When it comes to electrostatic discharge (ESD), most of us are well acquainted with the phenomenon when we touch a doorknob after petting our dog, or walking across a particularly wooly carpet. Such an interaction can register a voltage anywhere from 750V-7KV, and while that can be enough to set off a spark and give you a nasty shock, the consequences rarely last beyond a quick moment of discomfort and annoyance.
The procurement and handling of sensitive electronic inventory, however, is another matter entirely. Although some components are more sensitive to ESD than others, a charge as low as 50V is enough to permanently damage their internal circuitry and render them completely unsalvageable. While specialized ESD procedures were formally reserved only for certain designations of semiconductors — such as those embedded with Metal Oxide Semiconductor technology (MOS) designed to not dissipate charges in a controlled manner — today the trend toward miniaturization has led even some passive components to require additional precautionary measures. Some of these components are so sensitive, in fact, they do not have to make physical contact to be damaged.
In order to mitigate the potential risk of ESD-related collateral damage, your warehousing infrastructure (whether in-house or through a trusted supply chain partner) should have a series of detailed procedures in place designed to keep your inventory secure. At EDX, our approach comprises of two points of emphasis, handling and storage, and we have adopted separate processes for both that we employ for each component that passes through our doors.
In order to properly inspect and handle ESD-sensitive inventory, it’s imperative that the handler, as well as the handler’s environment, be grounded to the same potential. Electrostatic discharge is nothing more than a crude electric current, where a charge imbalance between two points pushes electrons to flow until equilibrium is reached. If there is no imbalance, there is no potential to establish a current. To accomplish this, your procedure should involve grounding as many elements within the vicinity as possible using a variety of equipment. ESD mats on the floor will prevent charge accumulating ground charge, and special ESD surfaces should be used during inspection and packaging. If more involved inspection protocols are required, consider investing in a set of ESD-safe tools, which are becoming increasingly available as demand for them has multiplied.
In addition to these procedures, specialists assigned to handle the components should, at minimum, wear antistatic wrist straps that ground the wearer to a conductor via connected wire. Antistatic shoes and clothing are also available for maximum protection should the components in question necessitate it.
The risk of ESD does not end with the handling process, and equal attention must be paid to the processes in place to protect your inventory during storage – especially if storage is required to support a particularly prolonged product life cycle. Raw die and wafer, for example, which is susceptible to oxidation as well as even the slightest discharge, requires highly-regulated environments specially designed to maintain them for many years. The desiccant ECD dry cabinets at EDX, for example, feature a unique electrically conductive powder paint surface-over-steel construction designed to ward off electrostatic discharge.
It must be said that while none of these recommendations require a significant investment on their own, investing in them to the scale high-level manufactures require may rack up quite a bill. This calls into play the need to work with your quality assurance team and engineers to determine what procedures and equipment are necessary. It’s certainly better to have too much ESD protection than not enough, but in a hyper-competitive marketplace where working capital is a precious commodity, a balance must be found between security and cost-effectiveness. Every component will come with its own inherent risk, needs, and sensitivities, and it’s up to you, your company, and your supply chain affiliates to determine where the line is between necessity and excess.