For the pcb copy board, 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.
01 Splicing
For graphics with simple lines, large line widths and spacing, and irregular deformations, cut the deformed part of the negative film, re-splice it against the hole positions of the drilling test board, and then copy it. Of course, this is for deformed lines Simple, large line width and spacing, irregularly deformed graphics; not suitable for negatives with high wire density and line width and spacing less than 0.2mm. When splicing, you need to pay as little as possible to damage 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 it is particularly effective for the correction of the solder mask film and the film of the power supply layer of the multilayer board.
02 PCB copy board change hole position method
Under the condition of mastering the operating 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 its length and width 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 good. 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 the correction of the film with dense lines or the uniform deformation of the film.
03 Land 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 overlapping copy, the pad is elliptical, and after overlapping copy, the edge of the line and disk will be 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.
04 Photography
Just use the camera to enlarge or reduce the deformed graphics. Generally, the film loss is relatively high, and it is necessary to debug multiple times to obtain a satisfactory circuit pattern. When taking pictures, the focus should be accurate to prevent distortion of the lines. 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 directions of the film is the same.
05 Hanging method
In view of the physical phenomenon that the negative film changes with the 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 already deformed negatives, other measures need to be taken. Because the negative film will change with the change of environmental temperature and humidity, when hanging the negative film, make sure that the humidity and temperature of the drying place and the working place are the same, and it must be in a ventilated and dark environment to prevent the negative film from being contaminated. This method is suitable for undeformed negatives and can also prevent the negatives from deforming after being copied.