Thermal Cycling Tests of Dummy Modules

• Setup• Pre-cycling resistance

measurements• IZM module results• Alenia module underway

Setup

• Modules built with CERN Flex V.2 and bare dummy module.

• Used Ecobond glue under MCC, pigtail bonding field, and 4 corners.

• Modules used for FE wirebonding tests prior to thermal cycling

• First cycled modules unconstrained, then attached to sector using CGL and UV-cure tacks on 4 corners.

• Cycled 21oC to –35oC in environmental chamber.

• Monitored module temperature and chain resistance in real time

Setup (cont.)

Only 4 columns monitored in real time during cycling

All columns measured on probe station before and after

Column Resistances (before cycling)

IZMAlenia

Bad chip

IZM Module results

• No change after 2 cycles of unconstrained module

• No change DURING 19 cycles of module on sector

• Open columns detected AFTER overnight storage at 21oC

RED = location of open column32/270 columns failed

On bad chip, all columns were open prior to tests & chip fell off after removing module from sector. Solder bumps left ½ on chip ½ on sensor.

Possible Explanation

• Results are consistent with differential movement of dummy chips and dummy sensor.• For example, assume sensor doesn’t move under cooldown(probably not correct, just

example), then contraction of each chip is about (2.5x10-6) x(either 3.7 or 5.5x103

microns)x56=0.5-0.8 microns.• Worst case is corners of chip, but we only measure columns.• Approximate strain is (0.5-0.8)/(20) or 2.5-3.8%.. Solder stress vs strain becomes non-linear

for strains above about 1%.• Creep rupture is possible explanation for failure after sitting.

UV Tack UV Tack

Carbon-carbon on sectorCGL

Alenia Module Tests Underway

• 3 Cycles to –35o unconstrained

• 3 Cycles to –35o mounted on sector

• Time at –35o 30-40 minutes/cycle

• Let sit for a day

• No failures yet

• Tests continuing