The issue is bare AL versus tin-plated AL.
Tin plated AL bus is not usually a problem for residential load centers. I would not be surprised to find maybe 80-90% of all 100A and smaller load centers are, and have been, AL bus for +30yrs. Also, I don't know of very many meter sockets that use copper bus either.
Actually Siemens as well as major other brands offer aluminum, copper or coper plated aluminum, this has been standard for a while for BR style panel boards including Square D Home Line, but you don't see many places stocking this choice as they stock what sells and cheap sells, but we got away from aluminum buss panels altogether as the failure rate was just too high and is a mess when you have a panel board embedded into a concrete wall with no choice but to re-gut it.
I have never seen a aluminum buss QO panel board, one I had though was after scrapping it with my knife proved to be tin-plated copper.
My experience in panels was T&B was the worst, when they purchased Zinco from Sylvania to make a run into the electrical distribution sector of our industry they found out that the Zinco name was already tarnished so they scrambled to come out with some of the worst panel boards I have ever seen, the neutral bars never had enough terminals for the neutrals or EGC's, I have never seen a copper buss T&B panel offered, the screws that bolted the main to the buss would always strip out not even coming close to their listed torque setting, and it seemed these were always loose when you got them, the KO's would break out all the way no mater how hard you tried just to remove the size you needed which was one of the things that prompted UL to change their standards on KO's, and don't even get me started on T&B's attempt at making meter packs as the same problem of stripping screws that held the busses together and you had to have the utility remove power so you could take it apart to get to the failed connections, but they were cheap and cheap sells:rant:
My second choice for a bad panel was Challenger brand, high buss failure and breaker failure as in wouldn't trip or would trip but not reset, again only seen aluminum busses but not sure if copper was ever offered?
Third I would say has to be the GE but only the half space breakers 30 amps and above, they just didn't have allot of contact area for that kind of amperage and I have seen many failures with these, the Nice thing was GE's always had BR stabs in between each set of half space (2) that allowed an easy fix but maybe not a code compliant one since GE didn't make a full 1" tandem but it would get you out of a jam, I often wondered if they did this with the intention of this failure in mind as no other manufacture had any kind of set up like this.
Then comes ITE/Siemens but only the aluminum buss versions, when panel was installed in a high moisture environment couldn't really fault them for this as high moisture environment should only get copper or copper plated busses other wise plenty of neutral bar terminals and over all not a bad panel but could have used a little more spring clamping on the buss which was a problem with the breaker stabs and the buss stabs seemed a little thin when compared to the SD Homelines but if you ordered the copper buss version you might as well install a QO panel as they were pricey when compared to the aluminum buss version.
Forgot all about Cutler Hammer which was not a common brand around here until City Electric Supply move into the area as that is their main brand, so I don't have much experience with them other then to say their classified panel gut retro fit kits were a life saver for the concrete embedded Siemens panels with the burned busses but did take some modifications to get it to fit properly, not a good thing as I had allot of time involved but was about the only choice I had given that Siemens had discontinued the 200 amp panels with the 4 stacked breakers as the main, any other type of panel mounting would have made it much better just to install a new complete panel, their BR series looks just like most other BR styled panels, but the CH style looks like the buss clips could be a failure problem like the GE half space as they don't look like they have enough contact area for higher amperages breakers, but I haven't took the chance to find out and haven't run into any in the field to say one way or the other so the jury is still out on them for me.
Well Square D Homeline panels what can I say, their buss stabs were much thicker the breaker stab spring grip much stronger clamping, and after they got away from the stacked neutral bar at the top always had plenty of neutral terminals, but one thing never made any sense to me, if you got a main breaker panel it came with the separate grounding bars factory mounted in them, but if you got a main lug panel they didn't, now tell me if that is not backward, and they were one of only a few that did not allow you to remove the jumper bar between the two sides to allow one side to be used as a ground bar and the other as the neutral bar, the MBJ screw was in the middle of this bar and even if you did manage to cut and twist this bar out of it, you no longer had a place to install the MBJ screw, but all in all they were very competitive in price for all the other brands, and I have never had a breaker to buss fail at the stab, so for the last 10 years this has been my choice when possible, the other thing is most places only stock the copper plated buss type, although I have seen a few aluminum ones and only a couple copper buss ones for high corrosion areas, I still have better results with the Homelines, and I still use the QO's for many commercial installs unless I need a high AIC or have many heavy loads which I use bolt it breaker panelboards.
ok now that I have given my opinion which is all that it is, have at it.:lol: