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Selection and Economics for Test Fixtures and Test Interconnect
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Transcript of Selection and Economics for Test Fixtures and Test Interconnect
ni.com
Greg Crouch
Selection and Economics of Test Fixtures and Test Interconnect
Circuit Check, Inc.
Director of Engineering Services Business Development
Scrap and failed good boards costs money.
Source: Teradyne
Visual
InspectionIn-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
Simple case example: How to loose $54,000 fast.Supplier build quantity of 1000 boards, and a first pass yield at 75%.
Visual
InspectionIn-Circuit
Test
Functional
Test
Rework Rework
Quoted at
beginning of
project plan
Actual
test
time
vs
Visual
InspectionIn-Circuit
Test
Functional
Test
Rework10 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
Visual
InspectionIn-Circuit
Test
Functional
Test
Rework
82.2 min quoted
1.57 loops actual
129.1 min actual
Ave 0.57
extra loops
Rework25.6 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
Visual
InspectionIn-Circuit
Test
Functional
Test
Rework10 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
Rework25.6 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)
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
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.
Simplify as much as possible
Test rack wiring
Maintenance accessibility
Things to think about..Test rack layout can reduce maintenance costs
Minimize hand made custom cabling.
Things to think about..Test rack layout can reduce maintenance costs
Cables between PXI andreceiver modules
PCB or hard-wired interface between
PXI and receiver modules
Things to think about..Test rack layout can reduce maintenance costs
Video
Things to think about..Test rack layout can reduce maintenance costs
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
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
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
Elevated Strain around BGAranges 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
FEA on Fixture Strain to DUT
Elevated Strain around BGA ranges from 482 to 710 µs
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.
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
Through Connector/Side Access Fixturing
Positive connector alignment via floating block assemblies.
Video
Test Repeatability
Product nest is adjustable within fixture allowing for variations in
part assembly.
Product nest is interchangeable for product variations
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
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
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
Full automation of DUT connectivity inside RF FixtureModular DUT connectivity inside RF Fixture
Fixturing within RF chambers
video
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
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, [email protected]
Local Field Engineer from Circuit Check:
https://www.circuitcheck.com/index.php/about-us/global-offices
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