When I was growing up, I often heard the phrase “stop giving me static,” uttered in angst by my mom. According to her, she was trying to confront my occasional back-talking or sass, both of which I would like to say that I have absolutely no recollection of, but you already know that’s not true. In reality, though, I would like to know where she got that phrase from because with what I’m doing today, static means something completely different.
In printed circuit board manufacturing, static is Electrostatic Discharge or ESD, and it can be a real problem if not contained and controlled. Thankfully there are a lot of processes and techniques that PCB contract manufacturers use to make sure that your board doesn’t suffer from ESD contamination. Let’s take a look here at what the different problems are with ESD in electronics manufacturing, and how they can be dealt with.
Potential Problems Due to ESD in Electronics Manufacturing
Many component failures can be traced back to problems with ESD during electronics assembly. It has been estimated that ESD may be responsible for up to a third of manufacturing product losses. Not only is ESD responsible for outright component failures, but often the damage is so slight that it can cause component failures later on during their normal expected life cycle.
In the case of an outright component failure, the damage will be instantaneous. A large enough ESD discharge can damage the internal circuitry of a component by melting metal, or causing an oxide punch-through where a conductive path is formed through the insulating layers. Although these problems can cause a lot of difficulties for manufacturing in that the part will have to be reworked, the larger problems are ESD discharges at lower levels of voltage. Lower levels of ESD will affect the metal and insulation of a part, but not to the point of complete failure. These issues are known as “latent defects,” and can shorten the life of a device causing them to malfunction later when the device is in use on a circuit board.
As components sizes continue to get smaller, their internal circuitry becomes even more susceptible to ESD damage. It is important therefore for PCB contract manufacturers to exercise the greatest amount of caution when handling sensitive devices. Here are some of the steps that are being taken.
Antistatic wrist straps are used to ground technicians working on electronics
Methods to Control ESD During Manufacturing
To protect the sensitive components from ESD contamination during manufacturing, there are four areas that PCB contract manufacturers will concentrate on:
- Component identification: Although sensitive devices are pre-packaged from the manufacturer in static controlled containers, it is still important for the PCB CM to identify which components are more sensitive than others, and handle them appropriately. Not only is this important for ESD, but for moisture-sensitive parts as well.
- Component handling: Once the components are in-house, the PCB CM needs to follow documented procedures for handling them. This includes their use within designated ESD protected areas of the manufacturing floor and ensuring that assembly technicians are trained and prepared for working with these parts.
- Establish ESD protected areas: Areas for working with ESD sensitive parts need to be set up with the correct tools and equipment to minimize the generation of static electricity. These areas need to be controlled to ensure that only workers trained in ESD control methods and are prepared with the proper equipment have access.
- Dissipate ESD: No matter what, the potential for ESD will never completely go away. Therefore, it is important that workers use proper ESD dissipation methods. These include using grounded wrist straps, wearing ESD-safe clothing and gloves, using ESD-safe tools, and working on anti-static floor mats.
In addition to the steps above that a CM will take to control ESD in the manufacturing of a printed circuit board, there are additional steps as well. The board should be designed to be as robust as possible against the effects of ESD. This includes using components that are more resistant to ESD and designing in more protective input circuitry. Also, once the board is manufactured it should be shipped in static controlled containers and handled by technicians trained in ESD control methods.
What Your Local PCB CM Should be Doing to Protect Your Boards from ESD
For over 30 years at VSE, we have been building circuit boards for different technologies and industries. As such we have accumulated a vast amount of knowledge about working with electrostatic sensitive devices, and have designed our ESD protection processes accordingly. Our component handling is tightly controlled to ensure that sensitive components are protected all the way from incoming receiving to final assembly. Our technicians are highly trained in ESD control methods, and their work stations are designed with electrostatic dissipation in mind.
