What is SMT? - China PCBA Supplier

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SMT patch stands for a series of technological processes based on PCB (Printed Circuit Board). SMT, or Surface Mount Technology, is the most popular technology and process in the electronics assembly industry.

Nowadays, electronic products require various SMT chip processing techniques since they are designed by PCB along with capacitors, resistors, and other electronic components, according to the circuit diagram. In order to pursue miniaturization, electronic products need surface mount components instead of previously used perforated plug-in components. This is especially true for integrated circuits (ICs), which are now larger and more highly integrated.

SMT Process

Solder Paste printing --> Parts Placement --> Reflow Soldering --> AOI Optical Inspection --> Maintenance --> Sub-board.

To meet customer needs and strengthen market competitiveness, factories now need to produce high-quality products at low cost and high output. The development of electronic components, integrated circuits (IC), and the diversified application of semiconductor materials is imperative. As the production process of international CPU and image processing device manufacturers such as Intel and AMD has advanced to more than 20 nanometers, the development of SMT, such as surface assembly technology and process, is not far behind.

SMT chip processing has many advantages, such as high assembly density, small size, and light weight of electronic products. The volume and weight of chip components are only about 1/10 of that of traditional plug-in components. After SMT is adopted, the volume of electronic products is usually reduced by 40%~60%, and the weight is reduced by 60%~80%. SMT is also known for high reliability, strong anti-vibration ability, low defect rate of solder joints, good high-frequency characteristics, and reduced electromagnetic and radio frequency interference. It is easy to realize automation and improve production efficiency, thus reducing costs by 30%~50%, saving materials, energy, equipment, manpower, time, etc.

Given the complexity of the process flow of SMT patch processing, many SMT patch processing factories have emerged, specializing in SMT patch processing. In Shenzhen, the electronics industry has seen a vigorous development, which has led to the prosperity of the SMT patch processing industry.

What is SMT?

SMT basic process components include: screen printing (or dispensing), placement (curing), reflow soldering, cleaning, testing, and repair

1. Silkscreen: The purpose of a screen printing machine, located at the forefront of the SMT production line, is to leak solder paste or patch glue onto the PCB pads to prepare them for the soldering of components.

2. Dispensing: The glue dispenser, positioned at the forefront of the SMT production line or behind the testing equipment, drips glue onto the fixed position of the PCB board to fix the components.

3. Mounting: The placement machine, located behind the screen printing machine in the SMT production line, accurately mounts the surface mount components to the fixed position of the PCB.

4. Curing: The curing oven, positioned behind the placement machine in the SMT production line, melts the patch glue to firmly bond the surface assembly components and the PCB board together.

5. Reflow soldering: Similarly, the reflow oven, located behind the placement machine in the SMT production line, melts the solder paste to firmly bond the surface assembly components and the PCB board together.

6. Cleaning: A washing machine is used to remove harmful solder residues such as flux on the assembled PCB board. Its location may not be fixed, it can be online or offline.

7. Inspection: To inspect the welding and assembly quality of the assembled PCB board, various equipment such as magnifying glass, microscope, online tester (ICT), flying probe tester, automatic optical inspection (AOI), X-RAY inspection system, functional tester, etc. can be used. The location of these tools can be configured at a suitable place on the production line according to the needs of the inspection.

8. Rework: Lastly, if PCB boards fail to detect faults, they can be reworked using tools such as soldering irons, rework stations, etc. These tools can be configured at any position in the production line.

Single Sided Assembly

Incoming Inspection => Silk Screen Solder Paste (Point Patch Glue) => Patch => Drying (Curing) => Reflow Soldering => Cleaning => Inspection => Repair

Double-sided assembly

A: Incoming inspection => PCB's A-side silk-screen solder paste (point SMD glue) => SMD PCB's B-side silk-screen solder paste (point SMD glue) => SMD => Drying => Reflow soldering ( It is best to only apply to side B => cleaning => inspection => repair.

B: Incoming inspection => PCB's A side silk screen solder paste (point patch glue) => SMD => Drying (curing) => A side reflow soldering => Cleaning => Turnover => PCB's B side point Patch glue => patch => curing => B surface wave soldering => cleaning => inspection => repair

This process is suitable for reflow soldering on the A side of the PCB and wave soldering on the B side. In the SMD assembled on the B side of the PCB, this process should be used when there are only SOT or SOIC (28) pins or less.

Double-sided Assembly Process

A: Incoming inspection, PCB A side silk screen solder paste (point patch glue), patch, drying (curing), A side reflow soldering, cleaning, flipping; PCB B side silk screen solder paste (point patch Glue), patch, drying, reflow soldering (preferably only for side B, cleaning, testing, and repairing)

This process is suitable for picking when large SMDs such as PLCC are attached to both sides of the PCB.

B: Incoming inspection, PCB A side silk screen solder paste (dot patch glue), patch, drying (curing), A side reflow soldering, cleaning, flipping; PCB B side dot patch glue, patch, Curing, B-side wave soldering, cleaning, inspection, rework) This process is suitable for reflow on the A-side of the PCB.