What is PCBA (PCB Assembly)?

What is PCBA?

PCBA, (Printed Circuit Board Assembly), is the finished product after components have a mechanical connection to a PCB, (Printed Circuit Board). These components can range from resistors and diodes to transformers and integrated circuits. The PCBA process tends to include a reflow furnace to heat the printed solder paste so that the components are formed onto the board.

The term PCBA is sometimes confused with the term PCB. PCB, in terms of circuit layers, is classified as either single layer, double layer, or multilayer. These boards can also be divided into a category: the flexibility of the board. There are 3 types of PCB in terms of flexibility, such as rigid board, flexible board, and flex-rigid board. This is different from the term PCBA since it is not a tangible object but rather a service. This service usually includes using SMT and DIP technologies so that all the components and parts are soldered/mounted on a PCB and therefore the electronic functions are complete.

The most basic PCBA process has three steps. It begins with a solder paste printing station. This is where solder paste gets printed onto the boards. After pasting, the components are placed on the board by a pick-and-place machine. When all components have been planted, the board is then ran through a reflow oven so that the board can be completed. Normally, the assembly process ends here. At ACME, we also include wave soldering, selective soldering, machine and visual inspection, and cleaning. One of the latest Nordson selective soldering machines is used to accurately solder in partially assembled PCBs. Our 3D AOI machine from YesTech inspects the components on the boards using not only the length and width, but also the height. This can check for correct solder heights, proper wetting, and missing components. The pictures taken from the 3D AOI are then reviewed by our quality control inspectors so that both real errors and false calls can be identified.

For more information and the services ACME PCB Assembly provides, call (310) 715-1898 or visit our website at http://boardassembly.com.

What is SMT Assembly?

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.