Precautions everyone should know when handling circuit boards and electronic components.
Circuit boards are populated with numerous types of electronic components such as transistors, diodes, integrated circuits, resistors, inductors, capacitors and wires. The components on the circuit board have varying currents flowing in them during operation.
During operation, Even the tiniest mistake can lead to short-circuiting on the board, which may result in damage to parts on the board or an electric shock. When the board is not powered (not operating) it is also vulnerable to damage from Electo-static Discharge (ESD).
What are the Risk Factors that Increase the Chances of Short-Circuiting?
Here are some of the most common risk factors that increase the chances of damaging a circuit board:
Touching Circuit Boards with Bare Hands
Human skin is a significant threat for circuit boards since electrostatic charges are present on the skin surface. Touching the circuit board when not properly protected from charge build-up can result in the transfer of electrostatic charges onto the components, causing either temporary or permanent damage to the circuit board. Many ESD events do not cause the board to be inoperable immediately but damage junction in the electronic parts. This damage leads to future failures. These are referred to as Latent Failures.
To prevent damage from ESD, you must have the person, environment and circuit board all at the same potential. This is done by having the board on a grounded surface and the person grounded to the same ground as the board. When the board is moved from place to place, it must first be inserted into a faraday cage, then the person ungrounds, moves the board, regrounds and then removes the board from the faraday cage.
Dust particles can settle in the tiniest of spaces. When dust builds up in aboard, it may create electrical paths that are not wanted and thus create inoperability or out of specification situations.
Low levels of humidity exacerbate static build-up. Higher voltage potentials and slower discharge of static build-up are very real in low humidity conditions. These charges can transfer to the circuit board and cause damage.
Circuit boards coming to the vicinity of or in contact with plastic or a Styrofoam will be exposed to potential ESD events and electric fields from the static build-up. The potentials are likely to result in ESD events. The electric fields around the static generative materials are, in many cases, sufficient in themselves to create damage to electronic components.
Overcrowded Circuit Board
When components are placed close to each other, it is possible that a person working on the board r makes a mistake while soldering the pins of various components or probing during troubleshooting. Inadvertent solder bridging or shorts between points while probing could damage the components on the board.
Which Components Are Most Sensitive to Electrostatic Charges?
The components on an electrical circuit board are made of different materials and have different functions; hence, they exhibit varying degrees of susceptibility to hazards. Let’s look at each a few of the electrical components present on circuit boards relative to their susceptibility to ESD damage.
According to Moore’s Law, the number of transistors on an average chip doubles every two years, which means we are dealing with double the transistors on a circuit board every two years. The increasing number of electrical components on a circuit board means that the chances of component damage are also increasing. As the number of transistors within an IC increases, the geometries are also decreasing, resulting in smaller band-gaps and potentially increased ESD susceptibility.
Diodes are also made up of semiconductor material and have one junction. When a forward bias is applied, above the threshold value, current starts flowing across the junction, and the diode conducts. s. Many different types of diodes might be present on a circuit board such as light-emitting diodes (LEDs), Schottky diodes, Zener diodes etc.
Just like transistors, diodes may be permanently damaged when encountering static charges.
Capacitors are made of metal plates which are separated by a layer of di-electric material. When a voltage is applied across the plates, the plates charge up according to the amount of voltage applied. This results in an imbalance of charge. This imbalanced charge is what the capacitor stores and makes it useful in electronics.
In case an electrostatic charge comes into contact with a capacitor, it might damage the capacitor permanently. ESD damage of a capacitor most often takes one of two forms. Either the ESD discharge exceeds the di-electric breakdown of the capacitors and “punches through” the di-electric creating a conductive path in the di-electric, or the capacitor’s plates are damaged (arc marks and vaporization of plate material) rendering the characteristics of the capacitor different than intended. The damage caused by electrostatic discharge on a capacitor is irreversible; hence, the component would have to be replaced on the circuit board.
How to Avoid Short-Circuiting on Circuit Boards?
To avoid damaging components on a circuit board or components in storage or transport, it is essential that you ground yourself first before handling boards or components. You must not wear clothes made of any material which gathers static charges such as wool, nylon or other synthetic materials. Cotton is the best. Moreover, you should wear an ESD wrist strap, which is an anti-static band that removes any charges present on your body by conducting it to ground.
Use Anti-Static Packaging
Storing circuit boards in anti-static packaging is an excellent way of avoiding a build-up of static charge. Ordinary plastic bags and packaging are not recommended for storing circuit boards because they are a source of electrostatic charges, ESD sensitive boards and components should be stored in a faraday cage (conductive bag, box, etc.).
Use Dissipative Work Surfaces
Using dissipative surfaces while working on circuit boards is yet another great precaution which you can take to save your components from damage. All you need to do is install an ESD safe work surface on your workstation, and you’re good to go. ESD worksurfaces are defined as having an impedance characteristic of at least 10000 ohms per square. Conductive surfaces are likely to be damaging to your work. As a charged object, including a circuit board, approaches a conductive work surface it is likely to discharge rapidly. This rapid dV/dt is the most damaging to electronics. The dissipative surface will result in a slower discharge and thus lower probability of damage.
Keep Circuit Boards in a humidity-Controlled Environment
Proper humidity will result in less static build-up while too much humidity can cause condensation and thus be damaging to electronics. Maintaining a relative humidity between 40 and 60% will significantly decrease the probability of ESD events. In dry environments, ionized air can be used to help reduce static build-up. An air ionizer will put ions into the air that will then combine with damaging charges, thus neutralizing the charge and the hazard. Ionization is NEVER an alternative to grounding personnel.
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