When designing PCB circuit boards, how do PCB manufacturers design the three most common drilling holes? The common three-bell drilling design of PCB is divided into three key points: "hole type", "hole attributes" and "spacing between holes" ;Let us learn together how to design the three common drilling holes in PCB!
1: The types of holes are divided into: via holes (Vai), plug-in holes (Pad holes), and non-copper mounting holes (Npth). Via holes (via): It only serves the purpose of electrical conduction and does not require soldering of plug-in devices. Its surface can be opened. Window (exposed pad), cover with oil or plug with oil. Plug-in hole (PadL): The pin hole that needs to be inserted into the device for soldering, and the pad surface must be exposed. No copper mounting holes, (Npth): screw holes, or device plastic fixing feet, which have no electrical properties and serve as positioning and fixing functions.
2: Hole attributes, board factory holes are defined with two attributes, metal and non-metal. Most of the metal holes are device pin holes, and some are metal screw holes, which can allow electrical conduction from top to bottom. Non-metallic holes are holes with no copper on the inner wall that are not connected up and down. They are also called mounting holes. The difference between the attributes of metal holes and non-metal holes is whether "Plated" is checked. If the hole is checked "Plated", the hole attribute is metal. If it is not checked, it is a non-metal hole. Non-metal holes normally have no outer diameter.
3: The spacing of via holes
a: The distance between vias (Via) and vias (Via): the edge spacing of vias in the same network is ≥8mil (0.2mm), and the edge spacing of vias in different networks is ≥12mil (0.3mm).
b: The distance between the plug-in hole and the plug-in: the distance between the hole edges is ≥ 17mil (0.45mm), and the limit is 12mil. When making the plug-in hole PCB, the drilling hole will be pre-drilled by 0.15mm. After drilling, the copper will be sunk to ensure that the hole diameter after sinking the copper is as large as the finished hole in the Pcb design. (hole edge spacing 0.45 = 0.15 hole compensation + 0.1 hole ring + 0.1 hole ring + 0.1 safety distance, unit mm)
c: The impact of near holes on production: If two holes are too close, it will affect the PCB production drilling process. If the two holes are too close, the material on one side will be too thin when drilling the second hole. The force on the drill tip will be uneven and the heat dissipation of the drill tip will be uneven, which will lead to the drill tip breaking, causing the PCB hole to collapse and become unsightly or missing holes. No conduction.
4: Slotted hole (long hole): The knife for drilling slotted holes is different from the knife for drilling round holes, so the minimum width of the metal groove is 0.45mm, and the length of the groove must be >2 times the groove width (<2 times the groove width will If a hole collapses, similar to a near hole, the entire groove will be deformed). The smallest non-metallic groove is 0.8mm wide, and the non-metallic groove is usually milled together with the plate frame.
5. Metal half hole and stamp hole Metal half hole: Metal half hole is the most common name of PCB board factory, and many hardware engineers will call it "stamp hole". The center of the metal half hole needs to be drawn on the center of the outline line, half inside the board and half outside the board. The minimum diameter of the half hole is 0.5mm, and the edge of the hole must be ≥0.5mm from edge to edge. Stamp holes: The so-called stamp holes in the board factory are copper-free holes that serve as bridges and separate boards. Half of them are inside the board and half are outside the board. The size of the stamp holes is generally 0.5mm without copper holes. The edge spacing is 0.3mm (the middle distance is 0.8mm). 5 holes, or a group of 5 or more (add more holes appropriately according to the size of the board and whether there are heavy components). .) According to the size of the board, use stamp holes to connect the impositions. There will be protruding burrs at the position of the holes after dividing the board. If the shape and structure require that there be no protruding burrs, then the stamp holes can be added inward toward the inside of the board.
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