A student is making a printed circuit board (PCB) for a moisture sensor that will be used in a garden irrigation system. The PCB will hold several electroni...
Question 1 Report
A student is making a printed circuit board (PCB) for a moisture sensor that will be used in a garden irrigation system. The PCB will hold several electronic components including resistors, a transistor and an LED.
(a) State two safety precautions that should be followed when soldering components onto a PCB. [2]
(b) Name the chemical solution used to remove unwanted copper from a PCB during the etching process. [1]
Answer Details
(a) Two safety precautions when soldering components onto a PCB: [2]
- Wear safety goggles to protect the eyes from splashes of hot molten solder, which can cause serious burns to the cornea.
- Use a heat-resistant mat beneath the work to protect the bench surface from the high temperature of the soldering iron tip (typically 350-400 degrees C) and any drips of solder.
Other acceptable precautions include: ensuring adequate ventilation to avoid inhaling flux fumes, never touching the tip of the soldering iron, tying back loose hair and clothing, and clamping the PCB in a holder rather than holding it by hand during soldering.
(b) The chemical solution used to etch (remove unwanted copper from) a PCB is ferric chloride (iron(III) chloride, FeCl3). [1]
Ferric chloride is an acidic solution that dissolves exposed copper from the PCB surface. The areas of copper that are to remain (forming the circuit tracks) are protected by an etch-resistant mask applied during the design transfer stage. The board is immersed in the warm ferric chloride solution and gently agitated until all unprotected copper has been dissolved away, leaving only the desired track pattern.
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