回答请以分号分隔 (1)Printed circuit board is a flat board that holds chips and other electronic components.The board is made of________(层)(typically 2 to 10)that interconnects components________(经由)copper pathways.The main printed circuit board in a system is called a“system board”or“motherboard,”________smaller ones that plug into the slots in the main board are called“boards”or“cards”. The printed circuit board of the 1960s connected________(分立器件)together.The circuit board of the 1990s interconnects chips,each containing________(几十万个)or millions of elementary components.The“printed”circuit is really an________(蚀刻电路).A________(铜箔)is placed over the________(玻璃纤维)or plastic base of each layer and covered with a photoresist.Light is shined through a________(负像)of the circuit paths onto the photoresist,hardening the areas that will remain________etching.When passed through an acid bath,the unhardened areas are washed away.The finished layers are then glued together.A________(相似的处理)creates the microminiaturized circuits________a chip.