The bottom layer of the paper carrier tape base paper is the key layer for bonding the intermediate layer and the lower sealing tape, which has high requirements for stiffness and surface smoothness. In order to ensure the overall quality of the paper, the bottom layer also needs to be made of sulfate coniferous wood pulp. The beating degree is usually controlled at 35 ~ 45 ° Sr. 0.5% ~ 3% binder or enhancer relative to the absolute dry pulp is usually added to improve the interlayer adhesion and the stiffness of the bottom layer paper. The commonly used binders and enhancers include starch, polyvinyl alcohol, sodium carboxymethylcellulose, polyacrylamide, etc.