How to Avoid Pits for Small-Sized Holes and Slots in Device Pins?
PCB board for plug-in device pins need to be drilled to insert the device, PCB drilling is a process of PCB plate making, is also a very important step. Mainly for the board holes, alignment needs to play a hole, the structure needs to be punched to do positioning, plug-in devices need to play pin holes and so on; multi-layer board drilling is not a one-time play through, some holes are buried in the board, some of the board on top of the punch through, so there will be a drill two drilling.
1. USB device pin oval slot and USB type device shell pins are generally oval pins, some USB device pins are relatively small, so the design of the slot hole is smaller than the production process capacity.
Because the industry’s smallest drilling machine slot knife is only 0.6mm, if the design of the slot hole is less than 0.45mm can not be produced. For example: the design of the device pin hole is only 0.3mm, the production of the use of 0.6mm slotting knife drilling, hole and then plated with copper after the finished product aperture is 0.45mm, the finished product aperture is larger than the pin aperture diameter of 0.15mm, the over-tolerance device soldering is not secure. Therefore, it is recommended to design the pin slot hole larger than 0.45mm.
2. The pin holes of the wiring components and the pins of some plug-in components are very small. When the designed plug-in hole is less than 0.5mm, the pin hole may be mistakenly treated as a via at the manufacturing end. Especially for files designed by Altium Designer software, all vias have windows when outputting Gerber, so it is easy to confuse small device pin holes with vias.
When the plug-in hole of the pin is mistakenly treated as a via, the problem is that the device cannot be plugged in without compensation for the aperture, or the window is cancelled together with the via. The pad is made of oil cover and cannot be welded.
3. high-voltage isolation to prevent pcb creepage milling slot, power supply boards are generally in the board will be designed to isolate the slot. Manufacturing end of the smallest milling cutter diameter is 0.8mm. less than 0.8mm milling slot is not convenient to produce, the cost is very high.
All non-metallic slots in the board are recommended to be designed larger than 0.8mm. Non-metallic grooves do not need to be copper-plated, the choice of milling grooves to reduce the cost of many, the cost of drilling grooves is high, and the efficiency is slow. Therefore, it is recommended that the design of non-metallic grooves at the design end of the design more than 0.8mm.
Design engineers often ask the board factory production, circuit board drilling compensation is how much, according to what tolerance compensation, especially the mounting holes (positioning holes) and plug-in holes, if the compensation is not in place or the design is not in place, it will affect the entire production and installation of the circuit board used.
General circuit board holes are divided into two kinds of holes, one with copper and no copper holes, copper is mainly used for soldering and conduit holes, no copper is mainly used for mounting and positioning use.
If it is metallization drilling, we need to drill copper-free holes on the PCB first, and then plating a layer of copper foil on the hole wall, then if the tin spraying process needs to make up 0.1-0.15mm, that is, the drilling tool needs to be used 0.2-0.25mm, the specific size of each factory according to the production process and machinery and equipment; if it is the OSP, gold plating process needs to make up 0.05-0.1mm or so; if it is the OSP, gold plating process needs to make up 0.05-0.1mm or so; if it is the OSP, gold plating process needs to make up 0.05-0.1mm or so. The specific size depends on the production process and mechanical equipment of each factory.
If it is a non-metallized hole, that is, no copper hole, then the compensation value is about 0.05mm, for example, 0.1mm hole needs to use 0.15mm drilling tool, of course, generally no copper hole is a relatively large hole, according to the actual size to do compensation correction.
Design engineers generally do not have to consider the compensation size of the board factory in the design process, the general manufacturer in the production process will default to the design of the hole information for the finished hole size, the circuit board manufacturer will be in the process of making the information, automatically designed to compensate for the tolerance. Produce the hole size that the design engineer wants.
