In the PCB circuit board production, the reflow furnace is prone to board bending and warping. So how to prevent PCB circuit board from going through the reflow furnace from board bending and warping, XPCB Limited is explained in detail below.
Since “temperature” is the main source of circuit board stress, as long as the temperature of the reflow furnace is reduced or the rate of heating and cooling of the circuit board production in the reflow furnace is slowed, the bending and warpage of the board can be greatly reduced. However, other side effects may occur, such as 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 of the material, the faster the circuit board starts to soften after entering the reflow furnace, and the time of becoming soft rubber state will also be longer. And the deformation of the circuit board will of course be more serious. The use of a higher Tg board can increase its ability to withstand stress and deformation, but the price of the relatively high material for the production of circuit boards is also relatively high.
In order to achieve the purpose of lighter and thinner for many electronic products, the thickness of the circuit board has left 1.0mm, 0.8mm, or even 0.6mm. Such a thickness must keep the circuit board from deforming after the reflow furnace, which is really a bit difficult. It is recommended that if there is no requirement for lightness and thinness, the thickness of the circuit board is preferably 1.6mm, which can greatly reduce the risk of bending and deformation of the board.
Since most of the reflow furnaces use chains to drive the circuit board forward, the larger the PCB size, the circuit board will dent and deform in the reflow furnace due to its own weight. So try to treat the long side of the circuit board as the edge of the board. Putting it on the chain of the reflow furnace can reduce the depression and deformation caused by the weight of the circuit board itself. The reduction in the number of panels is also based on this reason. Reach the lowest amount of depression deformation.
If the above methods are difficult to achieve, the last is to use the furnace tray to reduce the amount of deformation. The furnace tray can reduce the bending and warpage of the board because whether it is thermal expansion or cold contraction, it is hoped that the tray can fix the circuit board. After the temperature of the circuit board is lower than the Tg value and starts to harden again, the size of the garden can be maintained.
If the single-layer pallet cannot reduce the deformation of the circuit board, a cover must be added to clamp the circuit board with the upper and lower pallets. This can greatly reduce the problem of circuit board deformation through the reflow furnace. However, this furnace tray is quite expensive, and manual labor is required to place and recycle the trays.
Since V-Cut will destroy the structural strength of the panel between the circuit boards, try not to use the V-Cut sub-board or reduce the depth of the V-Cut.
XPCB Limited is a premium PCB & PCBA manufacturer based in China.
We specialize in multilayer flexible circuits, rigid-flex PCB, HDI PCB, and Rogers PCB.
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