Zhao Yongfeng, Yao Junxiong, Hu Chuanhong, Sun Yong, Xu Xiangqian, Zheng Lijuan, Wang Chengyong
Polytetrafluoroethylene (PTFE) has a high dielectric constant and low dielectric loss, which is considered an
ideal material for the dielectric layer in high-frequency microwave boards. However, when it is mechanically drilled, it is
easy to accumulate heat, resulting in problems such as poor chip removal, serious adhesion of debris, and residual stains on
the hole wall, which greatly affects the signal transmission capability and reliability of high-frequency microwave boards.
Therefore, this paper innovatively put forward the internal spraying cold air-assisted hole making process (internal cooling
for short) and compared the tool debris, chip adhesion, and tool wear when drilling holes for two typical high-frequency
microwave boards under the three processes of room temperature, external cooling, and internal cooling. The results show
that when processing flat glass fiber ceramic PTFE board, internal cold drilling can effectively improve chip entanglement,
but the effect of reducing tool wear is very limited; low temperature medium effectively reduces the plastic deformation of
the material in the cutting process, and it is more likely to form a short conical spiral chip under the conditions of external
and internal cooling. When processing E-type glass fiber PTFE board, due to the lack of ceramic and other hard filler
impact on the tool edge and flank surface, the tool wear under the three processing modes is significantly smaller than that
of flat glass fiber ceramic PTFE board; both internal and external cold drilling can effectively reduce the adhesion of chips
to the tool to prevent the spiral groove from clogging. In addition, due to the direct and effective role of the low temperature
medium in internal cold drilling, it can prevent the resin from reaching the molten state to a maximum extent, so as to avoid
the resin adhering to the tool and the surface of the chips. It is found that the internal cold drilling process is more suitable
for the microhole processing of E-type glass fiber PTFE boards, which can effectively promote the discharge of chips from
the holes and prevent the accumulation and aggregation of chips in the spiral groove of the tool.