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First
Published in EOS/ESD Technology Europe Spring 1990 Static Control Pays Return-on-investment (ROI) data show that ESD Control saves vastly more than it costs. Roger
J. Peirce 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: 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. 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: 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: 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:
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:
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Total cost of ESD controls = $122,000