Transcript Introduction n+1 Load Board Topology

Introducing
n+1
Load Board Topology
February, 2014
©Vektrex 2014; www.vektrex.com
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What Makes A Load Board Successful
Properties:
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Flexible to support testing of multiple sizes and types of devices
Efficient, reliable electrical connections
Support for series drive to reduce wiring and drivers needed
Individual device selection for measurements
Simple to design and manufacture
Low thermal resistance to provide for small temperature rises and
good temperature uniformity
Standardized across all company departments
Easy to work with – load, secure, maneuver and handle…etc.
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The Load Board Circuit Topology Influences
Reliability System In Many Ways
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Topology – the way LEDs are connected and powered
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Circuit board routing on load board printed circuit boards
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System wiring from drivers to load boards
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Connectors in reliability chambers
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Switching systems used for measurements
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Circuit Topologies
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2n provides 2
connections for each
LED
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4n adds 2 more to
support 4 wire (kelvin)
voltage measurements
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2n and 4n Topologies Increase System Cost
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Individual circuits for each LED increase wire count
• Copper wire costs can exceed 10-15% for reliability systems
designed with 2n and 4n topologies
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Many connections on load boards = large expensive connectors
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2n and 4n circuits complicate PCB layout, usually multiple layers
are required
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Switching systems are more complex with 2n and 4n topologies
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n+1 Simplifies Circuit, Reducing Costs
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2n provides 2
connections for each
LED
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4n adds 2 more to
support 4 wire (kelvin)
voltage measurements
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n+1 places LEDs in
series circuit to
minimize connections
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Topology Comparison
4n
2n
n+1
Load Board PCB Layout
Multilayer
Usually
Multilayer
Single Layer
Connector Pin Count
40 for 10
LEDs
20 for 10
LEDs
11 for 10
LEDs
Connector Type
Multiple
Double Sided
Double
Sided
Small
Single
Sided
Series Drive
Requires
External
Connections
Requires
External
Connections
Built Into
Topology
40 for 10
LEDs
20 for 10
LEDs
2 for 10
LEDs
Drive Cable Wires
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7
To Support Large Scale Testing 8 Groups Of 10 LEDs Are
Placed On A Single Load Board
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The LED Groups Can Be Powered With Just A Few Wires
Two Drive Wires Used Per Connector
For Reliability / Stress Operation
Channel 1
Channel 2
Channel 3
Channel 4
Pin 44
SpikeSafe 200
8 Channel
Pulsed/DC
Current Source
LED Group 1
LED Group 2
LED Group 3
LED Group 4
Load Board 80 DUT Type
LED Group 8
LED Group 7
LED Group 6
LED Group 5
Pin 1
Channel 5
Channel 6
Channel 7
Channel 8
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Dual Connectors Allow A 1-Layer PCB Design
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Dual symmetrical connectors
allow 1 layer PCB design
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Example Design - Surface Mount Devices
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Example Design - COB (Chip on Board) with
screw down
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A Single LED Can Be Isolated For Measurements
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4 Wire Connection Maintained
To Edge Of Load Board
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n+1 Topology Forms The Foundation For The
Highest Performance Load Boards
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Simple circuit
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Low pin count
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Reduced cable wire count
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Flexible, supports many different kinds of LEDs
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N+1 is standard in Vektrex reliability systems
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