Commercial Processes For Electrical & Mechanical Systems (AQA GCSE Design & Technology): Revision Note
Exam code: 8552
Pick and place assembly
Pick-and-place assembly uses automated equipment to position electronic components accurately onto printed circuit boards
How does pick and place assembly work?
Solder paste is applied to PCB pads using a stencil
Component reels or trays feed parts into the machine
A robotic head picks components and places them at programmed coordinates
The populated PCB normally passes through a reflow oven to melt the solder paste
Typical uses
Mobile phones, computers, controls and other high-volume electronic products
Quality and production
Cameras and sensors check position and orientation
Automation is fast and accurate for very small surface-mount components
Worked Example
Why is pick-and-place assembly suitable for modern PCBs?
[1 mark]
Answer
It places many tiny components quickly and accurately, with more consistency than manual assembly. [1]
Flow soldering
Flow soldering, often called wave soldering, joins through-hole components by passing the underside of a PCB over a controlled wave of molten solder
How does flow soldering work?
Components are inserted and held in the PCB
Flux is applied to clean and prepare the joints
The board is preheated
The underside contacts a solder wave, coating exposed pads and leads before cooling
Typical uses
Batch and mass production of through-hole electronic assemblies
Quality and production
Conveyor speed, solder temperature, flux and contact time must be controlled to prevent bridges, dry joints or heat damage
Worked Example
State one process setting that affects flow-soldering quality.
[1 mark]
Answer
Solder temperature, conveyor speed, flux quantity, preheat temperature or contact time. [1]
Examiner Tips and Tricks
When asked why an automated process like pick-and-place or flow soldering suits commercial manufacture, don't just write 'fast' or 'consistent' , explain what makes it consistent. For flow soldering, it's that every joint on the board passes over the same controlled wave of molten solder in a single pass, so hundreds of boards get identical joints without anyone soldering each one by hand.
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