PCB News - Reasons for size expansion and shrinkage during PCB processing

In the process of transferring the inner layer circuit pattern from the base material to several times of pressing until the outer layer circuit pattern is transferred, the warp and weft direction of the jigsaw will be different. From the entire PCB production FLOW-CHART, we can find out the reasons and procedures that may cause abnormal expansion and shrinkage of the board and poor dimensional consistency:

1.The dimensional stability of the incoming substrate, especially the dimensional consistency between each laminated cycle of the supplier.

Even if the dimensional stability of different cycle substrates of the same specification is within the specification requirements, the poor consistency between them can cause the first plate trial production to determine a reasonable inner layer compensation.The difference between them caused the graphics size of the subsequent mass-produced panels to be out of tolerance.

At the same time,there is also a material anomaly that the board is found to shrink after the outer layer graphics is transferred to the shape process in the production process, there were individual batches of boards that were found to have the width and the width of the panel during the data measurement before the shape processing.The length of the shipping unit has a serious shrinkage relative to the transfer magnification of the outer layer graphics, and the ratio reaches 3.6mil/10inch.

2.Panel design: The panel design of conventional panels is symmetrical, and there is no obvious impact on the graphic size of the finished PCB when the graphics transfer magnification is normal; however, some panels are in order to improve the utilization rate of sheet In the process of cost, the design of asymmetric structure is used, which will have a very obvious impact on the consistency of the figure size of the finished PCB in different distribution areas. We can even drill blind holes in the laser during the PCB processing. In the process of hole and outer pattern transfer exposure/solder resist exposure/character printing, it is found that the alignment of such asymmetrically designed plates in each link is more difficult to control and improve than conventional plates;

3.An inner layer graphics transfer process: here plays a very critical role in whether the size of the finished PCB boardmeets customer requirements; such as the large deviation of the film magnification compensation provided for an inner layer graphics transfer, it can not only directly lead to the finished PCB In addition to the pattern size that cannot meet customer requirements, it can also cause the subsequent alignment of the laser blind hole and its bottom connection plate to cause a decrease in the insulation performance between the LAYER TO LAYER and even a short circuit, as well as the through/blind hole alignment during the transfer of the outer layer pattern. problem.

The above is an introduction to the reasons for the size expansion and shrinkage of PCB board processing. Ipcb is also provided to PCB manufacturers and PCB manufacturing technology