Isn’t the expansion of the PCB industry incredible? In the last 100 years, we’ve gone from using brass wire and pieces of wood to etched copper traces and fiberglass substrates. New industries like the Internet of Things (IoT) and advanced driver assistance systems (ADAS) in cars are accelerating that growth. There are millions of PCBs in existence today, and that number will only continue to grow.
The funny thing is that we design PCBs to last for years and years, but the devices they power often only last a few. Every two years Moore’s Law decrees that our once state of the art PCBs are now obsolete. Then consumers throw them out and buy the next new gadget.
Since we design our PCBs to last, decomposition often becomes a problem and our electronic solutions can become environmental problems. Biodegradable PCBs can help solve the problem of electronic waste while giving PCB designers access to a wider range of material properties for our boards.
Is PCB Waste Really a Problem?
Is PCB waste really a problem? Not only is PCB rubbish real, but the durability and toxicity of PCBs also make it a problem.
Environmental groups estimate that 25,000,000 tons of electronic waste (e-waste) is produced worldwide every year. Nearly all (82%) of that waste ends up in landfills. While we take pride in our PCB designs, the devices they power are often made to a lower standard. Our PCB might last 20 years, but the smart fork they put it in only lasts 1. When that bad idea is buried in a landfill the PCB inside will still be there for years, leaching toxins into the ground.
Well, what if a board is recycled instead of thrown in a landfill? Most recycling processes are hazardous and have serious health risks. In addition, they are labor intensive. This means that boards have to be shipped to countries with low labor costs for recycling. These logistical tricks still ultimately result in high PCB recycling costs. The answer to both problems could be biodegradable PCBs. What if you could put a PCB in a landfill and it simply dissolves?
Biodegradable PCBs would be easier to recycle as well, lowering costs. We have our solution, but it is really possible?
Are “Green” PCBs Really Possible?
Biodegradable PCBs are not just some far-fetched hippie solution that will never happen. Researchers are already studying the materials that can make this a reality.
You may have thought I was crazy talking about dissolving PCBs, but they’re already here. Some researchers have made a water soluble PCB that measures temperature data and transmits that data wirelessly. The conductors in a dissolvable circuit are made from transient metals, such as tungsten or zinc. While these metals are not currently as conductive as copper, silver, or gold, researchers are working on increasing their conductivities. Replacing current metals, which can be toxic, with transient metals would be a big step forward.
The other side of the environmental equation is the PCB substrate. There is a wider variety of materials being studied for use in substrates. Everything from chicken feathers to soybean oil, to sodium carboxymethyl cellulose (Na-CMC). With multiple candidates, there are more opportunities for different substrate specifications as well.
Can Environmentally Friendly Boards Measure Up?
When I hear the words “environmentally friendly” I think flimsy. Obviously, this isn’t a quality we want in our PCBs. So how do green materials compare to traditional ones when it comes to material properties?
Mechanical Properties - The mechanical performance of “green” boards is a real concern. Even if your board is made from banana fibers, you don’t want it to be as weak as a leaf. Biomaterials in their current forms do not quite stack up against FR4 when it comes to strength. However, researchers are now moving into combining substrates materials, and expect to get boards with similar physical properties.
Thermal Properties - Thermal performance is another serious concern. You don’t want your board to catch fire during solder reflow or operation. Biomaterial substrates do have lower temperature thresholds than FR4, but low-temperature solders make manufacturing possible. As far as operation goes, one study using banana fibers operated successfully at 45 C. That’s still a bit low, but good thermal design and further research should push up the temperature range.
Dielectric Constants - Dielectric constants are a big concern as they are becoming more important in high-frequency circuits. This is an area where biodegradable boards compete on the same level as traditional boards. The same banana fiber study achieved dielectric constants between 2 and 36, well within the required range. In fact, the wide range of biomaterials should enable designers to choose between a greater range of dielectric constants for their circuits.
When it comes to material properties, environmentally friendly options are not quite there. However, further research into material options should yield advances in these arenas. Proof of concept circuits have already been created and tested. This shows that “green” boards are not just a foolish dream. As bio-based PCB options grow, they can help us solve the problem of e-waste and electronics recycling.
Board design techniques are getting a lot more complicated, and “green” PCBs will just add to the confusion. You need some good PCB design software to help pick up some of the slack and keep you focused on design. CircuitStudio has a wide range of advanced features that move with the times. If you want to design next gen circuits, you need cutting edge software like CircuitStudio.
Want to talk more about the future of biodegradable boards? Call an expert at Altium.