With the increasing requirement of high-power electronic components for PCB cooling ability, the market’s demand for metal base board is also rising, and higher processing requirements are also put forward for copper based PCB products.
Especially in the aspect of drilling, more and more copper base board are required to drill through holes below 0.5mm. If they are processed by conventional drilling methods, it is very easy to scrap the broken cutter.
In this paper, through the research on the drilling mechanism of copper base board, some schemes to improve the drilling technology are put forward, so as to improve the machining yield of small holes on copper base board.
Due to the diverse requirements of customers for heat dissipation or plate making, there are a variety of copper materials used for copper base board in the market, and the hardness of different types of copper substrates is also different.
At present, the main copper base board material used for copper content is higher, copper is characterized by good plasticity and strength, hardness is slightly lower, its heat dissipation performance is the best of all kinds of copper substrate.
From the point of view of PCB drilling, copper block has both “hard” and “soft” characteristics.
On the one hand, copper blocks are much harder than fr-4 and other organic materials or organic composite materials, which greatly increases the difficulty of cutting when drilling and it is easy to break the tool due to excessive wear.
On the other hand, the copper block has a certain plasticity, and the drilling process may cause the copper chips to adhere to the cutting head, which is prone to poor chip cutting and lead to knife breaking.
Especially when the cutting diameter of drilling hole is less than 0.7mm, the lateral cutting force and axial force that can be supported are very limited, and the chip shedding ability is very weak, which is a great challenge for drilling.
The above shows the main problems existing in the small hole machining process of copper base board at present: large wear, easy cutting and difficult heat dissipation. Although these problems are troublesome, they can be effectively alleviated by selecting the right bit, thus improving all aspects of drilling small holes in copper base board.
After selecting the appropriate tool, it is necessary to explore the drilling parameters of copper base to test whether the drilling effect can meet the requirements.
Taking the 0.5mm drill tool as an example, the coating drill tool with a sharp angle of 145° and a spiral angle of 40° is customized for the processing of copper base board. The other parameters are designed in accordance with the conventional design.
Based on the above groping test results, the drilling speed was set at 15krpm/min, the feeding speed was 0.1m/min, the drilling depth was 1.0mm, and the step drilling was carried out for 2 times. The hole drilling test of 0.5mm holes was carried out on the copper base board, and the uncoated and coated drill tool pairs were compared to the tool life test.
It can be seen that under the suitable processing parameters, the drilling tool does not break, and the hole shape is not damaged, as shown in figure 7 below. The comparison between coating and no coating shows the durability of the coating drilling tool.
The above proposed machining scheme optimizes the choice of cutting tools and parameters for small hole machining of copper base board. From the perspective of machining conditions, it also improves the poor quality of easily broken cutting tools and drilling holes for small hole machining of copper base board.
Although the processing efficiency is much lower than that of some professional hardware processing equipment, the advantage of this scheme is that the hole processing of copper base board can be realized based on the existing PCB drilling process without adding additional equipment, which reduces the technical threshold and input cost.