GateWave Northern, Inc.

Ironwood
Giga-Snap BGA connector
DC Measurement Results
prepared by
Gert Hohenwarter
8/19/2013
GateWave Northern, Inc.
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Table of Contents
TABLE OF CONTENTS.......................................................................................................................................................2
OBJECTIVE..................................................................................................................................................................... 3
METHODOLOGY.............................................................................................................................................................. 3
Setup........................................................................................................................................................................... 4
Test procedures........................................................................................................................................................... 6
Current carrying capability........................................................................................................................................7
Pulse testing............................................................................................................................................................. 10
..........................................................................................................................................................................................
GateWave Northern, Inc.
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Objective
The objective of these measurements is to determine the DC performance of an
Ironwood Giga-Snap BGA connector contact. Measurements are to determine current
carrying ability.
Methodology
A four terminal (Kelvin) measurement setup is used that includes a computer
controlled voltage source capable of delivering 10 A. The voltage developed across the
contact is measured with a HP 3456A DMM and yields a V-I record. A 4 terminal setup
(Kelvin measurement) setup is used and the DMM is operated in compensated mode to
remove the effects of thermo-electric voltages due to dissimilar metals.
For the current handling tests the temperature rise in the center of the pin is measured
with a 0.01” diameter thermocouple as drive current levels are gradually increased.
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Setup
The BGA connector contact is installed in a small block which is mounted on an Au
covered brass base plate (see Fig.1 and 2).
Figure 1 Test setup
The current/voltage probe consists of a copper post with suitably shaped surface.
This surface is Ni and Au plated. The post has two connections, thus allowing for a four
terminal measurement with very low residual resistance (about 1 milliOhm). It should
be kept in mind that in this setup the spring probe presses against two surfaces that are
very well heat sunk.
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Figure 2 BGA connector contact mounting plate example
Au over Ni plating was applied to all metal surfaces. Material type and thickness
specifications were identical to those used for PCBs.
The DUT with its plate is mounted in a test stand with XYZ adjustment capability:
Figure 3 Test stand
This setup has a micrometer screw that allows repeatable adjustments in the Z
direction. Also included is a transducer that converts Z position to an electrical signal
for the data acquisition.
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Test procedures
During I-V testing, the z value is adjusted to nominal operating position and drive
current is increased in steps of 0.05 A up to the maximum tolerable level. The dwell
time for each current step is 1 s for V/I curves. Once the data are available, they are
processed to reveal the resistance, power dissipation and temperature as a function of
drive current.
Pulse load testing is performed by providing a current pulse of 0.3 seconds length
followed by a pause long enough to facilitate 10% and 1% duty cycles. Current levels
are ramped to the maximum value and temperature rise determined is determined at
each step. The current handling capability is then determined for the allowable
temperature rise.
The thermal response time constant is a result of determining both rise and fall-times
and averaging the two values.
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Measurements
Current carrying capability
The measured current–voltage relationship of an Ironwood BGA connector contact is
recorded for gradually increasing drive current:
V and R as a function of drive current I
V[mV] / R [mOhms]
250
V
R
200
150
100
50
0
0
1
2
3
I [A]
4
GWN 404
Figure 4 Voltage and resistance as a function of drive current
There are no aberrations in the response.
Of interest is also the power dissipation in the contact:
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P as a function of drive current I
0.8
0.7
0.6
P [W]
0.5
0.4
0.3
0.2
0.1
0
0
1
2
3
I [A]
4
GWN 404
Figure 5 Power dissipation as a function of drive current
dP/dΙ [W/A]
dP/dI as a function of drive current I
0.50
0.45
0.40
0.35
0.30
0.25
0.20
0.15
0.10
0.05
0.00
0
1
2
3
I [A]
4
GWN 405
Figure 6 Derivative power dissipation as a function of drive current
Power dissipation follows a square law up to a current value of 3.1 A.
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∆T as a function of drive current I
25
∆T [deg C]
20
15
10
5
0
0
1
2
3
I [A]
4
GWN 405
Figure 7 Temperature rise as a function of drive current
The temperature rise above ambient temperature increases as drive currents
increase. At 3.4 A that value has reached 20 degrees C.
d(∆T)/dI as a function of drive current I
16.0
d(∆Τ)/dΙ [deg C/A]
14.0
12.0
10.0
8.0
6.0
4.0
2.0
0.0
0
1
2
3
I [A]
4
GWN 405
Figure 8 Derivative temperature rise as a function of drive current
\
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Pulse testing
During pulse testing current is turned on for 0.3 seconds and then set to zero for the
remainder of the cycle time (3 seconds for 10% and 30 seconds for 1%). As peak
current increases so does the temperature rise. Because of the thermal response time
of the contact, it does not, however, reach the full temperature value as in DC testing.
Hence the current carrying capability is higher under pulse conditions.
A graph shows temperature rise as a function of drive and duty cycle:
dT (I)
25
DC
50%
10%
1%
25%
dT [C]
20
15
10
5
0
0
2
4
6
I [A]
8
GWN 0111
Figure 9 Temperature rise as a function of drive current*
The difference between the 10% and 1% duty cycles is small since contact
temperature between pulses drops to almost ambient even for a 10% duty cycle.
Cause for this is the relatively short contact length and low thermal mass together with
heat sinking of the contact at either end. It results in a 850 msec thermal time constant,
which is short compared to the 3 second cycle time for the 10% case.
The resulting maximum currents are as follows:
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