Fowler Associates Labs

Static Control Pays

Return-on-investment (ROI) data show that ESD Control saves vastly more than it costs.

Roger J. Peirce
President, ESD Technical Services,
Bensalem, PA

The return on investment (ROI) in static control may be one of management's best investments. ESD control programs benefit the bottom line dramatically, even when redundant control strategies are included.

Data gathered from United States defense contractors over the last three years indicate that ROIs exceeding 20:1 and 30:1 are common. And, depending on the order in which static-control policies are implemented, inexpensive forms of static control sometimes generate large ROIs.

This is extremely important, not only for the corporate advocate of static control, but also for small contract manufacturers (with 50 people or less), which hesitate to implement ESD control because it will be too expensive.

In reality, the reverse is true. These data suggest that ROIs of 40:1 can be achieved by implementing a "perfect" ESD control program, and that returns ranging from 5:1 to 20:1 are possible with less effort. Thus, managers can feel confident about funding cost-effective programs drawing on the results of this study.

Study Background

The material reviewed here is anecdotal rather than based on tightly controlled studies. However, it is firmly rooted in experience. Over the past three years, ESD Technical Services has worked with about 200 defense contractor. Thirteen of these correlated improvements in yield, reduced rework, and reduced warranty repairs with the implementation of various ESD controls. They were handsomely repaid with data showing which controls made a difference in their bottom lines and which didn't. The insights gained were channeled into other business areas and saved a lot of money.

It is interesting to note that none of the 13 companies covered in the study started an ESD-control program to save money or for quality-assurance reasons. Rather, they were obliged to do so by military contract under the provisions of the United States government's MIL-STD-1686A.

In fact, of the close to 200 contractors we have worked with, few have started their ESD-control programs to achieve ROI. Many instituted ill-conceived, poorly monitored, "appearances-only" programs designed to satisfy government auditors and consequently squandered an opportunity to maximize profits.

This collection of ROI numbers is possible because each company was producing a mature product line, with previous yield, rework, field return, and warranty repair data available. Defense contractors are ideal candidates for this type of study because the same product is produced for periods of five years or more. Accumulation of controlled ROI data would be virtually impossible if the parts and processes were changing frequently or dramatically along with implementation of ESD controls. However, in this case, the only notable change in the manufacturing process was implementation of ESD controls.

The combined ROI results of the 13 firms studied are summarized below:
Minimum ROI = 5:1
Average ROI = 10:1
Highest ROI = 20:1

The average ROI was 10:1, which means that if a company spent $10,000 in ESD controls, it was a $100,000 return to the company through higher yields, reduced rework, and reduced warranty repairs.

Furthermore, the data in this study suggest that each company would have received an ROI closer to 40:1 if it had selected ESD controls more carefully.

The average expenditure of ESD materials among the 13 companies was $80,000, with an average first year's return of $800,000. It is significant that all 13 companies received ROIs of 5:1 or better. There was a strong correlation between management involvement and ROI.

Training of the work force, including management, also had significant impact on ROI. The average ROI for companies that instituted ESD control without formal employee training was 7:1. The average ROI with plantwide training (even if performed only briefly by supervisors) was almost twice that, at 13:1.

Skeptics at every facility studied insisted that no ESD damage was happening there. This is a common attitude among engineers without hard data. When the financial results were made available, however, attitudes changed quickly. This is another reason to correlate ESD control with bottom-line benefits; it works wonders getting agreement and cooperation on ESD controls.

One Case

One of the 13 companies studied had 150 workstations where static-sensitive parts were handled and 200 production employees. The facility produced PCB assemblies. The typical plant layout included receiving, stockroom assembly, wavesolder, conformal-coating, testing, and shipping areas.

The existing ESD program was a sham and, when audited, proved to be functionally nonexistent. Although wrist straps were "mandatory," over 25% of employees didn't wear them, and of those that did, more than 90% had straps that showed open circuits or high resistance to ground. Products were stored and transported throughout the facility in "pink" antistatic bags and other forms of packaging without static shielding.

In 1986, the company began upgrading its ESD-control program. Various controls were added over a three-year period and data were kept correlating improvements in yield, rework, and field returns with the introduction of the various controls. Table 1 summarizes those data.

Don't generalize based on this information. Each additional ESD-control strategy must address a different control problem in order to generate any return at all. This makes it much harder for each subsequent method to show a return, whether or not it is effective.
The data in Table 1 do not suggest that conductive floors, heel straps, ESD garments, and ionizers don't perform useful ESD-control functions- they do, but their outward efficacy will vary with the application and with strategies already adopted.

For example, four of the 13 companies in the study put in a conductive floor after adding wrist straps. None of the four saw much change in the bottom line after the flooring was installed. However, it is important to note that all four companies shielded their products electrostatically during transportation and storage with either conductive containers or static-shielding bags, and that wrist strap testing was performed at every station, every time a wrist strap was used.

All these safeguards would have had to fail before the beneficial effect of the floor-grounding system could have become noticeable. Ironically, the success of the floor-grounding system would work to prevent such failures from becoming visible.

At most firms, observed ROI will also vary with the sequence in which various static-control methods are adopted, and their relevance to the application. For example, some firms use ionization or conductive floors and heel straps as their first line of defense against static discharge, adding wrist straps as an additional defense.

Finally, regardless of which system had been installed first- floors or wrist straps- first-year savings would have been similar because the effect of either element is approximately the same and is realized in approximately the same work place. Much the same is true for other static-control strategies; ionizers and ESD-protective garments would have shown ROIs had they been installed first.

Case Discussion

In January 1986, the company installed new wrist straps and appropriate grounding for all production personnel. The wrist straps were tested daily and personnel were minimally trained in their use.

Between January and June, consistent, immediate savings in increased yields (for a return of $7,800), reduced rework ($8,000), and decreased field returns ($5,000) came to a total of $20,800 per month. This was a yearly ROI of 33.1 ($250,000 saved vs. $7,500 invested) due to implementation of wrist straps.

Based on these initial results, the company decided to invest in ESD controls for straightforward ROI purposes. In June 1986, all "pink" antistatic bags and packaging materials were replaced with bags designed to provide static shielding during transportation and storage. Again, outstanding financial rewards were realized.

An additional $22,500 savings per month was observed ($8,000 in increased yields, $12,000 in decreased rework, and $2,500 in decreased field returns), which remained constant over the next year. This ROI totaled 30:1 ($270,000 saved versus $9,000 invested).

With such positive results, further ESD controls were approved and implemented. In the hope that a two-pronged approach to grounding personnel would reap similar rewards, a conductive floor and personnel heel straps were implemented in the main production area.

However, after installation, few additional cost savings were observed. If a conductive floor was the only grounding element used, it would result in a good ROI relative to no grounding. However, form a strict ROI point of view, and in this application, grounding personnel both with wrist straps and through conductive floors may have been overkill.

Similarly, at this facility, little financial gain was observed when static-dissipative garments and benchtop ionizers were added. The ionizers were installed at 50 assembly stations to remove static charge from such items as plastic bottles and documents. The garments prevented street clothing from coming into contact with ESD-sensitive products.

In both cases, the controls accomplished their objectives, yet little ROI was observed. These facts, plus the data below, point to the most probable causes of ESD damage in electronic manufacturing facilities. Charged insulators at ESD workstations simply don't appear to cause much ESD damage. However, conductors- large conductive objects, people, and machinery (whether charged or not) - appear to play a large part in measurable damage.

Finally, this facility achieved modest ROIs by weeding out defective soldering irons (those with voltage spikes at the iron's tip). In this case, a static-control strategy also resulted in detection of irons defective for other reasons. A number of irons had been passing power-line (mains) switching transients and surges through to their tips. In some cases, ground connections were open or corroded, showing high resistances. Some irons were defective in other ways, but all were spotted as a result of the attempt to control ESD.

ROIs were also generated through elimination of worn-out static-shielding bags and bags with inner antistatic layers that caused ESD-sensitive items inside to become charged. ROI's of 30:1 and 9:1 were recorded for these packaging and soldering substrategies.

Combining all these ROI data, as if all controls had been instituted at one time, we get the following totals:
Total cost of ESD controls = $122,000
Total first-year cost savings = $590,000

The above total ROI is 4.83:1. It is extremely significant that the $590,000 total cost saving was completely realized from four controls that cost only $22,000. This picture, had those four controls been implemented, would have been as follows:
Total cost of ESD controls = $22,000
Total first-year cost savings = $590,000

These figures yield a ROI of 27:1

Which ESD controls provide the highest returns? A similar analysis was performed on the data from each of the 13 companies in the study with the overall approximate results given in Table 2. Our analysis of these data follows.

Grounding of personnel (40%). The simple practice of grounding people via wrist straps is perhaps the most inexpensive ESD control with the most benefits. Yet few companies take the steps necessary to ensure that wrist straps are working effectively on the employee.

Though not all authorities agree on the subject, based on our experience, we cannot recommend strongly enough the practice of testing wrist straps as frequently as possible because the testers pay for themselves almost instantly. As 40% of a company's total cost savings depend on the functionality of its wrist straps, ti behooves managers to install wrist-strap testers at all workstations.

Product shielding (40%). Large ROIs were also observed on all products that shield ESD-sensitive items during transport and storage, such as conductive containers and static-shielding bags. Consistent returns were evident from company to company, including immediate bottom-line increases when companies switched from antistatic packaging to either static-shielding bags or conductive containers.

Elimination of aged materials (12%). This figure indicates that companies are losing enormous amounts of money due to ESD damage caused by antistatic materials that have lost their effectiveness. Although this is a major problem, few companies try to prevent these looses, and most aren't aware of the problem. Our ROI data revealed the following costly issues:

Antistatic IC tubes. Clear, antistatic IC shipping tubes have a shelf life, and once the shelf life is reached, the tubes can charge IC's sliding within them. ESD damage can occur afterward when the charged ICs come into contact with people or handling equipment. Efforts taken either to replace the antistatic tubes or to ensure that charge was removed from the devices before contact resulted in measurable ROIs.

Antistatic packaging materials. Returns are realized when antistatic bags, and/or static-shielding bags are 100% tested to weed out aged, charge-generated bags. During this study, it was clear that ESD damage is occurring in the industry with very few people aware of either the failure mode or the enormity of the problem. The following case illustrates the situation.

Aged bags can charge ESD-sensitive items sliding about inside them. Three major ESD failure modes, each at a different firm, were traced to this problem during the study. The damage in each case occurred when operators opened bags and grasped circuit boards to remove them. The board assemblies discharged quickly, causing documented damage.

Substantial ROIs were seen if the ESD-sensitive assemblies were placed on static-dissipative work surfaces before being touched- a difficult maneuver. ROIs also resulted if aged, charge-generated bags were removed from use Indeed, 12% of the combined cost savings in the study resulted from fixing problems associated with aged antistatic materials.

Monitoring soldering equipment (5%). Significant ROIs were realized by monitoring soldering equipment to MIL-STD 2000 levels. The 2 Ohms, 2 mVolts, + 10 degrees F requirements of MIL-STD-2000 may seem overly stringent, but companies that weeded out irons failing these specifications saw savings due to reduced parts damage. The 5% of total savings that resulted might be attainable even with relaxed standards.

ESD-controlled taping of PCBs (2%). Static-controlled taping of PCBs also generated a return. Taping is often required before wave soldering and/or application of conformal coatings. Some success was achieved by applying tape in an environment bathed in ionized air, but tape removal generated large voltage spikes of very short duration that couldn't be reduced with the benchtop ionizers in general use.

The ROIs generated by training operators to do these taping operations with proper grounding, slowly, and in ionized air, will probably be insignificant when compared with performing such masking functions with the ESD-safe masking alternatives to be announced in 1990.

Benchtop ionizers. Ionizers provide large ROIs when used in clean rooms, in certain air-flow operations, for electrophoresis, in spray-coating operations, and when associated with automated machinery. However, benchtop ionizers used to remove charges from insulators at ESD workstations did not produce large ROIs.

ESD garments. Wearing ESD-protective garments over street clothes in ESD-protected areas did not produce large ROIs. In all cases, however, garments did protect ESD-sensitive items from charges found on street clothing.

Materials control. The removal of charge-generating materials found at ESD workstations (plastics, bottles, paper, and vinyl) did not result in confirmed ROIs.

Summary

Based on our experience and a review of the data, we conclude that:
1. ESD control programs can be instituted for ROI reasons. If the job is done right, 30:1 to 40:1 ROIs are achievable.
2. Management should be involved for maximum return and must enforce ESD controls. Managers can't afford to have undisciplined individuals stand in the way of such large cost savings.
3. Overaged, charge-generating, antistatic materials are causing tremendous damage. Weeding out nonfunctional antistatic materials produces a return. Afterward, buy high-quality static-shielding bags. Don't try to save money by purchasing inferior packaging. Also, pay attention to the lifetimes of clear antistatic IC shipping tubes. The alternative may be significant losses.
4. ROIs are achieved when a facility switches from antistatic packaging to static-shielding gabs and conductive containers.
5. Placing wrist-strap testers (better yet, constant monitors) at each workstation produces significant ROIs. It's also worthwhile to test and remove defective, dangerous soldering irons.
6. Most ESD damage is caused by large conductive objects (i.e., people and metals), while charged insulative objects (i.e., paper and plastic), at ESD workstations seem to cause less ESD damage. Static charges from operators' clothing don't cause much ESD damage.
7. PCB taping may be an area of ESD damage at most firms.