1. Cold Temperature Test Jig
Warwick WP
Warwick WP
Cold Temperature Test Jig
Sinead Farrington, Steve Snow, Nixon Tung Fai Yu
Vacuum chuck silicon seal update
Self heated TM module cold test – results and discussion

2. Vacuum chuck silicon seal update
Warwick WP
Vacuum chuck silicon seal update
Previously we showed that the latest vacuum chuck design (fig 1) with a silicon tube seal can maintain good vacuum down to -40C, securely holding down the module.
However the silicon tube was leaving residue mark on the module. (fig 2)
Several cleaning methods was used to clean the silicon tube: soapy water scrub; IPA in ultrasonic bath and acetone in ultrasonic bath.
The cleaned tubes were pressed against a clear plastic plate, however they all still left residue.
Our latest improvement is to add a layer of PTFE tape to cover the silicone tube. (fig 3)
Vacuum test (fig 3) showed a good vacuum is achieved, PTFE tape remain intact. Does not leave residue on the back of the module.
Fig 1. Warwick cold jig vacuum chuck design
Fig 2. Residue mark (purple) left on back of silicon wafer by silicon tube.
Fig 3. Improved vacuum seal with added PTFE tape.
A plastic lid is vacuumed down

3. Self heated TM module (1)
Warwick WP
Self heated TM module (1)
Measured TM hybrid (v1.0) resistive tracks (room temperature): left = 3.81Ω, right = 3.82Ω
HCC resistors soldered on: 4 x 0.68Ω resistors used ==> each HCC heat source = 0.34Ω
NTC Rs soldered on: EPCOS B57321V2102J60
Hybrid-to-test frame wirebonds added for NTC Resistors
Hybrids connected in series, through DC power tracks on test frame.
Heat calculated through measured current.
Power connection method for hybrid heater at Warwick.

4. Self heated TM module (2)
Warwick WP
Self heated TM module (2)
Cold jig setup with Peltier heat pump
Vacuum chuck with silicon tube and PTFE tape (left)
Module heat out is current controlled
Module voltage measured to verify power out
NTC resistor measured by a Keithley 2000 multimeter. Temperature manually calculated from fitted curves.

5. Self heated TM module (3)
Warwick WP
Self heated TM module (3)
Green: module temp
Orange: cold block temp
Red: coolant temp
Cool down time: ~3 hours
Began with room temperature tests, coolant set to 18C, with TM dissipating 3W, then 6W. Module temperature raised to 24C at 6W.
Hybrid to test frame wirebond broken, successful NTC reading during room temp test, but signal lost during cold test. However useful NTC measurement agrees exactly with vac chuck thermocouple measurement, <1C difference.
Coolant temperature dropped to -35C for colt test, with peltier on at 10V. Module reached -37C.
Module heat turned on to 1.1A (10W calculated) at -37C. But measured voltage showed power = 8W measured. Resistance dropped at low temp.
Looked up copper temperature/resistance coefficient, agrees with measured resistance change.
Inspection after cold test: nothing broken, all OK!

6. Discussion/ conclusion
Cold test with self-heated TM module successful, TM module dissipated 8W at -37 °C. TM module not broken.
Hybrid to test frame wirebond broken, need to give more loop height. (manual wire-bonder used). Maximum vertical movement “calculated” to be 1.3mm.
NTC resistor temperature followed exactly as thermocouple on vacuum chuck, difference smaller than rated component tolerance.
TM copper track resistance changes with temperature, 20% decrease from room temp (22°C ish) to -37°C, agrees with calculated 21.6% at 0.393%Ω/°C.

7. Work plan
Re-wire bond and cold test again to get full complete NTC R measurement
Smart scope survey continues, with some cold test as well
AUW

8. Warwick WP
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