature of the circuit board below the Tg values began to harden, can also maintain original size.
If the single-layer tray can not reduce the deformation of the circuit board, you must add a cover, the circuit board with the upper and lower two pallets clamped up, so that the circuit board can be greatly reduced through the reflow furnace deformation problem. However, this stove tray is quite expensive, but also have to add manually to place and recycle tray.
Since V-cut can destroy the structural strength of the boards between boards, try not to use v-cut splitters or reduce the depth of the V-cut.
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