ESD Control, Return On Investment

Ryne C. Allen

November 1999

I. Introduction to ESD Control Programs

ESD Control programs are an essential part of a quality process and are always needed when handling ESD sensitive electronic/semiconductor devices. The extent of the ESD Control program is determined by the ESD Sensitive (ESDS) devices themselves and how they are handled. Refer to article "How to Set Up an ESD Control Program" [1] for additional information.

Having ESD awareness and following through with an ESD Control program is essential in reducing quality failures due to ESD. ESD can affect product reliability with catastrophic damage which is readily apparent to latent degradation. Latent degradation is particularly expensive requiring costly inspection and rework cycles in-house or product failure in the field. Maintaining good ESD controls will improve product throughput or yield, increasing reliability in the field which improves customer satisfaction leading to increased future business.

One test equipment manufacturer noted that GMR heads were being damaged during or after testing. These heads are extremely sensitive to ESD, and require additional handling precautions.

It is very important when designing and implementing an ESD Control program to know the ESD susceptibility of the ESD Sensitive (ESDS) devices you are trying to protect. Classification of these devices should include all simulation models human body model (HBM), Machine Mode (MM), and Charged-device Model (CDM) that will properly characterize the devices' sensitivity when handled at various locations within the facility [6]. This will allow for the most economical program design.

Gene Chase, an ESD Consultant with ETS Inc., is quoted as saying "Millions of dollars are lost every year due to ESD [4]. Many of these incidents occur within the computer and communications industry." Examples of losses from ESD may be any of the following:

• Lost Time
• Loss of Connection
• Loss of Data
• Shocks to Personnel
• Upset to A System Requiring A Re-Boot
• Damage to Equipment
• Equipment Hardware Failure

To properly determine the return on investment (ROI) from your ESD Control program, you must collect return, repair and scrap cost data before and after implementation.

Terry O’Malley, former AT&T ESD Manager, had collected data from several AT&T facilities both before and after instituting an ESD Control program. The data speaks for itself; see figure 1 for a graph of two facilities that were monitored. There was over a 50% savings in return and repair costs found at both facilities after initiating their ESD Control programs.

Combined Cost Benefits of ESD Program Management [2]

Difference in component sensitivity between through-hole and surface mount devices is dependent on the architecture and technology packaged. Typically, surface mount devices have much smaller architecture making them more susceptible to ESD than through-hole packaged devices. The width of the circuitry conductors is as small as 0.10 micrometer (equal to 0.0001millimeter or 0.000004 inch). To pack more and more circuitry into small packages, the spacing isolating circuitry has been reduced and can be as little as 300 m m. A human being cannot feel ESD voltage until it reaches approximately 3,000 volts. A discharge of static electricity is literally a little lighting bolt, producing heat that can easily burn through microelectronic architecture some rated with a withstand voltage as low as volts.

Table I – Feature size and device power trends

 For IC packaging, the Input/Output (I/O) count has climbed from 600 to 1,000 to well over this now. This implies that the spacing between the I/Os have decreased dramatically and where wire bonding is used, the air gap becomes that much smaller making the neighboring I/Os even more susceptible to ESD. This can be seen as Ball Grid Array (BGA) chips have been replacing through-hole pin chip technology

The increasing sophistication of electronic devices has continued to make electronic devices more and more susceptible to ESD related damage. This is a trend that is expected to continue.

Dry areas further add to the susceptibility of ESD Sensitive (ESDS) devices. Table II shows normal activity within a production facility where turboelectric charging levels of operators and objects are given in voltages and shown to be dependent on relative humidity (RH). There can be over a 5 time increase in charge generation when the RH drops to 10%.

There are a slew of other factors that can add to the problems that need to be countered by a well designed ESD Control program, such as: employee knowledge with training; ESD Control products designed to protect the corresponding ESDS devices; program funding with management buy-in; employee compliance with internal discipline and audits, etc.

Conclusion:

A properly designed and successfully deployed ESD Control program is a proven money saver with an ROI of up to 1,000% per year. Another source reports that for every one-dollar invested in ESD control, ninety-five dollars comes back as money saved. Have you hugged your ESD Coordinator recently?

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