PXI-based automated test systems require well-engineered product interconnectivity and fixturing to the device under test to ensure signal integrity and tester longevity. Explore methods and trade-offs in the engineering, selection, and fabrication of the device interface connectivity required for today's complex electronics.

2. ni.com
Greg Crouch
Selection and Economics of Test Fixtures
and Test Interconnect
Circuit Check, Inc.
Director of Engineering Services Business Development
greg.crouch@circuitcheck.com

3. Scrap and failed good boards costs money.
Source: Teradyne

4. Visual
Inspection
In-Circuit
Test
Functional
Test
Rework Rework
A lot of variables that must align in a production process
Major variables to cost of test
– Programming Cost
– Equipment Cost
– Fixture Cost
– Maintenance Cost
– Test operators Cost
– Scrap Cost
– Re-test (false rejects) Cost
– Repair & Diagnostics Cost
– Field Return Cost
Source: Circuit Check; S. Scheiber ISBN:0-9656161-0-X

5. Simple case example: How to loose $54,000 fast.
Supplier build quantity of 1000 boards, and a first pass yield at 75%.
Visual
Inspection
In-Circuit
Test
Functional
Test
Rework Rework
Quoted at
beginning of
project plan
Actual
test
time
vs

6. Visual
Inspection
In-Circuit
Test
Functional
Test
Rework
10 min
4.2 loops actual
9.2 min actual
Ave of 3.2
extra
loops
Rework
Quoted at
beginning of
project plan
Actual
test
time
vs
7 min of re-testing
32 min of rework
7 min/brd x $250/hr (250/60=$4.16/min) = $ 29.12 / brd
32 min/brd x $75/hr (75/60=$1.25/min) = $40.00 / brd
Total: $69.12 / brd
250 brds x $49.12 / brd = $17,280.00
9.2 min – 2.2 min =
1000 boards, and a first pass yield of 75%
Line / Tester time
Technician Time
2.2 min quoted

7. Visual
Inspection
In-Circuit
Test
Functional
Test
Rework
82.2 min quoted
1.57 loops actual
129.1 min actual
Ave 0.57
extra loops
Rework
25.6 min
Quoted at
beginning of
project plan
Actual
test
time
vs
46.9 min of re-testing
~25.6 min of rework
46.9 min/brd x $150/hr (150/60=$2.50/min) = $ 117.25 / brd
25.6 min/brd x $75/hr (75/60=$1.25/min) = $ 32.00 / brd
Total: $ 149.25 / brd
250 brds x $149.25 / brd = $ 37,312.50
129.1 min – 82.2 min =
1000 boards, and a first pass yield of 75%
Line / Tester Time
Technician Time

8. Visual
Inspection
In-Circuit
Test
Functional
Test
Rework
10 min
12 min
quoted
1 Loop actual
12 min actual
2.2 min quoted
4.2 loops actual
9.2 min actual
82.2 min quoted
1.57 loops actual
129.1 min actual
3.2 extra
loops
0.57 extra
loops
Rework
25.6 min~ 70 min
Manual
labor
Quoted at
beginning of
project plan
Actual
test
time
vs
Line time quoted to run 1000 boards: 2.2 min/brd x 1000 brd = 36.6 hrs
7 min/brd x 250 brd = 29 hrs
29 hrs x $250 / hr = $ 7250.00
Additional time for 250 reworked boards
Key point: a lot more manual labor cost going into each board manufactured than you expect.
Lost Productivity
Missed opportunity from retesting boards (Un-utilized Line time)

9. Additional Impacts …
Testing DUTs more than once
 Re-testing products induces additional wear and tear on fixture
components (tooling pins, test probes, etc.) and the tester.
 Re-testing negatively impacts run and through-put rates.
Costs not calculated
 Damaged boards, un-repairable boards
 Late shipments, expedited shipping
 Field failures, RMA’s

10. What was the cause for the poor yield?
Things to think about that drive cost of test
 ATE architecture that can not last the life-cycle of the product and be updated and
maintained easily.
 Poor DUT to instrument interconnect from mass interconnect or wiring
 Poor fixturing causing test probe stress on the DUT during test.
 Not keeping up with the disruptions within the industry forcing new measurement
modalities.

11. Simplify as much as possible
 Test rack wiring
 Maintenance accessibility
Things to think about..
Test rack layout can reduce maintenance costs

12. Minimize hand made custom cabling.
Things to think about..
Test rack layout can reduce maintenance costs

13. Cables between PXI and
receiver modules
PCB or hard-wired interface between
PXI and receiver modules
Things to think about..
Test rack layout can reduce maintenance costs
Video

14. Things to think about..
Test rack layout can reduce maintenance costs

15. Fixture to DUT Registration
 Repeatable electrical and mechanical contact to
the DUT is essential for accurate measurements.
 .018 - .025 diameter test pads on boards make it is
easy to miss a target
 One missed contact and the product is destined to
false failure, false pass, and excess processing.
 PXI system does not get the correct measurement.
CL
CL
Probe center line centered
on test point center
Probe center line skewed
off test point center
Things to think about..
Poor probe-based fixturing can increase test costs

16.  Increase use of "socket-less" style probes
 Top-side guided probe technology mandatory
Probe Plate
Spacer Plate
Termination Plate
Probe
Termination
.100 - .075
Spacing
.039
Spacing
.050
Spacing
X-Probe Technology
.031
Spacing
Video
Things to think about..
Poor probe-based fixturing can increase test costs

17.  Multiple voltage levels per IC
 Easier to expose pins to electrical over-stress
 Voltage glitches exceed max spec ratings
 Damage from ‘over-driving’
 I/O logic levels differentiated by milli-volts
 Voltage instability can trigger unwanted logic
transitions
Source of unstable
tests & high false
fails
Source of device
stress and potential
damage
Things to think about..
Poor probe-based fixturing can increase test costs
video

18. Elevated Strain around BGA
ranges from 975 to 1783 µs
Things to think about..
Stress can causing unknown damage to the DUT
• Pushdown finger location and probe count have a dramatic affect on quality.
• How many probes equal 450 me on a typical BGA for a 0.092” thick board?
• 134 8.0 oz. probes,
• 261 4.1 oz. probes,
• 510 2.1 oz. probes

19. FEA on Fixture Strain to DUT
Elevated Strain around BGA
ranges from 482 to 710 µs

20. FEA Output – Strain after fixture modification
Elevated strain reduced to
acceptable levels of 92 to 202µs.
Strains were reduced across the board by
doubling the number of pushdown fingers.

21.  Through connector test i.e. how to access and what can be accessed
 Interconnect and fixtures that allow access through multitude connector types.
 Federal or industry specific regulations
 Test repeatability
 Mechatronics
 Blend of mechanical engineering, electrical engineering, computer control and information
technology.
 Ergonomics / reducing repetitive motion
 Drawer style fixtures, pneumatic operation, rotary fixtures
 Fixturing within RF chambers
 Many challenges come up with regard to product size and chamber size as well as metal content in
the fixtures.
 High-mix products
 Drop-in fixtuing adapters to leverage existing mechanics or automation
Disruptions within the industry; forcing new measurement methods

22. Through Connector/Side Access Fixturing
Positive connector alignment via floating
block assemblies.
Video

23. Test Repeatability
Product nest is
adjustable within fixture
allowing for variations in
part assembly.
Product nest is
interchangeable for
product variations

24. Mechatronics
Medical Automotive
Video

25. Multi-Cavities designed for rapid
loading & unloading
Drawer Load/unload
Rotating cavity with
Light Curtain safety
interlock
Multiple DUT load
with gravity feed
and auto discharge
Ergonomics / reducing repetitive motion
Video

26. Modular Replaceable Fixture
Four DUT drawer style fixture.
Complete fixture removable from base
ATE using mass interconnect.
Integrated Fixture with Drop-in
Top-plate of base ATE designed
as an integrated fixture. Uses
product specific drop-in plates.
Ergonomics / reducing repetitive motion
video

27. Ergonomics / reducing repetitive motion
 The more a product is handled, the
more likely it is to be damaged.
Extra handling caused
capacitor
damage
Rotary based fixturing
 High-volume and high-mix products
 Mission critical operations that must be quality assured and checked automatically
 Production rate increased throughput through concurrency
 Automated handling between manufacturing process steps
video

28. Full automation of DUT
connectivity inside RF FixtureModular DUT connectivity inside RF Fixture
Fixturing within RF chambers
video

29. High-mix products
Modular “drop-in’
adapters in addition to
mass interconnect.
Interchangeable PCBA adapters within the fixture help
with system reuse in higher product mix applications.
600 video
1000 Video

30. High-mix products
Line automation with quick change adapters video

31. Copyright © Circuit Check, Inc.
Additional Resources:
International Electronics Manufacturing Initiative (iNEMI
http://community.inemi.org/
Search for:
Manufacturing Test Strategy Cost Model
Test Strategy Project
Contacts:
Speaker:
Greg Crouch, greg.crouch@circuitcheck.com
Local Field Engineer from Circuit Check:
https://www.circuitcheck.com/index.php/about-us/global-offices