1206 and 0805 -- availability

Yes of course. 1206 resistors have higher power and voltage ratings than 0805 and smaller, so there's a steady demand for them (and larger).

And 1206 caps have higher voltage ratings than 0805, so they're available as well. My most recent design had about 50% 1210-sized or larger resistors and caps. But it was a special purpose 600-volt 10ns 20A switch.

Checking on the next size up, 1210, for capacitors you'll have trouble at low capacitance values, Digi-Key reported two choices for 1pF, and none in stock. For 10pF, one type was available, but it was rated at 1kV and cost $1.61. Interestingly, 1pF, etc., was readily available at the 1206 size.

But really, those parts are sooo big, why not get your 0805 scene in order? Those of us with big fat soldering irons and fat fingers like 0805, but many others have moved down to 0603, even for hand work.

I use a lot of 1206 caps in the microfarad range, because they're a lot more stable with voltage and less microphonic than the smaller ones.

I can still do hand work with 0402s in a pinch, at least under the Mantis. Sometimes you have to use a bunch of caps in parallel to avoid via inductance issues, and 0402s are great for that.

A top-side ground pour with lots of via stitching, plus several 0402 capacitors, following a ferrite bead in series, makes a pretty good high frequency decoupling network.

I sure wouldn't want to stuff a whole board with them, though!

Cheers

Phil Hobbs

As long as we're talking about selection--

Avoid huge ceramic caps, and chip/multilayer inductors (1812+). The IPC recommends 1210 as the largest, for good reliability. Strain on the package (from thermal expansion and board flex) can very easily fracture the ceramic package (which isn't a very strong material), leading to opens or shorts.

Personally, I'd be okay with 1812, as long as I'm not doing anything mission-critical.

Larger chips (and stacks!) are available with leadframes, which decouples lead stress. I never found them cheap enough to use, though. (If you need that much in one place, you're probably looking at a polymer or electrolytic aluminum cap instead.)

There are also flexible termination parts, which are popular for automotive use (not quite mission critical, but emphasizes reliability at low cost).

Chip resistors are built on alumina, which IS a strong ceramic, but the metallization may not adhere very well, so they can still fail open. They're good enough that large (2512+) resistors are reliable to use.

Tim

The sideways caps, like 0306's, are great for low inductance.

You can always rout out a paddle to sit the cap on. Piezoelectricity is more of a problem IME, but I don't do a lot of stuff for hostile environments.

I'm just in the middle of designing some large ceramics out of a detector board.

Cheers

Phil Hobbs

Depends on where you go. Digikey recently discontinued some Rohm 1206 resistors that were rated for 500 volts and Mouser appears to have quit carrying anything at all in the 1206 package.

Hul

mkr5000 wrote:

Mouser shows 42,044 choices for 1206 resistors and 18,867 for 1206 caps. I don't think that 1206 parts are going away.

However, they currently stock only 2,225 choices for 1206 resistors and

Last time I tried to get some 1206 capacitpors, they sent 0804 devices. Later, talking to their "technician", he couldn't find anything in that package. Of course, they may have restocked their inventory and it's certainly worth checking on the basis of your findings. For Mouser, or just about anyother distributer in this country, reducing inventory would be both likely and understandable in the current nature of the manufacturing business.

Hul

John Lark> > >Depends on where you go. Digikey recently discontinued some Rohm 1206