Single sided PCB assembly requires components to be assembled on only one side of the circuit board and is the least complex of PCB surface mount assembly processes. Double sided and variants of surface mount and lead-through combinations are discussed in Sections 9 and 10.
After solder pasting, the PCB travels down the production line to the component pick and place station. Modern picking systems generally utilize air suction pick-up nozzles to collect the component from the reel or packaging format. Components are accurately placed on to the PCB using automatic vision viewing and alignment technology. Each component is placed on to the previously pasted PCB pads, where the tacky consistency of the solder paste secures the component in place during other processes of the board assembly.
Pick and place speeds can exceed 10 placements per second when the PCB contains many small components. Larger components require a slower pick and travel. Poor mechanical set up of the pick and place tool can cause cracked and damaged components if the component travels too far into the solder paste. It illustrates a basic air pick up nozzle and single sided PCB with components placed ready for the solder heat stage.
Ideally, the PCB should pass through the solder heat process as soon as possible. Maximum acceptable dwell time is typically four hours. In free air, the solder paste deteriorates very quickly, causing unreliable PCB solder-ability. Also, solder paste remaining on the stencil for long periods, or solder paste containers left open, will cause solder-ability issues that are difficult to resolve, where operators are not conforming to company procedures. Again, this is a critical parameter when investigating component solder-ability failures.
