Can Product Designers destroy electronics (PCBs) with incorrect enclosure plastic?
The short answer is YES! In environments like those met in Saudi Arabia, the wrong choice of plastic can result in the destruction of electronics (PCBAs). The problem is insidious. ESD (electrostatic discharge) damage to electronics can be non-fatal at the time but nevertheless induce premature failure. ESD damage is a horror that no designer wants his or her product dogged with. Read on to learn how product designers may avoid this problem.
What is ESD and how does it damage electronics through incorrect product design plastic choices?
Human beings and the atmosphere become electrically charged. The most common example we all know is from touching something metal and getting an electric shock (it hurts!). Humans are the conduit through which discharge takes place.
When humans handle or are near to electronics (PCBAs – assembled printed circuit boards [PCBs]), these charges can flow and destroy the electronics.
The problem is that these discharges can transmit through plastics.
That electronics is in a plastic enclosure gives no guarantee of protection.
The solution lies, among other things, in the choice of plastic. If product designers are designing a product that could be at sites where ESD is a problem, they must make the right plastic material choice.
(Note that in relatively humid countries like Britain problems like this are much less severe).
What is the right way to protect electronics in a plastic enclosure?
The answer has two elements:
- Choose a plastic with the right ESD properties.
- Design the enclosure such that there is a dissipative path to ground through such plastics.
Plastic ESD properties: the ESD plastic property that is relevant is something known as the loss angle for the plastic, which it is not necessary to define here but is the degree to which the plastic allows charge to flow through itself. On data sheets it is defined as tanδ. Do not be fooled into thinking it is conducting (measure its resistance and the result will be very high) – it is dissipative, which means it will allow charge to flow.
Path to ground: this concept is more difficult to grasp, particularly for someone without a knowledge of electrical engineering. For the charge to dissipate in a controlled fashion without a spark, there must be a continuous, dissipative electrical path to the electrical ground point on the device. This means that every piece of dissipative plastic must connect intimately, and through them as a whole a path all the way to a piece of metal that is at electrical ground can be traced. No piece of plastic in the enclosure can be insulated from the others electrically. The EM would welcome approaches to explain this – feel free to Contact Us if such is needed.
A further myth that needs dispelling was stated by an injection moulding company – shows even seeming experts must be checked. The myth is that ESD plastics are black – not so – e.g. ESD mats are often blue.
The Product Design Opportunity
A product designer that bottoms out a choice of plastic that is ESD friendly, particularly if designing product for a country where ESD is atrocious like Saudi Arabia, gains a significant USP.
Please feel free to Contact Us if more information is needed or practical help can be given.