Survey: FPGA PCB layout

Ok, then you'd have to modify your statement "always" :-)

Am I the nitpicker or what?

A quad opamp doesn't have 1738 pins!

John

Well, yes, I was just wondering about whether Nico really always draws the physical package. Looks like he doesn't for smaller stuff.

With 1738 pins you can only hope that the FPGA has enough routing resources. That used to be a major pain in the early 90's. Don't know about nowadays since other guys design the parts with the big FPGAs. And I am glad I don't have to deal with BGA, at least not with large ones ...

The biggest ones we use are Sparten 3's with 456 balls on 1 mm centers. We haven't had any routing problems so far, doing pretty complex stuff at 128 MHz clock rates. Our in-house BGA soldering yield, to date, is exactly 100%. BGAs seem to be a lot easier to solder reliably than fine-pitch leaded parts. Easier to inspect, too, since you can't inspect them at all.

John

Bloggs has several times stated that he doesn't design electronics. He hasn't stated what he actually does.

John

I had a *lot* of routing problems with the SpartanXL series. I had lotsa logic left but if it would route it would take days. I didn't have any problems, at the time, with Virtex or Vertex-E. Now the Virtex-2s and 4s route in a small number of minutes with no errors.

I don't deal with them either. That's the layouter's job. ;-) Actually, right now I just work on what goes into them (though I had to completely redesign a badly screwed up board in December, which we *still* don't have back).

The latter is a concern in my field (medical). We need to be able to inspect. The other concern is involuntary board flexing. Most of my designs have to sustain under tortures such as freighter pilots ploughing through a storm in the Carribean in airplanes as old as a DC-3 or a trucker in Africa who is lead-footing it over a few hundred miles of washboard road.

X-Rays?

Sounds boring. No wonder he's usually bummed.

John

They tend not to penetrate through metal so well and are frowned upon at the work place.

Hi Joerg,

Actually I think a very significant fraction of companies (at least those hiring EEs) offer some sort of contribution to 401k plans, sometimes profit sharing, sometimes stock options, etc... but I concur that the old days of "company pensions" is pretty much gone.

Absolutely, but if you're an employer it's definitely a legitimate consideration that starting a bunch of 70-year-olds on a, say, decade-long "modernization" project is rather riskier than if you toss a few 50- or

I agree that one year seems too short, but trying to figure out how many years should be taken into consideration (which is effectively what happens in private companies if the company is contributing to your 401k) is not going to be easy either.

---Joel

I'm sure you know this, but plenty of places will X-ray BGAs to "inspect" them.

Mostly it's a mere pittance. And that's ok, I am a strong believer that everyone should pull their own weight. Except disabled people, of course.

True. However, we should embrace the Japanese concept of letting older folks teach the young ones, not lay them off.

Just make it the same as with 401(k), IRA, old style pension funds, social security etc. What counts is what you pay in over your whole career.

We can read such stories almost daily, just an example from this morning:

Guess who gets to pay the tab for the agency's legal defense?

I guess it depends on the employer...

Do you see anything bad about the old system of pensions (from private companies, ignore the government for the moment)? I see them more as "different" than particularly better or worse. These days you're personally responsible for more of your retirement planning, which has the upside that you can probably do a better job than some company-wide pension programs used to do, but the downside is that those who plan poorly (or not at all) end up needing that much more government assistance once they're retired.

Yes, agreed 100%.

The end result there is that if your employer requires you to move to, e.g., California for the last few years of employment you'll pretty much be forced to then immediately move when you hit retirement. I suppose that isn't particularly awful, since that fact would have been clear when the employer said, "move!"

Sheesh... screw the taxpyers with retiremend funding and then screw'em again when someone tries to blow the whistle. Nice...

---Joel

Yes, but that's expensive and it's not usually done on a production basis. We do have a video prism thing the lets us peek under the chip, with fair visibility three or maybe four balls in. But we don't routinely use it. The BGAs just work.

John

My company contributes 15% of employee salaries (including bonuses) to their 401K. It's tax deductable to the company, not taxable to the employees, and makes everybody happy. That's what really matters, after all.

But it's not a pension, in that the company has no obligations at all.

John

Yes, but all along I've had the impression that your company does a lot more for emplyee motivation than most others. 15% is huge.

And it shouldn't be. Employees must understand that investing it is their responsibility, not yours.

harder

But that's how it's done.

Right. Flip-chip mounting of chips to substrates has been done for at least forty years. It just works.