0402=0.4*2.54-0.2*2.54=1mm*0.5mm0805=0.8*2.54-0.5*2.54=2mm*1.25mm
1in=25.4mm0402=0.04*25.4-0.02*25.4=1mm*0.5mm0805=0.08*25.4-0.05*25.4=2mm*1.25mm
0402//0805是英制度量，1in=25.4mm0402就是10mm*05mm0805就是20.3mm*12.7mm
