Electrical – BGA prototyping practices

BGA chips are very unfriendly for prototyping with directly. Generally if a chip comes in BGA form, you should purchase a pre-made development board with the chip already attached. Even if you made your own PCB, they are very difficult to solder correctly with hobby level tools (Yes there are youtube videos of guys doing it with a candle and a hairdryer or something, but that's not the norm). The only BGA protoboard adapters I've heard of are from SchmartBoard -- but a quick look at their site only shows 1.27mm and 1.00mm pitch BGA adaptors, 0.8mm is too small for them. A random google search found these ZIF Sockets...but I suspect they may be out of their price range. Yes, that's right, pick your jaw up off the floor, that price is for a single piece.

EDIT: I just looked up the part number, ADS1298 from TI, and it comes in TQFP. Get that instead!! It will be much cheaper, easier, and save you a ton of headache instead of trying to prototype with the BGA part. When you're ready to sell a million of your gadgets, then you can hire a factory to solder on the BGA's for you, but until then, stick to the TQFP.

Now that question will open a can of worms! Basically, there is no way to accurately answer that question because there are so many factors involved. That being said...

The "quick" answer is that I wouldn't be concerned until the signal frequencies get near 1 MHz. Between 1 and 10 MHz I would be extra careful. And above 10 MHz I would have a PCB made. Of course there are exceptions, and this is what I would do, etc. But as a rough order of magnitude place to start, it works.

There are many issues involved with this, and I'll try to cover them here...

As others have stated, it's not the signal frequency but the rise/fall time of the signal edges. If you can slow down the edges (but not too much) then you'll have an easier time. FPGA's are great for this because you can change the slew rate and drive strength of the I/O Pins. In a synchronous system, this is more important on the clock lines than the data lines (I'm not saying that data isn't important, however.)

While doing proper signal termination is important, you can't do signal termination without knowing the characteristic impedance of the wire. And in a breadboard type system you won't know what the impedance is, no matter how hard you try. In this case, you'll simply end up twiddling with it until it just happens to work.

Pay attention to the signal return paths and loop currents. This is going to play the biggest part in making the system run fast. Of course, this is damn near impossible to do correctly with a breadboard, but those are the breaks. This is why people use power/gnd planes and 4+ layer PCB's.

I've ran PCIe (2.5 GHz) over wire-wrap-wire for about 5 inches. And I've ran PCIe over a "commercially available" wire for 12 inches. So you can get good performance from wire. It's all in how you use it.

A good breadboard can probably run faster than a bad 2-layer PCB.

Of course, most modern parts are in packages that require a PCB.