Solder paste printing --> parts placement --> reflow soldering -->AOI optical inspection --> maintenance --> sub-board.

Electronic products are pursuing miniaturization, and the previously used perforated plug-in components cannot be reduced. Electronic products have more complete functions, and the integrated circuits (ICs) used no longer have perforated components, especially large-scale, highly integrated ICs, which have to use surface patch components. With mass production of products and automation of production, the factory must produce high-quality products with low cost and high output to meet customer needs and strengthen market competitiveness. The development of electronic components, the development of integrated circuits (IC), and the diversified application of semiconductor materials. The revolution of electronic technology is imperative and chasing the international trend. It is conceivable that when the production processes of international cpu and image processing device manufacturers such as intel and amd have advanced to more than 20 nanometers, the development of smt, such as surface assembly technology and process, is not a case.

The advantages of SMT Patch processing: high assembly density, small size and light weight of electronic products. The volume and weight of patch components are only about 1/10 of that of traditional plug-in components. Generally, after SMT is adopted, the volume of electronic products is reduced by 40%~60%. The weight is reduced by 60%~80%. High reliability and strong anti-vibration ability. Low solder joint defect rate. Good high frequency characteristics. Reduce electromagnetic and radio frequency interference. It is easy to realize automation and improve production efficiency. Reduce costs by 30%~50%. Save materials, energy, equipment, manpower, time, etc.

It is precisely because of the complexity of the SMT Patch processing process that there are many SMT Patch processing factories that specialize in SMT Patch processing. In Shenzhen, thanks to the vigorous development of the electronics industry, SMT Patch processing has achieved an industry prosperity.

Patch process

1. Single-sided assembly

Incoming inspection => silk screen solder paste (point patch glue) => SMD => drying (curing) => reflow soldering => cleaning => inspection => repair

2. Double-sided assembly

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

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

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

3. Single-sided mixed packaging process

Incoming inspection => PCB's A-side silkscreen solder paste (point patch glue) => SMD => drying (curing) => reflow soldering => cleaning => plug-in => wave soldering => cleaning => inspection = > Rework

4. Double-sided mixed packaging process

A: Incoming inspection => PCB's B side point patch glue => SMD => curing => flip board => PCB's A side plug-in => wave soldering => cleaning => inspection => rework

Paste first, insert later, suitable for situations where there are more SMD components than separate components

B: Incoming inspection => PCB's A side plug-in (pin bend) => flip board => PCB's B side patch glue => patch => curing => flip board => wave soldering => cleaning => Inspection => Repair

Insert first, then paste, suitable for the situation where there are more separate components than SMD components

C: Incoming inspection => PCB A side silk screen solder paste => SMD => Drying => Reflow soldering => Plug-in, pin bending => Turnover => PCB B side point patch glue => SMD => curing => flipping => wave soldering => cleaning => inspection => rework A side mixed, B side mounted.

D: Incoming inspection => PCB's B side point patch glue => SMD => curing => flip board => PCB's A side silk screen solder paste => patch => A side reflow soldering => plug-in => B-side wave soldering => cleaning => inspection => rework A-side mixed assembly, B-side mounting. First paste on both sides of SMD, reflow soldering, then inserting, wave soldering E: Incoming inspection => PCB's B-side silk screen solder paste (point patch glue) => SMD => drying (curing) => reflow soldering = > Flip board => PCB A-side silk screen solder paste => SMD => Drying = Reflow soldering 1 (partial soldering can be used) => Plug-in => Wave soldering 2 (If there are few components, manual soldering can be used) => Cleaning => Inspection => Rework A side mounting and B side mixed mounting.

5. Double-sided assembly process

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

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 (point patch glue), SMD, drying (curing), A side reflow soldering, cleaning, flipping; PCB B side point patch glue, SMD, curing , B side wave soldering, cleaning, inspection, rework) This process is suitable for reflow on the A side of the PCB.

Process

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

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 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. Mounting: Its function is to accurately mount the surface mount 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 melt the patch glue, so that the surface assembly 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 melt the solder paste, so that the surface assembly 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 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 can be variable, online or offline.

7. 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 position can be configured in a suitable place on the production line according to the needs of inspection.

8. Rework: Its function is to rework the PCB board that has failed to detect. The tools used are soldering iron, rework station, etc. Configured at any position in the production line.