Fast Payback using TestWay
Written by Peter de Bruyn Kops
- Visit Acugen on www.acugen.com
TestWay pays for itself in numerous ways. This document gives a sampling of
payback avenues to help you appreciate what benefits TestWay can deliver.
These paybacks cover labor savings, reduced fixturing costs, shorter time
to market, higher circuit densities, accurate bidding, higher fault
coverage and shorter test times.
Labor savings in testability reviews
Manual testability reviews are difficult work and require a highly skilled
test engineer. For complex boards, a thorough review, done manually, can
take 5 days. By using TestWay, the review can be done in one day, and most
of this time is spent obtaining the right design files. At a fully loaded
cost of $800 per engineering day, TestWay can save $3200 on each complex
Greater consistency in testability reviews
Because of the laborious nature of testability reviews and the vast
amount of data to be sifted through, there is always the possibility
with manual reviews that some testability problem will be missed. How
often is something missed? What is the cost of missing a testability
The cost of a missed testability problem can show up as lower test coverage,
higher fixture cost and in many other ways. For payback calculation purposes,
consider just the waste of test engineering time, both to work around the
problem and sitting in meetings to see whose fault it is, who should fix it
and how to prevent it happening in the future. Depending on how extensive a
workaround is needed and how many people get involved in the meetings, added
labor costs could easily run 4 man-days, or $3200.
Reduced fixture costs
By taking into account boundary scan virtual test points, buffer and simple
logic virtual test points, and simple analog virtual test points, TestWay
can reduce the number of pins required on the fixture. Assuming a typical
board fixture uses 2000 of 100-mil nails ($3.50 each) and 200 of 50-mil
nails ($10 each), with a nail cost of $9000, a 30% reduction in the number
of nails will save $2700 per fixture.
Reduced tester costs
An important component of tester cost is the number of channels.
By reducing the number of test points on boards, fewer tester channels
will be required. Payback calculations are complicated by the
non-linear pricing of tester channels -- they come in groups on channel
cards, and after some number of cards are installed you need an additional
controller or card bay. This additional controller or expansion option can
be more expensive than the price of a TestWay license! If TestWay's test point
optimization eliminates the need to expand your tester across one of these
expensive new controller price points, TestWay pays for itself
Start test development from schematic data.
Labor savings in ATE file generation
Some ATE requires laborious manual creation of various files. The most
common type is device pinout models for devices used on the board.
For example, Victory (Acculogic, Asset Intertech, Intellitech) needs CHAR
models, Goepel needs CIC models, JTAG Technology needs a JTN netlists.
TestWay can generate all these files, plus more, automatically from schematic
design files. Let's assume you are a fast typist. If a new board requires
60 new models, at 10 minutes each including debug, you will spend 10 hours
generating the models, or $1000 per board. With TestWay, these files
are generated automatically.
Labor savings in layout
In the customary non-TestWay process, the first pass through layout assigns
testpoints based on geometric criteria. Test engineers typically work on
this list of test points, removing some and adding some. Adding test points
requires another pass through layout which consumes the layout engineer's
time. By assigning test points at the schematic stage and back
annotating them into the schematic files, TestWay can save this iteration
through the layout process. To calculate the magnitude of potential
savings, you will need to find out how much time the layout engineer
spends to put in the test engineer's manual test point additions and
then multiply by $100 per hour. If TestWay saves an average of one
iteration through layout, where each iteration takes a day of the layout
engineer's time, then the cost savings would be $800 per board.
Time to market by saving layout steps
Using TestWay prior to layout to assign test points and back annotate them
into the design files can save an iteration through layout. Since the
layout engineers are presumably busy on other projects, your design may
wait a while before they can get to it. This delay in layout can be on
the critical path in getting the first products shipped. What is the cost
of being one week late to market? If potential sales are large, or
seasonal, the amount at stake with a one week delay is much larger than
the cost of a TestWay license.
Time to market via concurrent engineering
Profitable, leading-edge, companies are usually the ones with a history
of on-time execution of new product introductions. They are often first
to market with new technology. Furthermore, new product schedules are
usually not padded with lots of extra time.
In the traditional new product process flow, test engineering work
begins when the board is released from physical layout. By using TestWay,
test engineering work can begin prior to layout, assigning test points,
determining test strategies, and even building the board-level test
program on the ATE. The gating items become the fixture and first
production boards. Depending on your process, potential time-to-market
savings can be weeks, which makes the cost of a TestWay license
Higher fault coverage
By uncovering testability issues during the design phase when they
can be fixed, TestWay users obtain higher fault coverage tests.
On complex boards, where the number of pins on the tester limits
potential fault coverage, TestWay users obtain higher coverage by using
TestWay's test point optimization features to allocate available tester
pins more optimally and minimize lost coverage.
Higher fault coverage produces large savings in system test, field service
and customer satisfaction, particularly for high volume products. Faults
found at board test cost one tenth what they cost to find at system test.
To calculate the dollar savings, you need to estimate how many boards
are manufactured (e.g., 10000), the average number of faults per board
before board testing (e.g., 1/10), and the cost to find a fault at system
test ($1000). If TestWay allows a coverage increase from 93 to 98 percent,
your payback is number of boards manufactured times number of
faults per board times 5% times the cost to find a fault at system test
($50000 in this example).
Higher density, saved real estate
Some types of test points consume board real estate, perhaps by requiring
a signal be especially routed to a pad on the bottom of the board. Test
points have to be a minimum distance from other test points and from
neighboring signal traces. While the impact of each test point is small,
the space adds up. Using TestWay to eliminate 1000 or 2000 unnecessary
testpoints on a complex board might make the difference between
board sizes, number of layers, or even whether particular functionality
What would you save by using a smaller board size or fewer routing
layers? These costs depend on how many boards will be manufactured,
so the savings could be significant at large volumes.
Faster flying probe tests
Flying probe tests can take a long time, with 45 minutes or more possible
for complex boards. For boards containing significant boundary scan,
TestWay can optimize the flying probe test to eliminate flying probe test
steps on Boundary-Scan testable areas of the board.
The resulting savings in flying probe test time obviously depends on the
amount of boundary scan on the board, but 50% savings are possible.
Assuming the fully-loaded cost of a flying probe tester is $100 per hour,
savings per complex board tested can be $35,000 per thousand boards
Quoting jobs, avoid the dogs
Contract test program development houses depend on accurate quoting in
order to maintain profitability. All you need is one dog job in ten,
with nasty testability problems that you missed in the quoting process,
and your profitability disappears. Either your test engineers have to put
out a heroic effort to work around the testability problems, or your sales
people spend many hours in renegotiation and damage control, or both.
By using TestWay in the pre-bid analysis, these iceberg-like jobs can be
priced at what they are worth, the customer's expectations set correctly, or
avoided altogether. To calculate estimated payback, you need to estimate the
percentage of jobs typically misbid and the cost overrun of the average misbid
job. If the overrun is 5 man-days (including use of equipment), the cost
penalty per misbid job would be about $4000. At one misbid job per month,
payback on using TestWay would be $4000 per month.
Contractors improve competitiveness
Contract test program development is a highly competitive business.
If your bid is too high, your competitor gets the order. If your bid
is too low, you do not cover your costs.
With TestWay to improve the consistency of your pre-bid testability reviews,
your bidding accuracy will improve for complex boards and result in more
Competitiveness is also improved because TestWay capabilities enhance bid
quality and the services you can offer your customers. For example, TestWay
reports fault coverage based on the design data and your test strategy. You
improve your standing with your customers by being able to set their
expectations accurately regarding fault coverage of the final test program. By
seeming more professional and in control of your process, you increase
customers' desire to do business with you and pay a price premium.