Page 57 - Building A Succesful Board-Test Strategy

What Is a Test Strategy? 43

project moves into the now empty space, fixed facilities costs per project remain
unchanged.
On the other hand, freeing up floor space can prevent overestimating a
factory's percent utilization. Managers who realize that a portion of the factory lies
idle can plan program or project expansion without budgeting for new facilities,
The impact of a factory's test strategy on product costs does not end with
shipment to customers. Field service and warranty repair generally cost far
more than eliminating those same faults during production. In addition, products
that do not perform to customers' expectations can erode future sales. One reason
for many companies' interest in environmental stress screening, despite its
logistical and economic consequences, is to remove problems in the factory that
otherwise would occur in the field. Manufacturers of so-called "ruggedized
PCs" differentiate their products from the competition by touting ESS and
other reliability programs in their manufacturing process, which in turn permits
premium pricing.
Field operations must create their own test strategies and methods. As stated,
the closer these methods are to their siblings in the factory, the lower the test-
development costs at that stage. A great deal also depends on field-service logis-
tics. Repair of expensive but fairly standard consumer products, such as PCs, often
involves swapping defective boards or modules and sending them back to the
factory for diagnosis and repair. Companies that rely on contract manufacturing
and test may merely return any bad boards from the field to the board vendor.
International manufacturing companies often maintain repair depots in
individual countries to minimize customs complications. These facilities are not as
elaborate as comparable operations in the factory, but they offer more capability
than a field engineer could carry to a customer site.
Field-test-strategy choices also determine costs to customers for keeping
inventories of replacement parts. Manufacturers of large systems may require
customers to stock a specific mix of spare parts as a sale or service-contract
condition.
Field-test strategies differ from their production counterparts in one impor-
tant respect. Factory testing must determine whether the product works. Products
returned from the field worked at one time but do not work anymore. Therefore,
even if the equipment is similar to the factory's arsenal, the failure diagnostics will
likely be somewhat different.

1.7.2 Committed vs. Out-of-Pocket Costs

Most discussions of life-cycle costs assume flexibility until someone actually
spends the money. One of the cornerstone principles of concurrent engineering is
that designers commit most of the money to develop and manufacture a product
before it ever leaves their hands—in fact, before there is an actual product at all.
Figure 1-13 illustrates a study by British Aerospace in the U.K. that demon-
strates this apparent dichotomy. The lower curve indicates the timing of money