Single sided printed circuit boards were developed in the early 1950s with the emergence of transistors, centered around the United States. At that time, the main production method was copper foil direct etching. From 1953 to 1955, Japan made the first paper phenolic copper foil substrate using imported copper foil, which was widely used in the field of radios. After the emergence of professional Japanese circuit board manufacturers in 1956, the manufacturing technology of single panels rapidly advanced. In terms of materials, in the early days, paper phenolic copper foil substrates were mainly used. However, due to factors such as low electrical insulation, poor welding heat resistance, and twisting of phenolic materials at that time, materials such as paper epoxy resin and fiberglass epoxy resin were gradually developed. Currently, single sided boards required for consumer electronic machines are almost made of paper phenolic substrate boards.

(1) Fatal defect: Due to its poor quality, significant impact may occur, which may cause damage and endanger human life, other equipment, other circuits, etc. This problem of poor quality must be completely eliminated.

(2) Serious defect: Due to its poor quality, the printed circuit board cannot be used for the intended purpose.

(3) Minor defects: Due to poor quality, the performance of printed circuit boards may be reduced and their lifespan may be shortened.

(4) Minor defects: Poor quality can reduce the value of the product, but do not affect the performance and lifespan of printed circuit boards.

(5) Conical hole: Due to the large gap between the upper and lower holes of the stamping model, the cross-sectional shape of the holes in the punched components is a horn shaped opening towards the assembly side of the components.

(6) MT surface: component assembly surface

(7) PT surface: welding surface