Printed Circuit Board Shape Processing Technology

1. The processing method of the printed board shape:
(1) Milling the shape. To use the CNC milling machine to process the shape, it is necessary to provide the milling shape data and the corresponding pipe hole files. These data are all provided by the programmer. Since the spacing between the printed boards cannot be very large, generally about 3mm, the diameter of the milling cutter is generally 3mm. First drill pipe holes on the milling bed, fix the printed board and the milling bed with pins, and then use the milling shape data to mill the shape.
(2) Punch the shape. When punching the shape with a punch, a mold is required, and the pipe position nails on the mold corresponding to the pipe position holes of the printed board. Generally, a hole of about φ3.0mm is selected as the pipe position hole.
(3) Open “V” grooves. Use a “V” groove cutter to cut the printed board into several parts that are connected to each other along the “V” groove line of the printed board design.
(4) Drill shapes. Use a drill press to drill holes along the outline. Usually “V” grooves and drill shapes are only used as auxiliary means of processing.

2. The choice of shape processing method.
The selection of the shape processing method is usually related to the customer’s requirements. The shape of the shape is related to the batch of processing. Generally, the milling shape is selected. When writing the milling shape data, pay attention to the selection of the cutting point and the direction of the cutting tool. It is necessary to ensure that the cutting direction of the cutting shape is 180 degrees from the cutting direction of the effective shape. Therefore, the cutting shape of the milling shape is opposite to the cutting direction of the milling groove. The influence of the cutting and starting actions on the shape; in the same way, if the inner groove has a convex angle, the cutting point for milling the inner groove is selected at the convex corner; if the inner groove has no convex angle, the cutting point is selected at a distance from the inner groove. Both sides are the radius of the milling cutter. In addition, when the knife is started at the lower knife point, since the right-angle side of the printed board has been milled, the extrusion of the milling cutter to the board will deform the right angle, and the shape will be deformed. A rounded corner with a radius of 0.8mm is added to the four corners to make the right angle shape. When it is not possible to add pipe holes in the printed board unit, add pipe holes on the side of the puzzle board, and add hanging points between the printed board units. After milling the shape, use a file to remove the hanging points. The punching shape can meet the needs of mass production, and the processing efficiency is high. Usually, the selection of the pipe position hole has a great influence on the shape processing quality and processing efficiency.

3. “V” groove and drill shape are very effective auxiliary means for shape processing.
Among them, opening “V” grooves is the most commonly used auxiliary means for shape processing. When the size of the printed board unit is small, in order to reduce the milling time, several printed boards can be assembled into one unit, and the “V” slot is opened after the shape is milled, which not only improves the efficiency of shape processing, but also helps cleaning boards and product packaging also improve the utilization rate of board materials.

For printed boards that cannot add pipe holes and are small in size, the number of hanging points can also be reduced (removing the hanging points by filing is a very troublesome work). Larger batches of panels are advantageous. When customers require crafted edges or a variety of plate patterns to be assembled together, “V” grooves are the preferred shape processing methods. Although opening the “V” groove has the advantage of high efficiency, it is restricted by the equipment (only refers to our “V” groove cutting machine), and the “V” groove spacing cannot be too large, and the “V” groove cannot be opened along the fold line. Compared with this, although the drilling profile is slower, it can overcome the above difficulties and also overcome the disadvantage of the larger diameter of the milling cutter. Adding stamp holes between the unit panels (a series of holes whose spacing between adjacent holes is greater than the hole diameter of about 0.2-0.5mm, and the hole diameter is less than 1.0mm) can meet customer requirements. Also, customers cannot open a variety of boards together. When the “V” groove is used, stamp holes can be added in the printing room (such as printed board A and printed board B).

If the printed board has an inner gap whose width d is smaller than the diameter of the milling cutter, the milling shape cannot be used for processing, and it can be achieved by drilling multiple times. When milling the shape, only the outer frame is milled, and the shadow area of ​​the object that is tangent to the two circles cannot be processed by the milling cutter. The shape processing can be completed. The processing method of adding hanging points between the printed boards, and then filing the hanging points after milling the shape was introduced. If stamp holes are added to the ink outline of the hanging points, the difficulty of filing the hanging points can be greatly reduced. There are inner grooves on this board. For example, using a 3.0mm milling cutter to mill the shape, if the width of the board slot is less than 8mm, the corresponding inner corner accounts for 3/8 of the brightness. 3/16 of the groove width reduces the inner angle. If the customer is still not satisfied, you can put a hole smaller than 1.0mm first, and then place a hole of -φ1.5mm, so that the inner angle is smaller than 0.5mm. The inner circle angle is less than 0.5mm.

4. The placement of the tube hole is an important factor in the shape processing.
Shape punching and milling shape are common methods of shape processing. They are very efficient in shape punching, but they are all inseparable from the corresponding pipe holes. Sometimes the placement of pipe holes has a great influence on shape processing.
Usually, two tube holes are added to the printed board unit, which are generally placed on the opposite corners of the board. In principle, the farther the distance is, the better the positioning. Place a tube position hole. In addition, for some special shapes, the number of tube holes will be more than two, and the positions may not necessarily be in the opposite corners. If there are process edges in the customer’s technical data, the tube holes are best added on the process edges, or at the corners of the board. Select two non-metallized holes with a diameter of 2.0-4.0mm as positioning holes.

It is very important to place the tube position holes of the punched shape. In order to improve the utilization rate of the mold and the labor productivity, the same mold is used for the printed boards with the same shape but different wiring. The process edge is added, which often requires full consultation with customer technical experts. Regardless of punching shape or milling shape, we like to add pipe holes in the printed board unit (or choose a certain type of holes as pipe holes), but unfortunately some customers do not allow pipe holes in the board and it is impossible to select a certain type of hole in the board as a pipe position hole, we have to use the outer pipe position to process the shape, that is, add a pipe position hole to the printed board unit. If there is an inner gap in the shape of the printed board unit, we can add a pipe hole to the inner gap, and add a stamp hole on one side of the gap to connect to the printed board unit. After milling the shape, break off the small pieces at the inner gap, file to remove the burrs, and the same method can be used to add pipe holes for punching the shape. If there are hollow grooves in the printed board unit, the pipe holes can be added to the inner groove. The three sides of the inner groove are processed by punching/milling, and the other side is connected to the printed board unit with a stamp hole. After the shape is processed, the small and medium pieces in the groove are removed. If the customer agrees, the center of the stamp hole and the center of the groove edge can be coincident. The process of filing burrs can be eliminated. In order to ensure the inner rounded corners, when punching the shape, the four corners of the slot can be punched away, and the middle part of one side of the slot is connected to the board through the stamp hole. Another structure is to add a process block on the edge of the board (the process block is more superior than the process edge), the process block is connected to the printed board unit with a stamp hole, the pipe position hole is added to the process block, and the process block is removed after punching/milling the shape. File the burrs, which can reduce the number of hanging points. When the punching shape is used for processing, the processing efficiency will be greatly improved, but the addition of process blocks will reduce the utilization rate of the panel. When punching the shape, it is not possible to add a common pipe hole for the mold in the board, and if the customer does not agree to add a stamp hole, then the outside of the board or the inside of the board is missing. Mill out the inner groove or the special pipe hole that is missing.

With the development of printed circuit board design, the shape processing technology is also developing. The above summary of my work may not be reasonable for all printed circuit board shape processing, but it is very useful for many printed board manufacturers.