Why are Computer Circuit Boards Green in Color?
One can always count on the chances of finding a circuit board at the heart of every electronic equipment or gadget, be it an elevator, an escalator, or even your good ol’ phone! Almost seems like they’re the heart and soul of the operations doesn’t it? Close enough! As the name suggests, one can say that Circuit Boards literally act as the circulatory system for the equipment by helping electricity required for its function pass through copper etched conductive pathways.
Circuit boards which are commonly known as Printed Circuit Boards (PCBs) are essentially boards that are used to connect electrical components mechanically using pathways, tracks or traces made of etchings on conductive copper sheets that are laminated onto a non-conductive surface. Before the invention of PCBs, boards with manual point to point wiring were used, however this was often laborious, messy and led to failures and circuits short at wire junctions due to cracking and wearing of insulations.
Now, the new PCBs aren’t as big as hulk or temperamental for sure compared to their predecessors, however they are very, very green. Now, have you ever wondered, why the color green? Out of a world colors to choose from, why this particular color?
Well before we answer that particular question, let’s take a brief look at the various parts of a board that make up the whole!
Think of the wafer thin board as a cake, a layered creamy cake! Now folks keep in mind you can’t eat it, but a colorful imagination never hurts anybody! So let’s name the layers of this circuit board cake, from the innermost to the outermost layer.
- Fiberglass
So the innermost layer or base of the circuit board is made of a non conductive rigid thick material and in most cases the material used is fiberglass. This board is a plain dull grayish brown in appearance.
2. Copper
On top the thick fiberglass layer lies the thin sheet of conductive copper which is laminated on the fiberglass with heat and adhesive. Depending on the type of board this layer can be seen either on one side of the glass or on both, which is called 2 — layered boards.
3. Solder mask
The layer atop the copper sheet is called the solder mask. It’s an insulative and protective layer that is laid over the copper sheet to protect unwanted contact from any metal or conductive material.
The solder mask layer is what gives the PCBs a distinct green color!
4. Silk Screen
This is the top or the outermost layer of a circuit board on which letters and markers are added for easier identification and assembly.
So now that we know the basic components of a circuit board and we have revealed the man/part behind the green i.e. the solder mask, let’s check out the why!
It’s important to understand that circuit boards don’t necessarily have to be green in color, but that it’s just the commonly used color for a multitude of reasons.
Why Are PCBs Green in Color?
I. Material Availability
Since the earliest epoxy resin used as a solder mask was green in color, it became a standard norm for usage, therefore more commercially available at highly affordable rates. It also acts as a better isolation wall between the pads. Board designers choose materials based on its availability, safety, affordability, applicability and thermal survivability.
II. Visual Fatigue Relief
Wavelength of green light has been known to have a relaxing effect for the eyes. This was important during a period where the boards were inspected manually. Green also provides an ample contrast between the color and the labeling on the silk screen thus making it legible and easier for the user to spot errors or use.
III. Superior Quality
Compared to the other colored solder mask epoxy available nowadays, green still takes the prize due to its better performance and lasting duration when compared to boards of other colors like red, blue, black etc. During testing, green solder mask boards showed the highest effectiveness in adverse conditions.
IV. Low Exposure
Refers to the amount of radiation exposure, so darker colors like blue, red, black and more require higher exposure rates. Whereas for green it’s comparatively lower and therefore it’s more preferred. Green solder masks also allow the user to achieve tighter tolerances on their board designs.
However it is important to note that the green in this epoxy is imparted by chlorine. This along with bromine present in the boards being halogens can have adverse effects on the environment and human health. Therefore, it is always viable to look for boards that come without a halogen based epoxy solder mask. PCB manufacturing also leaves the workers in the industry exposed to large quantities of hazardous chemicals, toxic metals, acids and more.
Despite the issues, they are largely outweighed by the benefits. Due to these numerous potential reasons, people, companies and factories often prefer green as the standard/ideal shade rather than experimenting with different colors for a functional and not aesthetic component of an electronic. “Why change a winning formula attitude when it reaps benefits and always works?” is their question.
