Graphitization by electroplating on holes or through holes on the edge of the PCB. Cut the edge of the board to form a series of half holes. These half holes are what we call stamp hole pads.
1. Disadvantages of stamp holes
①: After the board is separated, it has a saw-like shape. Some people call it a dog-tooth shape. It is easy to get in the shell and sometimes needs to be cut with scissors. Therefore, in the design process, a place should be reserved, and the board is generally reduced.
②: Increase the cost. The minimum stamp hole is 1.0MM hole, then this 1MM size is counted in the board.
2. The role of common stamp holes
Generally, the PCB is V-CUT. If you encounter a special-shaped or round-shaped board, it is possible to use the stamp hole. The board and board (or empty board) are connected by stamp holes, which mainly play a supporting role, and the board will not be scattered. If the mold is opened, the mold will not collapse. . Most commonly, they are used to create PCB stand-alone modules, such as Wi-Fi, Bluetooth, or core board modules, which are then used as stand-alone components to be placed on another board during PCB assembly.
3. General spacing of stamp holes
0.55mm~~3.0mm (depending on the situation, commonly used 1.0mm, 1.27mm)
What are the main types of stamp holes?
- Half hole
- Smaller hole with half hol
- Holes tangent to the edge of the board
4. Stamp hole requirements
Depending on the needs and end use of the board, there are some design attributes that need to be met. E.g:
①Size: It is recommended to use the largest possible size.
②Surface treatment: Depends on the end use of the board, but ENIG is recommended.
③ OL pad design: It is recommended to use the largest possible OL pad on the top and bottom.
④ Number of holes: It depends on the design; however, it is known that the smaller the number of holes, the more difficult the PCB assembly process.
Plated half-holes are available on both standard and advanced PCBs. For standard PCB designs, the minimum diameter of the c-shaped hole is 1.2 mm. If you need smaller c-shaped holes, the minimum distance between the two plated half holes is 0.55 mm.
Stamp Hole Manufacturing Process：
First, make the entire plated through hole as usual on the edge of the board. Then use a milling tool to cut the hole in half along with the copper. Since copper is more difficult to grind and can cause the drill to break, use a heavy duty milling drill at higher speeds. This results in a smoother surface. Each half-hole is then inspected in a dedicated station and deburred if necessary. This will make the stamp hole we want.