PCBA Tech - SMT production equipment and placement machine programming

The smt placement machine is a key and complex equipment in the entire SMT production. The smt placement machine has developed from an early low-speed mechanical placement machine to a high-speed optical centering placement machine, and has developed to a multi-functional, flexible connection and modularization.

1. Classification

1. According to the speed, it is divided into medium-speed placement machine, high-speed placement machine, and ultra-high-speed placement machine.

2. Divided by function: high-speed/ultra-high-speed placement machine: mainly based on chip components, and there are not many types of chip devices;

3. According to the degree of automation, it is divided into automatic placement machines: most placement machines are of this type.

4. According to the placement method, it is divided into sequential placement machines: it is to paste the components one by one on the PCB in order, and this type of placement machine is usually seen. Simultaneous placement machine: Using a dedicated hopper for placing cylindrical components, all components can be placed on the corresponding pads of the PCB in a single action. When the product is replaced, all materials are replaced, which is rarely used. Simultaneous on-line placement machine: It is composed of multiple placement heads, which sequentially mount PCBs at the same time.

Second, the process flow of precision placement machine

1. Place the circuit board with components on the tray as far as possible perpendicular to the bottom of the camera.

2. Turn on the switch of the placement machine

3. Go up the circuit board with the components and attach the original to the suction cup of the vacuum suction pen.

4. Place the missing printed board to be soldered on the tray, as far as possible perpendicular to the bottom of the camera.

5. Adjust the height knob of the vacuum suction pen to move it down until it is 1-2CM away from the printed circuit board.

6. Turn on the switch of the display, and by observing on the display, adjust the tray knob so that the pins of the IC chip are completely overlapped with the corresponding pads of the printed circuit board to be soldered.

7. Place the IC chip on the vacuum nozzle in a vertical manner and gently place it on the corresponding pad of the printed circuit board.

8. Since the suction nozzle has not been powered off, the suction nozzle cannot be removed immediately at this time, turn off the switch to stop the suction nozzle, and gently move the vacuum nozzle upward in the vertical direction, and the mounting is completed.

SMT placement machine programming

The main task of the placement machine is to accurately mount various components on the PCB board, which is controlled by a computer and a vision system. The basic principle of placement is to pick up the components from the feeder through a vacuum nozzle, and the recognition device The component shape and size are calibrated, and then the components are mounted according to the position coordinates set in the program. The entire mounting process is completed by the computer-controlled corresponding program. The main procedures include:

1. Position coordinate program of components (NC program)

2. Component outline size shape program (PARTS program, SUPPLY program)

3. Arrangement order of components on the placement machine (ARRAY program) 

4. Substrate recognition method (MARK program)

5. The outline coordinate size and positioning method of the PCB board (BOARD program) Take the Panasonic model as an example

The main content of each part of the program:  PCB board program:

It mainly includes: the outline size of the PCB board, the thickness of the substrate, and the positioning method of the PCB board. MARK program:

Mainly include: MARK point shape and size, MARK shape, MARK point recognition type, substrate material type, PCB board brightness selection (BOARD LIGHT). The vision system of the placement machine is a real-time image recognition system based on a computer. The camera detects the light intensity distribution signal of the MARK point within a given range, and is processed by a digital signal circuit into a digital image signal, and then divided into a certain number In the network pixels, the value of each pixel gives the average brightness of the MARK point. There are two ways to identify the MARK point: one is grayscale recognition (that is, grayscale resolution recognition), and the image Multi-level brightness is used to express the resolution. It specifies the discrete value at which the placement machine can distinguish the measured light intensity at a given point. Generally, 256 levels are used; the other is BINARY recognition, which is a grid covering the original image. size.