Any interference between the positioning pin of the light touch switch and the PCB positioning hole willaffect its SMT mounting process. If the tolerance fit is critical, there will be a certain risk of mechanical stress.Through the tolerance accumulation analysis of the positioning pin of the light touch switch and the PCB positioning hole, the minimum clearance between the positioning pin and the positioning hole is calculated to be -0.063mm, thatis, there is slight interference. Therefore, there is a risk that the positioning pin of the light touch switch cannot be inserted into the PCB positioning hole well during SMT mounting. Severe adverseconditions may be detected by visual inspection prior to reflow soldering. Minor defects will be left out to the next process and will cause some mechanical stress. Accordingto Root Square Sum analysis,Defective rate was 7153PPM. 
It is recommended to change the size and tolerance of PCB positioning hole from 0.7mm +/ -0.05mm to 0.8mm+/ -0.05mm. The tolerance accumulation analysis is carried out again for the optimized scheme. The results show that the minimum clearance between the positioning column and the positioning hole is +0.037mm, and the risk of interference is eliminated.
Post time: Aug-18-2021
