SMT

 

SMT(surface-mount technology) refers to one of the most popular technologies in the electronic assembly industry. Surface-mount technology (SMT) is an electronics manufacturing process that mounts Surface Mount Components(SMCs) precisely onto the surface of Printed Circuit Boards(PCBs) to create electrical interconnections between functional components and the interconnecting circuitry in the PCBs (leads-pads) by re-flow soldering or dip soldering.

In general, usual electronic products that use PCBs and a variety of capacitors, resistors and other electronic components in combination are designed according to the circuit diagram, so the various types of electrical appliances require diversified processes by SMT.

SMT Process
SMT basic process factors include screen printing, glue dispensing, SMC placement, curing, reflow soldering, cleaning, inspection, and rework.
1. Screen Printing
Use the screen printer located at the front end of the SMT production line to drop either solder paste or glue to the pads on PCB, preparing for components soldering.
2. Glue Dispensing
Use the glue dispenser located at the front end of the SMT production line or behind the testing equipment to drop glue onto the precise position of the PCB to fix the components onto the PCB.
3. SMC Placement
Use the pick-and-place machine located behind the screen printer in the SMT production line to accurately mount the SMC to the fixed position of the PCB.
4. Curing
Use the curing oven located behind the pick-and-place machine in the SMT production line to melt the glue so that the SMC are firmly bonded to the PCB.
5. Reflow Soldering
Melt the solder paste to hold the components in place. After SMC was placed, the PCB is conveyed into the reflow soldering oven, located behind the pick-and-place machine in the SMT production line.
6. Cleaning
Clean the PCB above the harmful solder residue such as flux after soldering by the cleaning machine, whose position can be variable, either in or off the SMT production line.
7. Inspection
Check assembled PCB for soldering quality and assembly quality. Used equipment include magnifying lens, microscope, in-circuit tester (ICT), flying probe tester, automated optical inspection (AOI), X-ray machine, function tester, etc., their locations can be configured in a suitable place in the production line according to the needs of inspection.
8. Rework
Use the soldering iron, rework station, etc. configured in any position in the SMT production line to rework the PCB that have been detected as faulty.