Board Assembly (SMT Assembly)
Board assembly is the production step where components are automatically placed on the printed circuit board and soldered in an oven. Its difference from hand soldering is not speed but repeatability: the amount of solder paste, the placement position and the temperature profile are applied identically on every board.
The process consists of three main steps:
- Paste printing: solder paste is passed onto the pads through a thin metal template called a stencil. The amount of paste directly determines the quality of the solder joint.
- Placement: an automatic machine positions the components onto the pads.
- Oven: the board is passed through a temperature profile in accordance with manufacturer data; the paste melts and the joint forms.
After that comes optical inspection and, if required, the assembly of large components soldered by hand. Connectors carrying high current and power components are usually in this second group.
The repeatability of assembly explains why it provides a separate level of quality in series production: as long as the same stencil and the same profile are used, the difference in solder joints between the hundredth board and the first board is minimised. Hand soldering at the prototype stage does not give this consistency; for this reason the first production batch is separately verified.
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