Mechanical and Cryogenic Teting of VLPC Flex Circuits Made by Litchfield, Cirexx, and Speedy Circuit
Four flex circuits were tested. They are categorized as: (1) Litchfield narrow; (2) Litchfield wide; (3) Cirexx wide; and (4) Speedy Circuit green. The cross sectional area of copper was calculated from trace resistance measurements. All the flex circuits had an acceptable amount of copper cross section. about 6 e-8 m{sup 2} for all except the Cirexx flex which had 4.5 e-8 m{sup 2}. The thickness of the ribbons was 0.006-inch for the Litchfield and about 0.004-inch for the Cirexx and Speed circuit. The room temperature resistivity ratio (RRR) was measured to be 15 for all the circuits. This was expected and means that the trace material resistivity at helium temperatures is 1/15th of what it is at room temperature. This is good from the standpoint of thermal heat load. Purer copper, with an RRR > 30 would result in an unacceptable heat load. The cryogenic cycling and bending tests to liquid nitrogen proved that both the Cirexx wide and Speedy circuit green were made of acceptable materials. Both Litchfield flex circuits had significant cracking of the coverlay when bent at cold temperatures and are not acceptable. The Litchfield narrow was in bad physical condition to start with and got worse through the testing with many more crazing cracks appearing. The crazing is bad enough that the coverlay began to peel and expose the copper beneath. This candidate is unacceptable. The Litchfield wide started out testing in good condition with no cracks. It ended up with much crazing in the coverlay. Within 1 mm of the edge of the coverlay at the cold end. the copper traces were bulged away from the base material. Traces became nadhered and lifted off of the base material at the ends where the coverlay was not present. Numerous electrical opens (7 out of 24 checked) were found at the end of the testing. Visual inspection of the opens leaves open the possibility that the traces are broken below the coverlay in the cold bend area. Obviously this candidate is unacceptable. The Cirexx wide was a mechanical sample with no promises made about it's electrical integrity, however of the traces checked all were fine after the brutal testing. This flex circuit appears suitable for the intended cryogenic and mechanical environment. The Speedy circuit came out as acceptable in the testing also. The material remained flexible at cryogenic temperatures. 2 out of24 traces were found open after the testing, but this was a mechanical sample and those traces were not checked beforehand so it is unknown if the testing caused the opens or they were there at the start. This sample was not presented as having final product electrical characteristics.
- Research Organization:
- Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC)
- DOE Contract Number:
- AC02-07CH11359
- OSTI ID:
- 1032098
- Report Number(s):
- FERMILAB-D0-EN-507; TRN: US1200465
- Country of Publication:
- United States
- Language:
- English
Similar Records
Exhaust Fan Temperature Switch
D0 Silicon Upgrade: Heat Transfer and Thermal Bowing Calculations of the D0 F-Diskl