PCBA Tech - SMT patch processing overview process and use precautions

SMT patch processing overview process

1. Overview of SMT chip processing SMT chip processing technology (abbreviation of Surface Mounted Technology) is currently a popular technology and process in the electronics assembly industry. It is a kind of

1. SMT patch processing overview

SMT chip processing technology (abbreviation for Surface Mounted Technology) is currently a popular technology and process in the electronics assembly industry.

It is a kind of surface assembly components without leads or short leads (SMC/SMD for short, chip components in Chinese) mounted on the surface of a printed circuit board or other substrates through reflow soldering or dip soldering, etc. Method to weld and assemble the circuit assembly technology.

2. SMT patch processing flow

The basic process components of SMT patch processing include: screen printing (or dispensing), placement (curing), reflow soldering, cleaning, inspection, and repair.

1. SMT patch screen printing: Its function is to leak solder paste or patch glue onto the PCB pads to prepare for the soldering of components. The equipment used is a screen printing machine (screen printing machine), located at the forefront of the SMT patch processing production line.

2. SMT patch dispensing: It is to drip glue onto the fixed position of the PCB board, and its main function is to fix the components on the PCB board. The equipment used is a glue dispenser, located at the forefront of the SMT production line or behind the testing equipment.

3. SMT chip placement: its role is to accurately install surface mount components to a fixed position on the PCB. The equipment used is a placement machine, located behind the screen printing machine in the SMT production line.

4. SMT patch curing: its function is to melt the patch glue, so that the surface mount components and the PCB board are firmly bonded together. The equipment used is a curing oven, located behind the placement machine in the SMT production line.

5. SMT patch reflow soldering: Its function is to melt the solder paste, so that the surface mount components and the PCB board are firmly bonded together. The equipment used is a reflow oven, located behind the placement machine in the SMT production line.

6. SMT patch cleaning: Its function is to remove the solder residues such as flux that are harmful to the human body on the assembled PCB board. The equipment used is a washing machine, and the location may not be fixed, it may be online or offline.

7. SMT patch inspection: its function is to inspect the welding quality and assembly quality of the assembled PCB board. The equipment used includes magnifying glass, microscope, online tester (ICT), flying probe tester, automatic optical inspection (AOI), X-RAY inspection system, functional tester, etc. The location can be configured in a suitable place on the production line according to the needs of the inspection.

8. SMT patch rework: its function is to rework the PCB boards that have been detected to be faulty. The tools used are soldering irons, rework stations, etc. Configured at any position in the production line.

SMT patch processing process and precautions for use

SMT patch processing flow: 1. The function of silk screen printing is to leak solder paste or patch glue onto the PCB pads to prepare for the soldering of components. The equipment used is a screen printing machine (screen printing machine), located in SMT production

SMT patch processing flow:

1. Silk screen

Its function is to print solder paste or patch glue onto the PCB pads to prepare for the soldering of components. The equipment used is a screen printing machine (screen printing machine), located at the forefront of the SMT production line.

2. Dispensing

It drops glue onto the fixed position of the PCB board, and its main function is to fix the components on the PCB board. The equipment used is a glue dispenser, located at the forefront of the SMT production line or behind the testing equipment.

3. Mounting

Its function is to accurately install the external assembly components to the fixed position of the PCB. The equipment used is a placement machine, located behind the screen printing machine in the SMT production line.

4. Curing

Its function is to ablate the patch glue, so that the surface assembled components and the PCB board are firmly bonded together. The equipment used is a curing oven, located behind the placement machine in the SMT production line.

5. Reflow soldering

Its function is to ablate the solder paste, so that the externally assembled components and the PCB board are firmly bonded together. The equipment used is a reflow oven, located behind the placement machine in the SMT production line.

6. Cleaning

Its function is to remove harmful welding residues such as flux on the assembled PCB board. The equipment used is a washing machine, and the orientation can be not fixed, and it can be online or offline. Precautions for the use of SMT patch processing:

1. When the technician uses a multimeter to measure the chip resistor, he should disconnect the power supply in the circuit, and disconnect one end of the chip resistor from the circuit to avoid parallel connection with other circuit components, which will affect the accuracy of the measurement.

Do not use two hands to touch the two ends of the meter at the same time when measuring the resistance. This will form the parallel connection of the patch resistance and the human body resistance, which will affect the accuracy of the measurement. If you need to measure high-precision chip resistors, you need to use a resistance bridge to measure.

2. Before using the resistance, use a multimeter to measure the resistance, and it can be used after checking. For chip resistors with text signs, make sure that the side with the signs is facing up during mounting for later inspection.

3. Potentiometers are prone to problems such as loud noises after use, and unpackaged potentiometers with switches have a higher probability of appearance. The main reason is that the resistance film is damaged and the contact resistance is unstable. In lighter conditions, alcohol can be used to clean the resistive film to remove dust and carbon powder caused by friction. If it is severe, consider replacing the potentiometer with a new one.