How does the automatic punching machine punch holes on the printed circuit board, and how to use the automatic pipe punching machine to punch holes on the printed circuit board? When the automatic pipe punching machine, the edge of the copper foil always rises. Therefore, it is not advisable to have circuits on both sides of the board, which will cause the pads to fall off. Another disadvantage of punching is the delamination of the pad and the breakage of the substrate at the connection hole.
In addition, punching will result in the formation of holes that are conical and have a fairly thick surface. Therefore, printed circuit boards that do not meet professional requirements have higher requirements for the surface smoothness of plated through holes; if the distance between the holes is too small, Then there may be cracks. In this case, the operating procedure should be changed, and the copper foil should not be etched before punching. In this way, the copper foil can provide reinforcement and help avoid cracks. It is used in large-volume consumer printed circuit board products, and this printed circuit board uses paper phenyl ester and epoxy-based substrates.
Punching a hole on a printed circuit board is a mechanical operation like drilling a hole. However, it is not as good as drilling on hole diameter accuracy, hole wall smoothness, and delamination of land and bottom plate. For paper benzoyl substrates (XXX and similar types), in order to avoid chipping, the temperature needs to be pre-heated to 50-70°C before punching. Substrates like XXXPC and FR-2 can be punched at room temperature, as long as the temperature is higher than 20°C. Non-woven strengthened glass substrates (epoxy and polyester) have good punching performance. With a die gap of 50-100μm, a smooth hole wall suitable for electroplating can be obtained.
During the punching process, the breakage rate of small punching holes is higher because:
1. The alignment is not standard enough: it can be easily found by precision inspection tools;
2. Poor design: This usually means that the punching hole is too small to meet the requirements
In order to process accurately, there must be a precise tolerance between the drilling machine and the punching hole. Generally, for paper substrates, the punching hole should be 0.002-0.004in larger than the drilling machine, and for glass substrates, it should be half of this tolerance.
Using the following techniques can reduce many problems in punching, such as delamination of pads.
1. Punching should be done on the copper clad surface;
2. Etch before punching;
3. The punched pad must be large enough.
The number of printed circuit boards is large enough, at least 2000, for punching to be economical. Therefore, large quantities of non-plated through-hole reinforced paper substrates are more suitable for punching, and others are suitable for drilling.
In general, large holes are easier to punch than small holes. For example, for strengthened paper substrates with holes smaller than 0.9mm and strengthened glass cloth substrates with holes smaller than 1.2mm, punching failure is very common. Therefore, the load of the automatic pipe punching machine depends on the type of substrate and their cutting force. The cutting force of the paper substrate is 1200 psi (maximum), and the maximum cutting force of the epoxy glass substrate is 20,000 psi. Therefore, the paper substrate should be able to withstand 16t pressure. In order to improve the safety factor, 32t withstand pressure is often used. Epoxy glass substrates have 70% higher compression resistance than paper phenylester substrates, and even simple boards require high compression resistance.