Surface-mount technology may be a method during which the electrical components are mounted directly onto the surface of a computer circuit board.
An electrical component mounted during this manner is mentioned as a surface-mount device (SMD).
Both technologies are used on equivalent board, with the through-hole technology used for components which are not suitable for surface mounting like large transformers.
An SMT component is typically smaller than its through-hole counterpart because it’s either smaller leads or no leads in the least. These can contain short pins or leads of varied styles, flat contacts, a matrix of solder balls (BGAs), or terminations on the body of the component.
In Surface Mounted Technology (SMT), components are placed directly onto the surface of a PCB to make what’s referred to as a surface-mount device (SMD).
Due to its efficiency and effectiveness, Surface Mounted Technology (SMT) has widely replaced through-hole technology methods for constructing PCBs, however, both methods are often utilized on an equivalent PCB. This is due to some components that are simply not suited to surface mounting.
Additionally, the tiny size of SMDs can create issues, therein the solder joint dimensions still grow smaller as advances are made toward ultra-fine pitch technology.
Ultimately, this means that less solder is able to be used for each joint which can result in voiding, and integrity issues.
The solder connections of SMDs are also capable of being damaged by potting compounds as they go through thermal cycling.
Lastly, SMT shouldn’t be used because of the sole attachment method for any components which will be subject to ongoing mechanical stress, as an example, connectors that are utilized to interface with the external devices which are often attached.
The Surface Mounted Technology (SMT) process starts during the planning phase when the various different components are selected and therefore the PCB is meant employing a software package like Orcad or Cadstar (others are available).
It is important to realize that the process starts at this stage as this is the best time to incorporate as many design features as possible that will make production straight forward and head-ache free.
Quite often circuits are taken from the schematic design phase to PCB layout with the foremost considerations being the functionality, which actually is extremely important, but design for manufacture and assembly (DFMA) should ideally be incorporated.
Once the PCB design has been finalized and components selected subsequent phase is to send the PCB data away to a PCB manufacturing company and components bought within the most suitable way to facilitate automation.
The PCB panel design should be considered and specification created including PCB surface finish to ensure that the format that the PCB’s are received is as expected and suitable for the machines to be used.
Components are available packaged in many different ways such as on reels, in tubes, or in trays as can been seen below.
Most are available on reels which are preferred but sometimes due to ‘Minimum Order Quantities (MOQ’s)’ components are quite often supplied in tubes or in short strips of tape. Both of those packaging types are often used but do need appropriate feeder types.
Components supplied loose in bags should be avoided if possible as can cause hand placements or the necessity for special feeding plates.
Without developed skills when manually soldering it is very easy to reflow the solder of an adjacent SMT component and displace it.
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Many types of SMT component packages can’t be installed in sockets, which give for straightforward installation or exchange of components to switch a circuit and straightforward replacement of failed components.