SMT, or surface-mount technology, is a method where the components are mounted or placed onto the surface of a PCB, or printed circuit board. There are some components that are unsuitable for SMT assembly, such as large transformers and heat-sinked power semiconductors, but that is where other processes come in play. Employing this technology speeds up the production process but the catch is the risk of defects due to component miniaturization and denser packing of boards. This type of assembly is also highly dependent on automation and medium to high-scale production. Here, at ACME PCB, we can work with components as small as 01005 and assemble high quantity boards to low quantity boards.
SMT assembly can be done on both sides of a PCB, although the board needs to be ran through a re flow oven after each side so that the components do not fall off when switching to the other half. The SMT process starts off with a screen-printing process that applies solder paste onto all the solder pads. These solder pads are where the components are placed. The pads are normally flat and made from either tin-lead, silver, or gold-plated copper. After the board is pasted, it is placed onto a conveyor belt and sent to a pick-and-place machine where reels of components are fed into the machine and then placed onto the PCB. These components are sometimes in static free trays or plastic tubes.
The last step in the SMT assembly process is the reflow soldering oven where the solder particles in the solder paste is melted and therefore bonding the component leads to the solder pads. At ACME PCB, we make sure to check each board for defects and errors before sending them to the reflow oven. After the heating process, the boards are put into our in-line washer to remove any traces of white residue, dirt, and other contaminants. If any leadless parts are used, they are inspected using our X-ray machine to ensure solder joint quality.
For business inquiries or quoting services, call ACME PCB Assembly at (310) 715-1898 or visit our website at http://boardassembly.com.