Busbar Copper Selection
- Vincent Wey
*wip
The goal of this page is to research the different copper sheet options provided by McMaster-Carr and to provide a recommendation.
Multipurpose 110 Copper
“Offering high electrical conductivity and formability, 110 copper is 99.9% pure. Also known as ETP copper, it's often used in electrical applications, such as for bus bars and wire connectors, as well as for flashing, gaskets, and rivets.” [1]
Softened (Annealed) Temper Sheets
o “annealing is a heat treatment that alters the physical and sometimes chemical properties of a material to increase its ductility and reduce its hardness, making it more workable.” [2]
o Annealed copper sheets are more ductile, and thus increasing forming capabilities. This would be useful when bending the busbars.
o Typically, around 10,000psi Yield Strength
1/8 to 1/4 Hard Temper Sheets
o H00 Cold-Rolled 1/8 Hard and H01 Cold-Rolled, high yield 1/4 Hard
o “H-series tempers are designed to produce materials with specific quantities of stress-relieved, cold work and cold-worked (drawn) tempers, HR-tempers, order-strengthening tempers and HT-Tempers by cold working.” [3]
o Around 20000psi (1/8 hard) and 28000psi (1/4 hard) for Yield Strength
o Essentially these sheets are stronger, requires more force to yield/bend
1/2 Hard Temper Sheets
o Similarly, these sheets are stronger and harder
o Yield Strength: 37,000 psi
Mirror-Like Multipurpose 110 Copper Sheets
“Polished on one side to a reflective, mirror-like finish, these sheets come covered with a protective peel-off film.” Yield Strength: 36,000 psi, Hardness: Rockwell B40 (Soft), Temper: H01 (1/4 Hard)
Probably don’t need reflective sheets, mostly aesthetic
Brushed Multipurpose 110 Copper Sheets
“One side of these sheets has a brushed finish with grain lines running in one direction to mask fingerprints. The brushed side comes covered with a protective peel-off film.” Yield Strength: 36,000 psi, Hardness: Rockwell B40 (Soft), Temper: H01 (1/4 Hard)
Also probably don’t need brushed sheets, mostly aesthetic, also have to remove a peel-off film
Super-Conductive 101 Copper Sheets and Bars
“With 99.99% copper content, 101 copper has higher purity than 110 copper, resulting in superior electrical conductivity.” [1]
Softened (Annealed) Temper Sheets
o Yield Strength: 10,000 psi
o Hardness: Rockwell F65 (Soft)
o Temper Rating: Softened (Annealed)
Also comes in 1/8, 1/4, 1/2 hard
101 vs 110
From McMaster-Carr:
101 is 99.99% copper, 110 is 99.90%, 101 offers superior electrical conductivity.
But how much more conductive is 101?
From McMaster-Carr both 101 and 110 have the same surface resistivity and thermal conductivity (10.3 Ohms, 226 Btu/hr. × ft./°F @ 68 ° F) when annealed.
Other sources have 101 and 110 at the same electrical conductivity rating of 101 (% IACS at 68F (20C) annealed.) [4] [5]
Both have similar yield strengths when annealed
101 slightly more expensive
For a 12”x12”x0.062” sheet:
110 is $54.34
101 is $62.99
They come in different thicknesses, 110 has a greater selection of choices, do we have a preference for thickness?
Busbars modeled as 1.5mm thick in CAD, 1.5mm ~ 0.06”
Final Recommendation
My final recommendation would be to go with the 101 superconductive copper. There should be a slight benefit in conductive performance due to the higher percentage of pure copper, which would reduce the amount of heat produced by the busbars. The slight increase in costs seems negligible, and therefore I would recommend going with 101 superconductive copper. But if the budget is an issue, 110 multipurpose should provide a very similar performance at a slightly lower cost. I would also recommend going with softened (annealed) tempered sheets. The annealed sheets are softer and should be easier to form, bend into shape or modify. They are also cheaper than the harder temper sheets (1/8, 1/4, 1/2). The lower strength should not be an issue since the busbars are not supporting any loads.
Links
[2] Annealing (materials science)
[3] What the Temper Designations of Copper Alloys Really Mean - National Bronze Manufacturing
[4] http://www.quantumalloys.com/data/electronic/alcopper.html