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For the PCB bottom plate, a little carelessness may cause the bottom plate to deform. If it is not improved, it will affect the quality and performance of the PCB copy board. If it is directly discarded, it will cause cost losses. Here are some ways to correct the deformation of the bottom plate.
One, splicing method
For graphics with simple lines, large line widths and spacing, and irregular deformations, cut the deformed part of the negative and re-splice the holes according to the hole positions of the drilling test board, and then copy them. Of course, this is for deformed lines. Simple, large line width and spacing, and irregularly deformed graphics; it is not suitable for negatives with high wire density and line width and spacing less than 0.2mm. When splicing, take care to minimize the damage to the wires and not the pads. When revising the version after splicing and copying, pay attention to the correctness of the connection relationship. This method is suitable for the film that is not too densely packed and the deformation of each layer of the film is inconsistent, and the correction of the solder mask film and the film of the power supply layer of the multilayer board is particularly effective.
Two, PCB board copy board to change the hole position method
Under the condition of mastering the operation technology of the digital programming instrument, first compare the negative film and the drilling test board, measure and record the length and width of the drilling test board respectively, and then on the digital programming instrument, according to the length and width of the two The size of the deformation, adjust the hole position, and adjust the adjusted drilling test board to cater to the deformed negative. The advantage of this method is that it eliminates the troublesome work of editing negatives, and can ensure the integrity and accuracy of the graphics. The disadvantage is that the correction of the negative film with very serious local deformation and uneven deformation is not effective. To use this method, you must first master the operation of the digital programming instrument. After the programming instrument is used to lengthen or shorten the hole position, the out-of-tolerance hole position should be reset to ensure accuracy. This method is suitable for correcting the negative film with dense lines, or the uniform deformation of the negative film of each layer.
Third, the pad overlap method
Enlarge the holes on the test board into the pads to overlap and deform the circuit piece to ensure the minimum ring width technical requirements. After the overlapping copy, the pad is elliptical, and after the overlapping copy, the edge of the line and the disk is halo and deformed. If the user has very strict requirements on the appearance of the PCB board, please use it with caution. This method is suitable for film with line width and spacing greater than 0.30mm, and the pattern lines are not too dense.
Four, photography
Just use the camera to enlarge or reduce the deformed graphics. Generally, the film loss is relatively high, and it requires multiple debugging to obtain a satisfactory circuit pattern. When taking pictures, the focus should be accurate to prevent the lines from being deformed. This method is only suitable for silver salt film, and it can be used when it is inconvenient to drill the test board again and the deformation ratio in the length and width direction of the film is the same.
Five, hanging method
In view of the physical phenomenon that the negative film changes with the change of environmental temperature and humidity, take the negative film out of the sealed bag before copying, and hang it for 4-8 hours under working environment conditions, so that the negative film has been deformed before copying. After copying, the chance of deformation is very small.
For the film that has been deformed, other measures need to be taken. Because the film will change with the change of environmental temperature and humidity, when hanging the film, make sure that the humidity and temperature of the hanging place is the same as that of the working place, and it needs to be in a ventilated and dark environment to prevent the film from being contaminated. This method is suitable for the negative film that has not been deformed, and can also prevent the negative film from deforming after copying.
