PCB Blog - Basic knowledge of PCB board shape processing

The blanking of printed circuit boards, holes and shapes can be processed by die punching. For PCBs that are simple to process or PCBs that are not very demanding, punching can be used. It is suitable for the production of low-level and high-volume PCB boards and PCB boards with low profile requirements, and its cost is low.

punching:
One or several dies are usually used to produce single-sided paper substrates with complex shapes and large quantities of holes, and epoxy glass cloth substrates with double-sided non-metallized holes. Shape processing: The shape of single-sided and double-sided printed boards is usually produced by die punching. According to the size of the printed board, it can be divided into upper blanking die and lower blanking die.

Composite processing: High precision is required between the holes and the holes of the printed board, and the holes and the shape are required to be high precision. At the same time, in order to shorten the manufacturing cycle and improve the productivity, the composite mold is used to process the holes and shapes of the single panel at the same time.

The key to processing printed boards with molds is the design and processing of molds, which requires technical knowledge. In addition, the installation and debugging of molds are also very important. At present, most of the molds of PCB board manufacturers are processed by foreign factories. Precautions for installing the mold:
1) Select the punch (including type, tonnage) according to the punching force calculated by the die design, the size of the die, the closing height, etc.
2) Start the punching machine, and comprehensively check whether the clutch, brake, slider and other parts are normal, whether the operating mechanism is reliable, and there is no continuous punching phenomenon.
3) The horns under the die, generally 2 pieces, must be ground at the same time on the grinder to ensure that the die is installed parallel and vertical. The intercalation of the horn should not hinder the blanking and at the same time be as close to the center of the mold as possible.
4) Prepare several sets of pressure plate and T-head pressure plate screws for use with the mold. The front end of the pressing plate cannot touch the straight wall of the lower die. An emery cloth should be placed between the contact surfaces, and the screws must be tightened.
5) When installing the mold, pay great attention to the screws and nuts on the lower mold not to touch the upper mold (the upper mold is lowered and closed).
6) When adjusting the mold, try to use manual instead of motor. 7. In order to improve the punching performance of the substrate, the paper substrate should be preheated. Its temperature is preferably 70 to 90 °C.

The hole and shape of the printed board are punched by the die, and the quality defects are as follows:
The surrounding of the hole is raised or the copper foil is warped or delaminated; there are cracks between the holes; the position of the hole is not vertical or the hole itself is not vertical; the burr is large; Jump up; scrap jam. The inspection and analysis steps are as follows: check whether the punching force and rigidity of the punch are sufficient; whether the mold design is reasonable and whether the rigidity is sufficient; whether the machining accuracy of the convex and concave molds, guide posts and guide sleeves is achieved, and whether the installation is concentric and vertical. Whether the fit clearance is uniform. If the gap between convex and concave is too small or too large, quality defects will occur, which is an important problem in mold design, processing, debugging and use. The edges of convex and concave dies are not allowed to fillet or chamfer. The punch is not allowed to have taper, especially when punching, neither positive taper nor reverse taper is allowed. During production, always pay attention to whether the edges of the convex and concave dies are worn. Whether the discharge port is reasonable and the resistance is small. Whether the pushing plate and the feeding rod are reasonable and the force is sufficient. The thickness of the sheet to be punched, the bonding force of the substrate, the glue content, the bonding force with the copper foil, the preheating humidity and time are also factors to be considered in the analysis of the quality defects of the punching on PCB board.