Causes And Improvement Of PCB Deformation 5

- May 24, 2017-

Improve strategy 


    How can it be possible to prevent the board from the back of the furnace bending and plate Alice of the situation?


    1. Reduce the effect of temperature on board stress


    Since the "temperature" is the main source of board stress, as long as the temperature of the reflow oven or slow down the board in the reflow furnace temperature and cooling rate, you can greatly reduce the bending and plate Alice of the situation. But there may be other side effects on the matter.


    2. Use high Tg sheet


    Tg is the glass transition temperature, that is, the material from the glass into the rubber state of the temperature, the lower the Tg value of the material, said the board into the back to the furnace after the softening of the faster, and into a soft rubber state Will become longer, the deformation of the board will certainly be more serious. The use of a higher Tg sheet can increase its ability to withstand stress and deformation, but the relative price of the material is relatively high.


    3. Increase the thickness of the board


    Many of the electronic products in order to achieve a more thin purpose, the thickness of the board has been left 1.0mm, 0.8mm, and even made a 0.6mm thickness, so that the thickness of the board to keep the reflow furnace is not deformed, really a little hard, It is recommended that if there is no light requirements, the board is best to use the thickness of 1.6mm, can greatly reduce the risk of bending and deformation.


    4. Reduce the size of the board and reduce the number of puzzle


    Since most of the reflowers have used chains to drive the board forward, the larger the board will be deformed in the reflow furnace due to its own weight, so try to place the long side of the board as a board Back to the furnace chain, you can reduce the weight of the circuit board caused by the deformation of the depression, the number of puzzle is also based on this reason, that is, when the furnace, as far as possible with a narrow vertical vertical furnace direction, can reach the lowest The amount of deformation of the depression.


    5. Use a furnace tray with a rule


    If the above method is difficult to do, and finally the use of the furnace tray (reflow carrier / template) to reduce the amount of deformation, and the furnace tray can reduce the reason for bending the board because of whether it is hot or cold shrink, all hope The tray can be fixed to the circuit board until the temperature of the circuit board below the Tg value began to re-hardened, you can also maintain the size of the garden. If the above method is difficult to do, and finally the use of the furnace tray (reflow carrier / template) to reduce the amount of deformation, and the furnace tray can reduce the reason for bending the board because of whether it is hot or cold shrink, all hope The tray can be fixed to the circuit board until the temperature of the circuit board below the Tg value began to re-hardened, you can also maintain the size of the garden.


    If the single-layer tray can not reduce the amount of deformation of the circuit board, you must add a layer of the lid, the circuit board with two trays up and down, so you can greatly reduce the circuit board back to the furnace deformation problems. But this furnace tray is very expensive, but also have to add artificial to the storage and recycling tray.


    6. Use the real connection, stamp hole, instead of V-Cut sub-board use


    Since V-Cut will destroy the strength of the board puzzle, try not to use V-Cut sub-board, or reduce the depth of V-Cut.

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