Electrochemisty and Engineering

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orpheus @ hackclub
After high school, I plan to study computer engineering, which generally does not involve much chemistry (or so I thought). However in Grade 12 Chemistry, the unit that stood out to me the most was electrochemistry. I have designed plenty of PCBs and used electronics in my everyday life. After learning about the redox reactions and galvanic cell, I have a better understanding why certain materials are used in computer components. After more research, I learned that computers and chemistry have more 'chemistry' than I thought!

By Selena

What are Printed Circuit Boards?

PCBs are flat boards made up of layers of insulation and conductive materials to make circuits and electronics compact and efficient. These insulating materials are usually made of fiber glass or expoxy and the conductive layers are copper. The copper layers are etched to make routes and make connections in the circuit. In the diagram below, you can see the red and blue copper routes in between the layers.
this is a 3D model of a PCB I designed!
However, PCBs can corrode overtime usually by the oxidation of the copper. Added moisture leads the copper to rust, where I learned that last semester. The lesson explored how the copper goes through a redox reaction with the oxygen and creates rust from migrating to the surface through the water droplet. By understanding this concept, I can apply this to electronics when preventing corrosion and being mindful of the materials my PCB is made out of. The ways it creates moisture is from high humidity, pollutants like smoke, temperature flucuations, and chemical exposure.
The follow reaction below explains the corrosion of copper:
Cu(s) + H2O(l) → CuO(s) + H2(g)

Corrosion on a PCB

In this reaction, the copper solid reacts with water to form copper oxide solid and hydrogen gas. The copper oxide is the rust that forms on the PCB demostrated from the diagram above. Rusted copper is not actually brown, but it turns into a greenish color. A good example of this is the Statue of Liberty where it was originally copper, but turned green!
We can reduce corrosion by
  • Galvanization: using a zinc protective coating on the copper to prevent moisture.
  • Material Selection: gold-plated components are not as reactive or certain copper alloys have greater resistance to corrosion.
    • reactivity series
  • Maintenance: monitoring humidity and inspected for potential pollutants can reduce the chance for corrosion in the future.

    • Batteries

    The most I've seen corrosion in old electronics is in the battery compartment, which is something else I learned in electrochemistry. In a battery, it's not just postive and negative, it's a whole system! Inside a battery, there's 2 solutions with metals that are connected by a wire and a salt bridge, making a loop between them. By making this loop, they are creating seperated redox half-reactions and flow electrons to each side through ions. There's plenty of different types of batteries out there, but they all need to produce a redox reaction for energy to flow through.
    Half reactions of the galvanic cell:
    Anode: Cu → Cu2+ + 2e-
    Cathode: 2Ag+ + 2e- → 2Ag
    In regards to corrosion, the most common cause in old electronics is acid leaking from the battery when the battery is not in use for long periods of time. The build up of hydrogen gas from the half reactions eventually exits and creates a hole for the acid to leak and corrode.
    This is why for computer engineers and manufacturers to be aware of the materials when working with PCBs to prevent faulty products and to maintain them. Or in my case, tinkering with them! Like I said earlier, I design my own PCBs and exploring the connection through electrochemistry has given me a better understanding of how they work. When working with them, I need to be mindful of the materials when I'm soldering components so I don't melt off the non-conductive layer or make sure to maintain my PCBs and batteries to prevent corrosion. Electrochemistry is definitley a topic that I will come back to in university, and looking into how it applies to what I'm currently working on makes me look forward to it!

    Sources