PCB Circuit Board Assembly Method and Nine Points For Attention

First, why the board

The circuit board needs to be affixed with components on the SMT patch line after the end of the PCB design of the entire disk, and each SMT processing factory will specify the most appropriate size of the circuit board according to the processing requirements of the assembly line, such as the size is too small or too large, and the tooling for fixing the circuit board on the assembly line can not be fixed. Then the question comes, what if the size of our circuit board itself is less than the size specified by the factory? That is, we need to put the circuit board together, put multiple circuit boards together into one piece. Patchwork can significantly improve efficiency for both high speed mounters and wave soldering.

When making a patchwork, it is easy to separate multiple boards to avoid damaging the circuit board when separating, and determine which type of patchwork is used according to the shape of the single variety of your patchwork. There are three main ways of PCB assembly: V-CUT, punching slot and stamp hole. The size of the board can not be too large, nor too small, generally very small board can be assembled processing or convenient welding and assembly.

1. PCB assembly mode - V-CUT

V-CUT refers to the combination of several boards or the same board together, and then after the PCB board processing is completed, a V-CUT machine is used to cut a V-shaped slot between the boards, which can be broken apart when in use. It's a popular way nowadays.

2. PCB piece-punching groove

Punching refers to the milling machine between the board and the board or inside the board as needed, which is equivalent to digging.

3. PCB Mosaic mode - stamp hole

The so-called stamp is to use a very small hole to link the plate to the plate, which looks like the zigzag shape on the stamp, so it is called the stamp hole link. Stamp hole links require high control burrs on all sides between plates, that is, only a little stamp hole can be used instead of V-wire.

Nine points to note PCB board:

1. The outer frame (clamping edge) of the PCB assembly should adopt a closed-loop design to ensure that the PCB assembly will not be deformed after it is fixed on the fixture;

2. PCB board width ≤260mm (SIEMENS line) or ≤300mm (FUJI line); If automatic dispensing is required, PCB board width × length ≤125mm×180mm;

3. PCB assembly shape as close to the square, recommended to use 2×2, 3×3,...... A jointed board; But don't put it together as a yin-yang board;

4. The center distance between the small plates is controlled between 75mm and 145mm;

5. When setting the reference anchor point, an open weld area larger than 1.5mm is usually set aside around the anchor point;

6. There can be no large devices or protruding devices near the connection point between the outer frame and the internal small board, the small board and the small board, and the edge of the components and the PCB board should be left with a space greater than 0.5mm to ensure the normal operation of the cutting tool;

7. four positioning holes are opened at the four corners of the outer frame of the plate, the aperture is 4mm±0.01mm; The strength of the hole should be moderate to ensure that it will not break during the process of upper and lower plates; The aperture and position accuracy should be high, the hole wall is smooth without burrs;

8. each small board in the PCB assembly must have at least three positioning holes, 3≤ aperture ≤6mm, no wiring or placement is allowed within 1mm edge positioning holes;

9. for the whole board positioning of PCB and the reference symbol for the positioning of fine-pitch devices, in principle, the QFP with a spacing of less than 0.65mm should be set in its diagonal position; The positioning reference symbols for the PCB sub-board should be used in pairs and arranged diagonally on the positioning elements;